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Thin-wall parts have the advantages of light weight and high structural strength and are widely used in industrial fields. As the increasing requirements for the form accuracy and surface quality, ultra-precision cutting has been increasingly used to manufacture thin-walled parts. However, due to the small effect range (less than 10  μ m) of residual stress caused by ultra-precision cutting, it cannot be accurately measured by the conventional methods. Therefore, the research on the residual stress and deformation of thin-walled parts under ultra-precision cutting are currently restricted. In this paper, we first introduced the GIXRD method to solve the technology absence for measuring the ultra-precision cutting conducted residual stress. Based on GIXRD, TEM and dynamic interferometer measurement, the relationship between grain state, residual stress and deformation of thin-walled parts was established. The research works had shown that reducing the cutting depth within a certain range was beneficial to reduce residual stress and deformation. However, there was an extreme point of the cutting parameter. If this extreme point was exceeded, the cutting action would gradually transform from shearing to pressing and pushing, resulting in an increase in residual stress. Therefore, there was an extremely small cutting parameter that minimized residual stress and deformation of the thin-walled member. The results were helpful to understand the mechanism of deformation of thin-walled parts from the perspective of grain size and residual stress, and accordingly established a deformation control method. [ABSTRACT FROM AUTHOR]

This paper analyzes two failure cases of creep-caused fracture of PbSn solder joint, including the joint between the wire and solder cup in the connector and the joint between the integrated circuit (IC) pins and the printed circuit board (PCB). The environment conditions, for the creep of PbSn solder joint is demonstrated, including the temperature and stress level. The stress origin and fracture morphology are summarized based on the failure analysis. Besides, the developing process of creep-caused fracture is explained. The paper comprehensively clarifies the creep mechanism of PbSn solder and consequently provides significant guidance for the reliable electronic assembly to avoid the creep-caused damage. [ABSTRACT FROM AUTHOR]

The frequency dependency property of viscoelastic material leads to the dynamic analysis of compound structures which are complex and costly. Furthermore, using commercial finite element software, it is difficult to carry out the dynamic response analysis with this characteristic. Based on finite element iterative and modal strain energy (MSE) method, a mode superposition algorithm was proposed to solve the dynamic response of viscoelastic damping structure in this paper. Through iterative and MSE method, the modal frequency and loss factor for each mode can be obtained. Before calculating the next order modal frequency, the modal mode and corresponding load are extracted and the response of node was calculated at first in this algorithm. As a consequence, the node displacement response can be solved by summarizing the response results of each independent mode in the required frequency range. Numerical calculation of U shaped pipe with viscoelastic damping layer illustrates that the method is simple and practical. Moreover, the simulations with this method agree quite well with the experimental derived results. In the meantime, the damping layer parameters study shows that the position of the damping layer has an obvious effect of reducing the vibration response of U shaped pipe, but the width of the damping layer has little influence. The procedure proposed in this paper can be extended to analyze other more complex structures with viscoelastic material. [ABSTRACT FROM AUTHOR]

The mechanical response of spherical indentation of superelastic shape memory alloys (SMAs) was theoretically studied in this paper. Firstly, the friction effect was examined. It was found that the friction influence is negligibly small. Secondly, the influence of the elasticity of the indenter was investigated. Numerical results indicate that this influence can not be neglected as long as the indentation depth is not very small. After that, this paper focused on the effect of transformation volume contraction. Our results show that the transformation volume contraction due to forward martensitic transformation can reduce the maximum indentation force and the spherical indentation hardness. These research results enhance our understanding of the spherical indentation responses, including the hardness of the smart material SMAs. [ABSTRACT FROM AUTHOR]

This paper presents a modified Split Hopkinson Pressure Bar (SHPB) technique to obtain compressive stress strain data for NBR rubber materials. An experimental technique with a modified the conventional SHPB has been developed for measuring the compressive stress strain responses of materials with low mechanical impedance and low compressive strengths, such as the rubber and the polymeric material. This paper uses an aluminum pressure bar to achieve a closer impedance match between the pressure bar and the specimen materials. In addition, a pulse shaper is utilized to lengthen the rising time of the incident pulse to ensure dynamic stress equilibrium and homogeneous deformation of NBR rubber materials. It is found that the modified technique can determine the dynamic deformation behavior of rubbers more accurately. [ABSTRACT FROM AUTHOR]

In particle or short-fiber reinforced composites, cracking of the reinforcements is a significant damage mode because the cracked reinforcements lose load carrying capacity. This paper deals with an incremental damage theory of particle or short-fiber reinforced composites. The composite undergoing damage process contains intact and broken reinforcements in a matrix. To describe the load carrying capacity of the cracked reinforcement, the average stress of a cracked ellipsoidal inhomogeneity in infinite body, which was proposed in the previous paper is introduced. An incremental constitutive relation of particle or short-fiber reinforced composites including the progressive cracking damage of the reinforcements have been developed based on the Eshelby's equivalent inclusion method and Mori and Tanaka's mean field concept. Influence of the cracking damage on the stress-strain response of the composites is demonstrated. [ABSTRACT FROM AUTHOR]

In this paper, the transport properties of the band-to-band-tunneling carbon nanotube field-effect transistors (BTBT-CNTFETs) under uniaxial strain are studied, with the nonequilibrium Green's function (NEGF) formalism. The effects of the uniaxial strain on the electrical properties, such as the ON current (ION)> OFF current (IOFF), ION/IOFF ratio, subthreshold swing and intrinsic delay are evaluated. It was observed that the uniaxial strain has strong effects on the transport properties of these transistors. The results show that appropriate uniaxial strain, although degrades the ON current and the intrinsic delay, it also decreases the power consumption of the BTBT-CNTFETs and as a result can be used for low-power applications. [ABSTRACT FROM AUTHOR]

In this paper, we study the preparation of titanate/polypyrrole core-shell rod-like composite particles. The mere titanate rod-like particles were prepared as core material and PPy was polymerized on their surface in different amounts. Rheological measurements showed that under an applied external electric field, shear stress of these materials significantly increased with amount of PPy in the shell layer. The yield stresses obtained from the Cho-Choi-Jhon model were correlated with dielectric properties of suspensions. Polarizability as a measure of particle polarization obtained from Havriliak-Negami model of dielectric spectra increases with the content of PPy in the samples. Furthermore, role of particle concentration and silicone oil viscosity was also investigated. [ABSTRACT FROM AUTHOR]

The End Coupling is the main component of the aluminum hot rolling equipment. The End Coupling is used for transmission of rotational power with heavy-duty load. Fracture of the End Coupling causes serious economic losses because an End Coupling is a very expensive component and it takes a long time to repair it. Therefore, preventing the destruction of the End Coupling is essential for ensuring a long mechanical life cycle. In this paper, a parameter study on the End Coupling was performed in order to minimize maximum stress of the End Coupling under static loads. As a result of an optimum design for life extension on the End Coupling, the maximum stress of the modified End Coupling was lower than that of the initial model by 29%. The fatigue analysis for fatigue life prediction of the modified End Coupling was performed using the commercial finite element method. In the results of the fatigue life analysis, the safety factor of the modified End Coupling was 1.123. Therefore, it was demonstrated that the modified End Coupling has infinite life. [ABSTRACT FROM AUTHOR]

This paper presents an oblique incidence technique for characterizing the ultrasonic nonlinearity of a stainless steel 316L alloy subjected to high-cycle fatigue testing. A rectangular hourglass-shaped specimen was prepared, and various fatigue-driven deformations were accumulated at several positions near the middle of the specimen. These locations were chosen to correspond to areas likely to exhibit stress concentration responses resulting in slip and dislocation evolution. The nonlinearity increased significantly near the center of the specimen and thus was strongly correlated with fatigue damage. An oblique incidence technique using longitudinal waveforms is a potentially viable method for characterizing the high-cycle fatigue deformation of 316L alloys. [ABSTRACT FROM AUTHOR]

In the present paper, a technique is presented for obtaining estimates for the natural frequencies of axisymmetric vibration for transversely isotropic material. The wave propagation of harmonic waves in hollow cylinder of transversely isotropic materials subjected to certain boundary conditions is studied. The two-dimensional equations of elastodynamic are solved in terms of displacement by using the technique of variables separation. The natural frequency of the plane vibrations in the case of harmonic vibrations has been obtained. The natural frequencies are calculated numerically and the effects of rotation is discussed. The numerical results obtained have been illustrated graphically to understand the behavior of natural frequency versus the ratio h. Comparisons are made with the result in the absence of rotation. [ABSTRACT FROM AUTHOR]

In this paper, we use molecular dynamics (MD) simulations and a modified analytic embedded-atom method to investigate the edge dislocation movement without imposed strain at 0 K. The obtained results indicate that the straight lines of the partial dislocations always preserve their original shapes and are parallel to each other during the simulation process. According to the energy of each atom, the positions of both partial dislocation cores are determined. Then the velocities in the period of the relaxation process are investigated in detail. The MD simulations reveal that the MD relaxation time dependence of the edge dislocation mobility is divided into two parts. First, during the initial period ranging from 0 to 6 ps, the relative velocity of the dislocation movement lineally increases with the incremental relaxation time. Second, in the latter period from 6 ps to the end of the simulated process the velocity decreases exponentially as the MD simulation time evolves. [ABSTRACT FROM AUTHOR]

In this paper the frictional heating effect on the propagation of surface crack under Hertzian contact loading based on the fracture mechanics is investigated. For the theoretical analysis of this effect, we estimated stress intensity factor of surface crack -tip in shear mode under Hertzian contact sliding friction. Theoretical results showed those thermal loads (Th), Peclet number (Pe) and crack angle (β) are very important factors on the propagation of surface crack under Hertzian contact loading. When thermal load(Th) and Peclet number(Pe) are constant, maximum variable range of stress intensity factor, ΔKII, is located in the range of surface crack angle 130°~150°. Non-dimensional parameter T consisting of thermal load and peclet number for evaluating ceramic wear behavior is introduced. [ABSTRACT FROM AUTHOR]

In the present paper we consider two representative methods for residual stress evaluation at the micro-scale: a (semi-)destructive method involving material removal and the measurement of strain relief; and a non-destructive X-ray diffraction technique involving the use of micro-focused synchrotron X-ray beam. A recently developed strain relief approach is described using a Focused Ion Beam (FIB) to create a circular trench of progressively increasing depth around a circular "island". Residual stress is evaluated by the comparison of the strain relief (measured by digital correlation of displacements or strains) with Finite Element simulations. The technique is illustrated for a thin TiN coating layer. The second approach uses focused synchrotron X-ray beams for white beam Laue diffraction. Demonstration experiments described involve in situ loading of commercially pure nickel foil. Procedures for validation and improvement of accuracy are discussed. [ABSTRACT FROM AUTHOR]

The present paper investigates the cross-sectional morphology of Multiwalled Carbon Nanotubes (MWNTs) restrained radially and circumferentially by an infinite surrounding elastic medium, subjected to uniform external hydrostatic pressure. In this study, a two-dimensional plane strain model is developed, assuming no variation of load and deformation along the tube axis. We find some characteristic cross-sectional shapes from the elastic buckling analysis. The effect of the surrounded elastic medium on the cross-sectional shape which occurs due to pressure buckling is focused on by the comparison with the shape for no elastic medium case in our discussion. It is suggested that in no embedded elastic medium cases, the cross-sectional shapes of inner tubes maintain circle or oval; on the other hand, an embedded medium may cause inner tube corrugation modes especially when the number of shells for MWNTs is small. [ABSTRACT FROM AUTHOR]

Laue diffraction, energy scanning and reciprocal space mapping are three micro-beam synchrotron X-ray diffraction techniques allowing the investigation of local misorientation induced by the dislocation substructure. In this paper a comparison between the three methods is presented, based on the mapping of a single 311 reflection from a grain within a Ni polycrystal specimen deformed to a tensile plastic strain of ~9%. Qualitatively it is observed that the maps obtained by different techniques all share the same features, although some deviations exist due to experimental limitations associated with each of the measurement techniques. [ABSTRACT FROM AUTHOR]

With the miniaturization of parts, size effect occurs. The isothermal forming processes are performed to obtain homogenizing deformation. In the paper, a serial of isothermal upsetting tests are carried out with billets of different dimensions. Difference of flow stress is accepted as the parameter to evaluate the size dependence of flow stress on billets dimensions. The experimental results show that size effect occurs clearly. With the increasing of temperature, the difference of flow stress becomes smaller, which means that the degree of size dependence is reduced. Scatter of flow stress is observed in the tests at room temperature. When the deformation temperature is raised, the fluctuation of flow stress tends towards decreasing. In order to investigate the effect of grain size, different grain size is obtained with the heat treatment process. At the same temperature, the difference of flow stress increases with the increasing of grain size. These phenomena can be explained from the viewpoint of polycrystalline structure of material. The anisotropy of individual grain is appeared obviously, which leads the fluctuation of flow stress. In the isothermal deformation, the effect of single grain is smaller than that at room temperature. [ABSTRACT FROM AUTHOR]

The paper aims at a numerical study of strength and deformation behaviors of rocks under different loading conditions in uniaxial compression with an elasto-plastic cellular automaton (EPCA2D) code. Two loading conditions, i.e. with and without considering frictions between loading platens and rock specimen's ends, are used in the failure processes of heterogeneous rocks. Rock specimens are assumed to be the same heterogeneity, i.e. the specimens with different sizes have the same probability of containing flaws. Under this condition, it is concluded that the strength and deformation behaviors of rocks are influenced by the heterogeneity a little. The mismatch of elastic properties of the platen and the rock in influencing the stress distribution at the ends of the specimen is the dominant cause for the so-called strength and deformation size effects, which in turn affects the final failure patterns of rocks. [ABSTRACT FROM AUTHOR]

In this paper, a two-dimensional nonlinear elastic-plastic mass-spring-damper-rod element model is employed to simulate the crush behavior of metallic foams. The density heterogeneity and pore fluid of metallic foams are considered. The metallic foams are compressed by applying a planar pulse loading or by giving a deformation rate. Several numerical results show the deformation patterns and the energy absorption regime of metallic foams under crush loading. The influence of heterogeneous density, cell fluid, loading intensity, deformation rate on the deformation and the energy absorption of metallic foams is assessed. [ABSTRACT FROM AUTHOR]

This paper deals with plastic deformations of a high tensile strength steel sheet (HTSS sheet) under biaxial stress condition including strain path. Using a cruciform specimen of a HTSS sheet of 780MPa-TS, experiments under proportional and non-proportional loadings were investigated. Numerical simulations of stress-strain responses for several strain paths after biaxial stretching were conducted using a large-strain cyclic plasticity model (Yoshida-Uemori model). The results of numerical simulation agrees well the corresponding experimental results, which is attributed to the accurate modeling of the backstress evolution of the anisotropic yield function. [ABSTRACT FROM AUTHOR]

Many materials exhibit a stress range dependent creep behavior. The power-law creep observed for a certain stress range changes to the viscous type creep if the stress value decreases. Recently published experimental data for advanced heat resistant steels indicates that the high creep exponent (in the range 5-12 for the power-law behavior) may decrease to the low value of approximately 1 within the stress range relevant for engineering structures. The aim of this paper is to confirm the stress range dependence of creep behavior based on the experimental data of stress relaxation. An extended constitutive model for the minimum creep rate is introduced to consider both the linear and the power law creep ranges. To take into account the primary creep behavior a strain hardening function is introduced. The material constants are identified for published experimental data of creep and relaxation tests for a 12%Cr steel bolting material at 500°C. The data for the minimum creep rate are well-defined only for moderate and high stress levels. To reconstruct creep rates for the low stress range the data of the stress relaxation test are applied. The results show a gradual decrease of the creep exponent with the decreasing stress level. Furthermore, they illustrate that the proposed constitutive model well describes the creep rates for a wide stress range. [ABSTRACT FROM AUTHOR]

In this paper, some available analytical models for the complete stress-strain curve for high-strength concrete (HSC) under uniaxial compression are examined and compared with experimental curves published in the literature. Based on these findings, a new analytical constitutive relation is proposed to generate the complete stress-strain curves for normal weight concrete subjected to uniaxial compression with a strength range of 60-120MPa. To demonstrate the validity of the model, comparisons are made with published experimental data for uniaxial compressive tests on high-strength concrete specimens. The present model is shown to give a quite good representation of mean behavior of the actual stress-strain response. [ABSTRACT FROM AUTHOR]

This paper is to understand and model the thermomechanical response of the rotary forged WHA, uniaxial compression and tension tests are performed on cylindrical samples, using a material testing machines and the split Hopkinson bar technique. True strains exceeding 40% are achieved in these tests over the range of strain rates from 0.001/s to about 7,000/s, and at initial temperatures from 77K to 1,073K. The results show: 1) the WHA displays a pronounced changing orientation due to mechanical processing, that is, the material is inhomogeneous along the section; 2) the dynamic strain aging occurs at temperatures over 700K and in a strain rate of 10-3 1/s; 3) failure strains decrease with increasing strain rate under uniaxial tension, it is about 1.2% at a strain rate of 1,000 1/s; and 4) flow stress of WHA strongly depends on temperatures and strain rates. Finally, based on the mechanism of dislocation motion, the parameters of a physically-based model are estimated by the experimental results. A good agreement between the modeling prediction and experiments was obtained. [ABSTRACT FROM AUTHOR]

As a lead-free solder, Sn96.5Ag3Cu0.5 has a wide application in electronic packaging. Since the solder materials usually work under cyclic temperature surroundings, creep constitutive relationships and cyclic behaviors are necessary to carry out the thermal stress analysis of a package with such a solder for its strength and life evaluations. This paper has investigated the creep constitutive relationships by constant (non-cyclic) loadings firstly, based on the creep test results at various stress and temperature levels. The complete form of the constitutive relationship containing both the linear viscous and hyperbola-sine creeps is proposed. Secondly, through the tests under cyclic stress loadings, the cyclic stress-strain relationships have been illustrated. [ABSTRACT FROM AUTHOR]

Drillstring is the most important tool in petroleum drilling engineering. Alternating stress has been found to be responsible for the premature failure of drillstring. Propagation of stress wave, induced by collision between tool-joints of drillstring and borehole wall, is studied in this paper. The condition that all the tool-joints of drill pipes (DPs) strike borehole wall at the same time has been considered. Because of symmetry, the middle cross section of the DP is simplified as fixed end, and mechanical model is established as the beam with both ends fixed. Propagation of lateral displacement wave and stress wave in the DP is investigated by means of Eigen-frequency method and the Finite Element Analysis software ANSYS. The theoretic results coincide with those obtained from numerical modeling very well and also explain the drillstring accidents in gas fields. [ABSTRACT FROM AUTHOR]

This paper introduces the jig set for the crash test and the crash test results of shear bolts which are designed to fail at train crash conditions. The tension and shear bolts are attached to Light Collision Safety Devices(LCSD) as a mechanical fuse when tension and shear bolts reach their failure load designed. The kinetic energy due to the crash is absorbed by the secondary energy absorbing device after LCSD are detached from the main body by the fracture of shear bolts. A single shear bolt was designed to fail at the load of 250 kN. The jig set designed to convert a compressive loading to a shear loading was installed to the high speed crash tester for dynamic shear tests. Two strain gauges were attached at the parallel section of the jig set to measure the load responses acting on the shear bolts. Crash tests were performed with a carrier whose mass was 250 kg and the initial speed of the carrier was 9 m/sec. From the quasi-static and dynamic experiments as well as the numerical analysis, the capacity of the shear bolts were accurately predicted for the crashworthiness design. [ABSTRACT FROM AUTHOR]

This paper is concerned with the evaluation of the dynamic failure load in the lap-shear tests of a spot weld. Dynamic lap-shear tests of a spot weld in SPRC340R were conducted with different tensile speeds ranging from 5×10-5 m/sec to 5.0 m/sec. Dynamic effects on the failure load of a spot weld are examined based on the experimental data. Experimental results indicate that failure strength increases with increasing loading rates. Finite element analyses of dynamic lap-shear tests were also performed considering the failure of a spot weld. A spot weld is modeled with a beam element and dynamic failure model is utilized in order to describe the failure of a spot weld in the simulation. The failure loads obtained from the analyses are compared to those from the lap-shear tests. The comparison shows that the failure loads obtained from the analyses are close in consistence with those obtained from the experiments. [ABSTRACT FROM AUTHOR]

The objective of this paper is to investigate into impact behaviors of a STS 304 sheet with a thickness of 0.7 mm in a free boundary condition subjected to impact loading by a hemispherical impact head using drop impact tests and the three-dimensional FE analyses. The drop impact tests and the FE analyses were conducted with different impact energy ranging from 37.0 J to 45.7 J. From the results of the impact tests, the influence of the impact energy on the force-deflection curve, the absorption mechanism of the impact energy and deformation behaviors of specimen were examined quantitatively. Through the FE analyses, the variation of stress-strain distributions and characteristics of the local deformation during the impact of the specimen were investigated. [ABSTRACT FROM AUTHOR]

This paper deals with the crashworthiness of an aluminum crash box for an auto-body with the various shapes of cross section such as a rectangle, a hexagon and an octagon. First, crash boxes with various cross sections were tested with numerical simulation to obtain the energy absorption capacity and the mean load. In case of the simple axial crush, the octagon shape shows higher mean load and energy absorption than the other two shapes. Secondly, the crash boxes were assembled to a simplified auto-body model for the overall crashworthiness. The model consists of a bumper, crash boxes, front side members and a sub-frame representing the behavior of a full car at the low speed impact. The analysis result shows that the rectangular cross section shows the best performance as a crash box which deforms prior to the front side member. The hexagonal and octagonal cross sections undergo torsion and local buckling as the width of cross section decreases while the rectangular cross section does not. The simulation result of the rectangular crash box was verified with the experimental result. The simulation result shows close tendency in the deformed shape and the load–displacement curve to the experimental result. [ABSTRACT FROM AUTHOR]

This paper aims to study dynamic properties of loess. This study is helpful to the subject on how to avoid or decrease the seismic disasters on loess ground. Dynamic triaxial tests are carried out with saturated remoulded soil samples taken form loess sites in Xi'an, China. Dynamic stress and strain relationship as well as the rule of the accumulated residual strain are obtained from the test results. Linear relationship between accumulated residual strain and vibration circle under constant amplitude circular loading is presented. A hypothesis about the accumulated residual strain is proposed. 1D dynamic constitutive relationship model which can well describe the real relationship between dynamic stress and strain under irregular dynamic loading is established. Numerical program with this model is developed and an example is tested. Numerical results of hysteresis loop, accumulated residual strain, amplitude of dynamic stress and damping ratio show good agreement with test results. It is indicated that the hypothesis of accumulated residual strain and the 1D dynamic constitutive relationship model can accurately simulate the dynamic triaxial tests of saturated remoulded loess. [ABSTRACT FROM AUTHOR]

This paper is concerned with development of a process map for sequential compression-backward extrusion of bulk AZ31 Mg alloy at the warm temperatures. In experiments, metal flows and crack initiations are carefully investigated and formability is examined systematically for various forming conditions such as forming temperature, punch speed, and a gap between a specimen and die. Then, a process map for the sequential compression-backward extrusion of bulk AZ31 Mg alloy at the warm temperature is proposed. In order to further understand deformation behaviors and damage evolution during warm forming process, thermo mechanical finite element analyses coupled with damage evolutions are carried out. In general, finite element predictions support experimental observation. Finally, it is concluded that the process map, proposed for the sequential compression-backward extrusion of AZ31 Mg alloy, is valid. [ABSTRACT FROM AUTHOR]

Metal forming processes such as hydroforming and sheet metal forming using tubular material and thin sheet metal have been widely used in lots of industrial fields for manufacturing of various parts that could be equipped with mechanical products. However, it is not easy to design sequential processes properly because there are various design variables that affect formability of the parts. Therefore preliminary evaluation of formability for the given process should be carried out to minimize time consumption and development cost. With the advances in finite element analysis technique over the decades, the formability evaluation using numerical simulation has been conducted in view of strain distribution and final shape. In this paper, the application of forming limit criteria is carried out for the tube hydroforming and sheet metal forming processes using theoretical background based on plastic instability conditions. Consequently, it is confirmed that the local necking and diffuse necking criteria of sheet are suitable for formability evaluation of both hydroforming and sheet metal forming processes. [ABSTRACT FROM AUTHOR]

At present, the failure criteria used in calculating the ultimate bearing capacity of soil slope are the Tresca and Mohr-Coulomb criteria. But the results are conservative and the potential strength of soil mass cannot be utilized sufficiently because these two criteria do not take into account the effect of the intermediate principal stress. In this paper the unified strength theory was used to analyze the ultimate bearing capacity of soil slope. The formula for calculating the ultimate bearing capacity of soil slope using the unified strength theory was established. At the end, a case history was analyzed and it indicated that the result of the unified strength theory is larger than that of the Mohr-Coulomb criterion. This indicates that calculation of ultimate bearing capacity of soil slope with the unified strength theory can sufficiently exploit the strength of material. Therefore, the calculation of ultimate bearing capacity of the soil slope based on the unified strength theory will be of great significance in future applications. [ABSTRACT FROM AUTHOR]

A small-batch product of large-sized parts is usually manufactured using incremental open-die forging. In order to control the overall change in the shape of a part, it is essential to be able to predict the shape changes that occur during each step. This paper addresses shape changes of a material according to the forging path. Rapid prediction of metal flows for continuing incremental deformation using theoretical methods is difficult. Accordingly, instead of a theoretical approach, an experiment that tests the tendency of the metal flow for development of forming processes is required. For the sake of convenience, simulative experiments are carried out using plasticine at room temperature. In present study, the tool movement is dominant parameters to with respect to changing the shape of the workpiece. [ABSTRACT FROM AUTHOR]

In this paper, top joint method is proposed to solve a practical engineering problem of temperature stress and temperature crack of super-long slab-column structure bearing temperature difference. From the study, it is shown that as for super-long slab-column structure undergoing temperature difference of inside and outside, joint located in bottom stories nearly has no influence on temperature stress and deformation while joint in top stories can significantly reduce temperature stress and deformation of super-long slab-column structures. In addition, comparison of joints located in top one story, top several stories and from bottom to top stories indicates that influences of them on temperature stress and deformation are similar. As for top joint method, among which cantilever plate method, double column method and corbel method are discussed and results indicate that influence effects of these methods on structures are similar. [ABSTRACT FROM AUTHOR]

In this paper an explicit dynamic finite element method model has been developed to investigate the strip deformation behavior between two adjacent stands in hot finishing mill. The effect of the roll speed ratio of second stand to first stand on tension and the tailing behavior of the strip has been discussed in details. It has been found that the strip accumulation occurs if the roll speed ratio is small. The tensile stress increases with the roll speed ratio. During the tailing process the accumulated strip caused by the small roll speed ratios knocks onto the roll, while the swing of the strip tail occurs for the large roll speed ratios and it strikes the roll as well. Both tailing phenomena will result in the strip tail pincher or roll damage in the real operation. [ABSTRACT FROM AUTHOR]

Shape control is always a key issue in the six-high rolling mill, in which the shifting of the intermediate roll and the work roll have been used to enhance the shape control capability. In this paper, a finite element method (FEM) model has been developed to simultaneously simulate the strip deformation and the roll stack deformation for the six-high rolling mill. The effects of the work-roll bending, the shifting of the intermediate roll and the work roll on the strip crown and edge drop are discussed in details. Results have shown that both higher bending force and more roll shifting will significantly reduce the strip crown. The edge drop is also reduced with the bending force and the roll shifting. [ABSTRACT FROM AUTHOR]

Customers for cold rolled strip products expect the good flatness and surface finish, consistent metallurgical properties and accurate strip thickness. These requirements demand accurate prediction model for rolling parameters. This paper presents a set-up optimization system developed to predict the rolling force during cold strip rolling. As the rolling force has the very nonlinear and time-varying characteristics, conventional methods with simple mathematical models and a coarse learning scheme are not sufficient to achieve a good prediction for rolling force. In this work, all the factors that influence the rolling force are analyzed. A hybrid mathematical roll force model and an adaptive neural network have been improved by adjusting the adaptive learning algorithm. A good agreement between the calculated results and measured values verifies that the approach is applicable in the prediction of rolling force during cold rolling of thin strips, and the developed model is efficient and stable. [ABSTRACT FROM AUTHOR]

This paper developed a hydro-elasto-plastic method to describe the mechanical behavior of the metal material under explosion load. Based on this method, the EXPLOSION-2D hydrocode was developed, and the shaped charges with steel liner and copper liner were numerically simulated, respectively. The simulation results agree well with experimental ones, which show that the proposed method is efficient for engineering design. [ABSTRACT FROM AUTHOR]

A material identification program AFDEX/MAT is presented in this paper. The program is based on the method for acquiring true stress-strain curves over large range of strains using engineering stress-strain curves obtained from a tensile test coupled with a finite element analysis. In the method, a tensile test is analyzed using a rigid-plastic finite element method combined with a perfect analysis model for its associated simple bar to provide the information of deformation. An initial reference true stress-strain curve, which predicts the necking point exactly, is modified iteratively to minimize the difference in tensile force between the experiments and predictions of the tensile test. It was applied to identifying the mechanical behaviors of two new pre-heat treated steels of ESW95 and ESW105 and a conventional Cr-Mo steel of SCM435. The predictions are compared with the experiments for the tensile test of the three materials, showing an excellent similarity. [ABSTRACT FROM AUTHOR]

Three-dimensional precision simulation of pore closing during cylinder upsetting is carried out in this paper. A matrix of pores on the longitudinal section of a cylindrical material is traced at the same time. Various ratios of pore-to-cylinder diameter are tested to reveal their effect on the pore closing phenomena. Hydrostatic pressure and effective strain as well as the order of pore closing are investigated in detail to find out major factors affecting pore closing. It is shown that the effective strain has a strong relationship with the pore closing phenomena and that the finishing time of pore closing increases as the ratio of pore-to-cylinder diameter increases but that the pore size effect becomes negligible if the ratio exceeds a critical value. An intelligent metal forming simulator AFDEX 3D is used. [ABSTRACT FROM AUTHOR]

During past decades, substantial studies on the external bonding of fiber reinforced polymer (FRP) strips to deficient reinforced concrete (RC) beams have been carried out for the well-known superior properties of the FRP. Several shear prediction models have been established by using the effective strain of the FRP or introducing an ultimate stress discount coefficient. And the latest design concept is the use of stress distribution factor. In this paper, an equivalent effective strain model of the FRP is presented, which contains the concepts of maximum strain, stress distribution factor and critical shear crack angle influences. To develop a simple and accurate approach for such equivalent effective strain, major influenced factors are investigated and analyzed by the statistical independent hypothetic tests on a database of 128 RC beams wrapped by the FRP. Finally, a simple and rational shear design proposal is given, which is more accurate than the existing models using the above database. [ABSTRACT FROM AUTHOR]

Split Hopkinson Pressure Bar (SHPB) has become a frequently used technique for measuring uni-axial compressive stress-strain relationship of various engineering materials under high strain rates. The pulse shape generated in the incident bar is sensitive to the length of the striker bar. In this paper, a finite element simulation of a Split Hopkinson Pressure Bar is performed to estimate the effect of varying length of striker bar on the stress-strain relationship of a material. A series of striker bars with different lengths, from 200mm to 350mm, are employed to obtain the stress-strain response of AL6061-T6 in both simulation and experiment. A comparison is made between the experimental and the computed stress-strain curves. Finally the influence of variation of striker bar length on the sample's stress-strain response is presented. [ABSTRACT FROM AUTHOR]

A series of dynamic triaxial tests are performed on normal anisotropic consolidation and over anisotropic consolidation specimens of loess. Based on the test results, the variable regularity of dynamic shear stress, axial strain and pore water pressure of loess under dynamic loading are measured and analyzed. The influences of the dynamic shear strength and pore water pressure at different over consolidation ratio are analyzed. The relationship between dynamic shear strength and over consolidation ratio of loess is obtained. The evaluating standard of dynamic shear strength of loess is discussed. Meanwhile, how to determine the effective dynamic shear strength index of normal anisotropic consolidated loess is also discussed in this paper. Several obtained conclusions can be referenced for studying the dynamic shear strength of loess foundation. [ABSTRACT FROM AUTHOR]

Due to the difference of nanotube diameters, the single-walled carbon nanotubes (SWCNTs) show the different energy and mechanical properties. In order to take the effect of the curvature of nanotubes into account in the modeling of those structures, the present paper proposes an atomistic based continuum model with using a type of modified Cauchy-Born to link the continuum strain energy to the interatomic potential. This modified Cauchy-Born is developed by incorporating the concept of differential mean value theorem into the standard Cauchy-Born rule. The present model not only can bridge the microscopic and macroscopic length scales, but also can investigate the curvature effect of a single layer film on the continuum level. Application of the current model to armchair carbon nanotubes and graphite shows an excellent prediction of the size dependent strain energy which are compared in a good agreement with the existing experimental and theoretical results. [ABSTRACT FROM AUTHOR]

In this paper, deformation behavior of Polymethylmethacrylate (PMMA) during thermal indentation was demonstrated by the finite element method using ABAQUS S/W. Forming conditions to reduce the elastic recovery and pile-up were proposed. Thermal nanoindentation experiments were carried out at the temperature range of 110 ~ 150 °C. The indenter was modeled as a rigid surface. The finite element analysis (FEA) approach is capable of reproducing the loading-unloading behavior for a thermal nanoindentation test and thus comparison between the experimental data and numerical results were demonstrated. The result of the investigation will be applied to the fabrication of the hyper-fine pattern. [ABSTRACT FROM AUTHOR]

This paper deals with the crash energy absorption and the local buckling characteristics of the expansion tube during the tube expanding processes. In order to improve energy absorption capacity of expansion tubes, local buckling characteristics of an expansion tube must be considered. The local buckling load and the absorbed energy during the expanding process were calculated for various types of tubes and punch shapes with finite element analysis. The energy absorption capacity of the expansion tube is influenced by the tube and the punch shape. The material properties of tubes are also important parameter for energy absorption. During the expanding process, local buckling occurs in some cases, which causes significant decreasing the absorbed energy of the expansion tube. Therefore, it is important to predict the local buckling load accurately to improve the energy absorption capacity of the expansion tube. Local buckling takes place relatively easily at the large punch angle and expansion ratio. Local buckling load is also influenced by both the tube radius and the thickness. In prediction of the local buckling load, modified Plantema equation was used for strain hardening and strain rate hardening. The modified Plantema equation shows a good agreement with the numerical result. [ABSTRACT FROM AUTHOR]

This paper focuses on a fundamental understanding of the plastic deformation mechanism in monocrystalline silicon subjected to nanoindentation. It was found that over a wide range of indentation loads from 100 μN to 30 mN and loading/unloading rates from 3.3 μN/s to 10 mN/s, the plasticity of silicon is mainly caused by stress-induced phase transitions. The results indicate that the critical contact pressure for phase transition at unloading is almost constant, independent of the maximum indentation load (Pmax) and loading/unloading rates. However, the shape of the load-displacement curves greatly relies on the loading/unloading conditions. In general, higher Pmax and lower unloading/loading rates favor an abrupt volume change and thus a discontinuity in the load-displacement curve, commonly referred to as pop-in and/or pop-out events; whereas smaller Pmax and rapid loading/loading processes tend to generate gradual slope changes of the curves. This study concludes that the difference in the curve shape change does not indicate the mechanism change of plastic deformation in silicon. [ABSTRACT FROM AUTHOR]

Equal channel angular pressing provides a convenient procedure for introducing an ultrafine grained microstructure into materials. In this paper, the deformation distribution of cylindrical billet with different diameters during equal channel angular pressing (ECAP) was simulated using 3D finite element models. The plastic strains in three perpendicular planes of the billet are predicted. And the influence of the friction between billet and channel on the equivalent plastic strain is also determined. The results show that the equivalent plastic strains are inhomogeneous in three directions and the inhomogeneity of the strain distribution inside ECAPed materials is slightly related to their diameters, which means larger scale UFG materials can be achieved via ECAP process. [ABSTRACT FROM AUTHOR]

This paper is concerned with the load-carrying capacities of a circular sandwich panel with metallic foam core subjected to quasi-static pressure loading. The analysis is performed with a newly developed yield criterion for the sandwich cross section. The large deflection response is estimated by assuming a velocity field, which is defined based on the initial velocity field and the boundary condition. A finite element simulation has been performed to validate the analytical solution for the simply supported cases. Good agreement is found between the theoretical and finite element predictions for the load-deflection response. [ABSTRACT FROM AUTHOR]