The Gurson model is extended by incorporating the subloading surface model in this article so as to describe the smooth elastic-plastic transition and possess the automatic controlling function to attract the stress to the yield surface and thus the stress is pulled-back to the yield surface when it goes out from the surface in numerical calculation with finite loading increment.

In this study, in order to establish the accurate evaluation method of fatigue properties of materials with compressive residual stress at surface applied by surface treatments, tension-compression fatigue tests were carried out under various kinds of compressive mean stresses by using ASTM CA6NM stainless cast steel with two control modes. In the case of the load control mode, the lower the mean stress value, the higher the fatigue limit because the setting stress level was loaded simply if the mean stress value beyond the compressive yield limit. In the case of the strain control mode, specimens yielded greatly at the first cycle, then the mean stress didn't change to the tensile side with increasing the loading cycles and continued to load at the same stress level. As the results, the fatigue life decreased remarkably and specimens fractured early in comparison with a case of fatigue tests under the load control mode because shakedown behavior was occurred.

To cope with the higher output of the engine, crankshaft is made to satisfy the required performance by heat treatment. During heat treatment, residual stress due to the phase transformation occurs. Therefore, not only the stress amplitude at the time of operation, it is necessary fatigue life prediction of complex stress state in consideration of the residual stress. In the past, a material modeling of non-heat treated carbon steel was reported sing the two scale model of the continuum damage mechanics, and subjected to life prediction in consideration of the average stress. In this study, the analysis method is applied to quenched crankshaft, to verify the usefulness of this study.

A study for diagraming and formulating fatigue strength of notched and un-notched specimens has been developed. As a result, two fundamental and important concepts have been proposed; a hypothesis of cyclic plastic adaptation and a size effect criterion based on a normalized yield zone growth curve. From the former concept, an equivalent cyclic stress ratio is derived as a primary parameter correlating a cyclic stress condition of the notched specimen with that of the un-notched specimen, and a fatigue strength diagram is formulated for a large-sized notch and un-notch type specimen. From the latter, a secondary parameter quantifying concretely the size effect is derived and inserted in the equation of the fatigue strength diagram. In the present paper, a principle and methodology, and a perspective of the approach are discussed with reviewing the outline of the study.

Stress strain relationships of foamed rubber was determined by mechanical characteristics of rubber matrix and microscopic structures. The microstructure consists of air voids, beams and walls. Numerical analysis method like finite element analysis (FEM-analysis) of foamed rubber considering microstructure require large computer resources. In this study, practical analysis method was develop by the three-dimensional finite element analysis using homogenization method. The microstructure of foamed rubber was assumed to have the periodic structure, homogenization theory was applied to FEM analysis of hyperelasticity. Using stress strain relationships of general polyurethane, the influence on mechanical characteristic by the change of the structure was confirmed. Thus, the parameters decided mechanical characteristic of foamed rubber was verified.

In this study, effect of microstructure of foam material on mechanical behavior was investigated. In order to develop the evaluation method, foam structure was assumed to have the periodical oval voids, and a homogenization FEM code for hyperelastic body was developed based on homogenization theory. Compression tests of the rubber specimens were conducted to verify developed homogenization FEM model. Results of 2-dimentional FEM showed good agreement with the compression test results. Effect of boundary conditions of compression tests and homogenization FEM were investigated.

Friction coefficient of rubber is known depending on pressure and slip velocity. The dependency is measured by laboratory tests using rubber sample. Obtained data are fitted and used for finite element tire simulationthe effect of the dependency compared by constant friction coefficient. Comparison shows that slip s. Tire driving, braking and cornering simulations are carried out to look into velocity dependency makes braking force decrease at larger slip ratio, and pressure dependency makes cornering force decrease at larger slip angle with larger load. Under large slip ration, slip velocity deviation in thpressure deviation in there is confirmed. More sophisticated friction model for rubber is expected for e tire footprint is confirmed, and under large slip angle and larger load, contact tire performance prediction on different road surfaces.

The description of stick-slip motion on contact surfaces having flexibility is important. However, conventional analysis mainly focuses on steady state of stick-slip motion, and thus the behavior at the onset of stick-slip motion is ignored. In this study, a numerical analysis of onset of stick-slip motion is conducted using rate- and state-dependent friction model, which can rationally describe the reciprocal transition between the static friction and the kinetic friction by a unified formulation.

The viscoelastic properties of the silicone rubber composites filled with nano silica particles were considered in terms of distinctive interphase layers on the nano a diameter of 300 nm or the micro-silica particles with a diameter of particles. The nano-1.5 μm were filled into the silica particles withsilicone rubber with several volume fractions of the particles to manufacture the rubber composites. Temperature variations of the viscoelastic properties of the composites were measured with a dynamic viscoelastometer. The viscoelastic properties in the particle size although the properties in the glassy state were independent of the size. The interphaserubbery state were clarified to be dependent on the layers enfolding the nano particles were observed on fracture surface and the micro particles were exposed on the fracture surface. The thickness of the interphase layer was determined as approximate 20 nm from the back operation of Guth and Gold's mixture law of dynamic storage modulus with the measured results.

We analyze the swelling-induced instability of swollen elastomer under biaxial extension using two scaling exponents. Two scaling exponents are introduced to extend the Flory-Rehner free energy function, and are adjusted based on the previous study. Results show that swelling-induced strain softening is apt to occur under equibiaxial extension compared to uniaxial extension. The additional tensile stress in a lateral direction enables it to occur in relatively poor solvents, and accelerates the onset point.

A swelling of a polymeric gel is a phenomenon to absorbs a solvent and largely deform with its volume change, while a residual swelling is a phenomenon that leads to a change in shape of a thin elastomer without a volume change by migration of free polymer chains. In order to drive the shape changes of thin composite elastomers due to residual swelling, consisting of two elastomer beams with a stiffness ratio, it is necessary to clarify the effect of residual swelling on the shape changes. Here we investigate the effect of the thickness ratio of bilayer on the bending curvatures and estimate the residual stain.

It is well known that the temperature variation associated with deformation of rubbers is mainly due to the Gough-Joule effect. However, quantitative evaluation of the temperature variation of rubbers under cyclic loading has not been studied very well. In this study, temperature variation of a chloroprene rubber subjected to uniaxial tensile cyclic loading is studied. The three-chain model is modified to describe the Mullins effect and residual strain under cyclic loading. The parameters of the model are identified experimentally at each loading condition. The temperature amplitude due to the Gough-Joule effect is predicted based on the modified three-chain model. The predicted temperature amplitude is compared to the temperature amplitude measured with an infrared thermography. As a result, it is shown that the prediction matches well with the experimental result.

In this paper, we describe an original method (PFT-RFM: Restoring Force Model of Power Function Type) for analyzing nonlinear vibrational properties of the seismic isolation laminated rubber. We also describe an original method (PFT-ELS: Equivalent Linear System using the restoring force model of Power Function Type) for analyzing response of the high-rise building structure with the seismic isolation laminated rubber for many earthquakes. We were able to verify the appropriateness of those methods by directly comparing the analysis result of those methods with the analysis result of the modified bilinear model. As a result, usability of PFT-RFM and PFT-ELS could be confirmed.

The radiated sound from the impacted body has not only the information of the impact force but also many types of information. For example, it has the information with respect to the defect in the impacted body. In this study, we propose the method in order to identify the defect shape in the impacted body by measuring the radiated sound pressure distribution and using FEM analysis. We measure fictionally the sound pressure distribution by moving a microphone and applying the same impact force to the body. The defect is identified by the actual experiment. The efficiency of the proposed method is confirmed.

The lead bronze is widely used as the sliding materials. However, the development of lead free copper alloy has been advanced, because the use restriction of lead is carried out. In this study, the application of AE method was examined for evaluating the characteristics of the bimetal materials of lead free copper alloy which changed the distribution of the hydrosulphide in which the slide characteristics are improved by the addition of sulfur. As the results, it was possible to show the possibility for evaluating the damage conditions by using the frequency analysis, m value and Ib value of the AE signals detected in tensile and fatigue test.

Mg alloy (i.e. the specific gravity is small and the mechanical characteristics are excellent) is necessary material for the weight reduction of structure. However, the use range as the structural member of that alloy narrows, because that is not suitable for the jointing by the welding. Therefore, the friction stirring welding (FSW) which is solid phase jointing began to be paid attention. However, the influences by using that technique for the alloy are not grasped sufficiently. In this study, the tensile and the fatigue test for the specimens (i.e. Mg alloy AZ 31 and that alloy jointed together by FWS) were carried out, and the influences of FSW to mechanical properties were evaluated by the characteristics of AE signals detected in those test. From the results obtained under this experimental conditions, it was proven that there was large difference to the generation behaviors of the AE events which were detected by each fracture type.

The propagation time of dispersive wave is evaluated by frequency filter using wavelet transform by Gabor function mother wavelet. Using S0 mode Lamb wave, the optimal frequency filter bandwidth of Gabor function for propagation time evaluation was discussed by changing γ parameter of Gabor function. The γ values which minimize propagation time evaluation error were observed for each frequency. At these γ values, the half-value-width of each wavelet coefficient was the narrowest compared to the other γ values. Thus to evaluate propagation time accurately, this optimal γ value which minimize the wavelet coefficient half-value-width should be used. At the optimal γ value, it was shown that the Gabor function could extract much information from original waveform at particular frequency, thus the evaluation error became lowest.

In this study, a time reversal method for Lamb waves based on mode conversion is proposed for the detection and localization of a defect in a plate. To verify its validity, numerical simulation using the elastodynamic finite integration technique (EFIT) is performed for a two-dimensional model of an isotropic elastic plate which has a surface crack. For the incidence of the lowest-order symmetric (S0) mode in a low frequency range, the lowest-order antisymmetric (A0) mode is generated at the crack due to mode conversion. The waveforms of the A0 mode are obtained from the out-of-plane velocities on both surfaces of the plate. After re-emitting the time-reversed A0 mode, focusing positions on the plate surface are identified. The re-emitted A0 modes create a focusing at the position of the crack.

The nonlinear acoustic parameter of cross-ply CFRP subjected to a tensile strain was experimentally evaluated. We specially concentrated on second-harmonic generation from a monochromatic wave to evaluate the nonlinear parameter of CFRP composites. On the first experiment, the nonlinear parameter increased significantly. By contrast, little increase of the nonlinear parameter of the same specimen was measured on the second experiment. The increase of the nonlinear parameter was discussed in the light of the strain history of the specimen. It has been found that irreversible damage increases the nonlinear acoustic parameter of the CFRP composites.

Carbon fiber reinforced thermoplastic (CFRTP) has high specific strength, rigidity and corrosion proof. CFRTP is used for structural members such as aircrafts, automobiles, blades of electricgenerating windmills and sporting goods. Because the mechanical strength of CFRTP depends on the volume fraction, the evaluation of the volume fraction of CFRTP is very important in the guarantee of quality. Thus, the nondestructive inspection method to detect the volume fraction in CFRTP is required. In this paper, we measured the conductivity of CFRTP from the reflection wave of the microwave. Using a theory model, the volume fraction was evaluated from the conductivity. As a result, the potential of microwave inspection to evaluate the volume fraction in CFRTP was presented.

Heating pipes used in oil refinery plants have problems of coke accumulation on their inner wall after long-term using. Inner wall coke disturbs normal thermal diffusion and this leads to serious accident due to creep failure of the heating pipe. Therefore, effective nondestructive testing technique has been required for quantitative measurement of coke thickness. In this study a new quantitative measurement technique of coke thickness is developed based on active infrared thermography method. Moving halogen lamp heat source is employed for active heating. Transient temperature distribution after active heating is measured by infrared thermography and processed by Fourier analysis to obtain the relationship between phase values and coke thickness.

The mechanoluminescence paint is focused on the technology to visualize the stress distribution. Since this method is capable of measuring the shear stress without volume change, it may be possible to measure the stress on the rotating shaft subjected to torsional load. Therefore, we aimed to monitor the shear stress axis undergoing torsion in this study. The proposed measurement system was verified whether or not appropriate.

A fatigue limit estimation method based on dissipated energy measurement with an infrared thermography has been proposed and got an increasing attention recently. However, a fundamental principle of the method has not been clarified yet. In addition, the method was still applied to a limited material in a previous study. Light weight metals which have high strength to weight ratio are positively used in engineering structures and components where light weight is required. Therefore, an applicability evaluation of the method to the light weight metals is worthwhile. As part of the applicability evaluation, the method was applied to a plate specimen made of aluminum alloy 6061-T6 in this study. An estimated fatigue limit by the method was compared with two types of fatigue strength which was calculated from the tensile strength of the investigated material and obtained from a literature. As a result, the method had a possibility to estimate the fatigue strength of the aluminum alloy 6061-T6 at 107 cycles, although the more detailed investigation was needed.

In recent years, fatigue limit estimation based on dissipated energy measurement has been attracting considerable attention. In this study, a system for microscopic measurements of dissipated energy was developed and this system was applied to a specimen whose grain size was greater than spatial resolution of the system to investigate the relationship between dissipated energy and microstructure in grain scale. It was revealed that measured dissipated energies were influenced by differences in emissivity due to unevenness of the black body coating on the specimen and the displacement of the specimen. Then, image process technique including a position correction of the specimen and an averaging filter was developped and its usefulness was demonstrated for reduction of the influence. The dissipated energy showed characteristic distribution for the specimen. Especially, the location where the highest dissipated energy was measured coincided with a crack initiation point. The area where high dissipated energy was measured corresponded to the area where a large number of slip bands was observed. Therefore, it was found that the system with the image process technique was able to evaluate the more detailed fatigue damage.

Sonic-IR, which is based on the thermographic detection of the temperature rise due to frictional heating at the defect faces under ultrasonic excitation, has an advantage in the detection of closed defects. In the present study, we investigate the fundamental physics of heat generation at defects by using the Sonic-IR method. A contact point between a hemisphere specimen and a beam specimen was observed, and the relationship between the temperature rise at the contact point and the contact position exhibited a distribution with several peaks. The distribution of heat generation corresponded with the distribution of vibration obtained by FEM analysis.

Location and size of wall thinning on the circular pipe inner wall was estimated by direct-current potential difference method which is one of non-destructive testing methods. Using carbon steel pipes for pressure service STPG370 as a test material, wall thinning part was formed on the inner surface of circular pipe by machine processing. Potential difference at around the wall thinning part was measured by applying direct current to the material. As a result, the largest normalized potential difference was observed at the wall thinning part showing gradual reduction as the position got away from the wall thinning part. As a result of estimation of wall thinning part by applying this value to a defect current modification method, estimated dimension was proved to be slightly smaller than the actual size even though the position was correctly estimated.

The present authors have proposed a new DC potential difference method using multi-microprobes and showed that the method can successfully make the residual life estimation for high temperature fatigue of an austenitic stainless steel JIS SUS316L at high temperatures of 765 to 923 K where multiple-site small cracks cause fatigue fracture. In order to clarify the effects of the growth of the multiple-site small cracks on the variation of potential difference values measured, the present paper has performed FEM steady-state current analyses as well as experimental analyses. The results showed that the growth of multiple-site small cracks following the Paris-type fatigue law can bring about the knee point of the diagram of the relationship between the standard deviation σ_V of normalized potential difference V/V₀ and normalized number of fatigue cycles N/N_f which has been proposed by the present authors.

The present authors have proposed a new DC potential method using multi-microprobes and showed that the method can successfully make the residual life estimation for high temperature fatigue of an austenitic stainless steel JIS SUS316L at high temperatures of 765 to 923 K where multiple-site small cracks cause fatigue fracture. In order to clarify the effects of spacing between probe pins and scan interval on the potential difference measurement, the present paper has performed FEM steady-state current analyses as well as experimental analyses and showed that the spacing between probe pins brings about larger standard deviation and the same mean value of the potential difference distributions measured whereas that the two levels of the scan intervals investigated here give the same values of the mean and the standard deviation. This implies that the proposed method is robust and is not so affected by the probepin spacing and the scan interval.

A problem determining the shape and rigidity of inclusions embedded deformable materials is considered. This problem is a typical inverse problem to find the internal constitutive relations of materials from the boundary conditions on the external surfaces during deformation. Deformation is done by instrumented indentation, which measures the indentation load and the penetration depth dynamically. As the preliminarywork, we started with analyzing the data obtained by a sphere indentation testing simulated by finite element method. Particularly, the effect of sample size on the results of indentation testing was examined.

This paper studies a method for evaluating the stress triaxiality and the fracture strains accurately considering the deformation of thin steel sheets which are used for an automobile body frame. Three-dimensional displacements and surface strains of thin steel sheets are measured using a stereovision. In particular, to measure the deformation of the board thickness of the steel sheets, the measurement is performed from the both sides of the steel sheet. Based on strain incremental theory, the stress triaxiality is evaluated from the measured strains considering the variation of the thickness of the steel sheets. The effectiveness of the proposed procedure is validated by applying it to the evaluation of the stress triaxiality of high strength steel sheets. Results show that the stress triaxiality and the fracture strains can be evaluated by the proposed method.

In this research, a thermal strain on an electronic packaging is measured by digital image correlation with its periodical systematic error elimination method. To evaluate the strain at micro area, a microscopic lens and micro particles for the speckle pattern is used. Prior to the evaluation of the thermal strain on the electronic packaging, the thermal strain of a brazed bi-metal is measured. Results show that the strain distribution not affected with periodical error is evaluated. In addition, the strain distribution affected by mismatch of thermal expansion coefficients is observed around the boundary. However, it seems that some methods such as an introduction of other micro particles for the speckle pattern should be considered to enhance the displacement measurement accuracy.

The measurement accuracy of strains and strain rates by digitak image correlation method (DIC) is investigated. Displacement distribution of non-deformed stationary object are measured by DIC using various focal lengths and F-numbers. Mean values and standard deviations of the strain and strain rate are evaluated. As a result, it is found that increase of the focal length reduces measurement accuracy and tends to be inversely proportional to observation magnification.

Once nerve cells which construct such as brain get damaged, it is difficult to regenerate. Therefore recently regenerative medicine applying stem cells is taken gathering attention. It's known that mechanical interactions between cells and extracellular matrix (ECM) are greatly concerned with cell differentiation. It has been studied mostly about cell-ECM mechanical interaction in two dimensions (2D), but enough knowledge was not obtained in three dimensions (3D). It has been reported to be able to control the cell differentiation by changing the elastic modulus of scaffold. But many of its mechanisms remain unknown. As a key to elucidate them, 3D mechanical interaction has been required. Thus we focused on digital volume correlation (DVC), which is a method of measuring 3D displacement and strain fields within an object by using a pair of 3D volume images. In this paper, we succeeded to differentiate human mesenchymal stem cells (hMSC) to nerve cell in 3D. Besides, we visualized mechanical fields around hMSC cultured in collagen gel by using DVC method based on confocal laser scanning microscopy. As a result, we found that hMSC in collagen gel interacts dynamically with their surrounding 3D microenvironment and the more advance differentiation, the bigger displacement of ECM. From these results, it was indicated that there is the relationship between hMSC differentiation and mechanical interactions.

Non-uniform strain distribution was measured and the effect of a crack on the distribution was investigated on fatigue specimens with a repair weld portion. The strain distribution in the initial loading showed that an elastic deformation mainly occurred in the welded portion while a large plastic deformation occurred in the base material. This behavior was reproduced qualitatively by the finite element analysis where the materials properties on the basis of the strain measurement were applied. The length of the region where a crack affected the strain distribution was defined on the basis of the strain between two facets across a crack. It was confirmed that the length corresponded to the crack length on the painted surface that was read from the images taken.

Evaluating long-term strength and mechanical properties of composite materials is important in order to use them as construction materials. When the matrix is polymer materials, the composite materials exhibit viscoelasticity. Therefore long-term strength prediction should be based on viscoelasticity. In this study, constant strain rate tests of PBT and short fiber reinforced PBT are performed. As a result, it is confirmed that time-temperature superposition principle can be applied the strength and elastic modulus of each material. And those shift factors coincide regardless of the fiber volume fraction. It is shown that the prediction of time dependence of the elastic modulus by shear lag model cannot be evaluated long-term elastic modulus correctly.

A new stress–strain curve estimation method was investigated through instrumented indentation technique using different sized and shaped indenters. For stress–strain curve estimation, the ball indentation technique was developed focusing on the effect of radius of ball indenter. Meanwhile, the pyramid indentation technique was developed focusing on the effect of included angle of pyramid indenter. The developed methods were applied to estimate stress-strain curve of rolled steel for welded structure. Then, advantages and limitations of the developed methods were discussed.

Pull-out tests were carried out for thin copper wires soldered to nickel rod by lead-free solder, and the bonding interface strength was examined. A large variation was observed in the maximum load of the pull-out tests while the load-displacement curves were similar in all tests. Since thecorrelation between the apparent bond length of solder and the maximum load was not clear, the actual bonded area was evaluated on the surface of each copper wire after the test using the Scanning Electron Microscope (SEM). The maximum load was correlated well with the actual bonded area, which shows that the pull-out strength can be evaluated by the actual bonded area.

An evaluation procedure of damage and fracture is introduced by using indentation technique in this paper. The damage and fracture are ordinary evaluated by tensile test, but it has difficulty to quantify them for soft material because of its large deformation. Then indentation technique is adopted as a material test for soft materials. The quantification procedure is depending on fundamental Hertzian contact theory, and it is extended for the evaluation. The extended theory is applied to the specimen of chicken, and the availability of the extended theory is discussed by the evaluated results of indentation test.

Polyimide (PI) film with a surface small defect subjected to tensile load is fractured by the crack propagation from the defect in the film thickness direction. However, the evaluation method of fracture toughness in this type of fracture hasn’t yet been established. In this paper, SENT tests were carried out using 125 μm-thick PI films with a surface pre-crack having different depths from 10 μm to 60 μm, and fracture processes focusing on crack opening and crack extension were observed with a color 3D laser scanning microscope. Based on the results, fracture toughnesses J_in in the direction of film thickness were calculated by using two different equations for SENT specimen. As a result, J_in values were clarified to have a slight dependency on pre-crack depth. The differences between J_in values calculated by the two equations were considered small, and fracture toughness was in the range from 0.4 to 1 kJ/m².

Acoust-elasticity is a non-destructive method not only to detect flaw in material but also to estimate quantitatively the change of microstructure. The method is often applied in the field of metallic materials but is a few in the field of ceramic materials. In the method the third order elastic constants can be obtained by measuring the ultrasonic velocities with varying the stress under uniaxial compressive loading, and seems to express material nonlinearity which caused by residual stress or the change of microstructure. In this paper, the method was applied to evaluate the degree of phase transformation in annealing of partially stabilized zirconia, in which the material was annealed for 100h at different temperatures of 200, 400 and 600°C. The third order elastic constants obtained for various temperatures showed that the material annealed in 200°C has a highly nonlinearity. This fact shows that it is possible to apply the acoust-elasticity to non-destructive evaluation of annealing effect.

Directivity of the Mach-Zehnder interferometer type optical fiber acoustic emission (AE) sensor having the U-shaped sensing region for the use of underwater measurement was discussed. It was demonstrated that detected waveforms by the sensor depend on the incidence angles of the AE waves although the amplitude of the first peak in the waveform caused by the arrival of the AE wave indicates no change. It was also found that directivity of the sensor tends to disappear by setting masking tubes on the sensing fiber that avoid the influence of undesirable elongation of the sensing region. Nearly omnidirectional sensor was successfully made with the effective ratio for receiving waves given by masking tubes was less than 50%. It was concluded that the J-shaped sensing region is preferable for waveform analyses by taking sensitivity of the sensor into accounts.

Raman microspectroscopy is powerful tool to analyze components and crystal structure of materials, and stress/strains in electronic devices and Nano/Micro electronic mechanical systems. However, the capability of conventional Raman microscopes to obtain two dimensional Raman images is limited. In order to obtain the 2D-images by conventional Raman microscopes, the laser spot is scanned on the surface of materials by moving the stage. Therefore, the time required for the 2D images obtained by typical point measurements is too long. In this study, we developed single focus-multi point micro-Raman spectrometer for two-dimensional Raman imaging with Raman spectrum of each point in the analyzed region. The characteristics of this instrument are that micro-lens array divides Raman scattered region into some square regions and that Raman scattered lights of each region are individually collected by using dimension transformation bundle fiber. Single focus-multi point micro-Raman spectrometer is applied to 2D-imagings of carbon and epoxy resin in carbon fiber reinforced plastics (FRP).

Displacement distribution in circular shaft specimen of steel during tensile test was measured using digital image correlation (DIC) method. Video image of the specimen surface was continuously taken during tensile test and static images were selected from the movie file after the test. Distribution of strain in axial direction was obtained from the displacement distribution and also diameter of the specimen was estimated based on strain distribution in vertical direction to the specimen axis. Distributions of strain and diameter of the specimen were observed during whole tensile test and stress-strain relation based on local deformation was considered.

We fabricated a sophisticated functionally graded TiNi shape memory alloy (SMA) via powder metallurgy and plastic working. The material can be utilized as a medical guidewire with varying bending rigidity values from high to low along the wire axis and an actuator. In general, sintered materials are not used under severe bending deformation conditions because of their low deformability; however it is necessary to consider the materials that can withstand such deformation, especially for a medical guidewire, which is made from sintered SMA. In this study, we investigated the bending fatigue properties of a sintered TiNi SMA wire via an alternating-plane bending fatigue test. From the experiment, we found that the fatigue life of this wire is much shorter than that of a wrought TiNi SMA wire because of its low density. We therefore conducted a cold rolling to improve the density of the sintered TiNi SMA and achieved longer fatigue life than that of a sintered TiNi SMA.

Fe-based shape memory alloy (Fe-SMA) is attempted to be applied to many engineering fields under different working environments(1) loaded at various deformation rates. Therefore, it is necessary to evaluate an amount of martensite which can control such excellent performances for increasing a reliability of the alloy. However, so far only resistance method can capture the amount of martensite during higher speed of deformation. In this study, the rate sensitivity of volume resistivity in the Fe-SMA is experimentally estimated during tensile tests at various strain rates by using the modified circuit based on Kelvin double bridge from the previous study. Then, the relationship between resistivity and volume fraction of martensite is clarified by X-ray diffraction method.

The effect of cold rolling on martensitic transformation temperature in cast Ti-50.5at%Ni shape memory alloy from self-propagating high temperature synthesis (SHS) ingot were studied. Shape memory alloy specimens were casted by lost-wax process from SHS ingot. The microstructural feature was analyzed by scanning electron microscopy (SEM). The elemental contents were analyzed Energy Dispersive X-ray Spectrometry (EDX). The structure was analyzed X-ray Diffraction (XRD). The heat treatment and the change of the transformation temperature by the rolling conditions were measured by differential scanning calorimetry (DSC).

NiTi shape memory alloys exhibit both shape memory effect and superelasticity. In general, the shape memory capacity of commercial products supplied as drawing wires is known to be limited below 7% strain. In order to get a larger shape memory strain than that, additional cold working through drawing with dices and a medium temperature annealing were applied. It might cause the work hardening and the re-orientation of grains into the favorable <111> direction along the tensile axis. As a result, we obtained the shape memory and superelastic strains of about 9%.

Fe-28Mn-6Si-5Cr alloy is a kind of shape memory alloys. Its shape memory effect is lower than that of Ni-Ti alloy. On the other hand, the alloy has superior machinability and weldability. In addition, the mechanical property is almost the same before and after the shape recovered. Therefore, it is considered that the alloy is applied to the structural elements such as a pipe joint. However, it is considered that the pipe joint is loaded at various deformation rates. In the past study, axial strength is estimated by the quasi-static test. However, it is difficult to find a research work which consider higher deformation rate. Thus, it is important to estimate the strength of pipe joint at high deformation rate. In this study, a push-out test is performed based on the SHPB method. In addition, the impact joint strength is defined by the strength when circumferential strain of the joint starts decreasing.

In order to develop the two-way rotary driving actuator using shape memory alloy (SMA) tapes, the graphical method to design the actuator was proposed based on the torsional deformation properties of SMA tapes. The blind model driven by the two-way rotary element was demonstrated. The results obtained are summarized as follows. (1) The torsional deformation properties of the SMA tape and the superelastic alloy (SEA) tape were obtained. The two-way rotary actuator was composed of the twisted SMA tape and the flat SEA tape in series. The twisting angle and torque which vary depending on temperature can be obtained based on the design chart. The behavior of the two-way rotary actuator with a simple mechanism can be estimated by the proposed design method. (2) The automatically opening and closing blind driven by sunlight was demonstrated. The blind was controlled by using the two-way rotary element with the SMA tape and the SEA tape. In the two-way rotary element, the SMA tape was heated by sunlight through the Fresnel lens. The behavior of the blind can be achieved based on the proposed design method of the two-way rotary driving element.