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Sample records for wear model nwm

  1. Nodal wear model: corrosion in carbon blast furnace hearths

    Directory of Open Access Journals (Sweden)

    Verdeja, L. F.

    2003-06-01

    Full Text Available Criterions developed for the Nodal Wear Model (NWM were applied to estimate the shape of the corrosion profiles that a blast furnace hearth may acquire during its campaign. Taking into account design of the hearth, the boundary conditions, the characteristics of the refractory materials used and the operation conditions of the blast furnace, simulation of wear profiles with central well, mushroom and elephant foot shape were accomplished. The foundations of the NWM are constructed considering that the corrosion of the refractory is a function of the temperature present at each point (node of the liquid metal-refractory interface and the corresponding physical and chemical characteristics of the corrosive fluid.

    Se aplican los criterios del Modelo de Desgaste Nodal (MDN para la estimación de los perfiles de corrosión que podría ir adquiriendo el crisol de un homo alto durante su campaña. Atendiendo al propio diseño del crisol, a las condiciones límites de contorno, a las características del material refractario utilizado y a las condiciones de operación del horno, se consiguen simular perfiles de desgaste con "pozo central", con "forma de seta" ó de "pie de elefante". Los fundamentos del MDN se apoyan en la idea de considerar que la corrosión del refractario es función de la temperatura que el sistema pueda presentar en cada punto (nodo de la intercara refractario-fundido y de las correspondientes características físico-químicas del fluido corrosivo.

  2. Multiscale Modeling of Wear Degradation

    KAUST Repository

    Moraes, Alvaro

    2016-01-06

    Cylinder liners of diesel engines used for marine propulsion are naturally subjected to a wear process, and may fail when their wear exceeds a specified limit. Since failures often represent high economical costs, it is utterly important to predict and avoid them. In this work [4], we model the wear process using a pure jump process. Therefore, the inference goal here is to estimate: the number of possible jumps, its sizes, the coefficients and the shapes of the jump intensities. We propose a multiscale approach for the inference problem that can be seen as an indirect inference scheme. We found that using a Gaussian approximation based on moment expansions, it is possible to accurately estimate the jump intensities and the jump amplitudes. We obtained results equivalent to the state of the art but using a simpler and less expensive approach.

  3. Multiscale Modeling of Wear Degradation

    KAUST Repository

    Moraes, Alvaro

    2015-01-07

    Cylinder liners of diesel engines used for marine propulsion are naturally subjected to a wear process, and may fail when their wear exceeds a specified limit. Since failures often represent high economical costs, it is utterly important to predict and avoid them. In this work [4], we model the wear process using a pure jump process. Therefore, the inference goal here is to estimate: the number of possible jumps, its sizes, the coefficients and the shapes of the jump intensities. We propose a multiscale approach for the inference problem that can be seen as an indirect inference scheme. We found that using a Gaussian approximation based on moment expansions, it is possible to accurately estimate the jump intensities and the jump amplitudes. We obtained results equivalent to the state of the art but using a simpler and less expensive approach.

  4. Multiscale Modeling of Wear Degradation

    KAUST Repository

    Moraes, Alvaro

    2014-01-06

    Cylinder liners of diesel engines used for marine propulsion are naturally subjected to a wear process, and may fail when their wear exceeds a specified limit. Since failures often represent high economical costs, it is utterly important to predict and avoid them. In this work [4], we model the wear process using a pure jump process. Therefore, the inference goal here is to estimate: the number of possible jumps, its sizes, the coefficients and the shapes of the jump intensities. We propose a multiscale approach for the inference problem that can be seen as an indirect inference scheme. We found that using a Gaussian approximation based on moment expansions, it is possible to accurately estimate the jump intensities and the jump amplitudes. We obtained results equivalent to the state of the art but using a simpler and less expensive approach.

  5. Mechanical modelling of tooth wear.

    Science.gov (United States)

    Karme, Aleksis; Rannikko, Janina; Kallonen, Aki; Clauss, Marcus; Fortelius, Mikael

    2016-07-01

    Different diets wear teeth in different ways and generate distinguishable wear and microwear patterns that have long been the basis of palaeodiet reconstructions. Little experimental research has been performed to study them together. Here, we show that an artificial mechanical masticator, a chewing machine, occluding real horse teeth in continuous simulated chewing (of 100 000 chewing cycles) is capable of replicating microscopic wear features and gross wear on teeth that resemble wear in specimens collected from nature. Simulating pure attrition (chewing without food) and four plant material diets of different abrasives content (at n = 5 tooth pairs per group), we detected differences in microscopic wear features by stereomicroscopy of the chewing surface in the number and quality of pits and scratches that were not always as expected. Using computed tomography scanning in one tooth per diet, absolute wear was quantified as the mean height change after the simulated chewing. Absolute wear increased with diet abrasiveness, originating from phytoliths and grit. In combination, our findings highlight that differences in actual dental tissue loss can occur at similar microwear patterns, cautioning against a direct transformation of microwear results into predictions about diet or tooth wear rate. © 2016 The Author(s).

  6. Model development of work roll wear in hot strip mill

    Science.gov (United States)

    Liu, Ziying; Guan, Yingping; Wang, Fengqin

    2017-06-01

    This paper, based on the analysis of the main factors(specific roll force, mean roll surface temperature, irregular edge wear and contact arc length) affecting roll wear, designed a new work roll wear model, the test data shows that the model can more accurately reflect the work roll wear, can be on-line prediction of work roll wear. The roll wear curve, including constant wear and irregular edge wear, presents a box shape, and the reasons also are showed in this paper. The top roll wear and bottom roll wear in the same mill are inconsistent, and the reasons are also analysed in this paper. Results show that the construction of the work roll mathematical model accords with the general law of work roll wear and tear; it can more accurately forecast roll wear online.

  7. Wear model of an excavator bucket

    Science.gov (United States)

    Sarychev, Vladimir D.; Granovskii, Alexey Yu.; Nevskii, Sergey A.; Konovalov, Sergey V.; Gromov, Victor E.

    2017-12-01

    A mathematical model describing wear of the interior faces of the excavator bucket during the long-termed operation is proposed. The model is based on the Navier-Stocks equation and boundary conditions. The bucket was modeled as a rectangular parallelepiped; one of its faces is permeable for a granular material, whereas the others meet the conditions of impermeability and adhesion. In the approximation of viscous fluid, motion equations of a granular material in the excavator bucket were solved by the finite elements method. The velocity distribution curves of material particles along the bucket surface are obtained. A vortex structure is revealed at the bottom-back wall edge of the bucket, and it is thought to be the reason for high wear in these zones. As shown by the granular material pressure distributed along the bucket walls, its maximum is at the bottom-back wall edge of the excavator bucket. It is considered to be the reason for high wear in the operation process. Therefore, the bottom and back walls of the excavator bucket should be coated with a composite armouring mesh via arc surfacing.

  8. Phenomenological modeling of abradable wear in turbomachines

    Science.gov (United States)

    Berthoul, Bérenger; Batailly, Alain; Stainier, Laurent; Legrand, Mathias; Cartraud, Patrice

    2018-01-01

    Abradable materials are widely used as coatings within compressor and turbine stages of modern aircraft engines in order to reduce operating blade-tip/casing clearances and thus maximize energy efficiency. However, rubbing occurrences between blade tips and coating liners may lead to high blade vibratory levels and endanger their structural integrity through fatigue mechanisms. Accordingly, there is a need for a better comprehension of the physical phenomena at play and for an accurate modeling of the interaction, in order to predict potentially unsafe events. To this end, this work introduces a phenomenological model of the abradable coating removal based on phenomena reported in the literature and accounting for key frictional and wear mechanisms including plasticity at junctions, ploughing, micro-rupture and machining. It is implemented within an in-house software solution dedicated to the prediction of full three-dimensional blade/abradable coating interactions within an aircraft engine low pressure compressor. Two case studies are considered. The first one compares the results of an experimental abradable test rig and its simulation. The second one deals with the simulation of interactions in a complete low-pressure compressor. The consistency of the model with experimental observations is underlined, and the impact of material parameter variations on the interaction and wear behavior of the blade is discussed. It is found that even though wear patterns are remarkably robust, results are significantly influenced by abradable coating material properties.

  9. Comparison of GNSS integrated water vapor and NWM reanalysis data over Central and South America

    Science.gov (United States)

    Fernandez, Laura Isabel; Mendoza, Luciano Pedro Oscar; Natali, María Paula; Meza, Amalia Margarita; Bianchi, Clara Eugenia

    2017-04-01

    Integrated water vapor (IWV) derived from Global Navigation Satellite Systems (GNSS) and Numerical Weather Models (NWM) reanalysis data were compared in order to assess the consistency between the different datasets over the extended geographical region of Central and South America. The investigation was performed for the seven-year period between 2007 and 2013. We analyzed two different reanalysis: the European Centre for Medium-Range Weather Forecast (ECMWF) reanalysis data (ERA Interim) and the Modern-Era Retrospective analysis for Research and Applications (MERRA2) from the National Aeronautics and Space Administration (NASA). The statistical analysis of the differences was performed in 110 GNSS sites (GPS +GLONASS), although the most interesting results came from the 73 sites which have more than 5 years of data. The study of the spatial distribution of the differences in the selected area involves different climate types, from polar to tropical, and it is characterized by large temporal variability of the integrated total humidity content. The inter-comparison was also performed on several time scales: from hours to years. In this study, not only the IWV values given by the different reanalysis where compared with the respective GNSS derived values but also the numeric integral of the IWV. This is nothing but the total vertically integrated water vapor of a unit air column each station but considering its real geopotential height. To that end, multilevel data from each reanalysis was also used. Moreover, the scarce coverage of operational radio sounding stations is noticeable in large areas of the selected region. Hence the contribution of IWV-GNSS is essential to improve the weather understanding. Considering that the atmospheric water vapor has a highly variable and complex distribution which knowledge is essential for weather prediction and local meteorological studies, this study aims to provide IWV-GNSS observations able to be assimilated by operational

  10. Analysis and Modelling of Electrode Wear in Resistance Spot Welding

    DEFF Research Database (Denmark)

    Madsen, Anders; Pedersen, Kim; Friis, Kasper Storgaard

    2010-01-01

    A model describing electrode wear as a function of weld number, initial tip diameter, truncated cone angle, welding current and electrode force is proposed. Excellent agreement between the model and experimental results is achieved, showing that the model can describe the change in electrode tip...

  11. Wear-caused deflection evolution of a slide rail, considering linear and non-linear wear models

    Science.gov (United States)

    Kim, Dongwook; Quagliato, Luca; Park, Donghwi; Murugesan, Mohanraj; Kim, Naksoo; Hong, Seokmoo

    2017-05-01

    The research presented in this paper details an experimental-numerical approach for the quantitative correlation between wear and end-point deflection in a slide rail. Focusing the attention on slide rail utilized in white-goods applications, the aim is to evaluate the number of cycles the slide rail can operate, under different load conditions, before it should be replaced due to unacceptable end-point deflection. In this paper, two formulations are utilized to describe the wear: Archard model for the linear wear and Lemaitre damage model for the nonlinear wear. The linear wear gradually reduces the surface of the slide rail whereas the nonlinear one accounts for the surface element deletion (i.e. due to pitting). To determine the constants to use in the wear models, simple tension test and sliding wear test, by utilizing a designed and developed experiment machine, have been carried out. A full slide rail model simulation has been implemented in ABAQUS including both linear and non-linear wear models and the results have been compared with those of the real rails under different load condition, provided by the rail manufacturer. The comparison between numerically estimated and real rail results proved the reliability of the developed numerical model, limiting the error in a ±10% range. The proposed approach allows predicting the displacement vs cycle curves, parametrized for different loads and, based on a chosen failure criterion, to predict the lifetime of the rail.

  12. A Multiple Model Prediction Algorithm for CNC Machine Wear PHM

    Directory of Open Access Journals (Sweden)

    Huimin Chen

    2011-01-01

    Full Text Available The 2010 PHM data challenge focuses on the remaining useful life (RUL estimation for cutters of a high speed CNC milling machine using measurements from dynamometer, accelerometer, and acoustic emission sensors. We present a multiple model approach for wear depth estimation of milling machine cutters using the provided data. The feature selection, initial wear estimation and multiple model fusion components of the proposed algorithm are explained in details and compared with several alternative methods using the training data. The final submission ranked #2 among professional and student participants and the method is applicable to other data driven PHM problems.

  13. An energy dissipation and cross shear time dependent computational wear model for the analysis of polyethylene wear in total knee replacements.

    Science.gov (United States)

    O'Brien, Sean T; Bohm, Eric R; Petrak, Martin J; Wyss, Urs P; Brandt, Jan-M

    2014-03-21

    The cost and time efficiency of computational polyethylene wear simulations may enable the optimization of total knee replacements for the reduction of polyethylene wear. The present study proposes an energy dissipation wear model for polyethylene which considers the time dependent molecular behavior of polyethylene, aspects of tractive rolling and contact pressure. This time dependent - energy dissipation wear model was evaluated, along with several other wear models, by comparison to pin-on-disk results, knee simulator wear test results under various kinematic conditions and knee simulator wear test results that were performed following the ISO 14243-3 standard. The proposed time dependent - energy dissipation wear model resulted in improved accuracy for the prediction of pin-on-disk and knee simulator wear test results compared with several previously published wear models. Crown Copyright © 2014. Published by Elsevier Ltd. All rights reserved.

  14. 3D Simulation Modeling of the Tooth Wear Process.

    Directory of Open Access Journals (Sweden)

    Ning Dai

    Full Text Available Severe tooth wear is the most common non-caries dental disease, and it can seriously affect oral health. Studying the tooth wear process is time-consuming and difficult, and technological tools are frequently lacking. This paper presents a novel method of digital simulation modeling that represents a new way to study tooth wear. First, a feature extraction algorithm is used to obtain anatomical feature points of the tooth without attrition. Second, after the alignment of non-attrition areas, the initial homogeneous surface is generated by means of the RBF (Radial Basic Function implicit surface and then deformed to the final homogeneous by the contraction and bounding algorithm. Finally, the method of bilinear interpolation based on Laplacian coordinates between tooth with attrition and without attrition is used to inversely reconstruct the sequence of changes of the 3D tooth morphology during gradual tooth wear process. This method can also be used to generate a process simulation of nonlinear tooth wear by means of fitting an attrition curve to the statistical data of attrition index in a certain region. The effectiveness and efficiency of the attrition simulation algorithm are verified through experimental simulation.

  15. A Predictive Multiscale Model of Wear

    Science.gov (United States)

    2011-03-09

    shear properties of chromium and iron oxides. A multiscale model that had been devised earlier by the PI for describing tensile load response was...quantum mechanics simulations of the tensile and shear properties of chromium and iron oxides. A multiscale model that had been devised earlier by the...type crystal, and Fe3O4 has a spinel structure. Both electronic and geometric structural differences will contribute to trends in mechanical

  16. Multiscale Modeling of Wear Degradation in Cylinder Liners

    KAUST Repository

    Moraes, Alvaro

    2014-03-20

    Every mechanical system is naturally subjected to some kind of wear process that, at some point, will cause failure in the system if no monitoring or treatment process is applied. Since failures often lead to high economical costs, it is essential both to predict and to avoid them. To achieve this, a monitoring system of the wear level should be implemented to decrease the risk of failure. In this work, we take a first step into the development of a multiscale indirect inference methodology for state-dependent Markovian pure jump processes. This allows us to model the evolution of the wear level and to identify when the system reaches some critical level that triggers a maintenance response. Since the likelihood function of a discretely observed pure jump process does not have an expression that is simple enough for standard nonsampling optimization methods, we approximate this likelihood by expressions from upscaled models of the data. We use the Master Equation (ME) to assess the goodness-of-fit and to compute the distribution of the hitting time to the critical level.

  17. A WEAR MODEL FOR DIESEL ENGINE EXHAUST VALVES

    Energy Technology Data Exchange (ETDEWEB)

    Blau, Peter Julian [ORNL

    2009-11-01

    The work summarized here comprises the concluding effort of a multi-year project, funded by the U.S. Department of Energy, Office of Vehicle Technologies. It supports the development of a better understanding of advanced diesel engine designs in which enhanced power density, energy efficiency, and emissions control place increasing demands upon the durability of engine materials. Many kinds of metallic alloys are used in engines depending on the operating stresses, temperatures, and chemical environments. Exhaust valves, for example, are subjected to high temperatures and repetitive surface contacts that place demands on durability and frictional characteristics of the materials. Valves must continue to seal the combustion chamber properly for thousands of hours of cyclic engine operation and under varying operating conditions. It was the focus of this effort to understand the wear processes in the valve-seat area and to develop a model for the surface deformation and wear of that important interface. An annotated bibliography is provided to illustrate efforts to understand valve wear and to investigate the factors of engine operation that affect its severity and physical manifestation. The project for which this modeling effort was the final task, involved construction of a high-temperature repetitive impact test system as well as basic tribology studies of the combined processes of mechanical wear plus oxidation at elevated temperatures. Several publications resulted from this work, and are cited in this report. The materials selected for the experimental work were high-performance alloys based on nickel and cobalt. In some cases, engine-tested exhaust valves were made available for wear analysis and to ensure that the modes of surface damage produced in experiments were simulative of service. New, production-grade exhaust valves were also used to prepare test specimens for experimental work along with the other alloy samples. Wear analysis of valves and seats

  18. Analysis of progressive cavity pumps specific wear processes using Bitter and Hutchings models

    Science.gov (United States)

    Popovici, A. I.; Popescu, M.; Antonescu, N. N.; Petrescu, F. N.

    2017-02-01

    Progressive cavitation pumps are designed to work in aggressive environments thus their wear is inevitable. The specific tribological coupling of these pumps is composed of a helical rotor with a single outward helix and a stator with a double inside helix. These elements are in relative motion and direct contact to each other and also in direct contact with the pumped oil. Therefore the main forms of wear of rotor-stator coupling elements are the abrasive wear and the erosion wear. In this paper is presented the analysis of erosion with Bitter and Hutchings models. The results are useful for estimation of progressive cavity pumps specific abrasive-erosive wear.

  19. Analysis of progressive cavity pumps specific wear processes using Finnie models

    Science.gov (United States)

    Popescu, M.; Popovici, A. I.; Petrescu, F. N.; Antonescu, N. N.

    2017-02-01

    Progressive cavitation pumps are designed to work in aggressive environments thus their wear is inevitable. The specific tribological coupling of these pumps is composed of a helical rotor with a single outward helix and a stator with a double inside helix. These elements are in relative motion and direct contact to each other and also in direct contact with the pumped oil. Therefore the main forms of wear of rotor-stator coupling elements are the abrasive wear and the erosion wear. In this paper is presented the analysis of erosion with Finnie models. The results are useful for estimation of progressive cavity pumps specific abrasive-erosive wear.

  20. A new in situ model to study erosive enamel wear, a clinical pilot study.

    NARCIS (Netherlands)

    Ruben, J.L.; Truin, G.J.; Bronkhorst, E.M.; Huysmans, M.C.D.N.J.M.

    2017-01-01

    OBJECTIVES: To develop an in situ model for erosive wear research which allows for more clinically relevant exposure parameters than other in situ models and to show tooth site-specific erosive wear effect of an acid challenge of orange juice on enamel. METHODS: This pilot study included 6

  1. A Multi-Stage Wear Model for Grid-to-Rod Fretting of Nuclear Fuel Rods

    Energy Technology Data Exchange (ETDEWEB)

    Blau, Peter Julian [ORNL

    2014-01-01

    The wear of fuel rod cladding against the supporting structures in the cores of pressurized water nuclear reactors (PWRs) is an important and potentially costly tribological issue. Grid-to-rod fretting (GTRF), as it is known, involves not only time-varying contact conditions, but also elevated temperatures, flowing hot water, aqueous tribo-corrosion, and the embrittling effects of neutron fluences. The multi-stage, closed-form analytical model described in this paper relies on published out-of-reactor wear and corrosion data and a set of simplifying assumptions to portray the conversion of frictional work into wear depth. The cladding material of interest is a zirconium-based alloy called Zircaloy-4, and the grid support is made of a harder and more wear-resistant material. Focus is on the wear of the cladding. The model involves an incubation stage, a surface oxide wear stage, and a base alloy wear stage. The wear coefficient, which is a measure of the efficiency of conversion of frictional work into wear damage, can change to reflect the evolving metallurgical condition of the alloy. Wear coefficients for Zircaloy-4 and for a polyphase zirconia layer were back-calculated for a range of times required to wear to a critical depth. Inputs for the model, like the friction coefficient, are taken from the tribology literature in lieu of in-reactor tribological data. Concepts of classical fretting were used as a basis, but are modified to enable the model to accommodate the complexities of the PWR environment. Factors like grid spring relaxation, pre-oxidation of the cladding, multiple oxide phases, gap formation, impact, and hydrogen embrittlement are part of the problem definition but uncertainties in their relative roles limits the ability to validate the model. Sample calculations of wear depth versus time in the cladding illustrate how GTRF wear might occur in a discontinuous fashion during months-long reactor operating cycles. A means to account for grid/rod gaps

  2. Effects of hard chrome and MoN-coated stainless steel on wear behaviour and tool life model under two-body abrasion wear testing

    Directory of Open Access Journals (Sweden)

    P. Srisattayakul

    2017-01-01

    Full Text Available The objectives of this study were to investigate the effect of the electroplated hard chrome (HC and the MoNcoated AISI 316 stainless steel coatings on weight loss under two-body abrasion wear testing and to predict the tool life of both materials used as a fishing net-weaving machine component, namely the hook. Both materials were used to carry out the wear experiments under two-body abrasion behavior. These specimens were wear tested with the in-house wear testing apparatus base on ASTM: G133-05 standard. The Taylor’s equation was used to formulate the tool life model whereas the Monte Carlo simulation was used to predict the tool life of the machine part. The results showed that the MoN-HC exhibited higher wear resistance than that of the HC.

  3. Model for the evaluation of root wear by histometric analysis.

    Science.gov (United States)

    de Oliveira, Guilherme José Pimentel Lopes; Silveira Faeda, Rafael; Marcantonio, Elcio; Marcantonio, Rosemary Adriana Chiérici

    2011-10-01

    Knowledge of the wear to the root surface caused by different instruments is essential in the choice of the type of tool used in relation to the phase of periodontal treatment which the patient is undergoing. The objective of this study was to present a new methodology for evaluating tooth wear produced by the instrumentation of the root surface. The present study used five teeth, the proximals of which were divided in three regions: coronal, median, and an apical. The coronal region was scaled with a curette, the apical region was irradiated with the Erbium, Chromium: Yttrium-Scandium-Gallium-Garnet laser (Er,Cr:YSGG laser) and the medial region was left untreated, which served as control. The teeth underwent a histological process and were analyzed histometrically. The t test (P laser presented less wear (113.37 ± 32.94 μm) in comparison to the regions that were scaled with manual curettes (169.83 ± 24.76 μm) (P < 0.05). The methodology proposed was efficient in the measurement of the wear caused by the root instrumentation and proved easy to execute, easy to reproduce, and of low cost and with high calibration accuracy. Copyright © 2010 Wiley-Liss, Inc.

  4. Modelling and measurement of wear particle flow in a dual oil filter system for condition monitoring

    DEFF Research Database (Denmark)

    Henneberg, Morten; Eriksen, René Lynge; Fich, Jens

    2016-01-01

    Wear debris is an indicator of the health of machinery, and the availability of accurate methods for characterising debris is important. In this work, a dual filter model for a gear oil system is used in conjunction with operational data to indicate three different system operating states....... The quantity of wear particles in gear oil is analysed with respect to system running conditions. It is shown that the model fits the data in terms of startup “particle burst” phenomenon, quasi-stationary conditions during operation, and clean-up filtration when placed out of operation. In order to establish...... oil. Using this model it is possible to draw conclusions on the filtration system performance and wear generation in the gears. Limitations of the proposed model are the lack of ability to describe noise and random burst spikes attributed to measurement error distributions. Trending of gear wear...

  5. Superior accuracy of model-based radiostereometric analysis for measurement of polyethylene wear

    DEFF Research Database (Denmark)

    Stilling, M; Kold, S; de Raedt, S

    2012-01-01

    The accuracy and precision of two new methods of model-based radiostereometric analysis (RSA) were hypothesised to be superior to a plain radiograph method in the assessment of polyethylene (PE) wear.......The accuracy and precision of two new methods of model-based radiostereometric analysis (RSA) were hypothesised to be superior to a plain radiograph method in the assessment of polyethylene (PE) wear....

  6. WEAR RATE PREDICTION OF GRINDING MEDIA USING BPNN AND MLR MODELS IN GRINDING OF SULPHIDE ORES

    Directory of Open Access Journals (Sweden)

    A. Azizi

    2016-06-01

    Full Text Available Nowadays steel balls wear is a major problem in mineral processing industries and forms a significant part of the grinding cost. Different factors are effective on balls wear. It is needed to find models which are capable to estimate wear rate from these factors. In this paper a back propagation neural network (BPNN and multiple linear regression (MLR method have been used to predict wear rate of steel balls using some significant parameters including, pH, solid content, throughout of grinding circuit, speed of mill, charge weight of balls and grinding time. The comparison between the predicted wear rates and the measured data resulted in the correlation coefficients (R, 0.977 and 0.955 for training and test data using BPNN model. However, the R values were 0.936 and 0.969 for training and test data by MLR method. In addition, the average absolute percent relative error (AAPE obtained 2.79 and 4.18 for train and test data in BPNN model, respectively. Finally, Analysis of the predictions shows that the BPNN and MLR methods could be used with good engineering accuracy to directly predict the wear rate of steel balls.

  7. Computer system for identification of tool wear model in hot forging

    Directory of Open Access Journals (Sweden)

    Wilkus Marek

    2016-01-01

    Full Text Available The aim of the research was to create a methodology that will enable effective and reliable prediction of the tool wear. The idea of the hybrid model, which accounts for various mechanisms of tool material deterioration, is proposed in the paper. The mechanisms, which were considered, include abrasive wear, adhesive wear, thermal fatigue, mechanical fatigue, oxidation and plastic deformation. Individual models of various complexity were used for separate phenomena and strategy of combination of these models in one hybrid system was developed to account for the synergy of various mechanisms. The complex hybrid model was built on the basis of these individual models for various wear mechanisms. The individual models expanded from phenomenological ones for abrasive wear to multi-scale methods for modelling micro cracks initiation and propagation utilizing virtual representations of granular microstructures. The latter have been intensively developed recently and they form potentially a powerful tool that allows modelling of thermal and mechanical fatigue, accounting explicitly for the tool material microstructure.

  8. Rat silicone hydrogel contact lens model: effects of high- versus low-Dk lens wear.

    Science.gov (United States)

    Zhang, Yunfan; Gabriel, Manal M; Mowrey-McKee, Mary F; Barrett, Ronald P; McClellan, Sharon; Hazlett, Linda D

    2008-11-01

    This study used a rat contact lens (CL) model to test if high- versus low-Dk lens wear caused changes in (1) conjunctival Langerhans cell (LC) number or location; (2) Bcl-2 expression; and (3) infection risk. Female, Lewis rats wore a high- or low-Dk CL continuously for 2 weeks. Afterward, corneas were harvested and processed for ADPase activity to identify LCs, for immunostaining and for real time-polymerase chain reaction. Contact lens-wearing rats also were challenged with Pseudomonas aeruginosa by placing a bacterial-soaked CL on the eye followed by topical delivery of bacteria. After 48 hrs, slit lamp examination and real time-polymerase chain reaction were used to evaluate the corneal response. Conjunctival LC were significantly increased after low- versus high-Dk CL wear (PDk lens wearing group. Bcl-2 mRNA levels were significantly decreased in low- versus high-Dk CL wearing rats, while Bax, FasL, caspase 3, and caspase 9 levels were unchanged. Immunostaining for Bcl-2 showed fewer positively stained epithelial cells in the low- versus high-Dk lens wearing group. After bacterial challenge, 30% of low- versus none of the high-Dk CL wearing corneas became infected and showed increased mRNA levels for several proinflammatory cytokines/chemokines, inducible nitric oxide synthase and matrix metalloproteinase-9. Low- versus high-Dk or non-CL wear led to an increased number of conjunctival LC, decreased Bcl-2 levels, and increased the risk of bacterial infection.

  9. To the question of modeling of wheels and rails wear processes

    Directory of Open Access Journals (Sweden)

    S.V. Myamlin

    2013-06-01

    Full Text Available Purpose. There is a need of wear process modeling in the wheel-rail system. This is related to the fact that the wear processes in this system are absolutely different in the initial and final stages. The profile change of rail and, especially, of the wheels caused by the wear significantly affects the rolling stock dynamics, traffic safety and the resource of the wheels and rails. Wear modeling and the traffic safety evaluation requires the accounting of the low frequency component forces (including the modeling of transitional areas affecting the wheel on the side of the rail and carriage in motion of rolling stock, so the statistical analysis is not possible. Methodology. The method of mathematical modeling of the wheel set and the rail interaction was used during the research conducting. Findings. As a result of the modeling of the wheel set motion on the rail track, the mathematic model with 19 freedom degrees was obtained. This model takes into account the axle torque and studies wheels constructions as the components of the mechanical systems, consisting of a hub and tire. Originality. The mathematic model allows evaluating the wear degree of the wheels and rails when using on the rolling stock not only all-metal wheel sets, but also compound ones with the use of spring wheels and independent rotation of semi-axes with the wheels. Practical value. The development of the improved mathematical model of freight car wheel set motion with differential rotation of the wheels and compound axles allows studying the wear processes of wheels and rails.

  10. IMPROVING TBO OF FREIGHT CAR BOGIES. GEOMETRY MODEL OF CENTER PAD WEAR

    Directory of Open Access Journals (Sweden)

    L. A. Muradian

    2017-02-01

    Full Text Available Purpose. The scientific work is aimed to: 1 analyze the technical condition of freight cars and technological methods used in the repair; 2 identify possible ways to improve resource of freight car bogies; 3 develop a mathematical model to describe the wear geometry of the original surface of bogie center pad at the corresponding life cycle of a freight car. Methodology. In order to solve the problem complex of increasing TBO of freight car bogies the methods for the synthesis, analysis and systematic approach were used. In addition, the use of mathematical modeling unit, solid state physics, the theory of friction and wear of solids. Findings. The analysis of the technical condition of freight cars has shown that up to 15% of the faults falls on the bogies. A separate element of the repaired bogie is a bolster. At this the center pad is recovered most often. The center pad wear is uneven and the technological methods used for the repair, do not allow providing uniform wear due to which there is a need in premature repairs. One of the ways to improve the center pad resource during repair is the application of welding or sputtering deposition, but with providing discrete strength and durability in the longitudinal and transverse directions of the car axis, respectively. In order to establish the boundaries of the distribution of renewable material along the center pad diameter it was considered the fatigue wear process in cooperation with center plate and described the geometry of the surface of the center pad wear. Originality. Technical condition of freight car bogies according to wear criterion was analyzed in the paper. It is shown that the dynamics of bogie faults has a positive character. In addition, a significant place among the repaired parts takes the bolster, and a special loaded place is the center pad. To describe the geometry of wear for the first time a mathematical model for determining the initial surface of the center pad in the

  11. ANN & ANFIS Models for Prediction of Abrasive Wear of 3105 Aluminium Alloy with Polyurethane Coating

    Directory of Open Access Journals (Sweden)

    H. Alimam

    2016-06-01

    Full Text Available The quest for safety and reliability has increased significantly after Industrial revolution, so is the case for coating industries. In this paper 3105 Aluminium alloy sheet is coated with organic polyurethane coating. After the implementation of coating, various processes are undergone to check its reliability under elevated conditions. ANN & ANFIS model were developed and trained with an objective to find abrasive wear during the process. ANN & ANFIS model were compared with the experimental results. It is observed that the abrasive wear of a coated specimen can be predicted accurately and precisely using ANN and ANFIS models.

  12. BAYESIAN INFERENCE OF HIDDEN GAMMA WEAR PROCESS MODEL FOR SURVIVAL DATA WITH TIES.

    Science.gov (United States)

    Sinha, Arijit; Chi, Zhiyi; Chen, Ming-Hui

    2015-10-01

    Survival data often contain tied event times. Inference without careful treatment of the ties can lead to biased estimates. This paper develops the Bayesian analysis of a stochastic wear process model to fit survival data that might have a large number of ties. Under a general wear process model, we derive the likelihood of parameters. When the wear process is a Gamma process, the likelihood has a semi-closed form that allows posterior sampling to be carried out for the parameters, hence achieving model selection using Bayesian deviance information criterion. An innovative simulation algorithm via direct forward sampling and Gibbs sampling is developed to sample event times that may have ties in the presence of arbitrary covariates; this provides a tool to assess the precision of inference. An extensive simulation study is reported and a data set is used to further illustrate the proposed methodology.

  13. Modeling of Complex Wear Behavior Associated with Grid-to-Rod Fretting in Light Water Nuclear Reactors

    Science.gov (United States)

    Blau, P. J.; Qu, J.; Lu, R.

    2016-11-01

    Fretting wear damage to fuel cladding from flow-induced vibrations can be a significant concern in the operation of light water nuclear reactors. For years, research on the grid-to-rod fretting (GTRF) phenomena has been underway in countries where nuclear power production is a significant industry. Under the auspices of the U.S. Department of Energy Consortium for Advanced Simulation of Light Water Reactors, an effort has been underway to develop and test an engineering wear model for zirconium alloy fuel rod cladding against a supporting grid. The multi-stage model accounts for oxide layers and wear rate transitions. This paper describes the basis for a GTRF engineering wear model, the physical significance of the wear factor it contains, and recent progress toward model validation based on a fretting wear testing apparatus that accounts for coolant temperature, pressure, and the presence of periodic impacts (gaps) in grid/rod contact.

  14. Modeling of wear behavior of Al/B{sub 4}C composites produced by powder metallurgy

    Energy Technology Data Exchange (ETDEWEB)

    Sahin, Ismail; Bektas, Asli [Gazi Univ., Ankara (Turkey). Dept. of Industrial Design Engineering; Guel, Ferhat; Cinci, Hanifi [Gazi Univ., Ankara (Turkey). Dept. of Materials and Metallurgy Engineering

    2017-06-01

    Wear characteristics of composites, Al matrix reinforced with B{sub 4}C particles percentages of 5, 10,15 and 20 produced by the powder metallurgy method were studied in this study. For this purpose, a mixture of Al and B{sub 4}C powders were pressed under 650 MPa pressure and then sintered at 635 C. The analysis of hardness, density and microstructure was performed. The produced samples were worn using a pin-on-disk abrasion device under 10, 20 and 30 N load through 500, 800 and 1200 mesh SiC abrasive papers. The obtained wear values were implemented in an artificial neural network (ANN) model having three inputs and one output using feed forward backpropagation Levenberg-Marquardt algorithm. Thus, the optimum wear conditions and hardness values were determined.

  15. Development of dynamic models of wagons on models 18-9810 and 18-9855 bogies taking into account wheel wear research

    Directory of Open Access Journals (Sweden)

    A. V. Saidova

    2013-04-01

    Full Text Available Purpose. Wear parameters clarification in wear simulation is an actual goal because of absence of corresponding data for freight cars in condition of using them on Russian railways. Research is devoted to development of dynamic models of wagons on three-peace two-axle models 18-9810 and 18-9855 bogies with maximum axle-loads 23,5 ts and 25 ts, and to choice of factors, with varying which parameters in the model of wheel wear can be identified. Methodology. The problem is solved by method of mathematic simulation in «MEDYNA» software. Wear calculation is based on abrasive wear theory (Archard’s theory. Findings. Clarification of wheels’ wear model may be done with varying of friction coefficient between wheel and rail for different wheel profile areas (flange and tread, wear coefficient in Archard’s model for mild and heavy wear and transition between them. Originality. Dynamic models of universal gondola on models 18-9810 and 18-9855 bogies are developed. It is established, that rail treads irregularities size effect wheel wear insignificantly, when car is running on circle track of constant radius. Practical value. Developed dynamic models of wagons on models 18-9810 and 18-9855 bogies may be used in wear simulation, determination of car running characteristics, interaction of car and rail of different type, construction, condition and etc. Research results of some factors influence on freight car wheel wear may be interesting for people, who study this problem.

  16. Paleo-tribology: development of wear measurement techniques and a three-dimensional model revealing how grinding dentitions self-wear to enable functionality

    Science.gov (United States)

    Erickson, Gregory M.; Sidebottom, Mark A.; Curry, John F.; Kay, David Ian; Kuhn-Hendricks, Stephen; Norell, Mark A.; Sawyer, W. Gregory; Krick, Brandon A.

    2016-06-01

    In most mammals and a rare few reptilian lineages the evolution of precise dental occlusion led to the capacity to form functional chewing surfaces due to pressures generated while feeding. The complex dental architectures of such teeth and the biomechanics of their self-wearing nature are poorly understood. Our research team composed of paleontologists, evolutionary biologists, and engineers have developed a protocol to: (1) determine the histological make-up of grinding dentitions in extant and fossil taxa; (2) ascertain wear-relevant material properties of the tissues; (3) determine how those properties relate to inter-tissue-biomechanics leading the dental functionality using a three-dimensional Archard’s wear model developed specifically for dental applications; (4) analyze those data in phylogenetic contexts to infer evolutionary patterns as they relate to feeding. Finally we discuss industrial applications that are emerging from our paleontologically-inspired research.

  17. A New Mathematical Model for Flank Wear Prediction Using Functional Data Analysis Methodology

    Directory of Open Access Journals (Sweden)

    Sonja Jozić

    2014-01-01

    Full Text Available This paper presents a new approach improving the reliability of flank wear prediction during the end milling process. In the present work, prediction of flank wear has been achieved by using cutting parameters and force signals as the sensitive carriers of information about the machining process. A series of experiments were conducted to establish the relationship between flank wear and cutting force components as well as the cutting parameters such as cutting speed, feed per tooth, and radial depth of cut. In order to be able to predict flank wear a new linear regression mathematical model has been developed by utilizing functional data analysis methodology. Regression coefficients of the model are in the form of time dependent functions that have been determined through the use of functional data analysis methodology. The mathematical model has been developed by means of applied cutting parameters and measured cutting forces components during the end milling of workpiece made of 42CrMo4 steel. The efficiency and flexibility of the developed model have been verified by comparing it with the separate experimental data set.

  18. Modelling of tunnelling processes and rock cutting tool wear with the particle finite element method

    Science.gov (United States)

    Carbonell, Josep Maria; Oñate, Eugenio; Suárez, Benjamín

    2013-09-01

    Underground construction involves all sort of challenges in analysis, design, project and execution phases. The dimension of tunnels and their structural requirements are growing, and so safety and security demands do. New engineering tools are needed to perform a safer planning and design. This work presents the advances in the particle finite element method (PFEM) for the modelling and the analysis of tunneling processes including the wear of the cutting tools. The PFEM has its foundation on the Lagrangian description of the motion of a continuum built from a set of particles with known physical properties. The method uses a remeshing process combined with the alpha-shape technique to detect the contacting surfaces and a finite element method for the mechanical computations. A contact procedure has been developed for the PFEM which is combined with a constitutive model for predicting the excavation front and the wear of cutting tools. The material parameters govern the coupling of frictional contact and wear between the interacting domains at the excavation front. The PFEM allows predicting several parameters which are relevant for estimating the performance of a tunnelling boring machine such as wear in the cutting tools, the pressure distribution on the face of the boring machine and the vibrations produced in the machinery and the adjacent soil/rock. The final aim is to help in the design of the excavating tools and in the planning of the tunnelling operations. The applications presented show that the PFEM is a promising technique for the analysis of tunnelling problems.

  19. New model to explain tooth wear with implications for microwear formation and diet reconstruction.

    Science.gov (United States)

    Xia, Jing; Zheng, Jing; Huang, Diaodiao; Tian, Z Ryan; Chen, Lei; Zhou, Zhongrong; Ungar, Peter S; Qian, Linmao

    2015-08-25

    Paleoanthropologists and vertebrate paleontologists have for decades debated the etiology of tooth wear and its implications for understanding the diets of human ancestors and other extinct mammals. The debate has recently taken a twist, calling into question the efficacy of dental microwear to reveal diet. Some argue that endogenous abrasives in plants (opal phytoliths) are too soft to abrade enamel, and that tooth wear is caused principally by exogenous quartz grit on food. If so, variation in microwear among fossil species may relate more to habitat than diet. This has important implications for paleobiologists because microwear is a common proxy for diets of fossil species. Here we reexamine the notion that particles softer than enamel (e.g., silica phytoliths) do not wear teeth. We scored human enamel using a microfabrication instrument fitted with soft particles (aluminum and brass spheres) and an atomic force microscope (AFM) fitted with silica particles under fixed normal loads, sliding speeds, and spans. Resulting damage was measured by AFM, and morphology and composition of debris were determined by scanning electron microscopy with energy-dispersive X-ray spectroscopy. Enamel chips removed from the surface demonstrate that softer particles produce wear under conditions mimicking chewing. Previous models posited that such particles rub enamel and create ridges alongside indentations without tissue removal. We propose that although these models hold for deformable metal surfaces, enamel works differently. Hydroxyapatite crystallites are "glued" together by proteins, and tissue removal requires only that contact pressure be sufficient to break the bonds holding enamel together.

  20. ANALYTICAL MODEL OF CALCULUS FOR INFLUENCE THE TRANSLATION GUIDE WEAR OVER THE MACHINING ACCURACY ON THE MACHINE TOOL

    Directory of Open Access Journals (Sweden)

    Ivona PETRE

    2010-10-01

    Full Text Available The wear of machine tools guides influences favorably to vibrations. As a result of guides wear, the initial trajectory of cutting tools motion will be modified, the generating dimensional accuracy discrepancies and deviations of geometrical shape of the work pieces. As it has already been known, the wear of mobile and rigid guides is determined by many parameters (pressure, velocity, friction length, lubrication, material. The choice of one or another analytic model and/or the experimental model of the wear is depending by the working conditions, assuming that the coupling material is known.The present work’s goal is to establish an analytic model of calculus showing the influence of the translation guides wear over the machining accuracy on machine-tools.

  1. Modelling and analysis of abrasive wear performance of composites ...

    African Journals Online (AJOL)

    These fibres can also be easily moulded to wide variety of shapes during composite preparation. However, modelling and analysis of behaviour of composites reinforced with short fibre drawn from agricultural resources has been studied to a limited extent. Particularly, the optimum size of short fibre just capable of ...

  2. Tooth wear

    Directory of Open Access Journals (Sweden)

    Tušek Ivan

    2014-01-01

    Full Text Available Tooth wear is the loss of dental hard tissue that was not caused by decay and represents a common clinical problem of modern man. In the etiology of dental hard tissue lesions there are three dominant mechanisms that may act synergistically or separately:friction (friction, which is caused by abrasion of exogenous, or attrition of endogenous origin, chemical dissolution of dental hard tissues caused by erosion, occlusal stress created by compression and flexion and tension that leads to tooth abfraction and microfracture. Wear of tooth surfaces due to the presence of microscopic imperfections of tooth surfaces is clinically manifested as sanding veneers. Tribology, as an interdisciplinary study of the mechanisms of friction, wear and lubrication at the ultrastructural level, has defined a universal model according to which the etiopathogenesis of tooth wear is caused by the following factors: health and diseases of the digestive tract, oral hygiene, eating habits, poor oral habits, bruxism, temporomandibular disorders and iatrogenic factors. Attrition and dental erosion are much more common in children with special needs (Down syndrome. Erosion of teeth usually results from diseases of the digestive tract that lead to gastroesophageal reflux (GER of gastric juice (HCl. There are two basic approaches to the assessment of the degree of wear and dental erosion. Depending on the type of wear (erosion, attrition, abfraction, the amount of calcium that was realised during the erosive attack could be determined qualitatively and quantitatively, or changes in optical properties and hardness of enamel could be recorded, too. Abrasion of teeth (abrasio dentium is the loss of dental hard tissue caused by friction between the teeth and exogenous foreign substance. It is most commonly provoked by prosthetic dentures and bad habits, while its effect depends on the size of abrasive particles and their amount, abrasive particle hardness and hardness of tooth

  3. Experimental study and modelling of the effect of microstructure on friction and wear mechanisms of low alloy steel

    Science.gov (United States)

    Trevisiol, C.; Jourani, A.; Bouvier, S.

    2017-12-01

    Few models are focused on the combined effects of microstructure and roughness on the tribological behavior of materials. Hardness is the material property mainly used in the tribological models which are usually at a macroscopic scale. For a dual-phase steel, experimental and predicted values of friction coefficients and specific wear resistances are compared. The investigated models are declined into two pressure distribution modes between the phases. Friction tests are performed between steel pins composed of a ferrite-martensite dual-phase microstructure against abrasive papers with various abrasive particle sizes ranging from 15 µm to 200 µm. By using heat treatments on a low alloy steel, dual-phase microstructures with various martensite volume fractions, ranging from 45% to 100%, are generated. As martensite volume fraction increases, the experimental and predicted results show that the specific wear resistance increases whereas the friction coefficient decreases. Furthermore, the latter evolutions depend on roughness. For a predominance of abrasive wear mechanisms generated by coarse abrasive particles (~200 µm), the experimental tribological parameters tend to follow the predicted ones associated to the mode characterized by equal pressures between the phases. Then, as the abrasive particle size decreases, abrasive wear mechanisms reduce whereas adhesive wear mechanisms increase and the experimental tribological parameters tend to follow the predicted ones associated to the mode characterized by equal wear rate between the phases.

  4. Corrosive wear forecasting of steel elements on the basis of mathematical modeling methods

    Directory of Open Access Journals (Sweden)

    Soloviev Alexey

    2016-01-01

    Full Text Available Life Extension and resistance increase of metal materials and constructions to the corrosion destruction processes is the most important scientific and technical problem. To solve this problem it is necessary to develop complex scientific research to study the corrosion phenomena, along with practical actions against corrosion directed to selecting new corrosion resistant metal materials and methods of their protection. This research is carried out for searching mathematical model which could predict corrosive wear in metal constructions with a certain accuracy taking into account design and the type of corrosion process.

  5. Effects of build parameters on linear wear loss in plastic part produced by fused deposition modeling

    Science.gov (United States)

    Mohamed, Omar Ahmed; Masood, Syed Hasan; Bhowmik, Jahar Lal

    2017-07-01

    Fused Deposition Modeling (FDM) is one of the prominent additive manufacturing technologies for producing polymer products. FDM is a complex additive manufacturing process that can be influenced by many process conditions. The industrial demands required from the FDM process are increasing with higher level product functionality and properties. The functionality and performance of FDM manufactured parts are greatly influenced by the combination of many various FDM process parameters. Designers and researchers always pay attention to study the effects of FDM process parameters on different product functionalities and properties such as mechanical strength, surface quality, dimensional accuracy, build time and material consumption. However, very limited studies have been carried out to investigate and optimize the effect of FDM build parameters on wear performance. This study focuses on the effect of different build parameters on micro-structural and wear performance of FDM specimens using definitive screening design based quadratic model. This would reduce the cost and effort of additive manufacturing engineer to have a systematic approachto make decision among the manufacturing parameters to achieve the desired product quality.

  6. Wear-dependent specific coefficients in a mechanistic model for turning of nickel-based superalloy with ceramic tools

    Science.gov (United States)

    López de Lacalle, Luis Norberto; Urbicain Pelayo, Gorka; Fernández-Valdivielso, Asier; Alvarez, Alvaro; González, Haizea

    2017-09-01

    Difficult to cut materials such as nickel and titanium alloys are used in the aeronautical industry, the former alloys due to its heat-resistant behavior and the latter for the low weight - high strength ratio. Ceramic tools made out alumina with reinforce SiC whiskers are a choice in turning for roughing and semifinishing workpiece stages. Wear rate is high in the machining of these alloys, and consequently cutting forces tends to increase along one operation. This paper establishes the cutting force relation between work-piece and tool in the turning of such difficult-to-cut alloys by means of a mechanistic cutting force model that considers the tool wear effect. The cutting force model demonstrates the force sensitivity to the cutting engagement parameters (ap, f) when using ceramic inserts and wear is considered. Wear is introduced through a cutting time factor, being useful in real conditions taking into account that wear quickly appears in alloys machining. A good accuracy in the cutting force model coefficients is the key issue for an accurate prediction of turning forces, which could be used as criteria for tool replacement or as input for chatter or other models.

  7. Multiscale Multiphysics-Based Modeling and Analysis on the Tool Wear in Micro Drilling

    Science.gov (United States)

    Niu, Zhichao; Cheng, Kai

    2016-02-01

    In micro-cutting processes, process variables including cutting force, cutting temperature and drill-workpiece interfacing conditions (lubrication and interaction, etc.) significantly affect the tool wear in a dynamic interactive in-process manner. The resultant tool life and cutting performance directly affect the component surface roughness, material removal rate and form accuracy control, etc. In this paper, a multiscale multiphysics oriented approach to modeling and analysis is presented particularly on tooling performance in micro drilling processes. The process optimization is also taken account based on establishing the intrinsic relationship between process parameters and cutting performance. The modeling and analysis are evaluated and validated through well-designed machining trials, and further supported by metrology measurements and simulations. The paper is concluded with a further discussion on the potential and application of the approach for broad micro manufacturing purposes.

  8. Hybrid ABC Optimized MARS-Based Modeling of the Milling Tool Wear from Milling Run Experimental Data

    Directory of Open Access Journals (Sweden)

    Paulino José García Nieto

    2016-01-01

    Full Text Available Milling cutters are important cutting tools used in milling machines to perform milling operations, which are prone to wear and subsequent failure. In this paper, a practical new hybrid model to predict the milling tool wear in a regular cut, as well as entry cut and exit cut, of a milling tool is proposed. The model was based on the optimization tool termed artificial bee colony (ABC in combination with multivariate adaptive regression splines (MARS technique. This optimization mechanism involved the parameter setting in the MARS training procedure, which significantly influences the regression accuracy. Therefore, an ABC–MARS-based model was successfully used here to predict the milling tool flank wear (output variable as a function of the following input variables: the time duration of experiment, depth of cut, feed, type of material, etc. Regression with optimal hyperparameters was performed and a determination coefficient of 0.94 was obtained. The ABC–MARS-based model's goodness of fit to experimental data confirmed the good performance of this model. This new model also allowed us to ascertain the most influential parameters on the milling tool flank wear with a view to proposing milling machine's improvements. Finally, conclusions of this study are exposed.

  9. Data-mining modeling for the prediction of wear on forming-taps in the threading of steel components

    Directory of Open Access Journals (Sweden)

    Andres Bustillo

    2016-10-01

    Full Text Available An experimental approach is presented for the measurement of wear that is common in the threading of cold-forged steel. In this work, the first objective is to measure wear on various types of roll taps manufactured to tapping holes in microalloyed HR45 steel. Different geometries and levels of wear are tested and measured. Taking their geometry as the critical factor, the types of forming tap with the least wear and the best performance are identified. Abrasive wear was observed on the forming lobes. A higher number of lobes in the chamber zone and around the nominal diameter meant a more uniform load distribution and a more gradual forming process. A second objective is to identify the most accurate data-mining technique for the prediction of form-tap wear. Different data-mining techniques are tested to select the most accurate one: from standard versions such as Multilayer Perceptrons, Support Vector Machines and Regression Trees to the most recent ones such as Rotation Forest ensembles and Iterated Bagging ensembles. The best results were obtained with ensembles of Rotation Forest with unpruned Regression Trees as base regressors that reduced the RMS error of the best-tested baseline technique for the lower length output by 33%, and Additive Regression with unpruned M5P as base regressors that reduced the RMS errors of the linear fit for the upper and total lengths by 25% and 39%, respectively. However, the lower length was statistically more difficult to model in Additive Regression than in Rotation Forest. Rotation Forest with unpruned Regression Trees as base regressors therefore appeared to be the most suitable regressor for the modeling of this industrial problem.

  10. Eye Wear

    Science.gov (United States)

    Eye wear protects or corrects your vision. Examples are Sunglasses Safety goggles Glasses (also called eyeglasses) Contact ... jobs and some sports carry a risk of eye injury. Thousands of children and adults get eye ...

  11. Tool flank wear model and parametric optimization in end milling of metal matrix composite using carbide tool: Response surface methodology approach

    Directory of Open Access Journals (Sweden)

    R. Arokiadass

    2012-04-01

    Full Text Available Highly automated CNC end milling machines in manufacturing industry requires reliable model for prediction of tool flank wear. This model later can be used to predict the tool flank wear (VBmax according to the process parameters. In this investigation an attempt was made to develop an empirical relationship to predict the tool flank wear (VBmax of carbide tools while machining LM25 Al/SiCp incorporating the process parameters such as spindle speed (N, feed rate (f, depth of cut (d and various % wt. of silicon carbide (S. Response surface methodology (RSM was applied to optimizing the end milling process parameters to attain the minimum tool flank wear. Predicted values obtained from the developed model and experimental results are compared, and error <5 percent is observed. In addition, it is concluded that the flank wear increases with the increase of SiCp percentage weight in the MMC.

  12. Mutant CCL2 protein coating mitigates wear particle-induced bone loss in a murine continuous polyethylene infusion model.

    Science.gov (United States)

    Nabeshima, Akira; Pajarinen, Jukka; Lin, Tzu-Hua; Jiang, Xinyi; Gibon, Emmanuel; Córdova, Luis A; Loi, Florence; Lu, Laura; Jämsen, Eemeli; Egashira, Kensuke; Yang, Fan; Yao, Zhenyu; Goodman, Stuart B

    2017-02-01

    Wear particle-induced osteolysis limits the long-term survivorship of total joint replacement (TJR). Monocyte/macrophages are the key cells of this adverse reaction. Monocyte Chemoattractant Protein-1 (MCP-1/CCL2) is the most important chemokine regulating trafficking of monocyte/macrophages in particle-induced inflammation. 7ND recombinant protein is a mutant of CCL2 that inhibits CCL2 signaling. We have recently developed a layer-by-layer (LBL) coating platform on implant surfaces that can release biologically active 7ND. In this study, we investigated the effect of 7ND on wear particle-induced bone loss using the murine continuous polyethylene (PE) particle infusion model with 7ND coating of a titanium rod as a local drug delivery device. PE particles were infused into hollow titanium rods with or without 7ND coating implanted in the distal femur for 4 weeks. Specific groups were also injected with RAW 264.7 as the reporter macrophages. Wear particle-induced bone loss and the effects of 7ND were evaluated by microCT, immunohistochemical staining, and bioluminescence imaging. Local delivery of 7ND using the LBL coating decreased systemic macrophage recruitment, the number of osteoclasts and wear particle-induced bone loss. The development of a novel orthopaedic implant coating with anti-CCL2 protein may be a promising strategy to mitigate peri-prosthetic osteolysis. Copyright © 2016 Elsevier Ltd. All rights reserved.

  13. Development and validation of a wear model for the analysis of the wheel profile evolution in railway vehicles

    Science.gov (United States)

    Auciello, J.; Ignesti, M.; Malvezzi, M.; Meli, E.; Rindi, A.

    2012-11-01

    The numerical wheel wear prediction in railway applications is of great importance for different aspects, such as the safety against vehicle instability and derailment, the planning of wheelset maintenance interventions and the design of an optimal wheel profile from the wear point of view. For these reasons, this paper presents a complete model aimed at the evaluation of the wheel wear and the wheel profile evolution by means of dynamic simulations, organised in two parts which interact with each other mutually: a vehicle's dynamic model and a model for the wear estimation. The first is a 3D multibody model of a railway vehicle implemented in SIMPACK™, a commercial software for the analysis of mechanical systems, where the wheel-rail interaction is entrusted to a C/C++user routine external to SIMPACK, in which the global contact model is implemented. In this regard, the research on the contact points between the wheel and the rail is based on an innovative algorithm developed by the authors in previous works, while normal and tangential forces in the contact patches are calculated according to Hertz's theory and Kalker's global theory, respectively. Due to the numerical efficiency of the global contact model, the multibody vehicle and the contact model interact directly online during the dynamic simulations. The second is the wear model, written in the MATLAB® environment, mainly based on an experimental relationship between the frictional power developed at the wheel-rail interface and the amount of material removed by wear. Starting from a few outputs of the multibody simulations (position of contact points, contact forces and rigid creepages), it evaluates the local variables, such as the contact pressures and local creepages, using a local contact model (Kalker's FASTSIM algorithm). These data are then passed to another subsystem which evaluates, by means of the considered experimental relationship, both the material to be removed and its distribution along

  14. Micro-EDM process modeling and machining approaches for minimum tool electrode wear for fabrication of biocompatible micro-components

    DEFF Research Database (Denmark)

    Puthumana, Govindan

    2017-01-01

    Micro-electrical discharge machining (micro-EDM) is a potential non-contact method for fabrication of biocompatible micro devices. This paper presents an attempt to model the tool electrode wear in micro-EDM process using multiple linear regression analysis (MLRA) and artificial neural networks...... linear regression model was developed for prediction of TWR in ten steps at a significance level of 90%. The optimum architecture of the ANN was obtained with 7 hidden layers at an R-sq value of 0.98. The predicted values of TWR using ANN matched well with the practically measured and calculated values...... (ANN). The governing micro-EDM factors chosen for this investigation were: voltage (V), current (I), pulse on time (Ton) and pulse frequency (f). The proposed predictive models generate a functional correlation between the tool electrode wear rate (TWR) and the governing micro-EDM factors. A multiple...

  15. Application of a Neural Network Model for Prediction of Wear Properties of Ultrahigh Molecular Weight Polyethylene Composites

    Directory of Open Access Journals (Sweden)

    Halil Ibrahim Kurt

    2015-01-01

    Full Text Available In the current study, the effect of applied load, sliding speed, and type and weight percentages of reinforcements on the wear properties of ultrahigh molecular weight polyethylene (UHMWPE was theoretically studied. The extensive experimental results were taken from literature and modeled with artificial neural network (ANN. The feed forward (FF back-propagation (BP neural network (NN was used to predict the dry sliding wear behavior of UHMWPE composites. Eleven input vectors were used in the construction of the proposed NN. The carbon nanotube (CNT, carbon fiber (CF, graphene oxide (GO, and wollastonite additives are the main input parameters and the volume loss is the output parameter for the developed NN. It was observed that the sliding speed and applied load have a stronger effect on the volume loss of UHMWPE composites in comparison to other input parameters. The proper condition for achieving the desired wear behaviors of UHMWPE by tailoring the weight percentage and reinforcement particle size and composition was presented. The proposed NN model and the derived explicit form of mathematical formulation show good agreement with test results and can be used to predict the volume loss of UHMWPE composites.

  16. The effect of lubricant selection on galling in a model wear test

    NARCIS (Netherlands)

    van der Heide, Emile; Huis in 't Veld, Bert; Schipper, Dirk J.

    2001-01-01

    Galling is a known failure mechanism in sheet metal forming (SMF) processes. As a result of this wear process, the amount of waste increases, the production process becomes hard to control and eventually expensive maintenance is required in order to continue production. Delaying or avoiding galling

  17. Geraniin suppresses RANKL-induced osteoclastogenesis in vitro and ameliorates wear particle-induced osteolysis in mouse model

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Fei; Zhai, Zanjing; Jiang, Chuan; Liu, Xuqiang; Li, Haowei; Qu, Xinhua [Department of Orthopedics, Shanghai Key Laboratory of Orthopedic Implant, Shanghai Ninth People' s Hospital, Shanghai Jiaotong University School of Medicine, Shanghai (China); Ouyang, Zhengxiao [Department of Orthopedics, Shanghai Key Laboratory of Orthopedic Implant, Shanghai Ninth People' s Hospital, Shanghai Jiaotong University School of Medicine, Shanghai (China); Department of Orthopaedics, Hunan Provincial Tumor Hospital and Tumor Hospital of Xiangya School of Medicine, Central South University, Changsha, Hunan 410013 (China); Fan, Qiming; Tang, Tingting [Department of Orthopedics, Shanghai Key Laboratory of Orthopedic Implant, Shanghai Ninth People' s Hospital, Shanghai Jiaotong University School of Medicine, Shanghai (China); Qin, An, E-mail: dr.qinan@gmail.com [Department of Orthopedics, Shanghai Key Laboratory of Orthopedic Implant, Shanghai Ninth People' s Hospital, Shanghai Jiaotong University School of Medicine, Shanghai (China); Gu, Dongyun, E-mail: dongyungu@gmail.com [Department of Orthopedics, Shanghai Key Laboratory of Orthopedic Implant, Shanghai Ninth People' s Hospital, Shanghai Jiaotong University School of Medicine, Shanghai (China); Engineering Research Center of Digital Medicine and Clinical Translation, Ministry of Education of PR China (China); School of Biomedical Engineering, Shanghai Jiao Tong University, 1954 Huashan Road, Shanghai 200030 (China)

    2015-01-01

    Wear particle-induced osteolysis and subsequent aseptic loosening remains the most common complication that limits the longevity of prostheses. Wear particle-induced osteoclastogenesis is known to be responsible for extensive bone erosion that leads to prosthesis failure. Thus, inhibition of osteoclastic bone resorption may serve as a therapeutic strategy for the treatment of wear particle induced osteolysis. In this study, we demonstrated for the first time that geraniin, an active natural compound derived from Geranium thunbergii, ameliorated particle-induced osteolysis in a Ti particle-induced mouse calvaria model in vivo. We also investigated the mechanism by which geraniin exerts inhibitory effects on osteoclasts. Geraniin inhibited RANKL-induced osteoclastogenesis in a dose-dependent manner, evidenced by reduced osteoclast formation and suppressed osteoclast specific gene expression. Specially, geraniin inhibited actin ring formation and bone resorption in vitro. Further molecular investigation demonstrated geraniin impaired osteoclast differentiation via the inhibition of the RANKL-induced NF-κB and ERK signaling pathways, as well as suppressed the expression of key osteoclast transcriptional factors NFATc1 and c-Fos. Collectively, our data suggested that geraniin exerts inhibitory effects on osteoclast differentiation in vitro and suppresses Ti particle-induced osteolysis in vivo. Geraniin is therefore a potential natural compound for the treatment of wear particle induced osteolysis in prostheses failure. - Highlights: • Geraniin suppresses osteoclasts formation and function in vitro. • Geraniin impairs RANKL-induced nuclear factor-κB and ERK signaling pathway. • Geraniin suppresses osteolysis in vivo. • Geraniin may be used for treating osteoclast related diseases.

  18. Dry Rolling Friction and Wear of Elastomer Systems and Their Finite Element Modelling

    OpenAIRE

    Xu, Dan

    2009-01-01

    Elastomers and their various composites, and blends are frequently used as engineering working parts subjected to rolling friction movements. This fact already substantiates the importance of a study addressing the rolling tribological properties of elastomers and their compounds. It is worth noting that until now the research and development works on the friction and wear of rubber materials were mostly focused on abrasion and to lesser extent on sliding type of loading. As the tribological ...

  19. Polyethylene wear debris produced in a knee simulator model: effect of crosslinking and counterface material.

    Science.gov (United States)

    Williams, Paul A; Brown, Cindy M; Tsukamoto, Riichro; Clarke, Ian C

    2010-01-01

    Polyethylene (PE) debris has been well studied in clinical retrievals and laboratory wear simulations of total hip replacements. However, little is known about PE debris from total knee replacements. In this study, we investigated the effects of crosslinking PE bearings and alternate counterface material. Mildly (35 kGy) and highly (70 kGy) crosslinked PE were studied in combination with CoCr and zirconia femoral counterfaces. Wear debris was isolated and its morphology characterized. Except for changes in PE debris size with the zirconia bearings, there were no morphological changes greater than 10%. The average submicron volume fraction decreased from about 65% to 45% with both increased crosslinking and changing counterface material from CoCr to zirconia. The averaged number of generated particles decreased by approximately fourfold with increased crosslinking and threefold with changing counterface material from CoCr to zirconia. This showed that the degree of PE crosslinking and the choice of counterface material were important factors in the PE wear debris production in total knee simulator replacements. (c) 2009 Wiley Periodicals, Inc.

  20. Modeling and prediction of surface roughness for running-in wear using Gauss-Newton algorithm and ANN

    Science.gov (United States)

    Hanief, M.; Wani, M. F.

    2015-12-01

    In this paper, surface roughness model for running-in and steady state of the wear process is proposed. In this work monotonously decreasing trend of surface roughness during running-in was assumed. The model was developed by considering the surface roughness as an explicit function of time during running-in, keeping other system parameters (velocity, load, hardness, etc.) constant. The proposed model being non-linear, optimal values of the model parameters were evaluated by Gauss-Newton (GN) algorithm. The experimental results adopted from the literature, for steel and Cu-Zn alloy specimens, were used for validation of the model. Artificial neural network (ANN) based model was also developed and was compared with the proposed model on the basis of statistical methods (coefficient of determination (R2), mean square error (MSE) and mean absolute percentage error (MAPE)).

  1. The robustness and accuracy of in vivo linear wear measurements for knee prostheses based on model-based RSA.

    Science.gov (United States)

    van Ijsseldijk, E A; Valstar, E R; Stoel, B C; Nelissen, R G H H; Reiber, J H C; Kaptein, B L

    2011-10-13

    Accurate in vivo measurements methods of wear in total knee arthroplasty are required for a timely detection of excessive wear and to assess new implant designs. Component separation measurements based on model-based Roentgen stereophotogrammetric analysis (RSA), in which 3-dimensional reconstruction methods are used, have shown promising results, yet the robustness of these measurements is unknown. In this study, the accuracy and robustness of this measurement for clinical usage was assessed. The validation experiments were conducted in an RSA setup with a phantom setup of a knee in a vertical orientation. 72 RSA images were created using different variables for knee orientations, two prosthesis types (fixed-bearing Duracon knee and fixed-bearing Triathlon knee) and accuracies of the reconstruction models. The measurement error was determined for absolute and relative measurements and the effect of knee positioning and true seperation distance was determined. The measurement method overestimated the separation distance with 0.1mm on average. The precision of the method was 0.10mm (2*SD) for the Duracon prosthesis and 0.20mm for the Triathlon prosthesis. A slight difference in error was found between the measurements with 0° and 10° anterior tilt. (difference=0.08mm, p=0.04). The accuracy of 0.1mm and precision of 0.2mm can be achieved for linear wear measurements based on model-based RSA, which is more than adequate for clinical applications. The measurement is robust in clinical settings. Although anterior tilt seems to influence the measurement, the size of this influence is low and clinically irrelevant. Copyright © 2011 Elsevier Ltd. All rights reserved.

  2. Stainless steel wear debris of a scoliotic growth guidance system has little local and systemic effect in an animal model.

    Science.gov (United States)

    Singh, Vaneet; Rawlinson, Jeremy; Hallab, Nadim

    2018-01-11

    Options to treat early-onset scoliosis include guided-growth systems with sliding action between rods and pedicle screws. The wear was previously measured in an in vitro test, and in this in vivo rabbit model, we evaluated the local and systemic biological response to the stainless steel debris. Compared to the previous study, a relatively higher volume of representative wear particles with a median particle size of 0.84 µm were generated. Bolus dosages were injected into the epidural space at L4-L5 for a minimum of 36 rabbits across three treatment groups (negative control, 1.5 mg, and 4.0 mg) and two timepoints (12 and 24 weeks). Gross pathology evaluated distant organs and the injection site with a dorsal laminectomy to examine the epidural space and dosing site. Peri-implanted particle tissues were stained for immunohistochemical and quantitatively analyzed for IL-6 and TNF-α cytokines. Based on ISO 10993-6:2007 scoring, particles in the high-dose group were primarily non-irritant (12 weeks) with one slightly irritant. At 24 weeks, inflammatory cell infiltration was nonexistent to minimal with all groups considered non-irritant at the injection site. Material characterization confirmed that particles detected in distant organs were stainless steel or contaminants. At 12 weeks, stainless steel groups demonstrated statistically increased amounts of cytokine levels compared to control but there was a statistical decrease for both at 24 weeks. These findings indicate that stainless steel wear debris, comparable to the expected usage from a simulated growth guidance system, had no discernible untoward biological effects locally and systemically in an animal model. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

  3. Synthesis and statistical modelling of dry sliding wear of Al 8011/6 vol.% AlB2 in situ composite

    Science.gov (United States)

    Kumar, Narendra; Singh, Sandeep Kumar; Gautam, Gaurav; Padap, Aditya Kumar; Mohan, Anita; Mohan, Sunil

    2017-10-01

    The present study has used response surface methodology (RSM) and central composite design (CCD) for modelling, using wear parameters to predict the wear performance of an Al 8011/6.0 vol.% AlB2 composite. The effect of applied load and sliding velocity was studied at five levels for a fixed sliding distance. To understand wear behaviour, sliding wear tests were planned according to CCD and performed on a pin-on-disc apparatus at ambient temperature. An analysis of variance (ANOVA) was conducted to show the relative significance of the parameters. A second-order regression model was developed to predict the wear loss and to establish the relationships between wear parameters. Response surface and contour plots were drawn to analyse the wear results. Worn surfaces were examined under scanning electron microscope (SEM), and energy dispersive spectroscopy (EDS) was used to interpret the operative wear mechanisms. Validation tests results show good agreement between experimental and predicted data. As an initial step of this study, AlB2 particles were reinforced in Al 8011 alloy by an in situ technique to synthesise an Al 8011/6.0 vol.% AlB2 composite. During synthesis an in situ reaction takes place between molten alloy and inorganic salt KBF4 at 850 °C, which leads to the formation of AlB2 particles. The composite was analysed by x-ray diffractometer (XRD) to detect the phases present, while optical and scanning electron microscopy (OM & SEM) were carried out to ascertain morphology and particle distribution. Hardness was evaluated by a Vickers hardness testing machine.

  4. Wear rates of resin composites.

    Science.gov (United States)

    Barkmeier, W W; Erickson, R I; Latta, M A; Wilwerding, T M

    2013-01-01

    SUMMARY A laboratory study was conducted to examine the wear of resin composite materials using a generalized wear simulation model. Ten specimens each of five resin composites (Esthet•X [EX], Filtek Supreme Plus [SP], Filtek Z250 [Z2], Tetric EvoCeram [EC], and Z100 Restorative [Z1]) were subjected to wear challenges of 100,000, 400,000, 800,000, and 1,200,000 cycles. The materials were placed in cylinder-shaped stainless-steel fixtures, and wear was generated using a flat stainless-steel antagonist in a slurry of polymethylmethacrylate beads. Wear (mean facet depth [μm] and volume loss [mm(3)]) was determined using a noncontact profilometer (Proscan 2000) with Proscan and ProForm software. Statistical analysis of the laboratory data using analysis of variance and Tukey's post hoc test showed a significant difference (p<0.05) for mean wear facet depth and volume loss for both the number of cycles and resin composite material. Linear regression analysis was used to develop predictive wear rates and volume loss rates. Linear wear was demonstrated with correlation coefficients (R(2)) ranging from 0.914 to 0.995. Mean wear values (mean facet depth [μm]) and standard deviations (SD) for 1200K cycles were as follows: Z1 13.9 (2.0), Z2 26.7 (2.7), SP 30.1 (4.1), EC 31.8 (2.3), and EX 67.5 (8.2). Volume loss (mm(3)) and SDs for 1200K cycles were as follows: Z1 0.248 (0.036), Z2 0.477 (0.044), SP 0.541 (0.072), EC 0.584 (0.037), and EX 1.162 (0.139). The wear rate (μm) and volume loss rate (mm(3)) per 100,000 cycles for the five resin composites were as follows: wear rate Z1 0.58, EC 1.27, Z2 1.49, SP 1.62, and EX 4.35, and volume loss rate Z1 0.009, EC 0.024, Z2 0.028, SP 0.029, and EX 0.075. The generalized wear model appears to be an excellent method for measuring relative wear of resin composite materials.

  5. NASA's Evolutionary Xenon Thruster (NEXT) Prototype Model 1R (PM1R) Ion Thruster and Propellant Management System Wear Test Results

    Science.gov (United States)

    VanNoord, Jonathan L.; Soulas, George C.; Sovey, James S.

    2010-01-01

    The results of the NEXT wear test are presented. This test was conducted with a 36-cm ion engine (designated PM1R) and an engineering model propellant management system. The thruster operated with beam extraction for a total of 1680 hr and processed 30.5 kg of xenon during the wear test, which included performance testing and some operation with an engineering model power processing unit. A total of 1312 hr was accumulated at full power, 277 hr at low power, and the remainder was at intermediate throttle levels. Overall ion engine performance, which includes thrust, thruster input power, specific impulse, and thrust efficiency, was steady with no indications of performance degradation. The propellant management system performed without incident during the wear test. The ion engine and propellant management system were also inspected following the test with no indication of anomalous hardware degradation from operation.

  6. Relationship Between Simulated Gap Wear and Generalized Wear of Resin Luting Cements.

    Science.gov (United States)

    Tsujimoto, A; Barkmeier, W W; Takamizawa, T; Latta, M A; Miayazaki, M

    The relationship between the simulated gap wear and generalized wear of resin luting cements was investigated. Five resin luting cements, G-Cem LinkForce (GL), Multilink Automix (MA), NX3 Nexus, Panavia V5 (PV), and RelyX Ultimate were evaluated and subsequently subjected to a wear challenge in a Leinfelder-Suzuki (Alabama) wear simulation device. Half of the specimens from each resin luting cement were photo-cured for 40 seconds and the other half were not photo-cured. The simulated gap and generalized wear were generated using a flat-ended stainless steel antagonist. Wear testing was performed in a water slurry of polymethyl methacrylate beads, and the simulated gap and generalized wear were determined using a noncontact profilometer (Proscan 2100) in conjunction with the Proscan and AnSur 3D software. A strong relationship was found between the gap wear and generalized wear simulation models. The simulated gap wear and generalized wear of the resin luting cements followed similar trends in terms of both volume loss and mean depth of wear facets with each curing method. Unlike the simulated gap wear and generalized wear of GL and PV, those of MA, NX, and RU were influenced by the curing method. The results of this study indicate that simulated gap wear of resin luting cements is very similar to simulated generalized wear. In most cases, dual curing appears to ensure greater wear resistance of resin luting cements than chemical curing alone. The wear resistance of some resin luting cements appears to be material dependent and is not influenced by the curing method.

  7. Prediction of Wear in Crosslinked Polyethylene Unicompartmental Knee Arthroplasty

    Directory of Open Access Journals (Sweden)

    Jonathan Netter

    2015-05-01

    Full Text Available Wear-related complications remain a major issue after unicompartmental arthroplasty. We used a computational model to predict knee wear generated in vitro under diverse conditions. Inverse finite element analysis of 2 different total knee arthroplasty designs was used to determine wear factors of standard and highly crosslinked polyethylene by matching predicted wear rates to measured wear rates. The computed wear factor was used to predict wear in unicompartmental components. The articular surface design and kinematic conditions of the unicompartmental and tricompartmental designs were different. Predicted wear rate (1.77 mg/million cycles was very close to experimental wear rate (1.84 mg/million cycles after testing in an AMTI knee wear simulator. Finite element analysis can predict experimental wear and may reduce the cost and time of preclinical testing.

  8. Can the PHS model (ISO7933) predict reasonable thermophysiological responses while wearing protective clothing in hot environments?

    Science.gov (United States)

    Wang, Faming; Kuklane, Kalev; Gao, Chuansi; Holmér, Ingvar

    2011-02-01

    In this paper, the prediction accuracy of the PHS (predicted heat strain) model on human physiological responses while wearing protective clothing ensembles was examined. Six human subjects (aged 29 ± 3 years) underwent three experimental trials in three different protective garments (clothing thermal insulation I(cl) ranges from 0.63 to 2.01 clo) in two hot environments (40 °C, relative humidities: 30% and 45%). The observed and predicted mean skin temperature, core body temperature and sweat rate were presented and statistically compared. A significant difference was found in the metabolic rate between FIRE (firefighting clothing) and HV (high visibility clothing) or MIL (military clothing) (p thermal insulations above 1.0 clo. The results showed that the PHS model generated unreliable predictions on body core temperature when human subjects wore thick protective clothing such as firefighting clothing (I(cl) > 1.0 clo). The predicted mean skin temperatures in three clothing ensembles HV, MIL and FIRE were also outside the expected limits. Thus, there is a need for further extension for the clothing insulation validation range of the PHS model. It is recommended that the PHS model should be amended and validated by individual algorithms, physical or physiological parameters, and further subject studies.

  9. Wear in human knees

    Directory of Open Access Journals (Sweden)

    M.L. Wang

    2015-06-01

    Full Text Available Wear occurs in natural knee joints and plays a pivotal factor in causing articular cartilage degradation in osteoarthritis (OA processes. Wear particles are produced in the wear process and get involved in inflammation of human knees. This review presents progresses in the mechanical and surface morphological studies of articular cartilages, wear particles analysis techniques for wear studies and investigations of human knee synovial fluid in wear of human knees. Future work is also included for further understanding of OA symptoms and their relations which may shed light on OA causes.

  10. EMG-driven models of human-machine interaction in individuals wearing the H2 exoskeleton

    NARCIS (Netherlands)

    Durandau, Guillaume; Sartori, Massimo; Bortole, Magdo; Moreno, Juan C.; Pons, José L.; Farina, Dario

    2016-01-01

    EMG-driven modeling has been mostly used offline and on powerful desktop computers, limiting the application of this technique to neurorehabilitation settings. In this paper, we demonstrate the use of EMG-driven modeling in online (i.e. in real-time) running on a fully portable embedded system and

  11. Model-based wear measurements in total knee arthroplasty : development and validation of novel radiographic techniques

    NARCIS (Netherlands)

    IJsseldijk, van E.A.

    2016-01-01

    The primary aim of this work was to develop novel model-based mJSW measurement methods using a 3D reconstruction and compare the accuracy and precision of these methods to conventional mJSW measurement. This thesis contributed to the development, validation and clinical application of model-based

  12. Experimental investigation on flank wear and tool life, cost analysis and mathematical model in turning hardened steel using coated carbide inserts

    Directory of Open Access Journals (Sweden)

    Ashok Kumar Sahoo

    2013-10-01

    Full Text Available Turning hardened component with PCBN and ceramic inserts have been extensively used recently and replaces traditional grinding operation. The use of inexpensive multilayer coated carbide insert in hard turning is lacking and hence there is a need to investigate the potential and applicability of such tools in turning hardened steels. An attempt has been made in this paper to have a study on turning hardened AISI 4340 steel (47 ± 1 HRC using coated carbide inserts (TiN/TiCN/Al2O3/ZrCN under dry environment. The aim is to assess the tool life of inserts and evolution of flank wear with successive machining time. From experimental investigations, the gradual growth of flank wear for multilayer coated insert indicates steady machining without any premature tool failure by chipping or fracturing. Abrasion is found to be the dominant wear mechanisms in hard turning. Tool life of multilayer coated carbide inserts has been found to be 31 minute and machining cost per part is Rs.3.64 only under parametric conditions chosen i.e. v = 90 m/min, f = 0.05 mm/rev and d = 0.5 mm. The mathematical model shows high determination coefficient, R2 (99% and fits the actual data well. The predicted flank wear has been found to lie very close to the experimental value at 95% confidence level. This shows the potential and effectiveness of multilayer coated carbide insert used in hard turning applications.

  13. A Wear Rule and Cutter Life Prediction Model of a 20-in. TBM Cutter for Granite: A Case Study of a Water Conveyance Tunnel in China

    Science.gov (United States)

    Liu, Quansheng; Liu, Jianping; Pan, Yucong; Zhang, Xiaoping; Peng, Xingxin; Gong, Qiuming; Du, Lijie

    2017-05-01

    Disc cutter wear is one of the comprehensive results of the rock-machine interaction in tunnel boring machine (TBM) tunneling. The replacement of the disc cutter is a time-consuming and costly activity that can significantly reduce the TBM utilization ( U) and advance rate (AR), and has a major effect on the total time and cost of TBM tunneling projects. Therefore, the importance of predicting the cutter life accurately can never be overemphasized. Most cutter wear prediction models are only suitable for 17-in. or smaller disc cutters. However, use of large-diameter disc cutters has been an irresistible trend for large-section hard rock TBMs. This study attempts to reveal the genuine wear rule of a 20-in. disc cutter and develop a new empirical model for predicting the cutter life in granite based on field data collected from a water conveyance tunnel constructed by the TBM tunneling method in China. The field data including the actual cutter wear and the geological parameters along the studied tunnel were compiled in a special database that was subjected to statistical analysis to reveal the genuine wear rule of a 20-in. disc cutter and develop the reasonable correlations between some common intact rock parameters and the disc cutter life. These equations were developed based on data from massive to very massive granite with a UCS range of 40-100 MPa, which can be applied for the assessment of the cutter life of a 20-in. disc cutter in similar hard rock projects with similar rock strengths and rock abrasivities.

  14. A proposed model of the response of the anophthalmic socket to prosthetic eye wear and its application to the management of mucoid discharge.

    Science.gov (United States)

    Pine, Keith R; Sloan, Brian H; Jacobs, Robert J

    2013-08-01

    Mucoid discharge associated with prosthetic eye wear can be a distressing condition that affects the quality of life of people who have lost an eye. Discharge is the second highest concern of experienced prosthetic eye wearers after health of the companion eye and is prevalent in anophthalmic populations. Specific causes of mucoid discharge such as infections and environmental allergens are well understood, but non-specific causes are unknown and an evidence based protocol for managing non-specific discharge is lacking. Current management is based on prosthesis removal and cleaning, and professional re-polishing of the prosthesis. Tear protein deposits accumulate on prosthetic eyes. These deposits mediate the response of the socket to prosthetic eye wear and their influence (good and bad) is determined by differing cleaning regimes and standards of surface finish. This paper proposes a three-phase model that describes the response of the socket to prosthetic eye wear. The phases are: An initial period of wear of a new (or newly-polished) prosthesis when homeostasis is being established (or re-established) within the socket; a second period (equilibrium phase) where beneficial surface deposits have built up on the prosthesis and wear is safe and comfortable, and a third period (breakdown phase) where there is an increasing likelihood of harm from continued wear. The proposed model provides a rationale for a personal cleaning regime to manage non-specific mucoid discharge. Professional care of prosthetic eyes is also important for the management of discharge and evidence for effective surface finishing is reported in this study. Taken together, the proposed regimes for personal and professional care comprise a protocol for managing discharge associated with prosthetic eye wear. The protocol describes prosthetic eye cleaning methods and frequency, and suggests minimum standards for professional polishing. If confirmed, the protocol has the potential to resolve the

  15. Epidural application of spinal instrumentation particulate wear debris: a comprehensive evaluation of neurotoxicity using an in vivo animal model.

    Science.gov (United States)

    Cunningham, Bryan W; Hallab, Nadim J; Hu, Nianbin; McAfee, Paul C

    2013-09-01

    The introduction and utilization of motion-preserving implant systems for spinal reconstruction served as the impetus for this basic scientific investigation. The effect of unintended wear particulate debris resulting from micromotion at spinal implant interconnections and bearing surfaces remains a clinical concern. Using an in vivo rabbit model, the current study quantified the neural and systemic histopathological responses following epidural application of 11 different types of medical-grade particulate wear debris produced from spinal instrumentation. A total of 120 New Zealand White rabbits were equally randomized into 12 groups based on implant treatment: 1) sham (control), 2) stainless steel, 3) titanium alloy, 4) cobalt chromium alloy, 5) ultra-high molecular weight polyethylene (UHMWPe), 6) ceramic, 7) polytetrafluoroethylene, 8) polycarbonate urethane, 9) silicone, 10) polyethylene terephthalate, 11) polyester, and 12) polyetheretherketone. The surgical procedure consisted of a midline posterior approach followed by resection of the L-6 spinous process and L5-6 ligamentum flavum, permitting interlaminar exposure of the dural sac. Four milligrams of the appropriate treatment material (Groups 2-12) was then implanted onto the dura in a dry, sterile format. All particles (average size range 0.1-50 μm in diameter) were verified to be endotoxin free prior to implantation. Five animals from each treatment group were sacrificed at 3 months and 5 were sacrificed at 6 months postoperatively. Postmortem analysis included epidural cultures and histopathological assessment of local and systemic tissue samples. Immunocytochemical analysis of the spinal cord and overlying epidural fibrosis quantified the extent of proinflammatory cytokines (tumor necrosis factor-α, tumor necrosis factor-β, interleukin [IL]-1α, IL-1β, and IL-6) and activated macrophages. Epidural cultures were negative for nearly all cases, and there was no evidence of particulate debris or

  16. Consideration of Wear Rates at High Velocity

    Science.gov (United States)

    2010-03-01

    Ayers and Second Lieutenant Julius Puentes pro- vided excellent support with dynamic model data, and slipper/rail specimens. Mr. Larry Perkins, Mr...Wear Research . . . . . . . . . . . . . . . . 29 1.10 Key Concepts from the Literature Search . . . . . . . . . 30 II. Metallographic Analysis...to AFIT for physical on-site investigation. 1.4 Description of Wear The literature search revealed that there are many different definitions of wear

  17. A quasi-2-dimensional model for respiration of the cornea with soft contact lens wear.

    Science.gov (United States)

    Takatori, Sho C; Radke, Clayton J

    2012-04-01

    Because neither the human cornea nor a soft contact lens (SCL) is of constant thickness, corneal oxygenation varies locally. To quantify the importance of cornea/SCL thickness variations on oxygen demand, we develop a quasi-2-dimensional (2D) respiration model that accounts for aerobic and anaerobic metabolism and bicarbonate buffering. Because metabolism is critical to oxygen demand, we extend the 1-dimensional (1D), 6-layer oxygen metabolic model of Chhabra et al. Lateral diffusion is shown to be negligible. Accordingly, we adopt the 1D reactive-diffusion metabolic model but apply it locally along the cornea/lens extent. This "quasi-2D" approximation permits 2D assessment of oxygen consumption, including the effects of carbon dioxide, glucose, and lactate, bicarbonate, and hydrogen ions. We use both an oxygen deficiency factor and an excess lactate factor to gauge corneal health after accounting for both cornea and contact lens thickness variations. The quasi-2D respiration model provides quantitative spatial resolution of corneal oxygenation with minimal expenditure of computation time. When only aerobic oxygen loss is included, our quasi-2D approach is in excellent agreement with the fully 2D results of Alvord et al. However, the quasi-2D model predicts 2D concentration profiles of glucose, lactate ions, bicarbonate ions, hydrogen ions, and carbon dioxide, as well as oxygen. Neglect of metabolic reactions and/or thickness variations leads to inaccurate prediction of oxygen demand, especially near the lens periphery. The quasi-2D respiration model indicates that lateral thickness variations and respiration kinetics are critical for assessing on-eye physiologic performance of an SCL. We find that oxygen deficiency factor and excess lactate factor are useful indices to gauge corneal hypoxia. A user-friendly computer program of the quasi-2D respiration model is available for lens design.

  18. A coupled near and far wake model for wind turbine aerodynamics

    DEFF Research Database (Denmark)

    Pirrung, Georg R.; Aagaard Madsen, Helge; Kim, Taeseong

    2016-01-01

    In this paper, an aerodynamic model consisting of a lifting line-based trailed vorticity model and a blade element momentum (BEM) model is described. The focus is on the trailed vorticity model, which is based on the near wake model (NWM) by Beddoes and has been extended to include the effects...

  19. Comparative wear mapping techniques

    DEFF Research Database (Denmark)

    Alcock, J.; Sørensen, Ole Toft; Jensen, S.

    1996-01-01

    Pin-on-disc tests of tungsten carbide pins against silicon carbide discs were performed and wear rate, mechanism and friction maps constructed. Correlations were observed between the wear mode and the friction of the pin-disc interface, and between the qualitative incidence of disruptive wear mec...

  20. Statistical model to predict dry sliding wear behaviour of Aluminium-Jute bast ash particulate composite produced by stir-casting

    Directory of Open Access Journals (Sweden)

    Gambo Anthony VICTOR

    2017-06-01

    Full Text Available A model to predict the dry sliding wear behaviour of Aluminium-Jute bast ash particulate composites produced by double stir-casting method was developed in terms of weight fraction of jute bast ash (JBA. Experiments were designed on the basis of the Design of Experiments (DOE technique. A 2k factorial, where k is the number of variables, with central composite second-order rotatable design was used to improve the reliability of results and to reduce the size of experimentation without loss of accuracy. The factors considered in this study were sliding velocity, sliding distance, normal load and mass fraction of JBA reinforcement in the matrix. The developed regression model was validated by statistical software MINITAB-R14 and statistical tool such as analysis of variance (ANOVA. It was found that the developed regression model could be effectively used to predict the wear rate at 95% confidence level. The wear rate of cast Al-JBAp composite decreased with an increase in the mass fraction of JBA and increased with an increase of the sliding velocity, sliding distance and normal load acting on the composite specimen.

  1. Mathematical Modelling and Optimization of Cutting Force, Tool Wear and Surface Roughness by Using Artificial Neural Network and Response Surface Methodology in Milling of Ti-6242S

    Directory of Open Access Journals (Sweden)

    Erol Kilickap

    2017-10-01

    Full Text Available In this paper, an experimental study was conducted to determine the effect of different cutting parameters such as cutting speed, feed rate, and depth of cut on cutting force, surface roughness, and tool wear in the milling of Ti-6242S alloy using the cemented carbide (WC end mills with a 10 mm diameter. Data obtained from experiments were defined both Artificial Neural Network (ANN and Response Surface Methodology (RSM. ANN trained network using Levenberg-Marquardt (LM and weights were trained. On the other hand, the mathematical models in RSM were created applying Box Behnken design. Values obtained from the ANN and the RSM was found to be very close to the data obtained from experimental studies. The lowest cutting force and surface roughness were obtained at high cutting speeds and low feed rate and depth of cut. The minimum tool wear was obtained at low cutting speed, feed rate, and depth of cut.

  2. Simulation and experiment of the effect of clearance of impeller wear-rings on the performance of centrifugal pump

    Science.gov (United States)

    Chen, S. X.; Pan, Z. Y.; Wu, Y. L.; Zhang, D. Q.

    2012-11-01

    The effect of clearance of impeller wear-rings on the performance of a centrifugal pump was investigated numerically and experimentally. The whole flow field model including front and back shrouds of pump was designed so as to accurately calculate the head and efficiency of the centrifugal pump. Based on RNG k-ε turbulence model, three wear-rings schemes were established, and the effects of clearance of impeller wear-rings on the hydraulic efficiency and mechanical efficiency of the centrifugal pump was analyzed, chiefly from the turbulent kinetic energy, vorticity and radial force angles. According to the results, it can be drawn that the head and total efficiency of the centrifugal pump increase as the clearance value of wear-rings narrows. The following reasons may account for it: firstly, as the clearance value of wear-rings declines, the turbulent kinetic energy and energy dissipation decrease within the impeller, and the impact of secondary flow at the inlet of impeller on the mainstream weakens slowly, which leads to a lower hydraulic loss, thus a higher hydraulic efficiency; secondly, radial force decreases with the clearance value of wear-rings, so the eccentric whirl of centrifugal pump is dampened, which results in a lower mechanical loss and a higher mechanical efficiency; thirdly, the front shroud leakage diminishes with the clearance value of wear-rings, therefore, the volume loss is reduced and volume efficiency improved. Finally, the first wear-ring scheme of impeller is adopted after comprehensive comparison of these three wear-ring schemes, because its efficiency is highest and it satisfies the requirements of the engineering application.

  3. Polymer wear evaluation

    DEFF Research Database (Denmark)

    Lagerbon, Mikkel; Sivebæk, Ion Marius

    2012-01-01

    Polymer wear plays an increasing role in manufacturing of machine parts for e.g. medical devices. Some of these have an expected lifetime of five to eight years during which very little wear of the components is acceptable. Too much wear compromises the dosage accuracy of the device and thereby...... the safety of the patients. Prediction of the wear of polymers is complicated by the low thermal conductivity of this kind of material. It implies that any acceleration of testing conditions by increased contact pressure and/or sliding velocity will make the polymer fail due to exaggerated heat buildup....... This is not the kind of wear observed in medical devices. In the present work a method was developed capable of evaluating the wear progression in polymer-polymer contacts. The configuration of the setup is injection moulded specimens consisting of an upper part having a toroid shape and a lower flat part. The sliding...

  4. Experimental assessment of precision and accuracy of radiostereometric analysis for the determination of polyethylene wear in a total hip replacement model.

    Science.gov (United States)

    Bragdon, Charles R; Malchau, Henrik; Yuan, Xunhua; Perinchief, Rebecca; Kärrholm, Johan; Börlin, Niclas; Estok, Daniel M; Harris, William H

    2002-07-01

    The purpose of this study was to develop and test a phantom model based on actual total hip replacement (THR) components to simulate the true penetration of the femoral head resulting from polyethylene wear. This model was used to study both the accuracy and the precision of radiostereometric analysis, RSA, in measuring wear. We also used this model to evaluate optimum tantalum bead configuration for this particular cup design when used in a clinical setting. A physical model of a total hip replacement (a phantom) was constructed which could simulate progressive, three-dimensional (3-D) penetration of the femoral head into the polyethylene component of a THR. Using a coordinate measuring machine (CMM) the positioning of the femoral head using the phantom was measured to be accurate to within 7 microm. The accuracy and precision of an RSA analysis system was determined from five repeat examinations of the phantom using various experimental set-ups of the phantom. The accuracy of the radiostereometric analysis, in this optimal experimental set-up studied was 33 microm for the medial direction, 22 microm for the superior direction, 86 microm for the posterior direction and 55 microm for the resultant 3-D vector length. The corresponding precision at the 95% confidence interval of the test results for repositioning the phantom five times, measured 8.4 microm for the medial direction, 5.5 microm for the superior direction, 16.0 microm for the posterior direction, and 13.5 microm for the resultant 3-D vector length. This in vitro model is proposed as a useful tool for developing a standard for the evaluation of radiostereometric and other radiographic methods used to measure in vivo wear.

  5. Wear-dependent specific coefficients in a mechanistic model for turning of nickel-based superalloy with ceramic tools

    Directory of Open Access Journals (Sweden)

    López de Lacalle Luis Norberto

    2017-09-01

    Full Text Available Difficult to cut materials such as nickel and titanium alloys are used in the aeronautical industry, the former alloys due to its heat-resistant behavior and the latter for the low weight - high strength ratio. Ceramic tools made out alumina with reinforce SiC whiskers are a choice in turning for roughing and semifinishing workpiece stages. Wear rate is high in the machining of these alloys, and consequently cutting forces tends to increase along one operation.

  6. Wear particles derived from metal hip implants induce the generation of multinucleated giant cells in a 3-dimensional peripheral tissue-equivalent model.

    Directory of Open Access Journals (Sweden)

    Debargh K Dutta

    Full Text Available Multinucleate giant cells (MGCs are formed by the fusion of 5 to 15 monocytes or macrophages. MGCs can be generated by hip implants at the site where the metal surface of the device is in close contact with tissue. MGCs play a critical role in the inflammatory processes associated with adverse events such as aseptic loosening of the prosthetic joints and bone degeneration process called osteolysis. Upon interaction with metal wear particles, endothelial cells upregulate pro-inflammatory cytokines and other factors that enhance a localized immune response. However, the role of endothelial cells in the generation of MGCs has not been completely investigated. We developed a three-dimensional peripheral tissue-equivalent model (PTE consisting of collagen gel, supporting a monolayer of endothelial cells and human peripheral blood mononuclear cells (PBMCs on top, which mimics peripheral tissue under normal physiological conditions. The cultures were incubated for 14 days with Cobalt chromium alloy (CoCr ASTM F75, 1-5 micron wear particles. PBMC were allowed to transit the endothelium and harvested cells were analyzed for MGC generation via flow cytometry. An increase in forward scatter (cell size and in the propidium iodide (PI uptake (DNA intercalating dye was used to identify MGCs. Our results show that endothelial cells induce the generation of MGCs to a level 4 fold higher in 3-dimentional PTE system as compared to traditional 2-dimensional culture plates. Further characterization of MGCs showed upregulated expression of tartrate resistant alkaline phosphatase (TRAP and dendritic cell specific transmembrane protein, (DC-STAMP, which are markers of bone degrading cells called osteoclasts. In sum, we have established a robust and relevant model to examine MGC and osteoclast formation in a tissue like environment using flow cytometry and RT-PCR. With endothelial cells help, we observed a consistent generation of metal wear particle- induced MGCs

  7. Parameter Estimation of Actuators for Benchmark Active Control Technology (BACT) Wind Tunnel Model with Analysis of Wear and Aerodynamic Loading Effects

    Science.gov (United States)

    Waszak, Martin R.; Fung, Jimmy

    1998-01-01

    This report describes the development of transfer function models for the trailing-edge and upper and lower spoiler actuators of the Benchmark Active Control Technology (BACT) wind tunnel model for application to control system analysis and design. A simple nonlinear least-squares parameter estimation approach is applied to determine transfer function parameters from frequency response data. Unconstrained quasi-Newton minimization of weighted frequency response error was employed to estimate the transfer function parameters. An analysis of the behavior of the actuators over time to assess the effects of wear and aerodynamic load by using the transfer function models is also presented. The frequency responses indicate consistent actuator behavior throughout the wind tunnel test and only slight degradation in effectiveness due to aerodynamic hinge loading. The resulting actuator models have been used in design, analysis, and simulation of controllers for the BACT to successfully suppress flutter over a wide range of conditions.

  8. Assessment of wear facets produced by the ACTA wear machine

    DEFF Research Database (Denmark)

    Benetti, Ana R; Larsen, Liselotte; Dowling, Adam H

    2016-01-01

    an assessment of the potential of the experimental RBC formulations for clinical usage. CONCLUSION: The 3D technique allowed for the assessment of mean maximum wear depth and mean total volumetric wear which enables tribological analyses of the wear facet and therefore the wear mechanisms operative. Employing...... the 2D profile technique ranks RBC materials in terms of in-vitro wear performance. CLINICAL SIGNIFICANCE: Confidence in the wear volume measurements can only be achieved if the wear facet is analysed with sufficient resolution using a 3D digital measurement technique. However, the employment of 2D...

  9. EFFECTIVE TOOL WEAR ESTIMATION THROUGH ...

    African Journals Online (AJOL)

    using TiN .coated K20 cemented carbide tool inserts to monitor the tool wear. In the early research, tool wear ... deformation, crack initiation, crack propagation and chipping. Such changes in material behavior will ... the coated carbide experienced rapid tool wear (up to a flank wear land of 0.11 Smm), followed by a slow.

  10. Contact Thermal Analysis and Wear Simulation of a Brake Block

    Directory of Open Access Journals (Sweden)

    Nándor Békési

    2013-01-01

    Full Text Available The present paper describes an experimental test and a coupled contact-thermal-wear analysis of a railway wheel/brake block system through the braking process. During the test, the friction, the generated heat, and the wear were evaluated. It was found that the contact between the brake block and the wheel occurs in relatively small and slowly moving hot spots, caused by the wear and the thermal effects. A coupled simulation method was developed including numerical frictional contact, transient thermal and incremental wear calculations. In the 3D simulation, the effects of the friction, the thermal expansion, the wear, and the temperature-dependent material properties were also considered. A good agreement was found between the results of the test and the calculations, both for the thermal and wear results. The proposed method is suitable for modelling the slowly oscillating wear caused by the thermal expansions in the contact area.

  11. Prediction of Cone Crusher Performance Considering Liner Wear

    Directory of Open Access Journals (Sweden)

    Yanjun Ma

    2016-12-01

    Full Text Available Cone crushers are used in the aggregates and mining industries to crush rock material. The pressure on cone crusher liners is the key factor that influences the hydraulic pressure, power draw and liner wear. In order to dynamically analyze and calculate cone crusher performance along with liner wear, a series of experiments are performed to obtain the crushed rock material samples from a crushing plant at different time intervals. In this study, piston die tests are carried out and a model relating compression coefficient, compression ratio and particle size distribution to a corresponding pressure is presented. On this basis, a new wear prediction model is proposed combining the empirical model for predicting liner wear with time parameter. A simple and practical model, based on the wear model and interparticle breakage, is presented for calculating compression ratio of each crushing zone along with liner wear. Furthermore, the size distribution of the product is calculated based on existing size reduction process model. A method of analysis of product size distribution and shape in the crushing process considering liner wear is proposed. Finally, the validity of the wear model is verified via testing. The result shows that there is a significant improvement of the prediction of cone crusher performance considering liner wear as compared to the previous model.

  12. Simulated Wear of Self-Adhesive Resin Cements.

    Science.gov (United States)

    Takamizawa, T; Barkmeier, W W; Latta, M A; Berry, T P; Tsujimoto, A; Miyazaki, M

    2016-01-01

    One of the primary areas of concern with luting agents is marginal gap erosion and attrition. The purpose of this laboratory study was to evaluate bulk and marginal slit (gap) generalized wear of self-adhesive resin cements. Three self-adhesive resin cements were used in this study: G-CEM LinkAce (LA), Maxcem Elite (ME), and RelyX Unicem2 Automix (RU). A custom stainless-steel fixture with a cavity 4.5 mm in diameter and 4 mm deep was used for simulated generalized (bulk) wear. For simulated marginal gap wear, a two-piece stainless-steel custom fixture was designed with a slit (gap) 300 μm wide and 3 mm in length. For both wear models, 20 specimens each for each of the three adhesive cements were made for both light-cure and chemical-cure techniques. The cured cements were polished with a series of carbide papers to a 4000-grit surface and subjected to 100,000 cycles using the slit (gap) wear model and 400,000 cycles for generalized (bulk) wear in a Leinfelder-Suzuki (Alabama machine) wear simulator (maximum load of 78.5 N). Flat-ended stainless-steel antagonists were used in a water slurry of poly(methylmethacrylate) beads for simulation of generalized contact-free area wear with both wear models. Before and after the wear challenges, the specimens were profiled with a Proscan 2100 noncontact profilometer, and wear (volume loss [VL] and mean facet depth [FD]) was determined using AnSur 3D software. Two-way analysis of variance (ANOVA) and Tukey post hoc tests were used for data analysis for the two wear models. Scanning electron microscopy (SEM) was used to examine polished surfaces of the resin cements and the worn surfaces after the wear challenges. The two-way ANOVA of VL using the generalized (bulk) wear model showed a significant effect among the three resin cement materials for the factor of resin cement (pcement and cure method (pcement (pcement and cure method (pcements and the resultant effect of the wear challenges. The worn surfaces of each cement were

  13. Effect of wearing a swimsuit on hydrodynamic drag of swimmer

    Directory of Open Access Journals (Sweden)

    Daniel Almeida Marinho

    2012-12-01

    Full Text Available The purpose of this study was to analyse the effect of wearing a swimsuit on swimmer's passive drag. A computational fluid dynamics analysis was carried out to determine the hydrodynamic drag of a female swimmer's model (i wearing a standard swimsuit; (ii wearing a last generation swimsuit and; (iii with no swimsuit, wearing light underwear. The three-dimensional surface geometry of a female swimmer's model with different swimsuit/underwear was acquired through standard commercial laser scanner. Passive drag force and drag coefficient were computed with the swimmer in a prone position. Higher hydrodynamic drag values were determined when the swimmer was with no swimsuit in comparison with the situation when the swimmer was wearing a swimsuit. The last generation swimsuit presented lower hydrodynamic drag values, although very similar to standard swimsuit. In conclusion, wearing a swimsuit could positively influence the swimmer's hydrodynamics, especially reducing the pressure drag component.

  14. The Devil Wears Prada

    African Journals Online (AJOL)

    Adele

    The film is based on the book. The Devil Wears Prada written by Lauren Weisberger, ... image and power driven industry that is haute couture and fashion today. Although Andrea's experience is the main ... creations not fit even for Halloween, designer and brand name jewellery and other fashion accessories. Anything from ...

  15. Comparative wear mapping techniques

    DEFF Research Database (Denmark)

    Alcock, J.; Sørensen, Ole Toft; Jensen, S.

    1996-01-01

    Pin surfaces were analysed by laser profilometry. Two roughness parameters, R(a) and the fractal dimension, were investigated as a first step towards methods of quantitative wear mechanism mapping. Both parameters were analysed for their relationship to the severity and prevalence of a mechanism....

  16. Polyethylene and metal wear particles: characteristics and biological effects.

    Science.gov (United States)

    Catelas, Isabelle; Wimmer, Markus A; Utzschneider, Sandra

    2011-05-01

    This paper first presents a brief overview about the mechanism of wear particle formation as well as wear particle characteristics in metal-on-polyethylene and metal-on-metal artificial hip joints. The biological effects of such particles are then described, focusing on the inflammatory response induced by each type of particles as well as on how metal wear products may be the source of a T lymphocyte-mediated specific immune response, early adverse tissue responses, and genotoxicity. Finally, some of the current in vivo models used for the analysis of tissue response to various wear particles are presented.

  17. Friction and wear behaviour of self lubricating bearing liners

    Science.gov (United States)

    Gay, Russell

    The thesis describes a numerical model for evaluating the variation of friction and wear of a self lubricating bearing liner over its useful wear life. Self-lubricating bearings have been in widespread use since the mid-1950s, particularly in the aerospace industry where they have the advantage of being low maintenance components. They are commonly used in relatively low speed, reciprocating applications such as control surface actuators, and usually consist of a spherical bearing with the inner and outer elements separated by a composite textile resin-bonded liner. A finite element model has been developed to predict the local stiffness of a particular liner at different states of wear. Results obtained using the model were used to predict the overall friction coefficient as it evolves due to wear, which is a novel approach. Experimental testing was performed on a bespoke flat-on-flat wear test rig with a reciprocating motion to validate the results of the friction model.. These tests were carried out on a commercially-available bearing liner, predominantly at a high contact pressure and an average sliding speed of 0.2 ms-1. Good agreement between predicted and experimentally measured wear was obtained when appropriate coefficients of friction were used in the friction model, and when the reciprocating sliding distance was above a critical value. A numerical wear model was also developed to predict the trend of backlash development in real bearing geometries using a novel approach. Results from the wear model were validated against full-scale bearing tests carried out elsewhere by the sponsoring company. Good agreement was obtained between the model predictions and the experimental results for the first 80% of the bearing wear life, and explanations for the discrepancy during the last 20% of the wear life have been proposed..

  18. Corrosive wear. Evaluation of wear and corrosive resistant materials; Noetningskorrosion. Utvaerdering av noetnings- och korrosionsbestaendiga material

    Energy Technology Data Exchange (ETDEWEB)

    Persson, H.; Hjertsen, D.; Waara, P.; Prakash, B.; Hardell, J.

    2007-12-15

    assumption that a 60% reduction of the thickness is acceptable. The changes of the operation conditions, particularly the lower rotating speed that the new design led to, have shifted the wear/corrosion condition so that corrosion is more dominating in the wear-corrosion. This is obvious as the SS2377, one of the softest of the evaluated materials, shows low wear rate due to its good corrosion resistant characteristics. The design of the screw has proved to be very crucial for wear-corrosion. The results from the wear-corrosion test show a number of effects that are more or less difficult to explain. One example is that the SS2377 have better wear resistance than the harder materials in both corrosion and in non-corrosive environment. The general conclusion from these testing is that the conditions at the screw have not been successfully imitated. For the prediction of the useful life, a wear-corrosion model has been developed to be used with operation data to follow and/or predict the wear-corrosion. Especially with SS2377, where the synergy effects between corrosion and abrasion is small, a good conformance can be reached. The model needs however further verification to become more general

  19. Quantitative wear particle analysis for osteoarthritis assessment.

    Science.gov (United States)

    Guo, Meizhai; Lord, Megan S; Peng, Zhongxiao

    2017-12-01

    Osteoarthritis is a degenerative joint disease that affects millions of people worldwide. The aims of this study were (1) to quantitatively characterise the boundary and surface features of wear particles present in the synovial fluid of patients, (2) to select key numerical parameters that describe distinctive particle features and enable osteoarthritis assessment and (3) to develop a model to assess osteoarthritis conditions using comprehensive wear debris information. Discriminant analysis was used to statistically group particles based on differences in their numerical parameters. The analysis methods agreed with the clinical osteoarthritis grades in 63%, 50% and 61% of particles for no osteoarthritis, mild osteoarthritis and severe osteoarthritis, respectively. This study has revealed particle features specific to different osteoarthritis grades and provided further understanding of the cartilage degradation process through wear particle analysis - the technique that has the potential to be developed as an objective and minimally invasive method for osteoarthritis diagnosis.

  20. Effects of attention deficit hyperactivity disorder signs and socio-economic status on sleep bruxism and tooth wear among schoolchildren: structural equation modelling approach.

    Science.gov (United States)

    Mota-Veloso, Isabella; Celeste, Roger Keller; Fonseca, Cynthia Pimenta; Soares, Maria Eliza Consolação; Marques, Leandro Silva; Ramos-Jorge, Maria Letícia; Ramos-Jorge, Joana

    2017-11-01

    The prevalence of both bruxism and attention deficit hyperactivity (ADHD) has increased in recent years. This study evaluated the direct and indirect effects of signs of ADHD, reported by parents/caregivers and teachers, with sleep bruxism. In addition, this study explores the effects of socio-economic status (SES) on sleep bruxism. This cross-sectional study was performed in Diamantina, Brazil, with 851 randomly selected schoolchildren aged 6-12 years. The schoolchildren were underwent an oral examination for the evaluation of bruxism. Moreover, parents/caregivers fill out a form for the assessment of sleep bruxism and sociodemographic factors. Parents/caregivers and teachers responded to the Swanson, Nolan and Pelham scale - version IV (SNAP-IV) for the assessment of ADHD signs. The structural equation modelling approach was used, and standardized coefficients to direct, indirect and total effects were calculated. ADHD signs had a significant moderate (SC = -0.19, P bruxism. SES had a significant indirect effect on bruxism via sucking habits. Moreover, SES had a significant direct (SC = -0.16, P = 0.01) and total effect on tooth wear (SC = -0.17, P bruxism among schoolchildren. © 2017 BSPD, IAPD and John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  1. Children with Autism Wearing Action Cameras: Changing Parent/Child Interactions Using Point-of-View Video Modeling

    Science.gov (United States)

    Stump, Keenan C.

    2017-01-01

    My dissertation research involves the implementation of a parent-provided point-of-view modeling (POVM) intervention created to improve social interaction between parents and their children with autism spectrum disorder (ASD). A series of studies ultimately lead to my dissertation study. The first manuscript entitled "Autism-Related Insurance…

  2. Wear of polymers and composites

    CERN Document Server

    Abdelbary, Ahmed

    2015-01-01

    In the field of tribology, the wear behaviour of polymers and composite materials is considered a highly non-linear phenomenon. Wear of Polymers and Composites introduces fundamentals of polymers and composites tribology. The book suggests a new approach to explore the effect of applied load and surface defects on the fatigue wear behaviour of polymers, using a new tribometer and thorough experiments. It discusses effects of surface cracks, under different static and cyclic loading parameters on wear, and presents an intelligent algorithm, in the form of a neural network, to map the relations

  3. Friction and wear calculation methods

    CERN Document Server

    Kragelsky, I V; Kombalov, V S

    1981-01-01

    Friction and Wear: Calculation Methods provides an introduction to the main theories of a new branch of mechanics known as """"contact interaction of solids in relative motion."""" This branch is closely bound up with other sciences, especially physics and chemistry. The book analyzes the nature of friction and wear, and some theoretical relationships that link the characteristics of the processes and the properties of the contacting bodies essential for practical application of the theories in calculating friction forces and wear values. The effect of the environment on friction and wear is a

  4. Pure mechanical wear loss measurement in corrosive wear

    Indian Academy of Sciences (India)

    Unknown

    Abstract. The method for the measurement of the pure mechanical wear loss for 321 stainless steel, 1045 steel and pure iron in the study of the synergy between corrosion and wear was studied. The methods studied included the measurement in distilled water, by cathodic protection and by adding inhibitor KI, and all were.

  5. Wear characteristics in a two-body wear test.

    Science.gov (United States)

    Wassell, R W; McCabe, J F; Walls, A W

    1994-07-01

    A previous report compared spherical steatite (ceramic enamel substitute) abraders with those of natural enamel in a two-body wear test. The wear rates and coefficients of friction of the two abraders against various composites and an amalgam were well correlated although the wear rates were slightly higher with steatite. This report investigates the characteristics of the worn abrader and specimen surfaces. Scanning electron microscopy and laser profilometry were used. Similar wear characteristics were found for the two types of abraders. Adhesive wear was evident for the amalgam, Dispersalloy (Johnson & Johnson), and the heat/pressure-cured microfill composite, Isosit (Ivoclar-Vivadent). Abrasion was seen with the hybrid composite, Occlusin (ICI), and, to a lesser extent, the microfill composite, Heliomolar (Ivoclar-Vivadent). The appearance of the worn small particle hybrid composite, Brilliant Dentin (Coltène), suggested that fatigue and delamination were involved. Laser profilometry showed that the hybrid composites caused much greater wear to the abraders than either the microfill composites or amalgam. The Ra values of the worn abraders and specimens were similar, suggesting conformal contact between them and endorsing the well controlled conditions of the wear test. The results of this and other publications suggest that steatite can be used as an alternative to enamel in performing two-body wear tests on dental composites. This should help significantly in materials evaluation and development.

  6. Pure mechanical wear loss measurement in corrosive wear

    Indian Academy of Sciences (India)

    The method for the measurement of the pure mechanical wear loss for 321 stainless steel, 1045 steel and pure iron in the study of the synergy between corrosion and wear was studied. The methods studied included the measurement in distilled water, by cathodic protection and by adding inhibitor KI, and all were ...

  7. Analysis of the application of the generalized monod kinetics model to describe the human corneal oxygen-consumption rate during soft contact lens wear.

    Science.gov (United States)

    Compañ, V; Aguilella-Arzo, M; Del Castillo, L F; Hernández, S I; Gonzalez-Meijome, J M

    2017-11-01

    This work is an analysis of the application of the generalized Monod kinetics model describing human corneal oxygen consumption during soft contact lens wear to models previously used by Chhabra et al. (J Biomed Mater Res B Appl Biomater, 2009a;90:202-209, Optom Vis Sci 2009b;86:454-466) and Larrea and Büchler (Invest Ophthalmol Vis Sci 2009;50:1076-1080). We use oxygen tension from in vivo estimations provided by Bonanno [Bonanno et al., Invest Ophthalmol Vis Sci 2002;43:371-376, and Bonanno et al 2009]. We consider four hydrogel and six silicone hydrogel lenses. The cornea is considered a single homogeneous layer, with constant oxygen permeability regardless of the type of lens worn. Our calculations yield different values for the maximum oxygen consumption rate Qc,max , whith differents oxygen tensions (high and low pc ) at the cornea-tears interface. Surprisingly, for both models, we observe an increase in oxygen consumption near an oxygen tension of 105 mmHg until a maximum is reached, then decreasing for higher levels of oxygen pressure. That is, when lowering the pressure of oxygen, the parameter Qc,max initially increases depending on the intensity of the change in pressure. Which, it could be related with the variation of the pH. Furthermore, it is also noted that to greater reductions in pressure, this parameter decreases, possibly due to changes in the concentration of glucose related to the anaerobic respiration. The averaged in vivo human corneal oxygen consumption rate of 1.47 × 10-4 cm3 of O2 /cm3 tissue s, with Monod kinetics model, considering all the lenses studied, is smaller than the average oxygen consumption rate value obtained using the Larrea and Büchler model. The impact that these calculations have on the oxygen partial pressure available at different depths in the corneal tissue is presented and discussed, taking into consideration previous models used in this study. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl

  8. Diffusion and Monod kinetics model to determine in vivo human corneal oxygen-consumption rate during soft contact lens wear.

    Science.gov (United States)

    Del Castillo, Luis F; da Silva, Ana R Ferreira; Hernández, Saul I; Aguilella, M; Andrio, Andreu; Mollá, Sergio; Compañ, Vicente

    2015-01-01

    We present an analysis of the corneal oxygen consumption Qc from non-linear models, using data of oxygen partial pressure or tension (P(O2) ) obtained from in vivo estimation previously reported by other authors. (1) METHODS: Assuming that the cornea is a single homogeneous layer, the oxygen permeability through the cornea will be the same regardless of the type of lens that is available on it. The obtention of the real value of the maximum oxygen consumption rate Qc,max is very important because this parameter is directly related with the gradient pressure profile into the cornea and moreover, the real corneal oxygen consumption is influenced by both anterior and posterior oxygen fluxes. Our calculations give different values for the maximum oxygen consumption rate Qc,max, when different oxygen pressure values (high and low P(O2)) are considered at the interface cornea-tears film. Present results are relevant for the calculation on the partial pressure of oxygen, available at different depths into the corneal tissue behind contact lenses of different oxygen transmissibility. Copyright © 2014. Published by Elsevier Espana.

  9. Modeling of the effect of tool wear per discharge estimation error on the depth of machined cavities in micro-EDM milling

    DEFF Research Database (Denmark)

    Puthumana, Govindan; Bissacco, Giuliano; Hansen, Hans Nørgaard

    2017-01-01

    In micro-EDM milling, real time electrode wear compensation based on tool wear per discharge (TWD) estimation permits the direct control of the position of the tool electrode frontal surface. However, TWD estimation errors will cause errors on the tool electrode axial depth. A simulation tool...... is developed to determine the effects of errors in the initial estimation of TWD and its propagation effect with respect to the error on the depth of the cavity generated. Simulations were applied to micro-EDM milling of a slot of 5000 μm length and 50 μm depth and validated through slot milling experiments...

  10. Tyre and road wear prediction

    NARCIS (Netherlands)

    Lupker, H.A.

    2003-01-01

    Both tyre wear and road polishing are complex phenomenon, which are obviously strongly related; the energy that polishes the road is the energy that wears the tyre. The both depend non-linearly on numerous parameters, like materials used, vehicle and road usage, environmental conditions (i.e.

  11. Switch wear leveling

    Science.gov (United States)

    Wu, Hunter; Sealy, Kylee; Gilchrist, Aaron

    2015-09-01

    An apparatus for switch wear leveling includes a switching module that controls switching for two or more pairs of switches in a switching power converter. The switching module controls switches based on a duty cycle control technique and closes and opens each switch in a switching sequence. The pairs of switches connect to a positive and negative terminal of a DC voltage source. For a first switching sequence a first switch of a pair of switches has a higher switching power loss than a second switch of the pair of switches. The apparatus includes a switch rotation module that changes the switching sequence of the two or more pairs of switches from the first switching sequence to a second switching sequence. The second switch of a pair of switches has a higher switching power loss than the first switch of the pair of switches during the second switching sequence.

  12. Wear-Out Sensitivity Analysis Project Abstract

    Science.gov (United States)

    Harris, Adam

    2015-01-01

    During the course of the Summer 2015 internship session, I worked in the Reliability and Maintainability group of the ISS Safety and Mission Assurance department. My project was a statistical analysis of how sensitive ORU's (Orbital Replacement Units) are to a reliability parameter called the wear-out characteristic. The intended goal of this was to determine a worst case scenario of how many spares would be needed if multiple systems started exhibiting wear-out characteristics simultaneously. The goal was also to determine which parts would be most likely to do so. In order to do this, my duties were to take historical data of operational times and failure times of these ORU's and use them to build predictive models of failure using probability distribution functions, mainly the Weibull distribution. Then, I ran Monte Carlo Simulations to see how an entire population of these components would perform. From here, my final duty was to vary the wear-out characteristic from the intrinsic value, to extremely high wear-out values and determine how much the probability of sufficiency of the population would shift. This was done for around 30 different ORU populations on board the ISS.

  13. Prolonging contact lens wear and making contact lens wear safer.

    Science.gov (United States)

    Foulks, Gary N

    2006-02-01

    To summarize the present status of safety and efficacy of contact lens wear. Literature review. Ovid Medline searches were performed on records from 1966 through 2005 using keywords: keratitis, contact lens complications, extended-wear contact lenses, and silicone-hydrogel contact lenses. Patients desire comfort, clarity of vision, and prolonged contact lens wear when contact lenses are used to correct refractive error. Practitioners desire patient satisfaction but also require maintenance of the integrity of the eye and no complications that jeopardize vision or health of the eye. Improvements in the oxygen permeability of the contact lens materials, design of the contact lens and its surface, and solutions for the maintenance of the lens have reduced but not eliminated the risks of infection, inflammation, and conjunctival papillary reaction associated with contact lens wear. The lessons of past and recent history suggest that patient education and practitioner participation in the management of contact lens wear continue to be critical factors for patient satisfaction and safety in the extended wear of contact lenses. The availability of highly oxygen permeable contact lenses has increased the tolerance and safety of extended contact lens wear, but patient instruction and education in proper use and care of lenses is required and caution is advised.

  14. Low friction wear resistant graphene films

    Science.gov (United States)

    Sumant, Anirudha V.; Berman, Diana; Erdemir, Ali

    2017-02-07

    A low friction wear surface with a coefficient of friction in the superlubric regime including graphene and nanoparticles on the wear surface is provided, and methods of producing the low friction wear surface are also provided. A long lifetime wear resistant surface including graphene exposed to hydrogen is provided, including methods of increasing the lifetime of graphene containing wear surfaces by providing hydrogen to the wear surface.

  15. Evaluating the accuracy of wear formulae for acetabular cup liners.

    Science.gov (United States)

    Wu, James Shih-Shyn; Hsu, Shu-Ling; Chen, Jian-Horng

    2010-02-01

    This study proposes two methods for exploring the wear volume of a worn liner. The first method is a numerical method, in which SolidWorks software is used to create models of the worn out regions of liners at various wear directions and depths. The second method is an experimental one, in which a machining center is used to mill polyoxymethylene to manufacture worn and unworn liner models, then the volumes of the models are measured. The results show that the SolidWorks software is a good tool for presenting the wear pattern and volume of a worn liner. The formula provided by Ilchmann is the most suitable for computing liner volume loss, but is not accurate enough. This study suggests that a more accurate wear formula is required. This is crucial for accurate evaluation of the performance of hip components implanted in patients, as well as for designing new hip components.

  16. Clinical measurement of tooth wear: Tooth Wear Indices

    OpenAIRE

    J. López Frías; Castellanos Cosano, Lizett; Martín González, Jenifer; Llamas Carreras, José María; Segura-Egea, Juan J.

    2012-01-01

    Attrition, erosion, and abrasion result in alterations to the tooth and manifest as tooth wear. Each classification corresponds to a different process with specific clinical features. Classifications made so far have no accurate prevalence data because the indexes do not necessarily measure a specific etiology, or because the study populations can be diverse in age and characteristics. Tooth wears (attrition, erosion and abrasion) is perceived internationally as a growing problem. However, th...

  17. Prediction of Polyethylene Wear Rates from Gait Biomechanics and Implant Positioning in Total Hip Replacement.

    Science.gov (United States)

    Ardestani, Marzieh M; Amenábar Edwards, Pedro P; Wimmer, Markus A

    2017-08-01

    Patient-specific gait and surgical variables are known to play an important role in wear of total hip replacements (THR). However a rigorous model, capable of predicting wear rate based on a comprehensive set of subject-specific gait and component-positioning variables, has to our knowledge, not been reported. (1) Are there any differences between patients with high, moderate, and low wear rate in terms of gait and/or positioning variables? (2) Can we design a model to predict the wear rate based on gait and positioning variables? (3) Which group of wear factors (gait or positioning) contributes more to the wear rate? Data on patients undergoing primary unilateral THR who performed a postoperative gait test were screened for inclusion. We included patients with a 28-mm metal head and a hip cup made of noncrosslinked polyethylene (GUR 415 and 1050) from a single manufacturer (Zimmer, Inc). To calculate wear rates from radiographs, inclusion called for patients with a series of standing radiographs taken more than 1 year after surgery. Further, exclusion criteria were established to obtain reasonably reliable and homogeneous wear readings. Seventy-three (83% of included) patients met all criteria, and the final dataset consisted of 43 males and 30 females, 69 ± 10 years old, with a BMI of 27.3 ± 4.7 kg/m(2). Wear rates of these patients were determined based on the relative displacement of the femoral head with regard to the cup using a validated computer-assisted X-ray wear-analysis suite. Three groups with low ( 0.2 mm/year) wear were established. Wear prediction followed a two-step process: (1) linear discriminant analysis to estimate the level of wear (low, moderate, or high), and (2) multiple linear and nonlinear regression modeling to predict the exact wear rate from gait and implant-positioning variables for each level of wear. There were no group differences for positioning and gait suggesting that wear differences are caused by a combination of wear

  18. Wear behaviour of Al 261

    Directory of Open Access Journals (Sweden)

    N. Mathan Kumar

    2016-03-01

    Full Text Available Al 2618 matrix material was mixed with the Silicon Nitride (Si3N4, Aluminium Nitride (AlN and Zirconium Boride (ZrB2 reinforced particles. AMC was synthesized successfully by the stir casting method with the various X-wt.% of reinforcements (X = 0,2,4,6,8. Tribological behaviour was studied in this composite with various temperature conditions. The working conditions were Temperature (°C, Load (N, Velocity (m/s and Sliding Distances (m. Before wear testing the mechanical behaviour has been analysed. EDAX was confirmed by the matrix material composition. The Al 2618 alloy and the reinforcement mixers were confirmed by the X-ray Diffraction analysis. Wear rate (mm3/m, Wear resistance (m/mm3, Specific Wear rate (m/Nm and Co-efficient of friction (μ were analysed with various conditions. The worn surfaces were analysed before and after wear testing by Scanning Electron Microscope (SEM. Influence of process parameters and Percentage of contribution were analysed by Taguchi and Analysis of Variance (ANOVA methods. Genetic Algorithm (GA was adopted for optimizing the best and mean of the wear rate and to identify the exact influence of input parameters.

  19. Tool Wear in Friction Drilling

    Energy Technology Data Exchange (ETDEWEB)

    Miller, Scott F [ORNL; Blau, Peter Julian [ORNL; Shih, Albert J. [University of Michigan

    2007-01-01

    This study investigated the wear of carbide tools used in friction drilling, a nontraditional hole-making process. In friction drilling, a rotating conical tool uses the heat generated by friction to soften and penetrate a thin workpiece and create a bushing without generating chips. The wear of a hard tungsten carbide tool used for friction drilling a low carbon steel workpiece has been investigated. Tool wear characteristics were studied by measuring its weight change, detecting changes in its shape with a coordinate measuring machine, and making observations of wear damage using scanning electron microscopy. Energy dispersive spectroscopy was applied to analyze the change in chemical composition of the tool surface due to drilling. In addition, the thrust force and torque during drilling and the hole size were measured periodically to monitor the effects of tool wear. Results indicate that the carbide tool is durable, showing minimal tool wear after drilling 11000 holes, but observations also indicate progressively severe abrasive grooving on the tool tip.

  20. Gear Tooth Wear Detection Algorithm

    Science.gov (United States)

    Delgado, Irebert R.

    2015-01-01

    Vibration-based condition indicators continue to be developed for Health Usage Monitoring of rotorcraft gearboxes. Testing performed at NASA Glenn Research Center have shown correlations between specific condition indicators and specific types of gear wear. To speed up the detection and analysis of gear teeth, an image detection program based on the Viola-Jones algorithm was trained to automatically detect spiral bevel gear wear pitting. The detector was tested using a training set of gear wear pictures and a blind set of gear wear pictures. The detector accuracy for the training set was 75 percent while the accuracy for the blind set was 15 percent. Further improvements on the accuracy of the detector are required but preliminary results have shown its ability to automatically detect gear tooth wear. The trained detector would be used to quickly evaluate a set of gear or pinion pictures for pits, spalls, or abrasive wear. The results could then be used to correlate with vibration or oil debris data. In general, the program could be retrained to detect features of interest from pictures of a component taken over a period of time.

  1. Critical component wear in heavy duty engines

    CERN Document Server

    Lakshminarayanan, P A

    2011-01-01

    The critical parts of a heavy duty engine are theoretically designed for infinite life without mechanical fatigue failure. Yet the life of an engine is in reality determined by wear of the critical parts. Even if an engine is designed and built to have normal wear life, abnormal wear takes place either due to special working conditions or increased loading.  Understanding abnormal and normal wear enables the engineer to control the external conditions leading to premature wear, or to design the critical parts that have longer wear life and hence lower costs. The literature on wear phenomenon r

  2. REDUCED ENGINE FRICTION AND WEAR

    Energy Technology Data Exchange (ETDEWEB)

    Ron Matthews

    2005-05-01

    This Final Technical Report discusses the progress was made on the experimental and numerical tasks over the duration of this project regarding a new technique for decreasing engine friction and wear via liner rotation. The experimental subtasks involved quantifying the reduction in engine friction for a prototype rotating liner engine relative to a comparable baseline engine. Both engine were single cylinder conversions of nominally identical production four-cylinder engines. Hot motoring tests were conducted initially and revealed that liner rotation decreased engine friction by 20% under motoring conditions. A well-established model was used to estimate that liner rotation should decrease the friction of a four-cylinder engine by 40% under hot motoring conditions. Hot motoring tear-down tests revealed that the crankshaft and valve train frictional losses were essentially the same for the two engines, as expected. However, the rotating liner engine had much lower (>70%) piston assembly friction compared to the conventional engine. Finally, we used the Instantaneous IMEP method to compare the crank-angle resolved piston assembly friction for the two engines. Under hot motoring conditions, these measurements revealed a significant reduction in piston assembly friction, especially in the vicinity of compression TDC when the lubrication regime transitions from hydrodynamic through mixed and into boundary friction. We have some remaining problems with these measurements that we expect to solve during the next few weeks. We will then perform these measurements under firing conditions. We also proposed to improve the state-of-the-art of numerical modeling of piston assembly friction for conventional engines and then to extend this model to rotating liner engines. Our research team first modeled a single ring in the Purdue ring-liner test rig. Our model showed good agreement with the test rig data for a range of speeds and loads. We then modeled a complete piston

  3. Retrospective Snow Analysis Across the Continental United States for the National Water Model

    Science.gov (United States)

    Karsten, L. R.; Gochis, D.; Dugger, A. L.; McCreight, J. L.; Barlage, M. J.; Fall, G. M.; Olheiser, C.

    2016-12-01

    For large portions of the United States, snow plays a vital role in hydrologic prediction. This is particularly true in the mountain west where snowmelt contributes up to 80% of total streamflow runoff. The Office of Water Prediction (OWP) will begin running the National Water Model (NWM) during the second half of 2016, which is a continental-scale implementation of the WRF-Hydro community hydrologic modeling framework. Assessing and benchmarking the performance of the snow component of the NWM is important for future research-to-operations activities and for forecasters to better understand NWM output. For this study, WRF-Hydro was ran using the same domain and physics options as the NWM (1 km LSM, 250m overland routing, and NHDPlus Version 2.1 channel network). The land surface component chosen is Noah-MP land surface model. Forcing from the National Land Data Assimilation System (NLDAS-2) was downscaled from the native 0.125 degree resolution to the 1 km modeling domain to drive the model. The model was ran over a 5-year retrospective period to gauge multi-year performance of the snow states. Output was analyzed against both in-situ observations, such as SNOTEL, and the Snow Data Assimilation System (SNODAS). In addition, gridded snow states and SNODAS grids were aggregated to Omernik-derived ecological regions. This was done in order to break up snow analysis by regions that share similar ecological and physiographic characteristics. Results show WRF-Hydro is able to capture peak timing across most of the mountain west fairly well. In terms of magnitudes, the model struggles across portions of the west with a low bias. This is especially true in the Cascades, which could be traced back to precipitation partitioning issues in the model. Across the central Rockies, the model exhibits a lower dry bias showing improved performance there. Previous literature suggests a dry bias in the precipitation out west may be contributing to model performance. East of the

  4. Demographic Factors Affect Ocular Comfort Ratings During Contact Lens Wear.

    Science.gov (United States)

    Naduvilath, Thomas; Papas, Eric B; Lazon de la Jara, Percy

    2016-08-01

    To determine if rating of ocular comfort during soft contact lens wear is affected by demographic factors. Retrospective analysis of ocular comfort ratings during soft contact lens wear extracted from 44 nonrandomized similar clinical trials (n = 986). Subjects wore one of seven daily wear silicone hydrogels (SiHy) in combination with one of nine lens care products (LCP), and two daily disposables lenses. The effects on comfort rating of demographic factors were examined after adjusting for lens and LCP effects using general linear model. Males reported lower comfort on insertion than females (7.9 ± 1.6 vs. 8.1 ± 1.6, p = 0.001). Over 45 years old had higher comfort ratings than those between 26 and 45 or gender, lens wear experience, ethnicity, and refractive status can influence the rating of ocular comfort in clinical studies. The confounding effects of such demographic factors can be controlled by implementing randomization and appropriate multivariable statistical analysis.

  5. Analysis of Wear Behavior of Thermoplastic Bio-Composite

    Science.gov (United States)

    Bajpai, Pramendra Kumar; Chaudhary, Vijay

    2017-08-01

    In the present work, response surface methodology (RSM) has been used to model and predict the wear properties of Bio-composites fabricated in this study. Polished stainless steel counterface has been used to analyze the wear response of the bio-composite under dry contact condition. Three process variables namely applied sliding speed, normal load, and sliding distance were taken to investigate their effect on output response (specific wear rate). Statistical analysis was performed in the form of the analysis of variance (ANOVA) to analyze the significance and interaction of experimental parameters. The mathematical relationship between sliding wear input process parameters and output responses has been established to determine the values of output responses.

  6. Detailed study of oxidation/wear mechanism in lox turbopump bearings

    Science.gov (United States)

    Chase, T. J.; McCarty, J. P.

    1993-12-01

    Wear of 440C angular contact ball bearings of the phase 2 high pressure oxygen turbopump (HPOTP) of the space shuttle main engine (SSME) has been studied by means of various advanced nondestructive techniques (NDT) and modeled with reference to all known material, design, and operation variables. Three modes dominating the wear scenario were found to be the adhesive/sheer peeling (ASP), oxidation, and abrasion. Bearing wear was modeled in terms of the three modes. Lacking a comprehensive theory of rolling contact wear to date, each mode is modeled after well-established theories of sliding wear, while sliding velocity and distance are related to microsliding in ball-to-ring contacts. Microsliding, stress, temperature, and other contact variables are evaluated with analytical software packages of SHABERTH(TM)/SINDA(TM) and ADORE(TM). Empirical constants for the models are derived from NIST experiments by applying the models to the NIST wear data. The bearing wear model so established precisely predicts quite well the average ball wear rate for the HPOTP bearings. The wear rate has been statistically determined for the entire population of flight and development bearings based on Rocketdyne records to date. Numerous illustrations are given.

  7. CFD Prediction of Erosion Wear in Centrifugal Slurry Pumps for Dilute Slurry Flows

    Directory of Open Access Journals (Sweden)

    K. V. Pagalthivarthi

    2011-12-01

    Full Text Available The paper discusses numerical prediction of erosion wear trends in centrifugal pump casing pumping dilute slurries. The casing geometry is considered two-dimensional. Discrete Phase Model (DPM in FLUENT 6.1® is utilized to obtain dilute slurry flow field through the pump casing employing two-way coupling. Standard k — ε model is used for turbulence. Effect of several operational parameters viz. pump flow rate, pump speed (RPM, particle diameter and various geometry conditions viz. tongue curvature, slope of the discharge pipe and casing width is studied. Qualitative trends of erosion wear is described for these operational and geometric parameters with an idea to lower the wear rates and to make the wear pattern along the casing wall as uniform as possible. For example, with increase in pump flow rate, wear rates tends to even out whereas with increased casing width, wear rates are found to decrease.

  8. Structurally Integrated Coatings for Wear and Corrosion

    Energy Technology Data Exchange (ETDEWEB)

    Beardsley, M. Brad; Sebright, Jason L.

    2008-11-18

    techniques, balanced with overall materials performance. State-of-the-art design and simulation capabilities were used to guide materials and process refinement. Caterpillar was the lead of the multi-partner collaborative project. Specific tasks were performed by the partners base on their unique capabilities. The project team was selected to include leaders in the field of material development, processing, modeling, and material characterization. Specifically, industrial members include the suppliers Deloro Stellite and Powder Alloy Corporation., who provided the experimental alloys and who aided in the development of the costs for the alloys, the Missouri University of Science and Technology and Iowa State University, who provided help in the alloy development and material characterization, QuesTek Innovations, a small company specializing the microstructural modeling of materials, and the DOE laboratories, Oak Ridge National Laboratory and National Energy Technology Laboratory (Albany), who provided unique coating process capability and wear characterization testing. The technologies developed in this program are expected to yield energy savings of about 50% over existing technologies, or 110 trillion BTUs per year by 2020 when fully implemented. Primary applications by Caterpillar are to replace the surface of machine components which are currently carburized and heat treated with new cladding materials with double the wear life. The new cladding technologies will consume less energy than carburizing. Thus, nearly 50% energy savings can be expected as a result from elimination of the heat treat process and the reduce wear of the materials. Additionally, when technologies from this project are applied on titanium or other non-ferrous substrates to make lighter weight, more wear resistant, and more efficient structures, significant fuel savings can be realized. With the anticipated drastic reduction in cost for refining titanium-containing ores, the usage of titanium

  9. Automotive brake wear: a review.

    Science.gov (United States)

    Wahid, Syed M S

    2018-01-01

    Road transport systems generate toxic particulate matter (PM) when in motion, that ultimately finds its way to the atmosphere. The PM produced by road transport systems can be broadly classified as exhaust and non-exhaust emissions. Exhaust emission is primarily due to product of combustion, as is the case of internal combustion engines and the PM is released to the atmosphere through the tail. Non-exhaust PM sources can be classified as sources such as emissions due to brake wear, tyre wear, road surface wear and resuspension. Both exhaust and non-exhaust sources generate PM of various sizes and shapes that has an impact on our health. Strict legislations by authorities have led to reduced exhaust emissions; however, due to the nature of complexity of PM generation by non-exhaust sources, effective control of non-exhaust emission still needs to be developed. Thus, as exhaust emissions are being controlled, non-exhaust is becoming a significant source of PM emission. The present paper reviews work done by previous researchers on non-exhaust PM and specifically, brake wear from road transport systems as this is one of the most important non-exhaust source of PM in the environment. The finding of the paper would be beneficial to policy makers and researchers.

  10. Should School Nurses Wear Uniforms?

    Science.gov (United States)

    Journal of School Health, 2001

    2001-01-01

    This 1958 paper questions whether school nurses should wear uniforms (specifically, white uniforms). It concludes that white uniforms are often associated with the treatment of ill people, and since many people have a fear reaction to them, they are not necessary and are even undesirable. Since school nurses are school staff members, they should…

  11. Analysis of Impact of Chosen Parameters on the Wear of Camshft

    Directory of Open Access Journals (Sweden)

    Burdzik R.

    2014-10-01

    Full Text Available The paper provides an analysis of the reasons for excessive wear of the camshafts system components based on models developed to describe the impact of selected material, technological and operational factors. The subject of the research was wear of camshaft cams studied in accordance with results of operation tests. Based on the said tests, the dependence of wear intensity of cams from their angular position was established. The respective calculation results enabled the function of cam fallibility to be determined.

  12. Wear performance of laser processed tantalum coatings

    Energy Technology Data Exchange (ETDEWEB)

    Dittrick, Stanley; Balla, Vamsi Krishna; Bose, Susmita; Bandyopadhyay, Amit, E-mail: amitband@wsu.edu

    2011-12-01

    This first generation investigation evaluates the in vitro tribological performance of laser-processed Ta coatings on Ti for load-bearing implant applications. Linear reciprocating wear tests in simulated body fluid showed one order of magnitude less wear rate, of the order of 10{sup -4} mm{sup 3}(N.m){sup -1}, for Ta coatings compared to Ti. Our results demonstrate that Ta coatings can potentially minimize the early-stage bone-implant interface micro-motion induced wear debris generation due to their excellent bioactivity comparable to that of hydroxyapatite (HA), high wear resistance and toughness compared to popular HA coatings. Highlights: {yields} In vitro wear performance of laser processed Ta coatings on Ti was evaluated. {yields} Wear tests in SBF showed one order of magnitude less wear for Ta coatings than Ti. {yields} Ta coatings can minimize early-stage micro-motion induced wear debris generation.

  13. The influence of die geometry on tool wear in deep drawing

    DEFF Research Database (Denmark)

    Eriksen, Morten

    1997-01-01

    This work shows by numerical simulation how the die edge geometry in a standard deep drawing process influences the maximum wear and the wear distribution over the die edge. By experiments with physical simulation of deep drawing, the numerical model is verified. The model is then used...

  14. The Delamination Theory of Wear - III

    Science.gov (United States)

    1977-12-01

    approximate, it shows excellent agreement with the above postulate and with experimental observations of wear. It was shown that void nucleation is...purposes: to predict wear arnd to reduce wear, Mathematical modelo are necessary in order to predict wear 40 qualitatively. They are also useful in the...the substrate and on the physical and chemical properties of the materials involved, There are a number of excellent references on coating techniques

  15. Complications Caused by Contact Lens Wearing

    OpenAIRE

    Beljan, Jasna; Beljan, Kristina; Beljan, Zdravko

    2013-01-01

    Complications in wearing contact lenses are very rare and caused by poor maintenance, over-extended wear and wearing of contact lenses in a polluted environment. Regular control by a professional person can efficiently reduce the number of complications. This paper describes the most common risks factors for complications, and complications of wearing contact lenses with the classification according to the anatomic parts of the eye: eyelids, tear film, limbus, corneal epithelium, corneal stro...

  16. Spectacle wear in children given spectacles through a school-based program.

    Science.gov (United States)

    Messer, Dawn H; Mitchell, G Lynn; Twelker, J Daniel; Crescioni, Mabel

    2012-01-01

    To investigate factors associated with spectacle wear in a group of primarily Native-American children provided spectacles free of charge through a school-based vision program. Spectacle wear was studied in 247 participants provided two pairs of spectacles the previous year. Univariate and multivariate logistic regression models assessed whether gender, race, parental education levels, family income, uncorrected distance visual acuity, refractive error, or the children's attitudes and beliefs about their vision and spectacles were associated with spectacle wear. Two thirds of the participants (165/247) were not wearing their spectacles at their annual examination. The most common reasons given for non-wear were lost (44.9%) or broken (35.3%) spectacles. A 1 diopter increase in myopic spherical equivalent was associated with more than a twofold increase in the odds of wearing spectacles [odds ratio (OR) = 2.5, 95% confidence interval (CI) = 1.7 to 3.7]. Among non-myopic participants, increasing amounts of astigmatism in the better- and worse-seeing eye were associated with an increased likelihood of spectacle wear (p ≤ 0.02). In multivariate analysis, only poorer uncorrected acuity in the better-seeing eye (p spectacle wear. For each line of poorer uncorrected acuity in the better-seeing eye, the likelihood that the participant was wearing spectacles increased by 60% (adjusted odds ratio = 1.6; 95% CI = 1.4 to 1.8). Not surprisingly, participants who reported never getting used to their spectacles were less likely to be wearing spectacles than those who reported getting used to wearing glasses in a few days (adjusted OR = 5.7, 95% CI = 1.9 to 17.5). Despite being provided with two pairs of spectacles, loss and breakage were the most commonly reported reasons for not wearing spectacles. The best predictive factor for determining whether participants were wearing spectacles was their uncorrected acuity.

  17. Needs and challenges in precision wear measurement

    Energy Technology Data Exchange (ETDEWEB)

    Blau, P.J.

    1996-01-10

    Accurate, precise wear measurements are a key element in solving both current wear problems and in basic wear research. Applications range from assessing durability of micro-scale components to accurate screening of surface treatments and thin solid films. Need to distinguish small differences in wear tate presents formidable problems to those who are developing new materials and surface treatments. Methods for measuring wear in ASTM standard test methods are discussed. Errors in using alterate methods of wear measurement on the same test specimen are also described. Human judgemental factors are a concern in common methods for wear measurement, and an experiment involving measurement of a wear scar by ten different people is described. Precision in wear measurement is limited both by the capabilities of the measuring instruments and by the nonuniformity of the wear process. A method of measuring wear using nano-scale indentations is discussed. Current and future prospects for incorporating advanced, higher-precision wear measurement methods into standards are considered.

  18. Study on Abrasive Wear of Brake Pad in the Large-megawatt Wind Turbine Brake Based on Deform Software

    Science.gov (United States)

    Zhang, Shengfang; Hao, Qiang; Sha, Zhihua; Yin, Jian; Ma, Fujian; Liu, Yu

    2017-12-01

    For the friction and wear issues of brake pads in the large-megawatt wind turbine brake during braking, this paper established the micro finite element model of abrasive wear by using Deform-2D software. Based on abrasive wear theory and considered the variation of the velocity and load in the micro friction and wear process, the Archard wear calculation model is developed. The influence rules of relative sliding velocity and friction coefficient in the brake pad and disc is analysed. The simulation results showed that as the relative sliding velocity increases, the wear will be more serious, while the larger friction coefficient lowered the contact pressure which released the wear of the brake pad.

  19. Fluoridation and tooth wear in Irish adults.

    LENUS (Irish Health Repository)

    Burke, F M

    2010-10-01

    The aim of this study was to determine the prevalence of tooth wear in adults in Ireland and its relationship with water fluoridation. The National Survey of Adult Oral Health was conducted in 2000\\/2001. Tooth wear was determined using a partial mouth examination assessing the upper and lower anterior teeth. A total of 2456 subjects were examined. In this survey, increasing levels and severity of tooth wear were associated with ageing. Men were more affected by tooth wear and were more likely to be affected by severe tooth wear than women. It was found that age, and gender were significant predictors of tooth wear (P < 0.01). Overall, there was no significant relationship between fluoridation and tooth wear in this study.

  20. Wear resistance of hydrophobic surfaces

    Science.gov (United States)

    Martinez, MA; Abenojar, J.; Pantoja, M.; López de Armentia, S.

    2017-05-01

    Nature has been an inspiration source to develop artificial hydrophobic surfaces. During the latest years the development of hydrophobic surfaces has been widely researched due to their numerous ranges of industrial applications. Industrially the use of hydrophobic surfaces is being highly demanded. This is why many companies develop hydrophobic products to repel water, in order to be used as coatings. Moreover, these coating should have the appropriated mechanical properties and wear resistance. In this work wear study of a hydrophobic coating on glass is carried out. Hydrophobic product used was Sika Crystal Dry by Sika S.A.U. (Alcobendas, Spain). This product is currently used on car windshield. To calculate wear resistance, pin-on-disk tests were carried out in dry and water conditions. The test parameters were rate, load and sliding distance, which were fixed to 60 rpm, 5 N and 1000 m respectively. A chamois was used as pin. It allows to simulate a real use. The friction coefficient and loss weight were compared to determinate coating resistance

  1. Analysis of Dry Sliding Wear Behaviour of Aluminium-Fly Ash Composites: The Taguchi Approach

    Directory of Open Access Journals (Sweden)

    Shanmughasundaram Palanisamy

    2013-01-01

    Full Text Available Dry sliding wear test was conducted on Al-fly ash composites employing pin-on-disc wear testing rig. The influence of parameters such as weight percentage of fly ash, load, and sliding speed on the wear rate of specimens was investigated. Specimens were fabricated by adapting a modified two-step stir casting method. The Taguchi and analysis of variance (ANOVA techniques were employed to investigate the influence of parameters on the wear rate of composite. Multiple linear regression models were developed to predict the wear rate of the composites. It was found that the weight percentage of fly ash was the most dominant factor influencing the wear rate followed by the applied load and sliding speed. The morphology of worn surfaces of the wear pins was analyzed by scanning electron microscope (SEM to analyze the wear behaviour. EDS analysis was carried out to investigate the mechanical mixed layer (MML, which forms on the worn surface of the wear pins.

  2. How do material properties influence wear and fracture mechanisms?

    Science.gov (United States)

    Rimnac, Clare; Pruitt, Lisa

    2008-01-01

    The wear and fracture mechanisms of ultra-high-molecular-weight polyethylene (UHMWPE) hip and knee implant components are of great interest. The material properties of UHMWPE are affected by ionizing radiation as used for sterilization and cross-linking. Cross-linking with high-dose irradiation has been shown to improve the wear resistance of UHMWPE. However, cross-linking leads to a loss in properties such as ductility and resistance to fatigue crack propagation. Highly cross-linked UHMWPE may be more susceptible than conventional UHMWPE to fracture under severe clinical conditions (eg, impingement). Contemporary hip and knee simulator studies provide good information with which new UHMWPE formulations can be screened for clinical wear performance. However, comparable methodologies are lacking for screening UHMWPEs for fracture resistance. Mechanical tests as well as computational material and structural models should be developed to evaluate the combined effect of material and geometry (structure) on fracture resistance under clinically relevant loading conditions.

  3. Advanced Wear Simulation for Bulk Metal Forming Processes

    Directory of Open Access Journals (Sweden)

    Behrens Bernd-Arno

    2016-01-01

    Full Text Available In the recent decades the finite element method has become an essential tool for the cost-efficient virtual process design in the metal forming sector in order to counter the constantly increasing quality standards, particularly from the automotive industry as well as intensified international competition in the forging industry. An optimized process design taking precise tool wear prediction into account is a way to increase the cost-efficiency of the bulk metal forming processes. The main objective of the work presented in this paper is a modelling algorithm, which allows predicting die wear with respect to a geometry update during the forming simulation. Changes in the contact area caused by geometry update lead to the different die wear distribution. It primarily concerns the die areas, which undergo high thermal and mechanical loads.

  4. Wear prediction on total ankle replacement effect of design parameters

    CERN Document Server

    Saad, Amir Putra Bin Md; Harun, Muhamad Noor; Kadir, Mohammed Rafiq Abdul

    2016-01-01

    This book develops and analyses computational wear simulations of the total ankle replacement for the stance phase of gait cycle. The emphasis is put on the relevant design parameters. The book presents a model consisting of three components; tibial, bearing and talar representing their physiological functions.

  5. Increased conformity offers diminishing returns for reducing total knee replacement wear.

    Science.gov (United States)

    Fregly, Benjamin J; Marquez-Barrientos, Carlos; Banks, Scott A; DesJardins, John D

    2010-02-01

    Wear remains a significant problem limiting the lifespan of total knee replacements (TKRs). Though increased conformity between TKR components has the potential to decrease wear, the optimal amount and planes of conformity have not been investigated. Furthermore, differing conformities in the medial and lateral compartments may provide designers the opportunity to address both wear and kinematic design goals simultaneously. This study used a computational model of a Stanmore knee simulator machine and a previously validated wear model to investigate this issue for simulated gait. TKR geometries with different amounts and planes of conformity on the medial and lateral sides were created and tested in two phases. The first phase utilized a wide range of sagittal and coronal conformity combinations to blanket a physically realistic design space. The second phase performed a focused investigation of the conformity conditions from the first phase to which predicted wear volume was sensitive. For the first phase, sagittal but not coronal conformity was found to have a significant effect on predicted wear volume. For the second phase, increased sagittal conformity was found to decrease predicted wear volume in a nonlinear fashion, with reductions gradually diminishing as conformity increased. These results suggest that TKR geometric design efforts aimed at minimizing wear should focus on sagittal rather than coronal conformity and that at least moderate sagittal conformity is desirable in both compartments.

  6. Wear Characteristics of Polymer -Based Composites

    Science.gov (United States)

    Şahin, Y.; Mirzayev, H.

    2015-11-01

    The dry wear of polytetrafluoroethylene (PTFE)-based composites, including bronze-filled composites (B60), glass-filled composites (G15), and carbon-filled composites (C25), produced by the mold casting method were investigated under different sliding conditions. The Taguchi L27 method and the analysis of variance were used to identify the effect of process parameters on the wear of tested materials. Experimental results showed that the wear resistance of G15 polymer composites was better than those of C25 and B60 ones. The specific wear rate decreased with increasing sliding distance and load, but partly decreased with increasing tensile strength.

  7. The prevalence of cervical tooth wear in patients with bruxism and other causes of wear.

    Science.gov (United States)

    Shah, Punit; Razavi, Sheri; Bartlett, David W

    2009-07-01

    The aim of this study was to investigate the prevalence of cervical wear lesions in three groups of patients: bruxists, combined tooth wear, and controls. The hypothesis was that those subjects presenting with bruxism were more likely to develop cervical wear lesions. Of 119 subjects, 31 were bruxists with a mean age 48.7 years [standard deviation (SD): 11.6]; 22 had combined wear, aged 43.5 years (14.2); and 66 controls aged 44.9 years (17.0). The clinical appearance of the tooth wear was used to recruit subjects to the bruxist and combined tooth wear groups. Control subjects were randomly selected from those attending for routine dental examination at two general dental practices. A tooth wear index (TWI) was used by two trained examiners to record the severity of wear in each group. There was a statistically significant difference between the controls and both the bruxist and combined tooth wear groups for wear on all surfaces (p < or = 0.001). There was no significant difference between the bruxist and the combined tooth wear group for wear on any surface. There was a statistically significant difference between the control group and both the bruxist and the combined tooth wear group for the severity of cervical wear (p < or = 0.005), but no difference between the bruxist and combined tooth wear groups. There was also no statistical difference in the number of cervical lesions between the groups. In this study, the likely cause of cervical tooth wear was multifactorial.

  8. Patient-Specific Contact Stress Does Not Predict Polyethylene Wear Rate in a Specific Pressfit Cup.

    Science.gov (United States)

    Matziolis, Georg; Krakow, Linda; Layher, Frank; Sander, Klaus; Bossert, Joerg; Brodt, Steffen

    2017-12-01

    The most common reason for revision total hip arthroplasty remains polyethylene wear. Development dysplasia of the hip and revision situations requires a conscious compromise of implant position. The surgeon should know about the consequence on wear via a possible change in hip contact force. The objective of this study is to investigate whether annual wear is dependent on hip contact force. Forty-five inserts (DuraLoc, DePuy) that were explanted in our department were included. Three-dimensional gravimetric determination of the wear was performed by fluid displacement. Then, the hip contact force was determined using radiographs according to the Blumentritt model. No correlation was found between patient-specific factors and the annual wear. The hip contact force estimated by the Blumentritt model also showed no correlation between hip contact force and annual wear. Two single model parameters correlated significantly with wear: VRECAB as a ratio of the lever length of the spinocrural and the pelvitrochanteric muscles and the angle Alpha as a measure of the position of the center of rotation in relation to the greater trochanter. The greater the ratio spinocrural/pelvitrochanteric lever arm (R = 0.408, P = .005) and the greater the Alpha angle (more valgus the femoral neck) (R = 0.377, P = .011) were, the greater was the wear. These results lead to the conclusion that neither patient-specific factors nor the estimated hip contact force have a major influence on annual wear in the case of DuraLoc cups. Only a coxa valga and a small femoral offset contribute in a limited amount to an increase in wear. Copyright © 2017 Elsevier Inc. All rights reserved.

  9. Wear monitoring of single point cutting tool using acoustic emission ...

    Indian Academy of Sciences (India)

    was carried out to study the wear monitoring in single point cutting tool using acoustic emission techniques. 2. Propagation of stress wave due to crater wear and flank wear. Figure 1 show the crater wear occurred on the rake face of the tool. This crater wear emits stress wave, which propagates as spherical wave front and ...

  10. Effect of microseparation and third-body particles on dual-mobility crosslinked hip liner wear.

    Science.gov (United States)

    Netter, Jonathan D; Hermida, Juan C; Chen, Peter C; Nevelos, James E; D'Lima, Darryl D

    2014-09-01

    Large heads have been recommended to reduce the risk of dislocation after total hip arthroplasty. One of the issues with larger heads is the risk of increased wear and damage in thin polyethylene liners. Dual-mobility liners have been proposed as an alternative to large heads. We tested the wear performance of highly crosslinked dual-mobility liners under adverse conditions simulating microseparation and third-body wear. No measurable increase in polyethylene wear rate was found in the presence of third-body particles. Microseparation induced a small increase in wear rate (2.9mm(3)/million cycles). A finite element model simulating microseparation in dual-mobility liners was validated using these experimental results. The results of our study indicate that highly crosslinked dual-mobility liners have high tolerance for third-body particles and microseparation. Copyright © 2014 Elsevier Inc. All rights reserved.

  11. Estimation of tool wear during CNC milling using neural network-based sensor fusion

    Science.gov (United States)

    Ghosh, N.; Ravi, Y. B.; Patra, A.; Mukhopadhyay, S.; Paul, S.; Mohanty, A. R.; Chattopadhyay, A. B.

    2007-01-01

    Cutting tool wear degrades the product quality in manufacturing processes. Monitoring tool wear value online is therefore needed to prevent degradation in machining quality. Unfortunately there is no direct way of measuring the tool wear online. Therefore one has to adopt an indirect method wherein the tool wear is estimated from several sensors measuring related process variables. In this work, a neural network-based sensor fusion model has been developed for tool condition monitoring (TCM). Features extracted from a number of machining zone signals, namely cutting forces, spindle vibration, spindle current, and sound pressure level have been fused to estimate the average flank wear of the main cutting edge. Novel strategies such as, signal level segmentation for temporal registration, feature space filtering, outlier removal, and estimation space filtering have been proposed. The proposed approach has been validated by both laboratory and industrial implementations.

  12. Polyethylene wear of mobile-bearing unicompartmental knee replacement at 20 years.

    Science.gov (United States)

    Kendrick, B J L; Simpson, D J; Kaptein, B L; Valstar, E R; Gill, H S; Murray, D W; Price, A J

    2011-04-01

    The Oxford unicompartmental knee replacement (UKR) was designed to minimise wear utilising a fully-congruent, mobile, polyethylene bearing. Wear of polyethylene is a significant cause of revision surgery in UKR in the first decade, and the incidence increases in the second decade. Our study used model-based radiostereometric analysis to measure the combined wear of the upper and lower bearing surfaces in 13 medial-compartment Oxford UKRs at a mean of 20.9 years (17.2 to 25.9) post-operatively. The mean linear penetration of the polyethylene bearing was 1.04 mm (0.307 to 2.15), with a mean annual wear rate of 0.045 mm/year (0.016 to 0.099). The annual wear rate of the phase-2 bearings (mean 0.022 mm/year) was significantly less (p = 0.01) than that of phase-1 bearings (mean 0.07 mm/year). The linear wear rate of the Oxford UKR remains very low into the third decade. We believe that phase-2 bearings had lower wear rates than phase-1 implants because of the improved bearing design and surgical technique which decreased the incidence of impingement. We conclude that the design of the Oxford UKR gives low rates of wear in the long term.

  13. Sliding wear resistance of iron aluminides

    Indian Academy of Sciences (India)

    Unknown

    ordered intermetallic alloy (Johnson et al 1990, 1994,. 1996; Maupin et al 1992, 1993; Tu and Liu 1997; Kim and Kim 1998). Maupin et al (1992, 1993) had shown that the Fe3Al alloy having DO3 structure possesses mar- ginally lower wear rate than those with B2 structure. The wear resistance of Fe3Al alloy was found to ...

  14. Effective tool wear estimation through multisensory information ...

    African Journals Online (AJOL)

    Effective tool wear estimation through multisensory information fusion using Artificial Neural Network. ... On-line tool wear monitoring plays a significant role in industrial automation for higher productivity and product quality. In addition, an intelligent system is required to make a timely decision for tool change in machining ...

  15. Truck tyre wear assessment and prediction

    NARCIS (Netherlands)

    Lupker, H.A.; Montanaro, F.; Donadio, D.; Gelosa, E.; Vis, M.A.

    2002-01-01

    Tyre wear is a complex phenomenon. It depends non-linearly on numerous parameters, like tyre compound and design, vehicle type and usage, road conditions and road surface characteristics, environmental conditions (e.g., temperature) and many others. Yet, tyre wear has many economic and ecological

  16. Asphalt wear and pollution transport

    Energy Technology Data Exchange (ETDEWEB)

    Lindgren, Asa [Division of Traffic Engineering, Lulea University of Technology Lulea (Sweden)

    1996-09-06

    Studded tires cause extensive wear of road surfaces during winter producing small particles. Besides transporting different adsorbed pollutants these particles also discharge metal ions by their own natural content. The major part (95%) of the asphalt is composed of stone fractions. The rest consists mainly of bitumen, which contains trace quantities of metals. Laboratory studies in this study have demonstrated different adsorbing properties of metal ions, as well as differences in adsorption when comparing stone materials. Two stone materials, a gabbro and a porphyry, have been tested for their adsorption properties concerning Pb, Cu, Zn and Cd. The gabbro showed better adsorption capacity than the porphyry. Gabbro has coarser grains, it is softer, and also has a higher content of most metals compared to the porphyry. In all tests lead and copper are more adsorbed than zinc and cadmium. All metal ions are released at about the same pH ({approx}4)

  17. Complications caused by contact lens wearing.

    Science.gov (United States)

    Beljan, Jasna; Beljan, Kristina; Beljan, Zdravko

    2013-04-01

    Complications in wearing contact lenses are very rare and caused by poor maintenance, over-extended wear and wearing of contact lenses in a polluted environment. Regular control by a professional person can efficiently reduce the number of complications. This paper describes the most common risks factors for complications, and complications of wearing contact lenses with the classification according to the anatomic parts of the eye: eyelids, tear film, limbus, corneal epithelium, corneal stroma and corneal endothelium. Every complication has been described by the characteristic signs and symptoms, etiology and pathology, as well as therapy and prognosis. The paper describes how to select adequate customers as contact lens users, with proper education in order to ensure minimal incidence of complications due to contact lens wear, thus attracting a lot of satisfied and healthy customers.

  18. Biologically Based Restorative Management of Tooth Wear

    Directory of Open Access Journals (Sweden)

    Martin G. D. Kelleher

    2012-01-01

    Full Text Available The prevalence and severity of tooth wear is increasing in industrialised nations. Yet, there is no high-level evidence to support or refute any therapeutic intervention. In the absence of such evidence, many currently prevailing management strategies for tooth wear may be failing in their duty of care to first and foremost improve the oral health of patients with this disease. This paper promotes biologically sound approaches to the management of tooth wear on the basis of current best evidence of the aetiology and clinical features of this disease. The relative risks and benefits of the varying approaches to managing tooth wear are discussed with reference to long-term follow-up studies. Using reference to ethical standards such as “The Daughter Test”, this paper presents case reports of patients with moderate-to-severe levels of tooth wear managed in line with these biologically sound principles.

  19. Wear monitoring of protective nitride coatings using image processing

    DEFF Research Database (Denmark)

    Rasmussen, Inge Lise; Guibert, M.; Belin, M.

    2010-01-01

    -meter with up to 105 19 repetitive cycles, eventually leaving the embedded TiN signal layer uncovered at the bottom the wear scar. 20 The worn surface was characterized by subsequent image processing. A color detection of the wear scar with 21 the exposed TiN layer by a simple optical imaging system showed......A double-layer model system, consisting of a thin layer of tribological titanium aluminum nitride (TiAlN) on 17 top of titanium nitride (TiN), was deposited on polished 100Cr6 steel substrates. The TiAlN top-coatings 18 were exposed to abrasive wear by a reciprocating wear process in a linear tribo...... a significant increase up to a factor of 2 of 22 the relative color values from the TiAlN top layers to the embedded TiN signal layers. This behavior agrees 23 well with the results of reflectance detection experiment with a red laser optical system on the same system. 24 Thus we have demonstrated that image...

  20. Synergetic approachto simulation of physical wear of engineering technical systems

    Directory of Open Access Journals (Sweden)

    Kirillov Andrey Mikhaylovich

    2015-05-01

    Full Text Available In course of time in structural elements of engineering technical systems defects and damages are accumulated, which is caused by loadings and environmental influence. The defects are any inconsistencies with normative documents, and damages are discontinuances of structure. The defects and damages lead to decrease of operational properties of structures (their bearing capacity, waterproofing, thermal resistance, etc. The occurrences of such character are called physical wear.In the article the authors show the possibility of phase trajectory use of the processes of physical wear, creep and cusp catastrophe for determinating the critical timepoint, corresponding to the beginning of the system damage catastrophic growth. The alternative approach to the description of the processes of physical wear and creep of pavement consisting in comparison of asphalt concrete creep curve and the curve of the mathematical model of cusp catastrophe, is received. The applied synergetic approach gives us the chance to improve the existing and create new methods of pavement resource forecasting and assessment of physical wear of any technical constructions.

  1. Does ultra-mild wear play any role for dry friction applications, such as automotive braking?

    Science.gov (United States)

    Osterle, Werner; Dmitriev, A I; Kloss, H

    2012-01-01

    Nanostructured third body films and/or storage of wear debris at the surfaces of the first bodies are deemed as prerequisites of sliding under ultra-mild wear conditions. Since such features have been observed experimentally on brake pads and discs, attempts were undertaken to study their sliding behaviour by modelling on the nanoscopic scale with an approach based on Movable Cellular Automata (MCA). The model rendered the possibility to study the influence of different nanostructures systematically and to assess the impact of different brake pad ingredients on the sliding behaviour, velocity accommodation and friction force stabilization at a sliding contact. Besides providing a review on previously published modelling results, some additional new graphs enabling better visualization of dynamic processes are presented. Although ultra-mild wear conditions were considered to be essential for achieving the desired tribological properties, transitions to mesoscopic and macroscopic wear mechanisms were studied as well. The final conclusion is that ultra-mild wear and corresponding smooth sliding behaviour play an important role during automotive braking, even though temporarily and locally events of severe wear may cause friction instabilities, surface damage and release of coarse wear particles.

  2. Effect of Heat Treatment on the Abrasive Wear Behavior of High Chromium Iron under Dry Sliding Condition

    Directory of Open Access Journals (Sweden)

    A.A. Ayeni

    2012-06-01

    Full Text Available The effect of heat treatment on the abrasive wear behavior of high chromium cast iron (NF253AHT under dry sliding condition has been investigated. Rectangular cross sectioned samples of the alloy were produced by sand casting. After casting, the samples were machined to equal dimensions of 50 mm x 15 mm x 10 mm and heat treated by annealing, hardening and tempering. Abrasive wear tests were carried out on the samples using the pin-on-disc wear test. The tests were carried out under restricted values of speed, load and time. Within this limit, the hardened sample displayed a superior wear resistance, while the annealed sample displayed the weakest wear resistance. A graphical model (wear map displaying all the wear regimes of the alloy, which may serve as a wear predictive tool was subsequently developed from the results of the wear tests. With the exception of the as-cast and annealed specimen, all other specimens (hardened and tempered have functioned adequately in wear prone environment, but with different degree of effectiveness. Hence, the hardened and tempered samples can be used in shot blast equipments and in the grinding of minerals.

  3. Dynamic SEM wear studies of tungsten carbide cermets. [friction and wear experiments

    Science.gov (United States)

    Brainard, W. A.; Buckley, D. H.

    1975-01-01

    Dynamic friction and wear experiments were conducted in a scanning electron microscope. The wear behavior of pure tungsten carbide and composite with 6 and 15 weight percent cobalt binder was examined, and etching of the binder was done to selectively determine the role of the binder in the wear process. Dynamic experiments were conducted as the tungsten carbide (WC) and bonded WC cermet surfaces were transversed by a 50 micron radiused diamond stylus. These studies show that the predominant wear process in WC is fracture initiated by plastic deformation, and the wear of the etched cermets is similar to pure WC. The presence of the cobalt binder reduces both friction and wear. The cementing action of the cobalt reduces granular separation, and promotes a dense polished layer because of its low shear strength film-forming properties. The wear debris generated from unetched surface is approximately the same composition as the bulk.

  4. Adhesive Wear of Rollers in Vacuum

    Science.gov (United States)

    Shaeef, Iqbal; Krantz, Timothy L.

    2012-01-01

    This work was done to support NASA's James Webb Space Telescope that is equipped with a Near Infrared Camera and Spectrograph and Micro Shutter Assembly (MSA). A MSA mechanism's qualification test in cryogenic vacuum at 30deg K for 96K cycles resulted in roller wear and formation of some debris. Lab tests in vacuum were conducted at NASA Glenn Research Center (GRC) to understand the wear of Ti6Al4V mated with 440F steel rollers. Misalignment angle was found to have the most significant effect on debris formation. At misalignment angle of 1.4deg, significant amount of wear debris were formed within 50,000 cycles. Very few wear particles were found for a zero misalignment angle, and the total wear was small even after 367,000 cycles. The mode of wear in all the tests was attributed to adhesion, which was clearly evident from video records as well as the plate-like amalgamated debris material from both rollers. The adhesive wear rate was found to be approximately proportional to the misalignment angle. The wear is a two-way phenomenon, and the mixing of both roller materials in wear debris was confirmed by x-ray fluorescence (XRF) and EDX spectra. While there was a net loss of mass from the steel rollers, XRF and energy dispersive x-ray (EDX) spectra showed peaks of Ti on steel rollers, and peaks of Fe on Ti rollers. These results are useful for designers in terms of maintaining appropriate tolerances to avoid misalignment of rolling elements and the resulting severe wear

  5. Energetic aspects of boring tools wear

    Directory of Open Access Journals (Sweden)

    Lazarová Edita

    2002-03-01

    Full Text Available In the process of rock desintegration a boring tool is subjected to the wear. From a viewpoint of the bit wear, changes on the contact of operating tool with rock at its one-shot and rerun load or overload by external forces are technically significant. Theis change results in the degradation of bit working properties and the output of desintegration also decreases. In the major part of cases, together with the bit wear, the contact area of a tool with a rock massifs enhanced and this fact causes an increase of fines (dust creation during the desintegration. The wear is always connected with a friction, forces action, deformation, damage, and the increased mechanical work consumption. As to energetic aspects of bit wear, the wear was observed as a function of bore length and in the most of cases as a dependence of the operating time. A linear dependence between the wear intensity (bit wear per unit of bore length and the specific energy of desintegration (energy consumed per volume unit of desintegrated rock was experimentally verified. Thus, the changes of bit wear can be implicitly observed by monitoring the specific energy. At the same time, the specific energy is a function of input parameters of the desintegration process and in the field of applicable external forces it shows an extreme (minimum. Therefore, the specific energy is useful for the extreme optimisation of the rock desintegration process from the viewpoint of the bit wear. It was mathematically proven that the tool output at the desintegration exponentially decreases with the amount of work consumed in the rock desintegration. The derivation of this knowledge comes out from the Krendelev equation.

  6. Development of Fuzzy Logic Tool to predict Wear Rate in Aluminum Composite

    Science.gov (United States)

    Prabha, Rajesh; Raja, Dhas. J. Edwin

    2017-10-01

    Industrial automation is the need of the hour. Success and failure of automation depends on the selection and efficient utilization of soft computing tools such as artificial neural network, expert systems, and fuzzy logic. This article explores the idea of constructing a fuzzy logic model to predict wear rate of fabricated composites under predetermined conditions of input variables such as applied load, sliding velocity and distance travelled. Taguchi design of experiments is employed for experimentation. 27 sets of experiments are performed by varying the parameters of applied load, sliding velocity and distance travelled. Experiment is repeated for average values of wear rate are measured to reduce experimental error. Matlab toolbox functions are used to build the model. Confirmatory experiments are done and the results are measured in terms of accuracy and time. It is found that the developed model predicts wear rate with acceptable limit. Hence the constructed model can be forwarded to predict wear rate of the developed composite under different conditions.

  7. Dynamic and kinematic effects in the friction and wear of rubber

    Science.gov (United States)

    Gerrard, David Peter

    Research is presented which focuses on the micro-mechanical processes that dominate the friction and wear of rubber. New test concepts and equipment were developed to study the dynamic and kinematic effects involved in these processes. Several new analytical tools were presented to explain the observed results in quantifiable terms. Experiments conducted on filled NR confirmed that a transition in wear behavior does not occur across a wide range of power inputs. Examination of the debris distributions across the contact revealed that an agglomeration process of intrinsic particles occurs, the extent of which is purely a function of distance from the contact's leading edge. This revelation is used to explain the commonly reported bimodal size distribution of debris generated during rubber wear and to expose the mechanical process that generates intrinsic debris as the primary cause of wear. The effect of contact length (i.e. extent of agglomeration) on corresponding friction and wear levels was studied. The effects of dynamically changing slip orientation on the properties of a coated abrasive and the friction and wear of a filled SBR were studied. The process of removal of intrinsic debris from a rubber surface was described in terms of a micro-mechanical fatigue fracture process that occurs at varying rates that are dependent on the frictional work acting on the average intrinsic nodule. The model was successfully tested against previously published data and new data and was shown to account for pressure and abrasive effects with one set of two constants. The potential effects of pattern morphologies on rubber friction and wear were examined as well. The wear patterns showed a clear tendency to roll up as opposed to peeling back. The intrinsic wear model was then applied to a description of pattern wear by assuming that the rate of intrinsic abrasion across a pattern is simply a function of the local pressure distribution which varies from the front to the back

  8. Dynamics Performance and Abrasive Wear of the Automotive Drive Shaft

    Directory of Open Access Journals (Sweden)

    Jian Mao

    2014-06-01

    Full Text Available An automotive drive shaft is used in a front drive transmission vehicle for transmitting rotary movement from the gearbox output shaft to the wheels with a constant velocity. This paper presents the kinematic model of ball joint and tripod joint with consideration of clearance and proposes a simplified dynamics model of the drive shaft. The simulation of the dynamics model is given by the measured data. Also, the abrasive wear of the ball type joint is tested on the experimental setup with consideration of full loading. The results show that the dynamics of the motion will be affected by the clearance when the loading changes its direction. The motion will be stable due to the damping. It can be found that the abrasive wear of ball joint largely depends on the relative sliding velocity from the experiments. This will probably affectthe dynamics performance and the impact force, which will also cause the other type of failures.

  9. Role of plastic deformation in wear of copper and copper - 10-percent-aluminum alloy in cryogenic fuels

    Science.gov (United States)

    Bill, R. C.; Wisander, D. W.

    1973-01-01

    High-purity copper specimens and a copper-aluminum (10%) alloy specimen were subjected to sliding against Type 440 C in cryogenic fuel environments. It was found that virtually all wear occurred by the plastic deformation of a recrystallized layer extending to about 10 micrometers below the wear scar surface of the copper or copper alloy. The wear debris was in the form of a layered structure adhering to the exit region of the wear scar. Measurements on the high purity copper specimens indicated that the wear rate was proportional to the applied load and to the sliding velocity squared. A physical model of the wear process is proposed to account for these observations.

  10. Wear Monitoring in Turning Operations Using Vibration and Strain Measurements

    Science.gov (United States)

    Scheffer, C.; Heyns, P. S.

    2001-11-01

    For the efficient and reliable operation of automated machining processes, the implementation of suitable tool condition monitoring (TCM) strategy is required. Various monitoring systems, utilising sophisticated signal processing techniques, have been widely researched for a number of different processes. Most monitoring systems developed up to date employ force, acoustic emission and vibration, or a combination of these and other techniques with a sensor integration strategy. With this work, the implementation of a monitoring system utilising simultaneous vibration and strain measurements on the tool tip, is investigated for the wear of synthetic diamond tools which are specifically used for the manufacturing of aluminium pistons. Contrary to many of the earlier investigations, this work was conducted in a manufacturing environment, with the associated constraints such as the impracticality of direct measurement of the wear. Data from the manufacturing process was recorded with two piezoelectric strain sensors and an accelerometer, each coupled to a DSPT Siglab analyser. A large number of features indicative of tool wear were automatically extracted from different parts of the original signals. These included features from the time and frequency domains, time-series model coefficients (as features) and features extracted from wavelet packet analysis. A correlation coefficient approach was used to automatically select the best features indicative of the progressive wear of the diamond tools. The self-organising map (SOM) was employed to identify the tool state. The SOM is a type of neural network based on unsupervised learning. A near 100% correct classification of the tool wear data was obtained by training the SOM with two independent data sets, and testing it with a third independent data set.

  11. Effect of Experimental Variables of Abrasive Wear on 3D Surface Roughness and Wear Rate of Al-4.5 % Cu Alloy

    Science.gov (United States)

    Ghosh, Debashis; Mallik, Manab; Mandal, Nilrudra; Dutta, Samik; Roy, Himadri; Lohar, Aditya Kumar

    2017-04-01

    This investigation was primarily carried out to examine the abrasive wear behavior of as cast Al-4.5 % Cu alloy. Wear tests have been carried out using an abrasive wear machine with emery paper embedded with SiC particles acting as abrasive medium. The experiments were planned using central composite design, with, load, cycle and grit size as input variables, whereas wear rate and 3D roughness were considered as output variable. Analysis of variance was applied to check the adequacy of the mathematical model and their respective parameters. Microstructural investigations of the worn surfaces have been carried out to explain the observed results and to understand the wear micro-mechanisms as per the planned experiments. Desirability function optimization technique was finally employed to optimize the controlling factors. The observed results revealed that, grit size plays a significant role in the variation of wear rate and 3D roughness as compared to load and cycles. Based on the significance of interactions, the regression equations were derived and verified further with a number of confirmation runs to assess the adequacy of the model. A close agreement (±10 %) between the predicted and experimentally measured results was obtained from this investigation.

  12. Crystal Orientation Dependence of Gallium Nitride Wear.

    Science.gov (United States)

    Zeng, Guosong; Sun, Wei; Song, Renbo; Tansu, Nelson; Krick, Brandon A

    2017-10-26

    We explore how crystallographic order and orientation affect the tribological (friction and wear) performance of gallium nitride (GaN), through experiments and theory. Friction and wear were measured in every direction on the c-plane of GaN through rotary wear experiment. This revealed a strong crystallographic orientation dependence of the sliding properties of GaN; a 60° periodicity of wear rate and friction coefficient was observed. The origin of this periodicity is rooted in the symmetry presented in wurtzite hexagonal lattice structure of III-nitrides. The lowest wear rate was found as 0.6 × 10 -7 mm 3 /Nm with , while the wear rate associated with had the highest wear rate of 1.4 × 10 -7 mm 3 /Nm. On the contrary, higher friction coefficient can be observed along while lower friction coefficient always appeared along . We developed a simple molecular statics approach to understand energy barriers associated with sliding and material removal; this calculated change of free energy associated with sliding revealed that there were smaller energy barriers sliding along as compared to the direction.

  13. Wear Characteristics of Metallic Biomaterials: A Review

    Directory of Open Access Journals (Sweden)

    Mohamed A. Hussein

    2015-05-01

    Full Text Available Metals are extensively used in a variety of applications in the medical field for internal support and biological tissue replacements, such as joint replacements, dental roots, orthopedic fixation, and stents. The metals and alloys that are primarily used in biomedical applications are stainless steels, Co alloys, and Ti alloys. The service period of a metallic biomaterial is determined by its abrasion and wear resistance. A reduction in the wear resistance of the implant results in the release of incompatible metal ions into the body that loosen the implant. In addition, several reactions may occur because of the deposition of wear debris in tissue. Therefore, developing biomaterials with high wear resistance is critical to ensuring a long life for the biomaterial. The aim of this work is to review the current state of knowledge of the wear of metallic biomaterials and how wear is affected by the material properties and conditions in terms of the type of alloys developed and fabrication processes. We also present a brief evaluation of various experimental test techniques and wear characterization techniques that are used to determine the tribological performance of metallic biomaterials.

  14. Dynamic simulation of a displacement-controlled total knee replacement wear tester.

    Science.gov (United States)

    Lanovaz, J L; Ellis, R E

    2008-07-01

    This paper presents a dynamic finite element method (FEM) model of a commercial displacement-controlled total knee replacement (TKR) wear tester. The first goal of the study was to validate the model, which included both the wear tester and the TKR components. Convergence simulations and experimental testing were performed. These included a novel experimental determination of the coefficient of friction and an evaluation of predicted joint contact areas by comparing simulation results with experimental data collected using pressure-sensitive film. The second goal of this study was to develop a procedure for implementing force-based testing protocols on a displacement-controlled TKR wear tester. A standard force-based cyclic wear-testing protocol was simulated using the FEM model and resulting displacement waveforms were extracted. These were used as control inputs to the physical wear tester and an experimental wear test was performed. Reaction loads on the tibial components were measured and compared with the simulated results. The model was capable of accurately predicting the tibial loads throughout the test cycle, verifying the model's contact mechanics. The study demonstrated the use of computational modelling to convert a force-based testing protocol into displacement-based control parameters for use in a displacement-controlled mechanical testing system.

  15. Fundamentals of friction and wear on the nanoscale

    CERN Document Server

    Gnecco, Enrico

    2014-01-01

    This book provides an updated review on the development of scanning probe microscopy and related techniques, and the availability of computational techniques not even imaginable a few decades ago. The 36 chapters cover instrumental aspects, theoretical models and selected experimental results, thus offering a broad panoramic view on fundamental issues in nanotribology which are currently being investigated. Compared to the first edition, several topics have been added, including triboluminescence, graphene mechanics, friction and wear in liquid environments, capillary condensation, and multisc

  16. Study on torsional fretting wear behavior of a ball-on-socket contact configuration simulating an artificial cervical disk

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Song [State Key Laboratory of Tribology, Tsinghua University, Beijing 100084 (China); Department of Mechanical Engineering, Tsinghua University, Beijing 100084 (China); Wang, Fei [School of Material Science and Engineering, China University of Mining and Technology, Xuzhou 221116 (China); Liao, Zhenhua [Department of Mechanical Engineering, Tsinghua University, Beijing 100084 (China); Biomechanics and Biotechnology Lab, Research Institute of Tsinghua University in Shenzhen, Shenzhen 518057 (China); Wang, Qingliang [School of Material Science and Engineering, China University of Mining and Technology, Xuzhou 221116 (China); Liu, Yuhong [State Key Laboratory of Tribology, Tsinghua University, Beijing 100084 (China); Department of Mechanical Engineering, Tsinghua University, Beijing 100084 (China); Liu, Weiqiang, E-mail: weiqliu@hotmail.com [Biomechanics and Biotechnology Lab, Research Institute of Tsinghua University in Shenzhen, Shenzhen 518057 (China); State Key Laboratory of Tribology, Tsinghua University, Beijing 100084 (China)

    2015-10-01

    A ball-on-socket contact configuration was designed to simulate an artificial cervical disk in structure. UHMWPE (ultra high molecular weight polyethylene) hot pressed by powders and Ti6Al4V alloy were selected as the material combination of ball and socket. The socket surface was coated by a ~ 500 nm C-DLC (carbon ion implantation-diamond like carbon) mixed layer to improve its surface nano hardness and wear resistance. The torsional fretting wear behavior of the ball-on-socket model was tested at different angular displacements under 25% bovine serum lubrication with an axial force of 100 N to obtain more realistic results with that in vivo. The fretting running regimes and wear damage characteristics as well as wear mechanisms for both ball and socket were studied based on 2D (two dimension) optical microscope, SEM (scanning electron microscope) and 3D (three dimension) profiles. With the increase of angular displacement amplitude from 1° to 7°, three types of T-θ (Torsional torque-angular displacement amplitude) curves (i.e., linear, elliptical and parallelogram loops) corresponding to running regimes of PSR (partial slip regime), MR (mixed regime) and SR (slip regime) were observed and analyzed. Both the central region and the edge zone of the ball and socket were damaged. The worn surfaces were characterized by wear scratches and wear debris. In addition, more severe wear damage and more wear debris appeared on the central region of the socket at higher angular displacement amplitude. The dominant damage mechanism was a mix of surface scratch, adhesive wear and abrasive wear for the UHMWPE ball while that for the coated socket was abrasive wear by PE particles and some polishing and rolling process on the raised overgrown DLC grains. The frictional kinetic behavior, wear type, damage region and damage mechanism for the ball-on-socket model revealed significant differences with those of a ball-on-flat contact while showing better consistency with that of in

  17. A Multidirectional Tribo-System: Wear of UHMWPE under Sliding, Rolling, and Rotation

    Science.gov (United States)

    Patten, Elias Wolfgang

    Total knee replacements (TKR) have become a successful surgical procedure for addressing end-stage osteoarthritis, with ultra-high molecular weight polyethylene and cobalt chrome alloy (UHMWPE/Co-Cr) serving as the bearing materials of choice for decades. However, more than 10% of TKRs fail and require revision surgery. The predominant challenge with UHMWPE is the particulate debris generated through wear-mediated processes; wear debris from the UHMWPE tibial bearing surface leading to loosening is still the main cause for post-fifth-year revisions. UHMWPE wear in hip arthroplasty has been linked to microstructural evolution at the surface from multidirectional sliding in the hip joint but little is known about how the microstructure responds to clinically relevant sliding conditions in the knee. This is likely because wear tests are typically performed under basic motion parameters with simplified geometry (pin-on-disk tests) while the knee has more complex kinematics: it is neither a ball-and-socket joint nor a simple hinge joint, but has 2D sliding, rolling/slip motion, and rotation. There is also disagreement over how to best quantify cross-shear and how to model how much wear it will cause. A custom multidirectional tribo-system was used to investigate the individual and combined effects of the different motions in TKR: 2D sliding, rolling, and rotation, for a total of eight separate kinematic conditions. The trends in wear rates and wear factors for these different motions were compared with many different definitions for magnitudes and ratios of cross-shear. Additionally, the wear surfaces were examined for wear mechanism and the microstructural changes in lamellae orientation for the different motions were analyzed. To mimic the tribological conditions of a condyle in a TKR, polished Co-Cr spheres were articulated against flat, smooth UHMWPE disks with physiologically relevant loading, speed, and lubrication conditions. The motion parameters were selected

  18. How Chronic Fatigue Syndrome Wears Patients Out

    Science.gov (United States)

    ... https://medlineplus.gov/news/fullstory_167452.html How Chronic Fatigue Syndrome Wears Patients Out Study suggests body amplifies fatigue ... what it's like for those who struggle with chronic fatigue syndrome, and researchers suggest in a new report that ...

  19. Wear and repair of stainless steel crowns

    National Research Council Canada - National Science Library

    Yilmaz, Y; Kara, N Belduz; Yilmaz, A; Sahin, H

    2011-01-01

    The purpose of this study was to determine the wear of stainless steel crowns (SSCs) in children, and compare the extent of microleakage in SSCs that had been repaired using either a cermet glass-ionomer cement...

  20. Implant wear mechanisms-basic approach

    Energy Technology Data Exchange (ETDEWEB)

    Bhatt, Himanshu; Goswami, Tarun [Department of Biomedical, Industrial and Human Factors Engineering, Wright State University, Dayton, OH 45435 (United States)

    2008-12-15

    Numerous parameters control the long-term performance of a total hip joint arthroplasty. The articulating motions between the femoral and the acetabular components produce wear debris in a hip implant. Surface roughness, clearance, coefficient of friction and sliding distance are found to be contributing parameters that affect wear rates. Wear produced in a hip implant leads to the loosening of a hip prosthesis and thus failure of the hip implant. Ultra-high-molecular-weight polyethylene (UHMWPE) has been successfully used as an acetabular weight bearing component in the THR applications. Cross-linked UHMWPE was found to improve the lifespan of an artificial hip. A gradient cross-linking of UHMWPE has been observed to be a recent development in implant bearing materials. During in vitro studies, gradient cross-linked UHMWPE showed nearly undetectable wear rates. (topical review)

  1. Mammalian dental function and wear: A review

    Directory of Open Access Journals (Sweden)

    Peter S. Ungar

    2015-03-01

    Full Text Available This paper presents a brief synopsis of work on relationships between mammalian tooth form and function, and considers the role of dental wear in studies of mammal teeth. Mammalian teeth function both as guides for chewing and as tools for initiating and propagating cracks through food items. They tend to vary in form and structure with the mechanical properties of foods a species has evolved to eat; and we can learn a lot about relationships between teeth and diet by comparing species. One area of special interest is tooth wear. Dental structure and chemistry combine in ways that lead wear to sculpt occlusal surfaces so a tooth can develop or maintain its functional efficiency. Dental wear, especially that on microscopic scales, can also serve as a proxy for diet in fossil species, as specific types of food leave distinctive patterns.

  2. Prediction of wear rates in comminution equipment

    DEFF Research Database (Denmark)

    Jensen, Lucas Roald Dörig; Fundal, Erling; Møller, Per

    2010-01-01

    Raw material comminution equipment may be exposed to excessive wear, which makes it difficult to operate minerals processing plants continuously because lengthy and unplanned shut-downs interrupt the overall process. In general, most comminution equipment is fine-tuned to operate at low vibrations...... and to achieve guaranteed performance. From an economical point of view, it is always preferred to replace all worn parts during the planned maintenance shutdowns. When operating comminution equipment, the wear rate receives little attention and is considered a secondary matter. However, experience shows......-resistant high chromium white cast iron (21988/JN/HBW555XCr21), a heat-treated wear resistant steel (Hardox 400) and a plain carbon construction steel (S235). Quartz, which accounts for the largest wear loss in the cement industry, was chosen as abrasive. Other process parameters such as velocity (1–7 m...

  3. STUDIES ON TOOL WEAR CONDITION MONITORING

    Directory of Open Access Journals (Sweden)

    Hüseyin Metin ERTUNÇ

    2001-01-01

    Full Text Available In this study, wear mechanisms on cutting tools, especially for the drill bits, during the cutting operation have been investigated. As the importance of full automation in industry has gained substantial importance, tool wear condition monitoring during the cutting operation has been the subject of many investigators. Tool condition monitoring is very crucial in order to change the tool before breakage. Because tool breakage can cause considerable economical damage to both the machine tool and workpiece. In this paper, the studies on the monitoring of drill bit wear in literature have been introduced; the direct/indirect techniques used and sensor fusion techniques have been summarized. The methods which were proposed to determine tool wear evolution as processing the sensor signals collected have been provided and their references have been given for detailed information.

  4. Effect of Wearing Socks, Stockings and Leather Shoe on Shoe Microclimate and Wear Comfort

    OpenAIRE

    三ツ井, 紀子; Michiko, Mitsui

    2001-01-01

    The effects of socks, stockings and leather shoe on wear comfort and microclimate between shoe and skin while exercising has been studied by seven women under laboratory conditions. Temperature and absolute humidity in wearing socks or stockings were higher than barefooted. Further under wearing shoes and socks or stockings they are increased. Temperature and absolute humidity at the measuring point were the highest between the first and the second toes. Inside socks or stockings with shoes a...

  5. Third abrasive wear mode: is it possible?

    Directory of Open Access Journals (Sweden)

    Ronaldo Câmara Cozza

    2014-04-01

    Full Text Available The objective of this paper is to propose an initial discussion on the characterization of a third abrasive wear mode. The results obtained in a previous work [1] under different test conditions revealed the occurrence of the superposition of the “rolling” and “grooving” abrasive wear modes. This phenomenon was denoted “micro-rolling abrasion” due to the observation that “rolling abrasion” was found to act on “grooving abrasion”.

  6. Pseudomembranous candidiasis in patient wearing full denture

    Directory of Open Access Journals (Sweden)

    Nurdiana Nurdiana

    2009-06-01

    Full Text Available Background: Oral candidiasis is a common opportunistic infection of the oral cavity caused by an overgrowth of Candida species, the commonest being Candida albicans. Candida albicans is a harmless commensal organism inhabiting the mouths but it can change into pathogen and invade tissue and cause acute and chronic disease. Dentures predispose to infection with Candida in as many as 65% of elderly people wearing full upper dentures. Purpose: The purpose of this case report is to discuss thrush in patient wearing full denture which rapidly developed. Case: This paper report a case of 57 year-old man who came to the Oral Medicine Clinic Faculty of Dentistry Airlangga University with clinical appearance of pseudomembranous candidiasis (thrush. Case Management: Diagnosis of this case is confirmed with microbiology examination. Patient was wearing full upper dentures, and from anamnesis known that patient wearing denture for 24 hours and he had poor oral hygiene. Patient was treated with topical (nystatin oral suspension and miconazole oral gel and systemic (ketoconazole antifungal. Patient also instructed not to wear his denture and cleaned white pseudomembrane on his mouth with soft toothbrush. Conclusion: Denture, habit of wearing denture for 24 hours, and poor oral hygiene are predisposing factors of thrush and it can healed completely after treated with topical and systemic antifungal.

  7. Effect of post weld heat treatment on wear resistance of hot forging cast steel die coated with surfacing layer

    Directory of Open Access Journals (Sweden)

    Xu Wujiao

    2015-01-01

    Full Text Available The wear resistance capability of die surfacing layer under different Post Weld Heat Treatments (PWHT was analysed by Finite Element Method (FEM simulation and experiments. Taking the hot forging process of crankshaft as example, a wear model of hot forging die coated with surfacing layer was established by the software DEFORM-3D. The simulation results indicate that the wear resistance capability of the die surfacing layer is optimal when tempering temperature and holding time are 550 ∘C and 4h respectively. To verify the wear calculation result, 16 groups of different PWHT orthogonal wear tests were performed under atmospheric condition at 400 ∘C. The wear test result shows a good agreement with the FEM simulation result. SEM observation of the wear debris shows that oxidative wear plays a dominant role in 400 ∘C among 16 specimens. Furthermore, when tempering temperature and holding time are 550 ∘C and 4h respectively, the alloy carbide dispersively distributes in the metallographic structure, which can improve the wear resistance of the surfacing.

  8. Effect of post-welding heat treatment on wear resistance of cast-steel die with surfacing layer

    Directory of Open Access Journals (Sweden)

    Xu Wujiao

    2015-01-01

    Full Text Available The wear resistance capability of die surfacing layer under different Post-Welding Heat Treatments (PWHT was analysed by Finite Element (FE simulation and experiments. Taking hot forging process of a crankshaft as an example, a wear model of the hot forging die coated with surfacing layer was established using FE software DEFORM-3D. The simulation results indicated that the wear resistance capability of the die surfacing layer is optimal when tempering temperature and holding time are 550 °C and 4 h respectively. To verify the wear computational results, 16 groups of PWHT orthogonal wear tests were performed at a temperature of 400 °C, which is a similar temperature to that occurs in an actual hot forging die. The wear-test result showed a good agreement with the FE simulation. SEM observation of the wear debris on 16 specimens showed that oxidative wear is dominant when the temperature was in 400 °C. Furthermore, when tempering temperature and holding time were 550 °C and 4 h respectively, the carbide alloy dispersively distributes in the metallographic structure, which helps to improve the wear resistance of the surfacing layer.

  9. Development and Performance Evaluation of an Abrasive Wear ...

    African Journals Online (AJOL)

    The wear of tillage tools is a major source of economic constraints to local farmers. Estimating wear in the field is time consuming and expensive. Abrasive wear testing machines developed in advanced countries are not available in Ghana. This makes the study of wear related problems at laboratory levels difficult in the ...

  10. Detection and Monitoring of Wear Using Imaging Methods

    NARCIS (Netherlands)

    Zhang, Jindang

    2006-01-01

    Wear is traditionally measured offline. A new methodology for online detection and monitoring of wear has been investigated in this thesis. This methodology consists of design of an online wear testing apparatus and development of techniques for online wear detection and monitoring using imaging

  11. The role of oxidation in the fretting wear process

    Science.gov (United States)

    Bill, R. C.

    1980-01-01

    Fretting experiments were conducted on titanium, a series of Ni-Cr-Al alloys and on some high temperature turbine alloys at room temperature and at elevated temperatures in air and in various inert environments. It was found that, depending on temperature and environment, the fretting behavior of the materials examined could be classified according to four general types of behavior. Briefly, these types of behavior were: (1) the complete absence of oxidation, as in inert environments, generally leading to low rates of fretting wear but high fretting friction; (2) gradual attrition of surface oxide with each fretting stroke, found in these experiments to operate in concert with other dominating mechanisms; (3) rapid oxidation at surface fatigue damage sites, resulting in undermining and rapid disintegration of the load bearing surface; and (4) the formation of coherent, protective oxide film, resulting in low rates of fretting wear. An analytical model predicting conditions favorable to the fourth type of behavior was outlined.

  12. An industrial tool wear monitoring system for interrupted turning

    Science.gov (United States)

    Scheffer, C.; Heyns, P. S.

    2004-09-01

    An effective wear-monitoring system for machine tool inserts could yield significant cost savings for manufacturers. Over the years, various methods have been proposed to achieve tool condition monitoring (TCM), and recently sensor-based approaches for indirectly estimating tool wear have become highly popular. One difficulty with collecting sensory information from machine tools is that the signal-to-noise ratio of useful information about the tool wear is extremely poor. This problem can be overcome by using advanced signal-processing methods and also by fusing the information obtained from numerous sensors into a single modelling or decision-making scheme such as neural networks (NNs). Neural networks are known for their capacity to solve problems effectively in cases where theoretical/analytical models cannot be established. Furthermore, NNs can handle noisy and incomplete data such as that typically obtained from machining operations. Although numerous authors have proposed the NN approach for TCM, various problems still hamper a practical method of applying the technique for industrial use. This paper proposes a technique which should overcome these difficulties. A cost-effective and reliable tool condition monitoring system (TCMS) was developed, utilising the advantages of NNs for a typical industrial machining operation. The operation considered is interrupted turning (facing and boring) of Aluminium alloy components for the automotive industry. The development and implementation of various hardware and software components for the proposed technique are described in this paper. The main advantages of the technique are its accuracy, reliability and cost-effectiveness.

  13. Wear-resistance of Aluminum Matrix Microcomposite Materials

    Directory of Open Access Journals (Sweden)

    M. Kandeva

    2011-03-01

    Full Text Available A procedure is developed for the study of wear of aluminum alloys AlSi7 obtained by casting, reinforced by TiC microparticles, before and after heat treatment. Tribological study is realized under conditions of friction on counterbody with fixed abrasive. Experimental results were obtained for mass wear, wear rate, wear intensity and wear-resistance of the alloys with different wt% of microparticles.

  14. Non-compliance in contact lens wear.

    Science.gov (United States)

    Claydon, B E; Efron, N

    1994-10-01

    Non-compliance is emerging as a critical issue in the contact lens field. This problem has been studied at depth in general health care situations and is seen as the responsibility of both practitioner and patient (client) working in a health care partnership. The contact lens practitioner and patient present a specific case for the study of non-compliance in areas such as hygiene, solution use, appointment attendance and wearing times. From 40 to 91% of contact lens patients have been reported as non-complaint in the use of recommended care and maintenance regimens and many of these are confused or ignorant about their behaviour. In order to arrive at a general set of conclusions from the studies published to date, it is important to understand the methodology of each study, it purpose, the definition of non-compliance used and the way the results were analysed and described. This review summarizes the research into non-compliance in the contact lens field to data. A set of general conclusions is drawn and a model for compliance in the context of contact lens practice is proposed.

  15. Wear Response of Aluminium 6061 Composite Reinforced with Red Mud at Elevated Temperature

    Directory of Open Access Journals (Sweden)

    R. Dabral

    2017-09-01

    Full Text Available The present work is focused on the investigations on dry sliding wear behaviour of aluminium metal matrix composite at room and elevated temperature. Aluminium metal matrix composites reinforced with red mud are prepared by stir casting method. The experiments are planned using Taguchi technique. An orthogonal array, analysis of variance and signal to noise ratio are used to check the influence of wear parameters like temperature, percentage of reinforcement, mesh size, load, sliding distance and sliding speed on dry sliding wear of composites. The optimal testing parameters are found and their values are calculated which are then compared with predicted values. A reasonable agreement is found between predicted and actual values. The model prepared in the present work can be effectively used to predict the specific wear rate of the composites.

  16. An approach to understanding tribological behaviour of dental composites through volumetric wear loss and wear mechanism determination; beyond material ranking.

    Science.gov (United States)

    Altaie, Asmaa; Bubb, Nigel L; Franklin, Paul; Dowling, Adam H; Fleming, Garry J P; Wood, David J

    2017-04-01

    To investigate the fundamental wear mechanisms of six resin-based composite (RBC) formulations during short-term in vitro wear testing. RBC materials were condensed into rectangular bar-shaped specimens and light irradiated using the ISO 4049 specimen manufacture and irradiation protocol. Wear testing (n=10 specimens for each RBC) was performed on a modified pin-on-plate wear test apparatus and wear facets were analysed for wear volume loss using a white light profilometer. The wear tested RBC specimens and their corresponding antagonists were analysed using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS), respectively to determine the wear mechanism. Data generated using the profilometer showed variations in the mean total wear volume (mm(3)) between the RBCs tested (psystem rather than relying on a simple wear ranking for the RBC materials as is routinely the case in dental research studies. Copyright © 2017 Elsevier Ltd. All rights reserved.

  17. Wear calculation possibility of slide-friction pair "shaft-plain bearing" for four-stroke engines

    Science.gov (United States)

    Springis, Guntis; Rudzitis, Janis; Avisane, Anita; Kumermanis, Maris

    2013-12-01

    The issues of the service life and its prediction for main four stroke engine parts such as shaft-plain bearing have always been of particular importance. The article determines the most suitable mathematical calculation model allowing considering the set of parameters needed for the slide-friction pair's calculation, thus achieving a result as precise as possible. Since the wear process is variable and many-sided it is influenced by very many different parameters, for example, the surface geometry (roughness, waviness, form deviation, etc.), the physical and mechanical conditions of the upper layer, component material, wear regime, wear temperature, etc. The offered wear calculation model taking into consideration as much as possible wear affecting parameters is based on the fatigue theory regularities of the friction surface's destroying, using the approach of probability theory.

  18. Patient compliance during contact lens wear: perceptions, awareness, and behavior.

    Science.gov (United States)

    Bui, Thai H; Cavanagh, H Dwight; Robertson, Danielle M

    2010-11-01

    Patient noncompliance with recommended hygienic practices in contact lens wear is often considered a significant risk factor for microbial keratitis and adverse contact lens-related events. Despite advancements in lens materials and care solutions, noncompliant behavior continues to hinder efforts to maximize contact lens safety. The objective of this pilot study was to assess the relationship between perceived and actual compliance with awareness of risk and behavior. One hundred sixty-two established contact lens wearers were sequentially evaluated after their routine contact lens examination at the Optometry Clinic at the University of Texas Southwestern Medical Center at Dallas, TX. Each patient was questioned by a single trained interviewer regarding his or her lens care practices and knowledge of risk factors associated with lens wear. Eighty-six percent of patients believed they were compliant with lens wear and care practices; 14% identified themselves as noncompliant. Using a scoring model, 32% demonstrated good compliance, 44% exhibited average compliance, and 24% were noncompliant; age was a significant factor (P = 0.020). Only 34% of patients who perceived themselves as compliant exhibited a good level of compliance (Plens case was the only behavior associated with a positive history for having experienced a prior contact lens-related complication (P = 0.002). Perceived compliance is not an indicator for appropriate patient behavior. A large proportion of patients remain noncompliant despite awareness of risk. Education alone is not a sufficient strategy to improve behavior; newer approaches aimed at improving compliance with lens care practices are urgently needed.

  19. Artificial Neural Networks for the Prediction of Wear Properties of Al6061-TiO2 Composites

    Science.gov (United States)

    Veeresh Kumar, G. B.; Pramod, R.; Shivakumar Gouda, P. S.; Rao, C. S. P.

    2017-08-01

    The exceptional performance of composite materials in comparison with the monolithic materials have been extensively studied by researchers. Among the metal matrix composites Aluminium matrix based composites have displayed superior mechanical properties. The aluminium 6061 alloy has been used in aeronautical and automotive components, but their resistance against the wear is poor. To enhance the wear properties, Titanium dioxide (TiO2) particulates have been used as reinforcements. In the present investigation Back propagation (BP) technique has been adopted for Artificial Neural Network [ANN] modelling. The wear experimentations were carried out on a pin-on-disc wear monitoring apparatus. For conduction of wear tests ASTM G99 was adopted. Experimental design was carried out using Taguchi L27 orthogonal array. The sliding distance, weight percentage of the reinforcement material and applied load have a substantial influence on the height damage due to wear of the Al6061 and Al6061-TiO2 filled composites. The Al6061 with 3 wt% TiO2 composite displayed an excellent wear resistance in comparison with other composites investigated. A non-linear relationship between density, applied load, weight percentage of reinforcement, sliding distance and height decrease due to wear has been established using an artificial neural network. A good agreement has been observed between experimental and ANN model predicted results.

  20. Conjunctival epithelial flap in continuous contact lens wear.

    Science.gov (United States)

    Graham, Andrew D; Truong, Tan N; Lin, Meng C

    2009-04-01

    Composed of sheets of cells detached from the underlying conjunctiva, conjunctival epithelial flap (CEF) is a recently reported phenomenon associated with contact lens wear with potential consequences for ocular health. Although CEF is generally asymptomatic, it is not known to what extent it might increase the longer-term risk of discomfort, inflammatory response, or infection. In this study, we use survival analysis methods to obtain unbiased estimates of the probability of developing CEF, the mean survival time free of CEF, and the effects of age, gender, ethnicity, and contact lens type. Two hundred four subjects were recruited for a continuous wear (CW) study of silicone hydrogel (SiH) and gas permeable (GP) contact lenses. Subjects were examined by optometrists throughout contact lens adaptation and CW periods. Statistical methods included the Kaplan-Meier nonparametric estimator of the survival function and the Cox proportional hazards model for estimating the relative effects of covariates. Of the 204 subjects, 72 (35%) developed CEF. In 64% of cases, CEFs were observed bilaterally. The majority of cases (90.3%) presented with CEF in the superior conjunctiva. Mean survival time free of CEF was longer for GP lenses (94.3 days) than for SiH lenses (76.5 days), and the probability of developing CEF was significantly greater for SiH lenses (p = 0.002). Although there was some evidence that women and non-Asians remain free of CEF longer, the effects of age, gender, and ethnicity were not statistically significant. There was a significantly increased risk of CEF in subjects wearing SiH lenses, compared with GP lenses. Subjects wearing SiH lenses remained free of CEF for a shorter time on average. Further study is needed to determine whether the increased incidence of CEF in CW with SiH lenses poses an increased risk of adverse ocular response or infection.

  1. Incisor wear and age in Yellowstone bison

    Science.gov (United States)

    Christianson, D.A.; Gogan, P.J.P.; Podruzny, K.M.; Olexa, E.M.

    2005-01-01

    Biologists commonly use tooth eruption and wear patterns or cementum annuli techniques to estimate age of ungulates. However, in some situations the accuracy or sampling procedures of either approach are undesirable. We investigated the progression of several quantitative measures of wear with age, using permanent first incisors from Yellowstone bison (Bison bison), and tested for differences between sexes and herds. We further investigated the relationship of wear and age to explore an age-estimation method. Labial-lingual width (LLW) correlated best with assigned age (r2=0.66, males; r2=0.76 females). Labial-lingual width differed between sexes, with females showing ∼0.2 mm more wear than males. Additionally, differences in rate of wear existed between bison of the northern and central Yellowstone herds (1.2 and 0.9 mm/year, respectively). We developed a regression formula to test the power of LLW as an estimator of Yellowstone bison age. Our method provided estimated ages within 1 year of the assigned age 73% and 82% of the time for female and male bison, respectively.

  2. Investigation on wear characteristic of biopolymer gear

    Science.gov (United States)

    Ghazali, Wafiuddin Bin Md; Daing Idris, Daing Mohamad Nafiz Bin; Sofian, Azizul Helmi Bin; Basrawi, Mohamad Firdaus bin; Khalil Ibrahim, Thamir

    2017-10-01

    Polymer is widely used in many mechanical components such as gear. With the world going to a more green and sustainable environment, polymers which are bio based are being recognized as a replacement for conventional polymers based on fossil fuel. The use of biopolymer in mechanical components especially gear have not been fully explored yet. This research focuses on biopolymer for spur gear and whether the conventional method to investigate wear characteristic is applicable. The spur gears are produced by injection moulding and tested on several speeds using a custom test equipment. The wear formation such as tooth fracture, tooth deformation, debris and weight loss was observed on the biopolymer spur gear. It was noted that the biopolymer gear wear mechanism was similar with other type of polymer spur gears. It also undergoes stages of wear which are; running in, linear and rapid. It can be said that the wear mechanism of biopolymer spur gear is comparable to fossil fuel based polymer spur gear, thus it can be considered to replace polymer gears in suitable applications.

  3. Dental Wear: A Scanning Electron Microscope Study

    Directory of Open Access Journals (Sweden)

    Luca Levrini

    2014-01-01

    Full Text Available Dental wear can be differentiated into different types on the basis of morphological and etiological factors. The present research was carried out on twelve extracted human teeth with dental wear (three teeth showing each type of wear: erosion, attrition, abrasion, and abfraction studied by scanning electron microscopy (SEM. The study aimed, through analysis of the macro- and micromorphological features of the lesions (considering the enamel, dentin, enamel prisms, dentinal tubules, and pulp, to clarify the different clinical and diagnostic presentations of dental wear and their possible significance. Our results, which confirm current knowledge, provide a complete overview of the distinctive morphology of each lesion type. It is important to identify the type of dental wear lesion in order to recognize the contributing etiological factors and, consequently, identify other more complex, nondental disorders (such as gastroesophageal reflux, eating disorders. It is clear that each type of lesion has a specific morphology and mechanism, and further clinical studies are needed to clarify the etiological processes, particularly those underlying the onset of abfraction.

  4. Influence of polygonal wear of railway wheels on the wheel set axle stress

    Science.gov (United States)

    Wu, Xingwen; Chi, Maoru; Wu, Pingbo

    2015-11-01

    The coupled vehicle/track dynamic model with the flexible wheel set was developed to investigate the effects of polygonal wear on the dynamic stresses of the wheel set axle. In the model, the railway vehicle was modelled by the rigid multibody dynamics. The wheel set was established by the finite element method to analyse the high-frequency oscillation and dynamic stress of wheel set axle induced by the polygonal wear based on the modal stress recovery method. The slab track model was taken into account in which the rail was described by the Timoshenko beam and the three-dimensional solid finite element was employed to establish the concrete slab. Furthermore, the modal superposition method was adopted to calculate the dynamic response of the track. The wheel/rail normal forces and the tangent forces were, respectively, determined by the Hertz nonlinear contact theory and the Shen-Hedrick-Elkins model. Using the coupled vehicle/track dynamic model, the dynamic stresses of wheel set axle with consideration of the ideal polygonal wear and measured polygonal wear were investigated. The results show that the amplitude of wheel/rail normal forces and the dynamic stress of wheel set axle increase as the vehicle speeds rise. Moreover, the impact loads induced by the polygonal wear could excite the resonance of wheel set axle. In the resonance region, the amplitude of the dynamic stress for the wheel set axle would increase considerably comparing with the normal conditions.

  5. The interactions between attrition, abrasion and erosion in tooth wear.

    Science.gov (United States)

    Shellis, R Peter; Addy, Martin

    2014-01-01

    Tooth wear is the result of three processes: abrasion (wear produced by interaction between teeth and other materials), attrition (wear through tooth-tooth contact) and erosion (dissolution of hard tissue by acidic substances). A further process (abfraction) might potentiate wear by abrasion and/or erosion. Knowledge of these tooth wear processes and their interactions is reviewed. Both clinical and experimental observations show that individual wear mechanisms rarely act alone but interact with each other. The most important interaction is the potentiation of abrasion by erosive damage to the dental hard tissues. This interaction seems to be the major factor in occlusal and cervical wear. The available evidence is insufficient to establish whether abfraction is an important contributor to tooth wear in vivo. Saliva can modulate erosive/abrasive tooth wear, especially through formation of pellicle, but cannot prevent it. © 2014 S. Karger AG, Basel.

  6. Temperature effect on IG-11 graphite wear performance

    Energy Technology Data Exchange (ETDEWEB)

    Luo Xiaowei [Institute of Nuclear Energy and New Energy Technology, Tsinghua University, Beijing 100084 (China)]. E-mail: xwluo@mail.tsnghua.edu.cn; Yu Suyuan [Institute of Nuclear Energy and New Energy Technology, Tsinghua University, Beijing 100084 (China); Sheng Xuanyu [Institute of Nuclear Energy and New Energy Technology, Tsinghua University, Beijing 100084 (China); He Shuyan [Institute of Nuclear Energy and New Energy Technology, Tsinghua University, Beijing 100084 (China)

    2005-10-01

    IG-11 graphite, used in the 10 MW high temperature gas-cooled test reactor (HTR-10), was tested under different temperatures on an SRV standard wear performance tester. The experiment temperatures were room temperature, 100, 200, 300 and 400 deg C. According to the reactor structure, the experiments were designed to test graphite-graphite and graphite-stainless steel wear. The wear debris was collected, and the worn surfaces and debris were observed under scanning electronic microscope (SEM). It was found that there were different wear mechanisms at different temperatures. The main wear mechanism at room temperature was abrasive wear; at 200 deg C, it was fatigue wear; at 400 deg C, adhesive wear was observed. This difference was mainly due to the change of stress distribution at the contact area. The distribution of wear debris was also analyzed by EDX particle analysis software.

  7. Friction and Wear Processes – Thermodynamic Approach

    Directory of Open Access Journals (Sweden)

    M. Banjac

    2014-12-01

    Full Text Available Tribology, as the scientific and professional discipline within the mechanical engineering, studies phenomena and processes on the interacting surfaces, in direct and indirect contact and in relative motion. It includes the study and application of the principles of friction, wear and lubrication, as well as phenomena connected with these processes. Given that a process involving friction is always accompanied by transformation of energy, more precisely an energy dissipation process which generates entropy, the concept of thermodynamic entropy production analysis represents one of appropriate tools for studying and analysing the behaviour of complex friction and wear processes. This paper presents a review of published works in which the thermodynamic approach was used in analysing the friction and wear processes in tribosystems.

  8. Adhesion and wear resistance of materials

    Science.gov (United States)

    Buckley, D. H.

    1986-01-01

    Recent studies into the nature of bonding at the interface between two solids in contact or a solid and deposited film have provided a better understanding of those properties important to the adhesive wear resistance of materials. Analytical and experimental progress are reviewed. For simple metal systems the adhesive bond forces are related to electronic wave function overlap. With metals in contact with nonmetals, molecular-orbital energy, and density of states, respectively can provide insight into adhesion and wear. Experimental results are presented which correlate adhesive forces measured between solids and the electronic surface structures. Orientation, surface reconstruction, surface segregation, adsorption are all shown to influence adhesive interfacial strength. The interrelationship between adhesion and the wear of the various materials as well as the life of coatings applied to substrates are discussed. Metallic systems addressed include simple metals and alloys and these materials in contact with themselves, both oxide and nonoxide ceramics, diamond, polymers, and inorganic coating compounds, h as diamondlike carbon.

  9. Wear Resistant Amorphous and Nanocomposite Coatings

    Energy Technology Data Exchange (ETDEWEB)

    Racek, O

    2008-03-26

    Glass forming materials (critical cooling rate <10{sup 4}K.s{sup -1}) are promising for their high corrosion and wear resistance. During rapid cooling, the materials form an amorphous structure that transforms to nanocrystalline during a process of devitrification. High hardness (HV 1690) can be achieved through a controlled crystallization. Thermal spray process has been used to apply coatings, which preserves the amorphous/nanocomposite structure due to a high cooling rate of the feedstock particles during the impact on a substrate. Wear properties have been studied with respect to process conditions and feedstock material properties. Application specific properties such as sliding wear resistance have been correlated with laboratory tests based on instrumented indentation and scratch tests.

  10. Epoxy matrix composites filled with micro-sized LD sludge: wear characterization and analysis

    Science.gov (United States)

    Purohit, Abhilash; Satapathy, Alok

    2016-02-01

    Owing to the very high cost of conventional filler materials in polymer composites, exploring the possibility of using low cost minerals and industrial wastes for this purpose has become the need of the hour. In view of this, the present work includes the development and the wear performance evaluation of a new class of composites consisting of epoxy and microsized LD sludge. LD sludge or the Linz-Donawitz Sludge (LDS) are the fine solid particles recovered after wet cleaning of the gas emerging from LD convertors during steel making. Epoxy composites filled with different proportions (0, 5, 10, 15 and 20 wt %) of LDS are fabricated by conventional hand lay-up technique. Dry sliding wear trials are performed on the composite specimens under different test conditions as per ASTM G 99 following a design of experiment approach based on Taguchi's orthogonal arrays. The Taguchi approach leads to the recognition of most powerful variables that predominantly control the wear rate. This parametric analysis reveals that LDS content and sliding velocity affects the specific wear rate more significantly than normal load and sliding distance. Furthermore with increase in LDS content specific wear rate of the composite decreases for a constant sliding velocity. The sliding wear behavior of these composites under an extended range of test conditions is predicted by a model based on the artificial neural network (ANN).

  11. Surface engineering for enhanced performance against wear

    CERN Document Server

    2013-01-01

    Surface Engineering constitutes a variety of processes and sub processes. Each chapter of this work covers specific processes by experts working in the area. Included for each topic are tribological performances for each process as well as results of recent research. The reader also will benefit from in-depth studies of diffusion coatings, nanocomposite films for wear resistance, surfaces for biotribological applications, thin-film wear, tribology of thermal sprayed coatings, hardfacing, plating for tribology and high energy beam surface modifications. Material scientists as well as engineers working with surface engineering for tribology will be particularly interested in this work.

  12. Wear Analysis of Wind Turbine Gearbox Bearings

    Energy Technology Data Exchange (ETDEWEB)

    Blau, Peter Julian [ORNL; Walker, Larry R [ORNL; Xu, Hanbing [ORNL; Parten, Randy J [ORNL; Qu, Jun [ORNL; Geer, Tom [ORNL

    2010-04-01

    The objective of this effort was to investigate and characterize the nature of surface damage and wear to wind turbine gearbox bearings returned from service in the field. Bearings were supplied for examination by S. Butterfield and J. Johnson of the National Wind Technology Center (NREL), Boulder, Colorado. Studies consisted of visual examination, optical and electron microscopy, dimensional measurements of wear-induced macro-scale and micro-scale features, measurements of macro- and micro-scale hardness, 3D imaging of surface damage, studies of elemental distributions on fracture surfaces, and examinations of polished cross-sections of surfaces under various etched and non-etched conditions.

  13. The effect of microstructure on abrasive wear of steel

    Science.gov (United States)

    Kešner, A.; Chotëborský, R.; Linda, M.

    2017-09-01

    Abrasive wear of agricultural tools is one of the biggest problems in currently being. The amount of abrasive wear, depending on the microstructure, has been investigated in this work. Steels 25CrMo4 and 51CrV4 were used in this work to determine the effect of the microstructure on the abrasive wear. These steels are commonly used for components that have to withstand abrasive wear.SEM analysis was used to detect the microstructure. The standardized ASTM G65 method was used to compare the abrasive wear of steels. The results show that the abrasive wear depends on the microstructure of steels.

  14. Effects of Load and Speed on Wear Rate of Abrasive Wear for 2014 Al Alloy

    Science.gov (United States)

    Odabas, D.

    2018-01-01

    In this paper, the effects of the normal load and sliding speed on wear rate of two-body abrasive wear for 2014 Al Alloy were investigated in detail. In order to understand the variation in wear behaviour with load and speed, wear tests were carried out at a sliding distance of 11 m, a speed of 0.36 m/s, a duration of 30 s and loads in the range 3-11 N using 220 grit abrasive paper, and at a speed range 0.09-0.90 m/s, a load of 5 N and an average sliding distance of 11 m using abrasive papers of 150 grit size under dry friction conditions. Before the wear tests, solution treatment of the 2014 Al alloy was carried out at temperatures of 505 and 520 °C for 1 h in a muffle furnace and then quenched in cold water at 15 °C. Later, the ageing treatment was carried out at 185 °C for 8 h in the furnace. Generally, wear rate due to time increased linearly and linear wear resistance decreased with increasing loads. However, the wear rate was directly proportional to the load up to a critical load of 7 N. After this load, the slope of the curves decreased because the excessive deformation of the worn surface and the instability of the abrasive grains began to increase. When the load on an abrasive grain reaches a critical value, the groove width is about 0.17 of the abrasive grain diameter, and the abrasive grains begin to fail. The wear rate due to time increased slightly as the sliding speed increased in the range 0.09-0.90 m/s. The reason for this is that changes arising from strain rate and friction heating are expected with increasing sliding speeds.

  15. Intelligent wear mode identification system for marine diesel engines based on multi-level belief rule base methodology

    Science.gov (United States)

    Yan, Xinping; Xu, Xiaojian; Sheng, Chenxing; Yuan, Chengqing; Li, Zhixiong

    2018-01-01

    Wear faults are among the chief causes of main-engine damage, significantly influencing the secure and economical operation of ships. It is difficult for engineers to utilize multi-source information to identify wear modes, so an intelligent wear mode identification model needs to be developed to assist engineers in diagnosing wear faults in diesel engines. For this purpose, a multi-level belief rule base (BBRB) system is proposed in this paper. The BBRB system consists of two-level belief rule bases, and the 2D and 3D characteristics of wear particles are used as antecedent attributes on each level. Quantitative and qualitative wear information with uncertainties can be processed simultaneously by the BBRB system. In order to enhance the efficiency of the BBRB, the silhouette value is adopted to determine referential points and the fuzzy c-means clustering algorithm is used to transform input wear information into belief degrees. In addition, the initial parameters of the BBRB system are constructed on the basis of expert-domain knowledge and then optimized by the genetic algorithm to ensure the robustness of the system. To verify the validity of the BBRB system, experimental data acquired from real-world diesel engines are analyzed. Five-fold cross-validation is conducted on the experimental data and the BBRB is compared with the other four models in the cross-validation. In addition, a verification dataset containing different wear particles is used to highlight the effectiveness of the BBRB system in wear mode identification. The verification results demonstrate that the proposed BBRB is effective and efficient for wear mode identification with better performance and stability than competing systems.

  16. Study on Rail Profile Optimization Based on the Nonlinear Relationship between Profile and Wear Rate

    Directory of Open Access Journals (Sweden)

    Jianxi Wang

    2017-01-01

    Full Text Available This paper proposes a rail profile optimization method that takes account of wear rate within design cycle so as to minimize rail wear at the curve in heavy haul railway and extend the service life of rail. Taking rail wear rate as the object function, the vertical coordinate of rail profile at range optimization as independent variable, and the geometric characteristics and grinding depth of rail profile as constraint conditions, the support vector machine regression theory was used to fit the nonlinear relationship between rail profile and its wear rate. Then, the profile optimization model was built. Based on the optimization principle of genetic algorithm, the profile optimization model was solved to achieve the optimal rail profile. A multibody dynamics model was used to check the dynamic performance of carriage running on optimal rail profile. The result showed that the average relative error of support vector machine regression model remained less than 10% after a number of training processes. The dynamic performance of carriage running on optimized rail profile met the requirements on safety index and stability. The wear rate of optimized profile was lower than that of standard profile by 5.8%; the allowable carrying gross weight increased by 12.7%.

  17. Sliding wear of conventional and nanostructured cemented carbides

    Energy Technology Data Exchange (ETDEWEB)

    Jia, K. [Stevens Inst. of Tech., Hoboken, NJ (United States). Dept. of Materials Science and Engineering; Fischer, T.E. [Stevens Inst. of Tech., Hoboken, NJ (United States). Dept. of Materials Science and Engineering

    1997-03-01

    The sliding wear mechanisms of cemented carbide and the effects of the microstructure scale on the wear resistance were investigated by performing a series of unlubricated sliding wear tests in air with pins of WC-Co composites sliding against silicon nitride disks. In the first approximation, the wear rate is proportional to the hardness with a wear coefficient k=6.9x10{sup -6} for all materials. In the conventional cermets, the wear coefficient k also depends on the grain size; materials with smaller WC grains exhibit a smaller wear resistance. This reduction, however, does not extend to the nanostructured materials which exhibit the above value for k: Their wear resistance is higher than that of conventional cermets in proportion to their hardness. The data can also be expressed in terms of cobalt content: The lower the cobalt content, the lower the wear; but two different such dependencies exist, one for the conventional and one for the nanostructured materials with lower wear. The sliding wear of WC-Co composites occurs on a very small scale: The worn surfaces show no evidence of fracture of plastic deformation. This wear behavior is explained by the hexagonal structure and the anisotropic mechanical behavior of the WC grains that are capable of shear in a limited number of planes but are not capable of triaxial deformation. The higher wear resistance of the nanostructured composites is related to their hardness which decreases the real area of contact. (orig.)

  18. Assessments of Hollow Cathode Wear in the Xenon Ion Propulsion System (XIPs(c)) by Numerical Analyses and Wear Tests

    Science.gov (United States)

    Mikellides, Ioannis G.; Katz, Ira; Goebel, Dan M.; Polk, James E.

    2008-01-01

    The standard approach presently followed by NASA to qualify electric propulsion for the required mission throughput has been based largely on life tests, which can be costly and time consuming. Revised electric propulsion lifequalification approaches are being formulated that combine analytical and/or computational methods with (shorter-duration) wear tests. As a model case, a wear test is being performed at JPL to assess the lifetime of the discharge hollow cathode in the Xenon Ion Propulsion System (XIPS(c)), a 25-cm ion engine developed by L-3 Communications Electron Technologies, Inc. for commercial applications. Wear and plasma data accumulated throughout this life-assessment program are being used to validate the existing 2-D hollow cathode code OrCa2D. We find that the OrCa2D steady-state solution predicts very well the time-averaged plasma data and the keeper voltage after 5500 hrs of operation in high-power mode. When the wave motion that occurs naturally in these devices is accounted for, based on an estimate of the maximum wave amplitude, the molybdenum-keeper erosion profile observed in the XIPS(c) discharge cathode is also reproduced within a factor of two of the observation. When the same model is applied to predict the erosion of a tantalum keeper we find that erosion is reduced by more than two orders of magnitude compared to the molybdenum keeper due the significantly lower sputtering yield of tantalum. A tantalum keeper would therefore allow keeper lifetimes that greatly exceed the present requirements for deep-space robotic missions considered by NASA. Moreover, such large reduction of the erosion renders the largest uncertainties in the models, which are associated with the wave amplitude estimates and the electron transport model, negligible.

  19. Healthy Contact Lens Wear and Care

    Centers for Disease Control (CDC) Podcasts

    2014-02-04

    In this podcast, CDC’s Dr. Jennifer Cope explains some basic steps for proper wear and care of soft contact lenses.  Created: 2/4/2014 by National Center for Emerging and Zoonotic Infectious Diseases (NCEZID).   Date Released: 2/4/2014.

  20. Friction measurement in a hip wear simulator.

    Science.gov (United States)

    Saikko, Vesa

    2016-05-01

    A torque measurement system was added to a widely used hip wear simulator, the biaxial rocking motion device. With the rotary transducer, the frictional torque about the drive axis of the biaxial rocking motion mechanism was measured. The principle of measuring the torque about the vertical axis above the prosthetic joint, used earlier in commercial biaxial rocking motion simulators, was shown to sense only a minor part of the total frictional torque. With the present method, the total frictional torque of the prosthetic hip was measured. This was shown to consist of the torques about the vertical axis above the joint and about the leaning axis. Femoral heads made from different materials were run against conventional and crosslinked polyethylene acetabular cups in serum lubrication. Regarding the femoral head material and the type of polyethylene, there were no categorical differences in frictional torque with the exception of zirconia heads, with which the lowest values were obtained. Diamond-like carbon coating of the CoCr femoral head did not reduce friction. The friction factor was found to always decrease with increasing load. High wear could increase the frictional torque by 75%. With the present system, friction can be continuously recorded during long wear tests, so the effect of wear on friction with different prosthetic hips can be evaluated. © IMechE 2016.

  1. Illumination methods for optical wear detection

    NARCIS (Netherlands)

    Zhang, Jindang; Regtien, Paulus P.L.

    2007-01-01

    The paper presents some results of a study on optical wear detection. The focus of the paper is on the illumination, to optimize the contrast of the images. Various illumination methods are compared: bright field versus dark field illumination, and various kind of light sources: laser light, diffuse

  2. Tribology: Friction, lubrication, and wear technology

    Science.gov (United States)

    Blau, Peter J.

    1993-06-01

    The topics are presented in viewgraph form and include the following: introduction and definitions of terms; friction concepts; lubrication technology concepts; wear technology concepts; and tribological transitions. This document is designed for educators who seek to teach these concepts to their students.

  3. Childhood intelligence and early tooth wear patterns.

    Science.gov (United States)

    Heikkinen, Tuomo; Rusanen, Jaana; Sato, Koshi; Pesonen, Paula; Harila, Virpi; Alvesalo, Lassi

    2017-02-20

    The aim of this study is to explore the relationships between early dental wear patterns and preschool IQ (Intelligence Quotient, by Stanford-Binet) of the child to illuminate the historic relationship of mental queries and bruxism. The dental study participants were 864 Euro-American preschool and school children whose IQs were tested for school maturity purposes at the age of 4 years, followed by dental data in a cross-sectional manner at the mean age of 7.8 years. Worn dentitions were classified as "symmetric" or "right-" and "left-sided," based on the faceting of the teeth. In general, the relationships of tooth wear and intelligence were scarce, reflecting social background factors. Statistically significant results between asymmetric wear and gender groups suggest that direction of jaw function has a role in the regulation of processes responsible for individual mental performance in childhood. Increased left-side tooth wear and early advantage in the intelligence test in girls is intriguing due to the fact that they reach maturity earlier than boys in verbal articulation, controlled in most cases by the limited area on the left side of the brain.

  4. ERRATUM: Work smart, wear your hard hat

    CERN Multimedia

    2003-01-01

    An error appeared in the article «Work smart, wear your hard hat» published in Weekly Bulletin 27/2003, page 5. The impact which pierced a hole in the hard hat worn by Gerd Fetchenhauer was the equivalent of a box weighing 5 kg and not 50 kg.

  5. Saliva Parameters and Erosive Wear in Adolescents

    NARCIS (Netherlands)

    Zwier, N.; Huysmans, M. C. D. N. J. M.; Jager, D. H. J.; Ruben, J.; Bronkhorst, E. M.; Truin, G. J.

    2013-01-01

    The aim of this study was to investigate the relationship between several parameters of saliva and erosive wear in adolescents. (Un-)stimulated saliva was collected from 88 adolescents with erosion and 49 controls (age 16 +/- 1 years). Flow rate, pH and buffer capacity were determined immediately.

  6. Tribology: Friction, lubrication, and wear technology

    Science.gov (United States)

    Blau, Peter J.

    1993-01-01

    The topics are presented in viewgraph form and include the following: introduction and definitions of terms; friction concepts; lubrication technology concepts; wear technology concepts; and tribological transitions. This document is designed for educators who seek to teach these concepts to their students.

  7. A quasi-stationary approach to particle concentration and distribution in gear oil for wear mode estimation

    DEFF Research Database (Denmark)

    Henneberg, Morten; Eriksen, René Lynge; Jørgensen, Bent

    2015-01-01

    Suspension of wear particles in gear oil with respect to the diversity of particle size combined with filter mechanisms has been analyzed. Coupling of wear modes from tribology is combined with particle size bins to show how a mathematical model can be expanded to include information gained from...... sensors that can segment particles into size bins. In order to establish boundary conditions for the model based on real data, a filtration test is included. Finally, the model is fitted to data from a gear in operation and differences between real data and the model are discussed. The findings show...... that particles less than 14 μm dominate the wear. Hence, it is concluded that abrasion dominate the wear, for the gear in operation, and it is concluded to be in quasi-stationary mode. The distribution of the particles is observed in conjunction with the particle quantity to determine a basis for normal...

  8. Instagram Shows How Diabetics Really Wear a Glucose Monitor

    Science.gov (United States)

    ... page: https://medlineplus.gov/news/fullstory_167648.html Instagram Shows How Diabetics Really Wear a Glucose Monitor ... and her colleagues searched the social media site Instagram. They found 353 posts featuring people wearing Dexcom ...

  9. Comparison of two measurement techniques for clinical wear

    DEFF Research Database (Denmark)

    Peters, M C; Delong, R; Pintado, M R

    1999-01-01

    Clinical wear of restorations is generally evaluated by marginal integrity over time. In this study, both a subjective and an objective method for wear assessment are compared, and the relative advantages and disadvantages of each are considered....

  10. Study on the tool wear of 3-D elliptical vibration cutting

    Directory of Open Access Journals (Sweden)

    J. Lin

    2017-07-01

    Full Text Available As always, the rapid wear of tools was one of the key factors limiting the precise turning of difficult-to-machine materials with diamond tool. 3-D elliptical vibration cutting has inherited many advantages of elliptical vibration cutting, such as the intermittent cutting property and friction reverse property. However, studies on the tool wear of three-dimensional elliptical vibration cutting has not been reported yet. The formation principle of 3-D cutting elliptical trajectory was analysed and a prediction model of tool wear was established in the present work. Besides, a self-developed three-dimensional elliptical vibration device was employed to conduct turning experiment. Compared with the proposed model, the experimental results showed a great agreement with the proposed prediction model. This work may provide a reference for the further optimization of the 3-D elliptical vibration cutting parameters.

  11. Nanoclay-Reinforced Glass-Ionomer Cements: In Vitro Wear Evaluation and Comparison by Two Wear-Test Methods

    Directory of Open Access Journals (Sweden)

    Muhammad A. Fareed

    2017-10-01

    Full Text Available Glass ionomer cement (GIC represents a major transformation in restorative dentistry. Wear of dental restoratives is a common phenomenon and the determination of the wear resistance of direct-restorative materials is a challenging task. The aim of this paper was to evaluate the wear resistance of novel glass ionomer cement by two wear-test methods and to compare the two wear methods.The wear resistance of a conventional glass ionomer cement (HiFi Advanced Health Care Kent, UK and cements modified by including various percentages of nanoclays (1, 2 and 4 wt % was measured by a reciprocating wear test (ball-on-flat and Oregon Health and Sciences University’s (OHSU wear simulator. The OHSU wear simulation subjected the cement specimens to three wear mechanisms, namely abrasion, three-body abrasion and attrition using a steatite antagonist. The abrasion wear resulted in material loss from GIC specimen as the steatite antagonist forced through the exposed glass particles when it travelled along the sliding path.The hardness of specimens was measured by the Vickers hardness test. The results of reciprocation wear test showed that HiFi-1 resulted in the lowest wear volume 4.90 (0.60 mm3 (p < 0.05, but there was no significant difference (p > 0.05 in the wear volume in comparison to HiFi, HiFi-2 and HiFi-4. Similarly, the results of OHSU wear simulator showed that the total wear volume of HiFi-4 1.49 (0.24 was higher than HiFi-1 and HiFi-2. However, no significant difference (p > 0.05 was found in the OHSU total wear volume in GICs after nanoclay incorporation. The Vickers hardness (HV of the nanoclay-reinforced cements was measured between 62 and 89 HV. Nanoclay addition at a higher concentration (4% resulted in higher wear volume and wear depth. The total wear volumes were less dependent upon abrasion volume and attrition volume. The total wear depths were strongly influenced by attrition depth and to some extent by abrasion depth. The addition of

  12. Characterization of patients who report compliant and non-compliant overnight wear of soft contact lenses.

    Science.gov (United States)

    Jansen, Meredith E; Chalmers, Robin; Mitchell, G Lynn; Kinoshita, Beth T; Lam, Dawn Y; McMahon, Timothy T; Richdale, Kathryn; Sorbara, Luigina; Wagner, Heidi

    2011-10-01

    To describe compliant and non-compliant overnight wear (EW) of soft contact lenses from a large observational study. A retrospective chart review of 3211 SCL patients with known EW status (aged 8-33yrs, SCL power +8.00 to -12.00D) captured data from 10,516 clinical visits (2006-2009). Status of EW was either daily wear (DW), compliant EW (overnight wear of US Food & Drug Administration (US FDA) EW-approved lenses), non-compliant EW (overnight wear of DW-approved lenses). The effect of demographic and clinical characteristics on the likelihood of reporting EW was examined using logistic regression. Additionally, the effect of these same characteristics on the likelihood of non-compliant EW was assessed with logistic models. Eight-hundred and eight patients (25.2%) reported EW. Non-compliant EW was reported by 6% of wearers (13 hydrogel, 2 silicone hydrogel brands) In multivariate models, patient age and lens replacement schedule were significant factors for EW (vs. DW) and for non-compliant (vs. compliant) EW (pgender, smoking, lens material, sphere power, and years of CL wear (p≤0.007, all). Young people (ages 18-25yrs), males, smokers, myopes, silicone hydrogel lens wearers and patients with >1yr of CL wear were significantly more likely to report EW. Non-compliant EW occurred often in young people and daily disposable wearers, though many brands had non-compliant EW use. Understanding who is likely to wear EW and non-compliant EW will help clinicians pointedly counsel patients more at risk on best practices with EW. Copyright © 2011 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.

  13. Tooth wear pattern analysis in a sample of Italian Early Bronze Age population. Proposal of a 3-D sampling sequence.

    Science.gov (United States)

    Masotti, Sabrina; Bogdanic, Nika; Arnaud, Julie; Cervellati, Franco; Gualdi-Russo, Emanuela

    2017-02-01

    The purpose of this study was to assess the prevalence, distribution and intensity of tooth wear in a sample of an ancient Italian population in order to explain the pattern in terms of dietary habits and/or non-dietary tooth-use behaviors during the Early Bronze Age, with a focus on possible age-group and sex differences. Well-preserved permanent teeth of individuals from the Bronze Age site of Ballabio (Lecco) in northern Italy were examined for tooth wear by different methods. Eight 3D models of teeth at increasing severity of wear were created. In total, 357 permanent teeth belonging to male and female individuals were included in the study. Dental wear was present in 96.6% of the total sample. Males showed significantly greater levels of wear than females in the mandibular teeth. Both sexes exhibited a significantly different wear direction between the anterior (oblique and flat) and posterior (oblique and concave) teeth. Significant age differences were observed in the direction and level of wear in the incisors, canines and premolars, with higher wear in the older group. Complete and rotatable virtual 3D images of different wear patterns are proposed. The findings of the present study confirm the data from archaeological studies on this site and on northern Italian habits during the Early Bronze Age suggesting a diet rich in vegetables. The observed wear patterns can be related both to the diet of this Bronze age population, based on hard and abrasive food requiring vigorous mastication, and to sex differences in cultural practices. Copyright © 2016 Elsevier Ltd. All rights reserved.

  14. Measurement and Evaluation of Wear Frogs Switches ŽSR

    Directory of Open Access Journals (Sweden)

    Urda Ján

    2014-05-01

    Full Text Available This paper deals with the measurement and evaluation of wear frogs switches ZSR. One of the main problems is the oversize wear. The possibilities analysis of this problem is offered through a set of switches and monitoring of selected parameters. One of these parameters is also monitoring the vertical wear

  15. 46 CFR 169.825 - Wearing of safety belts.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 7 2010-10-01 2010-10-01 false Wearing of safety belts. 169.825 Section 169.825 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) NAUTICAL SCHOOLS SAILING SCHOOL VESSELS Operations § 169.825 Wearing of safety belts. The master of each vessel shall ensure that each person wears...

  16. EXPERIMENTAL INVESTIGATION OF EROSIVE WEAR ON THE HIGH CHROME CAST IRON IMPELLER OF SLURRY DISPOSAL PUMP USING RESPONSE SURFACE METHODOLOGY

    Directory of Open Access Journals (Sweden)

    Jasbir Singh Ratol

    2012-07-01

    Full Text Available Erosive wear occurs on the impeller and volute casing of the slurry disposal pump due to the impact of the ash particles on the impeller with a high velocity. Due to erosive wear, pump life become very short. The service life of centrifugal pump, handling slurry can be increased by reducing the erosive wear. In the present work, the experimental investigation of erosive wear has been carried out on the high speed slurry erosion tester to understand the effects of the ash concentration in slurry, rotational speed of the pump impeller and ash particle size on erosive wear. The erosive wear behaviour of high chrome cast iron was investigated by Response surface methodology (RSM. Analysis of variance (ANOVA was used for statistical analysis and the modeled values for the response were obtained with the help of modeled equation. The result shows that the ash concentration in slurry and kinetic energy of the moving particles highly contributes to erosive wear of pump impeller as compared to the ash particle size.

  17. Experimental Investigation of Erosive Wear on the High Chrome Cast Iron Impeller of Slurry Disposal Pump Using Response Surface Methodology

    Directory of Open Access Journals (Sweden)

    Sunil Kumar

    2012-05-01

    Full Text Available Erosive wear occurs on the impeller and volute casing of the slurry disposal pump due to the impact of the ash particles on the impeller with a high velocity. Due to erosive wear, pump life become very short. The service life of centrifugal pump, handling slurry can be increased by reducing the erosive wear. In the present work, the experimental investigation of erosive wear has been carried out on the high speed slurry erosion tester to understand the effects of the ash concentration in slurry, rotational speed of the pump impeller and ash particle size on erosive wear. The erosive wear behavior of high chrome cast iron was investigated by Response surface methodology (RSM. Analysis of variance (ANOVA was used for statistical analysis and the modeled values for the response were obtained with the help of modeled equation. The result shows that the ash concentration in slurry and kinetic energy of the moving particles highly contributes to erosive wear of pump impeller as compared to the ash particle size.

  18. Correlation between vibration amplitude and tool wear in turning: Numerical and experimental analysis

    Directory of Open Access Journals (Sweden)

    Balla Srinivasa Prasad

    2017-02-01

    Full Text Available In this paper, a correlation between vibration amplitude and tool wear when in dry turning of AISI 4140 steel using uncoated carbide insert DNMA 432 is analyzed via experiments and finite element simulations. 3D Finite element simulations results are utilized to predict the evolution of cutting forces, vibration displacement amplitudes and tool wear in vibration induced turning. In the present paper, the primary concern is to find the relative vibration and tool wear with the variation of process parameters. These changes lead to accelerated tool wear and even breakage. The cutting forces in the feed direction are also predicted and compared with the experimental trends. A laser Doppler vibrometer is used to detect vibration amplitudes and the usage of Kistler 9272 dynamometer for recording the cutting forces during the cutting process is well demonstrated. A sincere effort is put to investigate the influence of spindle speed, feed rate, depth of cut on vibration amplitude and tool flank wear at different levels of workpiece hardness. Empirical models have been developed using second order polynomial equations for correlating the interaction and higher order influences of various process parameters. Analysis of variance (ANOVA is carried out to identify the significant factors that are affecting the vibration amplitude and tool flank wear. Response surface methodology (RSM is implemented to investigate the progression of flank wear and displacement amplitude based on experimental data. While measuring the displacement amplitude, R-square values for experimental and numerical methods are 98.6 and 97.8. Based on the R-square values of ANOVA it is found that the numerical values show good agreement with the experimental values and are helpful in estimating displacement amplitude. In the case of predicting the tool wear, R-square values were found to be 97.69 and 96.08, respectively for numerical and experimental measures while determining the tool

  19. Enhanced computational prediction of polyethylene wear in hip joints by incorporating cross-shear and contact pressure in additional to load and sliding distance: effect of head diameter.

    Science.gov (United States)

    Kang, Lu; Galvin, Alison L; Fisher, John; Jin, Zhongmin

    2009-05-11

    A new definition of the experimental wear factor was established and reported as a function of cross-shear motion and contact pressure using a multi-directional pin-on-plate wear testing machine for conventional polyethylene in the present study. An independent computational wear model was developed by incorporating the cross-shear motion and contact pressure-dependent wear factor into the Archard's law, in additional to load and sliding distance. The computational prediction of wear volume was directly compared with a simulator testing of a polyethylene hip joint with a 28 mm diameter. The effect of increasing the femoral head size was subsequently considered and was shown to increase wear, as a result of increased sliding distance and reduced contact pressure.

  20. Correlation between microstructure and wear behavior of AZX915 Mg-alloy reinforced with 12 wt% TiC particles by stir-casting process

    Directory of Open Access Journals (Sweden)

    Nagaraj M. Chelliah

    2016-12-01

    Full Text Available The present work concerns with correlation between microstructure and wear behavior of AZX915 Mg-alloy reinforced with 12 wt% of TiC particles by stir-casting process. Dry sliding tests were performed under ambient environment by using a pin-on-disc (EN8 steel configuration with a normal load of 50 N at a constant sliding speed of 2.50 ms−1. While as-cast composite experienced delamination wear, heat treated composite suffered from delamination and oxidation wear during dry sliding contact. Moreover, the heat treated composite exhibited lower friction and higher wear rate as compared to the as-cast composite. Friction and wear behavior were correlated with microstructures based on the concept of oxidation tendency and crack nucleation/propagation. Further, a schematic model has been proposed illustrating wear mechanisms from the point of view of subsurface microstructural evolution of the AZX915-TiCp composite.

  1. Effect of Heat Treatment on the Hardness and Wear of Grinding Balls

    Science.gov (United States)

    Aissat, Sahraoui; Sadeddine, Abdelhamid; Bradai, Mohand Amokrane; Younes, Rassim; Bilek, Ali; Benabbas, Abderrahim

    2017-09-01

    The effect quenching and tempering by different regimes on Rockwell hardness and wear processes of grinding balls 50 and 70 mm in diameter made of two melts of chromium-molybdenum cast iron is studied. The heating temperature for quenching is 850, 950, and 1050°C; the tempering temperature is 250, 400, and 600°C. Iron is analyzed in an electron microscope. Diffraction patterns are obtained. A model of cast iron wear is suggested and compared to the Davis model and to experimental results. An optimum heat treatment regime is proposed.

  2. Is tooth wear in the primary dentition predictive of tooth wear in the permanent dentition? Report from a longitudinal study.

    LENUS (Irish Health Repository)

    Harding, M A

    2010-03-01

    To determine the prevalence of tooth wear in the permanent dentition of a sample of 12-year-old school children and establish whether an association exists between tooth wear recorded now and tooth wear recorded in their primary dentition at age five.

  3. Multi-objective optimization of swash plate forging process parameters for the die wear/service life improvement

    Science.gov (United States)

    Hu, X. F.; Wang, L. G.; Wu, H.; Liu, S. S.

    2017-12-01

    For the forging process of the swash plate, the author designed a kind of multi-index orthogonal experiment. Based on the Archard wear model, the influences of billet temperature, die temperature, forming speed, top die hardness and friction coefficient on forming load and die wear were numerically simulated by DEFORM software. Through the analysis of experimental results, the best forging process parameters were optimized and determined, which could effectively reduce the die wear and prolong the die service life. It is significant to increase the practical production of enterprise, especially to reduce the production cost and to promote enterprise profit.

  4. Dental wear estimation using a digital intra-oral optical scanner and an automated 3D computer vision method.

    Science.gov (United States)

    Meireles, Agnes Batista; Vieira, Antonio Wilson; Corpas, Livia; Vandenberghe, Bart; Bastos, Flavia Souza; Lambrechts, Paul; Campos, Mario Montenegro; Las Casas, Estevam Barbosa de

    2016-01-01

    The objective of this work was to propose an automated and direct process to grade tooth wear intra-orally. Eight extracted teeth were etched with acid for different times to produce wear and scanned with an intra-oral optical scanner. Computer vision algorithms were used for alignment and comparison among models. Wear volume was estimated and visual scoring was achieved to determine reliability. Results demonstrated that it is possible to directly detect submillimeter differences in teeth surfaces with an automated method with results similar to those obtained by direct visual inspection. The investigated method proved to be reliable for comparison of measurements over time.

  5. Non-compliance with contact lens wear and care practices: a comparative analysis.

    Science.gov (United States)

    Robertson, Danielle M; Cavanagh, H Dwight

    2011-12-01

    To compare the effects of existing patient awareness of lens-related complications and underlying risk factors on actual patient behavior during contact lens wear and care practices in two different clinical study populations. Established contact lens wearers (n = 281) completed an anonymous written questionnaire on presenting to their habitual eye care practitioner in the Dallas-Fort Worth metroplex. Data were analyzed and compared against a second study population, which comprised established contact lens wearers (n = 152) who were sequentially evaluated after their routine contact lens examination at the University of Texas Southwestern Medical Center at Dallas, TX (UTSW). All patients were questioned regarding his or her lens care practices and knowledge of complications and risk factors associated with contact lens wear. Fifty-eight percent of patients in the general community could identify by name a complication associated with lens wear compared with 91% within the medical center. The most frequent complications reported were related to comfort and handling (72%, Dallas-Fort Worth) and infection (47%, UTSW). The majority of patients could correctly identify risk factors associated with lens-related complications; awareness for topping-off solutions, tap water exposure, and hygiene varied between groups. Overall, 85% of patients perceived themselves as compliant with their lens wear and care practices. Using a standard scoring model to determine actual compliance, 2% of patients demonstrated good compliance; however, only 0.4% of patients were fully compliant with contact lens wear and care practices. The data reveal some study bias in complication and risk awareness between populations; however, despite this limitation, a significant proportion of patients exhibited actual non-compliant behavior despite acknowledged awareness of risk. Although most patients consider themselves to be complying with standard practitioner guidelines for lens wear and care

  6. Spectacle-wear compliance in school children in Concepción Chile.

    Science.gov (United States)

    von-Bischhoffshausen, Fernando Barria; Muñoz, Beatriz; Riquelme, Ana; Ormeño, Maria Jose; Silva, Juan Carlos

    2014-12-01

    Although international policies promote programs for correction of refractive errors in school children, recent studies report low compliance with respect to spectacle wear. Our aim was to assess spectacle-wear compliance and identify associated visual factors among children participating in Chile's school spectacle provision program. A total of 270 school children were prescribed spectacles and monitored after 1 year. Visual acuity, refractive error, reasons for not wearing spectacles, and self-reported visual function were assessed. Compliance is reported as the proportion of children wearing spectacles at the 1-year visit. Factors associated with compliance and reasons for not wearing spectacles were examined using contingency table analyses. Logistic models were constructed to assess independently associated factors. Only 204 children (76%) participated in the 1-year follow-up. Mean age was 10 years (range 4-19 years); 58% were girls, 42% boys. Overall compliance was 58%. Spectacle use was independently associated with age and refractive error. Older children were less likely to be compliant (odds ratio, OR, 0.8, 95% confidence interval, CI, 0.76-0.92/year of increasing age). Compared with children with refractions of -0.75 to +0.75 diopters, both myopic and hyperopic children were more compliant (OR 4.93, 95% CI 2.28-10.67 and OR 2.37, 95% CI 1.06-5.31, respectively). Primary reasons for not wearing spectacles included breakage/loss in younger children, and disliking the appearance in teenagers. We found greater compliance in spectacle wear than that reported in most published studies. Guidelines for provision of children's spectacles should consider excluding children with mild refractive error and improving spectacle quality and appearance.

  7. No compelling positive association between ovarian hormones and wearing red clothing when using multinomial analyses.

    Science.gov (United States)

    Blake, Khandis R; Dixson, Barnaby J W; O'Dean, Siobhan M; Denson, Thomas F

    2017-04-01

    Several studies report that wearing red clothing enhances women's attractiveness and signals sexual proceptivity to men. The associated hypothesis that women will choose to wear red clothing when fertility is highest, however, has received mixed support from empirical studies. One possible cause of these mixed findings may be methodological. The current study aimed to replicate recent findings suggesting a positive association between hormonal profiles associated with high fertility (high estradiol to progesterone ratios) and the likelihood of wearing red. We compared the effect of the estradiol to progesterone ratio on the probability of wearing: red versus non-red (binary logistic regression); red versus neutral, black, blue, green, orange, multi-color, and gray (multinomial logistic regression); and each of these same colors in separate binary models (e.g., green versus non-green). Red versus non-red analyses showed a positive trend between a high estradiol to progesterone ratio and wearing red, but the effect only arose for younger women and was not robust across samples. We found no compelling evidence for ovarian hormones increasing the probability of wearing red in the other analyses. However, we did find that the probability of wearing neutral was positively associated with the estradiol to progesterone ratio, though the effect did not reach conventional levels of statistical significance. Findings suggest that although ovarian hormones may affect younger women's preference for red clothing under some conditions, the effect is not robust when differentiating amongst other colors of clothing. In addition, the effect of ovarian hormones on clothing color preference may not be specific to the color red. Copyright © 2017 Elsevier Inc. All rights reserved.

  8. QUALITY EVALUATION OF THE TPP POWER GENERATING UNITS WEAR RECONDITIONING

    Directory of Open Access Journals (Sweden)

    E. M. Farhadzadeh

    2016-01-01

    Full Text Available Reconditioning of the power generating unit worn equipment and devices is conducted during the scheduled repair period. Quality of wear reconditioning is evaluated by technical state and repair work implementation. Quality of the repair work execution characterizes logistical activities of the power station and the repair services and is rated by a five-grade scale. There are three technical conditions: adequate, subject to reservations, falling short of the technical standard documentation requirements. In practical work these constraints give place to essential ambiguity of the decision. Further to regulating techniques by way of informational support, the authors propose conducting the wear-reconditioning quality evaluation (repair quality accordingly the technical-and-economic indexes pattern of change. The paper recommends applying similarly the fivegrade system in evaluating the power generating unit technical state and distinguishes intolerable, dissatisfactory, fair, good and model estimates. The study demonstrates the assessment criteria dependence on the character of reliability and economical efficiency of performance variation after the repair with increase or decrease of the technical-and-economic indexes in reference to their mean, minimum and maximum values before the repair. The cases ascribed to intolerable quality of the wear reconditioning are those with one or more technical-and-economic indexes that not only failed to improve their values but deteriorated, and at that they became the worst amongst observable values. The model quality estimate of the wear reconditioning is allotted under condition that the power unit technical-and-economic index valuations after the repair not merely improved but also exceeded the best among those under observation. The developed method and algorithm for quality evaluation of the scheduled repair implementation contribute to practical realization of the independent monitoring. This monitoring

  9. Aluminum nanocomposites having wear resistance better than stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    An, Linan [University of Central Florida; Qu, Jun [ORNL; Luo, Jinsong [Chinese Academy of Sciences; Fan, Yi [Chinese Academy of Sciences; Zhang, Ligong [University of Central Florida; Liu, Jinling [University of Central Florida; Xu, Chengying [University of Central Florida; Blau, Peter Julian [ORNL

    2011-01-01

    Tribological behavior of alumina-particle-reinforced aluminum composites made by powder metallurgy process has been investigated. The nanocomposite containing 15 vol% of Al2O3 nanoparticles exhibits excellent wear resistance by showing significantly low wear rate and abrasive wear mode. The wear rate of the nanocomposite is even lower than stainless steel. We have also demonstrated that such excellent wear resistance only occurred in the composite reinforced with the high volume fraction of nanosized reinforcing particles. The results were discussed in terms of the microstructure of the nanocomposite.

  10. Finger wear detection for production line battery tester

    Science.gov (United States)

    Depiante, Eduardo V.

    1997-01-01

    A method for detecting wear in a battery tester probe. The method includes providing a battery tester unit having at least one tester finger, generating a tester signal using the tester fingers and battery tester unit with the signal characteristic of the electrochemical condition of the battery and the tester finger, applying wavelet transformation to the tester signal including computing a mother wavelet to produce finger wear indicator signals, analyzing the signals to create a finger wear index, comparing the wear index for the tester finger with the index for a new tester finger and generating a tester finger signal change signal to indicate achieving a threshold wear change.

  11. Wearing more than one hat?

    DEFF Research Database (Denmark)

    Høgedahl, Laust Kristian; Ibsen, Flemming

    This article investigates the use of collective industrial conflict in the public sector by analysing the Danish teacher lockout in 2013. The social partners in the public sector in Denmark (and the other Scandinavian countries) engage in negotiations and reach agreements regarding wages...... bargaining round and the teacher lockout in 2013. The article shows how the use of collective industrial conflicts in the public sector has a number of built-in systemic flaws, as the public employers are at one and the same time the budgetary authority and legislators. This is not a new finding, however...... and working conditions in accordance with a private model. This also applies to the use of the so-called weapons of conflict – strikes/blockades and lockouts/boycotts – in connection with labour disputes if the involved parties are unable to reach agreement through negotiations or mediation...

  12. Merging Real-Time Channel Sensor Networks with Continental-Scale Hydrologic Models: A Data Assimilation Approach for Improving Accuracy in Flood Depth Predictions

    Directory of Open Access Journals (Sweden)

    Amir Javaheri

    2018-01-01

    Full Text Available This study proposes a framework that (i uses data assimilation as a post processing technique to increase the accuracy of water depth prediction, (ii updates streamflow generated by the National Water Model (NWM, and (iii proposes a scope for updating the initial condition of continental-scale hydrologic models. Predicted flows by the NWM for each stream were converted to the water depth using the Height Above Nearest Drainage (HAND method. The water level measurements from the Iowa Flood Inundation System (a test bed sensor network in this study were converted to water depths and then assimilated into the HAND model using the ensemble Kalman filter (EnKF. The results showed that after assimilating the water depth using the EnKF, for a flood event during 2015, the normalized root mean square error was reduced by 0.50 m (51% for training tributaries. Comparison of the updated modeled water stage values with observations at testing locations showed that the proposed methodology was also effective on the tributaries with no observations. The overall error reduced from 0.89 m to 0.44 m for testing tributaries. The updated depths were then converted to streamflow using rating curves generated by the HAND model. The error between updated flows and observations at United States Geological Survey (USGS station at Squaw Creek decreased by 35%. For future work, updated streamflows could also be used to dynamically update initial conditions in the continental-scale National Water Model.

  13. Exposure and risks from wearing asbestos mitts

    Directory of Open Access Journals (Sweden)

    Tindall Matthew

    2005-10-01

    Full Text Available Abstract Background Very high fibre inhalation exposure has been measured while people were wearing personal protective equipment manufactured from chrysotile asbestos. However, there is little data that relates specifically to wearing asbestos gloves or mitts, particularly when used in hot environments such as those found in glass manufacturing. The aim of this study was to assess the likely personal exposure to asbestos fibres when asbestos mitts were used. Results Three types of work activity were simulated in a small test room with unused mitts and artificially aged mitts. Neither pair of mitts were treated to suppress the dust emission. The measured respirable fibre exposure levels ranged from Conclusion People who wore asbestos mitts were likely to have been exposed to relatively low levels of airborne chrysotile asbestos fibres, certainly much lower than the standards that were accepted in the 1960's and 70's. The cancer risks from this type of use are likely to be very low.

  14. Wear performance of monolithic dental ceramics with different surface treatments.

    Science.gov (United States)

    Preis, Verena; Weiser, Felix; Handel, Gerhard; Rosentritt, Martin

    2013-05-01

    To investigate the two-body wear performance of monolithic dental ceramics with different surface treatments. Standardized specimens (n = 8/ series) were fabricated from three monolithic dental ceramics (experimental translucent zirconia, experimental shaded zirconia, lithium disilicate). Four groups of each material were defined according to clinically relevant surface treatments: polished, polishedground, polished-ground-repolished, glazed. Two-body wear tests with steatite antagonists were performed in a chewing simulator. Surface roughness (R(a)) was controlled, and wear depths of specimens and antagonistic wear areas were calculated in relation to human enamel as reference. Statistical analysis of wear data was carried out using one-way ANOVA and Bonferroni multiple comparison test for post hoc analysis (α = .05). Scanning electron microscopy was applied for evaluating wear performance of ceramics and antagonists. Polished, ground, and repolished zirconia showed no wear, while glaze was abraded. Irrespective of the surface treatment, wear depth of lithium disilicate was significantly (P grinding and glazing. Steatite surfaces were smooth when opposed to polished/ground/repolished zirconia, and ploughed when opposed to glaze and lithium disilicate. Translucent and shaded experimental zirconia yielded superior wear behavior and lower antagonistic wear compared to lithium disilicate. A trend to higher ceramic and antagonistic wear was shown after grinding and glazing.

  15. Wirelessly Interrogated Wear or Temperature Sensors

    Science.gov (United States)

    Woodard, Stanley E.; Taylor, Bryant D.

    2010-01-01

    Sensors for monitoring surface wear and/or temperature without need for wire connections have been developed. Excitation and interrogation of these sensors are accomplished by means of a magnetic-field-response recorder. In a sensor of the present type as in the previously reported ones, the capacitance and, thus, the resonance frequency, varies as a known function of the quantity of interest that one seeks to determine. Hence, the resonance frequency is measured and used to calculate the quantity of interest.

  16. Wear Resistance Assessment of Fluoropolymer Coated Gears

    Directory of Open Access Journals (Sweden)

    Lidia Nedeloni

    2017-11-01

    Full Text Available Power transmissions that incorporate gears dissipate a significant amount of energy and noise. Thus, any improvement in their performance contributes to reducing energy consumption and noise pollution. In recent years, the opportunities offered by conventional technologies to increase gear performance have been fully exploited. Therefore, surface depositions on gear teeth have become increasingly important technologies in achieving objectives such as: improving energy performance, providing greater protection against superficial defects, increasing load capacity and reducing acoustic emissions generated during operation. However, gear coating technologies have begun to be developed, but the investigations are still insufficient. In this study, we carried out wear resistance investigations performed on fluoropolymer coatings for different working speeds, loads and lubrication conditions. The results point out that the deterioration rate of the coating increases with the increase of the working speed and the applied load. In addition, a slight lubrication, applied at the start of testing, leads to a noticeable improvement in wear behaviour. This study represents one step further in understanding the wear process of fluoropolymer coated gears

  17. Corrosion and wear in plasma electrosurgical devices

    Science.gov (United States)

    Gaspredes, J.; Ryan, T. P.; Stalder, K. R.; Woloszko, J.

    2017-02-01

    Data were previously reported on studies of the effects of electrical discharges on the corrosion and wear of simple, single-wire test devices immersed in isotonic saline 1 . This work showed that there are a wide variety of mechanisms that can explain various aspects of electrode mass loss, even with very simple electrode geometries and operating conditions. It was found that the electrode material composition played an important role. Subsequently, our studies were expanded to include more realistic device geometries and operating conditions. This paper shows the results of studies on wear characteristics of electrodes made from a variety of highly corrosion resistant metals and alloys, including Waspaloy, Hastelloy, Inconel, Havar, Monel, and other pure metals such as Hafnium. All of these metals underwent wear testing under clinically relevant conditions. Depending on the operating conditions, multiple discrete physical and chemical effects were observed at different locations on the surface of an individual millimeter-scale device electrode. Scanning electron microscope (SEM) micrographs, Energy-dispersive X-ray spectroscopy (EDS) and area loss data will be presented for a variety of test conditions and electrode materials.

  18. Wear of metal-free resin composite crowns after three years in service.

    Science.gov (United States)

    Zenthöfer, Andreas; Rammelsberg, Peter; Schmitt, Clemens; Ohlmann, Brigitte

    2013-01-01

    To compare differences between the wear behavior of two types of metal-free resin composite crown with a control after three years in clinical service. Sixty-six participants needing one to three posterior single crowns were fitted with 120 crowns. Abutment teeth were randomly assigned to three groups: 40 resin composite crowns with fiber-reinforced framework, 40 resin composite crowns without fiber-reinforced framework, and 40 metal-ceramic crowns. To assess wear, gypsum replicas of the crowns were fabricated and scanned with a 3D laser scanner at baseline and after three years. Differences between the groups were analyzed by use of mixed-effects regression models. Wear of resin composite crowns with fiber-reinforced framework (p=0.0043) and resin composite crowns without framework (p=0.0246) was significantly greater than in the metal-ceramic group. Wear of metal-free resin composite crowns after three years was significantly greater than that of metal-ceramic crowns, but the wear was still clinically acceptable.

  19. The Effect of Wear on the Performance of a Rotary Lip Seal.

    Science.gov (United States)

    Guo, Fei; Jia, Xiaohong; Longke, Wang; Salant, Richard F; Wang, Yuming

    2014-10-01

    Theoretical analysis, combined with experimental verification, is used to study the effect of wear on the performance of a rotary lip seal as characterized by the pumping rate and friction torque. The performance of a rotary lip seal is determined by the sealing lip surface microscopic characteristics and contact characteristics at the sealing zone. The variation of the contact characteristics with wear has been established based on the variation of the sealing lip profiles measured by using a trilinear coordinate measuring instrument. The impression method is used to copy the lip surface microtopography at different wear times and then an optical interferometer is used to measure the impression surface microtopography to obtain the variation of roughness with wear. The variations of the roughness, contact characteristics, and approximate contact temperature with wear are inserted into a mixed lubrication model to obtain the variations of the pumping rate and friction torque. A comparison of the simulated results with those from experimental measurement verifies the validity of the theoretical analysis.

  20. Wear and Life Characteristics of Microwave-Sintered Copper-Graphite Composite

    Science.gov (United States)

    Rajkumar, K.; Aravindan, S.; Kulkarni, M. S.

    2012-11-01

    Copper-graphite composite is an important tribological material used in electrical sliding contact applications like electrical brushes in motors and generators. The electrical sliding contact experiences multiple stresses such as mechanical pressure and temperature. Traditional life tests under normal operating condition would be a time-consuming process due to the longer expected life of the composite. Accelerated wear testing was carried out to evaluate the life characteristics of the composite. This work focuses on evaluation of tribological performance of microwave-sintered copper-graphite composite using accelerated wear testing methodology using high temperature pin-on-disc tribometer. Microstructural studies of worn out surfaces were carried out using SEM with EDAX. Reliability and analysis on life characteristics were performed on the time-to-failure data using temperature-nonthermal-accelerated life-stress model. The obtained times-to-failure data from the accelerated wear testing was extrapolated to normal usage condition. Temperature and pressure are significantly affecting the wear performance. Self-lubricating action of graphite and improvement in wear resistance is helpful in extending the life of copper graphite composite. The life of the composite obtained through testing at mean and 99% reliability are 18,725 and 16,950 h, respectively.

  1. Development of counting system for wear measurements using Thin Layer Activation and the Wearing Apparatus

    Energy Technology Data Exchange (ETDEWEB)

    França, Michel de A.; Suita, Julio C.; Salgado, César M., E-mail: mchldante@gmail.com, E-mail: suita@ien.gov.br, E-mail: otero@ien.gov.br [Instituto de Engenharia Nuclear (IEN/CNEN-RJ), Rio de Janeiro, RJ (Brazil)

    2017-07-01

    This paper focus on developing a counting system for the Wearing Apparatus, which is a device previously built to generate measurable wear on a given surface (Main Source) and to carry the fillings from it to a filter (second source). The Thin Layer Activation is a technique used to produce activity on one of the Wearing Apparatus' piece, this activity is proportional to the amount of material worn, or scrapped, from the piece's surface. Thus, by measuring the activity on those two points it is possible to measure the produced wear. The methodology used in this work is based on simulations through MCNP-X Code to nd the best specifications for shielding, solid angles, detectors dimensions and collimation for the Counting System. By simulating several scenarios, each one different from the other, and analyzing the results in the form of Counts Per Second, the ideal counting system's specifications and geometry to measure the activity in the Main Source and the Filter (second source) is chosen. After that, a set of previously activated stainless steel foils were used to reproduce the real experiments' conditions, this real experiment consists of using TLA and the Wearing Apparatus, the results demonstrate that the counting system and methodology are adequate for such experiments. (author)

  2. A Study of Slipper and Rail Wear Interaction at Low Speed

    Science.gov (United States)

    2014-06-19

    research done by Cinnamon et al.[15]. The JC plasticity parameters and can be found in the tables below. Table 2.1: High Strain Rate Johnson-Cook... extracted from the DADS data. The increment intervals for the 20 m s−1 and 40 m s−1 contact increments are 0.055 s to 0.146 s and 0.148 s to 0.2452 s...66 4.2.3 Model Validation Through Wear Comparison. With a multitude of wear simulations completed and the necessary data extracted , how does this

  3. Flank wears Simulation by using back propagation neural network when cutting hardened H-13 steel in CNC End Milling

    Science.gov (United States)

    Hazza, Muataz Hazza F. Al; Adesta, Erry Y. T.; Riza, Muhammad

    2013-12-01

    High speed milling has many advantages such as higher removal rate and high productivity. However, higher cutting speed increase the flank wear rate and thus reducing the cutting tool life. Therefore estimating and predicting the flank wear length in early stages reduces the risk of unaccepted tooling cost. This research presents a neural network model for predicting and simulating the flank wear in the CNC end milling process. A set of sparse experimental data for finish end milling on AISI H13 at hardness of 48 HRC have been conducted to measure the flank wear length. Then the measured data have been used to train the developed neural network model. Artificial neural network (ANN) was applied to predict the flank wear length. The neural network contains twenty hidden layer with feed forward back propagation hierarchical. The neural network has been designed with MATLAB Neural Network Toolbox. The results show a high correlation between the predicted and the observed flank wear which indicates the validity of the models.

  4. Load application for the contact mechanics analysis and wear prediction of total knee replacement.

    Science.gov (United States)

    Zhang, Jing; Chen, Zhenxian; Wang, Ling; Li, Dichen; Jin, Zhongmin

    2017-05-01

    Tibiofemoral contact forces in total knee replacement have been measured at the medial and lateral sites respectively using an instrumented prosthesis, and predicted from musculoskeletal multibody dynamics models with a reasonable accuracy. However, it is uncommon that the medial and lateral forces are applied separately to replace a total axial load according to the ISO standard in the majority of current finite element analyses. In this study, we quantified the different effects of applying the medial and lateral loads separately versus the traditional total axial load application on contact mechanics and wear prediction of a patient-specific knee prosthesis. The load application position played an important role under the medial-lateral load application. The loading set which produced the closest load distribution to the multibody dynamics model was used to predict the contact mechanics and wear for the prosthesis and compared with the total axial load application. The medial-lateral load distribution using the present method was found to be closer to the multibody dynamics prediction than the traditional total axial load application, and the maximum contact pressure and contact area were consistent with the corresponding load variation. The predicted total volumetric wear rate and area were similar between the two load applications. However, the split of the predicted wear volumes on the medial and the lateral sides was different. The lateral volumetric wear rate was 31.46% smaller than the medial from the traditional load application prediction, while from the medial-lateral load application, the lateral side was only 11.8% smaller than the medial. The medial-lateral load application could provide a new and more accurate method of load application for patient-specific preclinical contact mechanics and wear prediction of knee implants.

  5. Adherence to wearing therapeutic shoes among people with diabetes: a systematic review and reflections

    Directory of Open Access Journals (Sweden)

    Jarl G

    2016-08-01

    Full Text Available Gustav Jarl,1,2 Lars-Olov Lundqvist2 1Department of Prosthetics and Orthotics, Faculty of Medicine and Health, 2University Health Care Research Center, Faculty of Medicine and Health, Örebro University, Örebro, Sweden Introduction: Therapeutic shoes are prescribed to prevent diabetic foot ulcers, but adherence to wearing the shoes is often poor.  Aim: The aim of this study was to review the literature on factors that are associated with adherence to wearing therapeutic shoes and construct a model of adherence to aid future research and development in the field. Methods: We conducted a systematic search in PubMed, CINAHL, and PsycINFO for quantitative studies on factors associated with adherence to wearing therapeutic shoes among people with diabetes. Results: Six studies were included in the review. The studies focused mainly on patient-, therapy-, and condition-related adherence factors. There is some evidence (three to five studies that sex, diabetes duration, and ulcer history are not associated with adherence. The evidence for or against the other factors was weak (only one or two studies or conflicting. Conclusion: There is no conclusive evidence for using any factor to predict adherence to wearing therapeutic shoes, but there is some evidence against using certain factors for predicting adherence. Future studies should include a broader range of factors, including health system and social/economic factors, and they should investigate perceived costs and benefits of wearing therapeutic shoes in comparison with other shoes or no shoes. A seesaw model is presented illustrating the complex phenomenon of adherence. Further research is needed to identify factors associated with adherence to wearing therapeutic shoes, to enable the development of interventions to improve adherence and thereby reduce ulceration rates among people with diabetic foot complications.Keywords: Patient compliance, shoes, foot ulcer, diabetic foot, diabetes

  6. Dual mobility hip arthroplasty wear measurement: Experimental accuracy assessment using radiostereometric analysis (RSA).

    Science.gov (United States)

    Pineau, V; Lebel, B; Gouzy, S; Dutheil, J-J; Vielpeau, C

    2010-10-01

    The use of dual mobility cups is an effective method to prevent dislocations. However, the specific design of these implants can raise the suspicion of increased wear and subsequent periprosthetic osteolysis. Using radiostereometric analysis (RSA), migration of the femoral head inside the cup of a dual mobility implant can be defined to apprehend polyethylene wear rate. The study aimed to establish the precision of RSA measurement of femoral head migration in the cup of a dual mobility implant, and its intra- and interobserver variability. A total hip prosthesis phantom was implanted and placed under weight loading conditions in a simulator. Model-based RSA measurement of implant penetration involved specially machined polyethylene liners with increasing concentric wear (no wear, then 0.25, 0.5 and 0.75mm). Three examiners, blinded to the level of wear, analyzed (10 times) the radiostereometric films of the four liners. There was one experienced, one trained, and one inexperienced examiner. Statistical analysis measured the accuracy, precision, and intra- and interobserver variability by calculating Root Mean Square Error (RMSE), Concordance Correlation Coefficient (CCC), Intra Class correlation Coefficient (ICC), and Bland-Altman plots. Our protocol, that used a simple geometric model rather than the manufacturer's CAD files, showed precision of 0.072mm and accuracy of 0.034mm, comparable with machining tolerances with low variability. Correlation between wear measurement and true value was excellent with a CCC of 0.9772. Intraobserver reproducibility was very good with an ICC of 0.9856, 0.9883 and 0.9842, respectively for examiners 1, 2 and 3. Interobserver reproducibility was excellent with a CCC of 0.9818 between examiners 2 and 1, and 0.9713 between examiners 3 and 1. Quantification of wear is indispensable for the surveillance of dual mobility implants. This in vitro study validates our measurement method. Our results, and comparison with other studies using

  7. Wear and repair of stainless steel crowns.

    Science.gov (United States)

    Yilmaz, Y; Kara, N Belduz; Yilmaz, A; Sahin, H

    2011-03-01

    The purpose of this study was to determine the wear of stainless steel crowns (SSCs) in children, and compare the extent of microleakage in SSCs that had been repaired using either a cermet glass-ionomer cement (GIC) or a packable composite resin (CR). For the first aim, the occlusal surface thickness of 31 harvested SSCs (21 primary first and 10 second molars) and 18 unused SSCs was measured, and then examined under scanning electron microscopy. For the second aim, standardised holes were prepared on the occlusal surfaces of 20 SSCs, and then repaired using either a cermet GIC or packable CR. After their repair, the extent of microleakage was determined using 0.5% basic fuchsin and stereomicroscopy. The thickness of all the harvested SCCs was 5.3 μm less than that of the unused SCCs (p<0.02), and there were no significant differences between the thickness and occlusal wear rates of harvested SSCs from the first and second primary molars. Although neither of the two repair materials completely prevented microleakage, the number of specimens in which microleakage occurred after repair with a cermet GIC was significantly lower than the number of specimens in which a packable CR was used (p<0.05). We concluded that the occlusal surfaces of SSCs for first and second primary molars display wear. Although perforated SSCs can be repaired using either a cermet GIC or a packable CR, less microleakage occurs in SSCs that were repaired with a cermet GIC than those with a packable CR.

  8. Acanthamoeba keratitis and contact lens wear.

    Science.gov (United States)

    Lindsay, Richard G; Watters, Grant; Johnson, Richard; Ormonde, Susan E; Snibson, Grant R

    2007-09-01

    Acanthamoeba keratitis is a rare but serious complication of contact lens wear that may cause severe visual loss. The clinical picture is usually characterised by severe pain, sometimes disproportionate to the signs, with an early superficial keratitis that is often misdiagnosed as herpes simplex virus (HSV) keratitis. Advanced stages of the infection are usually characterised by central corneal epithelial loss and marked stromal opacification with subsequent loss of vision. In this paper, six cases of contact lens-related Acanthamoeba keratitis that occurred in Australia and New Zealand over a three-year period are described. Three of the patients were disposable soft lens wearers, two were hybrid lens wearers and one was a rigid gas permeable lens wearer. For all six cases, the risk factors for Acanthamoeba keratitis were contact lens wear with inappropriate or ineffective lens maintenance and exposure of the contact lenses to tap or other sources of water. All six patients responded well to medical therapy that involved topical use of appropriate therapeutic agents, most commonly polyhexamethylene biguanide and propamidine isethionate, although two of the patients also subsequently underwent deep lamellar keratoplasty due to residual corneal surface irregularity and stromal scarring. Despite the significant advances that have been made in the medical therapy of Acanthamoeba keratitis over the past 10 years, prevention remains the best treatment and patients who wear contact lenses must be thoroughly educated about the proper use and care of the lenses. In particular, exposure of the contact lenses to tap water or other sources of water should be avoided.

  9. Wear testing of total hip replacements under severe conditions.

    Science.gov (United States)

    Zietz, Carmen; Fabry, Christian; Reinders, Joern; Dammer, Rebecca; Kretzer, Jan Philippe; Bader, Rainer; Sonntag, Robert

    2015-07-01

    Controlled wear testing of total hip replacements in hip joint simulators is a well-established and powerful method, giving an extensive prediction of the long-term clinical performance. To understand the wear behavior of a bearing and its limits under in vivo conditions, testing scenarios should be designed as physiologically as possible. Currently, the ISO standard protocol 14242 is the most common preclinical testing procedure for total hip replacements, based on a simplified gait cycle for normal walking conditions. However, in recent years, wear patterns have increasingly been observed on retrievals that cannot be replicated by the current standard. The purpose of this study is to review the severe testing conditions that enable the generation of clinically relevant wear rates and phenomena. These conditions include changes in loading and activity, third-body wear, surface topography, edge wear and the role of aging of the bearing materials.

  10. Correlation between Wear Resistance and Lifetime of Electrical Contacts

    Directory of Open Access Journals (Sweden)

    Jian Song

    2012-01-01

    Full Text Available Electrical contacts are usually plated in order to prevent corrosion. Platings of detachable electrical contacts experience wear because of the motion between contacts. Once the protecting platings have been worn out, electrical contacts will fail rapidly due to corrosion or fretting corrosion. Therefore the wear resistance of the platings is a very important parameter for the long lifetime of electrical contacts. Many measures which improve the wear resistance can diminish the conductivity of the platings. Due to the fact that platings of electrical contacts must have both a high wear resistance and a high electrical conductivity, the manufacturing of high performance platings of electrical contacts poses a great challenge. Our study shows firstly the correlation between the wear resistance of platings and lifetime of electrical contacts and then the measures, which improve the wear resistance without impairing the electrical performance of the contacts.

  11. Control of erosive tooth wear: possibilities and rationale

    Directory of Open Access Journals (Sweden)

    Mônica Campos Serra

    2009-06-01

    Full Text Available Dental erosion is a type of wear caused by non bacterial acids or chelation. There is evidence of a significant increase in the prevalence of dental wear in the deciduous and permanent teeth as a consequence of the frequent intake of acidic foods and drinks, or due to gastric acid which may reach the oral cavity following reflux or vomiting episodes. The presence of acids is a prerequisite for dental erosion, but the erosive wear is complex and depends on the interaction of biological, chemical and behavioral factors. Even though erosion may be defined or described as an isolated process, in clinical situations other wear phenomena are expected to occur concomitantly, such as abrasive wear (which occurs, e.g, due to tooth brushing or mastication. In order to control dental loss due to erosive wear it is crucial to take into account its multifactorial nature, which predisposes some individuals to the condition.

  12. Tool Wear Feature Extraction Based on Hilbert Marginal Spectrum

    Science.gov (United States)

    Guan, Shan; Song, Weijie; Pang, Hongyang

    2017-09-01

    In the metal cutting process, the signal contains a wealth of tool wear state information. A tool wear signal’s analysis and feature extraction method based on Hilbert marginal spectrum is proposed. Firstly, the tool wear signal was decomposed by empirical mode decomposition algorithm and the intrinsic mode functions including the main information were screened out by the correlation coefficient and the variance contribution rate. Secondly, Hilbert transform was performed on the main intrinsic mode functions. Hilbert time-frequency spectrum and Hilbert marginal spectrum were obtained by Hilbert transform. Finally, Amplitude domain indexes were extracted on the basis of the Hilbert marginal spectrum and they structured recognition feature vector of tool wear state. The research results show that the extracted features can effectively characterize the different wear state of the tool, which provides a basis for monitoring tool wear condition.

  13. Tribocorrosion wear of austenitic and martensitic steels

    Directory of Open Access Journals (Sweden)

    G. Rozing

    2016-07-01

    Full Text Available This paper explores the impact of tribocorrosion wear caused by an aggressive acidic media. Tests were conducted on samples made of stainless steel AISI 316L, 304L and 440C. Austenitic steels were tested in their nitrided state and martensitic in quenched and tempered and then induction hardened state. Electrochemical corrosion resistance testing and analysis of the microstructure and hardness in the cross section was carried out on samples of selected steels. To test the possibility of applying surface modification of selected materials in conditions of use, tests were conducted on samples/parts in a worm press for final pressing.

  14. The corneal stroma during contact lens wear.

    Science.gov (United States)

    Jalbert, Isabelle; Stapleton, Fiona

    2005-03-01

    Recent technological advances have lead to novel descriptions of the microanatomy of the corneal stroma. In the first section of this review, these findings and the role they play in the maintenance of vital properties such as corneal transparency, mechanical strength, homeostasis, wound-healing response and metabolism are described. In the second part, contact lens induced stromal alterations such as acidosis, oedema, striae, thinning and opacities are reviewed as well as the more recently described phenomenon of microdot deposits and keratocyte loss with an emphasis on how lens wearing stromal effects can be minimised.

  15. Aging mourning doves by outer primary wear

    Science.gov (United States)

    Wight, H.M.; Blankenship, L.H.; Tomlinson, R.E.

    1967-01-01

    Many immature mourning doves (Zenaidura macroura) cannot be aged by the conventional white-tipped primary covert method if molt has proceeded beyond the 7th primary. A new method of aging doves in this group is based on the presence (immature) or absence (adult) of a buff-colored fringe on the tips of the 9th and 10th primaries. Experienced biologists were nearly 100 percent accurate in aging wings of 100 known-age doves from eastern and midwestern states. The technique is not as reliable for doves from southwestern United States because of added feather wear, apparently from harsh vegetative and soil conditions.

  16. THE WEAR RESISTANCE INCREASE OF CHROMIUM CAST IRON

    Directory of Open Access Journals (Sweden)

    V. M. Ilyushenko

    2016-01-01

    Full Text Available The article presents the results of the tests on the wear resistance of chromium cast irons of different compositions obtained in sand forms. It has been shown that increase of the wear resistance and mechanical properties of the cast iron is possible to obtain using the casting in metal molds. A further increase in wear resistance of parts produced in metal molds is possible by changing the technological parameters of casting and alloying by titanium.

  17. Wearable Android Android wear and Google Fit app development

    CERN Document Server

    Mishra, Sanjay M

    2015-01-01

    Software Development/Mobile/Android/Wearable/Fitness Build ""Wearable"" Applications on the Android Wear and Google Fit Platforms This book covers wearable computing and wearable application development particularly for Android Wear (smartwatches) and Google Fit (fitness sensors). It provides relevant history, background and core concepts of wearable computing and ubiquitous computing, as a foundation for designing/developing applications for the Android Wear and Google Fit platforms. This book is intended for Android wearable enthusiasts, technologists and software developers. Gain ins

  18. Students Wearing Police Uniforms Exhibit Biased Attention toward Individuals Wearing Hoodies.

    Science.gov (United States)

    Civile, Ciro; Obhi, Sukhvinder S

    2017-01-01

    Police provide an essential public service and they often operate in difficult circumstances, requiring high-speed cognition. Recent incidents involving apparent profiling and aggressive behavior have led to accusations that the police are sometimes biased. Given that previous research has shown a link between clothing and cognition, we investigated the question of whether the police uniform itself might induce a bias in social attention. To address this question, and using a Canadian university student sample, we assessed whether wearing a police uniform biases attention toward black faces compared to white faces, and low-status individuals compared to high-status individuals. In Experiment 1 ( n = 28), participants wore either a police-style uniform or mechanic overalls, and performed a shape categorization task in the presence of a distractor that could be either: a black face, a white face, a person wearing a hoodie (whom we propose will be associated with low SES), or a person wearing a suit (whom we propose will be associated with high SES). Participants wearing the police-style uniform exhibited biased attention, indexed by slower reaction times (RTs), in the presence of low-SES images. In Experiment 2 ( n = 28), we confirmed this bias using a modified Dot-Probe task - an alternate measure of attentional bias in which we observed faster RTs to a dot probe that was spatially aligned with a low SES image. Experiment 3 ( n = 56) demonstrated that attentional bias toward low-SES targets appears only when participants wear the police-style uniform, and not when they are simply exposed to it - by having it placed on the desk in front of them. Our results demonstrate that wearing a police-style uniform biases attention toward low-SES targets. Thus, wearing a police-style uniform may induce a kind of "status-profiling" in which individuals from low-status groups become salient and capture attention. We note that our results are limited to university students and

  19. Wear characteristics of a rheocast leaded aluminium metal - metal composite

    Energy Technology Data Exchange (ETDEWEB)

    Garg, R. (Roorkee Univ. (India). Dept. of Metallurgical Engineering); Mohan, S. (Banaras Hindu Univ., Varanasi (India). Dept. of Metallurgical Engineering); Agarwala, V. (Roorkee Univ. (India). Dept. of Metallurgical Engineering); Agarwala, R.C. (Roorkee Univ. (India). Dept. of Metallurgical Engineering)

    1993-10-01

    In Al-Pb alloys, boundary lubrication is provided by lead but the matrix with pure aluminium does not provide adequate strength at high loads and high sliding velocities. So in the present investigation an Al-Cu-Si alloy has been taken as the base material and lead has been incorporated by the rheocasting technique. Wear characteristics of the alloy have been investigated at different loads, sliding velocities and sliding distances. Bulk wear has been observed to increase almost linearly with applied load and sliding velocity, but with sliding distance the bulk wear shows a short period of running-in followed by a long steady-state wear. (orig.)

  20. Wear Behavior of an Unstable Knee: Stabilization via Implant Design?

    Directory of Open Access Journals (Sweden)

    Jörn Reinders

    2014-01-01

    Full Text Available Background. Wear-related failures and instabilities are frequent failure mechanisms of total knee replacements. High-conforming designs may provide additional stability for the joint. This study analyzes the effects of a ligamentous insufficiency on the stability and the wear behavior of a high-conforming knee design. Methods. Two simulator wear tests were performed on a high-conforming total knee replacement design. In the first, a ligamentous-stable knee replacement with a sacrificed anterior cruciate ligament was simulated. In the second, a ligamentous-unstable knee with additionally insufficient posterior cruciate ligament and medial collateral ligament was simulated. Wear was determined gravimetrically and wear particles were analyzed. Implant kinematics was recorded during simulation. Results. Significantly higher wear rates (P≤0.001 were observed for the unstable knee (14.58±0.56 mg/106 cycles compared to the stable knee (7.97 ± 0.87 mg/106 cycles. A higher number of wear particles with only small differences in wear particle characteristics were observed. Under unstable knee conditions, kinematics increased significantly for translations and rotations (P≤0.01. This increase was mainly attributed to higher tibial posterior translation and internal rotations. Conclusion. Higher kinematics under unstable test conditions is a result of insufficient stabilization via implant design. Due to the higher kinematics, increased wear was observed in this study.

  1. Friction and wear in polymer-based materials

    CERN Document Server

    Bely, V A; Petrokovets, M I

    1982-01-01

    Friction and Wear in Polymer-Based Materials discusses friction and wear problems in polymer-based materials. The book is organized into three parts. The chapters in Part I cover the basic laws of friction and wear in polymer-based materials. Topics covered include frictional interaction during metal-polymer contact and the influence of operating conditions on wear in polymers. The chapters in Part II discuss the structure and frictional properties of polymer-based materials; the mechanism of frictional transfer when a polymer comes into contact with polymers, metals, and other materials; and

  2. The hardness and sliding wear behaviour of a bainitic steel

    Energy Technology Data Exchange (ETDEWEB)

    Shipway, P.H. [Nottingham Univ. (United Kingdom). Dept. of Materials Engineering and Materials Design; Wood, S.J. [Nottingham Univ. (United Kingdom). Dept. of Materials Engineering and Materials Design; Dent, A.H. [Nottingham Univ. (United Kingdom). Dept. of Materials Engineering and Materials Design

    1997-03-01

    High-strength bainitic steels have a number of desirable mechanical properties and have thus been viewed as candidate materials for heavy wear applications. This work examines the role of transformation temperature on the wear resistance of isothermally formed bainite from a single alloy steel and compares it with wear resistance following other heat treatments such as quenching, quenching and tempering and normalisation. The sliding wear resistance was examined for a range of applied loads at a constant sliding velocity of 1 m s{sup -1}. Microstructural constituents of the steels were related to their wear resistance. The hardness of the bainitic steel was a function of the isothermal transformation temperature and its variation has been correlated with the transformation behaviour. However, the hardness of the materials did not correlate well with their wear resistance, with the hardest martensitic steel showing greater wear rates than the normalised steel. Bainitic microstructures formed at low transformation temperatures were found to have a high wear resistance which in many cases was a factor of two better than any of the other microstructures examined; this material had a good combination of hardness and toughness on the microstructural level due to the fine nature of the bainite formed with high dislocation density and the lack of embrittling martensite and cementite phases and it is proposed that these attributes confer its high wear resistance. (orig.)

  3. Patient comfort following thirty minutes of lens wear: piggy-back versus conventional rigid-lens wear

    Directory of Open Access Journals (Sweden)

    W. D.H. Gillan

    2014-08-01

    Full Text Available Discomfort when wearing contact lenses, especially rigid contact lenses, is a common complaint amongst neophyte as well as experienced contact lens wearers. Wearing a piggy-back system of contact lenses has been shown to improve comfort and wearing time, especially in keratoconic subjects. Twenty two normal subjects wore a rigid lens or a piggy-back system of lenses for thirty minutes and after a thirty minute break swopped the mode of lens wear and wore the second modality for a thirty minute period. This study suggests that a piggy-back lens system provides improved comfort compared to wearing a rigid lens on its own. The order of lens wear might, however, influence the perceived comfort.

  4. "Work smart, wear your hard hat"

    CERN Multimedia

    2003-01-01

    Falling objects and collisions are frequent occurrences in work sites and hazardous areas. Hard hats can help prevent many types of accident and can even save lives. Just imagine an 800 g spanner falling from a 13 m high scaffold onto the head of someone standing below - a nightmare scenario! The impact to the head is equivalent to that of a 5 kg weight falling from 2 metres. That is just what happened to Gerd Fetchenhauer when he was working on the UA1 experiment. Fortunately, he was wearing a hard hat at the time. "That hat saved my life," he explains. "It punched a hole right through the hat and I was a bit dazed for a couple of hours but otherwise I was OK." Since that day, Gerd Fetchenhauer, now working on CMS, is never seen on a work site without his hard hat on. Work sites have proliferated at CERN with the construction of the LHC and its detectors, and the wearing of hard hats is compulsory (not to mention life-saving). In the underground caverns and experiment halls, where gantry cranes and other h...

  5. Biomechanics of postoperative shoes: plantar pressure distribution, wearing characteristics and design criteria: a preliminary study.

    Science.gov (United States)

    Schuh, Reinhard; Trnka, Hans-Joerg; Sabo, Anton; Reichel, Martin; Kristen, Karl-Heinz

    2011-02-01

    Modern concepts in the postoperative treatment of first metatarsal osteotomies include special shoes that should decrease stress in the forefoot region. The purpose of this study was to determine plantar pressure distribution, wearing characteristics and stress-reducing effectiveness of five different types of commonly used postoperative shoes. Additionally, we wanted to modify the shoe that revealed the most favourable results in a way that improves forefoot relief as well as provides comfort to the patients. Eight persons consented to participate in the study. Plantar pressure distribution in five different types of postoperative shoes (Rathgeber(®) normal, Rathgeber(®) modified, 4. Darco(®) flat, Darco(®) VFE, Wocker(®)) was assessed using Mediologic(®) insoles. Also, subjective criteria considering wearing comfort, stability and rolling characteristics were evaluated. Based on the postoperative shoe revealing the most favourable results, further prototypes were developed. Each new model was targeted to meet the given requirements, minimal forefoot pressure, in a different way. The Rathgeber(®) modified model revealed the most favourable results concerning plantar pressure distribution as well as subjective wearing characteristics. Therefore, it was chosen for further modifications. After adding an extra layer of high elastic and springy material for shock absorption at the hallux region, forefoot relief and wearing characteristics showed improved results. The results of the present study indicate that damping material in the hallux region of postoperative shoes minimises stress in this region and improves patient's comfort.

  6. Variations in erosive wear of metallic materials with temperature via the electron work function

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Xiaochen; Yu, Bin [Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta, T6G 2V4 (Canada); Yan, X.G. [School of Mechanical Engineering, Taiyuan University of Science and Technology, Taiyuan, Shanxi (China); Li, D.Y., E-mail: dongyang.li@ualberta.ca [Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta, T6G 2V4 (Canada); School of Mechanical Engineering, Taiyuan University of Science and Technology, Taiyuan, Shanxi (China)

    2016-04-01

    Mechanical properties of metals are intrinsically determined by their electron behavior, which is largely reflected by the electron work function (EWF or φ). Since the work function varies with temperature, the dependence of material properties on temperature could be predicted via variations in work function with temperature. Combining a hardness – φ relationship and the dependence of work function on temperature, a temperature-dependent model for predicting solid-particle erosion is proposed. Erosive wear losses of copper, nickel, and carbon steel as sample materials were measured at different temperatures. Results of the tests are consistent with the theoretical prediction. This study demonstrates a promising parameter, electron work function, for looking into fundamental aspects of wear phenomena, which would also help develop alternative methodologies for material design. - Highlights: • Metallic materials' wear resistance is influenced by temperature. • Electron work function (EWF) intrinsically determines materials' wear resistance. • An EWF-based temperature-dependent solid-particle erosion model is proposed.

  7. Association of dietary habits and parental-reported sleep tooth grinding with tooth wear in children with mixed dentition.

    Science.gov (United States)

    Restrepo, Claudia; Manfredini, Daniele; Manrique, Ruben; Lobbezoo, Frank

    2017-12-20

    Tooth wear has a multifactorial etiology, thus it should be assessed within a multiple-variable framework. The objective of this investigation was to assess the association of dietary habits and parental-reported sleep tooth grinding (STG) with tooth wear in children with mixed dentition. One hundred twenty-one (N = 121) subjects (mean age 9.6 years) participated in a cross-sectional study. Wear of 1637 teeth was evaluated using the screening module of the Tooth Wear Evaluation System (TWES). Parental-report of STG was evaluated by means of the Children's Sleep Habits Questionnaire (CSHQ), whilst dietary habits were investigated by means of the Health Behaviour in School-Aged Children Food-Frequency Questionnaire (HBSC-FFQ). Data were analyzed with the Spearman correlation test and ordinal-multiple-variable regression analyses. Odds Ratio (OR) and ordinal OR were obtained for the independent variables included in the models. Parental-report of STG is not associated with tooth wear in the mixed dentition; some dietary habits were found to be correlated with specific tooth wear patterns, but the correlation values were weak. Associations were found between dietary habits and the increase-to-increase severity of occlusal/incisal and non-occlusal/non-incisal tooth wear of some teeth (OR > 2). A strong correlation of dietary habits and sleep tooth grinding with tooth wear in the mixed dentition was not demonstrated. However, dietary habits showed to have effects in terms of increase-to-increase severity.

  8. Nurse uniform wearing practices and associated factors among nurses working in Northwest Ethiopia: a cross-sectional institution based study.

    Science.gov (United States)

    Desta, Etaferahu Alamaw; Gebrie, Mignote Hailu; Dachew, Berihun Assefa

    2015-01-01

    Wearing uniforms help in the formation of professional identity in healthcare. It fosters a strong self image and professional identity which can lead to good confidence and better performance in nursing practice. However, most nurses in Ethiopia are not wearing nursing uniforms and the reasons remain unclear. Therefore, the aim of this research is to assess nurse uniform wearing practices among nurses and factors associated with such practice in hospitals in Northwest Ethiopia. A hospital based cross-sectional study was conducted from March to April, 2014 in five hospitals located in Northwest Ethiopia. A total 459 nurses participated in the study. Data was collected using a pre-tested self-administered questionnaire. Descriptive statistics were analyzed in order to characterize the study population. Bivariate and multiple logistic regression models were fitted. Odds ratios with 95 % confidence intervals were computed to identify factors associated with nursing uniform practice. Nurse uniform wearing practice was found to be 49.2 % of the total sample size. Around 35 % of the respondents that did not implement nurse uniform wearing practices stated that there was no specific uniform for nurses recommended by hospital management. In addition to this, nurse uniform wearing practices were positively associated with being female [AOR = 1.58, 95 % CI (1.02, 2.44)], studying nursing by choice [AOR =3.16, 95 % CI (2.03, 4.92)], and the appeal of nursing uniforms to nurses [AOR = 3.43 95 % CI (1.96, 5.98)]. Nurse uniform wearing practices were not exceptionally prevalent in Northwest Ethiopian hospitals. However, encouraging students to pursue interest-based careers and implementing a nurse uniform wearing policy may have the potential to improve such practices.

  9. Qualitative Assessment of Wear Resistance and Surface Hardness of Different Commercially Available Dental Porcelain: An in vitro Study.

    Science.gov (United States)

    Singh, Abhishek; Nagpal, Abhishek; Pawah, Salil; Pathak, Chetan; Issar, Gaurav; Sharma, Pankaj

    2016-09-01

    In an attempt to minimize wear damage to the enamel of antagonist teeth, new low and medium fusing ceramic materials have been developed. Manufacturers usually claim that these ceramics are wear-friendly because of their lower hardness, lower concentrations of crystal phase, and smaller crystal sizes. This study aimed to quantitatively analyze the wear strength of various commercially available dental porcelain with tooth enamel as well as the surface hardness of these dental porcelain. The basic model was designed as a pin on plate arrangement. The tooth specimens were mounted on the stylus which was centered on the ceramic specimen in a wear testing machine. The dental ceramic specimen was centered in the metal die. A load of 40 N was applied at a rate of 80 cycles/minute for 15 minutes. In the current study, mean wear depth (Ra) value, volumetric loss, and surface hardness were obtained by standard quantification method and were statistically evaluated. Ceramco-3 was reported to be most abrasive for enamel; however, Duceram love significantly more abraded itself than the other two, Ceramco-3 and Vita Alpha, and generated the lowest loss of enamel. Also, same abrasive type of wear was revealed for all three variants of tested ceramics. Ceramco-3 was the most abrasive for enamel, while surface roughness (mean wear depth) of Duceram love was maximum and for Ceramco-3 it was minimum. The value of surface roughness for Vita Alpha was in between Duceram love and Ceramco-3. Nonetheless, the mean surface hardness of Duceram love was found to be least and maximum for Vita Alpha. In situations of dental wear and wasting tooth disease (Attrition/Abrasion), Duceram can be applied in lieu of Ceramco-3 so as to prevent worsening of existing dentition. However, in younger patients Vita Alpha would offer maximum durability due to its greater surface hardness.

  10. Analysis of Wear Particles Formed in Boundary-Lubricated Sliding Contacts

    NARCIS (Netherlands)

    Akchurin, Aydar; Bosman, Rob; Lugt, Pieter Martin; van Drogen, Mark

    2016-01-01

    The wear process in a sliding contact results in generation of wear debris, which affects the system life. The impact depends on the wear particle properties, such as size, shape and number. In this paper, the wear particles formed during a cylinder-on-disk wear test were examined. PAO additive-free

  11. [The effects of wearing protective devices among residents and volunteers participating in the cleanup of the Hebei Spirit oil spill].

    Science.gov (United States)

    Lee, Seung-Min; Ha, Mina; Kim, Eun-Jung; Jeong, Woo-Chul; Hur, Jongil; Park, Seok Gun; Kwon, Hojang; Hong, Yun-Chul; Ha, Eun-Hee; Lee, Jong Seung; Chung, Bong Chul; Lee, Jeongae; Im, Hosub; Choi, Yeyong; Cho, Yong-Min; Cheong, Hae-Kwan

    2009-03-01

    To assess the protective effects of wearing protective devices among the residents and volunteers who participated in the cleanup of the Hebei Spirit oil spill. A total of 288 residents and 724 volunteers were surveyed about symptoms, whether they were wearing protective devices and potential confounding variables. The questionnaires were administered from the second to the sixth week following the accident. Spot urine samples were collected and analyzed for metabolites of 4 volatile organic compounds (VOCs), 2 polycyclic aromatic hydrocarbons (PAHs), and 6 heavy metals. The association between the wearing of protective devices and various symptoms was assessed using a multiple logistic regression adjusted for confounding variables. A multiple generalized linear regression model adjusted for the covariates was used to test for a difference in least-square mean concentration of urinary biomarkers between residents who wore protective devices and those who did not. Thirty nine to 98% of the residents and 62-98% of volunteers wore protective devices. Levels of fatigue and fever were higher among residents not wearing masks than among those who did wear masks (odds ratio 4.5; 95% confidence interval 1.23-19.86). Urinary mercury levels were found to be significantly higher among residents not wearing work clothes or boots (plevels between people who wore protective devices and those who did not, except for mercury, whose biological half-life is more than 6 weeks.

  12. A Proposed Methodology to Assess the Accuracy of 3D Scanners and Casts and Monitor Tooth Wear Progression in Patients.

    Science.gov (United States)

    Ahmed, Khaled E; Whitters, John; Ju, Xiangyang; Pierce, S Gareth; MacLeod, Charles N; Murray, Colin A

    2016-01-01

    The aim of this study was to detail and assess the capability of a novel methodology to 3D-quantify tooth wear progression in a patient over a period of 12 months. A calibrated stainless steel model was used to identify the accuracy of the scanning system by assessing the accuracy and precision of the contact scanner and the dimensional accuracy and stability of casts fabricated from three different types of impression materials. Thereafter, the overall accuracy of the 3D scanning system (scanner and casts) was ascertained. Clinically, polyether impressions were made of the patient's dentition at the initial examination and at the 12-month review, then poured in type IV dental stone to assess the tooth wear. The anterior teeth on the resultant casts were scanned, and images were analyzed using 3D matching software to detect dimensional variations between the patient's impressions. The accuracy of the 3D scanning system was established to be 33 μm. 3D clinical analysis demonstrated localized wear on the incisal and palatal surfaces of the patient's maxillary central incisors. The identified wear extended to a depth of 500 μm with a distribution of 4% to 7% of affected tooth surfaces. The newly developed 3D scanning methodology was found to be capable of assessing and accounting for the various factors affecting tooth wear scanning. Initial clinical evaluation of the methodology demonstrates successful monitoring of tooth wear progression. However, further clinical assessment is needed.

  13. A Novel Method for Assessment of Polyethylene Liner Wear in Radiopaque Tantalum Acetabular Cups: Clinical Validation in Patients Enrolled in a Randomized Controlled Trial.

    Science.gov (United States)

    Troelsen, Anders; Greene, Meridith E; Ayers, David C; Bragdon, Charles R; Malchau, Henrik

    2015-12-01

    Conventional radiostereometric analysis (RSA) for wear is not possible in patients with tantalum cups. We propose a novel method for wear analysis in tantalum cups. Wear was assessed by gold standard RSA and the novel method in total hip arthroplasty patients enrolled in a randomized controlled trial receiving either titanium or tantalum cups (n=46). The novel method estimated the center of the head using a model based on identification of two proximal markers on the stem and knowledge of the stem/head configuration. The novel method was able to demonstrate a pattern of wear that was similar to the gold standard in titanium cups. The novel method offered accurate assessment and is a viable solution for assessment of wear in studies with tantalum cups. Copyright © 2015 Elsevier Inc. All rights reserved.

  14. Investigation on two-body abrasive wear behavior of titanium ...

    African Journals Online (AJOL)

    Investigation on two-body abrasive wear behavior of titanium carbide filled glass fabric-epoxy composites- a Box-Behnken approach. ... International Journal of Engineering, Science and Technology ... The two-body abrasive wear behavior of Glass–Epoxy (G–E) composites has been evaluated by the addition of Titanium

  15. Anisotropy abrasive wear behavior of bagasse fiber reinforced ...

    African Journals Online (AJOL)

    Anisotropy abrasive wear behavior of bagasse fiber reinforced polymer composite. ... International Journal of Engineering, Science and Technology ... Three different types of abrasives wear behaviour have been observed in the composite in three orientations and follow the following trends: WNO < WAPO < WPO, where ...

  16. Assessment of mechanical and three-body abrasive wear peculiarity ...

    Indian Academy of Sciences (India)

    by using VIKOR method. Keywords. Mechanical property; three-body abrasive wear; Taguchi methodology; surface morphology; VIKOR ... wear behaviour of filled epoxy composite systems and concluded that low wt% of boron ... process, which was supported by SEM (scanning electron microscope) studies (reduced ...

  17. Tooth -Wear Lesions Among Patients Attending Tertiary Hospital in ...

    African Journals Online (AJOL)

    Tooth wear manifest in the form of abrasion, attrition, erosion and abfraction and can affect the quality of life of the sufferer. This was a prospective study of patients who ... We recommend oral hygiene advice, dietary counseling and regular dental examination for early detection. Key words: Tooth wear, lesion, prospective, ...

  18. Friction, Fretting and Wear: Emerging Materials and Technologies

    Indian Academy of Sciences (India)

    wear, erosion, galling, scuffing and damage. Though these issues have been ... applications ranging from pharmaceuticals, dental implants, mining, transportation, space and nuclear medicine underlines the ... of the mechanical behaviour of solids subjected to erosion, abrasion, fretting, fatigue, impact and wear caused by ...

  19. Fracture mechanics approach to estimate rail wear limits

    Science.gov (United States)

    2009-10-01

    This paper describes a systematic methodology to estimate allowable limits for rail head wear in terms of vertical head-height loss, gage-face side wear, and/or the combination of the two. This methodology is based on the principles of engineering fr...

  20. Clinical studies of dental erosion and erosive wear

    NARCIS (Netherlands)

    Huysmans, M.C.D.N.J.M.; Chew, H.P.; Ellwood, R.P.

    2011-01-01

    We define erosion as a partial demineralisation of enamel or dentine by intrinsic or extrinsic acids and erosive tooth wear as the accelerated loss of dental hard tissue through the combined effect of erosion and mechanical wear (abrasion and attrition) on the tooth surface. Most experts believe

  1. 16 CFR 423.6 - Textile wearing apparel.

    Science.gov (United States)

    2010-01-01

    ... 16 Commercial Practices 1 2010-01-01 2010-01-01 false Textile wearing apparel. 423.6 Section 423.6 Commercial Practices FEDERAL TRADE COMMISSION TRADE REGULATION RULES CARE LABELING OF TEXTILE WEARING APPAREL... the outside of the package or on a hang tag fastened to the product. (b) Care labels must state what...

  2. Using Noncontingent Reinforcement to Increase Compliance with Wearing Prescription Prostheses

    Science.gov (United States)

    Richling, Sarah M.; Rapp, John T.; Carroll, Regina A.; Smith, Jeanette N.; Nystedt, Aaron; Siewert, Brook

    2011-01-01

    We evaluated the effects of noncontingent reinforcement (NCR) on compliance with wearing foot orthotics and a hearing aid with 2 individuals. Results showed that NCR increased the participants' compliance with wearing prescription prostheses to 100% after just a few 5-min sessions, and the behavior change was maintained during lengthier sessions.…

  3. Barriers to Wearing Glasses Among Primary School Children in ...

    African Journals Online (AJOL)

    For those that genuinely had deep-rooted beliefs against wearing glasses, health education by teaching the benefits of wearing glasses could be of great help. We appeal to private eye care service deliverers to accommodate school children and to offer services to them at affordable costs including provision of glasses.

  4. A study on wear behaviour of Al/6101/graphite composites

    Directory of Open Access Journals (Sweden)

    Pardeep Sharma

    2017-03-01

    Full Text Available The current research work scrutinizes aluminium alloy 6101-graphite composites for their mechanical and tribological behaviour in dry sliding environments. The orthodox liquid casting technique had been used for the manufacturing of composite materials and imperilled to T6 heat treatment. The content of reinforcement particles was taken as 0, 4, 8, 12 and 16 wt.% of graphite to ascertain it is prospective as self-lubricating reinforcement in sliding wear environments. Hardness, tensile strength and flexural strength of cast Al6101 metal matrix and manufactured composites were evaluated. Hardness, tensile strength and flexural strength decreases with increasing volume fraction of graphite reinforcement as compared to cast Al6101 metal matrix. Wear tests were performed on pin on disc apparatus to assess the tribological behaviour of composites and to determine the optimum volume fraction of graphite for its minimum wear rate. Wear rate reduces with increase in graphite volume fraction and minimum wear rate was attained at 4 wt.% graphite. The wear was found to decrease with increase in sliding distance. The average co-efficient of friction also reduces with graphite addition and its minimum value was found to be at 4 wt.% graphite. The worn surfaces of wear specimens were studied through scanning electron microscopy. The occurrence of 4 wt.% of graphite reinforcement in the composites can reveal loftier wear possessions as compared to cast Al6101 metal matrix.

  5. Occlusal wear of provisional implant-supported restorations

    NARCIS (Netherlands)

    Santing, Hendrik J.; Kleverlaan, Cornelis J.; Werner, Arie; Feilzer, Albert J.; Raghoebar, Gerry M.; Meijer, Henny J. A.

    BACKGROUND: Implant-supported provisional restorations should be resistant to occlusal wear. PURPOSE: The purpose of this laboratory study was to evaluate three-body wear of three indirect laboratory composite resins, five chair side bis-acryl resin-based materials, and two chair side

  6. Multi technical analysis of wear mechanisms in axial piston pumps

    Science.gov (United States)

    Schuhler, G.; Jourani, A.; Bouvier, S.; Perrochat, J.-M.

    2017-05-01

    Axial piston pumps convert a motor rotation motion into hydraulic or pneumatic power. Their compactness and efficiency of approximately 0.9 make them suitable for actuation applications especially in aeronautics. However, they suffer a limited life due to the wear of their components. In the literature, studies of axial piston pumps deal with contact between its different elements under lubrication conditions. Nevertheless, they are more focused on analytic or numerical approaches. This study consists in an experimental analysis of worn pump components to highlight and understand wear mechanisms. Piston shoes are central components in the axial piston pump since they are involved in three tribological contacts. These three contacts are thereby studied: piston shoes/swashplate, piston shoes/pistons and piston shoes/shoes hold down plate (SHDP). To perform this analysis, helicopter hydraulic pumps after different operating times have been studied. The wear damage mechanisms and wear debris are analysed using SEM observations. 3D surface roughness measurements are then used to characterize worn surfaces. The observations reveal that in the contact between shoes and swashplate, the main wear mechanism is three-body abrasive wear due to coarse carbides removal. Between shoes and pistons, wear occurs in a less severe way and is mainly due to the debris generated in the first contact and conveyed by the lubricating fluid. In the third contact, the debris are also the prime cause of the abrasive wear and the generation of deep craters in the piston shoes.

  7. The Tooth Wear Evaluation System: development and applications

    NARCIS (Netherlands)

    Wetselaar, P.

    2016-01-01

    Tooth wear is a multifactorial condition, leading to the loss of dental hard tissues, viz., enamel and dentine. Because of its multifactorial etiology, tooth wear can manifest itself in many different representations, and therefore it can be difficult and demanding to diagnose and manage the

  8. Severe Tooth Wear: European Consensus Statement on Management Guidelines.

    NARCIS (Netherlands)

    Loomans, B.; Opdam, N.J.; Attin, T.; Bartlett, D.; Edelhoff, D.; Frankenberger, R.; Benic, G.; Ramseyer, S.; Wetselaar, P.; Sterenborg, B.; Hickel, R.; Pallesen, U.; Mehta, S.; Banerji, S.; Lussi, A.; Wilson, N.

    2017-01-01

    This paper presents European expert consensus guidelines on the management of severe tooth wear. It focuses on the definition of physiological vs pathological tooth wear and recommends diagnosis, prevention, counseling, and monitoring aimed at elucidating the etiology, nature, rate and means of

  9. Monitoring of dry sliding wear using fractal analysis

    NARCIS (Netherlands)

    Zhang, Jindang; Regtien, Paulus P.L.; Korsten, Maarten J.

    2005-01-01

    Reliable online monitoring of wear remains a challenge to tribology research as well as to the industry. This paper presents a new method for monitoring of dry sliding wear using digital imaging and fractal analysis. Fractal values, namely fractal dimension and intercept, computed from the power

  10. Size dependence of nanoscale wear of silicon carbide

    Science.gov (United States)

    Chaiyapat Tangpatjaroen; David Grierson; Steve Shannon; Joseph E. Jakes; Izabela Szlufarska

    2017-01-01

    Nanoscale, single-asperity wear of single-crystal silicon carbide (sc- SiC) and nanocrystalline silicon carbide (nc-SiC) is investigated using single-crystal diamond nanoindenter tips and nanocrystalline diamond atomic force microscopy (AFM) tips under dry conditions, and the wear behavior is compared to that of single-crystal silicon with both thin and thick native...

  11. Nitrocarburizing for wear, corrosion, and fatigue

    Energy Technology Data Exchange (ETDEWEB)

    Wahl, G. [Durferrit GmbH Thermotechnik, Hanau (Germany)

    1996-04-01

    Demands for higher strength and corrosion resistance at higher temperatures cannot always be met by advanced materials and designs alone. In many cases, surface engineering can provide required properties and extend service life. A thermochemical surface engineering treatment has been developed that improves the dynamic strength of parts and overcomes many corrosion and wear problems. Known as Melonite, the process was developed by Durferrite GmbH Thermotechnik, and is used to enhance the surface properties of steel and iron parts. The quench, quench-polish, and quench-polish-quench salt bath nitrocarburizing system can provide surface layers with a range of beneficial properties. This article will discuss details of the Melonite process, component properties after treatment, the effects of raising or lowering treatment temperatures, and environmental impact.

  12. Wear Properties of Nuclear Graphite IG-110 at Elevated Temperature

    Energy Technology Data Exchange (ETDEWEB)

    Wei, Dunkun; Kim, Jaehoon; Kim, Yeonwook [Chungnam National University, Daejeon (Korea, Republic of)

    2014-05-15

    The high temperature gas-cooled reactor (HTR-10) is designed to produce electricity and hydrogen. Graphite is used as reflector, support structures, and a moderator in reactor core; it has good resistance to neutron and is a suitable material at high temperatures. Friction is generated in the graphite structures for the core reflector, support structures, and moderator because of vibration from the HTR-10 fuel cycle flow. In this study, the wear characteristics of the isotropic graphite IG-110 used in HTR-10 were evaluated. The reciprocating wear test was carried out for graphite against graphite. The effects of changes in the contact load and sliding speeds at room temperature and 400℃ on the coefficient of friction and specific wear rate were evaluated. The wear behavior of graphite IG-110 was evaluated based on the wear surfaces.

  13. Enhanced DLC wear performance by the presence of lubricant additives

    Directory of Open Access Journals (Sweden)

    Romina Paula de Castro Costa

    2011-01-01

    Full Text Available Lubricant additives play significant role for reducing friction and wear of mechanical elements. The additives presented in 5W30 oil were developed for metal surfaces. However, they have been used in engine pieces covered with DLC coatings because they also offer the potential to reduce friction losses and wear in automotive applications. The friction and wear tests were carried out by using a UMT-CETR ball-on-disk tribometer in rotational mode under 5W30 synthetic oil at 100 °C. The X-ray photoelectron spectroscopy (XPS showed the presence of Mo and S in the wear tracks. These elements are from decomposition of ZDDP and MoDTC additives producing MoS2 in DLC surface, which offers enhanced durability by low wear rate.

  14. Quasi-nano wear mechanism under repeated impact contact loading

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    A new quasi-nano wear mechanism (QNWM) has been proposed in this paper based on the facts of wear curve turning under high energy impact contact loading.Its characteristic is that the wear rate of QNWM is only 1/10-1/3 that of delamination mechanism at the same energy density.The diameters of wear debris and pits on the worn surfaces fall into the quasi-nanometer scale (about 50-120 nm).The necessary and sufficient conditions,which bring about the QNWM,are:(i) the nano-structure (nano-crystalline + amorphous phase) in impact contact surface layer has formed by the intensive impact strain;(ii) the delamination wear cracking in sub-surface layer must be restrained;(iii) the microcracks of QNWM are produced in amorphous phase of surface nano-structure layer rather than in nano-crystalline.

  15. Gradients of occlusal wear in hunter-gatherers and agriculturalists.

    Science.gov (United States)

    Deter, Christina A

    2009-03-01

    Occlusal wear was recorded in maxillary teeth from three North American late Archaic (3385 +/- 365 cal BC) hunter-gatherer sites (n = 306) and late Anasazi-early Zuni agricultural sites ( approximately 1300 AD) (n = 87). Comparisons were undertaken using descriptive and inferential statistics to determine differences between these groups, and along the maxillary tooth row. The hunter-gatherers had a significantly greater percentage of occlusal wear than the agriculturalists. For both hunter-gatherers and agriculturalists, occlusal wear was greatest on the central incisors and first molars. The third molars had the least amount of wear. It was inferred from these results that the hunter-gatherers had a more abrasive diet, and different daily task activities compared to the agriculturalists. One further finding was that wear patterns on anterior and posterior teeth are influenced by the order that teeth erupt into the jaw, as well as diet and behavior. (c) 2008 Wiley-Liss, Inc.

  16. Surface folding in metals: a mechanism for delamination wear in sliding.

    Science.gov (United States)

    Mahato, Anirban; Guo, Yang; Sundaram, Narayan K; Chandrasekar, Srinivasan

    2014-09-08

    Using high-resolution, in situ imaging of a hard, wedge-shaped model asperity sliding against a metal surface, we demonstrate a new mechanism for particle formation and delamination wear. Damage to the residual surface is caused by the occurrence of folds on the free surface of the prow-shaped region ahead of the wedge. This damage manifests itself as shallow crack-like features and surface tears, which are inclined at very acute angles to the surface. The transformation of folds into cracks, tears and particles is directly captured. Notably, a single sliding pass is sufficient to damage the surface, and subsequent passes result in the generation of platelet-like wear particles. Tracking the folding process at every stage from surface bumps to folds to cracks/tears/particles ensures that there is no ambiguity in capturing the mechanism of wear. Because fold formation and consequent delamination are quite general, our findings have broad applicability beyond wear itself, including implications for design of surface generation and conditioning processes.

  17. Tool Wear and Life Span Variations in Cold Forming Operations and Their Implications in Microforming

    Directory of Open Access Journals (Sweden)

    Anders E. W. Jarfors

    2016-12-01

    Full Text Available The current paper aims to review tooling life span, failure modes and models in cold microforming processes. As there is nearly no information available on tool-life for microforming the starting point was conventional cold forming. In cold forming common failures are (1 over stressing of the tool; (2 abrasive wear; (3 galling or adhesive wear, and (4 fatigue failure. The large variation in tool life observed in production and how to predict this was reviewed as this is important to the viability of microforming based on that the tooling cost takes a higher portion of the part cost. Anisotropic properties of the tool materials affect tool life span and depend on both the as-received and in-service conditions. It was concluded that preconditioning of the tool surface, and coating are important to control wear and fatigue. Properly managed, the detrimental effects from surface particles can be reduced. Under high stress low-cycle fatigue conditions, fatigue failure form internal microstructures and inclusions are common. To improve abrasive wear resistance larger carbides are commonly the solution which will have a negative impact on tooling life as these tend to be the root cause of fatigue failures. This has significant impact on cold microforming.

  18. Effect of occlusal wear on bone loss and Periotest value of dental implants.

    Science.gov (United States)

    Engel, E; Gomez-Roman, G; Axmann-Krcmar, D

    2001-01-01

    Occlusal overload may contribute to the loss of osseointegration of oral implants, so some clinicians are reluctant to place implants in patients with signs of bruxism. This study evaluated the effect of occlusal wear as a probable sign of bruxism on bone loss and implant stability. The study investigated 379 patients who had worn implant-retained or implant-supported restorations for many years. Occlusal wear, patient age and gender, time of prosthetic loading, jaw, location in the dental arch, implant diameter, prosthesis construction, occlusal material, periimplantitis, and loosening of the prosthetic construction were recorded. One implant from each patient was selected for radiographic and Periotest measurements. The implant with the highest bone resorption was chosen. A forward stepwise multiple linear regression analysis was performed to analyze the effect of the explanatory variables on Periotest value and radiographic bone loss. The statistical models could account for part of the variation in bone loss rate and Periotest value. Some influence of time of loading, jaw, and implant diameter on bone loss or Periotest value was formally established. Occlusal wear failed to have any statistical impact on vertical annual bone loss rate or Periotest value. This study gave no indication that implants in patients with occlusal wear have an increased bone loss rate or Periotest value.

  19. WEAR PERFORMANCE OPTIMIZATION OF SILICON NITRIDE USING GENETIC AND SIMULATED ANNEALING ALGORITHM

    Directory of Open Access Journals (Sweden)

    SACHIN GHALME

    2017-12-01

    Full Text Available Replacing damaged joint with the suitable alternative material is a prime requirement in a patient who has arthritis. Generation of wear particles in the artificial joint during action or movement is a serious issue and leads to aseptic loosening of joint. Research in the field of bio-tribology is trying to evaluate materials with minimum wear volume loss so as to extend joint life. Silicon nitride (Si3N4 is non-oxide ceramic suggested as a new alternative for hip/knee joint replacement. Hexagonal Boron Nitride (hBN is recommended as a solid additive lubricant to improve the wear performance of Si3N4 . In this paper, an attempt has been made to evaluate the optimum combination of load and % volume of hBN in Si3N4 to minimize wear volume loss (WVL. The experiments were conducted according to Design of Experiments (DoE – Taguchi method and a mathematical model is developed. Further, this model is processed with Genetic Algorithm (GA and Simulated Annealing (SA to find out the optimum percentage of hBN in Si3N4 to minimize wear volume loss against Alumina (Al2O3 counterface. Taguchi method presents 15 N load and 8% volume of hBN to minimize WVL of Si3N4 . While GA and SA optimization offer 11.08 N load, 12.115% volume of hBN and 11.0789 N load, 12.128% volume of hBN respectively to minimize WVL in Si3N4. .

  20. Wear Potential Due to Low EHD Films During Elevated Temperatures

    Science.gov (United States)

    Leville, Alan; Ward, Peter

    2014-01-01

    An earlier study showed that EHD films could be accurately measured in a running bearing and that the EHD film eventually runs-in to a steady state value [1]. In the present paper, we report on additional tests conducted on bearings with more lubricants, wider speeds, and higher temperatures. The new results consistently show that all lubricants tested, including MAC-based lubricants have EHD film levels that are lower than model predictions in some situations. In addition, the MAC lubricants studied have lower film thickness than traditional hydrocarbons. Figure 1 is taken from [1] and shows room temperature data of MAC oil and Corey 100 oil, illustrating the smaller EHD film results when using this MAC oil. Since higher temperatures produce lower films by changing the viscosity, the concern we have is that the EHD films may be too small to prevent ball/race metal contact and resulting wear at lower speeds. Best bearing practices would have the EHD film thickness be at least three (3) times the composite surface roughness. In this paper, we will present measured EHD thicknesses of lubricant films at speeds up to several thousand RPM for bearing bore sizes from as low as 6 mm (0.2 in) to as large as 35 mm (1.4 in) using MAC, Corey and KG-80. Ambient temperatures from room temperature to 52C (125F) are used. Testing was done with the base oils as well as formulated greases. Greases eventually ran in to the same EHD values as the base oil but took longer times to get there. The results clearly indicate that wear is very possible in all steel bearings when using MAC lubricants and that this condition worsens with higher temperatures and smaller bearing size.

  1. Wear and abrasion resistance selection maps of biological materials.

    Science.gov (United States)

    Amini, Shahrouz; Miserez, Ali

    2013-08-01

    The mechanical design of biological materials has generated widespread interest in recent years, providing many insights into their intriguing structure-property relationships. A critical characteristic of load-bearing materials, which is central to the survival of many species, is their wear and abrasion tolerance. In order to be fully functional, protective armors, dentitious structures and dynamic appendages must be able to tolerate repetitive contact loads without significant loss of materials or internal damage. However, very little is known about this tribological performance. Using a contact mechanics framework, we have constructed materials selection charts that provide general predictions about the wear performance of biological materials as a function of their fundamental mechanical properties. One key assumption in constructing these selection charts is that abrasion tolerance is governed by the first irreversible damage at the contact point. The maps were generated using comprehensive data from the literature and encompass a wide range of materials, from heavily mineralized to fully organic materials. Our analysis shows that the tolerance of biological materials against abrasion depends on contact geometry, which is ultimately correlated to environmental and selective pressures. Comparisons with experimental data from nanoindentation experiments are also drawn in order to verify our predictions. With the increasing amount of data available for biological materials also comes the challenge of selecting relevant model systems for bioinspired materials engineering. We suggest that these maps will be able to guide this selection by providing an overview of biological materials that are predicted to exhibit the best abrasion tolerance, which is of fundamental interest for a wide range of applications, for instance in restorative implants and protective devices. Copyright © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  2. Finite Element Analysis Of Influence Of Flank Wear Evolution On Forces In Orthogonal Cutting Of 42CrMo4 Steel

    Directory of Open Access Journals (Sweden)

    Madajewski Marek

    2017-01-01

    Full Text Available This paper presents analysis of flank wear influence on forces in orthogonal turning of 42CrMo4 steel and evaluates capacity of finite element model to provide such force values. Data about magnitude of feed and cutting force were obtained from measurements with force tensiometer in experimental test as well as from finite element analysis of chip formation process in ABAQUS/Explicit software. For studies an insert with complex rake face was selected and flank wear was simulated by grinding operation on its flank face. The aim of grinding inset surface was to obtain even flat wear along cutting edge, which after the measurement could be modeled with CAD program and applied in FE analysis for selected range of wear width. By comparing both sets of force values as function of flank wear in given cutting conditions FEA model was validated and it was established that it can be applied to analyze other physical aspects of machining. Force analysis found that progression of wear causes increase in cutting force magnitude and steep boost to feed force magnitude. Analysis of Fc/Ff force ratio revealed that flank wear has significant impact on resultant force in orthogonal cutting and magnitude of this force components in cutting and feed direction. Surge in force values can result in transfer of substantial loads to machine-tool interface.

  3. Peripheral corneal infiltrates associated with contact lens wear.

    Science.gov (United States)

    Suchecki, J K; Ehlers, W H; Donshik, P C

    1996-01-01

    We describe the epidemiological and clinical characteristics of peripheral corneal infiltrates associated with contact lens wear. We conducted a retrospective study of 52 patients with contact lens associated peripheral corneal infiltrates. Demographic data, clinical characteristics of the infiltrates, contact lens parameters, treatment modality, and the time to resolution for the infiltrates were analyzed. Forty-four of the 52 patients in this study presented with a single infiltrate, while the remaining 8 patients had multiple infiltrates. Types of contact lenses worn were as follows: 40% of the patients wore disposable extended wear contact lenses; 21% wore conventional extended wear lenses; 19% wore conventional daily wear lenses; 12% used frequent replacement daily wear lenses; 6% wore rigid gas permeable (RGP) contact lenses; and 2% used disposable lenses as daily wear. Although there was no predilection for a specific quadrant of the cornea, when a subgroup of extended wear contact lens patients was analyzed, 19 of their 40 infiltrates were located in the superior quadrant. The epithelium was intact in 42% of the infiltrates, while 58% of the infiltrates had epithelial involvement, either punctate staining or frank defect. Eight of the 16 patients who had corneal cultures performed had positive cultures. All patients who had positive cultures used extended wear contact lenses. Smoking did not appear to have an effect on the associated inflammatory reaction, positive cultures, or time to resolution. Seventy-five percent of patients were treated with topical antibiotics. Antibiotic steroids were prescribed for 23% of patients, and 2% of patients were treated with topical steroids. The mean time to resolution for all infiltrates was 1.74 weeks. Focal peripheral infiltrates with or without epithelial disturbance represent a distinct clinical complication associated with contact lens wear. All patients in this study had resolution of their infiltrates without

  4. Prevalence and Indicators of Tooth Wear among Chinese Adults.

    Directory of Open Access Journals (Sweden)

    Zhao Wei

    Full Text Available Numerous epidemiological studies have focused on the prevalence and related indicators of tooth wear. However, no sufficient studies have been conducted with Chinese adults. The purpose of this study was to assess the prevalence of tooth wear and identify related indicators among adults aged 36 to 74 years in Wuhan City, P.R. China. A cross-sectional and analytic study was conducted with 720 participants, aged 35-49 yrs and 50-74 yrs, in 2014. Each age group included 360 participants, of which 50% were males and 50% were females. All participants completed a questionnaire before examination. Tooth wear was assessed using the modified Basic Erosive Wear Examination (BEWE index. The data were analyzed using the chi-square test and binary logistic regression analysis. The prevalence of tooth wear was 67.5% and 100% in the 35-49 and 50-74 age groups, respectively. The prevalence of dentin exposure was 64.7% and 98.3%, respectively. A significantly higher prevalence of tooth wear and dentin exposure was found in the 50-74 yr group than in the 35-49 yr group (p < 0.05. Critical indicators of tooth wear and dentin exposure included high frequency of acidic drinks and foods consumption, low socio-economic status, and unilateral chewing. The frequency of changing toothbrushes and the habit of drinking water during meals were associated with tooth wear. In addition, the usage of hard-bristle toothbrushes and consuming vitamin C and aspirin were found to be linked with dentin exposure. In conclusion, the prevalence of tooth wear and dentin exposure observed in Chinese adults was high, and the results revealed an association between tooth wear and socio-behavioral risk indicators.

  5. Wear behavior of pressable lithium disilicate glass ceramic.

    Science.gov (United States)

    Peng, Zhongxiao; Izzat Abdul Rahman, Muhammad; Zhang, Yu; Yin, Ling

    2016-07-01

    This article reports effects of surface preparation and contact loads on abrasive wear properties of highly aesthetic and high-strength pressable lithium disilicate glass-ceramics (LDGC). Abrasive wear testing was performed using a pin-on-disk device in which LDGC disks prepared with different surface finishes were against alumina pins at different contact loads. Coefficients of friction and wear volumes were measured as functions of initial surface finishes and contact loads. Wear-induced surface morphology changes in both LDGC disks and alumina pins were characterized using three-dimensional laser scanning microscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy. The results show that initial surface finishes of LDGC specimens and contact loads significantly affected the friction coefficients, wear volumes and wear-induced surface roughness changes of the material. Both wear volumes and friction coefficients of LDGC increased as the load increased while surface roughness effects were complicated. For rough LDGC surfaces, three-body wear was dominant while for fine LDGC surfaces, two-body abrasive wear played a key role. Delamination, plastic deformation, and brittle fracture were observed on worn LDGC surfaces. The adhesion of LDGC matrix materials to alumina pins was also discovered. This research has advanced our understanding of the abrasive wear behavior of LDGC and will provide guidelines for better utilization and preparation of the material for long-term success in dental restorations. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 968-978, 2016. © 2015 Wiley Periodicals, Inc.

  6. Law and the Wearing of Religious Symbols: European Bans on the Wearing of Religious Symbols in Education

    Science.gov (United States)

    Howard, Erica

    2011-01-01

    Written in accessible language, Law and the Wearing of Religious Symbols is a comprehensive analysis of a topical subject that is being widely debated across Europe. The book provides an overview of emerging case law from the European Court of Human Rights as well as from national courts and equality bodies in European countries on the wearing of…

  7. Reducing dropout of contact lens wear with Biotrue multipurpose solution

    Directory of Open Access Journals (Sweden)

    Rah MJ

    2014-01-01

    Full Text Available Marjorie J Rah, Mohinder M Merchea, Marianne Q DoktorBausch & Lomb Incorporated, Rochester, NY, USAPurpose: To evaluate whether the use of Biotrue multipurpose solution (MPS could significantly reduce the likelihood with which patients drop out of using daily wear contact lenses (CLs amongst 18–44-year-old frequent replacement CL wearers.Methods: Daily wear CL subjects habitually using MPSs (other than Biotrue MPS who reported an intent to imminently drop out of CL wear because of comfort and dryness complaints were recruited to participate in this investigation. Subjects were switched to Biotrue MPS and continued to use habitual CL types with the new MPS for 2 weeks. Subjects completed an online satisfaction questionnaire at baseline and after 2 weeks to assess the change in symptoms and the intent to drop out of CL wear. Six months after completion of the initial study, a follow-up survey was administered to a subset of the initial participants.Results: A total of 153 daily wear (silicone hydrogel and hydrogel subjects completed this 2-week study with Biotrue MPS. When measuring those with the highest propensity to drop out of lens wear (n=93 after switching to Biotrue MPS, 90% of subjects significantly reduced their likelihood of dropping out of CL wear (P<0.0001. Online interviews were conducted with 73 of the study participants 6 months after completion of the initial study. A total of 93% of participants responded that they were still wearing CLs at least once per week. Of the 7% of respondents who were not currently wearing lenses 6 months after the initial study, two had dropped out of lens wear completely, and three still wore lenses less than once per week.Conclusion: Patients intending to drop out of CL wear due to discomfort and dryness significantly reduced their propensity of discontinuing lens wear following use of Biotrue MPS. Six months after completion of the study, 93% of patients were still wearing CLs at least once per

  8. Prevalence of erosive tooth wear and associated factors in a group of Mexican adolescents.

    Science.gov (United States)

    González-Aragón Pineda, Álvaro Edgar; Borges-Yáñez, Socorro Aída; Lussi, Adrian; Irigoyen-Camacho, María Esther; Angeles Medina, Fernando

    2016-02-01

    Erosive tooth wear is the irreversible loss of dental hard tissue as a result of chemical processes. When the surface of a tooth is attacked by acids, the resulting loss of structural integrity leaves a softened layer on the tooth's surface, which renders it vulnerable to abrasive forces. The authors' objective was to estimate the prevalence of erosive tooth wear and to identify associated factors in a sample of 14- to 19-year-old adolescents in Mexico. The authors performed a cross-sectional study on a convenience sample (N = 417) of adolescents in a school in Mexico City, Mexico. The authors used a questionnaire and an oral examination performed according to the Lussi index. The prevalence of erosive tooth wear was 31.7% (10.8% with exposed dentin). The final logistic regression model included age (P < .01; odds ratio [OR], 1.64; 95% confidence interval [CI], 1.26-2.13), high intake of sweet carbonated drinks (P = .03; OR, 1.81; 95% CI, 1.06-3.07), and xerostomia (P = .04; OR, 2.31; 95% CI, 1.05-5.09). Erosive tooth wear, mainly on the mandibular first molars, was associated with age, high intake of sweet carbonated drinks, and xerostomia. Knowledge regarding erosive tooth wear in adolescents with relatively few years of exposure to causal factors will increase the focus on effective preventive measures, the identification of people at high risk, and early treatment. Copyright © 2016 American Dental Association. Published by Elsevier Inc. All rights reserved.

  9. Surface and Sliding Wear Behaviour of Different Coatings and Steels

    Directory of Open Access Journals (Sweden)

    Vera-Cárdenas E.E.

    2012-01-01

    Full Text Available In this work, the sliding wear behaviour of the coatings TiN, CrN and WC/C applied on steel substrates was studied using a reciprocating wear test machine. All tests were carried out in dry conditions, at room temperature (20-23 C and 45% - 50% relative humidity. The average sliding velocity was 0.08 m/s and an amplitude of 2 mm was used. The applied loads were 11.76 N (Po = 1.74 GPa and 7.84 N (Po = 1.52 GPa. Optical microscopy was used to observe the characteristics of wear scars and spalls and possible causes of their formation. The variation of the friction coefficient against the number of cycles was obtained. This was used to determine more precisely the time (number of cycles where the coating presented the first signs of wear, in addition Energy Dispersive X-ray analysis (EDS was performed, as well as Scanning Electron Microscopy (SEM and hardness tests on the wear traces, which reinforced the previous observations. Thus it was possible to know the wear life of different coatings and possible causes of variation. Increasing the load was an important factor in the variation of wear life results. But it is also important to consider other factors such as surface roughness and thickness of coatings.

  10. Enamel erosion and mechanical tooth wear in medieval Icelanders.

    Science.gov (United States)

    Richter, Svend; Eliasson, Sigfus Thor

    2016-01-01

    The Icelandic Sagas are an important source of information on the way of life and diet habits in Iceland and possibly other Nordic countries 1000 years ago. Archaeological human skull material worldwide has revealed extensive tooth wear, with the main cause believed to be coarse diet. From a graveyard near volcano Hekla, 66 skeletons dated from before 1104 were excavated. The purpose of this study was to determine the main causes of tooth wear in Icelanders 1000 years ago. Forty-nine skulls were available for research. Two methods were used to evaluate tooth wear and seven for age estimation. An attempt was made to determine the main causes of tooth wear in the light of likely diet and beverage consumption according to a computer search on food and drink customs described in the Icelandic Sagas. Tooth wear was extensive in all groups, increasing with age. The highest score was on first molars, with no difference between sexes. It had all the similarities seen in wear from coarse diet. In some instances it had similar characteristics to those seen in erosion in modern Icelanders consuming excessive amounts of soft drinks. According to the Sagas, acidic whey was a daily drink and used for preservation of food in Iceland until recently. Since acidic whey has considerably high dental erosive potential, it is postulated that consumption of acidic drinks and food, in addition to a coarse and rough diet, played a significant role in the dental wear of ancient Icelanders.

  11. Ferrography Wear Particles Image Recognition Based on Extreme Learning Machine

    Directory of Open Access Journals (Sweden)

    Qiong Li

    2017-01-01

    Full Text Available The morphology of wear particles reflects the complex properties of wear processes involved in particle formation. Typically, the morphology of wear particles is evaluated qualitatively based on microscopy observations. This procedure relies upon the experts’ knowledge and, thus, is not always objective and cheap. With the rapid development of computer image processing technology, neural network based on traditional gradient training algorithm can be used to recognize them. However, the feedforward neural network based on traditional gradient training algorithms for image segmentation creates many issues, such as needing multiple iterations to converge and easy fall into local minimum, which restrict its development heavily. Recently, extreme learning machine (ELM for single-hidden-layer feedforward neural networks (SLFN has been attracting attentions for its faster learning speed and better generalization performance than those of traditional gradient-based learning algorithms. In this paper, we propose to employ ELM for ferrography wear particles image recognition. We extract the shape features, color features, and texture features of five typical kinds of wear particles as the input of the ELM classifier and set five types of wear particles as the output of the ELM classifier. Therefore, the novel ferrography wear particle classifier is founded based on ELM.

  12. Relationship of engine bearing wear and oil rheology

    Energy Technology Data Exchange (ETDEWEB)

    Olson, D.H.

    1987-01-01

    Engine wear tests were conducted, using two different engine designs, with single and multigrade engine oils. In one engine there was a significant reduction in bearing wear when multigrade oils were used. For the other engine there was evidence of less bearing wear when multigrade oils were used. In both engines correlations were found among bearing wear, high-temperature high-shear-rate viscosity and oil elasticity. It has been shown that the minimum oil film thickness measured for the front main bearing in an operating engine is related to both oil viscosity and elasticity for multigrade oils. The study presented here is an attempt to extend that work to determine if the same oil rheological parameter can be used to establish a correlation to engine journal bearing wear. Two different engines were used and wear was measured for connecting rod big-ends bearings and main bearings. The results ranged from excellent to poor depending on the engine and bearing location within each engine. Despite the limited success in establishing correlations among the oil rheological properties and bearing wear, the results are being presented in the interest of stimulating further work in this important area.

  13. THEORETICAL DEPENDENCE OF WEAR VALUE OF FRICTION PAIR «CENETR PLATE – CENTER PAD» ON A FREIGHT CAR MILEAGE

    Directory of Open Access Journals (Sweden)

    L. A. Muradian

    2017-12-01

    Full Text Available Purpose. The paper considers the interaction of the cylindrical surfaces of the friction pair «center plate – center pad» of the freight car and theoretically investigates the wear process. It is also necessary to obtain the wear value dependence of center pad on the mileage, taking into account the power load, the physical-mechanical and tribo-technical properties of the interacting materials for the subsequent modeling and control of the value of overhaul mileage by the wear criterion of the corresponding resource-determining elements of freight cars. Методика. For theoretical studies of the wear value of friction pair «center plate – center pad» on the freight car mileage, the theory of friction and wear of solids was used. Findings. In this paper interaction of cylindrical surfaces of the friction pair «center plate – center pad» of a freight car in the form of a «shaft-sleeve» model is considered. Dependences of the permanent and variable wear of a given friction pair are proposed for cases in which forces act in the transverse and longitudinal directions. Obtained dependence of the wear value of center pad on the freight car mileage takes into account the power load, physical and mechanical and tribo-technical properties of the conjugated materials. On its basis, using new materials for repair with various properties, one may simulate the wear state of cylindrical surfaces of the friction pair «center plate – center pad», which will make it possible to control the value of overhaul mileage of freight car. Also (on the example of gondola 12-7023 on the basis of obtained expression there were constructed dependences of the average wear value of center pad for the cases of different values of the mileage use coefficient and the train movement speed. It was shown that with an increase in the train speed to 100 km/h, the average wear value of the gondola 12-7023 center pad is lower by 25% than at the speed of 80 km

  14. Clinical assessment of enamel wear caused by monolithic zirconia crowns.

    Science.gov (United States)

    Stober, T; Bermejo, J L; Schwindling, F S; Schmitter, M

    2016-08-01

    The purpose of this study was to measure enamel wear caused by antagonistic monolithic zirconia crowns and to compare this with enamel wear caused by contralateral natural antagonists. Twenty monolithic zirconia full molar crowns were placed in 20 patients. Patients with high activity of the masseter muscle at night (bruxism) were excluded. For analysis of wear, vinylpolysiloxane impressions were prepared after crown incorporation and at 6-, 12-, and 24-month follow-up. Wear of the occlusal contact areas of the crowns, of their natural antagonists, and of two contralateral natural antagonists (control teeth) was measured by use of plaster replicas and a 3D laser-scanning device. Differences of wear between the zirconia crown antagonists and the control teeth were investigated by means of two-sided paired Student's t-tests and linear regression analysis. After 2 years, mean vertical loss was 46 μm for enamel opposed to zirconia, 19-26 μm for contralateral control teeth and 14 μm for zirconia crowns. Maximum vertical loss was 151 μm for enamel opposed to zirconia, 75-115 μm for control teeth and 60 μm for zirconia crowns. Statistical analysis revealed significant differences between wear of enamel by zirconia-opposed teeth and by control teeth. Gender, which significantly affected wear, was identified as a possible confounder. Monolithic zirconia crowns generated more wear of opposed enamel than did natural teeth. Because of the greater wear caused by other dental ceramics, the use of monolithic zirconia crowns may be justified. © 2016 John Wiley & Sons Ltd.

  15. Improving Rail Wear and RCF Performance using Laser Cladding

    OpenAIRE

    Lewis, S.R.; Fretwell-Smith, S.; Goodwin, P.S.; Smith, L.; Lewis, R.; Aslam, M.; Fletcher, D.I.; Murray, K.; Lambert, R.

    2016-01-01

    Laser cladding has been considered as a method for improving the wear and RCF performance of standard grade rail. This paper presents results of small scale tests carried out to assess the wear and RCF performance of rail which had been laser clad. Using the laser cladding process premium metals can be deposited on to the working surface of standard rail with the aim of enhancing the wear and RCF life of the rail. Various laser clad samples were tested using a twin-disc method. The candidate ...

  16. Lubricity Additives and Wear with DME in Diesel Injection Pumps

    DEFF Research Database (Denmark)

    Nielsen, Kasper; Sorenson, Spencer C.

    1999-01-01

    In recent years it has been demonstrated that Dimethyl Ether (DME) possess many characteristics that could make it a successful alternative to diesel in the next century. High wear of the fuel injection system has been reported. This is caused by lack of natural protective constituents of Dimethyl...... wear of standard diesel jerk pump plungers elements were made with weight measurements, diameter measurements, 2-D and 3-D surface roughness measurements, and photography by a Michelson interferometer. Several lubricity additives were tested, but none reduced wear levels to those for diesel fuel...

  17. Evaluating and comparison between wear behavior of dental Amalgam

    Directory of Open Access Journals (Sweden)

    Fathi MH

    1999-06-01

    Full Text Available Wear characteristics of dental amalgams were investigated by in vivo and in vitro tests. Wear"nof dental amalgam was studied and evaluated using a three - body abrasion test and Pin-On-Disk"nmethod. Porcelain was used for preparing disk and materials such as toothpaste, artificial saliva and"nnaturally saliva were used as the third material that was contributed in tribologic system"nThe results showed that effects of various toothpastes on the wear of dental amalgam are considerably"ndifferent and size, shape and chemical composition of amalgam are important too.

  18. Wear Assessment in High Cycle Rolling Contact Fatigue Using Semi-Analytical Approach

    Directory of Open Access Journals (Sweden)

    Michal ŠOFER

    2013-06-01

    Full Text Available Presented paper deals with ratcheting prediction in the field of contact fatigue for the case of line contact. For the stated purposes, the wear model proposed by A. Mazzu [1] is used, which stands out for its simplicity and time efficiency. The model is based on non-linear kinematic and isotropic hardening rule of Chaboche and Lemaitre. Mazzu´s approach is used in order to estimate the wear of wheel specimen as well as plastic shear strain accumulation in case of rolling/sliding contact after cycles in range from 4.10^5 to 1.10^6. Obtained results are compared with experimental data, available on author´s department.

  19. Wear behavior of contacting between thin film coating on SKD11 ball and 304 stainless steel disk

    Directory of Open Access Journals (Sweden)

    Sriprasird, J.

    2007-11-01

    Full Text Available Wear is a well known problem in metal stamping die, especially on the die working with stainless steel workpiece, in which wear rate is severe. This research considered various types of material coating on tool surface which were regularly practised in modern stamping industry due to the ability to increase wear resistance. The model study of friction "Ball-on-disk" technique was employed throughout this work. The disk was made from stainless steel austenitic grade (SUS304. The ball was made from cold work tool steel, SKD11 (JIS and was hardened to 60±2 HRC. Ball surface conditions selected for this work were non-coated, coated by TiC-CVD, TiCN (TiC/TiCN/TiN Multilayer-CVD and TiCN (TiN/TiCN Double layer-PVD, and treated by VC-TD. Tests were carried out without lubricant. The results show that the coating film and the surface treatment has no effect on the friction coefficient but it can reduce wear rate by 64.1-99.7% at contact pressure condition less than 1,100 MPa. At the higher level of contact pressure, only 2 types of coating, TiCN (Multilayer-CVD and TiC-CVD, can reduce wear rate. The other two, which are TiCN (Double layer-PVD coating film and a surface treatment by VC-TD process, on the contrary increase the rate of wear significantly. This is due to delamination of coating film at high contact pressure. The coating particles of high hardness accelerate wear phenomenon on the tool surface. Therefore, proper selection of tool surface condition depends on level of contact pressure generated in the process.

  20. Automated visual inspection of brake shoe wear

    Science.gov (United States)

    Lu, Shengfang; Liu, Zhen; Nan, Guo; Zhang, Guangjun

    2015-10-01

    With the rapid development of high-speed railway, the automated fault inspection is necessary to ensure train's operation safety. Visual technology is paid more attention in trouble detection and maintenance. For a linear CCD camera, Image alignment is the first step in fault detection. To increase the speed of image processing, an improved scale invariant feature transform (SIFT) method is presented. The image is divided into multiple levels of different resolution. Then, we do not stop to extract the feature from the lowest resolution to the highest level until we get sufficient SIFT key points. At that level, the image is registered and aligned quickly. In the stage of inspection, we devote our efforts to finding the trouble of brake shoe, which is one of the key components in brake system on electrical multiple units train (EMU). Its pre-warning on wear limitation is very important in fault detection. In this paper, we propose an automatic inspection approach to detect the fault of brake shoe. Firstly, we use multi-resolution pyramid template matching technology to fast locate the brake shoe. Then, we employ Hough transform to detect the circles of bolts in brake region. Due to the rigid characteristic of structure, we can identify whether the brake shoe has a fault. The experiments demonstrate that the way we propose has a good performance, and can meet the need of practical applications.

  1. Orthoptic indications for contact lens wear.

    Science.gov (United States)

    Evans, Bruce J W

    2006-09-01

    Orthoptic anomalies are prevalent: they are encountered in at least 5% of patients seen in a typical primary eyecare practice. Several cases are reviewed that highlight the role of contact lenses in treating orthoptic anomalies. In particular, contact lenses are the preferred optical approach to the correction of anisometropia, and it is often argued that anisometropia should be corrected as young as possible. However, fitting contact lenses to patients, particularly children, with anisometropic amblyopia has been problematic because there is no immediate binocular acuity improvement when the contact lenses are inserted which reduces patient motivation. Continuous wear with silicone hydrogels represents a breakthrough for these cases and some illustrative case studies are given. The visual deficit in amblyopia can be reduced in some cases solely by fitting contact lenses, without the need for occlusion therapy. Other orthoptic uses of contact lenses are reviewed including: correcting motor deviations, occlusion, and infantile onset nystagmus. It is concluded that there are orthoptic anomalies where contact lenses are the preferred mode of correction. It is in patients' best interest for practitioners to discuss contact lenses in these cases.

  2. Standard test method for ranking resistance of plastics to sliding wear using block-on-ring wear test—cumulative wear method

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2003-01-01

    1.1 This test method covers laboratory procedures for determining the resistance of plastics to sliding wear. The test utilizes a block-on-ring friction and wear testing machine to rank plastics according to their sliding wear characteristics against metals or other solids. 1.2 An important attribute of this test is that it is very flexible. Any material that can be fabricated into, or applied to, blocks and rings can be tested. Thus, the potential materials combinations are endless. In addition, the test can be run with different gaseous atmospheres and elevated temperatures, as desired, to simulate service conditions. 1.3 Wear test results are reported as the volume loss in cubic millimetres for the block and ring. Materials of higher wear resistance will have lower volume loss. 1.4 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only. 1.5 This standard does not purport to address all of the safety concerns, if any, associated with it...

  3. To wear or not to wear: current contact lens use in the Royal Canadian Mounted Police.

    Science.gov (United States)

    Wells, G A; Brown, J J; Casson, E J; Easterbrook, M; Trottier, A J

    1997-04-01

    The Canadian Ophthalmological Society was asked by the Royal Canadian Mounted Police (RCMP) and the Canadian Human Rights Commission to render an opinion on the acceptability of contact lenses as a reasonable accommodation to the uncorrected visual acuity standard. Survey by mailed questionnaire. Canada. All RCMP general duty constables with a visual acuity code of V3, V4, V5 or V6 (n = 348) and a random sample of approximately 25% of the constables with an acuity code of V2 (n = 809). Of the 1040 questionnaires returned, 1037 were usable (final response rate 89.6%). Of the 1037 respondents 316 were in the V3 to V6 group and 721 were in the V2 group. Reported frequency of problems with spectacles or contact lenses, weighted according to sampling fraction. A total of 934 respondents indicated that they used some form of visual acuity correction while on duty; of the 934, 360 reported that they wore contact lenses at least some of the time. Approximately 75% of the spectacle wearers reported having to remove their spectacles because of fogging or rain. Although contact lens dislogement or fogging (21.2%) was less frequent than spectacle dislogement (59.2%), 35.4% of the contact lens wearers reported that they were unable to wear their lenses because of irritation on at least one occasion in the previous 2 years; the median length of time was 3.14 days. When the additional amount of time due to other causes is factored in, it is clear that contact lens users wear spectacles for substantial periods while on duty. Not only are RCMP general duty constables who usually wear contact lenses likely to have to wear spectacles at some time, but it is also possible that they will have to remove their spectacles and function in an uncorrected state in critical situations. Thus, altering the current standard to allow the use of contact lenses as a reasonable accommodation would not ensure effective and safe job performance.

  4. Generic atmospheric correction models for radar measurements

    Science.gov (United States)

    Li, Zhenhong; Yu, Chen; Crippa, Paola; Penna, Nigel

    2017-04-01

    Atmospheric effects (especially the part due to tropospheric water vapour) represent one of the major error sources of repeat-pass Interferometric Synthetic Aperture Radar (InSAR), and limit the accuracy of InSAR derived surface displacements. The spatio-temporal variations of atmospheric water vapour make it a challenge to measure small-amplitude surface displacements with InSAR. In previous studies, several InSAR atmospheric correction models have been successfully demonstrated: (1) Ground-based correction models such as those using Global Navigation Satellite System (GNSS) and/or surface meteorological observations, (2) Space-based correction models including those involving NASA Moderate Resolution Imaging Spectroradiometer (MODIS) and/or ESA Medium Resolution Imaging Spectrometer (MERIS), and (3) Numerical Weather Model (NWM) based corrections including those using the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-Interim and/or Weather Research and Forecasting (WRF) models. Each model has its own inherited limitations. For example, ground-based correction models are limited by the availability (and distribution) of ground observations, whilst MODIS/MERIS correction models are sensitive to the presence of clouds and there is often a time difference between space-based water vapour and radar observations. Similar to space-based correction models, NWM correction models might be impacted by the time difference between NWM and radar observations. Taking into account the inherent advantages and limitations of GNSS, MODIS and ECMWF water vapour products, we aim to develop a global and near-real-time mode InSAR atmospheric correction model. Tropospheric delays can be routinely retrieved from ground-based GNSS arrays in all-weather conditions and also in real-time. We develop an Iterative Tropospheric Decomposition (ITD) interpolation model that decouples the GNSS-estimated total tropospheric delays into (i) a stratified component highly correlated

  5. Hardfacing materials used in valves for seating and wear surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Knecht, W.G.

    1996-12-01

    Most valves and essentially all critical service valves utilize hardfacing materials for seating and wear surfaces to minimize wear and galling. The type of hardfacing materials used, the methods of deposition, and the quality of the final product all contribute to the wear characteristics, required operating force, and life of the final product. Over the last forty years the most prevalent hardfacing materials furnished to the commercial nuclear industry consisted of cobalt base and nickel base materials. In the last several years there has been extensive development and evaluation work performed on iron base hardfacing materials. This presentation will address the wear characteristics of the various materials and the importance of consistent quality of deposited materials necessary to achieve optimum product performance and longevity.

  6. Severe wear behaviour of alumina balls sliding against diamond ...

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 39; Issue 2. Severe wear behaviour of alumina balls sliding against diamond ceramic coatings. ANURADHA JANA NANDADULAL DANDAPAT MITUN DAS VAMSI KRISHNA BALLA SHIRSHENDU CHAKRABORTY RAJNARAYAN SAHA AWADESH KUMAR MALLIK.

  7. WEAR-RESISTANCE OF CHROMIC CAST IRONS OF EUTECTIC COMPOSITION

    Directory of Open Access Journals (Sweden)

    K. E. Baranovskij

    2009-01-01

    Full Text Available Casting of wear-resistant chrome cast irons in combined molds and iron chills is studied. Application of these ways of casting results in blending of carbides and increasing of hardness of castings.

  8. Friction and wear methodologies for design and control

    CERN Document Server

    Straffelini, Giovanni

    2015-01-01

    This book introduces the basic concepts of contact mechanics, friction, lubrication, and wear mechanisms, providing simplified analytical relationships that are useful for quantitative assessments. Subsequently, an overview on the main wear processes is provided, and guidelines on the most suitable design solutions for each specific application are outlined. The final part of the text is devoted to a description of the main materials and surface treatments specifically developed for tribological applications and to the presentation of tribological systems of particular engineering relevance. The text is up to date with the latest developments in the field of tribology and provides a theoretical framework to explain friction and wear problems, together with practical tools for their resolution. The text is intended for students on Engineering courses (both bachelor and master degrees) who must develop a sound understanding of friction, wear, lubrication, and surface engineering, and for technicians or professi...

  9. Wear properties of nanosilica filled epoxy polymers and FRP composites

    Directory of Open Access Journals (Sweden)

    A. Jumahat

    2015-09-01

    Full Text Available This paper is aimed to determine the wear properties of nanosilica filled epoxy polymers and FRP composites. Woven fiberglass has been deployed as the reinforcement material. The fibers were mixed with three different percentages of nanosilica-modified epoxy resin, i.e: 5wt%; 13wt%; 25wt%, in order to fabricate the desired samples of FRP composites. The effect of nanosilica on wear properties was evaluated using dry sliding wear and slurry tests. The results show that increasing the amount of nanosilica content has reduced the amount of accumulated mass loss. It was found that the FRP laminates with 25wt% of nanosilica have the highest wear resistance. The nanosilica filled fiber reinforced polymer composites have a high potential in tribological application such as ball bearing housing and snow sleds.

  10. Clinical studies of dental erosion and erosive wear

    National Research Council Canada - National Science Library

    Huysmans, M.C.D.N.J.M; Chew, H.P; Ellwood, R.P

    2011-01-01

    We define erosion as a partial demineralisation of enamel or dentine by intrinsic or extrinsic acids and erosive tooth wear as the accelerated loss of dental hard tissue through the combined effect...

  11. RGW: Goodman-Weare Affine-Invariant Sampling

    Science.gov (United States)

    Mantz, Adam B.

    2017-11-01

    RGW is a lightweight R-language implementation of the affine-invariant Markov Chain Monte Carlo sampling method of Goodman & Weare (2010). The implementation is based on the description of the python package emcee (ascl:1303.002).

  12. Mitigation of wear damage by laser surface alloying technique

    CSIR Research Space (South Africa)

    Adebiyi, ID

    2016-04-01

    Full Text Available , and alloys having these specific properties are usually very expensive and their use drastically increases components and production costs. Moreover, the economic implications of wear, in form of detrimental effects – and waste, are severe. This includes...

  13. Wearing courses for unpaved roads in southern Africa: a review

    CSIR Research Space (South Africa)

    Netterberg, F

    1988-07-01

    Full Text Available The requirements of and some specifications for wearing courses for unpaved roads are reviewed. It is concluded that further development of specifications is required, and that there is probably great scope for improvement of our unpaved roads...

  14. Wear deformation of ordered Fe-Al intermetallic alloys

    Energy Technology Data Exchange (ETDEWEB)

    Maupin, H.E. (US Bureau of Mines, Albany Research Center, OR (United States)); Wilson, R.D. (US Bureau of Mines, Albany Research Center, OR (United States)); Hawk, J.A. (US Bureau of Mines, Albany Research Center, OR (United States))

    1993-04-13

    The Bureau of Mines conducted abrasive wear research on DO[sub 3] ordered and disordered Fe[sub 3]Al intermetallics. The effect of abrasion on these alloys was studied through mixroscopy, X-ray diffraction and hardness measurements. The region near the wear surface undergoes dynamic recrystallization, i.e. the original microstructural morphology of micron-size grains is replaced by one with nanosize grains. Abrasion of the Fe[sub 3]Al alloys also results in a loss of the DO[sub 3] ordering in the wear surface region. The bulk temperature rise of the specimen during abrasion was approximately 28 C which is insufficient to cause recrystallization in these alloys. Therefore, the flash temperature due to interface frictional heating is considered more important than the bulk temperature when considering dynamic recrystallization as the transformation mechanism in the near wear surface region. (orig.)

  15. 32 CFR 507.12 - Possession and wearing.

    Science.gov (United States)

    2010-07-01

    ... PUBLIC RELATIONS MANUFACTURE AND SALE OF DECORATIONS, MEDALS, BADGES, INSIGNIA, COMMERCIAL USE OF... Force by any person not properly authorized to wear such device, or the use of any decoration, service... Secretary of the Air Force. ...

  16. Study of wear performance of deep drawing tooling

    Science.gov (United States)

    Naranje, Vishal G.; Karthikeyan, Ram; Nair, Vipin

    2017-09-01

    One of the most common challenges for many of the mechanical engineers and also in the field of materials science is the issue of occurrences of wear of the material parts which is used in certain applications that involves such surface interactions. In this paper, wear behaviour of particular grade High Carbon High Chromium Steel and many most famously D2, H13, O1 known as the Viking steel has been studied, evaluated and analyzed under certain processing parameters such as speed, load, track diameter and time required for deep drawing process to know it’s the wear rate and coefficient of friction. Also, the significance of the processing parameters which is used for wear testing analysis is also examined.

  17. An Anthropological Perspective: Another Dimension to Modern Dental Wear Concepts

    Directory of Open Access Journals (Sweden)

    John A. Kaidonis

    2012-01-01

    Full Text Available For many years, research on tooth wear by dental academics has been diametrically opposite to that of anthropological research, with each discipline having a different understanding as to the nature of the wear processes. Dental focus revolved around preventive and restorative considerations while the anthropological focus was a biological understanding related to human evolution, diet, environment, form, and function and included all the craniofacial structures. Introducing the anthropological perspective into modern dentistry gives an insight into the “bigger picture” of the nature and extent of tooth wear. By combining anthropological evidence with clinical knowledge and experience, it is most likely to provide the best-informed and biologically based approach to the management of tooth wear in modern societies.

  18. Adverse events in allergy sufferers wearing contact lenses

    Science.gov (United States)

    Urgacz, Agnieszka; Mrukwa, Ewa

    2015-01-01

    Allergy is the fifth leading chronic condition in industrialized countries among all ages, and the third most common chronic disease among children under 18 years old. Many of allergic patients also have problems with vision and want to improve their quality of life by wearing contact lenses. They are most frequently young and active individuals, for whom contact lenses provide greater convenience and more satisfying vision correction than spectacles. However, application of high quality and immunologically neutral products do not protect from allergic side reactions. Nowadays, eye-related allergy and contact lens wear concern larger and larger populations worldwide. The purpose of this review is to summarize the studies on ocular complications associated with wearing contact lenses. The article presents indications for allergic patients especially on the care system and wear schedule. PMID:26161062

  19. Friction and Wear Behavior of Selected Dental Ceramics

    Science.gov (United States)

    Park, Jongee; Pekkan, Gurel; Ozturk, Abdullah

    The purpose of this study was to determine the friction coefficients and wear rates of six commercially available dental ceramics including IPS Empress 2 (E2), Cergo Pressable Ceramic (CPC), Cercon Ceram (CCS) and Super porcelain EX-3 (SPE). Bovine enamel (BE) was also tested as a reference material for comparison purposes. Samples of the dental ceramics were prepared according to the instructions described by the manufacturers in disk-shape with nominal dimensions of 12 mm × 2 mm. The wear tests were performed by means of a pin-on-disk type tribometer. The friction coefficients and specific wear rates of the materials were determined at a load of 10 N and rotating speed of 0.25 cm/s without lubrication. Surface morphology of the wear tracks was examined using a scanning electron microscope. Statistical analyses were made using one-way ANOVA and Turkey's HSD (P < 0.05).

  20. Analysis of polymerization time on abrasive wear of dental resins

    Directory of Open Access Journals (Sweden)

    Eduardo Carlos Bianchi

    2010-03-01

    Full Text Available An evaluation was made of the abrasive wear of six composite thermofixed dental resins subjected to different polymerization times. The method of evaluation was based on sharpness measurements to quantify the abrasive wear resistance of the resins. To this end, a test bench was built, consisting of a rotating porcelain cylinder that wears out a resin-coated cylinder placed above it, thus causing vertical displacement of the contact as the wear progresses. The values of vertical displacement, i.e., the input variables, were read and recorded by means of a computer program to obtain the sharpness values. These data indicated that the resins displayed different behaviors as a function of the polymerization times applied, reinforcing the importance of using a practical and rapid method of analysis in order to ensure that the behavior of new materials is fully understood before they are launched on the market.

  1. Tooth wear: prevalence and associated factors in general practice patients.

    Science.gov (United States)

    Cunha-Cruz, Joana; Pashova, Hristina; Packard, J D; Zhou, Lingmei; Hilton, Thomas J

    2010-06-01

    To estimate the prevalence of tooth wear and to investigate factors associated with tooth wear in patients from general practices in the Northwest United States. Data on the diagnosis and treatment of oral diseases during the previous year were collected in a survey with a systematic random sample of patients (n= 1530) visiting general dentists from the Northwest Practice-based REsearch Collaborative in Evidence-based DENTistry (PRECEDENT) (n=80). Prevalence ratios (PRs) of moderate to severe occlusal and incisal tooth wear by patient characteristics were estimated using cluster-adjusted multiple binomial regression for adults (18+ years) and children/adolescents (3-17 years). For adults, the mean number of teeth with wear facets was 5.4 [95% confidence interval (CI) =4.6-6.2] and 51% of the adults had four or more teeth with wear. Participants 45-64 and 65+ years old were 1.3 (95% CI=1.1-1.6) and 1.4 (95% CI=1.1-1.8) times as likely to have 4+ teeth with moderate to severe wear facets as participants 18-44 years old. Adult males had a 20% (PR=1.2; 95% CI=1.1-1.4) higher prevalence of wear than adult females. Adults who were using, or had ever used occlusal splints had higher prevalence of tooth wear compared to those who never used such appliances (PR=1.3; 95% CI=1.0-1.5). Adults with any periodontal bone loss also had a 20% higher prevalence of wear than adults without periodontal disease (PR=1.2; 95% CI=1.0-1.4). For children/adolescents, the mean number of teeth with moderate to severe wear facets was 1.6 (95% CI=0.9-2.6) and 31% of the children had one or more teeth with wear facets. The adjusted prevalence ratio of tooth wear (1+ teeth with wear facets) for boys was 1.6 times as high (95% CI=1.1-2.4) as compared with girls. The prevalence of wear for children 12+ years old was 50% (PR=0.5; 95% CI=0.3-0.8) lower than that of children treatment, missing teeth, and race/ethnicity. Tooth wear is a prevalent condition in this population. Among adults, higher

  2. Corrosion and wear resistant metallic layers produced by electrochemical methods

    DEFF Research Database (Denmark)

    Christoffersen, Lasse; Maahn, Ernst Emanuel

    1999-01-01

    Corrosion and wear-corrosion properties of novel nickel alloy coatings with promising production characteristics have been compared with conventional bulk materials and hard platings. Corrosion properties in neutral and acidic environments have been investigated with electrochemical methods...

  3. Evaluation Of Saltstone Mixer Paddle Configuration For Improved Wear Resistance

    Energy Technology Data Exchange (ETDEWEB)

    Reigel, M. M.; Fowley, M. D.; Pickenheim, B. R.

    2012-09-27

    A soft metal with low wear resistance (6000 series aluminum), was used to minimize run time while maximizing wear rate. Two paddle configurations were tested, with the first four paddles after the augers replaced by the wear paddles. The first configuration was all flat paddles, with the first paddle not aligned with the augers and is consistent with present SPF mixer. The second configuration had helical paddles for the first three stages after the augers and a flat paddle at the fourth stage. The first helical paddle was aligned with the auger flight for the second configuration. The all flat paddle configuration wear rate was approximately double the wear rate of the helical paddles for the first two sets of paddles after the augers. For both configurations, there was little or no wear on the third and fourth paddle sets based on mass change, indicating that the fully wetted premix materials are much less abrasive than the un-wetted or partially wetted premix. Additionally, inspection of the wear surface of the paddles at higher magnification showed the flat paddles were worn much more than the helical and is consistent with the wear rates. Aligning the auger discharge flight with the first set of helical paddles was effective in reducing the wear rate as compared to the flat paddle configuration. Changing the paddle configuration from flat to helical resulted in a slight increase in rheological properties. Although, both tests produced grout-like material that is within the processing rage of the SPF, it should be noted that cement is not included in the premix and water was used rather than salt solution, which does affect the rheology of the fresh grout. The higher rheological properties from the helical wear test are most likely due to the reduced number of shearing paddles in the mixer. In addition, there is variation in the rheological data for each wear test. This is most likely due to the way that the dry feeds enter the mixer from the dry feeder. The

  4. INTRODUCTION TO THE ANALYSIS OF THE MECHANICS OF THE DIAMOND GRINDING PROCESS WITH THE ACCOUNT OF WEAR OF WHEEL GRAINS

    Directory of Open Access Journals (Sweden)

    Feodor NOVIKOV

    2017-12-01

    Full Text Available The work is devoted to the theoretical analysis of the mechanics of the diamond grinding process, taking into account the wear of the wheel grains for scientifically based choice of optimal processing conditions. A multiplicative probabilistic approach to the generalization of the cutting profile of a diamond grinding wheel in its consideration in a state of some steady wear during processing is considered. This is achieved by working the wheel in a mode of properly established self-sharpening or with the use of effective dressing methods. In this case, the linear wear of individual grains of diamond abrasive located on the working surface of the grinding wheel and opened to mechanical contact with the material being processed is assumed to proportionally to the depth of the introduction of grain into it. The analytical dependence of the maximum thickness of the cut is presented, and the relationship between the maximum grain wear and the accepted universal relative characteristic of the steady wear with the operational parameters of the tool and the grinding mode is shown. The obtained results can be used in the development of analytical models of processing productivity and microgeometric engineering of the treated surface, new approaches to increasing the efficiency of diamond grinding. The research is based on modern technical possibilities of controlling the state of the cutting relief of diamond-abrasive tools, especially in electro-physical-mechanical grinding technologies, for example, using the diamond-spark method developed at the Kharkov Polytechnic Institute.

  5. Impacts on daily performances related to wearing orthodontic appliances

    OpenAIRE

    Bernabe, E; Sheiham, A.; Oliveira, C. M.

    2008-01-01

    Objective: To assess the prevalence, intensity, and extent of the impacts on daily performances related to wearing different types of orthodontic appliances.Materials and Methods: A total of 1657 students, 15 to 16 years old, were randomly selected from those attending all secondary schools in Bauru, Sao Paulo, Brazil. Only those wearing orthodontic appliances at the time of the survey were included. Face-to-face structured interviews were done to collect information about impacts on quality ...

  6. Experiment on wear behavior of high pressure gas seal faces

    Science.gov (United States)

    Xu, Jing; Peng, Xudong; Bai, Shaoxian; Meng, Xiangkai; Li, Jiyun

    2014-11-01

    Current researches show that mechanical deformation of seal ring face makes fluid film clearance decrease at high pressure side, thus a divergent clearance is formed and face wear occurs more seriously at the high pressure side than that on the low pressure side. However, there is still lack of published experimental works enough to prove the theoretical results. In this paper, a spiral groove dry gas seal at high pressures is experimentally investigated so as to prove the face wear happened at the high pressure side of seal faces due to the face mechanical deformation, and the wear behavior affected by seal ring structure is also studied. The experimental results show that face wear would occur at the high pressure side of seal faces due to the deformation, thus the leakage and face temperature increase, which all satisfies the theoretical predictions. When sealed pressure is not less than 5 MPa, the pressure can provide enough opening force to separate the seal faces. The seal ring sizes have obvious influence on face wear. Face wear, leakage and face temperature of a dry gas seal with the smaller cross sectional area of seal ring are less than that of a dry gas seal with bigger one, and the difference of leakage rate between these two sizes of seal face width is in the range of 24%-25%. Compared with the effect of seal ring sizes, the effect of secondary O-ring seal position on face deformation and face wear is less. The differences between these two types of dry gas seals with different secondary O-ring seal positions are less than 5.9% when the rotational speed varies from 0 to 600 r/min. By linking face wear and sealing performance changes to the shift in mechanical deformation of seal ring, this research presents an important experimental method to study face deformation of a dry gas seal at high pressures.

  7. An Anthropological Perspective: Another Dimension to Modern Dental Wear Concepts

    OpenAIRE

    Kaidonis, John A.; Sarbin Ranjitkar; Dimitra Lekkas; Townsend, Grant C.

    2012-01-01

    For many years, research on tooth wear by dental academics has been diametrically opposite to that of anthropological research, with each discipline having a different understanding as to the nature of the wear processes. Dental focus revolved around preventive and restorative considerations while the anthropological focus was a biological understanding related to human evolution, diet, environment, form, and function and included all the craniofacial structures. Introducing the anthropologic...

  8. Wear Assessment of Conical Pick used in Coal Cutting Operation

    Science.gov (United States)

    Dewangan, Saurabh; Chattopadhyaya, Somnath; Hloch, Sergej

    2015-09-01

    Conical pick is a widely used tool for cutting coal in mines. It has a cemented carbide tip inserted in a steel body. Cemented carbide has been in use for many years for coal/rock cutting because it has the optimum combination of hardness, toughness and resistance against abrasive wear. As coal/rock is a heterogeneous substance, the cutting tool has to undergo various obstructions at the time of excavation that cause the tool to wear out. The cracks and fractures developing in the cemented carbide limit the life of the tool. For a long time, different wear mechanisms have been studied to develop improved grades of cemented carbide with high wear resistance properties. The research is still continuing. Moreover, due to the highly unpredictable nature of coal/rock, it is not easy to understand the wear mechanisms. In the present work, an attempt has been made to understand the wear mechanisms in four conical picks, which were used in a continuous miner machine for underground mining of coal. The wearing pattern of the conical pick indicates damage in its cemented carbide tip as well as the steel body. The worn out parts of the tools have been critically examined using scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) point analysis. Mainly four types of wear mechanisms, namely, coal/rock intermixing, plastic deformation, rock channel formation and crushing and cracking, have been detected. The presence of coal/rock material and their respective concentrations in the selected area of worn out surface were observed using the spectra generated by EDX analysis.

  9. Disposable contact lenses vs. contact lens maintenance for extended wear.

    Science.gov (United States)

    Josephson, J E; Caffery, B E; Campbell, I; Slomovic, A R

    1990-01-01

    We compared a disposable extended wear contact lens modality with conventional extended wear over a 6-week period. To do so, we refit 31 patients who had successfully worn conventional extended wear contact lenses for more than 1 year. One eye was fit with the AcuvueR disposable contact lens, and a new extended wear lens of the type the patient had been wearing was placed on the other eye. At weekly intervals the disposable lens was discarded and a new disposable lens inserted. At the same time, the conventional lens on the fellow eye was cleaned, disinfected, and reinserted. After 6 weeks the ocular response, subjective impressions, and condition of the lenses in the two eyes were compared. Both lenses were then cultured. Three subjects had to discontinue disposable lens wear because of adverse reactions to trapped cellular debris and corneal microcysts. Although the results were not statistically significant, the Acuvue lens appeared to perform better than or equal to the conventional lens in biomicroscopic observation, visual acuity measurement, and subjective patient preference. Eighty-seven percent of patients preferred to continue with the disposable system. There were no differences found in the type or degree of microbial contamination of the lenses.

  10. Evaluation of hardness and wear resistance of interim restorative materials.

    Science.gov (United States)

    Savabi, Omid; Nejatidanesh, Farahnaz; Fathi, Mohamad Hossein; Navabi, Amir Arsalan; Savabi, Ghazal

    2013-03-01

    The interim restorative materials should have certain mechanical properties to withstand in oral cavity. The aim of this study was to evaluate the hardness and wear resistance of interim restorative materials. Fifteen identical rectangular shape specimens with dimensions of 2 mm × 10 mm × 30 mm were made from 7 interim materials (TempSpan, Protemp 3 Garant, Revotek, Unifast LC, Tempron, Duralay, and Acropars). The Vickers hardness and abrasive wear of specimens were tested in dry conditions and after 1 week storage in artificial saliva. The depth of wear was measured using surface roughness inspection device. Data were subjected to Kruskal-Wallis and Mann-Whitney tests. The Pearson correlation coefficient was used to determine the relationship between hardness and wear (α =0.05). TempSpan had the highest hardness. The wear resistance of TempSpan (in dry condition) and Revotek (after conditioning in artificial saliva) was significantly higher (P materials (P = 0.281, r = -0.31). Hardness and wear resistance of interim resins are material related rather than category specified.

  11. Impact Wear of Structural Steel with Yield Strength of 235 MPa in Various Liquids

    NARCIS (Netherlands)

    Liu, Y.; Janssen, G.C.A.M.

    2017-01-01

    The wear of pipelines, used in slurry transport, results in high costs for maintenance and replacement. The wear mechanism involves abrasion, corrosion, impact, and the interaction among them. In this work, we study the effect of impact on the wear mechanism and wear rate. Results show that when the

  12. Policies for Probe-Wear Leveling in MEMS-Based Storage Devices

    NARCIS (Netherlands)

    Khatib, M.G.; Hartel, Pieter H.

    2009-01-01

    Probes (or read/write heads) in MEMS-based storage devices are susceptible to wear. We study probe wear, and analyze the causes of probe uneven wear. We show that under real-world traces some probes can wear one order of magnitude faster than other probes leading to premature expiry of some probes.

  13. Influence of Thermal Cycling on Flexural Properties and Simulated Wear of Computer-aided Design/Computer-aided Manufacturing Resin Composites.

    Science.gov (United States)

    Tsujimoto, A; Barkmeier, W W; Takamizawa, T; Latta, M A; Miyazaki, M

    The purpose of this study was to evaluate the influence of thermal cycling on the flexural properties and simulated wear of computer-aided design/computer-aided manufacturing (CAD/CAM) resin composites. The six CAD/CAM resin composites used in this study were 1) Lava Ultimate CAD/CAM Restorative (LU); 2) Paradigm MZ100 (PM); 3) CERASMART (CS); 4) Shofu Block HC (SB); 5) KATANA AVENCIA Block (KA); and 6) VITA ENAMIC (VE). Specimens were divided randomly into two groups, one of which was stored in distilled water for 24 hours, and the other of which was subjected to 10,000 thermal cycles. For each material, 15 specimens from each group were used to determine the flexural strength and modulus according to ISO 6872, and 20 specimens from each group were used to examine wear using a localized wear simulation model. The test materials were subjected to a wear challenge of 400,000 cycles in a Leinfelder-Suzuki device (Alabama machine). The materials were placed in custom-cylinder stainless steel fixtures, and simulated localized wear was generated using a stainless steel ball bearing (r=2.387 mm) antagonist in a water slurry of polymethyl methacrylate beads. Simulated wear was determined using a noncontact profilometer (Proscan 2100) with Proscan and AnSur 3D software. The two-way analysis of variance of flexural properties and simulated wear of CAD/CAM resin composites revealed that material type and thermal cycling had a significant influence (p0.05) between the two factors. The flexural properties and maximum depth of wear facets of CAD/CAM resin composite were different (pinfluenced (p>0.05) by thermal cycling, except in the case of VE. The volume losses in wear facets on LU, PM, and SB after 10,000 thermal cycles were significantly higher (pinfluenced by thermal cycling.

  14. Changes in orientation of attritional wear facets with implications for jaw motion in a mixed longitudinal sample of Propithecus edwardsi from Ranomafana National Park, Madagascar.

    Science.gov (United States)

    Blatch, Stephanie; Boyer, Doug M; King, Stephen J; Bunn, Jonathan M; Jernvall, Jukka; Wright, Patricia C

    2011-09-01

    In many mammalian species, the progressive wearing down of the teeth that occurs over an individual's lifetime has the potential to change dental function, jaw movements, or even feeding habits. The orientation of phase-I wear facets on molars reveals the direction of jaw movement during the power stroke of mastication. We investigated if and how molar wear facets change with increasing wear and/or age by examining a mixed longitudinal dataset of mandibular tooth molds from wild Propithecus edwardsi (N = 32 individuals, 86 samples). Measurements of the verticality of wear facets were obtained from three-dimensional digital models generated from μCT scans. Results show that verticality decreases over the lifetime of P. edwardsi, a change that implies an increasingly lateral translation of the jaw as the teeth move into occlusion. A more transverse phase-I power stroke supports the hypothesis that these animals chew to maximize longevity and functionality of their teeth, minimizing the "waste" of enamel, while maintaining sharp shearing crests. Results of this study indicate that wear facet verticality is more closely correlated with age than overall amount of tooth wear, measured as area of exposed dentin, suggesting that age-related changes in cranial morphology may be more responsible for adjustments in jaw motion over the lifetimes of Propithecus than wear-related changes inthe shape of occluding teeth. Finally, the rate of decrease in wear facet verticality with age is greater in males than in females suggesting differences in development and/or access to resources between the sexes in this species. 2011 Wiley-Liss, Inc.

  15. Detecting Safety Zone Drill Process Parameters for Uncoated HSS Twist Drill in Machining GFRP Composites by Integrating Wear Rate and Wear Transition Mapping

    Directory of Open Access Journals (Sweden)

    Sathish Rao Udupi

    2016-01-01

    Full Text Available The previous research investigations informed that the tool wear of any machining operation could be minimized by controlling the machining factors such as speed, feed, geometry, and type of cutting tool. Hence the present research paper aims at controlling the process parameters to minimize the drill tool wear, during the machining of Glass Fiber Reinforced Polymer (GFRP composites. Experiments were carried out to find the tool wear rate and a wear mechanism map of uncoated High Speed Steel (HSS drill of 10 mm diameter was developed for the drilling of GFRP composite laminates. The surface micrograph images on the drill land surface displayed dominant wear mechanisms induced on HSS drill during machining of GFRP and they were found to be adhesive wear, adhesive and abrasive wear, abrasive wear, and diffusion and fatigue wear. A “safety wear zone” was identified on the wear mechanism map, where the minimum tool wear of the HSS drill occurs. From the safety zone boundaries, it was inferred that the drill spindle speed should be set between 1200 and 1590 rpm and feed rate must be set within a range of 0.10–0.16 mm/rev for GFRP work and HSS tool combination to enhance the service life of 10 mm HSS drills and to minimize the tool wear.

  16. The influence of wearing schemes and supportive telephone calls on adherence in accelerometry measurement: results of a randomized controlled trial

    Directory of Open Access Journals (Sweden)

    van den Berg N

    2017-03-01

    Full Text Available Neeltje van den Berg,1,2 Sabina Ulbricht,2,3 Thea Schwaneberg,1,2 Kerstin Weitmann,1,2 Franziska Weymar,1–3 Stefan Groß,2,4 Marcus Dörr,2,4 Wolfgang Hoffmann1,2 1Institute for Community Medicine, University Medicine Greifswald, 2German Centre for Cardiovascular Research (DZHK, Partner Site Greifswald, 3Institute of Social Medicine and Prevention, University Medicine Greifswald, 4Department of Internal Medicine B, University Medicine Greifswald, Greifswald, Germany Background: Physical activity (PA can be assessed by accelerometer monitors. However, a high adherence to wearing this device is essential to obtain valid data. In this study, the influence of different wearing schemes and additional supportive phone calls (SPCs on adherence was examined. Methods: A randomized study with four groups was conducted in the context of a health examination program among participants aged 40–75 years without a history of cardiovascular diseases. Participants were recruited in different settings (general medical practices, job center, and health insurance. The participants were asked to wear an accelerometer for 7 consecutive days according to the wearing scheme “day and night” or “day only” and received or did not receive SPCs. Full adherence was defined as a total wearing time of 98 hours (between 8 am and 10 pm during 7 days. A generalized linear model was used to calculate the difference between the maximum possible and the observed adherence. Results: Adherence could be assessed for 249 participants (mean age: 56.40 years; standard deviation [SD] 9.83, 40% males. The mean wearing time was 84.04 hours (SD 20.75. Participants with the wearing scheme day and night were significantly more adherent than participants with the wearing scheme day only (incidence rate ratio [IRR] 0.63; P=0.005. SPCs had no additional effect on adherence (IRR 0.80; P=0.168. Conclusion: To assess PA, the wearing scheme day and night provides the best possible

  17. Effect of different dental ceramic systems on the wear of human enamel: An in vitro study.

    Science.gov (United States)

    Zandparsa, Roya; El Huni, Rabie M; Hirayama, Hiroshi; Johnson, Marc I

    2016-02-01

    The wear of tooth structure opposing different advanced dental ceramic systems requires investigation. The purpose of this in vitro study was to compare the wear of advanced ceramic systems against human enamel antagonists. Four ceramic systems (IPS e.max Press, IPS e.max CAD, Noritake Super Porcelain EX-3, and LAVA Plus Zirconia) and 1 control group containing human enamel specimens were used in this study (n = 12). All specimens were fabricated as disks 11 mm in diameter and 3 mm thick. The mesiopalatal cusps of the maxillary third molars were prepared to serve as the enamel styluses. All specimens were embedded individually in 25 mm(3) autopolymerizing acrylic resin blocks. Wear was measured with a cyclic loading machine and a newly designed wear simulator. All enamel styluses (cusps) were scanned using the Activity 880 digital scanner (SmartOptics). Data from the base line and follow-up scans were collected and compared with Qualify 2012 3-dimensional (3D) and 2D digital inspection software (Geomagic), which aligned the models and detected the geometric changes and the wear caused by the antagonist specimen. One-way ANOVA was used to analyze the collected data. After 125,000 bidirectional loading cycles, the mean loss of opposing enamel volume for the enamel disks in the control group was 37.08 μm(3), the lowest mean value for IPS e.max Press system was 39.75 μm(3); 40.58 μm(3) for IPS e.max CAD; 45.08 μm(3) for Noritake Super Porcelain EX-3 system; and 48.66 μm(3) for the Lava Plus Zirconia system. No statically significant differences were found among the groups in opposing enamel volume loss (P=.225) or opposing enamel height loss (P=.149). In terms of opposing enamel height loss, Lava Plus Zirconia system showed the lowest mean value of 27.5 μm. The mean value for the IPS e.max CAD system was 27.91 μm; 29.08 μm for the control enamel; 33.25 μm for the IPS e.max Press system; and 34.75 μm for the Noritake Super Porcelain EX-3 system. Within the

  18. Zirconia phase transformation in retrieved, wear simulated, and artificially aged ceramic femoral heads.

    Science.gov (United States)

    Parkes, Maria; Sayer, Kathryn; Goldhofer, Markus; Cann, Philippa; Walter, William L; Jeffers, Jonathan

    2017-12-01

    Zirconia in Zirconia toughened alumina ceramic hip replacements exists in an unstable state and can transform in response to stress giving the material improved fracture toughness. Phase transformation also occurs under hydrothermal conditions such as exist in vivo. To predict the hydrothermal aging that will occur in vivo accelerated aging procedures have been used, but validation of these models requires the study of retrieved hip joints. Here 26 retrievals are analysed to determine the degree of phase transformation in vivo. These were compared with virgin heads, heads that had undergone the accelerated aging process and heads wear tested to 5 million cycles in a hip simulator. Monoclinic content and surface roughness were measured using Raman spectroscopy and white light interferometry respectively. The monoclinic content for retrieved heads was 28.5% ± 7.8, greater than twice that in virgin, aged, or wear tested heads and did not have a significant correlation with time, contrary to the predictions of the hydrothermal aging model. The surface roughness for retrieved heads in the unworn area was not significantly different to that in virgin, aged, or unworn areas of wear tested heads. However in worn areas of the retrieved heads, the surface roughness was higher than observed in wear simulator testing. These results indicate that current testing methodologies do not fully capture the operational conditions of the material and the real performance of future new materials may not be adequately predicted by current pre-clinical testing methods. © 2017 The Authors. Journal of Orthopaedic Research Published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society 35:2781-2789, 2017. © 2017 The Authors. Journal of Orthopaedic Research Published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society.

  19. Standard guide for measuring the wear volumes of piston ring segments run against flat coupons in reciprocating wear tests

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2011-01-01

    1.1 This guide covers and describes a profiling method for use accurately measuring the wear loss of compound-curved (crowned) piston ring specimens that run against flat counterfaces. It does not assume that the wear scars are ideally flat, as do some alternative measurement methods. Laboratory-scale wear tests have been used to evaluate the wear of materials, coatings, and surface treatments that are candidates for piston rings and cylinder liners in diesel engines or spark ignition engines. Various loads, temperatures, speeds, lubricants, and durations are used for such tests, but some of them use a curved piston ring segment as one sliding partner and a flat or curved specimen (simulating the cylinder liner) as its counterface. The goal of this guide is to provide more accurate wear measurements than alternative approaches involving weight loss or simply measuring the length and width of the wear marks. 1.2 This standard does not purport to address all of the safety concerns, if any, associated with its ...

  20. Wear analysis of disc cutters of full face rock tunnel boring machine

    Science.gov (United States)

    Zhang, Zhaohuang; Meng, Liang; Sun, Fei

    2014-11-01

    Wear is a major factor of disc cutters' failure. No current theory offers a standard for the prediction of disc cutter wear yet. In the field the wear prediction method commonly used is based on the excavation length of tunnel boring machine(TBM) to predict the disc cutter wear and its wear law, considering the location number of each disc cutter on the cutterhead(radius for installation); in theory, there is a prediction method of using arc wear coefficient. However, the preceding two methods have their own errors, with their accuracy being 40% or so and largely relying on the technicians' experience. Therefore, radial wear coefficient, axial wear coefficient and trajectory wear coefficient are defined on the basis of the operating characteristics of TBM. With reference to the installation and characteristics of disc cutters, those coefficients are modified according to penetration, which gives rise to the presentation of comprehensive axial wear coefficient, comprehensive radial wear coefficient and comprehensive trajectory wear coefficient. Calculation and determination of wear coefficients are made with consideration of data from a segment of TBM project(excavation length 173 m). The resulting wear coefficient values, after modification, are adopted to predict the disc cutter wear in the follow-up segment of the TBM project(excavation length of 5621 m). The prediction results show that the disc cutter wear predicted with comprehensive radial wear coefficient and comprehensive trajectory wear coefficient are not only accurate(accuracy 16.12%) but also highly congruous, whereas there is a larger deviation in the prediction with comprehensive axial wear coefficient(accuracy 41%, which is in agreement with the prediction of disc cutters' life in the field). This paper puts forth a new method concerning prediction of life span and wear of TBM disc cutters as well as timing for replacing disc cutters.

  1. Factors Affecting the Wear Resistance of Forging Tools

    Directory of Open Access Journals (Sweden)

    Zwierzchowski M.

    2017-09-01

    Full Text Available The durability of forging tools is a function of many variables: tool heat treatment, surface quality, temperature, pressure, number of forgings, diffusion layers (nitriding and many others. The objective of study was to analyze and compare the working conditions of forging tools. For the analysis of selected flat surfaces of tools. Analyzed forging dies subjected to normal use. Presented results of laboratory tests . The effect of temperature and time on the properties of the surface layer of forging tools. The results were compared with the literature data. This article shows the results of microhardness tests for forging dies which have forged the corresponding number of forgings. The results of laboratory studies on microhardness of hot working steel 1.2344 in the furnace at various temperatures and time are also presented. The working conditions of the forging tools are very complex. The most often described in the literature are: thermal fatigue, abrasive wear, mechanical fatigue and cracks. The article discusses the effects of increased temperature on the surface properties of forging tools. Forging dies were made of hot work tool steel 1.2344. FEM modeling of changes in the surface layer should take into account changes in tool hardness as a function of time (number of forgings.

  2. Aplicación del MDN al estudio de la corrosión de los convertidores Peirce - Smith

    Directory of Open Access Journals (Sweden)

    Verdeja, L. F.

    2004-04-01

    Full Text Available The Nodal Wear Model (NWM constitutes a tool of applicable work study the processes of differential corrosion in the Peirce – Smith convertor (PSC with the purpose of reaching significant improvements in duration and productivity of the several alternatives that one could utilize of the coating. For the application of the NWM to CPS is necessary of the knowledge the mechanisms of existent waste and the definition of the corrosion equations. With the NWM the outputs of corrosion in the tuyere zone of CPS are interpreted.

    El Modelo de Desgaste Nodal (MDN constituye una herramienta de trabajo aplicable al estudio de los procesos de corrosión diferencial en los convertidores Peirce - Smith (CPS con el propósito de alcanzar mejoras significativas en duración y productividad de las diferentes alternativas que se puedan manejar del revestimiento. La aplicación del MDN al CPS precisa del conocimiento de los mecanismos de desgaste existentes y la definición de las ecuaciones de corrosión. Con el MDN se interpretan los resultados de corrosión en la zona de toberas del CPS.

  3. Surface roughness and wear of resin cements after toothbrush abrasion

    Directory of Open Access Journals (Sweden)

    Sérgio Kiyoshi ISHIKIRIAMA

    2015-01-01

    Full Text Available Increased surface roughness and wear of resin cements may cause failure of indirect restorations. The aim of this study was to evaluate quantitatively the surface roughness change and the vertical wear of four resin cements subjected to mechanical toothbrushing abrasion. Ten rectangular specimens (15 × 5 × 4 mm were fabricated according to manufacturer instructions for each group (n = 10: Nexus 3, Kerr (NX3; RelyX ARC, 3M ESPE (ARC; RelyX U100, 3M ESPE (U100; and Variolink II, Ivoclar/Vivadent (VL2. Initial roughness (Ra, µm was obtained through 5 readings with a roughness meter. Specimens were then subjected to toothbrushing abrasion (100,000 cycles, and further evaluation was conducted for final roughness. Vertical wear (µm was quantified by 3 readings of the real profile between control and brushed surfaces. Data were subjected to analysis of variance, followed by Tukey’s test (p < 0.05. The Pearson correlation test was performed between the surface roughness change and wear (p < 0.05. The mean values of initial/final roughness (Ra, µm/wear (µm were as follows: NX3 (0.078/0.127/23.175; ARC (0.086/0.246/20.263; U100 (0.296/0.589/16.952; and VL2 (0.313/0.512/22.876. Toothbrushing abrasion increased surface roughness and wear of all resin cements tested, although no correlation was found between those variables. Vertical wear was similar among groups; however, it was considered high and may lead to gap formation in indirect restorations.

  4. Relating factors to wearing personal radiation protectors among healthcare professionals.

    Science.gov (United States)

    Heo, Yunjeong; Chun, Hosun; Kang, Seonghoon; Lee, Wonjin; Jang, Taewon; Park, Jongtae

    2016-01-01

    With increasing use of medical radiologic procedures, wearing proper protector should be emphasized to reduce occupational radiation exposures. This research describes the rates of lead apron wearing for radiation protection and assessed occupational factors related to wearing rates for various types of healthcare professionals. We conducted a self-administered questionnaire survey through a website, on-site visits, fax, and mail. Of the 13,489 participants, 8858 workers who could not completely separate themselves from radiological procedure areas. Their general characteristics (sex and age), work history (job title, duration of employment, and hospital type), and practices (frequency of radiation procedures, ability to completely separate from radiation, and frequency of wearing protective lead aprons) were examined. The mean rate of lead apron wearing during radiologic procedures was 48.0 %. The rate was different according to sex (male: 52.9 %, female: 39.6 %), hospital type (general hospital: 63.0 %, hospital: 51.3 %, clinic: 35.6 %, dental hospital/clinic: 13.3 %, public health center: 22.8 %), and job title (radiologic technologist: 50.3 %, doctor: 70.3 %, dentist/dental hygienist: 15.0 %, nurse/nursing assistant: 64.5 %) (p lead aprons by radiologic technologists and nurses/nursing assistants was associated with hospital type and exposure frequency score. For doctors, apron wearing was associated with employment duration. For dentists/dental hygienists, apron wearing was associated with the exposure frequency score. To improve working environments for healthcare professionals exposed to radiation, it is necessary to consider related factors, such as job title, duration of employment, and hospital type, when utilizing a planning and management system to prevent radiation-related health problems.

  5. Fissure sealant materials: Wear resistance of flowable composite resins.

    Science.gov (United States)

    Asefi, Sohrab; Eskandarion, Solmaz; Hamidiaval, Shadi

    2016-01-01

    Background. Wear resistance of pit and fissure sealant materials can influence their retention. Wear characteristics of sealant materials may determine scheduling of check-up visits. The aim of this study was to compare wear resistance of two flowable composite resins with that of posterior composite resin materials. Methods. Thirty-five disk-shaped specimens were prepared in 5 groups, including two flowable composite resins (Estelite Flow Quick and Estelite Flow Quick High Flow), Filtek P90 and Filtek P60 and Tetric N-Ceram. The disk-shaped samples were prepared in 25-mm diameter by packing them into a two-piece aluminum mold and then light-cured. All the specimens were polished for 1minute using 600-grit sand paper. The samples were stored in distilled water at room temperature for 1 week and then worn by two-body abrasion test using "pin-on-disk" method (with distilled water under a 15-Nload at 0.05 m/s, for a distance of 100 meter with Steatite ceramic balls antagonists). A Profilometer was used for evaluating the surface wear. Data were analyzed with the one-way ANOVA. Results. Estelite Flow Quick exhibited 2708.9 ± 578.1 μm(2) and Estelite Flow Quick High Flow exhibited 3206 ± 2445.1 μm(2)of wear but there were no significant differences between the groups. They demonstrated similar wear properties. Conclusion. Estelite flowable composite resins have wear resistance similar to nano- and micro-filled and micro-hybrid composite resins. Therefore, they can be recommended as pit and fissure sealant materials in the posterior region with appropriate mechanical characteristics.

  6. Impact of Advertising on Tampon Wear-time Practices

    Directory of Open Access Journals (Sweden)

    Kara E. Woeller

    2015-01-01

    Full Text Available Objectives (1 To determine whether advertising nighttime tampon use for up to eight hours was understood to be consistent with label recommendations and (2 to determine whether television and print advertising with this message affected tampon wear times in adults and teens. Methods (1 A comprehension study (online advertising and follow-up questionnaire among women aged 14–49 years (300 per group who viewed either the test or a control advertising message; (2 Diary-based surveys of tampon wear times performed prior to ( n = 292 adults, 18–49 years, 74 teens, 12–17 years and after ( n = 287 adults, 104 teens the launch of national advertising. Results Significantly more test message viewers than controls stated tampons should be worn less than or equal to eight hours (93.6% vs. 88.6%, respectively, P = 0.049. A directionally higher percentage of test message viewers said they would use a pad if sleeping longer than eight hours (52% vs. 42% of controls. Among the women who used tampons longer than eight hours when sleeping, 52% reported they would wake up and change compared with 45% of controls. No significant difference between baseline and follow-up diary surveys was found among teens or adults in various measures of tampon wear time (mean wear times; usage intervals from less than two hours to more than 10 hours; percentage of tampons used for more than or equal to eight hours; frequency of wearing at least one tampon more than eight hours. Conclusions Advertising nighttime tampon wear for up to eight hours effectively communicated label recommendations but did not alter tampon wear times. The informational intervention had limited impact on established habits.

  7. Fissure sealant materials: Wear resistance of flowable composite resins

    Directory of Open Access Journals (Sweden)

    Sohrab Asefi

    2016-08-01

    Full Text Available Background. Wear resistance of pit and fissure sealant materials can influence their retention. Wear characteristics of sealant materials may determine scheduling of check-up visits. The aim of this study was to compare wear resistance of two flowable composite resins with that of posterior composite resin materials. Methods. Thirty-five disk-shaped specimens were prepared in 5 groups, including two flowable composite resins (Estelite Flow Quick and Estelite Flow Quick High Flow, Filtek P90 and Filtek P60 and Tetric N-Ceram. The disk-shaped samples were prepared in 25-mm diameter by packing them into a two-piece aluminum mold and then light-cured. All the specimens were polished for 1minute using 600-grit sand paper. The samples were stored in distilled water at room temperature for 1 week and then worn by two-body abrasion test using "pin-on-disk" method (with distilled water under a 15-Nload at 0.05 m/s, for a distance of 100 meter with Steatite ceramic balls antagonists. A Profilometer was used for evaluating the surface wear. Data were analyzed with the one-way ANOVA. Results. Estelite Flow Quick exhibited 2708.9 ± 578.1 μm2 and Estelite Flow Quick High Flow exhibited 3206 ± 2445.1 μm2of wear but there were no significant differences between the groups. They demonstrated similar wear properties. Conclusion. Estelite flowable composite resins have wear resistance similar to nano- and micro-filled and micro-hybrid composite resins. Therefore, they can be recommended as pit and fissure sealant materials in the posterior region with appropriate mechanical characteristics.

  8. How quantity and quality of brace wear affect the brace treatment outcomes for AIS.

    Science.gov (United States)

    Lou, Edmond H M; Hill, Douglas L; Raso, Jim V; Moreau, Marc; Hedden, Douglas

    2016-02-01

    To determine the reliability of a prognostic curve progression model and the role of the quantity and quality of brace wear for adolescent idiopathic scoliosis (AIS) brace treatment. To develop a curve progression model for full-time AIS brace treatment, 20 AIS subjects (Group 1) prescribed full-time thoracolumbar sacral orthosis (TLSO) were monitored and followed for 2 years beyond maturity. The developed curve progression model was: curve progression (in degrees) = 33 + 0.11 × Peterson risk (%) - 0.07 in-brace correction (%) - 0.45 × quality (%) - 0.48 × quantity (%) + 0.0062 × quantity × quality. To validate the model, 40 new (test) subjects (Group 2) who met the same inclusion criteria and used the same type of monitors, were monitored and followed for 2 years after bracing. For the 40 test subjects (Group 2), the average in-brace correction was 40 ± 22 %. The average quantity and quality of the brace wear were 56 ± 19 and 55 ± 17 %, respectively. Twelve subjects (30 %) progressed of which 10 subjects (25 %) required surgery and 28 subjects (70 %) showed no progression. The accuracy of the model to determine which patients would progress was 88 % (35/40) which was better than the Peterson's risk model (68 %; 26/40) alone. Patients who had the combined quantity times the quality over a threshold 43 % had a success treatment rate of 95 %. This study showed the prognostic model of brace treatment outcome on AIS patients treated with full-time TLSO was reliable. Both the quantity and quality of the brace wear were important factors in achieving successful brace treatment.

  9. Tribological and Wear Performance of Carbide Tools with TiB2 PVD Coating under Varying Machining Conditions of TiAl6V4 Aerospace Alloy

    Directory of Open Access Journals (Sweden)

    Jose Mario Paiva

    2017-11-01

    Full Text Available Tribological phenomena and tool wear mechanisms during machining of hard-to-cut TiAl6V4 aerospace alloy have been investigated in detail. Since cutting tool wear is directly affected by tribological phenomena occurring between the surfaces of the workpiece and the cutting tool, the performance of the cutting tool is strongly associated with the conditions of the machining process. The present work shows the effect of different machining conditions on the tribological and wear performance of TiB2-coated cutting tools compared to uncoated carbide tools. FEM modeling of the temperature profile on the friction surface was performed for wet machining conditions under varying cutting parameters. Comprehensive characterization of the TiB2 coated vs. uncoated cutting tool wear performance was made using optical 3D imaging, SEM/EDX and XPS methods respectively. The results obtained were linked to the FEM modeling. The studies carried out show that during machining of the TiAl6V4 alloy, the efficiency of the TiB2 coating application for carbide cutting tools strongly depends on cutting conditions. The TiB2 coating is very efficient under roughing at low speeds (with strong buildup edge formation. In contrast, it shows similar wear performance to the uncoated tool under finishing operations at higher cutting speeds when cratering wear predominates.

  10. High Density Infrared (HDI) Transient Liquid Coatings for Improved Wear and Corrosion Resistance

    Energy Technology Data Exchange (ETDEWEB)

    Ronald W. Smith

    2007-07-05

    This report documents a collaborative effort between Oak Ridge National Laboratory (ORNL), Materials Resources International and an industry team of participants to develop, evaluate and understand how high density infrared heating technology could be used to improve infiltrated carbide wear coatings and/or to densify sprayed coatings. The research included HDI fusion evaluations of infiltrated carbide suspensions such (BrazeCoat® S), composite suspensions with tool steel powders, thermally sprayed Ni-Cr- B-Si (self fluxing alloy) and nickel powder layers. The applied work developed practical HDI / transient liquid coating (TLC) procedures on test plates that demonstrated the ability to fuse carbide coatings for industrial applications such as agricultural blades, construction and mining vehicles. Fundamental studies helped create process models that led to improved process understanding and control. The coating of agricultural blades was demonstrated and showed the HDI process to have the ability to fuse industrial scale components. Sliding and brasive wear tests showed that high degree of wear resistance could be achieved with the addition of tool steel powders to carbide particulate composites.

  11. Virtual Sensors for On-line Wheel Wear and Part Roughness Measurement in the Grinding Process

    Science.gov (United States)

    Arriandiaga, Ander; Portillo, Eva; Sánchez, Jose A.; Cabanes, Itziar; Pombo, Iñigo

    2014-01-01

    Grinding is an advanced machining process for the manufacturing of valuable complex and accurate parts for high added value sectors such as aerospace, wind generation, etc. Due to the extremely severe conditions inside grinding machines, critical process variables such as part surface finish or grinding wheel wear cannot be easily and cheaply measured on-line. In this paper a virtual sensor for on-line monitoring of those variables is presented. The sensor is based on the modelling ability of Artificial Neural Networks (ANNs) for stochastic and non-linear processes such as grinding; the selected architecture is the Layer-Recurrent neural network. The sensor makes use of the relation between the variables to be measured and power consumption in the wheel spindle, which can be easily measured. A sensor calibration methodology is presented, and the levels of error that can be expected are discussed. Validation of the new sensor is carried out by comparing the sensor's results with actual measurements carried out in an industrial grinding machine. Results show excellent estimation performance for both wheel wear and surface roughness. In the case of wheel wear, the absolute error is within the range of microns (average value 32 μm). In the case of surface finish, the absolute error is well below Ra 1 μm (average value 0.32 μm). The present approach can be easily generalized to other grinding operations. PMID:24854055

  12. Interproximal wear versus incisors extraction to solve anterior lower crowding: A systematic review

    Directory of Open Access Journals (Sweden)

    Natália Valli de Almeida

    2015-02-01

    Full Text Available OBJECTIVE: To determine by means of a systematic review the best treatment, whether interproximal wear or incisor extraction, to correct anterior lower crowding in Class I patients in permanent dentition. METHODS: A literature review was conducted using MEDLINE, Scopus and Web of Science to retrieve studies published between January 1950 and October 2013. In selecting the sample, the following inclusion criteria were applied: studies involving interproximal wear and/or extraction of mandibular incisors, as well as Class I cases with anterior lower crowding in permanent dentition. RESULTS: Out of a total of 943 articles found after excluding duplicates, 925 were excluded after abstract analysis. After full articles were read, 13 were excluded by the eligibility criteria and one due to methodological quality; therefore, only fours articles remained: two retrospective and two randomized prospective studies. Data were collected, analyzed and organized in tables. CONCLUSION: Both interproximal wear and mandibular incisor extraction are effective in treating Class I malocclusion in permanent dentition with moderate anterior lower crowding and pleasant facial profile. There is scant evidence to determine the best treatment option for each case. Clinical decision should be made on an individual basis by taking into account dental characteristics, crowding, dental and oral health, patient's expectations and the use of set-up models.

  13. Virtual sensors for on-line wheel wear and part roughness measurement in the grinding process.

    Science.gov (United States)

    Arriandiaga, Ander; Portillo, Eva; Sánchez, Jose A; Cabanes, Itziar; Pombo, Iñigo

    2014-05-19

    Grinding is an advanced machining process for the manufacturing of valuable complex and accurate parts for high added value sectors such as aerospace, wind generation, etc. Due to the extremely severe conditions inside grinding machines, critical process variables such as part surface finish or grinding wheel wear cannot be easily and cheaply measured on-line. In this paper a virtual sensor for on-line monitoring of those variables is presented. The sensor is based on the modelling ability of Artificial Neural Networks (ANNs) for stochastic and non-linear processes such as grinding; the selected architecture is the Layer-Recurrent neural network. The sensor makes use of the relation between the variables to be measured and power consumption in the wheel spindle, which can be easily measured. A sensor calibration methodology is presented, and the levels of error that can be expected are discussed. Validation of the new sensor is carried out by comparing the sensor's results with actual measurements carried out in an industrial grinding machine. Results show excellent estimation performance for both wheel wear and surface roughness. In the case of wheel wear, the absolute error is within the range of microns (average value 32 μm). In the case of surface finish, the absolute error is well below Ra 1 μm (average value 0.32 μm). The present approach can be easily generalized to other grinding operations.

  14. Study on Composition, Microstructure and Wear Behavior of Fe-B-C Wear-Resistant Surfacing Alloys

    Science.gov (United States)

    Zhuang, Minghui; Li, Muqin; Wang, Jun; Ma, Zhen; Yuan, Shidan

    2017-11-01

    Fe-B-C alloy layers with various microstructures were welded on Q235 steel plates using welding powders/H08Mn2Si and welding wires composite surfacing technology. The relationship existing between the chemical composition, microstructure and wear resistance of the surfacing alloy layers was investigated by scanning electron microscopy, x-ray diffraction, electron backscatter diffraction and wear tests. The results demonstrated that the volume fractions and morphologies of the microstructures in the surfacing alloy layers could be controlled by adjusting the boron and carbon contents in the welding powders, which could further regulate the wear resistance of the surfacing alloy layers. The typical microstructures of the Fe-B-C surfacing alloy layers included dendritic Fe, rod-like Fe2B, fishbone-like Fe2B and daisy-like Fe3(C, B). The wear resistance of the alloy layers with various morphologies differed. The wear resistance order of the different microstructures was: rod-like Fe2B > fishbone-like Fe2B > daisy-like Fe3(C, B) > dendritic Fe. A large number of rod-like Fe2B with high microhardness could be obtained at the boron content of 5.70 5.90 wt.% and the carbon content of 0.50 0.60wt.%. The highest wear resistance of the Fe-B-C alloy layers reached the value of 24.1 g-1, which demonstrates the main microscopic cutting wear mechanism of the Fe-B-C alloy layers.

  15. Not only hard contact lens wear but also soft contact lens wear may be associated with blepharoptosis.

    Science.gov (United States)

    Bleyen, Isabel; Hiemstra, Coen A; Devogelaere, Thibaut; van den Bosch, Willem A; Wubbels, Rene J; Paridaens, Dion A

    2011-08-01

    The authors attempt to establish an association between prolonged hard and soft contact lens wear and ptosis. Single-center retrospective consecutive series. All patients between 18 and 50 years of age who were diagnosed with unilateral or bilateral ptosis between January 2002 and December 2005 (35 patients). In a retrospective consecutive series, we included all patients between 18 and 50 years of age, with unilateral or bilateral ptosis between January 2002 and December 2005. Patients with congenital ptosis, ophthalmic surgery or disease, trauma, giant papillary conjunctivitis, unknown duration of contact lens wear, or muscular or neurologic disorders were excluded. We compared this study group to a Dutch reference population (the total underlying population from which the ptosis cases derive). The group included 35 patients: 20 (57%) (ages 18 to 50 years, average 37 years) had been wearing hard contact lenses for, on average, 17.6 years (range 6 to 27 years); 9 (26%) (ages 18 to 45 years, average 30 years) had been wearing soft contact lenses for, on average, 9 years (range 1.5 to 20 years); and 6 (17%) (ages 23 to 39 years, average 33 years) had no history of contact lens wear. The odds ratio for soft contact lenses was 14.7 (4.2 to 50.7; CI = 95) and for hard contact lenses 97.8 (22.5 to 424). This study suggests that not only hard contact lens wear but also soft contact lens wear may be associated with ptosis. Copyright © 2011 Canadian Ophthalmological Society. Published by Elsevier Inc. All rights reserved.

  16. Characterization of polyethylene wear particle: The impact of methodology.

    Science.gov (United States)

    Schröder, Christian; Reinders, Jörn; Zietz, Carmen; Utzschneider, Sandra; Bader, Rainer; Kretzer, J Philippe

    2013-12-01

    Due to the prevalence of problems caused by wear particles, the reduced durability of total joint replacements is well documented. The characterization of wear debris enables the size and morphology of these wear particles to be measured and provides an assessment of the biological response in vivo. However, the impact of different methodologies of particle analysis is not yet clear. Hence, the aim of this investigation was to analyze the influence of different particle characterization methods performed by three research centers within the scope of a "round robin test". To obtain knowledge about possible pitfalls, single steps of the particle characterization process (storage, pore size of the filter, coating durations by gold sputtering and scanning electron microscopy (SEM) magnification) were analyzed. The round robin test showed significant differences between the research groups, especially for the morphology of the particles. The SEM magnification was identified as having the greatest influence on the size and shape of the particles, followed by the storage conditions of the wear particle containing lubricant. Gold sputter coating and filter pore size also exhibit significant effects. However, even though they are statistically significant, it should be emphasized that the differences are small. In conclusion, particle characterization is a complex analytical method with a multiplicity of influencing factors. It becomes apparent that a comparison of wear particle results between different research groups is challenging. Copyright © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  17. Manganese steel in impact wear testing; Manganhartstahl in Stossverschleisstest

    Energy Technology Data Exchange (ETDEWEB)

    Patzelt, B.; Hemmann, U.; Deters, L. [Magdeburg Univ. (Germany). Inst. fuer Maschinenkonstruktion

    2000-12-01

    Beating arms in impact crushers show high wear. In order to simulate the process of the mainly occuring impact wear, experimental investigations with a special test device were carried out. With this 11 different charges of manganese steel differing in their chemical composition were tested. The different chemical composition of the charges led to different results concerning the wear resistance. A significant interrelationship between wear resistance and macro-hardness of the charges of the manganese steel could be detected. With a faster rotor speed a considerable increase of wear could be determined as well. Microscopical investigations on worn test pieces exhibit a typical embedding of small particles of concrete into the metal matrix. (orig.) [German] Die Schlagleisten in Prallbrechern unterliegen einen hohen Verschleiss. Um den Prozess des hauptsaechlich auftretenden Stossverschleisses zu simulieren, wurden Modelluntersuchungen mit einer speziellen Pruefeinrichtung durchgefuehrt. Dabei konnten 11 verschiedene Chargen von Manganhartstahl, die sich im wesentlichen in ihrer chemischen Zusammensetzung unterschieden, untersucht werden. Die unterschiedliche chemische Zusammensetzung der einzelnen Chargen fuehrte zu unterschiedlichen Ergebnissen hinsichtlich der Verschleissbestaendigkeit der einzelnen Modellschlagleisten. Hierbei ist ein signifikanter Zusammenhang zwischen der Verschleissbestaendigkeit und der Makrohaerte der Manganhartstaehle zu erkennen. Die Umfangsgeschwindigkeit des Rotors der Pruefeinrichtung beeinflusst ebenfalls das Verschleissverhalten, und zwar fuehrte eine hoehere Umfangsgeschwindigkeit zu hoeherem Verschleiss. Mikroskopische Untersuchungen an geschaedigten Probekoerpern zeigten ein Einbetten von kleinsten Partikeln aus Beton im oberflaechennahen Stoffbereich der Metallmatrix. (orig.)

  18. Evolution of wear and friction along experimental faults

    Science.gov (United States)

    Boneh, Yeval; Chang, Jefferson C.; Lockner, David A.; Reches, Zeev

    2014-01-01

    We investigate the evolution of wear and friction along experimental faults composed of solid rock blocks. This evolution is analyzed through shear experiments along five rock types, and the experiments were conducted in a rotary apparatus at slip velocities of 0.002–0.97 m/s, slip distances from a few millimeters to tens of meters, and normal stress of 0.25–6.9 MPa. The wear and friction measurements and fault surface observations revealed three evolution phases: A) An initial stage (slip distances surface; B) a running-in stage of slip distances of 1–3 m with intense wear-rate, failure of many asperities, and simultaneous reduction of the friction coefficient and wear-rate; and C) a steady-state stage that initiates when the fault surface is covered by a gouge layer, and during which both wear-rate and friction coefficient maintain quasi-constant, low levels. While these evolution stages are clearly recognizable for experimental faults made from bare rock blocks, our analysis suggests that natural faults “bypass” the first two stages and slip at gouge-controlled steady-state conditions.

  19. Wear resistance of experimental titanium alloys for dental applications.

    Science.gov (United States)

    Faria, Adriana Cláudia Lapria; Rodrigues, Renata Cristina Silveira; Claro, Ana Paula Rosifini Alves; da Gloria Chiarello de Mattos, Maria; Ribeiro, Ricardo Faria

    2011-11-01

    The present study evaluated microstructure, microhardness and wear resistance of experimental titanium alloys containing zirconium and tantalum. Alloys were melted in arc melting furnace according to the following compositions: Ti-5Zr, Ti-5Ta and Ti-5Ta-5Zr (%wt). Hemispheres and disks were obtained from wax patterns that were invested and cast by plasma. Microstructures were evaluated using optical microscopy and X-ray diffraction (XRD) analysis and also Vickers microhardness was measured. Hemispherical samples and disks were used for 2-body wear tests, performed by repeated grinding of the samples. Wear resistance was assessed as height loss after 40,000 cycles. The data were compared using ANOVA and post-hoc Tukey test. Ti-5Zr presented a Widmanstätten structure and the identified phases were α and α' while Ti-5Ta and Ti-5Ta-5Zr presented α, β, α' and α" phases, but the former presented a lamellar structure, and the other, acicular. The microhardness of Ti-5Zr was significantly greater than other materials and cp Ti presented wear resistance significantly lower than experimental alloys. It was concluded that wear resistance was improved when adding Ta and Zr to titanium and Zr increased microhardness of Ti-5Zr alloy. Copyright © 2011 Elsevier Ltd. All rights reserved.

  20. Agave Chewing and Dental Wear: Evidence from Quids.

    Directory of Open Access Journals (Sweden)

    Emily E Hammerl

    Full Text Available Agave quid chewing is examined as a potential contributing behavior to hunter-gatherer dental wear. It has previously been hypothesized that the contribution of Agave quid chewing to dental wear would be observed in communities wherever phytolith-rich desert succulents were part of subsistence. Previous analysis of coprolites from a prehistoric agricultural site, La Cueva de los Muertos Chiquitos in Durango, Mexico, showed that Agave was a consistent part of a diverse diet. Therefore, quids recovered at this site ought to be useful materials to test the hypothesis that dental wear was related to desert succulent consumption. The quids recovered from the site were found to be largely derived from chewing Agave. In this study, the quids were found to be especially rich in phytoliths, and analysis of dental casts made from impressions left in the quids revealed flat wear and dental attrition similar to that of Agave-reliant hunter-gatherers. Based on evidence obtained from the analysis of quids, taken in combination with results from previous studies, it is determined that Agave quid chewing was a likely contributing factor to dental wear in this population. As such, our method provides an additional avenue of dental research in areas where quids are present.

  1. Agave Chewing and Dental Wear: Evidence from Quids.

    Science.gov (United States)

    Hammerl, Emily E; Baier, Melissa A; Reinhard, Karl J

    2015-01-01

    Agave quid chewing is examined as a potential contributing behavior to hunter-gatherer dental wear. It has previously been hypothesized that the contribution of Agave quid chewing to dental wear would be observed in communities wherever phytolith-rich desert succulents were part of subsistence. Previous analysis of coprolites from a prehistoric agricultural site, La Cueva de los Muertos Chiquitos in Durango, Mexico, showed that Agave was a consistent part of a diverse diet. Therefore, quids recovered at this site ought to be useful materials to test the hypothesis that dental wear was related to desert succulent consumption. The quids recovered from the site were found to be largely derived from chewing Agave. In this study, the quids were found to be especially rich in phytoliths, and analysis of dental casts made from impressions left in the quids revealed flat wear and dental attrition similar to that of Agave-reliant hunter-gatherers. Based on evidence obtained from the analysis of quids, taken in combination with results from previous studies, it is determined that Agave quid chewing was a likely contributing factor to dental wear in this population. As such, our method provides an additional avenue of dental research in areas where quids are present.

  2. Testing of a Fiber Optic Wear, Erosion and Regression Sensor

    Science.gov (United States)

    Korman, Valentin; Polzin, Kurt A.

    2011-01-01

    The nature of the physical processes and harsh environments associated with erosion and wear in propulsion environments makes their measurement and real-time rate quantification difficult. A fiber optic sensor capable of determining the wear (regression, erosion, ablation) associated with these environments has been developed and tested in a number of different applications to validate the technique. The sensor consists of two fiber optics that have differing attenuation coefficients and transmit light to detectors. The ratio of the two measured intensities can be correlated to the lengths of the fiber optic lines, and if the fibers and the host parent material in which they are embedded wear at the same rate the remaining length of fiber provides a real-time measure of the wear process. Testing in several disparate situations has been performed, with the data exhibiting excellent qualitative agreement with the theoretical description of the process and when a separate calibrated regression measurement is available good quantitative agreement is obtained as well. The light collected by the fibers can also be used to optically obtain the spectra and measure the internal temperature of the wear layer.

  3. The Biologic Response to Polyetheretherketone (PEEK) Wear Particles in Total Joint Replacement: A Systematic Review.

    Science.gov (United States)

    Stratton-Powell, Ashley A; Pasko, Kinga M; Brockett, Claire L; Tipper, Joanne L

    2016-11-01

    quantified PEEK-based particles produced using hip, knee, and spinal joint replacement simulators, the mean particle size was 0.23 µm to 2.0 µm. The absolute range reported was approximately 0.01 µm to 50 µm. Rod-like carbon particulates and granular-shaped PEEK particles were identified in human tissue by histologic analysis. Ten studies, including six animal models (rat, mouse, and rabbit), three cell line experiments, and two human tissue retreival studies, investigated the biologic response to PEEK-based particles. Qualitative histologic assessments showed immunologic cell infiltration to be similar for PEEK particles when compared with UHMWPE particles in all six of the animal studies identified. However, increased inflammatory cytokine release (such as tumor necrosis factor-α) was identified in only one in vitro study, but without substantial suppression in macrophage viability. Only one study tested the effects of particle size on cytotoxicity and found the largest unfilled PEEK particles (approximately 13 µm) to have a toxic effect; UHMWPE particles in the same size range showed a similar cytotoxic effect. Wear particles produced by PEEK-based bearings were, in almost all cases, in the phagocytozable size range (0.1-10 µm). The studies that evaluated the biologic response to PEEK-based particles generally found cytotoxicity to be within acceptable limits relative to the UHMWPE control, but inconsistent when inflammatory cytokine release was considered. To translate new and advanced materials into clinical use more quickly, the clinical relevance and validity of preclinical tests need to be improved. To achieve this for PEEK-based devices, human tissue retrieval studies including subsequent particle isolation and characterization analyses are required. In vitro cell studies using isolated wear particles from tissue or validated joint replacement simulators, instead of manufactured particles, are also required.

  4. Effect of Polyethylene Crosslinking and Bearing Design on Wear of Unicompartmental Arthroplasty.

    Science.gov (United States)

    Netter, Jonathan; Hermida, Juan C; D'Alessio, Jerry; Kester, Mark; D'Lima, Darryl D

    2015-08-01

    Wear and polyethylene damage continue to be important factors affecting outcomes of unicompartmental knee arthroplasty. We compared two design rationales for unicompartmental arthroplasty: fully congruent mobile bearings; or moderately conforming fixed bearings using experimental and computational wear simulation. Experimental wear rates were 3.89 (±0.12) mg/million cycles for the highly crosslinked Triathlon PKR fixed bearing compared to 18.35 (±0.19) mg/million cycles for the low crosslinked Oxford mobile bearing. Finite element analysis was used to calculate the effect of crosslinking and backside wear. Increase in polyethylene crosslinking reduced wear by 68% while backside wear comprised 46% of the total wear in the mobile bearing. Increasing conformity may not be the sole predictor of wear performance and highly crosslinked fixed-bearing polyethylene insert can also provide high wear performance. Copyright © 2015 Elsevier Inc. All rights reserved.

  5. The research on tool wear of high speed milling titanium alloy TC4

    Science.gov (United States)

    Shi, Hongliang; Wang, Zhichao; Ren, Huanhuan; Yuan, Haoteng

    2017-01-01

    In this paper, carbide cutting tools with physical vapor deposition (PVD) coating was used to high speed milling α+β phase TC4 titanium alloy. The PVD tool was used to study the process of milling TC4 titanium alloy tool wear patterns and wear mechanisms. The results showed that the PVD coating surface wear was small after cutter blade. The cutting life was long, it was suitable for processing of titanium alloy TC4, the wear of rake face was mainly adhesion wear and oxidation wear, the flank face was mainly boundary wear. That was because the adhesion wear of the rake face and the boundary wear of the flank face had a weakening effect on the cutting edge , which made the micro crack blade of the main cutting edge.

  6. A probabilistic-based approach to monitoring tool wear state and assessing its effect on workpiece quality in nickel-based alloys

    Science.gov (United States)

    Akhavan Niaki, Farbod

    mechanisms of tool failure were first identified and, based on the rapid catastrophic failure of the tool, a Bayesian inference method (i.e., Markov Chain Monte Carlo, MCMC) was used for parameter calibration of tool wear using a power mechanistic model. The calibrated model was then used in the state space probabilistic framework of a Kalman filter to estimate the tool flank wear. Furthermore, an on-machine laser measuring system was utilized and fused into the Kalman filter to improve the estimation accuracy. In the turning operation the behavior of progressive wear was investigated as well. Due to the nonlinear nature of wear in turning, an extended Kalman filter was designed for tracking progressive wear, and the results of the probabilistic-based method were compared with a deterministic technique, where significant improvement (more than 60% increase in estimation accuracy) was achieved. To fulfill the second objective of this research in understanding the underlying effects of wear on part quality in cutting nickel-based superalloys, a comprehensive study on surface roughness, dimensional integrity and residual stress was conducted. The estimated results derived from a probabilistic filter were used for finding the proper correlations between wear, surface roughness and dimensional integrity, along with a finite element simulation for predicting the residual stress profile for sharp and worn cutting tool conditions. The output of this research provides the essential information on condition monitoring of the tool and its effects on product quality. The low-cost Hall effect sensor used in this work to capture spindle power in the context of the stochastic filter can effectively estimate tool wear in both milling and turning operations, while the estimated wear can be used to generate knowledge of the state of workpiece surface integrity. Therefore the true functionality and efficiency of the tool in superalloy machining can be evaluated without additional high

  7. Wear Modalities and Mechanisms of the Mining Non-asbestos Composite Brake Material

    Science.gov (United States)

    Bao, Jiusheng; Yin, Yan; Zhu, Zhencai; Tong, Minming; Lu, Yuhao; Peng, Yuxing

    2013-08-01

    The mining brake material is generally made of composite materials and its wear has important influences on the braking performance of disc brakes. In order to improve the braking reliability of mine hoisters, this paper did some tribological investigations on the mining brake material to reveal its wear modalities and mechanisms. The mining non-asbestos brake shoe and 16Mn steel were selected as braking pairs and tested on a pad-on-disc friction tester. And a SEM was used to observe the worn surface of the brake shoe. It is shown that the non-asbestos brake material has mainly five wear modalities: adhesive wear, abrasive wear, cutting wear, fatigue wear and high heat wear. At the front period of a single braking the wear modality is mainly composed of some light mechanical wear such as abrasive, cutting and point adhesive. With the temperature rising at the back period it transforms to some heavy mechanical wear such as piece adhesive and fatigue. While in several repeated brakings once the surface temperature rises beyond the thermal-decomposition point of the bonding material, the strong destructive high heat wear takes leading roles on the surface. And a phenomenon called friction catastrophe (FC) occurs easily, which as a result causes a braking failure. It is considered that the friction heat has important influences on the wear modalities of the brake material. And the reduction of friction heat must be an effective technical method for decreasing wear and avoiding braking failures.

  8. Amorphous Metallic Alloys: Pathways for Enhanced Wear and Corrosion Resistance

    Science.gov (United States)

    Aditya, Ayyagari; Felix Wu, H.; Arora, Harpreet; Mukherjee, Sundeep

    2017-11-01

    Amorphous metallic alloys are widely used in bulk form and as coatings for their desirable corrosion and wear behavior. Nevertheless, the effects of heat treatment and thermal cycling on these surface properties are not well understood. In this study, the corrosion and wear behavior of two Zr-based bulk metallic glasses were evaluated in as-cast and thermally relaxed states. Significant improvement in wear rate, friction coefficient, and corrosion penetration rate was seen for both alloys after thermal relaxation. A fully amorphous structure was retained with thermal relaxation below the glass transition. There was an increase in surface hardness and elastic modulus for both alloys after relaxation. The improvement in surface properties was explained based on annihilation of free volume.

  9. Standard guide for determining synergism between wear and corrosion

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2009-01-01

    1.1 This guide covers and provides a means for computing the increased wear loss rate attributed to synergism or interaction that may occur in a system when both wear and corrosion processes coexist. The guide applies to systems in liquid solutions or slurries and does not include processes in a gas/solid system. 1.2 This guide applies to metallic materials and can be used in a generic sense with a number of wear/corrosion tests. It is not restricted to use with approved ASTM test methods. 1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

  10. Lumbar spine orthosis wearing. I. Restriction of gross body motions.

    Science.gov (United States)

    Lantz, S A; Schultz, A B

    1986-10-01

    The effects of wearing commonly prescribed low-back braces and corsets on restriction of gross body motions were investigated. A lumbosacral corset, a chairback brace, and a molded plastic thoracolumbosacral orthosis (TLSO) were studied. Four trunk movements (flexion, extension, lateral bending, and twisting) were examined in five healthy adult men when standing and sitting. All three orthoses restricted at least some gross body motion to approximately two thirds to one half of no-orthosis values. All three orthoses failed to provide restrictions of at least 10% in at least one motion. Mean motion restriction across all eight movements studied in all five subjects were largest when wearing the TLSO and least when wearing the corset. Gross body motion restrictions relieve lumbar trunk muscle and spine loads.

  11. Subjective assessment of contact lens wear by army aircrew.

    Science.gov (United States)

    Lattimore, M R; Cornum, R L

    1993-07-01

    Because 23% of Army aviators are ametropic, contact lenses have drawn increased attention as a spectacle substitute to solve system compatibility problems. From November 1988 until October 1991, a series of contact lens research protocols were conducted to develop a comprehensive database on contact lens wear in varied environments. Questionnaires were used to assess suitability and acceptability of routine contact lens wear. Responses from 202 subjects were obtained from September 1989 through September 1991. The questions explored operational and safety of flight issues of contact lens wear. Subjects overwhelmingly approved of contact lens use in all settings: 95% expressed greater combat readiness and effectiveness with contact lenses, 98% felt contact lens use (and maintenance) in the cockpit had no adverse impact on safety of flight, and 98% endorsed the routine use of contact lenses. These data highlight Army aircrew acceptance of contact lens use.

  12. Evaluation of Wear Resistance of Friction Materials Prepared by Granulation.

    Science.gov (United States)

    Ma, Yunhai; Liu, Yucheng; Menon, Carlo; Tong, Jin

    2015-10-21

    The tribological properties of friction materials prepared by hot-pressing pellets of different sizes were experimentally investigated. Friction and wear tests of the specimens were performed and morphological analysis was carried out by investigating images acquired with both scanning electron and confocal laser microscopes. The highest friction coefficient of friction materials was obtained with pellets having 1-5 mm size. The lowest wear rate was obtained with pellets having 8-10 mm size. Specimens processed by mixing pellets of different sizes had the highest density and the lowest roughness and were the least expensive to fabricate. The results show that granulation generally enabled increasing the friction coefficient, decreasing the wear rate, and reducing the number of defects on the surface of friction materials.

  13. Friction Induced Wear of Rapid Prototyping Generated Materials: A Review

    Directory of Open Access Journals (Sweden)

    A. Tsouknidas

    2011-01-01

    Full Text Available Additive manufacturing has been introduced in the early 80s and has gained importance as a manufacturing process ever since. Even though the inception of the implicated processes predominantly focused on prototyping purposes, during the last years rapid prototyping (RP has emerged as a key enabling technology for the fabrication of highly customized, functionally gradient materials. This paper reviews friction-related wear phenomena and the corresponding deterioration mechanisms of RP-generated components as well as the potential of improving the implicated materials' wear resistance without significantly altering the process itself. The paper briefly introduces the concept of RP technologies and the implicated materials, as a premises to the process-dependent wear progression of the generated components for various degeneration scenarios (dry sliding, fretting, etc..

  14. Effects of posterior ridge resorption and attachment wear on periimplant strain in mandibular two-implant-supported overdentures.

    Science.gov (United States)

    Jo, Deuk-Won; Dong, Jin-Keun

    2015-12-01

    Progressive resorption of the posterior residual ridge and attachment wear increase the rotational movement of mandibular 2-implant-supported overdentures (IODs). Limited information is available regarding the biomechanical effects of rotational movement on anterior implants during mastication. The purpose of this in vitro investigation was to analyze the effects of posterior ridge resorption and attachment wear, using simulated IODs to examine periimplant strain changes under dynamic loading conditions. Two dental implants were positioned in the canine regions of a mandibular edentulous cast. Two mandibular edentulous models were fabricated from the cast by using a fixture-level impression technique, and IODs reinforced with a cobalt-chromium cast framework were prepared using the laboratory models. Two different types of stud attachments (Locator and O-ring) were connected to each paired model and to the IOD. Using a dynamic load of 100 N, continuous stress-strain changes were recorded under 3 conditions: the original condition of the paired laboratory models and the IODs, following a 1-mm reduction of the posterior residual ridge support, and after performing a fatigue test to simulate attachment wear after reduction of the posterior ridge support. After these measurements, a scanning electron microscope (SEM) was used to analyze attachment wear. In all implants, the 1-mm posterior ridge reduction and attachment wear procedure did not remarkably elevate tensile forces compared with their original condition. All stress-strain curves showed phased strain changes caused by the rotational movement of the IODs. After the fatigue test, the shape of the stress-strain curve changed from a smooth curve to a polygonal line compared with that in the previous records. The Locator matrices showed more wear than the other attachment components. Neither attachment wear nor an increase of the IOD rotational movement caused by an approximately 1-mm decrease in the posterior

  15. Epidemiologic survey of erosive tooth wear in San Antonio, Texas.

    Science.gov (United States)

    Mungia, Rahma; Zarzabal, Lee A; Dang, Shichien C; Baez, Martha; Stookey, George K; Brown, John P

    2009-11-01

    To estimate the prevalence of erosive tooth wear in children aged 12-17 years in the southwest region of San Antonio, Texas, within Bexar County. A convenience sample of 307 children aged 12-17 years was selected from two junior high schools. The population consisted predominantly of Hispanic Mexican Americans. The true prevalence of erosive tooth wear within the US is known from only one study, and then only for limited sectors of the population. The Tooth Wear Index, Screening for Oral Health using the Association of State and Territorial Dental Directors (ASTDD) criteria and oral health and dietary assessment questionnaires were used as survey parameters. The questionnaire included data on detailed dietary habits relating primarily to the consumption of acidic beverages and foods. The overall prevalence of erosion within our convenience sample was 5.5 percent. All affected children showed erosive tooth wear low in severity and confined to the enamel with no exposed dentin. A chi-square test was performed to test for associations between the presence of erosion and consumption level of certain acidic foods at a significance level of 5 percent. Few significant and consistent associations were found between erosive tooth wear and consumption frequency categories of groups of acidic foods and beverages using a non-validated food intake questionnaire on purported risk foods. Soda drinks were associated. Mexican acidic foods were not. This study indicated a low prevalence and low severity of dental erosion in a convenience sample of children aged 12-17 years in southwest San Antonio, Texas. Issues of sampling and response bias preclude these findings being generalized to other populations and regions.The results should be viewed with caution. Because the local consumption of some purported risk foods appears to be increasing, this study provides a base-line for future assessments of erosive tooth wear in this population.

  16. Attitude and beliefs of Nigerian undergraduates to spectacle wear.

    Science.gov (United States)

    Ebeigbe, J A; Kio, F; Okafor, L I

    2013-06-01

    Uncorrected refractive error is a common cause of preventable visual impairment. Glasses are the cheapest and commonest form of correction of refractive errors. To achieve this, patients must exhibit good compliance to spectacle wear. Patients' attitude and perception of glasses and eye health could affect compliance to spectacle wear. To determine the attitude and beliefs of Nigerian undergraduates to spectacle wear. A cross sectional study of 500 undergraduates of the University of Benin, Nigeria. Age range was from 18 to 30 years, mean age 23 ± 2.7 years. There were 269 males and 231 females. Semi structured questionnaires were distributed to the participants and collected same day after completion. Two-thirds (68%) of the total population studied had not heard of refractive error. About a third (38%) believed wearing eyeglasses was one of the methods used to correct refractive error. Half (50%) believed they would wear spectacles if prescribed with one by their doctor. Sixty-four percent believed eyeglasses are harmful to the eyes; and 65% did not know that eyeglasses could be used to relieve other forms of ocular discomfort like headache and tearing. Fifty-seven per cent of respondents saw people who wore eyeglasses as visually handicapped, while 60% believed that eyeglasses were meant for old people. Majority of the respondents (56%) believed that they would be teased if they wore glasses. Knowledge of refractive errors and acceptance of glasses for the correction of refractive errors among Nigerian undergraduates is not encouraging. Public enlightenment programs to promote benefits of wearing prescribed spectacles are needed.

  17. Industrial tribology tribosystems, friction, wear and surface engineering, lubrication

    CERN Document Server

    Mang, Theo; Bartels, Thorsten

    2010-01-01

    Integrating very interesting results from the most important R & D project ever made in Germany, this book offers a basic understanding of tribological systems and the latest developments in reduction of wear and energy consumption by tribological measures. This ready reference and handbook provides an analysis of the most important tribosystems using modern test equipment in laboratories and test fields, the latest results in material selection and wear protection by special coatings and surface engineering, as well as with lubrication and lubricants.This result is a quick introductio

  18. Combination Thermal Barrier And Wear Coatings For Engines

    Science.gov (United States)

    Weingart, Mike; Moller, Paul

    1995-01-01

    Thermal-barrier layers covered with self-lubricating surface layers. Zirconia thermal-barrier coat applied to surface of combustion chamber in engine by plasma-arc spraying. Then PS-200 plasma-arc sprayed onto zirconia. Self-lubricating coat prevents sliding contact between thermal barrier and piston ring, effectively preventing both wear and production of additional heat via friction. Other combinations of thermal-barrier and self-lubricating, wear-resistant coating materials used as long as two materials adhere to each other, applied by use of similar or compatible processes, have similar coefficients of thermal expansion, sufficiently strong at high temperatures, and affordable.

  19. Patient compliance and its influence on contact lens wearing problems.

    Science.gov (United States)

    Collins, M J; Carney, L G

    1986-12-01

    One hundred consecutively presenting patients, fifty from each of two contact lens clinics, were questioned about the procedures encountered in care and maintenance of their contact lenses and asked to demonstrate their use of those procedures. Their clinic records were then analyzed for the occurrence of signs and symptoms that were related potentially to noncompliance with instructions and procedures, and that could not be otherwise explained. Only 26% of patients were fully complaint. Noncompliance with instructions was related strongly to the occurrence of signs and symptoms indicative of potential wearing problems. Improvements in the level of patient compliance with instructions is likely to bring about increased patient success with contact lens wearing.

  20. Effect of Lubricant Contaminants on Wear Rates of Lubricated Components.

    Science.gov (United States)

    1980-11-13

    34 Radiotracers Reveal Engine Wear During Detergent Oil Filtration Study," SAE Trans., Vol. 68, 1960, pp. 288-297. 45. Weber, K. H., "Hydrodynamic Theory of...Paper No. 71-Vibr.-96. 49. Naval Air Engineering Center/SKF Industries , " Oil Analysis Project," A/T A3400000/051B/5F53537401, 21 November 1974. 50...study on the effect of particulate contamination upon the wear rates of oil -vetted components normally used in lubrication systems. The components

  1. Wear Behaviour of Carbon Nanotubes Reinforced Nanocrystalline AA 4032 Composites

    Science.gov (United States)

    Senthil Saravanari, M. S.; Kumaresh Babu, S. P.; Sivaprasad, K.

    2016-09-01

    The present paper emphasizes the friction and wear properties of Carbon Nanotubes reinforced AA 4032 nanocomposites prepared by powder metallurgy technique. CNTs are multi-wall in nature and prepared by electric arc discharge method. Multi-walled CNTs are blended with AA 4032 elemental powders and compaction followed by sintering to get bulk nanocomposites. The strength of the composites has been evaluated by microhardness and the surface contact between the nanocomposites and EN 32 steel has been evaluated by Pin on disk tester. The results are proven that reinforcement of CNTs play a major role in the enhancement of hardness and wear.

  2. Engineering wear-resistant surfaces in automotive aluminum

    Science.gov (United States)

    Kavorkijan, V.

    2003-02-01

    Inadequate wear resistance and low seizure loads prevent the direct use of aluminum alloys in automotive parts subject to intensive friction combined with high thermal and mechanical loading, such as brake discs, pistons, and cylinder liners. To enable the use of aluminum alloys in the production of automotive brake discs and other wear-resistant products, the insertion of a monolithic friction cladding rather than surface coating has been considered in this work. Three experimental approaches, two based on the pressure-less infiltration of porous ceramic preforms and one based on the subsequent hot rolling of aluminum and metal-matrix composite strips, are currently under investigation.

  3. Factors affecting dental biofilm in patients wearing fixed orthodontic appliances

    OpenAIRE

    Mei, Li; Chieng, Joyce; Wong, Connie; Benic, Gareth; Farella, Mauro

    2017-01-01

    Abstract Background The aim of this study is to investigate the amount and the distribution of biofilm in patients wearing fixed appliances and its relation with age, gender, frequency of tooth brushing, and patient motivation. Methods The sample comprised 52 patients (15.5 ± 3.6 years old, 30 females and 22 males) wearing fixed orthodontic appliances. Dental biofilm was assessed using a modified plaque index (PI). A questionnaire was used to collect patient’s information, including gender, a...

  4. Investigation of Wear Resistant of Low-Alloyed and Chromium Cast Steel

    Directory of Open Access Journals (Sweden)

    A. Studnicki

    2012-04-01

    Full Text Available Results of investigations of wear resistant of two species of cast steel were introduced in the article (low-alloyed and chromium cast steel on the background of the standard material which was low alloy wear resistant steel about the trade name CREUSABRO ®8000. The investigations were executed with two methods: abrasive wears in the stream of loose particles (the stream of quartz sand and abrasive wears particles fixed (abrasive paper with the silicon carbide. Comparing the results of investigations in the experiments was based about the counted wear index which characterizes the wears of the studied material in the relation to the standard material.

  5. Friction and wear studies on the temperature dependence of brake-pad materials containing brass

    Directory of Open Access Journals (Sweden)

    Eddoumy Fatima

    2013-11-01

    Full Text Available Brake pad materials for automobile applications are basically polymer matrix composites. Various reinforcing constituents used in brake pads are organic, metallic and ceramic fillers which play among others an important role on the mechanical and thermal properties, and the wear resistance at high temperature. Friction and wear depend on various parameters such as the micro-chemical structure of the pad and of the metallic counter-face, the rotation speed, the pressure, and the contact surface temperature (M.G. Jacko 1983. This latter parameter can be locally as high as 600 up to 1.500 ∘C depending on the brake type (M.G. Jacko 1983; Blau 2001. Thermal models have been developed to study interface effects at contacting surfaces (Majcherczak, Dufrenoy et al. 2007. Frictional energy can be dissipated through different mechanisms such as oxidation, rise in temperature, formation of wear particles, entropy changes associated to viscoelastic and viscoplastic deformation, and noise generation (Eddoumy, Addiego et al. 2011. Studies of friction brake show that more than 95% of the dissipated energy is transformed into heat (Kasem, Thevenet et al.; Majcherczak, Dufrenoy et al. 2007. Thermal analysis is therefore a primordial step in the study of brake systems since it provides thermo-mechanical properties (Majcherczak, Dufrenoy et al. 2007. The influence of the addition of metallic fibers on the performance of organic friction composites has been investigated using friction tests (Qu, Zhang et al. 2004. Benefits or limitations of the different fibers have been reported, however the issues of thermo-mechanical properties or effect of temperature on friction and wear behavior were not yet investigated (Bijwe, Kumar et al. 2008. No effort was done to correlate the thermo-mechanical and thermal properties with the friction and wear behavior. An important prerequisite is to get a good understanding on how brake materials behave. However, a link

  6. Cognitive Workload and Fatigue in a Vigilance Dual Task: Miss Errors, False Alarms, and the Effect of Wearing Biometric Sensors While Working.

    Science.gov (United States)

    Guastello, Stephen J; Reiter, Katherine E; Malon, Matthew

    2016-10-01

    The effects of workload, fatigue, and practice on the performance of cognitive tasks are often intertwined. Previous research has shown that these influences can be separated with the two cusp catastrophe models. This study expanded an earlier investigation of the two models for workload and fatigue in a vigilance task to include a wider range of bifurcation variables that could affect the elasticity versus rigidity of the operator in response to workload and added performance variability resulting from fatigue. The study also responded to a concern in the literature that performance on cognitive tasks can be complicated by adaptive responses to artificial task situations and thus distort underlying cognitive events. Therefore, we also explored whether wearing biometric sensors, frequently used in workload studies, can affect performance dynamics. Participants were 279 undergraduates who responded to target stimuli that appeared on a simulated security camera display at three rates of speed while completing a secondary task. Participants worked alone, in pairs, or in pairs wearing GSR sensors. Results supported the efficacy of the two models and isolated the impact of wearing sensors on the fatigue process. The strongest control variables across both the workload and fatigue models were field independence, anxiety, indecisiveness, inflexibility, secondary task completion, working in pairs, and wearing the sensors. The contributing effect of wearing sensors could possibly extend to other types of wearable technologies.

  7. Milling tool wear diagnosis by feed motor current signal using an artificial neural network

    Energy Technology Data Exchange (ETDEWEB)

    Khajavi, Mehrdad Nouri; Nasernia, Ebrahim; Rostaghi, Mostafa [Dept. of Mechanical Engineering, Shahid Rajaee Teacher Training University, Tehran (Iran, Islamic Republic of)

    2016-11-15

    In this paper, a Multi-layer perceptron (MLP) neural network was used to predict tool wear in face milling. For this purpose, a series of experiments was conducted using a milling machine on a CK45 work piece. Tool wear was measured by an optical microscope. To improve the accuracy and reliability of the monitoring system, tool wear state was classified into five groups, namely, no wear, slight wear, normal wear, severe wear and broken tool. Experiments were conducted with the aforementioned tool wear states, and different machining conditions and data were extracted. An increase in current amplitude was observed as the tool wear increased. Furthermore, effects of parameters such as tool wear, feed, and cut depth on motor current consumption were analyzed. Considering the complexity of the wear state classification, a multi-layer neural network was used. The root mean square of motor current, feed, cut depth, and tool rpm were chosen as the input and amount of flank wear as the output of MLP. Results showed good performance of the designed tool wear monitoring system.

  8. Experimental Research on the Determination of the Coefficient of Sliding Wear under Iron Ore Handling Conditions

    Directory of Open Access Journals (Sweden)

    G. Chen

    2017-09-01

    Full Text Available The handling of iron ore bulk solids maintains an increasing trend due to economic development. Because iron ore particles have hard composites and irregular shapes, the bulk solids handling equipment surface can suffer from severe sliding wear. Prediction of equipment surface wear volume is beneficial to the efficient maintenance of worn areas. Archard’s equation provides a theoretical solution to predict wear volume. To use Archard’s equation, the coefficient of sliding wear must be determined. To our best knowledge, the coefficient of sliding wear for iron ore handling conditions has not yet been determined. In this research, using a pin-on-disk tribometer, the coefficients of sliding wear for both Sishen particles and mild steel are determined with regard to iron ore handling conditions. Both naturally irregular and spherical shapes of particles are used to estimate average values of wear rate. Moreover, the hardness and inner structures of Sishen particles are examined, which adds the evidence of the interpretation of wear results. It is concluded that the coefficients of sliding wear can vary largely for both Sishen particle and mild steel. The wear rate decreases from transient- to steady-state. The average coefficient of sliding wear is capable of predicting wear with respect to long distances at the steady-state. Two types of sliding friction are distinguished. In addition, it is found that the temperature rise of the friction pairs has negligible influence on wear rate.

  9. The Pandolf load carriage equation is a poor predictor of metabolic rate while wearing explosive ordnance disposal protective clothing.

    Science.gov (United States)

    Bach, Aaron J E; Costello, Joseph T; Borg, David N; Stewart, Ian B

    2017-03-01

    This investigation aimed to quantify metabolic rate when wearing an explosive ordnance disposal (EOD) ensemble (~33kg) during standing and locomotion; and determine whether the Pandolf load carriage equation accurately predicts metabolic rate when wearing an EOD ensemble during standing and locomotion. Ten males completed 8 trials with metabolic rate measured through indirect calorimetry. Walking in EOD at 2.5, 4.0 and 5.5km·h-1 was significantly (p ensemble by 49% (127W), 65% (213W) and 78% (345W), respectively. Mean bias (95% limits of agreement) between predicted and measured metabolism during standing, 2.5, 4 and 5.5km·h-1 were 47W (19 to 75W); -111W (-172 to -49W); -122W (-189 to -54W) and -158W (-245 to -72W), respectively. The Pandolf equation significantly underestimated measured metabolic rate during locomotion. These findings have practical implications for EOD technicians during training and operation and should be considered when developing maximum workload duration models and work-rest schedules. Practitioner Summary: Using a rigorous methodological design we quantified metabolic rate of wearing EOD clothing during locomotion. For the first time we demonstrated that metabolic rate when wearing this ensemble is greater than that predicted by the Pandolf equation. These original findings have significant implications for EOD training and operation.

  10. Debris and 1/f noise in sliding friction dynamics under wear conditions.

    Science.gov (United States)

    Vragovic, I; Molina, J M; Prieto, R; Duarte, M; Narciso, J; Louis, E

    2009-12-01

    Friction force time series showing irregular fluctuations have been since long considered one of the possible stick-slip regimes in sliding friction. However, it has not been until recently that a 1/f power spectrum in friction force time series derived from sliding friction experiments under wear conditions has been identified. A variety of models, mostly inspired in the field of earthquakes, has been explored, without reaching a fully satisfactory explanation of that behavior. Recently, the present authors have reported results of sliding friction experiments on steel with alumina pins, carried out with and without debris blowing, that proved the role of loose debris in determining the 1/f character of the friction force. A damped-forced harmonic oscillator with two friction terms was proposed to describe the dynamics of friction under wear conditions: one purely random, which accounts for surface roughness, and another inversely proportional to the amount of loose debris that was calculated by means of a modified sand-pile model. This paper presents a full discussion of the experiments that allowed to reach that conclusion and of the model proposed to rationalize the results. In addition, the results of experiments devised to understand the transition from friction with debris to friction without debris (experiment initiated without blowing and after some time switching on blowing) and vice versa are reported. The results of further studies of the wear track are presented, namely, the variation in the track width with sliding distance and results of chemical analyses and surface roughness measurements of the track, for both with or without debris blowing experiments. These additional data give further support to the crucial role of debris in the 1/f character of the friction force.

  11. Molecular wear of microtubules propelled by surface-adhered kinesins

    Science.gov (United States)

    Dumont, Emmanuel L. P.; Do, Catherine; Hess, Henry

    2015-02-01

    Wear is the progressive loss of material from a body caused by contact and relative movement and is a major concern in both engineering and biology. Advances in nanotechnology have allowed the origins of wear processes to be studied at the atomic and molecular scale, but also demand that wear in nanoscale systems can be predicted and controlled. Biomolecular systems can undergo a range of active movements at the nanoscale, which are enabled by the transduction of chemical energy into mechanical work by polymerization processes and motor proteins. The active movements are accompanied by dissipative processes that can be conceptually understood as ‘protein friction’. Here, we show that wear also occurs in an in vitro system consisting of microtubules gliding across a surface coated with kinesin-1 motor proteins, and that energetic considerations suggest a molecule-by-molecule removal of tubulin proteins. The rates of removal show a complex dependence on sliding velocity and kinesin density, which, in contrast to the friction behaviour between microtubules and kinesin-8, cannot be explained by simple chemical reaction kinetics.

  12. The Abrasive Wear Resistance of Chromium Cast Iron

    Directory of Open Access Journals (Sweden)

    Kopyciński D.

    2014-03-01

    Full Text Available The resistance of cast iron to abrasive wear depends on the metal abrasive hardness ratio. For example, hardness of the structural constituents of the cast iron metal matrix is lower than the hardness of ordinary silica sand. Also cementite, the basic component of unalloyed white cast iron, has hardness lower than the hardness of silica. Some resistance to the abrasive effect of the aforementioned silica sand can provide the chromium white cast iron containing in its structure a large amount of (Cr, Fe7C3 carbides characterised by hardness higher than the hardness of the silica sand in question. In the present study, it has been anticipated that the white cast iron structure will be changed by changing the type of metal matrix and the type of carbides present in this matrix, which will greatly expand the application area of castings under the harsh operating conditions of abrasive wear. Moreover, the study compares the results of abrasive wear resistance tests performed on the examined types of cast iron. Tests of abrasive wear resistance were carried out on a Miller machine. Samples of standard dimensions were exposed to abrasion in a double to-and-fro movement, sliding against the bottom of a trough filled with an aqueous abrasive mixture containing SiC + distilled water. The obtained results of changes in the sample weight were approximated with a power curve and shown further in the study.

  13. Wear Measurement of Ceramic Bearings in Gas Turbines

    Science.gov (United States)

    1990-03-01

    temperatures. The disk, on the other hand has a ring wear groove which has time to recover and cool during each revolution . In addition to the nuclear...Service de Physique Nucleaire a Basse Energie, La Documentation Francaise , Secretariat General Du Government, Direction De La Documentation, 16, Rue

  14. Experimental investigation of friction and wear behaviour of 304L ...

    African Journals Online (AJOL)

    Experimental investigation of friction and wear behaviour of 304L stainless steel sliding against different counterface in dry contact. ... Ife Journal of Science ... All the pairs exhibited initial rapid increase in coefficient of friction after which a variety of friction behavior, depending on the ball counterface, was observed. The flat ...

  15. Assessment of mechanical and three-body abrasive wear peculiarity ...

    Indian Academy of Sciences (India)

    The three-body abrasive wear characteristic of fabricated composites has been assessed under different operating conditions. For this, the three-body abrasion test is done on dry abrasion test rig (TR-50)and analysed using Taguchi's experimental design scheme and analysis of variance. The results obtained from these ...

  16. The measurement of enamel wear by four toothpastes.

    Science.gov (United States)

    Joiner, A; Pickles, M J; Lynch, S; Cox, T F

    2008-02-01

    To determine the enamel abrasivity of three whitening toothpastes and a silica toothpaste and to measure the brushing forces used. Polished human enamel blocks were indented with a Knoop diamond and attached to dentures of adult volunteers. The blocks were brushed ex vivo, twice per day with either a whitening toothpaste containing Perlite (White System), a commercial whitening toothpaste (A and B) or a silica toothpaste. After four and twelve-weeks, one block per subject was removed and the Knoop indent remeasured. From the changes in the indent length, the amount of enamel wear was calculated. The mean enamel wear (sd) for White System, silica toothpaste, whitening toothpaste A and B after four-weeks was 0.14 (0.15), 0.09 (0.16), 0.14 (0.12) and 0.89 (0.93) and after twelve-weeks was 0.24 (0.21), 0.37 (0.73), 0.36 (0.52) and 1.04 (0.98) microm respectively. After four-weeks, the differences in enamel wear between whitening toothpaste B and all other toothpastes were of statistical significance (p whitening toothpastes did not give significantly more enamel wear than a silica toothpaste after twelve-weeks in situ with ex vivo brushing.

  17. Abrasive wear behaviour of bio-active glass ceramics containing ...

    Indian Academy of Sciences (India)

    Unknown

    Abstract. In this study, abrasive wear behaviour of bio-active glass ceramic materials produced with two different processes is studied. Hot pressing process and conventional casting and controlled crystallization process were used to produce bio-active ceramics. Fracture toughness of studied material was calculated by.

  18. Attitude and Beliefs of Nigerian Undergraduates to Spectacle Wear ...

    African Journals Online (AJOL)

    Background: Uncorrected refractive error is a common cause of preventable visual impairment. Glasses are the cheapest and commonest form of correction of refractive errors. To achieve this, patients must exhibit good compliance to spectacle wear. Patients' attitude and perception of glasses and eye health could affect ...

  19. Corrosion and wear behaviour of multilayer pulse electrodeposited ...

    Indian Academy of Sciences (India)

    persion of nanoparticles in the metal matrix and affected coating microstructure and surface morphology [22]. The. Ni–Al2O3 nanocomposite coatings were widely studied due to their hardness and wear and corrosion resistance compared to electrodeposited pure nickel coatings [23]. The researchers have focused on the ...

  20. Combined Corrosion and Wear of Aluminium Alloy 7075-T6

    NARCIS (Netherlands)

    Liu, Y.; Mol, J.M.C.; Janssen, G.C.A.M.

    2016-01-01

    The aluminium alloy 7075-T6 is widely used in engineering. In some applications, like slurry transport, corrosion and abrasion occur simultaneously, resulting in early material failure. In the present work, we investigated the combined effect of corrosion and wear on the aluminium alloy 7075-T6. We

  1. development and performance evaluation of an abrasive wear ...

    African Journals Online (AJOL)

    User

    variance (ANOVA) using MINITAB Statistical. Software Release 15 (Minitab Statistical Pack- age, 2007). Treatment means were separated using least significant difference ... could be named as shin, leading face, front, middle, back and tail respectively. The shin. (point 'a'), experienced the greatest wear in all the five soils.

  2. In situ complement activation by polyethylene wear debris.

    NARCIS (Netherlands)

    DeHeer, D.H.; Engels, J.A.; Vries, A.S. de; Knapp, R.H.; Beebe, J.D.

    2001-01-01

    A frequent long-term complication of total joint arthroplasty is aseptic loosening, the end result of wear debris accumulation, synovitis, and osteolysis about the implant-bone or cement-bone interface. Complement, an effector system in plasma, synovial fluid, and tissue, has powerful chemotactic,

  3. Severe tooth wear: European consensus statement on management guidelines

    DEFF Research Database (Denmark)

    Loomans, Bas AC; Opdam, Niek JM; Attin, Thomas

    2017-01-01

    intervention should be delayed wherever possible, depending on patient wishes and the severity and activity of the wear. When restorative intervention is indicated and agreed with the patient, a conservative minimally invasive approach is recommended. Several examples of adhesive minimally invasive treatment...

  4. Microstructure and wear behaviour of FeAl-based composites ...

    Indian Academy of Sciences (India)

    resistance of FeAl-based alloys is found to be significantly improved on addition of Ti/Zr. This is attributed to the high hardness of alloy carbides. The lower ... exhibit superior wear resistance due to higher hardness of carbides [6,12,17,18]. However ..... Also, most of the literature is on composites fabricated through PM route ...

  5. Heat stress reduction of helicopter crew wearing a ventilated vest

    NARCIS (Netherlands)

    Reffeltrath, P.A.

    2006-01-01

    Background: Helicopter pilots are often exposed to periods of high heat strain, especially when wearing survival suits. Therefore, a prototype of a ventilated vest was evaluated on its capability to reduce the heat strain of helicopter pilots during a 2-h simulated flight. Hypothesis: It was

  6. Wear and Friction in a Controllable Pitch Propeller

    NARCIS (Netherlands)

    Godjevac, M.

    2010-01-01

    The author is a naval architect and this book is his PhD thesis. In this research the author focuses on friction in a controllable pitch propeller (CPP), formation of wear in a CPP system, and their mutual dependence. Instead of going deeply only in tribology aspects, the author tries to get an

  7. Wear Tests of a Potential Biolubricant for Orthopedic Biopolymers

    Directory of Open Access Journals (Sweden)

    Martin Thompson

    2015-03-01

    Full Text Available Most wear testing of orthopedic implant materials is undertaken with dilute bovine serum used as the lubricant. However, dilute bovine serum is different to the synovial fluid in which natural and artificial joints must operate. As part of a search for a lubricant which more closely resembles synovial fluid, a lubricant based on a mixture of sodium alginate and gellan gum, and which aimed to match the rheology of synovial fluid, was produced. It was employed in a wear test of ultra high molecular weight polyethylene pins rubbing against a metallic counterface. The test rig applied multidirectional motion to the test pins and had previously been shown to reproduce clinically relevant wear factors for ultra high molecular weight polyethylene. After 2.4 million cycles (125 km of sliding in the presence of the new lubricant, a mean wear factor of 0.099 × 10−6 mm3/Nm was measured for the ultra high molecular weight polyethylene pins. This was over an order of magnitude less than when bovine serum was used as a lubricant. In addition, there was evidence of a transfer film on the test plates. Such transfer films are not seen clinically. The search for a lubricant more closely matching synovial fluid continues.

  8. Effect of increasingly metallized hybrid reinforcement on the wear ...

    Indian Academy of Sciences (India)

    Abstract. Strength and ductility of pure magnesium have experienced simultaneous improvement due to the pres- ence of nanosize hybrid (yttria and copper) reinforcement. Increasing the vol% (i.e., 0.3–1.0) of ductile metallic copper particles in reinforcement has further enhanced the strength of magnesium. Wear behaviour ...

  9. Wear rate control of peek surfaces modified by femtosecond laser

    Science.gov (United States)

    Hammouti, S.; Pascale-Hamri, A.; Faure, N.; Beaugiraud, B.; Guibert, M.; Mauclair, C.; Benayoun, S.; Valette, S.

    2015-12-01

    This paper presents the effect of laser texturing on the tribological properties of PEEK surfaces under a ball-on-flat contact configuration. Thus, surfaces with circular dimples of various diameters and depth were created. Tests were conducted with a normal load of 5 N and a sliding velocity of 0.01 m s-1, using bovine calf serum at 37.5 °C as a lubricant. The tribological conditions including the sliding frequency and the lubricant viscosity indicate that tests were performed under boundary lubrication regime. Results showed that discs with higher dimple depth exhibited higher friction coefficient and caused more abrasive wear on the ball specimen. Nevertheless, tribosystems (ball and disc) with dimpled disc surfaces showed a higher wear resistance. In the frame of our experiments, wear rates obtained for tribosystems including dimpled surfaces were 10 times lower than tribosystems including limited patterned or untextured surfaces. Applications such as design of spinal implants may be concerned by such a surface treatment to increase wear resistance of components.

  10. Stochastic Distribution of Wear of Carbide Tools during Machining ...

    African Journals Online (AJOL)

    The increasing awareness of wear of carbide tools during machining operation has created doubts about the ability of this tool material to withstand stress and strain induced by the machining process. Manufacturers are beginning to question their dependence on carbide tools, seeing that they no longer meet their expected ...

  11. Development of wear resistant ceramic coatings for diesel engine components

    Energy Technology Data Exchange (ETDEWEB)

    Haselkorn, M.H. (Caterpillar, Inc., Peoria, IL (United States))

    1992-04-01

    Improved fuel economy and a reduction of emissions can be achieved by insulation of the combustion chamber components to reduce heat rejection. However, insulating the combustion chamber components will also increase the operating temperature of the piston ring/cylinder liner interface from approximately 150{degree}C to over 300{degree}C. Existing ring/liner materials can not withstand these higher operating temperatures and for this reason, new materials need to be developed for this critical tribological interface. The overall goal of this program is the development of piston ring/cylinder liner material pairs which would be able to provide the required friction and wear properties at these more severe operating conditions. More specifically, this program first selected, and then evaluated, potential d/wear resistant coatings which could be applied to either piston rings an or cylinder liners and provide, at 350{degree}C under lubricated conditions, coefficients of friction below 0.1 and wear rates of less than 25 {times} lO{sup {minus}6} mm/hour. The processes selected for applying the candidate wear resistant coatings to piston rings and/or cylinder liners were plasma spraying, chemical vapor, physical vapor and low temperature arc vapor deposition techniques as well as enameling techniques.

  12. Controlled wear of vitrified abrasive materials for precision grinding ...

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    same time, the number of cutting edges involved in the process decreases. This leads to the advantages promised by high-speed grinding which is characterised by a reduction in grinding forces, grinding wheel wear, and in workpiece surface roughness. Consequently, increasing the speed of the grinding wheel can lead ...

  13. Novel texture-based descriptors for tool wear condition monitoring

    Science.gov (United States)

    Antić, Aco; Popović, Branislav; Krstanović, Lidija; Obradović, Ratko; Milošević, Mijodrag

    2018-01-01

    All state-of-the-art tool condition monitoring systems (TCM) in the tool wear recognition task, especially those that use vibration sensors, heavily depend on the choice of descriptors containing information about the tool wear state which are extracted from the particular sensor signals. All other post-processing techniques do not manage to increase the recognition precision if those descriptors are not discriminative enough. In this work, we propose a tool wear monitoring strategy which relies on the novel texture based descriptors. We consider the module of the Short Term Discrete Fourier Transform (STDFT) spectra obtained from the particular vibration sensors signal utterance as the 2D textured image. This is done by identifying the time scale of STDFT as the first dimension, and the frequency scale as the second dimension of the particular textured image. The obtained textured image is then divided into particular 2D texture patches, covering a part of the frequency range of interest. After applying the appropriate filter bank, 2D textons are extracted for each predefined frequency band. By averaging in time, we extract from the textons for each band of interest the information regarding the Probability Density Function (PDF) in the form of lower order moments, thus obtaining robust tool wear state descriptors. We validate the proposed features by the experiments conducted on the real TCM system, obtaining the high recognition accuracy.

  14. (AJST) EFFECT OF HEAT TREATMENT ON WEAR RESISTANCE ...

    African Journals Online (AJOL)

    ABSTRACT: The effects of heat treatment on the hardness and by extension the wear resistance of locally produced grinding plate ... from the grinding plate and were heat treated at 840°C, 860°C and 880°C and quenched at different rate. Some of the ... during dry sliding at low loading conditions has been attributed to the ...

  15. Author: F Osman LEGISLATIVE PROHIBITIONS ON WEARING A ...

    African Journals Online (AJOL)

    10332324

    support of this, Weil26 stated that teachers and parents described an unmanageable situation at schools with .... authorities prohibited a primary school teacher from wearing a headscarf while teaching. Switzerland ... some disagreement as to how strict the separation between religion and the state should be, and what is ...

  16. On the Durability and Wear Resistance of Transparent Superhydrophobic Coatings

    Directory of Open Access Journals (Sweden)

    Ilker S. Bayer

    2017-01-01

    Full Text Available Transparent liquid repellent coatings with exceptional wear and abrasion resistance are very demanding to fabricate. The most important reason for this is the fact that majority of the transparent liquid repellent coatings have so far been fabricated by nanoparticle assembly on surfaces in the form of films. These films or coatings demonstrate relatively poor substrate adhesion and rubbing induced wear resistance compared to polymer-based transparent hydrophobic coatings. However, recent advances reported in the literature indicate that considerable progress has now been made towards formulating and applying transparent, hydrophobic and even oleophobic coatings onto various substrates which can withstand certain degree of mechanical abrasion. This is considered to be very promising for anti-graffiti coatings or treatments since they require resistance to wear abrasion. Therefore, this review intends to highlight the state-of-the-art on materials and techniques that are used to fabricate wear resistant liquid repellent transparent coatings so that researchers can assess various aptitudes and limitations related to translating some of these technologies to large scale stain repellent outdoor applications.

  17. CONTACT LENS WEAR AND THE OXYGEN ISSUE: A REVIEW

    African Journals Online (AJOL)

    increase both the prevalence and severity of all complication . About 33% of the complications encountered with contact lens wear are attributable to hypoxia, and thus the oxygen transmissibility of a contact lens is probably the most important single parameter in terms of maintaining the physiologic integrity of the cornea .

  18. High Temperature Solid Lubricant Coating for High Temperature Wear Applications

    Science.gov (United States)

    DellaCorte, Christopher (Inventor); Edmonds, Brian J (Inventor)

    2014-01-01

    A self-lubricating, friction and wear reducing composite useful over a wide temperature range is described herein. The composite includes metal bonded chromium oxide dispersed in a metal binder having a substantial amount of nickel. The composite contains a fluoride of at least one Group I, Group II, or rare earth metal, and optionally a low temperature lubricant metal.

  19. Wear resistance of polypropylene-SiC composite

    Science.gov (United States)

    Abenojar, J.; Enciso, B.; Martínez, MA; Velasco, F.

    2017-05-01

    In this work, the wear resistance of thermoplastic composites with a high amount of ceramic is evaluated. Composites made of polypropylene (PP) and silicon carbide (SiC) powder at 50 wt% were used with the final objective of manufacturing ablative materials. This is the first part of a project studying the wear resistance and the mechanical properties of those composites, to be used in applications like habitat industry. In theory, the exposure to high temperature of ablative materials involves the elimination of thermal energy by the sacrifice of surface polymer. In our case, PP will act as a heat sink, up to the reaction temperature (melting or sublimation), where endothermic chemical decomposition into charred material and gaseous products occurs. As the surface is eroded, it is formed a SiC like-foam with improved insulation performance. Composites were produced by extrusion and hot compression. The wear characterization was performed by pin-on-disk test. Wear test was carried out under standard ASTM G99. The parameters were 120 rpm speed, 15 N load, a alumina ball with 6 mm as pin and 1000 m sliding distance. The tracks were also observed by opto-digital microscope.

  20. Effect of casein phosphopeptide-amorphous calcium phosphate and acidulated phosphate fluoride gel on erosive enamel wear

    Directory of Open Access Journals (Sweden)

    Maryam HajeNorouz Ali Tehrani

    2011-01-01

    Conclusions: We concluded that although either CPP-ACP or APF can protect enamel against wear, their combination provides significant enamel wear reduction. These findings would lead to new strategies for the clinical management of tooth wear.

  1. Mechanisms for fatigue and wear of polysilicon structural thinfilms

    Energy Technology Data Exchange (ETDEWEB)

    Alsem, Daniel Henricus [Univ. of California, Berkeley, CA (United States)

    2006-01-01

    Fatigue and wear in micron-scale polysilicon structural films can severely impact the reliability of microelectromechanical systems (MEMS). Despite studies on fatigue and wear behavior of these films, there is still an on-going debate regarding the precise physical mechanisms for these two important failure modes. Although macro-scale silicon does not fatigue, this phenomenon is observed in micron-scale silicon. It is shown that for polysilicon devices fabricated in the MUMPs foundry and SUMMiT process stress-lifetime data exhibits similar trends in ambient air, shorter lifetimes in higher relative humidity environments and no fatigue failure at all in high vacuum. Transmission electron microscopy of the surface oxides of the samples show an approximate four-fold thickening of the oxide at stress concentrations after fatigue failure, but no thickening after fracture in air or after fatigue cycling in vacuo. It is found that such oxide thickening and fatigue failure (in air) occurs in devices with initial oxide thicknesses of ~4-20 nm. Such results are interpreted and explained by a reaction layer fatigue mechanism; specifically, moisture-assisted subcritical cracking within a cyclic stress-assisted thickened oxide layer occurs until the crack reaches a critical size to cause catastrophic failure. Polysilicon specimens from the SUMMiT process are used to study wear mechanisms in micron-scale silicon in ambient air. Worn parts are examined by analytical scanning and transmission electron microscopy, while temperature changes are monitored using infrared microscopy. These results are compared with the development of values of static coefficients of friction (COF) with number of wear cycles. Observations show amorphous debris particles (~50-100 nm) created by fracture through the silicon grains (~500 nm), which subsequently oxidize, agglomerate into clusters and create plowing tracks. A nano-crystalline layer (~20-200 nm) forms at worn regions. No dislocations or

  2. Manual toothbrush wear and consequences on plaque removal.

    Science.gov (United States)

    Muller-Bolla, M; Lupi-Pégurier, L; Bertrand, M F; Velly, A M

    2007-01-01

    The aim of this study was to determine the mean time interval before needing to discard different types of manual toothbrushes based on wear, and on the impact of progressive wear on plaque removal efficacy. Two cross-over randomized clinical trials involving the same 12 volunteers tested four toothbrushes of different designs. In Study 1, the brushes were the Butler 211 (BTB) and Fluocaril Sensia (FSTB). In Study 2, the brushes were Elmex InterX (ETB) and Elgydium Interactive (ELTB). In both trials, the volunteers randomly used one of the two toothbrushes for two minutes twice a day during the first week, and the other brush during the following week, and continued this alternating routine for two months. An image acquisition system and the Visilog 5.2 image analysis program were used to calculate the wear index (WI) after one and two months of use for each toothbrush. The OHI-S plaque index (PI) was recorded after one and three minutes of tooth brushing at one and two months. The Friedman or Kruskal-Wallis test was used to compare data. Except for the ELTB, the wear of the toothbrushes was greater during the first month of brushing than during the second. The total WI was FSTB 35.46 (range = 62.11), ELTB 30.14 (range = 67.92), ETB 48.77 (range = 123.87), and BTB 98.20 (range = 134.75). The differences were significant at p = 0.008. The post one-minute PI scores significantly increased with wear, except in the case of ELTB (p = 0.244). When comparing all toothbrushes' PI at the one and three-minute tooth brushing times, there were significant differences at one month among them at p < 0.0001. The amount of wear depended on the toothbrush design. It was greater for rectangular tooth brushing areas or when bristles had smaller diameters and different heights. With two-month-old toothbrushes, plaque removal was better when there was less measurable wear.

  3. Wear of double crown systems: electroplated vs. casted female part

    Directory of Open Access Journals (Sweden)

    Stefan Bayer

    2012-06-01

    Full Text Available OBJECTIVES: The wear of telescopic crowns is a common problem often reducing the patient's satisfaction with the denture and resulting in a renewal of the denture. The study aims to compare the wear behavior of conical crowns using electroplated copings (group E with standard telescopic crowns with cast female parts (group C. MATERIAL AND METHODS: 10 conical crowns were milled for each group of a cast gold alloy. The specimen of group E had a conicity of 2º. The cast secondary crowns of group C had a 0º design. The electroplated coping was established by direct electroforming. An apparatus accomplishing 10,000 wear cycles performed the wear test. The retentive forces and the correlating distance during insertion and separation were measured. The wear test was separated in a start phase, an initial wear phase and the long term wear period. The retention force value and the force-distance integral of the first 0.33 mm of each cycle were calculated. RESULTS: The retentive forces were significantly higher for group E and the integrals were significantly lower for this group except the integral at cycle 10,000. The changes of retention force and integral did not differ significantly between both groups in all phases. The change of the integrals as well as the integral at the particular cycles showed higher interquartile distances for group C. CONCLUSIONS: Within the limitations of this study the tested conical crowns showed clinically acceptable retentive properties. The values reached a range comparable to retentive elements tested in recent literature. The values of group C showed higher ranges. The force measured for group E was significantly higher than for group C but the integrals showed an opposite tendency. The results indicate that an exclusive analysis of the force is not sufficient as the integral is not equivalent to the force although it describes the retentive property of the system in a better way than the force over a distance is

  4. Problems of locomotive wheel wear in fleet replacement

    Directory of Open Access Journals (Sweden)

    L.P. Lingaytis

    2013-08-01

    Full Text Available Purpose. To conduct a research and find out the causes of defects appearing on the wheel thread of freight locomotives 2М62 and SIEMENS ER20CF. Methodology. To find the ways to solve this problem comparing the locomotive designs and their operating conditions. Findings. After examining the nature of the wheel wear the main difference was found: in locomotives of the 2M62 line wears the wheel flange, and in the locomotives SIEMENS ER20CF – the tread surface. After installation on the 2M62 locomotive the lubrication system of flanges their wear rate significantly decreased. On the new freight locomotives SIEMENS ER20CF the flange lubrication systems of the wheel set have been already installed at the factory, however the wheel thread is wearing. As for locomotives 2M62, and on locomotives SIEMENS ER20CF most wear profile skating wheels of the first wheel set. On both locomotive lines the 2М62 and the SIEMENS ER20CF the tread profile of the first wheel set most of all is subject to the wear. After reaching the 170 000 km run, the tread surface of some wheels begins to crumble. There was a suspicion that the reason for crumb formation of the wheel surface may be insufficient or excessive wheel hardness or its chemical composition. In order to confirm or deny this suspicion the following studies were conducted: the examination of the rim surface, the study of the wheel metal hardness and the document analysis of the wheel production and their comparison with the results of wheel hardness measurement. Practical value. The technical condition of locomotives is one of the bases of safety and reliability of the rolling stock. The reduction of the wheel wear significantly reduces the operating costs of railway transport. After study completion it was found that there was no evidence to suggest that the ratio of the wheel-rail hardness could be the cause of the wheel surface crumbling.

  5. Surface and sliding wear behaviour of different coatings and steels

    Energy Technology Data Exchange (ETDEWEB)

    Vera-Cardenas, E.E. [Universidad Politecnica de Pachuca, Zempoala, Hidalgo (Mexico)]. E-mail: evera@upp.edu.mx; Vite-Torres, M. [Instituto Politecnico Nacional, Mexico D.F. (Mexico)]. E-mail: drmanulvite9@hotmail.com; Lewis, R. [University of Sheffield (United Kingdom)]. E-mail: roger.lewis@sheffield.ac.uk

    2012-01-15

    In this work, the sliding wear behaviour of the coatings TiN, CrN and WC/C applied on steel substrates was studied using a reciprocating wear test machine. All tests were carried out in dry conditions, at room temperature (20-23 degrees Celsius and 45% - 50% relative humidity). The average sliding velocity was 0.08 m/s and an amplitude of 2 mm was used. The applied loads were 11.76 N (Po = 1.74 GPa) and 7.84 N (Po = 1.52 GPa). Optical microscopy was used to observe the characteristics of wear scars and spalls and possible causes of their formation. The variation of the friction coefficient against the number of cycles was obtained. This was used to determine more precisely the time (number of cycles) where the coating presented the first signs of wear, in addition Energy Dispersive X-ray analysis (EDS) was performed, as well as Scanning Electron Microscopy (SEM) and hardness tests on the wear traces, which reinforced the previous observations. Thus it was possible to know the wear life of different coatings and possible causes of variation. Increasing the load was an important factor in the variation of wear life results. But it is also important to consider other factors such as surface roughness and thickness of coatings. [Spanish] En este trabajo se estudio el comportamiento en desgaste por deslizamiento de los recubrimientos de TiN, CrN y WC/C aplicados sobre sustratos de acero. Las pruebas se realizaron con una maquina reciprocante en condiciones secas a temperatura ambiente (20-23 grados centigrados y 45% - 50% de humedad relativa). Se empleo una velocidad promedio de 0.08 m/s y una amplitud de 2 mm. Las cargas aplicadas fueron de 11.76N (Po = 1.74 GPa) y de 7.84 N (Po = 1.52 GPa). Se realizo microscopia optica para observar las caracteristicas de las zonas de desgaste y sus posibles causas de formacion. Se obtuvo graficamente la variacion del coeficiente de friccion con el numero de ciclos. Estos datos se emplearon para determinar con mayor precision el

  6. Fretting Wear Behaviors of Aluminum Cable Steel Reinforced (ACSR Conductors in High-Voltage Transmission Line

    Directory of Open Access Journals (Sweden)

    Xingchi Ma

    2017-09-01

    Full Text Available This work reports the fretting wear behavior of aluminum cable steel reinforced (ACSR conductors for use in high-voltage transmission line. Fretting wear tests of Al wires were conducted on a servo-controlled fatigue testing machine with self-made assistant apparatus, and their fretting process characteristics, friction force, wear damage, and wear surface morphology were detailed analyzed. The results show that the running regime of Al wires changes from a gross slip regime to a mixed regime more quickly as increasing contact load. With increasing amplitudes, gross slip regimes are more dominant under contact loads of lower than 30 N. The maximum friction force is relatively smaller in the NaCl solution than in a dry friction environment. The primary wear mechanisms in dry friction environments are abrasive wear and adhesive wear whereas abrasive wear and fatigue damage are dominant in NaCl solution.

  7. Public Service Announcement: Heart Disease Doesn't Care What You Wear

    Science.gov (United States)

    ... Home Current Issue Past Issues Public Service Announcement Heart Disease Doesn't Care What You Wear Past Issues / ... version of this page please turn Javascript on. Heart Disease Doesn't Care What You Wear IT'S THE # ...

  8. An in vitro study of the wear behaviour of dental composites

    Directory of Open Access Journals (Sweden)

    J.A. Arsecularatne

    2016-09-01

    The results revealed that two different wear mechanisms were dominant for the composites tested: fatigue wear for the anterior/posterior composites and, abrasion due to lateral crack formation and filler particle pull out for the anterior composite.

  9. Influence of heat treatment on the wear life of hydraulic fracturing tools

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Chao; Liu, Yonghong; Wang, Hanxiang; Qin, Jie; Shen, Yang; Zhang, Shihong [China University of Petroleum, Qingdao (China)

    2017-02-15

    Wear phenomenon has caused severe damage or failure of fracturing tools in oil and gas industry. In this paper, influence of heat treatment on the mechanical properties and wear resistance of fracturing tool made of lamellar graphite grey cast iron were investigated. The surface composition and microstructure were characterized by X-ray diffraction (XRD) and metallographic microscope. Sliding wear tests were performed to study the tribological behavior. Tests results showed that wear rates of treated specimens decreased by 33 %. Besides, worn morphology and wear debris were analyzed using Scanning electron microscope (SEM) and Energy dispersive Xray spectra (EDS). Wear failure mechanisms of specimens were identified. Furthermore, on-site experiment results indicated that wear loss of treated samples decreased by 37.5 %. The wear life of hydraulic fracturing tools can be improved obviously by the heat treatment.

  10. Study on Rail Profile Optimization Based on the Nonlinear Relationship between Profile and Wear Rate

    National Research Council Canada - National Science Library

    Jianxi Wang; Zhiqiang Ren; Jinjie Chen; Long Chen

    2017-01-01

      This paper proposes a rail profile optimization method that takes account of wear rate within design cycle so as to minimize rail wear at the curve in heavy haul railway and extend the service life of rail...

  11. FDI Spill‑Overs, Absorptive Capacity and Domestic Firms’ Technical Efficiency in Vietnamese Wearing Apparel Industry

    Directory of Open Access Journals (Sweden)

    Hoang Duong Vu

    2017-01-01

    Full Text Available This study empirically examines relationship between FDI spill-overs and technical efficiency of domestic firms and role of the absorptive capacity of domestic firms. Data on Vietnamese Annual Enterprises Survey are exploited to build a firm-level panel data on the Vietnamese wearing apparel industry from 2009 to 2013. By applying stochastic production frontier model, this paper shows that there are positive vertical spill-over effects but no horizontal effects. Moreover, this study finds the negative impact of the absorptive capacity of domestic firms on benefits reaped from FDI externalities.

  12. Analysing a Relationship Between Wheel Wear and Cutting Forces During Diamond Grinding

    Directory of Open Access Journals (Sweden)

    M. A. Shavva

    2014-01-01

    carbide (Т15К6 work pieces was experimentally made. Experiments were carried out on the universal flat-grinding machine 3G71M using a diamond grinding wheel 6А2 250х20х4х29х76 АС6 160/125 А1 100% М1-01 according to GOST 16170-91. When using this equipment, cutting operation conditions, namely grinding speed and longitudinal table feed were 35 m/s and 3 - 12 m/min, respectively.The work piece was clamped in a vise. Vise was set on the universal attachment. Device was installed on a three-component dynamometer brands Kistler 9257B to measure cutting forces.Grinding was carried out under the following operation conditions: traverse Strav= 3 m/min, depth of cutting t = 20 μm. Grinding used a water-based cooling emulsion. Wheel speed was 35m/s. The dynamometer was tuned to the frequency of signal equal to 250 Hz.After processing the experimental and calculated data were compared using the theoretical formulas. The maximum difference between them was 17%.Owing to the presented model it is possible to obtain data on the diamond tool wear during cutting through a change of the tangential component of the cutting force. With the definite maximum wear of diamond wheel it is possible to calculate a threshold value of the tangential component of the cutting force. When the threshold value of the tangential component of the cutting force is reached, a diamond wheel must be subjected to dressing. On-time wheel dressing allows us to avoid reducing quality of the machined surface.Control of forces in the cutting zone is difficult to organize; the procedure can be performed by power control of the grinding spindle through the current control.

  13. Mild wear modeling in the boundary lubrication regime

    NARCIS (Netherlands)

    Bosman, Rob

    2011-01-01

    Currently, the increasing demand for smaller and more efficient systems is increasing the stress put on interacting components. This forces components to operate in the boundary lubrication regime. In this lubrication regime, the normal load put on the components is no longer carried by the

  14. 3D Finite Element Modeling of Sliding Wear

    Science.gov (United States)

    2013-12-01

    Technical Report, 846th Test Squadron, 46th Test Group,Holloman AFB, New Mexico, 2004 49. Incropera , F. P. and D. P. DeWitt. Fundamentals of Heat and... Mass Transfer . John Wiley & Sons, New York, 1990. 50. Janna, W. S. Engineering Heat Transfer . CRC Press, Boca Raton, 2009. 51. Johnson, G.R. and...Influence The specific heat is defined as “the amount of heat required to increase the temperature of a unit mass by one degree” [104]. The specific

  15. Computer Aided Model Development for Automatic Tool Wear ...

    African Journals Online (AJOL)

    The pre-processing operations on the images (taken on photographic cards) included scanning, in order to transfer onto a computer and convert them to digital images. Thresholding and segmentation were done in order to convert the altered background of the scanned images to a pure white background; the images were ...

  16. The Impact of Low Accelerometer Wear Time on the Estimates and Application of Sedentary Behavior and Physical Activity Data in Adults.

    Science.gov (United States)

    McGrath, Ryan; Vella, Chantal A; Scruggs, Philip W; Peterson, Mark D; Williams, Christopher J; Paul, David R

    2017-12-01

    This investigation sought to determine how accelerometer wear (1) biased estimates of sedentary behavior (SB) and physical activity (PA), (2) affected misclassifications for meeting the Physical Activity Guidelines for Americans, and (3) impacted the results of regression models examining the association between moderate to vigorous physical activity (MVPA) and a clinically relevant health outcome. A total of 100 participants [age: 20.6 (7.9) y] wore an ActiGraph GT3X+ accelerometer for 15.9 (1.6) hours per day (reference dataset) on the hip. The BOD POD was used to determine body fat percentage. A data removal technique was applied to the reference dataset to create individual datasets with wear time ranging from 15 to 10 hours per day for SB and each intensity of PA. Underestimations of SB and each intensity of PA increased as accelerometer wear time decreased by up to 167.2 minutes per day. These underestimations resulted in Physical Activity Guidelines for Americans misclassification rates of up to 42.9%. The regression models for the association between MVPA and body fat percentage demonstrated changes in the estimates for each wear-time adherence level when compared to the model using the reference MVPA data. Increasing accelerometer wear improves daily estimates of SB and PA, thereby also improving the precision of statistical inferences that are made from accelerometer data.

  17. Surface chemical modification for exceptional wear life of MEMS materials

    Directory of Open Access Journals (Sweden)

    R. Arvind Singh

    2011-12-01

    Full Text Available Micro-Electro-Mechanical-Systems (MEMS are built at micro/nano-scales. At these scales, the interfacial forces are extremely strong. These forces adversely affect the smooth operation and cause wear resulting in the drastic reduction in wear life (useful operating lifetime of actuator-based devices. In this paper, we present a surface chemical modification method that reduces friction and significantly extends the wear life of the two most popular MEMS structural materials namely, silicon and SU-8 polymer. The method includes surface chemical treatment using ethanolamine-sodium phosphate buffer, followed by coating of perfluoropolyether (PFPE nanolubricant on (i silicon coated with SU-8 thin films (500 nm and (ii MEMS process treated SU-8 thick films (50 μm. After the surface chemical modification, it was observed that the steady-state coefficient of friction of the materials reduced by 4 to 5 times and simultaneously their wear durability increased by more than three orders of magnitude (> 1000 times. The significant reduction in the friction coefficients is due to the lubrication effect of PFPE nanolubricant, while the exceptional increase in their wear life is attributed to the bonding between the -OH functional group of ethanolamine treated SU-8 thin/thick films and the -OH functional group of PFPE. The surface chemical modification method acts as a common route to enhance the performance of both silicon and SU-8 polymer. It is time-effective (process time ≤ 11 min, cost-effective and can be readily integrated into MEMS fabrication/assembly processes. It can also work for any kind of structural material from which the miniaturized devices are/can be made.

  18. Advanced Wear-resistant Nanocomposites for Increased Energy Efficiency

    Energy Technology Data Exchange (ETDEWEB)

    Cook, B. A.; Harringa, J. L.; Russel, A. M.

    2012-12-01

    This report summarizes the work performed by an Ames-led project team under a 4-year DOE-ITP sponsored project titled, 'Advanced Wear-resistant Nanocomposites for Increased Energy Efficiency.' The Report serves as the project deliverable for the CPS agreement number 15015. The purpose of this project was to develop and commercialize a family of lightweight, bulk composite materials that are highly resistant to degradation by erosive and abrasive wear. These materials, based on AlMgB{sub 14}, are projected to save over 30 TBtu of energy per year when fully implemented in industrial applications, with the associated environmental benefits of eliminating the burning of 1.5 M tons/yr of coal and averting the release of 4.2 M tons/yr of CO{sub 2} into the air. This program targeted applications in the mining, drilling, machining, and dry erosion applications as key platforms for initial commercialization, which includes some of the most severe wear conditions in industry. Production-scale manufacturing of this technology has begun through a start-up company, NewTech Ceramics (NTC). This project included providing technical support to NTC in order to facilitate cost-effective mass production of the wear-resistant boride components. Resolution of issues related to processing scale-up, reduction in energy intensity during processing, and improving the quality and performance of the composites, without adding to the cost of processing were among the primary technical focus areas of this program. Compositional refinements were also investigated in order to achieve the maximum wear resistance. In addition, synthesis of large-scale, single-phase AlMgB{sub 14} powder was conducted for use as PVD sputtering targets for nanocoating applications.

  19. Not only hard contact lens wear but also soft contact lens wear may be associated with blepharoptosis

    NARCIS (Netherlands)

    I. Bleyen (Isabel); C.A. Hiemstra; T. Devogelaere (Thibaut); W.A. van den Bosch (Willem); R.J. Wubbels (René J.); A.D.A. Paridaens (Dion)

    2011-01-01

    textabstractObjective: The authors attempt to establish an association between prolonged hard and soft contact lens wear and ptosis. Design: Single-center retrospective consecutive series. Participants: All patients between 18 and 50 years of age who were diagnosed with unilateral or bilateral

  20. Standard test method for ranking resistance of materials to sliding wear using block-on-ring wear test

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2005-01-01

    1.1 This test method covers laboratory procedures for determining the resistance of materials to sliding wear. The test utilizes a block-on-ring friction and wear testing machine to rank pairs of materials according to their sliding wear characteristics under various conditions. 1.2 An important attribute of this test is that it is very flexible. Any material that can be fabricated into, or applied to, blocks and rings can be tested. Thus, the potential materials combinations are endless. However, the interlaboratory testing has been limited to metals. In addition, the test can be run with various lubricants, liquids, or gaseous atmospheres, as desired, to simulate service conditions. Rotational speed and load can also be varied to better correspond to service requirements. 1.3 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only. Wear test results are reported as the volume loss in cubic millimetres for both the block and ring. Materials...

  1. Heat transfer from humans wearing clothing

    NARCIS (Netherlands)

    Lotens, W.A.

    1993-01-01

    In this monograph the effects of clothing on human heat transfer are described. The description is based on the physics of heat and mass transfer, depending on the design of the clothing, the climate, and the activity of the wearer. The resulting model has been stepwise implemented in computer

  2. A Novel Method for Assessment of Polyethylene Liner Wear in Radiopaque Tantalum Acetabular Cups

    DEFF Research Database (Denmark)

    Troelsen, Anders; Greene, Meridith E; Ayers, David C

    2015-01-01

    Conventional radiostereometric analysis (RSA) for wear is not possible in patients with tantalum cups. We propose a novel method for wear analysis in tantalum cups. Wear was assessed by gold standard RSA and the novel method in total hip arthroplasty patients enrolled in a randomized controlled t...

  3. Bionic design methodology for wear reduction of bulk solids handling equipment

    NARCIS (Netherlands)

    Chen, G.; Schott, D.L.; Lodewijks, G.

    2016-01-01

    Large-scale handling of particulate solids can cause severe wear on bulk solids handling equipment surfaces. Wear reduces equipment life span and increases maintenance cost. Examples of traditional methods to reduce wear of bulk solids handling equipment include optimizing transport operations

  4. Reduction of Erosion Wear of Mean Pressure Cylinder of Steam Turbines Operating Beyond Critical Parameters

    Directory of Open Access Journals (Sweden)

    V. P. Kascheev

    2009-01-01

    Full Text Available The paper considers problems leading to erosion wear of flowing part of a mean pressure turbine cylinder operating beyond critical parameters. Explanation of erosion wear of flowing part of a mean pressure turbine cylinder which is proved in practice and recommendations for wear reduction are given in the paper

  5. A comparison of spectacle and contact lens wearing times in the ACHIEVE study.

    Science.gov (United States)

    Jones-Jordan, Lisa A; Chitkara, Monica; Coffey, Bradley; Jackson, John Mark; Manny, Ruth E; Rah, Marjorie J; Walline, Jeffrey J

    2010-05-01

    The aim was to compare vision correction wearing time between myopic children and teenagers in a clinical trial of contact lenses and spectacles. Parents of subjects in the Adolescent and Child Health Initiative for Vision Empowerment (ACHIEVE) study provided wearing times for spectacle and contact lens wear. Hours wearing primary correction and total correction were compared between the two treatment groups. Other factors hypothesised to be associated with wearing time were analysed. The average wearing time of the primary correction differed significantly with the wearing time for the spectacles group being 91.5 hours per week compared to 80.3 hours per week for the contact lens wearers (p lenses less than young spectacle wearers and older contact lens wearers. Low scores on an appearance quality-of-life scale were associated with longer wearing time in spectacle wearers compared to the low- and high-scoring contact lens wearers. Gender, spectacle satisfaction and activities were not related to wearing time. While contact lens wearers, on average, wear their contact lenses less than spectacle wearers, they spend roughly the same amount of time wearing a refractive correction. Higher refractive error resulted in longer wearing times for both spectacle and contact lens wearers. Younger contact lens wearers wore their contact lenses for shorter periods than the spectacle wearers, but still wore them, on average, 74.4 hours per week (about 10 hours per day), suggesting that contact lenses are a viable alternative mode of correction for children.

  6. Investigating the influence of sand particle properties on abrasive wear behaviour

    NARCIS (Netherlands)

    Woldman, M.; van der Heide, Emile; Schipper, Dirk J.; Tinga, Tiedo; Masen, Marc Arthur

    2012-01-01

    Abrasion by sand particles is an important factor causing excessive wear in machines operating in sandy environments. To prevent such machines from failing, knowledge about the abrasive wear process is required. This work focuses on the relation between abrasive particle properties and the wear they

  7. Investigation on the Tribological Behavior and Wear Mechanism of Five Different Veneering Porcelains

    Science.gov (United States)

    Min, Jie; Zhang, Qianqian; Qiu, Xiaoli; Zhu, Minhao; Yu, Haiyang; Gao, Shanshan

    2015-01-01

    Objectives The primary aim of this research was to investigate the wear behavior and wear mechanism of five different veneering porcelains. Methods Five kinds of veneering porcelains were selected in this research. The surface microhardness of all the samples was measured with a microhardness tester. Wear tests were performed on a ball-on-flat PLINT fretting wear machine, with lubrication of artificial saliva at 37°C. The friction coefficients were recorded by the testing system. The microstructure features, wear volume, and damage morphologies were recorded and analyzed with a confocal laser scanning microscope and a scanning electron microscope. The wear mechanism was then elucidated. Results The friction coefficients of the five veneering porcelains differ significantly. No significant correlation between hardness and wear volume was found for these veneering porcelains. Under lubrication of artificial saliva, the porcelain with higher leucite crystal content exhibited greater wear resistance. Additionally, leucite crystal size and distribution in glass matrix influenced wear behavior. The wear mechanisms for these porcelains were similar: abrasive wear dominates the early stage, whereas delamination was the main damage mode at the later stage. Furthermore, delamination was more prominent for porcelains with larger crystal sizes. Significance Wear compatibility between porcelain and natural teeth is important for dental restorative materials. Investigation on crystal content, size, and distribution in glass matrix can provide insight for the selection of dental porcelains in clinical settings. PMID:26368532

  8. Investigation on the Tribological Behavior and Wear Mechanism of Five Different Veneering Porcelains.

    Directory of Open Access Journals (Sweden)

    Jie Min

    Full Text Available The primary aim of this research was to investigate the wear behavior and wear mechanism of five different veneering porcelains.Five kinds of veneering porcelains were selected in this research. The surface microhardness of all the samples was measured with a microhardness tester. Wear tests were performed on a ball-on-flat PLINT fretting wear machine, with lubrication of artificial saliva at 37°C. The friction coefficients were recorded by the testing system. The microstructure features, wear volume, and damage morphologies were recorded and analyzed with a confocal laser scanning microscope and a scanning electron microscope. The wear mechanism was then elucidated.The friction coefficients of the five veneering porcelains differ significantly. No significant correlation between hardness and wear volume was found for these veneering porcelains. Under lubrication of artificial saliva, the porcelain with higher leucite crystal content exhibited greater wear resistance. Additionally, leucite crystal size and distribution in glass matrix influenced wear behavior. The wear mechanisms for these porcelains were similar: abrasive wear dominates the early stage, whereas delamination was the main damage mode at the later stage. Furthermore, delamination was more prominent for porcelains with larger crystal sizes.Wear compatibility between porcelain and natural teeth is important for dental restorative materials. Investigation on crystal content, size, and distribution in glass matrix can provide insight for the selection of dental porcelains in clinical settings.

  9. Investigation on the Tribological Behavior and Wear Mechanism of Five Different Veneering Porcelains.

    Science.gov (United States)

    Min, Jie; Zhang, Qianqian; Qiu, Xiaoli; Zhu, Minhao; Yu, Haiyang; Gao, Shanshan

    2015-01-01

    The primary aim of this research was to investigate the wear behavior and wear mechanism of five different veneering porcelains. Five kinds of veneering porcelains were selected in this research. The surface microhardness of all the samples was measured with a microhardness tester. Wear tests were performed on a ball-on-flat PLINT fretting wear machine, with lubrication of artificial saliva at 37°C. The friction coefficients were recorded by the testing system. The microstructure features, wear volume, and damage morphologies were recorded and analyzed with a confocal laser scanning microscope and a scanning electron microscope. The wear mechanism was then elucidated. The friction coefficients of the five veneering porcelains differ significantly. No significant correlation between hardness and wear volume was found for these veneering porcelains. Under lubrication of artificial saliva, the porcelain with higher leucite crystal content exhibited greater wear resistance. Additionally, leucite crystal size and distribution in glass matrix influenced wear behavior. The wear mechanisms for these porcelains were similar: abrasive wear dominates the early stage, whereas delamination was the main damage mode at the later stage. Furthermore, delamination was more prominent for porcelains with larger crystal sizes. Wear compatibility between porcelain and natural teeth is important for dental restorative materials. Investigation on crystal content, size, and distribution in glass matrix can provide insight for the selection of dental porcelains in clinical settings.

  10. Effect of Cl–on the corrosive wear of AISI 321 stainless steel in H 2 ...

    Indian Academy of Sciences (India)

    SO4 solution was studied via the corrosive wear rate, the load bearing capacity of passive film and the relationship between pitting and corrosive wear. There is a critical load at natural potential, below which the corrosive wear rate is slightly ...

  11. Wear of PEEK-OPTIMA® and PEEK-OPTIMA®-Wear Performance articulating against highly cross-linked polyethylene.

    Science.gov (United States)

    East, Rebecca H; Briscoe, Adam; Unsworth, Anthony

    2015-03-01

    The idea of all polymer artificial joints, particularly for the knee and finger, has been raised several times in the past 20 years. This is partly because of weight but also to reduce stress shielding in the bone when stiffer materials such as metals or ceramics are used. With this in mind, pin-on-plate studies of various polyetheretherketone preparations against highly cross-linked polyethylene were conducted to investigate the possibility of using such a combination in the design of a new generation of artificial joints. PEEK-OPTIMA(®) (no fibre) against highly cross-linked polyethylene gave very low wear factors of 0.0384 × 10(-6) mm(3)/N m for the polyetheretherketone pins and -0.025 × 10(-6) mm(3)/N m for the highly cross-linked polyethylene plates. The carbon-fibre-reinforced polyetheretherketone (PEEK-OPTIMA(®)-Wear Performance) also produced very low wear rates in the polyetheretherketone pins but produced very high wear in the highly cross-linked polyethylene, as might have been predicted since the carbon fibres are quite abrasive. When the fibres were predominantly tangential to the sliding plane, the mean wear factor was 0.052 × 10(-6) mm(3)/N m for the pins and 49.3 × 10(-6) mm(3)/N m for the highly cross-linked polyethylene plates; a half of that when the fibres ran axially in the pins (0.138 × 10(-6) mm(3)/N m for the pins and 97.5 × 10(-6) mm/ N m for the cross-linked polyethylene plates). PEEK-OPTIMA(®) against highly cross-linked polyethylene merits further investigation. © IMechE 2015.

  12. The Effects of Carbon Nanotubes on the Mechanical and Wear Properties of AZ31 Alloy

    Directory of Open Access Journals (Sweden)

    Mingyang Zhou

    2017-12-01

    Full Text Available Carbon nanotube (CNT-reinforced AZ31 matrix nanocomposites were successfully fabricated using a powder metallurgy method followed by hot extrusion. The influence of CNTs on microstructures, mechanical properties, and wear properties were systematically investigated by optical microscope (OM, scanning electron microscope (SEM, X-ray diffraction (XRD, hardness test, tensile test, and wear test. The results revealed that the nanocomposites showed a slightly smaller grain size compared with the matrix and uniform distribution that CNTs could achieve at proper content. As a result, the addition of CNTs could weaken basal plane texture. However, the yield strength and ultimate tensile strength of the composites were enhanced as the amount of CNTs increased up to 2.0 wt. %, reaching maximum values of 241 MPa (+28.2% and 297 MPa (+6.1%, respectively. The load transfer mechanism, Orowan mechanism, and thermal mismatch mechanism played important roles in the enhancement of the yield strength, and several classical models were employed to predict the theoretical values. The effect of CNT content on the friction coefficient and weight loss of the nanocomposites was also studied. The relationships between the amount of CNTs, the friction coefficient, and weight loss could be described by the exponential decay model and the Boltzmann model, respectively.

  13. Variations in voice level and fundamental frequency with changing background noise level and talker-to-listener distance while wearing hearing protectors: A pilot study

    DEFF Research Database (Denmark)

    Bouserhal, Rachel E.; MacDonald, Ewen; Falk, Tiago H.

    2016-01-01

    concern for people wearing hearing protection devices (HPD). Although practical, radio communication is cumbersome, as it does not distinguish designated receivers. A smarter radio communication protocol must be developed to alleviate this problem. Thus, it is necessary to model speech production in noise...... while wearing HPDs. Such a model opens the door to radio communication systems that distinguish receivers and offer more efficient communication between persons wearing HPDs. Design: This paper presents the results of a pilot study aimed to investigate the effects of occluding the ear on changes...... in voice level and fundamental frequency in noise and with varying talker-to-listener distance. Study sample: Twelve participants with a mean age of 28 participated in this study. Results: Compared to existing data, results show a trend similar to the open ear condition with the exception of the occluded...

  14. The Head that Wears a Crown

    DEFF Research Database (Denmark)

    Hansen, Bertel Teilfeldt

    2014-01-01

    This paper documents a positive effect of shifts in the power balance between different ethnic groups on the risk of civil conflict. Using a rationalist bargaining model, I show that commitment problems arising from the presidency shifting from one ethnic group to another will increase the risk...... of conflict onset in the period immediately following a change in the ethnic group holding presidency. The effect is greatest in the aftermath of previous conflicts and slowly tapers off over time. Further, shifts where the winning and losing ethnic groups are of similar sizes exhibit the largest and most...

  15. Effect of bionic coupling units' forms on wear resistance of gray cast iron under dry linear reciprocating sliding condition

    Science.gov (United States)

    Pang, Zuobo; Zhou, Hong; Xie, Guofeng; Cong, Dalong; Meng, Chao; Ren, Luquan

    2015-07-01

    In order to get close to the wear form of guide rails, the homemade linear reciprocating wear testing machine was used for the wear test. In order to improve the wear-resistance of gray cast iron guide rail, bionic coupling units of different forms were manufactured by a laser. Wear behavior of gray-cast-iron with bionic-coupling units has been studied under dry sliding condition at room temperature using the wear testing machine. The wear resistance was evaluated by means of weight loss measurement and wear morphology. The results indicated that bionic coupling unit could improve the wear resistance of gray cast iron. The wear resistance of gray cast iron with reticulation bionic coupling unit is the best. When the load and speed changed, reticulation bionic coupling unit still has excellent performance in improving the wear resistance of gray cast iron.

  16. Effect of carbon content on friction and wear of cast irons

    Science.gov (United States)

    Buckley, D. H.

    1977-01-01

    Friction and wear experiments were conducted with cast irons and wrought steels containing various amounts of carbon in the alloy structure in contact with 52100 steel. Gray cast irons were found to exhibit lower friction and wear characteristics than white cast irons. Further, gray cast iron wear was more sensitive to carbon content than was white. Wear with gray cast iron was linearly related to load, and friction was found to be sensitive to relative humidity and carbon content. The form, in which the carbon is present in the alloy, is more important, as the carbon content and no strong relationship seems to exist between hardness of these ferrous alloys and wear.

  17. An investigation into the mechanism of the polygonal wear of metro train wheels and its effect on the dynamic behaviour of a wheel/rail system

    Science.gov (United States)

    Jin, Xuesong; Wu, Lei; Fang, Jianying; Zhong, Shuoqiao; Ling, Liang

    2012-12-01

    This paper presents a detailed investigation conducted into the mechanism of the polygonal wear of metro train wheels through extensive experiments conducted at the sites. The purpose of the experimental investigation is to determine from where the resonant frequency that causes the polygonal wear of the metro train wheels originates. The experiments include the model tests of a vehicle and its parts and the tracks, the dynamic behaviour test of the vehicle in operation and the observation test of the polygonal wear development of the wheels. The tracks tested include the viaducts and the tunnel tracks. The structure model tests show that the average passing frequency of a polygonal wheel is approximately close to the first bending resonant frequency of the wheelset that is found by the wheelset model test and verified by the finite element analysis of the wheelset. Also, the dynamic behaviour test of the vehicle in operation indicates the main frequencies of the vertical acceleration vibration of the axle boxes, which are dominant in the vertical acceleration vibration of the axle boxes and close to the passing frequency of a polygonal wheel, which shows that the first bending resonant frequency of the wheelset is very exciting in the wheelset operation. The observation test of the polygonal wear development of the wheels indicates an increase in the rate of the polygonal wear of the wheels after their re-profiling. This paper also describes the dynamic models used for the metro vehicle coupled with the ballasted track and the slab track to analyse the effect of the polygonal wear of the wheels on the wheel/rail normal forces.

  18. Tooth wear and gingival recession in 210 orthodontically treated patients: a retrospective cohort study.

    Science.gov (United States)

    Mijuskovic, Marco; Gebistorf, Meret C; Pandis, Nikolaos; Renkema, Anne M; Fudalej, Piotr S

    2017-11-14

    To assess the association between tooth wear (TW) and gingival recession (GR). Two hundred and ten orthodontically treated participants (100 males) were evaluated. GR and TW were rated independently by four raters on plaster models at four time points: before treatment (T1), mean age 13.8 years (SD = 3.7); after treatment (T2), mean age 16.7 years (SD = 3.9); 3 years after treatment (T3), mean age 19.7 years (SD = 4.2); and 7 years after treatment (T4), mean age 23.9 years (SD = 4.8). Univariable and mulitvariable random effects logistic regression analyses were performed with scores for GR as dependent variables and with TW, age, gender, dental segments (maxillary and mandibular anterior and posterior segments), time points, and Angle classification as independent variables. Method reliability was assessed with kappa statistics. Mandibular incisors, mandibular and maxillary first premolars and maxillary first molars were most vulnerable to GR. The prevalence of GR increased during the observation period. At T1 20.5% participants had one or more recession sites, at T4 85.7 % of the participants had at least one GR. There was evidence of association between moderate/severe TW and GR-for a tooth with moderate/severe wear, the odds of recession were 23% higher compared to a tooth with no/mild wear (odds ratio 1.23; 95% CI: 1.08-1.40; P = 0.002). Age, dental segment, and time were also significant recession predictors, whereas gender was not. There is evidence that moderate/severe TW is associated with the presence of gingival recession. Clinical significance of this can be limited.

  19. Tribology and Tool Wear of Hot Dip Galvanized Zinc Magnesium Alloys on Cold Rolled Steel Sheets

    Science.gov (United States)

    Raab, A. E.; Berger, E.; Freudenthaler, J.; Leomann, F.; Walch, C.

    2011-05-01

    Recently zinc based coatings on cold rolled steel with improved functionality in terms of forming and/or corrosion behaviour have been intensively investigated in the steel industry1,2,3. One of the most promising products are zinc magnesium alloys produced in hot dip galvanizing process. These coatings were already introduced in construction industry a few years ago1. With some modifications the improved properties of the coating are also interesting for automotive industry. In the present work the tribological potential of hot dip galvanized zinc magnesium coatings (HDG/ZM) produced at an industrial line under regular production, was studied in terms of sliding properties, adhesive and abrasive tool wear. First a short introduction into surface morphology of HDG/ZM will be given. For the tribological characterization of the material, which is the main topic of the contribution, different tests were performed on hot dip galvanised zinc magnesium material and results were compared with classic hot dip galvanized zinc coating (HDG/Z). The investigations are mainly based on the strip draw test which allows the determination of the friction coefficient directly by using a constant contact pressure. Deep drawing property was tested by forming model cups. The abrasive tool wear was tested using a standard test for material used in automotive industry. The adhesive tool wear was investigated by characterizing the coating material transferred to the tool in the strip draw test. All performed tests show an improved drawability of HDG/ZM compared to classical HDG/Z reference material. However the most promising difference between HDG/ZM and HDG/Z is that galling was found to be less for HDG/ZM than for HDG/Z. Therefore HDG/ZM is an interesting system not only with respect to corrosion protection but also in terms of tribology and provides clear advantages in formability.

  20. Carbon-Based Wear Coatings: Properties and Applications

    Science.gov (United States)

    Miyoshi, Kazuhisa

    2003-01-01

    The technical function of numerous engineering systems - such as vehicles, machines, and instruments - depends on the processes of motion and on the surface systems. Many processes in nature and technology depend on the motion and dynamic behavior of solids, liquids, and gases. Smart surface systems are essential because of the recent technological push toward higher speeds, loads, and operating temperatures; longer life; lighter weight and smaller size (including nanotechnology); and harsh environments in mechanical, mechatronic, and biomechanical systems. If proper attention is not given to surface systems, then vehicles, machines, instruments, and other technical systems could have short lives, consume excessive energy, experience breakdowns, result in liabilities, and fail to accomplish their missions. Surface systems strongly affect our national economy and our lifestyles. At the NASA Glenn Research Center, we believe that proper attention to surface systems, especially in education, research, and application, could lead to economic savings of between 1.3 and 1.6 percent of the gross domestic product. Wear coatings and surface systems continue to experience rapid growth as new coating and surface engineering technologies are discovered, more cost-effective coating and surface engineering solutions are developed, and marketers aggressively pursue, uncover, and exploit new applications for engineered surface systems in cutting tools and wear components. Wear coatings and smart surface systems have been used widely in industrial, consumer, automotive, aerospace, and biomedical applications. This presentation expresses the author's views of and insights into smart surface systems in wear coatings. A revolution is taking place in carbon science and technology. Diamond, an allotrope of carbon, joins graphite, fullerenes, and nanotubes as its major pure carbon structures. It has a unique combination of extreme properties: hardness and abrasion resistance; adhesion