In this paper, multi two step variable amplitude load fatigue testing of spot-welded joints was carried out, and experimental values and values obtained by minor’s rule were compared. In addition, similar fatigue testing in high-tensile steel sheet SPFC590 was performed, and the possibility of fatigue life estimation by using the nominal structural stress was examined. (1) The experimental values of the fatigue life were greater than the estimated value if n₂/n₁ ≧ 1000. It revealed experimentally that the factor was a delay phenomenon of the crack growth caused by peak load. (2) Fatigue test results of SPFC590 showed a different tendency from that of SPCE. The fatigue life is substantially constant when n₂/n₁ ≧ 100, and were close to the estimated value using the nominal structural stress.

Fatigue damage of spot-welded joints by loading range below the fatigue limit under multi two steps variable amplitude load is estimated by the degree of influence α, according to the modified minor's rule. However, the verifying by experiment is not sufficient. The crack growth rate of the high loading range under variable amplitude is equal to the crack growth rate in the constant amplitude. Therefore, the crack propagation length caused by the high load ranges is the same as that of the constant amplitude. In this study, the crack length in single spot-welded joints under constant amplitude was observed. As a result, fatigue damage due to loading range below the fatigue limit can be evaluated by using the degree of influence α.

In order to investigate very high cycle fatigue properties of improved cold work steels, rotating bending fatigue tests were conducted at room temperature. Two types of fatigue specimens were provided to examine the effect of extracted direction to rolled direction of the material on fatigue strength. Time strength distributions at N=5×10⁶ cycles are estimated by the corresponding values along regression lines. In addition, fracture surfaces were observed by scanning electronic microscope (SEM).

In order to clarify the influence of various shaped surface crack on fracture strength of Al₂O₃/SiC ceramics, three-point bending tests were carried out. The tilted surface cracks or multiple surface cracks were introduced on the specimen surface. Test results showed that √area is available as a representative parameter of defect size for fracture strength evaluation. Evaluation equation of fracture strength based on the process zone size fracture criterion and the √area parameter was proposed. The predicted fracture strengths were in good agreement with the experimental fracture strengths.

In order to clarify the effect of punching process on fatigue strength properties of thin steel sheets, tension-compression fatigue tests were conducted. For the fatigue tests, processed and unprocessed specimens were prepared. The unprocessed specimen had the same shape as the processed specimen but had no punching process effect on the steel. Before the fatigue tests, hardness and residual stresses were measured. From the measurements, hardening near the punching processed surface, and positive residual stress were obtained. From the fatigue tests, fatigue lives and the fatigue crack behavior were obtained. By using these results, the effects of punching process were discussed.

This paper provides an estimation method of surface crack depth induced by wire EDM based on the fracture dynamics in case of electric conductive ceramics, Zirconia. The fracture dynamics model was used for this analysis. The cracks were evaluated experimentally by two other different methods. One of them was derived from ground removal amount of the W-EDMed surfaces that can recover the fracture strength. The other was derived from the rest of the crack depth and ground amount of the surface. These estimated values were compared to clarify the surface crack depth induced by W-EDM condition. A prediction method for the surface crack depth was considered based on the experimental results.

Icing is one of important problems that has to be prevented in jet engine of airplane. If thin ice layer deposited on the surface of blade is detached in fight, the debris is scattered and then impacts to a rear stage blade. Such impact of the debris could bring about catastrophic fracture of the blades. Numerical simulation is a powerful tool to understand how the icing is grown and detached. Thus, the icing phenomenon has been focused on the stand point of fluid mechanics. However, the knowledge for mechanical property of ice itself and the adhesion of the ice layer was still very poor. The aim of this study is to examine about the mechanical property including Young's modulus and fracture toughness and adhesive strength at a low temperature. As a result, it was found that the mechanical property and adhesive strength are strongly affected by testing temperature and loading speed.

In this study, the tensile behavior of TiNi super elastic alloy under various hydrogen environments was investigated by using thin wires with various diameters. Ductility and tensile strength of TiNi super elastic alloy which absorbed hydrogen decreased. At the same charging time, tensile strength decreased with decreasing wire diameter. Compared TiNi super elastic alloy with TiNi shape memory alloy, tensile strength of TiNi super elastic alloy is higher than that of TiNi shape memory alloy in spite of hydrogen charging times. However, there is little difference in growth behavior of brittle layer formed by hydrogen charging between TiNi super elastic alloy and TiNi shape memory alloy.

In this paper, the amount of variation in the fatigue life due to variations in the spot welding location and the nugget diameter of three spot-welded joints subjected to bending loading was determined quantitatively by sensitivity analysis. As a result, the effect on fatigue life due to variations in spot welding location was found to approximately the same as that of the nugget diameter. Further, the amount of change in fatigue strength due to the thickness for the tensile shear joints with nugget diameter5√t include components due to changes in nugget diameter. Both components have been separated by a sensitivity analysis. The ratio of the sheet thickness component and the nugget diameter component was 7:3. These analytical results were confirmed by the fatigue test.

In this study, effect of kinking damage on fatigue fracture behavior of PBO (Poly-p-Phenylene Benzobisoxazole) fiber was investigated in monofilament fatigue tests. Two types of the PBO fibers were used in the experiment. One was the conventional type. The other was high-modulus type with a higher crystal orientation than the conventional type. Kinking damages was created on surface of virgin fiber by winding bundle fibers to steel rod set to 0.625 mm. Load-controlled fatigue tests were carried out using a sinusoidal load with frequency 10 Hz and stress ratio of R = 0.5, and the load cell capacity was 10 N. It was found that fatigue strength with kinking damage was lower than that without kinking damage in neither AS fiber and HM fiber. Fatigue strength decrease of AS fiber and HM fiber with kinking damage in a low cycle area was larger than that in a high cycle area. The fatigue fracture of PBO fiber with kinking damage presented the different aspect at a high cycle area and a low cycle area in neither AS fiber and HM fiber.

We made a shear loading test on a “key support” which consisted of a shear key and upper and lower plates with keyways. We applied a horizontal displacement on the upper plate under a stable vertical load. During the test, the key showed the shear deformation and rotating displacement. With the rotation, the edge of the key raised the plate. After the edge was apart from the upper plate, the key support showed the ultimate strength against horizontal loading. The shear loading test under the different vertical load showed the similar deformation and rotation, but the ultimate strength differed from another vertical load case. This result indicated that the ultimate strength of the key support against horizontal load was dependent on the vertical load.

We numerically simulated a shear loading test of a shear key, and evaluated the mechanical behavior of the shear key with rolling and plastic deformation. We considered that the load-displacement relationship was influenced by contact condition of the key and the upper key plate, and compared the load-displacement relationship with rolling and deformation of the shear key. The horizontal load increased until the edge of key lifted the upper key plate. After the edge of key lifted the upper key plate, the gradient of load-displacement curve became small and the horizontal load became almost constant. Next, we conducted simulation with different condition of vertical load, and investigated the influence on horizontal load. The result of investigation showed the tendency that the maximum horizontal load became larger as the vertical load became larger. This result showed that the maximum horizontal load, nearly equal to the load of horizontal actuator necessary to lift upper key, seemed to be decided by the vertical load.

Delamination failure is one of the most important engineering issues for rolling contact machine elements. It is known that this failure is intimately related to shear-mode (mode II and mode III) fatigue crack growth. Generally, the shear-mode fatigue crack growth behavior and its threshold condition can be greatly influenced by the crack face interference. Therefore, understanding of the mechanism of friction and surface damage of crack faces is of importance and a new testing method that can examine appropriately these properties is required. In this study, the influences of the cyclic reciprocating sliding contact with micro-scale relative motion on the frictional behavior and the surface damage of a bearing steel were studied under dry condition. As a novel friction and wear testing method, a cyclic ring-on-ring test was conducted by making use of a hydraulic-controlled combined axial and torsional fatigue testing machine. The coefficient of kinetic friction was ranged from 0.4 to 1.0, the average value being about 0.75.

The effect of shot peening on the wear resistance of partially stabilized zirconia (PSZ) was investigated. PSZ plate specimens with shot peening (SP), without SP (Non-SP), and polished specimens after SP (SP+Polished) were prepared. Ball on plate tests were carried out using the specimens in air under dry condition. The wear volume of SP specimens was higher than Non-SP specimens, however, that of SP+Polished specimens was lower than that of Non-SP. The wear resistance of SP+Polished specimens increased because the surface dents introduced by SP were removed and the compressive residual stress and surface hardness were the highest among the specimens. This result indicates that the combination of SP and polishing is an effective method to increase the wear resistance of PSZ.

It is clarified that the frictional properties for material surface is controllable by machining a micro-pattern on the surface. In the previous research, it is considered that strain of materials such as spring-back can be reduced by controlling the frictional characteristics in the blank holder during the press forming. However, evaluation only by the experiment is difficult due to huge combinations between the shape of micro patterns and the arrangement density. Therefore, evaluation by numerical simulations is necessary for present study. In this research, evaluation of effects by the differences of the shape of micro-patterns and the arrangement density is conducted by the experimental method and numerical simulation.

The part of rail joint becomes the causes of the disadvantage points such as the ride discomfort, the undesired sound and the track maintenance, etc.. For restraining those points, the long rail made by welding the standard length rails has been developed. However, the problems of the overhang or the breakage caused by bucking have been pointed out. Therefore, several evaluation techniques for managing those have been proposed. In the previous study, we had presented the relationship between the increases of compression stress and the behaviors of the ultrasonic echo to that stress. Concretely, it was shown that there is high correlation between the increase of the maximum wavelet coefficient of that echo and each load stress. In this study, the compression test to the actual rail were carried out. As the results, it was proven that the coefficient was effective for the stress estimation because the correlation between the stress and the coefficient was provided.

The main method of analysis of interior stress is the division methods of test samples. Therefore, we need the specific skill to divide test samples. This research analyzes interior strain by formulation through geometric analyzing displacement and calculates interior stress. Therefore, we don't need the skill and knowledge of dividing test samples and we can analyze interior stress with a few formulations in a row. Also, we can calculate with fewer calculations in comparison to FEM. Comparing this result with FEM, the results are nearly the same in all cases except for the surface area.

In this study, a method for separating the value of the nominal structural stress, which was obtained by the nominal structural stress calculation method, on the value of each general loads component of nugget has been proposed. Since the stress and displacement of the circular plate by peeling load is the axis of symmetry, the boundary displacements are constant in the circumferential direction. Boundary displacement caused by the torsion is only a circumferential component, which is a constant value. Focusing on these viewpoints, the value of the nominal structural stress was separated values for each general loads. The proposed method was applied to the LP model, which is a spot welded structure. As a result, the usefulness of this method has been confirmed.

Graphene is the two-dimensional carbon allotrope. Graphene has a lot of remarkable properties which are useful for mechanical and electronic properties. Therefore, the application of graphene is expected in various fields. However, there are not useful methods to measure strain components in graphene. In this study, crystallographic orientations and strain measurements in single-layered graphene are conducted by polarized Raman microspectroscopy. Graphene has A_1g and doubly degenerate E_2g Raman active vibration modes. The changes of Raman intensities of each Raman line with polarization angle of irradiation laser are theoretically derived and the theoretical changes show good agreement with experimental results. Four point bending tests of graphene on cupper or silicon substrates are conducted. Under the strong bending strain, the doubly degenerate E_2g vibration mode splits in two modes, and the distance between these spitted peaks increases with increasing the applied strain. In A_1g an E_2g modes, the relationships between Raman shift and applied strain indicate the linearity with different slopes. Therefore, applicability of polarized Raman micro spectroscopy to strain measurements is confirmed.

We derive a solution for two elliptical voids that are free boundary to an elastic medium (matrix) of infinite extent under anti-plane problem. These two voids have different long and short radii and different central points. When there are two voids in the matrix, we consider the matrix as a part of poroelastic matrix. The matrix is subjected to arbitrary loading, for example, by uniform stress and concentrated force and so on. The solution is obtained as a series with an explicit general term involving the complex potential of the corresponding homogeneous problem. This procedure is referred to as heterogenization. Several numerical examples are presented with graphs.

Ice is one of the most common brittle solid materials in our life, but its physical properties such as those of inelastic collision and dynamic fracture, have not been entirely comprehended so far. In our former research, we have utilized our high-speed digital video camera and the numerical ED (Event-Driven) method to study the mechanical behavior of ice spheres colliding against a plate of ice. We have quantitatively clarified the influence of the relative impact velocity on the behavior of ice as a granular material. Here, we perform further dynamic impact experiments in our laboratory and three-dimensional numerical simulations of wave propagation and interaction to try to deepen our understanding of the mechanism of fracture development in ice spheres subjected to impact loading.

The purpose of this study is to research influence of mass of impactor on impact strength of an acrylic resin plate. Impact bending specimens were made of the resin plate thickness of 5mm. Different mass impactors were prepared. Two type three-point bending devices were used for this study. One type is for low mass impactors. This device shoots the impactors by compressed air. Another type is for high mass impactors. In this device, the impactor falls down through an acrylic resin tube. The minimum velocities required for fracture of the specimens were measured by a velocity sensor attached in devices. From the velocities and the mass of impactor, kinetic energies were calculated. From the experiments, rate dependence of the kinetic energy required for breaking the specimen was confirmed. In the low-mass range, the kinetic energy increased with the increase in the mass of impactor. On the other hand, in the high- mass range, the kinetic energy decreased with the increase in the mass. This boundary mass was 100g. In the low mass range, this phenomenon may be due to loading rate dependence in mechanical properties of this material. When the loading rate is high, the acrylic resin shows the brittle property. In the high mass range, the velocity of the impactor is low and the kinetic energy decreases by the mass effect of the impactor.

In the Charpy impact tests, the he absorbed energy of specimen are treated as material toughness. However, fracture mechanics approach are required for crack problems in materials. In this study, some experimental results are derived using two type specimens under various collision speeds. Numerical simulations for crack propagation in the Charpy specimen are operated based on the absorbed energy in these experiments. The dynamic J integral is calculated in numerical singular deformation field around crack tip. Similar numerical fracture toughness are indicated from the numerical simulations based on some experimental conditions.

Some dynamic fracture are caused by high speed collision. If defect is appeared near impact zone, crack propagation behavior from the defect depend on some factor about the collision. In this study, authors focused dynamic three point bending fracture experiments using sharp edge striker. Small slant of striker is assumed in numerical simulations. Dependence of fracture behavior on the slant angle of striker are discussed based on dynamic J integral distribution along crack tip front.

In this study, dynamic stress simulationwas carried out to investigate the stresses of the multilayer ceramic capacitor. Loading conditions were obtained from split hopkinson pressure bar tests. Simulations were carried out with a large scale simulator ADVENTURE Cluster which was based on FEM.The effect of time increment on maximum bending stress were discussed with implicit method and explicit method.Simulation resultsshowed that bending stresswith implicit method were found to be a slightlydifferent from the stresswith explicit method.

The multiplicative elastoplastic constitutive equation is formulated based on the extended subloading surface model with the translation of the elastic-core. It is to be the only unconventional elastoplasticty model extended to the multiplicative hyperelastic-based plasticity model which is capable of describing finite deformation/rotation exactly.

The novel evolution equations of the normal-yield ratio will be formulated in this article, which excludes the defects: 1) It is inapplicable to the cyclic loading behavior under variable stress amplitudes ranging from low and high stress levels, 2) It is requires the judgment whether the normal-yield ratio reaches the threshold value of elastic limit instead of the yield judgement.

The yield stress under cyclic load after applying the large simple shear to the specimens is estimated based on the Natural Strain theory. As for the method of determination of yield stress in each cycle, the tangent modulus in the principal deviatoric stress and deviatoric strain curve is adopted in the present study. Then, the change of yield stress with an increase of cycle number is examined under conditions of different size of pre-deformation and the different strain amplitude of simple shear. Moreover, the experimental results obtained from this method are compared with the results from the conventional proof stress.

The subloading surface model excluding a purely-elastic domain is capable of describing the cyclic loading behavior. The initial subloading surface model was extended to consider damage phenomenon to describe macroscopic softening behavior and degradation of Young's modulus by accumulation of microscopic damage. To describe the cyclic loading behavior more accurately, the extended subloading surface damage model is formulated introducing the damage effect that consider unilateral effect based on damage mechanics.We simulate elastoplastic damage behaviors of metal to assess availability proposed algorithm.

La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ (LSCF) is a mixed ionic-electronic conductor and one of the candidates to be used for oxygen separation membrane and cathode material for solid oxide fuel cell. The ionic conductivity of LSCF, which is still by several orders of magnitude lower than its electronic conductivity, needs to be further improved for higher performance of those devices. This study investigates a variation of oxygen deficiency of LSCF under uniaxial compression. An electrochemical cell consisting of YSZ (yttria stabilized zirconia )/LSCF/YSZ with glass sealing was prepared. The coulometric titration method was employed. The result demonstrated that the oxygen deficiency decreased by 0.0058 under 80 MPa of stress. The estimation based on the mechanical and thermo-chemical-mechanical properties, the oxygen deficiency could decrease by ~0.006 when the uniaxial compressive stress of 100 MPa is applied, which shows a relatively good agreement with the experimental result.

Dielectric elastomers, as a type of electroactive polymers, have shown great potential for applications. In this study, electromechanical properties of nylon fibers and styrene bars reinforced dielectric elastomer actuators (DEA) are evaluated. As a result the curvature of the styrene bars reinforced DEA is larger than that of the nylon fiber reinforced DEA at a given voltage. Moreover, the time dependence and cyclic dependence of the styrene bars reinforced DEA are investigated and discussed.

With the development of nanotechnology in recent years, many researchers have focused on the development of nanomaterials and nanostructures. To apply these nanomaterials and nanostructures into nanodevices, the measurement technology for measuring electrical properties at high spatial resolution has been requested. Therefore, our group has developed Microwave Atomic Force Microscopy (M-AFM) in order to assess electrical conductivity in a minute area. This paper describes influence of material surface on the measurement of local electrical conductivity using M-AFM. Results of this experiment indicate actually that M-AFM can measure electrical conductivity in a local area accurately without being affected by the material surface.

With the development of nanotechnology, different types of scanning probe microscopy (SPM) have been developed to satisfy the requirement of nanotechnology. The microwave detection system is combined on the atomic force microscopy (AFM) to evaluate the electrical properties of the materials simultaneously. It is found that when microwave is applied through the probe, the microwave has interaction with the material. In this paper, the mechanism of the interaction between the microwave and material is investigated. We evaluated the probes by the microwave atomic force microscope (M-AFM) and verified our theoretical work. The result implies that the interatomic force between the tip and sample can be utilized to evaluate the permittivity of semiconductor and insulator materials.

A Herbert pendulum is a pendulum type hardness tester. In Herbert hardness test, the pendulum with indenter as a fulcrum swings on the specimen and swing angle of the pendulum is measured. Hardness is evaluated using logarithmic decrement (damping hardness). In this study, damping hardness of metals, ceramics and plastics are measured. Correlations between damping hardness and mechanical properties are clarified for metals, ceramics and plastics. Damping hardness of metals and ceramics decreases with increase Vickers hardness. However, correlation between damping hardness and bending strength cannot be observed for ceramics and plastics.

Weight lighter is an essential technology in the aviation industry. Lattice structure has a very potential as a lightweight. Also Lattice structure has facilitated produced in 3D printers. However, 3D printer is under development, and has left a lot of challenges. In previous paper (2), in a tensile test of the lattice structure manufactured by the 3D printer, the maximum load of the test specimen was less than the maximum load of the analysis model. We predicted that the large surface roughness of the specimen is the cause. For its verification, we created detailed specimen CAD model including the roughness using an X-ray micro-CT scan. As a result of FEM analysis, the maximum load of the specimen manufactured by the 3D printer was found to be reduced.

The purpose of this research is to increase energy density and efficiency of electric generator made by dielectric elastomer (DE). With pure shear loading configuration, the energy density and efficiency was compared by controlling constant voltage and constant current. It was found that the energy density and efficiency with constant current method was higher than those with constant voltage method. Moreover, it was indicated that both the energy density and the efficiency increase with an increase in charging voltage.

Since UV photopolymer used in the MEMS is not excellent mechanical properties, it is necessary to improve the mechanical properties by composite materials. There are Cellulose Nano Fibers(CNF) in one of the reinforcement. Since It has Hydrophilic Groups, it is difficult to disperse by adding CNF to general hydrophobic photopolymer. For that reason mechanical properties were also decreased. In this study, we created a composite material by adding CNF to UV photopolymer. And we discussed the effects of the various addition conditions on the dispersibility of the CNF, and the effect of the mechanical properties evaluated by tensile testing of micro-specimens. Previous studies have used a method to freeze-drying the CNF, but the tensile strength has fallen greatly decreased. We were dispersed CNF in the photopolymer by Replacing water of CNF slurry in acetone by using centrifugation. Because it has improved dispersibility of the CNF, it was possible to suppress a decrease in fracture strain.

Nanowire (NW) is one-dimensional nanostructure with the diameter in nanoscale. Currently, we can fabricate NWs made from metal, metal oxide and semiconductor which could be utilized in various applications. In our previous study, we investigated a new fabrication method of Al NWs with high growth density by stress migration. It is generally known that Al is high conductivity and inexpensive material, therefore this method for mass production of Al NWs has a big advantage. However, the mechanism of fabrication has not been clear. In this study, we investigated the effect of surface roughness and etching depth induced by focused ion beam etching on the growth density of Al NWs. As a result, we found that etching depth strongly affects the growth density of Al NWs.

Currently, solar cells aremainlymade fromSi.However, due to the high cost and the limited resources of Si, new materials for solar cells are still needed. It has been proved that Cu₂O solar cells have a high theoretical energy conversion efficiency with a very low cost. However, the actual efficiency of Cu₂O solar battery is much lower than theoretical value. In this research, Cu₂O/Cu core-shell NWs are fabricated on the surface of the solar cell by the AAO template method to increase light receiving area. As a result, we succeed in fabricating Cu₂O/Cu core-shell NWs. The surface area of the solar cell is increased to about 151 times, which improve the solar energy conversion efficiency. And, we also find that the density of NWarrays effects the solar energy conversion efficiency.

In this study, atmospheric-controlled induction-heating fine particle peening (AIH-FPP) treatment was performed to modify high-temperature oxidation resistance of S45C steel. Cr and Ni particles were mechanically milled by planetary ball mills and used as shot particles of AIH-FPP treatment to create modified layer containing Cr and Ni element. High-temperature oxidation test was carried out to evaluate high-temperature oxidation resistance of AIH-FPP treated specimens. Created particles and specimens were analyzed using a scanning electron microscope (SEM), an energy dispersive X-ray spectrometer (EDX) and an X-ray diffraction (XRD). Results showed that AIH-FPP treated specimen exhibited better high-temperature oxidation resistance than untreated specimen.

The scaffold has been used to form a three-dimensional tissue in tissue engineering. It has been known that not only the mechanical properties of scaffold, but also the mechanical stress affect the cell function and tissue structure. However, it is difficult to observe the effect of mechanical stress on each cell in the case of the three-dimensional scaffold. In this study, the effect of tensile strain on the cell adhesion and cell proliferation ratio by using the planar nylon mesh scaffold was investigated. It was found that the cell proliferation ratio increased in case of large strain. It was suggested that the high stress effectively worked to cell proliferation.

This study deals with the computational modeling of growth phenomena typically encountered in biomaterials based on the continuum mechanics. Constitutive law of growing hyperelastic material is described as an initial value problem analogous to the finite strain elasto-plasticity theory. The implementation of this constitutive law into finite element methods is detailed. Some applications to the development of living tissue are presented.

This paper describes the relation between the flattening phenomenon in the cross section and the visco-plastic behavior in the catheter made of soft nylon resin reinforced with thin stainless wires. In particular, the flattening phenomenon occurs when the torsional moment is applied after axial load. Therefore, in this study, the occurrence region of the flattening phenomenon is examined based on the visco-plastic theory. In consideration of the shape of cross section gradually changing into the elliptical shape during the process of applying the torsional moment, the experimental equation for the torsional moment is derived based on the shear flow theory for determining the occurrence region of flattening phenomenon. Especially, in the present study, considering actual usage conditions of the catheter, the experiments are conducted in water condition and non-water condition.

The morphology and function of articular cartilage tissue is regenerated through the metabolic activity of cells stimulated by the mechanical loading. In this study, a biphasic multi-scale analyses scheme is adopted for stress evaluation occurred in the chondrocyte cell. The dynamic-explicit finite element (FE) method was employed for the solid phase and the smoothed particle hydrodynamics (SPH) method was used for the fluid phase. A macro-scale 3D human knee joint FE model was constructed based on magnetic resonance (MR) cross sectional images. Further, we derived the Representative volume element (RVE) based on the Multiphoton microscopy (MPM) observation to build a micro-scale FE model of cartilage tissue. We characterized three layers in the articular cartilage tissue. Parameters of the visco-anisotropic hyperelastic constitutive law and SPH models were determined using experimental results. Biphasic multi-scale FE and SPH analyses were carried out under the maximum loading condition in the normal walking motion. As a result, large flow velocity was observed around chondrocyte in the surface layer. The highest hydrostatic and shear stress occurred on chondrocyte in the surface layer. Numerical results shows a good agreement with experimental results.

In this study, the mechanical properties of a balloon catheter were examined under tensile loading condition. In the joint part, the outer tube fractured first, while in the shaft part, the inner tube fractured. The load-displacement curve of the joint part was well predicted using the Todo's model. The stress-strain curves of the inner and outer tubes were also well predicted using the total deformation theory with use of an exponential function for the stress-plastic strain relation.

Recently, there has been increase in demand for the biodegradable stent from the medical field. However, the ductility for expansion or the strength to sustain the tubular tissue of pure magnesium is not sufficient. Therefore this research aimed to develop the biodegradable magnesium alloy with combination of improved ductility and sufficient strength. The microstructure of magnesium ingot alloyed with Zinc and Calcium was improved by hot extrusion. To confirm the applicability of the developed ternary alloy to the stent, finite element analysis for expansion of the stent and the sustainability was conducted. The stent model was successfully expanded and the expansive force was enough to maintain the diameter. This result means that Mg-Zn-Ca alloy possessed excellent strength-ductility balance for the biodegradable stent.

In this paper, the compression post-buckling behavior of the rectangular plate with simply support on four sides, although without constraining in-plane displacement of two long side ends, are discussed using the effective width theory by Karman and the deflection equation of the plate. The out-of-plane and compressional in-plane displacements, and the stress distribution of the post-buckling with respect to compressive load are derived, and compared with the results by finite element method (FEM). The results are following; the derived equations of out-of-plane and in-plane displacements are sufficiently consistent with the results by FEM. The derived stress distribution shows intermediate characteristics.

This paper presents a re-formulation of the extended subloading surface model within the `unconventional plasticity' concept applicable to cyclic loadings. In addition to the usual additive decomposition of the small strain tensor into elastic and plastic parts, we primarily make a kinematic assumption in which the plastic strain tensor is further additively decomposed into an energetic and dissipative parts. The energetic part of the plastic strain is related to the back-stress for kinematic hardening via a hyperelastic-like constitutive equation without using a rate-type evolution law for the back-stress. Based on a similar idea, we introduce another additive decomposition of the plastic strain, and thereby a nonlinear evolution for the elastic-core tensor, i.e. a key internal variable in the extended subloading surface model, which stands for a stress state where the material exhibits most elastic responses, can be introduced in a reasonable way.

In metal forming, importance of precise fracture prediction has been increased. However, as the use of anisotropic cold rolled metals such as aluminum alloy sheets increased, fracture prediction has become difficult. In this study, fracture initiation is represented as the result of local bifurcation, which is analyzed mechanically reasonably by using a local bifurcation theory. To represent local bifurcation appropriately, we have adopted the 3D bifurcation theory based on the anisotropic plastic constitutive equation in which the rotation of stress rate tensor is introduced to express plastic instability. To evaluate this constitutive equation, the non-associated flow rule material model that has been proposed by the author is applied. In this report, fundamental formulas and analytical examples on formability evaluation are presented.

Kirigami is a traditional art of papercraft, which makes 3 dimensional structure from 2 dimensional sheet. Recent years, the mathematical foundations of kirigami and origami have been developed as well as the practical applications. In this research, we analyze the out-of-plane deformation of kirigami structrue under tensile force, and investigate the mechanism of the deformation based on beam theory. We simulate the process from in-plane deformation to out-of-plane deformation using molecular dynamics, and discuss the effect of stability and geometry parameters.