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Sample records for vickers indentation technique

  1. Cathodoluminescence study of vickers indentations in magnesium ...

    African Journals Online (AJOL)

    Vickers diamond pyramid indentations made in single crystal of magnesium oxide (MgO) were examined in an environmental scanning electron microscope interfaced with an AVS-2000 spectrophotometer for luminescence. Three distinct zones around the indentations were identified to exhibit cathodoluminescence, which ...

  2. Evaluation of Fracture Toughness of Tantalum Carbide Ceramic Layer: A Vickers Indentation Method

    Science.gov (United States)

    Song, Ke; Xu, Yunhua; Zhao, Nana; Zhong, Lisheng; Shang, Zhao; Shen, Liuliu; Wang, Juan

    2016-07-01

    A tantalum carbide (TaC) ceramic layer was produced on gray cast iron matrix by in situ technique comprising a casting process and a subsequent heat treatment at 1135 °C for 45 min. Indentation fracture toughness in TaC ceramic layer was determined by the Vickers indentation test for various loads. A Niihara approach was chosen to assess the fracture toughness of TaC ceramic layer under condition of the Palmqvist mode in the experiment. The results reveal that K IC evaluation of TaC ceramic layer by the Vickers indentation method strongly depends on the selection of crack system and K IC equations. The critical indentation load for Vickers crack initiation in TaC ceramic layer lies between 1 and 2 N and the cracks show typical intergranular fracture characteristics. Indentation fracture toughness calculated by the indentation method is independent of the indentation load on the specimen. The fracture toughness of TaC ceramic layer is 6.63 ± 0.34 MPa m1/2, and the toughening mechanism is mainly crack deflection.

  3. The characterization of Vicker`s microhardness indentations and pile-up profiles as a strain-hardening microprobe

    Energy Technology Data Exchange (ETDEWEB)

    Santos, C. Jr. [Nuclear Regulatory Commission, Washington, DC (United States). Div. of Engineering Technology; Odette, G.R.; Lucas, G.E.; Schroeter, B.; Klinginsmith, D. [California Univ., Santa Barbara, CA (United States). Dept. of Mechanical Engineering; Yamamoto, T. [Tohoku Univ., Sendai (Japan)

    1998-04-01

    Microhardness measurements have long been used to examine strength properties and changes in strength properties in metals, for example, as induced by irradiation. Microhardness affords a relatively simple test that can be applied to very small volumes of material. Microhardness is nominally related to the flow stress of the material at a fixed level of plastic strain. Further, the geometry of the pile-up of material around the indentation is related to the strain-hardening behavior of a material; steeper pile-ups correspond to smaller strain-hardening rates. In this study the relationship between pile-up profiles and strain hardening is examined using both experimental and analytical methods. Vickers microhardness tests have been performed on a variety of metal alloys including low alloy, high Cr and austenitic stainless steels. The pile-up topology around the indentations has been quantified using confocal microscopy techniques. In addition, the indentation and pile-up geometry has been simulated using finite element method techniques. These results have been used to develop an improved quantification of the relationship between the pile-up geometry and the strain-hardening constitutive behavior of the test material.

  4. Calibrated atomic force microscope measurements of vickers hardness indentations and tip production and characterisation for scanning tunelling microscope

    DEFF Research Database (Denmark)

    Jensen, Carsten P.

    Calibrated atomic force microscope measurements of vickers hardness indentations and tip production and characterisation for scanning tunelling microscope......Calibrated atomic force microscope measurements of vickers hardness indentations and tip production and characterisation for scanning tunelling microscope...

  5. On the Invariance of Hardness at Vickers Indentation of Pre-Stressed Materials

    Directory of Open Access Journals (Sweden)

    Per-Lennart Larsson

    2017-07-01

    Full Text Available The influence from residual surface stresses on global indentation properties, i.e., hardness and size of the contact area, have been studied quite frequently in recent years. A fundamental assumption when evaluating such tests is that the material hardness is independent of any residual stresses. This assumption has been verified in the case of cone indentation of classical Mises elastoplastic materials. However, a detailed investigation of this feature in the case of three-dimensional indentation, i.e., Vickers and Berkovic indentation, has not been presented previously. It is therefore the aim of the present study to remedy this shortcoming using finite element methods. The numerical results pertinent to Vickers indentation clearly show that the material hardness is independent of residual (or applied stresses (also in case of three-dimensional indentation problems. The limitations of the validity of hardness invariance are also discussed in some detail.

  6. Evaluation by Vickers indentation of fracture toughness of a phosphate biodegradable glass.

    Science.gov (United States)

    Clément, J; Torres, P; Gil, F J; Planell, J A; Terradas, R; Martinez, S

    1999-07-01

    Indentation tests are commonly used for the evaluation of fracture toughness of brittle materials, particularly glasses and ceramics, because this technique requires only a small polished area on the specimen surface from which a large number of data points can be generated rapidly. However, a wide variety of equations for the calculation of fracture toughness of ceramic materials by means of Vickers indentation are available. Such equations are obtained phenomenologically and their parameters adjusted in such a way that the KIC values obtained are in good agreement with those obtained by conventional methods. This is the reason why it is necessary to check which type of equation reproduces more accurately the results obtained by means of conventional methods for the material which is going to be investigated. In the present work seven different fracture toughness equations widely used in glass and ceramic studies are considered and the results are compared with those obtained by conventional methods, such as single-edge notch beam (SENB) specimens tested in three-point bending. The role played by the applied indentation load is considered. Copyright 1999 Kluwer Academic Publishers

  7. The Influence of Indenter Rotation Angle on The Quality of Vicker Tester Calibration

    Directory of Open Access Journals (Sweden)

    Jozef Petrík

    2011-10-01

    Full Text Available The object of submitted work is to analyze the influence of the rotation of the indenter (diamond pyramid and test force on the result of Vickers hardness tester calibration using uncertainty analysis, Measurement systems analysis (MSA, analysis of variance (ANOVA and Z-score. The rotation anmgle of indenter affects the values of hardness, repeatability rrel, maximal error Erel and relative expanded uncertainty Urel. The significance of the angle of indenter on the hardness and observed parameters of calibration no such as it of test force, but not negligible.

  8. Mapping residual stress fields from Vickers hardness indents using Raman microprobe spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Sparks, R.G.; Enloe, W.S.; Paesler, M.A.

    1988-12-01

    Micro-Raman spectroscopy is used to map the residual stress fields in the vicinity of Vickers hardness indents. Both 514.5 and 488.0 nm, light is used to excite the effect and the resulting shifted and broadened Raman peaks are analyzed using computer deconvolution. Half-wave plates are used to vary the orientation of the incident later light`s polarization state with respect to crystal orientation. The Raman scattered light is then analyzed for polarization dependences which are indicative of the various components of the Raman scattering tensor. Such studies can yield valuable information about the orientation of stress components in a well known stress field. The results can then be applied to the determination of stress components in machined semiconductor materials.

  9. On the interpretation of the indentation size effect (ISE) through gradient theory for Vickers and Berkovich indenters

    Science.gov (United States)

    Kampouris, Asterios K.; Konstantinidis, Avraam A.

    2016-12-01

    The so-called indentation size effect (ISE) observed mainly in nanoindentation measurements with prismatic tips, is theoretically modeled in this article with the use of gradient theory. It is shown that the ISE, i.e. the dependence of the calculated hardness value on the indentation depth, is rather an artifact of the geometry of the tip used, than a phenomenon related to the material tested. The model predictions are compared with nanoindentation measurements of Al specimens.

  10. Evaluation for rheological constitutive relations, using the indentation technique

    Science.gov (United States)

    Fang, Lei

    1992-01-01

    A simple experimental method of determining the rheological constitutive relations is proposed. The method relies upon an analysis of the frictionless contact of a rigid spherical indenter and the rheological materials. The proposal addresses problems in two fields: rheological constitutive models and contact mechanics. It attempts to evaluate the rheological constitutive relations using an indentation technique. A systematic, optimization-based material parameter/function indentation model is proposed. The identification algorithm is based on a modified Marquardt-Levenberg method. A new integral constitutive equation for viscoelastic materials is derived. The derivation is carried out so that a damage function is included in the model in a relatively convenient form. Inclusion of damage effects makes this constitutive equation considerably more general than the widely accepted K-BKZ integral model. The single-step and double-step stress relaxation indentation experiments on asphalt materials were performed. The K-BKZ, Wagner, and nonlinear Volterra models were evaluated. It is demonstrated that the new integral constitutive model shows a very good agreement with the experimental data. The idea of damage function is introduced not only to have a better fit of data, but the damage (or irreversibility) is observed experimentally. Also, the creep indentation tests on composites were presented. A multiaxial theory of creep deformation for particle-strengthened metal matrix composites (Zhu-Weng Theory) was evaluated. The goal of the proposed research is to develop the indentation technique for use in basic mechanical studies. From the indentation test, material response is measured. The data are used in conjunction with the material parameter identification model to optimally back calculate the constitutive relations. indentation test and other experiment method demonstrates the viability of the proposed approach.

  11. Use of indentation technique to measure elastic modulus of plasma-sprayed zirconia thermal barrier coating

    Energy Technology Data Exchange (ETDEWEB)

    Singh, J.P.; Sutaria, M. [Argonne National Lab., IL (United States). Energy Technology Div.; Ferber, M. [Oak Ridge National Lab., TN (United States)

    1997-01-01

    Elastic modulus of an yttria partially stabilized zirconia (YSZ) thermal barrier coating (TBC) was evaluated with a Knoop indentation technique. The measured elastic modulus values for the coating ranged from 68.4 {+-} 22.6 GPa at an indentation load of 50 g to 35.7 {+-} 9.8 at an indentation load of 300 g. At higher loads, the elastic modulus values did not change significantly. This steady-state value of 35.7 GPa for ZrO{sub 2} TBC agreed well with literature values obtained by the Hertzian indentation method. Furthermore, the measured elastic modulus for the TBC is lower than that reported for bulk ZrO{sub 2} ({approx} 190 GPa). This difference is believed to be due to the presence of a significant amount of porosity and microcracks in the TBCs. Hardness was also measured.

  12. Measurement of irradiation effects in a RPV steel by ball indentation technique and magnetic Barkhausen noise

    Science.gov (United States)

    Kim, In-Sup; Park, Duck-Gun; Byun, Thak-Sang; Hong, Jun-Hwa

    1999-12-01

    Effects of neutron dose on the mechanical and magnetic properties of a SA508-3 nuclear pressure vessel steel were investigated by using ball indentation test technique and magnetic Barkhausen noise (BN) measurements. The samples were irradiated in a research reactor up to 1018n/cm2 (E>1 MeV) at 70 °C. The yield strength and flow curve were evaluated from the indentation load-depth curves. The change of mechanical properties showed characteristic trend with respect to neutron dose, namely near plateau, rapid increase and slow increase. On the other hand, the BN varied in a reverse manner, a slow decrease up to a neutron dose of 1016n/cm2, followed by a rapid decrease up to a dose of 1018n/cm2.

  13. Study of the Tool Geometry Influence in Indentation for the Analysis and Validation of the New Modular Upper Bound Technique

    Directory of Open Access Journals (Sweden)

    Carolina Bermudo

    2016-07-01

    Full Text Available Focusing on incremental bulk metal forming processes, the indentation process is gaining interest as a fundamental part of these kinds of processes. This paper presents the analysis of the pressure obtained in indentation under the influence of different punch geometries. To this end, an innovative Upper Bound Theorem (UBT based solution is introduced. This new solution can be easily applied to estimate the necessary force that guarantees plastic deformation by an indentation process. In this work, we propose an accurate analytical approach to analyse indentation under different punches. The new Modular Upper Bound (MUB method presents a simpler and faster application. Additionally, its complexity is not considerably increased by the addition of more Triangular Rigid Zones. In addition, a two-dimensional indentation model is designed and implemented using the Finite Element Method (FEM. The comparison of the two methods applied to the indentation process analysed—the new Modular Upper Bound technique and the Finite Element Method—reveal close similarities, the new Modular Upper Bound being more computationally efficient.

  14. NIFS workshop on application of micro-indentation technique to evaluation of mechanical properties of fusion materials. Proceedings

    Energy Technology Data Exchange (ETDEWEB)

    Kurishita, Hiroaki; Katoh, Yutai [eds.] [Tohoku Univ., Oarai, Ibaraki (Japan). Oarai Branch, Inst. for Materials Research

    1996-11-01

    NIFS workshop on `Application of Micro-Indentation Technique to Evaluation of Mechanical Properties of Fusion Materials` were help in Toki on October 9, 1996, as a part of the activity of NIFS collaborative research on `Advanced Technologies for Small-Volume Mechanical Property Testing of Fusion Reactor Materials`. The major topics at the workshop included the application of micro- (and nano-) indentation technique to evaluation of tensile stress-strain property, interfacial mechanical property of composite and joining materials and hardening of this layers in ion-irradiated materials. This report compiles the abstract and viewgraphs for each presentation. (author)

  15. Safety evaluation of molten steel carrier by using instrument indentation technique

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jeong Ki; Kim, Yi Gon; Yoo, Dae Wha; Kim, Chung Youb [School of Mechanical Design Engineering, Chonnam National University, Yeosu (Korea, Republic of); Kim, Kwang Ho [Frontics Co., Ltd., Seoul (Korea, Republic of); Lee, Kyeong Ro [Dept. of Automotive Management, Joongbu University, Geumsan (Korea, Republic of)

    2014-02-15

    Because a molten steel carrier is used in high-temperature and corrosive environments, erosion and corrosion decrease the thickness of the structure and expand the vent hole for emitting gas generated from refractory bricks. This increases the stress throughout the structure and introduces a significant stress concentration around the vent hole. In addition, the high-temperature environment degrades mechanical properties such as the yield and tensile strengths. These problems seriously affect the safety of the structure. In this study, the safety of a 10-year-old structure was evaluated by analyzing the stress distribution and measuring the mechanical properties of the structure. The mechanical properties were directly measured on the structure surface using the instrument indentation technique.

  16. Determination of the Mechanical Properties of Plasma-Sprayed Hydroxyapatite Coatings Using the Knoop Indentation Technique

    Science.gov (United States)

    Hasan, Md. Fahad; Wang, James; Berndt, Christopher

    2015-06-01

    The microhardness and elastic modulus of plasma-sprayed hydroxyapatite coatings were evaluated using Knoop indentation on the cross section and on the top surface. The effects of indentation angle, testing direction, measurement location and applied load on the microhardness and elastic modulus were investigated. The variability and distribution of the microhardness and elastic modulus data were statistically analysed using the Weibull modulus distribution. The results indicate that the dependence of microhardness and elastic modulus on the indentation angle exhibits a parabolic shape. Dependence of the microhardness values on the indentation angle follows Pythagoras's theorem. The microhardness, Weibull modulus of microhardness and Weibull modulus of elastic modulus reach their maximum at the central position (175 µm) on the cross section of the coatings. The Weibull modulus of microhardness revealed similar values throughout the thickness, and the Weibull modulus of elastic modulus shows higher values on the top surface compared to the cross section.

  17. Elasticity modulus of rabbit middle ear ossicles determined by a novel micro-indentation technique.

    Science.gov (United States)

    Soons, Joris A M; Aernouts, Jef; Dirckx, Joris J J

    2010-05-01

    For the purpose of creating a finite element model of the middle ear, the ossicles can be modelled as rigid bodies or as linear elastic materials. The general elasticity parameters used are usually measured on larger bones like the femur. In order to obtain a highly realistic model, the actual elastic modulus (Young's modulus) of the ossicles themselves is needed. We developed a novel 2-needle indentation method of determining the Young's modulus of small samples based on Sneddon's solution. We introduce the second needle in such a way that small specimens can be clamped between the two needles and a symmetry plane is obtained, so that geometry-dependent sample deformations are avoided. A finite element calculated correction factor is used to compensate for the small thickness of the samples. The system was tested on several materials with known parameters in order to validate the technique, and was then used to determine the elasticity parameters of incus and malleus in rabbit. No significant differences between measurement locations were found, and we found an average Young's modulus of 16+/-3 GPa. Copyright (c) 2009 Elsevier B.V. All rights reserved.

  18. Quantitative Imaging of the Stress/Strain Fields and Generation of Macroscopic Cracks from Indents in Silicon

    Directory of Open Access Journals (Sweden)

    Brian K. Tanner

    2017-11-01

    Full Text Available The crack geometry and associated strain field around Berkovich and Vickers indents on silicon have been studied by X-ray diffraction imaging and micro-Raman spectroscopy scanning. The techniques are complementary; the Raman data come from within a few micrometres of the indentation, whereas the X-ray image probes the strain field at a distance of typically tens of micrometres. For example, Raman data provide an explanation for the central contrast feature in the X-ray images of an indent. Strain relaxation from breakout and high temperature annealing are examined and it is demonstrated that millimetre length cracks, similar to those produced by mechanical damage from misaligned handling tools, can be generated in a controlled fashion by indentation within 75 micrometres of the bevel edge of 200 mm diameter wafers.

  19. Indentation responses of piezoelectric films

    Science.gov (United States)

    Wang, J. H.; Chen, C. Q.; Lu, T. J.

    Frictionless indentation responses of transversely isotropic piezoelectric film/rigid substrate systems under circular cylindrical indenter (i.e., punch), conical indenter (i.e., cone), and spherical indenter (i.e., sphere) are investigated. Both insulating and conducting indenters are considered. The technique of Hankel transformation is employed to derive the corresponding dual integral equations for the mixed boundary value indentation problems. For the two limiting cases of infinitely thick and infinitely thin piezoelectric films, closed-form solutions are obtained. For piezoelectric films of finite thickness, a numerical method is constructed to solve the dual integral equations and semi-empirical models having only two unknown parameters are proposed for the responses of indentation force, electric charge and electric potential, and contact radius. With the two parameters inferred from the numerical results, the semi-empirical formulae are found to provide good estimates of the indentation responses for the two limiting cases of infinitely thick and thin piezoelectric films, as well as those in between. The inferred parameters in the proposed semi-empirical formulae for normalized indentation force and electric charge are checked against four different piezoelectric materials and are found to be insensitive to the selection of piezoelectric materials. It is believed that the proposed semi-empirical indentation formulae are useful in developing experimental indentation techniques to extract the material properties of piezoelectric films.

  20. The use of traditional and novel techniques to determine the hardness and indentation properties of immature radicular dentin treated with antibiotic medicaments followed by ethylenediaminetetraacetic acid

    OpenAIRE

    Yassen, Ghaeth H.; Al-Angari, Sarah S.; Platt,Jeffrey A.

    2014-01-01

    Objective: The objective was to investigate the effect of intracanal antibiotic medicaments followed by ethylenediaminetetraacetic acid (EDTA) on the indentation properties and hardness of radicular dentin using a BioDent reference point indenter and a traditional microhardness technique, respectively. Materials and Methods: Specimens with intact root canal dentin surfaces and polished radicular dentin specimens were obtained from immature human premolars. Each type of specimen was randomly a...

  1. Evaluation of flow properties in the weldments of vanadium alloys using a novel indentation technique

    Energy Technology Data Exchange (ETDEWEB)

    Gubbi, A.N.; Rowcliffe, A.F.; Lee, E.H.; King, J.F.; Goodwin, G.M. [Oak Ridge National Lab., TN (United States)

    1996-10-01

    Automated Ball Indentation (ABI) testing, was successfully employed to determine the flow properties of the fusion zone, heat affected zone (HAZ), and base metal of the gas tungsten arc (GTA) and electron beam (EB) welds of the V-4Cr-4Ti (large heat no. 832665) and the V-5Cr-5Ti (heat 832394) alloys. ABI test results showed a clear distinction among the properties of the fusion zone, HAZ, and base metal in both GTA and EB welds of the two alloys. GTA and EB welds of both V-4Cr-4Ti and V-5Cr-5Ti alloys show strengthening of both the fusion zone and the HAZ (compared to base metal) with the fusion zone having higher strength than the HAZ. These data correlate well with the Brinell hardness. On the other hand, GTA welds of both alloys, after a post-weld heat treatment of 950{degrees}C for 2 h, show a recovery of the properties to base metal values with V-5Cr-5Ti showing a higher degree of recovery compared to V-4Cr-4Ti. These measurements correlate with the reported recovery of the Charpy impact properties.

  2. Crystallographic Analysis of Nucleation at Hardness Indentations in High-Purity Aluminum

    DEFF Research Database (Denmark)

    Xu, Chaoling; Zhang, Yubin; Lin, Fengxiang

    2016-01-01

    Nucleation at Vickers hardness indentations has been studied in high-purity aluminum cold-rolled 12 pct. Electron channeling contrast was used to measure the size of the indentations and to detect nuclei, while electron backscattering diffraction was used to determine crystallographic orientation...

  3. Study of indentation induced cracks in MoSi2-reaction bonded SiC ...

    Indian Academy of Sciences (India)

    The infiltrated sample had a density > 92% of the theoretical density (TD) and microstructurally contained SiC, MoSi2, residual Si and unreacted C. The material was tested for indentation fracture toughness at room temperature with a Vicker's indenter and KIC was found to be 4.42 MPa√m which is around 39% higher than ...

  4. The relationship between vickers microhardness and compressive strength of functional surface geopolymers

    Science.gov (United States)

    Subaer, Ekaputri, Januari Jaya; Fansuri, Hamzah; Abdullah, Mustafa Al Bakri

    2017-09-01

    An experimental study to investigate the relationship between Vickers microhardness and compressive strength of geopolymers made from metakaolin has been conducted. Samples were prepared by using metakaolin activated with a sodium silicate solution at a different ratio of Si to Al and Na to Al and cured at 70oC for one hour. The resulting geopolymers were stored in an open air for 28 days before conducting any measurement. Bulk density and apparent porosity of the samples were measured by using Archimedes's method. Vickers microhardness measurements were performed on a polished surface of geopolymers with a load ranging from 0.3 - 1.0 kg. The topographic of indented samples were examined by using scanning electron microscopy (SEM). Compressive strength of the resulting geopolymers was measured on the cylindrical samples with a ratio of height to the diameter was 2:1. The results showed that the molar ratios of geopolymers compositions play important roles in the magnitude of bulk density, porosity, Vickers's microhardness as well as the compressive strength. The porosity reduced exponentially the magnitude of the strength of geopolymers. It was found that the relationship between Vickers microhardness and compressive strength was linear. At the request of all authors and with the approval of the proceedings editor, article 020188 titled, "The relationship between vickers microhardness and compressive strength of functional surface geopolymers," is being retracted from the public record due to the fact that it is a duplication of article 020170 published in the same volume.

  5. Indentation fatigue in silicon nitride, alumina and silicon carbide ...

    Indian Academy of Sciences (India)

    Repeated indentation fatigue (RIF) experiments conducted on the same spot of different structural ceramics viz. a hot pressed silicon nitride (HPSN), sintered alumina of two different grain sizes viz. 1 m and 25 m, and a sintered silicon carbide (SSiC) are reported. The RIF experiments were conducted using a Vicker's ...

  6. Mechanical properties of bovine cortical bone based on the automated ball indentation technique and graphics processing method.

    Science.gov (United States)

    Zhang, Airong; Zhang, Song; Bian, Cuirong

    2018-02-01

    Cortical bone provides the main form of support in humans and other vertebrates against various forces. Thus, capturing its mechanical properties is important. In this study, the mechanical properties of cortical bone were investigated by using automated ball indentation and graphics processing at both the macroscopic and microstructural levels under dry conditions. First, all polished samples were photographed under a metallographic microscope, and the area ratio of the circumferential lamellae and osteons was calculated through the graphics processing method. Second, fully-computer-controlled automated ball indentation (ABI) tests were performed to explore the micro-mechanical properties of the cortical bone at room temperature and a constant indenter speed. The indentation defects were examined with a scanning electron microscope. Finally, the macroscopic mechanical properties of the cortical bone were estimated with the graphics processing method and mixture rule. Combining ABI and graphics processing proved to be an effective tool to obtaining the mechanical properties of the cortical bone, and the indenter size had a significant effect on the measurement. The methods presented in this paper provide an innovative approach to acquiring the macroscopic mechanical properties of cortical bone in a nondestructive manner. Copyright © 2017 Elsevier Ltd. All rights reserved.

  7. Evaluation of multi-layered hardness in ion-irradiated stainless steel by nano-indentation technique

    Energy Technology Data Exchange (ETDEWEB)

    Oka, Hiroshi, E-mail: hiroshi_oka@eng.hokudai.ac.jp; Sato, Yutaka; Hashimoto, Naoyuki; Ohnuki, Somei

    2015-07-15

    Depth dependence of hardness in ion-irradiated 316 stainless steel was evaluated by the sectioning of damaged region and subsequent nano-indentation. The range of plastically deformed region by the nano-indentation was supplementarily investigated by transmission electron microscopy. When the indentation depth was the critical indentation depth, h{sub c}, which was derived from the Nix–Gao plot, the dislocation structure was observed from the specimen surface to right below the bottom of the ion-irradiated region. To verify the depth dependence of hardness, the “multi-layer model” was introduced in this study. The multi-layer model is based on the following assumptions; (1) the ion-irradiated region can be divided into sub-layers having their own local hardness, H{sub L}; (2) the hardness can be the product of f and H{sub L} in each sub-layer where f is the volume fraction of a deformation zone; and (3) the deformation zone can be a hemisphere. Eventually, through the sectioning and following nano-indentation, H{sub L} in each sub-layer was experimentally evaluated. Further the correlation between the displacement damage and the irradiation hardening ΔH in this study agreed with that of neutron irradiation experiments.

  8. Design of Vickers Hardness Loading Controller

    Directory of Open Access Journals (Sweden)

    Sihai Zhao

    2014-09-01

    Full Text Available Traditionally Vickers testing needs manual works, as a result, it will induce low precision and automatization. So this paper design a new type of loading controlling system, it is based on single chip computer 89S52, used PZT as the force generator in micro Vickers hardness testing. It primarily includes the designing of hardware, software of collecting data and PZT signals by AD667. This article has given the sketch of electrical circuit and controlling software, it also offers the experiment data. The experiments have showed that using this system can exactly control the loading results, and the average tolerance is less than 0.43 %.

  9. Vickers microhardness comparison of 4 composite resins with different types of filler.

    Directory of Open Access Journals (Sweden)

    René García-Contreras

    2015-10-01

    Full Text Available Composite resins are the material of choice to restore minimal invasive cavities; conversely, it is important to explore the mechanical properties of commercially available dental materials. Objective: To compare the Vickers microhardness (VHN of four available commercial composite resins using standardized samples and methods. Methodology: Composite cylinders were manufactured in a Teflon mould. We used the follow composite resins (n=4/gp: Microhybrid resins [Feeling Lux (Viarden and Amelogen Plus (Ultradent], Hybrid resin [Te-Econom Plus (Ivoclar] and Nanohybrid resin [Filtek Z350 (3M ESPE]. All samples were incubated in distilled water at 37ºC for five days. The test was carried out with microhardness indenter at 10 N, and a dwelling time of 10 s for 9 indentations across the specimens resulting in a total of 36 indentations for each group. Data were subjected to Kolmogorov-Smirnov normality test and ANOVA (post-hoc Tukey test. Results: The VHN mean values ranged from harder to softer as follows: Filtek Z350 (71.96±6.44 (p Amelogen Plus (59.90±4.40 (p Feeling lux (53.52±5.72> Te-Econom Plus (53.26±5.19. Conclusion: According to our results, the microhardness of the evaluated conventional composite resins can withstand the masticatory forces; however nanohybrid composite resins showed better Vickers microhardness and therefore are a more clinically suitable option for minimal invasion treatments.

  10. Estimation of fracture toughness of Zr 2.5% Nb pressure tube of Pressurised Heavy Water Reactor using cyclic ball indentation technique

    Energy Technology Data Exchange (ETDEWEB)

    Chatterjee, S., E-mail: subrata@barc.gov.in; Panwar, Sanjay; Madhusoodanan, K.; Rama Rao, A.

    2016-08-15

    Highlights: • Measurement of fracture toughness of pressure tube is required for its fitness assessment. • Pressure tube removal from the core consumes large amount of radiation for laboratory test. • A remotely operable In situ Property Measurement System (IProMS) has been designed in house. • Conventional and IProMS tests conducted on pressure tube spool pieces having different mechanical properties. • Correlation has been established between the conventional and IProMS estimated fracture properties. - Abstract: In Pressurised Heavy Water Reactors (PHWRs) fuel bundles are located inside horizontal pressure tubes made up of Zr 2.5 wt% Nb alloy. Pressure tubes undergo degradation during its service life due to high pressure, high temperature and radiation environment. Measurement of mechanical properties of degraded pressure tubes is important for assessing their fitness for further operation. Presently as per safety guidelines imposed by the regulatory body, a few pre-decided pressure tubes are removed from the reactor core at regular intervals during the planned reactor shut down to carry out post irradiation examination (PIE) in a laboratory which consumes lots of man-rem and imposes economic penalties. Hence a system is indeed felt necessary which can carry out experimental trials for measurement of mechanical properties of pressure tubes under in situ conditions. The only way to accomplish this important objective is to develop a system based on an in situ measurement technique. In the field of in situ estimation of properties of materials, cyclic ball indentation is an emerging technique. Presently, commercial systems are available for doing an indentation test either on the outside surface of a component at site or on a test piece in a laboratory. However, these systems cannot be used inside a pressure tube for carrying out ball indentation trials under in situ conditions. Considering the importance of such measurements, an In situ Property

  11. Using the ultrasound and instrumented indentation techniques to measure the elastic modulus of engineering materials; Medicion del modulo de elasticidad en materiales de ingenieria utilizando la tecnica de indentacion instrumentada y de ultrasonido

    Energy Technology Data Exchange (ETDEWEB)

    Meza, J. M.; Franco, E. E.; Farias, M. C. M.; Buiochi, F.; Souza, R. M.; Cruz, J.

    2008-07-01

    Currently, the acoustic and nano indentation techniques are two of the most used techniques for materials elastic modulus measurement. In this article fundamental principles and limitations of both techniques are shown and discussed. Last advances in nano indentation technique are also reviewed. an experimental study in ceramic, metallic, composite and single crystals was also done. Results shown that ultrasonic technique is capable to provide results in agreement with those reported in literature. However, ultrasonic technique does not allow measuring the elastic modulus of some small samples and single crystals. On the other hand, the nano indentation technique estimates the elastic modulus values in reasonable agreement with those measured by acoustic methods, particularly in amorphous materials, while in some policristaline materials some deviation from expected values was obtained. (Author) 29 refs.

  12. Change detection technique for muscle tone during static stretching by continuous muscle viscoelasticity monitoring using wearable indentation tester.

    Science.gov (United States)

    Okamura, Naomi; Kobayashi, Yo; Sugano, Shigeki; Fujie, Masakatsu G

    2017-07-01

    Static stretching is widely performed to decrease muscle tone as a part of rehabilitation protocols. Finding out the optimal duration of static stretching is important to minimize the time required for rehabilitation therapy and it would be helpful for maintaining the patient's motivation towards daily rehabilitation tasks. Several studies have been conducted for the evaluation of static stretching; however, the recommended duration of static stretching varies widely between 15-30 s in general, because the traditional methods for the assessment of muscle tone do not monitor the continuous change in the target muscle's state. We have developed a method to monitor the viscoelasticity of one muscle continuously during static stretching, using a wearable indentation tester. In this study, we investigated a suitable signal processing method to detect the time required to change the muscle tone, utilizing the data collected using a wearable indentation tester. By calculating a viscoelastic index with a certain time window, we confirmed that the stretching duration required to bring about a decrease in muscle tone could be obtained with an accuracy in the order of 1 s.

  13. TEM observations of Al{sub 72}Ni{sub 12}Co{sub 16} decagonal quasicrystal subjected to high-temperature indentation

    Energy Technology Data Exchange (ETDEWEB)

    Saito, K. [Department of Materials Science and Engineering, Akita University, Akita 010-8502 (Japan)]. E-mail: ksaito@ipc.akita-u.ac.jp; Arakaki, Y. [Department of Materials Science and Engineering, Akita University, Akita 010-8502 (Japan); Sugawara, S. [Department of Materials Science and Engineering, Akita University, Akita 010-8502 (Japan); Shindo, R. [Akita Prefecture Industrial Technology Center, Akita 010-1623 (Japan); Guo, J.Q. [National Institute for Materials Science, Tsukuba 305-0047 (Japan); Tsai, A.P. [National Institute for Materials Science, Tsukuba 305-0047 (Japan)

    2005-08-25

    The effect of high-temperature indentation testing on the microstructural change of a single-grained Al{sub 72}Ni{sub 12}Co{sub 16} decagonal quasicrystal (d-QC) has been investigated by transmission electron diffraction and microscopy (TEM) technique. A definite surface normal to the 10-fold axis of the d-QC was subjected to Vickers indentation test at an elevated temperature of 800 deg. C with a load of 1 kgf. The TEM investigation of this sample has evidently shown that there are specific types of defects densely distributed in the indented-region, such as grain-boundaries, dislocations and phason-related defects. Furthermore, high-resolution electron microscopy observations have revealed the widespread distribution of nanocrystalline domains in the indented-region, where groups of decagonal atom clusters have a periodic arrangement to form a rhombic lattice. On the basis of these observations, possible deformation mechanisms of the d-QC during high-temperature indentation will be discussed.

  14. Effect of substrate hardness and film structure on indentation depth criteria for film hardness testing

    Energy Technology Data Exchange (ETDEWEB)

    Manika, Ilze; Maniks, Janis [Institute of Solid State Physics, University of Latvia, 8 Kengaraga Str., Riga LV1063 (Latvia)], E-mail: manik@latnet.lv

    2008-04-07

    The indentation depth limits for the Vickers microhardness testing of amorphous, polycrystalline, multilayer and single crystal coatings were investigated. The coating/substrate hardness ratio was varied in the range from 0.01 to 20. The critical indentation depth h{sub c}, below which the substrate has a negligible effect on the hardness, was estimated from the experimentally obtained hardness versus indentation depth curves. The results show a marked effect of the coating structure on the size of the influence zone beneath the indenter. The indentation depth limits were found to increase in the row of single crystal {yields} polycrystalline {yields} amorphous coatings. The obtained indentation depth criteria are compared with the reference data obtained by using finite element and kinematic calculations.

  15. The interrelationship of microstructure and hardness of human coronal dentin using reference point indentation technique and micro-Raman spectroscopy.

    Science.gov (United States)

    Seyedmahmoud, Rasoul; McGuire, Jacob D; Wang, Yong; Thiagarajan, Ganesh; Walker, Mary P

    2017-10-01

    The aim of this paper is to determine the interrelationship between the microstructure - in terms of chemical composition and crystallinity - to the microhardness of coronal dentin. Dentin microhardness was tested by a novel reference point indenter and compared to the traditional Knoop hardness method. Micro-Raman spectroscopy was used to determine the chemical composition and crystallinity of dentin. From the occlusal groove to the border of the coronal pulp chamber, dentin hardness decreased from superficial dentin (SD) to deep dentin (DD). Mineral/organic matrix ratios (phosphate/CH and phosphate/amide I) also decreased from SD to DD; however, this change was significant (Phardness from superficial to deep dentin can potentially be explained by decreased mineral content and increased carbonate content, which is also associated with decreased crystallinity. Collectively, there is a positive association between dentin hardness and mineral content and a negative association between dentin hardness and carbonate content. Copyright © 2017 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  16. Investigation of Quasi-Static Indentation Response of Inkjet Printed Sandwich Structures under Various Indenter Geometries

    Directory of Open Access Journals (Sweden)

    Vishwesh Dikshit

    2017-03-01

    Full Text Available The objective of this investigation was to determine the quasi-static indentation response and failure mode in three-dimensional (3D printed trapezoidal core structures, and to characterize the energy absorbed by the structures. In this work, the trapezoidal sandwich structure was designed in the following two ways. Firstly, the trapezoidal core along with its facesheet was 3D printed as a single element comprising a single material for both core and facesheet (type A; Secondly, the trapezoidal core along with facesheet was 3D printed, but with variation in facesheet materials (type B. Quasi-static indentation was carried out using three different indenters, namely standard hemispherical, conical, and flat indenters. Acoustic emission (AE technique was used to capture brittle cracking in the specimens during indentation. The major failure modes were found to be brittle failure and quasi-brittle fractures. The measured indentation energy was at a maximum when using a conical indenter at 9.40 J and 9.66 J and was at a minimum when using a hemispherical indenter at 6.87 J and 8.82 J for type A and type B series specimens respectively. The observed maximum indenter displacements at failure were the effect of material variations and composite configurations in the facesheet.

  17. Investigation of Quasi-Static Indentation Response of Inkjet Printed Sandwich Structures under Various Indenter Geometries.

    Science.gov (United States)

    Dikshit, Vishwesh; Nagalingam, Arun Prasanth; Yap, Yee Ling; Sing, Swee Leong; Yeong, Wai Yee; Wei, Jun

    2017-03-14

    The objective of this investigation was to determine the quasi-static indentation response and failure mode in three-dimensional (3D) printed trapezoidal core structures, and to characterize the energy absorbed by the structures. In this work, the trapezoidal sandwich structure was designed in the following two ways. Firstly, the trapezoidal core along with its facesheet was 3D printed as a single element comprising a single material for both core and facesheet (type A); Secondly, the trapezoidal core along with facesheet was 3D printed, but with variation in facesheet materials (type B). Quasi-static indentation was carried out using three different indenters, namely standard hemispherical, conical, and flat indenters. Acoustic emission (AE) technique was used to capture brittle cracking in the specimens during indentation. The major failure modes were found to be brittle failure and quasi-brittle fractures. The measured indentation energy was at a maximum when using a conical indenter at 9.40 J and 9.66 J and was at a minimum when using a hemispherical indenter at 6.87 J and 8.82 J for type A and type B series specimens respectively. The observed maximum indenter displacements at failure were the effect of material variations and composite configurations in the facesheet.

  18. Investigation of Quasi-Static Indentation Response of Inkjet Printed Sandwich Structures under Various Indenter Geometries

    Science.gov (United States)

    Dikshit, Vishwesh; Nagalingam, Arun Prasanth; Yap, Yee Ling; Sing, Swee Leong; Yeong, Wai Yee; Wei, Jun

    2017-01-01

    The objective of this investigation was to determine the quasi-static indentation response and failure mode in three-dimensional (3D) printed trapezoidal core structures, and to characterize the energy absorbed by the structures. In this work, the trapezoidal sandwich structure was designed in the following two ways. Firstly, the trapezoidal core along with its facesheet was 3D printed as a single element comprising a single material for both core and facesheet (type A); Secondly, the trapezoidal core along with facesheet was 3D printed, but with variation in facesheet materials (type B). Quasi-static indentation was carried out using three different indenters, namely standard hemispherical, conical, and flat indenters. Acoustic emission (AE) technique was used to capture brittle cracking in the specimens during indentation. The major failure modes were found to be brittle failure and quasi-brittle fractures. The measured indentation energy was at a maximum when using a conical indenter at 9.40 J and 9.66 J and was at a minimum when using a hemispherical indenter at 6.87 J and 8.82 J for type A and type B series specimens respectively. The observed maximum indenter displacements at failure were the effect of material variations and composite configurations in the facesheet. PMID:28772649

  19. Blunt indentation of nuclear carbon materials

    Energy Technology Data Exchange (ETDEWEB)

    McEnaney; Hartley, M. [Department of Materials Science and Engineering, University of Bath, Bath (United Kingdom)

    1998-09-01

    Blunt indentation is a useful technique for investigating the resistance of nuclear carbon materials to contact stresses. The method is illustrated by describing the response of a series of graphites of widely different textures to blunt indentation loading. It is shown that there is a transition from a Hertzian type of cracking for very fine textured graphites to a response that is dominated by shear deformation and micro-cracking in coarser textured materials. Cyclic indentation loading is characterised by pronounced hysteresis and the associated energy dissipation can be used as a quantitative measure of the microstructural damage. Blunt indentation was also carried out on a series of thermally-oxidised nuclear grade graphites and it was shown that the extent of permanent deformation increased with extent of oxidation of the graphite. There was also a change in the deformation and fracture modes with increasing oxidation. The results show that the responses of these materials to blunt indentation are affected by both microstructure and porosity. Some blunt indentation measurements were also carried out on radiolytically oxidised graphites taken from UK AGRs. After correction for hardening effects, it was shown that there is a decrease in blunt indentation strength with increasing radiolytic oxidation, although with much scatter in the data. 16 refs.

  20. Indentation Behavior of Permanently Densified Oxide Glasses

    DEFF Research Database (Denmark)

    Bechgaard, Tobias Kjær; Januchta, Kacper; Kapoor, Saurabh

    Hot isostatic compression can be used as a post treatment method to tune the properties of glass materials as well as to obtain improved understanding of the pressure-induced structural changes and densification mechanisms, e.g., during sharp contact loading. Here, we review the pressure-induced ......Hot isostatic compression can be used as a post treatment method to tune the properties of glass materials as well as to obtain improved understanding of the pressure-induced structural changes and densification mechanisms, e.g., during sharp contact loading. Here, we review the pressure......-induced changes in density, structure, and indentation behavior of a range of oxide glasses, including silicates, borates, and phosphates. The effect of compression on the structure is analyzed through both Raman and NMR spectroscopy, while the mechanical properties are investigated using Vickers micro...... number distribution of network formers, the number of non-bridging oxygens, and the packing efficiency in the glasses....

  1. Characterization of Corneal Indentation Hysteresis.

    Science.gov (United States)

    Ko, Match W L; Dongming Wei; Leung, Christopher K S

    2015-01-01

    Corneal indentation is adapted for the design and development of a characterization method for corneal hysteresis behavior - Corneal Indentation Hysteresis (CIH). Fourteen porcine eyes were tested using the corneal indentation method. The CIH measured in enucleated porcine eyes showed indentation rate and intraocular pressure (IOP) dependences. The CIH increased with indentation rate at lower IOP ( 25 mmHg). The CIH was linear proportional to the IOP within an individual eye. The CIH was positively correlated with the IOP, corneal in-plane tensile stress and corneal tangent modulus (E). A new method based on corneal indentation for the measurement of Corneal Indentation Hysteresis in vivo is developed. To our knowledge, this is the first study to introduce the corneal indentation hysteresis and correlate the corneal indentation hysteresis and corneal tangent modulus.

  2. Prediction of the Vickers Microhardness and Ultimate Tensile Strength of AA5754 H111 Friction Stir Welding Butt Joints Using Artificial Neural Network.

    Science.gov (United States)

    De Filippis, Luigi Alberto Ciro; Serio, Livia Maria; Facchini, Francesco; Mummolo, Giovanni; Ludovico, Antonio Domenico

    2016-11-10

    A simulation model was developed for the monitoring, controlling and optimization of the Friction Stir Welding (FSW) process. This approach, using the FSW technique, allows identifying the correlation between the process parameters (input variable) and the mechanical properties (output responses) of the welded AA5754 H111 aluminum plates. The optimization of technological parameters is a basic requirement for increasing the seam quality, since it promotes a stable and defect-free process. Both the tool rotation and the travel speed, the position of the samples extracted from the weld bead and the thermal data, detected with thermographic techniques for on-line control of the joints, were varied to build the experimental plans. The quality of joints was evaluated through destructive and non-destructive tests (visual tests, macro graphic analysis, tensile tests, indentation Vickers hardness tests and t thermographic controls). The simulation model was based on the adoption of the Artificial Neural Networks (ANNs) characterized by back-propagation learning algorithm with different types of architecture, which were able to predict with good reliability the FSW process parameters for the welding of the AA5754 H111 aluminum plates in Butt-Joint configuration.

  3. Prediction of the Vickers Microhardness and Ultimate Tensile Strength of AA5754 H111 Friction Stir Welding Butt Joints Using Artificial Neural Network

    Directory of Open Access Journals (Sweden)

    Luigi Alberto Ciro De Filippis

    2016-11-01

    Full Text Available A simulation model was developed for the monitoring, controlling and optimization of the Friction Stir Welding (FSW process. This approach, using the FSW technique, allows identifying the correlation between the process parameters (input variable and the mechanical properties (output responses of the welded AA5754 H111 aluminum plates. The optimization of technological parameters is a basic requirement for increasing the seam quality, since it promotes a stable and defect-free process. Both the tool rotation and the travel speed, the position of the samples extracted from the weld bead and the thermal data, detected with thermographic techniques for on-line control of the joints, were varied to build the experimental plans. The quality of joints was evaluated through destructive and non-destructive tests (visual tests, macro graphic analysis, tensile tests, indentation Vickers hardness tests and t thermographic controls. The simulation model was based on the adoption of the Artificial Neural Networks (ANNs characterized by back-propagation learning algorithm with different types of architecture, which were able to predict with good reliability the FSW process parameters for the welding of the AA5754 H111 aluminum plates in Butt-Joint configuration.

  4. Prediction of the Vickers Microhardness and Ultimate Tensile Strength of AA5754 H111 Friction Stir Welding Butt Joints Using Artificial Neural Network

    Science.gov (United States)

    De Filippis, Luigi Alberto Ciro; Serio, Livia Maria; Facchini, Francesco; Mummolo, Giovanni; Ludovico, Antonio Domenico

    2016-01-01

    A simulation model was developed for the monitoring, controlling and optimization of the Friction Stir Welding (FSW) process. This approach, using the FSW technique, allows identifying the correlation between the process parameters (input variable) and the mechanical properties (output responses) of the welded AA5754 H111 aluminum plates. The optimization of technological parameters is a basic requirement for increasing the seam quality, since it promotes a stable and defect-free process. Both the tool rotation and the travel speed, the position of the samples extracted from the weld bead and the thermal data, detected with thermographic techniques for on-line control of the joints, were varied to build the experimental plans. The quality of joints was evaluated through destructive and non-destructive tests (visual tests, macro graphic analysis, tensile tests, indentation Vickers hardness tests and t thermographic controls). The simulation model was based on the adoption of the Artificial Neural Networks (ANNs) characterized by back-propagation learning algorithm with different types of architecture, which were able to predict with good reliability the FSW process parameters for the welding of the AA5754 H111 aluminum plates in Butt-Joint configuration. PMID:28774035

  5. Analysis of indentation creep

    Science.gov (United States)

    Don S. Stone; Joseph E. Jakes; Jonathan Puthoff; Abdelmageed A. Elmustafa

    2010-01-01

    Finite element analysis is used to simulate cone indentation creep in materials across a wide range of hardness, strain rate sensitivity, and work-hardening exponent. Modeling reveals that the commonly held assumption of the hardness strain rate sensitivity (mΗ) equaling the flow stress strain rate sensitivity (mσ...

  6. Impact of Indentation in Programming

    OpenAIRE

    Parvatham, Niranjan Kumar

    2013-01-01

    In computer programming languages, indentation formats program source code to improve readability. Programming languages make use of indentation to define program structure .Programmers use indentation to understand the structure of their programs to human readers. Especially, indentation is the better way to represent the relationship between control flow constructs such as selection statements or loops and code contained within and outside them. This paper describes about different indentat...

  7. Determination of Vickers microhardness on porous silicon surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Morales-Masis, M. [Department of Physics, Wright State University, Dayton OH 45435 (United States); Ramirez-Porras, A. [Centro de Investigacion en Ciencia e Ingenieria de Materiales (CICIMA) and Escuela de Fisica, Universidad de Costa Rica, San Pedro de Montes de Oca 2060 (Costa Rica)], E-mail: aramirez@fisica.ucr.ac.cr

    2008-02-29

    The Vickers microhardness values of two different sets of porous silicon layers were determined at applied load of 98 mN. The sets consisted of Boron-doped substrates anodized at diverse current densities for two different amounts of hydrofluoric acid (HF) in the etching solution. We found that the microhardness of the samples with lower content of HF at the anodization process showed higher values, whereas the Vickers parameter diminishes consistently for higher current densities. A possible explanation of this behavior is proposed.

  8. Indentation of a stretched elastomer

    Science.gov (United States)

    Zheng, Yue; Crosby, Alfred J.; Cai, Shengqiang

    2017-10-01

    Indentation has been intensively used to characterize mechanical properties of soft materials such as elastomers, gels, and soft biological tissues. In most indentation measurements, residual stress or stretch which can be commonly found in soft materials is ignored. In this article, we aim to quantitatively understand the effects of prestretches of an elastomer on its indentation measurement. Based on surface Green's function, we analytically derive the relationship between indentation force and indentation depth for a prestretched Neo-Hookean solid with a flat-ended cylindrical indenter as well as a spherical indenter. In addition, for a non-equal biaxially stretched elastomer, we obtain the equation determining the eccentricity of the elliptical contacting area between a spherical indenter and the elastomer. Our results clearly demonstrate that the effects of prestretches of an elastomer on its indentation measurement can be significant. To validate our analytical results, we further conduct correspondent finite element simulations of indentation of prestretched elastomers. The numerical results agree well with our analytical predictions.

  9. DETERMINATION OF VICKERS MICROHARDNESS IN β-Ga2O3 SINGLE CRYSTALS GROWN FROM THEIR OWN MELT

    Directory of Open Access Journals (Sweden)

    L. I. Guzilova

    2015-05-01

    Full Text Available The results of microhardness measurements of β-Ga2O3 single crystals for (001 crystallographic face are reported. The crystals were grown by the free crystallization with the "Garnet-2M" equipment. Microhardness values ​​ were determined by the Vickers method at varying loads. A four-sided diamond pyramid was used as an indenter. The average value of gallium oxide microhardness was equal to 8.91 GPa. We have carried out comparison of the values ​​obtained with the microhardness for the other wide bandgap semiconductors - epitaxial GaN layers grown on 6H-SiC and GaP layers grown on GaP:S. The findings are usable for machining process development of β-Ga2O3 single crystal substrates. In particular, silicon carbide and electrocorundum may be recommended for β-Ga2O3 machine processing.

  10. Mesoscopic Nonlinear Elastic Modulus of Thermal Barrier Coatings Determined by Cylindrical Punch Indentation

    Science.gov (United States)

    Eldridge, Jeffrey I.; Zhu, Dong-Ming; Miller, Robert A.

    2000-01-01

    Cylindrical punch indentations are performed to determine the effective modulus of a plasma-sprayed ZrO2-8Wt%Y2O3 thermal barrier coating (TBC) as a function of coating depth. Cylindrical punch indentations offer significant advantages over pointed (Vickers, Berkovich, or Knoop) indentations for materials that do not exhibit linear elastic behavior. Cyclic loading with a cylindrical punch clearly shows the TBCs to exhibit nonlinear elastic behavior with significant hysteresis that is related to the compaction and internal sliding within the plasma-spray splat microstructure. In addition, the effect of a high heat flux laser treatment was shown to produce a gradient both in the effective TBC modulus and degree of loading/unloading hysteresis with depth.

  11. Crystal Indentation Hardness

    Directory of Open Access Journals (Sweden)

    Ronald W. Armstrong

    2017-01-01

    Full Text Available There is expanded interest in the long-standing subject of the hardness properties of materials. A major part of such interest is due to the advent of nanoindentation hardness testing systems which have made available orders of magnitude increases in load and displacement measuring capabilities achieved in a continuously recorded test procedure. The new results have been smoothly merged with other advances in conventional hardness testing and with parallel developments in improved model descriptions of both elastic contact mechanics and dislocation mechanisms operative in the understanding of crystal plasticity and fracturing behaviors. No crystal is either too soft or too hard to prevent the determination of its elastic, plastic and cracking properties under a suitable probing indenter. A sampling of the wealth of measurements and reported analyses associated with the topic on a wide variety of materials are presented in the current Special Issue.

  12. Finite element simulation of Reference Point Indentation on bone.

    Science.gov (United States)

    Idkaidek, Ashraf; Agarwal, Vineet; Jasiuk, Iwona

    2017-01-01

    Reference Point Indentation (RPI) is a novel technique aimed to assess bone quality. Measurements are recorded by the BioDent instrument that applies multiple indents to the same location of cortical bone. Ten RPI parameters are obtained from the resulting force-displacement curves. Using the commercial finite element analysis software Abaqus, we assess the significance of the RPI parameters. We create an axisymmetric model and employ an isotropic viscoelastic-plastic constitutive relation with damage to simulate indentations on a human cortical bone. Fracture of bone tissue is not simulated for simplicity. The RPI outputs are computed for different simulated test cases and then compared with experimental results, measured using the BioDent, found in literature. The number of cycles, maximum indentation load, indenter tip radius, and the mechanical properties of bone: Young׳s modulus, compressive yield stress, and viscosity and damage constants, are varied. The trends in the RPI parameters are then investigated. We find that the RPI parameters are sensitive to the mechanical properties of bone. An increase in Young׳s modulus of bone causes the force-displacement loading and unloading slopes to increase and the total indentation distance (TID) to decrease. The compressive yield stress is inversely proportional to a creep indentation distance (CID1) and the TID. The viscosity constant is proportional to the CID1 and an average of the energy dissipated (AvED). The maximum indentation load is proportional to the TID, CID1, loading and unloading slopes, and AvED. The damage parameter is proportional to the TID, but it is inversely proportional to both the loading and unloading slopes and the AvED. The value of an indenter tip radius is proportional to the CID1 and inversely proportional to the TID. The number of load cycles is inversely proportional to an average of a creep indentation depth (AvCID) and the AvED. The indentation distance increase (IDI) is strongly

  13. Indentation and Observation of Anisotropic Soft Tissues Using an Indenter Device

    Directory of Open Access Journals (Sweden)

    Parinaz ASHRAFI

    2015-01-01

    Full Text Available Soft tissues of human body have complex structures and different mechanical behaviors than those of traditional engineering materials. There is a great urge to understand tissue behavior of human body. Experimental data is needed for improvement of soft tissue modeling and advancement in implants and prosthesis, as well as diagnosis of diseases. Mechanical behavior and responses change when tissue loses its liveliness and viability. One of the techniques for soft tissue testing is indentation, which is applied on live tissue in its physiological environment. Indentation affords several advantages over other types of tests such as uniaxial tension, biaxial tension, and simple shear and suction, thus it is of interest to develop new indentation techniques from which more valid data can be extracted. In this study a new indenter device was designed and constructed. Displacement and force rate cyclic loading, and relaxation experiments were conducted on human arm. The in-vivo force rate controlled cyclic loading test method which is novel is compared with the traditional displacement controlled cyclic loading tests. Anisotropic behavior of tissue cannot be determined by axisymmetric tips, therefore ellipsoid tips were used for examining anisotropy and inplane material direction of bulk soft tissues

  14. Reference point indentation is not indicative of whole mouse bone measures of stress intensity fracture toughness

    OpenAIRE

    Carriero, Alessandra; Bruse, Jan L.; Oldknow, Karla J.; Millán, José Luis; Farquharson, Colin; Shefelbine, Sandra J.

    2014-01-01

    Bone fragility is a concern for aged and diseased bone. Measuring bone toughness and understanding fracture properties of the bone are critical for predicting fracture risk associated with age and disease and for preclinical testing of therapies. A reference point indentation technique (BioDent) has recently been developed to determine bone's resistance to fracture in a minimally invasive way by measuring the indentation distance increase (IDI) between the first and last indentations over cyc...

  15. Mechanical properties of orthodontic wires derived by instrumented indentation testing (IIT) according to ISO 14577.

    Science.gov (United States)

    Zinelis, Spiros; Al Jabbari, Youssef S; Gaintantzopoulou, Marianna; Eliades, George; Eliades, Theodore

    2015-01-01

    The aim of this study was the characterization of mechanical properties of representative types of orthodontic wires employing instrumented indentation testing (IIT) according to ISO 14577. Segments were cut from ten wires. The first six are made of stainless steel (SS), two are made of Ni-Ti, and the last two are made of titanium molybdenum alloys (TMA). Then, the Martens hardness (HM), the Vickers hardness (HVIT) based on indentation hardness (H IT), the indentation modulus (E IT), the ratio of elastic to total work (η IT), and the traditional Vickers hardness (HV1) were measured by IIT. The results were statistically analyzed by one-way ANOVA followed by Student-Newman-Keuls (SNK) test at a = 0.05. The HVIT and HV1 data were analyzed by paired t test (a = 0.05). SS wires showed the highest hardness followed by TMA and Ni-Ti alloys. However, all wires showed significantly lower HVIT compared to corresponding HV1, a finding probably appended to elastic recovery around the indentation. E IT for all wires tested was determined much lower than the nominal values of the corresponding alloys due to the implication of residual stress field at the slope of unloading curve. Elastic to total work ratio was ranged from 45.8 to 64.4 % which is higher than that expected for ductile alloys (hardness and elastic index of materials tested, the intense residual stress field developed during the manufacturing process significantly affects the determination of modulus of elasticity.

  16. Determining the Elastic Modulus of Compliant Thin Films Supported on Substrates from Flat Punch Indentation Measurements

    Science.gov (United States)

    M.J. Wald; J.M. Considine; K.T. Turner

    2013-01-01

    Instrumented indentation is a technique that can be used to measure the elastic properties of soft thin films supported on stiffer substrates, including polymer films, cellulosic sheets, and thin layers of biological materials. When measuring thin film properties using indentation, the effect of the substrate must be considered. Most existing models for determining the...

  17. Reference point indentation is not indicative of whole mouse bone measures of stress intensity fracture toughness.

    Science.gov (United States)

    Carriero, Alessandra; Bruse, Jan L; Oldknow, Karla J; Millán, José Luis; Farquharson, Colin; Shefelbine, Sandra J

    2014-12-01

    Bone fragility is a concern for aged and diseased bone. Measuring bone toughness and understanding fracture properties of the bone are critical for predicting fracture risk associated with age and disease and for preclinical testing of therapies. A reference point indentation technique (BioDent) has recently been developed to determine bone's resistance to fracture in a minimally invasive way by measuring the indentation distance increase (IDI) between the first and last indentations over cyclic indentations in the same position. In this study, we investigate the relationship between fracture toughness KC and reference point indentation parameters (i.e. IDI, total indentation distance (TID) and creep indentation distance (CID)) in bones from 38 mice from six types (C57Bl/6, Balb, oim/oim, oim/+, Phospho1(-/-) and Phospho1 wild type counterpart). These mice bone are models of healthy and diseased bone spanning a range of fracture toughness from very brittle (oim/oim) to ductile (Phospho1(-/-)). Left femora were dissected, notched and tested in 3-point bending until complete failure. Contralateral femora were dissected and indented in 10 sites of their anterior and posterior shaft surface over 10 indentation cycles. IDI, TID and CID were measured. Results from this study suggest that reference point indentation parameters are not indicative of stress intensity fracture toughness in mouse bone. In particular, the IDI values at the anterior mid-diaphysis across mouse types overlapped, making it difficult to discern differences between mouse types, despite having extreme differences in stress intensity based toughness measures. When more locations of indentation were considered, the normalised IDIs could distinguish between mouse types. Future studies should investigate the relationship of the reference point indentation parameters for mouse bone in other material properties of the bone tissue in order to determine their use for measuring bone quality. Copyright © 2014

  18. Vacancy-type defects and hardness of helium implanted CLAM steel studied by positron-annihilation spectroscopy and nano-indentation technique

    Energy Technology Data Exchange (ETDEWEB)

    Xin Yong [Department of Physics, University of Science and Technology Beijing, Beijing 100083 (China); Ju Xin, E-mail: jux@ustb.edu.cn [Department of Physics, University of Science and Technology Beijing, Beijing 100083 (China); Qiu Jie [Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084 (China); Guo Liping; Chen Jihong; Yang Zheng [Accelerator Laboratories, School of Physics, Wuhan University, Wuhan, Hubei 430072 (China); Zhang Peng; Cao Xinzhong; Wang Baoyi [Key Laboratory of Nuclear Analysis Techniques, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China)

    2012-08-15

    Highlights: Black-Right-Pointing-Pointer Helium implantation is performed to CLAM steel at different temperatures. Black-Right-Pointing-Pointer Positron annihilation is used to investigate vacancy-type defects. Black-Right-Pointing-Pointer Nano-hardness is investigated to study irradiation induced hardening. Black-Right-Pointing-Pointer Vacancy-helium complexes are main defects after implantation. Black-Right-Pointing-Pointer Both helium-vacancy clusters and helium bubbles contribute to hardening. - Abstract: China Low Activation Martensitic (CLAM) steel was implanted with helium up to 1e + 16/cm{sup 2} at 300-873 K using 140 keV helium ions. Vacancy-type defects induced by implantation were investigated with positron beam Doppler broadening technique, and then nano-hardness measurements were performed to investigate helium-induced hardening effect. He implantation produced a large number of vacancy-type defects in CLAM steel, and the concentration of vacancy-type defects decreased with increasing temperature. Vacancy-helium complexes were main defects at different temperatures. Irradiation induced hardening was observed at all irradiation temperatures, and the peak value of hardness was at 473 K. The result suggested that both vacancy-helium complexes and helium bubbles had contribution to irradiation induced hardening. The decomposition and annihilation of irradiation-induced defects became more and more significant with increasing temperature, which induced the increment of hardness became more and more small.

  19. Optical properties and indentation hardness of thin-film acrylated epoxidized oil

    Science.gov (United States)

    Rahman, Mohammad Syuhaimi Ab.; Shaktur, Khaled Mohamed; Mohammad, Rahmah; Zalikha, Wan Aimi; Nawi, Norwimie; Mohd, Ahmad Faiza

    2012-02-01

    Epoxy acrylate has been widely used as optical resin for applications such as cladding, the core of a waveguide, and other photonic devices. In this study, sustainable resin from edible oil was used as an alternative to epoxy acrylate. Structural features and the transmission of planar thin-film resin from an ultraviolet-visible spectroscopy (UV-VIS) spectrometer were investigated upon UV exposure. It was found that high transmission still persists for all samples with and without an UV absorber for exposed and unexposed samples. The film was found to absorb strongly below 400 nm. A change in the cut-off wavelength was observed upon exposure. Thin-film hardness and its dynamic indentation in the load-unload mode with different test forces were evaluated. Vickers hardness and the elastic modulus were determined for unacrylated epoxidized soybean oil (ESO) and acrylated epoxidized soybean oil (AESO). It was found that the AESO has a higher Vickers hardness and elastic modulus than those of unacrylated thin film. The Vickers hardness and elastic modulus were found to increase as the applied test force increased. The refractive index, thickness, and modes present were characterized from a spin-coated planar thin film. The refractive index in the transverse electric mode (TE) and transverse magnetic mode (TM) were determined and compared for unacrylated and acrylated epoxidized oil.

  20. Continuous FEM simulation of the nanoindentation. Actual indenter tip geometries, material elastoplastic deformation laws and universal hardness

    Energy Technology Data Exchange (ETDEWEB)

    Bouzakis, K.D.; Michailidis, N.; Hadjiyiannis, S.; Skordaris, G. [Mechanical Engineering Dept., Aristoteles Univ. of Thessaloniki (Greece); Erkens, G. [CemeCon AG, Wuerselen (Germany)

    2002-09-01

    The precise knowledge of materials mechanical properties is always a core issue in every technical application. Through a developed finite elements method (FEM) continuous simulation of the nanoindentation, the applied force course versus the penetration depth is adequately simulated during the loading and unloading phases of this test, and the corresponding material stress-strain curves, as well as the universal hardness, are stepwise defined. Furthermore, the actual tip geometries of various indenters are approached and through equivalent magnitudes described. The results show that the defined material elastoplastic deformation characteristics are independent of the indenter type, as Vickers or Berkovich, since the existing indenter tip form deviations from their ideal geometry are considered. Furthermore, using the developed FEM-based nanoindentation simulation, the influence of the indenter tip geometry on the defined constitutive laws and the universal hardness is sufficiently elucidated. Various materials stress-strain curves and universal hardness courses versus the indentation depth, determined by means of the developed procedure, are presented. (orig.)

  1. Competing indentation deformation mechanisms in glass using different strengthening methods

    Directory of Open Access Journals (Sweden)

    Jian Luo

    2016-11-01

    Full Text Available Chemical strengthening via ion exchange, thermal tempering, and lamination are proven techniques for strengthening of oxide glasses. For each of these techniques, the strengthening mechanism is conventionally ascribed to the linear superposition of the compressive stress profile on the glass surface. However, in this work we use molecular dynamics simulations to reveal the underlying indentation deformation mechanism beyond the simple linear superposition of compressive and indentation stresses. In particular, the plastic zone can be dramatically different from the commonly assumed hemispherical shape, which leads to a completely different stress field and resulting crack system. We show that the indentation-induced fracture is controlled by two competing mechanisms: the compressive stress itself and a potential reduction in free volume that can increase the driving force for crack formation. Chemical strengthening via ion exchange tends to escalate the competition between these two effects, while thermal tempering tends to reduce it. Lamination of glasses with differential thermal expansion falls in between. The crack system also depends on the indenter geometry and the loading stage, i.e., loading vs. after unloading. It is observed that combining thermal tempering or high free volume content with ion exchange or lamination can impart a relatively high compressive stress and reduce the driving force for crack formation. Therefore, such a combined approach might offer the best overall crack resistance for oxide glasses.

  2. Mechanical properties study of particles reinforced aluminum matrix composites by micro-indentation experiments

    Directory of Open Access Journals (Sweden)

    Yuan Zhanwei

    2014-04-01

    Full Text Available By using instrumental micro-indentation technique, the microhardness and Young’s modulus of SiC particles reinforced aluminum matrix composites were investigated with micro-compression-tester (MCT. The micro-indentation experiments were performed with different maximum loads, and with three loading speeds of 2.231, 4.462 and 19.368 mN/s respectively. During the investigation, matrix, particle and interface were tested by micro-indentation experiments. The results exhibit that the variations of Young’s modulus and microhardness at particle, matrix and interface were highly dependent on the loading conditions (maximum load and loading speed and the locations of indentation. Micro-indentation hardness experiments of matrix show the indentation size effects, i.e. the indentation hardness decreased with the indentation depth increasing. During the analysis, the effect of loading conditions on Young’s modulus and microhardness were explained. Besides, the elastic–plastic properties of matrix were analyzed. The validity of calculated results was identified by finite element simulation. And the simulation results had been preliminarily analyzed from statistical aspect.

  3. Indentation of pressurized viscoplastic polymer spherical shells

    DEFF Research Database (Denmark)

    Tvergaard, Viggo; Needleman, A.

    2016-01-01

    The indentation response of polymer spherical shells is investigated. Finite deformation analyses are carried out with the polymer characterized as a viscoelastic/viscoplastic solid. Both pressurized and unpressurized shells are considered. Attention is restricted to axisymmetric deformations...... large strains are attained. The transition from an indentation type mode of deformation to a structural mode of deformation involving bending that occurs as the indentation depth increases is studied. The results show the effects of shell thickness, internal pressure and polymer constitutive...

  4. Mechanical properties study of particles reinforced aluminum matrix composites by micro-indentation experiments

    National Research Council Canada - National Science Library

    Yuan Zhanwei Li Fuguo Zhang Peng Chen Bo Xue Fengmei

    2014-01-01

    By using instrumental micro-indentation technique, the microhardness and Young's modulus of SiC particles reinforced aluminum matrix composites were investigated with micro- compression-tester (MCT...

  5. A scaling rule of indentation hardness of semiconductors

    Science.gov (United States)

    Yonenaga, Ichiro; Suzuki, Takayoshi

    2003-03-01

    We report a scaling rule of the indentation hardness of semiconductor crystals from room temperature to their melting. The Vickers hardness of fifteen semiconductors, Si, Ge, SiC, AlN, GaN, GaP, GaAs, GaSb, InP, InAs, InSb, ZnO, ZnSe, ZnTe and CdTe, has been investigated from room temperature to their melting points. The temperature dependences of the hardness H v of eleven of these semiconductors, namely those with a cubic structure, obey a universal relationship when H v and the temperature T are scaled respectively by the shear modulus G and by G b ^3 / k _B, with b being the magnitude of the Burgers vector and k B the Boltzmann constant. The scaling rule is the same as that found for the temperature dependence of the critical shear stress τ c for the 111 slip system. The result leads a link between hardness and macroscopic yielding (dislocation motion). The relationshipH v = (70 ˜ 100) τ c is deduced for the cubic semiconductors is about ten times as large as the value for metals.

  6. Deformation field heterogeneity in punch indentation

    Science.gov (United States)

    Murthy, Tejas G.; Saldana, Christopher; Hudspeth, Matthew; M'Saoubi, Rachid

    2014-01-01

    Plastic heterogeneity in indentation is fundamental for understanding mechanics of hardness testing and impression-based deformation processing methods. The heterogeneous deformation underlying plane-strain indentation was investigated in plastic loading of copper by a flat punch. Deformation parameters were measured, in situ, by tracking the motion of asperities in high-speed optical imaging. These measurements were coupled with multi-scale analyses of strength, microstructure and crystallographic texture in the vicinity of the indentation. Self-consistency is demonstrated in description of the deformation field using the in situ mechanics-based measurements and post-mortem materials characterization. Salient features of the punch indentation process elucidated include, among others, the presence of a dead-metal zone underneath the indenter, regions of intense strain rate (e.g. slip lines) and extent of the plastic flow field. Perhaps more intriguing are the transitions between shear-type and compression-type deformation modes over the indentation region that were quantified by the high-resolution crystallographic texture measurements. The evolution of the field concomitant to the progress of indentation is discussed and primary differences between the mechanics of indentation for a rigid perfectly plastic material and a strain-hardening material are described. PMID:24910521

  7. Discrete dislocation modelling of submicron indentation

    NARCIS (Netherlands)

    Widjaja, A; Van der Giessen, E; Needleman, A

    2005-01-01

    Indentation of a planar single crystal by a circular rigid indenter is analyzed using discrete dislocation plasticity. The crystal has three slip systems and is initially dislocation-free, but edge dislocations can nucleate from point sources inside the crystal. The lattice resistance to dislocation

  8. SPHERICAL INDENTATION OF SiC

    Energy Technology Data Exchange (ETDEWEB)

    Wereszczak, Andrew A [ORNL; Johanns, Kurt E [ORNL

    2007-01-01

    Instrumented Hertzian indentation testing was performed on several grades of SiCs and the results and preliminary interpretations are presented. The grades included hot-pressed and sintered compositions. One of the hot-pressed grades was additionally subjected to high temperature heat treatment to produce a coarsened grain microstructure to enable the examination of exaggerated grain size on indentation response. Diamond spherical indenters were used in the testing. Indentation load, indentation depth of penetration, and acoustic activity were continually measured during each indentation test. Indentation response and postmortem analysis of induced damage (e.g., ring/cone, radial and median cracking, quasi-plasticity) are compared and qualitatively as a function of grain size. For the case of SiC-N, the instrumented spherical indentation showed that yielding initiated at an average contact stress 12-13 GPa and that there was another event (i.e., a noticeable rate increase in compliance probably associated with extensive ring and radial crack formations) occurring around an estimated average contact stress of 19 GPa.

  9. Indentation of ellipsoidal and cylindrical elastic shells.

    Science.gov (United States)

    Vella, Dominic; Ajdari, Amin; Vaziri, Ashkan; Boudaoud, Arezki

    2012-10-05

    Thin shells are found in nature at scales ranging from viruses to hens' eggs; the stiffness of such shells is essential for their function. We present the results of numerical simulations and theoretical analyses for the indentation of ellipsoidal and cylindrical elastic shells, considering both pressurized and unpressurized shells. We provide a theoretical foundation for the experimental findings of Lazarus et al. [following paper, Phys. Rev. Lett. 109, 144301 (2012)] and for previous work inferring the turgor pressure of bacteria from measurements of their indentation stiffness; we also identify a new regime at large indentation. We show that the indentation stiffness of convex shells is dominated by either the mean or Gaussian curvature of the shell depending on the pressurization and indentation depth. Our results reveal how geometry rules the rigidity of shells.

  10. Indentation of Ellipsoidal and Cylindrical Elastic Shells

    KAUST Repository

    Vella, Dominic

    2012-10-01

    Thin shells are found in nature at scales ranging from viruses to hens\\' eggs; the stiffness of such shells is essential for their function. We present the results of numerical simulations and theoretical analyses for the indentation of ellipsoidal and cylindrical elastic shells, considering both pressurized and unpressurized shells. We provide a theoretical foundation for the experimental findings of Lazarus etal. [following paper, Phys. Rev. Lett. 109, 144301 (2012)PRLTAO0031-9007] and for previous work inferring the turgor pressure of bacteria from measurements of their indentation stiffness; we also identify a new regime at large indentation. We show that the indentation stiffness of convex shells is dominated by either the mean or Gaussian curvature of the shell depending on the pressurization and indentation depth. Our results reveal how geometry rules the rigidity of shells. © 2012 American Physical Society.

  11. Indentation Depth Dependent Mechanical Behavior in Polymers

    Directory of Open Access Journals (Sweden)

    Farid Alisafaei

    2015-01-01

    Full Text Available Various experimental studies have revealed size dependent deformation of materials at micro and submicron length scales. Among different experimental methods, nanoindentation testing is arguably the most commonly applied method of studying size effect in various materials where increases in the hardness with decreasing indentation depth are usually related to indentation size effects. Such indentation size effects have been observed in both metals and polymers. While the indentation size effects in metals are widely discussed in the literature and are commonly attributed to geometrically necessary dislocations, for polymer the experimental results are far sparser and there does not seem to be a common ground for their rationales. The indentation size effects of polymers are addressed in this paper, where their depth dependent deformation is reviewed along with the rationale provided in the literature.

  12. Indentation Curves in Viscoplastic Alloys: Mathematical Model, Fitting Procedures, and Application to the Room-Temperature Creep of an Al-Sn Alloy

    Directory of Open Access Journals (Sweden)

    V. H. Jacobo

    2016-01-01

    Full Text Available Hardness is an important design parameter but, in rate-dependent materials, its value depends on the indentation speed and dwell time during measurement. Dimensional analysis for indentation testing provides rigorous descriptions for the load-displacement curves of elastoplastic materials; viscoplastic materials can be treated likewise by neglecting the plastic part of the deformation, which is not accurate for most engineering alloys. This work presents a methodology for constructing model indentation curves taking into account concurrent viscous and plastic strains, as well as corrections for tip roundness, load frame compliance, and the point of first contact. A procedure is presented to calculate the parameters of a single model curve by fitting to multiple experimental curves, incorporating the numerical solutions of the differential equation describing viscoplastic behaviour. The procedure is applied to Vickers indentation in brass and steel calibration blocks and to a SAE783 Al-Sn alloy for journal bearings, where creep at room temperature is observed. The soundness of the approach is demonstrated by the large reduction of statistical uncertainty on the parameters describing the indentation curves. A rate-independent hardness will be found and a brief comment is provided on the comparison between creep analysis by indentation and uniaxial tension.

  13. Indentation methods for adhesion measurement in thermal barrier coating systems

    Science.gov (United States)

    Ma, Qin

    This thesis investigates the fundamentals of indentation-induced delamination of electron beam physical vapor deposition thermal barrier coatings (EB-PVD TBCs). Thermal barrier coatings are thin ceramic coatings used to insulate gas turbine components. In the as-processed state, TBCs are well-bonded to the metallic substrate they are deposited upon. However, as these coatings are exposed to high temperatures during turbine operation, they lose their adhesion. The goal of this thesis is to determine how to use indentation testing techniques, coupled with fracture mechanics principles, to track this loss of adhesion and to identify mechanisms causing it. This thesis addresses four primary topics. First, a detailed fracture mechanics analysis of indentation-induced delamination is made, including the quantification of energy release rates, interfacial toughnesses and mode mix. The second topic addressed is application of the indentation test to track toughness losses in TBC systems subjected to a variety of thermal exposures. Three subtopics are included: (1) mechanism-based tests for the isothermal dry air exposures; (2) mechanism-based tests for exposures with water vapor and (3) mechanism-based tests for cyclic thermal exposures. In the first subtopic, TGO thickening and TBC sintering are modeled. Various mechanisms that lead to toughness degradation are discussed and analyzed quantitatively. An Arrhenius analysis has been performed to understand accelerated testing methods. The second subtopic presents the results of toughness degradation and the evolution of microstructures due to isothermal exposure with water vapor. The third subtopic investigates the toughness degradation for cyclic thermal exposures in dry air. Piezospectroscopy method has been applied to track the evolution of residual stresses in the TGO layer with thermal cycles. Quantitative analysis has been provided to give insights into the effects of oxide damage during thermal cycling. The final two

  14. Surface tension measurement from the indentation of clamped thin films.

    Science.gov (United States)

    Xu, Xuejuan; Jagota, Anand; Paretkar, Dadhichi; Hui, Chung-Yuen

    2016-06-21

    We developed an indentation technique to measure the surface tension of relatively stiff solids. In the proposed method, a suspended thin solid film is indented by a rigid sphere and its deflection is measured by optical interferometry. The film deflection is jointly resisted by surface tension, elasticity and residual stress. Using a version of nonlinear von Karman plate theory that includes surface tension, we are able to separate the contribution of elasticity to the total tension in the film. Surface tension is determined by extrapolating the sum of surface tension and residual stress to zero film thickness. We measured the surface tension of polydimethylsiloxane (PDMS) using this technique and obtained a value of 19.5 ± 3.6 mN m(-1), consistent with the surface energy of PDMS reported in the literature.

  15. Analysis of ray trajectories of flexural waves propagating over generalized acoustic black hole indentations

    Science.gov (United States)

    Huang, Wei; Ji, Hongli; Qiu, Jinhao; Cheng, Li

    2018-03-01

    An Acoustic Black Hole (ABH) indentation embedded in thin-walled structures has been proved remarkably useful for broadband flexural wave focalization, in which the phase velocity of the flexural waves and the refractive index of the media undergo gradual changes from the outside towards the center of the indentation. A generalized two-dimensional ABH indentation can be defined by three geometric parameters: a power index, an extra thickness and a radius of a plateau at the indentation center. The dependence of the energy focalization on these parameters as well as the energy focalization process is of paramount importance for the understanding and design of effective ABH indentations. This work aims at investigating the energy focalization characteristics of flexural waves in such generalized ABH indentations. The calculation of the flexural ray trajectories is conducted to reveal and analyze the wave propagation features through numerical integration of the eikonal equation from the Geometric Acoustics Approximation (GAA). The theoretical results are verified by both experiment using wave visualization technique based on laser acoustic scanning method and finite element (FE) simulations. Finally, the influence of the geometric parameters on the flexural wave focalization characteristics in ABH indentations is discussed in detail.

  16. Effects of B sup + implantation on Palmqvist and Hertzian indentation response of Ti coated glass

    Energy Technology Data Exchange (ETDEWEB)

    Laugier, M.T. (Materials Research Centre, Univ. of Limerick (Ireland))

    1991-07-01

    Effects of 1x10{sup 16} ions cm{sup -2} 100 keV B{sup +} implantation on stress and cracking behaviour of Ti magnetron sputtered glass are investigated using indentation techniques. Compressive coating stresses ({proportional to}0.3 GPa before implantation, -0.5 GPa after implantation) were determined from reduced Palmqvist indentation crack lengths and inhibition of partial ring cracks, and lateral breakout in sliding Hertzian tests was observed in addition to reduced Palmqvist cracking. (orig.).

  17. Full-Field Indentation Damage Measurement Using Digital Image Correlation

    Directory of Open Access Journals (Sweden)

    Elías López-Alba

    2017-07-01

    Full Text Available A novel approach based on full-field indentation measurements to characterize and quantify the effect of contact in thin plates is presented. The proposed method has been employed to evaluate the indentation damage generated in the presence of bending deformation, resulting from the contact between a thin plate and a rigid sphere. For this purpose, the 3D Digital Image Correlation (3D-DIC technique has been adopted to quantify the out of plane displacements at the back face of the plate. Tests were conducted using aluminum thin plates and a rigid bearing sphere to evaluate the influence of the thickness and the material behavior during contact. Information provided by the 3D-DIC technique has been employed to perform an indirect measurement of the contact area during the loading and unloading path of the test. A symmetrical distribution in the contact damage region due to the symmetry of the indenter was always observed. In the case of aluminum plates, the presence of a high level of plasticity caused shearing deformation as the load increased. Results show the full-field contact damage area for different plates’ thicknesses at different loads. The contact damage region was bigger when the thickness of the specimen increased, and therefore, bending deformation was reduced. With the proposed approach, the elastic recovery at the contact location was quantified during the unloading, as well as the remaining permanent indentation damage after releasing the load. Results show the information obtained by full-field measurements at the contact location during the test, which implies a substantial improvement compared with pointwise techniques.

  18. From elasticity to capillarity in soft materials indentation

    Science.gov (United States)

    Pham, Jonathan T.; Schellenberger, Frank; Kappl, Michael; Butt, Hans-Jürgen

    2017-06-01

    For soft materials with Young's moduli below 100 kPa, quantifying mechanical and interfacial properties by small scale indentation is challenging because in addition to adhesion and elasticity, surface tension plays a critical role. Until now, microscale contact of very soft materials has only been studied by static experiments under zero external loading. Here we introduce a combination of the colloidal probe technique and confocal microscopy to characterize the force-indentation and force-contact radius relationships during microindentation of soft silicones. We confirm that the widespread Johnson-Kendall-Roberts theory must be extended to predict the mechanical contact for soft materials. Typically a liquid component is found within very soft materials. With a simple analytical model, we illustrate that accounting for this liquid surface tension can capture the contact behavior. Our results highlight the importance of considering liquid that is often associated with soft materials during small scale contact.

  19. On size-effects in single crystal wedge indentation

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof; Kysar, Jeffrey W.

    2012-01-01

    Wedge indentation in single crystals is studied numerically, with emphasis on size-effects on the micron scale. Under the assumption of a perfectly sharp wedge indenter, a linear relationship between indentation force and indentation depth would be predicted from conventional theories lacking con...

  20. Determination of mechanical properties from depth-sensing indentation data and results of finite element modeling

    Science.gov (United States)

    Isaenkova, M. G.; Perlovich, Yu A.; Krymskaya, O. A.; Zhuk, D. I.

    2016-04-01

    3D finite element model of indentation process with Berkovich tip was created. Using this model with different type of test materials, several series of calculations were made. These calculations lead to determination of material behavior features during indentation. Relations between material properties and its behavior during instrumented indentation were used for construction of dimensionless functions required for development the calculation algorithm, suitable to determine mechanical properties of materials by results of the depth-sensing indentation. Results of mechanical properties determination using elaborated algorithm for AISI 1020 steel grade were compared to properties obtained with standard compression tests. These two results differ by less than 10% for yield stress that evidence of a good accuracy of the proposed technique.

  1. Standard practice for instrumented indentation testing

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2007-01-01

    1.1 This practice defines the basic steps of Instrumented Indentation Testing (IIT) and establishes the requirements, accuracies, and capabilities needed by an instrument to successfully perform the test and produce the data that can be used for the determination of indentation hardness and other material characteristics. IIT is a mechanical test that measures the response of a material to the imposed stress and strain of a shaped indenter by forcing the indenter into a material and monitoring the force on, and displacement of, the indenter as a function of time during the full loading-unloading test cycle. 1.2 The operational features of an IIT instrument, as well as requirements for Instrument Verification Annex A1), Standardized Reference Blocks (Annex A2) and Indenter Requirements (Annex A3) are defined. This practice is not intended to be a complete purchase specification for an IIT instrument. 1.3 With the exception of the non-mandatory Appendix X4, this practice does not define the analysis necessary...

  2. PMMA microlens array fabricated by indentation process

    Science.gov (United States)

    Cirino, Giuseppe A.; Jasinevicius, Renato G.

    2017-02-01

    This work reports the fabrication of a PMMA-based spherical microlens array (MLA), targeting application of Shack-Hartmann wavefront sensor for lens characterization. The array present 10 by 10 elements, with f-number f/# = f/10 (1 mm diameter, 10 mm focal length). The fabrication method employs a computer-controlled mechanical indentation for the fabrication of an insert mold, and subsequent replication by injection molding on PMMA. After replication and de-molding, the PMMA surface containing the negative of the phase profile of the lens array was evaluated by optical profilometry technique, in terms of the surface quality as well as the replication fidelity. The RMS surface roughness level of approximately (λ/10) was found, considering operation in the visible range of spectrum. Optical characterization was based on the evaluation of the sharpness, FWHM, and maximum intensity, IMAX, values associated to the profiles of each of the 100 generated light spots, obtained in the back focal plane of the MLA. An average sharpness of FWHMAVG = 13.9 +/- 8% μm, and average maximum intensity of IMAX AVG = 0.72 +/- 7% a.u. was obtained.

  3. Nano indentation of particulate and polymer films

    CERN Document Server

    Akram, A

    2001-01-01

    A detailed knowledge of the formation and rupture mechanisms of agglomerates is essential when seeking to model equipment designed to produce and process such agglomerated particulate solids. In the work to be described the nano-indentation of two-dimensional agglomerate films was carried out in order to establish a means of identifying the generic breakage mechanisms of agglomerated systems. Data analysis techniques are developed that enable the individual inter-particle junction strengths to be calculated for a model system consisting of rather mono-dispersed colloidal silica particles (20-24 nm diameter) bound with a poly(methyl methacrylate). Applied load and penetration depth data in the range (10 mN and 500 nm respectively) are provided as a function of loading time during a continuous loading. It is argued that these data enable the sequence of the discrete binder bridge failures to be observed thus giving a quantitative indication of the breakage mechanism of this agglomerate system as well as reflect...

  4. Tomography of indentation cracks in feldspathic dental porcelain on zirconia.

    Science.gov (United States)

    Rueda, Astrid O; Seuba, Jordi; Anglada, Marc; Jiménez-Piqué, Emilio

    2013-03-01

    The objective of this work is to study the crack produced by spherical and sharp indentation on veneering feldspathic dental porcelain in order to understand the morphology of the cracks in the surface and beneath the indentation using a tomographic technique. The geometry of cracks produced under contact loading are directly related to the structural integrity and reliability of dental prosthesis. Monotonic Hertzian contact loading and nanoindentation tests were performed on feldspathic porcelain (VITA-VM9) coatings. Residual imprints and the cracks produced by the indentations were characterized by 3-dimensional reconstruction using focused ion beam tomography. Under nanoindentation, the propagating crack deflects due to the interaction with the leucite particles resulting in a crack with a complex morphology. Under spherical contact loading, multiple ring cracks were observed at the surface, with a conical shape beneath the residual imprint. These results will help to improve the mechanical performance of these materials by detecting potential causes of failure for the long term structural integrity and reliability of the prosthesis. Copyright © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  5. Quasi-Plastic Deformation of WC-Co Composites Loaded with a Spherical Indenter

    Science.gov (United States)

    Zhang, Haibo; Fang, Zhigang Zak; Belnap, J. Daniel

    2007-03-01

    The quasi-plastic deformation behavior of cemented tungsten carbide (WC-Co) materials was studied using Hertzian indentation techniques. The indentation stress-strain curves of three WC-10 wt pct Co alloys with different hardness values demonstrate that WC-Co alloys exhibit “quasi-plasticity” behavior under indentation load and the increase of indentation stress vs indentation strain bears similarity to “strain hardening” in ductile metals. The analysis of the subsurface indentation damage shows that the mechanisms of the quasi-plastic deformation of WC-Co material are the formation of microcracks. Microcracks were found at heavily damaged areas in all three alloys, and the number of microcracks was higher for the sample with the higher apparent quasi-plasticity. The threshold stress values for the onset of quasi-plastic deformation and formation of ring cracks were determined and used to evaluate the brittleness index of these materials. The correlation of the brittleness index with hardness values gives insight with regard to the brittle or quasi-plastic responses of WC-Co materials.

  6. Indentation modulus and hardness of viscoelastic thin films by atomic force microscopy: A case study

    Energy Technology Data Exchange (ETDEWEB)

    Passeri, D., E-mail: daniele.passeri@uniroma1.it [Dipartimento di Energetica, Universita di Roma ' La Sapienza' , Via A. Scarpa 16, 00161 Roma (Italy); Bettucci, A.; Biagioni, A.; Rossi, M.; Alippi, A. [Dipartimento di Energetica, Universita di Roma ' La Sapienza' , Via A. Scarpa 16, 00161 Roma (Italy); Tamburri, E. [Dipartimento di Scienze e Tecnologie Chimiche, Universita di Roma ' Tor Vergata' , Via della Ricerca Scientifica, 00133 Roma (Italy); Lucci, M.; Davoli, I. [Dipartimento di Fisica, Universita di Roma ' Tor Vergata' , Via della Ricerca Scientifica, 00133 Roma (Italy); Berezina, S. [Department of Physics, University of Zilina, 01026, Univerzitna 1 Zilina (Slovakia)

    2009-11-15

    We propose a nanoindentation technique based on atomic force microscopy (AFM) that allows one to deduce both indentation modulus and hardness of viscoelastic materials from the force versus penetration depth dependence, obtained by recording the AFM cantilever deflection as a function of the sample vertical displacement when the tip is pressed against (loading phase) and then removed from (unloading phase) the surface of the sample. Reliable quantitative measurements of both indentation modulus and hardness of the investigated sample are obtained by calibrating the technique through a set of different polymeric samples, used as reference materials, whose mechanical properties have been previously determined by standard indentation tests. By analyzing the dependence of the cantilever deflection versus time, the proposed technique allows one to evaluate and correct the effect of viscoelastic properties of the investigated materials, by adapting a post-experiment data processing procedure well-established for standard depth sensing indentation tests. The technique is described in the case of the measurement of indentation modulus and hardness of a thin film of poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate), deposited by chronoamperometry on an indium tin oxide (ITO) substrate.

  7. Characterization through nano indentation technique of mechanical properties of an aluminium alloy welded zone for hydrogen storage; Apport de la nanoindentation pour la caracterisation d'un cordon de soudure par faisceau d'electrons d'un reservoir d'hydrogene sous pression en alliage d'aluminium

    Energy Technology Data Exchange (ETDEWEB)

    Delobelle, P.; Perreux, D.; Russo, C. [Universite de Franche-Comte, Institut FEMTO-ST, UMR 6174, Depart. LMARC, 25 - Besancon (France); Meunier, E. [CEA Valduc (DRMN/SMCM/LCSi), 21 - Is-sur-Tille (France); Decamps, B. [Laboratoire de Chimie Metallurgique des Terres Rares, UPR 209, 94 - Vitry-Thiais, (France)

    2008-07-01

    In this study we use the nano indentation technique which is a powerful tool to characterise the mechanical properties of a welded bond. The Berkovich indentation has the advantage to test small material volumes compared to the conventional tensile tests. The welded process with electrons beam of hydrogen vessels induces different regions and the aim of this study is to characterize the differences of the mechanical properties of the different zones of the weld. To identify the stress-strain curves of the tested material, F.E. inverse method has been used. After treatment, for one pass, the hardness of the melted zone is greater than those of the base material and for the two passes, the hardness is still lower than those of the base material. The interface zones present a hardness which is always higher than those of the weld. A relation of the Hall-Petch type which correlates the evolution of the hardness with the zinc concentration and the grain size has been proposed. Moreover a relation between the normalized hardness and the hydrogen concentration CH has been found. The parameters of the stress-strain curves of the four regions; base material, interface, one and two passes melted zones, have been deduced. The identified laws are used in a F.E. model of a welded sphere to model its radial deformation under internal pressure loading. (authors)

  8. Stress Mapping in Glass-to-Metal Seals using Indentation Crack Lengths

    Energy Technology Data Exchange (ETDEWEB)

    Buchheit, Thomas E. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Component & Systems Analysis; Strong, Kevin [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Material Mechanics and Tribology; Newton, Clay S. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Material Mechanics and Tribology; Diebold, Thomas Wayne [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Material Mechanics and Tribology; Bencoe, Denise N. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Electronic, Optical and Nano; Stavig, Mark E. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Organic Materials Science; Jamison, Ryan Dale [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Transportation System Analysis

    2017-08-01

    Predicting the residual stress which develops during fabrication of a glass-to-metal compression seal requires material models that can accurately predict the effects of processing on the sealing glass. Validation of the predictions requires measurements on representative test geometries to accurately capture the interaction between the seal materials during a processing cycle required to form the seal, which consists of a temperature excursion through the glass transition temperature of the sealing glass. To this end, a concentric seal test geometry, referred to as a short cylinder seal, consisting of a stainless steel shell enveloping a commercial sealing glass disk has been designed, fabricated, and characterized as a model validation test geometry. To obtain data to test/validate finite element (FE) stress model predictions of this geometry, spatially-resolved residual stress was calculated from the measured lengths of the cracks emanating from radially positioned Vickers indents in the glass disk portion of the seal. The indentation crack length method is described, and the spatially-resolved residual stress determined experimentally are compared to FE stress predictions made using a nonlinear viscoelastic material model adapted to inorganic sealing glasses and an updated rate dependent material model for 304L stainless steel. The measurement method is a first to achieve a degree of success for measuring spatially resolved residual stress in a glass-bearing geometry and a favorable comparison between measurements and simulation was observed.

  9. Stress Mapping in Glass-to-Metal Seals using Indentation Crack Lengths.

    Energy Technology Data Exchange (ETDEWEB)

    Strong, Kevin [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Buchheit, Thomas E. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Diebold, Thomas Wayne [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Newton, Clay S. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Bencoe, Denise N. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Stavig, Mark E. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Jamison, Ryan Dale [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2017-08-01

    Predicting the residual stress which develops during fabrication of a glass-to-metal compression seal requires material models that can accurately predict the effects of processing on the sealing glass. Validation of the predictions requires measurements on representative test geometries to accurately capture the interaction between the seal materials during a processing cycle required to form the seal, which consists of a temperature excursion through the glass transition temperature of the sealing glass. To this end, a concentric seal test geometry, referred to as a short cylinder seal, consisting of a stainless steel shell enveloping a commercial sealing glass disk has been designed, fabricated, and characterized as a model validation test geometry. To obtain data to test/validate finite element (FE) stress model predictions of this geometry, spatially-resolved residual stress was calculated from the measured lengths of the cracks emanating from radially positioned Vickers indents in the glass disk portion of the seal. The indentation crack length method is described, and the spatially-resolved residual stress determined experimentally are compared to FE stress predictions made using a nonlinear viscoelastic material model adapted to inorganic sealing glasses and an updated rate dependent material model for 304L stainless steel. The measurement method is a first to achieve a degree of success for measuring spatially resolved residual stress in a glass-bearing geometry and a favorable comparison between measurements and simulation was observed.

  10. Evaluation of coating adhesion using a radial speckle interferometer combined with a micro-indentation test

    Science.gov (United States)

    Tendela, Lucas P.; Kaufmann, Guillermo H.

    2012-06-01

    This paper presents a technique to investigate coating adhesion which combines a radial in-plane speckle interferometer and a micro-indentation test. The proposed technique is based on the measurement of the radial in-plane displacement field produced by a micro-indentation introduced on the coated surface of the specimen. Using steel specimens coated with a thin coating of epoxy paint and subjected to different adhesive conditions, it is demonstrated that digital speckle pattern interferometry can be successfully used to measure the small local deformations generated by a micro-indentation. An empirical model, which allows to quantify the adhesion of a given coated-substrate system by the proposed combined technique, is finally presented.

  11. Indentation Size Effects in Single Crystal Copper as Revealed by Synchrotron X-ray Microdiffraction

    Energy Technology Data Exchange (ETDEWEB)

    Feng, G.; Budiman, A. S.; Nix, W. D.; Tamura, N.; Patel, J. R.

    2007-11-19

    The indentation size effect (ISE) has been observed in numerous nanoindentation studies on crystalline materials; it is found that the hardness increases dramatically with decreasing indentation size - a 'smaller is stronger' phenomenon. Some have attributed the ISE to the existence of strain gradients and the geometrically necessary dislocations (GNDs). Since the GND density is directly related to the local lattice curvature, the Scanning X-ray Microdiffraction ({mu}SXRD) technique, which can quantitatively measure relative lattice rotations through the streaking of Laue diffractions, can used to study the strain gradients. The synchrotron {mu}SXRD technique we use - which was developed at the Advanced Light Source (ALS), Berkeley Lab - allows for probing the local plastic behavior of crystals with sub-micrometer resolution. Using this technique, we studied the local plasticity for indentations of different depths in a Cu single crystal. Broadening of Laue diffractions (streaking) was observed, showing local crystal lattice rotation due to the indentation-induced plastic deformation. A quantitative analysis of the streaking allows us to estimate the average GND density in the indentation plastic zones. The size dependence of the hardness, as found by nanoindentation, will be described, and its correlation to the observed lattice rotations will be discussed.

  12. Using the ratio: maximum load over unload stiffness squared, Pm/Su², on the evaluation of machine stiffness and area function of blunt indenters on depth-sensing indentation equipment

    Directory of Open Access Journals (Sweden)

    Juan Manuel Meza

    2007-12-01

    Full Text Available Depth sensing indentation study was conducted in a Fischerscope H100V machine, equipped with a Vickers indenter with a tip roundness of approximately 1330 nm. Tests were carried out on soda-lime glass, fused silica, sapphire, aluminum (1100 alloy, high alloyed steel, titanium and copper. The widely used iterative method of Oliver and Pharr was unsuccessful in the attempts to analyze machine compliance and indenter area function. Therefore, an alternative procedure was adopted. The alternative procedure is based on the ratio between maximum load and unload stiffness squared, Pm/Su². It was found that this procedure, which is not iterative, gives good results. A careful study of the Pm/Su² ratio, lead us to conclude that the Fischercope machine has a low compliance which depends on the sample mounting. This low compliance in conjunction with the recent discovery of the dependence of beta factor on the tip roundness/maximum depth ratio, which appears in the relation between contact stiffness and contact area, explains why the iterative method does not converge. However, variations in beta and machine compliance produces deviation on the hardness and elastic modulus lower that 6% with respect to expected values for the materials and the machine studied in this work.

  13. Glasses with fictive temperature-independent properties: Minimization of indentation size effect and maximization of crack resistance

    Science.gov (United States)

    Gross, Timothy Michael

    2008-10-01

    The fictive temperature of a glass is defined as the temperature at which the glass would find itself in equilibrium if brought to it suddenly from its given state. The cooling rate from a glass melt affects the fictive temperature, at which the supercooled liquid freezes to form the glassy state. A faster cooling rate will shift the fictive temperature higher. Glasses can be defined as normal or anomalous by the dependence of physical glass properties on fictive temperature. Normal glasses exhibit decreasing density, hardness, refractive index, and Young's modulus with increasing fictive temperature. Anomalous glasses exhibit the opposite trend in these properties. Intermediate glasses were prepared by melting calcium aluminosilicate glasses which fall between normal and anomalous glass compositions. The fictive temperature of glasses can be modified by heat-treatment in the glass transition region. The fictive temperature will reach the heat-treatment temperature with time by structural relaxation. The properties of the newly developed intermediate glasses do not change as the fictive temperature is modified by heat treatment. It is also shown in this research that the fictive temperature of a glass can be increased by plastic deformation during Vickers indentation. A small region surrounding the indentation is plastically deformed and exhibits a fictive temperature increase. This fictive temperature increase will affect the properties in this region and influence indentation-related glass properties. The glass developed with fictive temperature-independent density having a composition of 96 mol% SiO2 2 mol% Al2O3 2 mol% CaO is shown to give a minimum in the indentation size effect (ISE) during Vickers microhardness testing. The indentation size effect is the load dependence on microhardness, i.e. microhardness increases at low loads. The amount of ISE is found to be proportional to the amount of newly formed surface area from shear bands and cracks in the

  14. Towards a standardized reference point indentation testing procedure.

    Science.gov (United States)

    Setters, Alexander; Jasiuk, Iwona

    2014-06-01

    We study the reference point indentation (RPI) technique which has a potential to directly measure mechanical properties of bone in patients. More specifically, we tested 6 month swine femoral cortical bone at mid-diaphysis region to investigate the effect of several testing variables on the RPI outputs. They include the force magnitude, preconditioning, variation within a sample and between samples, number of cycles, indentation surface (transverse versus longitudinal, polished versus unpolished), and micro-computed tomography radiation exposure. The force magnitude variation test shows that all RPI parameters increase linearly with the increasing force magnitude except the indentation distance increase which shows a cubic trend with a plateau for force magnitudes between 4N and 8N. Preconditioning does not affect the trends for a force magnitude variation test. The cycle variation test shows that most RPI parameters reach either a maximum or minimum at 15-20 cycles. Transverse surface measurements are more consistent than the longitudinal surface measurements, but a rough surface and periosteum on the longitudinal surface could account for this difference. Exposure to the micro-computed tomography radiation in general does not have effect on the RPI measurements. For the 6 month swine femoral cortical bone, testing using 6N force and 20 cycles with preconditioning on an unpolished longitudinal surface is recommended. This study advances our knowledge on how the RPI testing variables influence the RPI outputs and provides guidance on the RPI measurements. It may also serve as a framework for developing a standardized testing procedure for the RPI technique. Copyright © 2014 Elsevier Ltd. All rights reserved.

  15. Thermomechanical indentation of shape memory polymers

    Science.gov (United States)

    Qi, H. Jerry; Dunn, Martin L.; Long, Kevin; Castro, Francisco; Shandas, Robin

    2007-04-01

    Shape memory polymers (SMPs) are receiving increasing attention because of their ability to store a temporary shape for a prescribed period of time, and then when subjected to an environmental stimulus, recover an original programmed shape. They are attractive candidates for a wide range of applications in microsystems, biomedical devices, deployable aerospace structures, and morphing structures. In this paper we investigate the thermomechanical behavior of shape memory polymers due to instrumented indentation, a loading/deformation scenario that represents complex multiaxial deformation. The SMP sample is indented using a spherical indenter at a temperature T I (>T g). The temperature is then lowered to T II (T g) during free recovery the indentation impression disappears and the surface of the SMP recovers to its original profile. A recently-developed three-dimensional finite deformation constitutive model for the thermomechanical behavior of SMPs is then used with the finite element method to simulate this process. Measurement and simulation results are compared for cases of free and constrained recovery and good agreement is obtained, suggesting the appropriateness of the simulation approach for complex multiaxial loading/deformations that are likely to occur in applications.

  16. Indentation of elastically soft and plastically compressible solids

    DEFF Research Database (Denmark)

    Needleman, A.; Tvergaard, Viggo; Van der Giessen, E.

    2015-01-01

    rigid sharp indenter into a cylinder modeling indentation of a half space. The material is characterized by a finite strain elastic-viscoplastic constitutive relation that allows for plastic as well as elastic compressibility. Both soft elasticity and plastic compressibility significantly reduce...... in the hydrostatic stress level in the material below the indenter....

  17. Effect of dry cryogenic treatment on Vickers hardness and wear resistance of new martensitic shape memory nickel-titanium alloy

    National Research Council Canada - National Science Library

    Vinothkumar, Thilla Sekar; Kandaswamy, Deivanayagam; Prabhakaran, Gopalakrishnan; Rajadurai, Arunachalam

    2015-01-01

    The aim of this study is to investigate the role of dry cryogenic treatment (CT) temperature and time on the Vickers hardness and wear resistance of new martensitic shape memory (SM) nickel-titanium (NiTi) alloy...

  18. Substrate-dependent cell elasticity measured by optical tweezers indentation

    Science.gov (United States)

    Yousafzai, Muhammad S.; Ndoye, Fatou; Coceano, Giovanna; Niemela, Joseph; Bonin, Serena; Scoles, Giacinto; Cojoc, Dan

    2016-01-01

    In the last decade, cell elasticity has been widely investigated as a potential label free indicator for cellular alteration in different diseases, cancer included. Cell elasticity can be locally measured by pulling membrane tethers, stretching or indenting the cell using optical tweezers. In this paper, we propose a simple approach to perform cell indentation at pN forces by axially moving the cell against a trapped microbead. The elastic modulus is calculated using the Hertz-model. Besides the axial component, the setup also allows us to examine the lateral cell-bead interaction. This technique has been applied to measure the local elasticity of HBL-100 cells, an immortalized human cell line, originally derived from the milk of a woman with no evidence of breast cancer lesions. In addition, we have studied the influence of substrate stiffness on cell elasticity by performing experiments on cells cultured on two substrates, bare and collagen-coated, having different stiffness. The mean value of the cell elastic modulus measured during indentation was 26±9 Pa for the bare substrate, while for the collagen-coated substrate it diminished to 19±7 Pa. The same trend was obtained for the elastic modulus measured during the retraction of the cell: 23±10 Pa and 13±7 Pa, respectively. These results show the cells adapt their stiffness to that of the substrate and demonstrate the potential of this setup for low-force probing of modifications to cell mechanics induced by the surrounding environment (e.g. extracellular matrix or other cells).

  19. Evaluation of Polymerization Efficacy in Composite Resins via FT-IR Spectroscopy and Vickers Microhardness Test.

    Science.gov (United States)

    Jafarzadeh, Tahereh-Sadat; Erfan, Mohammad; Behroozibakhsh, Marjan; Fatemi, Mostafa; Masaeli, Reza; Rezaei, Yashar; Bagheri, Hossein; Erfan, Yasaman

    2015-01-01

    Background and aims. Polymerization efficacy affects the properties and performance of composite resin restorations.The purpose of this study was to evaluate the effectiveness of polymerization of two micro-hybrid, two nano-hybrid and one nano-filled ormocer-based composite resins, cured by two different light-curing systems, using Fourier transformation infrared (FT-IR) spectroscopy and Vickers microhardness testing at two different depths (top surface, 2 mm). Materials and methods. For FT-IR spectrometry, five cylindrical specimens (5mm in diameter × 2 mm in length) were prepared from each composite resin using Teflon molds and polymerized for 20 seconds. Then, 70-μm wafers were sectioned at the top surface and at2mm from the top surface. The degree of conversion for each sample was calculated using FT-IR spectroscopy. For Vickers micro-hardness testing, three cylindrical specimens were prepared from each composite resin and polymerized for 20 seconds. The Vickers microhardness test (Shimadzu, Type M, Japan) was performed at the top and bottom (depth=2 mm) surfaces of each specimen. Three-way ANOVA with independent variables and Tukey tests were performed at 95% significance level. Results. No significant differences were detected in degree of conversion and microhardness between LED and QTH light-curing units except for the ormocer-based specimen, CeramX, which exhibited significantly higher DC by LED. All the composite resins showed a significantly higher degree of conversion at the surface. Microhardness was not significantly affected by depth, except for Herculite XRV Ultra and CeramX, which showed higher values at the surface. Conclusion. Composite resins containing nano-particles generally exhibited more variations in degree of conversion and microhardness.

  20. Evaluation of Polymerization Efficacy in Composite Resins via FT-IR Spectroscopy and Vickers Microhardness Test

    Science.gov (United States)

    Jafarzadeh, Tahereh-Sadat; Erfan, Mohammad; Behroozibakhsh, Marjan; Fatemi, Mostafa; Masaeli, Reza; Rezaei, Yashar; Bagheri, Hossein; Erfan, Yasaman

    2015-01-01

    Background and aims. Polymerization efficacy affects the properties and performance of composite resin restorations.The purpose of this study was to evaluate the effectiveness of polymerization of two micro-hybrid, two nano-hybrid and one nano-filled ormocer-based composite resins, cured by two different light-curing systems, using Fourier transformation infrared (FT-IR) spectroscopy and Vickers microhardness testing at two different depths (top surface, 2 mm). Materials and methods. For FT-IR spectrometry, five cylindrical specimens (5mm in diameter × 2 mm in length) were prepared from each composite resin using Teflon molds and polymerized for 20 seconds. Then, 70-μm wafers were sectioned at the top surface and at2mm from the top surface. The degree of conversion for each sample was calculated using FT-IR spectroscopy. For Vickers micro-hardness testing, three cylindrical specimens were prepared from each composite resin and polymerized for 20 seconds. The Vickers microhardness test (Shimadzu, Type M, Japan) was performed at the top and bottom (depth=2 mm) surfaces of each specimen. Three-way ANOVA with independent variables and Tukey tests were performed at 95% significance level. Results. No significant differences were detected in degree of conversion and microhardness between LED and QTH light-curing units except for the ormocer-based specimen, CeramX, which exhibited significantly higher DC by LED. All the composite resins showed a significantly higher degree of conversion at the surface. Microhardness was not significantly affected by depth, except for Herculite XRV Ultra and CeramX, which showed higher values at the surface. Conclusion. Composite resins containing nano-particles generally exhibited more variations in degree of conversion and microhardness. PMID:26889359

  1. Evaluation of Polymerization Efficacy in Composite Resins via FT-IR Spectroscopy and Vickers Microhardness Test

    Directory of Open Access Journals (Sweden)

    Tahereh-Sadat Jafarzadeh

    2015-12-01

    Full Text Available Background and aims. Polymerization efficacy affects the properties and performance of composite resin restorations.The purpose of this study was to evaluate the effectiveness of polymerization of two micro-hybrid, two nano-hybrid and one nano-filled ormocer-based composite resins, cured by two different light-curing systems, using Fourier transformation infrared (FT-IR spectroscopy and Vickers microhardness testing at two different depths (top surface, 2 mm. Materials and methods. For FT-IR spectrometry, five cylindrical specimens (5mm in diameter × 2 mm in length were prepared from each composite resin using Teflon molds and polymerized for 20 seconds. Then, 70-μm wafers were sectioned at the top surface and at2mm from the top surface. The degree of conversion for each sample was calculated using FT-IR spectroscopy. For Vickers micro-hardness testing, three cylindrical specimens were prepared from each composite resin and polymerized for 20 seconds. The Vickers microhardness test (Shimadzu, Type M, Japan was performed at the top and bottom (depth=2 mm surfaces of each specimen. Three-way ANOVA with independent variables and Tukey tests were performed at 95% significance level. Results. No significant differences were detected in degree of conversion and microhardness between LED and QTH light-curing units except for the ormocer-based specimen, CeramX, which exhibited significantly higher DC by LED. All the composite resins showed a significantly higher degree of conversion at the surface. Microhardness was not significantly affected by depth, except for Herculite XRV Ultra and CeramX, which showed higher values at the surface. Conclusion. Composite resins containing nano-particles generally exhibited more variations in degree of conversion and microhardness.

  2. In situ spectroscopic study of the plastic deformation of amorphous silicon under non-hydrostatic conditions induced by indentation.

    Science.gov (United States)

    Gerbig, Y B; Michaels, C A; Bradby, J E; Haberl, B; Cook, R F

    2015-12-01

    Indentation-induced plastic deformation of amorphous silicon (a-Si) thin films was studied by in situ Raman imaging of the deformed contact region of an indented sample, employing a Raman spectroscopy-enhanced instrumented indentation technique. Quantitative analyses of the generated in situ Raman maps provide unique, new insight into the phase behavior of as-implanted a-Si. In particular, the occurrence and evolving spatial distribution of changes in the a-Si structure caused by processes, such as polyamorphization and crystallization, induced by indentation loading were measured. The experimental results are linked with previously published work on the plastic deformation of a-Si under hydrostatic compression and shear deformation to establish a sequence for the development of deformation of a-Si under indentation loading. The sequence involves three distinct deformation mechanisms of a-Si: (1) reversible deformation, (2) increase in coordination defects (onset of plastic deformation), and (3) phase transformation. Estimated conditions for the occurrence of these mechanisms are given with respect to relevant intrinsic and extrinsic parameters, such as indentation stress, volumetric strain, and bond angle distribution (a measure for the structural order of the amorphous network). The induced volumetric strains are accommodated solely by reversible deformation of the tetrahedral network when exposed to small indentation stresses. At greater indentation stresses, the increased volumetric strains in the tetrahedral network lead to the formation of predominately five-fold coordination defects, which seems to mark the onset of irreversible or plastic deformation of the a-Si thin film. Further increase in the indentation stress appears to initiate the formation of six-fold coordinated atomic arrangements. These six-fold coordinated arrangements may maintain their amorphous tetrahedral structure with a high density of coordination defects or nucleate as a new crystalline

  3. A novel numerical framework for self-similarity in plasticity: Wedge indentation in single crystals

    DEFF Research Database (Denmark)

    Juul, Kristian Jørgensen; Niordson, Christian Frithiof; Nielsen, Kim Lau Nielsen

    2017-01-01

    A novel numerical framework for analyzing self-similar problems in plasticity is developed and demonstrated. Self-similar problems of this kind include processes such as stationary cracks, void growth, indentation etc. The proposed technique offers a simple and efficient method for handling...

  4. Crystalline cellulose elastic modulus predicted by atomistic models of uniform deformation and nanoscale indentation

    Science.gov (United States)

    Xiawa Wu; Robert J. Moon; Ashlie Martini

    2013-01-01

    The elastic modulus of cellulose Iß in the axial and transverse directions was obtained from atomistic simulations using both the standard uniform deformation approach and a complementary approach based on nanoscale indentation. This allowed comparisons between the methods and closer connectivity to experimental measurement techniques. A reactive...

  5. Microhardness with depth sensing indentation. Instruments methods and applications; Mesure de durete submicronique instrumentee. Methode et applications

    Energy Technology Data Exchange (ETDEWEB)

    Poissonnet, S

    1999-07-01

    The study of applied surface layer or modified layers lead to the development of depth sensing indentation instruments in which measurements of penetration depth replaces optical measurements of surface impressions and sub-micron hardness may be determined. Indentation curves, depth-load, of elastoplastic materials give informations about plasticity and elasticity. After a description of the micro-indentation techniques we show few applications. Irradiation effects are measured in different materials like hafnium diboride, stainless steel or kapton. Hardness in oxide formed on metal study give informations. All these examples show that the nano-indentation is a powerful mean in the physical studies of materials because of a good statistic may be obtained and we have access to thin samples and to small phases. (author)

  6. Changes in Vickers hardness during the decomposition of bone: Possibilities for forensic anthropology.

    Science.gov (United States)

    Walden, Steven J; Evans, Sam L; Mulville, Jacqui

    2017-01-01

    The purpose of this study was to determine how the Vickers hardness (HV) of bone varies during soft tissue putrefaction. This has possible forensic applications, notably for determining the postmortem interval. Experimental porcine bone samples were decomposed in surface and burial deposition scenarios over a period of 6 months. Although the Vickers hardness varied widely, it was found that when transverse axial hardness was subtracted from longitudinal axial hardness, the difference showed correlations with three distinct phases of soft tissue putrefaction. The ratio of transverse axial hardness to longitudinal axial hardness showed a similar correlation. A difference of 10 or greater in HV with soft tissue present and signs of minimal decomposition, was associated with a decomposition period of 250 cumulative cooling degree days or less. A difference of 10 (+/- standard error of mean at a 95% confidence interval) or greater in HV associated with marked decomposition indicated a decomposition period of 1450 cumulative cooling degree days or more. A difference of -7 to +8 (+/- standard error of mean at a 95% confidence interval) was thus associated with 250 to 1450 cumulative cooling degree days' decomposition. The ratio of transverse axial HV to longitudinal HV, ranging from 2.42 to 1.54, is a more reliable indicator in this context and is preferable to using negative integers These differences may have potential as an indicator of postmortem interval and thus the time of body deposition in the forensic context. Crown Copyright © 2016. Published by Elsevier Ltd. All rights reserved.

  7. Material Flow Analysis in Indentation by Two-Dimensional Digital Image Correlation and Finite Elements Method.

    Science.gov (United States)

    Bermudo, Carolina; Sevilla, Lorenzo; Castillo López, Germán

    2017-06-21

    The present work shows the material flow analysis in indentation by the numerical two dimensional Finite Elements (FEM) method and the experimental two-dimensional Digital Image Correlation (DIC) method. To achieve deep indentation without cracking, a ductile material, 99% tin, is used. The results obtained from the DIC technique depend predominantly on the pattern conferred to the samples. Due to the absence of a natural pattern, black and white spray painting is used for greater contrast. The stress-strain curve of the material has been obtained and introduced in the Finite Element simulation code used, DEFORM™, allowing for accurate simulations. Two different 2D models have been used: a plain strain model to obtain the load curve and a plain stress model to evaluate the strain maps on the workpiece surface. The indentation displacement load curve has been compared between the FEM and the experimental results, showing a good correlation. Additionally, the strain maps obtained from the material surface with FEM and DIC are compared in order to validate the numerical model. The Von Mises strain results between both of them present a 10-20% difference. The results show that FEM is a good tool for simulating indentation processes, allowing for the evaluation of the maximum forces and deformations involved in the forming process. Additionally, the non-contact DIC technique shows its potential by measuring the superficial strain maps, validating the FEM results.

  8. Mechanical indentation improves cerebral blood oxygenation signal quality of functional near-infrared spectroscopy (fNIRS) during breath holding

    Science.gov (United States)

    Vogt, William C.; Romero, Edwin; LaConte, Stephen M.; Rylander, Christopher G.

    2013-03-01

    Functional near-infrared spectroscopy (fNIRS) is a well-known technique for non-invasively measuring cerebral blood oxygenation, and many studies have demonstrated that fNIRS signals can be related to cognitive function. However, the fNIRS signal is attenuated by the skin, while scalp blood content has been reported to influence cerebral oxygenation measurements. Mechanical indentation has been shown to increase light transmission through soft tissues by causing interstitial water and blood flow away from the compressed region. To study the effects of indentation on fNIRS, a commercial fNIRS system with 16 emitter/detector pairs was used to measure cerebral blood oxygenation at 2 Hz. This device used diffuse reflectance at 730 nm and 850 nm to calculate deoxy- and oxy-hemoglobin concentrations. A borosilicate glass hemisphere was epoxied over each sensor to function as both an indenter and a lens. After placing the indenter/sensor assembly on the forehead, a pair of plastic bands was placed on top of the fNIRS headband and strapped to the head to provide uniform pressure and tightened to approx. 15 N per strap. Cerebral blood oxygenation was recorded during a breath holding regime (15 second hold, 15 second rest, 6 cycles) in 4 human subjects both with and without the indenter array. Results showed that indentation increased raw signal intensity by 85 +/- 35%, and that indentation increased amplitude of hemoglobin changes during breath cycles by 313% +/- 105%. These results suggest that indentation improves sensing of cerebral blood oxygenation, and may potentially enable sensing of deeper brain tissues.

  9. Progressive evolution of microfabrics in high-temperature indentation creep experiments

    Science.gov (United States)

    Wassmann, S.; Dorner, D.; Stoeckhert, B.

    2014-12-01

    Microfabrics of natural rocks as well as of those deformed in laboratory experiments are studied post-mortem, the history of fabric evolution being inferred from a finite state. This is a major drawback when being interested in modification of fabrics related to progressive deformation. Here we present a novel approach to analyze and compare fabrics in different stages of evolution, taking spatial position to mimic a time series. Using this approach, evolution in time can be investigated on one sample deformed in a single indentation creep test. Such experiments at high temperatures and atmospheric pressure provide information on mechanical properties of rock-forming minerals as well as on microfabrics developed during inhomogeneous deformation underneath the indenter. Using a conventional creep apparatus, a cylindrical alumina indenter, 2 mm in diameter, is driven by a dead load into the flat surface of a specimen. A penetration depth of 1 mm is typically reached after hours to days, depending on material, applied temperature, and load. Previous experiments on natural, polycrystalline anhydrite carried out at temperatures between 700°C and 920 °C yield a stress exponent of 3.9 indicating deformation in the dislocation creep regime, consistent with microstructural observations (Dorner et al., 2014; Solid Earth). Within a cone-shaped region in front of the indenter, the original microfabric appears entirely unaffected. The neutral cone is mantled by highly deformed shear zones. During progressive indentation this structure of undeformed cone and shear zones propagates into the specimen. Thus, for a homogeneous starting material, serial sections of the deformed specimen normal to the indenter axis provide insight into fabrics in distinct stages of evolution. Microfabrics developed at different distance in front of the approaching indenter can be taken to represent a time series. A disadvantage of the technique is that the history of shear zone deformation is

  10. Vickers Hardness of Composite Resins Cured with LED and QTH Units

    Directory of Open Access Journals (Sweden)

    Alaghemand H

    2016-03-01

    Full Text Available Statement of Problem: One of the factors affecting the degree of polymerization of light-cured composites is the type of light-curing unit used. In addition, physicomechanical properties of the composite resins depend on the degree of conversion and polymerization. Objectives: Since the type of initiator in new composite resins is not explained by manufacturers, this study is an attempt to compare the depth of hardening, with two LED and QTH light-curing units. Materials and Methods: Fifteen samples prepared from Gradia Direct and Filtek Z250, both of which being universal, were cured with QTH (Astralis 7 and LED (Bluephase C8 light-curing units. All the samples were molded in polyester resin and cut from the middle by a disk. The hardness of the cut area was evaluated at 0, 0.5, 1, 1.5, 2, 2.5, 3, 3.5 and 4-mm depth intervals and also at the same interval as the width of the sample, with Vickers hardness machine, while the samples were placed in a darkroom. Data were statistically analyzed using one-way ANOVA, two-way ANOVA, t-test and post Hoc Tukey’s tests in SPSS, version 16. Results: Filtek Z250 was harder than Gradia Direct at all the depth with both light-curing units. The hardness of Filtek Z250 sample cured with Astralis 7 was higher than that cured with LED, but with Gradia Direct the LED unit resulted in higher hardness. Curing depth was not significantly different between the groups (p = 0.109. Conclusions: Vickers hardness number for both composites used in this study is in an acceptable range for clinical implications. The composites’ composition is important to be considered for selection of light unit. Based on the findings of the present study, LED did not present more curing depth compared with QTH.

  11. Effect of Preoperative Occlusal Matrices on the Vickers Microhardness of Composite Disks Polymerized with QTH and LED Lamps.

    Science.gov (United States)

    Castillo-Oyagüe, Raquel; Milward, Paul J; Martín-Cerrato, Alicia; Lynch, Christopher D

    2015-01-01

    This study aimed to assess the reliability of the preoperative occlusal matrix technique in terms of the surface Vickers microhardness (VMH) of the underlying composite restorative material. Two hundred microhybrid composite cylinders were built up and light-cured in a single-layer step, forming two experimental groups (N = 100) according to their heights (1.5 mm/2 mm). Each group was divided into five subgroups (N = 20) depending on the matrix thickness (no matrix/0.5 mm/1 mm/2 mm/3 mm). Half the specimens per subgroup (N = 10) were randomly polymerized with a quartz-tungsten-halogen (QTH) light-curing unit (LCU). The remaining half were cured using a light-emitting diode lamp. The top and bottom samples' sides were tested for VMH at 1 hour and 24 hours post-curing using a universal VMH machine. A multiple analysis of variance with repeated measurements for the "surface" factor and the Student-Newman-Keuls test were run (α = 0.05). Bottom/top microhardness ratios were compared with the empirically accepted limit (0.8). Surface topography was analyzed under a scanning electron microscope. The thinnest matrices provided the significantly best VMH values. LCU, disc height, and time also contributed to VMH. At 24 hours, 2-mm high discs polymerized with QTH resulted in inadequate microhardness ratios when 1-mm thick to 3-mm thick matrices were used. The thinnest matrices are the most recommendable ones. The esthetics and occlusal reproducibility achieved with customized occlusal matrices fabricated before cavity preparation have been widely demonstrated. However, their effect on the physical properties of the restorations deserves further investigation. Although more studies are necessary, the thinnest matrices seem to be the most suitable to preserve the composite surface VMH and the curing depth. © 2015 Wiley Periodicals, Inc.

  12. Indentation of elastically soft and plastically compressible solids

    NARCIS (Netherlands)

    Needleman, A.; Tvergaard, V.; Van der Giessen, E.

    The effect of soft elasticity, i.e., a relatively small value of the ratio of Young's modulus to yield strength and plastic compressibility on the indentation of isotropically hardening elastic-viscoplastic solids is investigated. Calculations are carried out for indentation of a perfectly sticking

  13. Nucleation at hardness indentations in cold rolled Al

    DEFF Research Database (Denmark)

    Xu, C.L.; Zhang, Yubin; Wu, G.L.

    2015-01-01

    Nucleation of recrystallization near hardness indentations has been investigated in slightly cold rolled high purity aluminium. Samples were cold rolled to 12% and 20% reductions in thickness and indentations were done with two different loads (500 g and 2000 g). The samples were annealed at 300 °C...

  14. Nanoscale Etching and Indentation of Silicon Surfaces with Carbon Nanotubes

    Science.gov (United States)

    Dzegilenko, Fedor N.; Srivastava, Deepak; Saini, Subhash

    1998-01-01

    The possibility of nanolithography of silicon and germanium surfaces with bare carbon nanotube tips of scanning probe microscopy devices is considered with large scale classical molecular dynamics (MD) simulations employing Tersoff's reactive many-body potential for heteroatomic C/Si/Ge system. Lithography plays a key role in semiconductor manufacturing, and it is expected that future molecular and quantum electronic devices will be fabricated with nanolithographic and nanodeposition techniques. Carbon nanotubes, rolled up sheets of graphene made of carbon, are excellent candidates for use in nanolithography because they are extremely strong along axial direction and yet extremely elastic along radial direction. In the simulations, the interaction of a carbon nanotube tip with silicon surfaces is explored in two regimes. In the first scenario, the nanotubes barely touch the surface, while in the second they are pushed into the surface to make "nano holes". The first - gentle scenario mimics the nanotube-surface chemical reaction induced by the vertical mechanical manipulation of the nanotube. The second -digging - scenario intends to study the indentation profiles. The following results are reported in the two cases. In the first regime, depending on the surface impact site, two major outcomes outcomes are the selective removal of either a single surface atom or a surface dimer off the silicon surface. In the second regime, the indentation of a silicon substrate by the nanotube is observed. Upon the nanotube withdrawal, several surface silicon atoms are adsorbed at the tip of the nanotube causing significant rearrangements of atoms comprising the surface layer of the silicon substrate. The results are explained in terms of relative strength of C-C, C-Si, and Si-Si bonds. The proposed method is very robust and does not require applied voltage between the nanotube tips and the surface. The implications of the reported controllable etching and hole-creating for

  15. Evaluation of Vickers hardness of different types of acrylic denture base resins with and without glass fibre reinforcement.

    Science.gov (United States)

    Farina, Ana Paula; Cecchin, Doglas; Soares, Rodrigo Gonçalves; Botelho, André Luís; Takahashi, Jessica Mie Ferreira Koyama; Mazzetto, Marcelo Oliveira; Mesquita, Marcelo Ferraz

    2012-06-01

    To evaluate the Vickers hardness of different acrylic resins for denture bases with and without the addition of glass fibres. It has been suggested that different polymerisation methods, as well as the addition of glass fibre (FV) might improve the hardness of acrylic. Five types of acrylic resin were tested: Vipi Wave (VW), microwave polymerisation; Vipi Flash (VF), auto-polymerisation; Lucitone (LT), QC20 (QC) and Vipi Cril (VC), conventional heat-polymerisation, all with or without glass fibre reinforcement (GFR) and distributed into 10 groups (n = 12). Specimens were then submitted to Vickers hardness testing with a 25-g load for 30 s. All data were submitted to anova and Tukey's HSD test. A significant statistical difference was observed with regard to the polymerisation method and the GFR (p hardness values, and VF and LT presented the lowest. In the presence of GFR, VC resin still presented the highest Vickers hardness values, and VF and QC presented the lowest. The acrylic resin VC and VW presented higher hardness values than VF and QC resins. Moreover, GFR increased the Vickers hardness of resins VW, VC and LT. © 2010 The Gerodontology Society and John Wiley & Sons A/S.

  16. A new approach to the estimation of surface free energy based on Vickers microhardness data

    Directory of Open Access Journals (Sweden)

    2009-03-01

    Full Text Available A relation between surface free energy (σMHV and Meyer’s lines cut-values has been established using Vickers microhardness (MHV method and empirical physical laws. This relation allows the calculation of σMHV only from MHV data. The parameters required are Meyer’s lines cut-values and the mean value of diagonal length of the impression at different loads applied (drealmean. Our study of 12 samples of ultra high molecular weight polyethylene (PE-UHMW showed that the new approach is applicable when the slope value of Meyer’s lines equals 2 (i.e. n = 2. A γ-60Co source was used for the irradiation of 11 samples (one of the samples investigated is un-irradiated at room temperature in air. Doses of 1, 2, 5, 10, 20, 50, 100, 200, 500, 1000 and 1500 kGy were applied. The values of σMHV obtained are in a good agreement with the literature. The dependence of σMHV on the dose applied strictly corresponds to the radiation effects theory. MHV was measured at seven different loads – 0.0123, 0.0245, 0.049, 0.098, 0.196, 0.392, 0.785 N at a loading time of 30 s.

  17. Residual stress and plastic anisotropy in indented 2024-T351 aluminum disks

    Energy Technology Data Exchange (ETDEWEB)

    Clausen, Bjorn [Los Alamos National Laboratory; Prime, Michael B [Los Alamos National Laboratory; Saurabh, Kabra [Los Alamos National Laboratory; Brown, Donald W [Los Alamos National Laboratory; Pagliaro, Pierluigi [UNIV OF PALEMO; Backlund, Peter [UNIV OF TEXAS; Shaw, Sanjiv [UNIV OF TEXAS; Criss, Everett [UCSD

    2009-01-01

    Recent studies have proven that generating a well defined residual stress state using the indented disk approach is an excellent way to validate experimental and modeling techniques for measuring and predicting residual stresses. The previous studies dealt with indented stainless steel disks, and included experimental determination of residual stresses using the Contour Method and neutron diffraction measurements. The measured residual stress states showed good agreement between the techniques, and a Finite Element Model predicted residual stress state based upon material properties determined form standard tension and compression/tension tests was also in good agreement with the measurements. In the present work, disks of 2024-T351 Aluminum were investigated. As before, the residual stress profile was measured using neutron diffraction and the Contour Method and Finite Element Modeling was employed to predict the residual stress profile. Analysis and comparison of the three techniques were complicated by the fact that the experimental data shows evidence of plastic anisotropy and strong Bauschinger effect within the indented disks.

  18. Fatigue Life of Postbuckled Structures with Indentation Damage

    Science.gov (United States)

    Davila, Carlos G.; Bisagni, Chiara

    2016-01-01

    The fatigue life of composite stiffened panels with indentation damage was investigated experimentally using single stringer compression specimens. Indentation damage was induced on one of the two flanges of the stringer. The experiments were conducted using advanced instrumentation, including digital image correlation, passive thermography, and in-situ ultrasonic scanning. Specimens with initial indentation damage lengths of 37 millimeters to 56 millimeters were tested in fatigue and the effects of cyclic load amplitude and damage size were studied. A means of comparison of the damage propagation rates and collapse loads based on a stress intensity measure and the Paris law is proposed.

  19. Fatigue Life of Postbuckled Structures with Indentation Damages

    Science.gov (United States)

    Davila, Carlos G.; Bisagni, Chiara

    2016-01-01

    The fatigue life of composite stiffened panels with indentation damage was investigated experimentally using single stringer compression specimens. Indentation damage was induced on one of the two flanges of each stringer. The experiments were conducted using advanced instrumentation, including digital image correlation, passive thermography, and in-situ ultrasonic scanning. Specimens with initial indentation damage lengths of 32 millimeters to 56 millimeters were tested quasi-statically and in fatigue, and the effects of cyclic load amplitude and damage size were studied. A means of comparison of the damage propagation rates and collapse loads based on a stress intensity measure and the Paris law is proposed.

  20. Indentation-flexure and low-velocity impact damage in graphite epoxy laminates

    Science.gov (United States)

    Kwon, Young S.; Sankar, Bhavani V.

    1993-01-01

    Static indentation-flexure and low-velocity impact tests were performed on quasi-isotropic and cross-ply graphite/epoxy composite laminates. The load-deflection relations in static tests and impact force history in impact tests were recorded. The damage was assessed by using ultrasonic C-scanning and photo-micrographic techniques. Some features of the static behavior were explained by simple analytical models. A good correlation existed between the load-deflection curves for static and impact loading. It was found that results from a few static indentation-flexure tests can be used to predict the impact force history and delamination radius in composite laminates due to low-velocity impact.

  1. Indentation-flexure and low-velocity impact damage in graphite/epoxy laminates

    Science.gov (United States)

    Kwon, Young S.; Sankar, Bhavani V.

    1992-01-01

    Static indentation and low velocity impact tests were performed on quasi-isotropic and cross ply graphite/epoxy composite laminates. The load deflection relations in static tests and impact force history in the impact tests were recorded. The damage was assessed by using ultrasonic C-scanning and photomicrographic techniques. The static behavior of the laminates and damage progression during loading, unloading, and reloading were explained by a simple plate delamination model. A good correlation existed between the static and impact responses. It was found that results from a few static indentation-flexture tests can be used to predict the response and damage in composite laminates due to a class of low velocity impact events.

  2. Indentation and needle insertion properties of the human eye

    Science.gov (United States)

    Matthews, A; Hutnik, C; Hill, K; Newson, T; Chan, T; Campbell, G

    2014-01-01

    Purpose Characterization of the biomechanical properties of the human eye has a number of potential utilities. One novel purpose is to provide the basis for development of suitable tissue-mimicking material. The purpose of this study was to determine the indentation and needle insertion characteristics on human eye globes and tissue strips. Methods An indenter assessed the elastic response of human eye globes and tissue strips under increasing compressive loads. Needle insertion determined the force (N) needed to penetrate various areas of the eye wall. Results The results demonstrated that globes underwent slightly greater indentation at the midline than at the central cornea, and corneal strips indented twofold more than scleral strips, although neither difference was significant (P=0.400 and P=0.100, respectively). Significant differences were observed among various areas of needle insertion (Peye construct with potential utility as a model for use in ophthalmology research and surgical teaching. PMID:24810571

  3. A 200 W Hall thruster with hollow indented anode

    Science.gov (United States)

    Ding, Yongjie; Sun, Hezhi; Wei, Liqiu; Li, Peng; Su, Hongbo; Peng, Wuji; Yu, Daren

    2017-10-01

    A hollow indented anode is proposed for increasing the neutral gas density in a discharge channel, in order to improve the performance of the thruster. The experimental results show that a hollow indented anode structure can effectively improve the performance, compared to a hollow straight anode under similar operating conditions, in terms of thrust, propellant utilization, ionization rate, and anode efficiency. Furthermore, simulations show that the indented anode can effectively increase the neutral gas density in a discharge channel and on the centerline of the channel, compared to a hollow straight anode. In addition, it can increase the ionization rate in the channel and the pre-ionization in the anode. Therefore, the hollow indented anode could be considered as an important design idea for improving thruster performance.

  4. Indentation of a floating elastic sheet: geometry versus applied tension

    Science.gov (United States)

    Box, Finn; Vella, Dominic; Style, Robert W.; Neufeld, Jerome A.

    2017-10-01

    The localized loading of an elastic sheet floating on a liquid bath occurs at scales from a frog sitting on a lily pad to a volcano supported by the Earth's tectonic plates. The load is supported by a combination of the stresses within the sheet (which may include applied tensions from, for example, surface tension) and the hydrostatic pressure in the liquid. At the same time, the sheet deforms, and may wrinkle, because of the load. We study this problem in terms of the (relatively weak) applied tension and the indentation depth. For small indentation depths, we find that the force-indentation curve is linear with a stiffness that we characterize in terms of the applied tension and bending stiffness of the sheet. At larger indentations, the force-indentation curve becomes nonlinear and the sheet is subject to a wrinkling instability. We study this wrinkling instability close to the buckling threshold and calculate both the number of wrinkles at onset and the indentation depth at onset, comparing our theoretical results with experiments. Finally, we contrast our results with those previously reported for very thin, highly bendable membranes.

  5. Characterization of residual stresses in zirconia veneered bilayers assessed via sharp and blunt indentation.

    Science.gov (United States)

    Wendler, Michael; Belli, Renan; Petschelt, Anselm; Lohbauer, Ulrich

    2015-08-01

    The present study evaluated the effect of the coefficient of thermal expansion (CTE) mismatch and the cooling protocol on the distribution of residual stresses and crack propagation in veneered zirconia bilayers. Ceramic discs with two different CTEs (Vita VM9 and Lava Ceram) were fired onto zirconia plates and cooled following a slow (0.5°C/s) or a fast (45°C/s) cooling protocol. The residual stress distribution throughout the veneer thickness was assessed by means of depth-wise Vickers indentation after sequentially sectioning the bilayers parallel compared to normal to the interface. A mathematical solution for the residual stress distribution was used as reference. Additionally, Hertzian cone crack propagation in the veneers was induced by cyclic contact loading and measured at different number of cycles to estimate the crack growth rate. The higher CTE mismatch of the VM9 group generated an important stress gradient with high compressive residual stresses near the interface, hindering the crack propagation. The low CTE mismatch group (Lava Ceram) developed only a slight stress gradient and higher cone crack growth rates. No differences were observed between the two cooling protocols applied regarding stress magnitude and crack propagation behavior. The CTE mismatch has a predominant role in the generation of residual stress gradients within the veneer, which directly influences contact-induced crack propagation. Based on the results, the cooling protocol had no significant effect on the residual stress distribution in zirconia-veneer bilayers. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  6. An Improved Approach to Fracture Toughness Assessment of Brittle Coating on Ductile Substrate Systems under Indentation

    Science.gov (United States)

    Demidova, Natalia V.

    substrate system, in order to obtain the required information for validating the proposed fracture toughness model. It is found that radial/median cracks are generated beneath the indenter within the coating layer in an elliptical shape and stopped at the interface under the indentation loads being used in the present experiments. Optical microscopy is employed to examine the surface (radial) crack lengths and the focused ion beam (FIB) technique is applied to dissecting the coating/substrate specimen and thereby allows for measuring the crack penetration depth; thus the full crack profile is determined. These tests have also verified the non-linear relationship between c3/2 (where c is a radial crack length) and the applied indentation load P, which is exhibited in the proposed fracture toughness model. The fracture toughness of the tested WC/10Co/4Cr coating/1080 steel substrate system is determined in terms of the proposed fracture toughness model, utilizing the experimental results. The fracture toughness value for this coating/substrate system is then compared to the known fracture toughness value of a similar brittle coating/ductile substrate system (WC/12Co coating/1020 low carbon steel substrate) and is found to be comparable. The proposed fracture toughness model best describes the experimental observation of cracking/fracture behavior of brittle coating/ductile substrate systems under indentation, compared with other existing models, which can be utilized to assess the fracture toughness of these coating/substrate systems. The developed approach makes a significant improvement in the existing fracture mechanics methods for fracture toughness assessment of brittle coating/ductile substrate systems.

  7. Influence of Indenter Tip Geometry on Elastic Deformation during Nanoindentation

    Science.gov (United States)

    Bei, H.; George, E. P.; Hay, J. L.; Pharr, G. M.

    2005-07-01

    Nanoindentation with a Berkovich indenter is commonly used to investigate the mechanical behavior of small volumes of materials. To date, most investigators have made the simplifying assumption that the tip is spherical. In reality, indenter tips are much more complex. Here, we develop a new method to describe the tip shape using the experimentally determined area function of the indenter at small depths (0 100 nm). Our analysis accurately predicts the elastic load-displacement curve and allows the theoretical strength of a material to be determined from pop-in data. Application of our new method to single crystal Cr3Si shows that the predicted theoretical strengths are within 12% of the ideal strength G/2π, where G is the shear modulus.

  8. Image analysis of moving seeds in an indented cylinder

    DEFF Research Database (Denmark)

    Buus, Ole; Jørgensen, Johannes Ravn

    2010-01-01

    work we will seek to understand more about the internal dynamics of the indented cylinder. We will apply image analysis to observe the movement of seeds in the indented cylinder. This work is laying the groundwork for future studies into the application of image analysis as a tool for autonomous......-Spline surfaces. Using image analysis, the seeds will be tracked using a kalman filter and the 2D trajectory, length, velocity, weight, and rotation will be sampled. We expect a high correspondence between seed length and certain spatially optimal seed trajectories. This work is done in collaboration with Westrup......The indented cylinder is used for sorting seeds. The seeds are physically manipulated in a way, such that sorting is based primarily on the length of individual seeds. Seeds are separated into at least two subsets: (1) seeds of a length a threshold (a scalar) and (2) seeds of a length the same...

  9. Buckling of Single-Crystal Silicon Nanolines under Indentation

    Directory of Open Access Journals (Sweden)

    Min K. Kang

    2008-01-01

    Full Text Available Atomic force microscope-(AFM- based indentation tests were performed to examine mechanical properties of parallel single-crystal silicon nanolines (SiNLs of sub-100-nm line width, fabricated by a process combining electron-beam lithography and anisotropic wet etching. The SiNLs have straight and nearly atomically flat sidewalls, and the cross section is almost perfectly rectangular with uniform width and height along the longitudinal direction. The measured load-displacement curves from the indentation tests show an instability with large displacement bursts at a critical load ranging from 480 μN to 700 μN. This phenomenon is attributed to a transition of the buckling mode of the SiNLs under indentation. Using a set of finite element models with postbuckling analyses, we analyze the indentation-induced buckling modes and investigate the effects of tip location, contact friction, and substrate deformation on the critical load of mode transition. The results demonstrate a unique approach for the study of nanomaterials and patterned nanostructures via a combination of experiments and modeling.

  10. Using nano-indentation and microscopy to obtain mechanical properties

    NARCIS (Netherlands)

    Lukovic, M.; Schlangen, E.; Savija, B.; Ye, G.; Copuroglu, O.

    2015-01-01

    Simulation of mechanical behaviour of heterogeneous materials is only possible if the local properties of the components are known. In recent years nano-indentation is being applied on different levels to obtain local mechanical properties. The aim of this paper is to explore various ways to obtain

  11. Hardness and elasticity of abrasive particles measured by instrumented indentation

    Czech Academy of Sciences Publication Activity Database

    Hvizdoš, P.; Zeleňák, Michal; Hloch, Sergej

    2016-01-01

    Roč. 8, č. 1 (2016), s. 869-871 ISSN 1805-0476 Institutional support: RVO:68145535 Keywords : abrasive * garnet * hardness * elasticity * instrumental indentation Subject RIV: JQ - Machines ; Tools http://www.mmscience.eu/content/file/archives/MM_Science_201601.pdf

  12. Standard hardness conversion tables for metals relationship among brinell hardness, vickers hardness, rockwell hardness, superficial hardness, knoop hardness, and scleroscope hardness

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2007-01-01

    1.1 Conversion Table 1 presents data in the Rockwell C hardness range on the relationship among Brinell hardness, Vickers hardness, Rockwell hardness, Rockwell superficial hardness, Knoop hardness, and Scleroscope hardness of non-austenitic steels including carbon, alloy, and tool steels in the as-forged, annealed, normalized, and quenched and tempered conditions provided that they are homogeneous. 1.2 Conversion Table 2 presents data in the Rockwell B hardness range on the relationship among Brinell hardness, Vickers hardness, Rockwell hardness, Rockwell superficial hardness, Knoop hardness, and Scleroscope hardness of non-austenitic steels including carbon, alloy, and tool steels in the as-forged, annealed, normalized, and quenched and tempered conditions provided that they are homogeneous. 1.3 Conversion Table 3 presents data on the relationship among Brinell hardness, Vickers hardness, Rockwell hardness, Rockwell superficial hardness, and Knoop hardness of nickel and high-nickel alloys (nickel content o...

  13. Load and depth sensing indentation as a tool to monitor a gradient in the mechanical properties across a polymer coating: A study of physical and chemical aging effects

    NARCIS (Netherlands)

    Boersma, A.; Soloukhin, V.A.; Brokken-Zijp, J.C.M.; With, G. de

    2004-01-01

    Load and depth sensing indentation has been used to characterize the elastic modulus and hardness of various polycarbonate films. This analytical technique is shown to be extremely suitable for the determination of gradients in these mechanical properties. Furthermore, it is demonstrated that such a

  14. Characterization of Rubbers from Spherical Punch - Plate Indentation Tests

    Directory of Open Access Journals (Sweden)

    Florina Carmen Ciornei

    2016-12-01

    Full Text Available Rubber plates with different compositions and hardness were tested by continuous indentation, using a spherical punch and hysteretic phenomenon was evidenced. The experimental data interpolation with polynomial functions is accurate and permits estimation of the lost work during loading cycles. The interpolation by power law functions is more convenient by using less parameters and having a form accepted in literature. From the rubbers tested, two were considered to present good damping properties.

  15. Analysis of the equivalent indenter concept used to extract Young’s modulus from a nano-indentation test: some new insights into the Oliver–Pharr method

    DEFF Research Database (Denmark)

    Andriollo, Tito; Thorborg, Jesper; Hattel, Jesper Henri

    2017-01-01

    In this paper a thorough analysis of the equivalent indenter concept applied to nano-indentation is carried out, motivated by the fact that previous works in the field have not considered the requirement of a consistent relation between contact depth and projected contact area. Dimensional analys...

  16. Assessment of the Local Residual Stresses of 7050-T7452 Aluminum Alloy in Microzones by the Instrumented Indentation with the Berkovich Indenter

    Science.gov (United States)

    He, M.; Huang, C. H.; Wang, X. X.; Yang, F.; Zhang, N.; Li, F. G.

    2017-09-01

    The local residual stresses in microzones are investigated by the instrumented indentation method with the Berkovich indenter. The parameters required for determination of residual stresses are obtained from indentation load-penetration depth curves constructed during instrumented indentation tests on flat square 7050-T7452 aluminum alloy specimens with a central hole containing the compressive residual stresses generated by the cold extrusion process. The force balance system with account of the tensile and compressive residual stresses is used to explain the phenomenon of different contact areas produced by the same indentation load. The effect of strain-hardening exponent on the residual stress is tuned-off by application of the representative stress σ_{0.033} in the average contact pressure assessment using the Π theorem, while the yield stress value is obtained from the constitutive function. Finally, the residual stresses are calculated according to the proposed equations of the force balance system, and their feasibility is corroborated by the XRD measurements.

  17. Assessment of the Local Residual Stresses of 7050-T7452 Aluminum Alloy in Microzones by the Instrumented Indentation with the Berkovich Indenter

    Science.gov (United States)

    He, M.; Huang, C. H.; Wang, X. X.; Yang, F.; Zhang, N.; Li, F. G.

    2017-10-01

    The local residual stresses in microzones are investigated by the instrumented indentation method with the Berkovich indenter. The parameters required for determination of residual stresses are obtained from indentation load-penetration depth curves constructed during instrumented indentation tests on flat square 7050-T7452 aluminum alloy specimens with a central hole containing the compressive residual stresses generated by the cold extrusion process. The force balance system with account of the tensile and compressive residual stresses is used to explain the phenomenon of different contact areas produced by the same indentation load. The effect of strain-hardening exponent on the residual stress is tuned-off by application of the representative stress σ_{0.033} in the average contact pressure assessment using the Π theorem, while the yield stress value is obtained from the constitutive function. Finally, the residual stresses are calculated according to the proposed equations of the force balance system, and their feasibility is corroborated by the XRD measurements.

  18. On the relationship between indentation hardness and modulus, and the damage resistance of biological materials.

    Science.gov (United States)

    Labonte, David; Lenz, Anne-Kristin; Oyen, Michelle L

    2017-07-15

    The remarkable mechanical performance of biological materials is based on intricate structure-function relationships. Nanoindentation has become the primary tool for characterising biological materials, as it allows to relate structural changes to variations in mechanical properties on small scales. However, the respective theoretical background and associated interpretation of the parameters measured via indentation derives largely from research on 'traditional' engineering materials such as metals or ceramics. Here, we discuss the functional relevance of indentation hardness in biological materials by presenting a meta-analysis of its relationship with indentation modulus. Across seven orders of magnitude, indentation hardness was directly proportional to indentation modulus. Using a lumped parameter model to deconvolute indentation hardness into components arising from reversible and irreversible deformation, we establish criteria which allow to interpret differences in indentation hardness across or within biological materials. The ratio between hardness and modulus arises as a key parameter, which is related to the ratio between irreversible and reversible deformation during indentation, the material's yield strength, and the resistance to irreversible deformation, a material property which represents the energy required to create a unit volume of purely irreversible deformation. Indentation hardness generally increases upon material dehydration, however to a larger extent than expected from accompanying changes in indentation modulus, indicating that water acts as a 'plasticiser'. A detailed discussion of the role of indentation hardness, modulus and toughness in damage control during sharp or blunt indentation yields comprehensive guidelines for a performance-based ranking of biological materials, and suggests that quasi-plastic deformation is a frequent yet poorly understood damage mode, highlighting an important area of future research. Instrumented

  19. A method to separate and quantify the effects of indentation size, residual stress and plastic damage when mapping properties using instrumented indentation

    Science.gov (United States)

    Hou, X. D.; Jennett, N. M.

    2017-11-01

    Instrumented indentation is a convenient and increasingly rapid method of high resolution mapping of surface properties. There is, however, significant untapped potential for the quantification of these properties, which is only possible by solving a number of serious issues that affect the absolute values for mechanical properties obtained from small indentations. The three most pressing currently are the quantification of: the indentation size effect (ISE), residual stress, and pile-up and sink-in—which is itself affected by residual stress and ISE. Hardness based indentation mapping is unable to distinguish these effects. We describe a procedure that uses an elastic modulus as an internal reference and combines the information available from an indentation modulus map, a hardness map, and a determination of the ISE coefficient (using self-similar geometry indentation) to correct for the effects of stress, pile up and the indentation size effect, to leave a quantified map of plastic damage and grain refinement hardening in a surface. This procedure is used to map the residual stress in a cross-section of the machined surface of a previously stress free metal. The effect of surface grinding is compared to milling and is shown to cause different amounts of work hardening, increase in residual stress, and surface grain size reduction. The potential use of this procedure for mapping coatings in cross-section is discussed.

  20. EVALUATION OF METALLIC MATERIALS PLASTICITY BY DYNAMIC INDENTATION METHOD

    Directory of Open Access Journals (Sweden)

    V. A. Rudnitsky

    2017-01-01

    Full Text Available The method of plasticity test of metallic materials realized by means of a dynamic dimpling of material by a spherical tip is offered. The measured value of plasticity is defined by a ratio of plastic and complete deformations in the formed indentation which considers influence of an elastic modulus of material. The dependence connecting plasticity and dynamic hardness of materials is received. Experiments on metals from 70 to 380 GPA having an elastic modulus and hardness up to 62 HRC are made.

  1. Evaluation of fracture toughness in dental ceramics using indentation and SEVNB (Single Edge V-Notched Beam)-method; Avaliacao da tenacidade a fratura de ceramicas dentarias atraves do metodo de entalhe - SEVNB (Single Edge V-Notched Beam)

    Energy Technology Data Exchange (ETDEWEB)

    Santos, L.A.; Santos, C.; Souza, R.C.; Ribeiro, S. [Universidade de Sao Paulo (DEMAR/EEL/USP), Lorena, SP (Brazil). Escola de Engenharia de Lorena. Dept. de Engenharia de Materiais. Polo Urbo-Industrial; Strecker, K. [Universidade Federal de Sao Joao del-Rei (DME/UFSJ), MG (Brazil). Dept. de Materiais Eletricos; Oberacker, R. [Karlsruhe Univ. (Germany)

    2009-07-01

    In this work, the fracture toughness of different ceramics based on Al{sub 2}O{sub 3} and ZrO{sub 2} were evaluated using, comparatively two methods, Vickers indentation and SEVNB (Single Edge V-Notched Beam) method. Al{sub 2}O{sub 3}, ZrO{sub 2}(3%Y{sub 2}O{sub 3}) micro-particled and ZrO{sub 2}(3%Y{sub 2}O{sub 3}) nanometric, ZrO{sub 2}-Al{sub 2}O{sub 3} and Al{sub 2}O{sub 3}-ZrO{sub 2} composites were sintered at different temperatures. Samples were characterized by relative density, X-ray diffraction, SEM, and mechanical evaluation by hardness, bending strength and fracture toughness obtained by ickers indentation and SEVNB-method. The results were presented comparing the densification and microstructural results. Furthermore, the advantages and limitations of each method were discussed. (author)

  2. Microstructural evolution of Ti-10Nb and Ti-15Nb alloys produced by the blended elemental technique

    Energy Technology Data Exchange (ETDEWEB)

    Martins, G.V.; Souza, J.V.C.; Machado, J.P.B., E-mail: givmartins@yahoo.com.br, E-mail: vitor@las.inpe.br, E-mail: joaopaulo@las.inpe.br [Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP (Brazil); Silva, C.R.M. [Universidade de Brasilia (UnB), Brasilia, DF (Brazil); Henriques, V.A.R., E-mail: vinicius@iae.cta.br [Instituto de Aeronautica e Espaco (DCTA/IAE/AMR), Sao Jose dos Campos, SP (Brazil). Centro Tecnico Aeroespacial; Borges Junior, L.A., E-mail: borges.jr@itelefonica.com.br [Centro Universitario de Volta Redonda (UNIFOA), Volta Redonda, RJ (Brazil)

    2009-07-01

    Alfa/beta titanium alloys have been intensely used for aerospace and biomedical applications. Production of powder metallurgy titanium alloys components may lead to a reduction in the cost of parts, compared to those produced by conventional cast and wrought (ingot metallurgy) processes, because additional working operations (machining, turning, milling, etc.) and material waste can be avoided. In this work, samples of Ti- 10, 15Nb (weight%) alloys were obtained by the blended elemental technique using hydride-de hydride (HDH) powders as raw material, followed by uniaxial and cold isostatic pressing with subsequent densification by sintering carried out in the range 900-1500 deg C. These alloys were characterized by X-ray diffractometry for phase composition, scanning electron microscopy for microstructure, Vickers indentation for hardness, Archimedes method for specific mass and resonance ultrasound device for elastic modulus. For the samples sintered at 1500 deg C it was identified α and β phases. It was observed the influence of the sintering temperatures on the final microstructure. With increasing sintering temperature, microstructure homogenization of the alloy takes place and at 1500 deg C this process is complete. The same behavior is observed for densification. Comparing to the Ti6Al4V alloy properties, these alloys hardness (sintered at 1500 deg C) are near and elastic modulus are 18% less. (author)

  3. Indentation analysis of active viscoelastic microplasmodia of P. polycephalum

    Science.gov (United States)

    Fessel, Adrian; Oettmeier, Christina; Wechsler, Klaus; Döbereiner, Hans-Günther

    2018-01-01

    Simple organisms like Physarum polycephalum realize complex behavior, such as shortest path optimization or habituation, via mechanochemical processes rather than by a network of neurons. A full understanding of these phenomena requires detailed investigation of the underlying mechanical properties. To date, micromechanical measurements on P. polycephalum are sparse and lack reproducibility. This prompts study of microplasmodia, a reproducible and homogeneous form of P. polycephalum that resembles the plasmodial ectoplasm responsible for mechanical stability and generation of forces. We combine investigation of ultra-structure and dimension of P. polycephalum with the analysis of data obtained by indentation of microplasmodia, employing a novel nonlinear viscoelastic scaling model that accounts for finite dimension of the sample. We identify the multi-modal distribution of parameters such as Young’s moduls, Poisson’s ratio, and relaxation times associated with viscous processes that cover five orders of magnitude. Results suggest a characterization of microplasmodia as porous, compressible structures that act like elastic solids with high Young’s modulus on short time scales, whereas on long time-scales and upon repeated indentation viscous behavior dominates and the effective modulus is significantly decreased. Furthermore, Young’s modulus is found to oscillate in phase with shape of microplasmodia, emphasizing that modeling P. polycephalum oscillations as a driven oscillator with constant moduli is not practicable.

  4. Quantitative Hardness Measurement by Instrumented AFM-indentation.

    Science.gov (United States)

    Caron, Arnaud

    2016-11-22

    In this work, a combination of amplitude-modulated non-contact atomic force microscopy and atomic force spectroscopy is applied for instrumented hardness measurements on an Au(111) surface with atomistic resolution of single plasticity events. A careful experimental procedure is described that includes the force sensor selection, its calibration, the calibration of the cantilever deflection detection system, and the minimization of instrumental drift for accurate and reproducible force-distance measurements. Also, a method for the data analysis is presented that allows the extraction of force-penetration curves from recorded force-distance curves. A typical curve displays a clear elastic deformation regime up to the first plasticity event, or pop-in, with a length in the range of one to two Burger's vectors. Later plasticity events exhibit the same magnitude. The work of plasticity is further extracted from the measurements. Finally, the hardness is determined in combination with the indentation curve using non-contact atomic force microscopy images of the remaining indents.

  5. Phase Transformation of Metastable Austenite in Steel during Nano indentation

    Energy Technology Data Exchange (ETDEWEB)

    Ahn, Taehong [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Lee, Sung Bo; Han, Heung Nam [Seoul National Univ., Seoul (Korea, Republic of); Park, Kyungtae [Hanbat National Univ., Daejeon (Korea, Republic of)

    2013-05-15

    These can produce geometrical softening accompanied by a sudden displacement excursion during load-controlled nanoindentation, which referred to in the literature as a pop-in. In this study, phase transformation of metastable austenite to stress-induced ε martensite which causes pop-ins during nanoindentation of steel will be reported and discussed. This study investigated the relationship between pop-in behavior of austenite in the early stage of nanoindentation and formation of ε martensite based on microstructural analyses. The load-displacement curve obtained from nanoindentation revealed stepwise pop-ins in the early stage of plastic deformation. From analyses of high resolution TEM images, a cluster of banded structure under the indent turned out a juxtaposition of (111) planes of γ austenite and (0001) planes of ε martensite. The calculation of displacement along indentation axis for (111) slip system by formation of ε martensite showed that geometrical softening can also occur by ε martensite formation when considering that the stress-induced ε martensite transformation is the predominant deformation mode in the early stage of plastic deformation and its monopartial nature as well. These microstructural investigations strongly suggest that the pop-in behavior in the early stage of plastic deformation of austenite is closely related to the formation of ε martensite.

  6. Endplate indentation of the fourth lumbar vertebra - biomed 2010.

    Science.gov (United States)

    Ash, Joseph H; Kerrigan, Jason R; Arregui-Dalmases, Carlos; Del Pozo, Eduardo; Crandall, Jeff

    2010-01-01

    This study presents the results of indentation tests on the superior vertebral endplate of the 4th lumbar vertebra (L4) of eleven male cadaveric subjects (65 +/- 7 years). Three locations on the superior endplate surface were loaded with a 7.9 mm spherical indentor at either a low (1 mm/s) or high (1000 mm/s) rate. Anterior midline and posterior right and left indentation locations were chosen to prevent local deformations and fractures from influencing the results of subsequent and preceding tests. Peak forces were higher in the dynamic tests (498 +/- 261 N) than in the quasi-static tests (451 +/- 256 N) on the posterior side, although the difference was not significant (p = 0.139). However, the peak forces in the anterior tests (304 +/-166 N) were significantly lower (p =0.0157) than in the posterior tests with the same loading rate. The variation in failure forces in the current study correlates with the variation in thickness of endplate cortical bone (between specimens and between anterior and posterior locations on the same specimen) as measured from small field of view computed tomography scans.

  7. Quasi-Static Indentation Analysis of Carbon-Fiber Laminates.

    Energy Technology Data Exchange (ETDEWEB)

    Briggs, Timothy [Sandia National Lab. (SNL-CA), Livermore, CA (United States); English, Shawn Allen [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Nelson, Stacy Michelle [Sandia National Lab. (SNL-CA), Livermore, CA (United States)

    2015-12-01

    A series of quasi - static indentation experiments are conducted on carbon fiber reinforced polymer laminates with a systematic variation of thicknesses and fixture boundary conditions. Different deformation mechanisms and their resulting damage mechanisms are activated b y changing the thickn ess and boundary conditions. The quasi - static indentation experiments have been shown to achieve damage mechanisms similar to impact and penetration, however without strain rate effects. The low rate allows for the detailed analysis on the load response. Moreover, interrupted tests allow for the incremental analysis of various damage mechanisms and pr ogressions. The experimentally tested specimens are non - destructively evaluated (NDE) with optical imaging, ultrasonics and computed tomography. The load displacement responses and the NDE are then utilized in numerical simulations for the purpose of model validation and vetting. The accompanying numerical simulation work serves two purposes. First, the results further reveal the time sequence of events and the meaning behind load dro ps not clear from NDE . Second, the simulations demonstrate insufficiencies in the code and can then direct future efforts for development.

  8. Influence of the final temperature of investment healting on the tensile strength and Vickers hardness of CP Ti and Ti-6Al-4V alloy

    Directory of Open Access Journals (Sweden)

    Pedro César Garcia Oliveira

    2007-02-01

    Full Text Available The aim of the work was to evaluate the influence of the temperature of investment healting on the tensile strength and Vickers hardness of CP Ti and Ti-6Al-4V alloy casting. Were obtained for the tensile strength test dumbbell rods that were invested in the Rematitan Plus investment and casting in the Discovery machine cast. Thirty specimens were obtained, fiftten to the CP Titanium and fifteen to the Ti-6Al-4V alloy, five samples to each an of the three temperatures of investment: 430ºC (control group, 480ºC and 530ºC. The tensile test was measured by means of a universal testing machine, MTS model 810, at a strain of 1.0 mm/min. After the tensile strenght test the specimens were secctioned, embedded and polished to hardness measurements, using a Vickers tester, Micromet 2100. The means values to tensile tests to the temperatures 430ºC, 480 and 530: CP Ti (486.1 - 501.16 - 498.14 -mean 495.30 MPa and Ti-6Al-4V alloy (961.33 - 958.26 - 1005.80 - mean 975.13 MPa while for the Vickers hardness the values were (198.06, 197.85, 202.58 - mean 199.50 and (352.95, 339.36, 344.76 - mean 345.69, respectively. The values were submitted to Analysis of Variance (ANOVA and Tukey,s Test that indicate differences significant only between the materials, but not between the temperature, for both the materias. It was conclued that increase of the temperature of investment its not chance the tensile strength and the Vickers hardness of the CP Titanium and Ti-6Al-4V alloy.

  9. Analysis of the equivalent indenter concept used to extract Young’s modulus from a nano-indentation test: some new insights into the Oliver-Pharr method

    Science.gov (United States)

    Andriollo, Tito; Thorborg, Jesper; Hattel, Jesper

    2017-06-01

    In this paper a thorough analysis of the equivalent indenter concept applied to nano-indentation is carried out, motivated by the fact that previous works in the field have not considered the requirement of a consistent relation between contact depth and projected contact area. Dimensional analysis is initially used to prove that the shape of the axisymmetric equivalent indenter can be regarded as a material property, provided that size-effects are negligible. Subsequently, it is shown that such shape can effectively be employed to describe the nano-indentation unloading stage by means of Sneddon's elastic solution which is formally valid only for indentation into a flat surface. This allows for formulating the problem of extracting Young's modulus from the unloading curve as an optimization problem. However, it is proved that the latter does not have a unique solution, due to the particular mathematical structure of the underlying equations; hence, additional constraints are needed to set restrictions on the admissible equivalent indenter shapes. An example of such constraint is hidden in some apparent inconsistencies of the well-known Oliver-Pharr method, which is demonstrated to be based on an equivalent conical indenter whose semi-apical angle depends on the ratio between residual and total penetration. Specifically, this angle tends to 90° when the material exhibits extensive inelastic deformation, whereas it reduces to the one characteristic of the real indenter for a perfectly elastic material. This provides a new physical explanation for the relatively good accuracy of the method even in presence of a non-negligible residual contact impression on the sample.

  10. Residual Stress State in Single-Edge Notched Tension Specimen Caused by the Local Compression Technique

    Directory of Open Access Journals (Sweden)

    Huang Yifan

    2016-12-01

    Full Text Available Three-dimensional (3D finite element analyses (FEA are performed to simulate the local compression (LC technique on the clamped single-edge notched tension (SE(T specimens. The analysis includes three types of indenters, which are single pair of cylinder indenters (SPCI, double pairs of cylinder indenters (DPCI and single pair of ring indenters (SPRI. The distribution of the residual stress in the crack opening direction in the uncracked ligament of the specimen is evaluated. The outcome of this study can facilitate the use of LC technique on SE(T specimens.

  11. Investigation on hardening behavior of metallic glass under cyclic indentation loading via molecular dynamics simulation

    Science.gov (United States)

    Zhao, Dan; Zhao, Hongwei; Zhu, Bo; Wang, Shunbo

    2017-09-01

    Mechanical behavior of a Cu-Zr metallic glass (MG) under cyclic indentation loading is investigated via molecular dynamics simulation. A large-depth indentation after cycling is conducted, and the indentation curves show that hardening behavior occurs with cyclic indentation amplitudes exceeding elastic range. The atomic Von Mises shear strain distributions during the large-depth indentation are investigated, and the pre-existing plastic deformation induced by cyclic indentation is found to be the main contributor to the hardening behavior. By monitoring the atom trajectories and Voronoi atom volume, structure densification and free volume reduction phenomenon are found in the area beneath indenter after cycles. The accumulations of irreversible shear strain during cycling induce the area beneath indenter experience atom structure transition and become densified, thus the sample becomes more resistant to further deformation. In addition, the effects of temperatures and loading rates on the hardening behavior are studied. With higher temperature, more homogenous deformation and plasticity are produced, and then inducing more severe hardening in the MG. While with lower loading rate, the hardening phenomenon is found to be less severe because of the localization of shear strain during cycling.

  12. Delamination of a strong film from a ductile substrate during indentation unloading

    NARCIS (Netherlands)

    Abdul-Baqi, A.; van der Giessen, E.

    2001-01-01

    In this work, a finite element method was performed to simulate the spherical indentation of a ductile substrate coated by a strong thin film. Our objective was to study indentation-induced delamination of the film from the substrate. The film was assumed to be linear elastic, the substrate was

  13. Indentations and Starting Points in Traveling Sales Tour Problems: Implications for Theory

    Science.gov (United States)

    MacGregor, James N.

    2012-01-01

    A complete, non-trivial, traveling sales tour problem contains at least one "indentation", where nodes in the interior of the point set are connected between two adjacent nodes on the boundary. Early research reported that human tours exhibited fewer such indentations than expected. A subsequent explanation proposed that this was because…

  14. Quasi-static indentation modelling of aluminium specimen using finite element analysis

    Directory of Open Access Journals (Sweden)

    Mayank Nirbhay

    2017-03-01

    Full Text Available The influence of different types of rigid hemispherical and conical indenters on a rectangular specimen of aluminium has been investigated, in the small indenter test. A 3-D finite-element FE model was used to carry out the computation of the elastic-plastic solution of different rigid hemispherical and conical indenters. Three hemispherical-headed and four conical-headed indenters were designed and developed for testing. FE software ABAQUS® has been used to determine the load vs. indenter-displacement curves, reaction forces, deformation contours and Von-Mises stresses. The FE model was validated by comparing the results with the experimental data received from the Hertz Contact Theory and was found to be in reasonably good agreement.

  15. Topographic evolution of a continental indenter: The eastern Southern Alps

    Science.gov (United States)

    Robl, Jörg; Heberer, Bianca; Prasicek, Günther; Neubauer, Franz; Hergarten, Stefan

    2017-04-01

    The topographic evolution of the eastern Southern Alps (ESA) is controlled by the Late Oligocene - Early Miocene indentation of the Adriatic microplate into an overthickened orogenic wedge emplaced on top of the European plate. Rivers follow topographic gradients that evolve during continental collision and in turn incise into bedrock counteracting the formation of topography. In principle, erosional surface processes tend to establish a topographic steady state so that an interpretation of topographic metrics in terms of the latest tectonic history should be straightforward. However, a series of complications impede deciphering the topographic record of the ESA. The Pleistocene glaciations locally excavated alpine valleys and perturbed fluvial drainages. The Late Miocene desiccation of the Mediterranean Sea and the uplift of the northern Molasse Basin led to significant base level changes in the far field of the ESA and the Eastern Alps (EA), respectively. Among this multitude of mechanisms, the processes that dominate the current topographic evolution of the ESA and the ESA-EA drainage divide have not been identified and a number of questions regarding the interaction of crustal deformation, erosion and climate in shaping the present-day topography remain. We demonstrate the expected topographic effects of each mechanism in a 1-dimensional model and compare them with observed channel metrics. Modern uplift rates are largely consistent with long-term exhumation in the ESA and with variations in the normalized steepness index (ksn) indicating a stable uplift and erosion pattern since Miocene times. We find that ksn increases with uplift rate and declines from the indenter tip in the northwest to the foreland basin in the southeast. The number and magnitude of knickpoints and the distortion in longitudinal channel profiles similarly decrease towards the east. Most knickpoints probably evolved during Pleistocene glaciation cycles, but may represent the incrementally

  16. Manual, In situ, Real-Time Nanofabrication using Cracking through Indentation

    Science.gov (United States)

    Nam, Koo Hyun; Suh, Young D.; Yeo, Junyeob; Woo, Deokha

    2016-01-01

    Nanofabrication has seen an increasing demand for applications in many fields of science and technology, but its production still requires relatively difficult, time-consuming, and expensive processes. Here we report a simple but very effective one dimensional (1D) nano-patterning technology that suggests a new nanofabrication method. This new technique involves the control of naturally propagating cracks initiated through simple, manually generated indentation, obviating the necessity of complicated equipment and elaborate experimental environments such as those that employ clean rooms, high vacuums, and the fastidious maintenance of processing temperatures. The channel fabricated with this technique can be as narrow as 10 nm with unlimited length and very high cross-sectional aspect ratio, an accomplishment difficult even for a state-of-the-art technology such as e-beam lithography. More interestingly, the fabrication speed can be controlled and achieved to as little as several hundred micrometers per second. Along with the simplicity and real-time fabrication capability of the technique, this tunable fabrication speed makes the method introduced here the authentic nanofabrication for in situ experiments.

  17. Effects of Crystalline Anisotropy and Indenter Size on Nanoindentation by Multiscale Simulation

    Directory of Open Access Journals (Sweden)

    Li Junwan

    2009-01-01

    Full Text Available Abstract Nanoindentation processes in single crystal Ag thin film under different crystallographic orientations and various indenter widths are simulated by the quasicontinuum method. The nanoindentation deformation processes under influences of crystalline anisotropy and indenter size are investigated about hardness, load distribution, critical load for first dislocation emission and strain energy under the indenter. The simulation results are compared with previous experimental results and Rice-Thomson (R-T dislocation model solution. It is shown that entirely different dislocation activities are presented under the effect of crystalline anisotropy during nanoindentation. The sharp load drops in the load–displacement curves are caused by the different dislocation activities. Both crystalline anisotropy and indenter size are found to have distinct effect on hardness, contact stress distribution, critical load for first dislocation emission and strain energy under the indenter. The above quantities are decreased at the indenter into Ag thin film along the crystal orientation with more favorable slip directions that easy trigger slip systems; whereas those will increase at the indenter into Ag thin film along the crystal orientation with less or without favorable slip directions that hard trigger slip systems. The results are shown to be in good agreement with experimental results and R-T dislocation model solution.

  18. Simultaneous estimation of Poisson's ratio and Young's modulus using a single indentation: a finite element study

    Science.gov (United States)

    Zheng, Y. P.; Choi, A. P. C.; Ling, H. Y.; Huang, Y. P.

    2009-04-01

    Indentation is commonly used to determine the mechanical properties of different kinds of biological tissues and engineering materials. With the force-deformation data obtained from an indentation test, Young's modulus of the tissue can be calculated using a linear elastic indentation model with a known Poisson's ratio. A novel method for simultaneous estimation of Young's modulus and Poisson's ratio of the tissue using a single indentation was proposed in this study. Finite element (FE) analysis using 3D models was first used to establish the relationship between Poisson's ratio and the deformation-dependent indentation stiffness for different aspect ratios (indentor radius/tissue original thickness) in the indentation test. From the FE results, it was found that the deformation-dependent indentation stiffness linearly increased with the deformation. Poisson's ratio could be extracted based on the deformation-dependent indentation stiffness obtained from the force-deformation data. Young's modulus was then further calculated with the estimated Poisson's ratio. The feasibility of this method was demonstrated in virtue of using the indentation models with different material properties in the FE analysis. The numerical results showed that the percentage errors of the estimated Poisson's ratios and the corresponding Young's moduli ranged from -1.7% to -3.2% and 3.0% to 7.2%, respectively, with the aspect ratio (indentor radius/tissue thickness) larger than 1. It is expected that this novel method can be potentially used for quantitative assessment of various kinds of engineering materials and biological tissues, such as articular cartilage.

  19. Influence of strain gradients on lattice rotation in nano-indentation experiments: A numerical study

    KAUST Repository

    Demiral, Murat

    2014-07-01

    In this paper the texture evolution in nano-indentation experiments was investigated numerically. To achieve this, a three-dimensional implicit finite-element model incorporating a strain-gradient crystal-plasticity theory was developed to represent accurately the deformation of a body-centred cubic metallic material. A hardening model was implemented to account for strain hardening of the involved slip systems. The surface topography around indents in different crystallographic orientations was compared to corresponding lattice rotations. The influence of strain gradients on the prediction of lattice rotations in nano-indentation was critically assessed. © 2014 Elsevier B.V..

  20. Modelling of excavation depth and fractures in rock caused by tool indentation

    Energy Technology Data Exchange (ETDEWEB)

    Kou Shaoquan; Tan Xiangchun; Lindqvist, P.A. [Luleaa Univ. of Technology (Sweden)

    1997-10-01

    The hydraulic regime after excavation in the near-field rock around deposition holes and deposition tunnels in a spent nuclear fuel repository is of concern for prediction of the saturation process of bentonite buffer and tunnel backfill. The hydraulic condition of main interest in this context is a result of the fracture network that is caused by the excavation. Modelling of the excavation disturbed zone in hard rocks caused by mechanical excavation has been carried out in the Division of Mining Engineering since 1993. This report contains an overview of the work conducted. The mechanical excavation is reasonably simplified as an indentation process of the interaction between rigid indenters and rocks. A large number of experiments have been carried out in the laboratory, and the results used for identifying crushed zones and fracture systems in rock under indentation are presented based on these experiments. The indentation causes crushing and damage of the rock and results in a crushed zone and a cracked zone. The indenter penetrates the rock with a certain depth when the force is over a threshold value relevant to the rock and tool. Outside the cracked zone there are basically three systems of cracks: median cracks, radial cracks, and side cracks. Fully developed radial cracks on each side of the indented area can connect with each other and join with median crack. This forms the so-called radial/median crack system. The influence of the mechanical properties of the rock is discussed based on our conceptual model, and the main factors governing the indentation event are summarised. The cracked zone is dealt with by an analytical fracture model. The side crack is simulated by applying the boundary element method coupled with fracture mechanics. Functional relationships are established relating either the indentation depth or the length of radial/median cracks to the various quantities characterising the physical event, namely the shape and the size of the

  1. Anterior chamber angle opening during corneoscleral indentation: the mechanism of whole eye globe deformation and the importance of the limbus.

    Science.gov (United States)

    Amini, Rouzbeh; Barocas, Victor H

    2009-11-01

    To determine how mechanical interaction among iris, cornea, limbus, sclera, and IOP contribute to angle opening during indentation of the cornea or sclera. A finite-element model of the globe was developed. The model consisted of three elastic isotropic segments--iris, cornea, and sclera--and a two-component anisotropic segment representing the limbus. The model was tested against published in vitro experiments and then applied to angle opening during indentation in vivo. Indentation of the central cornea with a cotton bud, indentation with a small or large eyecup during ultrasound biomicroscopy, indentation with a gonioscopy lens, and scleral indentation during goniosynechialysis were modeled. The anisotropic limbus model matched published data better than any isotropic model. Simulation of all clinical cases gave results in agreement with published observations. The model predicted angle opening during indentation by a cotton bud or small eyecup but angle narrowing when the sclera was indented by a large eyecup. The model of indentation gonioscopy showed narrowing of the angle on the indentation side and opening of the angle on the opposite side. Nonuniform opening of the angle was predicted when the scleral surface was indented. The two-component model of the stiff fibers embedded in a soft matrix captured the mechanical properties of the complex limbal region effectively. The success of this model suggests that, at least in part, corneoscleral mechanics drive angle opening rather than aqueous humor pressurization.

  2. Mechanophore activation in a crosslinked polymer matrix via instrumented indentation

    Science.gov (United States)

    Davis, Chelsea; Woodcock, Jeremiah; Beams, Ryan; Wang, Muzhou; Stranick, Stephan; Forster, Aaron; Gilman, Jeffrey

    Recent advances in mechanically-activated fluorophores will enable a host of unique scientific challenges and opportunities to be addressed. Several mechanophores (MPs) in polymers have been reported, yet the specific deformation required to activate these molecules in a bulk polymer network has not been sufficiently specified. In an effort to develop the mechano-activation/deformation relationship of a spirolactam-based MP, scratches were applied to a MP-functionalized glassy crosslinked material at varying normal loads and lateral displacement rates. This experimental design allowed strain and strain rate effects to be decoupled. The fluorescence activation was then observed. Areas of elastic and plastic deformation as well as brittle fracture were observed within each scratch as the normal loading of the indenter increased. The fluorescence intensity increased while the fluorescence lifetime decreased with increasing strain. Hyperspectral imaging revealed that the peak emission wavelength remained constant in the damage zone relative to the undeformed material. Contact mechanics models are employed to demonstrate that relatively high degrees of strain are required to initiate the ring-opening activation transition within the spirolactam-based MP. These self-reporting damage sensors can be incorporated within polymeric coatings to allow real time structural health monitoring for a myriad of applications.

  3. Bone indentation recovery time correlates with bond reforming time

    Science.gov (United States)

    Thompson, James B.; Kindt, Johannes H.; Drake, Barney; Hansma, Helen G.; Morse, Daniel E.; Hansma, Paul K.

    2001-12-01

    Despite centuries of work, dating back to Galileo, the molecular basis of bone's toughness and strength remains largely a mystery. A great deal is known about bone microsctructure and the microcracks that are precursors to its fracture, but little is known about the basic mechanism for dissipating the energy of an impact to keep the bone from fracturing. Bone is a nanocomposite of hydroxyapatite crystals and an organic matrix. Because rigid crystals such as the hydroxyapatite crystals cannot dissipate much energy, the organic matrix, which is mainly collagen, must be involved. A reduction in the number of collagen cross links has been associated with reduced bone strength and collagen is molecularly elongated (`pulled') when bovine tendon is strained. Using an atomic force microscope, a molecular mechanistic origin for the remarkable toughness of another biocomposite material, abalone nacre, has been found. Here we report that bone, like abalone nacre, contains polymers with `sacrificial bonds' that both protect the polymer backbone and dissipate energy. The time needed for these sacrificial bonds to reform after pulling correlates with the time needed for bone to recover its toughness as measured by atomic force microscope indentation testing. We suggest that the sacrificial bonds found within or between collagen molecules may be partially responsible for the toughness of bone.

  4. Indentation metrology of clamped, ultra-thin elastic sheets.

    Science.gov (United States)

    Vella, Dominic; Davidovitch, Benny

    2017-03-15

    We study the indentation of ultrathin elastic sheets clamped to the edge of a circular hole. This classical setup has received considerable attention lately, being used by various experimental groups as a probe to measure the surface properties and stretching modulus of thin solid films. Despite the apparent simplicity of this method, the geometric nonlinearity inherent in the mechanical response of thin solid objects renders the analysis of the resulting data a nontrivial task. Importantly, the essence of this difficulty is in the geometric coupling between in-plane stress and out-of-plane deformations, and hence is present in the behaviour of Hookean solids even when the slope of the deformed membrane remains small. Here we take a systematic approach to address this problem, using the membrane limit of the Föppl-von-Kármán equations. This approach highlights some of the dangers in the use of approximate formulae in the metrology of solid films, which can introduce large errors; we suggest how such errors may be avoided in performing experiments and analyzing the resulting data.

  5. Harder than Diamond: Superior Indentation Strength of Wurtzite BN and Lonsdaleite

    Science.gov (United States)

    Pan, Zicheng; Sun, Hong; Zhang, Yi; Chen, Changfeng

    2009-02-01

    Recent indentation experiments indicate that wurtzite BN (w-BN) exhibits surprisingly high hardness that rivals that of diamond. Here we unveil a novel two-stage shear deformation mechanism responsible for this unexpected result. We show by first-principles calculations that large normal compressive pressures under indenters can compel w-BN into a stronger structure through a volume-conserving bond-flipping structural phase transformation during indentation which produces significant enhancement in its strength, propelling it above diamond’s. We further demonstrate that the same mechanism also works in lonsdaleite (hexagonal diamond) and produces superior indentation strength that is 58% higher than the corresponding value of diamond, setting a new record.

  6. The effect of crystal orientation on the indentation response of commercially pure titanium: experiments and simulations

    National Research Council Canada - National Science Library

    T. B. Britton; H. Liang; F. P. E. Dunne; A. J. Wilkinson

    2010-01-01

    ...; the plastic response showing the more marked anisotropy. Recently developed high angular resolution EBSD has been utilized to examine selected indents, providing maps of elastic strain variations and lattice rotations...

  7. On the Measurement of Power Law Creep Parameters from Instrumented Indentation

    Science.gov (United States)

    Sudharshan Phani, P.; Oliver, W. C.; Pharr, G. M.

    2017-11-01

    Recently the measurement of the creep response of materials at small scales has received renewed interest largely because the equipment required to perform high-temperature nanomechanical testing has become available to an increasing number of researchers. Despite that increased access, there remain several significant experimental and modeling challenges in small-scale mechanical testing at elevated temperatures that are as yet unresolved. In this regard, relating the creep response observed with high-temperature instrumented indentation experiments to macroscopic uniaxial creep response is of great practical value. In this review, we present an overview of various methods currently being used to measure creep with instrumented indentation, with a focus on geometrically self-similar indenters, and their relative merits and demerits from an experimental perspective. A comparison of the various methods to use those instrumented indentation results to predict the uniaxial power law creep response of a wide range of materials will be presented to assess their validity.

  8. Finite Element Bond Modeling for Indented Wires in Pretensioned Concrete Crossties

    Science.gov (United States)

    2016-04-12

    Indented wires have been increasingly employed by : concrete crosstie manufacturers to improve the bond between : prestressing steel reinforcements and concrete, as bond can : affect several critical performance measures, including transfer : length,...

  9. Aqueous humour dynamics in anterior chamber under influence of cornea indentation

    Science.gov (United States)

    Zuhaila, I.; Jiann, L. Y.; Sharidan, S.; Fitt, A.

    2017-04-01

    The existing temperature different between the cornea and the pupil induces the aqueous humour (AH) to circulate in the anterior chamber (AC). The buoyancy forces produced by the temperature gradient has driven the AH to flow. Previous studies have shown that cornea indentation changes the structure of the AC. This imply that the cornea indentation may change the fluid flow behaviour in the AC. A mathematical model of AH flow has been developed in order to analyse the fluid mechanics concerning the indentation of the cornea. Naiver-Stokes equations is used to describe the flow of AH in the AC. The governing equations have been solved numerically using finite element method. The results show that the cornea indentation has slow down the circulation the AH in the AC.

  10. The Effect of the Vertex Angles of Wedged Indenters on Deformation during Nanoindentation

    Directory of Open Access Journals (Sweden)

    Xiaowen Hu

    2017-12-01

    Full Text Available In order to study the effect of the angle of wedged indenters during nanoindentation, indenters with half vertex angles of 60°, 70° and 80° are used for the simulations of nanoindentation on FCC aluminum (Al bulk material by the multiscale quasicontinuum method (QC. The load-displacement responses, the strain energy-displacement responses, and hardness of Al bulk material are obtained. Besides, atomic configurations for each loading situation are presented. We analyze the drop points in the load-displacement responses, which correspond to the changes of microstructure in the bulk material. From the atom images, the generation of partial dislocations as well as the nucleation and the emission of perfect dislocations have been observed with wedged indenters of half vertex angles of 60° and 70°, but not 80°. The stacking faults move beneath the indenter along the direction [ 1 1 ¯ 0 ] . The microstructures of residual displacements are also discussed. In addition, hardness of the Al bulk material is different in simulations with wedged indenters of half vertex angles of 60° and 70°, and critical hardness in the simulation with the 70° indenter is bigger than that with the 60° indenter. The size effect of hardness in plastic wedged nanoindentation is observed. There are fewer abrupt drops in the strain energy-displacement response than in the load-displacement response, and the abrupt drops in strain energy-displacement response reflect the nucleation of perfect dislocations or extended dislocations rather than partial dislocations. The wedged indenter with half vertex angle of 70° is recommended for investigating dislocations during nanoindentation.

  11. Evaluating the importance of the convex hull in solving the Euclidean version of the traveling salesperson problem: reply to Lee and Vickers (2000).

    Science.gov (United States)

    MacGregor, J N; Ormerod, T C

    2000-10-01

    Lee and Vickers (2000) suggest that the results of MacGregor and Ormerod (1996), showing that the response uncertainty to traveling salesperson problems (TSPs) increases with increasing numbers of nonboundary points, may have resulted as an artifact of constraints imposed in the construction of stimuli. The fact that similar patterns of results have been obtained for our "constrained" stimuli, for a stimulus constructed under different constraints, for 13 randomly generated stimuli, and for random and patterned 48-point problems provides empirical evidence that the results are not artifactual. Lee and Vickers further suggest that, even if not artifactual, the results are in principle limited to arrays of fewer than 50 points and that, beyond this, the total number of points and number of nonboundary points are "diagnostically equivalent." This claim seems to us incorrect, since arrays of any size can be constructed that will permit experimental tests of whether problem difficulty is influenced by the number of nonboundary points, or the total number of points, or both. We present a reanalysis of our original data using hierarchical regression analysis which indicates that both factors may influence problem complexity.

  12. Indentation response of a NiTi shape memory alloy: modeling and experiments

    Directory of Open Access Journals (Sweden)

    C. Maletta

    2012-07-01

    Full Text Available The indentation response of a pseudoelastic nickel-titanium based shape memory alloy (SMA has been analyzed. Indentation tests have been carried out at room temperature using a spherical diamond tip and indentation loads in the range 50-500 mN in order to promote a large stress-induced transformation zone in the indentation region and, consequently, to avoid local effects due to microstructural variations. The measured load-displacement data have been analyzed to obtain information on the pseudoelastic response of the alloy. To aid this analysis numerical simulations were performed, by using a commercial finite element (FE software code and a special constitutive model for SMAs, so as to understand better the microstructural evolution occurring during the indentation process. Finally, the FE model has been used to analyze the effects of temperature on the indentation response of the alloy. This analysis revealed a marked variation of both the maximum and residual penetration depths with increasing test temperature.

  13. Indentation Size Effect on Ag Nanoparticle-Modified Graphene/Sn-Ag-Cu Solders

    Science.gov (United States)

    Xu, L. Y.; Zhang, S. T.; Jing, H. Y.; Wang, L. X.; Wei, J.; Kong, X. C.; Han, Y. D.

    2018-01-01

    This paper presents the results for the indentation size effect (ISE) on the creep stress exponent and hardness of 0.03 wt.% Ag-modified graphene nanosheet Sn-Ag-Cu solder alloys, using constant loading/holding and multi-cycle (CMC) loading methods, respectively. At each maximum load, with increasing indentation depth, the creep exponent first decreased and then increased. At the same strain rate, the stress exponent also showed the same tendency, increasing as the indentation depth (peak load) increased and then decreased. The hardness was measured continuously with increasing indentation depth by the CMC loading method. The hardness did not exhibit a decrease as the indentation depth increased, which differs from the classical description of the ISE. After an initial decrease, the hardness then increased and finally decreased as the indentation depth increased. This study reviews the existing theories and formulations describing ISE with hardening effects. The experimental results fit well with the empirical formulation. The phenomenon of ISE accompanied by hardening effects has been explained physically via the interaction between geometrically necessary dislocations and grain boundaries.

  14. Indentation Size Effect on Ag Nanoparticle-Modified Graphene/Sn-Ag-Cu Solders

    Science.gov (United States)

    Xu, L. Y.; Zhang, S. T.; Jing, H. Y.; Wang, L. X.; Wei, J.; Kong, X. C.; Han, Y. D.

    2017-10-01

    This paper presents the results for the indentation size effect (ISE) on the creep stress exponent and hardness of 0.03 wt.% Ag-modified graphene nanosheet Sn-Ag-Cu solder alloys, using constant loading/holding and multi-cycle (CMC) loading methods, respectively. At each maximum load, with increasing indentation depth, the creep exponent first decreased and then increased. At the same strain rate, the stress exponent also showed the same tendency, increasing as the indentation depth (peak load) increased and then decreased. The hardness was measured continuously with increasing indentation depth by the CMC loading method. The hardness did not exhibit a decrease as the indentation depth increased, which differs from the classical description of the ISE. After an initial decrease, the hardness then increased and finally decreased as the indentation depth increased. This study reviews the existing theories and formulations describing ISE with hardening effects. The experimental results fit well with the empirical formulation. The phenomenon of ISE accompanied by hardening effects has been explained physically via the interaction between geometrically necessary dislocations and grain boundaries.

  15. Evaluation of sinking-in and cracking behavior of soda-lime glass under varying angle of trigonal pyramid indenter

    Directory of Open Access Journals (Sweden)

    Satoshi Yoshida

    2016-12-01

    Full Text Available It is well known that glass undergoes elastic and inelastic deformation under a sharp diamond indenter. Although brittle or less-brittle behavior of glass must be connected with such mechanical responses of glass under the indenter, there has been limited research on in-situ deformation behavior of glass during the loading and unloading indentation cycle. This is because most indentation tests were conducted using a commercial hardness tester for which this information is not available. In this study, the in-situ sinking-in region of glass during indentation test is determined using a custom-designed indentation microscope with trigonal pyramid indenters having different tip angles. It is found that both the shape of contact region and the amount of sinking-in are affected by indenter geometries, and that the projected contact region of the glass sample under Berkovich indenter is not a regular triangle, but a concave triangle with bowed-in edges. This is due to the larger amount of sinking-in under the face than under the ridge of indenter. It is also found that these deformation behaviors of glass are inseparably linked with contact damage or cracking in glass.

  16. On the origin of the mixed alkali effect on indentation in silicate glasses

    DEFF Research Database (Denmark)

    Kjeldsen, Jonas; Smedskjær, Morten Mattrup; Mauro, J. C.

    2014-01-01

    The compositional scaling of Vickers hardness (Hv) in mixed alkali oxide glasses manifests itself as a positive deviation from linearity as a function of the network modifier/modifier ratio, with a maximum deviation at the ratio of 1:1. In this work, we investigate the link between the indentatio...

  17. Mechanical characterization of soft materials using transparent indenter testing system and finite element simulation

    Science.gov (United States)

    Xuan, Yue

    Background. Soft materials such as polymers and soft tissues have diverse applications in bioengineering, medical care, and industry. Quantitative mechanical characterization of soft materials at multiscales is required to assure that appropriate mechanical properties are presented to support the normal material function. Indentation test has been widely used to characterize soft material. However, the measurement of in situ contact area is always difficult. Method of Approach. A transparent indenter method was introduced to characterize the nonlinear behaviors of soft materials under large deformation. This approach made the direct measurement of contact area and local deformation possible. A microscope was used to capture the contact area evolution as well as the surface deformation. Based on this transparent indenter method, a novel transparent indentation measurement systems has been built and multiple soft materials including polymers and pericardial tissue have been characterized. Seven different indenters have been used to study the strain distribution on the contact surface, inner layer and vertical layer. Finite element models have been built to simulate the hyperelastic and anisotropic material behaviors. Proper material constants were obtained by fitting the experimental results. Results.Homogeneous and anisotropic silicone rubber and porcine pericardial tissue have been examined. Contact area and local deformation were measured by real time imaging the contact interface. The experimental results were compared with the predictions from the Hertzian equations. The accurate measurement of contact area results in more reliable Young's modulus, which is critical for soft materials. For the fiber reinforced anisotropic silicone rubber, the projected contact area under a hemispherical indenter exhibited elliptical shape. The local surface deformation under indenter was mapped using digital image correlation program. Punch test has been applied to thin films of

  18. Effect of a post-polymerization treatments on the flexural strength and Vickers hardness of reline and acrylic denture base resins

    Directory of Open Access Journals (Sweden)

    Rosangela Seiko Seo

    2007-12-01

    Full Text Available This study evaluated the effect of water-bath and microwave post-polymerization treatments on the flexural strength and Vickers hardness of four autopolymerizing reline resins (Duraliner II-D, Kooliner-K, Tokuso Rebase Fast-TR and Ufi Gel Hard C-UGH and one heat-polymerized acrylic resin (Lucitone 550-L, processed using two polymerization cycles (short cycle - 90 minutes at 73ºC and 100ºC for 30 minutes; and long cycle - 9 hours at 71ºC. For each material, thirty specimens (64 x 10 x 3.3 mm were made and divided into 3 groups (n=10. Specimens were tested after: processing (control group; water-bath at 55ºC for 10 minutes (reline materials or 60 minutes (L; and microwave irradiation. Flexural strength tests were performed at a crosshead speed of 5 mm/min using a three-point bending device with a span of 50 mm. The flexural strengths values were calculated in MPa. One fragment of each specimen was submitted to Vickers hardness test. Data were analyzed by 2-way ANOVA followed by Tukey's HSD test (alpha=0.05. L microwaved specimens (short cycle exhibited significantly higher flexural strength means than its respective control group (p<0.05. Water-bath promoted a significant increase (p<0.05 in flexural strength of K and L (long cycle. The hardness of the tested materials was not influenced by the post-polymerization treatments. Post-polymerization treatments could be used to improve the flexural strength of some materials tested.

  19. Room-Temperature Indentation Creep and the Mechanical Properties of Rapidly Solidified Sn-Sb-Pb-Cu Alloys

    Science.gov (United States)

    Kamal, Mustafa; El-Bediwi, A.; Lashin, A. R.; El-Zarka, A. H.

    2016-05-01

    In this paper, we study the room-temperature indentation creep and the mechanical properties of Sn-Sb-Pb-Cu alloys. Rapid solidification from melt using the melt-spinning technique is applied to prepare all the alloys. The experimental results show that the magnitude of the creep displacement increases with the increase in both time and applied load, and the stress exponent increases with the increase in the copper content in the alloys which happens primarily due to the existence of the intermetallic compounds SbSn and Cu6Sn5. The calculated values of the stress exponent are in the range of 2.82 to 5.16, which are in good agreement with the values reported for the Sn-Sb-Pb-Cu alloys. We have also studied and analyzed the structure, elastic modulus, and internal friction of the Sn-Sb-Pb-Cu alloys.

  20. Modeling and analysis of ductility of brittle materials using indentation method

    Science.gov (United States)

    Sun, Guoyan; Lu, Zhe; Bai, Jianming; Yu, Fangsu

    2014-08-01

    Nowadays, many optical elements are fabricated by means of glass molding using hard and brittle inserts such as Silicon Carbide (SiC) and Silicon Nitride (Si3N4). However, for those hard-to-machine materials, the most feasible solution is still with ultra-precision grinding and following polishing. Hence, it is necessary and meaningful to study their plastic properties for the development of optical fabrication and ultra-precision manufacturing process. However, the conventional methods including compression test and indentation fracture mechanics are not sufficient to obtain the accurate parameters and still lack of reliable supporting of the machining process. To solve this problem, this paper presents a novel way to correlate the plastic properties to the indentation data using dimensional analysis for the two sorts of hard and brittle materials of SiC and Si3N4. Through integrating the data obtained by the indentation tests and the modeling method presented in this paper, stress-strain behavior, yield stress σy, yield strain epsilony and strain hardening exponent n could be determined. The processing performance of these two materials reflected by the above parameters are consistent with the conclusions drawing from the indentation crack development under varying loads during the indentation test, which verifies the effectiveness and feasibility of the presented modeling method.

  1. A Comparison of Quasi-Static Indentation Testing to Low Velocity Impact Testing

    Science.gov (United States)

    Nettles, Alan T.; Douglas, Michael J.

    2001-01-01

    The need for a static test method for modeling low-velocity foreign object impact events to composites would prove to be very beneficial to researchers since much more data can be obtained from a static test than from an impact test. In order to examine if this is feasible, a series of static indentation and low velocity impact tests were carried out and compared. Square specimens of many sizes and thickness were utilized to cover the array of types of low velocity impact events. Laminates with a n/4 stacking sequence were employed since this is by the most common type of engineering laminate. Three distinct flexural rigidities under two different boundary conditions were tested in order to obtain damage due to large deflections, contact stresses and both to examine if the static indentation-impact comparisons are valid under the spectrum of damage modes that can be experienced. Comparisons between static indentation and low velocity impact tests were based on the maximum applied transverse load. The dependent parameters examined included dent depth, back surface crack length, delamination area and to a limited extent, load-deflection behavior. Results showed that no distinct differences could be seen between the static indentation tests and the low velocity impact tests, indicating that static indentation can be used to represent a low velocity impact event.

  2. A Comparison of Quasi-Static Indentation to Low-Velocity Impact

    Science.gov (United States)

    Nettles, A. T.; Douglas, M. J.

    2000-01-01

    A static test method for modeling low-velocity foreign object impact events to composites would prove to be very beneficial to researchers since much more data can be obtained from a static test than from an impact test. In order to examine if this is feasible, a series of static indentation and low-velocity impact tests were carried out and compared. Square specimens of many sizes and thicknesses were utilized to cover the array of types of low velocity impact events. Laminates with a pi/4 stacking sequence were employed since this is by far the most common type of engineering laminate. Three distinct flexural rigidities -under two different boundary conditions were tested in order to obtain damage ranging from that due to large deflection to contact stresses and levels in-between to examine if the static indentation-impact comparisons are valid under the spectrum of damage modes that can be experienced. Comparisons between static indentation and low-velocity impact tests were based on the maximum applied transverse load. The dependent parameters examined included dent depth, back surface crack length, delamination area, and to a limited extent, load-deflection behavior. Results showed that no distinct differences could be seen between the static indentation tests and the low-velocity impact tests, indicating that static indentation can be used to represent a low-velocity impact event.

  3. Analysis of the Indented Cylinder by the use of Computer Vision

    DEFF Research Database (Denmark)

    Buus, Ole Thomsen

    The research summarised in this PhD thesis took advantage of methods from computer vision to experimentally analyse the sorting/separation ability of a specific type of seed sorting device – known as an “indented cylinder”. The indented cylinder basically separates incoming seeds into two sub......-groups: (1) “long” seeds and (2) “short” seeds (known as length-separation). The motion of seeds being physically manipulated inside an active indented cylinder was analysed using various computer vision methods. The data from such analyses were used to create an overview of the machine’s ability to separate...... all the complexities related to that as well. The project arrived at a number of results of high scientific and practical value to the area of applied computer vision and seed processing and agricultural technology in general. The results and methodologies were summarised in one conference paper...

  4. Deformation behavior of a zirconium based metallic glass during cylindrical indentation: in situ observations

    Energy Technology Data Exchange (ETDEWEB)

    Antoniou, A. [Aerospace Engineering and Mechanics, Ames Laboratory, Iowa State University, Ames, IA 50011 (United States); Bastawros, A.F. [Aerospace Engineering and Mechanics, Ames Laboratory, Iowa State University, Ames, IA 50011 (United States); Lo, C.C.H. [Materials and Engineering Physics, Ames Laboratory, Iowa State University, Ames, IA 50011 (United States); Biner, S.B. [Aerospace Engineering and Mechanics, Ames Laboratory, Iowa State University, Ames, IA 50011 (United States) and Materials and Engineering Physics, Ames Laboratory, Iowa State University, Ames, IA 50011 (United States)]. E-mail: sbbiner@iastate.edu

    2005-03-15

    An experimental methodology was developed which is simple and yet accurately elucidates the stress-state dependency of the deformation behavior of metallic glasses or similar amorphous systems. The methodology includes in situ observations of the evolution of the deformation behavior of metallic glasses under a cylindrical indenter. The set-up not only collects information on the load-displacement response of the system to the deformation, but also resolves the much-needed information on the temporal and spatial evolution of the shear bands. By employing various indenter radii, the critical shear stress for the nucleation of the shear bands is obtained. Experimental results for a zirconium based metallic glass where found to be consistently independent of the indenter radius and in close agreement with the uniaxial yield values.

  5. Evaluation of the material’s damage in gas turbine rotors by instrumented spherical indentation

    Directory of Open Access Journals (Sweden)

    D. Nappini

    2014-10-01

    Full Text Available Experimental indentations are carried out on items of two different materials, taken in several location of various components from high pressure gas turbine rotor which have seen an extensive service. The components object of investigation consisted in 1st and 2nd high pressure turbine wheels made in nickel-base superalloy (Inconel 718, the spacer ring (Inconel 718 and the compressor shaft made in CrMoV low alloy steel (ASTM A471 type10. Aim of the work is to set up the capability of the instrumented spherical indentation testing system to evaluate variations in the material properties due to damage, resulting from temperature field and stresses acting on components during service. To perform this task load-indentation depth curves will be acquired in various zones of the above mentioned components. The analysis of the results has allowed to identify an energy parameter which shows a linear evolution with the mean temperature acting on the components.

  6. Mapping Viscoelastic and Plastic Properties of Polymers and Polymer-Nanotube Composites using Instrumented Indentation.

    Science.gov (United States)

    Gayle, Andrew J; Cook, Robert F

    An instrumented indentation method is developed for generating maps of time-dependent viscoelastic and time-independent plastic properties of polymeric materials. The method is based on a pyramidal indentation model consisting of two quadratic viscoelastic Kelvin-like elements and a quadratic plastic element in series. Closed-form solutions for indentation displacement under constant load and constant loading-rate are developed and used to determine and validate material properties. Model parameters are determined by point measurements on common monolithic polymers. Mapping is demonstrated on an epoxy-ceramic interface and on two composite materials consisting of epoxy matrices containing multi-wall carbon nanotubes. A fast viscoelastic deformation process in the epoxy was unaffected by the inclusion of the nanotubes, whereas a slow viscoelastic process was significantly impeded, as was the plastic deformation. Mapping revealed considerable spatial heterogeneity in the slow viscoelastic and plastic responses in the composites, particularly in the material with a greater fraction of nanotubes.

  7. Preparation of bilayer-core osmotic pump tablet by coating the indented core tablet.

    Science.gov (United States)

    Liu, Longxiao; Xu, Xiangning

    2008-03-20

    In this paper, a bilayer-core osmotic pump tablet (OPT) which does not require laser drilling to form the drug delivery orifice is described. The bilayer-core consisted of two layers: (a) push layer and (b) drug layer, and was made with a modified upper tablet punch, which produced an indentation at the center of the drug layer surface. The indented tablets were coated by using a conventional pan-coating process. Although the bottom of the indentation could be coated, the side face of the indentation was scarcely sprayed by the coating solution and this part of the tablet remained at least partly uncoated leaving an aperture from which drug release could occur. Nifedipine was selected as the model drug. Sodium chloride was used as osmotic agent, polyvinylpyrrolidone as suspending agent and croscarmellose sodium as expanding agent. The indented core tablet was coated by ethyl cellulose as semipermeable membrane containing polyethylene glycol 400 for controlling the membrane permeability. The formulation of core tablet was optimized by orthogonal design and the release profiles of various formulations were evaluated by similarity factor (f(2)). It was found that the optimal OPT was able to deliver nifedipine at an approximate zero-order up to 24 h, independent on both release media and agitation rates. The preparation of bilayer-core OPT was simplified by coating the indented core tablet, by which sophisticated technology of the drug layer identification and laser drilling could be eliminated. It might be promising in the field of preparation of bilayer-core OPT.

  8. Estimating material elasticity by spherical indentation load-relaxation tests on viscoelastic samples of finite thickness.

    Science.gov (United States)

    Qiang, Bo; Greenleaf, James; Oyen, Michelle; Zhang, Xiaoming

    2011-07-01

    A two-step viscoelastic spherical indentation method is proposed to compensate for 1) material relaxation and 2) sample thickness. In the first step, the indenter is moved at a constant speed and the reaction force is measured. In the second step, the indenter is held at a constant position and the relaxation response of the material is measured. Then the relaxation response is fit with a multi-exponential function which corresponds to a three-branch general Maxwell model. The relaxation modulus is derived by correcting the finite ramp time introduced in the first step. The proposed model takes into account the sample thickness, which is important for applications in which the sample thickness is less than ten times the indenter radius. The model is validated numerically by finite element simulations. Experiments are carried out on a 10% gelatin phantom and a chicken breast sample with the proposed method. The results for both the gelatin phantom and the chicken breast sample agree with the results obtained from a surface wave method. Both the finite element simulations and experimental results show improved elasticity estimations by incorporating the sample thickness into the model. The measured shear elasticities of the 10% gelatin sample are 6.79 and 6.93 kPa by the proposed finite indentation method at sample thickness of 40 and 20 mm, respectively. The elasticity of the same sample is estimated to be 6.53 kPa by the surface wave method. For the chicken breast sample, the shear elasticity is measured to be 4.51 and 5.17 kPa by the proposed indentation method at sample thickness of 40 and 20 mm, respectively. Its elasticity is measured by the surface wave method to be 4.14 kPa.

  9. Tau-positive nuclear indentations in P301S tauopathy mice.

    Science.gov (United States)

    Fernández-Nogales, Marta; Santos-Galindo, María; Merchán-Rubira, Jesús; Hoozemans, Jeroen J M; Rábano, Alberto; Ferrer, Isidro; Avila, Jesús; Hernández, Félix; Lucas, José J

    2017-05-01

    Increased incidence of neuronal nuclear indentations is a well-known feature of the striatum of Huntington's disease (HD) brains and, in Alzheimer's disease (AD), neuronal nuclear indentations have recently been reported to correlate with neurotoxicity caused by improper cytoskeletal/nucleoskeletal coupling. Initial detection of rod-shaped tau immunostaining in nuclei of cortical and striatal neurons of HD brains and in hippocampal neurons of early Braak stage AD led us to coin the term "tau nuclear rods (TNRs)." Although TNRs traverse nuclear space, they in fact occupy narrow cytoplasmic extensions that fill indentations of the nuclear envelope and we will here refer to this histological hallmark as Tau-immunopositive nuclear indentations (TNIs). We reasoned that TNI formation is likely secondary to tau alterations as TNI detection in HD correlates with an increase in total tau, particularly of the isoforms with four tubulin binding repeats (4R-tau). Here we analyze transgenic mice that overexpress human 4R-tau with a frontotemporal lobar degeneration-tau point mutation (P301S mice) to explore whether tau alteration is sufficient for TNI formation. Immunohistochemistry with various tau antibodies, immunoelectron microscopy and double tau-immunofluorescence/DAPI-nuclear counterstaining confirmed that excess 4R-tau in P301S mice is sufficient for the detection of abundant TNIs that fill nuclear indentations. Interestingly, this does not correlate with an increase in the number of nuclear indentations, thus suggesting that excess total tau or an isoform imbalance in favor of 4R-tau facilitates tau detection inside preexisting nuclear indentations but does not induce formation of the latter. In summary, here we demonstrate that tau alteration is sufficient for TNI detection and our results suggest that the neuropathological finding of TNIs becomes a possible indicator of increased total tau and/or increased 4R/3R-tau ratio in the affected neurons apart from being an

  10. Double Indenters and Oblique Extrusion and Extension in Taiwan: the Colliding Seamount Analogy

    Science.gov (United States)

    Byrne, T.; Gourley, J. R.; Chan, Y.

    2005-12-01

    The island of Taiwan forms as the ENE-trending Chinese continental margin collides obliquely with the N-trending Luzon arc. Previous interpretations have treated the colliding margin as a relatively homogeneous basement high with lateral extrusion limited to southwestern Taiwan. Here, we present a new compilation of geologic, GPS and seismic data and propose that the collision can be more accurately represented as a series of colliding indenters, similar to the subduction of seamounts, and that lateral extrusion affects nearly the entire collision. The most recent indenter, the Peikang basement high, lies beneath the southern Coastal Plain and has been mapped through drilling and seismic reflection and refraction studies. The high is generating a prominent reentrant in the deformation front in the Coastal Plain and correlates arcward (in the direction of plate convergence) with a substantial increase in GPS measured shortening, the maximum elevation in Taiwan (3952 m), a slightly wider retro-wedge, and the area where the emerging colliding arc is highest and widest. A second, previously accreted, basement indenter appears to lie beneath the slate and pre-Tertiary metamorphic belts in the Central Range and lies at the apex of a second topographic reentrant east of the Puli Basin. The indenter also correlates arcward with an increase in GPS measured shortening and with an anomalous zone of shortening, rather than extension in the Central Range. A significant cluster of post-Chi-Chi earthquakes defines a steep, WNW-dipping reverse fault in the middle crust (15 to 30 km) that marks the western side of the indenter. This fault probably correlates with the eastern side of the Hsuehshan Range "popup" and with the Lishan fault. The compilation of data also suggests that the fold-and-thrust belt, Slate Belt and pre-Tertiary metamorphic basement are being extruded and extended obliquely as the indenters collide. Extrusion and extension are oblique because the plate

  11. Investigation into local cell mechanics by atomic force microscopy mapping and optical tweezer vertical indentation

    Science.gov (United States)

    Coceano, G.; Yousafzai, M. S.; Ma, W.; Ndoye, F.; Venturelli, L.; Hussain, I.; Bonin, S.; Niemela, J.; Scoles, G.; Cojoc, D.; Ferrari, E.

    2016-02-01

    Investigating the mechanical properties of cells could reveal a potential source of label-free markers of cancer progression, based on measurable viscoelastic parameters. The Young’s modulus has proved to be the most thoroughly studied so far, however, even for the same cell type, the elastic modulus reported in different studies spans a wide range of values, mainly due to the application of different experimental conditions. This complicates the reliable use of elasticity for the mechanical phenotyping of cells. Here we combine two complementary techniques, atomic force microscopy (AFM) and optical tweezer microscopy (OTM), providing a comprehensive mechanical comparison of three human breast cell lines: normal myoepithelial (HBL-100), luminal breast cancer (MCF-7) and basal breast cancer (MDA-MB-231) cells. The elastic modulus was measured locally by AFM and OTM on single cells, using similar indentation approaches but different measurement parameters. Peak force tapping AFM was employed at nanonewton forces and high loading rates to draw a viscoelastic map of each cell and the results indicated that the region on top of the nucleus provided the most meaningful results. OTM was employed at those locations at piconewton forces and low loading rates, to measure the elastic modulus in a real elastic regime and rule out the contribution of viscous forces typical of AFM. When measured by either AFM or OTM, the cell lines’ elasticity trend was similar for the aggressive MDA-MB-231 cells, which were found to be significantly softer than the other two cell types in both measurements. However, when comparing HBL-100 and MCF-7 cells, we found significant differences only when using OTM.

  12. Indentation of a spherical cavity in an elastic body by a rigid spherical inclusion: influence of non-classical interface conditions

    Science.gov (United States)

    Selvadurai, A. P. S.

    2016-03-01

    This paper examines the indentation of an elastic body by a rigid spherical inclusion. In contrast to conventional treatments where the contact between a rigid inclusion and the elastic medium is regarded as being perfectly bonded, we examine the influence of non-classical interface conditions including frictionless bilateral contact, separation and Coulomb friction on the load-displacement behaviour of the spherical rigid inclusion. Both analytical methods and boundary element techniques are used to examine the inclusion/elastic medium interaction problems. This paper also provides a comprehensive review of non-classical interface conditions between inclusions and the surrounding elastic media.

  13. Pressure ulcers, indentation marks and pain from cervical spine immobilization with extrication collars and headblocks: An observational study

    NARCIS (Netherlands)

    Ham, W.H.; Schoonhoven, L.; Schuurmans, M.J.; Leenen, L.P.

    2016-01-01

    OBJECTIVES: To describe the occurrence and severity of pressure ulcers, indentation marks and pain from the extrication collar combined with headblocks. Furthermore, the influence of time, injury severity and patient characteristics on the development of pressure ulcers, indentation marks and pain

  14. Pressure ulcers, indentation marks and pain from cervical spine immobilization with extrication collars and headblocks : An observational study

    NARCIS (Netherlands)

    Ham, Wietske H W; Schoonhoven, Lisette; Schuurmans, Marieke J; Leenen, Luke P H

    OBJECTIVES: To describe the occurrence and severity of pressure ulcers, indentation marks and pain from the extrication collar combined with headblocks. Furthermore, the influence of time, injury severity and patient characteristics on the development of pressure ulcers, indentation marks and pain

  15. Crack formation mechanisms during micro and macro indentation of diamond-like carbon coatings on elastic-plastic substrates

    DEFF Research Database (Denmark)

    Thomsen, N.B.; Fischer-Cripps, A.C.; Swain, M.V.

    1998-01-01

    In the present study crack formation is investigated on both micro and macro scale using spherical indenter tips. in particular, systems consisting of elastic coatings that are well adhered to elastic-plastic substrates are studied. Depth sensing indentation is used on the micro scale and Rockwell...... indentation on the macro scale. The predominant driving force for coating failure and crack formation during indentation is plastic deformation of the underlying substrate. The aim is to relate the mechanisms creating both delamination and cohesive cracking on both scales with fracture mechanical models...... in order to quantitatively determine coating fracture properties. A non-linear elastic-plastic finite element model of the coating system which is loaded with a spherical indenter is used to simulated stress and displacement distributions in the material. The simulations are used to predict the onset...

  16. Indentation of a rigid sphere into an elastic substrate with surface tension and adhesion.

    Science.gov (United States)

    Hui, Chung-Yuen; Liu, Tianshu; Salez, Thomas; Raphael, Elie; Jagota, Anand

    2015-03-08

    The surface tension of compliant materials such as gels provides resistance to deformation in addition to and sometimes surpassing that owing to elasticity. This paper studies how surface tension changes the contact mechanics of a small hard sphere indenting a soft elastic substrate. Previous studies have examined the special case where the external load is zero, so contact is driven by adhesion alone. Here, we tackle the much more complicated problem where, in addition to adhesion, deformation is driven by an indentation force. We present an exact solution based on small strain theory. The relation between indentation force (displacement) and contact radius is found to depend on a single dimensionless parameter: ω = σ ( μR ) -2/3 ((9 π /4) W ad ) -1/3 , where σ and μ are the surface tension and shear modulus of the substrate, R is the sphere radius and W ad is the interfacial work of adhesion. Our theory reduces to the Johnson-Kendall-Roberts (JKR) theory and Young-Dupre equation in the limits of small and large ω , respectively, and compares well with existing experimental data. Our results show that, although surface tension can significantly affect the indentation force, the magnitude of the pull-off load in the partial wetting liquid-like limit is reduced only by one-third compared with the JKR limit and the pull-off behaviour is completely determined by ω .

  17. Indentation of a rigid sphere into an elastic substrate with surface tension and adhesion

    Science.gov (United States)

    Hui, Chung-Yuen; Liu, Tianshu; Salez, Thomas; Raphael, Elie; Jagota, Anand

    2015-01-01

    The surface tension of compliant materials such as gels provides resistance to deformation in addition to and sometimes surpassing that owing to elasticity. This paper studies how surface tension changes the contact mechanics of a small hard sphere indenting a soft elastic substrate. Previous studies have examined the special case where the external load is zero, so contact is driven by adhesion alone. Here, we tackle the much more complicated problem where, in addition to adhesion, deformation is driven by an indentation force. We present an exact solution based on small strain theory. The relation between indentation force (displacement) and contact radius is found to depend on a single dimensionless parameter: ω=σ(μR)−2/3((9π/4)Wad)−1/3, where σ and μ are the surface tension and shear modulus of the substrate, R is the sphere radius and Wad is the interfacial work of adhesion. Our theory reduces to the Johnson–Kendall–Roberts (JKR) theory and Young–Dupre equation in the limits of small and large ω, respectively, and compares well with existing experimental data. Our results show that, although surface tension can significantly affect the indentation force, the magnitude of the pull-off load in the partial wetting liquid-like limit is reduced only by one-third compared with the JKR limit and the pull-off behaviour is completely determined by ω. PMID:25792953

  18. Young's modulus of peritubular and intertubular human dentin by nano-indentation tests.

    Science.gov (United States)

    Ziskind, Daniel; Hasday, Moran; Cohen, Sidney R; Wagner, H Daniel

    2011-04-01

    The local Young modulus of dry dentin viewed as a hierarchical composite was measured by nano-indentation using two types of experiments, both in a continuous stiffness measurement mode. First, tests were performed radially along straight lines running across highly mineralized peritubular dentin sections and through less mineralized intertubular dentin areas. These tests revealed a gradual decrease in Young's modulus from the bulk of the peritubular dentin region where modulus values of up to ∼40-42GPa were observed, down to approximately constant values of ∼17GPa in the intertubular dentin region. A second set of nano-indentation experiments was performed on the facets of an irregular polyhedron specimen cut from the intertubular dentin region, so as to probe the modulus of intertubular dentin specimens at different orientations relative to the tubular direction. The results demonstrated that the intertubular dentin region may be considered to be quasi-isotropic, with a slightly higher modulus value (∼22GPa) when the indenting tip axis is parallel to the tubular direction, compared to the values (∼18GPa) obtained when the indenting tip axis is perpendicular to the tubule direction. Copyright © 2010 Elsevier Inc. All rights reserved.

  19. Deformation mechanisms in TiN/(Ti,Al)N multilayers under depth-sensing indentation

    NARCIS (Netherlands)

    Carvalho, NJM; De Hosson, JTM

    TiN/(Ti,Al)N multilayer coatings prepared by physical vapour deposition onto steel Substrates were Subjected to depth-sensing indentation testing. The investigation was aimed at predicting their performance by identifying the contact-induced fracture mechanisms. Analysis of the load-displacement

  20. A Progressive Damage Model for Predicting Permanent Indentation and Impact Damage in Composite Laminates

    Science.gov (United States)

    Ji, Zhaojie; Guan, Zhidong; Li, Zengshan

    2017-10-01

    In this paper, a progressive damage model was established on the basis of ABAQUS software for predicting permanent indentation and impact damage in composite laminates. Intralaminar and interlaminar damage was modelled based on the continuum damage mechanics (CDM) in the finite element model. For the verification of the model, low-velocity impact tests of quasi-isotropic laminates with material system of T300/5228A were conducted. Permanent indentation and impact damage of the laminates were simulated and the numerical results agree well with the experiments. It can be concluded that an obvious knee point can be identified on the curve of the indentation depth versus impact energy. Matrix cracking and delamination develops rapidly with the increasing impact energy, while considerable amount of fiber breakage only occurs when the impact energy exceeds the energy corresponding to the knee point. Predicted indentation depth after the knee point is very sensitive to the parameter μ which is proposed in this paper, and the acceptable value of this parameter is in range from 0.9 to 1.0.

  1. Mechanical damage in a lithium-ion pouch cell under indentation loads

    Science.gov (United States)

    Luo, Hailing; Xia, Yong; Zhou, Qing

    2017-07-01

    The short circuit of lithium-ion batteries induced by mechanical abuse is a great concern in electric vehicle design. It remains a challenge to fully understand the nature of the mechanical damage process with the aim of improving battery crash safety. The present paper investigates the evolution of the damage process for a lithium-ion pouch cell under indentation by loading the cell to various force levels. A significant inflection point on the force-indentation curve is observed before the force peak. Post-mortem examinations indicate that the characteristic change in the local slope of the curve is related to the change occurring at the local interfaces, including three phenomena - formation of tight adhesion on the anode-separator interfaces, delamination in the separators and decoating of graphite particles from the anodes. Analysis of the fracture sequence at the onset of short circuit clearly shows that the number of short-circuited electrode pairs is equal to the number of anode layers adhered with delaminated separator material before fracture occurs. The experimental study in the present paper implies that the inflection point on the force-indentation curve may be an indicator of damage initiation inside pouch cells under indentation.

  2. Comparison of the aerodynamics of bridge cables with helical fillets and a pattern-indented surface

    DEFF Research Database (Denmark)

    Kleissl, K.; Georgakis, C.T.

    2012-01-01

    In this paper, the aerodynamics of bridge cables with helical fillets and a pattern-indented surface are examined. To this end, an extensive wind-tunnel test campaign was undertaken to measure the static force coefficients about the critical Reynolds number region, with varying relative cable...

  3. Indentation Size Effect (ISE) in Copper Subjected to Severe Plastic Deformation (SPD)

    Science.gov (United States)

    Gale, Joshua D.; Achuthan, Ajit; Morrison, David J.

    2014-05-01

    The characteristic length scale of deformation in copper specimens subjected to severe plastic deformation (SPD) through surface mechanical attrition treatment (SMAT) was studied with indentation experiments. Annealed copper disks were shot peened with 6-mm diameter tungsten carbide spheres with an average velocity of 2.3 m/s for 15 minutes in a vibrating chamber. The SMAT-treated specimens were cross-sectioned, and the exposed face was studied under nanoindentation in order to determine the effect of dislocation density on surface hardness and indentation size effect (ISE). Since the specimen preparation of the exposed face involved mechanical polishing, which in turn introduced additional SPD on the indenting face, the effect of mechanical polishing on hardness measurement was investigated first. To this end, the mechanically polished specimens were subjected to various durations of electrochemical polishing. Hardness measurements on these specimens showed that the effect of mechanical polishing was substantial for both microindentation and nanoindentation, the impact being significantly larger for nanoindentation. Consequently, the measured depth of influence of the SMAT process, determined on specimens subjected to longer durations of electrochemical polishing, shows larger values compared to those previously reported in the literature. The ISE shows a bilinear relationship between the square of hardness and the reciprocal of indentation depth. The slope of this behavior, corresponding to smaller indentation loads, which is a measure of the ISE associated with a strain gradient, shows a power-law relationship with an increase in the distance away from the SMAT surface, instead of the constant value expected with the Nix-Gao type model.

  4. Determination of the mechanical and physical properties of cartilage by coupling poroelastic-based finite element models of indentation with artificial neural networks.

    Science.gov (United States)

    Arbabi, Vahid; Pouran, Behdad; Campoli, Gianni; Weinans, Harrie; Zadpoor, Amir A

    2016-03-21

    One of the most widely used techniques to determine the mechanical properties of cartilage is based on indentation tests and interpretation of the obtained force-time or displacement-time data. In the current computational approaches, one needs to simulate the indentation test with finite element models and use an optimization algorithm to estimate the mechanical properties of cartilage. The modeling procedure is cumbersome, and the simulations need to be repeated for every new experiment. For the first time, we propose a method for fast and accurate estimation of the mechanical and physical properties of cartilage as a poroelastic material with the aid of artificial neural networks. In our study, we used finite element models to simulate the indentation for poroelastic materials with wide combinations of mechanical and physical properties. The obtained force-time curves are then divided into three parts: the first two parts of the data is used for training and validation of an artificial neural network, while the third part is used for testing the trained network. The trained neural network receives the force-time curves as the input and provides the properties of cartilage as the output. We observed that the trained network could accurately predict the properties of cartilage within the range of properties for which it was trained. The mechanical and physical properties of cartilage could therefore be estimated very fast, since no additional finite element modeling is required once the neural network is trained. The robustness of the trained artificial neural network in determining the properties of cartilage based on noisy force-time data was assessed by introducing noise to the simulated force-time data. We found that the training procedure could be optimized so as to maximize the robustness of the neural network against noisy force-time data. Copyright © 2016 Elsevier Ltd. All rights reserved.

  5. Chemical removal of necrotic periodontal ligament on delayed replanted teeth by sodium hypochlorite: morphological analysis and microhardness indentation test of cementum.

    Science.gov (United States)

    Bai, J; Qin, M; Zhao, Y-M; Huang, M-W; Ji, A-P

    2016-04-01

    To compare the efficacy of sodium hypochlorite (NaOCl) used at different concentrations and working times for removing necrotic periodontal ligament (PDL) from delayed replanted teeth and to observe the effects of NaOCl on surface structure and microhardness of cementum. A total of 88 healthy premolars with a single root extracted for orthodontic purposes were selected and kept dry at room temperature for 1 h. The teeth were divided into 11 groups: group 1 (control): roots were untreated; group 2: necrotic PDL was removed with gauze; groups 3-11: teeth were immersed in NaOCl at different concentrations (1, 2.5 and 5.25%) and for different working times (5, 10 and 15 min). The specimens in each group were inspected separately for cementum integrity and the presence of PDL remnants by histomorphometric analysis, confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). Another 14 healthy premolars with roots divided into two pieces were selected for Vickers microhardness indentation tests before and after NaOCl treatment. The data were analysed statistically using Wilcoxon signed-rank test of two-related samples (P = 0.05). In teeth treated with 1% NaOCl for 15 min or 5.25% NaOCl for 5 min, the cementum remained morphologically intact without cracks, and PDL remnants were absent. In the 1% NaOCl for 15 min group, the microstructure of cementum was arranged more regularly, as observed ×8000 magnification by SEM. Teeth in each of the other groups displayed cementum damage and/or the presence of PDL remnants. Microhardness tests revealed that treatment with 1% NaOCl for 15 min or 5.25% NaOCl for 5 min significantly decreased microhardness of root cementum (P < 0.05). Use of either 1% NaOCl for 15 min or 5.25% NaOCl for 5 min was effective at removing necrotic PDL from the delayed replanted teeth whilst having a minimal influence on cementum integrity. However, 1% NaOCl for 15 min was less damaging to cementum. © 2015 International Endodontic

  6. Assessing strain mapping by electron backscatter diffraction and confocal Raman microscopy using wedge-indented Si

    Energy Technology Data Exchange (ETDEWEB)

    Friedman, Lawrence H.; Vaudin, Mark D.; Stranick, Stephan J.; Stan, Gheorghe; Gerbig, Yvonne B.; Osborn, William; Cook, Robert F., E-mail: robert.cook@nist.gov

    2016-04-15

    The accuracy of electron backscatter diffraction (EBSD) and confocal Raman microscopy (CRM) for small-scale strain mapping are assessed using the multi-axial strain field surrounding a wedge indentation in Si as a test vehicle. The strain field is modeled using finite element analysis (FEA) that is adapted to the near-indentation surface profile measured by atomic force microscopy (AFM). The assessment consists of (1) direct experimental comparisons of strain and deformation and (2) comparisons in which the modeled strain field is used as an intermediate step. Direct experimental methods (1) consist of comparisons of surface elevation and gradient measured by AFM and EBSD and of Raman shifts measured and predicted by CRM and EBSD, respectively. Comparisons that utilize the combined FEA–AFM model (2) consist of predictions of distortion, strain, and rotation for comparison with EBSD measurements and predictions of Raman shift for comparison with CRM measurements. For both EBSD and CRM, convolution of measurements in depth-varying strain fields is considered. The interconnected comparisons suggest that EBSD was able to provide an accurate assessment of the wedge indentation deformation field to within the precision of the measurements, approximately 2×10{sup −4} in strain. CRM was similarly precise, but was limited in accuracy to several times this value. - Highlights: • We map strain by electron backscatter diffraction and confocal Raman microscopy. • The test vehicle is the multi-axial strain field of wedge-indented silicon. • Strain accuracy is assessed by direct experimental intercomparison. • Accuracy is also assessed by atomic force microscopy and finite element analyses. • Electron diffraction measurements are accurate; Raman measurements need refinement.

  7. The use of field indentation microprobe in measuring mechanical properties of welds

    Energy Technology Data Exchange (ETDEWEB)

    Haggag, F.M.; Wong, H.; Alexander, D.J.; Nanstad, R.K.

    1989-01-01

    A field indentation microprobe (FIM) was conceived for evaluating the structural integrity of metallic components (including base metal, welds, and heat-affected zones) in situ in a nondestructive manner. The FIM consists of an automated ball indentation (ABI) unit for determining the mechanical properties (yield strength, flow properties, estimates of fracture toughness, etc.) and a nondestructive evaluation (NDE) unit (consisting of ultrasonic transducers and a video camera) for determining the physical properties such as crack size, material pileup around indentation, and residual stress presence and orientation. The laboratory version used in this work performs only ABI testing. ABI tests were performed on stainless steel base metal (type 316L), heat-affected zone, and welds (type 308). Excellent agreement was obtained between yield strength and flow properties (true-stress/true-plastic-strain curve) measured by the ABI tests and those from uniaxial tensile tests conducted on 308 stainless steel welds, thermally aged at 343/degree/C for different times, and on the base material. 4 refs., 17 figs.

  8. Ultrawide band gaps in beams with double-leaf acoustic black hole indentations.

    Science.gov (United States)

    Tang, Liling; Cheng, Li

    2017-11-01

    Band gaps in conventional phononic crystals (PCs) are attractive for applications such as vibration control, wave manipulation, and sound absorption. Their practical implementations, however, are hampered by several factors, among which the large number of cells required and their impractically large size to ensure the stopbands at reasonably low frequencies are on the top of the list. This paper reports a type of beam carved inside with two double-leaf acoustic black hole indentations. By incorporating the local resonance effect and the Bragg scattering effect generated by a strengthening stud connecting the two branches of the indentations, ultrawide band gaps are achieved. Increasing the length of the stud or reducing the residual thickness of the indentation allows the tuning of the band gaps to significantly enlarge the band gaps, which can exceed 90% of the entire frequency range of interest. Experimental results show that with only three cells, the proposed beam allows considerable vibration energy attenuation within an ultra-broad frequency range including the low frequency range, which conventional PCs can hardly reach. Meanwhile, the proposed configuration also enhances the structural integrity, thus pointing at promising applications in vibration control and a high performance wave filter design.

  9. Assessment of surface caking of powders using the ball indentation method.

    Science.gov (United States)

    Chen, Qinqin; Zafar, Umair; Ghadiri, Mojtaba; Bi, Jinfeng

    2017-04-15

    Powder caking is a ubiquitous problem, which could significantly decrease product quality and lead to economic losses. Hence it is important to know the conditions under which it occurs. The caking behaviour of three powder materials (PVP, HPC and CaHPO 4 ) has been investigated by the ball indentation method (BIM) as affected by relative humidity (RH), temperature and time. The resistance to powder flow, as indicated by the hardness is measured by a ball indenting the powder bed surface. The surface hardness increases with increasing RH and temperature, indicating caking of the powder bed. Moreover, the temperature and RH show a coupled effect on powder caking. Irreversible caking is formed in PVP and HPC at 75% RH; the particles coalesce and the volume of powder bed is significantly reduced with time. However, the caking of CaHPO 4 is reversible. To examine the caking mechanism of PVP and HPC, the critical glass transition RH is determined at 25°C and 45°C. The values are 63% and 53% RH for PVP and 61% and 50% RH for HPC, respectively. The glass transition moisture content in the ball indentation experiments is comparable with that determined by the dynamic vapor sorption measurement. BIM could be a fast and effective method for the assessment of powder surface caking. Copyright © 2017 Elsevier B.V. All rights reserved.

  10. Pressure ulcers, indentation marks and pain from cervical spine immobilization with extrication collars and headblocks: An observational study.

    Science.gov (United States)

    Ham, Wietske H W; Schoonhoven, Lisette; Schuurmans, Marieke J; Leenen, Luke P H

    2016-09-01

    To describe the occurrence and severity of pressure ulcers, indentation marks and pain from the extrication collar combined with headblocks. Furthermore, the influence of time, injury severity and patient characteristics on the development of pressure ulcers, indentation marks and pain was explored. Observational. Level one trauma centre in the Netherlands. Adult trauma patients admitted to the Emergency Department in an extrication collar combined with headblocks. Between January and December 2013, 342 patients were included. Study outcomes were incidence and severity of pressure ulcers, indentation marks and pain. The following dependent variables were collected: time in the cervical collar and headblocks, Glasgow Coma Scale, Mean Arterial Pressure, haemoglobin, Injury Severity Score, gender, age, and Body Mass Index. 75.4% of the patients developed a category 1 and 2.9% a category 2 pressure ulcer. Indentation marks were observed in 221 (64.6%) patients; 96 (28.1%) had severe indentation marks. Pressure ulcers and indentation marks were observed most frequently at the back, shoulders and chest. 63.2% experienced pain, of which, 38.5% experienced severe pain. Pain was mainly located at the occiput. Female patients experienced significantly more pain (NRS>3) compared to male patients (OR=2.14, 95% CI 1.21-3.80) None of the investigated variables significantly increased the probability of developing PUs or indentation marks. The high incidence of category 1 pressure ulcers and severe indentation marks indicate an increased risk for pressure ulcer development and may well lead to more severe PU lesions. Pain due to the application of the extrication collar and headblocks may lead to undesirable movement (in order to relieve the pressure) or to bias clinical examination of the cervical spine. It is necessary to revise the current practice of cervical spine immobilization. Copyright © 2016 Elsevier Ltd. All rights reserved.

  11. Characterization of Rockwell hardness indenter Tip using image processing and optical profiler and evaluation of measurement uncertainty

    Directory of Open Access Journals (Sweden)

    Moona G.

    2014-01-01

    Full Text Available Hardness is a measure of the resistance of a material to be penetrated and eroded by sharp projections of other materials such as diamond. The process of creating sharp projections on any test surface is known as indentation. Hardness measurement of any material is the result of a complex process of deformation during indentation. The indenter tip geometry, which includes radius of curvature at the tip and tip angle, affects the hardness measurement by influencing the nature of the penetration process on the test surface, because every indenter deforms the specimen surface with a different geometry. The controlled indenter geometry can improve the consistency of hardness measurement. In this paper we report the estimation of two important geometrical parameters, radius of curvature and tip angle of a Rockwell indenter by using a simple method of image processing and compare the results with those obtained with a traceable 3D optical profiler. Evaluation of uncertainty in measuremts is carried out as per ISO guidelines (ISO-GUM and a detailed uncertainty budget is presented. The tip angle estimted is 119.95 degree. The radius of curvature is estimted to be 199.96 ± 0.80μm by image analysis which agrees well with the value estimated by using optical profiler i.e. 199.12 μm.

  12. Hardening Effect Analysis by Modular Upper Bound and Finite Element Methods in Indentation of Aluminum, Steel, Titanium and Superalloys

    Science.gov (United States)

    Bermudo, Carolina; Sevilla, Lorenzo; Martín, Francisco; Trujillo, Francisco Javier

    2017-01-01

    The application of incremental processes in the manufacturing industry is having a great development in recent years. The first stage of an Incremental Forming Process can be defined as an indentation. Because of this, the indentation process is starting to be widely studied, not only as a hardening test but also as a forming process. Thus, in this work, an analysis of the indentation process under the new Modular Upper Bound perspective has been performed. The modular implementation has several advantages, including the possibility of the introduction of different parameters to extend the study, such as the friction effect, the temperature or the hardening effect studied in this paper. The main objective of the present work is to analyze the three hardening models developed depending on the material characteristics. In order to support the validation of the hardening models, finite element analyses of diverse materials under an indentation are carried out. Results obtained from the Modular Upper Bound are in concordance with the results obtained from the numerical analyses. In addition, the numerical and analytical methods are in concordance with the results previously obtained in the experimental indentation of annealed aluminum A92030. Due to the introduction of the hardening factor, the new modular distribution is a suitable option for the analysis of indentation process. PMID:28772914

  13. OPPORTUNITY ESTIMATION OF OPTICAL METHOD APPLICATION IN PROBLEM OF KINEMATIC CHARACTERISTICS REGISTRATION OF DYNAMIC INDENTING PROCESS

    Directory of Open Access Journals (Sweden)

    Evgeniya I. Ivanova

    2017-07-01

    Full Text Available Subject of Research. A stereoscopic method of technical vision is proposed for recording the kinematic characteristics of the dynamic indentation process in determining the physico-mechanical properties of materials. The proposed method makes it possible to determine the values of the indenter motion speed with high accuracy. Method. The method is based on the use of two high-speed video cameras immovably fixed on one flat platform. Cameras allow for synchronous recording of the indentation process. The objectives and orientation of cameras in the stereo system provide intersection of the visual fields and the required depth of the image space field. Measurement of the movement speed is performed by triangulation method. The distance between the conjugate points of the recorded object on the stereo images is inversely proportional to the distance between the pair of cameras and the corresponding point of the object in the three-dimensional space. Based on the analysis of images obtained by spatially separated cameras, the coordinates of the object point are determined. Main Results. The experimental setup consisted of two high-speed monochrome camcorders Evercam 4000-32-M, rigidly fixed through stereo. Synchronous recording was kept at a speed of 4000 frames/s with a resolution of 1280 × 860 pixels. The indenter was made in the form of a steel ball with a mass of 230 g with a diameter of 38 mm and fell onto an aluminum disk 10 mm thick from a height of 310 mm. Video images from cameras were transferred to a personal computer for processing. The analysis of the obtained data was carried out in the MATLAB system with the help of a specially written software module. The sensitivity of the proposed method made it possible to determine confidently the values of the maximum approach speed of a steel ball equal to 2.39 m/s and a rebound velocity of 1.2 m/s. The random component of the method error did not exceed 2.5%. Practical Relevance. The

  14. Atomic force microscopy indentation and inverse analysis for non-linear viscoelastic identification of breast cancer cells.

    Science.gov (United States)

    Nguyen, Nhung; Shao, Yue; Wineman, Alan; Fu, Jianping; Waas, Anthony

    2016-07-01

    Breast cancer cells (MCF-7 and MCF-10A) are studied through indentation with spherical borosilicate glass particles in atomic force microscopy (AFM) contact mode in fluid. Their mechanical properties are obtained by analyzing the recorded reaction force-time response. The analysis is based on comparing experimental data with predictions from finite element (FE) simulation. Here, FE modeling is employed to simulate the AFM indentation experiment which is neither a displacement nor a force controlled test. This approach is expected to overcome many underlying problems of the widely used models such as Hertz contact model due to its capability to capture the contact behaviors between the spherical indentor and the cell, account for cell geometry, and incorporate with large strain theory. In this work, a non-linear viscoelastic (NLV) model in which the viscoelastic part is described by Prony series terms is used for the constitutive model of the cells. The time-dependent material parameters are extracted through an inverse analysis with the use of a surrogate model based on a Kriging estimator. The purpose is to automatically extract the NLV properties of the cells with a more efficient process compared to the iterative inverse technique that has been mostly applied in the literature. The method also allows the use of FE modeling in the analysis of a large amount of experimental data. The NLV parameters are compared between MCF-7 and MCF-10A and MCF-10A treated and untreated with the drug Cytochalasin D to examine the possibility of using relaxation properties as biomarkers for distinguishing these types of breast cancer cells. The comparisons indicate that malignant cells (MCF-7) are softer and exhibit more relaxation than benign cells (MCF-10A). Disrupting the cytoskeleton using the drug Cytochalasin D also results in a larger amount of relaxation in the cell's response. In addition, relaxation properties indicate larger differences as compared to the elastic moduli

  15. A Comparison of Rebound to Indentation Tonometry in Supine Sedated Children with Glaucoma.

    Science.gov (United States)

    AlHarkan, Dora H; Al-Shamlan, Fatemah T; Edward, Deepak P; Khan, Arif O

    2016-01-01

    To compare intraocular pressure (IOP) measurements by rebound tonometry (Icare PRO; Icare Finland Oy, Helsinki, Finland) to measurements by indentation tonometry (Pneumotonometer Model 30 classic and Tono-Pen XL; Reichert, Buffalo, NY, USA) in supine sedated children with glaucoma. Prospective comparative observational study of Saudi Arabian children with glaucoma undergoing chloral hydrate sedation for ophthalmic examination (February 2012 - February 2013). Nonglaucomatous eyes were included as controls. Eyes with corneal scars or prior corneal transplant or lamellar surgery were excluded. Fifty-two eyes (26 OD, 26 OS) of 28 children were included. Thirty-six eyes had glaucoma (32 primary congenital glaucoma, two Sturge-Weber related, and two aphakia related). Sixteen eyes did not have glaucoma (six with pediatric cataract, five normal eyes, two strabismic eyes, two eyes with simple megalocornea, and one eye had peripheral corneal laceration repair. In the glaucoma group, the mean IOP was 17.55 ± 5.97 mmHg (range, 8-31.5 mmHg) with the Icare PRO and 20 ± 6.4 mmHg (range, 8-35.5 mmHg) with the Pneumotonometer from 20.47 ± 6.81 mmHg (range, 10-43 mmHg) with the Tono-Pen XL. The Icare PRO readings were significantly lower than each of the indentation tonometers. For the control group, there was no statistically significant difference in IOP measured by the Icare PRO and the indentation tonometers. In this population of supine sedated children with glaucoma, IOP measurements with the Icare PRO tend to be lower than readings from the Pneumotonometer and Tono-Pen XL.

  16. Towards Humanlike Social Touch for Prosthetics and Sociable Robotics: Handshake Experiments and Finger Phalange Indentations

    Science.gov (United States)

    Cabibihan, John-John; Pradipta, Raditya; Chew, Yun Zhi; Ge, Shuzhi Sam

    The handshake has become the most acceptable gesture of greeting in many cultures. Replicating the softness of the human hand can contribute to the improvement of the emotional healing process of people who have lost their hands by enabling the concealment of prosthetic hand usage during handshake interactions. Likewise, sociable robots of the future will exchange greetings with humans. The soft humanlike hands during handshakes would be able to address the safety and acceptance issues of robotic hands. This paper investigates the areas of contact during handshake interactions. After the areas of high contact were known, indentation experiments were conducted to obtain the benchmark data for duplication with synthetic skins.

  17. Indentation in the Right Ventricle by an Incomplete Pericardium on 3-Dimensional Reconstructed Computed Tomography

    Directory of Open Access Journals (Sweden)

    Hak Ju Kim

    2017-08-01

    Full Text Available We report the case of a 17-year-old girl who presented with an indentation in the right ventricle caused by an incomplete pericardium on preoperative 3-dimensional reconstructed computed tomography. She was to undergo surgery for a partial atrioventricular septal defect and secundum atrial septal defect. Preoperative electrocardiography revealed occasional premature ventricular beats. We found the absence of the left side of the pericardium intraoperatively, and this absence caused strangulation of the diaphragmatic surface of the right ventricle. After correcting the lesion, the patient’s rhythm disturbances improved.

  18. On the use of Raman spectroscopy and instrumented indentation for characterizing damage in machined carbide ceramics

    Science.gov (United States)

    Groth, Benjamin Peter

    Machining is a necessary post-processing step in the manufacturing of many ceramic materials. Parts are machined to meet specific dimensions, with tight tolerances, not attainable from forming alone, as well as to achieve a desired surface finish. However, the machining process is very harsh, often employing the use of high temperatures and pressures to achieve the wanted result. In the case of silicon carbide, a material with extremely high hardness and stiffness, machining is very difficult and requires machining conditions that are highly aggressive. This can leave behind residual stresses in the surface of the material, cause unwanted phase transformations, and produce sub-surface deformation that can lead to failure. This thesis seeks to determine the effect of various machining conditions on the Raman spectra and elastic properties of sintered silicon carbide materials. Sample sets examined included hot-pressed silicon carbide tiles with four different surface finishes, as well as "ideal" single crystal silicon carbide wafers. The surface finishes studied were as follows: an as-pressed finish; a grit blast finish; a harsh rotary ground finish; and a mirror polish. Each finish imparts a different amount, as well as type, of deformation to the sample and are each utilized for a specific application. The sample surfaces were evaluated using a combination of Raman spectroscopy, for phase identification and stress analysis, and nanoindentation, for obtaining elastic properties and imparting uniform controlled deformation to the samples. Raman spectroscopy was performed over each sample surface using 514- and 633-nm wavelength excitation, along with confocal and non-confocal settings to study depth variation. Surfaces stresses were determined using peak shift information extracted from Raman spectra maps, while other spectral variations were used to compare levels of machining damage. Elastic modulus, hardness, and plastic work of indentation maps were generated

  19. Quantitative Study of the Elastic Modulus of Loosely Attached Cells in AFM Indentation Experiments

    OpenAIRE

    Dokukin, Maxim E.; Guz, Nataliia V.; Sokolov, Igor

    2013-01-01

    When measuring the elastic (Young’s) modulus of cells using AFM, good attachment of cells to a substrate is paramount. However, many cells cannot be firmly attached to many substrates. A loosely attached cell is more compliant under indenting. It may result in artificially low elastic modulus when analyzed with the elasticity models assuming firm attachment. Here we suggest an AFM-based method/model that can be applied to extract the correct Young’s modulus of cells loosely attached to a subs...

  20. Dissolved inorganic carbon, alkalinity, temperature, salinity and other variables collected from discrete sample and profile observations using CTD, bottle and other instruments from the JOHN V. VICKERS in the Bering Sea, North Pacific Ocean and South Pacific Ocean from 1992-08-16 to 1992-10-21 (NODC Accession 0115003)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NODC Accession 0115003 includes chemical, discrete sample, physical and profile data collected from JOHN V. VICKERS in the Bering Sea, North Pacific Ocean and South...

  1. Chipping fracture resistance of dental CAD/CAM restorative materials: part 2. Phenomenological model and the effect of indenter type.

    Science.gov (United States)

    Quinn, G D; Giuseppetti, A A; Hoffman, K H

    2014-05-01

    The edge chipping resistances of six CAD/CAM dental restoration materials are analyzed and correlated to other mechanical properties. A new quadratic relationship that is based on a phenomenological model is presented. The purpose of this study was to further analyze the edge chipping resistance of the brittle materials evaluated in Part 1. One objective was to determine why some force-distance trends were linear and others were nonlinear. A second objective was to account for differences in chipping resistance with indenter type. Edge chipping experiments were conducted with different indenters, including some custom-made sharp conical indenters. A new force - distance quadratic expression was correlated to the data and compared to the linear and power law trends. The new quadratic function was an excellent fit in every instance. It can account for why some materials can be fit by a linear trend, while others can be fit by the power law trend. The effects of indenter type are accounted for variations in crack initiation and by the wedging stresses once an indentation hole is created. The new quadratic force - edge distance function can be used with edge chipping data for all brittle materials, not just those evaluated in this study. The data trends vary from linear to nonlinear depending upon the material's hardness, fracture toughness, and elastic modulus. Copyright © 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  2. Sub-micron indent induced plastic deformation in copper and irradiated steel; Deformation plastique induite par l'essai d'indentation submicronique, dans le cuivre et l'acier 316L irradie

    Energy Technology Data Exchange (ETDEWEB)

    Robertson, Ch

    1999-07-01

    In this work we aim to study the indent induced plastic deformation. For this purpose, we have developed a new approach, whereby the indentation curves provides the mechanical behaviour, while the deformation mechanisms are observed thanks to Transmission Electron Microscopy (TEM). In order to better understand how an indent induced dislocation microstructure forms, numerical modeling of the indentation process at the scale of discrete dislocations has been worked out as well. Validation of this modeling has been performed through direct comparison of the computed microstructures with TEM micrographs of actual indents in pure Cu (001]. Irradiation induced modifications of mechanical behaviour of ion irradiated 316L have been investigated, thanks to the mentioned approach. An important hardening effect was reported from indentation data (about 50%), on helium irradiated 316L steel. TEM observations of the damage zone clearly show that this behaviour is associated with the presence of He bubbles. TEM observations of the indent induced plastic zone also showed that the extent of the plastic zone is strongly correlated with hardness, that is to say: harder materials gets a smaller plastic zone. These results thus clearly established that the selected procedure can reveal any irradiation induced hardening in sub-micron thick ion irradiated layers. The behaviour of krypton irradiated 316L steel is somewhat more puzzling. In one hand indeed, a strong correlation between the defect cluster size and densities on the irradiation temperature is observed in the 350 deg. C - 600 deg. C range, thanks to TEM observations of the damage zone. On the other hand, irradiation induced hardening reported from indentation data is relatively small (about 10%) and shows no dependence upon the irradiation temperature (within the mentioned range). In addition, it has been shown that the reported hardening vanishes following appropriate post-irradiation annealing, although most of the TEM

  3. Finite Element Analysis of Aluminum Honeycombs Subjected to Dynamic Indentation and Compression Loads

    Directory of Open Access Journals (Sweden)

    A.S.M. Ayman Ashab

    2016-03-01

    Full Text Available The mechanical behavior of aluminum hexagonal honeycombs subjected to out-of-plane dynamic indentation and compression loads has been investigated numerically using ANSYS/LS-DYNA in this paper. The finite element (FE models have been verified by previous experimental results in terms of deformation pattern, stress-strain curve, and energy dissipation. The verified FE models have then been used in comprehensive numerical analysis of different aluminum honeycombs. Plateau stress, σpl, and dissipated energy (EI for indentation and EC for compression have been calculated at different strain rates ranging from 102 to 104 s−1. The effects of strain rate and t/l ratio on the plateau stress, dissipated energy, and tearing energy have been discussed. An empirical formula is proposed to describe the relationship between the tearing energy per unit fracture area, relative density, and strain rate for honeycombs. Moreover, it has been found that a generic formula can be used to describe the relationship between tearing energy per unit fracture area and relative density for both aluminum honeycombs and foams.

  4. The indentation of pressurized elastic shells: from polymeric capsules to yeast cells

    KAUST Repository

    Vella, D.

    2011-08-10

    Pressurized elastic capsules arise at scales ranging from the 10 m diameter pressure vessels used to store propane at oil refineries to the microscopic polymeric capsules that may be used in drug delivery. Nature also makes extensive use of pressurized elastic capsules: plant cells, bacteria and fungi have stiff walls, which are subject to an internal turgor pressure. Here, we present theoretical, numerical and experimental investigations of the indentation of a linearly elastic shell subject to a constant internal pressure. We show that, unlike unpressurized shells, the relationship between force and displacement demonstrates two linear regimes. We determine analytical expressions for the effective stiffness in each of these regimes in terms of the material properties of the shell and the pressure difference. As a consequence, a single indentation experiment over a range of displacements may be used as a simple assay to determine both the internal pressure and elastic properties of capsules. Our results are relevant for determining the internal pressure in bacterial, fungal or plant cells. As an illustration of this, we apply our results to recent measurements of the stiffness of baker\\'s yeast and infer from these experiments that the internal osmotic pressure of yeast cells may be regulated in response to changes in the osmotic pressure of the external medium.

  5. High temperature indentation behavior of eutectic lead-free solder materials

    Directory of Open Access Journals (Sweden)

    Worrack H.

    2010-06-01

    Full Text Available Electronic malfunction caused by thermal stresses is one major problem in modern electronic industries. Therefore, the precise knowledge of the mechanical solder material properties as a function of temperature is required. Nanoindentation and its potential of recording load-displacement curves is a widely-used miniature test for the determination of Young’s modulus and hardness values. Furthermore, such tests can be performed in a temperature range from Room Temperature (RT up to +500°C by using a Hot-Stage add on. In this paper the lead-free solder alloys Sn91Zn9 and Sn42Bi58, and also copper and fused silica, which is used for the indenter calibration are investigated. The results for quartz and copper agree with the published values in several references. However, the Young’s modulus of Sn42Bi58 as a function of temperature differs from the values presented in the literature. Due to delayed material response in the unloading regime it must be assumed that creep effects lead to an incorrect automatic data evaluation. Investigation and understanding of the creep behavior is part of this paper. For this purpose a visco-elastic material model is used to model the indentation response at elevated temperatures and to determine the corresponding viscous material constants.

  6. Depth-sensing nano-indentation on a myelinated axon at various stages

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Wei-Chin; Liao, Jiunn-Der [Department of Materials Science and Engineering, National Cheng Kung University, 1 University Road, Tainan 70101, Taiwan (China); Lin, Chou-Ching K [Department of Neurology, National Cheng Kung University, 1 University Road, Tainan 70101, Taiwan (China); Ju, Ming-Shaung, E-mail: jdliao@mail.ncku.edu.tw [Department of Mechanical Engineering, National Cheng Kung University, 1 University Road, Tainan 70101, Taiwan (China)

    2011-07-08

    A nano-mechanical characterization of a multi-layered myelin sheath structure, which enfolds an axon and plays a critical role in the transmission of nerve impulses, is conducted. Schwann cells co-cultured in vitro with PC12 cells for various co-culture times are differentiated to form a myelinated axon, which is then observed using a transmission electron microscope. Three major myelination stages, with distinct structural characteristics and thicknesses around the axon, can be produced by varying the co-culture time. A dynamic contact module and continuous depth-sensing nano-indentation are used on the myelinated structure to obtain the load-on-sample versus measured displacement curve of a multi-layered myelin sheath, which is used to determine the work required for the nano-indentation tip to penetrate the myelin sheath. By analyzing the harmonic contact stiffness versus the measured displacement profile, the results can be used to estimate the three stages of the multi-layered structure on a myelinated axon. The method can also be used to evaluate the development stages of myelination or demyelination during nerve regeneration.

  7. Dynamic, regional mechanical properties of the porcine brain: indentation in the coronal plane.

    Science.gov (United States)

    Elkin, Benjamin S; Ilankova, Ashok; Morrison, Barclay

    2011-07-01

    Stress relaxation tests using a custom designed microindentation device were performed on ten anatomic regions of fresh porcine brain (postmortem time Prony series representation was used to describe the shear relaxation modulus for each anatomic region tested. Prony series parameters fit to load data from indentations performed to ∼10% strain differed significantly by anatomic region. The gray and white matter of the cerebellum along with corpus callosum and brainstem were the softest regions measured. The cortex and hippocampal CA1/CA3 were found to be the stiffest. To examine the large strain behavior of the tissue, multistep indentations were performed in the corona radiata to strains of 10%, 20%, and 30%. Reduced relaxation functions were not significantly different for each step, suggesting that quasi-linear viscoelastic theory may be appropriate for representing the nonlinear behavior of this anatomic region of porcine brain tissue. These data, for the first time, describe the dynamic and short time scale behavior of multiple anatomic regions of the porcine brain which will be useful for understanding porcine brain injury biomechanics at a finer spatial resolution than previously possible.

  8. Experimental creep behavior of porcine liver under indentation with laparoscopic grasper for MIS applications

    Directory of Open Access Journals (Sweden)

    Cheng-mo Cai

    2017-06-01

    Full Text Available Mechanical response of soft tissues behaved disparate due to fast and large deformation during surgical grasping, so there is a need for experimental databases of biomechanical characteristics of soft tissue under the contact of MIS tool, which are more useful for designing new surgical instruments, training inexperienced surgeons, improving surgical simulations and developing surgical robotics system. A novel indentation test to simulate the real-time surgical operation condition was present in this paper. The creep behavior of porcine liver in vitro was studied under uniaxial indentation by using MIS grasper. The nominal stress between the grasper and the liver was 0.02 to 0.1 MPa, the loading velocity was 1 to 3 mm/s, and the holding time was 300 s to simulate clamping tissue operation. Results showed that the creep process of the liver during 300 s of duration can be divided into three stages: loading stage I, transition creep stage II and steady creep stage III. The creep characteristic of liver behaves time-dependent, load-dependent and strongly loading velocity-dependent due to its nonlinear viscoelastic characteristics and hysteresis characteristics. These creep behavior might also be associated with the deformation, migration and biochemical reaction of the liver cells. The phenomenological model derived in this paper may describe the creep behavior of the liver. The results would provide experimental databases and phenomenological models for investigating biomechanical characteristics of soft tissue under the contact of MIS tool.

  9. Simultaneous Measurement of Multiple Mechanical Properties of Single Cells Using AFM by Indentation and Vibration.

    Science.gov (United States)

    Zhang, Chuang; Shi, Jialin; Wang, Wenxue; Xi, Ning; Wang, Yuechao; Liu, Lianqing

    2017-12-01

    The mechanical properties of cells, which are the main characteristics determining their physical performance and physiological functions, have been actively studied in the fields of cytobiology and biomedical engineering and for the development of medicines. In this study, an indentation-vibration-based method is proposed to simultaneously measure the mechanical properties of cells in situ, including cellular mass (m), elasticity (k), and viscosity (c). The proposed measurement method is implemented based on the principle of forced vibration stimulated by simple harmonic force using an atomic force microscope (AFM) system integrated with a piezoelectric transducer as the substrate vibrator. The corresponding theoretical model containing the three mechanical properties is derived and used to perform simulations and calculations. Living and fixed human embryonic kidney 293 (HEK 293) cells were subjected to indentation and vibration to measure and compare their mechanical parameters and verify the proposed approach. The results that the fixed sample cells are more viscous and elastic than the living sample cells and the measured mechanical properties of cell are consistent within, but not outside of the central region of the cell, are in accordance with the previous studies. This work provides an approach to simultaneous measurement of the multiple mechanical properties of single cells using an integrated AFM system based on the principle force vibration and thickness-corrected Hertz model. This study should contribute to progress in biomedical engineering, cytobiology, medicine, early diagnosis, specific therapy and cell-powered robots.

  10. Molecular dynamics simulation of nano-indentation of (111) cubic boron nitride with optimized Tersoff potential

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Yinbo [College of Aerospace Engineering, Chongqing University, Chongqing 400044 (China); Peng, Xianghe, E-mail: xhpeng@cqu.edu.cn [College of Aerospace Engineering, Chongqing University, Chongqing 400044 (China); State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044 (China); Fu, Tao; Huang, Cheng; Feng, Chao [College of Aerospace Engineering, Chongqing University, Chongqing 400044 (China); Yin, Deqiang [School of Manufacturing Science and Engineering, Sichuan University, Chengdu 610065 (China); Wang, Zhongchang, E-mail: zcwang@wpi-aimr.tohoku.ac.jp [College of Aerospace Engineering, Chongqing University, Chongqing 400044 (China); Advanced Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan)

    2016-09-30

    Highlights: • We optimize Tersoff potential to simulate the cBN better under nanoidentation. • Dislocations slip more easily along <110> and <112> directions on the {111} plane. • Shuffle-set dislocation slip along <112> direction on {111} plane first. • A tetrahedron structure is found in the initial stage of the indentation. - Abstract: We conduct molecular dynamics simulation of nanoindentation on (111) surface of cubic boron nitride and find that shuffle-set dislocations slip along <112> direction on {111} plane at the initial stage of the indentation. The shuffle-set dislocations are then found to meet together, forming surfaces of a tetrahedron. We also find that the surfaces are stacking-fault zones, which intersect with each other, forming edges of stair-rod dislocations along <110> direction. Moreover, we also calculate the generalized stacking fault (GSF) energies along various gliding directions on several planes and find that the GSF energies of the <112>{111} and <110>{111} systems are relatively smaller, indicating that dislocations slip more easily along <110> and <112> directions on the {111} plane.

  11. Driving force for indentation cracking in glass: composition, pressure and temperature dependence

    Science.gov (United States)

    Rouxel, Tanguy

    2015-01-01

    The occurrence of damage at the surface of glass parts caused by sharp contact loading is a major issue for glass makers, suppliers and end-users. Yet, it is still a poorly understood problem from the viewpoints both of glass science and solid mechanics. Different microcracking patterns are observed at indentation sites depending on the glass composition and indentation cracks may form during both the loading and the unloading stages. Besides, we do not know much about the fracture toughness of glass and its composition dependence, so that setting a criterion for crack initiation and predicting the extent of the damage yet remain out of reach. In this study, by comparison of the behaviour of glasses from very different chemical systems and by identifying experimentally the individual contributions of the different rheological processes leading to the formation of the imprint—namely elasticity, densification and shear flow—we obtain a fairly straightforward prediction of the type and extent of the microcracks which will most likely form, depending on the physical properties of the glass. Finally, some guidelines to reduce the driving force for microcracking are proposed in the light of the effects of composition, temperature and pressure, and the areas for further research are briefly discussed. PMID:25713446

  12. Static Indentation Load Capacity of the Superelastic 60NiTi for Rolling Element Bearings

    Science.gov (United States)

    DellaCorte, Christopher; Moore, Lewis E., III; Clifton, Joshua S.

    2012-01-01

    The nickel-rich, binary nickel-titanium alloys, such as 60NiTi (60Ni-40Ti by wt%), are emerging as viable materials for use in mechanical components like rolling element bearings and gears. 60NiTi is a superelastic material that simultaneously exhibits high hardness and a relatively low elastic modulus (approx.100 GPa). These properties result in the potential to endure extremely high indentation loads such as those encountered in bearings, gears and other mechanical components. In such applications, quantifying the load that results in permanent deformation that can affect component performance and life is important. In this paper, the static load capacity is measured by conducting indentation experiments in which 12.7 mm diameter balls made from the ceramic Si3N4 are pressed into highly polished, hardened 60NiTi flat plates. Hertz stress calculations are used to estimate contact stress. The results show that the 60NiTi surface can withstand an approximately 3400 kN load before significant denting (>0.6 microns deep) occurs. This load capacity is approximately twice that of high performance bearing steels suggesting that the potential exists to make highly resilient bearings and components from such materials.

  13. Fragmentation of copper current collectors in Li-ion batteries during spherical indentation

    Science.gov (United States)

    Wang, Hsin; Watkins, Thomas R.; Simunovic, Srdjan; Bingham, Philip R.; Allu, Srikanth; Turner, John A.

    2017-10-01

    Large, areal, brittle fracture of copper current collector foils has been observed by 3D x-ray computed tomography (XCT) of a spherically indented Li-ion cell. This fracture is hidden and non-catastrophic to a degree because the graphite layers deform plastically, and hold the materials together so that the cracks in the foils cannot be seen under optical and electron microscopy. The cracking of copper foils could not be immediately confirmed when the cell is opened for post-mortem examination. However, 3D XCT on the indented cell reveals ;mud cracks; within the copper layer and an X-ray radiograph on a single foil of the Cu anode shows clearly that the copper foil has broken into multiple pieces. This failure mode of anodes in Li-ion cell has very important implications on the behavior of Li-ion cells under mechanical abuse conditions. The fragmentation of current collectors in the anode must be taken into consideration for the electrochemical responses which may lead to capacity loss and affect thermal runaway behavior of the cells.

  14. An investigation of the physico-mechanical properties of pharmaceutical compounds by compaction simulator and nano-indentation

    Science.gov (United States)

    Bordawekar, Mangesh

    In early development, pharmaceutical formulation scientists are often faced with challenges of developing robust and scalable formulations in extremely stringent timelines based on limited API quantities. Hence, tablet formulation development would benefit significantly from tools that enable predictive analysis based on limited quantities of API to enable selection of excipients with appropriate physico-mechanical properties that would result in robust and scalable formulations. With the recent technological advances, especially in sensor technologies, tools such as the compaction simulator, and instrumented nanoindentation offer hitherto unavailable means of assessing material properties with limited quantities. The goal of this work was to evaluate the physico-mechanical properties of selected pharmaceutical excipients and active pharmaceutical ingredients using a macro-scale analysis technique (compaction simulator), and a micro-scale analysis technique (nanoindentation tester) and compare the results obtained from these techniques in order to determine whether a rank order correlation exists between the two. Excipients representing diverse physic-mechanical properties, and a group of APIs were selected for the study. For the compaction simulator studies, tablets were uniaxially compressed using a flat faced 11.28mm round tooling on the STYLCAM® 200R compaction simulator, to a target final porosity at two different cam speeds (5 rpm and 25 rpm). The force displacement profiles, plastic, elastic, and total compression energies, plasticity index, energy density and the Heckel plots were determined for each compact. These compacts were further analyzed with a Berkovich geometry indenter. The plasticity index, hardness, elastic modulus, as well as creep and relaxation were determined from the force-displacement profiles. The nature of force-displacement curves was studied to differentiate compounds based on predominant mechanisms of deformation. Compaction

  15. Instrumentated indentation test at high temperature for the characterization of irradiated materials; Instrumentierte Eindringpruefung bei Hochtemperatur fuer die Charakterisierung bestrahlter Materialien

    Energy Technology Data Exchange (ETDEWEB)

    Albinski, Bartlomiej

    2014-07-01

    Predicting the behavior of structural materials assigned to the use in future fusion reactors is an essential part in their development and design. Mechanical testing characterizes the new designed materials. In these tests, the expected operating conditions, i. e. high temperatures and radiation damage, have to be simulated. For this purpose, instrumented indentation is a particularly capable testing method. The relationship of force and indentation depth recorded during the indentation of a hard tip into a specimen allows to predict the mechanical parameters of the tested material. Stress and strain appearing in the material can be excerpted when using a spherical indenter tip. Consequently, besides material's hardness and Young's modulus its properties in the plastic regime can be described. Reproducing the operating conditions of a fusion reactor for the indentation test bases on two aspects. First, irradiated samples need to be tested by remote-handling methods. Second, the samples have to be heated for the experiment. Both of these requirements lead to a new testing device that allows instrumented indentation on irradiation damaged materials in a remote-handled way at temperatures up to 650 C. Installation, set-up and initial operation of this newly designed apparatus are described. This includes design and integration of the components contributing to the indentation test, the systems for measurement and feedback control of the testing parameters sample temperature, indentation force, indentation depth and time as well as supporting gear and peripherals. Existing boundary conditions have to be incorporated in this process. Experimental verification and calibration of each subsystem is done. The proper interaction between the subsystems proves the functional capability and reliability of the new high-temperature indentation device. Material tests were accomplished on a reduced-activation ferritic-martensitic steel, tungsten and tantalum using the

  16. Comparing damage from low-velocity impact and quasi-static indentation in automotive carbon/epoxy and glass/polyamide-6 laminates

    NARCIS (Netherlands)

    Spronk, S.W.F.; Kersemans, M.; Gilabert, F. A.; Sevenois, R.D.B.; Garoz, D.; Kassapoglou, C.; Van Paepegem, W.

    2018-01-01

    The results of a low-velocity impact programme on both carbon/epoxy and glass/polyamide-6 composite laminates are compared to the results of quasi-static indentation. Cross-ply and quasi-isotropic stacking sequences are impacted and quasi-static indentation tests are performed up to the same

  17. Mapping the indentation between the Iberian and Eurasian plates beneath the Western Pyrenees/Eastern Cantabrian Mountains from receiver function analysis

    Science.gov (United States)

    Díaz, J.; Pedreira, D.; Ruiz, M.; Pulgar, J. A.; Gallart, J.

    2012-10-01

    In the last decades, active seismic profiling in the northern part of the Iberian Peninsula has evidenced that the Alpine collision between the Iberian and Eurasian plates resulted in a complex crustal structure, with the Iberian crust underthrusting the Eurasian crust and reaching depths of at least 45-50 km beneath the Pyrenean chain and the Cantabrian Mountains. In the transition between these two zones the situation is particularly complex, as evidenced in previous wide-angle and passive seismic studies. This contribution focuses in getting new clues on the crustal structure of this transitional zone through receiver function (RF) analysis of teleseismic data recorded at permanent and temporary stations located in both the Spanish and French sides of the Western Pyrenees. Different techniques (H-κ stacking, pseudo-migration, synthetic 2D modeling) have been considered in the analysis. Passive seismic data from previous temporary deployments in the zone have been reworked and added to the discussion. A first order result is that passive seismic data are broadly consistent with the indentation of the Iberian and Eurasian crusts inferred from active seismic profiling, thus providing a completely independent confirmation of this feature. For the first time, an Iberian Moho underlying the Eurasian crust is documented from RF beneath the stations located at the Northern side of the Pyrenean range. Moreover, clear indications of dipping interfaces are observed at some stations. The new RF results suggest that in the crustal indentation beneath the Basque Massifs area, the Eurasian crust extends farther south with respect to the image inferred from active seismic data. This new geometry implies that the Pamplona transfer zone has played a major role in the regional geodynamic history.

  18. In-depth hardness profiles of stainless steel and Ni-Ti endodontic instrument cross-sections by nano-indentation.

    Science.gov (United States)

    Zinelis, S; Akhtar, R; Tsakiridis, P; Watts, D C; Silikas, N

    2008-09-01

    To evaluate the in-depth hardness profiles of Stainless Steel (SS) and nickel titanium (Ni-Ti) endodontic instrument cross-sections using a nano-indentation technique. Three SS (Reamer, K and Hedström) and three Ni-Ti (ProFile, NRT and Liberator) instruments were studied. After embedding and metallographic preparation the in-depth hardness profiles of instrument cross-sections were measured starting from the cutting surface towards the centre to a depth of 2000 nm using an MTS XP nanoindenter with a Berkovich diamond indenter. The results of hardness measurements of outer (near to cutting edge) and inner locations were statistically analyzed by two-way anova followed by SNK test (alpha = 0.05). For all instrument cross-sections the maximum hardness was obtained at the outer surface followed by hardness attenuation towards the centre of the cross section. The statistical analysis of hardness classified the instruments, for both outer and innermost locations, to the following decreasing order: Reamer > K > Hedström > Profile > NRT shank (without thermal treatment) > NRT tip (with thermal treatment) > Liberator. The maximal hardness, at the outer surface of endodontic instruments, can be attributed to the residual stresses developed due to cutting and thermal effects during the manufacturing process. The increased outer layer hardness may have a beneficial effect on the cutting ability and wear resistance of endodontic instruments. All endodontic instruments had a decrease in hardness towards their centre. This implies that the surface hardness of contemporary endodontic instruments is significantly enhanced by the consequences of manufacturing processes.

  19. Depassivation-repassivation behavior of type-312L stainless steel in NaCl solution investigated by the micro-indentation

    Energy Technology Data Exchange (ETDEWEB)

    Yamamoto, Takatoshi [Graduate School of Engineering, Hokkaido University, Kita-13 Jo, Nishi-8 Chome, Kita-ku, 060-8628 Sapporo (Japan)], E-mail: t-yama@eng.hokudai.ac.jp; Fushimi, Koji; Seo, Masahiro [Graduate School of Engineering, Hokkaido University, Kita-13 Jo, Nishi-8 Chome, Kita-ku, 060-8628 Sapporo (Japan); Tsuri, Shiro [JFE Steel Co., Minamiwatarida-cho, Kawasaki-ku, 210-0855 Kawasaki (Japan); Adachi, Tetsuo [Nippon Yakin Kogyo Co., Ltd., Kyobashi, Chuo-ku, 104-8365 Tokyo (Japan); Habazaki, Hiroki [Graduate School of Engineering, Hokkaido University, Kita-13 Jo, Nishi-8 Chome, Kita-ku, 060-8628 Sapporo (Japan)

    2009-07-15

    Repassivation behavior of type-312L stainless steel containing 6% of molybdenum was examined in NaCl solution using in situ micro-indentation technique, together with type-304 and 316L stainless steels. High stability of the passive film formed on the type-312L stainless steel was also examined by depth profiling analysis of passive films using glow discharge optical emission spectroscopy (GDOES). In 0.9 mol dm{sup -3} NaCl solution at 296 K the type-304 and 316L stainless steels are passive only up to 0.3 V (SHE), above which pitting corrosion occurs. In contrast, no pitting corrosion occurs on type-312L stainless steel. Despite the significant difference of the pitting corrosion resistance, the repassivation kinetics of the three stainless steels, examined by micro-indentation at 0.3 V (SHE), is similar. The presence of molybdenum in the stainless steel does not influence the repassivation kinetics. The charge required to repassivate the ruptured type-312L stainless steel surface increases approximately linearly with the potential, even though the passivity-maintaining current increased markedly at potentials close to the transpassive region. Repassivation occurs without accompanying significant dissolution of steel, regardless of the stability of passive state. Depth profiling analyses of the passive films on the type-312L stainless steels formed at several potentials revealed that molybdenum species enrich in the outer layer of the passive film, below which chromium-enriched layer is present. The permeation of chloride ions may be impeded by the outer layer containing molybdate, enhancing the resistance against the localized corrosion of the type-312L stainless steel.

  20. Characterization of damage mechanisms associated with reference point indentation in human bone.

    Science.gov (United States)

    Beutel, Bryan G; Kennedy, Oran D

    2015-06-01

    Measurement of bone mineral density (BMD) is the clinical gold standard in cases of compromised skeletal integrity, such as with osteoporosis. While BMD is a useful measurement to index skeletal health, it is also limited since it cannot directly assess any mechanical properties. The ability to directly assess mechanical properties of bone tissue would be clinically important. Reference point indentation (RPI) is a technology that has been designed to try and achieve this goal. While RPI has been shown to detect altered bone tissue properties, the underlying physical mechanism of these measurements has not been characterized. Thus, we designed a study whereby the contribution of (1) test cycle number and (2) test load level to RPI test-induced sub-surface damage was characterized and quantified. Standardized specimens were prepared from cadaveric human tibiae (n=6), such that 12 replicates of each testing condition could be carried out. A custom rig was fabricated to accurately position and map indentation sites. One set of tests was carried out with 1, 5, 10, 15 and 20 cycles (Max Load: 8 N, Freq: 2 Hz), and a second set of tests was carried out with Load levels of 2, 4, 6, 8 or 10 N (Cycle number: 20, Freq: 2 Hz). The RPI parameter Loading Slope (LS) was cycle dependent at 5, 10, 15 and 20 cycles (pbasal level of 2 N (p<0.05). The damage area parameter in both protocols was significantly different from baseline at the three upper levels tested (i.e. 10, 15, 20 cycles and 6, 8, 10 N, in cycle and load variant protocols, respectively). Specimens were scanned by micro-computed tomography, which showed no material or microstructural differences between samples, and processed for histological analyses and damage quantification. Consistent microdamage patterns were present with evidence of damage via compaction at the indented regions. While damage in the direction of loading was established early, the damage area then increased radially with cycle number. These data

  1. Influence of loading path and precipitates on indentation creep behavior of wrought Mg–6 wt% Al–1 wt% Zn magnesium alloy

    Energy Technology Data Exchange (ETDEWEB)

    Nautiyal, Pranjal [Discipline of Mechanical Engineering, Indian Institute of Information Technology, Design & Manufacturing, Jabalpur, Madhya Pradesh 482005 (India); Department of Applied Mechanics, Indian Institute of Technology, Delhi 110016 (India); Jain, Jayant [Department of Applied Mechanics, Indian Institute of Technology, Delhi 110016 (India); Agarwal, Arvind, E-mail: agarwala@fiu.edu [Department of Mechanical and Materials Engineering, Florida International University, Miami, FL 33174 (United States)

    2016-01-05

    This study reports the effect of loading path and precipitates on indentation induced creep behavior of AZ61 magnesium alloy. Indentation creep tests were performed on solution-treated and peak-aged extruded AZ61 magnesium alloy, and Atomic Force Microscopy (AFM) investigations were carried out to study deformation mechanisms. Twinning is the dominant creep mechanism for indentation along the extrusion direction (ED) in solution-treated alloy. A combination of slip and twinning appears to be the prominent mechanisms for indentation creep perpendicular to ED. Creep flow is arrested for indentation perpendicular to ED, due to slip–twin interactions. Influence of precipitates on creep deformation was also studied. Aged specimen exhibited higher creep resistance than solution-treated specimen. Unlike solution-treated specimens, twinning was not observed in aged alloy. Creep in aged specimen was attributed to slip.

  2. Development of nanoindentation techniques for characterizing local mechanical properties of soft materials

    Science.gov (United States)

    Wood, Charles David

    Indentation has become a popular mechanical characterization technique due to the promise of high-resolution maps of material stiffness. Due to the far-reaching nature of the testing framework, indentation tests can occur on nearly any material type and on any length scale. In this dissertation, we will look at three different materials systems and demonstrate new and unique uses for the indentation framework. These results will provide information not available by other methodologies, thereby proving its universal value. Two different indentation schemes are employed, either probing the top surface of cross-section samples or by probing into the thickness of a thin film. The differences between each of the studies highlight the importance of sample geometry/orientation, contact conditions, material response, etc. First, we will use indentation to probe local regions near carbon nanotube/glass fiber hybrid composites in an epoxy matrix. Indentations were performed to determine the radial gradient of modulus enhancements from the glass fiber surface. The results from indentation demonstrated that spatial reinforcement due to the presence of nanotubes was tied to fiber morphology and not the local morphology of carbon nanotubes. Secondly, we look at rubber and filler interaction on two different levels; macroscale and nanoscale. On the nanoscale, we show that interactions at the filler/polymer interface create regions of altered polymer mobility. These regions are influenced by geometric and chemical confinement, which increase the stiffness of these small regions (soft materials, such as hydrogels and tissues, pose rather unique challenges when they are tested mechanically. However, with tissues and gels, the sensitivity of the machines is challenged and therefore protocols must be developed to produce accurate results. We validate indentation results on a variety of soft materials and demonstrate the proper corrections for these materials. Once validated

  3. Processing, nano indentation and scratch testing of alumina-coated YTZP

    Energy Technology Data Exchange (ETDEWEB)

    Valle, J.; Anglada, M.; Ferrari, B.; Baudin, C.

    2015-10-01

    In this work, alumina-coated YTZP materials are proposed as means to combine the mechanical reliability of YTZP with the stiffness and hardness of alumina. Additionally, compressive stresses are developed in the alumina coating when cooling from the sintering temperature due to the thermal expansion mismatch between alumina and YTZP. The proposed processing method involves dipping of pre-sintered YTZP specimens in stable alumina suspensions and co-sintering of the dipped specimens. The influence of the processing parameters on the macro and microstructure of the materials has been established. Berkovich indentation has been performed to determine the Young's modulus of the substrates and coatings. The structural integrity of the coatings has been analysed using scratch tests. The Young's modulus. The optimised specimens present high resistance to scratch up to loads of 150 N. (Author)

  4. Development of lowdrag aerodynamically stable with indented processing; Indento kako wo hodokoshita seishin keburu no kaihatsu

    Energy Technology Data Exchange (ETDEWEB)

    Hojo, T.; Yamazaki, S.; Okada, H.

    1998-10-29

    A wind-resistant design of cables for large cable-stayed bridges is required as a measure against rain-wind induced vibration. In such bridges, many cables are arranged in a short pitch, which causes a large drag force on the cables. Therefore, reduction of drag force on cables is essential for rationalizing bridge design, as well as restraint of vibration. This paper describes studies on a new cable having both a low drag co-efficient force and rain-vibration suppressing effects. Through many investigations using wind tunnel tests, an indented cable was developed as a countermeasure against rain-wind induced vibration, and finally it was applied to the Tatara Bridge which is the largest cable-stayed bridge in the world. (author)

  5. A Numerical Framework for Self-Similar Problems in Plasticity: Indentation in Single Crystals

    DEFF Research Database (Denmark)

    Juul, Kristian Jørgensen; Niordson, Christian Frithiof; Nielsen, Kim Lau

    procedures that may be associated with severe numerical difficulties relating to sufficient discretization, moving contact points, etc. In the present work, self-similarity is exploited to construct the numerical framework that offers a simple and efficient method to handle self-similar problems in history......A new numerical framework specialized for analyzing self-similar problems in plasticity is developed. Self-similarity in plasticity is encountered in a number of different problems such as stationary cracks, void growth, indentation etc. To date, such problems are handled by traditional Lagrangian...... obtained without encountering many of the issues related to the traditional procedures and guarantees that it is indeed the self-similar solution that has been found....

  6. A combination of concave/convex surfaces for field-enhancement optimization: the indented nanocone.

    Science.gov (United States)

    García-Etxarri, Aitzol; Apell, Peter; Käll, Mikael; Aizpurua, Javier

    2012-11-05

    We introduce a design strategy to maximize the Near Field (NF) enhancement near plasmonic antennas. We start by identifying and studying the basic electromagnetic effects that contribute to the electric near field enhancement. Next, we show how the concatenation of a convex and a concave surface allows merging all the effects on a single, continuous nanoantenna. As an example of this NF maximization strategy, we engineer a nanostructure, the indented nanocone. This structure, combines all the studied NF maximization effects with a synergistic boost provided by a Fano-like interference effect activated by the presence of the concave surface. As a result, the antenna exhibits a NF amplitude enhancement of ~ 800, which transforms into ~1600 when coupled to a perfect metallic surface. This strong enhancement makes the proposed structure a robust candidate to be used in field enhancement based technologies. Further elaborations of the concept may produce even larger and more effective enhancements.

  7. Indentation recovery in GdPO4 and observation of deformation twinning

    Directory of Open Access Journals (Sweden)

    Taylor M. Wilkinson

    2016-09-01

    Full Text Available A series of nanoindentation tests on both single and polycrystalline specimens of a monazite rare-earth orthophosphate, GdPO4, revealed frequent observation of anomalous unloading behavior with a large degree of recovery, where previously this behavior had only been observed in xenotime-structure rare-earth orthophosphates. An indentation site in the polycrystalline sample was examined using TEM to identify the deformation mechanism responsible for recovery. The presence of a twin along the (100 orientation, along with a series of stacking faults contained within the deformation site, provide evidence that the mechanism of recovery in GdPO4 is the collapse of deformation twins during unloading.

  8. Investigation on the Interface Characteristics of the Thermal Barrier Coating System through Flat Cylindrical Indenters

    Directory of Open Access Journals (Sweden)

    Shifeng Wen

    2014-01-01

    Full Text Available Thermal barrier coating (TBC systems are highly advanced material systems and usually applied to insulate components from large and prolonged heat loads by utilizing thermally insulating materials. In this study, the characteristics of the interface of thermal barrier coating systems have been simulated by the finite-element method (FEM. The emphasis was put on the stress distribution at the interface which is beneath the indenter. The effect of the interface roughness, the thermally grown oxide (TGO layer's thickness, and the modulus ratio (η of the thin film with the substrate has been considered. Finite-element results showed that the influences of the interface roughness and the TGO layer's thickness on stress distribution were important. At the same time, the residual stress distribution has been investigated in detail.

  9. Influence of tip indentation on the adhesive behavior of viscoelastic polydimethylsiloxane networks studied by atomic force microscopy

    NARCIS (Netherlands)

    Pickering, J.P.; Vancso, Gyula J.

    2001-01-01

    A commercial atomic force microscope (AFM) outfitted with a custom control and data acquisition system was used to investigate the adhesive nature of a viscoelastic polydimethylsiloxane (PDMS) network. Due to the complex dependence of the adhesion of this sample on factors such as indentation,

  10. Quantitative study of the elastic modulus of loosely attached cells in AFM indentation experiments.

    Science.gov (United States)

    Dokukin, Maxim E; Guz, Nataliia V; Sokolov, Igor

    2013-05-21

    When measuring the elastic (Young's) modulus of cells using AFM, good attachment of cells to a substrate is paramount. However, many cells cannot be firmly attached to many substrates. A loosely attached cell is more compliant under indenting. It may result in artificially low elastic modulus when analyzed with the elasticity models assuming firm attachment. Here we suggest an AFM-based method/model that can be applied to extract the correct Young's modulus of cells loosely attached to a substrate. The method is verified by using primary breast epithelial cancer cells (MCF-7) at passage 4. At this passage, approximately one-half of cells develop enough adhesion with the substrate to be firmly attached to the substrate. These cells look well spread. The other one-half of cells do not develop sufficient adhesion, and are loosely attached to the substrate. These cells look spherical. When processing the AFM indentation data, a straightforward use of the Hertz model results in a substantial difference of the Young's modulus between these two types of cells. If we use the model presented here, we see no statistical difference between the values of the Young's modulus of both poorly attached (round) and firmly attached (close to flat) cells. In addition, the presented model allows obtaining parameters of the brush surrounding the cells. The cellular brush observed is also statistically identical for both types of cells. The method described here can be applied to study mechanics of many other types of cells loosely attached to substrates, e.g., blood cells, some stem cells, cancerous cells, etc. Copyright © 2013 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  11. Mechanical characterization of micro/nanoscale structures for MEMS/NEMS applications using nanoindentation techniques.

    Science.gov (United States)

    Li, Xiaodong; Bhushan, Bharat; Takashima, Kazuki; Baek, Chang-Wook; Kim, Yong-Kweon

    2003-01-01

    Mechanical properties of micro/nanoscale structures are needed to design reliable micro/nanoelectromechanical systems (MEMS/NEMS). Micro/nanomechanical characterization of bulk materials of undoped single-crystal silicon and thin films of undoped polysilicon, SiO(2), SiC, Ni-P, and Au have been carried out. Hardness, elastic modulus and scratch resistance of these materials were measured by nanoindentation and microscratching using a nanoindenter. Fracture toughness was measured by indentation using a Vickers indenter. Bending tests were performed on the nanoscale silicon beams, microscale Ni-P and Au beams using a depth-sensing nanoindenter. It is found that the SiC film exhibits higher hardness, elastic modulus and scratch resistance as compared to other materials. In the bending tests, the nanoscale Si beams failed in a brittle manner with a flat fracture surface. The notched Ni-P beam showed linear deformation behavior followed by abrupt failure. The Au beam showed elastic-plastic deformation behavior. FEM simulation can well predict the stress distribution in the beams studied. The nanoindentation, scratch and bending tests used in this study can be satisfactorily used to evaluate the mechanical properties of micro/nanoscale structures for use in MEMS/NEMS.

  12. Photoplastic effect in polycarbonate using microhardness ...

    Indian Academy of Sciences (India)

    Vickers microhardness indentation technique has been employed to detect the photoplastic effect in the transparent polycarbonate specimens in darkness and under mercury illumination. For low applied loads, the hardening of specimens under illumination confirms the positive photoplastic effect that causes ...

  13. Thermomechanics of calendering, indenting and laminating porous webs: Computer-aided theory and experiments

    Science.gov (United States)

    Aggelidis, Costas Nickolaos

    2007-12-01

    Calendering is the name of a forming process in the polymer industry, of a finishing operation in papermaking, and of a post-coating smoothing step. Common to all three is flow of a solid-like material between two counter-rotating rolls. Experiments of paper calendering reveal the effects of nip loading and roll surface temperature on the surface roughness, gloss, and elastic properties of paper, as well as on the porosity reduction of the surface layers of paper handsheets from images of a two-photon confocal microscope. Lamination refers to pressing together two substrates with adhesive between. It also is commonly done between two counter-rotating rolls. A simple theoretical model and experiments of lamination of three-layer composites show the effects of web tensions, nip loading and roll speed on the curl and hang of the laminate, air entrapment and delamination. The deformation in calendering commonly spans viscous, elastic, plastic, and various combinations of these. A constitutive theory of poro-elasto-viscoplastic materials for finite deformations is developed based on thermodynamics of internal variables and the principle of maximum dissipation. Internal variables represent changes of deviatoric and total elastic stress-free states, i.e. deviatoric and isotropic yielding. Two scalar potentials, the free energy and the yield or dissipation function, describe the evolution of the elastic stress-free states. Indentation is commonly used to estimate material properties, like modulus and hardness, and visualize the deformation of the surface zones. A spherical cavity model for finite elasto-poro-plastic materials predicts the effect of isotropic yielding or change of total elastic stress-free state on indentation load and the size of plastic region. A calendering model of slab analysis for plastic and poro-plastic materials reveals the effects of the friction coefficient and of isotropic yielding on the stress distribution and densification in the calendering

  14. A viscoelastic analysis of the P56 mouse brain under large-deformation dynamic indentation.

    Science.gov (United States)

    MacManus, David B; Pierrat, Baptiste; Murphy, Jeremiah G; Gilchrist, Michael D

    2017-01-15

    The brain is a complex organ made up of many different functional and structural regions consisting of different types of cells such as neurons and glia, as well as complex anatomical geometries. It is hypothesized that the different regions of the brain exhibit significantly different mechanical properties which may be attributed to the diversity of cells within individual brain regions. The regional viscoelastic properties of P56 mouse brain tissue, up to 70μm displacement, are presented and discussed in the context of traumatic brain injury, particularly how the different regions of the brain respond to mechanical loads. Force-relaxation data obtained from micro-indentation measurements were fit to both linear and quasi-linear viscoelastic models to determine the time and frequency domain viscoelastic response of the pons, cortex, medulla oblongata, cerebellum, and thalamus. The damping ratio of each region was also determined. Each region was found to have a unique mechanical response to the applied displacement, with the pons and thalamus exhibiting the largest and smallest force-response, respectively. All brain regions appear to have an optimal frequency for the dissipation of energies which lies between 1 and 10Hz. We present the first mechanical characterization of the viscoelastic response for different regions of mouse brain. Force-relaxation tests are performed under large strain dynamic micro-indentation, and viscoelastic models are used subsequently, providing time-dependent mechanical properties of brain tissue under loading conditions comparable to what is experienced in TBI. The unique mechanical properties of different brain regions are highlighted, with substantial variations in the viscoelastic properties and damping ratio of each region. Cortex and pons were the stiffest regions, while the thalamus and medulla were most compliant. The cerebellum and thalamus had highest damping ratio values and those of the medulla were lowest. The reported

  15. Shear transformation zone activation during deformation in bulk metallic glasses characterized using a new indentation creep technique

    Science.gov (United States)

    J.B. Puthoff; H.B. Cao; Joseph E. Jakes; P.M. Voyles; D.S. Stone

    2009-01-01

    We have developed a novel type of nanoindentation creep experiment, called broadband nanoindentation creep (BNC), and used it to characterize the thermal activation of shear transformation zones (STZs) in three BMGs in the Zr-Cu-Al system. Using BNC, material hardness can be determined across a wide range of strain rates (10–4 to 10 s–...

  16. Stress state of the box shell under the indentation of two inclusions

    Directory of Open Access Journals (Sweden)

    Vladimir А. Grishin

    2015-03-01

    Full Text Available Thin-walled structures are widely used in various fields in modern technologies of mechanical engineering, construction, aviation industry, shipbuilding, rocket engineering, oil, gas and other industries. Variety of forms of such structures, various loading conditions and pinning, presence of defects and inhomogeneities lead to wide range of different formulations of the problems of research on strength characteristics of such structures and methods used for this purpose. The characteristic feature of this type of problems is the difficulty of their analytical or numerical solving. Assessment of convergence of numerical method solution requires the ability to compare the numerical results with analytical solution results of the corresponding problem.The research is devoted to solving the problem of stress state of box-shell with rectangular profile and infinite length under the indentation of two symmetrically arranged thin rigid inclusions. The problem is reduced to a system of integral equations. The solution is sought in the space of functions that have nonintegrable singularities using the apparatus of the regularization of divergent integrals. Obtained infinite system of linear algebraic equations is solved by the method of reduction. There are obtained the numerical values of the upsettings of inclusions depending on inclusions length and ratios of geometric dimensions of the cross-section of the shell.

  17. Particle-induced indentation of the alveolar epithelium caused by surface tension forces

    Science.gov (United States)

    Kojic, M.; Tsuda, A.

    2010-01-01

    Physical contact between an inhaled particle and alveolar epithelium at the moment of particle deposition must have substantial effects on subsequent cellular functions of neighboring cells, such as alveolar type-I, type-II pneumocytes, alveolar macrophage, as well as afferent sensory nerve cells, extending their dendrites toward the alveolar septal surface. The forces driving this physical insult are born at the surface of the alveolar air-liquid layer. The role of alveolar surfactant submerging a hydrophilic particle has been suggested by Gehr and Schürch's group (e.g., Respir Physiol 80: 17–32, 1990). In this paper, we extended their studies by developing a further comprehensive and mechanistic analysis. The analysis reveals that the mechanics operating in the particle-tissue interaction phenomena can be explained on the basis of a balance between surface tension force and tissue resistance force; the former tend to move a particle toward alveolar epithelial cell surface, the latter to resist the cell deformation. As a result, the submerged particle deforms the tissue and makes a noticeable indentation, which creates unphysiological stress and strain fields in tissue around the particle. This particle-induced microdeformation could likely trigger adverse mechanotransduction and mechanosensing pathways, as well as potentially enhancing particle uptake by the cells. PMID:20634359

  18. Randomness and Statistical Laws of Indentation-Induced Pop-Out in Single Crystal Silicon.

    Science.gov (United States)

    Huang, Hu; Zhao, Hongwei; Shi, Chengli; Zhang, Lin; Wan, Shunguang; Geng, Chunyang

    2013-04-12

    Randomness and discreteness for appearance of pop-out of the single crystal silicon with a (100) orientation were studied by a self-made indentation device. For a given maximum penetration load, the load Ppo for appearance of pop-out fluctuates in a relatively large range, which makes it hard to study the effect of the loading/unloading rate on the load Ppo. Experimental results with different maximum penetration loads indicate that the critical penetration load for appearance of pop-out is in the range of 15 mN~20 mN for the current used single crystal silicon. For a given maximum penetration load, the load Ppo for appearance of pop-out seems random and discrete, but in the point of statistics, it has an obviously increasing trend with increase of the maximum penetration load and also the fraction Ppo/Pmax approximately keeps in the range of 0.2~0.5 for different maximum penetration loads changing from 15 mN to 150 mN.

  19. Non-integer viscoelastic constitutive law to model soft biological tissues to in-vivo indentation.

    Science.gov (United States)

    Demirci, Nagehan; Tönük, Ergin

    2014-01-01

    During the last decades, derivatives and integrals of non-integer orders are being more commonly used for the description of constitutive behavior of various viscoelastic materials including soft biological tissues. Compared to integer order constitutive relations, non-integer order viscoelastic material models of soft biological tissues are capable of capturing a wider range of viscoelastic behavior obtained from experiments. Although integer order models may yield comparably accurate results, non-integer order material models have less number of parameters to be identified in addition to description of an intermediate material that can monotonically and continuously be adjusted in between an ideal elastic solid and an ideal viscous fluid. In this work, starting with some preliminaries on non-integer (fractional) calculus, the "spring-pot", (intermediate mechanical element between a solid and a fluid), non-integer order three element (Zener) solid model, finally a user-defined large strain non-integer order viscoelastic constitutive model was constructed to be used in finite element simulations. Using the constitutive equation developed, by utilizing inverse finite element method and in vivo indentation experiments, soft tissue material identification was performed. The results indicate that material coefficients obtained from relaxation experiments, when optimized with creep experimental data could simulate relaxation, creep and cyclic loading and unloading experiments accurately. Non-integer calculus viscoelastic constitutive models, having physical interpretation and modeling experimental data accurately is a good alternative to classical phenomenological viscoelastic constitutive equations.

  20. Viscoelastic properties of the P17 and adult rat brain from indentation in the coronal plane.

    Science.gov (United States)

    Elkin, Benjamin S; Morrison, Barclay

    2013-11-01

    This technical brief serves as an update to our previous work characterizing the region-dependence of viscoelastic mechanical properties of the P17 and adult rat brain in the coronal plane (Elkin et al., 2011, "A Detailed Viscoelastic Characterization of the P17 and Adult Rat Brain," J. Neurotrauma, 28, pp. 2235-2244.). Here, modifications to the microindentation device provided for the reliable measurement of load during the ramp portion of load relaxation microindentation tests. In addition, a correction factor for finite sample thickness was incorporated to more accurately assess the intrinsic mechanical properties of the tissue.The shear relaxation modulus was significantly dependent on the anatomic region and developmental age, with a general increase in stiffness with age and increased stiffness in the hippocampal and cortical regions compared with the white matter and cerebellar regions of the brain. The shear modulus ranged from ∼0.2 kPa to ∼2.6 kPa depending on region, age, and time scale. Best-fit Prony series parameters from least squares fitting to the indentation data from each region are reported, which describe the shear relaxation behavior for each anatomic region within each age group at both short (<10 ms) and long (∼20 s) time scales. These data will be useful for improving the biofidelity of finite element models of rat brain deformation at short time scales, such as models of traumatic brain injury.

  1. If Cell Mechanics Can Be Described by Elastic Modulus: Study of Different Models and Probes Used in Indentation Experiments

    Science.gov (United States)

    Guz, Nataliia; Dokukin, Maxim; Kalaparthi, Vivekanand; Sokolov, Igor

    2014-01-01

    Here we investigated the question whether cells, being highly heterogeneous objects, could be described with the elastic modulus (effective Young’s modulus) in a self-consistent way. We performed a comparative analysis of the elastic modulus derived from the indentation data obtained with atomic force microscopy (AFM) on human cervical epithelial cells (both normal and cancerous). Both sharp (cone) and dull (2500-nm radius sphere) AFM probes were used. The indentation data were processed through different elastic models. The cell was approximated as a homogeneous elastic medium that had either 1), smooth hemispherical boundary (Hertz/Sneddon models) or 2), the boundary covered with a layer of glycocalyx and membrane protrusions (“brush” models). Consistency of these approximations was investigated. Specifically, we tested the independence of the elastic modulus of the indentation depth, which is assumed in these models. We demonstrated that only one model showed consistency in treating cells as a homogeneous elastic medium, namely, the brush model, when processing the indentation data collected with the dull AFM probe. The elastic modulus demonstrated strong depth dependence in all models: Hertz/Sneddon models (no brush taken into account), and when the brush model was applied to the data collected with sharp conical probes. We conclude that it is possible to describe the elastic properties of the cell body by means of an effective elastic modulus, used in a self-consistent way, when using the brush model to analyze data collected with a dull AFM probe. The nature of these results is discussed. PMID:25099796

  2. Nano-indentation creep properties of the S2 cell wall lamina and compound corner middle lamella [abstract

    Science.gov (United States)

    Joseph E. Jakes; Charles R. Frihart; James F. Beecher; Donald S. Stone

    2010-01-01

    Bulk wood properties are derived from an ensemble of processes taking place at the micron-scale, and at this level the properties differ dramatically in going from cell wall layers to the middle lamella. To better understand the properties of these micron-scaled regions of wood, we have developed a unique set of nano-indentation tools that allow us to measure local...

  3. Indentation of the Pamirs with respect to the northern margin of Tibet: Constraints from the Tarim basin sedimentary record

    Science.gov (United States)

    Blayney, Tamsin; Najman, Yani; Dupont-Nivet, Guillaume; Carter, Andy; Millar, Ian; Garzanti, Eduardo; Sobel, Ed; Rittner, Martin; Ando, Sergio; Gao, Zhaojie; Vezzoli, Giovanni

    2017-04-01

    The Pamirs represent the indented westward continuation of the northern margin of the Tibetan Plateau, dividing the Tarim and Tajik basins. Their evolution may be a key factor influencing aridification of the Asian interior, yet the tectonics of the Pamir Salient are poorly understood. We present a provenance study of the Aertashi section, a Paleogene to late Neogene clastic succession deposited in the Tarim basin to the north of the NW margin of Tibet (the West Kunlun) and to the east of the Pamirs. Our detrital zircon U-Pb ages coupled with zircon fission track, bulk rock Sm-Nd, and petrography data document changes in contributing source terranes during the Oligocene to Miocene, which can be correlated to regional tectonics. We propose a model for the evolution of the Pamir and West Kunlun (WKL), in which the WKL formed topography since at least 200 Ma. By 25 Ma, movement along the Pamir-bounding faults such as the Kashgar-Yecheng Transfer System had commenced, marking the onset of Pamir indentation into the Tarim-Tajik basin. This is coincident with basinward expansion of the northern WKL margin, which changed the palaeodrainage pattern within the Kunlun, progressively cutting off the more southerly WKL sources from the Tarim basin. An abrupt change in the provenance and facies of sediments at Aertashi has a maximum age of 14 Ma; this change records when the Pamir indenter had propagated sufficiently far north that the North Pamir was now located proximal to the Aertashi region. Reference: Blayney, T., et al. (2016), Indentation of the Pamirs with respect to the northern margin of Tibet: Constraints from the Tarim basin sedimentary record, Tectonics, 35, doi:10.1002/ 2016TC004222.

  4. Relationship between thin-film bond strength as measured by a scratch test, and indentation hardness for bonding agents.

    Science.gov (United States)

    Kusakabe, Shusuke; Rawls, H Ralph; Hotta, Masato

    2016-03-01

    To evaluate thin-film bond strength between a bonding agent and human dentin, using a scratch test, and the characteristics and accuracy of measurement. One-step bonding agents (BeautiBond; Bond Force; Adper Easy Bond; Clearfil tri-S Bond) and two-step bonding agents (Cleafil SE Bond; FL-Bond II) were investigated in this study. Flat dentin surfaces were prepared for extracted human molars. The dentin surfaces were ground and bonding agents were applied and light cured. The thin-film bond strength test of the specimens was evaluated by the critical load at which the coated bonding agent failed and dentin appeared. The scratch mark sections were then observed under a scanning electron microscope. Indentation hardness was evaluated by the variation in depth under an applied load of 10gf. Data were compared by one-way ANOVA with the Scheffé's post hoc multiple comparison test (phardness were analyzed using analysis of correlation and covariance. The thin-film bond strength of two-step bonding agents were found to be significantly higher than that of one-step bonding agents with small standard deviations. Scratch marks consistently showed adhesive failure in the vicinity of the bonding agent/dentin interface. The indentation hardness showed a trend that two-step bonding agents have greater hardness than one-step bonding agents. A moderately significant correlation (r(2)=0.31) was found between thin-film bond strength and indentation hardness. Thin-film bond strength test is a valid and reliable means of evaluating bond strength in the vicinity of the adhesive interface and is more accurate than other methods currently in use. Further, the thin-film bond strength is influenced by the hardness of the cued bonding agent. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  5. Comparison of the aerodynamics of bridge cables with helical fillets and a pattern-indented surface in normal flow

    DEFF Research Database (Denmark)

    Kleissl, Kenneth; Georgakis, Christos

    2011-01-01

    Over the last two decades, several bridge cable manufacturers have introduced surface modi-fications on the high-density polyethylene (HDPE) sheathing that is often installed for the protection of inner strands. The main goal of this is rain rivulet impedance, leading to the suppression of rain......-wind induced vibrations (RWIVs). The modifications are based on re-search undertaken predominantly in Europe and Japan, with two different systems prevailing; HDPE tubing fitted with helical surface fillets and HDPE tubing with pattern-indented sur-faces. In the US and Europe, helical fillets dominate, whilst...

  6. Impact of soft contact lens edge design and midperipheral lens shape on the epithelium and its indentation with lens mobility.

    Science.gov (United States)

    Wolffsohn, James S; Drew, Thomas; Dhallu, Sandeep; Sheppard, Amy; Hofmann, Greg J; Prince, Mark

    2013-09-11

    To evaluate the influence of soft contact lens midperipheral shape profile and edge design on the apparent epithelial thickness and indentation of the ocular surface with lens movement. Four soft contact lens designs comprising of two different plano midperipheral shape profiles and two edge designs (chiseled and knife edge) of silicone-hydrogel material were examined in 26 subjects aged 24.7 ± 4.6 years, each worn bilaterally in randomized order. Lens movement was imaged enface on insertion, at 2 and 4 hours with a high-speed, high-resolution camera simultaneous to the cross-section of the edge of the contact lens interaction with the ocular surface captured using optical coherence tomography (OCT) nasally, temporally, and inferiorly. Optical imaging distortions were individually corrected for by imaging the apparent distortion of a glass slide surface by the removed lens. Apparent epithelial thickness varied with edge position (P design. Horizontal and vertical lens movement did not change with time postinsertion. Vertical motion was affected by midperipheral lens shape profile (P design (P designs. Dynamic OCT coupled with high-resolution video demonstrated that soft contact lens movement and image-corrected ocular surface indentation were influenced by both lens edge design and midperipheral lens shape profiles.

  7. Multi-Material 3-D Viscoelastic Model of a Transtibial Residuum from In-vivo Indentation and MRI Data

    CERN Document Server

    Sengeh, David Moinina; Petron, Arthur; Herr, Hugh

    2016-01-01

    Although the socket is critical in a prosthetic system for a person with limb amputation, the methods of its design are largely artisanal. A roadblock for a repeatable and quantitative socket design process is the lack of predictive and patient specific biomechanical models of the residuum. This study presents the evaluation of such a model using a combined experimental-numerical approach. The model geometry and tissue boundaries are derived from MRI. The soft tissue non-linear elastic and viscoelastic mechanical behavior was evaluated using inverse finite element analysis (FEA) of in-vivo indentation experiments. A custom designed robotic in-vivo indentation system was used to provide a rich experimental data set of force versus time at 18 sites across a limb. During FEA, the tissues were represented by two layers, namely the skin-adipose layer and an underlying muscle-soft tissue complex. The non-linear elastic behavior was modeled using 2nd order Ogden hyperelastic formulations, and viscoelasticity was mod...

  8. Assessment of mechanical behavior of PLA composites reinforced with Mg micro-particles through depth-sensing indentations analysis.

    Science.gov (United States)

    Cifuentes, S C; Frutos, E; Benavente, R; Lorenzo, V; González-Carrasco, J L

    2017-01-01

    This work deals with the mechanical characterization by depth-sensing indentation (DSI) of PLLA and PLDA composites reinforced with micro-particles of Mg (up to 15wt%), which is a challenging task since the indented volume must provide information of the bulk composite, i.e. contain enough reinforcement particles. The composites were fabricated by combining hot extrusion and compression moulding. Physico-chemical characterization by TGA and DSC indicates that Mg anticipates the thermal degradation of the polymers but does not compromise their stability during processing. Especial emphasis is devoted to determine the effect of strain rate and Mg content on mechanical behavior, thus important information about the visco-elastic behavior and time-dependent response of the composites is obtained. Relevant for the intended application is that Mg addition increases the elastic modulus and hardness of the polymeric matrices and induces a higher resistance to flow. The elastic modulus obtained by DSI experiments shows good agreement with that obtained by uniaxial compression tests. The results indicate that DSI experiments are a reliable method to calculate the modulus of polymeric composites reinforced with micro-particles. Taking into consideration the mechanical properties results, PLA/Mg composite could be used as substitute for biodegradable monolithic polymeric implants already in the market for orthopedics (freeform meshes, mini plates, screws, pins, …), craniomaxillofacial, or spine. Copyright © 2016 Elsevier Ltd. All rights reserved.

  9. Determination of elastic modulus of claystone: Nano-/micro-indentation and meso-compression tests used to investigate impact of alkaline fluid propagation over 18 years

    Directory of Open Access Journals (Sweden)

    Danièle Bartier

    2017-06-01

    Full Text Available Micro-mechanical properties of a claystone were tested after undergoing alkaline perturbation on site (Tournemire, CD borehole for 18 years. In a saturated context and outside the excavation disturbed zone (EDZ, the claystone exhibits a 11.6-mm black rim at the cement/paste interface, which shows a different mechanical behaviour from the rest of the claystone. Three sets of measurements of elastic modulus were performed using: (i nano-indentation tests with a constant indentation depth of 2 μm, (ii micro-indentation tests with a constant indentation depth of 20 μm, and (iii meso-compression tests with a constant displacement of 200 μm. The increase of the modulus of deformability in the black rim is between 15 GPa and 20 GPa according to the scale. Moreover, an overall decrease of the modulus of deformability from the smallest to the largest scale is observed in each zone. In view of the mineralogy and petrographic observations, higher values of modulus of deformability in the black rim are related to carbonate content and its distribution. Precipitation of cementitious carbonates as inclusions and very thin partings leads to hardening of the claystone.

  10. Development of experimental verification techniques for non-linear deformation and fracture on the nanometer scale.

    Energy Technology Data Exchange (ETDEWEB)

    Moody, Neville Reid; Bahr, David F.

    2005-11-01

    This work covers three distinct aspects of deformation and fracture during indentations. In particular, we develop an approach to verification of nanoindentation induced film fracture in hard film/soft substrate systems; we examine the ability to perform these experiments in harsh environments; we investigate the methods by which the resulting deformation from indentation can be quantified and correlated to computational simulations, and we examine the onset of plasticity during indentation testing. First, nanoindentation was utilized to induce fracture of brittle thin oxide films on compliant substrates. During the indentation, a load is applied and the penetration depth is continuously measured. A sudden discontinuity, indicative of film fracture, was observed upon the loading portion of the load-depth curve. The mechanical properties of thermally grown oxide films on various substrates were calculated using two different numerical methods. The first method utilized a plate bending approach by modeling the thin film as an axisymmetric circular plate on a compliant foundation. The second method measured the applied energy for fracture. The crack extension force and applied stress intensity at fracture was then determined from the energy measurements. Secondly, slip steps form on the free surface around indentations in most crystalline materials when dislocations reach the free surface. Analysis of these slip steps provides information about the deformation taking place in the material. Techniques have now been developed to allow for accurate and consistent measurement of slip steps and the effects of crystal orientation and tip geometry are characterized. These techniques will be described and compared to results from dislocation dynamics simulations.

  11. Investigation on the crystal growth, molecular structure and nonlinear optical susceptibilities of 2-[2-(4-Ethoxy-phenyl)-vinyl]-1-ethyl-stilbazolium iodide (EESI) by Z-scan technique using He-Ne laser for third-order nonlinear optical applications

    Science.gov (United States)

    Senthil, K.; Kalainathan, S.; Kondo, Y.; Hamada, F.; Yamada, M.

    2017-05-01

    Organic 2-[2-(4-Ethoxy-phenyl)-vinyl]-1-ethyl-stilbazolium iodide (EESI), a derivative of the stilbazolium family single crystal was synthesized by condensation method. Nearly perfect as-gown single crystals of EESI structure was confirmed by single-crystal X-ray diffraction studies. The crystal has a triclinic system with the space group P-1, the molecule consists of one pyridinium cation, one iodide anion, and 0·5H2O molecules. The nature of charge transfer, molecular properties, electrostatic potential map, and HOMO-LUMO energy gap of EESI have been theoretically investigated by Sparton'10 V1.0.1 program. The optical transparency of EESI was studied by Uv-Visible spectral analysis. The growth features were observed during the etching studies using a Carl Zeiss optical microscope (50X magnification). The mechanical behavior of the crystal was estimated by Vickers microhardness test, which shows reverse indentation size effect (RISE) with good mechanical stability. Both the dielectric constant and dielectric loss increases with the increasing temperature and attain almost constant at higher frequencies, which justify the crystal quality and essential parameter for electro-optic device applications. The complex impedance analysis explains the electrical property of EESI. TGA and DTA measurements determined the thermal stability of the grown crystal. Laser-induced damage threshold energy measurements exhibit that the excellent resistance with good threshold energy up to 2.08 GW/cm2 that was found to be more than that of some known organic and inorganic NLO crystals. Photoconductivity of EESI crystal confirms that the positive photoconductivity nature. Also, the third-order nonlinear optical (NLO) properties of EESI were investigated by using the single beam Z-scan technique under the Visible light (632.8 nm) region. The results show that EESI has effective third-order nonlinear optical property with the nonlinear refractive index n2 =1.787×10-11m2/W, third

  12. Mapping the climate: guidance on appropriate techniques to map climate variables and their uncertainty

    Directory of Open Access Journals (Sweden)

    N. R. Kaye

    2012-02-01

    Full Text Available Maps are a crucial asset in communicating climate science to a diverse audience, and there is a wealth of software available to analyse and visualise climate information. However, this availability makes it easy to create poor maps as users often lack an underlying cartographic knowledge. Unlike traditional cartography, where many known standards allow maps to be interpreted easily, there is no standard mapping approach used to represent uncertainty (in climate or other information. Consequently, a wide range of techniques have been applied for this purpose, and users may spend unnecessary time trying to understand the mapping approach rather than interpreting the information presented. Furthermore, communicating and visualising uncertainties in climate data and climate change projections, using for example ensemble based approaches, presents additional challenges for mapping that require careful consideration. The aim of this paper is to provide background information and guidance on suitable techniques for mapping climate variables, including uncertainty. We assess a range of existing and novel techniques for mapping variables and uncertainties, comparing "intrinsic" approaches that use colour in much the same way as conventional thematic maps with "extrinsic" approaches that incorporate additional geometry such as points or features. Using cartographic knowledge and lessons learned from mapping in different disciplines we propose the following 6 general mapping guidelines to develop a suitable mapping technique that represents both magnitude and uncertainty in climate data:

    indent:1em;">– use a sensible sequential or diverging colour scheme;

    indent:1em;">– use appropriate colour symbolism if it is applicable;

    indent:1em;">– ensure the map is usable by colour blind people;

    indent:1em;">– use a data classification scheme that does not misrepresent the data

  13. Mechanical properties of metal-organic frameworks: An indentation study on epitaxial thin films

    Science.gov (United States)

    Bundschuh, S.; Kraft, O.; Arslan, H. K.; Gliemann, H.; Weidler, P. G.; Wöll, C.

    2012-09-01

    We have determined the hardness and Young's modulus of a highly porous metal-organic framework (MOF) using a standard nanoindentation technique. Despite the very low density of these films, 1.22 g cm-3, Young's modulus reaches values of almost 10 GPa for HKUST-1, demonstrating that this porous coordination polymer is substantially stiffer than normal polymers. This progress in characterizing mechanical properties of MOFs has been made possible by the use of high quality, oriented thin films grown using liquid phase epitaxy on modified Au substrates.

  14. Qualification of the indentation test for the local characterization of nuclear facility materials. Final report; Qualifizierung des Eindruckversuchs zur lokalen Charakterisierung kerntechnischer Werkstoffe. Abschlussbericht

    Energy Technology Data Exchange (ETDEWEB)

    Tandler, Martin; Seifert, Thomas; Schlesinger, Michael; Mohrmann, Ralf; Kilgus, Normen; Venugopal, Ravula

    2007-12-21

    With the aid of the registrating indentation test, the project intends to characterise the operational changes in the local material properties of nuclear materials by a quasi-nondestructive indentation test. The focus was on the materials 22NiMoCr3-7 and X6CrNiNb18-10, both of which are widely used in nuclear engineering. As the accuracy of the method depends on experimental influencing factors like surface treatment, intrinsic stresses, or material anisotropy, these influences are to be quantified and will be considered in the evaluation of the material characteristics. The influencing parameters will be investigated experimentally and numerically by FE simulations so that their influence can be distinguished from the actual material behaviour. (orig.)

  15. Improvement of cathode-electrolyte interfaces of tubular solid oxide fuel cells by fabricating dense YSZ electrolyte membranes with indented surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Dehua; Liu, Mingfei; Xie, Kui; Sheng, Jin; Liu, Xingqin; Meng, Guangyao [Department of Materials Science and Engineering, University of Science and Technology of China, Hefei 230026 (China); Wang, Yonghong; Peng, Xiaobo [Institute of Materials Science and Engineering, Hefei University of Technology (China)

    2008-01-03

    To improve cathode-electrolyte interfaces of solid oxide fuel cells (SOFCs), dense YSZ electrolyte membranes with indented surfaces were fabricated on tubular NiO/YSZ anode supports by two comparable methods. Electrochemistry impedance spectroscopy (EIS) and current-voltage tests of the cells were carried out to characterize the cathode-electrolyte interfaces. Results showed that the electrode polarization resistances of the modified cells were reduced by 52% and 35% at 700 C, and the maximum power densities of cells were remarkably increased, even by 146.6% and 117.8% at lower temperature (700 C), respectively. The indented surfaces extended the active zone of cathode and enhanced interfacial adhesion, which led to the major improvement in the cell performance. (author)

  16. Nano Indentation Inspection of the Mechanical Properties of Gold Nitride Thin Films

    Directory of Open Access Journals (Sweden)

    Armen Verdyan

    2007-10-01

    Full Text Available The morphology and the local mechanical properties of gold nitride thin films were studied by atomic force microscope (AFM. Gold nitride films were deposited for the first time on silicon substrate without any buffer layer at room temperature by reactive pulsed laser ablation deposition (RPLD. The films were fabricated on (100 Si wafers by RPLD technique in which KrF excimer laser was used to ablate a gold target in N2 atmosphere (0.1 GPa-100 Pa and ambient temperature. Scanning electron microscopy (SEM and atomic force microscopy inspections showed that the films were flat plane with rms roughness in the range of 35.1 nm-3.6 nm, depending on the deposition pressure. Rutherford backscattering spectrometry (RBS and energy dispersion spectroscopy (EDS used to detect the nitrogen concentration in the films, have revealed a composition close to Au3N. The film

  17. Diagnosis of early colorectal cancer invasion depth by quantitative evaluation of the basal indentation in CT colonography.

    Science.gov (United States)

    Miyasaka, Mitsutoshi; Tsurumaru, Daisuke; Nishimuta, Yusuke; Asayama, Yoshiki; Kawanami, Satoshi; Oki, Eiji; Hirahashi, Minako; Honda, Hiroshi

    2016-12-01

    To investigate the feasibility of diagnosing the invasion depth of early colorectal cancer (CRC) by quantitatively evaluating the basal indentation (BI)-i.e., the intestinal lateral deformity-in CT colonography (CTC). 34 early CRCs (13 Tis CRCs and 21 T1 CRCs) in 32 patients who underwent a preoperative CTC were retrospectively examined. Two radiologists calculated the depth of the BI on a computed tomographic air-contrast enema (CT enema) image, the depth of the BI due to the geometric function (BI-G) on a cross-sectional multiplanar reconstruction (CS-MPR) image, and the ratio of the BI to the BI-G (i.e., the "BI ratio") for each lesion. The BI ratios of the Tis and T1 CRCs were compared. The BI ratios were significantly higher in the T1 CRCs than in the Tis CRCs (p quantitatively evaluating the BI can improve the accuracy of diagnosis of early CRC invasion depth.

  18. Elastic properties of indium nitrides grown on sapphire substrates determined by nano-indentation: In comparison with other nitrides

    Directory of Open Access Journals (Sweden)

    Ichiro Yonenaga

    2015-07-01

    Full Text Available The hardness of wurtzite indium nitride (α-InN films of 0.5 to 4 μm in thickness was measured by the nano-indentation method at room temperature. After investigation of crystalline quality by x-ray diffraction, the hardness and Young’s modulus were determined to be 8.8 ± 0.4 and 184 ± 5 GPa, respectively, for the In (0001- and N ( 000 1 ̄ -growth faces of InN films. The bulk and shear moduli were then derived to be 99 ± 3 and 77 ± 2 GPa, respectively. The Poisson’s ratio was evaluated to be 0.17 ± 0.03. The results were examined comprehensively in comparison with previously reported data of InN as well as those of other nitrides of aluminum nitride and gallium nitride. The underlying physical process determining the moduli and hardness was examined in terms of atomic bonding and dislocation energy of the nitrides and wurtzite zinc oxide.

  19. True Gold or Pyrite: A Review of Reference Point Indentation for Assessing Bone Mechanical Properties In Vivo.

    Science.gov (United States)

    Allen, Matthew R; McNerny, Erin Mb; Organ, Jason M; Wallace, Joseph M

    2015-09-01

    Although the gold standard for determining bones' mechanical integrity is the direct measure of mechanical properties, clinical evaluation has long relied on surrogates of mechanical properties for assessment of fracture risk. Nearly a decade ago, reference point indentation (RPI) emerged as an innovative way to potentially assess mechanical properties of bone in vivo. Beginning with the BioDent device, and then followed by the newer generation OsteoProbe, this RPI technology has been utilized in several publications. In this review we present an overview of the technology and some important details about the two devices. We also highlight select key studies, focused specifically on the in vivo application of these devices, as a way of synthesizing where the technology stands in 2015. The BioDent machine has been shown, in two clinical reports, to be able to differentiate fracture versus nonfracture patient populations and in preclinical studies to detect treatment effects that are consistent with those quantified using traditional mechanical tests. The OsteoProbe appears able to separate clinical cohorts yet there exists a lack of clarity regarding details of testing, which suggests more rigorous work needs to be undertaken with this machine. Taken together, RPI technology has shown promising results, yet much more work is needed to determine if its theoretical potential to assess mechanical properties in vivo can be realized. © 2015 American Society for Bone and Mineral Research.

  20. Respective roles of organic and mineral components of human cortical bone matrix in micromechanical behavior: an instrumented indentation study.

    Science.gov (United States)

    Bala, Y; Depalle, B; Douillard, T; Meille, S; Clément, P; Follet, H; Chevalier, J; Boivin, G

    2011-10-01

    Bone is a multiscale composite material made of both a type I collagen matrix and a poorly crystalline apatite mineral phase. Due to remodeling activity, cortical bone is made of Bone Structural Units (BSUs) called osteons. Since osteon represents a fundamental level of structural hierarchy, it is important to investigate the relationship between mechanical behavior and tissue composition at this scale for a better understanding of the mechanisms of bone fragility. The aim of this study is to analyze the links between ultrastructural properties and the mechanical behavior of bone tissue at the scale of osteon. Iliac bone biopsies were taken from untreated postmenopausal osteoporotic women, embedded, sectioned and microradiographed to assess the degree of mineralization of bone (DMB). On each section, BSUs of known DMB were indented with relatively high load (~500 mN) to determine local elastic modulus (E), contact hardness (H(c)) and true hardness (H) of several bone lamellae. Crystallinity and collagen maturity were measured by Fourier Transform InfraRed Microspectroscopy (FTIRM) on the same BSUs. Inter-relationships between mechanical properties and ultrastructural components were analyzed using multiple regression analysis. This study showed that elastic deformation was only explained by DMB whereas plastic deformation was more correlated with collagen maturity. Contact hardness, reflecting both elastic and plastic behaviors, was correlated with both DMB and collagen maturity. No relationship was found between crystallinity and mechanical properties at the osteon level. Copyright © 2011 Elsevier Ltd. All rights reserved.

  1. Indentation creep behavior of cold sprayed aluminum amorphous/nano-crystalline coatings

    Energy Technology Data Exchange (ETDEWEB)

    Babu, P. Suresh [International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Balapur, Hyderabad 500005, Andhra Pradesh (India); Nanomechanics and Nanotribology Laboratory, Department of Mechanical and Materials Engineering, Florida International University, Miami, FL 33174 (United States); Jha, R.; Guzman, M. [Nanomechanics and Nanotribology Laboratory, Department of Mechanical and Materials Engineering, Florida International University, Miami, FL 33174 (United States); Sundararajan, G. [International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Balapur, Hyderabad 500005, Andhra Pradesh (India); Agarwal, Arvind, E-mail: agarwala@fiu.edu [Nanomechanics and Nanotribology Laboratory, Department of Mechanical and Materials Engineering, Florida International University, Miami, FL 33174 (United States)

    2016-03-21

    In this study, we report room temperature creep properties of cold sprayed aluminum amorphous/nanocrystalline coating using nanoindentation technique. Creep experiments were also performed on heat treated coatings to study the structural stability and its influence on the creep behavior. The peak load and holding time were varied from 1000 to 4000 µN and 0 to 240 s respectively. Stress exponent value (n) vary from 5.6 to 2.3 in as-sprayed (AS) coatings and 7.2–4.8 in heat treated (HT) coatings at peak load of 1000–4000 µN at 240 s hold time. Higher stress exponent value indicates heat treated coatings have more resistance to creep deformation than as-sprayed coatings. Relaxed, partially crystallized structure with less porosity, and stronger inter-splat boundaries restrict the deformation in heat treated coatings as compared to greater free volume generation in amorphous as-sprayed coatings. The computed activation volume of heat treated coatings is twice of as-sprayed coatings indicating greater number of atom participation in shear band formation in heat treated coatings. The proposed mechanism was found to be consistent with the stress exponent values.

  2. Effect of Localized Mechanical Indentation on Skin Water Content Evaluated Using OCT

    Directory of Open Access Journals (Sweden)

    Abhijit A. Gurjarpadhye

    2011-01-01

    Full Text Available The highly disordered refractive index distribution in skin causes multiple scattering of incident light and limits optical imaging and therapeutic depth. We hypothesize that localized mechanical compression reduces scattering by expulsing unbound water from the dermal collagen matrix, increasing protein concentration and decreasing the number of index mismatch interfaces between tissue constituents. A swept-source optical coherence tomography (OCT system was used to assess changes in thickness and group refractive index in ex vivo porcine skin, as well as changes in signal intensity profile when imaging in vivo human skin. Compression of ex vivo porcine skin resulted in an effective strain of −58.5%, an increase in refractive index from 1.39 to 1.50, and a decrease in water volume fraction from 0.66 to 0.20. In vivo OCT signal intensity increased by 1.5 dB at a depth of 1 mm, possibly due to transport of water away from the compressed regions. These finding suggest that local compression could be used to enhance light-based diagnostic and therapeutic techniques.

  3. Contact mechanics at nanometric scale using nanoindentation technique for brittle and ductile materials.

    Science.gov (United States)

    Roa, J J; Rayon, E; Morales, M; Segarra, M

    2012-06-01

    In the last years, Nanoindentation or Instrumented Indentation Technique has become a powerful tool to study the mechanical properties at micro/nanometric scale (commonly known as hardness, elastic modulus and the stress-strain curve). In this review, the different contact mechanisms (elastic and elasto-plastic) are discussed, the recent patents for each mechanism (elastic and elasto-plastic) are summarized in detail, and the basic equations employed to know the mechanical behaviour for brittle and ductile materials are described.

  4. FE simulation of the indentation deformation of SiC modified vinylester composites in respect to their abrasive wear performance

    Directory of Open Access Journals (Sweden)

    2008-10-01

    Full Text Available The abrasive sliding friction and wear behaviours of silicon carbide (SiC filled vinylester (VE composites were investigated. The average grain size of the incorporated SiC particles was varied, holding the volume content of them in every case at 16 vol%. Mechanical properties (hardness, compression modulus, yield stress of the filled and neat VE were determined. The tribological properties were investigated in block (composite – on – ring (steel test configuration. The steel counter bodies were covered with abrasive papers of different graining. Coefficient of friction (COF and specific wear rate of the VE + SiC composites were determined. It was observed that the wear resistance increases with increasing average filler grain size and with decreasing abrasiveness of the counter surface. The COF of the VE + SiC composites is independent of the size of the incorporated particles, but it is strongly influenced by the abrasiveness of the counter body. The worn surfaces of the VE + SiC systems were analysed in scanning electron microscope (SEM to deduce the typical wear mechanisms. The size effect of the SiC filler particles onto the abrasive wear characteristics was investigated by assuming that the roughness peaks of the abrasive paper and the indenter of the microhardness test cause similar micro scaled contact deformations in the composites. Therefore FE method was used to simulate the micro scaled deformation process in the VE + SiC systems during microindentation tests. The FE results provided valuable information on how to explain the size effect of the incorporated SiC filler.

  5. Novel approaches to determining residual stresses by ultramicroindentation techniques: Application to sandblasted austenitic stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Frutos, E. [Centro de Bioingenieria, Biomateriales y Nanomedicina, CIBER-BBN, Instituto de Salud Carlos III (Spain)] [Centro Nacional de Investigaciones Metalurgicas, CENIM-CSIC, 28040 Madrid (Spain); Multigner, M. [Centro Nacional de Investigaciones Metalurgicas, CENIM-CSIC, 28040 Madrid (Spain)] [Centro de Bioingenieria, Biomateriales y Nanomedicina, CIBER-BBN, Instituto de Salud Carlos III (Spain); Gonzalez-Carrasco, J.L., E-mail: jlg@cenim.csic.es [Centro Nacional de Investigaciones Metalurgicas, CENIM-CSIC, 28040 Madrid (Spain)] [Centro de Bioingenieria, Biomateriales y Nanomedicina, CIBER-BBN, Instituto de Salud Carlos III (Spain)

    2010-07-15

    This research addresses the determination of residual stresses in sandblasted austenitic steel by ultramicroindentation techniques using a sharp indenter, of which the sensitivity to residual stress effects is said to be inferior to that of spherical ones. The introduction of an angular correction in the model of Wang et al. which relates variations in the maximum load to the presence of residual stresses is proposed. Similarly, the contribution to the hardness of grain size refinement and work hardening, developed as a consequence of the severe plastic deformation during blasting, is determined in order to avoid overestimation of the residual stresses. Measurements were performed on polished cross sections along a length of several microns, thus obtaining a profile of the residual stresses. Results show good agreement with those obtained by synchrotron radiation on the same specimens, which validates the method and demonstrates that microindentation using sharp indenters may be sensitive to the residual stress effect.

  6. Evaluation by instrumented indentation of the damage caused by gamma radiation on polymeric materials; Avaliacao por indentacao instrumentada dos danos causados pela radiacao gama em materiais polimericos

    Energy Technology Data Exchange (ETDEWEB)

    Rosa, M.P.; Azevedo, E.C.; Miquelin, C.A.; Soboll, D.S., E-mail: helunica@yahoo.com.b [Universidade Tecnologica Federal do Parana (DAFIS/UTFPR), Curitiba, PR (Brazil). Dept. Academico de Fisica

    2010-07-01

    Several materials with densities close to water are used as phantoms in dosimetry. Such materials are damaged because they are exposed to radiation, the surface layers suffer the largest changes. This damage can be assessed by instrumented indentation. This paper investigates the variations in hardness and elastic modulus of samples of polymethyl-methacrylate, polyvinyl chloride, polyacetal and polypropylene before and after being irradiated with gamma radiation dose 500 Gy, using a Nanoindeter XP, with applied loads between 1 mN and 400 mN. The results are discussed correlating the variations in the mechanical properties of polymers with their applications. (author)

  7. Etude et modélisation de la fatigue de contact en présence d’indentation dans le cas de roulements tout acier et hybrides

    OpenAIRE

    Tonicello, Emmanuel

    2012-01-01

    The nitrided 32CrMoV13 steel is a gradient properties material used for the production of aeronautical bearing rings. The principal advantages are its surface hardness and core ductility, useful against debris denting. Moreover, to improve rolling bearing performances, ceramic balls (silicon nitride Si3N4) instead of steel (M50). The present study aims to investigate the contact fatigue performance in presence of indentation for two pairs of materials (nitrided 32CrMoV13 steel / M50 and nitri...

  8. Identification of material parameters using indentation test —study of the intrinsic dimensionality of P-h curves and residual imprints

    Directory of Open Access Journals (Sweden)

    Meng Liang

    2016-01-01

    Full Text Available Instrumented indentation test has been used to determine material parameters with two different sources of information. Based on the recent shape-manifold identification approach, we formally demonstrate, in the scope of manifold, the non-uniqueness of the solution to the inverse problem based on load-displacement curves. The identifiability is also compared for P-h curve and imprint mapping, highlighting the manifold’s ability to estimate the maximum number of independent material parameters that may be determined with a given experimental setup.

  9. Comparison of irradiated 15Kh2MFA material mechanical properties using conventional testing methods and innovative approach of small punch testing (SPT) and automated ball indentation (ABIT)

    Science.gov (United States)

    Kopriva, R.; Petelova, P.; Eliasova, I.; Kytka, M.; Culek, M.

    2017-02-01

    Article describes two innovative testing methods - Small Punch Testing (SPT) and Automated Ball Indentation Test (ABIT) - which are based on the determination and evaluation of material properties from miniaturized testing specimens. These methods are very promising due to minimum material needed for testing and also in case of testing highly irradiated materials of components that are not included in standard surveillance programs. The test results were obtained for reactor pressure vessel (RPV) base material 15Ch2MFA in both states - initial unirradiated and irradiated. Subsequently results were compared with standard tensile tests to prove applicability of these testing methods for the evaluation of degradation of irradiated structural materials of nuclear power plants.

  10. 'In vitro' assessment to instrumented indentation hardness tests in enamel of bovine teeth, before and after dental bleaching by laser; Avaliacao in vitro' de ensaios instrumentados de dureza em esmalte de dente bovino, antes e apos clareamento dental a laser

    Energy Technology Data Exchange (ETDEWEB)

    Britto Junior, Francisco Meira

    2004-07-01

    The laser enamel bleaching is a common used procedure due to its satisfactory esthetic results. The possible changes on the dental structures caused by the bleaching technique are of great importance. The enamel superficial microhardness changes through instrumented indentation hardness on bovine teeth were analyzed in this present study. The samples were divided in two halves, one being the control and the other irradiated with a diode laser (808 nm) or with a Nd:YAG laser (1064 nm) to activate the Whiteness HP bleaching gel (hydrogen peroxide at 35%). It was possible to conclude that there was a statistical significant increase on the enamel superficial microhardness (Group I, sample 1 and Group II, sample 1) despite this increase did not seem to indicate a concern regarding the enamel surface resistance change. There was not a significant statistical change on the enamel microhardness on the other samples. The final conclusion is that there was no superficial enamel morphological change after these treatments. (author)

  11. Experimental techniques; Techniques experimentales

    Energy Technology Data Exchange (ETDEWEB)

    Roussel-Chomaz, P. [GANIL CNRS/IN2P3, CEA/DSM, 14 - Caen (France)

    2007-07-01

    This lecture presents the experimental techniques, developed in the last 10 or 15 years, in order to perform a new class of experiments with exotic nuclei, where the reactions induced by these nuclei allow to get information on their structure. A brief review of the secondary beams production methods will be given, with some examples of facilities in operation or under project. The important developments performed recently on cryogenic targets will be presented. The different detection systems will be reviewed, both the beam detectors before the targets, and the many kind of detectors necessary to detect all outgoing particles after the reaction: magnetic spectrometer for the heavy fragment, detection systems for the target recoil nucleus, {gamma} detectors. Finally, several typical examples of experiments will be detailed, in order to illustrate the use of each detector either alone, or in coincidence with others. (author)

  12. Porosity-induced relaxation of strains in GaN layers studied by means of micro-indentation and optical spectroscopy

    KAUST Repository

    Najar, Adel

    2012-05-04

    We report the fabrication of porous GaNnanostructures using UV-assisted electroless etching of bulk GaN layer grown on c-plane sapphire substrate in a solution consisting of HF:CH3OH:H2O2. The morphology of the porous GaNnanostructures was characterized for different etching intervals using high resolution scanning electron microscopy. The geometry and size of resultant pores do not appear to be affected by the etching time; however, the pore density was augmented for longer etching time. Micro-indentation tests were carried out to quantify the indentation modulus for different porous GaNnanostructures. Our results reveal a relationship between the elastic properties and the porosity kinetics, i.e., a decrease of the elastic modulus was observed with increasing porosity. The photoluminescence(PL) and Raman measurements carried out at room temperature for the etched samples having a high degree of porosity revealed a strong enhancement in intensity. Also, the peak of the PL wavelength was shifted towards a lower energy. The high intensity of PL was correlated to an increase of scattered photons within the porous media and to the reduction of the dislocation density.

  13. Dynamic Fracture Toughness of TaC/CNTs/SiC CMCs Prepared by Spark Plasma Sintering

    Directory of Open Access Journals (Sweden)

    Qiaoyun Xie

    2015-01-01

    Full Text Available This study focuses on the fracture toughness of TaC and carbon nanotubes (CNTs reinforced SiC ceramic matrix composites (CMCs, prepared by spark plasma sintering (SPS technique. A high densification of 98.4% was achieved under the sintering parameter of 133°C/min, 1800°C, and 90 MPa pressure. Vickers indentation was employed to measure the indentation toughness on the polished surface of ceramic samples, SEM was applied to directly observe the crack propagation after indentation, and split Hopkinson pressure bar (SHPB was developed to determine the dynamic fracture toughness within the ceramic samples subjected to an impact in a three-point bending configuration.

  14. Influence of the Molecular Adhesion Force on the Indentation Depth of a Particle into the Wafer Surface in the CMP Process

    Directory of Open Access Journals (Sweden)

    Zhou Jianhua

    2014-01-01

    Full Text Available By theoretical calculation, the external force on the particle conveyed by pad asperities and the molecular adhesion force between particle and wafer are compared and analyzed quantitatively. It is confirmed that the molecular adhesion force between particle and wafer has a great influence on the chemical mechanical polishing (CMP material removal process. Considering the molecular adhesion force between particle and wafer, a more precise model for the indentation of a particle into the wafer surface is developed in this paper, and the new model is compared with the former model which neglected the molecular adhesion force. Through theoretical analyses, an approach and corresponding critical values are applied to estimate whether the molecular adhesion force in CMP can be neglected. These methods can improve the precision of the material removal model of CMP.

  15. Nano-indentation investigations of (As2Se3)1-x: Snx and (As4S3Se3)1-x: Snx glasses

    Science.gov (United States)

    Harea, D. V.; Harea, E. E.; Iaseniuc, O. V.; Iovu, M. S.

    2015-02-01

    Experimental results on some physical and optical properties of (As2Se3)1-x:Snx and (As4S3Se3)1-x:Snx (x = 0-10 at %) glasses and amorphous films (d~2.0 μm) are presented. The bulk chalcogenide glasses are studied by X-ray diffraction spectroscopy and nanoindentation methods. It is established that the addition of these amounts of tin (x = 0-10 at %) does not lead to significant changes in the physical properties of the glass, such as values of stress and Young's modulus related to the modification of the density and compactness. It has been found that the addition of these amounts of tin in (As4S3Se3)1-x:Snx does not lead to significant changes in the glass physical properties, such as values of stress and Young's modulus related to the modification of the density and compactness. The study of the photoplastic effect is performed in situ, with illumination of the bulk and thin film samples during indentation as well as their indentation after illumination with a green laser (λ = 532 nm) at a power of P = 50 mV/cm2. The hardness is calculated from load-displacement curves by the Oliver-Pharr method. A sharp increase in hardness is registered if the tin concentration exceeds a value of 34% Sn. The hardness H of (As2Se3)1-x:Snx films varies between 115 and 130 kg/mm2. It is found that the hardness H of amorphous thin films is generally higher than the hardness of bulk samples with the same chemical composition. In this study, we are focused on the mechanical characteristics of high-purity As2Se3: Snx thin films. Keyword: Chalcogenide glasses, hardness,

  16. Comparative effect of different polymerization techniques on residual monomer and hardness properties of PMMA-based denture resins.

    Science.gov (United States)

    Ayaz, Elif Aydogan; Durkan, Rukiye; Koroglu, Ayşegul; Bagis, Bora

    2014-12-30

    The aim of this study was to compare the residual monomer and microhardness of poly(methyl methacrylate) (PMMA)-based denture resins processed by using autoclave and conventional water bath techniques. To determine the amount of residual methyl methacrylate (MMA) monomer, disk-shaped specimens (n=5) were prepared from 3 different acrylic resins (Meliodent, Paladent and Qc-20). Control groups were polymerized in water bath for 30 minutes at 100°C. The study groups were prepared in an autoclave device for 60°C/30 min followed 130°C/10 min and the other group for 60°C/30 min followed by 130°C/20 min. According to standard calibration curves, ultraviolet spectrophotometry at 230 nm was used to determine the residual monomer. For the Vickers hardness measurements, disk-shaped specimens (n=5) were prepared for each test group. Hardness measurements were performed with a Vickers hardness tester under a 4.91-N press load for a 30 seconds, after immersion in distilled water at 37ºC for 48 hours. The data were analyzed by ANOVA and Tukey HSD test (phardness for all resin groups (p0.05). The autoclave polymerization technique exhibited significantly lower residual monomer content and greater hardness than conventional heat polymerization.

  17. Vickers Hardness Measurements of the M855 Cartridge Case Base

    Science.gov (United States)

    2009-04-01

    EMT B MACHAK PICATINNY ARSENAL NJ 07806-5000 5 COMMANDER US ARMY TACOM ARDEC AMSRD AAR AEP E D CARLUCCI K LAUGHLIN S...R COATES T EHLERS L MAGNESS B SCHUSTER AMSRD ARL WM TD T BJERKE T WEERASOORIYA AMSRD ARL WM TE B RINGERS 18 INTENTIONALLY LEFT BLANK.

  18. Determination of the mechanical properties and fracture mechanisms of YSZ and GDC for electrolyte-supported SOFCs by instrumented indentation test; Determinacion de las propiedades mecanicas y mecanismos de fractura de electrolitos soportados de YSZ y GDC mediante ensayos de indentacion instrumentada

    Energy Technology Data Exchange (ETDEWEB)

    Roa, J. J.; Morales, M.; Capdevila, X. G.; Segarra, M.

    2010-07-01

    The main purpose of this work is to evaluate the different mechanical properties and the different fracture mechanisms activated during the instrumented indentation process of the electrolytes based on Yttria stabilized zirconia (YSZ) and gadolinia doped ceria (GDC), for solid oxide fuel cells (SOFCs). Both materials, with a thickness of 200 {mu}m, were shaped by uniaxial pressing at 500 MPa, and sintered at 1400 degree centigrade. Mechanical properties such as hardness (H) and Young's modulus (E) have been studied at different penetration depths using the Oliver and Pharr equations. The different fracture mechanisms activated during the instrumented indentation process have been studied at constant penetration depth of 500 nm, performed with a diamond Berkovich tip indenter. The residual indentation imprints have been observed with atomic force microscopy (AFM). The hardness and Young's modulus for YSZ electrolytes are higher than for GDC materials, due to the different fracture mechanism activated during the indentation process. As a result, the electrolytes of YSZ presented trans- and intergranular fracture mechanisms, depending on the place of the residual indentation imprint (in the grain boundary or in the middle of the grain, respectively). However, the GDC electrolyte revealed radical cracks at the corners of the residual nano indentation imprints, thus producing a phenomenon known as chipping. (Author)

  19. A rate-jump method for characterization of soft tissues using nanoindentation techniques

    KAUST Repository

    Tang, Bin

    2012-01-01

    The biomechanical properties of soft tissues play an important role in their normal physiological and physical function, and may possibly relate to certain diseases. The advent of nanomechanical testing techniques, such as atomic force microscopy (AFM), nano-indentation and optical tweezers, enables the nano/micro-mechanical properties of soft tissues to be investigated, but in spite of the fact that biological tissues are highly viscoelastic, traditional elastic contact theory has been routinely used to analyze experimental data. In this article, a novel rate-jump protocol for treating viscoelasticity in nanomechanical data analysis is described. © 2012 The Royal Society of Chemistry.

  20. Acquired Techniques

    DEFF Research Database (Denmark)

    Lunde Nielsen, Espen; Halse, Karianne

    2013-01-01

    Acquired Techniques - a Leap into the Archive, at Aarhus School of Architecture. In collaboration with Karianne Halse, James Martin and Mika K. Friis. Following the footsteps of past travelers this is a journey into tools and techniques of the architectural process. The workshop will focus upon...

  1. Mechanical properties of polycrystalline RuSr{sub 2}GdCu{sub 2}O{sub 8} superconductor

    Energy Technology Data Exchange (ETDEWEB)

    Brum Leite Gusmao Pinheiro, Lincoln; Serbena, Francisco Carlos; Foerster, Carlos Eugenio; Rodrigues, Pedro Junior [Departamento de Fisica, Universidade Estadual de Ponta Grossa, Av. Gen. Carlos Cavalcanti 4748, 84030-000 Ponta Grossa, Parana (Brazil); Jurelo, Alcione Roberto, E-mail: arjurelo@uepg.b [Departamento de Fisica, Universidade Estadual de Ponta Grossa, Av. Gen. Carlos Cavalcanti 4748, 84030-000 Ponta Grossa, Parana (Brazil); Chinelatto, Adilson Luiz [Departamento de Engenharia de Materiais, Universidade Estadual de Ponta Grossa, Av. Gen. Carlos Cavalcanti 4748, 84030-000 Ponta Grossa, Parana (Brazil); Junior, Jorge Luiz Pimentel [Instituto de Fisica, Universidade Federal do Rio Grande do Sul, Caixa Postal 15.051, 91.501-970 Porto Alegre, Rio Grande do Sul (Brazil)

    2011-03-15

    Research highlights: {yields} Hardness and elastic modulus of Ru-1212 phase measured by instrumented indentation are reported. {yields} Polycrystalline samples were produced by a solid state reaction technique. {yields} Samples were also characterized by SEM, XRD and electrical resistivity measurements. {yields} Hardness and elastic modulus were 8.6 GPa and 145 GPa, respectively. {yields} These values are comparable with those of Y-123. - Abstract: The main objective of this paper is to report the room temperature hardness and elastic modulus of the RuSr{sub 2}GdCu{sub 2}O{sub 8} superconductor phase by instrumented indentation. Polycrystalline samples were produced by a solid state reaction technique. The samples were also characterized by scanning electron microscopy, X-ray diffraction and electrical resistivity measurements. The influence of porosity on the mechanical properties was avoided by considering only those indentations inside the grains. The hardness and elastic modulus were 8.6 GPa and 145 GPa, respectively. These values are comparable with those of Y-123. The indentation fracture toughness evaluated after conventional Vickers indentation was 1.9 MPa m{sup 1/2}.

  2. Dating Techniques

    Indian Academy of Sciences (India)

    Absolute dating technique (such as stylistic affiliation, association with datable deposits, amino acid study of protein in pigments, and direct radiocarbon dating of the organic fraction of pigments or desert varnish).

  3. Intensity techniques

    DEFF Research Database (Denmark)

    Jacobsen, Finn

    2008-01-01

    The Handbook of Signal Processing in Acoustics will compile the techniques and applications of signal processing as they are used in the many varied areas of Acoustics. The Handbook will emphasize the interdisciplinary nature of signal processing in acoustics. Each Section of the Handbook...... from different areas, will find the self-contained chapters accessible and will be interested in the similarities and differences between the approaches and techniques used in different areas of acoustics....

  4. Elastic properties of Nafion, polybenzimidazole and poly [2,5-benzimidazole] membranes determined by AFM tip nano-indentation

    Energy Technology Data Exchange (ETDEWEB)

    Franceschini, Esteban A. [Departamento de Fisica de Materia Condensada, Centro Atomico Constituyentes, Comision Nacional de Energia Atomica (CNEA), 1650 San Martin, Buenos Aires (Argentina); Corti, Horacio R. [Departamento de Fisica de Materia Condensada, Centro Atomico Constituyentes, Comision Nacional de Energia Atomica (CNEA), 1650 San Martin, Buenos Aires (Argentina); Instituto de Quimica Fisica de los Materiales, Medio Ambiente y Energia (INQUIMAE), Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Pabellon II, Ciudad Universitaria, 1428 Buenos Aires (Argentina)

    2009-03-15

    The mechanical properties of polybenzimidazole (PBI) and poly [2,5-benzimidazole] (ABPBI) membranes, possible candidates to replace Nafion as proton exchange membranes in direct methanol fuel cells (DMFC), were studied. It was observed by AFM imaging that the morphology of the ABPBI membranes strongly depends on the casting procedure, performed at high temperature from methanesulphonic acid and at low temperature from formic acid. The elastic moduli of the undoped and phosphoric acid doped membranes were determined using the AFM force spectroscopy technique and the differences observed with doped and undoped PBI and Nafion membranes, were discussed in terms of the electrostatic and swelling forces between polymer chains. The analysis of the force curves indicates differences in the mechanical behavior of doped PBI and ABPBI membranes compared to Nafion, which could have practical consequences on the stability of the membrane electrode assemblies. (author)

  5. Indentation hardness: A simple test that correlates with the dissipated-energy predictor for fatigue-life in bovine pericardium membranes for bioprosthetic heart valves.

    Science.gov (United States)

    Tobaruela, Almudena; Rojo, Francisco Javier; García Paez, José María; Bourges, Jean Yves; Herrero, Eduardo Jorge; Millán, Isabel; Alvarez, Lourdes; Cordon, Ángeles; Guinea, Gustavo V

    2016-08-01

    The aim of this study was to evaluate the variation of hardness with fatigue in calf pericardium, a biomaterial commonly used in bioprosthetic heart valves, and its relationship with the energy dissipated during the first fatigue cycle that has been shown to be a predictor of fatigue-life (García Páez et al., 2006, 2007; Rojo et al., 2010). Fatigue tests were performed in vitro on 24 pericardium specimens cut in a root-to-apex direction. The specimens were subjected to a maximum stress of 1MPa in blocks of 10, 25, 50, 100, 250, 500, 1000 and 1500 cycles. By means of a modified Shore A hardness test procedure, the hardness of the specimen was measured before and after fatigue tests. Results showed a significant correlation of such hardness with fatigue performance and with the energy dissipated in the first cycle of fatigue, a predictor of pericardium durability. The study showed indentation hardness as a simple and reliable indicator of mechanical performance, one which could be easily implemented in improving tissue selection. Copyright © 2016 Elsevier Ltd. All rights reserved.

  6. Characterizing the influence of matrix ductility on damage phenomenology in continuous fiber-reinforced thermoplastic laminates undergoing quasi-static indentation

    KAUST Repository

    Yudhanto, Arief

    2017-12-12

    The use of thermoplastic matrix was known to improve the impact properties of laminated composites. However, different ductility levels can exist in a single family of thermoplastic matrix, and this may consequently modify the damage phenomenology of thermoplastic composites. This paper focuses on the effect of matrix ductility on the out-of-plane properties of thermoplastic composites, which was studied through quasi-static indentation (QSI) test that may represent impact problem albeit the speed difference. We evaluated continuous glass-fiber reinforced polypropylene thermoplastic composites (GFPP), and selected homopolymer PP and copolymer PP that represent ductile and less ductile matrices, respectively. Several cross-ply laminates were selected to study the influence of ply thicknesses and relative orientation of interfaces on QSI properties of GFPP. It is expected that GFPP with ductile matrix improves energy absorption of GFPP. However, the damage mechanism is completely different between GFPP with ductile and GFPP with less ductile matrices. GFPP with ductile matrix exhibits smaller damage zone in comparison to the one with less ductile matrix. Higher matrix ductility inhibits the growth of ply cracking along the fiber, and this causes the limited size of delamination. The stacking sequence poses more influence on less ductile composites rather than the ductile one.

  7. Decomposition techniques

    Science.gov (United States)

    Chao, T.T.; Sanzolone, R.F.

    1992-01-01

    Sample decomposition is a fundamental and integral step in the procedure of geochemical analysis. It is often the limiting factor to sample throughput, especially with the recent application of the fast and modern multi-element measurement instrumentation. The complexity of geological materials makes it necessary to choose the sample decomposition technique that is compatible with the specific objective of the analysis. When selecting a decomposition technique, consideration should be given to the chemical and mineralogical characteristics of the sample, elements to be determined, precision and accuracy requirements, sample throughput, technical capability of personnel, and time constraints. This paper addresses these concerns and discusses the attributes and limitations of many techniques of sample decomposition along with examples of their application to geochemical analysis. The chemical properties of reagents as to their function as decomposition agents are also reviewed. The section on acid dissolution techniques addresses the various inorganic acids that are used individually or in combination in both open and closed systems. Fluxes used in sample fusion are discussed. The promising microwave-oven technology and the emerging field of automation are also examined. A section on applications highlights the use of decomposition techniques for the determination of Au, platinum group elements (PGEs), Hg, U, hydride-forming elements, rare earth elements (REEs), and multi-elements in geological materials. Partial dissolution techniques used for geochemical exploration which have been treated in detail elsewhere are not discussed here; nor are fire-assaying for noble metals and decomposition techniques for X-ray fluorescence or nuclear methods be discussed. ?? 1992.

  8. Miscellaneous Techniques

    Science.gov (United States)

    Jha, Shyam N.

    Nondestructive way of determining the food quality is the need of the hour. Till now major methods such as colour measurements and their modeling; machine vision systems; X-ray, CT and MRI; NIR spectroscopy; electronic nose and tongue; and ultrasonic technology have been discussed in detail. These techniques, in general, are considered to be sophisticated and costly, and therefore probably are not being adopted as fast as it should be. I am however of the reverse opinion. While going through these techniques, it has been seen that majority of quality parameters have been measured and correlated with the signals obtained using different equipment.

  9. Tribological Properties of Al-SiC Metal Matrix Composites: A Comparison Between Sand Cast and Squeeze Cast Techniques

    Science.gov (United States)

    Ghosh, S.; Sahoo, P.; Sutradhar, G.

    2014-10-01

    Tribological behaviour of Al-SiC metal matrix composites prepared using two different fabrication techniques, viz. sand cast and squeeze cast techniques are studied in a multi- tribotester (TR-25, DUCOM, India) under dry sliding conditions and ambient atmosphere for varying volume fraction of reinforcement, applied load and sliding speed. Friction increases with increase in applied load and sliding speed and volume fraction of reinforcement. Wear test results show increased wear rates at higher load and speed, while increase in SiC volume fraction yields decrease in wear rate. Corrosion study conducted in 3.5 % NaCl solution shows that squeeze cast composites have better corrosion resistance than sand cast composites. Vickers's microhardness test shows improved hardness properties for squeeze cast composites compared to sand cast ones. The microstructure study of wear tracks reveals domination of abrasive wear with minor traces of adhesive wear.

  10. Bulk Mechanical Properties Testing of Metallic Marginal Glass Formers

    Directory of Open Access Journals (Sweden)

    Thien Q. Phan

    2016-01-01

    Full Text Available We developed a unique three-point bend testing apparatus to measure bulk mechanical properties of a model metallic glass alloy (SAM2X5 with nominal composition Fe49.7Cr17.1Mn1.9Mo7.4W1.6B15.2C3.8Si2.4 prepared by spark plasma sintering. The relatively large sample sizes in the present work allowed for the preparation of test specimens with a macroscale cross section (in the millimeter range with well-controlled sample dimensions closer to standardized tests. Wire saw cutting allowed for a relatively sharp notch radius (3x smaller than previous studies and minimal sample damage. We determined that Young’s modulus and notch fracture toughness measured by our three-point bending apparatus are 230 GPa and 4.9 MPa·m1/2. Also, Vickers indentation and flexure testing provided consistent results for Young’s modulus. Indentation fracture toughness measured by Vickers indentation produced values at least 50% lower than by flexure. The microscale mechanical properties testing technique presented in this work and subsequent analyses are applicable to specimens of other compositions or ones prepared by other methods.

  11. Structural imprints at the front of the Chocó-Panamá indenter: Field data from the North Cauca Valley Basin, Central Colombia

    Science.gov (United States)

    Suter, F.; Sartori, M.; Neuwerth, R.; Gorin, G.

    2008-11-01

    The northern Andes are a complex area where tectonics is dominated by the interaction between three major plates and accessory blocks, in particular, the Chocó-Panamá and Northern Andes Blocks. The studied Cauca Valley Basin is located at the front of the Chocó-Panamá Indenter, where the major Romeral Fault System, active since the Cretaceous, changes its kinematics from right-lateral in the south to left-lateral in the north. Structural studies were performed at various scales: DEM observations in the Central Cordillera between 4 and 5.7°N, aerial photograph analyses, and field work in the folded Oligo-Miocene rocks of the Serranía de Santa Barbara and in the flat-lying, Pleistocene Quindío-Risaralda volcaniclastic sediments interfingering with the lacustrine to fluviatile sediments of the Zarzal Formation. The data acquired allowed the detection of structures with a similar orientation at every scale and in all lithologies. These families of structures are arranged similarly to Riedel shears in a right-lateral shear zone and are superimposed on the Cretaceous Romeral suture. They appear in the Central Cordillera north of 4.5°N, and define a broad zone where 060-oriented right-lateral distributed shear strain affects the continental crust. The Romeral Fault System stays active and strain partitioning occurs among both systems. The southern limit of the distributed shear strain affecting the Central Cordillera corresponds to the E-W trending Garrapatas-Ibagué shear zone, constituted by several right-stepping, en-échelon, right-lateral, active faults and some lineaments. North of this shear zone, the Romeral Fault System strike changes from NNE to N. Paleostress calculations gave a WNW-ESE trending, maximum horizontal stress, and 69% of compressive tensors. The orientation of σ1 is consistent with the orientation of the right-lateral distributed shear strain and the compressive state characterizing the Romeral Fault System in the area: it bisects the

  12. West-directed thrusting south of the eastern Himalayan syntaxis indicates clockwise crustal flow at the indenter corner during the India-Asia collision

    Science.gov (United States)

    Haproff, Peter J.; Zuza, Andrew V.; Yin, An

    2018-01-01

    Whether continental deformation is accommodated by microplate motion or continuum flow is a central issue regarding the nature of Cenozoic deformation surrounding the eastern Himalayan syntaxis. The microplate model predicts southeastward extrusion of rigid blocks along widely-spaced strike-slip faults, whereas the crustal-flow model requires clockwise crustal rotation along closely-spaced, semi-circular right-slip faults around the eastern Himalayan syntaxis. Although global positioning system (GPS) data support the crustal-flow model, the surface velocity field provides no information on the evolution of the India-Asia orogenic system at million-year scales. In this work, we present the results of systematic geologic mapping across the northernmost segment of the Indo-Burma Ranges, located directly southeast of the eastern Himalayan syntaxis. Early research inferred the area to have experienced either right-slip faulting accommodating northward indentation of India or thrusting due to the eastward continuation of the Himalayan orogen in the Cenozoic. Our mapping supports the presence of dip-slip thrust faults, rather than strike-slip faults. Specifically, the northern Indo-Burma Ranges exposes south- to west-directed ductile thrust shear zones in the hinterland and brittle fault zones in the foreland. The trends of ductile stretching lineations within thrust shear zones and thrust sheets rotate clockwise from the northeast direction in the northern part of the study area to the east direction in the southern part of the study area. This clockwise deflection pattern of lineations around the eastern Himalayan syntaxis mirrors the clockwise crustal-rotation pattern as suggested by the crustal-flow model and contemporary GPS velocity field. However, our finding is inconsistent with discrete strike-slip deformation in the area and the microplate model.

  13. Electrochemical Techniques

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Gang; Lin, Yuehe

    2008-07-20

    Sensitive and selective detection techniques are of crucial importance for capillary electrophoresis (CE), microfluidic chips, and other microfluidic systems. Electrochemical detectors have attracted considerable interest for microfluidic systems with features that include high sensitivity, inherent miniaturization of both the detection and control instrumentation, low cost and power demands, and high compatibility with microfabrication technology. The commonly used electrochemical detectors can be classified into three general modes: conductimetry, potentiometry, and amperometry.

  14. Experimental Techniques

    DEFF Research Database (Denmark)

    Wyer, Jean

    2013-01-01

    Gas-phase ion spectroscopy requires specialised apparatus, both when it comes to measuring photon absorption and light emission (fluorescence). The reason is much lower ion densities compared to solution-phase spectroscopy. In this chapter different setups are described, all based on mass spectro...... in data interpretation, and the advantages and disadvantages of the different techniques are clarified. New instrumental developments involving cryo-cooled storage rings, which show great promise for the future, are briefly touched upon....

  15. Astrophysical techniques

    CERN Document Server

    Kitchin, CR

    2013-01-01

    DetectorsOptical DetectionRadio and Microwave DetectionX-Ray and Gamma-Ray DetectionCosmic Ray DetectorsNeutrino DetectorsGravitational Radiation Dark Matter and Dark Energy Detection ImagingThe Inverse ProblemPhotographyElectronic ImagingScanningInterferometrySpeckle InterferometryOccultationsRadarElectronic ImagesPhotometryPhotometryPhotometersSpectroscopySpectroscopy SpectroscopesOther TechniquesAstrometryPolarimetrySolar StudiesMagnetometryComputers and The Internet.

  16. Mechanical Properties and Durability of Advanced Environmental Barrier Coatings in Calcium-Magnesium-Alumino-Silicate Environments

    Science.gov (United States)

    Miladinovich, Daniel S.; Zhu, Dongming

    2011-01-01

    Environmental barrier coatings are being developed and tested for use with SiC/SiC ceramic matrix composite (CMC) gas turbine engine components. Several oxide and silicate based compositons are being studied for use as top-coat and intermediate layers in a three or more layer environmental barrier coating system. Specifically, the room temperature Vickers-indentation-fracture-toughness testing and high-temperature stability reaction studies with Calcium Magnesium Alumino-Silicate (CMAS or "sand") are being conducted using advanced testing techniques such as high pressure burner rig tests as well as high heat flux laser tests.

  17. Comparison of mechanical properties of glass-bonded sodalite and borosilicate glass high-level waste forms

    Energy Technology Data Exchange (ETDEWEB)

    O' Holleran, T. P.; DiSanto, T.; Johnson, S. G.; Goff, K. M.

    2000-05-09

    Argonne National Laboratory has developed a glass-bonded sodalite waste form to immobilize the salt waste stream from electrometallurgical treatment of spent nuclear fuel. The waste form consists of 75 vol.% crystalline sodalite and 25 vol.% glass. Microindentation fracture toughness measurements were performed on this material and borosilicate glass from the Defense Waste Processing Facility using a Vickers indenter. Palmqvist cracking was confined for the glass-bonded sodalite waste form, while median-radial cracking occurred in the borosilicate glass. The elastic modulus was measured by an acoustic technique. Fracture toughness, microhardness, and elastic modulus values are reported for both waste forms.

  18. Metallurgical and mechanical characterization of mild steel-mild ...

    Indian Academy of Sciences (India)

    in dimensions made on the weld zone, but larger in dimensions made on the base metal. This clearly indicates that the weld zone has a higher hardness as compared to base metal. Micro. (a). (b). Figure 5. (a) Vicker's microhardness indentation shown by white circle, (b) Vickers microhardness value at various zones.

  19. THE RESEARCH TECHNIQUES FOR ANALYSIS OF MECHANICAL AND TRIBOLOGICAL PROPERTIES OF COATING-SUBSTRATE SYSTEMS

    Directory of Open Access Journals (Sweden)

    Kinga CHRONOWSKA-PRZYWARA

    2014-06-01

    Full Text Available The article presents research techniques for the analysis of both mechanical and tribological properties of thin coatings applied on highly loaded machine elements. In the Institute of Machine Design and Exploitation, AGH University of Science and Technology students of the second level of Mechanical Engineering study tribology attending laboratory class. Students learn on techniques for mechanical and tribological testing of thin, hard coatings deposited by PVD and CVD technologies. The program of laboratories contains micro-, nanohardness and Young's modulus measurements by instrumental indentations and analysys of coating to substrate adhesion by scratch testing. The tribological properties of the coating-substrate systems are studied using various techniques, mainly in point contact load conditions with ball-on-disc and block-on-ring tribomiters as well as using ball cratering method in strongly abrasive suspensions.

  20. Terahertz Techniques

    CERN Document Server

    Bründermann, Erik; Kimmitt, Maurice FitzGerald

    2012-01-01

    Research and development in the terahertz portion of the electromagnetic spectrum has expanded very rapidly during the past fifteen years due to major advances in sources, detectors and instrumentation. Many scientists and engineers are entering the field and this volume offers a comprehensive and integrated treatment of all aspects of terahertz technology. The three authors, who have been active researchers in this region over a number of years, have designed Terahertz Techniques to be both a general introduction to the subject and a definitive reference resource for all those involved in this exciting research area.

  1. INVESTIGATION OF SINGLE-PASS/DOUBLE-PASS TECHNIQUES ON FRICTION STIR WELDING OF ALUMINIUM

    Directory of Open Access Journals (Sweden)

    N.A.A. Sathari

    2014-12-01

    Full Text Available The aim of this research is to study the effects of single-pass/ double-pass techniques on friction stir welding of aluminium. Two pieces of AA1100 with a thickness of 6.0 mm were friction stir welded using a CNC milling machine at rotational speeds of 1400 rpm, 1600 rpm and 1800 rpm respectively for single-pass and double-pass. Microstructure observations of the welded area were studied using an optical microscope. The specimens were tested by using a tensile test and Vickers hardness test to evaluate their mechanical properties. The results indicated that, at low rotational speed, defects such as ‘surface lack of fill’ and tunnels in the welded area contributed to a decrease in mechanical properties. Welded specimens using double-pass techniques show increasing values of tensile strength and hardness. From this investigation it is found that the best parameters of FSW welded aluminium AA1100 plate were those using double-pass techniques that produce mechanically sound joints with a hardness of 56.38 HV and 108 MPa strength at 1800 rpm compared to the single-pass technique. Friction stir welding, single-pass/ double-pass techniques, AA1100, microstructure, mechanical properties.

  2. Combinatorial techniques

    CERN Document Server

    Sane, Sharad S

    2013-01-01

    This is a basic text on combinatorics that deals with all the three aspects of the discipline: tricks, techniques and theory, and attempts to blend them. The book has several distinctive features. Probability and random variables with their interconnections to permutations are discussed. The theme of parity has been specially included and it covers applications ranging from solving the Nim game to the quadratic reciprocity law. Chapters related to geometry include triangulations and Sperner's theorem, classification of regular polytopes, tilings and an introduction to the Eulcidean Ramsey theory. Material on group actions covers Sylow theory, automorphism groups and a classification of finite subgroups of orthogonal groups. All chapters have a large number of exercises with varying degrees of difficulty, ranging from material suitable for Mathematical Olympiads to research.

  3. Nitriding molybdenum: Effects of duration and fill gas pressure when using 100-Hz pulse DC discharge technique

    Science.gov (United States)

    Ikhlaq, U.; R., Ahmad; Shafiq, M.; Saleem, S.; S. Shah, M.; Hussain, T.; A. Khan, I.; K., Abbas; S. Abbas, M.

    2014-10-01

    Molybdenum is nitrided by a 100-Hz pulsed DC glow discharge technique for various time durations and fill gas pressures to study the effects on the surface properties of molybdenum. X-ray diffractometry (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM) are used for the structural and morphological analysis of the nitrided layers. Vickers' microhardness tester is utilized to investigate surface microhardness. Phase analysis shows the formation of more molybdenum nitride molecules for longer nitriding durations at fill gas pressures of 2 mbar and 3 mbar (1 bar = 105 Pa). A considerable increase in surface microhardness (approximately by a factor of 2) is observed for longer duration (10 h) and 2-mbar pressure. Longer duration (10 h) and 2-mbar fill gas pressure favors the formation of homogeneous, smooth, hard layers by the incorporation of more nitrogen.

  4. Techniques de combustion Combustin Techniques

    Directory of Open Access Journals (Sweden)

    Perthuis E.

    2006-11-01

    Full Text Available L'efficacité d'un processus de chauffage par flamme est étroitement liée à la maîtrise des techniques de combustion. Le brûleur, organe essentiel de l'équipement de chauffe, doit d'une part assurer une combustion complète pour utiliser au mieux l'énergie potentielle du combustible et, d'autre part, provoquer dans le foyer les conditions aérodynamiques les plus propices oux transferts de chaleur. En s'appuyant sur les études expérimentales effectuées à la Fondation de Recherches Internationales sur les Flammes (FRIF, au Groupe d'Étude des Flammes de Gaz Naturel (GEFGN et à l'Institut Français du Pétrole (IFP et sur des réalisations industrielles, on présente les propriétés essentielles des flammes de diffusion aux combustibles liquides et gazeux obtenues avec ou sans mise en rotation des fluides, et leurs répercussions sur les transferts thermiques. La recherche des températures de combustion élevées conduit à envisager la marche à excès d'air réduit, le réchauffage de l'air ou son enrichissement à l'oxygène. Par quelques exemples, on évoque l'influence de ces paramètres d'exploitation sur l'économie possible en combustible. The efficiency of a flame heating process is closely linked ta the mastery of, combustion techniques. The burner, an essential element in any heating equipment, must provide complete combustion sa as to make optimum use of the potential energy in the fuel while, at the same time, creating the most suitable conditions for heat transfers in the combustion chamber. On the basis of experimental research performed by FRIF, GEFGN and IFP and of industrial achievements, this article describesthe essential properties of diffusion flames fed by liquid and gaseous fuels and produced with or without fluid swirling, and the effects of such flames on heat transfers. The search for high combustion temperatures means that consideration must be given to operating with reduced excess air, heating the air or

  5. Assessment of measurement techniques to determine the interfacial properties of bilayer dental ceramics

    Science.gov (United States)

    Anunmana, Chuchai

    The clinical success of all-ceramic dental restorations depends on the quality of interfacial bonding between ceramic layers. In addition, the residual stress in the structure that developed during ceramic processing is one of the important factors that contributes to the quality of the bond. Because all-ceramic restorations are usually fabricated as bilayer or trilayer structures and failures of all-ceramic restorations have been frequently reported as chipping or delamination of the veneer layers, the interfacial quality of bilayer dental ceramic restorations was investigated. However, most of the published bond test data reflect strength values that are inversely related to cross-sectional areas and failure locations are frequently disregarded or bond strength values are misinterpreted. In addition, residual tensile stresses that develop in the structures because of thermal expansion/contraction mismatches may also adversely affect interfacial fracture resistance. The first objective of this study was to determine the interfacial toughness of bonded bilayer ceramics using two different approaches. The results indicate that the short-bar chevron-notch test and a controlled-flaw microtensile test can induce interfacial failure that represents true bonding quality. The second objective of this study was to test the hypothesis that residual stresses estimated from an indentation technique are not significantly different from residual stresses that are calculated based on fractography and flexural strength. The indentation technique may be useful as a simplified method to determine residual stresses in bilayer dental ceramics. The results of this study demonstrate that there is no significant difference in mean residual stresses determined from the two techniques. Because of relationship between residual stresses and apparent interfacial toughness, estimates of residual stresses can now be estimated more rapidly by measuring the apparent interfacial toughness of

  6. Investigation of surface and subsurface profile, techniques of measurement, and replication of the Chinese Magic Mirror

    Science.gov (United States)

    Kang Min, Eden T.; Watt, Sook May; Sreemathy, Parthasarathy; Huang, Lei; Asundi, Anand

    2013-06-01

    The Chinese magic mirror is an ancient convex bronze mirror, it reflects parallel light rays to form a unique image within the reflected patch of light by altering the reflected ray paths. Using Phase Measuring Reflectometry (PMR), surface irregularities of a micron range were found to be present on the mirror; these irregularities concentrate and disperse reflected light rays, giving rise to brighter and darker patches on the reflected image, forming a contrast, allowing the unique pattern to be observed. To ascertain location and nature of the surface defects that come in forms of indentations and raised platforms, other measurement techniques were employed. Reverse engineering then facilitated the exploration of reproduction of a very own original Chinese Magic Mirror with the use of optical principles behind the mirror.

  7. Evaluation of hardening behaviors in ion-irradiated Fe–9Cr and Fe–20Cr alloys by nanoindentation technique

    Energy Technology Data Exchange (ETDEWEB)

    Li, Shilei; Wang, Yanli [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China); Dai, Xianyuan [Fujian Fuqing Nuclear Power Co., Ltd., Fuqing, Fujian Province, 350318 (China); Liu, Fang [Department of Physics, Chalmers University of Technology, SE-41296 Gothenburg (Sweden); Li, Jinyu [Institute of Modern Physics, Chinese Academy of Science, Lanzhou 730000 (China); Wang, Xitao, E-mail: xtwang@ustb.edu.cn [Collaborative Innovation Center of Steel Technology, University of Science and Technology Beijing, Beijing 100083 (China)

    2016-09-15

    The ion irradiation hardening behaviors of Fe–9 wt% Cr and Fe–20 wt% Cr model alloys were investigated by nanoindentation technique. The specimens were irradiated with 3 MeV Fe{sup 11+} ions at room temperature up to 1 and 5 dpa for Fe–9Cr alloy and 1 and 2.5 for Fe–20Cr alloy. The ratio of average hardness in the same depth of irradiated and unirradiated (Hirr. av/Hunirr. av) was used to determine the critical indentation depth hcrit to eliminate the softer substrate effect. The Nix–Gao model was used to explain the indentation size effect. Irradiation hardening is clearly observed in both Fe–9Cr alloy and Fe–20Cr alloy after ion irradiation. The differences of ISE and irradiation hardening behaviors between Fe–9Cr and Fe–20Cr alloys are considered to be due to their different microstructures and microstructural evolution under ion irradiation.

  8. A Novel Technique Using Customized Headgear for Fixation of Rigid External Distraction Device in an Infant With Crouzon Syndrome.

    Science.gov (United States)

    Hariri, Firdaus; Rahman, Zainal Ariff Abdul; Mahdah, Saridah; Mathaneswaran, Vickneswaran; Ganesan, Dharmendra

    2015-11-01

    Rigid external distraction device is often indicated for superior midfacial advancement in pediatric syndromic craniosynostosis patients. Even though the technique is proven reliable to treat the functional issues related to the craniofacial deformity, major complications associated with its fixation, such as intracranial pin perforation and migration have been reported. We report a novel technique of using a customized headgear to prevent intracranial pin perforation over a very thin temporal bone region in an 8-month-old infant with Crouzon syndrome who underwent monobloc Le Fort III distraction osteogenesis using a combination of bilateral internal and a rigid external distraction device. The customized headgear provides a protective platform at the temporal region thus preventing intracranial pin perforation and allows stable fixation during the early phase of consolidation period to prevent central component relapse. The headgear can be used short term when rigid external distractor is indicated in infant patient but requires close monitoring because of risks of skin necrosis and temporal region indentation.

  9. Cogeneration techniques; Les techniques de cogeneration

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1999-10-01

    This dossier about cogeneration techniques comprises 12 parts dealing successively with: the advantages of cogeneration (examples of installations, electrical and thermal efficiency); the combustion turbine (principle, performances, types); the alternative internal combustion engines (principle, types, rotation speed, comparative performances); the different configurations of cogeneration installations based on alternative engines and based on steam turbines (coal, heavy fuel and natural gas-fueled turbines); the environmental constraints of combustion turbines (pollutants, techniques of reduction of pollutant emissions); the environmental constraints of alternative internal combustion engines (gas and diesel engines); cogeneration and energy saving; the techniques of reduction of pollutant emissions (pollutants, unburnt hydrocarbons, primary and secondary (catalytic) techniques, post-combustion); the most-advanced configurations of cogeneration installations for enhanced performances (counter-pressure turbines, massive steam injection cycles, turbo-chargers); comparison between the performances of the different cogeneration techniques; the tri-generation technique (compression and absorption cycles). (J.S.)

  10. Study of microstress state of P91 steel using complementary mechanical Barkhausen, magnetoacoustic emission, and X-ray diffraction techniques

    Energy Technology Data Exchange (ETDEWEB)

    Augustyniak, Bolesław, E-mail: bolek@mif.pg.gda.pl; Piotrowski, Leszek; Maciakowski, Paweł; Chmielewski, Marek [Faculty of Applied Physics and Mathematics, Gdansk University of Technology, 80-233 Gdansk (Poland); Lech-Grega, Marzena; Żelechowski, Janusz [The Institute of Non-Ferrous Metals, 32-050 Skawina (Poland)

    2014-05-07

    The paper deals with assessment of microstress state of martensite P91 steel using three complementary techniques: mechanical Barkhausen emission, magnetoacoustic emission (MAE), and X-ray diffraction (XRD) profile analysis. Magnetic coercivity Hc and microstructure were investigated with inductive magnetometry and magnetic force microscopy (MFM), respectively. Internal stress level of P91 steel was modified by heat treatment. Steel samples were austenitized, quenched, and then tempered at three temperatures (720 °C, 750 °C, and 780 °C) during increasing time (from 15 min up to 240 min). The microstrain level ε{sub i} was evaluated using Williamson–Hall method. It was revealed that during tempering microstrain systematically decreases from ε{sub i} = 2.5 × 10{sup −3} for as quenched state down to ε{sub i} = 0.3 × 10{sup −3} for well tempered samples. Both mechanical hardness (Vicker's HV) and magnetic hardness (coercivity) decrease almost linearly with decreasing microstrain while the MAE and MBE intensities strongly increase. Tempering leads to evident shift of the MeBN intensity maximum recorded for the first load towards lower applied strain values and to increase of MAE intensity. This indicates that the microstress state deduced by magnetic techniques is correlated with microstrains evaluated with XRD technique.

  11. Subjection and subjectification / technique and techniques

    Directory of Open Access Journals (Sweden)

    Emanuele Clarizio

    2013-03-01

    Full Text Available The Course on The Hermeneutic of the Subject problematizes a theme that goes through the whole Foucault’s thought, that of technique. The article, through a dialogue among Foucault, Heidegger and Simondon, aims to trace the development of this theme, also asking the way the technique works when related to processes of subjection and subjectification.

  12. A new technique to make transparent teeth without decalcifying: description of the methodology and micro-hardness assessment.

    Science.gov (United States)

    Malentacca, Augusto; Lajolo, Carlo

    2015-01-01

    Diaphanisation and other in vitro endodontic models (i.e., plastic blocks, micro-CT reconstruction, computerised models) do not recreate real root canal working conditions: a more realistic endodontic model is essential for testing endodontic devices and teaching purposes. The aim of this study was to describe a new technique to construct transparent teeth without decalcifying and evaluate the micro-hardness of so treated teeth. Thirty freshly extracted teeth were randomly divided into three groups as follows: 10 non-treated teeth (4 molars, 3 premolars, 3 incisors; control group - G1), 10 teeth were diaphanised (4 molars, 4 premolars, 2 incisors - G2) and 10 teeth were treated with the new proposed technique (2 molars, 6 premolars, 2 incisors - G3). Vickers hardness tester (MHT-4 and AxioVision microscope, Carl Zeiss, 37030 Gottingen, Germany - load=50 g, dwell time=20s, slope=5, 50× magnification) was used to determine microhardness (Vickers Hardness Number - VHN). Statistical analysis was performed using the Intercooled Stata 8.0 software (Stata Corporation, College Station, TX, USA). Only groups 1 and 3 could be tested for hardness because diaphanised teeth were too tender and elastic. Differences in enamel VHN were observed between G1 (mean 304.29; DS=10.44; range 283-321) and G3 (mean 318.51; DS=14.36; range 295.5-339.2) - (p<0.05); differences in dentine VHN were observed between G1 (mean 74.73; DS=6.62; range 63.9-88.1) and G3 (mean 64.54; DS=5.55; range 51.2-72.3) - (p<0.05). G3 teeth presented a slightly lower VHN compared to G1, probably due to some little structural differences among groups, and were dramatically harder than the diaphanised teeth. The described technique, thus, can be considered ideal for testing endodontic instruments and for teaching purposes. Copyright © 2014 Elsevier GmbH. All rights reserved.

  13. Fast deposition of thick diamond-like carbon films by ion-beam technique

    Science.gov (United States)

    Liao, Bin; Yu, Jingjing; Wang, Yudong; Bian, Baoan; Jiang, Qili; Luo, Jun; Zhang, Xu; Wu, Xianying; Ying, Minju

    2017-08-01

    A diamond-like carbon film doped with TiC nanocrystallites (TiC-DLC) with a thickness of 35.8 μm was successfully prepared on a stainless steel substrate by employing a combination of metal vapor vacuum arc and filtered cathode vacuum arc techniques. A maximum deposition rate of 0.25 μm/min was achieved for TiC-DLC films. The structure and properties of the TiC-DLC films were systematically analyzed using different methods such as transmission electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, scanning electron microscopy, X-ray diffraction, and friction and wear tests. The results indicated that typical a-C:H films containing nano-sized TiC grains were deposited which exhibit improved mechanical properties such as high cohesive strength, Vickers hardness, and capacity against high temperature. Parameter windows for C2H2 flow rate and solenoid current were also provided for the deposition of TiC-DLC films to meet the requirements for using the material for specific commercial applications.

  14. Low-level laser therapy, at 60 J/cm2 associated with a Biosilicate® increase in bone deposition and indentation biomechanical properties of callus in osteopenic rats

    Science.gov (United States)

    Fangel, Renan; Sérgio Bossini, Paulo; Cláudia Renno, Ana; Araki Ribeiro, Daniel; Chenwei Wang, Charles; Luri Toma, Renata; Okino Nonaka, Keico; Driusso, Patrícia; Antonio Parizotto, Nivaldo; Oishi, Jorge

    2011-07-01

    We investigate the effects of a novel bioactive material (Biosilicate®) and low-level laser therapy (LLLT), at 60 J/cm2, on bone-fracture consolidation in osteoporotic rats. Forty female Wistar rats are submitted to the ovariectomy, to induce osteopenia. Eight weeks after the ovariectomy, the animals are randomly divided into four groups, with 10 animals each: bone defect control group; bone defect filled with Biosilicate group; bone defect irradiated with laser at 60 J/cm2 group; bone defect filled with Biosilicate and irradiated with LLLT, at 60 J/cm2 group. Laser irradiation is initiated immediately after surgery and performed every 48 h for 14 days. Histopathological analysis points out that bone defects are predominantly filled with the biomaterial in specimens treated with Biosilicate. In the 60-J/cm2 laser plus Biosilicate group, the biomaterial fills all bone defects, which also contained woven bone and granulation tissue. Also, the biomechanical properties are increased in the animals treated with Biosilicate associated to lasertherapy. Our results indicate that laser therapy improves bone repair process in contact with Biosilicate as a result of increasing bone formation as well as indentation biomechanical properties.

  15. Surface science techniques

    CERN Document Server

    Bracco, Gianangelo

    2013-01-01

    The book describes the experimental techniques employed to study surfaces and interfaces. The emphasis is on the experimental method. Therefore all chapters start with an introduction of the scientific problem, the theory necessary to understand how the technique works and how to understand the results. Descriptions of real experimental setups, experimental results at different systems are given to show both the strength and the limits of the technique. In a final part the new developments and possible extensions of the techniques are presented. The included techniques provide microscopic as well as macroscopic information. They cover most of the techniques used in surface science.

  16. Three dimension magnetic resonance lumbosacral radiculography by principles of the selective excitation technique imaging in the diagnosis of symptomatic foraminal stenosis

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Ji Kyung; Byun, Woo Mok [Yeungnam Univ., Daegu (Korea, Republic of)

    2012-06-15

    To investigate significance of three dimension (3D) magnetic resonance (MR) lumbosacral radiculography by principles of the selective excitation technique (Proset) in the diagnosis of symptomatic foraminal stenosis. A total of 288 foramina in 48 patients were analyzed (from L3 4 to L5 S1). Conventional spin echo sequence and 3D coronal fast field echo sequences with selective water excitation by Proset were acquired. Through conventional MR imaging, the presence of lumbar foraminal stenosis was evaluated. Three morphologic changes (swelling, indentation, and tilting angle abnormality) of corresponding nerve roots were assessed on 3D MR lumbosacral radiculography. Relationships between the three morphologic findings and corresponding symptoms were evaluated. In 288 foramina, symptomatic and asymptomatic foraminal stenoses were found in 49 and 14 foramina, respectively. In symptomatic foraminal stenosis, swelling, indentation and tilting angle abnormality of the nerve root were found in 36, 18, and 10 foramina, respectively. One or more of the three findings was found in 46 foramina. In 12 foramina with asymptomatic foraminal stenosis, no morphologic changes were found. A statistically significant difference among three morphologic changes of nerve root in symptomatic foraminal stenosis was found ({chi}2 test, p < 0.001). 3D MR lumbosacral radiculography by Proset was useful for the detection of morphologic changes of the nerve root for the diagnosis of symptomatic foraminal stenosis.

  17. Airway Clearance Techniques (ACTs)

    Medline Plus

    Full Text Available ... decisions about your health care. CF Genetics: The Basics CF Mutations Video Series CFTR2 Personalized Medicine Types ... of Breathing Technique Airway Clearance Techniques Autogenic Drainage Basics of Lung Care Chest Physical Therapy Coughing and ...

  18. Airway Clearance Techniques (ACTs)

    Medline Plus

    Full Text Available ... of treatment options. Airway Clearance Active Cycle of Breathing Technique Airway Clearance Techniques Autogenic Drainage Basics of ... Pulmonary Exacerbations Clinical Care Guidelines SCREENING & TREATING DEPRESSION & ANXIETY GUIDELINES Clinician Resources As a clinician, you’re ...

  19. Airway Clearance Techniques (ACTs)

    Medline Plus

    Full Text Available ... CF Treatments and Therapies Airway Clearance Airway Clearance Techniques (ACTs) There are different ways to clear your ... for fitting ACTs into daily life Airway Clearance Techniques | Webcast To learn more about how you can ...

  20. Healthy Cooking Techniques

    Science.gov (United States)

    Healthy Lifestyle Nutrition and healthy eating Healthy-cooking techniques capture the flavor and nutrients of food without ... in expensive cookware. You can use basic cooking techniques to prepare food in healthy ways. By using ...

  1. Airway Clearance Techniques (ACTs)

    Medline Plus

    Full Text Available ... many challenges, including medical, social, and financial. By learning more about how you can manage your disease every day, you can ... Clearance Active Cycle of Breathing Technique (ACBT) Airway Clearance Techniques ( ...

  2. Airway Clearance Techniques (ACTs)

    Medline Plus

    Full Text Available ... Airway Clearance Airway Clearance Techniques (ACTs) There are different ways to clear your airways. Most are easy ... to loosen mucus from airway walls. See how different airway clearance techniques work to help you clear ...

  3. Semiconductor Research Experimental Techniques

    CERN Document Server

    Balkan, Naci

    2012-01-01

    The book describes the fundamentals, latest developments and use of key experimental techniques for semiconductor research. It explains the application potential of various analytical methods and discusses the opportunities to apply particular analytical techniques to study novel semiconductor compounds, such as dilute nitride alloys. The emphasis is on the technique rather than on the particular system studied.

  4. Techniques for characterizing lignin

    Science.gov (United States)

    Nicole M. Stark; Daniel J. Yelle; Umesh P. Agarwal

    2016-01-01

    Many techniques are available to characterize lignin. The techniques presented in this chapter are considered nondegradative, which are commonly applied to lignin. A brief discussion of lignin structure is included with this chapter to aid the reader in understanding why the discussed characterization techniques are appropriate for the study of lignin. Because the...

  5. The backcross sterility technique

    Science.gov (United States)

    V. C. Mastro; A. Pellegrini-Toole

    1991-01-01

    The sterile insect technique (SIT) and the induced inherited (F1) sterility technique have been investigated for a number of lepidopterous pests, including the gypsy moths. Another technique, backcross sterility, which could potentially prove as or more useful for control of pest species has been developed for the control of only one lepidopteran...

  6. Studies on the growth, structural, optical, mechanical properties of 8-hydroxyquinoline single crystal by vertical Bridgman technique

    Energy Technology Data Exchange (ETDEWEB)

    Prabhakaran, SP. [Crystal Growth and Thin Film Laboratory, Department of Physics, Bharathidasan University, Tiruchirappalli 620 024, Tamil Nadu (India); Babu, R. Ramesh, E-mail: rampap2k@yahoo.co.in [Crystal Growth and Thin Film Laboratory, Department of Physics, Bharathidasan University, Tiruchirappalli 620 024, Tamil Nadu (India); Velusamy, P.; Ramamurthi, K. [Crystal Growth and Thin Film Laboratory, Department of Physics, Bharathidasan University, Tiruchirappalli 620 024, Tamil Nadu (India)

    2011-11-15

    Highlights: {yields} Growth of bulk single crystal of 8-hydroxyquinoline (8-HQ) by vertical Bridgman technique for the first time. {yields} The crystalline perfection is reasonably good. {yields} The photoluminescence spectrum shows that the material is suitable for blue light emission. -- Abstract: Single crystal of organic nonlinear optical material, 8-hydroxyquinoline (8-HQ) of dimension 52 mm (length) x 12 mm (dia.) was grown from melt using vertical Bridgman technique. The crystal system of the material was confirmed by powder X-ray diffraction analysis. The crystalline perfection of the grown crystal was examined by high-resolution X-ray diffraction study. Low angular spread around 400'' of the diffraction curve and the low full width half maximum values show that the crystalline perfection is reasonably good. The recorded photoluminescence spectrum shows that the material is suitable for blue light emission. Optical transmittance for the UV and visible region was measured and mechanical strength was estimated from Vicker's microhardness test along the growth face of the grown crystal.

  7. Low current beam techniques

    Energy Technology Data Exchange (ETDEWEB)

    Saint, A.; Laird, J.S.; Bardos, R.A.; Legge, G.J.F. [Melbourne Univ., Parkville, VIC (Australia). School of Physics; Nishijima, T.; Sekiguchi, H. [Electrotechnical Laboratory, Tsukuba (Japan).

    1993-12-31

    Since the development of Scanning Transmission Microscopy (STIM) imaging in 1983 many low current beam techniques have been developed for the scanning (ion) microprobe. These include STIM tomography, Ion Beam Induced Current, Ion Beam Micromachining and Microlithography and Ionoluminense. Most of these techniques utilise beam currents of 10{sup -15} A down to single ions controlled by beam switching techniques This paper will discuss some of the low beam current techniques mentioned above, and indicate, some of their recent applications at MARC. A new STIM technique will be introduced that can be used to obtain Z-contrast with STIM resolution. 4 refs., 3 figs.

  8. Investigation on crystalline perfection, mechanical, piezoelectric and ferroelectric properties of L-tartaric acid single crystal

    Energy Technology Data Exchange (ETDEWEB)

    Murugan, G. Senthil, E-mail: nanosen@gmail.com; Ramasamy, P., E-mail: nanosen@gmail.com [Centre for Crystal Growth, SSN College of Engineering, Kalavakkam, Tamilnadu - 603110 (India)

    2014-04-24

    Polar organic nonlinear optical material, L-tartaric acid single crystals have been grown from slow evaporation solution growth technique. Single crystal X-ray diffraction study indicates that the grown crystal crystallized in monoclinic system with space group P2{sub 1}. Crystalline perfection of the crystal has been evaluated by high resolution X-ray diffraction technique and it reveals that the crystal quality is good and free from structural grain boundaries. Mechanical stability of the crystal has been analyzed by Vickers microhardness measurement and it exhibits reverse indentation size effect. Piezoelectric d{sub 33} co-efficient for the crystal has been examined and its value is 47 pC/N. The ferroelectric behaviour of the crystal was analyzed by polarization-electric field hysteresis loop measurement.

  9. Fabrication of Dense ZrO2/CNT Composites: Influence of Bead-Milling Treatment

    Science.gov (United States)

    Suárez, Gustavo; Jang, Byung-Koog; Aglietti, Esteban F.; Sakka, Yoshio

    2013-09-01

    Highly concentrated zirconia-carbon nanotube (CNT) water suspensions were prepared using an advanced milling technique. The bead-milling operation parameters were optimized for this system and used to prepare zirconia-stabilized water-based suspensions with different CNT contents. The effects of different milling conditions were studied. The particle dispersion was evaluated by SEM observations on dried suspension. Green's density and SEM observations of compacts were used to follow the colloidal dispersability of the composites. Materials of tetragonal zirconia and CNTs were prepared with a high concentration of CNTs (1, 5, and 10 wt pct CNT). The homogeneous dispersion and distribution of the fibers in the bulk material after slip casting of the suspension were examined. The samples were sintered using spark plasma sintering (SPS) at 1473 K (1200 °C) and finally, fully dense materials were obtained. The mechanical properties were evaluated using the Vickers indentation technique.

  10. Inverse-FEM Characterization of a Brain Tissue Phantom to Simulate Compression and Indentation Caracterización de tejido cerebral artificial utilizando Inverse-FEM para simular indentación y comprensión

    Directory of Open Access Journals (Sweden)

    Elizabeth Mesa-Múnera

    2012-12-01

    Full Text Available The realistic simulation of tool-tissue interactions is necessary for the development of surgical simulators and one of the key element for it realism is accurate bio-mechanical tissue models. In this paper, we determined the mechanical properties of soft tissue by minimizing the difference between experimental measurements and the analytical or simulated solution of the deformation. Then, we selected the best model parameters that fit the experimental data to simulate a bonded compression and a needle indentation with a flat-tip. We show that the inverse FEM allows accurate material property estimation. We also validated our results using multiple tool-tissue interactions over the same specimen.Una simulación realista de la interacción tejido-herramienta es necesaria para desarrollar simuldores quirúrgicos, y la presición en modelos biomecánicos de tejidos es determinante para cumplir tal fin. Los trabajos previos han caracterizado las propiedades de tejidos blandos; sin embargo, ha faltado una validación apropiada de los resultados. En este trabajo se determinaron las propiedades mecánicas de un tejido blando minimizando la diferencia entre las mediciones experimentales y la solución analítica o simulada del problema. Luego, fueron seleccionados los parámetros que mejor se ajustaron a los datos experimentales para simular una compresión con fricción y la indentación de una aguja con punta plana. Se concluye que el inverse-FEM permite la precisa estimación de las propiedades del material. Además, estos resultados fueron validados con varias interacciones tejido-herramienta sobre el mismo espécimen.

  11. Principles of fluorescence techniques

    CERN Document Server

    2016-01-01

    Fluorescence techniques are being used and applied increasingly in academics and industry. The Principles of Fluorescence Techniques course will outline the basic concepts of fluorescence techniques and the successful utilization of the currently available commercial instrumentation. The course is designed for students who utilize fluorescence techniques and instrumentation and for researchers and industrial scientists who wish to deepen their knowledge of fluorescence applications. Key scientists in the field will deliver theoretical lectures. The lectures will be complemented by the direct utilization of steady-state and lifetime fluorescence instrumentation and confocal microscopy for FLIM and FRET applications provided by leading companies.

  12. Persian fencing techniques

    Directory of Open Access Journals (Sweden)

    Manouchehr Moshtagh Khorasani

    2012-07-01

    Full Text Available There are numerous manuscripts, poems and stories that describe, specifically and in detail, the different techniques used in Persian swordsmanship. The present article explains the origins and the techniques of Persian swordsmanship. The article also describes the traditional code of conduct for Persian warriors. Additionally, it describes an array of techniques that were deployed in actual combat in Iran’s history. Some of these techniques are represented via the miniatures that are reproduced herein. This is the first article on Persian swordsmanship published in any periodical.

  13. Materials characterization techniques

    National Research Council Canada - National Science Library

    Zhang, Sam; Li, L; Kumar, Ashok

    2009-01-01

    "With an emphasis on practical applications and real-world case studies, Materials Characterization Techniques presents the principles of widely used advanced surface and structural characterization...

  14. Available post-irradiation examination techniques at Romanian institute for nuclear research

    Energy Technology Data Exchange (ETDEWEB)

    Parvan, Marcel; Sorescu, Antonius; Mincu, Marin; Uta, Octavian; Dobrin, Relu

    2005-01-01

    The Romanian Institute for Nuclear Research (INR) has a set of nuclear facilities consisting of TRIGA 14 MW(th) materials testing reactor and LEPI (Romanian acronym for post-irradiation examination laboratory) which enable to investigate the behaviour of the nuclear fuel and materials under various irradiation conditions. The available techniques of post-irradiation examination (PIE) and purposes of PIE for CANDU reactor fuel are as follows. 1) Visual inspection and photography by periscope: To examine the surface condition such as deposits, corrosion etc. 2) Eddy current testing: To verify the cladding integrity. 3) Profilometry and length measurement performed both before and after irradiation: To measure the parameters which highlight the dimensional changes i.e. diameter, length, diametral and axial sheath deformation, circumferential sheath ridging height, bow and ovality. 4) Gamma scanning and Tomography: To determine the burnup, axial and radial fission products activity distribution and to check for flux peaking and loading homogeneity. 5) Puncture test: To measure the pressure, volume and composition of fission gas and the inner free volume. 6) Optical microscopy: To highlight the structural changes and hydriding, to examine the condition of the fuel-sheath interface and to measure the oxide thickness and Vickers microhardness. 7) Mass spectrometry: To measure the burnup. 8) Tensile testing: To check the mechanical properties. So far, non-destructive and destructive post-irradiation examinations have been performed on a significant number of CANDU fuel rods (about 100) manufactured by INR and irradiated to different power histories in the INR 14 MW(th) TRIGA reactor. These examinations have been performed as part of the Romanian research programme for the manufacturing, development and safety of the CANDU fuel. The paper describes the PIE techniques and some results. (Author)

  15. Emerging optical nanoscopy techniques

    Directory of Open Access Journals (Sweden)

    Montgomery PC

    2015-09-01

    Full Text Available Paul C Montgomery, Audrey Leong-Hoi Laboratoire des Sciences de l'Ingénieur, de l'Informatique et de l'Imagerie (ICube, Unistra-CNRS, Strasbourg, France Abstract: To face the challenges of modern health care, new imaging techniques with subcellular resolution or detection over wide fields are required. Far field optical nanoscopy presents many new solutions, providing high resolution or detection at high speed. We present a new classification scheme to help appreciate the growing number of optical nanoscopy techniques. We underline an important distinction between superresolution techniques that provide improved resolving power and nanodetection techniques for characterizing unresolved nanostructures. Some of the emerging techniques within these two categories are highlighted with applications in biophysics and medicine. Recent techniques employing wider angle imaging by digital holography and scattering lens microscopy allow superresolution to be achieved for subcellular and even in vivo, imaging without labeling. Nanodetection techniques are divided into four subcategories using contrast, phase, deconvolution, and nanomarkers. Contrast enhancement is illustrated by means of a polarized light-based technique and with strobed phase-contrast microscopy to reveal nanostructures. Very high sensitivity phase measurement using interference microscopy is shown to provide nanometric surface roughness measurement or to reveal internal nanometric structures. Finally, the use of nanomarkers is illustrated with stochastic fluorescence microscopy for mapping intracellular structures. We also present some of the future perspectives of optical nanoscopy. Keywords: microscopy, imaging, superresolution, nanodetection, biophysics, medical imaging

  16. Analog signal isolation techniques

    Energy Technology Data Exchange (ETDEWEB)

    Beadle, E.R.

    1992-12-31

    This paper discusses several techniques for isolating analog signals in an accelerator environment. The techniques presented here encompass isolation amplifiers, voltage-to-frequency converters (VIFCs), transformers, optocouplers, discrete fiber optics, and commercial fiber optic links. Included within the presentation of each method are the design issues that must be considered when selecting the isolation method for a specific application.

  17. Analog signal isolation techniques

    Energy Technology Data Exchange (ETDEWEB)

    Beadle, E.R.

    1992-01-01

    This paper discusses several techniques for isolating analog signals in an accelerator environment. The techniques presented here encompass isolation amplifiers, voltage-to-frequency converters (VIFCs), transformers, optocouplers, discrete fiber optics, and commercial fiber optic links. Included within the presentation of each method are the design issues that must be considered when selecting the isolation method for a specific application.

  18. Techniques of Wastewater Treatment

    Indian Academy of Sciences (India)

    In the first part of this article, we have learned about the need and importance of wastewater treatment and conven- tional methods of treatment. Currently the need is to develop low power consuming and yet effective techniques to handle complex wastes. As a result, new and advanced techniques are being studied and in ...

  19. A Technique: Exposure Therapy

    Directory of Open Access Journals (Sweden)

    Serkan AKKOYUNLU

    2013-08-01

    Conclusion: Exposure with response prevention is a basic and effective technique. Every cognitive behavior therapist must be able to implement this technique and be cognizant of pearls of this procedure. (Journal of Cognitive Behavioral Psychotherapy and Research 2013, 2: 121-128 [JCBPR 2013; 2(2.000: 121-128

  20. Point of Technique

    African Journals Online (AJOL)

    .

    Minimally invasive techniques are becoming popular choice for the recent times. These techniques are lowering the cost ... Through a skin incision which extends 2 cm medially from the left anterior-superior iliac Spine ... very invasive surgical procedure , less invasive procedures are becoming the first treatment options and ...

  1. Contamination Control Techniques

    Energy Technology Data Exchange (ETDEWEB)

    EBY, J.L.

    2000-05-16

    Welcome to a workshop on contamination Control techniques. This work shop is designed for about two hours. Attendee participation is encouraged during the workshop. We will address different topics within contamination control techniques; present processes, products and equipment used here at Hanford and then open the floor to you, the attendees for your input on the topics.

  2. Emerging optical nanoscopy techniques

    Science.gov (United States)

    Montgomery, Paul C; Leong-Hoi, Audrey

    2015-01-01

    To face the challenges of modern health care, new imaging techniques with subcellular resolution or detection over wide fields are required. Far field optical nanoscopy presents many new solutions, providing high resolution or detection at high speed. We present a new classification scheme to help appreciate the growing number of optical nanoscopy techniques. We underline an important distinction between superresolution techniques that provide improved resolving power and nanodetection techniques for characterizing unresolved nanostructures. Some of the emerging techniques within these two categories are highlighted with applications in biophysics and medicine. Recent techniques employing wider angle imaging by digital holography and scattering lens microscopy allow superresolution to be achieved for subcellular and even in vivo, imaging without labeling. Nanodetection techniques are divided into four subcategories using contrast, phase, deconvolution, and nanomarkers. Contrast enhancement is illustrated by means of a polarized light-based technique and with strobed phase-contrast microscopy to reveal nanostructures. Very high sensitivity phase measurement using interference microscopy is shown to provide nanometric surface roughness measurement or to reveal internal nanometric structures. Finally, the use of nanomarkers is illustrated with stochastic fluorescence microscopy for mapping intracellular structures. We also present some of the future perspectives of optical nanoscopy. PMID:26491270

  3. Microscopic techniques in biotechnology

    National Research Council Canada - National Science Library

    Hoppert, M

    2003-01-01

    ... techniques. Over the past 50 years, electron microscopy has opened new pathways for biologists to understand structure-function interrelations at the subcellular level. New lightbased optical techniques involving the detection of fluorescent molecules have introduced a new dimension of imaging into light microscopy, enabling cellular events to be studied in vivo d...

  4. Study of the mechanical properties of CeO{sub 2} layers with the nanoindentation technique

    Energy Technology Data Exchange (ETDEWEB)

    Roa, J.J., E-mail: joanjosep_roa@ub.ed [Centro DIOPMA, Departamento de Ciencia de los Materiales e Ingenieria Metalurgica, Facultad de Quimica, Universidad de Barcelona, C/Marti i Franques, 1, 08028, Barcelona (Spain); Gilioli, E.; Bissoli, F.; Pattini, F.; Rampino, S. [IMEM-CNR, Area delle Scienze 37/A, 43010 Fontanini-Parma (Italy); Capdevila, X.G.; Segarra, M. [Centro DIOPMA, Departamento de Ciencia de los Materiales e Ingenieria Metalurgica, Facultad de Quimica, Universidad de Barcelona, C/Marti i Franques, 1, 08028, Barcelona (Spain)

    2009-11-02

    The mechanical properties of CeO{sub 2} layers that are undoped or doped with other elements (e.g. Zr and Ta) are a topic of special interest specially in the manufacturing of superconductor buffer layers by pulsed electron deposition. Nowadays, the trend is to produce small devices (i.e. coated conductors), and the correct mechanical characterization is critical. In this sense, nanoindentation is a powerful technique widely employed to determine the mechanical properties of small volumes. In this study, the nanoindentation technique allow us determine the hardness (H) and Young's modulus (E) by sharp indentation of different buffer layers to explore the deposition process of CeO{sub 2} that is undoped or doped with Zr and Ta, and deposited on Ni-5%W at room temperature. This study was carried out on various samples at different ranges of applied loads (from 0.5 to 500 mN). Scanning electron microscopy images show no cracking for CeO{sub 2} doped with Zr, as the doping agent increases the toughness fracture of the CeO{sub 2} layer. This system, presents better mechanical stability than the other studied systems. Thus, the H for Zr-CeO{sub 2} is around 2.75 . 10{sup 6} Pa, and the elastic modulus calculated using the Bec et al. and Rar et al. models equals 249 . 10{sup 6} Pa and 235 . 10{sup 6} Pa respectively.

  5. A Method to Compare the Thermal Shock Resistances and the Severity of Quenching Conditions of Brittle Solids

    Science.gov (United States)

    Osterstock, F.; Legendre, B.

    1997-03-01

    The thermal shock behavior and resistance of brittle materials are mostly investigated through the determination of a critical quenching temperature difference, Δ T_c. This technique, however, needs a large number of, almost, identical samples and is thus poorly adapted to products being in the stage of research and development. In order to overcome this difficulty, the indentation technique has been used in this work. The residual contact stresses, created during indentation, permit a stage of stable extension of the indentation cracks under the action of further stressing. The relative increase of radial crack length as a function of Vickers indentation load, c/c_0 vs. P, is taken as a criterion, or indicator, of relative thermal shock resistance, or of the severities of quenching conditions. This is validated, first in quenching materials whose empirical ranking is well established, and second in varying parameters of the Biot number. Finally, are two batches of a functional ceramic compared. The proposed criterion reflects the competition between the toughness of the quenched material, as an intrinsic property, and the thermal transient stresses, as a consequence of the physical properties of both the quenched sample and the quenching medium. Possibilities for extending the developed approach towards a more accurate description of quenching phenomena and stress states such as to refine theoretical models are discussed. La détermination d'une différence de température critique, Δ T_c, est la technique la plus souvent utilisée dans l'étude de la résistance et du comportement au choc thermique des matériaux fragiles. Elle nécessite cependant un grand nombre d'échantillons, presque identiques et est donc peu adaptée aux produits dans le stade de recherche et développement. Afin de lever cet obstacle, la méthode de l'indentation de dureté est utilisée dans ce travail. L'indentation crée des contraintes résiduelles de contact qui permettent une

  6. Fiber laser welding of dual-phase galvanized sheet steel (DP590): traditional analysis and new quality assessment techniques

    Science.gov (United States)

    Miller, Stephanie; Pfeif, Erik; Kazakov, Andrei; Baumann, Esther; Dowell, Marla

    2016-03-01

    Laser welding has many advantages over traditional joining methods, yet remains underutilized. NIST has undertaken an ambitious initiative to improve predictions of weldability, reliability, and performance of laser welds. This study investigates butt welding of galvanized and ungalvanized dual-phase automotive sheet steels (DP 590) using a 10 kW commercial fiber laser system. Parameter development work, hardness profiles, microstructural characterization, and optical profilometry results are presented. Sound welding was accomplished in a laser power range of 2.0 kW to 4.5 kW and travel speed of 2000 mm/min to 5000 mm/min. Vickers hardness ranged from approximately 2 GPa to 4 GPa across the welds, with limited evidence of heat affected zone softening. Decreased hardness across the heat affected zone directly correlated to the appearance of ferrite. A technique was developed to non-destructively evaluate weld quality based on geometrical criteria. Weld face profilometry data were compared between light optical, metallographic sample, and frequency-modulated continuous-wave laser detection and ranging (FMCW LADAR) methods.

  7. Spectrometric techniques 4

    CERN Document Server

    Vanasse, George A

    2013-01-01

    Spectrometric Techniques, Volume IV discusses three widely diversified areas of spectrometric techniques. The book focuses on three spectrometric methods. Chapter 1 discusses the phenomenology and applications of Coherent Anti-Stokes Raman Spectroscopy (CARS), the most commonly used optical technique that exploit the Raman effect. The second chapter is concerned with diffraction gratings and mountings for the Vacuum Ultraviolet Spectral Region. Chapter 3 accounts the uses of mass spectrometry, detectors, types of spectrometers, and ion sources. Physicists and chemists will find the book a go

  8. Computer techniques for electromagnetics

    CERN Document Server

    Mittra, R

    1973-01-01

    Computer Techniques for Electromagnetics discusses the ways in which computer techniques solve practical problems in electromagnetics. It discusses the impact of the emergence of high-speed computers in the study of electromagnetics. This text provides a brief background on the approaches used by mathematical analysts in solving integral equations. It also demonstrates how to use computer techniques in computing current distribution, radar scattering, and waveguide discontinuities, and inverse scattering. This book will be useful for students looking for a comprehensive text on computer techni

  9. Separation techniques: Chromatography

    Science.gov (United States)

    Coskun, Ozlem

    2016-01-01

    Chromatography is an important biophysical technique that enables the separation, identification, and purification of the components of a mixture for qualitative and quantitative analysis. Proteins can be purified based on characteristics such as size and shape, total charge, hydrophobic groups present on the surface, and binding capacity with the stationary phase. Four separation techniques based on molecular characteristics and interaction type use mechanisms of ion exchange, surface adsorption, partition, and size exclusion. Other chromatography techniques are based on the stationary bed, including column, thin layer, and paper chromatography. Column chromatography is one of the most common methods of protein purification. PMID:28058406

  10. TECHNIQUE IN TEACHING LITERATURE

    Directory of Open Access Journals (Sweden)

    Jaftiyatur Rohaniyah

    2012-05-01

    Full Text Available This article tries to explore a particular technique in literature classroom. Literature is a content subject and compulsory subject, such as: poetry, prose, drama, etc. which give for the college students who take course in English language education. The paper focuses on using small group discussion technique included pre-discussion activities, whilst-discussion activities, and postdiscussion activities and how to implement them in teaching English poetry for the EFL/ESL students of English language education program. This technique is intended to help students in improving their poetry comprehension and motivating them to learn literary subject especially poetry.

  11. Spectrometric techniques 2

    CERN Document Server

    Vanasse, George A

    2013-01-01

    Spectrometric Techniques, Volume II provides information pertinent to vacuum ultraviolet techniques to complete the demonstration of the diversity of methods available to the spectroscopist interested in the ultraviolet visible and infrared spectral regions. This book discusses the specific aspects of the technique of Fourier transform spectroscopy.Organized into five chapters, this volume begins with an overview of the large number of systematic effects in the recording of an interferogram. This text then examines the design approach for a Fourier transform spectrometer with focus on optics.

  12. Electrical termination techniques

    Science.gov (United States)

    Oakey, W. E.; Schleicher, R. R.

    1976-01-01

    A technical review of high reliability electrical terminations for electronic equipment was made. Seven techniques were selected from this review for further investigation, experimental work, and preliminary testing. From the preliminary test results, four techniques were selected for final testing and evaluation. These four were: (1) induction soldering, (2) wire wrap, (3) percussive arc welding, and (4) resistance welding. Of these four, induction soldering was selected as the best technique in terms of minimizing operator errors, controlling temperature and time, minimizing joint contamination, and ultimately producing a reliable, uniform, and reusable electrical termination.

  13. Spectrometric techniques 3

    CERN Document Server

    Vanasse, George A

    2013-01-01

    Spectrometric Techniques, Volume III presents the applications of spectrometric techniques to atmospheric and space studies. This book reviews the spectral data processing and analysis techniques that are of broad applicability.Organized into five chapters, this volume begins with an overview of the instrumentation used for obtaining field data. This text then reviews the contribution that space-borne spectroscopy in the thermal IR has made to the understanding of the planets. Other chapters consider the instruments that have recorded the planetary emission spectra. This book discusses as well

  14. A new technique for determining orientation and motion of a 2-D, non-planar magnetopause

    Directory of Open Access Journals (Sweden)

    A. Blagau

    2010-03-01

    Full Text Available For a four-point mission like Cluster, the differences in position and time when the satellites detect the magnetopause or any other discontinuity, can be used to infer the discontinuity local orientation, thickness and motion. This timing technique, commonly assuming a planar geometry, offers an independent check for various single-spacecraft techniques. In the present paper we propose an extension of the timing method, capable of determining in a self-consistent way the macroscopic parameters of a two-dimensional, non-planar discontinuity. Such a configuration can be produced by a local bulge or indentation in the magnetopause, or by a large amplitude wave traveling on this surface, and is recognized in Cluster data when the single spacecraft techniques provide different individual normals contained roughly in the same plane. The model we adopted for the magnetopause assumes a layer of constant thickness of either cylindrical or parabolic shape, which has one or two degrees of freedom for the motion in the plane of the individual normals. The method was further improved by incorporating in a self-consistent way the requirement of minimum magnetic field variance along the magnetopause normal. An additional assumption, required in a previously proposed non-planar technique, i.e. that the non-planarity has negligible effects on the minimum variance analysis, is thus avoided. We applied the method to a magnetopause transition for which the various planar techniques provided inconsistent results. By contrast, the solutions obtained from the different implementations of the new 2-D method were consistent and stable, indicating a convex shape for the magnetopause. These solutions perform better than the planar solutions from the normal magnetic field variance perspective. The magnetopause dynamics and the presence of a non-zero normal magnetic field component in the analyzed event are discussed.

  15. Proton exchange membrane fuel cell systems engineering at Vickers Shipbuilding and Engineering Limited (VSEL)

    Science.gov (United States)

    Seymour, C. M.

    1992-01-01

    A project, jointly funded by VSEL and CJB Developments Limited, is aimed at the development of complete power generation systems based on PEM fuel cell technology. Potential markets for such systems are seen as being very broadly based, ranging from military land and marine systems through to commercial on-site power generation and transport. From the outset the project was applications driven, the intent being to identify market requirements, in terms of system specifications and to use these to produce development targets. The two companies have based their work on the Ballard PEM stack and have focused their efforts on the development of supporting systems. This benefits all three companies as it allows Ballard to obtain applications information on which to base future research and VSEL/CJBD are able to capitalise on the advanced development of the Ballard stack. Current work is focused on the production of a 20 kW, methanol fuelled, power generation system demonstrator, although work is also in hand to address a wider range of fuels including natural gas. The demonstrator, when complete, will be used to indicate the potential benefits of such systems and to act as a design aid for the applications phase of the project. Preliminary work on this next phase is already in hand, with studies to assess both systems and fuel cell stack design requirements for specific applications and to generate concept designs. Work to date has concentrated on the development of a methanol reformer, suitable for integration into a fuel cell system and on extensive testing and evaluation of the Ballard fuel cell stacks. This testing has covered a wide range of operating parameters, including different fuel and oxidant combinations. The effect of contaminants on the performance and life of the fuel cells is also under evaluation. PEM fuel cells still require a great deal of further development if they are to gain widespread commercial acceptance. A recent study conducted by VSEL in conjunction with the UK Department of Energy has addressed the fuel cell cost and performance requirements in order to both focus future research and to aid understanding of the time-scale to reach full commercialisation.

  16. Influence of polymerization time and depth of cure of resin composites determined by Vickers hardness

    Directory of Open Access Journals (Sweden)

    Marco Lombardini

    2012-01-01

    Conclusion: Among the materials tested, the nanofilled and the nanohybrid resin composites were rather insensible to thickness variations. Miicrohybrid composites, instead, had features different from one another.

  17. Clinical techniques of invertebrates.

    Science.gov (United States)

    Braun, Matthew E; Heatley, J Jill; Chitty, John

    2006-05-01

    This article highlights techniques and equipment needed to successfully restrain, diagnose, and treat gastropods (including snails and slugs) and arthropods (including spiders, scorpions, honey-bees, cockroaches, silkworms, phasmids, centipedes, and millipedes). A review of current clinical techniques for invertebrates kept as pets and those kept for agricultural use is provided. The specific techniques of restraint, assessment of hydration, fluid therapy, diagnostic sampling, imaging, exoskeleton repair, ectoparasite control and removal, euthanasia, and postmortem examination are reviewed for use in the invertebrate patient. The authors intend this article to stimulate further research and reporting on appropriate and humane techniques for use in these species and to increase the ability of the veterinary practitioner to successfully attend to these animals.

  18. Airway Clearance Techniques (ACTs)

    Medline Plus

    Full Text Available ... CYSTIC FIBROSIS Learn about cystic fibrosis, a genetic lung disorder that affects the pancreas and other organs, ... Clearance Techniques (ACTs) Autogenic Drainage (AD) Basics of Lung Care Chest Physical Therapy Coughing and Huffing High- ...

  19. Airway Clearance Techniques (ACTs)

    Medline Plus

    Full Text Available ... a Family Parenting as an Adult With CF Treatments & Therapies People with cystic fibrosis are living longer ... to specialized CF care and a range of treatment options. Airway Clearance Active Cycle of Breathing Technique ...

  20. Airway Clearance Techniques (ACTs)

    Medline Plus

    Full Text Available ... Team Your cystic fibrosis care team includes a group of CF health care professionals who partner with ... Airway Clearance Airway Clearance Techniques (ACTs) There are different ways to clear your airways. Most are easy ...

  1. Airway Clearance Techniques (ACTs)

    Medline Plus

    Full Text Available ... Treatments and Therapies Airway Clearance Airway Clearance Techniques (ACTs) There are different ways to clear your airways. ... or caregiver. Older kids and adults can choose ACTs that they can do on their own. Share ...

  2. Airway Clearance Techniques (ACTs)

    Medline Plus

    Full Text Available ... a Family Parenting as an Adult With CF Treatments & Therapies People with cystic fibrosis are living longer and ... to specialized CF care and a range of treatment options. Airway Clearance Active Cycle of Breathing Technique ( ...

  3. Airway Clearance Techniques (ACTs)

    Medline Plus

    Full Text Available ... Twitter YouTube Instagram Email DONATE Breadcrumb Navigation Home Life With CF Treatments and Therapies Airway Clearance Airway Clearance Techniques (ACTs) There are different ways to clear your airways. Most are easy to ...

  4. RFCM Techniques Chamber Facility

    Data.gov (United States)

    Federal Laboratory Consortium — FUNCTION: Provides the capability to develop radio-frequency countermeasure (RFCM) techniques in a controlled environment from 2.0 to 40.0 GHz. The configuration of...

  5. Microwave Breast Imaging Techniques

    DEFF Research Database (Denmark)

    Zhurbenko, Vitaliy; Rubæk, Tonny

    2010-01-01

    This paper outlines the applicability of microwave radiation for breast cancer detection. Microwave imaging systems are categorized based on their hardware architecture. The advantages and disadvantages of various imaging techniques are discussed. The fundamental tradeoffs are indicated between...

  6. Airway Clearance Techniques (ACTs)

    Medline Plus

    Full Text Available ... Techniques Autogenic Drainage Basics of Lung Care Chest Physical Therapy Coughing and Huffing High-Frequency Chest Wall ... Clinical Care Guidelines Chronic Medications to Maintain Lung Health Clinical Care Guidelines Lung Transplants Clinical Care Guidelines ...

  7. Plant tissue culture techniques

    Directory of Open Access Journals (Sweden)

    Rolf Dieter Illg

    1991-01-01

    Full Text Available Plant cell and tissue culture in a simple fashion refers to techniques which utilize either single plant cells, groups of unorganized cells (callus or organized tissues or organs put in culture, under controlled sterile conditions.

  8. The MST Radar Technique

    Science.gov (United States)

    Balsley, B. B.

    1985-01-01

    The past ten year have witnessed the development of a new radar technique to examine the structure and dynamics of the atmosphere between roughly 1 to 100 km on a continuous basis. The technique is known as the MST (for Mesosphere-Stratosphere-Troposphere) technique and is usable in all weather conditions, being unaffected by precipitation or cloud cover. MST radars make use of scattering from small scale structure in the atmospheric refractive index, with scales of the order of one-half the radar wavelength. Pertinent scale sizes for middle atmospheric studies typically range between a fraction of a meter and a few meters. The structure itself arises primarily from atmospheric turbulence. The technique is briefly described along with the meteorological parameters it measures.

  9. Airway Clearance Techniques (ACTs)

    Medline Plus

    Full Text Available ... Make a Charitable Gift Our Corporate Supporters Workplace Engagement DONATE YOUR PROPERTY eCards for a Cure About ... airway walls. See how different airway clearance techniques work to help you clear the thick, sticky mucus ...

  10. Efficient Vocabulary Testing Techniques

    Directory of Open Access Journals (Sweden)

    L. V. Mykhailiuk

    2016-12-01

    Full Text Available The article deals with the problem of teaching vocabulary. Different aspects of vocabulary (pronunciation, spelling, grammar, collocation, meaning, word formation are considered alongside with efficient vocabulary testing techniques.

  11. Assisted reproductive techniques.

    Science.gov (United States)

    Huang, Jack Yu Jen; Rosenwaks, Zev

    2014-01-01

    Assisted reproductive technologies (ART) encompass fertility treatments, which involve manipulations of both oocyte and sperm in vitro. This chapter provides a brief overview of ART, including indications for treatment, ovarian reserve testing, selection of controlled ovarian hyperstimulation (COH) protocols, laboratory techniques of ART including in vitro fertilization (IVF), and intracytoplasmic sperm injection (ICSI), embryo transfer techniques, and luteal phase support. This chapter also discusses potential complications of ART, namely ovarian hyperstimulation syndrome (OHSS) and multiple gestations, and the perinatal outcomes of ART.

  12. TECHNIQUE OF JEJUNOSTOMY

    OpenAIRE

    E. Tarcoveanu

    2005-01-01

    Feeding difficulties is an important problem of some patients (postoperative feeding in major interventions, acute pancreatitis etc.). Many of these patients are managed by jejunostomy. This paper presents the surgical technique for temporary or permanent jejunostomy by laparoscopic and open approach. Standard technique is Witzel jejunostomy but in some cases it is indicated other types of interventions: Stamm, Liffmann, Albert or Roux jejunostomy. It is also presented postoperative complic...

  13. Optimization techniques in statistics

    CERN Document Server

    Rustagi, Jagdish S

    1994-01-01

    Statistics help guide us to optimal decisions under uncertainty. A large variety of statistical problems are essentially solutions to optimization problems. The mathematical techniques of optimization are fundamentalto statistical theory and practice. In this book, Jagdish Rustagi provides full-spectrum coverage of these methods, ranging from classical optimization and Lagrange multipliers, to numerical techniques using gradients or direct search, to linear, nonlinear, and dynamic programming using the Kuhn-Tucker conditions or the Pontryagin maximal principle. Variational methods and optimiza

  14. Scheduling Cranes at an Indented Berth

    NARCIS (Netherlands)

    Beens, Marie-Anne; Ursavas, Evrim

    2016-01-01

    Container terminals are facing great challenges in order to meet the shipping industry’s requirements. An important fact within the industry is the increasing vessel sizes. Actually, within the last decade the ship size in the Asia-Europe trade has effectively doubled. However, port productivity has

  15. The Mechanics of Axisymmetric Indentation Revisited

    Science.gov (United States)

    2013-07-01

    2nd ed.; Cambridge University Press: London, 1966. 23. Hankel, H. Bestimmte integrale mit cylinderfunctionen. Math. Ann. 1875, 8, 453–470. 24...Gegenbauer, L. B. Über einige bestimmte Integrale . Sitz. Math. Natur. Klasse Akad. Wiss. Wien 1875, 70, 433–443. 25. Erdélyi, A. Tables of Integral Transforms

  16. Analysis of a weld of an hydrogen tank under pressure: contribution of the nano-indentation for the characterization; Analyse d'une soudure d'un reservoir d'hydrogene sous pression: apport de la nanoindentation pour la caracterisation

    Energy Technology Data Exchange (ETDEWEB)

    Russo, C.; Delobelle, P.; Perreux, D. [Laboratoire de Mecanique Appliquee R. Chaleat (LMARC), Institut FEMTO-ST, UFC and CNRS, 25 - Besancon (France); Russo, C.; Munier, E. [CEA Valduc, 21 - Is-sur-Tille (France); Decamps, B. [Institut de Chimie et des Materiaux Paris-Est vient, CNRS, CMTR-ICMPE, 94 - Thiais (France)

    2007-07-01

    This work deals with the size of an hydrogen spherical tank under pressure, composed of two half shell in aluminium alloy AZ5G machined in a forged bar and welded by electrons beam by a circumference. In this work, it is shown what the nano-indentation test can bring here. The influence of the tempering heat treatment after welding, the grains diameter and the loss in alloy elements (Zn and Mg) on the local mechanical properties of the weld bead has been revealed. In the same way, a hardening of the alloy due to the hydrogen penetration and leading to an increase of the dislocations density is observed. (O.M.)

  17. Review on different experimental techniques developed for recording force-deformation behaviour of soft tissues; with a view to surgery simulation applications.

    Science.gov (United States)

    Afshari, Elnaz; Rostami, Mostafa; Farahmand, Farzam

    2017-05-01

    Different experimental techniques which have been developed to obtain data related to force-deformation behaviour of soft tissues play an important role in realistically simulating surgery processes as well as medical diagnoses and minimally invasive procedures. Indeed, an adequate quantitative description of soft-tissue-mechanical-behaviour requires high-quality experimental data to be obtained and analysed. In this review article we will first scan the motivations and basic technical issues on surgery simulation. Then, we will concentrate on different experimental techniques developed for recording force-deformation (stress-strain) behaviour of soft tissues with focussing on the in-vivo experimental setups. We will thoroughly review the available techniques by classifying them to four groups; elastography, indentation, aspiration and grasping techniques. The evolutions, advantages and limitations of each technique will be presented by a historical review. At the end, a discussion is given with the aim of summarising the proposed points and predicting the future of techniques utilised in extracting data related to force-deformation behaviour.

  18. Laser prostate enucleation techniques.

    Science.gov (United States)

    Lerner, Lori B; Rajender, Archana

    2015-10-01

    Laser treatment of benign prostatic hyperplasia (BPH) through enucleation techniques has become increasingly more utilized in the field of urology. Laser enucleation of the prostate (LEP) is a transurethral procedure that employs several different types of lasers to dissect the adenoma from the surgical capsule in a retrograde fashion. We review basic laser physics and current laser prostate enucleation techniques. Holmium-LEP (HoLEP), Thulium-LEP (ThuLEP), Greenlight-LEP (GreenLEP) and Diode-LEP (DiLEP) applications are discussed. We summarize the current literature with respect to functional outcomes and complications. Although each laser device used for prostate enucleation has the same goal of removal of the adenoma from the surgical capsule, each has unique characteristics (i.e. wavelength, absorption rates) that must be understood by the practicing surgeon. Mastery of one LEP technique does not necessarily translate into facile use of an alternative enucleation energy source and/or approach. The various LEP techniques have demonstrated similar, if not superior, postoperative results to transurethral resection of the prostate (TURP), the current gold standard in the treatment of BPH. This article outlines the current LEP techniques and should serve as a quick reference for the practicing urologist.

  19. Determination of intrinsic polarization for K{sub 2}ZnCl{sub 4} single crystal grown by Czochralski technique for ferroelectric applications

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Sonu [Crystal Lab, Department of Physics & Astrophysics, University of Delhi, Delhi-7 (India); Ray, Geeta [Crystal Lab, Department of Physics & Astrophysics, University of Delhi, Delhi-7 (India); Physics Department, Miranda House, University of Delhi, Delhi-7 (India); Sinha, Nidhi [Crystal Lab, Department of Physics & Astrophysics, University of Delhi, Delhi-7 (India); Department of Electronics, SGTB Khalsa College, University of Delhi, Delhi-7 (India); Kumar, Binay, E-mail: b3kumar69@yahoo.co.in [Crystal Lab, Department of Physics & Astrophysics, University of Delhi, Delhi-7 (India)

    2017-04-01

    Large sized single crystal of K{sub 2}ZnCl{sub 4} (KZC) was grown by Czochralski (Cz) technique. Structural parameters of KZC were determined by Single crystal X-ray diffraction (SCXRD). From DSC analysis and temperature dependent dielectric measurement, KZC crystal was found to show Curie phase transition at 151 °C. TG/DTA confirmed the melting point that was found to be 443 °C. The value of piezoelectric charge coefficient (d{sub 33}) for KZC crystal was found to be 32 pC/N demonstrating their applicability in transducers and piezoelectric devices. Ferroelectric P-E loop for the grown crystal was traced at room temperature and the intrinsic polarization obtained by PUND measurement was found to be 0.1398 μC/cm{sup 2} indicating its applicability in switching devices. The energy band gap for KZC single crystal was found to be 6.13 eV. Vickers micro-hardness test revealed soft nature of KZC single crystals. - Highlights: • Large sized K{sub 2}ZnCl{sub 4} (KZC) single crystal was grown by Czochralski technique. • It possesses high Curie temperature as 151 °C. • d{sub 33} coefficient was found to be 32 pC/N. • Intrinsic polarization measured by PUND. • Its direct band gap energy was calculated to be 6.13 eV.

  20. Study on growth, structural, optical, thermal and mechanical properties of organic single crystal ethyl p-amino benzoate (EPAB) grown using vertical Bridgman technique

    Science.gov (United States)

    Muthuraja, A.; Kalainathan, S.

    2017-02-01

    Ethyl p-aminobenzoate (EPAB) single crystal was grown using vertical Bridgman technique (VBT). The crystal system of grown crystal was identified, and lattice parameters have been measured from the powder X-ray diffraction (PXRD). The optical transparency of EPAB single crystal was 55%, and the cut-off wavelength was found to be 337 nm. The thermal stability of EPAB single crystal was analyzed by thermogravimetric analysis. Etching studie were carried out for the grown crystal using different solvents, and etch pit density (EPD) was calculated and compared. Vickers microhardness (Hv) measurements revealed that EPAB belongs to the category of soft material. The dielectric studies reveal that the dielectric constant and dielectric loss of grown crystal decreases with increasing frequency for various temperatures. The third-order nonlinear optical property of EPAB was investigated and compared with other organic crystals. The evaluation of third-order optical properties such as nonlinear refractive index (n2), nonlinear absorption (β) and third-order nonlinear susceptibility (χ3) have found to be in the range of 10-11 m2/W, 10-4 m/W and 10-5 esu respectively. The Laser damage threshold energy of EPAB was measured using Nd: YAG laser. The blue emission of the grown crystal was identified by photoluminescence (PL) spectra measurements. The second harmonic generation (SHG) for the grown EPAB crystal was confirmed by Kurtz powder technique.

  1. Radiation techniques for acromegaly

    Directory of Open Access Journals (Sweden)

    Minniti Giuseppe

    2011-12-01

    Full Text Available Abstract Radiotherapy (RT remains an effective treatment in patients with acromegaly refractory to medical and/or surgical interventions, with durable tumor control and biochemical remission; however, there are still concerns about delayed biochemical effect and potential late toxicity of radiation treatment, especially high rates of hypopituitarism. Stereotactic radiotherapy has been developed as a more accurate technique of irradiation with more precise tumour localization and consequently a reduction in the volume of normal tissue, particularly the brain, irradiated to high radiation doses. Radiation can be delivered in a single fraction by stereotactic radiosurgery (SRS or as fractionated stereotactic radiotherapy (FSRT in which smaller doses are delivered over 5-6 weeks in 25-30 treatments. A review of the recent literature suggests that pituitary irradiation is an effective treatment for acromegaly. Stereotactic techniques for GH-secreting pituitary tumors are discussed with the aim to define the efficacy and potential adverse effects of each of these techniques.

  2. Telescopes and Techniques

    CERN Document Server

    Kitchin, C R

    2013-01-01

    Telescopes and Techniques has proved itself in its first two editions, having become probably one of the most widely used astronomy texts, both for amateur astronomers and astronomy and astrophysics undergraduates. Both earlier editions of the book were widely used for introductory practical astronomy courses in many universities. In this Third Edition the author guides the reader through the mathematics, physics and practical techniques needed to use today's telescopes (from the smaller models to the larger instruments installed in many colleges) and how to find objects in the sky. Most of the physics and engineering involved is described fully and requires little prior knowledge or experience. Both visual and electronic imaging techniques are covered, together with an introduction to how data (measurements) should be processed and analyzed. A simple introduction to radio telescopes is also included. Brief coverage of the more advanced topics of photometry and spectroscopy are included, but mainly to enable ...

  3. Neuronavigation. Principles. Surgical technique.

    Science.gov (United States)

    Ivanov, Marcel; Ciurea, Alexandru Vlad

    2009-01-01

    Neuronavigation and stereotaxy are techniques designed to help neurosurgeons precisely localize different intracerebral pathological processes by using a set of preoperative images (CT, MRI, fMRI, PET, SPECT etc.). The development of computer assisted surgery was possible only after a significant technological progress, especially in the area of informatics and imagistics. The main indications of neuronavigation are represented by the targeting of small and deep intracerebral lesions and choosing the best way to treat them, in order to preserve the neurological function. Stereotaxis also allows lesioning or stimulation of basal ganglia for the treatment of movement disorders. These techniques can bring an important amount of confort both to the patient and to the neurosurgeon. Neuronavigation was introduced in Romania around 2003, in four neurosurgical centers. We present our five-years experience in neuronavigation and describe the main principles and surgical techniques.

  4. Novel food processing techniques

    Directory of Open Access Journals (Sweden)

    Vesna Lelas

    2006-12-01

    Full Text Available Recently, a lot of investigations have been focused on development of the novel mild food processing techniques with the aim to obtain the high quality food products. It is presumed also that they could substitute some of the traditional processes in the food industry. The investigations are primarily directed to usage of high hydrostatic pressure, ultrasound, tribomechanical micronization, microwaves, pulsed electrical fields. The results of the scientific researches refer to the fact that application of some of these processes in particular food industry can result in lots of benefits. A significant energy savings, shortening of process duration, mild thermal conditions, food products with better sensory characteristics and with higher nutritional values can be achieved. As some of these techniques act also on the molecular level changing the conformation, structure and electrical potential of organic as well as inorganic materials, the improvement of some functional properties of these components may occur. Common characteristics of all of these techniques are treatment at ambient or insignificant higher temperatures and short time of processing (1 to 10 minutes. High hydrostatic pressure applied to various foodstuffs can destroy some microorganisms, successfully modify molecule conformation and consequently improve functional properties of foods. At the same time it acts positively on the food products intend for freezing. Tribomechanical treatment causes micronization of various solid materials that results in nanoparticles and changes in structure and electrical potential of molecules. Therefore, the significant improvement of some rheological and functional properties of materials occurred. Ultrasound treatment proved to be potentially very successful technique of food processing. It can be used as a pretreatment to drying (decreases drying time and improves functional properties of food, as extraction process of various components

  5. Millimicrosecond pulse techniques

    CERN Document Server

    Lewis, Ian A D

    1959-01-01

    Millimicrosecond Pulse Techniques, Second Edition focuses on millimicrosecond pulse techniques and the development of devices of large bandwidth, extending down to comparatively low frequencies (1 Mc/s). Emphasis is on basic circuit elements and pieces of equipment of universal application. Specific applications, mostly in the field of nuclear physics instrumentation, are considered. This book consists of eight chapters and opens with an introduction to some of the terminology employed by circuit engineers as well as theoretical concepts, including the laws of circuit analysis, Fourier analysi

  6. Dermal exposure assessment techniques.

    Science.gov (United States)

    Fenske, R A

    1993-12-01

    Exposure of the skin to chemical substances can contribute significantly to total dose in many workplace situations, and its relative importance will increase when airborne occupational exposure limits are reduced, unless steps to reduce skin exposure are undertaken simultaneously. Its assessment employs personal sampling techniques to measure skin loading rates, and combines these measurements with models of percutaneous absorption to estimate absorbed dose. Knowledge of dermal exposure pathways is in many cases fundamental to hazard evaluation and control. When the skin is the primary contributor to absorbed dose, dermal exposure measurements and biological monitoring play complementary roles in defining occupational exposures. Exposure normally occurs by one of three pathways: (i) immersion (direct contact with a liquid or solid chemical substance); (ii) deposition of aerosol or uptake of vapour through the skin; or (iii) surface contact (residue transfer from contaminated surfaces). Sampling methods fall into three categories: surrogate skin; chemical removal; and fluorescent tracers. Surface sampling represents a supplementary approach, providing an estimate of dermal exposure potential. Surrogate skin techniques involve placing a chemical collection medium on the skin. Whole-body garment samplers do not require assumptions relating to distribution, an inherent limitation of patch sampling. The validity of these techniques rests on the ability of the sampling medium to capture and retain chemicals in a manner similar to skin. Removal techniques include skin washing and wiping, but these measure only what can be removed from the skin, not exposure: laboratory removal efficiency studies are required for proper interpretation of data. Fluorescent tracer techniques exploit the visual properties of fluorescent compounds, and combined with video imaging make quantification of dermal exposure patterns possible, but the need to introduce a chemical substance (tracer

  7. Modern recording techniques

    CERN Document Server

    Huber, David Miles

    2013-01-01

    As the most popular and authoritative guide to recording Modern Recording Techniques provides everything you need to master the tools and day to day practice of music recording and production. From room acoustics and running a session to mic placement and designing a studio Modern Recording Techniques will give you a really good grounding in the theory and industry practice. Expanded to include the latest digital audio technology the 7th edition now includes sections on podcasting, new surround sound formats and HD and audio.If you are just starting out or looking for a step up

  8. Wireless communications algorithmic techniques

    CERN Document Server

    Vitetta, Giorgio; Colavolpe, Giulio; Pancaldi, Fabrizio; Martin, Philippa A

    2013-01-01

    This book introduces the theoretical elements at the basis of various classes of algorithms commonly employed in the physical layer (and, in part, in MAC layer) of wireless communications systems. It focuses on single user systems, so ignoring multiple access techniques. Moreover, emphasis is put on single-input single-output (SISO) systems, although some relevant topics about multiple-input multiple-output (MIMO) systems are also illustrated.Comprehensive wireless specific guide to algorithmic techniquesProvides a detailed analysis of channel equalization and channel coding for wi

  9. Craniospinal irradiation techniques

    Energy Technology Data Exchange (ETDEWEB)

    Scarlatescu, Ioana, E-mail: scarlatescuioana@gmail.com; Avram, Calin N. [Faculty of Physics, West University of Timisoara, Bd. V. Parvan 4, 300223 Timisoara (Romania); Virag, Vasile [County Hospital “Gavril Curteanu” - Oradea (Romania)

    2015-12-07

    In this paper we present one treatment plan for irradiation cases which involve a complex technique with multiple beams, using the 3D conformational technique. As the main purpose of radiotherapy is to administrate a precise dose into the tumor volume and protect as much as possible all the healthy tissues around it, for a case diagnosed with a primitive neuro ectoderm tumor, we have developed a new treatment plan, by controlling one of the two adjacent fields used at spinal field, in a way that avoids the fields superposition. Therefore, the risk of overdose is reduced by eliminating the field divergence.

  10. Simple Driving Techniques

    DEFF Research Database (Denmark)

    Rosendahl, Mads

    2002-01-01

    Driving was introduced as a program transformation technique by Valentin Turchin in some papers around 1980. It was intended for the programming language REFAL and used in metasystem transitions based on super compilation. In this paper we present one version of driving for a more conventional lisp......-like language. Our aim is to extract a simple notion of driving and show that even in this tamed form it has much of the power of more general notions of driving. Our driving technique may be used to simplify functional programs which use function composition and will often be able to remove intermediate data...

  11. Surface science techniques

    CERN Document Server

    Walls, JM

    2013-01-01

    This volume provides a comprehensive and up to the minute review of the techniques used to determine the nature and composition of surfaces. Originally published as a special issue of the Pergamon journal Vacuum, it comprises a carefully edited collection of chapters written by specialists in each of the techniques and includes coverage of the electron and ion spectroscopies, as well as the atom-imaging methods such as the atom probe field ion microscope and the scanning tunnelling microscope. Surface science is an important area of study since the outermost surface layers play a crucial role

  12. Radiographic constant exposure technique

    DEFF Research Database (Denmark)

    Domanus, Joseph Czeslaw

    1985-01-01

    The constant exposure technique has been applied to assess various industrial radiographic systems. Different X-ray films and radiographic papers of two producers were compared. Special attention was given to fast film and paper used with fluorometallic screens. Radiographic image quality was tes...... was tested by the use of ISO wire IQI's and ASTM penetrameters used on Al and Fe test plates. Relative speed and reduction of kilovoltage obtained with the constant exposure technique were calculated. The advantages of fast radiographic systems are pointed out...

  13. Advanced Techniques in Biophysics

    CERN Document Server

    Arrondo, José Luis R

    2006-01-01

    Technical advancements are basic elements in our life. In biophysical studies, new applications and improvements in well-established techniques are being implemented every day. This book deals with advancements produced not only from a technical point of view, but also from new approaches that are being taken in the study of biophysical samples, such as nanotechniques or single-cell measurements. This book constitutes a privileged observatory for reviewing novel applications of biophysical techniques that can help the reader enter an area where the technology is progressing quickly and where a comprehensive explanation is not always to be found.

  14. Alexander Technique and Dance Technique: Applications in the Studio

    Science.gov (United States)

    Nettl-Fiol, Rebecca

    2006-01-01

    Integrating principles from the Alexander Technique into a dance technique class can provide tools for facilitating a more coordinated use of the self. While the methodologies of Alexander Technique and dance technique may present differences, there are ways of applying the principles of Alexander within the context of a dance technique class that…

  15. Crystal growth, structural, low temperature thermoluminescence and mechanical properties of cubic fluoroperovskite single crystal (LiBaF3)

    Science.gov (United States)

    Daniel, D. Joseph; Ramasamy, P.; Ramaseshan, R.; Kim, H. J.; Kim, Sunghwan; Bhagavannarayana, G.; Cheon, Jong-Kyu

    2017-10-01

    Polycrystalline compounds of LiBaF3 were synthesized using conventional solid state reaction route and the phase purity was confirmed using powder X-ray diffraction technique. Using vertical Bridgman technique single crystal was grown from melt. Rocking curve measurements have been carried out to study the structural perfection of the grown crystal. The single peak of diffraction curve clearly reveals that the grown crystal was free from the structural grain boundaries. The low temperature thermoluminescence of the X-ray irradiated sample has been analyzed and found four distinguishable peaks having maximum temperatures at 18, 115, 133 and 216 K. Activation energy (E) and frequency factor (s) for the individual peaks have been studied using Peak shape method and the computerized curve fitting method combining with the Tmax- TStop procedure. Nanoindentation technique was employed to study the mechanical behaviour of the crystal. The indentation modulus and Vickers hardness of the grown crystal have values of 135.15 GPa and 680.81 respectively, under the maximum indentation load of 10 mN.

  16. Variational Monte Carlo Technique

    Indian Academy of Sciences (India)

    ias

    Major ad- vances of the MC techniques were made during World. War II by scientists such as John Von Neumann, En- rico Fermi, S M Ulam and Nicholas Metropolis working on the development of nuclear weapons in Los Alamos. National Laboratory, USA [10, 11]. 3. Monte Carlo Integration Using Importance. Sampling.

  17. Electronic waste recycling techniques

    CERN Document Server

    Bernardes, Andréa

    2015-01-01

    This book presents an overview of the characterization of electronic waste. In addition, processing techniques for the recovery of metals, polymers and ceramics are described. This book serves as a source of information and as an educational technical reference for practicing scientists and engineers, as well as for students.

  18. Techniques of Wastewater Treatment

    Indian Academy of Sciences (India)

    Techniques of Wastewater Treatment. 1. Introduction to Effluent Treatment and Industrial Methods. Amol A Kulkarni, Mugdha Deshpande and A B Pandit. Amol A Kulkarni is a PhD student from the Chemi- cal Engineering division in UDCT and is working on the characterization of non-linear dynamics in chemical reactors.

  19. Maintenance Resources Evaluation Technique.

    Science.gov (United States)

    1999-03-01

    Happ W. William. Gert: " Graphical Evaluation and Review Technique; Part 1. Fundamentals," The Journal of Industrial Engineering. Vol.: XVII No.5...1975. He received his commission in December 1979 upon graduation from Escuela de Aviation Militär. Then, he attended the Escuela de Ingenieria

  20. Classifying variability modeling techniques

    NARCIS (Netherlands)

    Sinnema, Marco; Deelstra, Sybren

    Variability modeling is important for managing variability in software product families, especially during product derivation. In the past few years, several variability modeling techniques have been developed, each using its own concepts to model the variability provided by a product family. The

  1. Airway Clearance Techniques (ACTs)

    Medline Plus

    Full Text Available ... toddlers will need help from a parent or caregiver. Older kids and adults can choose ACTs that they can do on their ... (clapping) or vibration to loosen mucus from airway walls. See how different airway clearance techniques work to help you clear the thick, sticky mucus ...

  2. 8. Algorithm Design Techniques

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 2; Issue 8. Algorithms - Algorithm Design Techniques. R K Shyamasundar. Series Article Volume 2 Issue 8 August 1997 pp 6-17. Fulltext. Click here to view fulltext PDF. Permanent link: http://www.ias.ac.in/article/fulltext/reso/002/08/0006-0017 ...

  3. 3. Techniques of Cartography

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 4; Issue 8. Mapmakers Techniques of Cartography. Harini Nagendra. Series Article Volume 4 Issue 8 August 1999 pp 8-15. Fulltext. Click here to view fulltext PDF. Permanent link: http://www.ias.ac.in/article/fulltext/reso/004/08/0008-0015 ...

  4. Assessing Classroom Assessment Techniques

    Science.gov (United States)

    Simpson-Beck, Victoria

    2011-01-01

    Classroom assessment techniques (CATs) are teaching strategies that provide formative assessments of student learning. It has been argued that the use of CATs enhances and improves student learning. Although the various types of CATs have been extensively documented and qualitatively studied, there appears to be little quantitative research…

  5. Multisensor Data Integration Techniques

    Science.gov (United States)

    Evans, D. L.; Blake, P. L.; Conel, J. E.; Lang, H. R.; Logan, T. L.; Mcguffie, B. A.; Paylor, E. D.; Singer, R. B.; Schenck, L. R.

    1985-01-01

    The availability of data from sensors operating in several different wavelength regions had led to the development of new techniques and strategies for both data management and image analysis. Work is ongoing to develop computer techniques for analysis of integrated data sets. These techniques include coregistration of multisensor images, rectification of radar images in areas of topographic relief to ensure pixel to pixel registration with planimetric data sets, calibration of data so that signatures can be applied to remote areas, normalization of data acquired with disparate sensors and determination of extended spectral signatures of surface units. In addition, software is being developed to analyze coregistrated digital terrain and image data so that automated stratigraphic and structural analyses can be performed. These software procedures include: strike and dip determination, terrain profile generation, stratigraphic column generation, stratigraphic thickness measurements, structural cross-section generation, and creation of 3-D block diagrams. These techniques were applied to coregistered LANDSAT 4 Thematic Mapper (TM), Thermal Infrared Multispectral Scanner (TIMS), and multipolarization synthetic aperture radar (SAR) data of the Wind River Basin in Wyoming.

  6. Airway Clearance Techniques (ACTs)

    Medline Plus

    Full Text Available ... NACFC Carolyn and C. Richard Mattingly Leadership in Mental Health Care Award Mary M. Kontos Award NACFC Reflections ... help your infant or child manage their lung health, watch parents of children with CF and a respiratory therapist talk about the different techniques they use for airway ... Autogenic Drainage Positive Expiratory Pressure High-Frequency Chest ...

  7. Nanotribological and nanomechanical characterization of human hair using a nanoscratch technique

    Energy Technology Data Exchange (ETDEWEB)

    Wei Guohua [Nanotribology Laboratory for Information Storage and MEMS/NEMS, Ohio State University, 650 Ackerman Road, Suite 255, Columbus, OH 43202 (United States); Bhushan, Bharat [Nanotribology Laboratory for Information Storage and MEMS/NEMS, Ohio State University, 650 Ackerman Road, Suite 255, Columbus, OH 43202 (United States)]. E-mail: bhushan.2@osu.edu

    2006-06-15

    Human hair ({approx}50-100 {mu}m in diameter) is a nanocomposite biological fiber with well-characterized microstructures, and is of great interest for both cosmetic science and materials science. Characterization of nanotribological and nanomechanical properties of human hair including the coefficient of friction and scratch resistance is essential to develop better shampoo and conditioner products and advance biological and cosmetic science. In this paper, the coefficient of friction and scratch resistance of Caucasian and Asian hair at virgin, chemo-mechanically damaged, and conditioner-treated conditions are measured using a nanoscratch technique with a Nano Indenter II system. The scratch tests were performed on both the single cuticle cell and multiple cuticle cells of each hair sample, and the scratch wear tracks were studied using scanning electron microscopy (SEM) after the scratch tests. The effect of soaking on the coefficient of friction, scratch resistance, hardness and Young's modulus of hair surface were also studied by performing experiments on hair samples which had been soaked in de-ionized water for 5 min. The nanotribological and nanomechanical properties of human hair as a function of hair structure (hair of different ethnicity), damage, treatment and soaking are discussed.

  8. Micro and nanohardness testing of laser welds

    Czech Academy of Sciences Publication Activity Database

    Šebestová, H.; Čtvrtlík, Radim; Chmelíčková, H.; Tomáštík, J.

    2014-01-01

    Roč. 15, č. 3 (2014), s. 247-253 ISSN 1454-9069 R&D Projects: GA TA ČR TA01010517 Institutional support: RVO:68378271 Keywords : Vickers microhardness * depth sensing indentation * laser welding Subject RIV: JP - Industrial Processing Impact factor: 1.658, year: 2014

  9. Scratch Hardness and Wear Performance of Laser-Melted Steels : Effects of Anisotropy

    NARCIS (Netherlands)

    Beurs, H. de; Minholts, G.; Hosson, J.Th.M. De

    Effects of the orientation of dendrites on the scratch hardness and wear performance of laser-melted steels have been investigated. Scratch experiments have been carried out with a Vickers indenter and wear experiments with a pin-on-disk tester. The deformed structure is investigated, using

  10. Mechanical characterization of microwave sintered zinc oxide

    Indian Academy of Sciences (India)

    Unknown

    II, Echo Ultrasound, USA). A 15 MHz transducer was used for this purpose. For each sintering condition, at least three to five samples were used to obtain the average data. The hardness data was obtained for the load range. (0⋅1–20 N) using a microhardness tester fitted with a. Vicker's square pyramidal indenter. Similarly ...

  11. Techniques to Bring Up Mucus

    Science.gov (United States)

    ... COPD: Lifestyle Management Techniques to Bring Up Mucus Techniques to Bring Up Mucus Make an Appointment Refer ... breathing may become difficult, and infection may occur. Techniques to remove mucus are often done after using ...

  12. Brain Vascular Imaging Techniques

    Directory of Open Access Journals (Sweden)

    Bàrbara Laviña

    2016-12-01

    Full Text Available Recent major improvements in a number of imaging techniques now allow for the study of the brain in ways that could not be considered previously. Researchers today have well-developed tools to specifically examine the dynamic nature of the blood vessels in the brain during development and adulthood; as well as to observe the vascular responses in disease situations in vivo. This review offers a concise summary and brief historical reference of different imaging techniques and how these tools can be applied to study the brain vasculature and the blood-brain barrier integrity in both healthy and disease states. Moreover, it offers an overview on available transgenic animal models to study vascular biology and a description of useful online brain atlases.

  13. Network acceleration techniques

    Science.gov (United States)

    Crowley, Patricia (Inventor); Awrach, James Michael (Inventor); Maccabe, Arthur Barney (Inventor)

    2012-01-01

    Splintered offloading techniques with receive batch processing are described for network acceleration. Such techniques offload specific functionality to a NIC while maintaining the bulk of the protocol processing in the host operating system ("OS"). The resulting protocol implementation allows the application to bypass the protocol processing of the received data. Such can be accomplished this by moving data from the NIC directly to the application through direct memory access ("DMA") and batch processing the receive headers in the host OS when the host OS is interrupted to perform other work. Batch processing receive headers allows the data path to be separated from the control path. Unlike operating system bypass, however, the operating system still fully manages the network resource and has relevant feedback about traffic and flows. Embodiments of the present disclosure can therefore address the challenges of networks with extreme bandwidth delay products (BWDP).

  14. Review of halftoning techniques

    Science.gov (United States)

    Ulichney, Robert A.

    1999-12-01

    Digital halftoning remains an active area of research with a plethora of new and enhanced methods. While several fine overviews exist, this purpose of this paper is to review retrospectively the basic classes of techniques. Halftoning algorithms are presented by the nature of the appearance of resulting patterns, including white noise, recursive tessellation, the classical screen, and blue noise. The metric of radially averaged power spectra is reviewed, and special attention is paid to frequency domain characteristics. The paper concludes with a look at the components that comprise a complete image rendering system. In particular when the number of output levels is not restricted to be a power of 2. A very efficient means of multilevel dithering is presented based on scaling order- dither arrays. The case of real-time video rendering is considered where the YUV-to-RGB conversion is incorporated in the dithering system. Example illustrations are included for each of the techniques described.

  15. Laser beam shaping techniques

    Energy Technology Data Exchange (ETDEWEB)

    DICKEY,FRED M.; WEICHMAN,LOUIS S.; SHAGAM,RICHARD N.

    2000-03-16

    Industrial, military, medical, and research and development applications of lasers frequently require a beam with a specified irradiance distribution in some plane. A common requirement is a laser profile that is uniform over some cross-section. Such applications include laser/material processing, laser material interaction studies, fiber injection systems, optical data image processing, lithography, medical applications, and military applications. Laser beam shaping techniques can be divided into three areas: apertured beams, field mappers, and multi-aperture beam integrators. An uncertainty relation exists for laser beam shaping that puts constraints on system design. In this paper the authors review the basics of laser beam shaping and present applications and limitations of various techniques.

  16. [Molecular techniques in mycology].

    Science.gov (United States)

    Rodríguez-Tudela, Juan Luis; Cuesta, Isabel; Gómez-López, Alicia; Alastruey-Izquierdo, Ana; Bernal-Martínez, Leticia; Cuenca-Estrella, Manuel

    2008-11-01

    An increasing number of molecular techniques for the diagnosis of fungal infections have been developed in the last few years, due to the growing prevalence of mycoses and the length of time required for diagnosis when classical microbiological methods are used. These methods are designed to resolve the following aspects of mycological diagnosis: a) Identification of fungi to species level by means of sequencing relevant taxonomic targets; b) early clinical diagnosis of invasive fungal infections; c) detection of molecular mechanisms of resistance to antifungal agents; and d) molecular typing of fungi. Currently, these methods are restricted to highly developed laboratories. However, some of these techniques will probably be available in daily clinical practice in the near future.

  17. Nozzle fabrication technique

    Science.gov (United States)

    Wells, Dennis L. (Inventor)

    1988-01-01

    This invention relates to techniques for fabricating hour glass throat or convergent divergent nozzle shapes, and more particularly to new and improved techniques for forming rocket nozzles from electrically conductive material and forming cooling channels in the wall thereof. The concept of positioning a block of electrically conductive material so that its axis is set at a predetermined skew angle with relation to a travelling electron discharge machine electrode and thereafter revolving the body about its own axis to generate a hyperbolic surface of revolution, either internal or external is novel. The method will generate a rocket nozzle which may be provided with cooling channels using the same control and positioning system. The configuration of the cooling channels so produced are unique and novel. Also the method is adaptable to nonmetallic material using analogous cutting tools, such as, water jet, laser, abrasive wire and hot wire.

  18. Signal integrity characterization techniques

    CERN Document Server

    Bogatin, Eric

    2009-01-01

    "Signal Integrity Characterization Techniques" addresses the gap between traditional digital and microwave curricula all while focusing on a practical and intuitive understanding of signal integrity effects within the data transmission channel. High-speed interconnects such as connectors, PCBs, cables, IC packages, and backplanes are critical elements of differential channels that must be designed using today's most powerful analysis and characterization tools.Both measurements and simulation must be done on the device under test, and both activities must yield data that correlates with each other. Most of this book focuses on real-world applications of signal integrity measurements - from backplane for design challenges to error correction techniques to jitter measurement technologies. The authors' approach wisely addresses some of these new high-speed technologies, and it also provides valuable insight into its future direction and will teach the reader valuable lessons on the industry.

  19. Landing techniques in volleyball.

    Science.gov (United States)

    Lobietti, Roberto; Coleman, Simon; Pizzichillo, Eduardo; Merni, Franco

    2010-11-01

    Knee injuries such as anterior cruciate ligament lesions and patellar tendonitis are very frequent in volleyball, and are often attributed to micro traumas that occur during the landing phase of airborne actions. The aim of the present study was to compare different jumping activities during official men's and women's volleyball games. Twelve top-level matches from the Italian men's and women's professional leagues were analysed. The jumps performed during the games were classified according to the landing technique used by the player (left or right foot or both feet together), court position, and ball trajectory. Chi-square analyses were performed to detect differences in landing techniques between the sexes, court positions, and trajectories when serving, attacking, blocking, and setting. Significant differences (P injuries.

  20. Whole cell entrapment techniques.

    Science.gov (United States)

    Trelles, Jorge A; Rivero, Cintia W

    2013-01-01

    Microbial whole cells are efficient, ecological, and low-cost catalysts that have been successfully applied in the pharmaceutical, environmental, and alimentary industries, among others. Microorganism immobilization is a good way to carry out the bioprocess under preparative conditions. The main advantages of this methodology lie in their high operational stability, easy upstream separation and bioprocess scale-up feasibility. Cell entrapment is the most widely used technique for whole cell immobilization. This technique-in which the cells are included within a rigid network-is porous enough to allow the diffusion of substrates and products, protects the selected microorganism from the reaction medium, and has high immobilization efficiency (100 % in most cases).

  1. Miniaturization Techniques for Accelerators

    Energy Technology Data Exchange (ETDEWEB)

    Spencer, James E.

    2003-05-27

    The possibility of laser driven accelerators [1] suggests the need for new structures based on micromachining and integrated circuit technology because of the comparable scales. Thus, we are exploring fully integrated structures including sources, optics (for both light and particle) and acceleration in a common format--an accelerator-on-chip (AOC). Tests suggest a number of preferred materials and techniques but no technical or fundamental roadblocks at scales of order 1 {micro}m or larger.

  2. Laparoscopic adrenalectomy: Surgical techniques

    Directory of Open Access Journals (Sweden)

    Matthew J Mellon

    2008-01-01

    Full Text Available Since its first description in 1992, laparoscopic adrenalectomy has become the gold standard for the surgical treatment of most adrenal conditions. The benefits of a minimally invasive approach to adrenal resection such as decreased hospital stay, shorter recovery time and improved patient satisfaction are widely accepted. However, as this procedure becomes more widespread, critical steps of the operation must be maintained to ensure expected outcomes and success. This article reviews the surgical techniques for the laparoscopic adrenalectomy.

  3. Streak camera techniques

    Energy Technology Data Exchange (ETDEWEB)

    Avara, R.

    1977-06-01

    An introduction to streak camera geometry, experimental techniques, and limitations are presented. Equations, graphs and charts are included to provide useful data for optimizing the associated optics to suit each experiment. A simulated analysis is performed on simultaneity and velocity measurements. An error analysis is also performed for these measurements utilizing the Monte Carlo method to simulate the distribution of uncertainties associated with simultaneity-time measurements.

  4. Emerging technology and techniques

    Directory of Open Access Journals (Sweden)

    Gopi Naveen Chander

    2015-01-01

    Full Text Available A technique of fabricating feldspathic porcelain pressable ingots was proposed. A 5 ml disposable syringe was used to condense the powder slurry. The condensed porcelain was sintered at 900΀C to produce porcelain ingots. The fabricated porcelain ingots were used in pressable ceramic machines. The technological advantages of pressable system improve the properties, and the fabricated ingot enhances the application of feldspathic porcelain.

  5. Suggestive techniques in advertising

    OpenAIRE

    Sora, Olena

    2011-01-01

    In my thesis I focused on a detailed analysis of suggestive techniques that appear in contemporary advertising. The issue of the effects of advertising has existed for many years and still staying timely. On the one side there are entrepreneurs and advertising agencies that are trying to influence opinions and suggest motivation for consuming. On the other side there is a potential customer, who is trying to obtain information about the product he needs and at the same time not letting anybod...

  6. Site characterization techniques

    Science.gov (United States)

    ,

    1995-01-01

    Geoelectrical methods have been used since the 1920's to search for metallic ore deposits. During the last decade, traditional mining geophysical techniques have been adapted for environmental site characterization. Geoelectrical geophysics is now a well developed engineering specialty, with different methods to focus both on a range of targets and on depths below the surface. Most methods have also been adapted to borehole measurements.

  7. Scalp imaging techniques

    Science.gov (United States)

    Otberg, Nina; Shapiro, Jerry; Lui, Harvey; Wu, Wen-Yu; Alzolibani, Abdullateef; Kang, Hoon; Richter, Heike; Lademann, Jürgen

    2017-05-01

    Scalp imaging techniques are necessary tools for the trichological practice and for visualization of permeation, penetration and absorption processes into and through the scalp and for the research on drug delivery and toxicology. The present letter reviews different scalp imaging techniques and discusses their utility. Moreover, two different studies on scalp imaging techniques are presented in this letter: (1) scalp imaging with phototrichograms in combination with laser scanning microscopy, and (2) follicular measurements with cyanoacrylate surface replicas and light microscopy in combination with laser scanning microscopy. The experiments compare different methods for the determination of hair density on the scalp and different follicular measures. An average terminal hair density of 132 hairs cm-2 was found in 6 Caucasian volunteers and 135 hairs cm-2 in 6 Asian volunteers. The area of the follicular orifices accounts to 16.3% of the skin surface on average measured with laser scanning microscopy images. The potential volume of the follicular infundibulum was calculated based on the laser scanning measurements and is found to be 4.63 mm3 per cm2 skin on average. The experiments show that hair follicles are quantitatively relevant pathways and potential reservoirs for topically applied drugs and cosmetics.

  8. Techniques for Wireless Applications

    KAUST Repository

    Gaaloul, Fakhreddine

    2012-05-01

    Switching techniques have been first proposed as a spacial diversity techniques. These techniques have been shown to reduce considerably the processing load while letting multi-antenna systems achieve a specific target performance. In this thesis, we take a different look at the switching schemes by implementing them for different other wireless applications. More specifically, this thesis consists of three main parts, where the first part considers a multiuser environment and an adaptive scheduling algorithm based on the switching with post-selection scheme for statistically independent but non-identically distributed channel conditions. The performance of this switched based scheduler is investigated and a multitude of performance metrics are presented. In a second part, we propose and analyze the performance of three switched-based algorithms for interference reduction in the downlink of over-loaded femtocells. For instance, performance metrics are derived in closed-form and these metrics are used to compare these three proposed schemes. Finally in a third part, a switch based opportunistic channel access scheme is proposed for a cognitive radio system and its performance is analyzed in terms of two new proposed metrics namely the average cognitive radio access and the waiting time duration.

  9. Empirical techniques in finance

    CERN Document Server

    Bhar, Ramaprasad

    2005-01-01

    This book offers the opportunity to study and experience advanced empi- cal techniques in finance and in general financial economics. It is not only suitable for students with an interest in the field, it is also highly rec- mended for academic researchers as well as the researchers in the industry. The book focuses on the contemporary empirical techniques used in the analysis of financial markets and how these are implemented using actual market data. With an emphasis on Implementation, this book helps foc- ing on strategies for rigorously combing finance theory and modeling technology to extend extant considerations in the literature. The main aim of this book is to equip the readers with an array of tools and techniques that will allow them to explore financial market problems with a fresh perspective. In this sense it is not another volume in eco- metrics. Of course, the traditional econometric methods are still valid and important; the contents of this book will bring in other related modeling topics tha...

  10. Investigation of physical and mechanical properties of (BaSnO3)x(Bi,Pb)-2223 composite

    Science.gov (United States)

    Habanjar, K.; Barakat, M. M. E.; Awad, R.

    2017-07-01

    The effect of BaSnO3 nanoparticles addition on the structural and mechanical properties of (Bi,Pb)-2223 superconducting phase by means of X-rays diffraction analysis (XRD), scanning electron microscope (SEM), electrical resistance and Vickers microhardness measurement was studied. BaSnO3 nanomaterial and (BaSnO3)x(Bi,Pb)-2223 superconducting samples were prepared using co-precipitation method and standard solid-state reaction techniques, respectively. From XRD data, the addition of BaSnO3 into (Bi,Pb)-2223 phase does not affect the tetragonal structure and the lattice parameters. SEM images indicate that the microstructure of (Bi,Pb)-2223 was enhanced by adding BaSnO3 nanoparticles by filling its pores and voids. The superconducting transition temperature Tc as well as the critical transport current density Jc, estimated from electrical resistivity measurements, are increased up to x = 0.5 wt%, then decreased with further increase in x. Vickers microhardness measurements Hv were carried out at room temperature as a function of applied. The experimental Hv results were analysed in view of Meyer’s law, Hays and Kendall (HK) approach, elastic/plastic deformation (EPD) and proportional specimen resistance (PSR). All samples exhibit normal indentation size effect (ISE), in addition to that, the analysis shows that the Hays and Kendall model is the most suitable one to describe the load independent microhardness for (BaSnO3)x(Bi,Pb)-2223 superconducting samples.

  11. Rapid mixing kinetic techniques.

    Science.gov (United States)

    Martin, Stephen R; Schilstra, Maria J

    2013-01-01

    Almost all of the elementary steps in a biochemical reaction scheme are either unimolecular or bimolecular processes that frequently occur on sub-second, often sub-millisecond, time scales. The traditional approach in kinetic studies is to mix two or more reagents and monitor the changes in concentrations with time. Conventional spectrophotometers cannot generally be used to study reactions that are complete within less than about 20 s, as it takes that amount of time to manually mix the reagents and activate the instrument. Rapid mixing techniques, which generally achieve mixing in less than 2 ms, overcome this limitation. This chapter is concerned with the use of these techniques in the study of reactions which reach equilibrium; the application of these methods to the study of enzyme kinetics is described in several excellent texts (Cornish-Bowden, Fundamentals of enzyme kinetics. Portland Press, 1995; Gutfreund, Kinetics for the life sciences. Receptors, transmitters and catalysis. Cambridge University Press, 1995).There are various ways to monitor changes in concentration of reactants, intermediates and products after mixing, but the most common way is to use changes in optical signals (absorbance or fluorescence) which often accompany reactions. Although absorbance can sometimes be used, fluorescence is often preferred because of its greater sensitivity, particularly in monitoring conformational changes. Such methods are continuous with good time resolution but they seldom permit the direct determination of the concentrations of individual species. Alternatively, samples may be taken from the reaction volume, mixed with a chemical quenching agent to stop the reaction, and their contents assessed by techniques such as HPLC. These methods can directly determine the concentrations of different species, but are discontinuous and have a limited time resolution.

  12. High voltage test techniques

    CERN Document Server

    Kind, Dieter

    2001-01-01

    The second edition of High Voltage Test Techniques has been completely revised. The present revision takes into account the latest international developments in High Voltage and Measurement technology, making it an essential reference for engineers in the testing field.High Voltage Technology belongs to the traditional area of Electrical Engineering. However, this is not to say that the area has stood still. New insulating materials, computing methods and voltage levels repeatedly pose new problems or open up methods of solution; electromagnetic compatibility (EMC) or components and systems al

  13. Optical techniques in optogenetics

    Science.gov (United States)

    Mohanty, Samarendra K.; Lakshminarayananan, Vasudevan

    2015-07-01

    Optogenetics is an innovative technique for optical control of cells. This field has exploded over the past decade or so and has given rise to great advances in neuroscience. A variety of applications both from the basic and applied research have emerged, turning the early ideas into a powerful paradigm for cell biology, neuroscience, and medical research. This review aims at highlighting the basic concepts that are essential for a comprehensive understanding of optogenetics and some important biological/biomedical applications. Further, emphasis is placed on advancement in optogenetics-associated light-based methods for controlling gene expression, spatially controlled optogenetic stimulation and detection of cellular activities.

  14. Western Blot Techniques.

    Science.gov (United States)

    Kim, Brianna

    2017-01-01

    The Western blot is an important laboratory technique that allows for specific identification and characterization of proteins. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE)-separated proteins are electophoretically transferred to a polyvinylidene fluoride (PVDF) membrane which is then incubated with specific antibodies, then developed to show the protein of interest. Here, we describe the transfer and detection of Outer surface protein A (OspA), a protein only found on the surface of Borrelia burgdorferi, the bacteria responsible for Lyme disease.

  15. Improved mortar setup technique

    CSIR Research Space (South Africa)

    De Villiers, D

    2008-10-01

    Full Text Available 2008 Brisbane October 2008 Improved mortar setup technique Danie de Villiers CSIR, Defence Piece Safety and Security program ABSTRACT Mortars will still play an important roll in modern warfare. This paper describes a unique way... of mirror R – right side of mirror F – front side of mirror B – back side of mirror After setup the mortar will be in front of the mirror and the target at the back of the mirror. On the dial are three marks to be used when reading the bearing value...

  16. Psoriatic arthritis: imaging techniques

    Directory of Open Access Journals (Sweden)

    E. Lubrano

    2012-06-01

    Full Text Available Imaging techniques to assess psoriatic arthritis (PsA include radiography, ultrasonography (US, magnetic resonance imaging (MRI, computed tomography (CT and bone scintigraphy. The radiographic hallmark of PsA is the combination of destructive changes (joint erosions, tuft resorption, osteolysis with bone proliferation (including periarticular and shaft periostitis, ankylosis, spur formation and non-marginal syndesmophytes. US has an increasing important role in the evaluation of PsA. In fact, power Doppler US is useful mainly for its ability to assess musculoskeletal (joints, tendons, entheses and cutaneous (skin and nails involvement, to monitor efficacy of therapy and to guide steroid injections at the level of inflamed joints, tendon sheaths and entheses. MRI allows direct visualization of inflammation in peripheral and axial joints, and peripheral and axial entheses, and has dramatically improved the possibilities for early diagnosis and objective monitoring of the disease process in PsA. MRI has allowed explaining the relationships among enthesitis, synovitis and osteitis in PsA, supporting a SpA pattern of inflammation where enthesitis is the primary target of inflammation. CT has little role in assessment of peripheral joints, but it may be useful in assessing elements of spine disease. CT accuracy is similar to MRI in assessment of erosions in sacroiliac joint involvement, but CT is not as effective in detecting synovial inflammation. Bone scintigraphy lacks specificity and is now supplanted with US and MRI techniques.

  17. Other imaging techniques.

    Science.gov (United States)

    Isard, H J

    1984-02-01

    Images of the breast can now be produced by five modalities: x-ray, heat, sound, light, and magnetism. X-ray mammography is generally accepted as the most accurate of these in the detection of breast cancer, and the standard by which the others are judged. Despite the obvious attraction of nonionizing techniques, the economic factor attendant on multiple studies requires consideration. Nuclear magnetic resonance (NMR) is currently being investigated in several clinics, but as yet there is no large series of documented cases. This report addresses itself to thermography, ultrasonography and diaphanography (transillumination). The unique characteristics of each and their respective roles in evaluation of the breast, particularly in the detection of breast cancer, will be discussed. When used in conjunction with mammography, potential advantages include: enhanced diagnostic accuracy, reduction of unnecessary surgery, and, in proven cases of breast cancer, prognostic capability. Thus far it has not been demonstrated that any of the nonionizing techniques can serve as a sole screening modality for breast cancer detection in asymptomatic women.

  18. Charge Breeding Techniques

    CERN Document Server

    Wenander, F

    2004-01-01

    The numerous newly built and forthcoming post-accelerators for radioactive ions, produced with the isotope separator on-line (ISOL) technique, all have a need for an efficient method to accelerate the precious primary ions. By increasing the ion charge-to-mass ratio directly after the radioactive ion production stage, a short and compact linear accelerator can be employed. Not only the efficiency, but also the rapidity of such a charge-to-mass increasing process, called charge breeding, is a crucial factor for the often short-lived radioisotopes. The traditional foil or gas stripping technique was challenged some five to ten years ago by novel schemes for charge breeding. The transformation from 1+ to n+ charged ions takes place inside an Electron Beam Ion Source/Trap (EBIS/T) or Electron Cyclotron Resonance Ion Source/Trap (ECRIS/T) by electron-ion collisions. These charge breeders are located in the low-energy part of the machine before the accelerating structures. Because of the capability of these devices...

  19. Ash tracer technique

    Energy Technology Data Exchange (ETDEWEB)

    Hald, P.

    1995-12-01

    This report describes the ash tracer technique which has been developed, used and evaluated for description of the extent of burnout for Cerrejon coal and wheat straw converted in a pressurized entrained-flow reactor. The uncertainty in the calculated extent of burnout depends on the uncertainty in the ash percentages determined for fuel and fuel sample. The uncertainty increases with decreasing amounts of material used for the ash percent determinations, as the natural variation within the fuel and fuel sample becomes obvious. Ash percentages for the original fuels have an absolute deviation within 0.2% with a remaining ash amount of minimum 100 mg and of 2% when using thermogravimetric analysis equipment where 0.4 - 4 mg was remaining. Repeated ash percent determinations by thermogravimetric analysis equipment of 40 samples showed an average absolute deviation of 3%. A temperature of 1000 deg. C is shown to be the best choice for the ash percent determinations in order to reduce the uncertainties. collection of representative straw samples is shown to make higher demands to the sampling procedure than collection of those for coal. A representative sample collection is shown to be easier from combustion experiments that form gasification and pyrolysis experiments. The ash tracer technique is verified by elemental ash analyses. (au) 14 tabs., 6 refs.

  20. Techniques de hacking

    CERN Document Server

    Erickson, Jon

    2008-01-01

    Dans cet ouvrage, Jon Erickson présente les bases de la programmation en C du point de vue du hacker et dissèque plusieurs techniques de hacking, passées et actuelles, afin de comprendre comment et pourquoi elles fonctionnent. Même si vous ne savez pas programmer, ce livre vous donnera une vue complète de la programmation, de l'architecture des machines, des communications réseau et des techniques de hacking existantes. Associez ces connaissances à l'environnement Linux fourni et laissez libre cours à votre imagination. Avec ce livre vous apprendrez à : • programmer les ordinateurs en C, en assembleur et avec des scripts shell ; • inspecter les registres du processeur et la mémoire système avec un débogueur afin de comprendre précisément ce qui se passe ; Vous découvrirez comment les hackers parviennent à : • corrompre la mémoire d'un système, en utilisant les débordements de tampons et les chaînes de format, pour exécuter un code quelconque ; • surpasser les mesures de sécurit...

  1. Advanced Coating Removal Techniques

    Science.gov (United States)

    Seibert, Jon

    2006-01-01

    An important step in the repair and protection against corrosion damage is the safe removal of the oxidation and protective coatings without further damaging the integrity of the substrate. Two such methods that are proving to be safe and effective in this task are liquid nitrogen and laser removal operations. Laser technology used for the removal of protective coatings is currently being researched and implemented in various areas of the aerospace industry. Delivering thousands of focused energy pulses, the laser ablates the coating surface by heating and dissolving the material applied to the substrate. The metal substrate will reflect the laser and redirect the energy to any remaining protective coating, thus preventing any collateral damage the substrate may suffer throughout the process. Liquid nitrogen jets are comparable to blasting with an ultra high-pressure water jet but without the residual liquid that requires collection and removal .As the liquid nitrogen reaches the surface it is transformed into gaseous nitrogen and reenters the atmosphere without any contamination to surrounding hardware. These innovative technologies simplify corrosion repair by eliminating hazardous chemicals and repetitive manual labor from the coating removal process. One very significant advantage is the reduction of particulate contamination exposure to personnel. With the removal of coatings adjacent to sensitive flight hardware, a benefit of each technique for the space program is that no contamination such as beads, water, or sanding residue is left behind when the job is finished. One primary concern is the safe removal of coatings from thin aluminum honeycomb face sheet. NASA recently conducted thermal testing on liquid nitrogen systems and found that no damage occurred on 1/6", aluminum substrates. Wright Patterson Air Force Base in conjunction with Boeing and NASA is currently testing the laser remOval technique for process qualification. Other applications of liquid

  2. Evaluation of microindentation properties of epitaxial 3C–SiC/Si thin films

    Energy Technology Data Exchange (ETDEWEB)

    Geetha, D. [Department of Physics, Anna University, Chennai 600025 (India); Sophia, P. Joice [UIST, St. Paul the Apostle, Ohrid 6000 (Macedonia, The Former Yugoslav Republic of); Arivuoli, D. [Crystal Growth Centre, Anna University, Chennai 600025 (India)

    2016-06-01

    The microhardness characteristics of 3C–SiC/Si films grown by vapor phase epitaxy were investigated using Vickers and Knoop indenters. The observed hardness behavior at lower load range is being attributed to indentation size effect while the substrate hardness effect is found to be prominent at higher loads. The related mechanical properties such as fracture toughness, brittleness index, and yield stress were also evaluated. In order to study the nature and behavior of the surface topography during the deformation process for the applied load, detailed atomic force microscopy images were obtained around the indented regions of the samples. It revealed that the indents formed at higher loads showed fracture characteristics with a pattern of radial cracks propagating from the indent corners.

  3. Technique murale picturale

    Directory of Open Access Journals (Sweden)

    Claude Coupry

    2009-09-01

    Full Text Available Après des études remarquables publiées, entre autres, dans Peindre à Auxerre au Moyen Âge, IXe-XIVe siècles, l’étude technique et analytique des peintures murales n’avait pas donné lieu à de nouvelles recherches méthodologiques en dépit des travaux de terrain (Souvigny, Stavelot… où l’archéologie du bâti avait permis des rencontres entre archéologues, historiens de l’art et restaurateurs particulièrement impliqués pour la période qui nous intéresse, de la basse Antiquité au haut Moyen Âge.Ce...

  4. Differential doppler heterodyning technique

    DEFF Research Database (Denmark)

    Lading, Lars

    1971-01-01

    Measuring velocity without disturbing the moving object is possible by use of the laser doppler heterodyning technique. Theoretical considerations on the doppler shift show that the antenna property of the photodetector can solve an apparent conflict between two different ways of calculating...... the detected doppler frequency. It is found that the doppler frequency for this particular setup is independent of the direction of detection. Investigations of the signal-to-noise ratio (SNR) show that the maximum SNR-considering the optical setup-is obtained by measuring the frequency difference between two...... doppler-shifted beams rather than by measuring the shift of a single beam by comparing it with a reference beam. Measurements seem to be in agreement with the theoretical consideration...

  5. Effects of Contact Damage and Residual Stress in Dental Layered Ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Chung, J.W.; Choi, S.C. [Hanyang University, Seoul (Korea)

    2000-03-01

    Effects of contact damage and residual stress for two kinds of dental restorative layered ceramics, porcelain/alumina and porcelain/zirconia bilayers, were observed with Hertzian and Vickers indentation methods. Indentation stress-strain behavior of each material, strength degradation of the coating material, and crack propagation behavior in the coating layer after Vickers indentation were examined by and optical microscope. As a result, porcelain as coating materials showed the classical brittleness. It was inferred that damage and strength in two bilayer systems were dependent on thermal expansion mismatch between the coating material and the substrate, which affected the strength degradation. Residual stress resulting from thermal expansion mismatch was formed in the coating layer, and specially in the case of porcelain/zirconia, residual stress was eliminated as coating thickness decreased. (author). 17 refs., 6 figs.

  6. Nano-Indentation of Anisotropic Material: Numerical Approaches to Extract Elasticities from Nano-Indentation

    OpenAIRE

    Sveaass, Tore

    2013-01-01

    Division of Biomechanics participates in a project together with Department of Cancer Research and Molecular Medicine, NTNU, on effects of proton pump inhibitor medication on bone quality. This common anti-stomach acid medication seems to result in an increased bone fragility in humans. As a step towards comparing mechanical properties at micro level, between sick and healthy bone tissue, mice femur have been tested at micro level using the increasingly popular tool, nanoindentation. Futher, ...

  7. Mechanical characterization of MgB{sub 2} thin films using nanoindentation technique

    Energy Technology Data Exchange (ETDEWEB)

    Ozmetin, A.E., E-mail: eozmetin@meliksah.edu.tr [Meliksah University, Materials Science and Mechanical Engineering Department, Kayseri (Turkey); Sahin, O. [Mustafa Kemal University, Micro/Nanomechanic Characterization Laboratory, Hatay (Turkey); Ongun, E.; Kuru, M. [Meliksah University, Materials Science and Mechanical Engineering Department, Kayseri (Turkey)

    2015-01-15

    Highlights: • MgB{sub 2} thin films deposited via single composite Mg + B target by RF magnetron sputtering. • Samples were heat treated at 590 °C in a vacuum oven at 2 × 10{sup −6} Torr base pressure. • Several measures were implemented to reduce the oxygen in the deposition chamber. • Structural properties were characterized by grazing incident XRD and SEM. • Mechanical properties have been investigated by using nanoindentation method. - Abstract: Mechanical properties of MgB{sub 2} thin films deposited by RF magnetron sputtering technique have been studied. MgB{sub 2} thin films were deposited approximately 300 nm on Si substrate above room temperature, and the thin films were subsequently annealed. Great care has been taken to reduce O{sub 2} in the chamber during deposition. Structural and mechanical properties of MgB{sub 2} thin films were investigated using the Scanning Electron Microscopy (SEM), X-ray diffraction (XRD) and nanoindentation techniques. Unloading segments of nanoindentation curves analyzed using Oliver–Pharr method. Both reduced elastic modulus and nanohardness values show load dependence, i.e., indentation size effect (ISE). Proportional specimen resistance (PSR) model was used to calculate the load independent nanohardness value. Load-independent hardness value was calculated using the proportional specimen resistance (PSR) model. XRD and SEM results show that the MgB{sub 2} thin films have fine grain size. Nanoindentation results show that hardness and elastic modulus values were 11.72 GPa and 178.13 GPa, respectively.

  8. Changes in urological surgical techniques

    Directory of Open Access Journals (Sweden)

    Oktay Üçer

    2010-06-01

    Full Text Available Recently, laparoscopic and afterwards robotic techniques have constituted most of urologic surgery procedures. Open surgery may give place to robotic surgery due to possible widespread use of robots in the future. Studies, that compare these two techniques are usually designed about radical prostatectomy, since it is the most common operation performed by using these techniques. In literature,robotic surgery seems more advantageous than other techniques but the most important disadvantage of this technique is cost-effective problems. In present review,history of open, laparoscopic and robotic surgery, and comparison of advantages, disadvantages and cost of these techniques have been discussed with literature.

  9. Comparison Of Clustering Techniques And A Univariate Technique ...

    African Journals Online (AJOL)

    Comparison Of Clustering Techniques And A Univariate Technique In The Site Selection On Multilocation Trial. ... The experiment was carried out in four zones of Kwara Agricultural Development Programmes and each of these techniques was used to group the sixteen locations into groups of similar locations and a critical ...

  10. Mechanical properties of chemical vapor deposited diamond

    Science.gov (United States)

    Kant, Avinash

    The hardness, elastic modulus, subcritical crack growth and fracture toughness of chemical vapor deposited (CVD) polycrystalline diamond films have been investigated on thick (˜100 to 300 mum) free-standing films with regard to the composition, microstructure, failure mechanisms and measurement techniques. The rationale for this study was the uncertainty in measuring these properties in previous research and the variability in the composition and microstructure of the material, which may affect these properties. Two predominant micro-hardness measurement techniques, namely Vickers and Knoop indentation, were employed. Existing Young's modulus measurement techniques such as dynamic resonance and nano-indentation were reviewed for modulus measurement on these films. The validity of indentation fracture toughness measurement for CVD diamond films using micro-hardness indentation has been established based on comparison with the conventional method of tensile testing of pre-notched compact-tension samples. The fracture toughness, Ksbc, of diamond was measured using indentation methods and for the first time by the tensile testing of pre-notched fracture-mechanics type compact-tension samples. Measured Ksbc values were found to be between 5 and 7 MPa-msp{1/2} by either method. Studies on subcritical crack growth (i.e., at stress intensities less than Ksbc) indicated that CVD diamond is essentially immune to stress-corrosion cracking under sustained loads in room air, water and acid environments. Extensive studies of the microstructure and mechanisms of failure were conducted. A commonly known toughening mechanism for ceramics by weakening the grain boundary in order to promote intergranular failure and grain bridging, has been implemented to improve the toughness of CVD diamond films. Several films with nominally the same thickness but small differences in their non-diamond content were studied and a significant variation in the toughness measurements was observed

  11. INTERNAL ENVIRONMENT ANALYSIS TECHNIQUES

    Directory of Open Access Journals (Sweden)

    Caescu Stefan Claudiu

    2011-12-01

    Full Text Available Theme The situation analysis, as a separate component of the strategic planning, involves collecting and analysing relevant types of information on the components of the marketing environment and their evolution on the one hand and also on the organization’s resources and capabilities on the other. Objectives of the Research The main purpose of the study of the analysis techniques of the internal environment is to provide insight on those aspects that are of strategic importance to the organization. Literature Review The marketing environment consists of two distinct components, the internal environment that is made from specific variables within the organization and the external environment that is made from variables external to the organization. Although analysing the external environment is essential for corporate success, it is not enough unless it is backed by a detailed analysis of the internal environment of the organization. The internal environment includes all elements that are endogenous to the organization, which are influenced to a great extent and totally controlled by it. The study of the internal environment must answer all resource related questions, solve all resource management issues and represents the first step in drawing up the marketing strategy. Research Methodology The present paper accomplished a documentary study of the main techniques used for the analysis of the internal environment. Results The special literature emphasizes that the differences in performance from one organization to another is primarily dependant not on the differences between the fields of activity, but especially on the differences between the resources and capabilities and the ways these are capitalized on. The main methods of analysing the internal environment addressed in this paper are: the analysis of the organizational resources, the performance analysis, the value chain analysis and the functional analysis. Implications Basically such

  12. Neutron detection technique

    CERN Document Server

    Oblath, N S

    2000-01-01

    The Sudbury Neutrino Observatory (SNO) has the ability to measure the total flux of all active flavors of neutrinos using the neutral current reaction, whose signature is a neutron. By comparing the rates of the neutral current reaction to the charged current reaction, which only detects electron neutrinos, one can test the neutrino oscillation hypothesis independent of solar models. It is necessary to understand the neutron detection efficiency of the detector to make use of the neutral current reaction. This report demonstrates a coincidence technique to identify neutrons emitted from the sup 2 sup 5 sup 2 Cf neutron calibration source. The source releases on average four neutrons when a sup 2 sup 5 sup 2 Cf nucleus spontaneously fissions. Each neutron is detected as a separate event when the neutron is captured by a deuteron, releasing a gamma ray of approximately 6.25 MeV. This gamma ray is in turn detected by the photomultiplier tube (PMT) array. By investigating the time and spatial separation between n...

  13. Dose Reduction Techniques

    CERN Document Server

    Waggoner, L O

    2000-01-01

    As radiation safety specialists, one of the things we are required to do is evaluate tools, equipment, materials and work practices and decide whether the use of these products or work practices will reduce radiation dose or risk to the environment. There is a tendency for many workers that work with radioactive material to accomplish radiological work the same way they have always done it rather than look for new technology or change their work practices. New technology is being developed all the time that can make radiological work easier and result in less radiation dose to the worker or reduce the possibility that contamination will be spread to the environment. As we discuss the various tools and techniques that reduce radiation dose, keep in mind that the radiological controls should be reasonable. We can not always get the dose to zero, so we must try to accomplish the work efficiently and cost-effectively. There are times we may have to accept there is only so much you can do. The goal is to do the sm...

  14. Restrictive techniques: gastric banding

    Directory of Open Access Journals (Sweden)

    Katia Cristina da Cunha

    2006-03-01

    Full Text Available Surgery for the treatment of severe obesity has a definite role onthe therapeutic armamentarium all over the world. Initiated 40years ago, bariatric surgery has already a long way thanks tohundred of surgeons, who had constantly searched for the besttechnique for the adequate control of severe obesity. Among theimportant breakthroughs in obesity surgery there is theadjustable gastric band. It is a sylastic band, inflatable andadjustable, which is placed on the top of the stomach in order tocreate a 15-20 cc pouch, with an outlet of 1.3cm. The adjustablegastric band has also a subcutaneous reservoir through whichadjustments can be made, according to the patient evolution.The main feature of the adjustable gastric band is the fact thatis minimal invasive, reversible, adjustable and placedlaparoscopically. Then greatly diminishing the surgical traumato the severe obese patient. Belachew and Favretti’s techniqueof laparoscopic application of the adjustable gastric band isdescribed and the evolution of the technique during this years,as we has been practiced since 1998. The perioperative care ofthe patient is also described, as well as the follow-up and shortand long term controls.

  15. Motion Transplantation Techniques: A Survey

    NARCIS (Netherlands)

    van Basten, Ben|info:eu-repo/dai/nl/30484800X; Egges, Arjan|info:eu-repo/dai/nl/304822779

    2012-01-01

    During the past decade, researchers have developed several techniques for transplanting motions. These techniques transplant a partial auxiliary motion, possibly defined for a small set of degrees of freedom, on a base motion. Motion transplantation improves motion databases' expressiveness and

  16. and use of barrier techniques

    African Journals Online (AJOL)

    consistent use of barrier techniques. Key-words: Attitudes, Dentists, Hepatitis B vaccination,. Barrier techniques. Résumé. Objectif: Virus Hépatite B constitue une menace importante pour le bien ... vacination contre hépatite B ct l'utilisation des techniques do la barriere. .... to staff and rarely from dentist to patients However,.

  17. Cationic hetero diffusion and mechanical properties of yttria-stabilized zirconia: influence of irradiation; Heterodiffusion cationique et proprietes mecaniques de la zircone stabilisee a l'oxyde d'yttrium: influence de l'irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Menvie Bekale, V

    2007-12-15

    Cubic yttria-stabilized zirconia (YSZ) is a promising material as target for the transmutation of radioactive waste. In this context, the present work is dedicated to the study of the atomic transport and the mechanical properties of this ceramic, as well as the influence of irradiation on these properties. The preliminary step concerns the synthesis of YSZ cubic zirconia ceramic undoped and doped with rare earths to form homogeneous Ce-YSZ or Gd-YSZ solid solutions with the highest density. The diffusion experiments of Ce and Gd in YSZ or Ce-YSZ were performed in air from 900 to 1400 C, and the depth profiles were established by SIMS. The bulk diffusion decreases when the ionic radius of diffusing element increases. The comparison with literature data of activation energies for bulk diffusion suggests that the cationic diffusion occurs via a vacancy mechanism. The diffusion results of Ce in YSZ irradiated with 4 or 20 MeV Au ions show a bulk diffusion slowing-down at 1000 and 1100 C when the radiation damage becomes important (30 dpa). The mechanical properties of YSZ ceramics irradiated with 944 MeV Pb ions and non irradiated samples were studied by Vickers micro indentation and Berkovitch nano indentation techniques. The hardness of the material increases when the average grain size decreases. Furthermore, the hardness and the toughness increase with irradiation fluence owing to the occurrence of compressive residual stresses in the irradiated area. (author)

  18. Studies on fracture toughness of dental ceramics.

    Science.gov (United States)

    Taira, M; Nomura, Y; Wakasa, K; Yamaki, M; Matsui, A

    1990-11-01

    One important mechanical property of dental ceramics is fracture toughness, KIC, which represents the serviceability in the oral cavity, such as the resistance to marginal fracture. KIC values of several dental ceramics, natural tooth enamel and industrial ceramics were examined by use of the indentation microfracture (IM) method. This technique was based on the series of radial cracks emanating from the corners of the Vickers indentation. It was observed that appropriate load levels should be selected on each specimen to induce radial/median cracks. For feldspatic dental porcelains, larger loads of 10, 20 and 30 kg were needed to determine their KIC values in the range 1.5-2.1 MN.m-3/2. For natural tooth enamel and a new apatite-based castable glass-ceramic, a smaller force of 1 kg was sufficient to decide the respective KIC values of about 0.9 and 1.8 MN.m-3/2. The KIC values of most dental ceramics examined were slightly higher than that of soda lime glass, but less than one-third that of zirconia. It was confirmed that the IM method is simple and cost-effective for evaluation of KIC of dental ceramics.

  19. Technique development for modulus, microcracking, hermeticity, and coating evaluation capability characterization of SiC/SiC tubes

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Xunxiang [Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States); Ang, Caen K. [Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States); Singh, Gyanender P. [Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States); Katoh, Yutai [Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)

    2016-08-01

    Driven by the need to enlarge the safety margins of nuclear fission reactors in accident scenarios, research and development of accident-tolerant fuel has become an important topic in the nuclear engineering and materials community. A continuous-fiber SiC/SiC composite is under consideration as a replacement for traditional zirconium alloy cladding owing to its high-temperature stability, chemical inertness, and exceptional irradiation resistance. An important task is the development of characterization techniques for SiC/SiC cladding, since traditional work using rectangular bars or disks cannot directly provide useful information on the properties of SiC/SiC composite tubes for fuel cladding applications. At Oak Ridge National Laboratory, experimental capabilities are under development to characterize the modulus, microcracking, and hermeticity of as-fabricated, as-irradiated SiC/SiC composite tubes. Resonant ultrasound spectroscopy has been validated as a promising technique to evaluate the elastic properties of SiC/SiC composite tubes and microcracking within the material. A similar technique, impulse excitation, is efficient in determining the basic mechanical properties of SiC bars prepared by chemical vapor deposition; it also has potential for application in studying the mechanical properties of SiC/SiC composite tubes. Complete evaluation of the quality of the developed coatings, a major mitigation strategy against gas permeation and hydrothermal corrosion, requires the deployment of various experimental techniques, such as scratch indentation, tensile pulling-off tests, and scanning electron microscopy. In addition, a comprehensive permeation test station is being established to assess the hermeticity of SiC/SiC composite tubes and to determine the H/D/He permeability of SiC/SiC composites. This report summarizes the current status of the development of these experimental capabilities.

  20. Techniques in Broadband Interferometry

    Energy Technology Data Exchange (ETDEWEB)

    Erskine, D J

    2004-01-04

    This is a compilation of my patents issued from 1997 to 2002, generally describing interferometer techniques that modify the coherence properties of broad-bandwidth light and other waves, with applications to Doppler velocimetry, range finding, imaging and spectroscopy. Patents are tedious to read in their original form. In an effort to improve their readability I have embedded the Figures throughout the manuscript, put the Figure captions underneath the Figures, and added section headings. Otherwise I have resisted the temptation to modify the words, though I found many places which could use healthy editing. There may be minor differences with the official versions issued by the US Patent and Trademark Office, particularly in the claims sections. In my shock physics work I measured the velocities of targets impacted by flyer plates by illuminating them with laser light and analyzing the reflected light with an interferometer. Small wavelength changes caused by the target motion (Doppler effect) were converted into fringe shifts by the interferometer. Lasers having long coherence lengths were required for the illumination. While lasers are certainly bright sources, and their collimated beams are convenient to work with, they are expensive. Particularly if one needs to illuminate a wide surface area, then large amounts of power are needed. Orders of magnitude more power per dollar can be obtained from a simple flashlamp, or for that matter, a 50 cent light bulb. Yet these inexpensive sources cannot practically be used for Doppler velocimetry because their coherence length is extremely short, i.e. their bandwidth is much too wide. Hence the motivation for patents 1 & 2 is a method (White Light Velocimetry) for allowing use of these powerful but incoherent lamps for interferometry. The coherence of the illumination is modified by passing it through a preparatory interferometer.

  1. Ultrasonic techniques for fluids characterization

    CERN Document Server

    Povey, Malcolm J W

    1997-01-01

    This book is a comprehensive and practical guide to the use of ultrasonic techniques for the characterization of fluids. Focusing on ultrasonic velocimetry, the author covers the basic topics and techniques necessaryfor successful ultrasound measurements on emulsions, dispersions, multiphase media, and viscoelastic/viscoplastic materials. Advanced techniques such as scattering, particle sizing, and automation are also presented. As a handbook for industrial and scientific use, Ultrasonic Techniques for Fluids Characterization is an indispensable guide to chemists and chemical engineers using ultrasound for research or process monitoring in the chemical, food processing, pharmaceutical, cosmetic, biotechnology,and fuels industries. Key Features * Appeals to anyone using ultrasound to study fluids * Provides the first detailed description of the ultrasound profiling technique for dispersions * Describes new techniques for measuring phase transitions and nucleation, such as water/ice and oil/fat * Presents the l...

  2. Luminescence techniques: Instrumentation and methods

    DEFF Research Database (Denmark)

    Bøtter-Jensen, L.

    1997-01-01

    This paper describes techniques, instruments and methods used in luminescence dating and environmental dosimetry in many laboratories around the world. These techniques are based on two phenomena - thermally stimulated luminescence and optically stimulated luminescence. The most commonly used...... luminescence stimulation and detection techniques are reviewed and information is given on recent developments in instrument design and on the stale of the art in luminescence measurements and analysis. (C) 1998 Elsevier Science Ltd. All rights reserved....

  3. Optical pulses, lasers, measuring techniques

    CERN Document Server

    Früngel, Frank B A

    1965-01-01

    High Speed Pulse Technology: Volume II: Optical Pulses - Lasers - Measuring Techniques focuses on the theoretical and engineering problems that result from the capacitor discharge technique.This book is organized into three main topics: light flash production from a capacitive energy storage; signal transmission and ranging systems by capacitor discharges and lasers; and impulse measuring technique. This text specifically discusses the air spark under atmospheric conditions, industrial equipment for laser flashing, and claims for light transmitting system. The application of light impulse sign

  4. Radar interferometry persistent scatterer technique

    CERN Document Server

    Kampes, Bert M

    2014-01-01

    This volume is devoted to the Persistent Scatterer Technique, the latest development in radar interferometric data processing. It is the only book on Permanent Scatterer (PS) technique of radar interferometry, and it details a newly developed stochastic model and estimator algorithm to cope with possible problems for the application of the PS technique. The STUN (spatio-temporal unwrapping network) algorithm, developed to cope with these issues in a robust way, is presented and applied to two test sites.

  5. The Matador Technique: A technique to improve prostatic ...

    African Journals Online (AJOL)

    A. Pai

    electromagnetic fusion sensors [6] and robotic-assisted needle placement [7–10]. However, further clinical trials are required before these techniques can be widely used. The benefit of the Matador Technique is a marked reduction of prostatic rotation by simultaneous insertion of the first two nee- dles on either side of the ...

  6. Microfluidic Techniques for Analytes Concentration

    Directory of Open Access Journals (Sweden)

    Cunlu Zhao

    2017-01-01

    Full Text Available Microfluidics has been undergoing fast development in the past two decades due to its promising applications in biotechnology, medicine, and chemistry. Towards these applications, enhancing concentration sensitivity and detection resolution are indispensable to meet the detection limits because of the dilute sample concentrations, ultra-small sample volumes and short detection lengths in microfluidic devices. A variety of microfluidic techniques for concentrating analytes have been developed. This article presents an overview of analyte concentration techniques in microfluidics. We focus on discussing the physical mechanism of each concentration technique with its representative advancements and applications. Finally, the article is concluded by highlighting and discussing advantages and disadvantages of the reviewed techniques.

  7. Developing Fighting Technique Through Visualization

    Directory of Open Access Journals (Sweden)

    Tim Lajcik

    2012-07-01

    Full Text Available Visualization is a training technique that involves creating a detailed mental “movie” of successful performance. This article describes a type of visualization called “mental rehearsal” and explains how it can be used to reinforce the neuromuscular pattern of proper fighting technique. Drawing on his experience as a professional fighter and college coach, his studies in sport psychology as a college student, and his exposure to mental training techniques at the U.S. Olympic Training Center, the author reveals how to use mental imagery to facilitate the mastery of martial art technique.    

  8. Algorithms Design Techniques and Analysis

    CERN Document Server

    Alsuwaiyel, M H

    1999-01-01

    Problem solving is an essential part of every scientific discipline. It has two components: (1) problem identification and formulation, and (2) solution of the formulated problem. One can solve a problem on its own using ad hoc techniques or follow those techniques that have produced efficient solutions to similar problems. This requires the understanding of various algorithm design techniques, how and when to use them to formulate solutions and the context appropriate for each of them. This book advocates the study of algorithm design techniques by presenting most of the useful algorithm desi

  9. Comparison of Composite Restoration Techniques

    Directory of Open Access Journals (Sweden)

    András Katona

    2016-01-01

    Full Text Available This article briefly presents the classification, and possible ways of application of composites. Our objective was to compare three different restoration technique in class II cavity preparations, with the aim to determine which technique is the most advantageous in practical point of view. Artificial teeth fabricated from self-curing acrylic resin were used as models. Comparison of marginal sealing was performed macroscopically via direct visual inspection and via tactile control. Two parameters were examined on esthetic evaluation, which were the anatomical shape and the optical appearance. The time required to prepare the restorations were also measured. After the evaluation of the results, the bulk-fill technique was demonstrated to require the shortest time to be performed. This was followed by the oblique (Z technique, whereas the horizontal incremental technique appeared to be the most time-consuming method. Based on the esthetic evaluation, a remarkable difference can be observed between the bulk-fill technique and the other two incremental techniques, while the mean scores for the oblique and the horizontal techniques were comparable. Based on the results of the visual inspection and instrumental examination, there were no differences in terms of marginal sealing between the three applied methods. Based on these, the use of the appropriate incremental technique can reduce the development of secondary caries and increasing the longevity of composite restorations.

  10. GPU Pro advanced rendering techniques

    CERN Document Server

    Engel, Wolfgang

    2010-01-01

    This book covers essential tools and techniques for programming the graphics processing unit. Brought to you by Wolfgang Engel and the same team of editors who made the ShaderX series a success, this volume covers advanced rendering techniques, engine design, GPGPU techniques, related mathematical techniques, and game postmortems. A special emphasis is placed on handheld programming to account for the increased importance of graphics on mobile devices, especially the iPhone and iPod touch.Example programs and source code can be downloaded from the book's CRC Press web page. 

  11. Parachute technique for partial penectomy

    Directory of Open Access Journals (Sweden)

    Fernando Korkes

    2010-04-01

    Full Text Available PURPOSE: Penile carcinoma is a rare but mutilating malignancy. In this context, partial penectomy is the most commonly applied approach for best oncological results. We herein propose a simple modification of the classic technique of partial penectomy, for better cosmetic and functional results. TECHNIQUE: If partial penectomy is indicated, the present technique can bring additional benefits. Different from classical technique, the urethra is spatulated only ventrally. An inverted "V" skin flap with 0.5 cm of extension is sectioned ventrally. The suture is performed with vicryl 4-0 in a "parachute" fashion, beginning from the ventral portion of the urethra and the "V" flap, followed by the "V" flap angles and than by the dorsal portion of the penis. After completion of the suture, a Foley catheter and light dressing are placed for 24 hours. CONCLUSIONS: Several complex reconstructive techniques have been previously proposed, but normally require specific surgical abilities, adequate patient selection and staged procedures. We believe that these reconstructive techniques are very useful in some specific subsets of patients. However, the technique herein proposed is a simple alternative that can be applied to all men after a partial penectomy, and takes the same amount of time as that in the classic technique. In conclusion, the "parachute" technique for penile reconstruction after partial amputation not only improves the appearance of the penis, but also maintains an adequate function.

  12. Passage Retrieval: A Probabilistic Technique.

    Science.gov (United States)

    Melucci, Massimo

    1998-01-01

    Presents a probabilistic technique to retrieve passages from texts having a large size or heterogeneous semantic content. Results of experiments comparing the probabilistic technique to one based on a text segmentation algorithm revealed that the passage size affects passage retrieval performance; text organization and query generality may have an…

  13. Software Agent Techniques in Design

    DEFF Research Database (Denmark)

    Hartvig, Susanne C

    1998-01-01

    This paper briefly presents studies of software agent techniques and outline aspects of these which can be applied in design agents in integrated civil engineering design environments.......This paper briefly presents studies of software agent techniques and outline aspects of these which can be applied in design agents in integrated civil engineering design environments....

  14. A disposition of interpolation techniques

    NARCIS (Netherlands)

    Knotters, M.; Heuvelink, G.B.M.

    2010-01-01

    A large collection of interpolation techniques is available for application in environmental research. To help environmental scientists in choosing an appropriate technique a disposition is made, based on 1) applicability in space, time and space-time, 2) quantification of accuracy of interpolated

  15. Magnetic characterization techniques for nanomaterials

    CERN Document Server

    2017-01-01

    Sixth volume of a 40 volume series on nanoscience and nanotechnology, edited by the renowned scientist Challa S.S.R. Kumar. This handbook gives a comprehensive overview about Magnetic Characterization Techniques for Nanomaterials. Modern applications and state-of-the-art techniques are covered and make this volume an essential reading for research scientists in academia and industry.

  16. Single Cell Electrical Characterization Techniques

    Directory of Open Access Journals (Sweden)

    Muhammad Asraf Mansor

    2015-06-01

    Full Text Available Electrical properties of living cells have been proven to play significant roles in understanding of various biological activities including disease progression both at the cellular and molecular levels. Since two decades ago, many researchers have developed tools to analyze the cell’s electrical states especially in single cell analysis (SCA. In depth analysis and more fully described activities of cell differentiation and cancer can only be accomplished with single cell analysis. This growing interest was supported by the emergence of various microfluidic techniques to fulfill high precisions screening, reduced equipment cost and low analysis time for characterization of the single cell’s electrical properties, as compared to classical bulky technique. This paper presents a historical review of single cell electrical properties analysis development from classical techniques to recent advances in microfluidic techniques. Technical details of the different microfluidic techniques are highlighted, and the advantages and limitations of various microfluidic devices are discussed.

  17. Single Cell Electrical Characterization Techniques.

    Science.gov (United States)

    Mansor, Muhammad Asraf; Ahmad, Mohd Ridzuan

    2015-06-04

    Electrical properties of living cells have been proven to play significant roles in understanding of various biological activities including disease progression both at the cellular and molecular levels. Since two decades ago, many researchers have developed tools to analyze the cell's electrical states especially in single cell analysis (SCA). In depth analysis and more fully described activities of cell differentiation and cancer can only be accomplished with single cell analysis. This growing interest was supported by the emergence of various microfluidic techniques to fulfill high precisions screening, reduced equipment cost and low analysis time for characterization of the single cell's electrical properties, as compared to classical bulky technique. This paper presents a historical review of single cell electrical properties analysis development from classical techniques to recent advances in microfluidic techniques. Technical details of the different microfluidic techniques are highlighted, and the advantages and limitations of various microfluidic devices are discussed.

  18. Strongly correlated systems experimental techniques

    CERN Document Server

    Mancini, Ferdinando

    2015-01-01

    The continuous evolution and development of experimental techniques is at the basis of any fundamental achievement in modern physics. Strongly correlated systems (SCS), more than any other, need to be investigated through the greatest variety of experimental techniques in order to unveil and crosscheck the numerous and puzzling anomalous behaviors characterizing them. The study of SCS fostered the improvement of many old experimental techniques, but also the advent of many new ones just invented in order to analyze the complex behaviors of these systems. Many novel materials, with functional properties emerging from macroscopic quantum behaviors at the frontier of modern research in physics, chemistry and materials science, belong to this class of systems. The volume presents a representative collection of the modern experimental techniques specifically tailored for the analysis of strongly correlated systems. Any technique is presented in great detail by its own inventor or by one of the world-wide recognize...

  19. New techniques in CT angiography.

    Science.gov (United States)

    Lell, Michael M; Anders, Katharina; Uder, Michael; Klotz, Ernst; Ditt, Hendrik; Vega-Higuera, Fernando; Boskamp, Tobias; Bautz, Werner A; Tomandl, Bernd F

    2006-10-01

    Computed tomographic (CT) angiography has been improved significantly with the introduction of four- to 64-section spiral CT scanners, which offer rapid acquisition of isotropic data sets. A variety of techniques have been proposed for postprocessing of the resulting images. The most widely used techniques are multiplanar reformation (MPR), thin-slab maximum intensity projection, and volume rendering. Sophisticated segmentation algorithms, vessel analysis tools based on a centerline approach, and automatic lumen boundary definition are emerging techniques; bone removal with thresholding or subtraction algorithms has been introduced. These techniques increasingly provide a quality of vessel analysis comparable to that achieved with intraarterial three-dimensional rotational angiography. Neurovascular applications for these various image postprocessing methods include steno-occlusive disease, dural sinus thrombosis, vascular malformations, and cerebral aneurysms. However, one should keep in mind the potential pitfalls of these techniques and always double-check the final results with source or MPR imaging. .(c) RSNA, 2006.

  20. Advanced Pattern Recognition Techniques (Techniques avancees de reconnaissance de forme)

    Science.gov (United States)

    1998-09-01

    we will need a teacher, vances in pattern recognition techniques have come to tell us that our favourite group is, e.g. Darjeeling from better...34Estimating the Time-Delay and Frequency-Decay Parameter of Scattering Components using a Modified MUSIC Algorithm," IEEE Trans. on Antennas and Prop...available Modified MUSIC Algorithm," IEEE Trans. on from Fourier techniques. Antennas and Propagation, Vol. 42, No. 10, pp. 1412-1419, October, 1994. 11