Directory of Open Access Journals (Sweden)
Walt Wells
2008-01-01
Full Text Available Our objective in this paper is to solve a second order differential equation for a long, simply supported column member subjected to a lateral axial load using Heun's numerical method. We will use the solution to find the critical load at which the column member will fail due to buckling. We will calculate this load using Euler's derived analytical approach for an exact solution, as well as Euler's Numerical Method. We will then compare the three calculated values to see how much they deviate from one another. During the critical load calculation, it will be necessary to calculate the moment of inertia for the column member.
Axial loaded MRI of the lumbar spine
Energy Technology Data Exchange (ETDEWEB)
Saifuddin, A. E-mail: asaifuddin@aol.com; Blease, S.; MacSweeney, E
2003-09-01
Magnetic resonance imaging is established as the technique of choice for assessment of degenerative disorders of the lumbar spine. However, it is routinely performed with the patient supine and the hips and knees flexed. The absence of axial loading and lumbar extension results in a maximization of spinal canal dimensions, which may in some cases, result in failure to demonstrate nerve root compression. Attempts have been made to image the lumbar spine in a more physiological state, either by imaging with flexion-extension, in the erect position or by using axial loading. This article reviews the literature relating to the above techniques.
Test Setup for Axially Loaded Piles in Sand
DEFF Research Database (Denmark)
Thomassen, Kristina
The test setup for testing axially static and cyclic loaded piles in sand is described in the following. The purpose for the tests is to examine the tensile capacity of axially loaded piles in dense fully saturated sand. The pile dimensions are chosen to resemble full scale dimension of piles used...... in offshore pile foundations today....
Testing of Axially Loaded Bucket Foundation with Applied Overburden Pressure
DEFF Research Database (Denmark)
Vaitkunaite, Evelina; Ibsen, Lars Bo; Nielsen, Benjaminn Nordahl
This report analyses laboratory testing data performed with a bucket foundation model subjected to axial loading. The examinations were conducted at the Geotechnical laboratory of Aalborg University. The report aims at showing and discussing the results of the static and cyclic axial loading tests...... on the bucket foundation model. Finally, a cyclic loading interaction diagram is given that can be applied for a full-scale bucket foundation design....
Static Tension Tests on Axially Loaded Pile Segments in Sand
DEFF Research Database (Denmark)
Thomassen, Kristina; Andersen, Lars Vabbersgaard; Ibsen, Lars Bo
This paper provides laboratory test results of static axially loaded piles in sand. With a newly developed test setup, the pile-soil interface friction was investigated by using an open-ended steel pile segment with a diameter of 0.5 m. Use of a pile length of 1 m enabled the pile-soil interface...
Test Procedure for Axially Loaded Piles in Sand
DEFF Research Database (Denmark)
Thomassen, Kristina
The test procedure described in the following is used when examining the effects of static or cyclic loading on the skin friction of an axially loaded pile in dense sand. The pile specimen is only loaded in tension to avoid any contribution from the base resistance. The pile dimensions are chosen...... to resemble full scale dimension of piles used in offshore pile foundations today. In this report is given a detailed description of the soil preparation and pile installation procedures as well data acquisition methods....
In vivo axial loading of the mouse tibia.
Melville, Katherine M; Robling, Alexander G; van der Meulen, Marjolein C H
2015-01-01
Noninvasive methods to apply controlled, cyclic loads to the living skeleton are used as anabolic procedures to stimulate new bone formation in adults and enhance bone mass accrual in growing animals. These methods are also invaluable for understanding bone signaling pathways. Our focus here is on a particular loading model: in vivo axial compression of the mouse tibia. An advantage of loading the tibia is that changes are present in both the cancellous envelope of the proximal tibia and the cortical bone of the tibial diaphysis. To load the tibia of the mouse axially in vivo, a cyclic compressive load is applied up to five times a week to a single tibia per mouse for a duration lasting from 1 day to 6 weeks. With the contralateral limb as an internal control, the anabolic response of the skeleton to mechanical stimuli can be studied in a pairwise experimental design. Here, we describe the key parameters that must be considered before beginning an in vivo mouse tibial loading experiment, including methods for in vivo strain gauging of the tibial midshaft, and then we describe general methods for loading the mouse tibia for an experiment lasting multiple days.
A Nonlocal Model for Carbon Nanotubes under Axial Loads
Directory of Open Access Journals (Sweden)
Raffaele Barretta
2013-01-01
Full Text Available Various beam theories are formulated in literature using the nonlocal differential constitutive relation proposed by Eringen. A new variational framework is derived in the present paper by following a consistent thermodynamic approach based on a nonlocal constitutive law of gradient-type. Contrary to the results obtained by Eringen, the new model exhibits the nonlocality effect also for constant axial load distributions. The treatment can be adopted to get new benchmarks for numerical analyses.
Dynamic Response of Axially Loaded Euler-Bernoulli Beams
DEFF Research Database (Denmark)
Bayat, M.; Barari, Amin; Shahidi, M.
2011-01-01
The current research deals with application of a new analytical technique called Energy Balance Method (EBM) for a nonlinear problem. Energy Balance Method is used to obtain the analytical solution for nonlinear vibration behavior of Euler-Bernoulli beams subjected to axial loads. Analytical expr...... to the conventional methods, only one iteration leads to high accuracy of the solutions which are valid for a wide range of vibration amplitudes....
Comparison of design methods for axially loaded buckets in sand
DEFF Research Database (Denmark)
Vaitkunaite, Evelina; Nielsen, Benjaminn Nordahl; Ibsen, Lars Bo
2015-01-01
A study of the present knowledge about the bucket resistance for axial loading was performed considering analytical and numerical design methods as well as physical models. A case study was performed with two bucket foundations of equal diameter, but different skirt lengths installed in dense sand....... Itwas found that bearing capacity from the surcharge increases approximately twice if the foundation skirt is two times longer. However, the predicted compressive soil capacity can differ by 3.6 times depending on the chosen bearing capacity parameters. Few methods are available for the estimation...
Yeow, C H; Lee, P V S; Goh, J C H
2010-01-19
Anterior tibial loading is a major factor involved in the anterior cruciate ligament (ACL) injury mechanism during ski impact landing. We sought to investigate the direct contribution of axial impact compressive load to anterior tibial load during simulated ski landing impact of intact knee joints without quadriceps activation. Twelve porcine knee specimens were procured. Four specimens were used as non-impact control while the remaining eight were mounted onto a material-testing system at 70 degrees flexion and subjected to simulated landing impact, which was successively repeated with incremental actuator displacement. Four specimens from the impacted group underwent pre-impact MRI for tibial plateau angle measurements while the other four were subjected to histology and microCT for cartilage morphology and volume assessment. The tibial plateau angles ranged from 29.4 to 38.8 degrees . There was a moderate linear relationship (Y=0.16X; R(2)=0.64; p<0.001) between peak axial impact compressive load (Y) and peak anterior tibial load (X). The anterior and posterior regions in the impacted group sustained surface cartilage fraying, superficial clefts and tidemark disruption, compared to the control group. MicroCT scans displayed visible cartilage deformation for both anterior and posterior regions in the impacted group. Due to the tibial plateau angle, increased axial impact compressive load can directly elevate anterior tibial load and hence contribute to ACL failure during simulated landing impact. Axial impact compressive load resulted in shear cartilage damage along anterior-posterior tibial plateau regions, due to its contribution to anterior tibial loading. This mechanism plays an important role in elevating ACL stress and cartilage deformation during impact landing.
Dynamic impedance of piles in visco-elastic material considering axial loads
Institute of Scientific and Technical Information of China (English)
JIANG Jian-guo; ZHOU Xu-hong; ZHANG Jia-sheng
2005-01-01
The dynamic impedance function of pile in visco-elastie material considering axial loads under lateral dynamic force was analyzed, and the beam dynamic differential equation was used to induce the dynamic impedance function. After analyzing the edge conditions, the dynamic impedance functions were deduced. Contrasted with the result that does not consider axial loads, the axial loads have obvious influence on the dynamic impedance function.And the results show that the dimensionless prarmeter of the dynamic impedance will change from 6 % to 9 % when considering axial loads, and dimensionless prarmeter of the dynamic impedance of the coupling horizontal-sway will increase by 31 %.
Subjected to Axial Compressive Load and Transverse Magnetic Field
Directory of Open Access Journals (Sweden)
Mei-Feng Liu
2010-01-01
Full Text Available The interactive behaviors between transverse magnetic fields and axial loads of a magnetoelastic (ME beam subjected to general boundary conditions are investigated. In particular, the instability criterion for the magneto-mechanical buckling problem is intricately discussed based on the structure characteristics and the initial conditions. The equation of motion for the proposed physical model is introduced according to the Hamilton's principle, and the stability criterion is obtained by using the method of multiple scales implemented on both spatial and time domains. Eventually a so-called Schrodinger equation with cubic nonlinearity (NLS can be generated by suitably changing the variables; as a result, the stable criterion for the magnetoelastic beam can be acquired after dissecting the nonlinear Schrodinger equation and requiring the imaginary part of the time domain solution to be vanished. Stability criterion curve for the dispersion equation of the ME beam is firstly depicted in order to reveal the magnificent influence of the structure characteristic itself, followed by the instability constraint due to the variation of initial conditions and the observation locations. The results indicate that the prior one actually denotes a parabola, whereas the latter one is sometimes a diamond-like or ellipse-like region spotting along the prior one.
Ding, Lan; Zhu, Hong-Ping; Wu, Li
2016-07-01
The propagation and attenuation properties of waves in ordered and disordered periodic composite Timoshenko beams, which consider the effects of axial static load and structural damping, resting on elastic foundations are studied when the system is subjected to moving loads of constant amplitude with a constant velocity. The transfer matrix methodology is adopted to formulate the model in a reference coordinate system moving with the load. The localization factor is calculated to determine the wave velocity pass bands and stop bands. The interactions between the static axial load and moving load, structural damping and disorder on the bands are analyzed.
Institute of Scientific and Technical Information of China (English)
TIAN Zhimin; WU Ping'an; JIA Jianwei
2008-01-01
Experimental investigation into impact-resistant behavior of reactive powder concrete (RPC)-filled steel tubular columns was conducted, and dynamic response of the columns under axial impact loading was studied by means of numerical simulation method.Increase coefficient of load carrying capacity and ratio of load carrying capacity between steel tube and RPC core of columns were obtained.
LOAD CARRYING CAPABILITY OF LIQUID FILLED CYLINDRICAL SHELL STRUCTURES UNDER AXIAL COMPRESSION
Directory of Open Access Journals (Sweden)
QASIM H. SHAH
2011-08-01
Full Text Available Empty and water filled cylindrical Tin (Sn coated steel cans were loaded under axial compression at varying loading rates to study their resistance to withstand accidental loads. Compared to empty cans the water filled cans exhibit greater resistance to axially applied compression loads before a complete collapse. The time and load or stroke and load plots showed three significant load peaks related to three stages during loading until the cylinder collapse. First peak corresponds to the initial structural buckling of can. Second peak occurs when cylindrical can walls gradually come into full contact with water. The third peak shows the maximum load carrying capability of the structure where pressurized water deforms the can walls into curved shape until can walls fail under peak pressure. The collapse process of water filled cylindrical shell was further studied using Smooth Particle Hydrodynamics (SPH technique in LSDYNA. Load peaks observed in the experimental work were successfully simulated which substantiated the experimental work.
Kheiralla, Lamia Sayed; Younis, Jihan Farouk
2014-02-01
This study compared the biomechanical responses of 3 single crowns supported by 3 different implants under axial and off-axial loading. A standard implant (3.75 mm diameter, 13 mm length), a mini implant (3 mm diameter, 13 mm length), and a short-wide implant (5.7 mm diameter, 8 mm length) were embedded in epoxy resin by the aid of a surveyor to ensure their parallelism. Each implant supported a full metal crown made of Ni-Cr alloy with standardized dimensions. Strain gauges and finite element analysis (FEA) were used to measure the strain induced under axial and off-axial functional loads of 300 N. Results showed that mini implants recorded the highest microstrains, under both axial and off-axial loading. All implants showed a considerable increase in strain values under off-axial loading. Standard and short-wide implants proved to be preferable in supporting crowns, as the standard implant showed the lowest strains under axial and off-axial loading using FEA simulation, while the short-wide implant showed the lowest strains under nonaxial loading using strain gauge analysis.
Directory of Open Access Journals (Sweden)
Belinda Pingguan-Murphy
2012-08-01
Full Text Available OBJECTIVES: The promotion of extracellular matrix synthesis by chondrocytes is a requisite part of an effective cartilage tissue engineering strategy. The aim of this in vitro study was to determine the effect of bi-axial cyclic mechanical loading on cell proliferation and the synthesis of glycosaminoglycans by chondrocytes in threedimensional cultures. METHOD: A strain comprising 10% direct compression and 1% compressive shear was applied to bovine chondrocytes seeded in an agarose gel during two 12-hour conditioning periods separated by a 12-hour resting period. RESULTS: The bi-axial-loaded chondrocytes demonstrated a significant increase in glycosaminoglycan synthesis compared with samples exposed to uni-axial or no loading over the same period (p<0.05. The use of a free-swelling recovery period prior to the loading regime resulted in additional glycosaminoglycan production and a significant increase in DNA content (p<0.05, indicating cell proliferation. CONCLUSIONS: These results demonstrate that the use of a bi-axial loading regime results in increased matrix production compared with uni-axial loading.
Physical Modelling of Bucket Foundations Subjected to Axial Loading
DEFF Research Database (Denmark)
Vaitkunaite, Evelina
displacement rates and tensile cyclic loading. A new laboratory testing facility is constructed allowing large scale foundation model testing under long-term cyclic loadings. Another test set-up - a pressure tank – is employed for the displacement rate analysis. The extensive testing campaign provides valuable...
Comparison of Design Methods for Axially Loaded Driven Piles in Cohesionless Soil
DEFF Research Database (Denmark)
Thomassen, Kristina; Andersen, Lars Vabbersgaard; Ibsen, Lars Bo
2012-01-01
For offshore wind turbines on deeper waters, a jacket sub-structure supported by axially loaded piles is thought to be the most suitable solution. The design method recommended by API and two CPT-based design methods are compared for two uniform sand profiles. The analysis show great difference...... in the predictions of bearing capacities calculated by means of the three methods for piles loaded in both tension and compression. This implies that further analysis of the bearing capacity of axially loaded piles in sand should be conducted....
Optimum design of laminated composite under axial compressive load
Indian Academy of Sciences (India)
N G R Iyengar; Nilesh Vyas
2011-02-01
In the present study optimal design of composite laminates, with and without rectangular cut-out, is carried out for maximizing the buckling load. Optimization study is carried out for obtaining the maximum buckling load with design variables as ply thickness, cut-out size and orientation of cut-out with respect to laminate. Buckling load is evaluated using a ‘simple higher order shear deformation theory’ based on four unknown displacements $u,v,w_b$ and $w_s$. A C1 continuous shear flexible finite element based on HSDT model is developed using Hermite cubic polynomial. It is observed that for thick anti-symmetric laminates, the non-dimensional buckling load decreases with increase in aspect ratio and increase in fibre orientation angle. There is a decrease in the non-dimensional buckling load of symmetric laminate in the presence of cut-out.
An exact dynamic stiffness matrix for axially loaded double-beam systems
Indian Academy of Sciences (India)
Li Xiaobin; Xu Shuangxi; Wu Weiguo; Li Jun
2014-06-01
An exact dynamic stiffness method is presented in this paper to determine the natural frequencies and mode shapes of the axially loaded double-beam systems,which consist of two homogeneous and prismatic beams with a distributed spring in parallel between them.The effects of the axial force, shear deformation and rotary inertia are considered, as shown in the theoretical formulation. The dynamic stiffness influence coefficients are formulated from the governing differential equations of the axially loaded double-beam system in free vibration by using the Laplace transform method. An example is given to demonstrate the effectiveness of this method, in which ten boundary conditions are investigated and the effect of the axial force on the natural frequencies and mode shapes of the double-beam system are further discussed.
Dávila, A.; Márquez, S.; Landgrave, E.; Vázquez, Z.; Vera, K.; Caudillo, C.
2015-06-01
A computerized system for real-time displacement visualization using carrier fringes in an electronic speckle in-plane sensitive interferometer allows force calibration for micro-displacement analysis of rat bones and verification of axial loading conditions. Once the force has been calibrated and the load is applied along the bone axis, the difference-of-phase method is used to obtain the phase map, which after phase unwrapping, allows the evaluation of the displacements produced by the bone deformation. The proposed method avoids common loading mistakes using first carrier fringes to assure that the loads are within the measuring capabilities of the in-plane interferometer and the Carré phase-stepping method to compensate for linear phase step miscalibration. The experimental results obtained with the calibration of loading forces and axial loading verification show the advantages of the system proposed here over a system which uses a cantilever configuration to make a similar bone deformation analysis.
Directory of Open Access Journals (Sweden)
Ye-Wei Zhang
2013-01-01
Full Text Available Nonlinear targeted energy transfer (TET is applied to suppress the excessive vibration of an axially moving string with transverse wind loads. The coupling dynamic equations used are modeled by a nonlinear energy sink (NES attached to the string to absorb vibrational energy. By a two-term Galerkin procedure, the equations are discretized, and the effects of vibration suppression by numerical methods are demonstrated. Results show that the NES can effectively suppress the vibration of the axially moving string with transverse wind loadings, thereby protecting the string from excessive movement.
Weatherholt, Alyssa M; Fuchs, Robyn K; Warden, Stuart J
2013-01-01
The mouse tibial axial compression loading model has recently been described to allow simultaneous exploration of cortical and trabecular bone adaptation within the same loaded element. However, the model frequently induces cortical woven bone formation and has produced inconsistent results with regards to trabecular bone adaptation. The aim of this study was to investigate bone adaptation to incremental load magnitudes using the mouse tibial axial compression loading model, with the ultimate goal of revealing a load that simultaneously induced lamellar cortical and trabecular bone adaptation. Adult (16 weeks old) female C57BL/6 mice were randomly divided into three load magnitude groups (5, 7 and 9N), and had their right tibia axially loaded using a continuous 2-Hz haversine waveform for 360 cycles/day, 3 days/week for 4 consecutive weeks. In vivo peripheral quantitative computed tomography was used to longitudinally assess midshaft tibia cortical bone adaptation, while ex vivo micro-computed tomography and histomorphometry were used to assess both midshaft tibia cortical and proximal tibia trabecular bone adaptation. A dose response to loading magnitude was observed within cortical bone, with increasing load magnitude inducing increasing levels of lamellar cortical bone adaptation within the upper two thirds of the tibial diaphysis. Greatest cortical bone adaptation was observed at the midshaft where there was a 42% increase in estimated mechanical properties (polar moment of inertia) in the highest (9N) load group. A dose response to load magnitude was not clearly evident within trabecular bone, with only the highest load (9N) being able to induce measureable adaptation (31% increase in trabecular bone volume fraction at the proximal tibia). The ultimate finding was that a load of 9N (engendering a tensile strain of 1833 με on medial surface of the midshaft tibia) was able to simultaneously induce measurable lamellar cortical and trabecular bone adaptation
Aeroelasticity of Axially Loaded Aerodynamic Structures for Truss-Braced Wing Aircraft
Nguyen, Nhan; Ting, Eric; Lebofsky, Sonia
2015-01-01
This paper presents an aeroelastic finite-element formulation for axially loaded aerodynamic structures. The presence of axial loading causes the bending and torsional sitffnesses to change. For aircraft with axially loaded structures such as the truss-braced wing aircraft, the aeroelastic behaviors of such structures are nonlinear and depend on the aerodynamic loading exerted on these structures. Under axial strain, a tensile force is created which can influence the stiffness of the overall aircraft structure. This tension stiffening is a geometric nonlinear effect that needs to be captured in aeroelastic analyses to better understand the behaviors of these types of aircraft structures. A frequency analysis of a rotating blade structure is performed to demonstrate the analytical method. A flutter analysis of a truss-braced wing aircraft is performed to analyze the effect of geometric nonlinear effect of tension stiffening on the flutter speed. The results show that the geometric nonlinear tension stiffening effect can have a significant impact on the flutter speed prediction. In general, increased wing loading results in an increase in the flutter speed. The study illustrates the importance of accounting for the geometric nonlinear tension stiffening effect in analyzing the truss-braced wing aircraft.
Polymeric complex micelle loaded with axially substituted silicon(Ⅳ) phthalocyanine
Institute of Scientific and Technical Information of China (English)
Bao Quan Huang
2009-01-01
A novel axially substituted silicon(IV) phthalocyanine,namely di-pyridyloxy axially substituted silicon(Ⅳ) phthalocyanine 2 was synthesized and characterized by UV/vis,IR,elemental analysis,MS as well as 1H NMR spectroscopy.Hydrophobic 2 was encapsulated by amphiphilic triblock copolymer poly[Nε-(benzyloxycarbonyl-lysine]-poly(ethylene glycol)-poly [Nε-(benzyl oxycarbonyl) (PLL(Z)-b-PEG-b-PLL(Z)) to form hydrophobic 2-loaded polymeric complex miceile (PIC) (2-loaded PIC).Atom force microscopy (AFM) image showed that 2-loaded PIC formed a spherical nanocarrier with approximately 35-50 nm in diameter.The fluorescence intensity and lifetime of 2-loaded PIC was significantly enhanced by the incorporation 2 into PIC nanocarrier.
Hérisson, Benjamin; Challamel, Noël; Picandet, Vincent; Perrot, Arnaud
2016-09-01
The static behavior of the Fermi-Pasta-Ulam (FPU) axial chain under distributed loading is examined. The FPU system examined in the paper is a nonlinear elastic lattice with linear and quadratic spring interaction. A dimensionless parameter controls the possible loss of convexity of the associated quadratic and cubic energy. Exact analytical solutions based on Hurwitz zeta functions are developed in presence of linear static loading. It is shown that this nonlinear lattice possesses scale effects and possible localization properties in the absence of energy convexity. A continuous approach is then developed to capture the main phenomena observed regarding the discrete axial problem. The associated continuum is built from a continualization procedure that is mainly based on the asymptotic expansion of the difference operators involved in the lattice problem. This associated continuum is an enriched gradient-based or nonlocal axial medium. A Taylor-based and a rational differential method are both considered in the continualization procedures to approximate the FPU lattice response. The Padé approximant used in the continualization procedure fits the response of the discrete system efficiently, even in the vicinity of the limit load when the non-convex FPU energy is examined. It is concluded that the FPU lattice system behaves as a nonlocal axial system in dynamic but also static loading.
Energy Technology Data Exchange (ETDEWEB)
Zhang, Chaobi; Chen, Jian Yun; Xu, Qiang; Li, Jing [School of Civil and Hydraulic Engineering, Dalian University of Technology, Dalian (China)
2015-08-15
In order to analyze the mechanical properties of two-way different configurations of prestressed concrete members subjected to axial loading, a finite element model based on the nuclear power plant containments is demonstrated. This model takes into account the influences of different principal stress directions, the uniaxial or biaxial loading, and biaxial loading ratio. The displacement-controlled load is applied to obtain the stress-strain response. The simulated results indicate that the differences of principal stress axes have great effects on the stress-strain response under uniaxial loading. When the specimens are subjected to biaxial loading, the change trend of stress with the increase of loading ratio is obviously different along different layout directions. In addition, correlation experiments and finite element analyses were conducted to verify the validity and reliability of the analysis in this study.
Influence of axial load on the lateral pile groups response in cohesionless and cohesive soil
Institute of Scientific and Technical Information of China (English)
Jasim M. ABBASA[1; Zamri CHIK[2; Mohd Raihan TAHA[2
2015-01-01
The lateral response of single and group of piles under simultaneous vertical and lateral loads has been analyzed using a 3D finite element approach. The response in this assessment considered lateral pile displacement and lateral soil resistance and corresponding p-y curve. As a result, modified p-y curves for lateral single pile response were improved with respect to the influence of increasing axial load intensities. The improved plots can be used for lateral loaded pile design and to produce the group action design p-multiplier curves and equations. The effect of load combination on the lateral pile group response was performed on three pile group configurations （i.e., 2 × 1, 2 × 2 and 3 × 2） with four pile spacings （i.e., s = 2D, 4D, 6D and 8D）. As a result, design curves were developed and applied on the actual case studies and similar expected cases for assessment of pile group behavior using improved p-multiplier. A design equation was derived from predicted design curves to be used in the evaluation of the lateral pile group action taking into account the effect of axial load intensities. It was found that the group interaction effect led to reduced lateral resistance for the pile in the group relative to that for the single pile in case of pure lateral load. While, in case of simultaneous combined loads, large axial load intensities （i.e., more than 6H, where H is lateral load values） will have an increase inp-multiplier by approximately 100% and will consequently contribute to greater group piles capacities.
The multi-axial material fatigue under the combined loading with mean stress in three dimensions
Directory of Open Access Journals (Sweden)
Fojtík F.
2009-12-01
Full Text Available This contribution describes the application of Fuxa's conjugated strength criterion on the experimental results under combined loading of specimens made from common construction steel 11523.0, melt T31052. The specimens were stepwise loaded by the torque amplitude, combination of torque amplitude and tension pre-stress, further by the amplitude of the torque in combination with inner overpressure and axial tension force. The last set of specimens was loaded by the torque amplitude in combination with inner and external overpressure and with axial tension force. To obtain the data required as the input values for the conjugated criterion the stress/strain analysis of the specimens by the finite element method in software ANSYS was performed. The experiments were performed on modified testing machine equipped by overpressure chamber.
Calculation of multi-layer plate damper under one-axial load
Hui, Yan; Lu, Zhang; Hong-Yuan, Jiang; Alexander, M. Ulanov
2016-02-01
A multi-layer damper with waved plates under one-axial load is considered. A method of theoretical calculation of its energy dissipation coefficient is proposed. An experimental research of own frequencies and vibration transfer ratios for different parameters of damper structure, harmonic vibration load and random load is performed. Results of this research are approximated by functions; it is possible to use these functions for the calculation of the damper too. Project supported by the Programme of Introducing Talents of Discipline to Universities (Grant No. B07018).
Mathieson, Haley Aaron
This thesis investigates experimentally and analytically the structural performance of sandwich panels composed of glass fibre reinforced polymer (GFRP) skins and a soft polyurethane foam core, with or without thin GFRP ribs connecting skins. The study includes three main components: (a) out-of-plane bending fatigue, (b) axial compression loading, and (c) in-plane bending of sandwich beams. Fatigue studies included 28 specimens and looked into establishing service life (S-N) curves of sandwich panels without ribs, governed by soft core shear failure and also ribbed panels governed by failure at the rib-skin junction. Additionally, the study compared fatigue life curves of sandwich panels loaded under fully reversed bending conditions (R=-1) with panels cyclically loaded in one direction only (R=0) and established the stiffness degradation characteristics throughout their fatigue life. Mathematical models expressing fatigue life and stiffness degradation curves were calibrated and expanded forms for various loading ratios were developed. Approximate fatigue thresholds of 37% and 23% were determined for non-ribbed panels loaded at R=0 and -1, respectively. Digital imaging techniques showed significant shear contribution significantly (90%) to deflections if no ribs used. Axial loading work included 51 specimens and examined the behavior of panels of various lengths (slenderness ratios), skin thicknesses, and also panels of similar length with various rib configurations. Observed failure modes governing were global buckling, skin wrinkling or skin crushing. In-plane bending involved testing 18 sandwich beams of various shear span-to-depth ratios and skin thicknesses, which failed by skin wrinkling at the compression side. The analytical modeling components of axially loaded panels include; a simple design-oriented analytical failure model and a robust non-linear model capable of predicting the full load-displacement response of axially loaded slender sandwich panels
Vibration analysis of nanomechanical mass sensor using carbon nanotubes under axial tensile loads
Natsuki, Toshiaki; Matsuyama, Nobuhiro; Shi, Jin-Xing; Ni, Qing-Qing
2014-09-01
Carbon nanotubes (CNTs) are nanomaterials with many potential applications due to their excellent mechanical and physical properties. In this paper, we proposed that CNTs with clamped boundary condition under axial tensile loads were considered as CNT-based resonators. Moreover, the resonant frequencies and frequency shifts of the CNTs with attached mass were investigated based on two theoretical methods, which are Euler-Bernoulli beam theory and Rayleigh's energy method. Using the present methods, we analyzed and discussed the effects of the aspect ratio, the concentrated mass and the axial force on the resonant frequency of the CNTs. The results indicate that the length of CNTs could be easily changed and could provide higher sensitivity as nanomechanical mass sensor. Moreover, the resonant frequency shifts of the CNT resonator increase significantly with increasing tensile load acting on the CNTs.
Directory of Open Access Journals (Sweden)
Yijie Huang
2015-01-01
Full Text Available A new mechanical model for analysing the behaviour of axially loaded recycled aggregate concrete filled steel tubes (RACFSTs stub columns is presented in this study. The model is derived from the typical elastoplasticity, the nonlinear elastic mechanics, and the properties of materials. Based on the mechanical model, a novel numerical program is developed. The mechanical model and the numerical program are adopted to study the effect of recycled coarse aggregate (RCA replacement percentage on RACFST mechanical behaviour. The complete load-deformation relationship of specimens, the steel tube axial and circumferential stresses, and the performance of the confined core concrete and the variation of interaction are also investigated. The analytical results indicate that this model is able to capture the mechanical behaviour of RACFST. It is also found that the axial and circumferential stresses of steel tube change nonlinearly during the loading stages. It is concluded that the behaviour of the confined core concrete is significantly influenced by the confining pressure. The steel tube confinement could improve the mechanical behaviour of RAC effectively and the RCA replacement percentage slightly changes the response of core concrete. Finally, the relations between confined core concrete and confining pressure are analysed.
Concrete-Filled-Large Deformable FRP Tubular Columns under Axial Compressive Loading
Directory of Open Access Journals (Sweden)
Omar I. Abdelkarim
2015-10-01
Full Text Available The behavior of concrete-filled fiber tubes (CFFT polymers under axial compressive loading was investigated. Unlike the traditional fiber reinforced polymers (FRP such as carbon, glass, aramid, etc., the FRP tubes in this study were designed using large rupture strains FRP which are made of recycled materials such as plastic bottles; hence, large rupture strain (LRS FRP composites are environmentally friendly and can be used in the context of green construction. This study performed finite element (FE analysis using LS-DYNA software to conduct an extensive parametric study on CFFT. The effects of the FRP confinement ratio, the unconfined concrete compressive strength ( , column size, and column aspect ratio on the behavior of the CFFT under axial compressive loading were investigated during this study. A comparison between the behavior of the CFFTs with LRS-FRP and those with traditional FRP (carbon and glass with a high range of confinement ratios was conducted as well. A new hybrid FRP system combined with traditional and LRS-FRP is proposed. Generally, the CFFTs with LRS-FRP showed remarkable behavior under axial loading in strength and ultimate strain. Equations to estimate the concrete dilation parameter and dilation angle of the CFFTs with LRS-FRP tubes and hybrid FRP tubes are suggested.
Prediction of the critical buckling load of multi-walled carbon nanotubes under axial compression
Timesli, Abdelaziz; Braikat, Bouazza; Jamal, Mohammad; Damil, Noureddine
2017-02-01
In this paper, we propose a new explicit analytical formula of the critical buckling load of double-walled carbon nanotubes (DWCNT) under axial compression. This formula takes into account van der Waals interactions between adjacent tubes and the effect of terms involving tube radii differences generally neglected in the derived expressions of the critical buckling load published in the literature. The elastic multiple Donnell shells continuum approach is employed for modelling the multi-walled carbon nanotubes. The validation of the proposed formula is made by comparison with a numerical solution. The influence of the neglected terms is also studied.
BUCKLING BEHAVIOUR OF SINGLE-WALLED CARBON NANOTUBES UNDER AXIAL LOADING
Directory of Open Access Journals (Sweden)
Grzegorz Litak
2017-03-01
Full Text Available We investigate a single walled Carbon Nanotube under an axially directed compressive line loading applied at both of its edges. The expected buckling behavior we study by application of a molecular computation approach. We formulate a global potential and search for its minimum to obtain the equilibrium configuration. Using besides the main parameter, which is the value of the loading, as second parameter the diameter of the tube, we are able to define the critical value of the diameter, for which we obtain the coincident case of local shell buckling.
Behavior of R/C Cylindrical Panel Subjected to Combined Axial and Shear Loadings
Hara, Takashi
2009-01-01
p. 1722-1730 Reinforced concrete (R/C) cylindrical panels have been applied to the roof or the underground structures. Also, in constructing a high rise building, an R/C wall is often used to improve the lateral rigidity of the building comparing with beam column systems under wind or seismic loading. In this paper, the behavior of R/C cylindrical shell under combined axial and lateral shear loadings is analyzed numerically. R/C cylindrical shells are often adopted for the core wa...
DYNAMIC BUCKLING OF DOUBLE-WALLED CARBON NANOTUBES UNDER STEP AXIAL LOAD
Institute of Scientific and Technical Information of China (English)
Chengqi Sun; Kaixln Liu
2009-01-01
An approximate method is presented in this paper for studying the dynamic buckling of double-walled carbon nanotubes (DWNTs) under step axial load. The analysis is based on the continuum mechanics model, which takes into account the van der Waals interaction between the outer and inner nanotubes. A buckling condition is derived, from which the critical buckling load and associated buckling mode can be determined. As examples, numerical results are worked out for DWNTs under fixed boundary conditions. It is shown that, due to the effect of van der Waals forces, the critical buckling load of a DWNT is enhanced when inserting an inner tube into a single-walled one. The paper indicates that the critical buckling load of DWNTs for dynamic buckling is higher than that for static buckling. The effect of the radii is also examined. In addition, some of the results are compared with the previous ones.
Reassessing the Plastic Hinge Model for Energy Dissipation of Axially Loaded Columns
Directory of Open Access Journals (Sweden)
R. M. Korol
2014-01-01
Full Text Available This paper investigates the energy dissipation potential of axially loaded columns and evaluates the use of a plastic hinge model for analysis of hi-rise building column collapse under extreme loading conditions. The experimental program considered seven axially loaded H-shaped extruded aluminum structural section columns having slenderness ratios that would be typical of floor-to-ceiling heights in buildings. All seven test specimens initially experienced minor-axis overall buckling followed by formation of a plastic hinge at the mid-height region, leading to local buckling of the flanges on the compression side of the plastic hinge, and eventual folding of the compression flanges. The experimental energy absorption, based on load-displacement relations, was compared to the energy estimates based on section plastic moment resistance based on measured yield stress and based on measured hinge rotations. It was found that the theoretical plastic hinge model underestimates a column’s actual ability to absorb energy by a factor in the range of 3 to 4 below that obtained from tests. It was also noted that the realizable hinge rotation is less than 180°. The above observations are based, of course, on actual columns being able to sustain high tensile strains at hinge locations without fracturing.
Parametric Equation of Stress Concentration Factor for Circular X-Joints Under Axial Loads
Institute of Scientific and Technical Information of China (English)
QU Shu-ying; ZHANG Guo-dong; ZHANG Bao-feng; WANG Xin-jian
2007-01-01
In engineering practice,tubular X-joints have been widely used in offshore structures.The fatigue failure of tubular X-joints in offshore engineering is mainly caused by axial tensile stress.In this study,the stress concentration factor distribution along the weld toe in the hot spot stress region for tubular X-joints subject to axial loads have been analyzed by use of finite element method.Through numerical analysis,it has been found that the peak stress concentration factor is located at the saddle position.Thereafter,80 models have been analyzed,and the effect of the geometric parameters of a tubular X-joint on the stress concentration factor has been investigated.Based on the experimental values of the numerical stress concentration factor,a parametric equation to calculate the stress concentration factor of tubular X-joints has been proposed.The accuracy of this equation has been verified against the requirement of the Fatigue Guidance Review Panel,and the proposed equation is found capable of producing reasonably accurate stress concentration factor values for tubular X-joints subject to axial loads.
Strength and Deformation of Axially Loaded Fiber-Reinforced Polymer Sheet Confined Concrete Columns
Institute of Scientific and Technical Information of China (English)
李静; 钱稼茹; 蒋剑彪
2004-01-01
Experimental results of 29 axially loaded fiber-reinforced polymer sheet (FS) confined concrete columns and two reference plain concrete columns are introduced. Twenty four column specimens were confined with carbon fiber sheet (CFS) and five column specimens were hybrid confined with both CFS and glass fiber sheet (GFS). The influence of aspect ratio, FS material, initial axial force ratio, and FS confinement degree on the strength and deformation of columns were studied. Based on the experimental results, the equations of complete stress-strain curve of CFS confined concrete are proposed. These equations are suitable for the nonlinear analysis of square and rectangular section columns. Suggestions of applying FS to confine concrete columns are presented.
Lignos, Dimitrios; Cravero, Julien; Elkady, Ahmed Mohamed Ahmed
2016-01-01
This paper discusses the findings from a large-scale experimental program that characterized the hysteretic behavior of typical steel wide-flange columns in steel moment-resisting frames (MRFs). The test specimens were tested in a cantilever configuration with a fixed point of inflection. The main testing parameters included various lateral and axial loading histories, the applied axial compressive load and the local slenderness of the cross-section. It is shown that (a) steel columns subject...
Lager, J. R.
1975-01-01
A cylindrical shell structure 3.66 m (144 in.) high by 4.57 m (180 in.) diameter was designed using a wide variety of materials and structural concepts to withstand design ultimate combined loading 1225.8 N/cm (700 lb/in.) axial compression and 245.2 N/cm (140 lb/in.) torsion. The overall cylinder geometry and design loading are representative of that expected on a high performance space tug vehicle. The relatively low design load level results in designs that use thin gage metals and fibrous-composite laminates. Fabrication and structural tests of small panels and components representative of many of the candidate designs served to demonstrate proposed fabrication techniques and to verify design and analysis methods. Three of the designs evaluated, honeycomb sandwich with aluminum faceskins, honeycomb sandwich with graphite/epoxy faceskins, and aluminum truss with fiber-glass meteoroid protection layers, were selected for further evaluation.
Salehi-Khojin, Amin; Jalili, Nader
2007-04-01
Unlike widely-used carbon nanotubes, boron nitride nanotubes (BNNTs) have shown to possess stable semiconducting behavior and strong piezoelectricity. Such properties along with their outstanding mechanical properties and thermal conductivity, make BNNTs promising candidate reinforcement materials for a verity of applications especially nanoelectronic and nanophotonic devices. Motivated by these abilities, we aim to study the buckling behavior of BNNT-reinforced piezoelectric polymeric composites when subjected to combined electro-thermo-mechanical loadings. For this, the multi-walled structure of BNNT is considered as elastic media and a set of concentric cylindrical shell with van der Waals interaction between them. Using three-dimensional equilibrium equations, Donnell shell theory is utilized to show that the axially compressive resistance of BNNT varies with applying thermal and electrical loads. The effect of BNNT piezoelectric property on the buckling behavior of the composites is demonstrated. More specifically, it is shown that applying direct and reverse voltages to BNNT changes the buckling loads for any axial and circumferential wavenumbers. Such capability could be uniquely utilized when designing BNNT-reinforced composites.
Dynamic Behaviours of a Single Soft Rock-Socketed Shaft Subjected to Axial Cyclic Loading
Directory of Open Access Journals (Sweden)
Ben-jiao Zhang
2016-01-01
Full Text Available The soft rock was simulated by cement, plaster, sand, water, and concrete hardening accelerator in this paper. Meanwhile, uniaxial compressive strength tests and triaxial compression tests were conducted to study the mechanical properties of simulated soft rock samples. Model tests on a single pile socketed in simulated soft rock under axial cyclic loading were conducted by using a device which combined test apparatus with a GCTS dynamic triaxial system. Test results show that the optimal mix ratio is cement : plaster : medium sand : water : concrete hardening accelerator = 4.5% : 5.0% : 84.71% : 4.75% : 1.04%. The static load ratio (SLR, cyclic load ratio (CLR, and the number of cycles affect the accumulated deformation and cyclic secant modulus of the pile head. The accumulated deformation increases with increasing numbers of cycles. However, the cyclic secant modulus of pile head increases and then decreases with the growth in the number of cycles and finally remains stable after 50 cycles. According to the test results, the development of accumulated settlement was analysed. Finally, an empirical formula for accumulated settlement, considering the effects of the number of cycles, the static load ratio, the cyclic load ratio, and the uniaxial compressive strength, is proposed which can be used for feasibility studies or preliminary design of pile foundations on soft rock subjected to traffic loading.
Test Procedure for Axially Loaded Bucket Foundations in Sand (Large Yellow Box)
DEFF Research Database (Denmark)
Vaitkunaite, Evelina
This is a practical guide for preparing the soil, running a CPT test, installing a scaled bucket foundation model and running a test in the large yellow sand box cos(Kristina) in the geotechnical laboratory at Aalborg University. The test procedure is used for the examination of statically...... and cyclically axially loaded bucket foundation model In dense sand. The foundation model in scale of approximately 1:10 compared to the prototype size. The guide describes the step-by-step procedure for tests with and without surface pressure. A detailed description of test setup using the large yellow sand box...
Stadelmann, Vincent A; Hocke, Jean; Verhelle, Jensen; Forster, Vincent; Merlini, Francesco; Terrier, Alexandre; Pioletti, Dominique P
2009-02-01
A combined experimental/numerical study was performed to calculate the 3D octahedral shear strain map in a mouse tibia loaded axially. This study is motivated by the fact that the bone remodelling analysis, in this in vivo mouse model should be performed at the zone of highest mechanical stimulus to maximise the measured effects. Accordingly, it is proposed that quantification of bone remodelling should be performed at the tibial crest and at the distal diaphysis. The numerical model could also be used to furnish a more subtle analysis as a precise correlation between local strain and local biological response can be obtained with the experimentally validated numerical model.
Tunable Clamped–Guided Arch Resonators Using Electrostatically Induced Axial Loads
Alcheikh, Nouha
2017-01-04
We present a simulation and experimental investigation of bi-directional tunable in-plane clamped-guided arch microbeam resonators. Tensile and compressive axial forces are generated from a bi-directional electrostatic actuator, which modulates the microbeam stiffness, and hence changes its natural frequency to lower or higher values from its as-fabricated value. Several devices of various anchor designs and geometries are fabricated. We found that for the fabricated shallow arches, the effect of the curvature of the arch is less important compared to the induced axial stress from the axial load. We have shown that the first mode resonance frequency can be increased up to twice its initial value. Additionally, the third mode resonance frequency can be increased up to 30% of its initial value. These results can be promising as a proof-of-concept for the realization of wide-range tunable microresonators. The experimental results have been compared to finite-element simulations, showing good agreement among them.
The flow field investigations of no load conditions in axial flow fixed-blade turbine
Yang, J.; Gao, L.; Wang, Z. W.; Zhou, X. Z.; Xu, H. X.
2014-03-01
During the start-up process, the strong instabilities happened at no load operation in a low head axial flow fixed-blade turbine, with strong pressure pulsation and vibration. The rated speed can not reach until guide vane opening to some extent, and stable operation could not be maintained under the rated speed at some head, which had a negative impact on the grid-connected operation of the unit. In order to find the reason of this phenomenon, the unsteady flow field of the whole flow passage at no load conditions was carried out to analyze the detailed fluid field characteristics including the pressure pulsation and force imposed on the runner under three typical heads. The main hydraulic cause of no load conditions instability was described. It is recommended that the power station should try to reduce the no-load running time and go into the high load operation as soon as possible when connected to grid at the rated head. Following the recommendations, the plant operation practice proved the unstable degree of the unit was reduced greatly during start up and connect to the power grid.
Directory of Open Access Journals (Sweden)
Rabee Shamass
2015-01-01
Full Text Available A large number of authors in the past have concluded that the flow theory of plasticity tends to overestimate significantly the buckling load for many problems of plates and shells in the plastic range, while the deformation theory generally provides much more accurate predictions and is consequently used in practical applications. Following previous numerical studies by the same authors focused on axially compressed cylinders, the present work presents an analytical investigation which comprises the broader and different case of nonproportional loading. The analytical results are discussed and compared with experimental and numerical findings and the reason for the apparent discrepancy on the basis of the so-called “buckling paradox” appears once again to lay in the overconstrained kinematics on the basis of the analytical and numerical approaches present in the literature.
On the performance of circular concrete-filled high strength steel columns under axial loading
Directory of Open Access Journals (Sweden)
Mohamed Mahmoud El-Heweity
2012-06-01
Full Text Available This work presents a numerical study to investigate the performance of circular high-strength steel tubes filled with concrete (CFT under monotonic axial loading. A model is developed to implement the material constitutive relationships and non-linearity. Calibration against previous experimental data shows good agreement. A parametric study is then conducted using the model and compared with codes provisions. Strength and ductility of confined concrete are of primary concern. Variables considered are yield stress of steel tube and column diameter. The assessment of column performance is based on axial load carrying capacities and enhancements of both strength and ductility due to confinement. Two parameters namely strength enhancement factor (Kf and ductility index (μ are clearly defined and introduced for assessment. Results indicate that both concrete strength and ductility of CFT columns are enhanced but to different extents. The ductile behaviors are significantly evident. The increase in yield stress of steel tube has a minimal effect on concrete strength but pronounced effect on concrete ductility. However, reduction in ductility is associated with using high-tensile steel of Grade 70. The overall findings indicate that the use of high-strength tube in CFT columns is not promising. This finding may seriously be considered in seismic design.
Operating characteristics of heavy loaded cylindrical journal bearing with variable axial profile
Directory of Open Access Journals (Sweden)
Stanislaw Strzelecki
2005-12-01
Full Text Available During the operation of turbounit its bearings displace as a result of heat elongation of bearings supports. It changes the static deflection line of rotor determined during assembly of the turbounit, causing an increase in the stresses on the bearing edges and a decrease in the dynamic state of the machine. One of possibilities to avoid the edge stresses is to apply the bearings with variable axial profile, e.g. hyperboloidal, convex profile in the axial cross-section of bearing. Application of journal bearings with hyperboloidal profile allows to extend the bearing operation range without the stress concentration on the edges of bush. These bearings successfully carry the extreme load in conditions of misaligned axis of journal and the bush eliminating the necessity of using self-aligning bearings. Operating characteristics of bearing include the resulting force, attitude angle, oil film pressure and temperature distributions, minimum oil film thickness, maximum oil film temperature. In literature there is a lack of data on the operating characteristics of heavy loaded hyperboloidal journal bearings operating at the conditions of adiabatic oil film and static equilibrium position of the journal. For the hyperboloidal bearing the operating characteristics have been obtained. Different values of length to diameter ratio, assumed shape and inclination ratio coefficients have been assumed. Iterative solution of the Reynolds', energy and viscosity equations was applied. Adiabatic oil film, laminar flow in the bearing gap as well as aligned and misaligned orientation of journal in the bush were considered.
Effect of Axial Pre-Compression on Lateral Performance of Masonry Under Cyclic Loading
Directory of Open Access Journals (Sweden)
Syed HassanFarooq
2011-10-01
Full Text Available Strengthening of masonry against seismic events is very essential and getting maximum attention of researchers around the globe. An extensive experimental program was carried out to study the in-plane lateral performance of un-reinforced masonry, strengthened and retrofitted masonry wall panels under lateral cyclic loading. Twenty tests were carried out; four tests under monotonic lateral loading, twelve tests under static cyclic loading and four tests under pure compression. The test results were analyzed in five groups and this paper presents the analysis of group 4, which deals with effect of axial pre-compression on masonry seismic performance. Three single leaf panels with aspect ratio of 0.67 having size 1.65x1.1m were constructed using same material and workmanship. All the three un-reinforced walls were tested under 0, 0.5 and 1.0MPa vertical pre-compression and displacement controlled static cyclic loading. The wall tested under 0.5MPa pre-compression was reference specimen. The key parameters studied were hysterics behavior, peak lateral load, ultimate lateral displacement, energy dissipation, ductility, response factor and damping ratio. It was observed that level of axial pre-compression has significant effect on lateral capacity, failure mode and performance of masonry. In case of zero pre-compression the lateral capacity was very less and wall went into rocking failure at early stages of loading. Increase in pre-compression to 1.0MPa enhanced the lateral capacity by a factor of 1.92 times. After analysis of test results, it is found that pre-compression has significant effect on lateral capacity, failure mode and performance of masonry. In case of zero pre-compression the lateral capacity was very less and wall went into rocking failure at early stages of loading. Increase in pre-compression to 1.0MPa enhanced the lateral capacity by a factor of 1.92 times. After analysis of test results, it is found that pre-compression has very
Institute of Scientific and Technical Information of China (English)
Youtang Li; Shuai Tan; Hongyan Duan
2008-01-01
The extra-low cyclic fracture problem of medium carbon steel under axial fatigue loading was investigated.Several problems,such as the relations of the cycle times to the depth and tip radius of the notch,loading frequency,loading range and the parameters of fracture design for medium carbon steel on condition of extra-low axial fatigue loading were discussed based on the experiments.Experimental results indicated that the tension-pressure fatigue loading mode was suitable for extra-low cyclic fatigue fracture design of medium carbon steel and it resulted in low energy consumption,fracture surface with high quality,low cycle times,and high efficiency.The appropriate parameters were as follows:loading frequency 3-5 Hz,notch tip radius r=(0.2-0.3)mm,opening angle α=60°,and notch depth t=(0.14-0.17)D.
The effect of variable stator on performance of a highly loaded tandem axial flow compressor stage
Eshraghi, Hamzeh; Boroomand, Masoud; Tousi, Abolghasem M.; Fallah, Mohammad Toude; Mohammadi, Ali
2016-06-01
Increasing the aerodynamic load on compressor blades helps to obtain a higher pressure ratio in lower rotational speeds. Considering the high aerodynamic load effects and structural concerns in the design process, it is possible to obtain higher pressure ratios compared to conventional compressors. However, it must be noted that imposing higher aerodynamic loads results in higher loss coefficients and deteriorates the overall performance. To avoid the loss increase, the boundary layer quality must be studied carefully over the blade suction surface. Employment of advanced shaped airfoils (like CDAs), slotted blades or other boundary layer control methods has helped the designers to use higher aerodynamic loads on compressor blades. Tandem cascade is a passive boundary layer control method, which is based on using the flow momentum to control the boundary layer on the suction surface and also to avoid the probable separation caused by higher aerodynamic loads. In fact, the front pressure side flow momentum helps to compensate the positive pressure gradient over the aft blade's suction side. Also, in comparison to the single blade stators, tandem variable stators have more degrees of freedom, and this issue increases the possibility of finding enhanced conditions in the compressor off-design performance. In the current study, a 3D design procedure for an axial flow tandem compressor stage has been applied to design a highly loaded stage. Following, this design is numerically investigated using a CFD code and the stage characteristic map is reported. Also, the effect of various stator stagger angles on the compressor performance and especially on the compressor surge margin has been discussed. To validate the CFD method, another known compressor stage is presented and its performance is numerically investigated and the results are compared with available experimental results.
The Effect of Variable Stator on Performance of a Highly Loaded Tandem Axial Flow Compressor Stage
Institute of Scientific and Technical Information of China (English)
Hamzeh Eshraghi; Masoud Boroomand; Abolghasem M.Tousi; Mohammad Toude Fallah; Ali Mohammadi
2016-01-01
Increasing the aerodynamic load on compressor blades helps to obtain a higher pressure ratio in lower rotational speeds.Considering the high aerodynamic load effects and structural concerns in the design process,it is possible to obtain higher pressure ratios compared to conventional compressors.However,it must be noted that imposing higher aerodynamic loads results in higher loss coefficients and deteriorates the overall performance.To avoid the loss increase,the boundary layer quality must be studied carefully over the blade suction surface.Employment of advanced shaped airfoils (like CDAs),slotted blades or other boundary layer control methods has helped the designers to use higher aerodynamic loads on compressor blades.Tandem cascade is a passive boundary layer control method,which is based on using the flow momentum to control the boundary layer on the suction surface and also to avoid the probable separation caused by higher aerodynamic loads.In fact,the front pressure side flow momentum helps to compensate the positive pressure gradient over the aft blade's suction side.Also,in comparison to the single blade stators,tandem variable stators have more degrees of freedom,and this issue increases the possibility of finding enhanced conditions in the compressor off-design performance.In the current study,a 3D design procedure for an axial flow tandem compressor stage has been applied to design a highly loaded stage.Following,this design is numerically investigated using a CFD code and the stage characteristic map is reported.Also,the effect of various stator stagger angles on the compressor performance and especially on the compressor surge margin has been discussed.To validate the CFD method,another known compressor stage is presented and its performance is numerically investigated and the results are compared with available experimental results.
Multisized Inert Particle Loading for Solid Rocket Axial Combustion Instability Suppression
Directory of Open Access Journals (Sweden)
David R. Greatrix
2012-01-01
Full Text Available In the present investigation, various factors and trends, related to the usage of two or more sets of inert particles comprised of the same material (nominally aluminum but at different diameters for the suppression of axial shock wave development, are numerically predicted for a composite-propellant cylindrical-grain solid rocket motor. The limit pressure wave magnitudes at a later reference time in a given pulsed firing simulation run are collected for a series of runs at different particle sizes and loading distributions and mapped onto corresponding attenuation trend charts. The inert particles’ presence in the central core flow is demonstrated to be an effective means of instability symptom suppression, in correlating with past experimental successes in the usage of particles. However, the predicted results of this study suggest that one needs to be careful when selecting more than one size of particle for a given motor application.
Wave dispersion characteristics of axially loaded magneto-electro-elastic nanobeams
Ebrahimi, Farzad; Barati, Mohammad Reza; Dabbagh, Ali
2016-11-01
The analysis of wave propagation behavior of a magneto-electro-elastic functionally graded (MEE-FG) nanobeam is performed in the framework of classical beam theory. To capture small-scale effects, the nonlocal elasticity theory of Eringen is applied. Furthermore, the material properties of nanobeam are assumed to vary gradually through the thickness based on power-law form. Nonlocal governing equations of MEE-FG nanobeam have been derived employing Hamilton's principle. The results of present research have been validated by comparing with those of previous investigations. An analytical solution of governing equations is utilized to obtain wave frequencies, phase velocities and escape frequencies. Effects of various parameters such as wave number, nonlocal parameter, gradient index, axial load, magnetic potential and electric voltage on wave dispersion characteristics of MEE-FG nanoscale beams are studied in detail.
Directory of Open Access Journals (Sweden)
Fouad Khairallah
2013-12-01
Full Text Available While there is abundant research information on ordinary confined concrete, there are little data on the behavior of Self-Compacting Concrete (SCC under such condition. Due to higher shrinkage and lower coarse aggregate content of SCC compared to that of Normal Concrete (NC, its composite performance under confined conditions needs more investigation. This paper has been devoted to investigate and compare the mechanical behavior of confined concrete circular columns cast with SCC and NC under concentric axial loading. The parameters affecting are including concrete compressive strength and confinement configuration. Twenty column specimens were casted and confined using four confinement techniques, CFRP wrap, FRP tube, GFRP wrap, and spiral steel hoops. The performance of the tested column specimens is evaluated based on mode of failure, load–displacement curve, stress–strain characteristics, ultimate strength, ductility, and degree of confinement.
Simulating of marble subjected to uni-axial loading using index-parabola damage model
Institute of Scientific and Technical Information of China (English)
温世游; 李夕兵; 骆达成
2001-01-01
The limitations of several existing classical rock damage models were critically appraised. Thereafter, a description of a new model to estimate the response of rock was provided. The results of an investigation lead to the development and confirmation of a new index-parabola damage model. The new model is divided into two parts, fictitious damage and real damage and bordered by the critical damage point. In fictitious damage, the damage variable follows the index distribution, while in the real damage a parabolic distribution is used. Thus, the so-called index-parabola damage model is derived. The proposed damage model is applied to simulate the damage procedure of marble under uni-axial loading. The results of the tests show that the proposed model is in excellent agreement with experimental data, in particular the nonlinear characteristic of rock deformation is adequately represented.
Hyer, M. W.; Paraska, P. J.
1990-01-01
The study focuses on the axisymmetric deformation response of unsymmetrically laminate cylinders loaded in axial compression by known loads. A geometrically nonlinear analysis is used. Though buckling is not studied, the deformations can be considered to be the prebuckling response. Attention is directed at three 16 layer laminates: a (90 sub 8/0 sub 8) sub T; a (0 sub 8/90 sub 8) sub T and a (0/90) sub 4s. The symmetric laminate is used as a basis for comparison, while the two unsymmetric laminates were chosen because they have equal but opposite bending-stretching effects. Particular attention is given to the influence of the thermally-induced preloading deformations that accompany the cool-down of any unsymmetric laminate from the consolidation temperature. Simple support and clamped boundary conditions are considered. It is concluded that: (1) The radial deformations of an unsymmetric laminate are significantly larger than the radial deformations of a symmetric laminate, although for both symmetric and unsymmetric laminates the large deformations are confined to a boundary layer near the ends of the cylinder; (2) For this nonlinear problem the length of the boundary layer is a function of the applied load; (3) The sign of the radial deformations near the supported end of the cylinder depends strongly on the sense (sign) of the laminate asymmetry; (4) For unsymmetric laminates, ignoring the thermally-induced preloading deformations that accompany cool-down results in load-induced deformations that are under predicted; and (5) The support conditions strongly influence the response but the influence of the sense of asymmetry and the influence of the thermally-induced preloading deformations are independent of the support conditions.
Directory of Open Access Journals (Sweden)
Branimir Pavić
2012-10-01
Full Text Available The design of intermediate shaft with axially movablesplined joint must be adapted to the variable position of theshaft axis, i.e. to the change of the joint angle during operation.This design is also used for the reduction of axial forces whichare caused by inaccuracy in the production and assembling ofC(ll·dan mechanisms. The axial force which is generated by frictionof contact swfaces in the splined joint is the function of themagnitude of the transfeJTed torsion moments, splined dimensions,lubrication conditions, and materials used for contactswfaces. It will cause additional bearing loads at cross journalsand in the shaft supports, as well as unallowed vibrations andnoise during operation, thus affecting the safety and lifetime ofthe Cardan mechanism. The theoretical and empirical analysisof Cm·dan mechanisms, which have been studied with andwithout axial forces in the splinedjoint and its effect on durabilityof mechanism elements have been presented.
A Developed Methodology in Design of Highly Loaded Tandem Axial Flow Compressor Stage
Directory of Open Access Journals (Sweden)
Masoud Boroomand
2016-01-01
Full Text Available This study, primarily reports the development of a 3D design procedure for axial flow tandem compressor stages and then the method is used to design a highly loaded tandem stage. In order to investigate the effects of such arrangement, another stage with conventional loading with single blade for both rotor and stator rows is designed with similar specification. In order to ease the comparison of results, chord lengths and hub/shroud geometries are selected with the same dimensions. At the next stage a three dimensional numerical model is developed to predict the characteristic performance of both tandem and conventional stages. The model is validated with the experimental results of NASA-67 stage and the level of the accuracy of the model is presented. Employing the model to simulate the performance of both stages at design and offdesign operating points show that, tandem stage can provide higher pressure ratio with acceptable efficiency. In another word, tandem stage is capable having the same pressure ratio at lower rotational speed. The safe operation domain and loss mechanism in tandem stage are also discussed in this report.
Fan Yang; Hao-ru Zhao; Chao Liu
2016-01-01
In order to investigate the influence of adjustable outlet guide vane on the hydraulic performance of axial-flow pump at part loads, the axial-flow pump with 7 different outlet guide vane adjustable angles was simulated based on the RNG k-ε turbulent model and Reynolds time-averaged equations. The Vector graphs of airfoil flow were analyzed in the different operating conditions for different adjustable angles of guide vane. BP-ANN prediction model was established about the effect of adjustabl...
Institute of Scientific and Technical Information of China (English)
Jiang Songqing; Li Yongchi; Hu Xiuzhang; Zheng Jijia
2000-01-01
The Initial Imperfection Amplified Criterion is applied to investigate the geometric nonlinear dynamic buckling of statically preloaded ring-stiffened cylindrical shells under axial fluid-solid impact. Tak ing account of the effects of large deformation and initial geometric imperfection, the governing equations are obtained by the Galerkin method and solved by the Runge-Kutta method. The effects of static preloading (uniform external radial pressure) on the buckling features and the load-carrying ability of ring-stiffened cy lindrical shells against axial impact are discussed.
Flow performance of highly loaded axial fan with bowed rotor blades
Chen, L.; Liu, X. J.; Yang, A. L.; Dai, R.
2013-12-01
In this paper, a partial bowed rotor blade was proposed for a newly designed high loaded axial fan. The blade was positively bowed 30 degrees from hub to 30 percent spanwise position. Flows of radial blade and bowed blade fans were numerically compared for various operation conditions. Results show that the fan's performance is improved. At the designed condition with flow coefficient of 0.52, the efficiency of the bowed blade fan is increased 1.44% and the static pressure rise is increased 11%. Comparing the flow structures, it can be found that the separated flow in the bowed fan is reduced and confined within 20 percent span, which is less than the 35 percent in the radial fan. It means that the bowed blade generates negative blade force and counteracts partial centrifugal force. It is alleviates the radial movements of boundary layers in fan's hub region. Flow losses due to 3D mixing are reduced in the rotor. Inlet flow to downstream stator is also improved.
Elastic Plastic Stress Distributions in Weld-bonded Lap Joint under Axial Loading
Directory of Open Access Journals (Sweden)
Essam A. Al-Bahkali
2014-06-01
Full Text Available Weld-bonding process is increasingly used in many industries such like automobile and aerospace. It offers significant improvements of sheet metal joints in static, dynamic, corrosion, noise resistance, stiffness and impact toughness properties. A full understanding of this process, including the elastic-plastic stress distribution in the joint, is a must for joints design and automation of manufacturing. Also, the modelling and analysis of this process, though it is complex, proves to be of prime importance. Thus, in this study a systematic experimental and theoretical study employing Finite Element Analysis (FEA is conducted on the weld-bonded joint, fabricated from Austenitic Stainless steel (AISI 304 sheets of 1.00 mm thickness and Epoxy adhesive Araldite 2011, subjected to axial loading. Complete 3-D finite element models are developed to evaluate the normal, shear and triaxial Von Mises stresses distributions across the entire joint, in both the elastic and plastic regions. The, needed quantities and properties, for the FE modelling and analysis, of the base metals and the adhesive, such like the elastic-plastic properties, modulus of elasticity, fracture limit, the nugget and Heat Affected Zones (HAZ properties, etc., are obtained from the experiments. The stress distribution curves obtained are found to be consistent with those obtained from the FE models and in excellent agreement with the experimental and theoretical published data, particularly in the elastic region. Furthermore, the stress distribution curves obtained for the weld-bonded joint display the best uniform smooth distribution curves compared to those obtained for the spot and bonded joint cases. The stress concentration peaks at the edges of the weld-bonded region, are almost eliminated resulting in achieving the strongest joint.
DEFF Research Database (Denmark)
Madsen, Rasmus; Jensen, Tue Secher; Pope, Malcolm;
2007-01-01
STUDY DESIGN: A method comparison study. OBJECTIVE: To investigate the effect of body position and axial load of the lumbar spine on disc height, lumbar lordosis, and dural sac cross-sectional area (DCSA). SUMMARY OF BACKGROUND DATA.: The effects of flexion and extension on spinal canal diameters...... imaging (MRI) scans were performed during upright standing and supine positions with and without axial load. In section 2, MRI scans were performed exclusively in supine positions, one with flexion of the lumbar spine (psoas-relaxed position), an extended position (legs straight), and an extended position...... of precautions taken to secure immobility during the vertical scans. This seemingly makes our standing posture less valuable as a standard of reference. In section 2, DCSA was reduced at all 5 lumbar levels after extension, and further reduced at 2 levels after adding compression (P
Moiseev, Yu B
2014-01-01
The study was concerned with the human spinal column reaction to axial static and dynamic loading. Fresh segments of the column from dorsal vertebra XI to lumber vertebra II were exposed to axial static (20 mm/min) and dynamic (200 and 500 mm/min) loading. Measured variables included load value, whole segment deformation, anterior surfaces of intervertebral disk Th(XI)-Th(XII) and dorsal vertebra XII, and acoustic emission signals indicative of spongy bone microdestruction. It was found that vertebral body deformation augmented less in comparison with the intervertebral disk and that central parts of the spinal end plates compress greater than peripheral. This difference was more considerable due to static loading rather than dynamic. To produce deformation of a spinal segment by dynamic loading same as by the static one, it is necessary to overcome a stronger resistance of a larger number of trabecular bones. Herefrom it follows that, first, to cause an equal segment compression the dynamic load must be heavier than static and, which is of paramount practical significance, dynamic strength of the column is markedly higher than static. Secondly, spinal stiffness during impact is higher as compared with the static condition. Thirdly, same degree of deformation due to dynamic loading should result in a larger volume of microdestructions comparing with static loading, which is testified by a reliable difference in the number of AE signals accumulated prior to fracture. The number of AE signals amounts to 444.2 ± 308.2 and 85.0 ± 36.6 in case of the dynamic and static loading, respectively (p < 0.05 according to Student's t-criterion).
Directory of Open Access Journals (Sweden)
Nicolae APOSTOLESCU
2013-03-01
Full Text Available This work describes a computer application to calculate the values of the factors which are used to determine the tensile rupture load of a lug under axial, transverse or oblique loading. It can be used as a procedure for identifying potential failure modes. Lugs are connector-type elements widely used as structural supports for pin connections in aerospace industry. Failure modes in lugs are functions of lug geometry and material mechanical properties. For a lug under axial load three modes of lug failure are considered: tension, shear and bearing. Under transverse load the load to cause rupture or unacceptable permanent deformation of the lug is given. Tension mode failure usually occurs in materials of low ductility. In materials with high ductility, the failure mode of a lug can be either tensile or shear tear-out, depending on the lug geometry. The application has a graphical interface that allows the user to use them with much ease and view immediately the results and provides a flexible ad-hoc print reports and diagrams that allow to present analysis information. It includes Microsoft Excel Object Library as reference to the Excel material properties file.
Directory of Open Access Journals (Sweden)
Achillopoulou Dimitra
2014-12-01
Full Text Available The study deals with the investigation of the effect of casting deficiencies- both experimentally and analytically on axial yield load or reinforced concrete columns. It includes 6 specimens of square section (150x150x500 mm of 24.37 MPa nominal concrete strength with 4 longitudinal steel bars of 8 mm (500 MPa nominal strength with confinement ratio ωc=0.15. Through casting procedure the necessary provisions defined by International Standards were not applied strictly in order to create construction deficiencies. These deficiencies are quantified geometrically without the use of expensive and expertise non-destructive methods and their effect on the axial load capacity of the concrete columns is calibrated trough a novel and simplified prediction model extracted by an experimental and analytical investigation that included 6 specimens. It is concluded that: a even with suitable repair, load reduction up to 22% is the outcome of the initial construction damage presence, b the lower dispersion is noted for the section damage index proposed, c extended damage alters the failure mode to brittle accompanied with longitudinal bars buckling, d the proposed model presents more than satisfying results to the load capacity prediction of repaired columns.
Lorenz, Andrea; Rothstock, Stephan; Bobrowitsch, Evgenij; Beck, Alexander; Gruhler, Gerhard; Ipach, Ingmar; Leichtle, Ulf G; Wülker, Nikolaus; Walter, Christian
2013-05-31
Cartilage defects and osteoarthritis (OA) have an increasing incidence in the aging population. A wide range of treatment options are available. The introduction of each new treatment requires controlled, evidence based, histological and biomechanical studies to identify potential benefits. Especially for the biomechanical testing there is a lack of established methods which combine a physiologic testing environment of complete joints with the possibility of body-weight simulation. The current in-vitro study presents a new method for the measurement of friction properties of cartilage on cartilage in its individual joint environment including the synovial fluid. Seven sheep knee joints were cyclically flexed and extended under constant axial load with intact joint capsule using a 6° of freedom robotic system. During the cyclic motion, the flexion angle and the respective torque were recorded and the dissipated energy was calculated. Different mechanically induced cartilage defect sizes (16 mm², 50 mm², 200 mm²) were examined and compared to the intact situation at varying levels of the axial load. The introduced setup could significantly distinguish between most of the defect sizes for all load levels above 200 N. For these higher load levels, a high reproducibility was achieved (coefficient of variation between 4% and 17%). The proposed method simulates a natural environment for the analysis of cartilage on cartilage friction properties and is able to differentiate between different cartilage defect sizes. Therefore, it is considered as an innovative method for the testing of new treatment options for cartilage defects.
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Dilipkumar Bhanudasji Alone
2014-01-01
Full Text Available This paper presents experimental results of a single stage transonic axial flow compressor coupled with low porosity bend skewed casing treatment. The casing treatment has a plenum chamber above the bend slots. The depth of the plenum chamber is varied to understand its impact on the performance of compressor stage. The performance of the compressor stage is evaluated for casing treatment and plenum chamber configurations at two axial locations of 20% and 40%. Experimental results reveal that the stall margin of the compressor stage increases with increase in the plenum chamber volume. Hot-wire measurements show significant reduction in the turbulence intensity with increase in the plenum chamber volume compared to that with the solid casing at the stall condition. At higher operating speeds of 80% and at 20% axial coverage, the stall margin of the compressor increases by 20% with half and full plenum depth. The improvement in the peak stage efficiency observed is 4.6% with half plenum configuration and 3.34% with the full plenum configuration. The maximum improvement in the stall margin of 29.16% is obtained at 50% operating speed with full plenum configurations at 40% axial coverage.
Impact of Periodic Unsteadiness on Performance and Heat Load in Axial Flow Turbomachines
Sharma, Om P.; Stetson, Gary M.; Daniels, William A,; Greitzer, Edward M.; Blair, Michael F.; Dring, Robert P.
1997-01-01
Results of an analytical and experimental investigation, directed at the understanding of the impact of periodic unsteadiness on the time-averaged flows in axial flow turbomachines, are presented. Analysis of available experimental data, from a large-scale rotating rig (LSRR) (low speed rig), shows that in the time-averaged axisymmetric equations the magnitude of the terms representing the effect of periodic unsteadiness (deterministic stresses) are as large or larger than those due to random unsteadiness (turbulence). Numerical experiments, conducted to highlight physical mechanisms associated with the migration of combustor generated hot-streaks in turbine rotors, indicated that the effect can be simulated by accounting for deterministic stress like terms in the time-averaged mass and energy conservation equations. The experimental portion of this program shows that the aerodynamic loss for the second stator in a 1-1/2 stage turbine are influenced by the axial spacing between the second stator leading edge and the rotor trailing edge. However, the axial spacing has little impact on the heat transfer coefficient. These performance changes are believed to be associated with the change in deterministic stress at the inlet to the second stator. Data were also acquired to quantify the impact of indexing the first stator relative to the second stator. For the range of parameters examined, this effect was found to be of the same order as the effect of axial spacing.
Kiani, Keivan
2015-11-01
This study is devoted to examine load-bearing capacity of a nanosystem composed of two adjacent perpendicular single-walled carbon nanotubes (SWCNTs) which are embedded in an elastic matrix. Accounting for the nonlocality and the intertube van der Waals forces, the governing equations are established based on the nonlocal Euler-Bernoulli, Timoshenko, and higher-order beam theories. These are sets of coupled integro-ordinary differential equations whose analytical solutions are unavailable. Hence, an efficient meshless methodology is proposed and the discrete governing equations are obtained via Galerkin approach. By solving the resulting set of eigenvalue equations, the axial buckling load of the elastically embedded nanosystem is evaluated. The roles of the radius and slenderness ratio of the constitutive SWCNTs, free distance between two tubes, small-scale parameter, aspect ratio, transverse and rotational stiffness of the surrounding matrix on the axial buckling load of the nanosystem are comprehensively addressed. The obtained results can be regarded as a pivotal step for better understanding the mechanism of elastic buckling of more complex systems such as elastically embedded-orthogonal membranes or even forests of SWCNTs.
Nijhuis, A; Rolando, G
2011-01-01
The ITER cable-in-conduit conductors (CICCs) are built up from sub-cable bundles, wound in different stages, which are twisted to counter coupling loss caused by time-changing external magnet fields. The selection of the twist pitch lengths has major implications for the performance of the cable in the case of strain sensitive superconductors, i.e. Nb3Sn, as the electromagnetic and thermal contraction loads are large but also for the heat load from the AC coupling loss. Reduction of the transverse load and warm-up cool-down degradation can be reached by applying longer twist pitches in a particular sequence for the sub-stages, offering a large cable transverse stiffness, adequate axial flexibility and maximum allowed lateral strand support. Analysis of short sample (TF conductor) data reveals that increasing the twist pitch can lead to a gain of the effective axial compressive strain of more than 0.3 % with practically no degradation from bending. For reduction of the coupling loss, specific choices of the ca...
Dynamic stability of slender columns with semi-rigid connections under periodic axial load: theory
Directory of Open Access Journals (Sweden)
Oliver Giraldo-Londoño
2014-01-01
Full Text Available La estabilidad dinámica de una columna elástica prismática esbelta con conexiones semirrígidas en ambos extremos de rigidez idéntica y con desplazamiento lateral entre los dos extremos totalmente inhibido sujetos a cargas axiales paramétricos incluyendo los efectos combinados de inercia rotacional y amortiguación externas se investiga de una manera clásica. Expresiones cerradas que se pueden utilizar para predecir las regiones de inestabilidad dinámica de columnas esbeltas son desarrolladas haciendo uso de la teoría de Floquet. La solución propuesta es capaz de capturar el fenómeno de estabilidad en columnas sometidas a cargas axiales periódicas utilizando un solo elemento de columna. El método propuesto y las ecuaciones correspondientes se pueden utilizar para investigar los efectos del amortiguamiento, la inercia rotacional de la columna, y las conexiones semirrígidas en el análisis de estabilidad de columnas esbeltas sometidas a cargas axiales periódicas. Los efectos producidos por las deformaciones por cizallamiento a lo largo de la columna, así como los producidos por la inercia axial, el acoplamiento entre las deflexiones longitudinales y transversales y la curvatura no se tienen en cuenta. Estudios de sensibilidad que muestran los efectos de la inercia rotacional, el amortiguamiento y las conexiones semi-rígidas en la estabilidad dinámica de columnas sometidas a cargas axiales paramétricas son presentados en una publicación adjunta.
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Abdellatif Khamlichi
2010-01-01
Full Text Available Problem statement: Many modern structures are made from thin shells. Design of these elements depends to a large extent on their buckling behavior which is hugely affected by the initial geometric imperfections. Approach: For axially compressed isotropic circular cylindrical shells, axisymmetric localized geometric imperfections were found to reduce severely the buckling strength. Among various axisymmetric shapes of localized defects that were investigated, the entering triangular form was recognized to yield the most adverse case. Since multiple localized defects may be present in the same shell structure and interact, studying their mutual effect on the buckling load is of great importance for shell design. Results: In this study, the effect of two interacting entering triangular localized axisymmetric initial geometric imperfections on shell buckling strength under uniform axial compression was modeled by means of the finite element method. A special software package which was dedicated to buckling analysis of quasi axisymmetric shells was used in order to compute the buckling load either via the linear Euler buckling analysis or through the full non linear iterative procedure. A set of five factors including shell aspect ratios, defect characteristics and the distance separating the localized initial geometric imperfections had been found to govern the buckling problem. A statistical approach based on the Taguchi method was used then to study their relative influence on the buckling load reduction. It was shown by comparison with the single imperfection case that further diminution of the critical load was obtained. Conclusion/Recommendations: In the range of investigated parameters, the distance separating the localized geometric imperfections and imperfection wavelength were found to yield major influences on the critical load. Further studies must be performed in order to assess shell buckling strength in the presence of more than two
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Fan Yang
2016-01-01
Full Text Available In order to investigate the influence of adjustable outlet guide vane on the hydraulic performance of axial-flow pump at part loads, the axial-flow pump with 7 different outlet guide vane adjustable angles was simulated based on the RNG k-ε turbulent model and Reynolds time-averaged equations. The Vector graphs of airfoil flow were analyzed in the different operating conditions for different adjustable angles of guide vane. BP-ANN prediction model was established about the effect of adjustable outlet guide vane on the hydraulic performance of axial-flow pump based on the numerical results. The effectiveness of prediction model was verified by theoretical analysis and numerical simulation. The results show that, with the adjustable angle of guide vane increasing along clockwise, the high efficiency area moves to the large flow rate direction; otherwise, that moves to the small flow rate direction. The internal flow field of guide vane is improved by adjusting angle, and the flow separation of tail and guide vane inlet ledge are decreased or eliminated, so that the hydraulic efficiency of pumping system will be improved. The prediction accuracy of BP-ANN model is 1%, which can meet the requirement of practical engineering.
A cylindrical shell with an axial crack under skew-symmetric loading.
Yuceoglu, U.; Erdogan, F.
1973-01-01
The skew-symmetric problem for a cylindrical shell containing an axial crack is considered. It is assumed that the material has a special orthotropy - namely, that the shear modulus may be evaluated from the measured Young's moduli and Poisson ratios and is not an independent material constant. The problem is solved within the confines of an eighth-order linearized shallow shell theory. As numerical examples, the torsion of an isotropic cylinder and that of a specially orthotropic cylinder (titanium) are considered. The membrane and bending components of the stress intensity factor are calculated and are given as functions of a dimensionless shell parameter. In the torsion problem for the axially cracked cylinder the bending effects appear to be much more significant than that found for the circumferentially cracked cylindrical shell. Also, as the shell parameter increases, unlike the results found in the pressurized shell, the bending stresses around crack ends do not change sign.
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Oscar A. Cevallos
2015-11-01
Full Text Available In the construction industry, the use of natural fabrics as a reinforcement for cement-based composites has shown great potential. The use of these sustainable composites to provide strengthening or repair old masonry structures that exhibit structural problems mainly due to a poor tensile strength of the mortar/brick joints is revealed to be a promising area of research. One of the most significant load conditions affecting the mechanical response of masonry structures occurs when axial bending loads are applied on the resistant cross-section. In this study, three different types of masonry elements were built using clay bricks and a lime-based mortar. After 28 days, the samples were subjected to concentric and eccentric compressive loads. In order to produce significant bending effects, the compressive loads were applied with large eccentricity, and a sudden failure characterized the behavior of the unreinforced masonry (URM elements. The tested masonry specimens were repaired using fabric-reinforced cementitious matrix (FRCM composites produced using bi-directional flax and polyparaphenylene benzobisoxazole (PBO fabrics. The mechanical behavior of the URM and repaired samples was compared in terms of load-displacement and moment-curvature responses. Furthermore, the results achieved using flax-FRCM composites were compared with those of using PBO-FRCM composites.
Wang, Yuewu; Wu, Dafang
2016-10-01
Dynamic response of an axially functionally graded (AFG) beam under thermal environment subjected to a moving harmonic load is investigated within the frameworks of classical beam theory (CBT) and Timoshenko beam theory (TBT). The Lagrange method is employed to derive the equations of thermal buckling for AFG beam, and then with the critical buckling temperature as a parameter the Newmark-β method is adopted to evaluate the dynamic response of AFG beam under thermal environments. Admissible functions denoting transverse displacement are expressed in simple algebraic polynomial forms. Temperature-dependency of material constituent is considered. The rule of mixture (Voigt model) and Mori-Tanaka (MT) scheme are used to evaluate the beam's effective material properties. A ceramic-metal AFG beam with immovable boundary condition is considered as numerical illustration to show the thermal effects on the dynamic behaviors of the beam subjected to a moving harmonic load.
Energy Technology Data Exchange (ETDEWEB)
Sofiyev, A.H., E-mail: asofiyev@mmf.sdu.edu.t [Department of Civil Engineering, Suleyman Demirel University, 32260 Isparta (Turkey)
2010-12-15
In this study, the buckling analysis of the simply supported truncated conical shell made of functionally graded materials (FGMs) is presented. The FGM truncated conical shell subjected to an axial compressive load and resting on Winkler-Pasternak type elastic foundations. The material properties of functionally graded shells are assumed to vary continuously through the thickness. The modified Donnell type stability and compatibility equations are solved by Galerkin's method and the critical axial load of FGM truncated conical shells with and without elastic foundations have been found analytically. The appropriate formulas for homogenous and FGM cylindrical shells with and without elastic foundations are found as a special case. Several examples are presented to show the accuracy and efficiency of the formulation. Finally, parametric studies on the buckling of FGM truncated conical and cylindrical shells on elastic foundations are being investigated. These parameters include; power-law and exponential distributions of FGM, Winkler foundation modulus, Pasternak foundation modulus and aspect ratios of shells.
Post-buckling capacity of bi-axially loaded rectangular steel plates
DEFF Research Database (Denmark)
Jönsson, Jeppe; Bondum, T. H.
2012-01-01
Results from a detailed numerical investigation of the post-buckling behaviour of rectangular simply supported steel plates subjected to biaxial in-plane loading are presented. The Steel plates are loaded through forced edge displacements. The effects of initial imperfections, aspect ratio, plate...
Modeling of FRP-jacketed RC columns subject to combined axial and lateral loads
Lee, Chung-Sheng
2006-01-01
To successfully use the fiber-reinforced-polymer (FRP) overlay technique for the seismic retrofit and the blast- hardening of RC columns, the mechanical behavior of the FRP-confined concrete needs to be understood and its response needs to be accurately predicted. Although a number of studies have been conducted to-date, it is still not clear how the main parameters affect the axial stress- strain response of a FRP-confined concrete cylinder. In particular, while it is understood that FRP jac...
Analysis of the axial electric field in a plasma-loaded-helix travelling wave tube
Institute of Scientific and Technical Information of China (English)
Xie Hong-Quan; Liu Pu-Kun
2006-01-01
A helix type slow wave structure filled with plasma is immersed in a strong longitudinal magnetic field. Taking into account the effect of the plasma and the dielectric, the system is separated radially into three regions. By means of the sheath model and Maxwell equation, the distribution of the electromagnetic field is established. Using the boundary conditions of each region, the dispersion relation of the slow wave structure is derived. The trend of change for the radial profile of the axial electric field is analysed respectively in different plasma densities, plasma column radius and dielectric constant by numerical computation. Some useful results are obtained on the basis of the discussion.
Dynamic stability of simply supported composite cylindrical shells under partial axial loading
Dey, Tanish; Ramachandra, L. S.
2015-09-01
The parametric vibration of a simply supported composite circular cylindrical shell under periodic partial edge loadings is discussed in this article. Donnell's nonlinear shallow shell theory considering first order shear deformation theory is used to model the shell. The applied partial edge loading is represented in terms of a Fourier series and stress distributions within the cylindrical shell are determined by prebuckling analysis. The governing equations of the dynamic instability of shells are derived in terms of displacements (u-v-w) and rotations (φx, φθ). Employing the Galerkin and Bolotin methods the dynamic instability regions are computed. Using the expression for the stress function derived in this paper, the pre-buckling stresses in the cylindrical shell due to partial loading can be calculated explicitly. Numerical results are presented to show the influence of radius-to-thickness ratio, different partial edge loading distributions and shear deformation on the dynamic instability regions. The linear and nonlinear responses in the stable and unstable regions are presented to bring out the characteristic features of the dynamic instability regions, such as the existence of beats, its dependence on forcing frequency and effect of nonlinearity on the response. The effect of dynamic load amplitude on the nonlinear response is also studied. It is found that for higher values of dynamic loading, the shell exhibits chaotic behavior.
Yusuf Yesilce
2012-01-01
In the existing reports regarding free and forced vibrations of the beams, most of them studied a uniform beam carrying various concentrated elements using Bernoulli-Euler Beam Theory (BET) but without axial force. The purpose of this paper is to utilize the numerical assembly technique to determine the exact frequency-response amplitudes of the axially-loaded Timoshenko multi-span beam carrying a number of various concentrated elements (including point masses, rotary inertias, linear springs...
Performance of a highly loaded two stage axial-flow fan
Ruggeri, R. S.; Benser, W. A.
1974-01-01
A two-stage axial-flow fan with a tip speed of 1450 ft/sec (442 m/sec) and an overall pressure ratio of 2.8 was designed, built, and tested. At design speed and pressure ratio, the measured flow matched the design value of 184.2 lbm/sec (83.55kg/sec). The adiabatic efficiency at the design operating point was 85.7 percent. The stall margin at design speed was 10 percent. A first-bending-mode flutter of the second-stage rotor blades was encountered near stall at speeds between 77 and 93 percent of design, and also at high pressure ratios at speeds above 105 percent of design. A 5 deg closed reset of the first-stage stator eliminated second-stage flutter for all but a narrow speed range near 90 percent of design.
Energy Technology Data Exchange (ETDEWEB)
Singh, Punit; Nestmann, Franz [Institute for Water and River Basin Management (IWG), University of Karlsruhe, Kaiser Str. 12, D 76128 Karlsruhe (Germany)
2010-09-15
A detailed experimental investigation of the effects of exit blade geometry on the part-load performance of low-head, axial flow propeller turbines is presented. Even as these turbines find important applications in small-scale energy generation using micro-hydro, the relationship between the layout of blade profile, geometry and turbine performance continues to be poorly characterized. The experimental results presented here help understand the relationship between exit tip angle, discharge through the turbine, shaft power, and efficiency. The modification was implemented on two different propeller runners and it was found that the power and efficiency gains from decreasing the exit tip angle could be explained by a theoretical model presented here based on classical theory of turbomachines. In particular, the focus is on the behaviour of internal parameters like the runner loss coefficient, relative flow angle at exit, mean axial flow velocity and net tangential flow velocity. The study concluded that the effects of exit tip modification were significant. The introspective discussion on the theoretical model's limitation and test facility suggests wider and continued experimentation pertaining to the internal parameters like inlet vortex profile and exit swirl profile. It also recommends thorough validation of the model and its improvement so that it can be made capable for accurate characterization of blade geometric effects. (author)
Present knowledge about Laboratory Testing of Axial Loading on Suction Caissons
DEFF Research Database (Denmark)
Manzotti, E.; Vaitkunaite, Evelina; Ibsen, Lars Bo
on the structure is resisted by push-pull loads on the vertical axis of each suction caisson. Relevant works where this situation is examined by means of laboratory testing are summarized in this article, then different conclusions are followed by discussion and comparison. In the initial theoretical section...
Pellicano, F.; Amabili, M.
2006-05-01
In the present paper the dynamic stability of circular cylindrical shells subjected to static and dynamic axial loads is investigated. Both Donnell's nonlinear shallow shell and Sanders-Koiter shell theories have been applied to model finite-amplitude static and dynamic deformations. Results are compared in order to evaluate the accuracy of these theories in predicting instability onset and post-critical nonlinear response. The effect of a contained fluid on the stability and the post-critical behaviour is analyzed in detail. Geometric imperfections are considered and their influence on the dynamic instability and post-critical behaviour is investigated. Chaotic dynamics of pre-compressed shells is investigated by means of nonlinear time-series techniques, extracting correlation dimension and Lyapunov exponents.
A rotational and axial motion system load frame insert for in situ high energy x-ray studies
Energy Technology Data Exchange (ETDEWEB)
Shade, Paul A., E-mail: paul.shade.1@us.af.mil; Schuren, Jay C.; Turner, Todd J. [Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson AFB, Ohio 45433 (United States); Blank, Basil [PulseRay, Beaver Dams, New York 14812 (United States); Kenesei, Peter; Goetze, Kurt; Lienert, Ulrich; Almer, Jonathan [Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Suter, Robert M. [Carnegie Mellon University, Pittsburgh, Pennsylvania 15213 (United States); Bernier, Joel V.; Li, Shiu Fai [Engineering Directorate, Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Lind, Jonathan [Carnegie Mellon University, Pittsburgh, Pennsylvania 15213 (United States); Engineering Directorate, Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)
2015-09-15
High energy x-ray characterization methods hold great potential for gaining insight into the behavior of materials and providing comparison datasets for the validation and development of mesoscale modeling tools. A suite of techniques have been developed by the x-ray community for characterizing the 3D structure and micromechanical state of polycrystalline materials; however, combining these techniques with in situ mechanical testing under well characterized and controlled boundary conditions has been challenging due to experimental design requirements, which demand new high-precision hardware as well as access to high-energy x-ray beamlines. We describe the design and performance of a load frame insert with a rotational and axial motion system that has been developed to meet these requirements. An example dataset from a deforming titanium alloy demonstrates the new capability.
Deformation Behavior and TExture Evolution of Steel Alloys under Axial-Torsional Loading
Energy Technology Data Exchange (ETDEWEB)
Siriruk, A.; Kant, M.; Penumadu, D.; Garlea, E.; Vogel, S.
2011-06-01
Using hollow cylinder samples with suitable geometry obtained from round bar stock, the deformation behavior of bcc Fe based 12L14 steel alloy is evaluated under multi-axial conditions. A stacked strain gage rosette and extensometer mounted on the cylindrical surface at the mid height of the specimen provided strain tensor as a function of applied stress for pure tensile and torsion tests prior to yielding. This study examines elastic and yield behavior and effects of these with respect to texture evolution. Hollow cylinder specimen geometry (tubes) with small wall thickness and relatively (to its thickness) large inner diameter is used. The variation of observed yield surface in deviatoric plane and the effect on mode of deformation (tension versus torsion versus its combination) on stress-strain behavior is discussed. Bulk texture was studied using neutron time-of-flight diffractometer at High-Pressure-Preferred Orientation (HIPPO) - Los Alamos Neutron Science Center (LANSCE) instrument and the evolution of texture and related anisotropy for pure tension versus torsion are also included.
Eigenvalues of an axially loaded cantilever beam with an eccentric end rigid body
Lajimi, S Amir Mousavi
2014-01-01
An analytical form of the characteristic equation for a vertically mounted cantilever beam with an end rigid body is obtained and solved for the eigenvalues of the structure. The effect of the weight of the structure is taken into consideration by estimating the load as a function of the length of the beam. The mass, rotary inertia and eccentricity of the end rigid body are demonstrated to considerably affect the eigenvalues of the structure.
Institute of Scientific and Technical Information of China (English)
沈惠申
2004-01-01
A compressive postbuckling analysis is presented for a laminated cylinderical panel with piezoelectric actuators subjected to the combined action of mechanical, electrical and thermal loads. The temperature field considered is assumed to be a uniform distribution over the panel surface and through the panel thickness and the electric field is assumed to be the transverse component Ez only. The material properties are assumed to be independent of the temperature and the electric field. The governing equations are based on the classicalshell theory with von Ka rman-Donnell-type of kinematic nonlinearity. The nonlinear prebuckling deformations and initial geometric imperfections of the panel are both taken into account. A boundary layer theory of shell buckling, which includes the effects of nonlinearprebuckling deformations, large deflections in the postbuckling range, and initial geometric imperfections of the shell, is extended to the case of hybrid laminated cylindrical panels of finite length. A singular perturbation technique is employed to determine the buckling loads and postbuckling equilibrium paths. The numerical illustrations concern the compressive postbuckling behavior of perfect and imperfect, cross-ply laminated cylindrical thin panels with fully covered or embedded piezoelectric actuators under different sets of thermal and electrical loading conditions. The effects played by temperature rise, applied voltage,stacking sequence, the character of in-plane boundary conditions, as well as initial geometric imperfections are studied.
Carolus, Thomas
The paper examines the acoustic and aerodynamic performance of low-pressure axial fan rotors with a hub/tip ratio of 0.45. Six rotors were designed for the same working point by means of the well-known airfoil theory. The condition of an equilibrium between the static pressure gradient and the centrifugal forces is maintained. All rotors have unequally spaced blades to diminish tonal noise. The rotors are tested in a short cylindrical housing without guide vanes. All rotors show very similar flux-pressure difference characteristics. The peak efficiency and the noise performance is considerably influenced by the chosen blade design. The aerodynamically and acoustically optimal rotor is the one with the reduced load at the hub and increased load in the tip region under satisfied equilibrium conditions. It runs at the highest aerodynamic efficiency, and its noise spectrum is fairly smooth. The overall sound pressure level of this rotor is up to 8 dB (A) lower compared to the other rotors under consideration.
Optimization of functionally graded foam-filled conical tubes under axial impact loading
Energy Technology Data Exchange (ETDEWEB)
Mohammadiha, O.; Beheshti, H. [University of Isfahan, Isfahan (Iran, Islamic Republic of)
2014-05-15
Metallic foams as a filler in thin-walled structures can improve their crash worthiness characteristics. In this article, nonlinear parametric finite element simulations of FGF foam-filled conical tube are developed and the effect of various design parameters such as density grading, number of grading layers and the total mass of FGF tube on resulting mode shapes, specific energy absorption and initial peak load is investigated. Multi design optimization (MDO) technique and the geometrical average method, both are based on FE model are applied to maximize the specific energy absorption and minimize the impact peak force by estimating the best wall thickness and gradient exponential parameter 'm' that controls the variation of foam density. The results obtained from the optimizations indicated that functionally graded foam material, with graded density, is a suitable candidate for enhancing the crash worthiness characteristics of the structure compared to uniform density foam.
Seismic vulnerability evaluation of axially loaded steel built-up laced members II: evaluations
Lee, Kangmin; Bruneau, Michel
2008-06-01
The test results described in Part 1 of this paper (Lee and Bruneau, 2008) on twelve steel built-up laced members (BLMs) subjected to quasi-static loading are analyzed to provide better knowledge on their seismic behavior. Strength capacity of the BLM specimens is correlated with the strength predicted by the AISC LRFD Specifications. Assessments of hysteretic properties such as ductility capacity, energy dissipation capacity, and strength degradation after buckling of the specimen are performed. The compressive strength of BLMs is found to be relatively well predicted by the AISC LRFD Specifications. BLMs with smaller kl/r were ductile but failed to reach the target ductility of 3.0 before starting to fracture, while those with larger kl/r could meet the ductility demand in most cases. The normalized energy dissipation ratio, E C/ E T and the normalized compressive strength degradation, C r″/ C r of BLMs typically decrease as normalized displacements δ/ δ b,exp increase, and the ratios for specimens with larger kl/r dropped more rapidly than for specimens with smaller kl/r; similar trends were observed for the monolithic braces. The BLMs with a smaller slenderness ratio, kl/r, and width-to-thickness ratio, b/t, experienced a larger number of inelastic cycles than those with larger ratios.
Seismic vulnerability evaluation of axially loaded steel built-up laced members Ⅱ: evaluations
Institute of Scientific and Technical Information of China (English)
Kangmin Lee; Michel Bruneau
2008-01-01
The test results described in Part 1 of this paper (Lee and Bruneau, 2008) on twelve steel built-up laced members(BLMs) subjected to quasi-static loading are analyzed to provide better knowledge on their seismic behavior. Strengthcapacity of the BLM specimens is correlated with the strength predicted by the AISC LRFD Specifications. Assessmentsof hysteretic properties such as ductility capacity, energy dissipation capacity, and strength degradation after buckling of thespecimen are performed. The compressive strength of BLMs is found to be relatively well predicted by the AISC LRFDSpecifications. BLMs with smaller kl/r were ductile but failed to reach the target ductility of 3.0 before starting to fracture,while those with larger kl/r could meet the ductility demand in most cases. The normalized energy dissipation ratio, ECETand the normalized compressive strength degradation, Cr"/Cr of BLMs typically decrease as normalized displacements δ/δbexpincrease, and the ratios for specimens with larger kl/r dropped more rapidly than for specimens with smaller kl/r; similartrends were observed for the monolithic braces. The BLMs with a smaller slenderness ratio, kl/r, and width-to-thickness ratio,b/t, experienced a larger number of inelastic cycles than those with larger ratios.
Ductile Fracture of AHSS Sheets under Multi-axial Loading: Experiments and Modeling
Dunand, M.; Mohr, D.
2011-08-01
Fracture experiments on TRIP-assisted steel sheets covering a wide range of stress states (from shear to equibiaxial tension) are performed to create a comprehensive experimental database to calibrate and evaluate the shear-modified Gurson model (Nielsen and Tvergaard, 2010) and the Modified Mohr-Coulomb (MMC) fracture model (Bai and Wierzbicki, 2010). The experimental program includes notched tensile tests as well as fracture experiments on butterfly-shaped specimens under combined tension and shear loading. Both phenomenological fracture models are physics-inspired and take the effect of the first and third stress tensor invariants into account in predicting the onset of ductile fracture. The MMC model is based on the assumption that the initiation of fracture is determined by a critical stress state, while the shear-modified Gurson model assumes void growth as the governing mechanism. The model accuracy is quantified based on the predictions of the displacements to fracture for experiments which have not been used for calibration. It is found that the MMC model predictions agree well with all experiments (less than 4% error), while less accurate predictions are observed for the shear-modified Gurson model. A comparison of plots of the strain to fracture as a function of the stress triaxiality and the normalized third invariant reveals significant differences between the two models except within the vicinity of stress states that have been used for calibration.
Institute of Scientific and Technical Information of China (English)
卢亦焱; 李娜; 李杉; 梁鸿骏
2015-01-01
An experimental study on the compressive behavior of steel fiber reinforced concrete-filled steel tube columns is presented. Specimens were tested to investigate the effects of the concrete strength, the thickness of steel tube and the steel fiber volume fraction on the ultimate strength and the ductility. The experimental results indicate that the addition of steel fibers in concrete can significantly improve the ductility and the energy dissipation capacity of the concrete-filled steel tube columns and delay the local buckling of the steel tube, but has no obvious effect on the failure mode. It has also been found that the addition of steel fibers is a more effective method than using thicker steel tube in enhancing the ductility, and more advantageous in the case of higher strength concrete. An analytical model to estimate the load capacity is proposed for steel tube columns filled with both plain concrete and steel fiber reinforced concrete. The predicted results are in good agreement with the experimental ones obtained in this work and literatures.
Directory of Open Access Journals (Sweden)
Suchart Limkatanyu
2013-01-01
Full Text Available Nonlocal and surface effects are incorporated into a bar-elastic substrate element to account for small-scale and size-dependent effects on axial responses of nanowires embedded in elastic substrate media. The virtual displacement principle, employed to consistently derive the governing differential equation as well as the boundary conditions, forms the core of the displacement-based finite element formulation of the nanowire-elastic substrate element. The element displacement shape functions, analytically derived based on homogeneous solution to the governing differential equilibrium equation of the problem, result in the exact element stiffness matrix and equivalent load vector. Two numerical simulations employing the proposed model are performed to study characteristics and behavior of the nanowire-substrate system. The first simulation involves investigation of responses of the wire embedded in elastic substrate. The second examines influences of several system parameters on the contact stiffness and reveals the size-dependent effect on the effective Young's modulus of the system.
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Wei Li
2016-10-01
Full Text Available The interior defect-induced fracture of surface-hardened metallic materials in the long life region has become a key issue on engineering design. In the present study, the axial loading test with fully reversed condition was performed to examine the fatigue property of a surface-carburized low alloy gear steel in the long life region. Results show that this steel represents the duplex S-N (stress-number of cycles characteristics without conventional fatigue limit related to 107 cycles. Fatigue cracks are all originated from the interior inclusions in the matrix region due to the inhabitation effect of carburized layer. The inclusion induced fracture with fisheye occurs in the short life region below 5 × 105 cycles, whereas the inclusion induced fracture with fine granular area (FGA and fisheye occurs in the long life region beyond 106 cycles. The stress intensity factor range at the front of FGA can be regarded as the threshold value controlling stable growth of interior long crack. The evaluated maximum inclusion size in the effective damage volume of specimen is about 27.29 μm. Considering the size relationships between fisheye and FGA, and inclusion, the developed life prediction method involving crack growth can be acceptable on the basis of the good agreement between the predicted and experimental results.
Determination of Yield in Inconel 718 for Axial-Torsional Loading at Temperatures up to 649 C
Gil, Christopher M.; Lissenden, Cliff J.; Lerch, Bradley A.
1998-01-01
An experimental program has been implemented to determine small offset yield loci under axial-torsional loading at elevated temperatures. The nickel-base superalloy Inconel 718 (IN718) was chosen for study due to its common use in aeropropulsion applications. Initial and subsequent yield loci were determined for solutioned IN718 at 23, 371, and 454 C and for aged (precipitation hardened) IN718 at 23 and 649 C. The shape of the initial yield loci for solutioned and aged IN718 agreed well with the von Mises prediction. However, in general, the centers of initial yield loci were eccentric to the origin due to a strength-differential (S-D) effect that increased with temperature. Subsequent yield loci exhibited anisotropic hardening in the form of translation and distortion of the locus. This work shows that it is possible to determine yield surfaces for metallic materials at temperatures up to at least 649 C using multiple probes of a single specimen. The experimental data is first-of-its-kind for a superalloy at these very high temperatures and will facilitate a better understanding of multiaxial material response, eventually leading to improved design tools for engine designers.
Directory of Open Access Journals (Sweden)
Frederico Martins Alves da Silva
2015-01-01
Full Text Available This work investigates the influence of Young’s modulus, shells thickness, and geometrical imperfection uncertainties on the parametric instability loads of simply supported axially excited cylindrical shells. The Donnell nonlinear shallow shell theory is used for the displacement field of the cylindrical shell and the parameters under investigation are considered as uncertain parameters with a known probability density function in the equilibrium equation. The uncertainties are discretized as Hermite-Chaos polynomials together with the Galerkin stochastic procedure that discretizes the stochastic equation in a set of deterministic equations of motion. Then, a general expression for the transversal displacement is obtained by a perturbation procedure which identifies all nonlinear modes that couple with the linear modes. So, a particular solution is selected which ensures the convergence of the response up to very large deflections. Applying the standard Galerkin method, a discrete system in time domain that considers the uncertainties is obtained and solved by fourth-order Runge-Kutta method. Several numerical strategies are used to study the nonlinear behavior of the shell considering the uncertainties in the parameters. Special attention is given to the influence of the uncertainties on the parametric instability and time response, showing that the Hermite-Chaos polynomial is a good numerical tool.
Directory of Open Access Journals (Sweden)
Wenbin SUN
2014-12-01
Full Text Available Comparing with the circular concrete columns confined with fiber reinforced polymer (FRP wrap or tube, the rectilinear confined columns were reported much less. Due to the non-uniform distribution of confining pressure in the rectilinear confined columns, the FRP confinement effectiveness was significant reduced. This paper presents findings of an experimental program where nine prefabricated rectangular cross-section CFRP tubes with CFRP integrated crossties filled concrete to form concrete-filled FRP tube (CFFT short columns and three plain concrete control specimens were tested. All specimens were axially loaded until failure. The rest results showed that the stress-strain curves of CFFTs consisted of two distinct branches, an ascending branch before the concrete peak stress was reaches and a second branch that terminated when the tube ruptured, and that the CFFTs with integrated crossties experienced most uniform confinement pressure distribution. Test research also found that the stress-strain curves of CFFTs indicated an increase in ductility. These demonstrate that this confinement system can produce higher lateral confinement stiffness. DOI: http://dx.doi.org/10.5755/j01.ms.20.4.6035
Energy Technology Data Exchange (ETDEWEB)
Ehlers, R.
1986-01-01
For a linear-elastic cylinder with an axial through crack subject to internal pressure loading, stress intensity factors and crack opening areas were calculated by the finite element method. Wall thickness and crack length were varied for constant mean radius of the cylinder, thus varying the shell parameter lambda with 2.5
Liu, Yang; Shu, Dong-Wei
2014-08-01
Delaminations in structures may significantly reduce the stiffness and strength of the structures and may affect their vibration characteristics. As structural components, beams have been used for various purposes, in many of which beams are often subjected to axial loads and static end moments. In the present study, an analytical solution is developed to study the coupled bending-torsion vibration of a homogeneous beam with a single delamination subjected to axial loads and static end moments. Euler-Bernoulli beam theory and the "free mode" assumption in delamination vibration are adopted. This is the first study of the influences of static end moments upon the effects of delaminations on natural frequencies, critical buckling loads and critical moments for lateral instability. The results show that the effects of delamination on reducing natural frequencies, critical buckling load and critical moment for lateral instability are aggravated by the presence of static end moment. In turn, the effects of static end moments on vibration and instability characteristics are affected by the presence of delamination. The analytical results of this study can serve as a benchmark for finite element method and other numerical solutions.
Directory of Open Access Journals (Sweden)
Mehrdad Nasirshoaibi
2015-01-01
Full Text Available Based on the Rayleigh beam theory, the forced transverse vibrations of a closed double single-walled carbon nanotube (SWCNT system containing a fluid with a Pasternak layer in-between are investigated. It is assumed that the two single-walled carbon nanotubes of the system are continuously joined by a Pasternak layer and both sides of SWCNTs containing a fluid are closed. The dynamic responses of the system caused by arbitrarily distributed continuous loads are obtained. The effect of compressive axial load on the forced vibrations of the double single-walled carbon nanotube system is discussed for one case of particular excitation loading. The properties of the forced transverse vibrations of the system are found to be significantly dependent on the compressive axial load. The steady-state vibration amplitudes of the SWCNT decrease with increasing of length of SWCNT. Vibrations caused by the harmonic exciting forces are discussed, and conditions of resonance and dynamic vibration absorption are formulated. The SWCNT-type dynamic absorber is a new concept of a dynamic vibration absorber (DVA, which can be applied to suppress excessive vibrations of corresponding SWCNT systems.
Institute of Scientific and Technical Information of China (English)
于强
2011-01-01
The research on the rule of short fatigue crack growth rate by multi-axial loading remains a new frontier in recent years.The equivalence of proportioned multi-axial loading and uni-axial loading are analyzed.The hypothesis of inability for proportioned multi-axial loading to alter the mechanical properties of the materials is put forward.Therefore,the formula of short fatigue crack growth rate by multi-axial loading can be derived by adopting the principle of energy density on the critical plane and making an analogy to the research of uni-axial loading.%多轴加载下疲劳短裂纹的研究,是近几年来才触及的一个新领域。文章分析了多轴比例载荷与单轴载荷的等效性。提出了多轴比例加载不会改变材料力学性能的假设,在临界面上用能量密度法,类比单轴加载的研究过程,导出了多轴比例加载下疲劳短裂纹扩展速度的计算公式。
Kimura, S.; Steinbach, G. C.; Watenpaugh, D. E.; Hargens, A. R.
2001-01-01
STUDY DESIGN: Axial load-dependent changes in the lumbar spine of supine healthy volunteers were examined using a compression device compatible with magnetic resonance imaging. OBJECTIVE: To test two hypotheses: Axial loading of 50% body weight from shoulder to feet in supine posture 1) simulates the upright lumbar spine alignment and 2) decreases disc height significantly. SUMMARY OF BACKGROUND DATA: Axial compression on the lumbar spine has significantly narrowed the lumbar dural sac in patients with sciatica, neurogenic claudication or both. METHODS: Using a device compatible with magnetic resonance imaging, the lumbar spine of eight young volunteers, ages 22 to 36 years, was axially compressed with a force equivalent to 50% of body weight, approximating the normal load on the lumbar spine in upright posture. Sagittal lumbar magnetic resonance imaging was performed to measure intervertebral angle and disc height before and during compression. RESULTS: Each intervertebral angle before and during compression was as follows: T12-L1 (-0.8 degrees +/- 2.5 degrees and -1.5 degrees +/- 2.6 degrees ), L1-L2 (0.7 degrees +/- 1.4 degrees and 3.3 degrees +/- 2.9 degrees ), L2-L3 (4.7 degrees +/- 3.5 degrees and 7.3 degrees +/- 6 degrees ), L3-L4 (7.9 degrees +/- 2.4 degrees and 11.1 degrees +/- 4.6 degrees ), L4-L5 (14.3 degrees +/- 3.3 degrees and 14.9 degrees +/- 1.7 degrees ), L5-S1 (25.8 degrees +/- 5.2 degrees and 20.8 degrees +/- 6 degrees ), and L1-S1 (53.4 degrees +/- 11.9 degrees and 57.3 degrees +/- 16.7 degrees ). Negative values reflect kyphosis, and positive values reflect lordosis. A significant difference between values before and during compression was obtained at L3-L4 and L5-S1. There was a significant decrease in disc height only at L4-L5 during compression. CONCLUSIONS: The axial force of 50% body weight in supine posture simulates the upright lumbar spine morphologically. No change in intervertebral angle occurred at L4-L5. However, disc height at L4-L
Directory of Open Access Journals (Sweden)
Oliver Giraldo-Londoño
2014-01-01
Full Text Available La estabilidad dinámica de una columna elástica prismática esbelta con conexiones semirrígidas en ambos extremos de rigidez idéntica y con desplazamiento lateral entre los dos extremos totalmente inhibido sujetos a cargas axiales paramétricas incluyendo los efectos combinados de inercia rotacional y amortiguación externas fue presentada en una publicación adjunta. Expresiones cerradas que se pueden utilizar para predecir las regiones inestabilidad dinámica de columnas esbeltas se desarrollan haciendo uso de la teoría de Floquet. Las ecuaciones propuestas son sencillas y fáciles de aplicar. La solución propuesta es capaz de capturar el fenómeno de estabilidad en columnas sometidas a cargas axiales periódicas utilizando un solo elemento de columna. El método propuesto y las ecuaciones correspondientes se pueden utilizar para investigar los efectos del amortiguamiento, la inercia rotacional de la columna, y las conexiones semirrígidas en el análisis de estabilidad de columnas esbeltas sometidas a cargas axiales periódicas. Estudios de sensibilidad presentados en esta publicación muestran los efectos de la inercia rotacional, el amortiguamiento y las conexiones semi-rígidas en la estabilidad dinámica de columnas sometidas a cargas axiales paramétricas. Los estudios analíticos indican que el comportamiento dinámico de columnas bajo carga periódica está fuertemente afectado por la rigidez a la flexión de las conexiones de los dos apoyos y por el amortiguamiento externo, pero no tanto por la inercia rotacional. Tres ejemplos se presentan en detalle y los resultados calculados se comparan con los reportados por otros investigadores.
Gil, Christopher M.
1998-01-01
An experimental program to determine flow surfaces has been established and implemented for solution annealed and aged IN718. The procedure involved subjecting tubular specimens to various ratios of axial-torsional stress at temperatures between 23 and 649 C and measuring strain with a biaxial extensometer. Each stress probe corresponds to a different direction in stress space, and unloading occurs when a 30 microstrain (1 micro eplison = 10(exp -6) mm/mm) offset is detected. This technique was used to map out yield loci in axial-torsional stress space. Flow surfaces were determined by post-processing the experimental data to determine the inelastic strain rate components. Surfaces of constant inelastic strain rate (SCISRS) and surfaces of constant inelastic power (SCIPS) were mapped out in the axial-shear stress plane. The von Mises yield criterion appeared to closely fit the initial loci for solutioned IN718 at 23 C. However, the initial loci for solutioned IN718 at 371 and 454 C, and all of the initial loci for aged IN718 were offset in the compression direction. Subsequent loci showed translation, distortion, and for the case of solutioned IN718, a slight cross effect. Aged IN718 showed significantly more hardening behavior than solutioned IN718.
Pham, M. S.; Creuziger, A.; Iadicola, M.; Rollett, A. D.
2017-02-01
This study investigates the joint impact of preferred texture and latent hardening on the plastic anisotropy of face centered cubic (FCC) materials. The main result is that both aspects have significant impact on the anisotropy, but the two can either counteract each other or synergistically reinforce each other to maximize anisotropy. Preferred texture results in significant anisotropy in plastic yielding. However, the latent hardening significantly alters the texture-induced anisotropy. In addition, one latent hardening type can cancel out the anisotropy of another type. Consequently, if all dislocation-based latent hardening types are included at the same level as the self-hardening, the result might not reveal the complexity of plastic anisotropy. The present study of the synergistic influence of detailed latent hardening and texture presented helps provide new insights into the complex anisotropic behavior of FCC materials during multi-axial forming. the stress at which the material initially yields is not a function of material orientation with respect to the frame of the test (i.e., isotropic yielding); there exists a multi-axial yield locus that is described by a single value of stress that corresponds to yield in uniaxial tension (i.e., stress equivalency); on hardening, the multi-axial yield locus expands by the same amount in every direction in the π-plane, which is the plane that has its normal parallel to [111] in the deviatoric stress space (i.e., isotropic hardening); there is an associated flow rule, i.e., the strain increment is normal to the yield locus.
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Yusuf Yesilce
2012-01-01
Full Text Available In the existing reports regarding free and forced vibrations of the beams, most of them studied a uniform beam carrying various concentrated elements using Bernoulli-Euler Beam Theory (BET but without axial force. The purpose of this paper is to utilize the numerical assembly technique to determine the exact frequency-response amplitudes of the axially-loaded Timoshenko multi-span beam carrying a number of various concentrated elements (including point masses, rotary inertias, linear springs and rotational springs and subjected to a harmonic concentrated force and the exact natural frequencies and mode shapes of the beam for the free vibration analysis. The model allows analyzing the influence of the shear and axial force and harmonic concentrated force effects and intermediate concentrated elements on the dynamic behavior of the beams by using Timoshenko Beam Theory (TBT. At first, the coefficient matrices for the intermediate concentrated elements, an intermediate pinned support, applied harmonic force, left-end support and right-end support of Timoshenko beam are derived. After the derivation of the coefficient matrices, the numerical assembly technique is used to establish the overall coefficient matrix for the whole vibrating system. Finally, solving the equations associated with the last overall coefficient matrix one determines the exact dynamic response amplitudes of the forced vibrating system corresponding to each specified exciting frequency of the harmonic force. Equating the determinant of the overall coefficient matrix to zero one determines the natural frequencies of the free vibrating system (the case of zero harmonic force and substituting the corresponding values of integration constants into the related eigenfunctions one determines the associated mode shapes. The calculated vibration amplitudes of the forced vibrating systems and the natural frequencies of the free vibrating systems are given in tables for different values of
Guo, Xin; Fan, Yubo; Li, Zong-Ming
2009-03-01
Transecting the transverse carpal ligament (TCL) is a routine procedure to surgically treat carpal tunnel syndrome; yet, its mechanical consequences on carpal bones are unclear. In this study, our intent was to perform a computational analysis of carpal biomechanics resulting from TCL release. A three-dimensional finite element model of the wrist was constructed, which included all the carpal bones, the distal ulna and radius, the proximal metacarpals and the interosseous ligaments. Cartilage layers of each bone were modeled manually according to anatomic visualization software. The TCL was also modeled in three dimensions and added to the bone model. A 100-Newton axial load was applied to the upper section of the second and third metacarpals. The effects of dividing the TCL on the displacements of the carpal bones and the contact stress distribution in the midcarpal joints were studied using a finite element analysis method. When the TCL was divided, the axial compressive load resulted in the carpal bones deviating more radially. More specifically, the carpal bones on the radial side of the capitate and lunate (i.e. the trapezium, trapezoid, and scaphoid) moved further toward the radius, and the carpal bones on the ulnar side of the capitate and lunate (i.e. hamate, triquetrum, and pisiform) moved further toward the metacarpals. The contact stresses and contact locations in the midcarpal joints changed as a result of dividing the TCL. The changes in displacements of carpal bones and the contact stress distributions in the midcarpal joints due to TCL release may be implicated for some of the postoperative complications associated with carpal tunnel release.
Lampropoulos, A. P.; Dritsos, S. E.
2008-07-01
In this study, the technique of seismic strengthening existing reinforced concrete columns and beams using additional concrete layers and jackets is examined. The finite element method and the finite element program ATENA is used in this investigation. When a reinforced jacket or layer is being constructed around a column it is already preloaded due to existing service loads. This effect has been examined for different values of the axial load normalized to the strengthened column. The techniques of strengthening with a concrete jacket or a reinforced concrete layer on the compressive side of the column are examined. Another phenomenon that is examined in this study is the shrinkage of the new concrete of an additional layer used to strengthen an existing member. For this investigation, a simply supported beam with an additional reinforced concrete layer on the tensile side is examined. The results demonstrate that the effect of preloading is important when a reinforced concrete layer is being used with shear connectors between the old and the new reinforcement. It was also found that the shrinkage of the new concrete reduces the strength of the strengthened beam and induces an initial sliding between the old and the new concrete.
Institute of Scientific and Technical Information of China (English)
Zhen-zhen PENG; Xin-min CHEN; Jun WANG; Ai-jie LI; Zu-jie XU
2013-01-01
Objective:This study investigated the effect of proximal contact strength on the three-dimensional displacements of cantilever fixed partial denture (CFPD) under vertically concentrated loading with digital laser speckle (DLS) technique.Methods:Fresh mandible of beagle dog was used to establish the implant-supported CFPD for specimen.DLS technique was employed for measuring the three-dimensional displacement of the prosthesis under vertically concentrated loading ranging from 200 to 3000 g.The effect of the contact tightness on the displacement of CFPD was investigated by means of changing the contact tightness.Results:When an axial concentrated loading was exerted on the pontic of the implant-supported CFPD,the displacement of the CFPD was the greatest.The displacement of the prosthesis decreased with the increase of contact strength.When the contact strength was 0,0.95,and 3.25 N,the displacement of the buccolingual direction was smaller than that of the mesiodistal direction but greater than that of the occlusogingival direction.When the force on the contact area was 6.50 N,the mesiodistal displacement of the prosthesis was the biggest while the buccolingual displacement was the smallest.Conclusions:The implantsupported CFPD is an effective therapy for fully or partially edentulous patients.The restoration of the contact area and the selection of the appropriate contact strength can reduce the displacement of the CFPD,and get a better stress distribution.The most appropriate force value is 3.25 N in this study.
Indian Academy of Sciences (India)
Cengiz Erdonmez; C Erdem Imrak
2011-12-01
Due to the complex geometry of wires within a wire rope, it is difﬁcult to model and analyse independent wire rope core accurately (IWRC). In this paper, a more realistic three-dimensional modelling approach and ﬁnite element analysis of wire ropes are explained. Single helical geometry is enough to model simple straight strand while IWRC has a more complex geometry by inclusion of double helical wires in outer strands. Taking the advantage of the double helical wires, three-dimensional IWRCs modelling is applied for both right regular lay and lang lay IWRCs. Wire-by-wire based results are gathered by using the proposed modelling and analysis method under various loading conditions. Illustrative examples are given for those show the accuracy and the robustness of the present FE analysis scheme with considering frictional properties and contact interactions between wires. FE analysis results are compared with the analytical and available test results and show reasonable agreement with a simpler and more practical approach.
DEFF Research Database (Denmark)
Witting, Nanna; Andersen, Linda K; Vissing, John
2016-01-01
musculature involvement in the majority of myopathies in which paraspinal musculature was examined. Even in diseases named after a certain pattern of non-axial muscle affection, such as facioscapulohumeral and limb girdle muscular dystrophies, affection of the axial musculature was often severe and early...
Mahadev, Sthanu
Continued research and development efforts devoted in recent years have generated novel avenues towards the advancement of efficient and effective, slender laminated fiber-reinforced composite members. Numerous studies have focused on the modeling and response characterization of composite structures with particular relevance to thin-walled cylindrical composite shells. This class of shell configurations is being actively explored to fully determine their mechanical efficacy as primary aerospace structural members. The proposed research is targeted towards formulating a composite shell theory based prognosis methodology that entails an elaborate analysis and investigation of thin-walled cylindrical shell type laminated composite configurations that are highly desirable in increasing number of mechanical and aerospace applications. The prime motivation to adopt this theory arises from its superior ability to generate simple yet viable closed-form analytical solution procedure to numerous geometrically intense, inherent curvature possessing composite structures. This analytical evaluative routine offers to acquire a first-hand insight on the primary mechanical characteristics that essentially govern the behavior of slender composite shells under typical static loading conditions. Current work exposes the robustness of this mathematical framework via demonstrating its potential towards the prediction of structural properties such as axial stiffness and bending stiffness respectively. Longitudinal ply-stress computations are investigated upon deriving the global stiffness matrix model for composite cylindrical tubes with circular cross-sections. Additionally, this work employs a finite element based numerical technique to substantiate the analytical results reported for cylindrically shaped circular composite tubes. Furthermore, this concept development is extended to the study of thin-walled, open cross-sectioned, curved laminated shells that are geometrically
Institute of Scientific and Technical Information of China (English)
2013-01-01
斜群桩受水平荷载作用时，群桩中的基桩受到径向荷载、轴向荷载和弯矩的共同作用。为研究轴向荷载对斜桩水平承载特性的影响，完成了3根单桩以及1组1×2斜桩的大尺寸模型试验。试验结果表明：轴向拉力作用会降低斜桩的水平刚度和极限承载力；而轴向压力作用则会使其水平刚度和极限承载力提高。基于桩侧浅层土体楔形破坏假定，推导了考虑轴向荷载影响的斜桩水平极限土抗力计算公式，提出了桩侧土抗力的p-y曲线方法，并通过模型试验及现场试验验证其合理性。%When batter pile group are under lateral load, the foundation piles in pile group are subjected to radial load, axial load and bending moment. In order to study the influence of axial load on lateral bearing capacity of batter piles, large-scale model tests of three single piles and a 1×2 batter pile group have been conducted in a larger soil tank. It is found that the upward axial force on the pile top decreases the lateral stiffness and the lateral ultimate bearing capacity of batter pile; while the downward axial force enhances the horizontal stiffness and the lateral ultimate bearing capacity of batter pile. Based on the assumption of wedge failure of the shallow soil around piles, considering the influence of axial load on piles, a formula for calculating the lateral ultimate resistance force of soil is deduced. Then, a p-y curve method for resistance force of soil around piles is proposed. Finally, the formula and the proposed p-y curve method for batter pile are verified by model tests and field tests.
Institute of Scientific and Technical Information of China (English)
吴炎海; 方映平; 冯文贤; 蔡杨
2015-01-01
Axial static loading test was carried out on 6 recycled aggregate concrete filled circular steel tubular long columns. The whole loading process and failure modes were observed,and the curves of specimens about load-deformation and load-strain were plotted. The influences of the test parameters namely slenderness ratio and confine-ment index on deformation and the bearing capacities of specimens were analyzed. By domestic and foreign relevant specifications,the ultimate bearing capacity of the specimens were calculated and compared with the measured val-ues. The results indicated that the failure process of recycled aggregate concrete filled steel tubular long columns un-der axial compression includes elastic stage,elastic-plastic stage and plastic stage,and all the failure modes are elas-tic-plastic instability;Both the slenderness ratio and confinement index affect the mechanical performance of recy-cled aggregate concrete filled steel tubular long columns under axial loading,and the confinement index is more ob-vious;Finally,the calculation and design method of recycled aggregate filled steel tubular long columns under axial loading were proposed.%进行6根圆钢管再生混凝土长柱轴压的静力加载试验，观察试件受力的全过程和破坏形态，绘制出各试件的荷载-变形和荷载-应变关系曲线，分析长径比和套箍系数2个变化参数对试件变形和承载力的影响规律，采用国内外相关规程计算各试件的极限承载力并与实测值进行对比。结果表明：钢管再生混凝土轴压长柱受力过程经历了弹性阶段、弹塑性阶段和塑性下降阶段，均为弹塑性失稳破坏；长径比和套箍系数对钢管再生混凝土轴压长柱的受力性能均有影响，其中套箍系数影响较大；最后对于钢管再生混凝土长柱轴压的承载力计算及构件的设计提出建议。
Institute of Scientific and Technical Information of China (English)
王军民
2016-01-01
Through the elaboration on the mechanism of axial flow fan stall and in combination with double stage adjustable-blade axial flow induced draft fan stall in actual production of a power plant, the paper ana-lyzes the deep-seated causes of the stall and thus puts forward the principle of stall handling of induced draft fan in high load and effective measures for install prevention.%通过阐述轴流通风机失速的机理，结合某发电厂实际生产中双级动叶可调式轴流引风机失速的现象，分析发生失速的深层次原因，提出机组高负荷下处理引风机失速异常的原则以及防止失速的有效措施。
Directory of Open Access Journals (Sweden)
Achoura D.
2012-09-01
Full Text Available Dans cette étude, on présente les résultats expérimentaux obtenus sur des poteaux mixtes béton-acier mince réalisés par soudures. Un total de 24 profilés en acier, et en forme de I a été testé sous charge de compression uni-axiale à l’âge de 28 jours. les spécimens ont été réparties comme suit: 4 à vides, 4 partiellement remplies avec un béton ordinaire sans l’addition des connecteurs, 4 renforcés par des connecteurs de cisaillements de type cornière en U, 4 autres l’ont été avec des connecteurs de cisaillements type goujons et 8 restants ont été renforcés avec des liens transversaux d’espacement 100mm, 50mm, soudés aux bouts des ailes opposées. Les principaux paramètres étudiés sont: l’élancement du profilé, le type de connecteur de renforcement. A partir des résultats d’essais obtenus, il est confirmé que les parois minces sont plus sensibles de l’apparition au voilement et la longueur des profilés a un effet considérable sur la capacité portante et le mode de rupture. L’addition des connecteurs de renforcement a confirmé l’augmentation de la charge ultime par rapport aux profilés sans connecteurs. In the present work, results of tests conducted on thin welded steel-concrete stubs are presented. A total of 24 stubs an I steel section were tested under axial compression at 28 days after the date of casting, 4 were empty, 4 filled with normal concrete, 8 columns had shear connecters welded along the centreline of the web, and 8 columns had steel rods welded between the tips of opposing flanges on both sides of the spacing of the transverse link 100 mm and 50 mm. The main parameters studied were: the heel height, and type of connector strengthening. From the test results, it is confirmed that the thin walls are more sensitive to the appearance local buckling and the length of the profiles has a significant effect on the bearing capacity and failure mode. The bearing capacity was increased
Institute of Scientific and Technical Information of China (English)
陈仁朋; 任宇; 陈云敏
2011-01-01
刚性桩在高铁低矮路堤加固中广泛应用。利用浙江大学大型地基与边坡工程模型试验系统,开展了饱和粉土地基中刚性单桩动力加载大比例模型试验,对不同静偏荷载及循环荷载组合作用下的桩基性状进行了研究。通过模型桩身安装的各类传感器,对桩顶累积沉降、桩身轴力、桩–土界面孔压及正应力变化进行了监测。试验发现,循环剪切会引起桩–土界面土颗粒重排,导致桩–土界面孔压及有效应力状态发生改变。循环荷载比CLR对桩基累积沉降、桩侧应力状态发展影响显著。根据试验结果,对累积沉降发展规律进行了归纳,分析并讨论了桩侧应力状态变化机理。%Stiff pile-supported low embankments have been widely adopted in high-speed railway lines in China.Large-scale model tests are carried out to investigate the response of a single stiff pile subjected to axial dynamic loading in silts.Tests are conducted by means of the large foundation and slope engineering simulation system in Zhejiang University.Various combinations of static and cyclic loadings are applied in tests.The pile used in the tests are instrumented with load cells,pore pressure probes and pressure cells.The accumulated settlement,axial force,pore pressure and radial total stress along the pile are monitored.The test results indicate that the cyclic loading causes soil particle rearrangement,which leads to a change in stress state at soil-pile interface.The accumulated settlement and stresses acting on pile shaft are greatly influenced by the cyclic loading ratio（CLR）.The development of the accumulated settlement with different CLRs is summarized and presented.The possible mechanisms responsible for stress changes at soil-pile interface are discussed.
Institute of Scientific and Technical Information of China (English)
顾威; 李宏男; 孙国帅
2013-01-01
Four damaged concrete filled steel tube columns strengthened with carbon fiber reinforced plastics (CFRP) and four contrast columns were tested. All specimens were notched in the central zone to simulate the loss of section due to corrosion. All specimens were axially loaded while strain and displacement were measured to demonstrate the effectiveness of this repair concept. Influences of the CFRP confinement and the aspect ratio on the load bearing capacity of the columns are analyzed. The test results show that within the scope of the test, CFRP would enhance the load bearing capacity of the damaged concentrically compressed concrete filled steel tube columns effectively; the increase rate of load bearing capacity due to CFRP decreases with the increase of aspect ratio. A calculating method is also presented, capable of predicting the axial load strength of concrete filled CFRP steel tube members. Experimental results are in good agreement with the predicted values.%采用4个受损轴压钢管混凝土柱试件和4个用碳纤维复合材料(carbon fiber reinforced plastics,CFRP)加固的受损轴压钢管混凝土试件进行对比试验研究,分析两者的受力机理,评价CFRP加固受损轴压钢管混凝土承载力提高效果.结果表明:由于CFRP的环向约束,受损钢管混凝土的钢管和核心混凝土的径向变形受到了限制,受损钢管混凝土轴压承载力有不同程度提高,且其提高效果随着长细比的增加而变小；提出了加固前后受损钢管混凝土承载力计算方法,其计算结果与试验结果吻合良好.
Institute of Scientific and Technical Information of China (English)
丁发兴; 应小勇; 余志武; 欧进萍
2011-01-01
分析现有钢管轻骨料混凝土轴压短柱力学性能实验结果,提出轻骨料混凝土轴对称三轴受压轴向应力-应变关系,应用连续介质力学,确立圆钢管轻骨料混凝土同心圆柱体共同受压时的计算模型,建立了圆钢管轻骨料混凝土组合弹性模量理论计算公式和组合应力-应变关系的理论表达式,编制相应计算程序.结果表明,核心混凝土由于受钢管约束,其纵向应力有较大提高,延性得到显著改善,钢管在为轻骨料混凝土提供径向约束的同时,其纵向应力大幅降低;钢管对轻骨料混凝土的约束效果要低于对普通混凝土的约束效果.通过大量参数分析,得到钢管轻骨料混凝土轴压短柱极限承载力计算公式和组合应力-应变关系全曲线,计算与实验结果吻合良好.%Based on the experimental results of mechanical properties of lightweight aggregate concrete filled circular steel tubular (LCFST) stub columns under axial compression, the axial stress-axial strain relations of concrete under axisymmetric triaxial compression were proposed. Based on continuum mechanics, the calculation model for LCFST stub columns of concentric cylinders of circular steel tube with concrete core under concentrically loaded conditions was determined. The theoretical calculation formulas for composite elastic modulus and composite stress-strain relations of the stub columns were presented. A FORTRAN program for the elasto-plastic analysis of LCFST stub columns under concentric loading was developed. The reliability of the present method and program was validated by the test results from references. The behavior of LCFST stub columns was analyzed. The analysis results indicated that for confinement by steel tube, the axial stress of lightweight aggregate concrete core increased greatly and the ductility was improved, while the axial stress of steel tube decreased rapidly for confinement effect. Compared with normal concrete filled
Kurtz, S M; Pruitt, L A; Jewett, C W; Foulds, J R; Edidin, A A
1999-08-01
The mechanical behavior and evolution of crystalline morphology during large deformation of eight types of virgin and crosslinked ultra high molecular weight polyethylene (UHMWPE) were studied using the small punch test and transmission electron microscopy (TEM). We investigated the hypothesis that both radiation and chemical crosslinking hinder molecular mobility at large deformations, and hence promote strain hardening and molecular alignment during the multiaxial loading of the small punch test. Chemical crosslinking of UHMWPE was performed using 0.25% dicumyl peroxide (GHR 8110, GUR 1020 and 1050), and radiation crosslinking was performed using 150 kGy of electron beam radiation (GUR 1150). Crosslinking increased the ultimate load at failure and decreased the ultimate displacement of the polyethylenes during the small punch test. Crosslinking also increased the near-ultimate hardening behavior of the polyethylenes. Transmission electron microscopy was used to characterize the crystalline morphology of the bulk material, undeformed regions of the small punch test specimens, and deformed regions of the specimens oriented perpendicular and parallel to the punch direction. In contrast with the virgin polyethylenes, which showed only subtle evidence of lamellar alignment, the crosslinked polyethylenes exhibited enhanced crystalline lamellae orientation after the small punch test, predominantly in the direction parallel to the punch direction or deformation axis. Thus, the results of this study support the hypothesis that crosslinking promotes strain hardening during multiaxial loading because of increased resistance to molecular mobility at large deformations effected by molecular alignment. The data also illustrate the sensitivity of large deformation mechanical behavior and crystalline morphology to the method of crosslinking and resin of polyethylene.
Institute of Scientific and Technical Information of China (English)
钟大虎; 夏辉; 窦益华; 曹银萍
2014-01-01
为校核螺旋屈曲管柱的强度安全性，基于弹簧理论与第四强度理论，推导出螺旋屈曲状态下管柱内、外侧相当应力的计算公式，并以油田常用规格油套管为例，探讨了轴向压力对管柱内、外侧最大相当应力的影响。算例结果表明，螺旋屈曲管柱内侧最大相当应力恒大于外侧；管柱内、外侧最大相当应力随轴向压力的增大而增大。轴向压力由200KN 增大至800KN 时，管柱内、外侧最大相当应力分别增大170%和413.8%。研究弥补了传统管柱力学分析的不足，提供了螺旋屈曲管柱安全性研究新方法，同时也可为现场安全施工提供参考。%To make clear stress distribution and variation of helical buckling tubing string, the formulas of equivalent stresses inside and outside of the tubing string were deduced based on the spring theory and the fourth strength theory. Taking tubing string and casing commonly used in oilfield as object, stress calculation programs were compiled to explore the influence of axial compression load on equivalent VonMises stress. From the analysis, we can see that the equivalent VonMises stresses inside of the helical buckling tubing string were higher than that outside. The equivalent VonMises stress increased with the axial compression load, and the increase is 170 percent and 413.8 percent respectively for stress inside and outside of the tubing string with compression load increased from 200KN to 800KN. The proposed method used for the helical buckling tubing string covered the shortage of traditional tubular mechanics effectively and can also provide reference for the field application.
Chen, Kan; Liu, Xiang; Matsuki, Takayuki
2015-01-01
Inspired by the abundant experimental observation of axial vector states, we study whether the observed axial vector states can be categorized into the conventional axial vector meson family. In this paper we carry out analysis based on the mass spectra and two-body Okubo-Zweig-Iizuka-allowed decays. Besides testing the possible axial vector meson assignments, we also predict abundant information for their decays and the properties of some missing axial vector mesons, which are valuable to further experimental exploration of the observed and predicted axial vector mesons.
Institute of Scientific and Technical Information of China (English)
徐蔚蔚; 邵增务; 裴洪; 周建国; 黄吉军; 俞旭东; 熊蠡茗
2009-01-01
Objective To investigate the protective effects of nicotinamide against axial loading-induced rabbit intervertebral disc (IVD) degeneration. Methods Twenty-four Japanese white rabbits were randomly divided into 6 groups. Rabbit lumbar disc degeneration model was established by the controllable axial pressure of 98 N. The rabbits were given nicotinamide orally following the grouping. In group l,two rabbits were equipped with the controllable axial pressure device but not subjected to pressure or nicotinamide; In group 2, two rabbits were administered nicotinamide of 50 mg/(kg·d) for one week by gastric ga-vage; In group 3,five rabbits were loaded with controllable axial pressure of 98 N for one week; In group 4,five rabbits were loaded with controllable axial pressure of 98 N for one week,then restored one week by the removal of the pressure; In group 5.five rabbits were loaded with controllable axial pressure of 98 N for one week,and given nicotinamide of 50 mg/ (kg ? D) for one week prior to the removal of the pressure; In group 6,five rabbits were loaded with controllable axial pressure of 98 N for one week and restored one week, and simultaneously given nicotinamide of 50 mg/(kg·d) for two weeks via gastric ga-vage. The rabbit lumbar MRI and Thompson grades were used to score IVD degeneration; HE staining,type Ⅱ collagen immu-nohistochemistry staining and Safranin O-Fast Green staining were done to assess the histological changes in the IVD matrix; P16INK4A immunohistochemistry staining was used to detect the state of cell senescence. Results ① Immunohistochemistry staining of type Ⅱ collagen demonstrated that the pathological changes of IVDs were alleviated, and contents of collagen were increased by 53. 2% in the nicotinamide-treated groups as compared with group 4(P<0. 01) ;②Safranin O-Fast Green staining intensity of both nucleus pulposus (NP) and annular fibrosus in group 2 was increased as compared with group 1. The staining intensity in NP of
Directory of Open Access Journals (Sweden)
Adriano Gonçalves
2001-06-01
Full Text Available Para estruturas utilizadas no setor aeroespacial, os requisitos de baixo peso, alta resistência e rigidez, além de estabilidade dimensional, têm propiciado o aumento da utilização de materiais compósitos nas suas manufaturas. Em particular, cascas cilíndricas ou estruturas construídas pela junção de cilindros de paredes finas, confeccionadas em fibra de carbono e resina epóxi, são amplamente utilizadas neste tipo de aplicação. Neste trabalho, um programa experimental foi desenvolvido para determinar as tensões de falha, os módulos de elasticidade e o modo de falha de 47 cilindros com diâmetro interno de 40 mm e espessura nominal de 0,6 mm (com exceção de 2 corpos de prova, fabricados em carbono/epóxi, quando submetidos a cargas compressivas uniaxiais. Os espécimes testados possuíam diferentes razões entre comprimento e diâmetro (variando de 2,50 a 11,25 e seqüências de laminação variadas (orientações de camadas. Os resultados dos ensaios foram comparados aos obtidos em análises realizadas com programas de elementos finitos e os fatores que influenciaram o comportamento mecânico destes cilindros foram analisados.The requirements of low weight and dimensional stability, combined with high strength and stiffness, for aerospace structures has prompted an increasing use of fiber reinforced materials in manufacturing such structures. In particular, carbon/epoxy cylinders have been widely used in aerospace applications. In this work, an experimental program was developed to determine failure loads, modulus of elasticity and failure modes of 47 carbon/epoxy cylinders shells under compressive loads. The specimens tested had several different length/diameter (from 2.50 to 11.25 ratios and laminate lay-up. These results were compared to the analytical results from finite element code and the most important factors influencing the mechanical behavior of this type of structure were analyzed.
Lajnef, N.; Burgueño, R.; Borchani, W.; Sun, Y.
2014-05-01
A major obstacle limiting the development of deployable sensing and actuation solutions is the scarcity of power. Converted energy from ambient loading using piezoelectric scavengers is a possible solution. Most of the previously developed research focused on vibration-based piezoelectric harvesters which are typically characterized by a response with a narrow natural frequency range. Several techniques were used to improve their effectiveness. These methods focus only on the transducer’s properties and configurations, but do little to improve the stimuli from the source. In contrast, this work proposes to focus on the input deformations generated within the structure, and the induction of an amplified amplitude and up-converted frequency toward the harvesters’ natural spectrum. This paper introduces the concept of using mechanically-equivalent energy converters and frequency modulators that can transform low-amplitude and low-rate service deformations into an amplified vibration input to the piezoelectric transducer. The introduced concept allows energy conversion within the unexplored quasi-static frequency range (≪1 Hz). The post-buckling behavior of bilaterally constrained columns is used as the mechanism for frequency up-conversion. A bimorph cantilever polyvinylidene fluoride (PVDF) piezoelectric beam is used for energy conversion. Experimental prototypes were built and tested to validate the introduced concept and the levels of extractable power were evaluated for different cases under varying input frequencies. Finally, finite element simulations are reported to provide insight into the scalability and performance of the developed concept.
Energy Technology Data Exchange (ETDEWEB)
Nascimento, J.L.; Irmao, M.A.S.; Araujo, A.L.; Silva, A.A. [Universidade Federal de Campina Grande (UFCG), PB (Brazil). Dept. de Engenharia Mecanica
2004-07-01
Structures and mechanical components, subjects to conditions of loading in operation, accumulate faults during your useful lives. The detection and condition monitoring of the faults is essential of the point of view of the efficiency and safety. Efforts have been accomplished, in the sense of constituting models and methodologies that indicate the most opportune moment for the shut down industrial plant, seeking your maintenance. In the present work, it intends an alternative method for the detection and the condition monitoring of faults in a cantilever bar by the analysis of your longitudinal displacement. The methodology is constituted basically in simulating the computational model of the bar for Finite Element Method (FEM), where the faults are characterized by one of the elements with reduced transverse section. The existence of two classes of angular coefficients is noticed, that will be the analysis parameters, where the first tells respect the intact element and the second the damaged element, both different ones for each position and depth of simulated faults. The same ones are thrown as input in a Artificial Neural Networks, that once trained is capable to identify the position and the depth efficiently in that meets the faults. (author)
Institute of Scientific and Technical Information of China (English)
王玉银; 耿悦; 张素梅
2011-01-01
针对钢管混凝土拱桥中普遍采用的钢管微膨胀高性能混凝土,考虑轴压比、加载龄期等因素的影响,进行了圆钢管微膨胀混凝土轴心受压短柱的长期变形试验研究。采用逐步积分法,将5种不同混凝土收缩、徐变模型进行适当修正,应用于钢管微膨胀混凝土轴心受压短柱的长期变形分析,并将分析结果与试验结果进行对比。分析了含钢率、加载龄期、持荷时间、混凝土强度等因素对钢管微膨胀混凝土构件长期静力性能的影响。研究结果表明：修正后的EC2,MC90及AFREM模型在分析加载龄期不超过28d的钢管微膨胀混凝土构件在轴向荷载作用下的长期变形性能时具有较高的精度;核心混凝土时效作用对钢管微膨胀混凝土构件长期静力响应的影响显著。%Aimed at high performance concrete-filled steel tubular（CFST） with expansive additive which has been widely adopted in CFST arch bridges,considering the influence of axial compression ratio and loading age,test study of long-term deformation of circular CFST stubs with expansive additive under axial loading was carried out.Using step-by-step integration method,5 different concrete models of shrinkage and creep were modified,then modified models were applied to long-term deformation analysis of CFST stubs with expansive additive.Analysis result and test result were compared.The influences of ratio of steel area over concrete area,loading age,duration of loading,strength of the core concrete,etc.on the long-term static performance of these CFST specimens were analyzed.Results show that the modified models EC2,MC90 and AFREM can well predict the long-term deformation performance of CFST stubs with expansive additive loaded before 28 days.Time-effects of core concrete have considerable influence on the long-term static response of CFST specimens with expansive additive.
Institute of Scientific and Technical Information of China (English)
宋生志; 邵永波
2011-01-01
For typical tubular T-joint under axial loading, the failure generally occurs near the weld toe on the chord surface due to the fact that the stiffness of the chord in radial direction is much smaller than that of the brace in axial direction as well as the existence of high stress concentration along the weld toe. The static strength of tubular T-joints can be improved by filling concrete into the chord. Finite element analysis is con ducted to analyze 6 T-joint models under axial compression and tension by using sofware ABAQUS to prove that filling concrete in the chord is effective to improve the static strength. Different failure modes under axial compression and tension between tubular T-joint with circular hollow section and Concrete-Filled Circular Tu bular ( CFCT)T-joint are clarified. Thereafter, parametric investigation for CFCT T-joint, which involves the parameters of chord thickness T, the brace/chord diameter ratio β, the chord diameter/thickness ratio 2γ , the yield strength of the steel tube fy , and the compressive strength of concrete fc , is carried out. From the para metric study , the effect of parameters on the static strength of CFCT T-joints is concluded.%T型圆管节点在支管轴向力作用下,破坏位置一般出现在主管表面的焊趾处.主要是因为主管的径向刚度远小于支管的轴向刚度,并且节点部位存在较大的应力集中.为提高T型管节点的静力强度,可通过在主管中填充混凝土以提高其径向刚度来实现.为了研究主管填充混凝土对T型管节点静力强度的影响,用有限元分析软件(ABAQUS)首先对6个模型分别在支管轴向压力和拉力作用下进行分析,结果发现主管中填充混凝土对节点静力强度的提高是非常有效的.同时得出主管填充混凝土与未填充混凝土节点不同的破坏模态.然后,对圆钢管混凝土T型节点进行参数分析,参数主要包括主管厚度T、支主管管径比β、主管的径厚比2
Institute of Scientific and Technical Information of China (English)
南波; 武岳; 孙浩田
2015-01-01
The spacecraft skeletal structure is usually made of lightweight, high strength composite CFRP material, whose stability capacity is an important indicator of the structural safety performance. Firstly, pultruded CFRP short pipe compression test was done in this paper, focusing on the stiffness, ultimate strength and microscopic failure mode of carbon fiber reinforced resin matrix. Secondly, based on the Hashin failure criteria and using ANSYS finite element software to do numerical simulation showed that the numerical results from Hashin failure criterion can bet⁃ter predict the ultimate bearing capacity in the failure mode of CFRP composites. Next, the Hashin failure criteria are further compared with experiment by using the arc-length method to do numerical simulation for five types of CFRP slender pipes, rendering the load mid⁃span deflection curve of the whole process, summarizing the character⁃istics of its destruction, and deformation characteristics. The simulation results are in good agreement with experi⁃ment. Based on this, a large number of parameter analyses are evaluated and the experimental results are compared with the numerical analysis result. The relationship curve between stability factor Φ and slenderness ratio λ of the pultruded slender CFRP pipe was derived by the least squares fitting calculation. This research is convenient for the application in engineering practice.%航天器骨架结构通常由轻质高强CFRP（carbon fiber reinforced polymer）复合材料管制成，其稳定承载力成为结构安全性能的一项重要指标。对CFRP短管进行轴压试验，重点研究碳纤维增强复合材料的刚度、极限强度以及细观破坏模式。基于Hashin破坏准则进行二次开发，采用ANSYS有限元软件对试验过程进行了数值模拟，数值结果表明，Hashin破坏准则可以较好地预测CFRP复合材料破坏时的极限承载力。基于Hashin破坏准则，采用
Wang, Jun; Peng, Zhenzhen; Li, Aijie; Xu, Zujie; Chen, Xinmin
2013-12-01
The purpose of this study was to investigate the effect of four kinds of different contact strength on the three-dimensional displacement of an implant-supported fixed bridge using digital laser speckle photography method. An in vitro model of beagle mandible with an implant-supported fixed bridge in its right premolar region was developed. The bridge was Au-Pt metal-ceramic. The contact was recovered to four different tightnesses, named 0, 1, 2, and 3. Different axial concentrated static load was applied to abutments and bridge respectively. The three-dimensional displacement of the implant-supported fixed bridge was measured using digital laser speckle photographic method. The results demonstrated that the influence of contact tightness was mainly on the mesio-distal and buccal lingual parts. When the contact tightness reached number 3, the regularity of displacement distribution was changed. The present study proved that digital laser speckle photography was an effective method of measuring the micro-displacement. One of the criterions of contact recovering decreased the implant displacement effectively without changing the regularity of displacement distribution.
Directory of Open Access Journals (Sweden)
Anamaria Siriani de Oliveira
2006-02-01
extremidad libre con la carga rotacional externa (ELCR. Se seleccionaron 20 voluntarias (23,2 años ± 0,9 sedentarias. Ellos estimaron el grosor en mm. de los tríceps del brazo, los bíceps del brazo, pectoral mayor, trapecio y deltoides. El registro electromiográfico de superficie se hizo, durante la realización de los ejercicios con EFCA y de los con ELCR, usando 100% de la resistencia máxima establecidos previamente. Se compararon los valores de RMS normalizados por la reducción máxima voluntaria a través de modelo de efectos mixtos con un nivel de significancia de 5%. En estas condiciones experimentales, los resultados del estudio presente mostraron que ejercicios similares, clasificados por la condición de la extremidad y la dirección de la carga aplicada al miembro superior, promoven niveles similares de electromiografía con actividad en sólo parte de los músculos estudiados. Estos descubrimientos cuestionan la capacidad del sistema de la clasificación usada en este estudio para predecir el tipo de respuesta muscular esperada en el logro de tareas diferentes de misma clasificación.The knowledge of the electromyographic activity produced during shoulder exercises can help in determining its clinical applicability. The purpose of this study was to assess the influence of the load direction and the extremity condition on the electrical activity of the shoulder girdle and upper limb muscles during exercises with fixed distal extremity and external axial load (FEAL and mobile extremity with rotational external load (MERL. Twenty 23.2 ± 0.9 years old female sedentary volunteers were selected. The triceps brachii, biceps brachii, major pectoral, trapezium and deltoid muscles were assessed. The surface electromyography was recorded during two FEAL and two MERL exercises using 100% of the previously established maximal resistance. The RMS values normalized by the maximal voluntary contraction were compared by a mixed effect model with 5% significance level. In
Institute of Scientific and Technical Information of China (English)
张宇; 管仁伟; 安伟; 徐峰
2013-01-01
在不同工况下,采用商业软件Numeca的Fine/Turbo模块,对包含叶轮、导叶、弯管、喇叭管的轻载型轴流泵进行了全流道的三维湍流数值模拟计算,并在与已有试验数据进行了较好吻合的基础上,对其内部流场进行了详细地数值分析,通过分析轴流泵内部的流动特点,找出了造成原模型流动损失的可能原因,发现由于局部结构设计不合理,流道内产生了漩涡区.针对这一问题提出了改进措施,采用商业软件Numeca的Design3D模块对叶轮叶型压力面和吸力面进行多参数化优化.结果表明,控制压力面、吸力面型线可以有效控制叶片出口处的漩涡,改进后的流道内存在的涡团和流动损失减少,叶轮的水力效和扬程等性能参数相对提高.%Using a commercial software Numeca Fine/Turbo, a numerical algorithm is presented to simulate three-dimensional turbulent flow for a light load type axial flow pump impeller, including the impeller, the guide vane and the bend pipe under different conditions. Through analyzing the axial flow pump internal flow characteristics, we find out the flow loss of the original model, such as vast vortexes areas and wall flow separations. Furthermore, we use the Numeca/Design3D software to optimize the parameters and to redesign the blade profile. The results show that changing the pressure and suctione lines can effectively control the blade of the swirl, resulting in the vortex and flow loss reduction and increasing the efficiency of the impeller hydraulic lift.
Institute of Scientific and Technical Information of China (English)
韩强; 杜修力; 赵彦; 王利辉
2013-01-01
To investigate the seismic performance of reinforced concrete (RC) rectangular hollow bridge piers, cyclic testing on five well-confined specimens was performed under constant axial load and biaxial bending. The test variables included axial load ratio, longitudinal reinforcement ratio and lateral reinforcement ratio. The results show that these specimens are flexural failure modes; biaxial force and displacement hysteretic loops show significant stiffness and strength degradation, pinching effect and coupling interaction of the structural seismic resistances in both directions; the ductility coefficient, varying from 3. 5 to 5. 7, and the equivalent viscous damping ratio, varying from 0. 19 to 0. 26, can meet the requirements of seismic design; RC rectangular hollow bridge piers with configurations of lateral reinforcement subject to bi-directional earthquake components have excellent earthquake resistance, and can substitute for current hollow RC rectangular section configurations described in the Chinese Guideline for Seismic Design of Highway Bridges (JTG/T B02-01-2008); and the length of the plastic hinge region is found to approach one sixth of the the hollow RC rectangular bridge pier height for all specimen piers, which is far less than the currently specified minimum value in Chinese Guideline, so the length of plastic hinge region is more concentrated for RC rectangular hollow bridge piers.%为了研究水平双向地震作用下矩形空心桥墩的抗震性能,对约束良好但轴压比和纵向、横向配筋率不同的5个钢筋混凝土(RC)矩形空心桥墩在轴力和双向弯曲作用下的性能进行了循环试验研究.结果表明:试件破坏形态为桥墩底部形成塑性铰的弯曲形破坏,桥墩双向力-位移滞回曲线显示了双向压弯状态下RC矩形空心桥墩刚度和强度退化、捏拢效应以及2个水平方向抗震性能的相互影响；试件桥墩的延性系数在3.5～5.7之间,等效粘滞阻尼系数在0
Institute of Scientific and Technical Information of China (English)
叶卉; 曲慧; 姜岩
2016-01-01
采用有限元软件ABAQUS建立冲击荷载下一端固支一端可轴向移动的T型管节点的有限元分析模型。基于该模型，研究了轴力作用下普通和局部加厚T型管节点在横向冲击荷载下的破坏模态，并对冲击力时程曲线、位移时程曲线、能量耗散等抗冲击性能指标进行了分析。分析结果表明：增加主管的厚度可以显著提高试件的节点抗弯刚度，降低节点区域的损伤；但当主管加厚部分的长度达到一定值，节点抗冲击性能将不再提高，研究结果可为管节点的抗冲击设计和损伤修复提供依据。%A finite element analysis model is established on the base of the finite element software ABAQUS to sim-ulate the dynamic performance of tubular T-joint with/ without reinforced chord under impact loading. One end of the joint model is simulated as fixed support, and the other end is modeled as a sliding support which can only move in the axial direction. Based on the finite element model, the failure modes of T-joint with/ without reinforced by increasing the thickness of the chord on the joint zone are defined, and the impact indexes of the two types of joints, such as time history curve of impact load, time history curve of lateral displacement and energy consump-tion, are investigated. It can be concluded that the flexural stiffness is improved, and the damage of joint zone is reduced after the tubular T-joint is thickened around the joint zone. However, the length of the reinforced joint zone plays the role of a little role in improving the impact performances of tubular T-joint when it exceeds certain value. The analysis results could be served as a reference for the anti-impact design and repair of damaged tubular joint.
Institute of Scientific and Technical Information of China (English)
周建国; 杨述华; 杨操; 邵增务; 徐蔚蔚; 郭兵; 俞旭东; 熊蠡茗
2009-01-01
的椎间盘恢复.%BACKGROUND:Recent studies have demonstrated that Niacinamide is capable of promoting the proliferation of intervertebral cells and improving intervertebral disc degeneration.Overloading is thought to the main cause of intervertebral disc degeneration.However,the protective effects of Niacinamide in loading induced intervertebral disc degeneration remains uncertain,OBJECTIVE:To investigate the protective effects of Niacinamide against axial loading induced degeneration of rabbit lumbar disc.DESIGN,TIME AND SETTING:A randomized controlled experiment was carded out in the Central Laboratory and the Laboratory of Department of Orthopaedics,Union Hospital Affiliated to Tongji Medical College,Huazhong University of Science and Technology from November 2008 to April 2009.MATERIALS:Twenty-four Japanese white rabbits (4 months old,weighing 2.0 kg).Niacinamide was supplied by Tianjin Damao Chemical Reagent Factory.METHODS:Twenty-four Japanese white rabbits were randomly divided into 6 groups.The controllable axial loading induced rabbit lumbar disc degeneration model was adopted to impose 98N pressure on the rabbit discs to induce degeneration.Various doses of Niacinamide were given intragastrically to the rabbits in different groups:2 rabbits in group 1,the loading device was installed without pressing,and no Niacinamide was given;2 rabbits in group 2,given 50 mg/kg Niacinamide for 1 week;5 rabbits in group 3,loaded with 98N for 1 week;5 rabbits in group 4,loaded with 98N for 1 week,then the pressure was released for another week's recovery;5 rabbits in group 5,loaded with 98N and given 50 mg/kg Niacinamide for 1 week;5 rabbits in group 6,loaded with 98N for 1 week and then the pressure was released for another week's recovery,50 mg/kg Niacinamide was continually given during the 2 weeks.MAIN OUTCOME MEASURES:Magnetic resonance image and Thompson's grading system were used to assess degeneration degree of the discs;hematoxylin and eosin staining,immunohistochemical staining for type Ⅱ collagen
Institute of Scientific and Technical Information of China (English)
李国荣; 朱晓东; 田步升; 陈海丰
2011-01-01
Objective To test the total artificial heart with axial flow pumps in a mock circuit, and explore the physiological basis of the control program. Methods The prototype of the total artificial heart was constructed by 2 axial flow pumps as substitute for the left and right heart pump respectively. The two blood pumps were housed in a rigid shell, with diameter of 65 mm and length of 70 mm. The performance of the total artificial heart was tested by concatenating the 2 axial flow pumps in a mock circuit. Results When the preload was fixed, the cardiac output was gradually decreased with the increase in afterload. The inhibitory effect of the afterload on cardiac output was attenuated by increasing the pump flow rate. In the current study, the speed of the left and right pumps were set at 11 000 r/min and 8 500 r/min respectively, which led to a flow rate of 5 Umin against 13.3 kPa(100 mmHg)after load. However, when the afterload increased to 26.7 kPa(200 mmHg), the flow rate dropped to 0. Improved pump speed could effectively compensate this trend and the increase in preload did not obviously affect the output of artificial heart when the afterload was fixed. It was ohserved that when the preload was changed from 0.27 kPa(2 mmHg) to 1.87 kPa(14 mmHg), the output of the total artificial heart maintained at 7 L/min. Conclusion It is demonstrated that the cardiac output of the artificial heart is significantly restrained by the afterload while the preload exhibited little influence on it. Further investigation is needed to explore the significance of the difference in the load response characteristic between the artificial heart employed in the current study and the natural heart.%目的 在体外模拟循环台测试轴流泵式全人工心脏的基本负荷反应特性,为探索生理性控制方案提供基础.方法 轴流泵式全人工心脏样机采用2个轴流泵共同设置在刚性外壳中,直径65mm,长度70mm.于模拟循环台
Dynamic buckling of double-walled carbon nanotubes under axial impact loading%轴向冲击载荷作用下双壁碳纳米管的动力屈曲
Institute of Scientific and Technical Information of China (English)
姚小虎; 张晓晴; 韩强
2011-01-01
Using the modified finite element method, the nonlinear shell-spring finite element model is established with taking the van der waals force into account. Based on the B-R motion criterion, the dynamic bucking behaviors of multi-walled carbon nanotubes are examined systemically. The dynamic critical loads for buckling and failure of double-walled carbon nanotubes under axial impact load are obtained. It is shown that in the dynamic buckling process of multi-walled carbon nanotubes, the deformation of each wall is harmonious to each other and the change of interlayer spacing is very small. The magnitude and the duration of impact load as well as the length of carbon nanotube have greater effects on the dynamic buckling of carbon nanotubes. For the shorter carbon nanotubes, asymmetrical buckling mode appears earlier. The simulations further show that the stress wave propagation in carbon nanotubes induces the asymmetrical buckling mode. In the dynamic buckling process of carbon nanotubes, there are four circumferential lobes that can be observed obviously, and their wave crest and trough of the lobes change alternately.%应用改进的有限元方法,建立考虑层间范德华力作用的壳-弹簧非线性有限元模型,基于B-R运动准则,系统地研究了双壁碳纳米管的动力屈曲问题,得到了轴向冲击载荷作用下双壁碳纳米管的临界动力屈曲载荷和临界动力失效载荷.研究结果表明,在动力屈曲过程中,双壁碳纳米管层间距的变化非常小,各管的变形相互协调;碳纳米管中应力波的传播导致碳纳米管出现非对称屈曲模态,可明显观测到四个环向波瓣,沿着碳纳米管的轴线方向,四个波瓣的波峰和波谷交替变化.对碳纳米管动力屈曲问题的研究表明,冲击载荷的大小和持续时间对碳纳米管的动力屈曲有较大影响,同时碳纳米管的长度对碳纳米管的动力屈曲也有较大的影响,较短的碳纳米管较早出现非对称屈曲模态.
Institute of Scientific and Technical Information of China (English)
郑宝锋; 舒赣平; 沈晓明
2012-01-01
ANSYS is employed to study the overall buckling properties of stainless steel cold formed tubular columns under axial load. Non-linear property of material, the effect of cold-formed, local and overall imperfection as well as the residual stress are considered in this model. The comparisons between test results and the calculated results are performed in order to verify the FEM model. Comparisons indicate that the developed FEM model could represent the test exactly and the deviations in average are limited in 5%. Then the influences of varieties of factor are valued. The results of parameterized analysis conclude that： the influence of the increase strength in the corner region, the parameters variation of the material property and the amplitude of the overall imperfection could cause considerable changes in the buckling strength of stainless columns; shifts in section types almost do not influence the buckling strength. The conclusion could be regarded as the foundation of the design method for cold-formed stainless steel columns.%采用有限元软件ANSYS对不锈钢冷成型管截面轴心受压长柱进行模拟，有限元模型中考虑不锈钢材料的非线性本构关系、冷加工效应、构件的初始缺陷以及构件中的残余应力。将模拟结果与国内外的试验数据进行对比。对比表明：有限元模型能够准确地模拟不锈钢构件的受力全过程，模拟平均误差小于5％；对影响不锈钢轴心受压构件受力性能的因素进行分析，分析表明：方矩管截面的转角区冷加工效应，不锈钢材料力学性能参数变化以及构件的整体缺陷取值对构件的整体稳定性能影响较大，而不锈钢构件的截面对稳定系数影响很小。分析结论可作为建立不锈钢轴心受压构件稳定承载力设计公式的参考。
圆端形钢管混凝土短柱轴压性能仿真分析%Simulation Analysis of Round-ended Rectangular CFST Stub Columns Under Axial Load
Institute of Scientific and Technical Information of China (English)
李培鹏; 任志刚
2014-01-01
基于ABAQUS内核脚本接口,运用Python语言编写圆端形钢管混凝土的参数化建模程序,采用Von Mises、Concrete Smeared Cracking、Concrete Damaged Plasticity 3种混凝土材料模型,开展了圆端型钢管混凝土短柱轴压性能非线性有限元分析,并与已有实验结果进行比较,以校验模型的适用性.最后,分析了不同截面高宽比对构件约束效应和承载性能的影响.结果表明:基于脚本语言的参数化建模方法很大程度上提高了构件建模和分析效率;ConcreteDamaged Plasticity模型相对其他两种模型更具合理性;截面半圆和直边附近区域分别为核心混凝土的强/弱约束区,整体约束效应随着高宽比增大而减弱;约束效应的减弱对极限承载力的影响不明显,但会导致构件塑性和延性的明显减小.%Based on the scripting interface of ABAQUS,the round-ended rectangular CFST parametric modeling program was written in Python language.The nonlinear finite element analysis of round-ended CFST under axial load was conducted using three concrete material models—Von Mises,Concrete Smeared Cracking,Concrete Damaged Plasticity.Then,the analysis results were compared with the experimental data to verify the applicability of the models.The influences of confinement effect and bearing behavior on the specimens under different cross-sectional aspect ratios were also explored.The experimental results showed that the parametric modeling method based on scripting language greatly can improve the efficiency of modeling and analysis.The Damaged Plasticity model is more reasonable than the other two models.The areas around semicircular and straight edge are respectively the strong and weak confinement region of the core concrete,and confinement effect weakens with the increase of aspect ratio.The weakening confinement effect has trifling impact on ultimate bearing capacities of round-ended rectangular CFST,but it can lead to an apparent decrease of
Institute of Scientific and Technical Information of China (English)
付小超; 李元齐; 沈祖炎
2016-01-01
为研究开口冷弯厚壁型钢构件在轴向滞回荷载作用下的抗震性能,首先选取了3根壁厚t>6 mm的冷弯内卷边槽钢进行轴向滞回试验,然后建立相关的ANSYS有限元模型进行模拟计算,在与试验结果对比的基础上,选取了不同的腹板宽厚比(h/t=25~90)、绕弱轴长细比(λy=30~90)的构件进行参数化分析计算.研究结果表明:宽厚比、长细比是影响冷弯型钢抗震性能的两个主要因素,宽厚比(h/t)越大抗震性能越差,长细比(λy)越大抗震性能同样也越差,设计时应尽量避免选择长细比和宽厚比均较大的构件.%In order to investigate the hysteretic behaviors of opening cold-formed thick-walled steel members under the axial cyclic loading, three cold-formed steel columns were tested. On the basis of compared with the test results, a finite element method ( FEM) in ANSYS was established. The in-fluence of width-thickness ratio ( h/t) rang from 25 to 90 for web and slenderness ratio about the weak axis y (λy ) rang from 30 to 90 of such members were investigated by FEM. Analysis results in-dicated that the width-thickness ratio and the slenderness ratio about the weak axis y are the most important factors to affect the hysteretic behaviors. So, the cold-formed steels which with great width-thickness ratio ( h/t) and great slenderness ratio (λy ) should be avoided in designing, because they will lead to poor seismic performance.
Strength analysis of concrete sandwich panel with wire mesh under axial loading%钢丝网架混凝土夹芯墙板轴心受压承载力分析
Institute of Scientific and Technical Information of China (English)
谢群; 王帅; 刘春
2015-01-01
Concrete sandwich panels with steel wire mesh are widely used in multi-storey residential buildings and office buildings with the advantages of low self-weight,high strength as well as convenient construction.To better understand the structural behavior and ensure application safety, three typical methods recommended by different codes for strength prediction of panels subjected to axial compressive loading have been presented with the assumption of full composite section character. The analysis results which have been compared with the existing experimental results show that the parameter of slenderness ratio has great effect on the compressive behavior of concrete sandwich panel and all the three methods are not expected to be applicable any more in the cases that slenderness ratio is more than 25 for the sake of poor structural safety.The ratio of predicted ultimate strength obtained from recommended formula of domestic codes to the peak load in experimental analysis ranges from 0.75 to 1.3 which means that the strength is much overestimated with big divergence and these methods couldn’t be applied to strength analysis for the sake of structural safety.While the strength arising from ACI318 -11 method could reach 70% ~90% the testing value which provides satisfactory result with more reliability and better agreement with testing data for concrete sandwich panel structural design.%钢丝网架混凝土夹芯墙板作为一种轻质、高强、施工便捷的构件已广泛应用于多层住宅和办公楼，研究该类墙板的受力性能可有效确保其结构使用安全。文章选用三种代表性的计算方法对该类墙板的轴压承载力进行了理论分析，并将计算结果与已有的试验数据进行了对比研究。结果表明：高厚比对墙板受压性能影响较大，当墙板高厚比超过25时，现有的理论不再适用于轴压承载力计算；三种计算方法的结果对比可知，采用国家规范 GB 50010—2010
Institute of Scientific and Technical Information of China (English)
魏冬; 夏群; 苗军; 白剑强; 刘佳男; 李宏达
2016-01-01
BACKGROUND:The cervical spine of the human body is an important structure carrying the head and connecting the spine. Its volume is smal, but its flexibility was great. Activity frequency was highest. Simultaneously, cervical spine is the most complicated bony structure of geometric and kinematic characteristics of human body, bears the physiological load of the head, has functions of flexion and extension, lateral bending and rotation. Therefore, the cervical spine has become one of the most vulnerable structures with degenerative diseases of the spine. Analysis of upper cervical spine biomechanics, recognition and understanding of its normal function and mechanical mechanism wil provide a theoretical basis for better treatment of upper cervical spine disorders. OBJECTIVE:To observe thein vivothree-dimensional kinematics of the upper cervical spine in healthy human beings under physiological load with dual fluorescence X-ray imaging system and spiral CT. METHODS:Seventeen healthy volunteers were recruited for this study. The vertebral segment motion of each subject was reconstructed with three-dimensional computed tomography and solid modeling software.In vivo cervical vertebral motion during functional postures was observed with dual fluoroscopic imaging. Coordinate systems were established at the vertebral center to obtain the intervertebral range of motion. RESULTS AND CONCLUSION: (1) During the flexion-extension motion, significant differences in the distance in coronal axis, sagittal axis and angle of rotation were detected in C1-2 and C2-3segments. (2) During the left-right bending motion, the angle of rotation was obviously greater at C1-2 segment than that at C2-3segment. During the left-right twisting motion, significant differences in distance of the vertical axis and the coronal axis, lateral flexion angle and rotation angle were detectable between C1-2and C2-3 segments. (3) These findings confirmed that dual fluorescence X-ray imaging system combined
Altered Axial Skeletal Development
The axial skeleton is routinely examined in standard developmental toxicity bioassays and has proven to be sensitive to a wide variety of chemical agents. Dysmorphogenesis in the skull, vertebral column and ribs has been described in both human populations and in laboratory anima...
Anamaria Siriani de Oliveira; Carina Maria de Souza Freitas; Francisco Henrique Monaretti; Francislei Ferreira; Reinaldo Noguti; Fausto Bérzin
2006-01-01
O conhecimento da atividade eletromiográfica produzida durante a realização de exercícios para o ombro pode auxiliar na determinação de sua aplicabilidade clínica. O objetivo desta pesquisa foi avaliar a influência da direção da carga e condição da extremidade na atividade elétrica de músculos da cintura escapular e membro superior durante a realização de exercícios com a extremidade distal fixa e carga externa axial (EFCA) e extremidade livre com carga externa rotacional (ELCR). Foram seleci...
Axial flow heat exchanger devices and methods for heat transfer using axial flow devices
Energy Technology Data Exchange (ETDEWEB)
Koplow, Jeffrey P.
2016-02-16
Systems and methods described herein are directed to rotary heat exchangers configured to transfer heat to a heat transfer medium flowing in substantially axial direction within the heat exchangers. Exemplary heat exchangers include a heat conducting structure which is configured to be in thermal contact with a thermal load or a thermal sink, and a heat transfer structure rotatably coupled to the heat conducting structure to form a gap region between the heat conducting structure and the heat transfer structure, the heat transfer structure being configured to rotate during operation of the device. In example devices heat may be transferred across the gap region from a heated axial flow of the heat transfer medium to a cool stationary heat conducting structure, or from a heated stationary conducting structure to a cool axial flow of the heat transfer medium.
Effect of weld reinforcement on axial plastic buckling of welded steel cylindrical shells
Institute of Scientific and Technical Information of China (English)
Chu-lin YU; Zhi-ping CHEN; Ji WANG; Shun-juan YAN; Li-cai YANG
2012-01-01
The effect of weld reinforcement on axial plastic buckling of welded steel cylindrical shells is investigated through experimental and numerical buckling analysis using six welded steel cylindrical shell specimens.The relationship between the amplitude of weld reinforcement and the axial plastic buckling critical load is explored.The effect of the material yield strength and the number of circumferential welds on the axial plastic buckling is studied.Results show that circumferential weld reinforcement represents a severe imperfect form of axially compressed welded steel cylindrical shells and the axial plastic buckling critical load decreases with the increment of the mean amplitude of circumferential weld reinforcement.The material yield strength and the number of circumferential welds are found to have no significant effect on buckling waveforms; however,the axial plastic buckling critical load can be decreased to some extent with the increase of the number of circumferential welds.
An Assessment of Cumulative Axial and Torsional Fatigue in a Cobalt-Base Superalloy
Kalluri, Sreeramesh; Bonacuse, Peter J.
2010-01-01
Cumulative fatigue under axial and torsional loading conditions can include both load-order (higMow and low/high) as well as load-type sequence (axial/torsional and torsional/axial) effects. Previously reported experimental studies on a cobalt-base superalloy, Haynes 188 at 538 C, addressed these effects. These studies characterized the cumulative axial and torsional fatigue behavior under high amplitude followed by low amplitude (Kalluri, S. and Bonacuse, P. J., "Cumulative Axial and Torsional Fatigue: An Investigation of Load-Type Sequance Effects," in Multiaxial Fatigue and Deformation: Testing and Prediction, ASTM STP 1387, S. Kalluri, and P. J. Bonacuse, Eds., American Society for Testing and Materials, West Conshohocken, PA, 2000, pp. 281-301) and low amplitude followed by high amplitude (Bonacuse, P. and Kalluri, S. "Sequenced Axial and Torsional Cumulative Fatigue: Low Amplitude Followed by High Amplitude Loading," Biaxial/Multiaxial Fatigue and Fracture, ESIS Publication 31, A. Carpinteri, M. De Freitas, and A. Spagnoli, Eds., Elsevier, New York, 2003, pp. 165-182) conditions. In both studies, experiments with the following four load-type sequences were performed: (a) axial/axial, (b) torsional/torsional, (c) axial/torsional, and (d) torsional/axial. In this paper, the cumulative axial and torsional fatigue data generated in the two previous studies are combined to generate a comprehensive cumulative fatigue database on both the load-order and load-type sequence effects. This comprehensive database is used to examine applicability of the Palmgren-langer-Miner linear damage rule and a nonlinear damage curve approach for Haynes 188 subjected to the load-order and load-type sequencing described above. Summations of life fractions from the experiments are compared to the predictions from both the linear and nonlinear cumulative fatigue damage approaches. The significance of load-order versus load-type sequence effects for axial and torsional loading conditions
Dynamic response of the occipito-atlanto-axial (C0-C1-C2) complex in right axial rotation.
Chang, H; Gilbertson, L G; Goel, V K; Winterbottom, J M; Clark, C R; Patwardhan, A
1992-05-01
The torque-angular deformation in right axial rotation until failure of the ligamentous occipito-atlanto-axial complex subjected to variable loading rate (dynamic) axial torque was characterized using a biaxial MTS system. A special fixture and gear box that permitted right axial rotation of the specimen until failure without imposing any additional constraints were used to obtain the data. The specimens were divided into three groups and tested until failure at three different dynamic loading rates: 50, 100, and 400 degrees/s. A previous study by the authors provided data for quasi-static (4 degrees/s) loading conditions. The torque versus rotation curves can be divided into two straight regions and two transition zones. The plots clearly indicated that at loading rates higher than 4 degrees/s, the specimens became stiffer in the region of steadily increasing resistance prior to failure. The increase in stiffness was maximum at 100 degrees/s. The stiffness decreased somewhat at 400 degrees/s in comparison with 100 degrees/s, but this decrease was not significant. The resulting torque-right axial rotation curves were also examined to estimate the magnitude of maximum resistance (torque) and the corresponding angular rotation value. The average maximum resistance torque increased from 13.6 Nm at 4 degrees/s to 27.8 Nm at 100 degrees/s. The corresponding right angular rotation data (65-78 degrees), however, did not show any significant variation with loading rate. Posttest dissection of the specimens indicated that the type of injury observed was related to the rate of axial loading imposed on a specimen during testing.(ABSTRACT TRUNCATED AT 250 WORDS)
Buckling localization in a cylindrical panel under axial compression
DEFF Research Database (Denmark)
Tvergaard, Viggo; Needleman, A.
2000-01-01
Localization of an initially periodic buckling pattern is investigated for an axially compressed elastic-plastic cylindrical panel of the type occurring between axial stiffeners on cylindrical shells. The phenomenon of buckling localization and its analogy with plastic flow localization in tensile...... test specimens is discussed in general. For the cylindrical panel, it is shown that buckling localization develops shortly after a maximum load has been attained, and this occurs for a purely elastic panel as well as for elastic-plastic panels. In a case where localization occurs after a load maximum......, but where subsequently the load starts to increase again, it is found that near the local load minimum, the buckling pattern switches back to a periodic type of pattern. The inelastic material behavior of the panel is described in terms of J(2) corner theory, which avoids the sometimes unrealistically high...
FINITE ELEMENT ANALYSIS OF AXIAL FEED BAR ROLLING
Institute of Scientific and Technical Information of China (English)
C.G. Xu; G.H. Liu; G.S. Ren; Z. Shen; C.P. Ma; W. W. Ren
2007-01-01
A flexible technique of hot working of bars by axial feed rolling was introduced. The processdeformation, strain field, stress field, and temperature field of the parts are analyzed by finite elementmethod (FEM)-simulation software DEFORM-3D. The material flow rule and tool load have beeninvestigated.
Build Axial Gradient Field by Using Axial Magnetized Permanent Rings
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
Axial magnetic field produced by an axial magnetized permanent ring was studied. For two permanent rings, if they are magnetized in the same directions, a nearly uniform axial field can be produced. If they are magnetized in opposite direction,an axial gradient magnetic field can be generated, with the field range changing from -B0 to B0. A permanent magnet with a high axial gradient field was fabricated, the measured results agree with the PANDIRA calculation very well. For wider usage,it is desirable for the field gradient to be changed. Some methods to produce the variable gradient field are presented. These kinds of axial gradient magnetic field can also be used as a beam focusing for linear accelerator if the periodic field can be produced along the beam trajectory. The axial magnetic field is something like a solenoid, large stray field will leak to the outside environment if no method is taken to control them. In this paper, one method is illustrated to shield off the outside leakage field.
High Power Disk Loaded Guide Load
Energy Technology Data Exchange (ETDEWEB)
Farkas, Z.D.; /SLAC
2006-02-22
A method to design a matching section from a smooth guide to a disk-loaded guide, using a variation of broadband matching, [1, 2] is described. Using this method, we show how to design high power loads. The load consists of a disk-loaded coaxial guide operating in the TE{sub 01}-mode. We use this mode because it has no electric field terminating on a conductor, has no axial currents, and has no current at the cylinder-disk interface. A high power load design that has -35 dB reflection and a 200 MHz, -20 dB bandwidth, is presented. It is expected that it will carry the 600 MW output peak power of the pulse compression network. We use coaxial geometry and stainless steel material to increase the attenuation per cell.
Notari, Alessio
2016-01-01
We analyze in detail the background cosmological evolution of a scalar field coupled to a massless abelian gauge field through an axial term $\\frac{\\phi}{f_\\gamma} F \\tilde{F}$, such as in the case of an axion. Gauge fields in this case are known to experience tachyonic growth and therefore can backreact on the background as an effective dissipation into radiation energy density $\\rho_R$, which which can lead to inflation without the need of a flat potential. We analyze the system, for momenta $k$ smaller than the cutoff $f_\\gamma$, including numerically the backreaction. We consider the evolution from a given static initial condition and explicitly show that, if $f_\\gamma$ is smaller than the field excursion $\\phi_0$ by about a factor of at least ${\\cal O} (20)$, there is a friction effect which turns on before that the field can fall down and which can then lead to a very long stage of inflation with a generic potential. In addition we find superimposed oscillations, which would get imprinted on any kind of...
Institute of Scientific and Technical Information of China (English)
肖海兵; 赵均海; 孙楚平; 彭宁; 孙珊珊
2012-01-01
Based on the unified strength theory, considering the effects of the intermediate principal stress and the differences of the multi-axial strength criterion for the lightweight aggregate concrete and common concrete, by introducing parameter αu and/βu, loop tensile stress σθ , longitudinal compressive stress σ, and radial compressiye stress σ of the thin- walled steel tube in ultimate bearing condition were obtained. Thus the calculation formula of ultimate bearing capacity of thin-walled steel tube short columns filled with lightweight aggregate concrete was deduced, and the influence complication was analyzed. Compared with the obtained solution and the test results in reference, good agreement can be found. The results indicate that the unified strength theory has the good applicability in the calculation of ultimate bearing capacity of thin-walled steel tube short columns filled with lightweight aggregate concrete. The results can provide theoretical foundation for the design of thin-walled steel tube filled with lightweight aggregate concrete.%运用统一强度理论,考虑中间主应力的影响,引入参数αu,βu确定薄壁钢管在极限荷载时的环向拉应力σθ、纵向压应力σz和径向压应力σr,并考虑轻骨料混凝土与普通混凝土多轴强度准则差异的影响,推导出薄壁钢管轻骨料混凝土轴压短柱的极限承载力公式,并对影响因素进行了分析。将本文计算结果与文献试验数据进行比较,结果吻合良好,表明将统一强度理论运用于薄壁钢管轻骨料混凝土轴压短柱承载力计算是可行的。该结果为薄壁钢管轻骨料混凝土的优化设计提供了一定的理论依据。
Institute of Scientific and Technical Information of China (English)
王海燕; 童贤鑫
2012-01-01
Currently, engineering method is usually used to compute the load carrying capacity of the panels in a design process. In this paper, three major engineering methods are briefly described and investigated. These methods are evaluated through the comparison of calculated results and test data, for the stiffed panels of the central wing and fuselage of an aircraft. It is shown that the results from ultimate load method are safer and more consistent with the experimental data. The reasonable allowable stress for central wing of the aircraft is specified according to the previous comparisons and analysis. Finally, eleven types of stiffened panels under axi- al compression of the aircraft fuselage are calculated by using ultimate load method. The results agree well with the experimental data. It is approved that this method can meet the requirement more accurately and utility in engineering design.%目前飞机设计中主要采用工程方法计算加筋壁板的承载能力。本文介绍并评述了分段处理法、John-son法和极限载荷法三种常用的工程方法，为了探讨哪种方法能更加满足工程需要，采用这三种方法对某型飞机中央翼加筋壁板及其试验件分别进行计算，表明其中极限载荷法的计算结果偏于安全，与试验结果吻合较好，并采用此法确定了中央翼加筋壁板的承载能力。最后采用极限载荷法进一步计算该型飞机机身11种构型加筋壁板轴压试验件，破坏载荷计算值与试验结果相当吻合，从而证实了极限载荷法是一种计算轴压加筋壁板承载能力更准确、实用的工程方法。
Institute of Scientific and Technical Information of China (English)
吴昊; 仲政
2016-01-01
工程中的大多数构件承受着比例或非比例多轴疲劳荷载作用,而非比例强化效应会大大影响其多轴疲劳寿命.精确预测金属材料在多轴非比例荷载下的低周疲劳寿命需要同时考虑等向强化、随动强化及非比例强化效应下的材料本构关系,并在临界面上计算出相应应力应变值,根据不同疲劳失效形式选取不同类型的失效模型来确定疲劳寿命.本文针对这一过程中重要知识点进行阐述,并介绍了相关模型与理论.%Many engineering components are subjected to multiaxial fatigue loading which can be proportional or non-proportional.The non-proportional hardening effect has a significant influence on multiaxial fatigue life.Accurate prediction of the low cycle fatigue life of metallic materials under multiaxial non-proportional loading should employ constitutive relations considering isotropic hardening,kinematic hardening and non-proportional hardening effects simultaneously.By calculating the corresponding stress and strain components on the critical plane,the fatigue life could be estimated with the help of different fatigue failure models.This paper gives an overview of the concepts concerning the fatigue life predictions,as well as the related models and theories.
Study of axial magnetic effect
Energy Technology Data Exchange (ETDEWEB)
Braguta, Victor [IHEP, Protvino, Moscow region, 142284 Russia ITEP, B. Cheremushkinskaya street 25, Moscow, 117218 (Russian Federation); School of Biomedicine, Far Eastern Federal University, Ajax 10 Building 25, Russian island, Vladivostok, 690922 (Russian Federation); Chernodub, M. N. [CNRS, Laboratoire de Mathématiques et Physique Théorique, Université François-Rabelais Tours, Fédération Denis Poisson, Parc de Grandmont, 37200 Tours, France Department of Physics and Astronomy, University of Gent, Krijgslaan 281, S9, B-9000 Gent (Belgium); School of Biomedicine, Far Eastern Federal University, Ajax 10 Building 25, Russian island, Vladivostok, 690922 (Russian Federation); Goy, V. A. [School of Natural Sciences, Far Eastern Federal University, Sukhanova street 8, Vladivostok, 690950 (Russian Federation); Landsteiner, K. [Instituto de Física Teórica UAM/CSIC, C/ Nicolás Cabrera 13-15, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Molochkov, A. V. [School of Biomedicine, Far Eastern Federal University, Ajax 10 Building 25, Russian island, Vladivostok, 690922 (Russian Federation); Ulybyshev, M. [ITEP, B. Cheremushkinskaya street 25, Moscow, 117218 Russia Institute for Theoretical Problems of Microphysics, Moscow State University, Moscow, 119899 (Russian Federation)
2016-01-22
The Axial Magnetic Effect manifests itself as an equilibrium energy flow of massless fermions induced by the axial (chiral) magnetic field. Here we study the Axial Magnetic Effect in the quenched SU(2) lattice gauge theory with massless overlap fermions at finite temperature. We numerically observe that in the low-temperature hadron phase the effect is absent due to the quark confinement. In the high-temperature deconfinement phase the energy flow is an increasing function of the temperature which reaches the predicted asymptotic T{sup 2} behavior at high temperatures. We find, however, that energy flow is about one order of magnitude lower compared to a theoretical prediction.
Institute of Scientific and Technical Information of China (English)
郭彦林; 王永海
2011-01-01
The buckling behavior of a compressed column braced with two spring supports, as the equivalent model of three-storey multi-column frame, was investigated systemically in the previous study. It was observed that, with the bracing stiffness increasing, the buckling mode of the column changed from symmetric single wave to antisymmetric double waves before the fully fixed supported reaction was reached. Obviously, two lateral supports in the equivalent model were independent, and the stiffness of the supports was the same even under different buckling mode. However, the two lateral supports of the column were not independent in three-storey multi-column frame subjected to different buckling modes, and the interaction between lateral bracing stiffness of columns and different buckling modes needs to be taken account. In this study , the out-plane lateral bracing stiffness of the columns under different buckling modes in three-storey multi-column frame was obtained via theoretical derivation, so that the column braced with two lateral spring supports could be treated as an equivalent model where the column has different lateral brace stiffness under corresponding buckling mode. The elastic buckling load and effective slenderness of the multi-column were obtained by using the results obtained from the equivalent model. The ultimate load-carrying capacity of three-storey multi-column frame with imperfections was analyzed by using finite element method. The random out-plane imperfection distributions of different columns in the frame were considered in the study above. It was proved that the design approach of the equivalent model could be used to estimate the load-carrying capacity of three-storey multi-column frame.%对带两个等跨布置侧向弹簧支撑的轴压柱（三层通高群柱的面外稳定性等效模型）的研究表明，随着柱子受到支撑作用的增强，柱子最低阶屈曲模态会依次经历单波、双波及三波（完全支撑）三种
Institute of Scientific and Technical Information of China (English)
费骏; 赖震; 魏威; 石仕元; 沈健; 廖胜辉
2013-01-01
Objective:To study the influence of axial load on lumbar spine tuberculosis stability with a three-dimen-sional finite element model, and to provide the necessary biomechanical theoretical basis for the treatment of spinal tuberculosis. Methods:A normal material FE model of L2~L5 Lumbar model and 5 different types of tuberculosis models were generated by using specially designed modeling system after CT data collected from a volunteer sub-ject and then the same axial loading conditions were applied to do comparison. Results:After axial loading,lumbar tuberculosis stability was affected by tuberculosis:the average stiffness of A,B,C,D,and E lumbar spinal tuberculo-sis models were 233,239,275,253,and 217 N/mm,with a 22% reduction at most when compared to 277 N/mm of the normal model. For stress result, tuberculosis located in the cortical bone brought serious impact, with large stress concentration. Tuberculosis also seriously influenced the mechanical conduction of the intervertebral disc. Conclusion:Tuberculosis can affect lumbar stability;different locations of tuberculosis produces the corresponding stress concentration. These findings may have guiding significance on the clinical diagnosis.%目的：研究轴向加载对腰椎结核三维有限元模型稳定性的影响，为临床治疗腰椎结核提供生物力学理论依据。方法：选取自愿者采集CT数据，采用专用生物力学软件建立正常材质的L2~L5节段腰椎模型和5种不同的结核模型，在相同的轴向加载条件下进行分析。结果：通过轴向加载发现，正常腰椎的平均刚度为277N/mm，A、B、C、D、E五型结核腰椎的平均压缩刚度分别为233N/mm、239N/mm、275N/mm、253N/mm和217N/mm。腰椎结核模型平均刚度比正常模型最大减小近22%；在应力方面，结核破坏区域位于骨皮质时影响最大，出现大的应力集中情况；同时，结核破坏对于椎间盘的力学传导有很大影响。结论：腰椎结
Multi-axial mechanical stimulation of tissue engineered cartilage: Review
Directory of Open Access Journals (Sweden)
S D Waldman
2007-04-01
Full Text Available The development of tissue engineered cartilage is a promising new approach for the repair of damaged or diseased tissue. Since it has proven difficult to generate cartilaginous tissue with properties similar to that of native articular cartilage, several studies have used mechanical stimuli as a means to improve the quantity and quality of the developed tissue. In this study, we have investigated the effect of multi-axial loading applied during in vitro tissue formation to better reflect the physiological forces that chondrocytes are subjected to in vivo. Dynamic combined compression-shear stimulation (5% compression and 5% shear strain amplitudes increased both collagen and proteoglycan synthesis (76 ± 8% and 73 ± 5%, respectively over the static (unstimulated controls. When this multi-axial loading condition was applied to the chondrocyte cultures over a four week period, there were significant improvements in both extracellular matrix (ECM accumulation and the mechanical properties of the in vitro-formed tissue (3-fold increase in compressive modulus and 1.75-fold increase in shear modulus. Stimulated tissues were also significantly thinner than the static controls (19% reduction suggesting that there was a degree of ECM consolidation as a result of long-term multi-axial loading. This study demonstrated that stimulation by multi-axial forces can improve the quality of the in vitro-formed tissue, but additional studies are required to further optimize the conditions to favour improved biochemical and mechanical properties of the developed tissue.
Notari, Alessio; Tywoniuk, Konrad
2016-12-01
We analyze in detail the background cosmological evolution of a scalar field coupled to a massless abelian gauge field through an axial term phi/fγ F ~F, such as in the case of an axion. Gauge fields in this case are known to experience tachyonic growth and therefore can backreact on the background as an effective dissipation into radiation energy density ρR, which can lead to inflation without the need of a flat potential. We analyze the system, for momenta k smaller than the cutoff fγ, including the backreaction numerically. We consider the evolution from a given static initial condition and explicitly show that, if fγ is smaller than the field excursion phi0 by about a factor of at least Script O (20), there is a friction effect which turns on before the field can fall down and which can then lead to a very long stage of inflation with a generic potential. In addition we find superimposed oscillations, which would get imprinted on any kind of perturbations, scalars and tensors. Such oscillations have a period of 4-5 efolds and an amplitude which is typically less than a few percent and decreases linearly with fγ. We also stress that the curvature perturbation on uniform density slices should be sensitive to slow-roll parameters related to ρR rather than dot phi2/2 and we discuss the existence of friction terms acting on the perturbations, although we postpone a calculation of the power spectrum and of non-gaussianity to future work and we simply define and compute suitable slow roll parameters. Finally we stress that this scenario may be realized in the axion case, if the coupling 1/fγ to U(1) (photons) is much larger than the coupling 1/fG to non-abelian gauge fields (gluons), since the latter sets the range of the potential and therefore the maximal allowed phi0~ fG.
Uni-axial compaction of a granular material
Morland, L. W.; Sawicki, A.; Milne, P. C.
1993-11-01
S HEARING OF GRANULAR materials causes rearrangement of the granular structure which induces irreversible volume decrease and shear strain, in addition to reversible strain. The model adopted describes the reversible compression and shear by hypoelastic laws, and the irreversible compaction and shear by evolutionary laws. The latter are differential relations defining the progress of irreversible strain as an appropriate time-independent monotonie loading parameter increases, which incorporate dependence on the current state, and which prescribe a direction for the irreversible shear strain increment. The model is described by four material functions and two material constants, and has been shown to determine valid initial response to applied shear stress. We apply the model to the compaction of a granular material in uni-axial strain, which is described by two simultaneous differential equations for the axial stress and compaction with the axial strain as independent variable, together with algebraic relations for the pressure and lateral stress. The equation forms for loading-increasing axial stress—and unloading—decreasing axial stress-are distinct. Reformulation as differential equations for the pressure and the principal stress difference shows that the pressure derivative depends only on two of the material functions and one constant. The axial strain and lateral stress measured during a complete load-unload cycle on a sand determine the pressure and stress difference derivatives which are correlated directly with the model differential relations. Two material functions and one constant are determined by an optimization procedure from the complete loadunload ressure data, then the remaining two functions and constant from the stress difference data. Solution of the resulting model differential equations reproduces accurately the axial strain and lateral stress variations during the experimental loading cycle. In addition, model predictions for load
Energy Technology Data Exchange (ETDEWEB)
Newman, J.B.
1968-01-01
Thermal radient bowing of rod type fuel elements can be analyzed in terms of the deflections of a precurved beam. The fundamental aspects of an analysis of axially compressed multispan beams are given. Elasticity of supports in both axial and transverse directions is considered; the technique is applicable to problems in which the axial thrust depends on the transverse deflection as well as problems with prescribed axial thrust. The formulas presented constitute the theory for a computer program of broad applicability, not only in the analysis of fuel rod bowing, but also to almost any multispan beam, particularly when the effects of axial loads cannot be neglected. 17 references. (NSA 22: 22866)
Institute of Scientific and Technical Information of China (English)
吴钰川
2015-01-01
In view of the problem of elastic and plastic buckling for axial loaded the cylindrical shells made of functionally graded materials,we employ the finite element software ABAQUS to conduct a nu-merical simulation and analysis. The laminated model and the model of TTO are used in the analysis, which takes full consideration of the physical characteristic of the material,namely,the influence of the physical nonlinearity and the geometrical nonlinear buckling. The influence of the shell thickness and component parameters on the buckling critical state is analyzed through calculating the critical load and deformation pattern of elastic-plastic functionally graded material cylindrical shell buckling.%针对功能梯度材料圆柱壳的考虑缺陷的弹塑性屈曲问题，采用有限元软件ABAQUS进行了数值模拟与分析。分析中采用叠层模型和TTO模型，充分考虑了材料的物性特性，即材料的物理非线性和前屈曲几何非线性的影响。计算得到缺陷作用下的弹塑性功能梯度材料圆柱壳的屈曲临界荷载和变形模式，研究了壳体厚度、组分参数对屈曲临界状态的影响。
Axial Current and Noether Charge
Mahato, Prasanta
2012-01-01
A decade ago, a Lagrangian density has been proposed by the author where only the local symmetries of the Lorentz subgroup of (A)ds group is retained. This formalism has been found to produce some results encompassing that of standard Einstein-Hilbert formalism. In the present article, the conserved axial vector matter currents, constructed in some earlier paper, have been found to be a result of Noether's theorem. PACS: 04.20.Fy, 04.20.Cv, 11.40.-q Keywords: Torsion, Axial Current, Noether's Theorem
Relativistic RPA in axial symmetry
Arteaga, D Pena; 10.1103/PhysRevC.77.034317
2009-01-01
Covariant density functional theory, in the framework of self-consistent Relativistic Mean Field (RMF) and Relativistic Random Phase approximation (RPA), is for the first time applied to axially deformed nuclei. The fully self-consistent RMF+RRPA equations are posed for the case of axial symmetry and non-linear energy functionals, and solved with the help of a new parallel code. Formal properties of RPA theory are studied and special care is taken in order to validate the proper decoupling of spurious modes and their influence on the physical response. Sample applications to the magnetic and electric dipole transitions in $^{20}$Ne are presented and analyzed.
Institute of Scientific and Technical Information of China (English)
屠永清; 刘林林; 叶英华
2012-01-01
为了实现对多室式钢管混凝土T形柱轴压稳定性能的研究，进行6个中长柱试件及4个短柱对照试件的轴压试验，重点考察前者的破坏形态、荷载-变形关系及截面尺寸对承载力的影响。试验结果表明，中长柱的力学行为与短柱有较大不同，其破坏属于整体弯曲破坏，增大腹板高度对承载能力会产生有利影响。同时，将改进Mander模型后所得的混凝土本构关系引入有限元软件ABAQUS中，对试验进行了有限元模拟，其结果与试验结果吻合较好。在试验及有限元分析的基础上确定了中长柱与短柱之间的界限长细比，并对这一新型结构柱稳定承载力的计算方法进行了探讨，给出可供实际应用参考的计算公式。%In order to acquire the stability properties of multi-cell T-shaped concrete-filled steel tubular （MT-CFST） columns, axial compressive experiments of 6 intermediate long specimens and 4 stub specimens were presented. The failure modes, relationships between axial load and deformation and the effects of cross section dimensions on the bearing capacities of the specimens were investigated. It is demonstrated that the mechanical behaviors of MT-CFST middle long columns are different from stub columns. Their ultimate failure modes belong to buckling failure and the enhancement of web height could enhance the bearing capacities. A constitutive relationship of the concrete core is suggested by modifying Mander＇ s concrete model. Finite element analysis of the specimens is carried using ABAQUS and the calculation results are in good agreement with the experimental results. Based on the experiment and finite element analysis, the slenderness ratio limit between intermediate long columns and stub columns is suggested and subsequently a simplified formula for stable bearing capacities of MT-CFST columns is proposed.
Institute of Scientific and Technical Information of China (English)
许维军; 马杰; 王晓天
2015-01-01
球柱组合壳结构是潜艇耐压壳体的主要结构形式，在实际的工程中受到水下爆炸作用或者发生撞击时，球柱组合壳结构承受冲击载荷时易发生动力屈曲现象。采用有限元分析方法，对球柱组合壳结构在轴向冲击作用下的弹性和弹塑性动力屈曲问题进行研究，同时采用应力波理论分析了不同的几何参数（如厚度）、物理参数（如切线模量、屈服强度），以及条件参数（如载荷峰值）等对球柱组合壳结构的弹塑性动力屈曲行为的影响。通过研究得出以下结论：结构动力屈曲的过程中不能忽略应力波效应，简单地将弹塑性材料定义为弹性材料会影响到分析结果的准确性。%Sphere‐cylinder combined shell is main structural form of submarine pressure hull .When it is subjected to impact load come from underwater explosion or collision in the actual engineering ,dy‐namic buckling of sphere‐cylinder combined shell structure is liable to be induced .This paper focus on the investigation on the elastic and elastoplastic dynamic buckling problems of sphere‐cylinder com‐bined shell structure under axial impact load .The dynamic buckling behaviour is analyzed by using FEM ,and the influence of different geometric parameters such as thickness ,physical parameters such as tangent modulus ,yield strength and condition parameters such as peak value of load on the elasto‐plastic dynamic buckling behaviour of sphere‐cylinder combined shell structure are studied by applying stress wave theory .Conclusions are drawn as follows :the stress wave effect cannot be neglected in the analysis of structure dynamic buckling ,and the elastoplastic material is simply defined as elastic material will affect the accuracy of analysis results .
Parametric Analysis of Composite Reinforced Wood Tubes Under Axial Compression
Cabrero, J.; Heiduschke, A.; Haller, P. (P.)
2010-01-01
Wood tubes combine economy, an efficient use of the material and optimal structural performance. They can be optionally reinforced with technical fibers and/or textiles laminated to the outer wood surface. The paper presents the outcomes of a parametric study on the performance of wood reinforced tubes submitted to axial compression. Simple analytical models were applied to estimate the load-carrying capacity of the tubes and their failure mechanisms. Analytical and numerical models were deve...
Experimental investigations on an axial grooved cryogenic heat pipe
Directory of Open Access Journals (Sweden)
Senthil Kumar Muniappan
2012-01-01
Full Text Available This paper deals with development and studies of a trapezoidal axial grooved nitrogen heat pipe. A special liquid nitrogen cryostat has been designed and developed for evaluating the performance of heat pipe where the condenser portion is connected to the cold sink externally. Experiments have been performed on the heat pipe as well as on an equivalent diameter copper rod at different heat loads. The steady state performance of the heat pipe is compared with that of copper rod.
Dynamic buckling of elastic-plastic cylindrical shells and axial stress waves
Institute of Scientific and Technical Information of China (English)
徐新生; 苏先樾; 王仁
1995-01-01
The mechanism for bifurcation of elastic-plastic buckling of the semi-infinite cylindrical shell under impacting axial loads is proposed based on the theory of stress wave. Numerical results on three kinds of end supports and step and impulse loads are given.
Institute of Scientific and Technical Information of China (English)
刘林林; 屠永清; 叶英华
2011-01-01
对钢管混凝土T形柱进行合理的改进，提出多室式钢管混凝土T形柱（MT-CFST柱）。进行12个短柱试件的轴压试验并对其破坏过程作了详细描述，给出试件的轴压应力．纵向平均应变曲线，同时也考察试件的破坏形态及截面各尺寸、板件布置方式、钢板厚度、混凝土强度等因素对试件力学性能的影响。试验结果表明：多室式钢管混凝土T形柱能较好地增强T形截面内钢材对混凝土的约束作用，发挥两种材料的组合性能；试件的破坏以局部鼓曲和整体剪切两种形式为主，轴压性能受腹板高度、钢板厚度及混凝土强度的影响较大。同时，参考国内外4种钢管混凝土规范中的计算方法对试件的承载力进行计算，经过对比后发现，按ECA规范计算的结果与试验结果符合最好。%Multi-cell T-shaped concrete-filled steel tubular （MT-CFST） column is an improvement of T-shaped concretefilled steel tubular （T-CFST） column. Twelve MT-CFST stub columns under axial compression were tested and the failure processes were described in detail. The axial stress-longitudinal average strain curves were provided, and the effects of the factors including cross section dimension, steel plate layout, thickness of the steel plate and concrete strength on the mechanical behaviors of the specimens were discussed. It is shown that MT-CFST stub columns may enhance the interaction between the two component materials and take advantage of their performances. The primary failure modes of the specimens involved local bulge failure and shear failure. Properties of the MT-CFST columns are mainly influenced by the web length, steel plate thickness and the concrete strength. The axial load capacities of the specimens were calculated according to four design codes for CFST columns. The comparison between the calculations and experimental data indicates that the EC4 method provides much better estimate of
Axial structure of the nucleon
Energy Technology Data Exchange (ETDEWEB)
Veronique Bernard; Latifa Elouadrhiri; Ulf-G Meissner
2002-01-01
We review the current status of experimental and theoretical understanding of the axial nucleon structure at low and moderate energies. Topics considered include (quasi)elastic (anti)neutrino-nucleon scattering, charged pion electroproduction off nucleons and ordinary as well as radiative muon capture on the proton.
Thermophoresis of Axially Symmetric Bodies
2007-11-02
Sweden Abstract. Thermophoresis of axially symmetric bodies is investigated to first order in the Knudsen-mimber, Kn. The study is made in the limit...derived. Asymptotic solutions are studied. INTRODUCTION Thermophoresis as a phenomenon has been known for a long time, and several authors have approached
A survey of buckling of conical shells subjected to axial compression and external pressure
Directory of Open Access Journals (Sweden)
O. Ifayefunmi
2014-07-01
Full Text Available The paper reviews literature on buckling of conical shells subjected to three loading conditions: (i axial compression only, (ii external pressure only and (iii combined loading. The review is from the theoretical as well as experimental points of view. This review covers known experiments on cones from (1958 – 2012. The literature review is split thematically into the following categories: theoretical prediction of axially compressed cones, theoretical prediction of externally pressurized cones, theoretical prediction of cones under combined loading, buckling experiments on axially compressed cones, buckling experiments on externally pressurized cones, buckling experiments on cones subjected to combined loading, buckling experiments on composite conical shells, equivalent cylinder approach, effect of initial geometric imperfection on the buckling behaviour of cones and effect of imperfect boundary conditions on the buckling behaviour of cones.
Axial Non-linear Dynamic Soil-Pile Interaction - Keynote
Directory of Open Access Journals (Sweden)
Holeyman A.
2014-01-01
Full Text Available This keynote lecture describes recent analytical and numerical advances in the modeling of the axial nonlinear dynamic interaction between a single pile and its embedding soil. On one hand, analytical solutions are developed for assessing the nonlinear axial dynamic response of the shaft of a pile subjected to dynamic loads, and in particular to vibratory loads. Radial inhomogeneity arising from shear modulus degradation is evaluated over a range of parameters and compared with those obtained by other authors and by a numerical radial discrete model simulating the pile and soil movements from integration of the laws of motion. New approximate non linear solutions for axial pile shaft behaviour developed from general elastodynamic equations are presented and compared to existing linear solutions. The soil non linear behaviour and its ability to dissipate mechanical energy upon cyclic loading are shown to have a significant influence on the mechanical impedance provided by the surrounding soil against pile shaft movement. The limitations of over-simplified modelling of pile response are highlighted.
FAST Mast Structural Response to Axial Loading: Modeling and Verification
Knight, Norman F., Jr.; Elliott, Kenny B.; Templeton, Justin D.; Song, Kyongchan; Rayburn, Jeffery T.
2012-01-01
The International Space Station s solar array wing mast shadowing problem is the focus of this paper. A building-block approach to modeling and analysis is pursued for the primary structural components of the solar array wing mast structure. Starting with an ANSYS (Registered Trademark) finite element model, a verified MSC.Nastran (Trademark) model is established for a single longeron. This finite element model translation requires the conversion of several modeling and analysis features for the two structural analysis tools to produce comparable results for the single-longeron configuration. The model is then reconciled using test data. The resulting MSC.Nastran (Trademark) model is then extended to a single-bay configuration and verified using single-bay test data. Conversion of the MSC. Nastran (Trademark) single-bay model to Abaqus (Trademark) is also performed to simulate the elastic-plastic longeron buckling response of the single bay prior to folding.
Optimization of axial blowers. Optimierung von Axial-Ventilatoren
Energy Technology Data Exchange (ETDEWEB)
Bolte, W.
1992-08-01
For the optimum possible design of axial blowers, trials are evaluated in the article, which are based on the grid profile examined by N. Scholz. The computation for the pressure number and the primary degree of efficiency are shown as well as the evaluation of the effect of the Reynolds and mach number on the degree of efficiency and determination of the secondary losses. In a final example, the dimensions of a blower are computed from the data determined during the trials. (orig.).
Nitinol stent design - understanding axial buckling.
McGrath, D J; O'Brien, B; Bruzzi, M; McHugh, P E
2014-12-01
Nitinol׳s superelastic properties permit self-expanding stents to be crimped without plastic deformation, but its nonlinear properties can contribute towards stent buckling. This study investigates the axial buckling of a prototype tracheobronchial nitinol stent design during crimping, with the objective of eliminating buckling from the design. To capture the stent buckling mechanism a computational model of a radial force test is simulated, where small geometric defects are introduced to remove symmetry and allow buckling to occur. With the buckling mechanism ascertained, a sensitivity study is carried out to examine the effect that the transitional plateau region of the nitinol loading curve has on stent stability. Results of this analysis are then used to redesign the stent and remove buckling. It is found that the transitional plateau region can have a significant effect on the stability of a stent during crimping, and by reducing the amount of transitional material within the stent hinges during loading the stability of a nitinol stent can be increased.
Institute of Scientific and Technical Information of China (English)
王春刚; 宋代军; 张壮南
2012-01-01
In order to investigate the stability behavior of channels with complex edge stiffeners under axial load between fixed-ends, a total of 292 members with different parameters such as width-to-thickness ratio of flanges, section shapes, length of column, stiffener length were selected to be studied by nonlinear finite element analysis. The influence of the above parameters on stability behavior of channels with complex edge stiffeners were studied. It is shown that fixed-ended columns are more prone to distortional buckling. When width-to-thickness ratio of flanges is big, the overall instability mode tends to perform the flexural-torsional buckling. The ultimate load-carrying capacity of members decreases with the increase in the flange width-to-thickness ratio and slenderness ratio. With differences of width-to-thickness ratio of flanges, two different rules were shown about the influence of edge stiffeners on the loadcarrying efficiency of members.%为研究复杂卷边槽钢轴压固支构件的稳定性能，选取不同的翼缘宽厚比、截面形式、构件长度、卷边长度等几何参数，对共计292个构件进行非线性有限元分析，研究上述参数对复杂卷边槽钢固支构件稳定性能的影响。结果表明：固支构件较易发生畸变屈曲，翼缘宽厚比较大时，构件的整体失稳模式多为弯扭屈曲。构件的极限承载力随着翼缘宽厚比、构件长细比的增大而减小，卷边对构件承载效率的影响随翼缘宽厚比的不同而呈现两种不同的规律。
View of the Axial Field Spectrometer
1980-01-01
The Axial Field Spectrometer, with the vertical uranium/scintillator calorimeter and the central drift chamber retracted for service. One coil of the Open Axial Field Magnet is just visible to the right.
Axial Spondyloarthritis: An Evolving Concept
Directory of Open Access Journals (Sweden)
Nelly Ziadé
2015-07-01
Full Text Available Axial spondyloarthritis (AxSpA is the prototype of a family of inter-related yet heterogeneous diseases sharing common clinical and genetic manifestations: the spondyloarthritides (SpAs. The condition mainly affects the sacroiliac joints and axial skeleton, and has a clear classification scheme, wider epidemiological data, and distinct therapeutic guidelines when compared with other SpAs. However, the concept of AxSpA has not been immutable over time and has evolved tremendously on many levels over the past decades. This review identifies the evolution of the AxSpA concept at two levels. First, at the level of classification, the old classifications and rationales leading to the current Assessment of SpondyloArthritis international Society (ASAS classification are reviewed, and the advantages and drawbacks are discussed. Second, at the therapeutic level, current and future treatments are described and treatment strategies are discussed.
[Axial spondyloarthritis and ankylosing spondylitis].
Nordström, Dan; Kauppi, Markku
2010-01-01
Current classification criteria for ankylosing spondylitis do not allow diagnosis before radiographic changes are visible in sacroiliacal joints. The the new axial spondyloarthropathy (SpA) criteria include axial SpA without radiographic changes as well as established ankylosing spondylitis, recognizing them as a continuum of the same disease. This is of major importance as the burden of early SpA is comparable to that of later stage disease. Diagnosis relies on inflammatory MRI findings which is the most significant change compared to earlier criteria. Emerging data on the efficacy of tumor necrosis factor (TNF) alpha blocking therapies already in early but also in established disease have given new promising alternatives for treatment of this often very cumbersome disease, that rarely responds to classic DMARDs.
Torsional and axial damping properties of the AZ31B-F magnesium alloy
Anes, V.; Lage, Y. E.; Vieira, M.; Maia, N. M. M.; Freitas, M.; Reis, L.
2016-10-01
Damping properties for the AZ31B-F magnesium alloy were evaluated for pure axial and pure shear loading conditions at room temperature. Hysteretic damping results were measured through stress-strain controlled tests. Moreover, the magnesium alloy viscous damping was measured with frequency response functions and free vibration decay, both results were obtained by experiments. The axial and shear damping ratio (ASDR) has been identified and described, specifically for free vibration conditions.
Stability of axially restrained steel columns under temperature action
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
The in-plane elastic buckling of a steel column under thermal loading is investigated. The column is pinned at its ends, with two linear elastic springs that model the restraint provided by adjacent members in a structural assemblage or an elastic foundation. Across a section, the temperature is assumed to be linearly distributed. Based on a nonlinear strain-displacement relationship, the energy method is used to obtain the equilibrium and buckling equations. Then the buckling of columns with three different thermal loading cases is studied. The results show that the analytical formulas can be used to evaluate the critical temperature for elastic buckling. The thermal gradient plays a positive role in improving the stability of columns. Comparing these predictions with uniform temperature distribution over cross section, it can be shown that the buckling load is seriously underestimated. It can also be found that axial restraints can significantly affect the column elastic buckling loads. The critical temperature decreases with an increase of restraint stiffness. Furthermore, the effect of axial stiffness increases when increasing the thermal gradients and decreasing the slenderness ratio of columns.
Golimumab for treatment of axial spondyloarthritis.
Rios Rodriguez, Valeria; Poddubnyy, Denis
2016-02-01
Axial spondyloarthritis comprises two forms: nonradiographic (nonradiographic axial spondyloarthritis) and radiographic (better known as ankylosing spondylitis), which are often considered as two stages of one disease. Historically, all currently available TNF-α inhibitors were first investigated in ankylosing spondylitis and later on in nonradiographic axial spondyloarthritis. This year, EMA has granted golimumab approval for the treatment of active nonradiographic axial spondyloarthritis based on the recently published data from the GO-AHEAD study. This article summarizes recent data on efficacy and safety of golimumab in the treatment of ankylosing spondylitis and nonradiographic axial spondyloarthritis.
Study on signal characteristic analysis of multi-axis load measurement sensors
Hwang, Sang-Kyun; Hwang, Hui-Yun
2016-11-01
This study suggested a tactile sensor with piezoelectric sensors in a fibrous shape to detect multi-axial loads (vertical load and horizontal load) simultaneously for the skins of unmanned robots. The sensor was designed by finite element analyses. A simple detecting scheme of the multi-axial loads was constructed by lab-scale experiments. Verification tests of the developed tactile sensor confirmed that applied vertical and horizontal loads could be detected with less than 4% error.
Axial and Centrifugal Compressor Mean Line Flow Analysis Method
Veres, Joseph P.
2009-01-01
This paper describes a method to estimate key aerodynamic parameters of single and multistage axial and centrifugal compressors. This mean-line compressor code COMDES provides the capability of sizing single and multistage compressors quickly during the conceptual design process. Based on the compressible fluid flow equations and the Euler equation, the code can estimate rotor inlet and exit blade angles when run in the design mode. The design point rotor efficiency and stator losses are inputs to the code, and are modeled at off design. When run in the off-design analysis mode, it can be used to generate performance maps based on simple models for losses due to rotor incidence and inlet guide vane reset angle. The code can provide an improved understanding of basic aerodynamic parameters such as diffusion factor, loading levels and incidence, when matching multistage compressor blade rows at design and at part-speed operation. Rotor loading levels and relative velocity ratio are correlated to the onset of compressor surge. NASA Stage 37 and the three-stage NASA 74-A axial compressors were analyzed and the results compared to test data. The code has been used to generate the performance map for the NASA 76-B three-stage axial compressor featuring variable geometry. The compressor stages were aerodynamically matched at off-design speeds by adjusting the variable inlet guide vane and variable stator geometry angles to control the rotor diffusion factor and incidence angles.
Prediction of Axial Capacity of Concrete-Filled Square Steel Tubes Using Neural Networks
Institute of Scientific and Technical Information of China (English)
Zhu Meichun; Wang Qingxiang; Feng Xiufeng
2005-01-01
The application of artificial neural network to predict the ultimate beating capacity of CFST ( concrete-filled square steel tubes)short columns under axial loading is explored. Input parameters consiste of concrete compressive strength, yield strength of steel tube, confinement index, sectional dimension and width-to-thickness ratio. The ultimate bearing capacity is the only output parameter. A multilayer feedforward neural network is used to describe the nonlinear relationships between the input and output variables.Fifty-five experimental data of CFST short columns under axial loading are used to train and test the neural network. A comparison between the neural network model and three parameter models shows that the neural network model possesses good accuracy and could be a practical method for predicting the ultimate strength of axially loaded CFST short columns.
Dynamic Stability of Euler Beams under Axial Unsteady Wind Force
Directory of Open Access Journals (Sweden)
You-Qin Huang
2014-01-01
Full Text Available Dynamic instability of beams in complex structures caused by unsteady wind load has occurred more frequently. However, studies on the parametric resonance of beams are generally limited to harmonic loads, while arbitrary dynamic load is rarely involved. The critical frequency equation for simply supported Euler beams with uniform section under arbitrary axial dynamic forces is firstly derived in this paper based on the Mathieu-Hill equation. Dynamic instability regions with high precision are then calculated by a presented eigenvalue method. Further, the dynamically unstable state of beams under the wind force with any mean or fluctuating component is determined by load normalization, and the wind-induced parametric resonant response is computed by the Runge-Kutta approach. Finally, a measured wind load time-history is input into the dynamic system to indicate that the proposed methods are effective. This study presents a new method to determine the wind-induced dynamic stability of Euler beams. The beam would become dynamically unstable provided that the parametric point, denoting the relation between load properties and structural frequency, is located in the instability region, no matter whether the wind load component is large or not.
Failure processes in embedded monolayer graphene under axial compression.
Androulidakis, Charalampos; Koukaras, Emmanuel N; Frank, Otakar; Tsoukleri, Georgia; Sfyris, Dimitris; Parthenios, John; Pugno, Nicola; Papagelis, Konstantinos; Novoselov, Kostya S; Galiotis, Costas
2014-06-12
Exfoliated monolayer graphene flakes were embedded in a polymer matrix and loaded under axial compression. By monitoring the shifts of the 2D Raman phonons of rectangular flakes of various sizes under load, the critical strain to failure was determined. Prior to loading care was taken for the examined area of the flake to be free of residual stresses. The critical strain values for first failure were found to be independent of flake size at a mean value of -0.60% corresponding to a yield stress up to -6 GPa. By combining Euler mechanics with a Winkler approach, we show that unlike buckling in air, the presence of the polymer constraint results in graphene buckling at a fixed value of strain with an estimated wrinkle wavelength of the order of 1-2 nm. These results were compared with DFT computations performed on analogue coronene/PMMA oligomers and a reasonable agreement was obtained.
Axial Vibration Confinement in Nonhomogenous Rods
Directory of Open Access Journals (Sweden)
S. Choura
2005-01-01
Full Text Available A design methodology for the vibration confinement of axial vibrations in nonhomogenous rods is proposed. This is achieved by a proper selection of a set of spatially dependent functions characterizing the rod material and geometric properties. Conditions for selecting such properties are established by constructing positive Lyapunov functions whose derivative with respect to the space variable is negative. It is shown that varying the shape of the rod alone is sufficient to confine the vibratory motion. In such a case, the vibration confinement requires that the eigenfunctions be exponentially decaying functions of space, where the notion of spatial domain stability is introduced as a concept dual to that of the time domain stability. It is also shown that vibration confinement can be produced if the rod density and/or stiffness are varied with respect to the space variable while the cross-section area is kept constant. Several case studies, supporting the developed conditions imposed on the spatially dependent functions for vibration confinement in vibrating rods, are discussed. Because variation in the geometric and material properties might decrease the critical buckling loads, we also discuss the buckling problem.
Institute of Scientific and Technical Information of China (English)
钟轶峰; 张亮亮
2011-01-01
The governing partial differential equations （PDEs） were deduced from the asymptotically correct geometrically nonlinear theory to research the buckling and mode jumping behavior of clamped supported composite laminates with antisymmetric angle- ply under bi - axial compressive load. The two coupled fourth - order partial differential equations （PDEs）, namely, the compatibility equation and the dynamic governing equation were transformed into a system of nonlinear ordinary differential equations （ODEs）. Then a relatively simpler solution method was developed. The generalized Galerkin method was used to solve boundary value problems corresponding to antisymmetric angle-ply composite plates. The post-buckling patterns with different complexity before and after mode jumping were analyzed. An numerical example of 4- layers clamped composite laminates shows that the numerical results in the primary post-buckling region from the present method agree well with the finite element analysis （FEA）. The FEA may lose its convergence when solution comes close the secondary point, while the analytic method can explore deeply into the post-buckling realm and accuratty capture the mode jumping phenomenon. Only the pure symmetric modes may be used to qualitatively predict the primary post- buckling branch, the secondary bifurcation load and the remote jumped branch of the composite laminates with antisymmetric angle-ply.%为有效分析双轴受压反对称角铺设复合材料层压板在固支边界下的后屈曲性能，由渐近修正几何非线性理论推导其双耦合四阶偏微分方程（即应变协调方程和稳定性控制方程），通过双Fourier级数将耦合非线性控制偏微分方程转换为系列非线性常微分方程，从而获得相对简单的求解方法。使用广义Galerkin方法求解与角交铺设复合层合板相关的边界值问题，研究了模态跃迁前后不同复杂程度的后屈曲模式。对四层固支边界
2015-08-06
COVERED (From - To) 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d...by mutual capacitance between the elements. Reactive loads are positioned in said HF/VHF element at regular intervals for optimizing performance of...capacitance between the elements. Reactive loads are positioned in said HF/VHF element at regular intervals for optimizing performance of the antenna in
Indian Academy of Sciences (India)
K Athiannan; R Palaninathan
2004-02-01
This paper presents experimental studies on buckling of cylindrical shell models under axial and transverse shear loads. Tests are carried out using an experimental facility specially designed, fabricated and installed, with provision for in-situ measurement of the initial geometric imperfections. The shell models are made by rolling and seam welding process and hence are expected to have imperfections more or less of a kind similar to that of real shell structures. The present work thus differs from most of the earlier investigations. The measured maximum imperfections $\\delta_{\\text{max}}$ are of the order of $\\pm 3t$ (t = thickness). The buckling loads obtained experimentally are compared with the numerical buckling values obtained through ﬁnite element method (FEM). In the case of axial buckling, the imperfect geometry is obtained in four ways and in the case of transverse shear buckling, the FE modelling of imperfect geometry is done in two ways. The initial geometric imperfections affect the load carrying capacity. The load reduction is considerable in the case of axial compression and is marginal in the case of transverse shear buckling. Comparisons between experimental buckling loads under axial compression, reveal that the extent of imperfection, rather than its maximum value, in a specimen inﬂuences the failure load. Buckling tests under transverse shear are conducted with and without axial constraints. While differences in experimental loads are seen to exist between the two conditions, the numerical values are almost equal. The buckling modes are different, and the experimentally observed and numerically predicted values are in complete disagreement.
Axial Vector $Z'$ and Anomaly Cancellation
Ismail, Ahmed; Tsao, Kuo-Hsing; Unwin, James
2016-01-01
Whilst the prospect of new $Z'$ gauge bosons with only axial couplings to the Standard Model (SM) fermions is widely discussed, examples of anomaly-free renormalisable models are lacking in the literature. We look to remedy this by constructing several motivated examples. Specifically, we consider axial vectors which couple universally to all SM fermions, as well as those which are generation-specific, leptophilic, and leptophobic. Anomaly cancellation typically requires the presence of new coloured and charged chiral fermions, and we argue that the masses of these new states must generally be comparable to that of the axial vector. Finally, an axial vector mediator could provide a portal between SM and hidden sector states, and we also consider the possibility that the axial vector couples to dark matter. If the dark matter relic density is set due to freeze-out via the axial vector, this strongly constrains the parameter space.
Analyses of axial, lateral and circumferential deformations of rock specimen in triaxial compression
Institute of Scientific and Technical Information of China (English)
WANG Xue-bin
2008-01-01
The axial, lateral and circumferential strains were analyzed for a rock specimen subjected to shear failure in the form of a shear band bisecting the specimen in triaxial compression. Plastic deformation of the specimen stemmed from shear strain localization initiated at the peak shear stress. Beyond the onset of strain localization, the axial, lateral and circumferential strains were decomposed into two parts, respectively. One is the elas-tic strain described by general Hooke's law. The other is attributable to the plastic shear slips along shear band with a certain thickness dependent on the internal length of rock.The post-peak circumferential strain-axial strain curve of longer specimen is steeper than that of shorter specimen, as is consistent with the previous experiments. In elastic stage,the circumferential strain-axial strain curve exhibits nonlinear characteristic, as is in agreement with the previous experiment since confining pressure is loaded progressively until a certain value is reached. When the confining pressure is loaded completely, the circumferential strain-axial strain curve is linear in elastic and strain-softening stages. The predicted circumferential strain-axial strain curve in elastic and strain- softening stages agrees with the previous experiment.
Nonlinear vibrations and imperfection sensitivity of a cylindrical shell containing axial fluid flow
del Prado, Z.; Gonçalves, P. B.; Païdoussis, M. P.
2009-10-01
The high imperfection sensitivity of cylindrical shells under static compressive axial loads is a well-known phenomenon in structural stability. On the other hand, less is known of the influence of imperfections on the nonlinear vibrations of these shells under harmonic axial loads. The aim of this work is to study the simultaneous influence of geometric imperfections and an axial fluid flow on the nonlinear vibrations and instabilities of simply supported circular cylindrical shells under axial load. The fluid is assumed to be non-viscous and incompressible and the flow to be isentropic and irrotational. The behavior of the thin-walled shell is modeled by Donnell's nonlinear shallow-shell equations. It is subjected to a static uniform compressive axial pre-load plus a harmonic axial load. A low-dimensional modal expansion, which satisfies the relevant boundary and continuity conditions, and takes into account all relevant nonlinear modal interactions observed in the past in the nonlinear vibrations of cylindrical shells with and without flow is used together with the Galerkin method to derive a set of eight coupled nonlinear ordinary differential equations of motion which are, in turn, solved by the Runge-Kutta method. The shell is considered to be initially at rest, in a position corresponding to a pre-buckling configuration. Then, a harmonic excitation is applied and conditions for parametric instability and dynamic snap-through are sought. The results clarify the marked influence of geometric imperfections and fluid flow on the dynamic stability boundaries, bifurcations and basins of attraction.
Diabetes mellitus and the eye: axial length
Huntjens, B.; O’Donnell, C.
2006-01-01
Background and aims: The refractive error of the eye is dependent on its axial length. Refractive error is known to fluctuate significantly in poorly controlled diabetic patients. Recently it has been reported that human eyes fluctuate in axial length during the day. However, this change is not detectable in all subjects, suggesting physiological influences such as diet. The purpose of this study was to investigate fluctuations in axial length and blood glucose levels (BGLs) in diabetic patie...
System Study for Axial Vane Engine Technology
Badley, Patrick R.; Smith, Michael R.; Gould, Cedric O.
2008-01-01
The purpose of this engine feasibility study was to determine the benefits that can be achieved by incorporating positive displacement axial vane compression and expansion stages into high bypass turbofan engines. These positive-displacement stages would replace some or all of the conventional compressor and turbine stages in the turbine engine, but not the fan. The study considered combustion occurring internal to an axial vane component (i.e., Diesel engine replacing the standard turbine engine combustor, burner, and turbine); and external continuous flow combustion with an axial vane compressor and an axial vane turbine replacing conventional compressor and turbine systems.
Stability of perfect and imperfect cylindrical shells under axial compression and torsion
Institute of Scientific and Technical Information of China (English)
袁喆; 霍世慧; 耿小亮
2014-01-01
Stability analyses of perfect and imperfect cylindrical shells under axial compression and torsion were presented. Finite element method for the stability analysis of perfect cylindrical shells was put forward through comparing critical loads and the first buckling modes with those obtained through theoretical analysis. Two typical initial defects, non-circularity and uneven thickness distribution, were studied. Critical loads decline with the increase of non-circularity, which exist in imperfect cylindrical shells under both axial compression and torsion. Non-circularity defect has no effect on the first buckling mode when cylindrical shell is under torsion. Unfortunately, it has a completely different buckling mode when cylindrical shell is under axial compression. Critical loads decline with the increase of thickness defect amplitude, which exist in imperfect cylindrical shells under both axial compression and torsion, too. A greater wave number is conducive to the stability of cylindrical shells. The first buckling mode of imperfect cylindrical shells under torsion maintains its original shape, but it changes with wave number when the cylindrical shell is under axial compression.
A mechanical model of an axial piston machine
Löfstrand Grip, Rasmus
2009-01-01
A mechanical model of an axial piston-type machine with a so-called wobble plate and Z-shaft mechanism is presented. The overall aim is to design and construct an oil-free piston expander demonstrator as a first step to realizing an advanced and compact small-scale steam engine system. The benefits of a small steam engine are negligible NOx emissions (due to continuous, low-temperature combustion), no gearbox needed, fuel flexibility (e.g., can run on biofuel and solar), high part-load effici...
Directory of Open Access Journals (Sweden)
Peter Svenonius
2007-01-01
Full Text Available Many languages have specialized locative words or morphemes translating roughly into words like ‘front,’ ‘back,’ ‘top,’ ‘bottom,’ ‘side,’ and so on. Often, these words are used instead of more specialized adpositions to express spatial meanings corresponding to ‘behind,’ ‘above,’ and so on. I argue, on the basis of a cross-linguistic survey of such expressions, that in many cases they motivate a syntactic category which is distinct from both N and P, which I call AxPart for ‘Axial Part’; I show how the category relates to the words which instantiate it, and how the meaning of the construction is derived from the combination of P[lace] elements, AxParts, and the lexical material which expresses them.
Unsteady Flows in Axial Turbomachines
Marble, F. E.; Rannie, W. D.
1957-01-01
Of the various unsteady flows that occur in axial turbomachines certain asymmetric disturbances, of wave length large in comparison with blade spacing, have become understood to a certain extent. These disturbances divide themselves into two categories: self-induced oscillations and force disturbances. A special type of propagating stall appears as a self-induced disturbance; an asymmetric velocity profile introduced at the compressor inlet constitutes a forced disturbance. Both phenomena have been treated from a unified theoretical point of view in which the asymmetric disturbances are linearized and the blade characteristics are assumed quasi-steady. Experimental results are in essential agreement with this theory wherever the limitations of the theory are satisfied. For the self-induced disturbances and the more interesting examples of the forced disturbances, the dominant blade characteristic is the dependence of total pressure loss, rather than the turning angle, upon the local blade inlet angle.
TE_01 High Power Disk Loaded Guide Load
Energy Technology Data Exchange (ETDEWEB)
Farkas, Z.D.; /SLAC
2005-06-01
A method to design a matching section from a smooth guide to a disk-loaded guide, using a variation of broadband matching, [1, 2] is described. Using this method, we show how to design high power loads, attenuators and filters. The load consists of a disk-loaded coaxial guide operating in the TE{sub 01}-mode. We use this mode because it has no electric field terminating on a conductor, has no axial currents, and has no current at the cylinder-disk interface. A high power load design that has -35 dB reflection and a 200 MHz, -20 dB bandwidth, is presented. It is expected that it will carry the 600 MW output peak power of the pulse compression network. We use coaxial geometry and stainless steel material to increase the attenuation per cell.
Novel Musculoskeletal Loading and Assessment System
Downs, Meghan E.
2017-01-01
Ground based and ISS (International Space Station) exercise research have shown that axial loading via two-point loading at the shoulders and load quality (i.e. consistent load and at least 1:1 concentric to eccentric ratio) are extremely important to optimize musculoskeletal adaptations to resistance exercise. The Advanced Resistance Exercise Device (ARED) is on ISS now and is the "state of the art" for resistance exercise capabilities in microgravity; however, the ARED is far too large and power consuming for exploration vehicles. The single cable exercise device design selected for MPCV (Multi-Purpose Crew Vehicle), does not readily allow for the two-point loading at the shoulders.
Health and imaging outcomes in axial spondyloarthritis
Machado, P.M.
2016-01-01
This thesis focuses on the assessment and monitoring of health and imaging outcomes in axial spondyloarthritis (SpA) and the relationship between these outcomes. Four major contributions to the understanding and management of axial SpA were made: 1) the improvement and facilitation of the assessment
Institute of Scientific and Technical Information of China (English)
姚行友; 郭彦利
2016-01-01
对26根屈服强度为235 MPa的腹板开孔和未开孔冷弯薄壁型钢截面轴压构件进行畸变屈曲承载力试验研究,分析构件的屈曲模式和极限承载力.将我国及北美相关规范计算的构件承载力以及非线性有限元数值模拟结果与试验结果进行分析比较,并对腹板开孔冷弯薄壁型钢截面轴压构件的承载力合理计算模式进行研究.结果表明:对于中等长度腹板开孔冷弯薄壁型钢截面轴压构件主要出现局部、畸变和整体屈曲的相关作用;腹板开孔对构件畸变屈曲稳定承载力有一定的降低作用;采用折减构件有效截面面积的修正方法可计算开孔构件的畸变屈曲稳定承载力;非线性有限元方法可用于腹板开孔冷弯薄壁型钢构件的屈曲模式和极限承载力的分析.%In order to research the distortional buckling mode and load-carrying capacity of cold-formed thin-walled steel members with holes, compression tests were conducted on 26 intermediate length columns with and without web holes.For each specimen, a shell finite element eigenbuckling analysis and nonlinear analysis were also conducted such that the influence of the hole on local, distortional, and global elastic buckling responses could also be got.The comparison of ultimate strength between test results and calculated results using relevant codes was made.The calculated method for cold-formed thin-walled steel columns with web holes was proposed.The results showed that the interaction of local buckling, distortional buckling, and overall buckling usually would occur in the intermediate length member under axial compression, and the web holes had a little influence on the elastic buckling strength and the distortional buckling ultimate strength of columns, the ultimate strength of the members with holes in web could be predicted using a reduced effective area, and the nonlinear finite element method could be used to analyse the buckling mode and
2013-12-01
to the balance piston, and initiation of lubrication oil to the bearings via an air driven oil mist system. A pre-test checklist is provided in...Mech, and Aero. Eng., Naval Postgraduate School, Monterey, CA. Sept 2013. [2] A. J. Wennerstrom, Design of Highly Loaded Axial-Flow Fans and
Mechanical Behaviors of Silt Rock Subjected to Coupling Static and Impact Loads
Institute of Scientific and Technical Information of China (English)
ZHOU Zilong; LI Xibing; HONG Liang; MA Chunde
2006-01-01
Experiments of silt rock subjected to coupling loads were carried out on tailormade equipment.With a constant dynamic load,the behaviors of eight sets of siltite specimens were investigated with different axial static loads.The experimental results show that the modulus of the specimens under coupling loads increases at first and then decreases with the increase of axial static pressure.The failure model of the specimens also varies.Keeping the dynamic load constant,when the axial static pressure is Iow,the specimen breaks in two simply.With the increase of axial static pressure,the cone-shaped fragment appeares.When the axial static pressure reaches 90% of the static strength of rock,the specimen smashes into amount of small fragments.
The Effect of Axial Stress on YBCO Coils
Energy Technology Data Exchange (ETDEWEB)
Sampson, W.; Anerella, M.; Cozzolino, J.P.; Gupta, R.C.; Shiroyanagi, Y.; Evangelou, E.
2011-03-28
The large aspect ratio of typical YBCO conductors makes them ideal for constructing solenoids from pancake style coils. An advantage of this method is that each subunit can be tested before assembly into the finished magnet. The fact that conductors are available in relatively short lengths is another reason for using such a fabrication technique. The principal drawback is the large number of joints required to connect the coils together. When very high field solenoids such as those contemplated for the muon collider are built in this way the magnetic forces between pancakes can be very large. Extensive measurements have been made on the effect of stress on short lengths of conductor, but there is little or no data on the effect of intercoil loading. The experiment described in this paper was designed to test the ability of YBCO coils to withstand these forces. A spiral wound 'pancake' coil made from YBCO coated conductor has been stressed to a pressure of 100MPa in the axial direction at 77K. In this case axial refers to the coil so that the force is applied to the edge of the conductor. The effect on the critical current was small and completely reversible. Repeatedly cycling the pressure had no measureable permanent effect on the coil. The small current change observed exhibited a slight hysteretic behaviour during the loading cycle.
Uncertainty in Loading and Control of an Active Column Critical to Buckling
Directory of Open Access Journals (Sweden)
G.C. Enss
2012-01-01
Full Text Available Buckling of load-carrying column structures is an important design constraint in light-weight structures as it may result in the collapse of an entire structure. When a column is loaded by an axial compressive load equal to its individual critical buckling load, a critically stable equilibrium occurs. When loaded above its critical buckling load, the passive column may buckle. If the actual loading during usage is not fully known, stability becomes highly uncertain.
Axial force measurement for esophageal function testing
Institute of Scientific and Technical Information of China (English)
Flemming H Gravesen; Peter Funch-Jensen; Hans Gregersen; Asbjφrn Mohr Drewes
2009-01-01
The esophagus serves to transport food and fluid from the pharynx to the stomach. Manometry has been the "golden standard" for the diagnosis of esophageal motility diseases for many decades. Hence, esophageal function is normally evaluated by means of manometry even though it reflects the squeeze force (force in radial direction) whereas the bolus moves along the length of esophagus in a distal direction. Force measurements in the longitudinal (axial) direction provide a more direct measure of esophageal transport function. The technique used to record axial force has developed from external force transducers over in-vivo strain gauges of various sizes to electrical impedance based measurements. The amplitude and duration of the axial force has been shown to be as reliable as manometry. Normal, as well as abnormal, manometric recordings occur with normal bolus transit, which have been documented using imaging modalities such as radiography and scintigraphy. This inconsistency using manometry has also been documented by axial force recordings. This underlines the lack of information when diagnostics are based on manometry alone. Increasing the volume of a bag mounted on a probe with combined axial force and manometry recordings showed that axial force amplitude increased by 130% in contrast to an increase of 30% using manometry. Using axial force in combination with manometry provides a more complete picture of esophageal motility, and the current paper outlines the advantages of using this method.
Axial force measurement for esophageal function testing.
Gravesen, Flemming H; Funch-Jensen, Peter; Gregersen, Hans; Drewes, Asbjørn Mohr
2009-01-14
The esophagus serves to transport food and fluid from the pharynx to the stomach. Manometry has been the "golden standard" for the diagnosis of esophageal motility diseases for many decades. Hence, esophageal function is normally evaluated by means of manometry even though it reflects the squeeze force (force in radial direction) whereas the bolus moves along the length of esophagus in a distal direction. Force measurements in the longitudinal (axial) direction provide a more direct measure of esophageal transport function. The technique used to record axial force has developed from external force transducers over in-vivo strain gauges of various sizes to electrical impedance based measurements. The amplitude and duration of the axial force has been shown to be as reliable as manometry. Normal, as well as abnormal, manometric recordings occur with normal bolus transit, which have been documented using imaging modalities such as radiography and scintigraphy. This inconsistency using manometry has also been documented by axial force recordings. This underlines the lack of information when diagnostics are based on manometry alone. Increasing the volume of a bag mounted on a probe with combined axial force and manometry recordings showed that axial force amplitude increased by 130% in contrast to an increase of 30% using manometry. Using axial force in combination with manometry provides a more complete picture of esophageal motility, and the current paper outlines the advantages of using this method.
Ranjbartoreh, A R; Su, D; Wang, G
2012-06-01
Carbon nanotubes are hexagonally configured carbon atoms in cylindrical structures. Exceptionally high mechanical strength, electrical conductivity, surface area, thermal stability and optical transparency of carbon nanotubes outperformed other known materials in numerous advanced applications. However, their mechanical behaviors under practical loading conditions remain to be demonstrated. This study investigates the critical axial properties of pristine and defected single- and multi-walled carbon nanotubes under axial compression. Molecular dynamics simulation method has been employed to consider the destructive effects of Stone-Wales and atom vacancy defects on mechanical properties of armchair and zigzag carbon nanotubes under compressive loading condition. Armchair carbon nanotube shows higher axial stability than zigzag type. Increase in wall number leads to less susceptibility of multi-walled carbon nanotubes to defects and higher stability of them under axial compression. Atom vacancy defect reveals higher destructive effect than Stone-Wales defect on mechanical properties of carbon nanotubes. Critical axial strain of single-walled carbon nanotube declines by 67% and 26% due to atom vacancy and Stone-Wales defects.
New Anomaly of the Axial-Vector Current
Institute of Scientific and Technical Information of China (English)
HE Han-Xin
2001-01-01
By computing the axial-vector current operator equation, we find the anomalous axial-vector curl equation besides the well-known anomalous axial-vector divergence equation (the Adler-Bell-Jackiw anomaly) and discuss its implication.``
A new bi-axial cantilever beam design for biomechanics force measurements.
Lin, Huai-Ti; Trimmer, Barry A
2012-08-31
The demand for measuring forces exerted by animals during locomotion has increased dramatically as biomechanists strive to understand and implement biomechanical control strategies. In particular, multi-axial force transducers are often required to capture animal limb coordination patterns. Most existing force transducers employ strain gages arranged in a Wheatstone bridge on a cantilever beam. Bi-axial measurements require duplicating this arrangement in the transverse direction. In this paper, we reveal a method to embed a Wheatstone bridge inside another to allow bi-axial measurements without additional strain gages or additional second beams. This hybrid configuration resolves two force components from a single bridge circuit and simplifies fabrication for the simultaneous assessment of normal and transverse loads. This design can be implemented with two-dimensional fabrication techniques and can even be used to modify a common full bridge cantilever force transducer. As a demonstration of the new design, we built a simple beam which achieved bi-axial sensing capability that outperformed a conventional half-bridge-per-axis bi-axial strain gage design. We have used this design to measure the ground reaction forces of a crawling caterpillar and a caterpillar-mimicking soft robot. The simplicity and increased sensitivity of this method could facilitate bi-axial force measurements for experimental biologists.
ANALYSIS OF THE AXIAL GAP VS FIBERBOARD MOISTURE CONTENT IN A 9975 SHIPPING PACKAGE
Energy Technology Data Exchange (ETDEWEB)
Daugherty, W.
2013-09-30
The fiberboard assembly within a 9975 shipping package contains a modest amount of moisture, which can migrate to the cooler regions of the package when an internal heat load is present. Typically, this leads to increased moisture levels in the bottom fiberboard layers, along with elevated chloride levels which can leach from the fiberboard. Concerns have been raised that this condition could lead to corrosion of the stainless steel drum. It has been postulated that checking the axial gap at the top of the package against the current 1 inch maximum criterion provides a sufficient indication regarding the integrity of the fiberboard and drum. This report estimates the increase in axial gap that might be expected for a given moisture increase in the bottom fiberboard layers, and the likelihood that the increase will create a nonconforming condition that will lead to identification of the moisture increase. Using data relating the fiberboard moisture content with the degree of compaction under load, the present analysis indicates that the axial gap will increase by 0.282 inch as the bottom fiberboard layers approach the saturation point. This increase will cause approximately 58% of packages with otherwise nominal package component dimensions to fail the axial gap criterion, based on a survey of axial gap values recorded in K-Area surveillance activities. As the moisture content increases above saturation, the predicted increase in axial gap jumps to 0.405 inch, which would result in 92% or more of all packages failing the axial gap criterion. The data and analysis described in this report are specific to cane fiberboard. While it is expected that softwood fiberboard will behave similarly, such behavior has not yet been demonstrated.
MULTIAXIAL CREEP-FATIGUE LIFE EVALUATION UNDER PROPORTIONAL LOADING
Institute of Scientific and Technical Information of China (English)
Y.Noguchi; M.Miyahara
2004-01-01
A new method was proposed for the multiaxial creep-fatigue life evaluation under proportional loadings. Because this method was derived from the strain range partitioning method with a multiaxiality factor, it was possible to consider the influence of both creep-fatigue interaction and multiaxial stress state on fatigue life. In order to predict the combined axial-torsional fatigue life the damage under combined loading was defined as linear summation of the damages under axial loading and torsional loading.Axial-torsional creep-fatigue tests were carried out using tubular specimens of 316LC austenitic stainless steel and the ferritic rotor steel. This rotor steel was developed for the permanent magnet type eddy current retarder in heavy trucks. Experimentally obtained lives of both steels were well corresponded with the lives predicted by the proposed method. It was found that the proposed method was effective in multiaxial fatigue life evaluation under proportional creep-fatigue loadings.
Eddy current loss calculation and thermal analysis of axial-flux permanent magnet couplers
Directory of Open Access Journals (Sweden)
Di Zheng
2017-02-01
Full Text Available A three-dimensional magnetic field analytical model of axial-flux permanent magnet couplers is presented to calculate the eddy current loss, and the prediction of the copper plate temperature under various loads is analyzed. The magnetic field distribution is calculated, and then the eddy current loss is obtained, with the magnetic field analytical model established in cylindrical coordinate. The influence of various loads on eddy current loss is analyzed. Furthermore, a thermal model of axial-flux permanent magnet couplers is established by taking the eddy current loss as the heat source, using the electromagnetic-thermal coupled method. With the help of the thermal model, the influence of various loads on copper plate temperature rise is also analyzed. The calculated results are compared with the results of finite element method and measurement. The comparison results confirm the validity of the magnetic field analytical model and thermal model.
DEFF Research Database (Denmark)
Kock, Carsten Weber; Vesth, Allan
The report describes Load measurements carried out on a given wind turbine. The aim of the measurement program regarding the loads on the turbine is to verify the basic characteristics of the wind turbine and loads on the blades, the rotor and the tower, using [Ref 1], [Ref2] and [Ref 3]. Regarding...... the fatigue loads, the rotor, blades and tower moments are presented. The fatigue loads are evaluated using rainflow counting described in detail in Ref. [1]. The 1Hz equivalent load ranges are calculated at different wind speeds. All information regarding the instrumentation is collected in [ref 4] and [ref...
Axial Super-resolution Evanescent Wave Tomography
Pendharker, Sarang; Newman, Ward; Ogg, Stephen; Nazemifard, Neda; Jacob, Zubin
2016-01-01
Optical tomographic reconstruction of a 3D nanoscale specimen is hindered by the axial diffraction limit, which is 2-3 times worse than the focal plane resolution. We propose and experimentally demonstrate an axial super-resolution evanescent wave tomography (AxSET) method that enables the use of regular evanescent wave microscopes like Total Internal Reflection Fluorescence Microscope (TIRF) beyond surface imaging, and achieve tomographic reconstruction with axial super-resolution. Our proposed method based on Fourier reconstruction achieves axial super-resolution by extracting information from multiple sets of three-dimensional fluorescence images when the sample is illuminated by an evanescent wave. We propose a procedure to extract super-resolution features from the incremental penetration of an evanescent wave and support our theory by 1D (along the optical axis) and 3D simulations. We validate our claims by experimentally demonstrating tomographic reconstruction of microtubules in HeLa cells with an axi...
Axial thermal rotation of slender rods.
Li, Dichuan; Fakhri, Nikta; Pasquali, Matteo; Biswal, Sibani Lisa
2011-05-06
Axial rotational diffusion of rodlike polymers is important in processes such as microtubule filament sliding and flagella beating. By imaging the motion of small kinks along the backbone of chains of DNA-linked colloids, we produce a direct and systematic measurement of axial rotational diffusivity of rods both in bulk solution and near a wall. The measured diffusivities decrease linearly with the chain length, irrespective of the distance from a wall, in agreement with slender-body hydrodynamics theory. Moreover, the presence of small kinks does not affect the chain's axial diffusivity. Our system and measurements provide insights into fundamental axial diffusion processes of slender objects, which encompass a wide range of entities including biological filaments and linear polymer chains.
How to diagnose axial spondyloarthritis early
Rudwaleit, M.; van der Heijde, D.; Khan, M.; Braun, J.; Sieper, J.
2004-01-01
Background: Chronic low back pain (LBP), the leading symptom of ankylosing spondylitis (AS) and undifferentiated axial spondyloarthritis (SpA), precedes the development of radiographic sacroiliitis, sometimes by many years.
Axial force measurement for esophageal function testing
DEFF Research Database (Denmark)
Gravesen, Flemming Holbæk; Funch-Jensen, Peter; Gregersen, Hans
2009-01-01
force transducers over in-vivo strain gauges of various sizes to electrical impedance based measurements. The amplitude and duration of the axial force has been shown to be as reliable as manometry. Normal, as well as abnormal, manometric recordings occur with normal bolus transit, which have been...... force (force in radial direction) whereas the bolus moves along the length of esophagus in a distal direction. Force measurements in the longitudinal (axial) direction provide a more direct measure of esophageal transport function. The technique used to record axial force has developed from external...... documented using imaging modalities such as radiography and scintigraphy. This inconsistency using manometry has also been documented by axial force recordings. This underlines the lack of information when diagnostics are based on manometry alone. Increasing the volume of a bag mounted on a probe...
SELF-SIMILAR SOLUTIONS OF FRACTURE DYNAMICS PROBLEMS ON AXIALLY SYMMETRY
Institute of Scientific and Technical Information of China (English)
吕念春; 程靳; 程云虹; 屈德志
2001-01-01
By the theory of complex functions, a penny-shaped crack on axially symmetric propagating problems for composite materials was studied. The general representations of the analytical solutions with arbitrary index of self-similarity were presented for fracture elastodynamics problems on axially symmetry by the ways of self-similarity under the /addershaped loads. The problerns dealt with can be transformed into Riemann-Hilbert problems and their closed analytical solutions are obtained rather simple by this method. After those analytical solutions are utilized by using the method of rotational superposition theorem in conjunction with that of Smirnov-Sobolev, the solutions of arbitrary complicated problems can be obtained.
The effect of loading rate on pile bearing capacity of saturated sand
Archeewa, E.
2005-01-01
Pile load tests are commonly used by engineers to determine its bearing capacity. At present, there are three methods of pile load tests: the static, the dynamic and the quasi-static test. The static pile load test is done by applying an axial load on the pile with a long duration. The dynamic and q
Numerical simulation of axial flow compressors.
Jesuino Takachi Tomita
2002-01-01
This work deals with the numerical simulation of axial flow compressors, from design to performance prediction. The stage performance prediction uses the meanline flow properties. Stage-stacking is used to analyse a multi-stage compressor. A computer program, written in FORTRAN, was developed and is able to design an axial flow compressor given air mass flow, total pressure ratio, overall efficiency and design speed. All geometrical data relevant to the compressor performance prediction is ca...
Nonperturbative Aspects of Axial Vector Vertex
Institute of Scientific and Technical Information of China (English)
ZONG Hong-Shi; CHEN Xiang-Song; WANG Fan; CHANG Chao-Hsi; ZHAO En-Guang
2002-01-01
It is shown how the axial vector current of current quarks is related to that of constituent quarks within the framework of the global color symmetry model.Gluon dressing of the axial vector vertex and the quark self-energy functions are described by the inhomogeneous Bethe-Salpeter equation in the ladder approximation and the Schwinger Dyson equation in the rainbow approximation,respectively.
Mandibular reconstruction using an axially vascularized tissue-engineered construct
Directory of Open Access Journals (Sweden)
Khalil Mohamed R
2011-03-01
Full Text Available Abstract Background Current reconstructive techniques for continuity defects of the mandible include the use of free flaps, bone grafts, and alloplastic materials. New methods of regenerative medicine designed to restore tissues depend mainly on the so-called extrinsic neovascularization, where the neovascular bed originates from the periphery of the construct. This method is not applicable for large defects in irradiated fields. Methods We are introducing a new animal model for mandibular reconstruction using intrinsic axial vascularization by the Arterio-Venous (AV loop. In order to test this model, we made cadaveric, mechanical loading, and surgical pilot studies on adult male goats. The cadaveric study aimed at defining the best vascular axis to be used in creating the AV loop in the mandibular region. Mechanical loading studies (3 points bending test were done to ensure that the mechanical properties of the mandible were significantly affected by the designed defect, and to put a base line for further mechanical testing after bone regeneration. A pilot surgical study was done to ensure smooth operative and post operative procedures. Results The best vascular axis to reconstruct defects in the posterior half of the mandible is the facial artery (average length 32.5 ± 1.9 mm, caliber 2.5 mm, and facial vein (average length 33.3 ± 1.8 mm, caliber 2.6 mm. Defects in the anterior half require an additional venous graft. The defect was shown to be significantly affecting the mechanical properties of the mandible (P value 0.0204. The animal was able to feed on soft diet from the 3rd postoperative day and returned to normal diet within a week. The mandible did not break during the period of follow up (2 months. Conclusions Our model introduces the concept of axial vascularization of mandibular constructs. This model can be used to assess bone regeneration for large bony defects in irradiated fields. This is the first study to introduce the
Wave propagation in axially moving periodic strings
Sorokin, Vladislav S.; Thomsen, Jon Juel
2017-04-01
The paper deals with analytically studying transverse waves propagation in an axially moving string with periodically modulated cross section. The structure effectively models various relevant technological systems, e.g. belts, thread lines, band saws, etc., and, in particular, roller chain drives for diesel engines by capturing both their spatial periodicity and axial motion. The Method of Varying Amplitudes is employed in the analysis. It is shown that the compound wave traveling in the axially moving periodic string comprises many components with different frequencies and wavenumbers. This is in contrast to non-moving periodic structures, for which all components of the corresponding compound wave feature the same frequency. Due to this "multi-frequency" character of the wave motion, the conventional notion of frequency band-gaps appears to be not applicable for the moving periodic strings. Thus, for such structures, by frequency band-gaps it is proposed to understand frequency ranges in which the primary component of the compound wave attenuates. Such frequency band-gaps can be present for a moving periodic string, but only if its axial velocity is lower than the transverse wave speed, and, the higher the axial velocity, the narrower the frequency band-gaps. The revealed effects could be of potential importance for applications, e.g. they indicate that due to spatial inhomogeneity, oscillations of axially moving periodic chains always involve a multitude of frequencies.
An Unbroken Axial Vector Current Conservation Law
Sharafiddinov, Rasulkhozha S
2015-01-01
The mass, energy and momentum of the neutrino of a true flavor have an axial-vector nature. As a consequence, the left-handed truly neutral neutrino in an axial-vector field of emission can be converted into a right-handed one and vice versa. This predicts the unidenticality of masses, energies and momenta of neutrinos of the different components. Recognizing such a difference in masses, energies, momenta and accepting that the left-handed axial-vector neutrino and the right-handed antineutrino of true neutrality refer to long-lived C-odd leptons, and the right-handed truly neutral neutrino and the left-handed axial-vector antineutrino are of short-lived fermions of C-oddity, we would write a new CP-even Dirac equation taking into account the flavor symmetrical axial-vector mass, energy and momentum matrices. Their presence explains the spontaneous mirror symmetry violation, confirming that an axial-vector current conservation law has never violated. They reflect the availability of a mirror Minkowski space i...
DEFF Research Database (Denmark)
Vesth, Allan; Kock, Carsten Weber
The report describes Load measurements carried out on a given wind turbine. The aim of the measurement program regarding the loads on the turbine is to verify the basic characteristics of the wind turbine and loads on the blades, the rotor and the tower, using [Ref 1], [Ref2] and [Ref 3]. Regardi...
Prince, D. C., Jr.; Wisler, D. C.; Hilvers, D. E.
1975-01-01
The results of a program of experimental and analytical research in casing treatments over axial compressor rotor blade tips are presented. Circumferential groove, axial-skewed slot and blade angle slot treatments were tested at low speeds. With the circumferential groove treatment the stalling flow was reduced 5.8% at negligible efficiency sacrifice. The axial-skewed slot treatment improved the stalling flow by 15.3%; 1.8 points in peak efficiency were sacrificed. The blade angle slot treatment improved the stalling flow by 15.0%; 1.4 points in peak efficiency were sacrificed. The favorable stalling flow situations correlated well with observations of higher-than-normal surface pressures on the rotor blade pressure surfaces in the tip region, and with increased maximum diffusions on the suction surfaces. Annulus wall pressure gradients, especially in the 50 to 75% chord region, are also increased and blade surface pressure loadings are shifted toward the trailing edge for treated configurations.
Simultaneous Optical Measurements of Axial and Tangential Steady-State Blade Deflections
Kurkov, Anatole P.; Dhadwal, Harbans S.
1999-01-01
Currently, the majority of fiber-optic blade instrumentation is being designed and manufactured by aircraft-engine companies for their own use. The most commonly employed probe for optical blade deflection measurements is the spot probe. One of its characteristics is that the incident spot on a blade is not fixed relative to the blade, but changes depending on the blade deformation associated with centrifugal and aerodynamic loading. While there are geometrically more complicated optical probe designs in use by different engine companies, this paper offers an alternate solution derived from a probe-mount design feature that allows one to change the probe axial position until the incident spot contacts either a leading or a trailing edge. By tracing the axial position of either blade edge one is essentially extending the deflection measurement to two dimensions, axial and tangential. The blade deflection measurements were obtained during a wind tunnel test of a fan prototype.
Experimental and Numerical Investigation of an Axial Rotary Blood Pump.
Schüle, Chan Yong; Thamsen, Bente; Blümel, Bastian; Lommel, Michael; Karakaya, Tamer; Paschereit, Christian Oliver; Affeld, Klaus; Kertzscher, Ulrich
2016-04-18
Left ventricular assist devices (LVADs) have become a standard therapy for patients with severe heart failure. As low blood trauma in LVADs is important for a good clinical outcome, the assessment of the fluid loads inside the pump is critical. More specifically, the flow features on the surfaces where the interaction between blood and artificial material happens is of great importance. Therefore, experimental data for the near-wall flows in an axial rotary blood pump were collected and directly compared to computational fluid dynamic results. For this, the flow fields based on unsteady Reynolds-averaged Navier-Stokes simulations-computational fluid dynamics (URANS-CFD) of an axial rotary blood pump were calculated and compared with experimental flow data at one typical state of operation in an enlarged model of the pump. The focus was set on the assessment of wall shear stresses (WSS) at the housing wall and rotor gap region by means of the wall-particle image velocimetry technique, and the visualization of near-wall flow structures on the inner pump surfaces by a paint erosion method. Additionally, maximum WSS and tip leakage volume flows were measured for 13 different states of operation. Good agreement between CFD and experimental data was found, which includes the location, magnitude, and direction of the maximum and minimum WSS and the presence of recirculation zones on the pump stators. The maximum WSS increased linearly with pressure head. They occurred at the upstream third of the impeller blades and exceeded the critical values with respect to hemolysis. Regions of very high shear stresses and recirculation zones could be identified and were in good agreement with simulations. URANS-CFD, which is often used for pump performance and blood damage prediction, seems to be, therefore, a valid tool for the assessment of flow fields in axial rotary blood pumps. The magnitude of maximum WSS could be confirmed and were in the order of several hundred Pascal.
Multiaxial fatigue criterion based on parameters from torsion and axial S-N curve
Directory of Open Access Journals (Sweden)
M. Margetin
2016-07-01
Full Text Available Multiaxial high cycle fatigue is a topic that concerns nearly all industrial domains. In recent years, a great deal of recommendations how to address problems with multiaxial fatigue life time estimation have been made and a huge progress in the field has been achieved. Until now, however, no universal criterion for multiaxial fatigue has been proposed. Addressing this situation, this paper offers a design of a new multiaxial criterion for high cycle fatigue. This criterion is based on critical plane search. Damage parameter consists of a combination of normal and shear stresses on a critical plane (which is a plane with maximal shear stress amplitude. Material parameters used in proposed criterion are obtained from torsion and axial S-N curves. Proposed criterion correctly calculates life time for boundary loading condition (pure torsion and pure axial loading. Application of proposed model is demonstrated on biaxial loading and the results are verified with testing program using specimens made from S355 steel. Fatigue material parameters for proposed criterion and multiple sets of data for different combination of axial and torsional loading have been obtained during the experiment.
Optimization of residual heat removal pump axial thrust and axial bearing
Energy Technology Data Exchange (ETDEWEB)
Schubert, F.
1996-12-01
The residual heat removal (RHR) pumps of German 1300 megawatt pressurized-water reactor (PWR) power plants are of the single stage end suction type with volute casing or with diffuser and forged circular casing. Due to the service conditions the pumps have to cover the full capacity range as well as a big variation in suction static pressure. This results in a big difference in the axial thrust that has to be borne by the axial bearing. Because these pumps are designed to operate without auxiliary systems (things that do not exist can not fail), they are equipped with antifriction bearings and sump oil lubrication. To minimize the heat production within the bearing casing, a number of PWR plants have pumps with combined axial/radial bearings of the ball type. Due to the fact that the maximum axial thrust caused by static pressure and hydrodynamic forces on the impeller is too big to be borne by that type of axial bearing, the impellers were designed to produce a hydrodynamic axial force that counteracts the static axial force. Thus, the resulting axial thrust may change direction when the static pressure varies.
Axial super-resolution evanescent wave tomography
Pendharker, Sarang; Shende, Swapnali; Newman, Ward; Ogg, Stephen; Nazemifard, Neda; Jacob, Zubin
2016-12-01
Optical tomographic reconstruction of a 3D nanoscale specimen is hindered by the axial diffraction limit, which is 2-3 times worse than the focal plane resolution. We propose and experimentally demonstrate an axial super-resolution evanescent wave tomography (AxSET) method that enables the use of regular evanescent wave microscopes like Total Internal Reflection Fluorescence Microscope (TIRF) beyond surface imaging, and achieve tomographic reconstruction with axial super-resolution. Our proposed method based on Fourier reconstruction achieves axial super-resolution by extracting information from multiple sets of three-dimensional fluorescence images when the sample is illuminated by an evanescent wave. We propose a procedure to extract super-resolution features from the incremental penetration of an evanescent wave and support our theory by 1D (along the optical axis) and 3D simulations. We validate our claims by experimentally demonstrating tomographic reconstruction of microtubules in HeLa cells with an axial resolution of $\\sim$130 nm. Our method does not require any additional optical components or sample preparation. The proposed method can be combined with focal plane super-resolution techniques like STORM and can also be adapted for THz and microwave near-field tomography.
Axial super-resolution evanescent wave tomography.
Pendharker, Sarang; Shende, Swapnali; Newman, Ward; Ogg, Stephen; Nazemifard, Neda; Jacob, Zubin
2016-12-01
Optical tomographic reconstruction of a three-dimensional (3D) nanoscale specimen is hindered by the axial diffraction limit, which is 2-3 times worse than the focal plane resolution. We propose and experimentally demonstrate an axial super-resolution evanescent wave tomography method that enables the use of regular evanescent wave microscopes like the total internal reflection fluorescence microscope beyond surface imaging and achieve a tomographic reconstruction with axial super-resolution. Our proposed method based on Fourier reconstruction achieves axial super-resolution by extracting information from multiple sets of 3D fluorescence images when the sample is illuminated by an evanescent wave. We propose a procedure to extract super-resolution features from the incremental penetration of an evanescent wave and support our theory by one-dimensional (along the optical axis) and 3D simulations. We validate our claims by experimentally demonstrating tomographic reconstruction of microtubules in HeLa cells with an axial resolution of ∼130 nm. Our method does not require any additional optical components or sample preparation. The proposed method can be combined with focal plane super-resolution techniques like stochastic optical reconstruction microscopy and can also be adapted for THz and microwave near-field tomography.
Reducing axial mixing in flotation columns
Energy Technology Data Exchange (ETDEWEB)
Al Taweel, A.M.; Ramadan, A.M. [Technical Univ. of Nova Scotia, Halifax (Canada). Chemical Engineering Dept.; Moharam, M.R.; Hassan, T.A. [Al Azhar Univ., Cairo (Egypt); El Mofty, S.M. [Cairo Univ., Giza (Egypt)
1995-10-01
The axial mixing characteristics of a pilot-scale flotation column were investigated with the objective of identifying means to mitigate the extent of axial mixing that adversely affects its grade/recovery performance. A wide range of design and operating conditions wa investigated and the experimental results, obtained using the dynamic response method, were analyzed using three axial mixing models. The dynamic response of the column can best be described using the axial dispersion model. The results obtained suggest that the value of the axial dispersion coefficient, E{sub L}, can be significantly reduced by judicial selection of hydrodynamic conditions and/or the use of column inserts that suppress the onset of hydrodynamic instabilities inherent to the operation of conventional flotation columns. Up to 40% reduction in the value of E{sub L} was thus obtained by using spargers that produce more uniform bubble sizes, while up to 30% reductions were obtained by controlling the residual frother concentration. 33 refs., 7 figs.
1984-01-01
overburden pressure in tons/sq ft. v Bazaraa (1967) presented a set of equations to correct the field blow count for the effects of overburden pressure: N 4...1, pp. 381-386. 3. Bazaraa , A. R., (1967), "Use of the Standard Penetration Test for Estimating Settlements of Shallow Foundations On Sand", Ph.D
Low-Friction, High-Stiffness Joint for Uniaxial Load Cell
Lewis, James L.; Le, Thang; Carroll, Monty B.
2007-01-01
A universal-joint assembly has been devised for transferring axial tension or compression to a load cell. To maximize measurement accuracy, the assembly is required to minimize any moments and non-axial forces on the load cell and to exhibit little or no hysteresis. The requirement to minimize hysteresis translates to a requirement to maximize axial stiffness (including minimizing backlash) and a simultaneous requirement to minimize friction. In practice, these are competing requirements, encountered repeatedly in efforts to design universal joints. Often, universal-joint designs represent compromises between these requirements. The improved universal-joint assembly contains two universal joints, each containing two adjustable pairs of angular-contact ball bearings. One might be tempted to ask why one could not use simple ball-and-socket joints rather than something as complex as universal joints containing adjustable pairs of angularcontact ball bearings. The answer is that ball-and-socket joints do not offer sufficient latitude to trade stiffness versus friction: the inevitable result of an attempt to make such a trade in a ball-and-socket joint is either too much backlash or too much friction. The universal joints are located at opposite ends of an axial subassembly that contains the load cell. The axial subassembly includes an axial shaft, an axial housing, and a fifth adjustable pair of angular-contact ball bearings that allows rotation of the axial housing relative to the shaft. The preload on each pair of angular-contact ball bearings can be adjusted to obtain the required stiffness with minimal friction, tailored for a specific application. The universal joint at each end affords two degrees of freedom, allowing only axial force to reach the load cell regardless of application of moments and non-axial forces. The rotational joint on the axial subassembly affords a fifth degree of freedom, preventing application of a torsion load to the load cell.
Performance studies on an axial flow compressor stage
Sitaram, N.
1986-12-01
A low-speed, medium loaded axial flow compressor stage is studied experimentally and theoretically. The flow compressor facility, composed of an inlet guide vane row, a rotor blade row, and a stator blade row, and the principles of the streamline curvature method (SCM) and the Douglas-Neumann cascade program are described. The radial distribution of the flow properties, the rotor blade static pressure distribution, and the lift coefficient and relative flow angle derived experimentally and theoretically are compared. It is determined that there is good correlation between the experimental flow properties and the SCM data, the Douglas-Neumann cascade program and experimental rotor blade static pressure data, and the experimental and theoretical lift coefficients only in the midspan region. Modifications to the SCM and the Douglas-Neumann cascade program in order to improve their accuracy are discussed.
Improving the lattice axial vector current
Energy Technology Data Exchange (ETDEWEB)
Horsley, R. [Edinburgh Univ. (United Kingdom). School of Physics and Astronomy; Nakamura, Y. [RIKEN Advanced Institute for Computational Science, Kobe (Japan); Perlt, H.; Schiller, A. [Leipzig Univ. (Germany). Inst. fuer Theoretische Physik; Rakow, P.E.L. [Liverpool Univ. (United Kingdom). Theoretical Physics Div.; Schierholz, G. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Zanotti, J.M. [Adelaide Univ. (Australia). CSSM, Dept. of Physics
2015-11-15
For Wilson and clover fermions traditional formulations of the axial vector current do not respect the continuum Ward identity which relates the divergence of that current to the pseudoscalar density. Here we propose to use a point-split or one-link axial vector current whose divergence exactly satisfies a lattice Ward identity, involving the pseudoscalar density and a number of irrelevant operators. We check in one-loop lattice perturbation theory with SLiNC fermion and gauge plaquette action that this is indeed the case including order O(a) effects. Including these operators the axial Ward identity remains renormalisation invariant. First preliminary results of a nonperturbative check of the Ward identity are also presented.
Axial flow positive displacement worm gas generator
Murrow, Kurt David (Inventor); Giffin, Rollin George (Inventor); Fakunle, Oladapo (Inventor)
2010-01-01
An axial flow positive displacement engine has an inlet axially spaced apart and upstream from an outlet. Inner and outer bodies have offset inner and outer axes extend from the inlet to the outlet through first, second, and third sections of a core assembly in serial downstream flow relationship. At least one of the bodies is rotatable about its axis. The inner and outer bodies have intermeshed inner and outer helical blades wound about the inner and outer axes respectively. The inner and outer helical blades extend radially outwardly and inwardly respectively. The helical blades have first, second, and third twist slopes in the first, second, and third sections respectively. The first twist slopes are less than the second twist slopes and the third twist slopes are less than the second twist slopes. A combustor section extends axially downstream through at least a portion of the second section.
Axial symmetry and conformal Killing vectors
Mars, M; Mars, Marc; Senovilla, Jose M.M.
1993-01-01
Axisymmetric spacetimes with a conformal symmetry are studied and it is shown that, if there is no further conformal symmetry, the axial Killing vector and the conformal Killing vector must commute. As a direct consequence, in conformally stationary and axisymmetric spacetimes, no restriction is made by assuming that the axial symmetry and the conformal timelike symmetry commute. Furthermore, we prove that in axisymmetric spacetimes with another symmetry (such as stationary and axisymmetric or cylindrically symmetric spacetimes) and a conformal symmetry, the commutator of the axial Killing vector with the two others mush vanish or else the symmetry is larger than that originally considered. The results are completely general and do not depend on Einstein's equations or any particular matter content.
Atlanto-axial infection after acupuncture.
Robinson, A; Lind, C R P; Smith, R J; Kodali, V
2015-12-11
A 67-year-old man presented with neck cellulitis following acupuncture for cervical spondylosis. Blood cultures were positive for methicillin-sensitive Staphylococcus aureus. Increased neck pain and bacteraemia prompted MRI, which showed atlanto-axial septic arthritis without signs of infection of the tissues between the superficial cellulitic area and the atlanto-axial joint, thus making direct extension of infection unlikely. It is more likely that haematogenous spread of infection resulted in seeding in the atlanto-axial joint, with the proximity of the arthritis and acupuncture site being coincidental. Acupuncture is a treatment option for some indolent pain conditions. As such, acupuncture services are likely to be more frequently utilised. A history of acupuncture is rarely requested by the admitting doctor and seldom offered voluntarily by the patient, especially where the site of infection due to haematogenous spread is distant from the needling location. Awareness of infectious complications following acupuncture can reduce morbidity through early intervention.
Improving the lattice axial vector current
Horsley, R; Perlt, H; Rakow, P E L; Schierholz, G; Schiller, A; Zanotti, J M
2015-01-01
For Wilson and clover fermions traditional formulations of the axial vector current do not respect the continuum Ward identity which relates the divergence of that current to the pseudoscalar density. Here we propose to use a point-split or one-link axial vector current whose divergence exactly satisfies a lattice Ward identity, involving the pseudoscalar density and a number of irrelevant operators. We check in one-loop lattice perturbation theory with SLiNC fermion and gauge plaquette action that this is indeed the case including order $O(a)$ effects. Including these operators the axial Ward identity remains renormalisation invariant. First preliminary results of a nonperturbative check of the Ward identity are also presented.
Growth-induced axial buckling of a slender elastic filament embedded in an isotropic elastic matrix
O'Keeffe, Stephen G.
2013-11-01
We investigate the problem of an axially loaded, isotropic, slender cylinder embedded in a soft, isotropic, outer elastic matrix. The cylinder undergoes uniform axial growth, whilst both the cylinder and the surrounding elastic matrix are confined between two rigid plates, so that this growth results in axial compression of the cylinder. We use two different modelling approaches to estimate the critical axial growth (that is, the amount of axial growth the cylinder is able to sustain before it buckles) and buckling wavelength of the cylinder. The first approach treats the filament and surrounding matrix as a single 3-dimensional elastic body undergoing large deformations, whilst the second approach treats the filament as a planar, elastic rod embedded in an infinite elastic foundation. By comparing the results of these two approaches, we obtain an estimate of the foundation modulus parameter, which characterises the strength of the foundation, in terms of the geometric and material properties of the system. © 2013 Elsevier Ltd. All rights reserved.
Fatigue Failure Results for Multi-Axial versus Uniaxial Stress Screen Vibration Testing
Directory of Open Access Journals (Sweden)
Wayne E. Whiteman
2002-01-01
Full Text Available To date, the failure potential and prediction between simultaneous multi-axial versus sequentially applied uniaxial vibration stress screen testing has been the subject of great debate. In most applications, current vibration tests are done by sequentially applying uniaxial excitation to the test specimen along three orthogonal axes. The most common standards for testing military equipment are published in MIL-STD-810F and NAVMAT P-9492. Previous research had shown that uniaxial testing may be unrealistic and inadequate. This current research effort is a continuing effort to systematically investigate the differences between fatigue damage mechanisms and the effects of uniaxial versus tri-axial testing. This includes assessing the ability of the tri-axial method in predicting the formation of damage mechanisms, specifically looking at the effects of stress or fatigue failure. Multi-axial testing achieves the synergistic effect of exciting all modes simultaneously and induces a more realistic vibration stress loading condition. As such, it better approximates real-world operating conditions. This paper provides the latest results on the differences between multi-axial and uniaxial testing of a simple notched cantilever beam.
Effect of Solid Properties on Axial Liquid Dispersion in Bubble Column
Directory of Open Access Journals (Sweden)
Ali Raad Mohammed Jawad
2012-01-01
Full Text Available Experiments were conducted to study axial liquid dispersion coefficient in slurry bubble column of 0.15 m inside diameter and 1.6 m height using perforated plate gas distributor of 54 holes of a size equal to 1 mm diameter and with a 0.24 free area of holes to the cross sectional area of the column. The three phase system consists of air, water and PVC used as the solid phase. The effect of solid loading (0, 30 and 60 kg/m3 and solid diameter (0.7, 1.5 and 3 mm on the axial liquid dispersion coefficient at different axial location (25, 50 and 75 cm and superficial gas velocity covered homogeneous-heterogeneous flow regime (1-10 cm/s were studied in the present work. The results show that the axial liquid dispersion coefficient increases with increasing superficial gas velocity, axial distance, solid concentration and an inverse relationship with particles diameter
Analysis of a Liquid Nitrogen-Cooled Tri-Axial High-Temperature Superconducting Cable System
Demko, J. A.; Lue, J. W.; Gouge, M. J.; Fisher, P. W.; Lindsay, D.; Roden, M.
2004-06-01
This tri-axial high-temperature superconducting (HTS) cable design uses three concentric superconducting layers for the phase conductors, separated by a cold dielectric material. The design offers an efficient HTS cable configuration by reducing the amount of superconductor needed and places all three phases in a single cryostat. The tri-axial cable cooling circuit analyzed includes heat loads at the ends for the cable terminations and cable heat loads due to ac, dielectric, and thermal losses. The HTS cable critical current and ac loss are functions of the local temperature that must be determined by the analysis. The radial heat transfer also has an influence on these parameters due to the relatively low thermal conductivity of the dielectric material separating the HTS phases. The study investigates whether the tri-axial cable must be cooled both inside the former and outside of the cable. In this study, the range of operating parameters for a tri-axial HTS cable system and refrigeration requirements are determined based on expected HTS tape performance.
Directory of Open Access Journals (Sweden)
Rajeev Kumar
2014-07-01
Full Text Available A finite element model of fractured tibia with Joshi’s External Stabilizing System (JESS mounted on it was developed using 3D beam elements in the ANSYS software. The model was loaded in axial compression and the average axial stiffness of the model was calculated. The analytical value of axial stiffness was compared with reported experimental value to validate the finite element model. The validated model was used to carry out parametric studies on the model to determine the axial properties of JESS. It was observed that axial stiffness of JESS increased by 58% when k-wire diameter was varied from 2 mm to 4 mm while keeping other geometric configurations of the device constant; however, the axial stiffness of the device does not show any significant improvement when the diameter of medio-lateral pins in diaphyseal hold were increased. The findings should help in understanding the axial properties of JESS so that it can be used judiciously in clinical applications.
Axial Nucleon form factors from lattice QCD
Alexandrou, C; Carbonell, J; Constantinou, M; Harraud, P A; Guichon, P; Jansen, K; Korzec, T; Papinutto, M
2010-01-01
We present results on the nucleon axial form factors within lattice QCD using two flavors of degenerate twisted mass fermions. Volume effects are examined using simulations at two volumes of spatial length $L=2.1$ fm and $L=2.8$ fm. Cut-off effects are investigated using three different values of the lattice spacings, namely $a=0.089$ fm, $a=0.070$ fm and $a=0.056$ fm. The nucleon axial charge is obtained in the continuum limit and chirally extrapolated to the physical pion mass enabling comparison with experiment.
Optimization of Axial Intensity Point Spread Function
Institute of Scientific and Technical Information of China (English)
WANG Haifeng; GAN Fuxi; CHEN Zhongyu
2001-01-01
It is known that for the converged laser beam, the axial intensity distribution corresponds to a Gaussian curve, that is, the intensity on the focal plane is the peak intensity. When it defocuses, the intensity would decrease rapidly. In optical data storage, for instance, we expect the intensity within a certain distance to be almost equal. In this paper, we propose to use a pure phase superresolution apodizer to optimize the axial intensity distribution of the converged laser beam and at the same time improve the resolution. The intensity point spread function remains almost identical in a wide range within the focal depth.
«FLARES» IN AXIAL SPONDYLOARTHRITIS
Directory of Open Access Journals (Sweden)
Sh. F. Erdes
2016-01-01
Full Text Available The clear definition of the concept of «flare in axial spondyloarthritis» is of paramount importance for clinical trials and routine practice in particular. It will be able to unify the characteristics of outcomes over a particular period of time on the one hand and to standardize therapeutic approaches on the other. On 4 February 2016, the journal Annals of Rheumatic Diseases published the on-line paper «Preliminary definitions of 'flare' in axial spondyloarthritis, based on pain, BASDAI and ASDAS-CRP: an ASAS initiative» by L. Gossec et al., which was devoted to this topic.
POST-BUCKLING OF A CANTILEVER ROD WITH VARIABLE CROSS-SECTIONS UNDER COMBINED LOAD
Institute of Scientific and Technical Information of China (English)
吴莹; 李世荣; 滕兆春
2003-01-01
Based on the geometrically nonlinear theory of axially extensible elastic rods,the governing equations of post-buckling of a clamped-free rod with variable cross-sections,subjected to a combined load, a concentrated axial load P at the free end and a nonuniformly distributed axial load q, are established. By using shooting method, the strong nonlinear boundary value problems are numerically solved. The secondary equilibrium paths and the post-buckling configurations of the rod with linearly varied cross-sections are presented.
Case Study of CPT-based Design Methods for Axial Capacity of Driven Piles in Sand
DEFF Research Database (Denmark)
Thomassen, Kristina; Ibsen, Lars Bo; Andersen, Lars Vabbersgaard
2012-01-01
Today the design of onshore axially loaded driven piles in cohesionless soil is commonly made on basis of CPT-based methods because field investigations have shown strong correlation between the local shaft friction and the CPT cone resistance. However, the recommended design method for axially....... Thus, several CPT-based methods have been proposed for the design of offshore driven piles in cohesionless soil such as the UWA-05, ICP-05, and NGI-99 methods. This article treats a case study where the API-method as well as the UWA-05 and NGI-99 methods are compared using CPT-data from an offshore...... location with dense to very dense sand. The design of the piles in the jacket foundation shows that API-00 for both the tension and the compression loads predicted much longer piles than the CPT-based methods. Variation of the pile length and pile diameter shows that NGI-99 and UWA-05 predicts almost...
Static Load Distribution in Ball Bearings
Ricci, Mario
2010-01-01
A numerical procedure for computing the internal loading distribution in statically loaded, single-row, angular-contact ball bearings when subjected to a known combined radial and thrust load is presented. The combined radial and thrust load must be applied in order to avoid tilting between inner and outer rings. The numerical procedure requires the iterative solution of Z + 2 simultaneous nonlinear equations - where Z is the number of the balls - to yield an exact solution for axial and radial deflections, and contact angles. Numerical results for a 218 angular-contact ball bearing have been compared with those from the literature and show significant differences in the magnitudes of the ball loads, contact angles, and the extent of the loading zone.
Advanced AC permanent magnet axial flux disc motor for electric passenger vehicle
Kliman, G. B.
1982-01-01
An ac permanent magnet axial flux disc motor was developed to operate with a thyristor load commutated inverter as part of an electric vehicle drive system. The motor was required to deliver 29.8 kW (40 hp) peak and 10.4 kW (14 hp) average with a maximum speed of 11,000 rpm. It was also required to run at leading power factor to commutate the inverter. Three motors were built.
Design, Test, and Evaluation of a Transonic Axial Compressor Rotor with Splitter Blades
2013-09-01
Postgraduate School NPSMF NPS Military Fan NTG No Tip Gap PS Pressure Side SB Splitter Blade SS Suction Side SolidWorks A solid modeling...lubrication oil to the TASR and drive turbine bearings via an air driven oil mist system. A pre-test checklist is provided in McNab [8] Appendix C...modern high- performance compressor rotors. 79 LIST OF REFERENCES [1] A. J. Wennerstrom, Design of Highly Loaded Axial-Flow Fans and Compressors, White
Investigations on Experimental Impellers for Axial Blowers
Encke, W.
1947-01-01
A selection of measurements obtained on experimental impellers for axial blowers will be reported. In addition to characteristic curves plotted for low and for high peripheral velocities, proportions and blade sections for six different blower models and remarks on the design of blowers will be presented.
Excitation modes in non-axial nuclei
Energy Technology Data Exchange (ETDEWEB)
Leviatan, A.; Ginnochio, J.N.
1990-01-01
Excitation modes of non-axial quadrupole shapes are investigated in the framework of interacting boson models. Both {gamma}-unstable and {gamma}-rigid nuclear shapes are considered for systems with one type of boson as well as with proton-neutron bosons. 6 refs.
Ankylosing Spondylitis versus Nonradiographic Axial Spondyloarthritis
DEFF Research Database (Denmark)
Glintborg, Bente; Sørensen, Inge J; Østergaard, Mikkel
2017-01-01
OBJECTIVE: To compare baseline disease activity and treatment effectiveness in biologic-naive patients with nonradiographic axial spondyloarthritis (nr-axSpA) and ankylosing spondylitis (AS) who initiate tumor necrosis factor inhibitor (TNFi) treatment and to study the role of potential confounders...
Wave propagation in axially moving periodic strings
DEFF Research Database (Denmark)
Sorokin, Vladislav S.; Thomsen, Jon Juel
2017-01-01
The paper deals with analytically studying transverse waves propagation in an axially moving string with periodically modulated cross section. The structure effectively models various relevant technological systems, e.g. belts, thread lines, band saws, etc., and, in particular, roller chain drive...
Determining Aerodynamic Loads Based on Optical Deformation Measurements
Liu, Tianshu; Barrows, D. A.; Burner, A. W.; Rhew, R. D.
2001-01-01
This paper describes a videogrammetric technique for determining aerodynamic loads based on optical elastic deformation measurements. The data reduction methods are developed to extract the normal force and pitching moment from beam deformation data. The axial force is obtained by measuring the axial translational motion of a movable shaft in a spring/bearing device. Proof-of-concept calibration experiments are conducted to assess the accuracy of this optical technique.
Effects of inflow conditions on discrete frequency noise generated by small, axial flow fans
Washburn, K. B.; Lauchle, G. C.
1985-09-01
Discrete frequency acoustic radiation is generated by subsonic axial flow fans through both steady and unsteady blade loading. Steady loading is a function of pumping requirement, and unsteady loading is generated by spatially periodic inflow distortions. The latter effect is the dominant generation mechanism when small fans are used to cool electronic equipment. Fans mounted to exhaust out of a device ingest distortions created by all objects within the unit. This work represents an empirical survey of noise generated by small axial flow cooling fans in the presence of upstream obstructions and various inlet configurations. The obstructions include a cylinder, a thin rectangle, a thick rectangle, and an electronic card gate model. Each of these represents obstructions found in a typical installation. Simple and modified inlet baffles, finger guards, and honeycomb flow straighteners are investigated. Design recommendations are offered to minimize discrete tone generation. These include aerodynamic shaping of unaviodable obstructions, a minimum axial distance of 0.3 fan radii for obstructions in the inlet, the avoidance of blockage in lateral inflow and the use of an inlet baffle to smooth inlet distortions. Account is taken of the spatial restictions of typical installations.
Secondary flow, turbulent diffusion and mixing in axial-flow compressors
Wisler, D. C.; Bauer, R. C.; Okiishi, T. H.
1987-05-01
The relative importance of convection by secondary flows and diffusion by turbulence as mechanisms responsible for mixing in multistage, axial-flow compressors has been investigated by using the ethylene tracer-gas technique and hot wire anemometry. The tests were conducted at two loading levels in a large, low-speed, four-stage compressor. The experimental results show that considerable cross-passage and spanwise fluid motion can occur and that both secondary flow and turbulent diffusion can play important roles in the mixing process, depending upon location in the compressor and loading level.
Excitation of a cylindrical cavity by a helical current and an axial electron beam current
Davidovich, M. V.; Bushuev, N. A.
2013-07-01
The explicit expressions (in the Vainshtein and Markov forms) are derived for the excitation of a cylindrical cavity with perfectly conducting walls and with impedance end faces. Excitation of a cylindrical cavity and a cylindrical waveguide with a preset nonuniform axial electron-beam current and a helical current with a variable pitch, which is excited by a concentrated voltage source and is loaded by a preset pointlike matched load, is considered. For the helical current, the integro-differential equation is formulated. The traveling-wave tube (TWT) is simulated in the preset beam current approximation taking into account the nonuniform winding of the spiral coil, nonuniform electron beam, and losses.
Wang, Jiaojiao; Shi, Gang; Shi, Yongjiu
2014-12-01
To investigate the seismic behavior of I-section columns made of 460 MPa high strength steel (HSS), six specimens were tested under constant axial load and cyclic horizontal load. The specimens were designed with different width-to-thickness ratios and loaded under different axial load ratios. For each specimen, the failure mode was observed and hysteretic curve was measured. Comparison of different specimens on hysteretic characteristic, energy dissipation capacity and deformation capacity were further investigated. Test results showed that the degradation of bearing capacity was due to local buckling of flange and web. Under the same axial load ratio, as width-to-thickness ratio increased, the deformation area of local buckling became smaller. And also, displacement level at both peak load and failure load became smaller. In addition, the full extent of hysteretic curve, energy dissipation capacity, ultimate story drift angle decreased, and capacity degradation occurred more rapidly with the increase of width-to-thickness ratio or axial load ratio. Based on the capacity of story drift angle, limiting values which shall not be exceeded are suggested respectively for flange and web plate of 460 MPa HSS I-section columns when used in SMFs and in IMFs in the case of axial load ratio no more than 0.2. Such values should be smaller when the axial load ratio increases.
Energy Technology Data Exchange (ETDEWEB)
Ansarifar, Gholam Reza; Saadatzi, Saeed [Dept. of Nuclear Engineering, Faculty of Advanced Sciences and Technology, University of Isfahan, Isfahan (Iran, Islamic Republic of)
2015-12-15
One of the most important operations in nuclear power plants is load following, in which an imbalance of axial power distribution induces xenon oscillations. These oscillations must be maintained within acceptable limits otherwise the nuclear power plant could become unstable. Therefore, bounded xenon oscillation is considered to be a constraint for the load following operation. In this paper, the design of a sliding mode control (SMC), which is a robust nonlinear controller, is presented. SMC is a means to control pressurized water nuclear reactor (PWR) power for the load following operation problem in a way that ensures xenon oscillations are kept bounded within acceptable limits. The proposed controller uses constant axial offset (AO) strategy to ensure xenon oscillations remain bounded. The constant AO is a robust state constraint for the load following problem. The reactor core is simulated based on the two-point nuclear reactor model with a three delayed neutron groups. The stability analysis is given by means of the Lyapunov approach, thus the control system is guaranteed to be stable within a large range. The employed method is easy to implement in practical applications and moreover, the SMC exhibits the desired dynamic properties during the entire output-tracking process independent of perturbations. Simulation results are presented to demonstrate the effectiveness of the proposed controller in terms of performance, robustness, and stability. Results show that the proposed controller for the load following operation is so effective that the xenon oscillations are kept bounded in the given region.
Masi, Alfonse T.
2014-01-01
Ankylosing spondylitis and axial spondyloarthropathy have characteristic age- and sex-specific onset patterns, typical entheseal lesions, and marked heritability, but the integrative mechanisms causing the pathophysiological and structural alterations remain largely undefined. Myofascial tissues are integrated in the body into webs and networks which permit transmission of passive and active tensional forces that provide stabilizing support and help to control movements. Axial myofascial hype...
Dynamics and statics of flexible axially symmetric shallow shells
Directory of Open Access Journals (Sweden)
2006-01-01
Full Text Available In this work, we propose the method for the investigation of stochastic vibrations of deterministic mechanical systems represented by axially symmetric spherical shells. These structure members are widely used as sensitive elements of pressure measuring devices in various branches of measuring and control industry, machine design, and so forth. The proposed method can be easily extended for the investigation of shallow spherical shells, goffer-type membranes, and so on. The so-called charts of control parameters for a shell subjected to a transversal uniformly distributed and local harmonic loading force and resistance moment are constructed. The scenarios of the transition of vibration of shallow-type system into chaotic state are investigated with the use of the theory of differential equations and the theory of nonlinear dynamics. The method of the control of chaotic vibrations of flexible spherical shells subjected to a transversal harmonic load through a synchronized action of either harmonic resistance moment or force is proposed, illustrated, and discussed.
Directory of Open Access Journals (Sweden)
Filippo Cassarà
2013-03-01
Full Text Available Recent research addressed the main role of hepcidin in the regulation of iron metabolism. However, while this mechanism could be relevant in causing iron load in Thalassemia Intermedia and Sickle-Cell Anemia, its role in Thalassemia Major (TM is marginal. This is mainly due to the high impact of transfusional requirement into the severe increase of body iron. Moreover, the damage of iron load may be worsened by infections, as HCV hepatitis, or liver and endocrinological damage. One of the most relevant associations was found between splenectomy and increase of risk for mortality due,probably, to more severe iron load. These issues suggest as morbidity and mortality of this group of patients they do not depend only by our ability in controlling heart damage but even in preventing or treating particular infections and complications. This finding is supported by the impairment of survival curves in patients with complications different from heart damage. However, because, during recent years different direct and indirect methods to detect iron overload in patients affected by secondary hemochromatosis have been implemented, our ability to maintain under control iron load is significantly improved. Anyway, the future in iron load management remains to be able to have an iron load map of our body for targeting chelation and other medical treatment according to the single organ damage.
Energy Technology Data Exchange (ETDEWEB)
Parviainen, A.
2005-07-01
This thesis presents an alternative approach to the analytical design of surface-mounted axial-flux permanent-magnet machines. Emphasis has been placed on the design of axial-flux machines with a one-rotor-two-stators configuration. The design model developed in this study incorporates facilities to include both the electromagnetic design and thermal design of the machine as well as to take into consideration the complexity of the permanent-magnet shapes, which is a typical requirement for the design of high-performance permanent-magnet motors. A prototype machine with rated 5 kW output power at 300 min{sup -1} rotation speed has been designed and constructed for the purposes of ascertaining the results obtained from the analytical design model. A comparative study of low-speed axial-flux and low-speed radial-flux permanent-magnet machines is presented. The comparative study concentrates on 55 kW machines with rotation speeds 150 min{sup -1}, 300 min{sup -1} and 600 min{sup -1} and is based on calculated designs. A novel comparison method is introduced. The method takes into account the mechanical constraints of the machine and enables comparison of the designed machines, with respect to the volume, efficiency and cost aspects of each machine. It is shown that an axial-flux permanent-magnet machine with one-rotor-two-stators configuration has generally a weaker efficiency than a radial-flux permanent-magnet machine if for all designs the same electric loading, air-gap flux density and current density have been applied. On the other hand, axial-flux machines are usually smaller in volume, especially when compared to radial-flux machines for which the length ratio (axial length of stator stack vs. air-gap diameter) is below 0.5. The comparison results show also that radial-flux machines with a low number of pole pairs, p < 4, outperform the corresponding axial-flux machines. (orig.)
Directory of Open Access Journals (Sweden)
Sanjib C. Chowdhury
2017-02-01
Full Text Available Ballistic impact induces multiaxial loading on Kevlar® and polyethylene fibers used in protective armor systems. The influence of multiaxial loading on fiber failure is not well understood. Experiments show reduction in the tensile strength of these fibers after axial and transverse compression. In this paper, we use molecular dynamics (MD simulations to explain and develop a fundamental understanding of this experimental observation since the property reduction mechanism evolves from the atomistic level. An all-atom MD method is used where bonded and non-bonded atomic interactions are described through a state-of-the-art reactive force field. Monotonic tension simulations in three principal directions of the models are conducted to determine the anisotropic elastic and strength properties. Then the models are subjected to multi-axial loads—axial compression, followed by axial tension and transverse compression, followed by axial tension. MD simulation results indicate that pre-compression distorts the crystal structure, inducing preloading of the covalent bonds and resulting in lower tensile properties.
Axial flow positive displacement worm compressor
Murrow, Kurt David (Inventor); Giffin, Rollin George (Inventor); Fakunle, Oladapo (Inventor)
2010-01-01
An axial flow positive displacement compressor has an inlet axially spaced apart and upstream from an outlet. Inner and outer bodies have offset inner and outer axes extend from the inlet to the outlet through first and second sections of a compressor assembly in serial downstream flow relationship. At least one of the bodies is rotatable about its axis. The inner and outer bodies have intermeshed inner and outer helical blades wound about the inner and outer axes respectively. The inner and outer helical blades extend radially outwardly and inwardly respectively. The helical blades have first and second twist slopes in the first and second sections respectively. The first twist slopes are less than the second twist slopes. An engine including the compressor has in downstream serial flow relationship from the compressor a combustor and a high pressure turbine drivingly connected to the compressor by a high pressure shaft.
Direct optical nanoscopy with axially localized detection
Bourg, N; Dupuis, G; Barroca, T; Bon, P; Lécart, S; Fort, E; Lévêque-Fort, S
2014-01-01
Evanescent light excitation is widely used in super-resolution fluorescence microscopy to confine light and reduce background noise. Herein we propose a method of exploiting evanescent light in the context of emission. When a fluorophore is located in close proximity to a medium with a higher refractive index, its near-field component is converted into light that propagates beyond the critical angle. This so-called Supercritical Angle Fluorescence (SAF) can be captured using a hig-NA objective and used to determine the axial position of the fluorophore with nanometer precision. We introduce a new technique for 3D nanoscopy that combines direct STochastic Optical Reconstruction Microscopy (dSTORM) imaging with dedicated detection of SAF emission. We demonstrate that our approach of a Direct Optical Nanoscopy with Axially Localized Detection (DONALD) yields a typical isotropic 3D localization precision of 20 nm.
Piping inspection carriage having axially displaceable sensor
Zollinger, William T.; Treanor, Richard C.
1994-01-01
A pipe inspection instrument carriage for use with a pipe crawler for performing internal inspections of piping surfaces. The carriage has a front leg assembly, a rear leg assembly and a central support connecting the two assemblies and for mounting an instrument arm having inspection instruments. The instrument arm has a y-arm mounted distally thereon for axially aligning the inspection instrumentation and a mounting block, a linear actuator and axial movement arm for extending the inspection instruments radially outward to operably position the inspection instruments on the piping interior. Also, the carriage has a rotation motor and gear assembly for rotating the central support and the front leg assembly with respect to the rear leg assembly so that the inspection instruments azimuthally scan the piping interior. The instrument carriage allows performance of all piping inspection operations with a minimum of moving parts, thus decreasing the likelihood of performance failure.
Multimode interaction in axially excited cylindrical shells
2014-01-01
Cylindrical shells exhibit a dense frequency spectrum, especially near the lowest frequency range. In addition, due to the circumferential symmetry, frequencies occur in pairs. So, in the vicinity of the lowest natural frequencies, several equal or nearly equal frequencies may occur, leading to a complex dynamic behavior. So, the aim of the present work is to investigate the dynamic behavior and stability of cylindrical shells under axial forcing with multiple equal or nearly equal natural fr...
Axial flux permanent magnet brushless machines
Gieras, Jacek F; Kamper, Maarten J
2008-01-01
Axial Flux Permanent Magnet (AFPM) brushless machines are modern electrical machines with a lot of advantages over their conventional counterparts. They are being increasingly used in consumer electronics, public life, instrumentation and automation system, clinical engineering, industrial electromechanical drives, automobile manufacturing industry, electric and hybrid electric vehicles, marine vessels and toys. They are also used in more electric aircrafts and many other applications on larger scale. New applications have also emerged in distributed generation systems (wind turbine generators
Consistent formulation of the spacelike axial gauge
Energy Technology Data Exchange (ETDEWEB)
Burnel, A.; Van der Rest-Jaspers, M.
1983-12-15
The usual formulation of the spacelike axial gauge is afflicted with the difficulty that the metric is indefinite while no ghost is involved. We solve this difficulty by introducing a ghost whose elimination is such that the metric becomes positive for physical states. The technique consists in the replacement of the gauge condition nxA = 0 by the weaker one partial/sub 0/nxAroughly-equal0.
Direct optical nanoscopy with axially localized detection
Bourg, N.; Mayet, C.; Dupuis, G.; Barroca, T.; Bon, P.; Lécart, S.; Fort, E.; Lévêque-Fort, S.
2015-09-01
Evanescent light excitation is widely used in super-resolution fluorescence microscopy to confine light and reduce background noise. Here, we propose a method of exploiting evanescent light in the context of emission. When a fluorophore is located in close proximity to a medium with a higher refractive index, its near-field component is converted into light that propagates beyond the critical angle. This so-called supercritical-angle fluorescence can be captured using a high-numerical-aperture objective and used to determine the axial position of the fluorophore with nanometre precision. We introduce a new technique for three-dimensional nanoscopy that combines direct stochastic optical reconstruction microscopy (dSTORM) with dedicated detection of supercritical-angle fluorescence emission. We demonstrate that our approach of direct optical nanoscopy with axially localized detection (DONALD) typically yields an isotropic three-dimensional localization precision of 20 nm within an axial range of ∼150 nm above the coverslip.
Golimumab for the treatment of axial spondyloarthritis.
Gelfer, Gita; Perry, Lisa; Deodhar, Atul
2016-01-01
Axial spondyloarthritis (axSpA) is a chronic, immune-mediated inflammatory disease of the axial skeleton that includes ankylosing spondylitis (AS) and non-radiographic axial spondyloarthritis (nr-axSpA). Patients with AS experience chronic pain due to sacroiliac joint and spinal inflammation, and may develop spinal ankylosing with syndesmophyte formation. Tumor necrosis factor α inhibitors (TNFi) have shown promise in the management of AS and axSpA by targeting the underlying inflammatory process, and providing symptomatic relief. Whether they alter the progression of the disease is uncertain. Golimumab is a fully human IgG1 monoclonal antibody that targets and downregulates the pro-inflammatory cytokine TNF-α. The use of golimumab has been shown to reduce the signs and symptoms of axSpA as well as improve patient function and quality reported outcomes. This review focuses on the biological rationale and the results of clinical trials with golimumab for the treatment of axSpA.
Lei, Xiao; Narsu, B.; Yun, Guohong; Li, Jiangang; Yao, Haiyan
2016-05-01
Surface effects play a deterministic role in the physical and mechanical properties of nanosized materials and structures. In this paper, we present a self-consistent theoretical scheme for describing the elasticity of nanowires. The natural frequency and the critical compression force of axial buckling are obtained analytically, taking into consideration the influences of lower symmetry, additional elastic parameters, surface reconstruction, surface elasticity, and residual surface stress. Applications of the present theory to elastic systems for the axially oriented Si and Cu nanowires and Ag axially oriented nanowires yield good agreement with experimental data and calculated results. The larger positive value of the new elastic parameter c12α taken into account for Si oriented nanowires drives the curves of natural frequency and critical compression force versus thickness towards the results obtained from density functional theory simulation. Negative surface stress decreases the critical load for axial buckling, thus making the nanowires very easy to bend into various structures. The present study is envisaged to provide useful insights for the design and application of nanowire-based devices.
Measurement of axial radiation properties in Z-pinch dynamic hohlraum at Julong-1
Meng, Shijian; Hu, Qingyuan; Ning, Jiaming; Ye, Fan; Huang, Zhanchang; Qin, Yi; Wang, Dong; Xu, Zeping; Xu, Rongkun
2017-01-01
Axial radiation properties in Z-pinch dynamic hohlraum is investigated experimentally for the first time at Julong-1 facility in China, employing a load that contains a cylindrical CHO foam placed at the central axis position of the nested tungsten wire array. Time-resolved axially radiating images indicate that the velocity of the radiating shock is 31.9 ± 5.6 cm/μs in shot 0181. At t = -6.5 ns with respect to the peak of radially radiated power at stagnation, the annular width is estimated to be ˜1 mm and the intensities distribution in the shock implies a good azimuthal symmetry of radiation pressure. Axial power is found to peak prior to the arrival of the shock to the axis, which is explained by the balance between shock heating and radiating cooling. Utilizing the end-on radiation images and axial power, the peak radiation temperature in dynamic hohlraum is obtained to be ˜65 eV.
Institute of Scientific and Technical Information of China (English)
Bai Jiangbo; Xiong Junjiang
2014-01-01
This paper seeks to outline the temperature effect on the buckling properties of ultra-thin-walled lenticular collapsible composite tube (LCCT) subjected to axial compression. The buckling tests of the LCCT specimens subjected to axial compression were carried out on INSTRON-500N servo-hydraulic machine in dry state and at the temperatures of 25 ?C, 100 ?C and ?80 ?C. The load-displacement curves and buckling initiation loads were measured and the buckling initiation mechanism was discussed from experimental observations. Experiments show that the buckling initiation load, on average, is only about 2.2% greater at the low temperature of ?80 ?C than at the room temperature of 25 ?C due to the material hardening, demonstrating an insignificant increase in the buckling initiation load, whereas it is about 19.5%lower at the high temperature of 100 ?C than at the room temperature owing to the material softening, implying a significant decrease in the buckling initiation load. The failure mode of the LCCT in axial compres-sion tests at three different temperatures can be reckoned to be characteristic of the buckling initi-ation and propagation around the central region until rupture. The finite element (FE) model is presented to simulate the buckling initiation mechanism based on the eigenvalue-based methodol-ogy. Good correlation between experimental and numerical results is achieved.
Masi, Alfonse T
2014-01-01
Ankylosing spondylitis and axial spondyloarthropathy have characteristic age- and sex-specific onset patterns, typical entheseal lesions, and marked heritability, but the integrative mechanisms causing the pathophysiological and structural alterations remain largely undefined. Myofascial tissues are integrated in the body into webs and networks which permit transmission of passive and active tensional forces that provide stabilizing support and help to control movements. Axial myofascial hypertonicity was hypothesized as a potential excessive polymorphic trait which could contribute to chronic biomechanical overloading and exaggerated stresses at entheseal sites. Such a mechanism may help to integrate many of the characteristic host, pathological, and structural features of ankylosing spondylitis and axial spondyloarthritis. Biomechanical stress and strain were recently documented to correlate with peripheral entheseal inflammation and new bone formation in a murine model of spondyloarthritis. Ankylosing spondylitis has traditionally been classified by the modified New York criteria, which require the presence of definite radiographic sacroiliac joint lesions. New classification criteria for axial spondyloarthritis now include patients who do not fulfill the modified New York criteria. The male-to-female sex ratios clearly differed between the two patient categories - 2:1 or 3:1 in ankylosing spondylitis and 1:1 in non-radiographic axial spondyloarthritis - and this suggests a spectral concept of disease and, among females, milder structural alterations. Magnetic resonance imaging of active and chronic lesions in ankylosing spondylitis and axial spondyloarthritis reveals complex patterns, usually interpreted as inflammatory reactions, but shows similarities to acute degenerative disc disease, which attributed to edema formation following mechanical stresses and micro-damage. A basic question is whether mechanically induced microinjury and immunologically mediated
Institute of Scientific and Technical Information of China (English)
Hongwei MA; Baihe LI
2008-01-01
This paper presents a numerical investigation of effects of axial non-uniform tip clearances on the aerodynamic performance of a transonic axial compressor rotor (NASA Rotor 37). The three-dimensional steady flow field within the rotor passage was simulated with the datum tip clearance of 0.356 mm at the design wheel speed of 17188.7 rpm. The simulation results are well consistent with the measurement results, which verified the numeri-cal method. Then the three-dimensional steady flow field within the rotor passage was simulated respectively with different axial non-uniform tip clearances. The calculation results showed that optimal axial non-uniform tip clearances could improve the compressor performance, while the efficiency and the pressure ratio of the com-pressor were increased. The flow mechanism is that the axial non-uniform tip clearance can weaken the tip leak-age vortex, blow down low-energy fluids in boundary layers and reduce both flow blockage and tip loss.
Gamp, Alexander
2013-01-01
We begin by giving a description of the radio-frequency generator-cavity-beam coupled system in terms of basic quantities. Taking beam loading and cavity detuning into account, expressions for the cavity impedance as seen by the generator and as seen by the beam are derived. Subsequently methods of beam-loading compensation by cavity detuning, radio-frequency feedback and feedforward are described. Examples of digital radio-frequency phase and amplitude control for the special case of superconducting cavities are also given. Finally, a dedicated phase loop for damping synchrotron oscillations is discussed.
Moazami, Nader; Fukamachi, Kiyotaka; Kobayashi, Mariko; Smedira, Nicholas G; Hoercher, Katherine J; Massiello, Alex; Lee, Sangjin; Horvath, David J; Starling, Randall C
2013-01-01
The recent success of continuous-flow circulatory support devices has led to the growing acceptance of these devices as a viable therapeutic option for end-stage heart failure patients who are not responsive to current pharmacologic and electrophysiologic therapies. This article defines and clarifies the major classification of these pumps as axial or centrifugal continuous-flow devices by discussing the difference in their inherent mechanics and describing how these features translate clinically to pump selection and patient management issues. Axial vs centrifugal pump and bearing design, theory of operation, hydrodynamic performance, and current vs flow relationships are discussed. A review of axial vs centrifugal physiology, pre-load and after-load sensitivity, flow pulsatility, and issues related to automatic physiologic control and suction prevention algorithms is offered. Reliability and biocompatibility of the two types of pumps are reviewed from the perspectives of mechanical wear, implant life, hemolysis, and pump deposition. Finally, a glimpse into the future of continuous-flow technologies is presented.
Strength and stability analysis of a single-walled black phosphorus tube under axial compression
Cai, Kun; Wan, Jing; Wei, Ning; Qin, Qing H.
2016-07-01
Few-layered black phosphorus materials currently attract much attention due to their special electronic properties. As a consequence, a single-layer black phosphorus (SLBP) nanotube has been theoretically built. The corresponding electronic properties of such a black phosphorus nanotube (BPNT) were also evaluated numerically. However, unlike graphene formed with 2sp2 covalent carbon atoms, SLBP is formed with 3sp3 bonded atoms. It means that the structure from SLBP will possess lower Young’s modulus and mechanical strength than those of carbon nanotubes. In this study, molecular dynamics simulation is performed to investigate the strength and stability of BPNTs affected by the factors of diameter, length, loading speed and temperature. Results are fundamental for investigating the other physical properties of a BPNT acting as a component in a nanodevice. For example, buckling of the BPNT happens earlier than fracture, before which the nanostructure has very small axial strain. For the same BPNT, a higher load speed results in lower critical axial strain and a nanotube with lower axial strain can still be stable at a higher temperature.
Deformation and failure mechanisms of 18650 battery cells under axial compression
Zhu, Juner; Zhang, Xiaowei; Sahraei, Elham; Wierzbicki, Tomasz
2016-12-01
An important deformation mode during ground impacts of battery packs made of cylindrical battery cells is axial compression. This type of loading subjects the cell to a complex deformation pattern and failure mechanism. The design of endcaps plays an important role in such deformations. To explore the sequence of deformation and the underlying failure mechanisms, a combined experimental/numerical study was carried out. Tests were conducted on 18650 cells, and the deformation of each component was carefully investigated and documented. There are four different stages in the force-displacement curve, corresponding with deformation of various components in the endcap assembly. A short circuit happens at a displacement of 4 mm. To clarify these observations, a detailed Finite Element model was set up, covering the geometry and the mechanical property of almost all the components of the cell. Using the simulation results, the sequence of the axial compression was revealed, which was subsequently validated by Micro CT scans as well as analytical solutions. Based on the precise analysis of the mechanical behavior, the cause of the short circuit during axial loading was clarified. Two failure mechanisms in the separator at the top section of the cell explain the possible causes of short circuit.
The influence of stiffeners on axial crushing of glass-fabric-reinforced epoxy composite shells
Directory of Open Access Journals (Sweden)
A. Vasanthanathan
2017-01-01
Full Text Available A generic static and impact experimental procedure has been developed in this work aimed at improving the stability of glass fabric reinforced epoxy shell structures by bonding with axial stiffeners. Crashworthy structures fabricated from composite laminate with stiffeners would offer energy absorption superior to metallic structures under compressive loading situations. An experimental material characterisation of the glass fabric reinforced epoxy composite under uni-axial tension has been carried out in this study. This work provides a numerical simulation procedure to describe the static and dynamic response of unstiffened glass fabric reinforced epoxy composite shell (without stiffeners and stiffened glass fabric reinforced epoxy composite shell (with axial stiffeners under static and impact loading using the Finite Element Method. The finite element calculation for the present study was made with ANSYS®-LS-DYNA® software. Based upon the experimental and numerical investigations, it has been asserted that glass fabric reinforced epoxy shells stiffened with GFRP stiffeners are better than unstiffened glass fabric reinforced epoxy shell and glass fabric reinforced epoxy shell stiffened with aluminium stiffeners. The failure surfaces of the glass fabric reinforced epoxy composite shell structures tested under impact were examined by SEM.
Surface strains induced by measured loads on teeth in vivo: a methodological study.
Nohl, F S; Setchell, D J
2000-03-01
Visual feedback enabled three subjects to apply predetermined near-axial loads to the incisal edge of an intact maxillary central incisor. In two subjects, principal strains and orientations developed on the labial surface of the intact incisor were resolved from strains recorded with a multiple element strain gauge. Load application was accurate and precise enough to allow resolution of strains induced by target loads of 10 to 50 N. Axially orientated compressive labial surface strains were induced by measured loads. The method could be used to validate bench-top stress analyses and investigate the effects of restoration on the structural integrity of teeth.
Analysis of Axial Flow Ventilation Fans by Vortex - Method.
Hardin, Richard Anthony
A steady vortex-lattice method is used to solve the lifting surface equation for an axial flow fan. The type of fan studied is designed for industrial and ventilation applications and in thermofluid systems such as cooling towers. The fan blades are thin cambered surfaces manufactured from metal sheets. The numerical approach is inviscid and results in a boundary value problem with viscous effects partially accounted for by application of drag coefficient data. A non-linear wake alignment procedure is used to account for the effects of vorticity shedding in the wake and variation in wake geometry with operating conditions. The wake alignment procedure is semi-free with wake input parameters required for accurate use of the technique. A study of the wake parameters was conducted and gave trends in the variation of their values with flow rate. At "free-air" conditions, flow visualization estimates of these parameters were found to agree with those from the computations. Comparisons are made between the measured and predicted fan performance with and without a surrounding duct. The comparison of the results were especially good at the "free-air" condition using wake parameters determined from flow visualization and an inlet velocity profile measured using hot-wire anemometry. To enable better understanding of basic flow phenomena and to provide data for verification of numerical analyses, a method for measuring unsteady surface pressure on a rotating axial-flow fan blade was devised. Unsteadiness of pressure on the blade surfaces is due to the effects of upstream fan motor supports and other installation features. A pressure transducer and signal amplification circuit were mounted on a circuit board at the rotating hub with signals taken off the rotating shaft through copper disk-mercury slip rings. The pressure difference across the blade was determined and the data were corrected for time lag and distortion caused by the length of tubing. The pressure difference
Van den Ende, D.; Almeida, P.M.R.; Dingemans, T.J.; Van der Zwaag, S.
2007-01-01
The invention relates to a load sensor comprising a polymer matrix and a piezo-ceramic material such as PZT, em not bedded in the polymer matrix, which together form a compos not ite, wherein the polymer matrix is a liquid crystalline resin, and wherein the piezo-ceramic material is a PZT powder for
Csernus, Marilyn
Carbohydrate loading is a frequently used technique to improve performance by altering an athlete's diet. The objective is to increase glycogen stored in muscles for use in prolonged strenuous exercise. For two to three days, the athlete consumes a diet that is low in carbohydrates and high in fat and protein while continuing to exercise and…
Modeling of thermo-mechanical fatigue and damage in shape memory alloy axial actuators
Wheeler, Robert W.; Hartl, Darren J.; Chemisky, Yves; Lagoudas, Dimitris C.
2015-04-01
The aerospace, automotive, and energy industries have seen the potential benefits of using shape memory alloys (SMAs) as solid state actuators. Thus far, however, these actuators are generally limited to non-critical components or over-designed due to a lack of understanding regarding how SMAs undergo thermomechanical or actuation fatigue and the inability to accurately predict failure in an actuator during use. The purpose of this study was to characterize the actuation fatigue response of Nickel-Titanium-Hafnium (NiTiHf) axial actuators and, in turn, use this characterization to predict failure and monitor damage in dogbone actuators undergoing various thermomechanical loading paths. Calibration data was collected from constant load, full cycle tests ranging from 200-600MPa. Subsequently, actuator lifetimes were predicted for four additional loading paths. These loading paths consisted of linearly varying load with full transformation (300-500MPa) and step loads which transition from zero stress to 300-400MPa at various martensitic volume fractions. Thermal cycling was achieved via resistive heating and convective cooling and was controlled via a state machine developed in LabVIEW. A previously developed fatigue damage model, which is formulated such that the damage accumulation rate is general in terms of its dependence on current and local stress and actuation strain states, was utilized. This form allows the model to be utilized for specimens undergoing complex loading paths. Agreement between experiments and simulations is discussed.
Thermo-mechanical vibration of rotating axially functionally graded nonlocal Timoshenko beam
Azimi, Majid; Mirjavadi, Seyed Sajad; Shafiei, Navvab; Hamouda, A. M. S.
2017-01-01
The free vibration analysis of rotating axially functionally graded nanobeams under an in-plane nonlinear thermal loading is provided for the first time in this paper. The formulations are based on Timoshenko beam theory through Hamilton's principle. The small-scale effect has been considered using the nonlocal Eringen's elasticity theory. Then, the governing equations are solved by generalized differential quadrature method. It is supposed that the thermal distribution is considered as nonlinear, material properties are temperature dependent, and the power-law form is the basis of the variation of the material properties through the axial of beam. Free vibration frequencies obtained are cantilever type of boundary conditions. Presented numerical results are validated by comparing the obtained results with the published results in the literature. The influences of the nonlocal small-scale parameter, angular velocity, hub radius, FG index and also thermal effects on the frequencies of the FG nanobeams are investigated in detail.
Optimization of inverse model identification for multi-axial test rig control
Directory of Open Access Journals (Sweden)
Müller Tino
2016-01-01
Full Text Available Laboratory testing of multi-axial fatigue situations improves repeatability and allows a time condensing of tests which can be carried out until component failure, compared to field testing. To achieve realistic and convincing durability results, precise load data reconstruction is necessary. Cross-talk and a high number of degrees of freedom negatively affect the control accuracy. Therefore a multiple input/multiple output (MIMO model of the system, capturing all inherent cross-couplings is identified. In a first step the model order is estimated based on the physical fundamentals of a one channel hydraulic-servo system. Subsequently, the structure of the MIMO model is optimized using correlation of the outputs, to increase control stability and reduce complexity of the parameter optimization. The identification process is successfully applied to the iterative control of a multi-axial suspension rig. The results show accurate control, with increased stability compared to control without structure optimization.
Axial compression behavior of concrete masonry wallettes strengthened with cement mortar overlays
Directory of Open Access Journals (Sweden)
F. L. De Oliveira
Full Text Available This paper presents the results of a series of axial compression tests on concrete block wallettes coated with cement mortar overlays. Different types of mortars and combinations with steel welded meshes and fibers were tested. The experimental results were discussed based on different theoretical approaches: analytical and Finite Element Method models. The main conclusions are: a the application of mortar overlays increases the wall strength, but not in a uniform manner; b the strengthening efficiency of wallettes loaded in axial compression is not proportional to the overlay mortar strength because it can be affected by the failure mechanisms of the wall; c steel mesh reinforced overlays in combination with high strength mortar show better efficiency, because the steel mesh mitigates the damage effects in the block wall and in the overlays themselves; d simplified theoretical methods of analysis as described in this paper can give satisfactory predictions of masonry wall behavior up to a certain level.
Aerodynamic Modelling and Optimization of Axial Fans
DEFF Research Database (Denmark)
Sørensen, Dan Nørtoft
A numerically efficient mathematical model for the aerodynamics oflow speed axial fans of the arbitrary vortex flow type has been developed.The model is based on a blade-element principle, whereby therotor is divided into a number of annular streamtubes.For each of these streamtubes relations...... for velocity, pressure andradial position are derived from the conservationlaws for mass, tangential momentum and energy.The resulting system of equations is non-linear and, dueto mass conservation and pressure equilibrium far downstream of the rotor,strongly coupled.The equations are solved using the Newton...
Single Band Helical Antenna in Axial Mode
Directory of Open Access Journals (Sweden)
Parminder Singh
2012-11-01
Full Text Available Helical antennas have been widely used in a various useful applications, due to their low weight and low profile conformability, easy and cheap realization.Radiation properties of this antenna are examined both theoretically and experimentally. In this paper, an attempt has been made to investigate new helical antenna structure for Applications. CST MWS Software is used for the simulation and design calculations of the helical antennas. The axial ratio, return loss, VSWR, Directivity, gain, radiation pattern is evaluated. Using CST MWS simulation software proposed antenna is designed/simulated and optimized. The antenna exhibits a single band from 0 GHz to 3 GHz for GPS and several satellite applications
Tunable axial potentials for atom chip waveguides
Stickney, James A; Imhof, Eric; Kroese, Bethany R; Crow, Jonathon A R; Olson, Spencer E; Squires, Matthew B
2014-01-01
We present a method for generating algebraically precise magnetic potentials along the axis of a cold atom waveguide near the surface of an atom chip. With a single chip design consisting of several wire pairs, various axial potentials can be created, including double wells, triple wells, and pure harmonic traps with suppression of higher order terms. We characterize the error along a harmonic trap between the expected algebraic form and magnetic field simulations and find excel- lent agreement, particularly at small displacements from the trap center. Finally, we demonstrate experimental control over the bottom fields of an asymmetric double well potential.
Cervical Spine Axial Rotation Goniometer Design
Directory of Open Access Journals (Sweden)
Emin Ulaş Erdem
2012-06-01
Full Text Available To evaluate the cervical spine rotation movement is quiet harder than other joints. Configuration and arrangement of current goniometers and devices is not always practic in clinics and some methods are quiet expensive. The cervical axial rotation goniometer designed by the authors is consists of five pieces (head apparatus, chair, goniometric platform, eye pads and camera. With this goniometer design a detailed evaluation of cervical spine range of motion can be obtained. Besides, measurement of "joint position sense" which is recently has rising interest in researches can be made practically with this goniometer.
Aerodynamics of Advanced Axial-Flow Turbomachinery.
1980-11-30
cementing in place short segments of lb ga. (1.2 mm I.D.) hypodermic tubing in drillud holes carefully aligned normal to the sidewall profile at the...PRESSURE I REFERENCE SCANPREF I I SYSTEM 0YTE NECKED- PRF NEEDLE VALVE PE PRRSSUE TRANSDUCER AMPLIF IER] POSITIONER TEMPERATURES I STO BE READ I...Compressors. U.S. NASA SP-36. 1965. 23. Hearsey, R. M. A Revised Computer Program for Axial Compressor Design Volume 1: Theory , Descriptions and User’s
Composite Axial Flow Propulsor for Small Aircraft
2005-01-01
This work focuses on the design of an axial flow ducted fan driven by a reciprocating engine. The solution minimizes the turbulization of the flow around the aircraft. The fan has a rotor - stator configuration. Due to the need for low weight of the fan, a carbon/epoxy composite material was chosen for the blades and the driving shaft.The fan is designed for optimal isentropic efficiency and free vortex flow. A stress analysis of the rotor blade was performed using the Finite Element Method....
Axial Tomography from Digitized Real Time Radiography
Zolnay, A. S.; McDonald, W. M.; Doupont, P. A.; McKinney, R. L.; Lee, M. M.
1985-01-18
Axial tomography from digitized real time radiographs provides a useful tool for industrial radiography and tomography. The components of this system are: x-ray source, image intensifier, video camera, video line extractor and digitizer, data storage and reconstruction computers. With this system it is possible to view a two dimensional x-ray image in real time at each angle of rotation and select the tomography plane of interest by choosing which video line to digitize. The digitization of a video line requires less than a second making data acquisition relatively short. Further improvements on this system are planned and initial results are reported.
FINITE ELEMENT FOR STRESS-STRAIN STATE MODELING OF TWO-LAYERED AXIALLY SYMMETRIC SHELLS
Directory of Open Access Journals (Sweden)
K. S. Kurochka
2015-07-01
Full Text Available Subject of Research. Computation of composite material designs requires application of numerical methods. The finiteelement method usage is connected with surface approximation problems. Application of volumetric and laminar elements leads to systems with large sizes and a great amount of computation. The objective of this paper is to present an equivalent two-layer mathematical model for evaluation of displacements and stresses of cross-ply laminated cone shells subjected to uniformly distributed load. An axially symmetric element for shell problems is described. Method. Axially symmetric finite element is proposed to be applied in calculations with use of correlation for the inner work of each layer separately. It gives the possibility to take into account geometric and physical nonlinearities and non-uniformity in the layers of the shell. Discrete mathematical model is created on the base of the finite-element method with the use of possible motions principle and Kirchhoff–Love assumptions. Hermite element is chosen as a finite one. Cone shell deflection is considered as the quantity sought for. Main Results. One-layered and two-layered cone shells have been considered for proposed mathematical model verification with known analytical and numerical analytical solutions, respectively. The axial displacements of the two-layered cone are measured with an error not exceeding 5.4 % for the number of finite elements equal to 30. The proposed mathematical model requires fewer nodes to define the finite element meshing of the system and much less computation time. Thereby time for finding solution decreases considerably. Practical Relevance. Proposed model is applicable for computation of multilayered designs under axially symmetric loads: composite high-pressure bottles, cylinder shaped fiberglass pipes, reservoirs for explosives and flammable materials, oil and gas storage tanks.
Testing Studies on Rock Failure Modes of Statically Loads Under Dynamic Loading
Institute of Scientific and Technical Information of China (English)
YE Zhouyuan; LI Xibing; LIU Xiling; MA Chunde; YIN Tubing
2008-01-01
By means of the improved split Hopkionson pressure bar(SHPB) with axial pre-pressure and confined pressure,two series of experiments on sandstone are earned out to research the failure mode of rock during the course of exploitation of resources in deep.One is under the conditions that the confining pressure is fixed and the axial pressure is changeable.The other is under the conditions that the confining pressure becomes and the axial pressure is fixed.It is found that samples break up evenly after impacting when axial static pressures are low,there is great disparity in size of fragments when axial static pressures are high,and the main bodies of samples after the tests under the combination of dynamic and static loads frequently show the type of V or X.The samples are more close-grained at the elastic stage and impacts make many cracks be generated and developed,as makes samples more crackable.At the initial phase of damage stage,the static pressures make some cracks in the samples which are undeveloped and the impacts' role is similar to that at the elastic stage.At the metaphase or anaphase of damage stage,these cracks in the samples develop adequately and the impacts mainly accelerate samples' failure.The main bodies of samples show the type of V or X after impacting due to the confining pressures' restraining samples' lateral formation at the elastic stage or the initial phase of damage stage,the main bodies of samples have almost formed at the stage loading static pressures and the results after impacting usually are similar to those under the axial pressures tests.
PLASTIC LIMIT LOAD ANALYSIS OF DEFECTIVE PIPELINES
Institute of Scientific and Technical Information of China (English)
ChenGang; LiuYinghua; XuBingye
2003-01-01
The integrity assessment of defective pipelines represents a practically important task of structural analysis and design in various technological areas, such as oil and gas industry, power plant engineering and chemical factories. An iterative algorithm is presented for the kinematic limit analysis of 3-D rigid-perfectly plastic bodies. A numerical path scheme for radial loading is adopted to deal with complex multi-loading systems. The numerical procedure has been applied to carry out the plastic collapse analysis of pipelines with part-through slot under internal pressure, bending moment and axial force. The effects of various shapes and sizes of part-through slots on the collapse loads of pipelines are systematically investigated and evaluated. Some typical failure modes corresponding to different configurations of slots and loading forms are studied.
Institute of Scientific and Technical Information of China (English)
金梦飞; 刘昕露; 吕呈; 孙德发
2014-01-01
Based on the contrast analysis of the Effective Width Method and the Direct Strength Method, analysis and discussion are mentioned about the ultimate load-carrying capacities of 1 mm thickness Q345 cold-formed thin-wall steel lipped channel columns. The calculation and test results showed that, it is relative safety in calculation the lipped channel columns according to GB 50018-2002 Technical Code of Cold-Formed Thin-wall Steel Structure.%在分析比较有效宽度法( EWM)和直接强度法( DSM)的基础上，以1 mm厚Q345冷弯薄壁卷边槽钢柱为例，对其极限承载力进行了较深入的探讨和对比分析，计算与试验结果表明：按GB 50018-2002冷弯薄壁型钢结构技术规范计算槽钢柱是可行的。
Single Rod Vibration in Axial Flow
Weichselbaum, Noah; Wang, Shengfu; Bardet, Philippe
2013-11-01
Fluid structure interaction of a single rod in axial flow is a coupled dynamical system present in many application including nuclear reactors, steam generators, and towed antenna arrays. Fluid-structure response can be quantified thanks to detailed experimental data where both structure and fluid responses are recorded. Such datum deepen understanding of the physics inherent to the system and provide high-dimensionality quantitative measurements to validate coupled structural and CFD codes with various level of complexity. In this work, single rods fixed on both ends in a concentric pipe, are subjected to an axial flow with Reynolds number based on hydraulic diameter of Re =4000. Rods of varying material stiffness and diameter are utilized in the experiment resulting in a range of dimensionless U between 0.5 and 1, where U = (ρA/EI)1/2uL. Experimental measurements of the velocity field around the rod are taken with PIV from time-resolved Nd:YLF laser and a high speed CMOS camera. Three-dimensional and temporal vibration and deflection of the rod is recorded with shadowgraphy utilizing two sets of pulsed high power LED and dedicated CMOS camera. Through integration of these two diagnostics, it is possible to reconstruct the full FSI domain providing unique validation data.
Axial residual stresses in boron fibers
Behrendt, D. R.
1978-01-01
A method of measuring axial residual stresses in boron fibers is presented. With this method, the axial residual stress distribution as a function of radius is determined from the fiber surface to the core including the average residual stress in the core. Such measurements on boron on tungsten (B/W) fibers show that the residual stresses for 102, 142, 203, and 366 micron diam fibers are similar, being compressive at the surface and changing monotonically to a region of tensile stress within the boron. At approximately 25% of the original radius, the stress reaches a maximum tensile stress of about 860 MN sq m and then decreases to a compressive stress near the tungsten boride core. Data are presented for 203-micron diam B/W fibers that show annealing above 900 C reduces the residual stresses. A comparison between 102-micron diam B/W and boron on carbon (B/C) show that the residual stresses are similar in the outer regions of the fibers, but that large differences near and in the core are observed. Fracture of boron fibers is discussed.
High temperature superconducting axial field magnetic coupler: realization and test
Belguerras, L.; Mezani, S.; Lubin, T.; Lévêque, J.; Rezzoug, A.
2015-09-01
Contactless torque transmission through a large airgap is required in some industrial applications in which hermetic isolation is necessary. This torque transmission usually uses magnetic couplers, whose dimension strongly depends on the airgap flux density. The use of high temperature superconducting (HTS) coils to create a strong magnetic field may constitute a solution to reduce the size of the coupler. It is also possible to use this coupler to replace a torque tube in transmitting the torque produced by a HTS motor to its load. This paper presents the detailed construction and tests of an axial field HTS magnetic coupler. Pancake coils have been manufactured from BSCCO tape and used in one rotor of the coupler. The second rotor is mainly composed of NdFeB permanent magnets. Several tests have been carried out showing that the constructed coupler is working properly. A 3D finite element (FE) model of the studied coupler has been developed. Airgap magnetic field and torque measurements have been carried out and compared to the FE results. It has been shown that the measured and the computed quantities are in satisfactory agreement.
Investigation of unsteady flow in axial turbine stage
Directory of Open Access Journals (Sweden)
Němec Martin
2012-04-01
Full Text Available The never ending process to increase the efficiency of turbine stages introduced an idea to create an axial turbine stage test rig as part of closed loop transonic wind tunnel at Vyzkumny a zkusebni letecky ustav (VZLU. Studying of unsteady flow field behaviours in turbine stages is nowadays essential in the development process. Therefore, the test rig was designed with focusing on possibility of detailed studying of unsteady flow fields in turbine stages. New methodologies and new instrumentations were developed at VZLU and successfully integrated to gain valuable information from experiments with turbine stages. Two different turbine stages were tested during the facility introduction process. The measurement of these two models demonstrated how flexible the test rig is. One of them was an enlarged model of small gas turbine stage. The other was scaled-down model of stage of intermediate-pressure steam turbine. The external characteristics of both models were acquired during experiments as well as the detailed unsteady flow field measurement. Turbine stages were tested in various regimes in order to check the capabilities of the facility, methodology and instrumentation together. The paper presents results of unsteady flow field investigation in the enlarged turbine stage with unshrouded rotor. The interaction of structures developed in a stator with the rotor flow field is depicted and the influence of turbine load on evolution of secondary flows in rotor is analysed.
Prosthetic abutment influences bone biomechanical behavior of immediately loaded implants
Camargos, Germana de Villa; SOTTO-MAIOR,Bruno Salles; Silva,Wander José da; Priscilla Cardoso LAZARI; Del Bel Cury, Altair Antoninha
2016-01-01
Abstract This study aimed to evaluate the influence of the type of prosthetic abutment associated to different implant connection on bone biomechanical behavior of immediately and delayed loaded implants. Computed tomography-based finite element models comprising a mandible with a single molar implant were created with different types of prosthetic abutment (UCLA or conical), implant connection (external hexagon, EH or internal hexagon, IH), and occlusal loading (axial or oblique), for both i...
Study on the Axial Dispersion of Liquid in Column Flotation
Institute of Scientific and Technical Information of China (English)
周鵾; 曾爱武; 高长宝; 余国琮
2003-01-01
An experimental study on the axial dispersion of liquid was carried out in a 0.382-m-ID flotation column packed with different structured packings or free of packings. The correlations of axial Peclet numbers with the liquid and gas superficial Reynolds numbers were developed for various packings. Among the packings tested, it is found that in the column packed with 250Y or 350Y packings the axial dispersion is the lowest. The addition of frother can decrease the axial dispersion. By the simulation analysis of the one-dimension dispersion model of packed flotation column, it is found that small axial dispersion, high collection rate constant and low axial liquid velocity can increase the collection zone recovery.
Shen, Hui-Shen
2010-06-01
Buckling and postbuckling analysis is presented for axially compressed microtubules (MTs) embedded in an elastic matrix of cytoplasm. The microtubule is modeled as a nonlocal shear deformable cylindrical shell which contains small scale effects. The surrounding elastic medium is modeled as a Pasternak foundation. The governing equations are based on higher order shear deformation shell theory with a von Kármán-Donnell-type of kinematic nonlinearity and include the extension-twist and flexural-twist couplings. The thermal effects are also included and the material properties are assumed to be temperature-dependent. The small scale parameter e (0) a is estimated by matching the buckling load from their vibrational behavior of MTs with the numerical results obtained from the nonlocal shear deformable shell model. The numerical results show that buckling load and postbuckling behavior of MTs are very sensitive to the small scale parameter e (0) a. The results reveal that the MTs under axial compressive loading condition have an unstable postbuckling path, and the lateral constraint has a significant effect on the postbuckling response of a microtubule when the foundation stiffness is sufficiently large.
Vittori, Miloš; Srot, Vesna; Žagar, Kristina; Bussmann, Birgit; van Aken, Peter A; Čeh, Miran; Štrus, Jasna
2016-08-01
Skeletal elements that are exposed to heavy mechanical loads may provide important insights into the evolutionary solutions to mechanical challenges. We analyzed the microscopic architecture of dactylus claws in the woodlice Porcellio scaber and correlated these observations with analyses of the claws' mineral composition with energy dispersive X-ray spectrometry (EDX), electron energy loss spectroscopy (EELS) and selected area electron diffraction (SAED). Extraordinarily, amorphous calcium phosphate is the predominant mineral in the claw endocuticle. Unlike the strongly calcified exocuticle of the dactylus base, the claw exocuticle is devoid of mineral and is highly brominated. The architecture of the dactylus claw cuticle is drastically different from that of other parts of the exoskeleton. In contrast to the quasi-isotropic structure with chitin-protein fibers oriented in multiple directions, characteristic of the arthropod exoskeleton, the chitin-protein fibers and mineral components in the endocuticle of P. scaber claws are exclusively axially oriented. Taken together, these characteristics suggest that the claw cuticle is highly structurally anisotropic and fracture resistant and can be explained as adaptations to predominant axial loading of the thin, elongated claws. The nanoscale architecture of the isopod claw may inspire technological solutions in the design of durable machine elements subjected to heavy loading and wear.
Schmidt, Hendrik; Heuer, Frank; Wilke, Hans-Joachim
2009-01-01
Dynamic stabilization devices have been introduced to clinics as an alternative to rigid fixation. The stiffness of these devices varies widely, whereas the optimal stiffness, achieving a predefined stabilization of the spine, is unknown. This study was focused on the determination of stiffness values for posterior stabilization devices achieving a flexible, semi-flexible or rigid connection between two vertebrae. An extensively validated finite element model of a lumbar spinal segment L4-5 with an implanted posterior fixation device was used in this study. The model was exposed to pure moments of 7.5 and 20Nm around the three principal anatomical directions, simulating flexion, extension, lateral bending and axial rotation. In parametrical studies, the influence of the axial and bending fixator stiffness on the spinal range of motion was investigated. In order to examine the validity of the computed results, an in-vitro study was carried out. In this, the influence of two posterior stabilization devices (DSS and rigidly internal fixator) on the segmental stabilization was investigated. The finite element (FE)-model predicted that each load direction caused a pairing of stiffness relations between axial and bending stiffness. In flexion and extension, however, the bending stiffness had a neglectable effect on the segmental stabilization, compared to the axial stiffness. In contrast, lateral bending and axial rotation were influenced by both stiffness parameters. Except in axial rotation, the model predictions were in a good agreement with the determined in-vitro data. In axial rotation, the FE-model predicted a stiffer segmental behavior than it was determined in the in-vitro study. It is usually expected that high stiffness values are required for a posterior stabilization device to stiffen a spinal segment. We found that already small stiffness values were sufficient to cause a stiffening. Using these data, it may possible to develop implants for certain clinical
A technique to determine a desired preparation axial inclination.
Parker, M Harry; Ivanhoe, John R; Blalock, John S; Frazier, Kevin B; Plummer, Kevin D
2003-10-01
The guidelines recommended in the literature for the convergence angle of a crown preparation vary from 3 to 24 degrees. There is a lack of guidelines on techniques to achieve a specific axial inclination. The purpose of this article was to present a practical technique, with a diamond rotary cutting instrument of known axial inclination, to determine the diamond rotary cutting instrument angulations required to achieve the desired axial inclination of a preparation.
Design and Test of a Transonic Axial Splittered Rotor
2015-06-15
geometric rendering and analysis of a transonic axial compressor rotor with splitter blades. Predictive numerical simulations were conducted and...ANSYS-CFX) for the geometric rendering and analysis of a transonic axial compressor rotor with splitter blades. Predictive numerical simulations were...that uses commercial-off-the-shelf software ( MATLAB , SolidWorks, and ANSYS-CFX) for the geometric rendering and analysis of a transonic axial
Rotordynamics of Turbine Labyrinth Seals with Rotor Axial Shifting
Jinxiang Xi; Rhode, David L.
2006-01-01
Rotors in high-performance steam turbines experience a significant axial shifting during starting and stopping processes due to thermal expansion, for example. This axial shifting could significantly alter the flow pattern and the flow-induced rotordynamic forces in labyrinth seals, which in turn, can considerably affect the rotor-seal system performance. This paper investigates the influence of the rotor axial shifting on leakage rate as well as rotordynamic forces in hi...
Gravesen, F H; McMahon, B P; Drewes, A M; Gregersen, H
2008-03-01
The oesophagus serves to transport food and fluid from the pharynx to the stomach. Oesophageal function is usually evaluated by means of manometry which is a proxy of the force in the radial direction. However, force measurements in the axial direction will provide a better measure of oesophageal transport function. The aim of this study was to develop a probe based on electrical impedance measurements to quantify the axial force generated by oesophageal contractions, i.e. probe elongation was associated with the axial force. Calibration with weights up to 200 g was done. The dispersion, creep, temperature and bending dependence were studied at the bench. Subsequently, the probe was tested in vivo in a healthy human volunteer. The probe showed good reproducibility and the dispersion was <0.04. Some dependence on temperature, creep and bending was found. Interpolation of the calibration curves made it possible to compensate for temperature fluctuations. The maximum deviation was 6.1 +/- 3.7% at loads of 50 g. The influence of creep showed a maximum net creep of 6.1 g after 8 s. The swallowed bolus size correlated with the axial force measurements (P = 0.038) but not with manometric measurements. In conclusion, the new technique measures axial force in the oesophagus and may in the future provide valuable information about oesophageal function.
Does total disc arthroplasty in C3/C4-segments change the kinematic features of axial rotation?
Wachowski, Martin Michael; Wagner, Markus; Weiland, Jan; Dörner, Jochen; Raab, Björn Werner; Dathe, Henning; Gezzi, Riccardo; Kubein-Meesenburg, Dietmar; Nägerl, Hans
2013-06-21
We analyze how kinematic properties of C3/C4-segments are modified after total disc arthroplasty (TDA) with PRESTIGE(®) and BRYAN(®) Cervical Discs. The measurements were focused on small ranges of axial rotation (TDA. External parameters: constant axially directed pre-load, constant flexional/extensional and lateral-flexional pre-torque. The applied axial torque and IHA-direction did not run parallel. The IHA-direction was found to be rotated backwards and largely independent of the rotational angle, amount of axial pre-load, size of pre-torque, and TDA. In the intact segments pre-flexion/extension hardly influenced IHA-positions. After TDA, IHA-position was shifted backwards significantly (BRYAN-TDA: ≈8mm; PRESTIGE-TDA: ≈6mm) and in some segments laterally as well. Furthermore it was significantly shifted ventrally by pre-flexion and dorsally by pre-extension. The rate of lateral IHA-migration increased significantly after BRYAN-TDA during rightward or leftward rotations. In conclusion after the TDA the IHA-positions shifted backwards with significant increase in variability of the IHA-positions after the BRYAN-TDA more than in PRESTIGE-TDA. The TDA-procedure altered the segment kinematics considerably. TDA causes additional translations of the vertebrae, which superimpose the kinematics of the adjacent levels. The occurrence of adjacent level disease (ALD) is not excluded after the TDA for kinematical reasons.
Huy, N.Q.
2010-01-01
Pile testing, which plays an importance role in the field of deep foundation design, is performed by static and non-static methods to provide information about the following issues: (Poulos, 1998) - The ultimate capacity of a single pile. - The load-displacement behavior of a pile. - The performance of a pile during the test conditions. - The integrity of a pile (pile integrity test). For the purposes of verification the design axial capacity and the static load – settlement behavior of piles...
Energy Dissipation in Sandwich Structures During Axial Compression
DEFF Research Database (Denmark)
Urban, Jesper
2002-01-01
The purpose of this paper is to investigate the energy dissipation in sandwich structures during axial crushing. Axial crushing tests on six sandwich elements are described. The sandwich elements consist of a polyurethane core and E-glass/Polyester skin. The elements compare to full-scale structu......The purpose of this paper is to investigate the energy dissipation in sandwich structures during axial crushing. Axial crushing tests on six sandwich elements are described. The sandwich elements consist of a polyurethane core and E-glass/Polyester skin. The elements compare to full...
Modular functional organisation of the axial locomotor system in salamanders.
Cabelguen, Jean-Marie; Charrier, Vanessa; Mathou, Alexia
2014-02-01
Most investigations on tetrapod locomotion have been concerned with limb movements. However, there is compelling evidence that the axial musculoskeletal system contributes to important functions during locomotion. Adult salamanders offer a remarkable opportunity to examine these functions because these amphibians use axial undulations to propel themselves in both aquatic and terrestrial environments. In this article, we review the currently available biological data on axial functions during various locomotor modes in salamanders. We also present data showing the modular organisation of the neural networks that generate axial synergies during locomotion. The functional implication of this modular organisation is discussed.
Buckling of un-stiffened cylindrical shell under non-uniform axial conpressive stress
Institute of Scientific and Technical Information of China (English)
宋昌永
2002-01-01
This paper provides a review of recent research advances and trends in the area of stability of un-stiffened circular cylindrical shells subjected to general non-uniform axial compressive stresses. Only the more important and interesting aspects of the research, judged from a personal viewpoint, are discussed. They can be crudely classified into four categories: (1) shells subjected to non-uniform loads; (2) shells on discrete supports; (3) shells with intended cutouts/holes; and (4) shells with non-uniform settlements.
Transitional DDES computations of the NREL Phase-VI rotor in axial flow conditions
DEFF Research Database (Denmark)
Sørensen, Niels N.; Schreck, Scott
2014-01-01
In the present article we describe CFD simulations of the well known NREL Phase-VI rotor in axial flow conditions using a newly developed technique of combining turbulence modeling by the Delayed Detached Eddy Simulation (DDES) technique with laminar/turbulent transition modeling by a correlation...... based method. We demonstrate how the power production around the onset of stall is very dependent on the turbulence intensity in the inflow. Additionally, we compare with measurements and illustrate how the unsteady loads from the DDES simulations can provide valuable insight in the transient behavior...
Buckling of un—stiffened cylindrical shell under non—uniform axial compressive stress
Institute of Scientific and Technical Information of China (English)
宋昌永
2002-01-01
This paper provides a review of recent research advances and trends in the area of stability of unstiffened circular cylindrical shells subjected to general non-uniform axial compressive stresses.Only the more important and interesting aspects of the research,judged from a personal viewpoint,are discussed.They can be crudely classified into four categories:(1) shells subjected to non-uniform loads;(2) shells on discrete supports;(3) shells with intended cutouts/holes;and (4) shells with non-uniform settlements.
Casimir Energy in the Axial Gauge
Esposito, G; Kirsten, K; Esposito, Giampiero; Kamenshchik, Alexander Yu.; Kirsten, Klaus
2000-01-01
The zero-point energy of a conducting spherical shell is studied by imposing the axial gauge via path-integral methods, with boundary conditions on the electromagnetic potential and ghost fields. The coupled modes are then found to be the temporal and longitudinal modes for the Maxwell field. The resulting system can be decoupled by studying a fourth-order differential equation with boundary conditions on longitudinal modes and their second derivatives. The exact solution of such equation is found by using a Green-function method, and is obtained from Bessel functions and definite integrals involving Bessel functions. Complete agreement with a previous path-integral analysis in the Lorenz gauge, and with Boyer's value, is proved in detail.
The Axial Part Phrase in Japanese
Directory of Open Access Journals (Sweden)
Kaori Takamine
2007-01-01
Full Text Available In this paper, I investigate the categorial status of spatial terms in locative/directional expressions in Japanese. I will show that a certain class of spatial terms have a distinct categorial status from both regular postpositions and nouns. On one hand, syntactic diagnostics such as doubling, coordination by to, and co-occurrence with demonstratives indicate that these spatial terms belong to a nominal category rather than to a postpositional category. On the other hand, the fact that these spatial terms are modified by range modifiers indicates that they are more similar to regular postpositions than to nouns. On the basis of these diagnostics, I will argue that spatial terms in Japanese need to be assigned a new category Axial Part Phrase which is proposed by Svenonius 2006.
Composite Axial Flow Propulsor for Small Aircraft
Directory of Open Access Journals (Sweden)
R. Poul
2005-01-01
Full Text Available This work focuses on the design of an axial flow ducted fan driven by a reciprocating engine. The solution minimizes the turbulization of the flow around the aircraft. The fan has a rotor - stator configuration. Due to the need for low weight of the fan, a carbon/epoxy composite material was chosen for the blades and the driving shaft.The fan is designed for optimal isentropic efficiency and free vortex flow. A stress analysis of the rotor blade was performed using the Finite Element Method. The skin of the blade is calculated as a laminate and the foam core as a solid. A static and dynamic analysis were made. The RTM technology is compared with other technologies and is described in detail.
Aerodynamics of advanced axial-flow turbomachinery
Serovy, G. K.; Kavanagh, P.; Kiishi, T. H.
1980-01-01
A multi-task research program on aerodynamic problems in advanced axial-flow turbomachine configurations was carried out at Iowa State University. The elements of this program were intended to contribute directly to the improvement of compressor, fan, and turbine design methods. Experimental efforts in intra-passage flow pattern measurements, unsteady blade row interaction, and control of secondary flow are included, along with computational work on inviscid-viscous interaction blade passage flow techniques. This final report summarizes the results of this program and indicates directions which might be taken in following up these results in future work. In a separate task a study was made of existing turbomachinery research programs and facilities in universities located in the United States. Some potentially significant research topics are discussed which might be successfully attacked in the university atmosphere.
Aerodynamic modelling and optimization of axial fans
Energy Technology Data Exchange (ETDEWEB)
Noertoft Soerensen, Dan
1998-01-01
A numerically efficient mathematical model for the aerodynamics of low speed axial fans of the arbitrary vortex flow type has been developed. The model is based on a blade-element principle, whereby the rotor is divided into a number of annular stream tubes. For each of these stream tubes relations for velocity, pressure and radial position are derived from the conservation laws for mass, tangential momentum and energy. The equations are solved using the Newton-Raphson methods, and solutions converged to machine accuracy are found at small computing costs. The model has been validated against published measurements on various fan configurations, comprising two rotor-only fan stages, a counter-rotating fan unit and a stator-rotor stator stage. Comparisons of local and integrated properties show that the computed results agree well with the measurements. Optimizations have been performed to maximize the mean value of fan efficiency in a design interval of flow rates, thus designing a fan which operates well over a range of different flow conditions. The optimization scheme was used to investigate the dependence of maximum efficiency on 1: the number of blades, 2: the width of the design interval and 3: the hub radius. The degree of freedom in the choice of design variable and constraints, combined with the design interval concept, provides a valuable design-tool for axial fans. To further investigate the use of design optimization, a model for the vortex shedding noise from the trailing edge of the blades has been incorporated into the optimization scheme. The noise emission from the blades was minimized in a flow rate design point. Optimizations were performed to investigate the dependence of the noise on 1: the number of blades, 2: a constraint imposed on efficiency and 3: the hub radius. The investigations showed, that a significant reduction of noise could be achieved, at the expense of a small reduction in fan efficiency. (EG) 66 refs.
Preclinical mouse models for assessing axial compression of long bones during exercise.
Stadelmann, Vincent A; Brun, Julia; Bonnet, Nicolas
2015-01-01
The aim of this laboratory method is to describe two approaches for the investigation of bone responses to mechanical loading in mice in vivo. The first is running exercise, because it is easily translatable clinically, and the second is axial compression of the tibia, because it is precisely controllable. The effects of running exercise, and in general physical activity, on bone tissue have been shown to be both direct through mechanical loading (ground impact and muscle tension) and indirect through metabolic changes. Therefore, running exercise has been considered the most convenient preclinical model for demonstrating the general idea that exercise is good for bone health, either early in age for increasing peak bone mass or later in age by slowing down bone loss. However, numerous combinations of protocols have been reported, which makes it difficult to formulate a simple take-home message. This laboratory method also provides a detailed description of in vivo direct mechanical axial compression of the mouse tibia. The effects of mechanical loading depend on the force (strain), frequency, waveform and duration of application, and they range from bone anabolism with low bone remodeling, inducing lamellar bone accumulation, to bone catabolism with high bone remodeling, leading to microdamage, woven bone formation and bone loss. Direct in vivo loading models are extensively used to study mechanotransduction pathways, and contribute by this way to the development of new bone anabolism treatments. Although it is particularly difficult to assemble an internationally adopted protocol description, which would give reproducible bone responses, here we have attempted to provide a comprehensive guide for best practice in performing running exercise and direct in vivo mechanical loading in the laboratory.
Accuracy and repeatability of a new method for measuring facet loads in the lumbar spine.
Wilson, Derek C; Niosi, Christina A; Zhu, Qingan A; Oxland, Thomas R; Wilson, David R
2006-01-01
We assessed the repeatability and accuracy of a relatively new, resistance-based sensor (Tekscan 6900) for measuring lumbar spine facet loads, pressures, and contact areas in cadaver specimens. Repeatability of measurements in the natural facet joint was determined for five trials of four specimens loaded in pure moment (+/- 7.5 N m) flexibility tests in axial rotation and flexion-extension. Accuracy of load measurements in four joints was assessed by applying known compressive loads of 25, 50, and 100 N to the natural facet joint in a materials testing machine and comparing the known applied load to the measured load. Measurements of load were obtained using two different calibration approaches: linear and two-point calibrations. Repeatability for force, pressure, and area (average of standard deviation as a percentage of the mean for all trials over all specimens) was 4-6% for axial rotation and 7-10% for extension. Peak resultant force in axial rotation was 30% smaller when calculated using the linear calibration method. The Tekscan sensor overestimated the applied force by 18 +/- 9% (mean+/-standard deviation), 35 +/- 7% and 50 +/- 9% for compressive loads of 100, 50, and 25 N, respectively. The two-point method overestimated the loads by 35 +/- 16%, 45 +/- 7%, and 56 +/- 10% for the same three loads. Our results show that the Tekscan sensor is repeatable. However, the sensor measurement range is not optimal for the small loads transmitted by the facets and measurement accuracy is highly dependent on calibration protocol.
Aerothermal optimization of partially shrouded axial turbines[Dissertation 17138
Energy Technology Data Exchange (ETDEWEB)
Porreca, L.
2007-07-01
This work presents the results of an aerodynamic and thermal study of three different shrouded axial turbine configurations (turbomachinery). The blade geometry of the turbine stages and the tip clearances of the test cases under investigation are identical although the shroud design is different. The first test case (RRD) is representative of a full shroud geometry while the second (CPS) and third (EPS) test cases adopt different partial shroud arrangements. In the EPS case, a shroud platform is added to cover the blade throat. Partial shrouds are sometimes used in industrial application in order to benefit from the aerodynamic advantage of shrouded configuration as well as reducing thermal load and mechanical stress on the blade root. However, the optimal compromise between mechanical issues and aerodynamic performances is still an open issue due to the resulting highly 3-dimensional unsteady flow field, difficulty of achieve an optimal cooling and severe heat load on the shroud sealing fins. An experimental investigation is carried out in order to quantify the effect of the shroud geometry on the aerodynamic performances and to study the resultant flow field in all test cases. The analysis has been conducted in an experimental low-speed axial turbine facility at the Turbomachinery Laboratory at ETH Zurich. Steady and fast response aerodynamic probe technology (FRAP) has been used to characterize the flow field. Moreover, a stereoscopic PIV technique has been design and applied in this experimental facility for the first time. The flow field analysis shows that the effect of the shroud geometry is significant from 60% blade height span to the tip. Tip leakage vortex in the first rotor is originated in the partial shroud test cases while the full shroud case present only a weak indigenous tip passage vortex. Secondary flows development in the following second stator resulted to be greatly affected by the leakage/main flow interaction of the first rotor. The
Energy Technology Data Exchange (ETDEWEB)
Kosyna, G.; Krasmann, H. (Technische Univ. Braunschweig, Pfleiderer-Inst. fuer Stroemungsmaschinen (Germany))
1992-08-01
When installing blowers, it is not always possible to ensure an optimum fluidic afflux, which can thus produce a change in the operating behaviour compared with the design. Using as an example an axial blower blade with small hub ratio and high aerodynamic blade load, under simulated non-rotation symmetrical allflux conditions, it was possible to show that with the examined distrubance configuration no extreme worsening was produced with regard to the achievable pressure increases and efficiencies of the blower stage. (orig.).
Sadowski, Tomasz
2016-01-01
This book discusses complex loadings of turbine blades and protective layer Thermal Barrier Coating (TBC), under real working airplane jet conditions. They obey both multi-axial mechanical loading and sudden temperature variation during starting and landing of the airplanes. In particular, two types of blades are analyzed: stationary and rotating, which are widely applied in turbine engines produced by airplane factories.
Three-dimensional loading model for periodontal ligament regeneration in vitro.
Berendsen, A.D.; Smit, T.H.; Walboomers, X.F.; Everts, V.; Jansen, J.A.; Bronckers, A.L.
2009-01-01
In this study we present a new three-dimensional (3D) model to study effects of mechanical loading on tendon/ligament formation in vitro. The model mimics a functional periodontal ligament (PDL), which anchors dental roots to the jaw bone and transfers the axial load of mastication to the jaw bone.
Three-dimensional loading model for periodontal ligament regeneration in vitro
A.D. Berendsen; T.H. Smit; X.F. Walboomers; V. Everts; J.A. Jansen; A.L.J.J. Bronckers
2009-01-01
In this study we present a new three-dimensional (3D) model to study effects of mechanical loading on tendon/ligament formation in vitro. The model mimics a functional periodontal ligament (PDL), which anchors dental roots to the jaw bone and transfers the axial load of mastication to the jaw bone.
Global design optimization for an axial-flow tandem pump based on surrogate method
Li, D. H.; Zhao, Y.; Y Wang, G.
2013-12-01
Tandem pump, compared with multistage pump, goes without guide vanes between impellers. Better cavitation performance and significant reduction of the axial geometry scale is important for high-speed propulsion. This study presents a global design optimization method based on surrogated method for an axial-flow tandem pump to enhance trade-off performances: energy and cavitation performances. At the same time, interactions between impellers and impacts on the performances are analyzed. Fixed angle of blades in impellers and phase angle are performed as design variables. Efficiency and minimum average pressure coefficient (MAPC) on axial sectional surface in front impeller are the objective function, which can represent energy and cavitation performances well. Different surrogate models are constructed, and Global Sensitivity Analysis and Pareto Front method are used. The results show that, 1) Influence from phase angle on performances can be neglected compared with other two design variables, 2) Impact ratio of fixed angle of blades in two impellers on efficiency are the same as their designed loading distributions, which is 4:6, 3) The optimization results can enhance the trade-off performances well: efficiency is improved by 0.6%, and the MAPC is improved by 4.5%.
Polymer-based flexible capacitive sensor for three-axial force measurements
Dobrzynska, J. A.; Gijs, M. A. M.
2013-01-01
We have developed a flexible-substrate-based three-axial force sensor, composed of finger-shaped electrode capacitors, whose operation is based on the measurement of a capacitance change induced upon applying a three-axial load. The electrode design supports high sensitivity to shear forces. An overall flexibility of the sensor and elasticity of the capacitor's dielectric is obtained by integrating three polymers in the sensor's technology process, namely polyimide, parylene-C, and polydimethylsiloxane, combined with standard metallization processes. We have theoretically modeled the sensor's capacitance and its three-axial force sensitivity. The unit capacitors have static capacitances in the range of 20 pF. The electro-mechanical characterization of the capacitors reveals in the normal direction a sensitivity Sz = 0.024 kPa-1 for pressures <10 kPa, whereas for higher pressures the measured sensitivity Sz = 6.6 × 10-4 kPa-1. Typical measured shear force sensitivity Sx = 2.8 × 10-4 kPa-1. These values give our transducer high potential for use in skin-like sensing applications.
Pektaş, Ömer; Tönük, Ergin
2014-11-01
At the interface between the jawbone and the roots of natural teeth, a thin, elastic, shock-absorbing tissue, called the periodontal ligament, forms a cushion which provides certain flexibility under mechanical loading. The dental restorations supported by implants, however, involve comparatively rigid connections to the jawbone. This causes overloading of the implant while bearing functional loading together with neighboring natural teeth, which leads to high stresses within the implant system and in the jawbone. A dental implant, with resilient components in the upper structure (abutment) in order to mimic the mechanical behavior of the periodontal ligament in the axial direction, was designed, analyzed in silico, and produced for mechanical testing. The aims of the design were avoiding high levels of stress, loosening of the abutment connection screw, and soft tissue irritations. The finite element analysis of the designed implant revealed that the elastic abutment yielded a similar axial mobility with the natural tooth while keeping stress in the implant at safe levels. The in vitro mechanical testing of the prototype resulted in similar axial mobility predicted by the analysis and as that of a typical natural tooth. The abutment screw did not loosen under repeated loading and there was no static or fatigue failure.
Improved axial position detection in optical tweezers measurements
DEFF Research Database (Denmark)
Dreyer, Jakob Kisbye; Berg-Sørensen, Kirstine; Oddershede, Lene
2004-01-01
We investigate the axial position detection of a trapped microsphere in an optical trap by using a quadrant photodiode. By replacing the photodiode with a CCD camera, we obtain detailed information on the light scattered by the microsphere. The correlation of the interference pattern with the axial...
Through flow analysis within axial flow turbomachinery blade rows
Girigoswami, H.
1986-09-01
Using Katsanis' Through Flow Code, inviscid flow through an axial flow compressor rotor blade as well as flow through inlet guide vanes are analyzed and the computed parameters such as meridional velocity distribution, axial velocity distribution along radial lines, and velocity distribution over blade surfaces are presented.
An Unbroken Axial-Vector Current Conservation Law
Sharafiddinov, Rasulkhozha S.
2016-04-01
The mass, energy and momentum of the neutrino of a true flavor have an axial-vector nature. As a consequence, the left-handed truly neutral neutrino in an axial-vector field of emission can be converted into a right-handed one and vice versa. This predicts the unidenticality of masses, energies and momenta of neutrinos of the different components. Recognizing such a difference in masses, energies, momenta and accepting that the left-handed axial-vector neutrino and the right-handed antineutrino of true neutrality refer to long-lived C-odd leptons, and the right-handed truly neutral neutrino and the left-handed axial-vector antineutrino are of short-lived fermions of C-oddity, we would write a new CP-even Dirac equation taking into account the flavor symmetrical axial-vector mass, energy and momentum matrices. Their presence explains the spontaneous mirror symmetry violation, confirming that an axial-vector current conservation law has never violated. They reflect the availability of a mirror Minkowski space in which a neutrino is characterized by left as well as by right space-time coordinates. Therefore, it is not surprising that whatever the main purposes experiments about a quasielastic axial-vector mass say in favor of an axial-vector mirror Minkowski space-time.
A new approach to radial and axial gauges
Weigert, Heribert; Heinz, Ulrich
1992-03-01
We develop a new path integral formulation of QCD in radial and axial gauges. This formalism yields free propagators which are free of gauge poles. We find that radial gauges are ghost free. In axial gauges ghosts cannot generally be excluded from the formalism due to the need to fix the residual gauge freedom.
On Stationary Axially Symmetric Solutions in Brans-Dicke Theory
Kirezli, Pınar
2015-01-01
Stationary axially symmetric Brans-Dicke-Maxwell solutions are re-examined in the framework of the Brans-Dicke theory. We see that, employing a particular parametrization of the standard axially symmetric metric simplifies the procedure of obtaining the Ernst equations for axially symmetric electro-vacuum space-times for this theory. This analysis also permit us to construct a two parameter extension in both Jordan and Einstein frames of an old solution generating technique frequently used to construct axially symmetric solutions for Brans-Dicke theory from a seed solution of General Relativity. As applications of this technique, several known and new solutions are constructed including a general axially symmetric BD-Maxwell solution of Plebanski-Demianski with vanishing cosmological constant, i.e. the Kinnersley solution and general magnetized Kerr-Newman type solutions. Some physical properties and circular motion of test particles for a particular subclass of Kinnersley solution, i.e. Kerr-Newman-NUT type ...
Axial vibration analysis of nanocones based on nonlocal elasticity theory
Institute of Scientific and Technical Information of China (English)
Shu-Qi Guo; Shao-Pu Yang
2012-01-01
Carbon nanocones have quite fascinating electronic and structural properties,whose axial vibration is seldom investigated in previous studies.In this paper,based on a nonlocal elasticity theory,a nonuniform rod model is applied to investigate the small-scale effect and the nonuniform effect on axial vibration of nanocones.Using the modified Wentzel-Brillouin-Kramers (WBK) method,an asymptotic solution is obtained for the axial vibration of general nonuniform nanorods.Then,using similar procedure,the axial vibration of nanocones is analyzed for nonuniform parameters,mode number and nonlocal parameters.Explicit expressions are derived for mode frequencies of clamped-clamped and clamped-free boundary conditions.It is found that axial vibration frequencies are highly overestimated by the classical rod model because of ignorance of the effect of small length scale.
A multi-axial ferroelastic switching model using the homogenized energy approach
Oates, William S.; Peng, Xiao
2009-03-01
A new constitutive modeling framework is presented to predict polarization reorientation from mechanical loading in ferroelectric materials. The modeling framework employs a homogenized energy approach to predict the reorientation of local polarization variants in response to multi-axial mechanical loading. Single crystal energy relations are given and integrated into a polycrystal model using a reduced order modeling technique that employs a set of stochastic parameters which accommodate material inhomogeneities. The homogenized energy approach provides a methodology that simplifies computations required to predict nonlinear polarization reorientation from applied stresses. The new formulation circumvents the need for large scale minimization problems of multi-well energy potentials and facilitates constitutive model integration into finite element codes and nonlinear control designs. The theory is presented, numerically implemented, and compared with experiments on lead zirconate titanate given in the literature.
Hill, Craig; Vanness, Katherine; Stewart, Andy; Polagye, Brian; Aliseda, Alberto
2016-11-01
Turbulence-induced unsteady forcing on turbines extracting power from river, tidal, or ocean currents will affect performance, wake characteristics, and structural integrity. A laboratory-scale axial-flow turbine, 0 . 45 m in diameter, incorporating rotor speed sensing and independent blade pitch control has been designed and tested with the goal of increasing efficiency and/or decreasing structural loading. Laboratory experiments were completed in a 1 m wide, 0.75 m deep open-channel flume at moderate Reynolds number (Rec =6104 -2105) and turbulence intensity (T . I . = 2 - 10 %). A load cell connecting the hub to the shaft provided instantaneous forces and moments on the device, quantifying turbine performance under unsteady inflow and for different controls. To mitigate loads, blade pitch angles were controlled via individual stepper motors, while a six-axis load cell mounted at the root of one blade measured instantaneous blade forces and moments, providing insights into variable loading due to turbulent inflow and blade-tower interactions. Wake characteristics with active pitch control were compared to fixed blade pitch and rotor speed operation. Results are discussed in the context of optimization of design for axial-flow Marine Hydrokinetic turbines.
DEFF Research Database (Denmark)
2009-01-01
A load testing circuit a circuit tests the load impedance of a load connected to an amplifier. The load impedance includes a first terminal and a second terminal, the load testing circuit comprising a signal generator providing a test signal of a defined bandwidth to the first terminal of the load...
Directory of Open Access Journals (Sweden)
M.A. Radhika
2013-02-01
Full Text Available In general aerospace, civil and mechanical (ACM structures are often subjected to some or the other forms of loading during their service life. It has been reported that about 75% of aerospace structures fail due to fatigue cyclic loading. The civil-structural components are subjected to some form of axial and transverse loading which continuously deteriorates the health of the structure. Mechanical components are also subjected to stresses due to contact pressures between several components. Thus for ACM structures, effective monitoring through-out the entire life is required as these often involve public life and huge investments. Owing to such necessity, researchers around the world are continuously working on the development of smart sensor based effective monitoring techniques. Piezo electric (PZT transducer based electromechanical impedance (EMI is one such technique which was developed for structural health monitoring (SHM. In this technique, PZT transducers are usually attached to the structure to be monitored and are then subjected to unit sinusoidal electric voltage to generate the electromechanical (EM admittance signatures when interrogated to the desired frequency range of excitations. These signatures consist of real (conductance and imaginary (susceptance parts which serve as indicator to predict the structural health. Any deviations in these signatures during the monitoring period indicate disturbance in the structure. However, the EMI technique was not widely explored for structural load monitoring (such as fatigue cyclic load, monotonous load, axial and transverse load compared to damage detection. In this paper, systematic experiments were presented on the specimens for axial load variations, transverse load variations, monotonous and fatigue load variation with discussions on boundary effect and buckling effects. For axial, fatigue, monotonic load, the conductance was found to be effective where as for transverse load
Prosthetic abutment influences bone biomechanical behavior of immediately loaded implants.
Camargos, Germana de Villa; Sotto-Maior, Bruno Salles; Silva, Wander José da; Lazari, Priscilla Cardoso; Del Bel Cury, Altair Antoninha
2016-05-31
This study aimed to evaluate the influence of the type of prosthetic abutment associated to different implant connection on bone biomechanical behavior of immediately and delayed loaded implants. Computed tomography-based finite element models comprising a mandible with a single molar implant were created with different types of prosthetic abutment (UCLA or conical), implant connection (external hexagon, EH or internal hexagon, IH), and occlusal loading (axial or oblique), for both immediately and delayed loaded implants. Analysis of variance at 95%CI was used to evaluate the peak maximum principal stress and strain in bone after applying a 100 N occlusal load. The results showed that the type of prosthetic abutment influences bone stress/strain in only immediately loaded implants. Attachment of conical abutments to IH implants exhibited the best biomechanical behavior, with optimal distribution and dissipation of the load in peri-implant bone.
Prosthetic abutment influences bone biomechanical behavior of immediately loaded implants
Directory of Open Access Journals (Sweden)
Germana de Villa CAMARGOS
2016-01-01
Full Text Available Abstract This study aimed to evaluate the influence of the type of prosthetic abutment associated to different implant connection on bone biomechanical behavior of immediately and delayed loaded implants. Computed tomography-based finite element models comprising a mandible with a single molar implant were created with different types of prosthetic abutment (UCLA or conical, implant connection (external hexagon, EH or internal hexagon, IH, and occlusal loading (axial or oblique, for both immediately and delayed loaded implants. Analysis of variance at 95%CI was used to evaluate the peak maximum principal stress and strain in bone after applying a 100 N occlusal load. The results showed that the type of prosthetic abutment influences bone stress/strain in only immediately loaded implants. Attachment of conical abutments to IH implants exhibited the best biomechanical behavior, with optimal distribution and dissipation of the load in peri-implant bone.
Axially Symmetric Post-Newtonian Stellar Systems
Directory of Open Access Journals (Sweden)
Camilo Akímushkin
2010-06-01
Full Text Available We introduce a method to obtain self-consistent, axially symmetric disklike stellar models in the first post-Newtonian (1PN approximation. By using in the field equations of the 1PN approximation a distribution function (DF corresponding to a Newtonian model, two fundamental equations determining the 1PN corrections are obtained. The rotation curves of the corrected models differs from the classical ones and the corrections are clearly appreciable with values of the mass and radius of a typical galaxy. On the other hand, the relativistic mass correction can be ignored for all models. Resumen. Presentamos un método para obtener modelos estelares discoidales, axialmente simétricos, auto-consistentes en la primera aproximación post-Newtoniana (1PN. Usando en las ecuaciones de campo de la aproximación 1PN una función de distribución conocida (DF que corresponde a un modelo Newtoniano, se obtienen dos ecuaciones fundamentales para determinar las correcciones 1PN. Las curvas de rotación de los modelos corregidos difieren de las clásicas y las correcciones son claramente apreciables con los valores de la masa y el radio de una galaxia típica. Por otro lado, la corrección relativista de la masa se puede ignorar para todos los modelos.
Multimode interaction in axially excited cylindrical shells
Directory of Open Access Journals (Sweden)
Silva F. M. A.
2014-01-01
Full Text Available Cylindrical shells exhibit a dense frequency spectrum, especially near the lowest frequency range. In addition, due to the circumferential symmetry, frequencies occur in pairs. So, in the vicinity of the lowest natural frequencies, several equal or nearly equal frequencies may occur, leading to a complex dynamic behavior. So, the aim of the present work is to investigate the dynamic behavior and stability of cylindrical shells under axial forcing with multiple equal or nearly equal natural frequencies. The shell is modelled using the Donnell nonlinear shallow shell theory and the discretized equations of motion are obtained by applying the Galerkin method. For this, a modal solution that takes into account the modal interaction among the relevant modes and the influence of their companion modes (modes with rotational symmetry, which satisfies the boundary and continuity conditions of the shell, is derived. Special attention is given to the 1:1:1:1 internal resonance (four interacting modes. Solving numerically the governing equations of motion and using several tools of nonlinear dynamics, a detailed parametric analysis is conducted to clarify the influence of the internal resonances on the bifurcations, stability boundaries, nonlinear vibration modes and basins of attraction of the structure.
New treatment targets for axial spondyloarthritis.
Sieper, Joachim
2016-12-01
Axial spondyloarthritis (axSpA) patients can be divided into those with structural damage in the SI joint visible on X-rays, termed radiographic axSpA or AS, and those in an earlier phase of the disease, without structural damage in the SI joint, termed non-radiographic axSpA. TNF-blockers have been shown to be highly effective in the treatment of active axSpA. Interestingly, conventional DMARDs and also non-TNF-blocker biologics targeting IL-1, IL-6 and T cells (abatacept) are not effective. Recent interest has focused on the cytokines IL-23 and IL-17 as potential treatment targets in axSpA. An open-label trial with ustekinumab showed a good efficacy in AS patients. Two placebo-controlled phase 3 trials with a mAb blocking IL-17, secukinumab, showed a good reduction in disease activity, similar to that shown for TNF blockers. Probably triggered by inflammation, new bone formation is another hallmark in AS and a potentially important treatment target. However, a previously reported inhibitory effect of NSAID treatment could not be confirmed in a recent NSAID trial.
Computerized axial tomography in clinical pediatrics.
McCullough, D C; Kufta, C; Axelbaum, S P; Schellinger, D
1977-02-01
Computerized axial tomography (CAT), a noninvasive radiologie method, provides a new dimension in screening and diagnosis of intracranial pathology. Evaluation of 725 scans in infants and children demonstrates that CAT may be performed with negligible risk, although sedation and restraint are essential to the successful performance of studies in children under 6 years of age. CAT is the preferred initial diagnostic method in suspected hydrocephalls and is accurate in the detection and precise localization of brain tumors. The management of hydrocephalus and brain tumors has been significantly altered by the availability of CAT. Few invasive neuroradiologic procedures are required and pneumography is especially curtailed. Serial scanning is the best available method of monitoring ventricular alterations in hydrocephalus, tumor size during radiotherapy or chemotherapy, and postoperative recurrence of benign neoplasms. Complex intracranial anomalies are detectable with computerized tomography, but complete definition of pathology often requires angiography and air studies. Limited clinical experience in detecting neonatal intraventricular hemorrhage suggests that CAT will be a valuable tool for futlre investigations of that problem.
Axial electron channeling statistical method of site occupancy determination
Institute of Scientific and Technical Information of China (English)
YE; Jia
2001-01-01
［1］Johnson, W., Sowerby, R., Venter, R. D., Plane Strain Slip Line Fields for Metal Deformation Processes——A Source Book and Bibliography, New York: Pergamon Press, 1982.［2］Hill, R., The Mathematical Theory of Plasticity, Oxford: Oxford University Press, 1950.［3］Sokolovsky, V. V., Theory of Plasticity(in Russia), Moskow: Nat. Tech. Press, 1950.［4］Kachanov, L. M., Foundations Theory of Plasticity, London: North-Holland, 1975.［5］Shield, R. T., On the plastic flow of metal condition of axial symmetry, Proc. Roy. Soc., 1955, 233A: 267.［6］Lippmann, H., IUTAM Symposium on Metal Forming Plasticity, New York: Springer-Verlag, 1979.［7］Spencer, A. J. M., The approximate solution of certain problem of axially-symmetric plastic flow, J. Mech. Phys. Solids, 1964, 12: 231.［8］Wang, R., Xiong, Z. H., Wang, W. B., Foundation of Plasticity (in Chinese), Beijing: Science Press, 1982.［9］Collins, I. E., Dewhurst, P., A slip line field analysis of asymmetrical hot rolling, International Journal of Mechanical Science, 1975, 17: 643.［10］Collins, I. F., Slip line field analysis of forming processes in plane strain and axial symmetry, Advanced Technology of Plasticity, 1984, 11: 1074.［11］Yu, M. H., Yang, S. Y., Liu, C. Y. et al., Unified plane-strain slip line field theory system, J. Civil Engineering (in Chinese), 1997, 30(2): 14［12］Simmons, J. A., Hauser, F., Dorn, E., Mathematical Theories of Plastic Deformation Under Impulsive Loading, Berkeley-Los Angeles: University of California Press, 1962.［13］Lin, C. C., On a perturbation theory based on the method of characteristies, J. Math. Phys., 1954, 33: 117—134.［14］Hopkins, H. G., The method of characteristics and its applications to the theory of stress waver in solids, in Engineering Plasticity, Combridge: Combridge University Press, 1968, 277—315.［15］Shield, R. T., The plastic indentation of a layer by a flat punch, Quart. Appl. Math., 1955, 13: 27.［16］Haar, A., von
Load Bearing Equipment for Bone and Muscle Project
Terrier, Douglas; Clayton, Ronald G.; Shackelford, Linda
2015-01-01
Axial skeletal loads coupled with muscle torque forces around joints maintain bone. Astronauts working in pairs to exercise can provide high eccentric loads for each other that are most effective. A prototype of load bearing equipment that will allow astronauts to perform exercises using each other for counter force generation in a controlled fashion and provide eccentric overload is proposed. A frame and attachments that can be rapidly assembled for use and easily stored will demonstrate feasibility of a design that can be adapted for ISS testing and Orion use.
Directory of Open Access Journals (Sweden)
F. Aguilar Parés
1999-01-01
Full Text Available Durante el movimiento de un material en un transportador de sinfín surge una fuerza en dirección axial que influye en laselección de uno de los cojinetes de apoyo del equipo. En el artículo aparecen algunas soluciones constructivas que tienen encuentan la fuerza axial. Por otro lado se establece la relación entre la fuerza axial y el empuje axial y se precisa de quiendepende el sentido del empuje axial. Por último se propone un modelo matemático que relaciona la fuerza axial con la potenciarequerida por el equipo.Palabras claves: Transportador de sinf in, fuerza axial , empuje axial ._________________________________________________________________________AbstractDuring the movement of material in a screw conveyor surge a force in axial direction that influence in the selection of one ofthe equipment support bearings. Some constructive solutions appear in the article for considering the axial force. In the otherhand it is established the relation between axial force and axial thurst and it is precised whose direction thurst axial depend of.Finally it is proposed a mathematic model that relates the axial force with the power required by the equipment.Key words: Screw conveyor, axial force, axial thurst .
The influence of mechanical loading on osseointegration: an animal study
Institute of Scientific and Technical Information of China (English)
FAN YuBo; XIU KaiHua; DONG Xiang; ZHANG Ming
2009-01-01
Osseointegration of implant provides a stable support for the prosthesis under functional loads. The timing of loading is a critical parameter that can govern the success of the osseointegration of implant. However, it is not clear whether the early loading can affect the success of osseointegration, or whether the no-loading healing period can be shortened. This paper presents an animal study conducted to investigate how external loads influence the osseointegration at the initial stage of healing. Titanium implants were inserted into the goat tibia laterally, and different axial Ioadings were applied to the im-plants in 4 weeks after surgery. After the 2 weeks period of early loading, animals were sacrificed and the tibia bones with the implants were cut off from the bodies. Then mechanical test was employed to find out the differences in the pull-out force, and shear strength at the bone-implant interface between the non-loaded and the loaded implants. The implant-bone interfaces were analyzed by histomor-phometric method, SEM (scanning electron micrograph) and EDS (energy density spectrum). The re-sults indicated that the bone-implant interface did not well integrate 4 weeks after surgery, and the fi-brous tissue could be found at the interfaces of the specimens without Ioadings. While the results of loaded specimens with 10 N axial force showed that that parts of the interface were well integrated, indicating that the early mild loading may play a positive role in the process of the osseointegration. The results support that a certain range of external loading would influence the process of osseointe, gration, and appropriate mechanical loading can be applied to shorten the osseointegration period after surgery.
Design of a biaxial mechanical loading bioreactor for tissue engineering.
Bilgen, Bahar; Chu, Danielle; Stefani, Robert; Aaron, Roy K
2013-04-25
We designed a loading device that is capable of applying uniaxial or biaxial mechanical strain to a tissue engineered biocomposites fabricated for transplantation. While the device primarily functions as a bioreactor that mimics the native mechanical strains, it is also outfitted with a load cell for providing force feedback or mechanical testing of the constructs. The device subjects engineered cartilage constructs to biaxial mechanical loading with great precision of loading dose (amplitude and frequency) and is compact enough to fit inside a standard tissue culture incubator. It loads samples directly in a tissue culture plate, and multiple plate sizes are compatible with the system. The device has been designed using components manufactured for precision-guided laser applications. Bi-axial loading is accomplished by two orthogonal stages. The stages have a 50 mm travel range and are driven independently by stepper motor actuators, controlled by a closed-loop stepper motor driver that features micro-stepping capabilities, enabling step sizes of less than 50 nm. A polysulfone loading platen is coupled to the bi-axial moving platform. Movements of the stages are controlled by Thor-labs Advanced Positioning Technology (APT) software. The stepper motor driver is used with the software to adjust load parameters of frequency and amplitude of both shear and compression independently and simultaneously. Positional feedback is provided by linear optical encoders that have a bidirectional repeatability of 0.1 μm and a resolution of 20 nm, translating to a positional accuracy of less than 3 μm over the full 50 mm of travel. These encoders provide the necessary position feedback to the drive electronics to ensure true nanopositioning capabilities. In order to provide the force feedback to detect contact and evaluate loading responses, a precision miniature load cell is positioned between the loading platen and the moving platform. The load cell has high accuracies of 0
Design of a Biaxial Mechanical Loading Bioreactor for Tissue Engineering
Bilgen, Bahar; Chu, Danielle; Stefani, Robert; Aaron, Roy K.
2013-01-01
We designed a loading device that is capable of applying uniaxial or biaxial mechanical strain to a tissue engineered biocomposites fabricated for transplantation. While the device primarily functions as a bioreactor that mimics the native mechanical strains, it is also outfitted with a load cell for providing force feedback or mechanical testing of the constructs. The device subjects engineered cartilage constructs to biaxial mechanical loading with great precision of loading dose (amplitude and frequency) and is compact enough to fit inside a standard tissue culture incubator. It loads samples directly in a tissue culture plate, and multiple plate sizes are compatible with the system. The device has been designed using components manufactured for precision-guided laser applications. Bi-axial loading is accomplished by two orthogonal stages. The stages have a 50 mm travel range and are driven independently by stepper motor actuators, controlled by a closed-loop stepper motor driver that features micro-stepping capabilities, enabling step sizes of less than 50 nm. A polysulfone loading platen is coupled to the bi-axial moving platform. Movements of the stages are controlled by Thor-labs Advanced Positioning Technology (APT) software. The stepper motor driver is used with the software to adjust load parameters of frequency and amplitude of both shear and compression independently and simultaneously. Positional feedback is provided by linear optical encoders that have a bidirectional repeatability of 0.1 μm and a resolution of 20 nm, translating to a positional accuracy of less than 3 μm over the full 50 mm of travel. These encoders provide the necessary position feedback to the drive electronics to ensure true nanopositioning capabilities. In order to provide the force feedback to detect contact and evaluate loading responses, a precision miniature load cell is positioned between the loading platen and the moving platform. The load cell has high accuracies of 0
Directory of Open Access Journals (Sweden)
Beat eMeier
2015-06-01
Full Text Available In prospective memory tasks different kinds of load can occur. Adding a prospective memory task can impose a load on ongoing task performance. Adding ongoing task load can affect prospective memory performance. The existence of multiple target events increases prospective load and adding complexity to the to-be-remembered action increases retrospective load. In two experiments, we systematically examined the effects of these different types of load on prospective memory performance. Results showed an effect of prospective load on costs in the ongoing task for categorical targets (Experiment 2, but not for specific targets (Experiment 1. Retrospective load and ongoing task load both affected remembering the retrospective component of the prospective memory task. We suggest that prospective load can enhance costs in the ongoing task due to additional monitoring requirements. Retrospective load and ongoing task load seem to impact the division of resources between the ongoing task and retrieval of the retrospective component, which may affect disengagement from the ongoing task. In general, the results demonstrate that the different types of load affect prospective memory differentially.
Active axial spondyloarthritis: potential role of certolizumab pegol
Directory of Open Access Journals (Sweden)
Ranatunga S
2014-02-01
Full Text Available Sriya Ranatunga, Anne V Miller Department of Internal Medicine, Southern Illinois University School of Medicine, Springfield, IL, USA Abstract: The axial spondyloarthropathies are a group of chronic inflammatory diseases that predominantly affect the axial joints. This group includes ankylosing spondylitis and nonradiographic axial spondyloarthropathy. While the pathogenesis of axial spondyloarthropathies is not clear, immunologically active tissues primarily include the entheses, ie, the areas where ligaments, tendons, and joint capsules attach to bone and to the annulus fibrosis at the vertebrae. One of the major mediators of the immune response in this group of diseases is tumor necrosis factor-alpha (TNFα. Blockade of TNFα results in reduced vascularity and inflammatory cell infiltration in the synovial tissues of affected joints. Certolizumab pegol (CZP is an Fc-free, PEGylated anti-TNFα monoclonal antibody. CZP has unique properties that differ from other available TNFα inhibitors by virtue of its lack of an Fc region, which minimizes potential Fc-mediated effects, and its PEGylation, which improves drug pharmacokinetics and bioavailability. It has been shown in clinical trials that CZP improves patient outcomes and reduces inflammation in the sacroiliac joints and spine in both ankylosing spondylitis and nonradiographic axial spondyloarthropathies. These data support CZP as a treatment option for axial spondyloarthropathies. Keywords: axial spondyloarthropathy, certolizumab pegol, anti-tumor necrosis factor-alpha, therapy
Gearbox Reliability Collaborative Investigation of High-Speed-Shaft Bearing Loads
Energy Technology Data Exchange (ETDEWEB)
Keller, Jonathan [National Renewable Energy Lab. (NREL), Golden, CO (United States); Guo, Yi [National Renewable Energy Lab. (NREL), Golden, CO (United States)
2016-06-01
The loads and contact stresses in the bearings of the high speed shaft section of the Gearbox Reliability Collaborative gearbox are examined in this paper. The loads were measured though strain gauges installed on the bearing outer races during dynamometer testing of the gearbox. Loads and stresses were also predicted with a simple analytical model and higher-fidelity commercial models. The experimental data compared favorably to each model, and bearing stresses were below thresholds for contact fatigue and axial cracking.
Dynamic Analysis of Axial Magnetic Forces for DVD Spindle Motors
Institute of Scientific and Technical Information of China (English)
2000-01-01
The axial magnetic force, induced by the complicated flux linkage distribution from rotor magnet and stator slotted, is constructed by different relative heights and calculated by 3D finite element method (FEM) to analyze the dynamic characteristics for a DVD spindle motor. The axial magnetic force is designed to provide an axial stiffness and govern the natural frequency of the dynamic performance. According to the simulation results and experimental measurements, the dynamic behaviors are significantly improved with a variation of relative height of rotor magnet and stator slotted on a DVD spindle motor.
The axial charges of the hidden-charm pentaquark states
Wang, Guang-Juan; Zhu, Shi-Lin
2016-01-01
With the chiral quark model, we have calculated the axial charges of the pentaquark states with $(I,I_3)=(\\frac{1}{2},\\frac{1}{2})$ and $J^{P}=\\frac{1}{2}^{\\pm},\\frac{3}{2}^{\\pm},\\frac{5}{2}^{\\pm}$. The $P_c$ states with the same $J^P$ quantum numbers but different color-spin-flavor configurations have very different axial charges, which encode important information on their underlying structures. For some of the $J^{P}=\\frac{3}{2}^{\\pm}$ or $\\frac{5}{2}^{\\pm}$ pentaquark states, their axial charges are much smaller than that of the proton.
Tensile Property of Bi-axial Warp Knitted Structure
Institute of Scientific and Technical Information of China (English)
沈为
2003-01-01
The tensile property of bi-axial warp knitted fabrics is tested and compared with that of the plain weave fabric. The results show that there are obvious differences between the tensile property of a bi-axial warp knitted fabric and that of a plain weave fabric.The former can give fuller play to the property of a high modulus yarn than the latter. The tensile strength of a bi-axial warp knitted fabric is linear with the number of yarns in the direction of force.
Gravitational waves from the axial perturbations of hyperon stars
Institute of Scientific and Technical Information of China (English)
Wen De-Hua; Yan Jing; Liu Xue-Mei
2012-01-01
The eigen-frequencies of the axial w-mode oscillations of hyperon stars are examined.It is shown that as the appearance of hyperons softens the equation of state of the super-density matter,the frequency of gravitational waves from the axial w-mode of hyperon star becomes smaller than that of a traditional neutron star at the same stellar mass.Moreover,the eigenfrequencies of hyperon stars also have scaling universality.It is shown that the EURO thirdgeneration gravitational-wave detector has the potential to detect the gravitational-wave signal emitted from the axial w-mode oscillations of a hyperon star.
Revealing atropisomer axial chirality in drug discovery.
LaPlante, Steven R; Edwards, Paul J; Fader, Lee D; Jakalian, Araz; Hucke, Oliver
2011-03-07
An often overlooked source of chirality is atropisomerism, which results from slow rotation along a bond axis due to steric hindrance and/or electronic factors. If undetected or not managed properly, this time-dependent chirality has the potential to lead to serious consequences, because atropisomers can be present as distinct enantiomers or diastereoisomers with their attendant different properties. Herein we introduce a strategy to reveal and classify compounds that have atropisomeric chirality. Energy barriers to axial rotation were calculated using quantum mechanics, from which predicted high barriers could be experimentally validated. A calculated rotational energy barrier of 20 kcal mol(-1) was established as a suitable threshold to distinguish between atropisomers and non-atropisomers with a prediction accuracy of 86%. This methodology was applied to subsets of drug databases in the course of which atropisomeric drugs were identified. In addition, some drugs were exposed that were not yet known to have this chiral attribute. The most valuable utility of this tool will be to predict atropisomerism along the drug discovery pathway. When used in concert with our compound classification scheme, decisions can be made during early discovery stages such as "hit-to-lead" and "lead optimization," to foresee and validate the presence of atropisomers and to exercise options of removing, further stabilizing, or rendering the chiral axis of interest more freely rotatable via SAR design, thereby decreasing this potential liability within a compound series. The strategy can also improve drug development plans, such as determining whether a drug or series should be developed as a racemic mixture or as an isolated single compound. Moreover, the work described herein can be extended to other chemical fields that require the assessment of potential chiral axes.
Modeling the Impact Behavior of AD85 Ceramic Under Multi-Axial Loading
1993-05-01
effects of’ microcracks cvotui-, can be introduced into the constitutive equations through appropriate physicall 1,ascd lawsiequat ions. Microcrack...Condensed Matter - 1989 and Shock Compression of Condensed Matter - 1991, Elsevier Science Publishers, B.V., 1990, 1992. 2. RAJENDRAN, A. M., and COOK, W...Ceramics. Shock Compression of Condensed Matter. Elsevier Science Publishers, B.V., 1992, p. 447-450. 6. GRADY, D. Spall Strength of Condensed Matter
Study of the Progressive Failure of Composites under Axial Loading with Varying Strain Rates
2011-12-01
2. Test Specimen Geometries ................................................................19 3. Vacuum-Assisted Resin Transfer Molding ( VARTM ...20 Figure 14. Main components of the VARTM ...Molding ( VARTM ) Vacuum-Assisted Resin Transfer Molding is a process which involves placing dry fibers in a mold and adding the resin separately. The
Directory of Open Access Journals (Sweden)
Suryani Samsudin
2013-02-01
Full Text Available The development of precast sandwich concrete has gained acceptance worldwide in conjunction with the Industrial Building System (IBS. The advancement and improvement of using wall panel has gone through a lot of achievements through the last decade. The usage of precast lightweight sandwich panel has become the alternative to conventional construction using brick wall. The usage of this panel system contributes to a sustainable and environmental friendly construction. This paper presents an overview of the latest development in precast concrete sandwich panel as an IBS. The purpose of this paper is to provide comprehensive information on latest research development of sandwich panel for building construction purposes. The information on sandwich panel’s composition, material, properties, strength, availability, and its usage as structural element are reported. An innovative concept used in the design of these systems and the use of lightweight materials is also discussed.
2016-05-01
supporting force analysis of a static pressure pipe that is to be used in the Defence Science and Technology Group Transonic Wind Tunnel test...Technology Group Transonic Wind Tunnel test facility. The static pressure pipe analysed herein was modelled as a slender propped cantilever beam...the Defence Science and Technology Group Transonic Wind Tunnel facility. A layout diagram of the static pressure pipe installation is shown in
2006-06-24
1018 steel, 6061 Al and OFHC Cu. They argued that the infra-red measurement generally underestimated the conversion ratio (70% of conversion of work...O.-G., Hopperstad, O.S., Malo, K.A., Pedersen, K. O., 2002. Modelling of plastic anisotropy in heat-treated aluminium extrusions. J. Mat
Directory of Open Access Journals (Sweden)
Yasuyuki Nishi
2016-01-01
Full Text Available We proposed a portable and ultra-small axial flow hydraulic turbine that can generate electric power comparatively easily using the low head of open channels such as existing pipe conduits or small rivers. In addition, we proposed a simple design method for axial flow runners in combination with the conventional one-dimensional design method and the design method of axial flow velocity uniformization, with the support of three-dimensional flow analysis. Applying our design method to the runner of an ultra-small axial flow hydraulic turbine, the performance and internal flow of the designed runner were investigated using CFD analysis and experiment (performance test and PIV measurement. As a result, the runners designed with our design method were significantly improved in turbine efficiency compared to the original runner. Specifically, in the experiment, a new design of the runner achieved a turbine efficiency of 0.768. This reason was that the axial component of absolute velocity of the new design of the runner was relatively uniform at the runner outlet in comparison with that of the original runner, and as a result, the negative rotational flow was improved. Thus, the validity of our design method has been verified.
Electrical load detection aparatus
DEFF Research Database (Denmark)
2010-01-01
A load detection technique for a load comprising multiple frequency-dependant sub-loads comprises measuring a representation of the impedance characteristic of the load; providing stored representations of a multiplicity of impedance characteristics of the load; each one of the stored representat...
Radial breathing mode of carbon nanotubes subjected to axial pressure.
Lei, Xiao-Wen; Ni, Qing-Qing; Shi, Jin-Xing; Natsuki, Toshiaki
2011-08-11
In this paper, a theoretical analysis of the radial breathing mode (RBM) of carbon nanotubes (CNTs) subjected to axial pressure is presented based on an elastic continuum model. Single-walled carbon nanotubes (SWCNTs) are described as an individual elastic shell and double-walled carbon nanotubes (DWCNTs) are considered to be two shells coupled through the van der Waals force. The effects of axial pressure, wave numbers and nanotube diameter on the RBM frequency are investigated in detail. The validity of these theoretical results is confirmed through the comparison of the experiment, calculation and simulation. Our results show that the RBM frequency is linearly dependent on the axial pressure and is affected by the wave numbers. We concluded that RBM frequency can be used to characterize the axial pressure acting on both ends of a CNT.
Time Domain Terahertz Axial Computed Tomography Non Destructive Evaluation Project
National Aeronautics and Space Administration — We propose to demonstrate key elements of feasibility for a high speed automated time domain terahertz computed axial tomography (TD-THz CT) non destructive...
Time Domain Terahertz Axial Computed Tomography Non Destructive Evaluation Project
National Aeronautics and Space Administration — In this Phase 2 project, we propose to develop, construct, and deliver to NASA a computed axial tomography time-domain terahertz (CT TD-THz) non destructive...
ANALYSIS OF PULSATILE BLOOD FLOW IN AXIALLY MOVING ARTERIES
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
In order to study motional properties of pulsatile blood flow in axially moving arteries, the authors derived some expressions of the pulsatile blood flow from the basic equations of motion for blood and vascular walls, including an axial blood velocity equation, a flow rate equation and a wall shear stress equation, which described not only the overall axial movement of the arteries but also the elastic properties of the vascular walls, discussed the effects of the arterial wall elasticity on the wall shear stress in coronary arteries in terms of these expressions, and analyzed changes of motional properties of pulsatile blood flow between an elastic arterial tube model and a rigid tube model. The results proved the inference by J.E. Moore Jr. et al. (1994) that the axial movement of arteries be as important in determining coronary artery hemodynamics as the elastic property of the vascular wall.
The geometrical theory of diffraction for axially symmetric reflectors
DEFF Research Database (Denmark)
Rusch, W.; Sørensen, O.
1975-01-01
The geometrical theory of diffraction (GTD) (cf. [1], for example) may be applied advantageously to many axially symmetric reflector antenna geometries. The material in this communication presents analytical, computational, and experimental results for commonly encountered reflector geometries...
Axial Stringy System of the Kerr Spinning Particle
Burinskii, A
2004-01-01
The structure of classical spinning particle based on the Kerr-Newman black hole (BH) solution is investigated. For large angular momentum, $|a|>>m$, the BH horizons disappear exposing a naked ringlike source which is a circular relativistic string. It was shown recently that electromagnetic excitations of this string lead to the appearance of an extra axial stringy system which consists of two half-infinite strings of opposite chirality. In this paper we consider the relation of this stringy system to the Dirac equation. We also show that the axial strings are the Witten superconducting strings and describe their structure by the Higgs field model where the Higgs condensate is used to regularize axial singularity. We argue that this axial stringy system may play the role of a classical carrier of the wave function.
Open-Axial-Field Magnet at ISR intersection I8
1979-01-01
This axial field spectrometer left the central collision region unobstructed in order to ease analysis of secondary particles emitted at large angle. The ISR circulating beams were passing through a hole in the magnet poles.
Axial mesodermal dysplasia complex: a new case with parental consanguinity.
Mota, C R; Azevedo, M; Rocha, G; Manuela, F; Coelho, R; Lima, M R
2000-01-01
A female is described with axial mesodermal dysplasia complex (AMDC) born to a consanguineous couple. This is thought to be the first description of a patient with AMDC born to consanguineous parents.
Energy Technology Data Exchange (ETDEWEB)
Rautenberg, M., E-mail: mrautenb@gmail.com [AREVA, AREVA NP, 10 rue Juliette Récamier, 69456 Lyon (France); CIRIMAT, CNRS/UPS/INPT, 4 allée Emile Monso, 31030 Toulouse (France); Poquillon, D. [CIRIMAT, CNRS/UPS/INPT, 4 allée Emile Monso, 31030 Toulouse (France); Pilvin, P. [LIMATB, University Bretagne-Sud, rue de Saint-Maudé, 56321 Lorient (France); Grosjean, C. [AREVA, AREVA NP, 10 rue Juliette Récamier, 69456 Lyon (France); CIRIMAT, CNRS/UPS/INPT, 4 allée Emile Monso, 31030 Toulouse (France); Cloué, J.M. [AREVA, AREVA NP, 10 rue Juliette Récamier, 69456 Lyon (France); Feaugas, X. [LEMMA, Université de La Rochelle, Avenue Michel Crépeau, 17042 La Rochelle (France)
2014-04-01
Zirconium alloys are widely used in the nuclear industry. Several components, such as cladding or guide tubes, undergo strong mechanical loading during and after their use inside the pressurized water reactors. The current requirements on higher fuel performances lead to the developing on new Zr based alloys exhibiting better mechanical properties. In this framework, creep behaviors of recrystallized Zircaloy-4 and M5™, have been investigated and then compared. In order to give a better understanding of the thermal creep anisotropy of Zr-based alloys, multi-axial creep tests have been carried out at 673 K. Using a specific device, creep conditions have been set using different values of β = σ{sub zz}/σ{sub θθ}, σ{sub zz} and σ{sub θθ} being respectively the axial and hoop creep stresses. Both axial and hoop strains are measured during each test which is carried out until stationary creep is stabilized. The steady-state strain rates are then used to build isocreep curves. Considering the isocreep curves, the M5™ alloy shows a largely improved creep resistance compared to the recrystallized Zircaloy-4, especially for tubes under high hoop loadings (0 < β < 1). The isocreep curves are then compared with simulations performed using two different mechanical models. Model 1 uses a von Mises yield criterion, the model 2 is based on a Hill yield criterion. For both models, a coefficient derived from Norton law is used to assess the stress dependence.
Axial Anomaly in Lattice Abelian Gauge Theory in Arbitrary Dimensions
Fujiwara, T; Wu, K; Fujiwara, Takanori; Suzuki, Hiroshi; Wu, Ke
1999-01-01
Axial anomaly of lattice abelian gauge theory in hyper-cubic regular lattice in arbitrary even dimensions is investigated by applying the method of exterior differential calculus. The topological invariance, gauge invariance and locality of the axial anomaly determine the explicit form of the topological part. The anomaly is obtained up to a multiplicative constant for finite lattice spacing and can be interpreted as the Chern character of the abelian lattice gauge theory.
Axially astigmatic surfaces: different types and their properties
Malacara-Doblado, Daniel; Malacara-Hernandez, Daniel; Garcia-Marquez, Jorge L.
1996-12-01
Axially astigmatic surfaces have different curvatures in orthogonal diameters. Toroidal and spherocylindrical optical surfaces are two mathematically different special cases of axially astigmatic surfaces as noted by Menchaca and Malacara (1986), but they are almost identical in the vicinity of the optical axis. The different between these two surfaces increases when the distance to the optical axis increases. We study the general properties of astigmatic surfaces and some special interesting cases.
Watson's theorem and the $N\\Delta(1232)$ axial transition
Alvarez-Ruso, L; Nieves, J; Vacas, M J Vicente
2016-01-01
We present a new determination of the $N\\Delta$ axial form factors from neutrino induced pion production data. For this purpose, the model of Hernandez et al., Phys. Rev. D76, 033005 (2007) is improved by partially restoring unitarity. This is accomplished by imposing Watson's theorem on the dominant vector and axial multipoles. As a consequence, a larger $C_5^A(0)$, in good agreement with the prediction from the off-diagonal Goldberger-Treiman relation, is now obtained.
Method to Measure Tone of Axial and Proximal Muscle
2011-01-01
The control of tonic muscular activity remains poorly understood. While abnormal tone is commonly assessed clinically by measuring the passive resistance of relaxed limbs1, no systems are available to study tonic muscle control in a natural, active state of antigravity support. We have developed a device (Twister) to study tonic regulation of axial and proximal muscles during active postural maintenance (i.e. postural tone). Twister rotates axial body regions relative to each other about the ...
Axially symmetric volume constrained anisotropic mean curvature flow
Palmer, Bennett
2011-01-01
We study the long time existence theory for a non local flow associated to a free boundary problem for a trapped non liquid drop. The drop has free boundary components on two horizontal plates and its free energy is anisotropic and axially symmetric. For axially symmetric initial surfaces with sufficiently large volume, we show that the flow exists for all time. Numerical simulations of the curvature flow are presented.
Complete multipactor suppression in an X-band dielectric-loaded accelerating structure
Energy Technology Data Exchange (ETDEWEB)
Jing, C. [Euclid Techlabs, LLC, 5900 Harper Rd, Solon, Ohio 44139, USA; High Energy Physics Division, Argonne National Laboratory, Argonne, Illinois 60439, USA; Gold, S. H. [Plasma Physics Division, Naval Research Laboratory, Washington, DC 20375, USA; Fischer, Richard [Plasma Physics Division, Naval Research Laboratory, Washington, DC 20375, USA; Gai, W. [High Energy Physics Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
2016-05-09
Multipactor is a major issue limiting the gradient of rf-driven Dielectric-Loaded Accelerating (DLA) structures. Theoretical models have predicted that an axial magnetic field applied to DLA structures may completely block the multipactor discharge. However, previous attempts to demonstrate this magnetic field effect in an X-band traveling-wave DLA structure were inconclusive, due to the axial variation of the applied magnetic field, and showed only partial suppression of the multipactor loading [Jing et al., Appl. Phys. Lett. 103, 213503 (2013)]. The present experiment has been performed under improved conditions with a uniform axial magnetic field extending along the length of an X-band standing-wave DLA structure. Multipactor loading began to be continuously reduced starting from 3.5 kG applied magnetic field and was completely suppressed at 8 kG. Dependence of multipactor suppression on the rf gradient inside the DLA structure was also measured.
Aerodynamics and combustion of axial swirlers
Fu, Yongqiang
A multipoint lean direct injection (LDI) concept was introduced recently in non-premixed combustion to obtain both low NOx emissions and good combustion stability. In this concept, a key feature is the injection of finely atomized fuel into the high-swirling airflow at the combustor dome that provides a homogenous, lean fuel-air mixture. In order to achieve the fine atomization and mixing of the fuel and air quickly and uniformly, a good swirler design should be studied. The focus of this dissertation is to investigate the aerodynamics and combustion of the swirling flow field in a multipoint Lean Direct Injector combustor. A helical axial-vaned swirler with a short internal convergent-divergent venturi was used. Swirlers with various vane angles and fuel nozzle insertion lengths have been designed. Three non-dimensional parameter effects on non-reacting, swirling flow field were studied: swirler number, confinement ratio and Reynolds number. Spray and combustion characteristics on the single swirler were studied to understand the mechanism of fuel-air mixing in this special configuration. Multi-swirler interactions were studied by measuring the confined flow field of a multipoint swirler array with different configurations. Two different swirler arrangements were investigated experimentally, which include a co-swirling array and a counter-swirling array. In order to increase the range of stability of multipoint LDI combustors, an improved design were also conducted. The results show that the degree of swirl and the level of confinement have a clear impact on the mean and turbulent flow fields. The swirling flow fields may also change significantly with the addition of a variety of simulated fuel nozzle insertion lengths. The swirler with short insertion has the stronger swirling flow as compared with the long insertion swirler. Reynolds numbers, with range of current study, will not alter mean and turbulent properties of generated flows. The reaction of the spray
Slow axial drift in three-dimensional granular tumbler flow
Zaman, Zafir; D'Ortona, Umberto; Umbanhowar, Paul B.; Ottino, Julio M.; Lueptow, Richard M.
2013-07-01
Models of monodisperse particle flow in partially filled three-dimensional tumblers often assume that flow along the axis of rotation is negligible. We test this assumption, for spherical and double cone tumblers, using experiments and discrete element method simulations. Cross sections through the particle bed of a spherical tumbler show that, after a few rotations, a colored band of particles initially perpendicular to the axis of rotation deforms: particles near the surface drift toward the pole, while particles deeper in the flowing layer drift toward the equator. Tracking of mm-sized surface particles in tumblers with diameters of 8-14 cm shows particle axial displacements of one to two particle diameters, corresponding to axial drift that is 1-3% of the tumbler diameter, per pass through the flowing layer. The surface axial drift in both double cone and spherical tumblers is zero at the equator, increases moving away from the equator, and then decreases near the poles. Comparing results for the two tumbler geometries shows that wall slope causes axial drift, while drift speed increases with equatorial diameter. The dependence of axial drift on axial position for each tumbler geometry is similar when both are normalized by their respective maximum values.
Axial scanning in confocal microscopy employing adaptive lenses (CAL).
Koukourakis, Nektarios; Finkeldey, Markus; Stürmer, Moritz; Leithold, Christoph; Gerhardt, Nils C; Hofmann, Martin R; Wallrabe, Ulrike; Czarske, Jürgen W; Fischer, Andreas
2014-03-10
In this paper we analyze the capability of adaptive lenses to replace mechanical axial scanning in confocal microscopy. The adaptive approach promises to achieve high scan rates in a rather simple implementation. This may open up new applications in biomedical imaging or surface analysis in micro- and nanoelectronics, where currently the axial scan rates and the flexibility at the scan process are the limiting factors. The results show that fast and adaptive axial scanning is possible using electrically tunable lenses but the performance degrades during the scan. This is due to defocus and spherical aberrations introduced to the system by tuning of the adaptive lens. These detune the observation plane away from the best focus which strongly deteriorates the axial resolution by a factor of ~2.4. Introducing balancing aberrations allows addressing these influences. The presented approach is based on the employment of a second adaptive lens, located in the detection path. It enables shifting the observation plane back to the best focus position and thus creating axial scans with homogeneous axial resolution. We present simulated and experimental proof-of-principle results.
Reactive control of subsonic axial fan noise in a duct.
Liu, Y; Choy, Y S; Huang, L; Cheng, L
2014-10-01
Suppressing the ducted fan noise at low frequencies without varying the flow capacity is still a technical challenge. This study examines a conceived device consisting of two tensioned membranes backed with cavities housing the axial fan for suppression of the sound radiation from the axial fan directly. The noise suppression is achieved by destructive interference between the sound fields from the axial fan of a dipole nature and sound radiation from the membrane via vibroacoustics coupling. A two-dimensional model with the flow effect is presented which allows the performance of the device to be explored analytically. The air flow influences the symmetrical behavior and excites the odd in vacuo mode response of the membrane due to kinematic coupling. Such an asymmetrical effect can be compromised with off-center alignment of the axial fan. Tension plays an important role to sustain the performance to revoke the deformation of the membrane during the axial fan operation. With the design of four appropriately tensioned membranes covered by a cylindrical cavity, the first and second blade passage frequencies of the axial fan can be reduced by at least 20 dB. The satisfactory agreement between experiment and theory demonstrates that its feasibility is practical.
Axial blanket for 16NGF Angra 1 fuel type
Energy Technology Data Exchange (ETDEWEB)
Sadde, Luciano Martins; Faria, Eduardo Fernandes [Industrias Nucleares do Brasil (INB), Resende, RJ (Brazil)]. E-mails: sadde@inb.gov.br; faria@inb.gov.br; Sang-Keun You [Korea Nuclear Fuel Co. Ltd. (KNFC), Taejon (Korea, Republic of)]. E-mail: skyou@knfc.co.kr
2007-07-01
Angra-1, Kori-2 and Krsko are nuclear power plants with the same design. However, the fuel assemblies have some differences in design due to the countries strategies and the differences in the fabrication process. The 16NGF (16x16 Next Generation Fuel) was developed by INB, KNFC and Westinghouse in order to be used in these three nuclear power plants and the 'Axial Blanket' is one of the new features for the 16NGF design. The main purpose of the Axial Blanket Optimization study is to determine which axial blanket enrichment and length would provide the better fuel cycle cost benefit. All of the calculations were performed using Gadolinium as Burnable Absorber and solid pellets type for Axial Blanket. The results indicate 1.8 w/o U235 enrichment and 8 inches length as the best option of Axial Blanket from the fuel cycle cost benefit standpoint. The economy is about 1.8%. The difference in the reload cost in the range between 1.5 and 2.6 w/o U235 enrichment and for the 6 and 8 inches length is not so significant. Due that, from the Fq limit standpoint and also for longer cycle length requirements, a higher axial blanket enrichment (2.6 w/o) and shorter length (6 inches) is recommended. (author)
Distribution load estimation (DLE)
Energy Technology Data Exchange (ETDEWEB)
Seppaelae, A.; Lehtonen, M. [VTT Energy, Espoo (Finland)
1998-08-01
The load research has produced customer class load models to convert the customers` annual energy consumption to hourly load values. The reliability of load models applied from a nation-wide sample is limited in any specific network because many local circumstances are different from utility to utility and time to time. Therefore there is a need to find improvements to the load models or, in general, improvements to the load estimates. In Distribution Load Estimation (DLE) the measurements from the network are utilized to improve the customer class load models. The results of DLE will be new load models that better correspond to the loading of the distribution network but are still close to the original load models obtained by load research. The principal data flow of DLE is presented
Energy Technology Data Exchange (ETDEWEB)
Castillo, A.; Torres, M.; Ortiz, J. J.; Perusquia, R.; Hernandez, J. L.; Montes, J. L. [ININ, 52750 La Marquesa, Estado de Mexico (Mexico)]. e-mail: jacm@nuclear.inin.mx
2008-07-01
In the present work the preliminary results were obtained with the zoctli system whose purpose is the axial design of assembly of nuclear fuel under certain considerations. For the mentioned design well-know cells were already used and that they have been proven in diverse cycles of operation in the nuclear power plant of Laguna Verde. The design contemplates fuels assemblies of 10x10 and with 2 water channels. The assembly was distributed in 6 axial zones according to its structure. In order to take to end the optimization is was used the well-known technique like Path relinking and to find the group of previous solutions required by this technique uses the technical Taboo search. In order to work with Path relinking, 5 trajectories was taken in to account from a set of 5 previous solutions generated with theTaboo search, the update of the group of solutions is carried out in dynamic form. In the case of the Taboo search it was used a list of variable size, it was implement an aspiration approach, it was used the vector of frequencies and due to the cost of the evaluation of the objective function, only it was review 5% of the vicinity. For the objective function was considered the limit thermal, the axial profile of power, the effective multiplication factor and the margin of having turned off in cold. In order to prove the design system, it was used a balance cycle with a value of reference of 0.9928 for the effective multiplication factor that is equivalent to a produced energy of 10896 MWd/TU at the end of operation to full power. The designed assemblies were placed both in one of lots different from fresh assemblies on which it counts the referred cycle. At the end one a comparison with the results obtained with other techniques and under similar conditions is made. The results obtained until the moment show an appropriate performance of the system. It is possible to indicate that a small inconvenient is the amount of consumed resources of calculation during
DEFF Research Database (Denmark)
Dyrbye, Claes; Hansen, Svend Ole
pressure to structural response) and design criteria. Starting with an introduction of the wind load chain, the book moves on to meteorological considerations, atmospheric boundary layer, static wind load, dynamic wind load and scaling laws used in wind-tunnel tests. The dynamic wind load covers vibrations......Wind loads have to be taken into account when designing civil engineering structures. The wind load on structures can be systematised by means of the wind load chain: wind climate (global), terrain (wind at low height), aerodynamic response (wind load to pressure), mechanical response (wind...
Distribution load estimation - DLE
Energy Technology Data Exchange (ETDEWEB)
Seppaelae, A. [VTT Energy, Espoo (Finland)
1996-12-31
The load research project has produced statistical information in the form of load models to convert the figures of annual energy consumption to hourly load values. The reliability of load models is limited to a certain network because many local circumstances are different from utility to utility and time to time. Therefore there is a need to make improvements in the load models. Distribution load estimation (DLE) is the method developed here to improve load estimates from the load models. The method is also quite cheap to apply as it utilises information that is already available in SCADA systems
Miller, D. P.; Prahst, P. S.
1995-01-01
An axial compressor test rig has been designed for the operation of small turbomachines. A flow test was run to calibrate and determine the source and magnitudes of the loss mechanisms in the compressor inlet for a highly loaded two-stage axial compressor test. Several flow conditions and inlet guide vane (IGV) angle settings were established, for which detailed surveys were completed. Boundary layer bleed was also provided along the casing of the inlet behind the support struts and ahead of the IGV. Several computational fluid dynamics (CFD) calculations were made for selected flow conditions established during the test. Good agreement between the CFD and test data were obtained for these test conditions.
Köller, W; Funke, F; Hartmann, F
1981-04-01
49 specimens were studied in 67 axial compression tests; the duration test varied between 2 and 6 hours. All discs showed marked creep; after a big decrease in the first minutes the rate of creep decreases still slightly. Additional the results reveal a decreasing axial deformability with time. In the beginning of a test quickly the viscoelastic behavior alters to such a steady state that the disc behaves more like an elastic body. Loss of mass normally observed after compression tests is due to loss of liquid, but liquid absorption during mechanical load is possible too. The long term biochmechanical behavior is reproducible very well; a second experiment done with the same disc yields nearly the same results.
Multi-axial active isolation for seismic protection of buildings
Chang, Chia-Ming
Structural control technology has been widely accepted as an effective means for the protection of structures against seismic hazards. Passive base isolation is one of the common structural control techniques used to enhance the performance of structures subjected to severe earthquake excitations. Isolation bearings employed at the base of a structure naturally increase its flexibility, but concurrently result in large base displacements. The combination of base isolation with active control, i.e., active base isolation, creates the possibility of achieving a balanced level of control performance, reducing both floor accelerations as well as base displacements. Many theoretical papers have been written by researchers regarding active base isolation, and a few experiments have been performed to verify these theories; however, challenges in appropriately scaling the structural system and modeling the complex nature of control-structure interaction have limited the applicability of these results. Moreover, most experiments only focus on the implementation of active base isolation under unidirectional excitations. Earthquakes are intrinsically multi-dimensional, resulting in out-of-plane responses, including torsional responses. Therefore, an active isolation system for buildings using multi-axial active control devices against multi-directional excitations must be considered. The focus of this dissertation is the development and experimental verification of active isolation strategies for multi-story buildings subjected to bi-directional earthquake loadings. First, a model building is designed to match the characteristics of a representative full-scale structure. The selected isolation bearings feature low friction and high vertical stiffness, providing stable behavior. In the context of the multi-dimensional response control, three, custom-manufactured actuators are employed to mitigate both in-plane and out-of-plane responses. To obtain a high-fidelity model of the
Plate Fin Heat Exchanger Model with Axial Conduction and Variable Properties
Energy Technology Data Exchange (ETDEWEB)
Hansen, B.J.; White, M.J.; Klebaner, A.; /Fermilab
2011-06-10
Future superconducting radio frequency (SRF) cavities, as part of Project X at Fermilab, will be cooled to superfluid helium temperatures by a cryogenic distribution system supplying cold supercritical helium. To reduce vapor fraction during the final Joule-Thomson (J-T) expansion into the superfluid helium cooling bath, counter-flow, plate-fin heat exchangers will be utilized. Due to their compact size and ease of fabrication, plate-fin heat exchangers are an effective option. However, the design of compact and high-effectiveness cryogenic heat exchangers operating at liquid helium temperatures requires consideration of axial heat conduction along the direction of flow, in addition to variable fluid properties. Here we present a numerical model that includes the effects of axial conduction and variable properties for a plate fin heat exchanger. The model is used to guide design decisions on heat exchanger material choice and geometry. In addition, the J-T expansion process is modeled with the heat exchanger to analyze the effect of heat load and cryogenic supply parameters. A numerical model that includes the effects of axial conduction and variable properties for a plate fin heat exchanger was developed and the effect of various design parameters on overall heat exchanger size was investigated. It was found that highly conductive metals should be avoided in the design of compact JT heat exchangers. For the geometry considered, the optimal conductivity is around 3.5 W/m-K and can range from 0.3-10 W/m-K without a large loss in performance. The model was implemented with an isenthalpic expansion process. Increasing the cold side inlet temperature from 2K to 2.2 K decreased the liquid fraction from 0.856 to 0.839 which corresponds to a 0.12 g/s increase in supercritical helium supply needed to maintain liquid level in the cooling bath. Lastly, it was found that the effectiveness increased when the heat load was below the design value. Therefore, the heat exchanger
Directory of Open Access Journals (Sweden)
R.Citarella
2015-01-01
Full Text Available An edge crack propagation in a steel bar of circular cross-section undergoing multiaxial fatigue loads is simulated by Finite Element Method (FEM. The variation of crack growth behaviour is studied under axial and combined in phase axial+torsional fatigue loading. Results show that the cyclic Mode III loading superimposed on the cyclic Mode I leads to a fatigue life reduction. Numerical calculations are performed using the FEM software ZENCRACK to determine the crack path and fatigue life. The FEM numerical predictions have been compared against corresponding experimental and numerical data, available from literature, getting satisfactory consistency.
Investigation of axial power gradients near a control rod tip
Energy Technology Data Exchange (ETDEWEB)
Loberg, John, E-mail: John.Loberg@fysast.uu.se [Uppsala University, Department of Physics and Astronomy, Division of Applied Nuclear Physics, Box 525, SE-75120 Uppsala (Sweden); Osterlund, Michael, E-mail: Michael.Osterlund@fysast.uu.se [Uppsala University, Department of Physics and Astronomy, Division of Applied Nuclear Physics, Box 525, SE-75120 Uppsala (Sweden); Bejmer, Klaes-Hakan, E-mail: Klaes-Hakan.Bejmer@vattenfall.com [Vattenfall Nuclear Fuel AB, Jaemtlandsgatan 99, 162 60 Vaellingby, Stockholm (Sweden); Blomgren, Jan, E-mail: Jan.Blomgren@vattenfall.com [Vattenfall Nuclear Fuel AB, Jaemtlandsgatan 99, 162 60 Vaellingby, Stockholm (Sweden); Kierkegaard, Jesper, E-mail: Jesper.Kierkegaar@vattenfall.com [Vattenfall Nuclear Fuel AB, Jaemtlandsgatan 99, 162 60 Vaellingby, Stockholm (Sweden)
2011-07-15
Highlights: > Pin power gradients near BWR control rod tips have been investigated. > A control rod tip is modeled in MCNP and compared to simplified 2D/3D geometry. > Small nodes increases pin power gradients; standard nodes underestimates gradients. > The MCNP results are validated against axial gamma scan of a controlled fuel pin. - Abstract: Control rod withdrawal in BWRs induces large power steps in the adjacent fuel assemblies. This paper investigates how well a 2D/3D method, e.g., CASMO5/SIMULATE5 computes axial pin power gradients adjacent to an asymmetrical control-rod tip in a BWR. The ability to predict pin power gradients accurately is important for safety considerations whereas large powers steps induced by control rod withdrawal can cause Pellet Cladding Interaction. The computation of axial pin power gradients axially around a control rod tip is a challenging task for any nodal code. On top of that, asymmetrical control rod handles are present in some BWR designs. The lattice code CASMO requires diagonal symmetry of all control rod parts. This introduces an error in computed pin power gradients that has been evaluated by Monte Carlo calculations. The results show that CASMO5/SIMULATE5, despite the asymmetrical control rod handle, is able to predict the axial pin power gradient within 1%/cm for axial nodal sizes of 15-3.68 cm. However, a nodal size of 3.68 cm still causes underestimations of pin power gradients compared with 1 cm nodes. Furthermore, if conventional node sizes are used, {approx}15 cm, pin power gradients can be underestimated by over 50% compared with 1 cm nodes. The detailed axial pin power profiles from MCNP are corroborated by measured gamma scan data on fuel rods irradiated adjacent to control rods.
Institute of Scientific and Technical Information of China (English)
LI Xiaohe; LI Zhijun; GAO Shang
2015-01-01
Objective:To analysis through the mouth atlanto-axial vertebral anterior plate fixation in finite element for the development of the segmental anterior fixation surgery and to provide the reference of inner plant im-provement. Methods:One case, male, 36 years old, 64 kg weight was randomly selected from January 2014 to our hospital to check no-skull - atlanto-axial vertebral disease . It was scanned by 0. 625 mm thin layer, Image data were rebuilted in the Mimics 16. 01 software, Pro/ENGINEER 4. 0 software was used to rebuilt atlanto-axial vertebral anterior plate, After reconstruction of steel screw 3 d model according to the classic through the mouth , the model was imported into Mimics 16. 01 and the model surface was meshed and material was assigned, The mod-el was forced 80 N vertical loading, the surface was applied 15 nm torque, to simulat three motion state example, forward bends, stretch, side-bending, The stress and deformation of screw and rod were measured. Results: At-lanto-axial vertebral three-dimensional reconstruction model were divided into 14 514 individual grid, 7 257 nodes, the model was loaded, The stress of upper screw root in bend was biggest (62. 34 ±5. 52) Mpa (F=73. 23, P<0. 05, the difference was statistically significant). A screw of the root and the top, lateral stress was the largest, respectively were (78. 42 ± 5. 5. 14) Mpa (F=112. 32, P<0. 05);(95. 48 ± 7. 12 Mpa (F=62. 32, P<0. 05), the difference was statistical significance; Under three different motion state and a screw root stress, Upper screw root stress in bending forward was greater than the lower (forward bends, stretch and lateral bending state , t value were 12. 2, 9. 23, 22. 98, P<0. 05, differences were statistically significant), and in the lateral current screw root stress was greater than the upper; In the same movement state, the top was greater than the root, the differences were statistically significant (forward bends, stretch and lateral bending state after
Axial length as a risk factor to branch retinal vein occlusion
Timmerman, EA; deLavalette, VWR; vandenBrom, HJB
1997-01-01
Purpose: To determine whether axial length is a factor in branch retinal vein occlusion. Methods: Axial length measurements in a group of 24 patients with a unilateral branch retinal Vein occlusion were compared with the axial length measurements in a control group. axial length measurements were ta
Development and Testing of an Axial Halbach Magnetic Bearing
Eichenberg, Dennis J.; Gallo, Christopher A.; Thompson, William K.
2006-01-01
The NASA Glenn Research Center has developed and tested a revolutionary Axial Halbach Magnetic Bearing. The objective of this work is to develop a viable non-contact magnetic thrust bearing utilizing Halbach arrays for all-electric flight, and many other applications. This concept will help to reduce harmful emissions, reduce the Nation s dependence on fossil fuels and mitigate many of the concerns and limitations encountered in conventional axial bearings such as bearing wear, leaks, seals and friction loss. The Axial Halbach Magnetic Bearing is inherently stable and requires no active feedback control system or superconductivity as required in many magnetic bearing designs. The Axial Halbach Magnetic Bearing is useful for very high speed applications including turbines, instrumentation, medical systems, computer memory systems, and space power systems such as flywheels. Magnetic fields suspend and support a rotor assembly within a stator. Advanced technologies developed for particle accelerators, and currently under development for maglev trains and rocket launchers, served as the basis for this application. Experimental hardware was successfully designed and developed to validate the basic principles and analyses. The report concludes that the implementation of Axial Halbach Magnetic Bearings can provide significant improvements in rotational system performance and reliability.
Design and Simulation of Axial Flow Maglev Blood Pump
Directory of Open Access Journals (Sweden)
Huachun Wu
2011-03-01
Full Text Available The axial flow maglev blood pump (AFMBP has become a global research focus and emphasis for artificial ventricular assist device, which has no mechanical contact, mechanical friction, compact structure and light weight, can effectively solve thrombus and hemolysis. Magnetic suspension and impeller is two of the important parts in the axial flow maglev blood pump, and their structure largely determines the blood pump performance. The research adopts electromagnetic and fluid finite element analysis, and puts forward a method to design the magnetic suspension and impeller of axial flow blood pump, which tacks into account the small volume of axial blood pump. The magnetic bearing’s characteristics are evaluated by electromagnetic finite element analysis. The Blades have been designed by calculating aerofoil bone line, and make simulation analysis for different thicken ways of blade by Fluent software, and make a conclusion that the blade thickened with certain rules has better characteristics in the same conditions. The results will provide some guidance for design of axial flow maglev blood pump, and establish theoretical basis for application of the implantable artificial heart pump.
Light Weakly Coupled Axial Forces: Models, Constraints, and Projections
Kahn, Yonatan; Mishra-Sharma, Siddharth; Tait, Tim M P
2016-01-01
We investigate the landscape of constraints on MeV-GeV scale, hidden U(1) forces with nonzero axial-vector couplings to Standard Model fermions. While the purely vector-coupled dark photon, which may arise from kinetic mixing, is a well-motivated scenario, several MeV-scale anomalies motivate a theory with axial couplings which can be UV-completed consistent with Standard Model gauge invariance. Moreover, existing constraints on dark photons depend on products of various combinations of axial and vector couplings, making it difficult to isolate the effects of axial couplings for particular flavors of SM fermions. We present a representative renormalizable, UV-complete model of a dark photon with adjustable axial and vector couplings, discuss its general features, and show how some UV constraints may be relaxed in a model with nonrenormalizable Yukawa couplings at the expense of fine-tuning. We survey the existing parameter space and the projected reach of planned experiments, briefly commenting on the relevan...
Amphiregulin Antibody and Reduction of Axial Elongation in Experimental Myopia
Directory of Open Access Journals (Sweden)
Wen Jun Jiang
2017-03-01
Full Text Available To examine the mechanism of ocular axial elongation in myopia, guinea pigs (age: 2–3 weeks which either underwent unilateral or bilateral lens-induced myopization (group 1 or which were primarily myopic at baseline (group 2 received unilateral intraocular injections of amphiregulin antibody (doses: 5, 10, or 15 μg three times in intervals of 9 days. A third group of emmetropic guinea pigs got intraocular unilateral injections of amphiregulin (doses: 0.25, 0.50 or 1.00 ng, respectively. In each group, the contralateral eyes received intraocular injections of Ringer's solution. In intra-animal inter-eye comparison and intra-eye follow-up comparison in groups 1 and 2, the study eyes as compared to the contralateral eyes showed a dose-dependent reduction in axial elongation. In group 3, study eyes and control eyes did not differ significantly in axial elongation. Immunohistochemistry revealed amphiregulin labelling at the retinal pigment epithelium in eyes with lens-induced myopization and Ringer's solution injection, but not in eyes with amphiregulin antibody injection. Intraocular injections of amphiregulin-antibody led to a reduction of lens-induced axial myopic elongation and of the physiological eye enlargement in young guinea pigs. In contrast, intraocularly injected amphiregulin in a dose of ≤1 ng did not show a significant effect. Amphiregulin may be one of several essential molecular factors for axial elongation.
Axial clamp for nuclear reactor head penetration conoseal joints
Energy Technology Data Exchange (ETDEWEB)
Hackley, T.A.
1987-03-31
A method is described for forming a sealed coupling between two bodies, each body presenting an annular abutment surface. The respective bodies are arranged so that their respective annular abutment surfaces are axially adjacent one another, defining a space therebetween, wherein a deformable gasket is disposed within the space. The method comprises: providing one of the bodies with an annular projection; providing the other body with threads for receiving an annular locknut which can be tightened to bear against the annular projection of the one body; applying an external axial forced to the bodies for compressing the abutment surfaces together against the gasket to form a seal between the bodies; immobilizing the bodies relative to one another while the external force is being applied to the bodies by hand-tightening an annular locknut via the threads of the other body until the locknut abuts the annular projection of the one body, substantially preventing relative axial movement between the bodies when the external axial force is withdrawn; and withdrawing the external axial force applied to the bodies, leaving the two bodies coupled together via the seal.
An Axial-Vector Photon in a Mirror World
Sharafiddinov, Rasulkhozha S.
2016-03-01
The unity of symmetry laws emphasizes, in the case of a mirror CP-even Dirac Lagrangian, the ideas of the left- and right-handed axial-vector photons referring to long- and short-lived bosons of true neutrality, respectively. Such a difference in lifetimes expresses the unidenticality of masses, energies and momenta of axial-vector photons of the different components. They define the unified field theory equation of C-odd particles with an integral spin. Together with a new equation of a theory of truly neutral particles with the half-integral spin, the latter reflects the availability in their nature of the second type of the local axial-vector gauge transformation responsible for origination in the Lagrangian of C-oddity of an interaction Newton component giving an axial-vector mass to all the interacting particles and fields. The mirror axial-vector mass, energy and momentum operators constitute a CP-invariant equation of quantum mechanics, confirming that each of them can individually influence on matter field. Thereby, findings suggest at the level of the mass-charge structure of gauge invariance a new equation for the C-noninvariant Lagrangian.
Light Weakly Coupled Axial Forces: Models, Constraints, and Projections
Energy Technology Data Exchange (ETDEWEB)
Kahn, Yonatan [Princeton U.; Krnjaic, Gordan [Fermilab; Mishra-Sharma, Siddharth [Princeton U.; Tait, Tim P. [UC, Irvine
2016-09-28
We investigate the landscape of constraints on MeV-GeV scale, hidden U(1) forces with nonzero axial-vector couplings to Standard Model fermions. While the purely vector-coupled dark photon, which may arise from kinetic mixing, is a well-motivated scenario, several MeV-scale anomalies motivate a theory with axial couplings which can be UV-completed consistent with Standard Model gauge invariance. Moreover, existing constraints on dark photons depend on products of various combinations of axial and vector couplings, making it difficult to isolate the effects of axial couplings for particular flavors of SM fermions. We present a representative renormalizable, UV-complete model of a dark photon with adjustable axial and vector couplings, discuss its general features, and show how some UV constraints may be relaxed in a model with nonrenormalizable Yukawa couplings at the expense of fine-tuning. We survey the existing parameter space and the projected reach of planned experiments, briefly commenting on the relevance of the allowed parameter space to low-energy anomalies in pi^0 and 8-Be* decay.
Method to measure tone of axial and proximal muscle.
Gurfinkel, Victor S; Cacciatore, Timothy W; Cordo, Paul J; Horak, Fay B
2011-12-14
The control of tonic muscular activity remains poorly understood. While abnormal tone is commonly assessed clinically by measuring the passive resistance of relaxed limbs, no systems are available to study tonic muscle control in a natural, active state of antigravity support. We have developed a device (Twister) to study tonic regulation of axial and proximal muscles during active postural maintenance (i.e. postural tone). Twister rotates axial body regions relative to each other about the vertical axis during stance, so as to twist the neck, trunk or hip regions. This twisting imposes length changes on axial muscles without changing the body's relationship to gravity. Because Twister does not provide postural support, tone must be regulated to counteract gravitational torques. We quantify this tonic regulation by the restive torque to twisting, which reflects the state of all muscles undergoing length changes, as well as by electromyography of relevant muscles. Because tone is characterized by long-lasting low-level muscle activity, tonic control is studied with slow movements that produce "tonic" changes in muscle length, without evoking fast "phasic" responses. Twister can be reconfigured to study various aspects of muscle tone, such as co-contraction, tonic modulation to postural changes, tonic interactions across body segments, as well as perceptual thresholds to slow axial rotation. Twister can also be used to provide a quantitative measurement of the effects of disease on axial and proximal postural tone and assess the efficacy of intervention.
An Axial Vector Photon in a Mirror World
Sharafiddinov, Rasulkhozha S
2015-01-01
The unity of symmetry laws emphasizes, in the case of a mirror CP-even Dirac Lagrangian, the ideas of the left- and right-handed axial-vector photons referring to long- and short-lived bosons of true neutrality, respectively. Such a difference in lifetimes expresses the unidenticality of masses, energies and momenta of axial-vector photons of the different components. They define the unified field theory equation of C-odd particles with an integral spin. Together with a new equation of a theory of truly neutral particles with the half-integral spin, the latter reflects the availability in their nature of the second type of the local axial-vector gauge transformation responsible for origination in the Lagrangian of C-oddity of an interaction Newton component giving an axial-vector mass to all the interacting particles and fields. The mirror axial-vector mass, energy and momentum operators constitute a CP-invariant equation of quantum mechanics, confirming that each of them can individually influence on matter ...
Directory of Open Access Journals (Sweden)
Jabulani R. Barber
2014-01-01
Full Text Available The mechanical response of thirteen different helical multi-walled carbon nanocoils to axial compression is reported. Each nanocoil was attached to the apex of a cantilever probe tip; its dimensions and orientation relative to the tip apex were determined with scanning electron microscopy. The atomic force microscope was employed to apply a cyclic axial load on the nanocoil. Its mechanical response was determined by simultaneous collection of the thermal resonance frequency, displacement, and oscillation amplitude of the cantilever-nanotube system in real time. Depending upon compression parameters, each coil underwent buckling, bending, and slip-stick motion. Characteristic features in the thermal resonance spectrum and in the force and oscillation amplitude curves for each of these responses to induced stress are presented. Following compression studies, the structure and morphology of each nanocoil were determined by transmission electron microscopy. The compression stiffness of each nanocoil was estimated from the resonant frequency of the cantilever at the point of contact with the substrate surface. From this value, the elastic modulus of the nanocoil was computed and correlated with the coiled carbon nanotube’s morphology.
Low-pressure reversible axial fan with straight profile blades and relatively high efficiency
Directory of Open Access Journals (Sweden)
Spasić Živan T.
2012-01-01
Full Text Available The paper presents the design and operating characteristics of a model of reversible axial fan with only one impeller, whose reversibility is achieved by changing the direction of rotation. The fan is designed for the purpose of providing alternating air circulation in wood dryers in order to reduce the consumption of electricity for the fan and increase energy efficiency of the entire dryer. To satisfy the reversibility of flow, the shape of the blade profile is symmetrical along the longitudinal and transversal axes of the profile. The fan is designed with equal specific work of all elementary stages, using the method of lift forces. The impeller blades have straight mean line profiles. The shape of the blade profile was adopted after the numerical simulations were carried out and high efficiency was achieved. Based on the calculation and conducted numerical simulations, a physical model of the fan was created and tested on a standard test rig, with air loading at the suction side of the fan. The operating characteristics are shown for different blade angles. The obtained maximum efficiency was around 0.65, which represents a rather high value for axial fans with straight profile blades.
Gui, Xingmin; Zhu, Fang; Wan, Ke; Jin, Donghai
2013-10-01
Swept blades have been widely used in the transonic fan/compressor of aircraft engines with the aids of 3D CFD simulation since the design concept of controlling the shock structure was firstly proposed and successfully tested by Dr. Wennerstrom in the 1980s. However, some disadvantage phenomenon has also been induced by excessively 3D blade geometries on the structure stress insufficiency, vibration and reliability. Much confusion in the procedure of design practice leading us to recognize a new view on the flow mechanism of sweep aerodynamical induction: the new radial equilibrium established by the influence of inlet circumferential fluctuation (CF) changes the inlet flows of blading and induces the performance modification of axial fans/compressors blade. The view is verified by simplified models through numerical simulation and circumferentially averaged analysis in the present paper. The results show that the CF source items which originate from design parameters, such as the spanwise distributions of the loading and blading geometries, contribute to the changing of averaged incidence spanwise distribution, and further more affect the performance of axial fans/compressors with swept blades.
Inception mechanism and suppression of rotating stall in an axial-flow fan
Nishioka, T.
2013-12-01
Inception patterns of rotating stall at two stagger-angle settings for the highly loaded rotor blades were experimentally investigated in a low-speed axial-flow fan. Rotor-tip flow fields were also numerically investigated to clarify the mechanism behind the rotating stall inception. The stall inception patterns depended on the rotor stagger-angle settings. The stall inception from a rotating instability was confirmed at the design stagger-angle settings. The stall inception from a short length-scale stall cell (spike) was also confirmed at the small stagger-angle setting. The spillage of tip-leakage flow and the tip-leakage vortex breakdown influence the rotating stall inception. An air-separator has been developed based on the clarified inception mechanism of rotating stall. The rotating stall was suppressed by the developed air-separator, and the operating range of fan was extended towards low flow rate. The effect of developed air-separator was also confirmed by application to a primary air fan used in a coal fired power plant. It is concluded from these results that the developed air-separator can provide a wide operating range for an axial-flow fan.
Advanced axial field D.C. motor development for electric passenger vehicle
Jones, W. J.
1982-01-01
A wound-field axial-flux dc motor was developed for an electric vehicle drive system. The motor is essentially an axial-flux version of the classical Gramme-ring winding motor, but the active conductors are recessed into slots cut into the two opposite faces of the laminated tape-wound core ring. Three motors were built and tested in the program. The second (functional) model was a six-pole machine which weighed 88.5 kg. It developed 16.9 km (33.0 hp), and a max speed of 4800 rpm. Full load efficiency was 92% and predicted SAE D-cycle efficiency was 88%. The last engineering) model was a 4-pole machine with compoles, allowing a weight reduction to 45 kg (100 lbs.) while addressing some manufacturability problems. The engineering model was rated at 13.2 kw (17.6 hp) at 3000 rpm, with a peak power of 19.8 km (26.4 hp) and a max speed of 7200 rpm. Initial test results on this motor showed poor commutation and efficiency; the program was terminated without resolution of these problems.
Design and Analysis of an Axially Laminated Reluctance Motor for Variable-Speed Applications
Directory of Open Access Journals (Sweden)
BESER, E. K.
2013-02-01
Full Text Available In this paper, an axially laminated reluctance motor is presented. First, a set of a finite element analysis (FEA on three different axially laminated rotor geometries was carried out and torque profiles of the rotors were predicted. The effect of the stator slot skewing on the torque profiles were also examined in the analysis. After deciding the rotor geometry, the mathematical model of the proposed motor was formed in terms of a,b,c variables and simulations were performed. Motor prototype and motor drive were introduced. Torque profiles of the motor were measured for different current values and load test were realized. Experimental results were compared to analysis and simulation results. There is a good accordance between experimental and simulation results. When the proposed motor is operated with electrical 120? mode as a brushless DC motor, the torque versus speed characteristic shows a DC series motor characteristic and speed of the motor can be easily controlled by regulating the bus voltage. These features make the proposed motor convenient for variable-speed applications such as electrical vehicles.
Performance Test and Flow Measurement of Contra-Rotating Axial Flow Pump
Institute of Scientific and Technical Information of China (English)
Akinori Furukawa; Toru Shigemitsu; Satoshi Watanabe
2007-01-01
An application of contra-rotating rotors has been proposed against a demand for developing higher specific speed axial flow pump. In the present paper, the advantage and disadvantage of using contra-rotating rotors are described in comparison with conventional type of rotor-stator, based on theoretical and experimental investigations. The advantages are as follows: (1) The pump is inherently designed as smaller sized and at lower rotational speed. (2) A stable head-characteristic curve for flow rate with negative slope appears. (3)As the rear rotor rotational speed is varied as independent control of front rotor, the wider range of high performance operation is obtained by rear rotor speed control in addition to front rotor speed control. The disadvantages are as follows: (1) The structure of double shaft system becomes complex. (2) The pump performance is inferior at over flow rate as the rear rotor loading is weakened. (3) The blade rows interaction from rear rotor to front rotor more strongly appears. Then the rear rotor design is a key to achieve higher pump performance. Some methods to overcome these disadvantages will be discussed in more details toward wider usage of contra-rotating axial flow pump in various industrial fields.
Grinding efficiency of abutment tooth with both dentin and core composite resin on axial plane.
Miho, Otoaki; Sato, Toru; Matsukubo, Takashi
2015-01-01
The purpose of this study was to evaluate grinding efficiency in abutment teeth comprising both dentin and core composite resin in the axial plane. Grinding was performed over 5 runs at two loads (0.5 or 0.25 N) and two feed rates (1 or 2 mm/sec). The grinding surface was observed with a 3-D laser microscope. Tomographic images of the grinding surfaces captured perpendicular to the feed direction were also analyzed. Using a non-ground surface as a reference, areas comprising only dentin, both dentin and core composite resin, or only core composite resin were analyzed to determine the angle of the grinding surface. Composite resins were subjected to the Vickers hardness test and scanning electron microscopy. Data were statistically analyzed using a one-way analysis of variance and multiple comparison tests. Multiple regression analysis was performed for load, feed rate, and Vickers hardness of the build-up material depending on number of runs. When grinding was performed at a constant load and feed rate, a greater grinding angle was observed in areas comprising both dentin and composite resin or only composite resin than in areas consisting of dentin alone. A correlation was found between machinability and load or feed rate in areas comprising both dentin and composite resin or composite resin alone, with a particularly high correlation being observed between machinability and load. These results suggest that great caution should be exercised in a clinical setting when the boundary between the dentin and composite resin is to be ground, as the angle of the grinding surface changes when the rotating diamond point begins grinding the composite resin.
Meng, Qingbin; Zhang, Mingwei; Han, Lijun; Pu, Hai; Nie, Taoyi
2016-10-01
Characteristics of energy accumulation, evolution, and dissipation in uniaxial cyclic loading and unloading compression of 30 sandstone rock specimens under six different loading rates were explored. Stress-strain relations and acoustic emission characteristics of the deformation and failure of rock specimens were analyzed. The densities and rates of stored energy, elastic energy, and dissipated energy under different loading rates were confirmed, and an effective approach for the equivalent energy surface was presented. The energy evolution of rock deformation and failure were revealed. It turns out that the rock deformation behavior under uniaxial cyclic loading and unloading compression remained almost unchanged compared with that of uniaxial compression. The degree of match between reloading stress-strain curves and previous unloading curves was high, thereby demonstrating the memory function of rock masses. The intensity of acoustic emission fluctuated continually during the entire cyclic process. Emissions significantly increased as the stress exceeded the unloading level. The peak of acoustic emission increased with increasing loading stress level. Relationships between energy density and axial load indicate that the rock mass possesses a certain energy storage limitation. The energy evolution of rock masses is closely related to the axial loading stress, rather than to the axial loading rate. With increasing axial loading stress, stored energy varied most rapidly, followed by that of the elastic energy, then dissipated energy. Energy accumulation dominates prior to the axial load reaching peak strength; thereafter, energy dissipation becomes dominant. The input energy causes the irreversible initiation and extension of microcracks in the rock body. Elastic energy release leads to sudden instability of rock bodies and drives rock damage.
Energy Technology Data Exchange (ETDEWEB)
Ansari, R., E-mail: r_ansari@guilan.ac.i [Department of Mechanical Engineering, University of Guilan, P.O. Box 3756, Rasht (Iran, Islamic Republic of); Sahmani, S.; Rouhi, H. [Department of Mechanical Engineering, University of Guilan, P.O. Box 3756, Rasht (Iran, Islamic Republic of)
2011-02-28
Eringen's nonlocality is incorporated into the shell theory to include the small-scale effects on the axial buckling of single-walled carbon nanotubes (SWCNTs) with arbitrary boundary conditions. To this end, the Rayleigh-Ritz solution technique is implemented in conjunction with the set of beam functions as modal displacement functions. Then, molecular dynamics simulations are employed to obtain the critical buckling loads of armchair and zigzag SWCNTs, the results of which are matched with those of nonlocal shell model to extract the appropriate values of nonlocal parameter. It is found that in contrast to the chirality, boundary conditions have a considerable influence on the proper values of nonlocal parameter.
Aerodynamic parametric studies and sensitivity analysis for rotor blades in axial flight
Chiu, Y. D.; Peters, David A.
1991-01-01
The analytical capability is offered for aerodynamic parametric studies and sensitivity analyses of rotary wings in axial flight by using a 3D undistorted wake model in curved lifting line theory. The governing equations are solved by both the Multhopp Interpolation technique and the Vortex Lattice method. The singularity from the bound vortices is eliminated through the Hadamard's finite part concept. Good numerical agreement between both analytical methods and finite differences methods are found. Parametric studies were made to assess the effects of several shape variables on aerodynamic loads. It is found, e.g., that a rotor blade with out-of-plane and inplane curvature can theoretically increase lift in the inboard and outboard regions respectively without introducing an additional induced drag.
Aerodynamic parameter studies and sensitivity analysis for rotor blades in axial flight
Chiu, Y. Danny; Peters, David A.
1991-01-01
The analytical capability is offered for aerodynamic parametric studies and sensitivity analyses of rotary wings in axial flight by using a 3-D undistorted wake model in curved lifting line theory. The governing equations are solved by both the Multhopp Interpolation technique and the Vortex Lattice method. The singularity from the bound vortices is eliminated through the Hadamard's finite part concept. Good numerical agreement between both analytical methods and finite differences methods are found. Parametric studies were made to assess the effects of several shape variables on aerodynamic loads. It is found, e.g., that a rotor blade with out-of-plane and inplane curvature can theoretically increase lift in the inboard and outboard regions respectively without introducing an additional induced drag.
Optimization Design and Experimental Study of Low-Pressure Axial Fan with Forward-Skewed Blades
Directory of Open Access Journals (Sweden)
Li Yang
2007-01-01
Full Text Available This paper presents an experimental study of the optimization of blade skew in low pressure axial fan. Using back propagation (BP neural network and genetic algorithm (GA, the optimization was performed for a radial blade. An optimized blade is obtained through blade forward skew. Measurement of the two blades was carried out in aerodynamic and aeroacoustic performance. Compared to the radial blade, the optimized blade demonstrated improvements in efficiency, total pressure ratio, stable operating range, and aerodynamic noise. Detailed flow measurement was performed in outlet flow field for investigating the responsible flow mechanisms. The optimized blade can cause a spanwise redistribution of flow toward the blade midspan and reduce tip loading. This results in reduced significantly total pressure loss near hub and shroud endwall region, despite the slight increase of total pressure loss at midspan. In addition, the measured spectrums show that the broadband noise of the impeller is dominant.
Institute of Scientific and Technical Information of China (English)
LI Yang; LIU Jie; OUYANG Hua; DU Zhao-Hui
2008-01-01
This article presents the flow mechanism analysis and experimental study of a forward-skewed impeller and a radial impeller in low pressure axial fan. The forward-skewed blade was obtained by the optimization design of the radial blade and CFD technique. Measurement of the two blades was carried out in aerodynamic and aeroacoustic performance. Compared to the radial blade, the forward-skewed blade has demonstrated the improvements in efficiency, total pressure ratio, Stable Operating Range (SOR) and less aerodynamic noise. Detailed flow measurement and computation were performed for outlet flow field for investigating the responsible flow mechanisms. The results show the forward-skewed blade can cause a spanwise redistribution of flow toward the blade mid-span and reduce tip loading. This results in reduced significantly total pressure loss near hub and shroud endwall region, despite the slight increase of total pressure loss at mid-span.
Fatigue damage rule of LY12CZ aluminium alloy under sequential biaxial loading
Wang, YingYu; Zhang, DaChuan; Yao, WeiXing
2014-01-01
A series of biaxial two-level variable amplitude loading tests are conducted on smooth tubular specimens of LY12CZ aluminium alloy. The loading paths of 90° out-of-phase, 45° out-of-phase and 45° in-phase are utilized. The fatigue damage cumulative rules under two-level step loading of three loading paths are analyzed. By introducing a parameter α which is a function of the phase lag angle between the axial and the torsional loading, a new multiaxial nonlinear fatigue damage cumulative model is proposed. The proposed model is evaluated by the experimental data for two-level loading, multi-level loading of LY12CZ aluminium alloy, and multi-level loading of 45 steel. Fatigue lives predicted are within a factor of 2 scatter band.
Survey of Design Points for Low Wire Count PRS Loads
Terry, Robert E.; Apruzese, John P.
2003-10-01
Plasma radiation source loads of a few larger diameter wires offer a relatively unexplored path to energetic implosions via the creation of a focused axial stagnation of dense wire cores amidst the assembled precursor plasma. Initial studies^a of low wire count loads show promising results with respect to initial inductance and available stagnation energy. Here we examine the trade space of stagnation energy, machine current, implosion time, and delivered mass for several drivers in common use. a. R.E.Terry, J.P.Apruzese, 14th IEEE Pulse Power Conference Proc., June, 2003.
Dynamic Behavior of Axially Functionally Graded Pipes Conveying Fluid
Directory of Open Access Journals (Sweden)
Chen An
2017-01-01
Full Text Available Dynamic behavior of axially functionally graded (FG pipes conveying fluid was investigated numerically by using the generalized integral transform technique (GITT. The transverse vibration equation was integral transformed into a coupled system of second-order differential equations in the temporal variable. The Mathematica’s built-in function, NDSolve, was employed to numerically solve the resulting transformed ODE system. Excellent convergence of the proposed eigenfunction expansions was demonstrated for calculating the transverse displacement at various points of axially FG pipes conveying fluid. The proposed approach was verified by comparing the obtained results with the available solutions reported in the literature. Moreover, parametric studies were performed to analyze the effects of Young’s modulus variation, material distribution, and flow velocity on the dynamic behavior of axially FG pipes conveying fluid.
Liquid Axial Mixing in Packed Tower at Elevated Pressure
Institute of Scientific and Technical Information of China (English)
唐忠利; 张鹏; 等
2003-01-01
Liquid phase axial mixing was measured with the tracer technique in a packed column with inner diameter of 0.15m,in which the structured packing,Mellapak 350Y,was installed.Tap water as the liquid phase flowed down through the column and stagnant gas was at elevated pressure ranging from atmospheric to 2.0MPa.The model parameters of Bo andθwere estimated with the least square method in the time domain.As liquid flow rate was increased,the liquid axial mixing decreased.under our experimental conditions,the effect of pressure on Bo number on single liquid phase was negligible,and eddy diffusion was believed to be the primary cause of axial mixing in liquid phase.
Unsteady cooperative flow type in the axial compressor
Institute of Scientific and Technical Information of China (English)
ZHENG Xinqian; ZHOU Sheng; HOU Anping; XIONG Jinsong
2005-01-01
For increasing the performance of the axial compressor, a method for realizing unsteady cooperative flow type is proposed in this paper as a critical objective in the new generation of the axial compressor design system. Unsteady excitations were utilized to trigger the transformation from the unsteady natural flow pattern into the unsteady cooperative flow pattern, resulting in increment of aerodynamic performances of axial compressor. Numerical simulations show that distinct positive effect can be obtained for the 2D cascade in a wide range of subsonic working conditions. No positive effect can be observed under the 2D supersonic working conditions and unsteady excitations have little influence on the flow field space-time structure. However, positive effect can be obtained under the 3D transsonic working conditions. In addition, engineering applications of unsteady cooperative flow type are discussed.
Investigation of Aluminum-Copper Tube Hydroforming with Axial Feeding
Parto D., M.; Seyedkashi, S. M. H.; Liaghat, Gh.; Naeini, H. Moslemi; Panahizadeh R., V.
2011-01-01
Hydroforming of a two-layered Aluminum-Copper tube is investigated numerically and experimentally. Pressure is applied through a nonlinear path along with symmetrical axial feeding. ABAQUS/Explicit commercial code is used for finite element simulation of the process. ASTM C11000 Copper alloy is used as inner layer and ASTM AA1050A Aluminum alloy is used as outer layer. The simulation results show that the part can be successfully formed under internal pressure of 40 MPa with 8 mm axial displacement. Stress distributions on both inner and outer tubes are compared and maximum thinning on their wall is also discussed. Different friction conditions are applied on the process using different coefficients of friction and their effects are investigated on thinning percentage of inner and outer tubes and also on axial feeding. It is observed that finite element results are in good agreement with experimental results.
Numerical analysis of cavitation within slanted axial-flow pump
Institute of Scientific and Technical Information of China (English)
张睿; 陈红勋
2013-01-01
In this paper, the cavitating flow within a slanted axial-flow pump is numerically researched. The hydraulic and cavitation performance of the slanted axial-flow pump under different operation conditions are estimated. Compared with the experimental hydraulic performance curves, the numerical results show that the filter-based model is better than the standard k-e model to predict the parameters of hydraulic performance. In cavitation simulation, compared with the experimental results, the proposed numerical method has good predicting ability. Under different cavitation conditions, the internal cavitating flow fields within slanted axial-flow pump are investigated. Compared with flow visualization results, the major internal flow features can be effectively grasped. In order to explore the origin of the cavitation performance breakdown, the Boundary Vorticity Flux (BVF) is introduced to diagnose the cavitating flow fields. The analysis results indicate that the cavitation performance drop is relevant to the instability of cavitating flow on the blade suction surface.
Bistability between equatorial and axial dipoles during magnetic field reversals
Gissinger, Christophe; Schrinner, Martin; Dormy, Emmanuel
2012-01-01
Numerical simulations of the geodynamo in presence of an heterogeneous heating are presented. We study the dynamics and the structure of the magnetic field when the equatorial symmetry of the flow is broken. If the symmetry breaking is sufficiently strong, the m = 0 axial dipolar field is replaced by an hemispherical magnetic field, dominated by an oscillating m = 1 magnetic field. Moreover, for moderate symmetry breaking, a bistability between the axial and the equatorial dipole is observed. In this bistable regime, the axial magnetic field exhibits chaotic switches of its polarity, involving the equatorial dipole during the transition period. This new scenario for magnetic field reversals is discussed within the framework of the Earth's dynamo.
Bistability between equatorial and axial dipoles during magnetic field reversals.
Gissinger, Christophe; Petitdemange, Ludovic; Schrinner, Martin; Dormy, Emmanuel
2012-06-08
Numerical simulations of the geodynamo in the presence of heterogeneous heating are presented. We study the dynamics and the structure of the magnetic field when the equatorial symmetry of the flow is broken. If the symmetry breaking is sufficiently strong, the m=0 axial dipolar field is replaced by a hemispherical magnetic field, dominated by an oscillating m=1 magnetic field. Moreover, for moderate symmetry breaking, a bistability between the axial and the equatorial dipole is observed. In this bistable regime, the axial magnetic field exhibits chaotic switches of its polarity, involving the equatorial dipole during the transition period. This new scenario for magnetic field reversals is discussed within the framework of Earth's dynamo.
Mahato, Niladri Kumar; Murthy, S Sathiya Narayana
2013-03-01
The calcaneus is axially loaded at its articular interface with the talus. A large bulk of this load is transmitted to the ground across the non-articular tubercles at the plantar surface of the bone. A small part of the incumbent load sustained by the calcaneus is directed towards the forefoot at the calcaneo-cuboid junction. This study investigates the proportion of load distributed across the articular and non-articular surfaces of the calcaneus. The present study demonstrates strong and significant correlation between some of the load bearing variables and suggests the need for further investigations to understand the effect of angular aspects of axial loading on the calcaneus. Accounting for the relative distribution of weight across the articular and non-articular areas may enable us to appreciate the internal trabecular structure of the calcaneus in light of its clinical importance.
Regional brain axial and radial diffusivity changes during development.
Kumar, Rajesh; Nguyen, Haidang D; Macey, Paul M; Woo, Mary A; Harper, Ronald M
2012-02-01
The developing human brain shows rapid myelination and axonal changes during childhood, adolescence, and early adulthood, requiring successive evaluations to determine normative values for potential pathological assessment. Fiber characteristics can be examined by axial and radial diffusivity procedures, which measure water diffusion parallel and perpendicular to axons and show primarily axonal status and myelin changes, respectively. Such measures are lacking from widespread sites for the developing brain. Diffusion tensor imaging data were acquired from 30 healthy subjects (age 17.7 ± 4.6 years, range 8-24 years, body mass index 21.5 ± 4.5 kg/m(2), 18 males) using a 3.0-Tesla MRI scanner. Diffusion tensors were calculated, principal eigenvalues determined, and axial and radial diffusivity maps calculated and normalized to a common space. A set of regions of interest was outlined from widespread brain areas within rostral, thalamic, hypothalamic, cerebellar, and pontine regions, and average diffusivity values were calculated using normalized diffusivity maps and these regions of interest masks. Age-related changes were assessed with Pearson's correlations, and gender differences evaluated with Student's t-tests. Axial and radial diffusivity values declined with age in the majority of brain areas, except for midhippocampus, where axial diffusivity values correlated positively with age. Gender differences emerged within putamen, thalamic, hypothalamic, cerebellar, limbic, temporal, and other cortical sites. Documentation of normal axial and radial diffusivity values will help assess disease-related tissue changes. Axial and radial diffusivities change with age,with fiber structure and organization differing between sexes in several brain areas. The findings may underlie gender-based functional characteristics, and mandate partitioning age- and gender-related changes during developmental brain pathology evaluation.
Effect of axial groove and resin luting cements on the retention of complete cast metal crowns
Directory of Open Access Journals (Sweden)
K Rajkumar
2009-01-01
Full Text Available Background : The design of the tooth preparation and the cementing medium are important consid-erations in the retention of crowns and fixed partial dentures. The purpose of this invitro study was to determine the effect of axial groove on the retention of complete cast metal crowns using two resin luting cements. Methods: Forty freshly extracted intact human molar teeth were prepared in their long axis to receive complete cast metal crowns. The specimens were randomly divided into two groups (one control and one study group. An axial groove of uniform size and shape was made on the prepared teeth under the study group. Axial surface area of prepared teeth specimens was measured. Complete cast metal crowns were fabricated for each specimen. Specimens of each group were divided into subgroups of 10 samples and were cemented with two resin luting cements, RelyX Unicem® and Calibra®, re-spectively. The cemented crowns were loaded in tension using a Universal Instron testing machine. The maximal tensile strength was recorded. Data were compared using the Mann-Whitney U test (α=0.05. Results: No significant differences in the tensile stress values were noted between the control (mean: 5.76±0.392 MPa and study (mean: 5.93±0.751 MPa groups cemented with RelyX Unicem. No sig-nificant differences in the tensile stress values were noted between the control (mean: 4.92±0.641 MPa and study (mean: 5.15 ±0.478 MPa groups cemented with Calibra. However, significant dif-ference in the tensile stress values was found between the two resin cements in the control and study groups. Conclusion: Axial groove placed in tooth preparations for resin bonded complete cast metal crowns had no statistically significant effect on retention. The use of (RelyX Unicem® yielded greater reten-tion values when compared to Calibra®.
The axial topographic high at intermediate and fast spreading ridges
Carbotte, Suzanne M.; MacDonald, Ken C.
1994-12-01
An axial topographic high is commonly observed at both fast spreading ridges and some segments of intermediate spreading ridges. At fast rates the axial high is primarily created by the buoyancy of hot rock and magma beneath the rise. As newly formed crust is transported off axis, little vestige of an axial high is observed on the ridge flanks. In contrast, at intermediate rates, a significant component of the positive topography may be a volcanic construction, preserved on the ridge flanks as abyssal hills, which are slit axial volcanoes. We suggest this difference in the nature of the axial high reflects a lithosphere strong enough to support construction of a volcanic crestal ridge at intermediate spreading rates, but only rarely at fast rates. Relict overlap ridges, found within the discordant zones left by overlapping spreading centers, is one class of ridge-flank topography which appears to have a significant volcanic constructional component even at fast spreading ridges. Unlike topography away from these discontinuities, the relief and shape of overlapping spreading centers is preserved as relict ridge tips are rafted onto the ridge flanks. Reduced magma supply at these discontinuities may give rise to an axial lithosphere strong enough to support volcanic construction of overlap ridges. Low axial lithospheric strength may also account for the lack of normal faults within the innermost 1-2 km of fast, and some intermediate, spreading ridges. With a thin/weak brittle layer at the ridge crest, tensile failure will predominate and few normal faults will form. Depths to the axial magma chamber reflector observed in multi-channel seismic data limit the thickness of the brittel layer on axis to less than 1-2 km for much of the East Pacific Rise (EPR). This depth is comparable to depths over which tensile failure within the oceanic crust will predominate, estimated from the Griffith criteria for fracture initiation (approx. 0.5-1.5 km). As the brittle layer
Recent Results on High-Pressure Axial Blowers
Eckert, B.
1947-01-01
Considerable progress has, in recent times, been attained in the development of the high-pressure axial blower by well-planned research. The efforts are directed toward improving the efficiencies, which are already high for the axial blower, and in particular the delivery pressure heads. For high pressures multistage arrangements are used. Of fundamental importance is the careful design of all structural parts of the blower that are subject to the effects of the flow. In the present report, several recent results and experiences are reported, which are based on results of German engine research.
The seismic design of axial blower using Ansys
Energy Technology Data Exchange (ETDEWEB)
Im, Hyung Bin; Kim, Kang Sung; Heo, Jin Wook; Chung, Jin Tai [Hanyang Univ., Seoul (Korea, Republic of)
2001-07-01
The seismic design for an axial blower is the procedure in which the Required Response Spectrum(RRS) is computed by using the Floor Response Spectrum(FRS). The seismic design is very important to reduce severe damages from an earthquake; therefore, the seismic design has been a great concern in engineering society. In this study, after finite element modeling is established by using Ansys, the modal data are obtained such as the natural frequencies, the participation factor, and so on. With these data, the RRS is acquired by a numerical approach. The seismic safety of the axial blower is evaluated.
Fermion decoupling and the axial anomaly on the lattice
Banerjee, H; De, Asit K.
1999-01-01
By an explicit calculation of the continuum limit of the triangle graph amplitude in lattice QED we show that in the axial Ward identity the ABJ anomaly exactly cancels the pseudoscalar density term in the limit of infinite fermion mass $m$. The result, a reflection of decoupling of the heavy fermion, provides a convenient framework for computing the flavor-singlet or U(1) axial anomaly in non-Abelian gauge theories on lattice. Our calculations on the lattice are performed using Wilson fermions but the results are general.
Vector and Axial Currents in Wilson Chiral Perturbation Theory
Aoki, Sinya; Sharpe, Stephen R
2009-01-01
We reconsider the construction of the vector and axial-vector currents in Wilson Chiral Perturbation Theory (WChPT), the low-energy effective theory for lattice QCD with Wilson fermions. We discuss in detail the finite renormalization of the currents that has to be taken into account in order to properly match the currents. We explicitly show that imposing the chiral Ward identities on the currents does, in general, affect the axial-vector current at O(a). As an application of our results we compute the pion decay constant to one loop in the two flavor theory. Our result differs from previously published ones.
Self-collimated axial jets from thin accretion disks
Tirabassi, Giulio; Carlevaro, Nakia; Benini, Riccardo
2012-01-01
We show how an appropriate stationary crystalline structure of the magnetic field can induce a partial fragmentation of the accretion disk, generating an axial jet composed of hot rising plasma twisted in a funnel-like structure by the rotation of the system. The most important feature of the obtained jet is its high degree of collimation, naturally arising from the condition for its existence. The presence of non-zero dissipative effects allows the plasma ejection throughout the axial jet and the predicted values of the accretion rate are in agreement with observations.
An effective theory for QCD with an axial chemical potential
Andrianov, Alexander A; Espriu, Domenec; Planells, Xumeu
2013-01-01
We consider the low energy realization of QCD in terms of meson fields when an axial chemical potential is present; a situation that may be relevant in heavy ion collisions. We shall demonstrate that the presence of an axial charge constitutes an explicit source of parity breaking. The eigenstates of strong interactions do not have a definite parity and interactions that would otherwise be forbidden compete with the familiar ones. In this work, we first focus on scalars and pseudoscalars that are described by a generalized linear sigma model; and next, we give some hints on how the Vector Meson Dominance model describes the vector sector.
Instability of Meridional Axial System in f(R) Gravity
Sharif, M
2015-01-01
We analyze dynamical instability of non-static reflection axial stellar structure by taking into account generalized Euler's equation in metric $f(R)$ gravity. Such an equation is obtained by contracting Bianchi identities of usual anisotropic and effective stress-energy tensors, which after using radial perturbation technique gives modified collapse equation. In the realm of $R+\\epsilon R^n$ gravity model, we investigate instability constraints at Newtonian and post-Newtonian approximations. We find that instability of meridional axial self-gravitating system depends upon static profile of structure coefficients while $f(R)$ extra curvature terms induce stability to the evolving celestial body.
Spectral analysis in thin tubes with axial heterogeneities
Ferreira, Rita
2015-01-01
In this paper, we present the 3D-1D asymptotic analysis of the Dirichlet spectral problem associated with an elliptic operator with axial periodic heterogeneities. We extend to the 3D-1D case previous 3D-2D results (see [10]) and we analyze the special case where the scale of thickness is much smaller than the scale of the heterogeneities and the planar coefficient has a unique global minimum in the periodic cell. These results are of great relevance in the comprehension of the wave propagation in nanowires showing axial heterogeneities (see [17]).
Creep Damage Characteristics of Soft Rock under Disturbance Loads
Institute of Scientific and Technical Information of China (English)
Fu Zhiliang; Guo Hua; Gao Yanfa
2008-01-01
This article focuses on the process of rock creep damage and micro-damage evolution properties of gray green mudstone under impacting disturbance load conditions for the first time using the real time computerized tomography (CT) testing technique. The results indicate that axial load comes into limit strength neighborhood, rock micro-crack links into larger crack, creep rate increases in a short time, larger plastic deformation happens; this is called disturbance accelerating creep stage. When rock is within limit strength neighborhood, there occurs creep micro-damage under smaller disturbance load. When disturbance load is larger, rock directly enters into disturbance accelerating creep stage, failure occurs instantaneously. On the basis of experimental research, the CT scanning method was used to describe the creep micro-damage of soft rock, also helpful in the prediction of roadways' service life and evaluation of geotechnicai engineering stability.
Institute of Scientific and Technical Information of China (English)
Yujie LIU; Qing GAO; Guozheng KANG
2011-01-01
Based on the time-dependent strain cyclic characteristics and fatigue behaviors of SS304 stainless steel under multi-axial cyclic loading at 700℃, and in the frameof unified visoco-plastic cyclic constitutive model and continuum damage mechanics theory, the damage-coupled multi-axial time-dependent constitutive model and fatigue failure model were proposed. In the model, the evolution equation of damage was introduced in and the time-dependent effects, e.g. holding time, loading rate, were taken into account. The model was applied to the simulation of whole-life cyclic deformation behaviors and prediction of LCF life for SS304 stainless steel in multiaxial time-dependent low cycle fatigue tests. It is shown that the simulated results agree well with experimental ones.
Constitutive model of rock under static-dynamic coupling loading and experimental investigation
Institute of Scientific and Technical Information of China (English)
LI Xi-bing; ZUO Yu-jun; WANG Wei-hua; MA Chun-de; ZHOU Zi-long
2006-01-01
The importance of study on constitutive model of statically loaded rock experiencing dynamic load is set forth, and the studying methods on dynamic constitutive model are classified according to the current studying status. By way of combining statistic damage model and viscoelastic model, uni-axial and multi-axial constitutive models of statically loaded rock experiencing dynamic load (static-dynamic coupling constitutive model) under intermediate strain rate are established. The verification experiment on 2D constitutive model under different static stress and dynamic stress with different frequencies is designed and performed. It is found that there is a good agreement between the experimental stress-strain curves and the theoretical stress-strain curves.
Regularity of acoustic radiation at ascending load on a pair of friction from a composite material
Directory of Open Access Journals (Sweden)
С. Ф. Філоненко
2013-07-01
Full Text Available In this article the simulation the results of acoustic emission signals formed by friction surfaces with composite materials at load increasing were showed. The results showed that at increase of axial load increases the amplitude of the resulting parameters of acoustic emission signals, such as the average amplitude, its standard deviation and variance. Thus were obtained the basic changes of amplitude parameters generated signals. Was determined that the variation of the percentage increase in the average amplitude, its standard deviation and variance were the same type of character, with well approximate by linear functions. The results showed that with growing of axial load the percent increase in average amplitude of the resulting acoustic emission signals. Also, an analysis of the energy parameters of acoustic emission with increasing axial load on the friction pair with composite materials was conducted. The simulation results showed that the percentage increase in the average level of energy and its standard deviation are approximate by linear functions. At the same time the greatest percentage increase with increasing axial load on the friction pair is observed in the dispersion of the average energy of the resulting acoustic emission signals. The results showed that at experimental study of the acoustic emission signals with increasing axial load on the friction pair with composite materials greatest growth is expected in the average amplitude of the resulting AE signals. The growth of its standard deviation and variance will be not significant. At the same time, the greatest growth is expected in the dispersion of the average energy of acoustic emission signals
THE CRITICAL LOAD PARAMETER OF A TIMOSHENKO BEAM WITH ONE-STEP CHANGE IN CROSS SECTION
Directory of Open Access Journals (Sweden)
Goran Janevski
2014-12-01
Full Text Available The paper analyzes the transverse vibration of a Timoshenko beam with one-step change in cross-section when subjected to an axial force. The axial force is equal in both of the beam portions. Three types of beam which occur commonly in engineering application are considered. The frequency equation of the Timoshenko beam with one-step change in cross-section is expressed as the fourth order determinant equated to zero. The critical compressive axial force is expressed as a function of the critical load parameter which is tabulated for four classical boundary conditions. Apart from the results presented in Tables, the paper also provides calculated values of the critical load parameter for other values of system parameters along with the graphic representation of their dependence on the step position parameter.
Silicon nanowire-based ring-shaped tri-axial force sensor for smart integration on guidewire
Han, Beibei; Yoon, Yong-Jin; Hamidullah, Muhammad; Tsu-Hui Lin, Angel; Park, Woo-Tae
2014-06-01
A ring-shaped tri-axial force sensor with a 200 µm × 200 µm sensor area using silicon nanowires (SiNWs) as piezoresistive sensing elements is developed and characterized. The sensor comprises a suspended ring structure located at the center of four suspended beams that can be integrated on the distal tip of a guidewire by passing through the hollow core of the sensor. SiNWs with a length of 6 µm and a cross section of 90 nm × 90 nm are embedded at the anchor of each silicon bridge along direction as the piezoresistive sensing element. Finite element analysis has been used to determine the location of maximum stress and the simulation results are verified with the experimental measurements. Taking advantage of the high sensitivity of SiNWs, the fabricated ring-shaped sensor is capable of detecting small displacement in nanometer ranges with a sensitivity of 13.4 × 10-3 µm-1 in the z-direction. This tri-axial force sensor also shows high linearity (>99.9%) to the applied load and no obvious hysteresis is observed. The developed SiNW-based tri-axial force sensor provides new opportunities to implement sensing capability on medical instruments such as guidewires and robotic surgical grippers, where ultra-miniaturization and high sensitivity are essential.
Dong, Xiaomin
2016-01-01
An axial flux permanent magnet energy harvester (AFPMEH) is proposed and analyzed for a vehicle magneto-rheological (MR) damper. The relationship between the output voltage and the input excitations are analytically developed. Under different constant rotation speeds and sinusoidal excitations, the harvesting energy is numerically computed for different loads of pure resistance and coil in the MR damper. To check the performance of the proposed AFPMEH for the MR damper, the AFPMEH and MR damper are fabricated individually. Experiments are performed to measure the harvesting energy of the AFPMEH and the damping characteristics of the MR damper under different excited conditions. The excited conditions include three constant rotation speeds and sinusoidal inputs. Load inputs of the pure resistance and the coil of the MR damper are considered. The results show that the time history of the generated voltage of the AFPMEH in experiment is agreed well with that of the AFPMEH in simulation. Under constant rotation speeds, the root mean square (rms) of loaded voltage will increase with the increment of load, whereas the rms of power will be affected by the amplitude of load. The MR damper powered by the AFPMEH can almost obtain the similar damping characteristics of that external power supply. Under sinusoidal inputs, the rms of loaded voltage will increase with the increment of external loads, whereas the rms of power will be almost kept as a constant. The damping range of the MR damper can also be enlarged over 30% comparing to off-state damping force. A quarter car model with an MR damper powered by the AFPMEH is developed to investigate the control performance. The on-off skyhook control is adopted to tune the input current of the MR damper. The vibration performance of the MR suspension is investigated under different roads and vehicle speeds. The numerical results show that the MR suspension with the AFPMEH under on-off skyhook control can achieve better ride comfort
Optimal design of multi-conditions for axial flow pump
Shi, L. J.; Tang, F. P.; Liu, C.; Xie, R. S.; Zhang, W. P.
2016-11-01
Passage components of the pump device will have a negative flow state when axial pump run off the design condition. Combined with model tests of axial flow pump, this paper use numerical simulation and numerical optimization techniques, and change geometric design parameters of the impeller to optimal design of multi conditions for Axial Flow Pump, in order to improve the efficiency of non-design conditions, broad the high efficient district and reduce operating cost. The results show that, efficiency curve of optimized significantly wider than the initial one without optimization. The efficiency of low flow working point increased by about 2.6%, the designed working point increased by about 0.5%, and the high flow working point increased the most, about 7.4%. The change range of head is small, so all working point can meet the operational requirements. That will greatly reduce operating costs and shorten the period of optimal design. This paper adopted the CFD simulation as the subject analysis, combined with experiment study, instead of artificial way of optimization design with experience, which proves the reliability and efficiency of the optimization design of multi-operation conditions of axial-flow pump device.
3-D Simulation of Vertical-Axial Tidal Current Turbine
Directory of Open Access Journals (Sweden)
Zhiyang Zhang
2016-12-01
Full Text Available Vertical-axial tidal current turbine is the key for the energy converter, which has the advantages of simple structure, adaptability to flow and uncomplex convection device. It has become the hot point for research and application recently. At present, the study on the hydrodynamic performance of vertical-axial tidal current turbine is almost on 2-D numerical simulation, without the consideration of 3-D effect. CFD (Computational Fluid Dynamics method and blade optimal control technique are used to improve accuracy in the prediction of tidal current turbine hydrodynamic performance. Numerical simulation of vertical-axial tidal current turbine is validated. Fixed and variable deflection angle turbine are comparatively studied to analysis the influence of 3-D effect and the character of fluid field and pressure field. The method, put the plate on the end of blade, of reduce the energy loss caused by 3-D effect is proposed. The 3-D CFD numerical model of vertical-axial tidal current turbine hydrodynamic performance in this study may provide theoretical, methodical and technical reference for the optimal design of turbine.
On aspects of vibration of axially moving continua
Hageraats-Ponomareva, S.
2009-01-01
In axially moving structures like conveyor belt systems, magnetic tapes, and so on, vibrations occur due to the presence of different kinds of imperfections in the systems. For these structures internal resonances can lead to severe vibrations. Resonance free conveyor belt systems can be constructed
Dynamic Behaviors of Axially Moving Viscoelastic Plate with Varying Thicknessn
Institute of Scientific and Technical Information of China (English)
ZHOU Yinfeng; WANG Zhongmin
2009-01-01
Structural components of varying thickness draw increasing attention these days due to economy and light-weight considerations. In view of the absence of research in vibration analysis of viscoelastic plate with varying thickness, this study devotes to investigate the dynamic behaviors of axially moving viscoelastic plate with varying thickness. Based on the thin plate theory and the two-dimensional viscoelastic differential constitutive relation, the differential equation of motion of the axially moving viscoelastic rectangular plate is derived, the plate constituted by Kelvin-Voigt model has linearly varying thickness in the y-direction. The dimensionless complex frequencies of axially moving viscoelastic plate with four edges simply supported are calculated by the differential quadrature method, curves of real parts and imaginary parts of the first three-order dimensionless complex frequencies versus dimensionless moving speed are obtained, the effects of the aspect ratio, thickness ratio, the dimensionless moving speed and delay time on the dynamic behaviors of the axially moving viscoelastic rectangular plate with varying thickness are analyzed. When other parameters keep constant, with the decrease of thickness ratio, the real parts of the first three-order natural frequencies decrease, and the critical divergence speeds of various modes decrease too, moreover, whether the delay time is large or small, the frequencies are all complex numbers.
View of the Axial Field Spectrometer (R807)
1980-01-01
In this view of the Axial Field Spectrometer at I8, the vertical uranium/scintillator hadron calorimeter (just left of centre) is retracted to give access to the cylindrical central drift chamber. The yellow iron structure served as a filter to identify muons, with MWPCs and the array of Cherenkov counters to the right.
Axially and spherically symmetric solitons in warm plasma
Dvornikov, Maxim
2010-01-01
We study the existence of stable axially and spherically symmetric plasma structures on the basis of the new nonlinear Schrodinger equation (NLSE) accounting for nonlocal electron nonlinearities. The numerical solutions of NLSE having the form of spatial solitions are obtained and their stability is analyzed. We discuss the possible application of the obtained results to the theoretical description of natural plasmoids in the atmosphere.
An axially symmetric solution of metric-affine gravity
Vlachynsky, E J; Obukhov, Yu N; Hehl, F W
1996-01-01
We present an exact stationary {\\it axially symmetric} vacuum solution of metric-affine gravity (MAG) which generalises the recently reported spherically symmetric solution. Besides the metric, it carries nonmetricity and torsion as post-Riemannian geometrical structures. The parameters of the solution are interpreted as mass and angular momentum and as dilation, shear and spin charges.
Further comment on pion electroproduction and the axial form factor
Bernard, V; Meißner, Ulf G; Mei{\\ss}ner, Ulf-G.
2001-01-01
We show that a recent claim (H.Haberzettl, Phys. Rev. Lett. 85 (2000) 3576) that one cannot extract the nucleon weak axial form factor G_A (t) from charged pion threshold electroproduction is incorrect. Thus previous calculations remain valid and threshold charged pion electroproduction experiments can indeed be used to determine G_A (t), and they should certainly be pursued.
The cause of axial rotation of the scoliotic spine
Lemmers, L.G.; Sanders, M.M.; Cool, J.C.; Grootenboer, H.J.
1991-01-01
To explain the cause of axial rotation in a scoliotic vertebral column, the influence of the gravitation force on a spine with a C-scoliosis has been investigated by means of a mechanical model. In this model the gravitation force takes hold of the three-dimensionally curved vertebral column eccentr
On the generation techniques of axially symmetric stationary metrics
Indian Academy of Sciences (India)
S Chaudhuri
2002-03-01
In the present paper, a relationship between the method of Gutsunaev–Manko and the soliton technique (for two-soliton solutions) of Belinskii–Zakharov, for generating solutions of axially symmetric stationary space-times in general relativity is discussed.
Numerical Study of Axial Turbulent Flow Over Long Cylinders
1992-04-01
DATAV [NZ/2, MTH, 3, MR] and as DATAP[NZ/2, MTH, MR], respectively. The first index indicates the axial (streamwise) wave number I = 1, ... , NZ/2...MTH + 12, 12 !5 MTH/2, -[(THGR -1) *MTH + 12- MTH/2], I2> MTH/2. The third index in DATAV indicates the velocity component according to/3 = 3 (1 -4 V
Chondrocyte activity is increased in psoriatic arthritis and axial spondyloarthritis
DEFF Research Database (Denmark)
Gudmann, Natasja Stæhr; Munk, Heidi Lausten; Christensen, Anne Friesgaard
2016-01-01
BACKGROUND: Psoriatic arthritis (PsA) and axial spondyloarthritis (axSpA) are chronic inflammatory rheumatic diseases with complex origins. Both are characterized by altered extracellular matrix remodeling in joints and entheses that results in destructive and osteochondral proliferative lesions...
Etanercept for the treatment of non-radiographic axial spondyloarthritis.
Rios Rodriguez, Valeria; Poddubnyy, Denis
2016-01-01
Presently, tumor necrosis factor α antagonist therapy is the only effective alternative treatment to nonsteroidal anti-inflammatory drugs for the entire spectrum of axial spondyloarthritis, including non-radiographic and radiographic (=ankylosing spondylitis) forms. Recently, etanercept has been approved by the European Medicines Agency for the treatment of non-radiographic axial spondyloarthritis, increasing the number of available treatment options for this indication. The latest data on etanercept concerning clinical efficacy and safety in short-term and long-term treatment of patients with non-radiographic axial spondyloarthritis who do not respond to the first-line therapy with non-steroidal anti-inflammatory drugs suggests good efficacy and safety profiles similar to that observed previously in ankylosing spondylitis. This article reviews recent data on the efficacy and safety of etanercept and is focused on the treatment of non-radiographic axial spondyloarthritis. This article will also discuss the role of etanercept in the context of current and developing treatment options.
A cylindrical drift chamber with azimuthal and axial position readout
Energy Technology Data Exchange (ETDEWEB)
Bar-Yam, Z.; Cummings, J.P.; Dowd, J.P.; Eugenio, P.; Hayek, M.; Kern, W.; King, E.; Shenhav, N.; Chung, S.U.; Hackenburg, R.W.; Olchanski, C.; Weygand, D.P.; Willutzki, H.J.; Brabson, B.B.; Crittenden, R.R.; Dzierba, A.R.; Gunter, J.; Lindenbusch, R.; Rust, D.R.; Scott, E.; Smith, P.T.; Sulanke, T.; Teige, S.; Denisov, S.; Dushkin, A.; Kochetkov, V.; Lipaev, V.; Popov, A.; Shein, I.; Soldatov, A.; Anoshina, E.V.; Bodyagin, V.A.; Demianov, A.I.; Gribushin, A.M.; Kodolova, O.L.; Korotkikh, V.L.; Kostin, M.A.; Ostrovidov, A.I.; Sarycheva, L.I.; Sinev, N.B.; Vardanyan, I.N.; Yershov, A.A.; Adams, T.; Bishop, J.M.; Cason, N.M.; Sanjari, A.H.; LoSecco, J.M.; Manak, J.J.; Shephard, W.D.; Stienike, D.L.; Taegar, S.A.; Thompson, D.R.; Brown, D.S.; Pedlar, T.; Seth, K.K.; Wise, J.; Zhao, D.; Adams, G.S.; Napolitano, J.; Nozar, M.; Smith, J.A.; Witkowski, M. [Massachusetts Univ., North Dartmouth, MA (United States)]|[Brookhaven National Laboratory, Upton, L.I., NY 11973 (United States)]|[Indiana University, Bloomington, IN 47405 (United States)]|[Institute for High Energy Physics, Protvino (Russian Federation)]|[Institute of Nuclear Physics, Moscow State University, Moscow (Russian Federation)]|[University of Notre Dame, Notre Dame, IN 46556 (United States)]|[Northwestern University, Evanston, IL 60208 (United States)]|[Rensselaer Polytechnic Institute, Troy, NY 12180 (United States)
1997-02-21
A cylindrical multiwire drift chamber with axial charge-division has been constructed and used in experiment E852 at Brookhaven National Laboratory. It serves as a trigger element and as a tracking device for recoil protons in {pi}{sup -}p interactions. We describe the chamber`s design considerations, details of its construction, electronics, and performance characteristics. (orig.).
Spiral thickenings in the axial Parenchyma of Chrysobalanaceae
Welle, ter B.J.H.
1976-01-01
Spiral thickenings in the axial parenchyma, seldom recorded in the secondary xylem of the dicotyledons so far, are described for a number of genera and/or species of Chrysobalanaceae. In 66 out of 99 samples investigated, representing most genera of the Chrysobalanaceae, spiral thickenings proved to
On the Applications of Axial Representation of Trigonometric Functions
Siadat, M. Vali
2006-01-01
In terms of modern pedagogy, having visual interpretation of trigonometric functions is useful and quite helpful. This paper presents, pictorially, an easy approach to prove all single angle trigonometric identities on the axes. It also discusses the application of axial representation in calculus--finding the derivative of trigonometric functions.
Observers in spacetimes with spherical and axial symmetries
Gusin, Pawel; Kusnierz, Bartosz; Radosz, Andrzej
2015-01-01
We introduce in the explicit form the tetrads of arbitrary observers in spacetimes with spherical and axial symmetries. The observers confined to the equatorial plane are parametrized by the pair of functions. We apply this description in the analysis of the null-geodesics in the observers' frames. The observers with the constant acceleration are distinguished.
Periodicity effects of axial waves in elastic compound rods
DEFF Research Database (Denmark)
Nielsen, R. B.; Sorokin, S. V.
2015-01-01
Floquet analysis is applied to the Bernoulli-Euler model for axial waves in a periodic rod. Explicit asymptotic formulae for the stop band borders are given and the topology of the stop band pattern is explained. Eigenfrequencies of the symmetric unit cell are determined by the Phase-closure Prin...
Axial dispersion in flowing red blood cell suspensions
Podgorski, Thomas; Losserand, Sylvain; Coupier, Gwennou
2016-11-01
A key parameter in blood microcirculation is the transit time of red blood cells (RBCs) through an organ, which can influence the efficiency of gas exchange and oxygen availability. A large dispersion of this transit time is observed in vivo and is partly due to the axial dispersion in the flowing suspension. In the classic Taylor-Aris example of a solute flowing in a tube, the combination of molecular diffusion and parabolic velocity profile leads to enhanced axial dispersion. In suspensions of non-Brownian deformable bodies such as RBCs, axial dispersion is governed by a combination of shear induced migration and shear-induced diffusion arising from hydrodynamic interactions. We revisit this problem in the case of RBC pulses flowing in a microchannel and show that the axial dispersion of the pulse eventually saturates with a final extension that depends directly on RBC mechanical properties. The result is especially interesting in the dilute limit since the final pulse length depends only on the channel width, exponent of the migration law and dimensionless migration velocity. In continuous flow, the dispersion of transit times is the result of complex cell-cell and cell-wall interactions and is strongy influenced by the polydispersity of the blood sample. The authors acknowledge support from LabEx TEC21 and CNES.