When we walk, the quadriceps muscle and hamstring are active. The quadriceps muscle is the muscles that extend the knee and the hamstring is the muscles that bend the knee. The muscle weakness of these muscles causes falls and knee pain. Measuring instruments that measure these muscle strengths are used in clinical practice. However, since it does not take into consideration the position of muscle and bone attachment, it cannot be measured under conditions that maximize muscle strength. The purpose of this study is to develop a muscle strength measuring device of the quadriceps femoris and hamstring under conditions that maximize muscle strength taking into consideration the position of muscle and bone attachment. In this study, muscular strength was measured for 7 men in their 20s and 7 females in their 20s. As a result, we could measure muscular strength of the quadriceps femoris and hamstring under conditions that maximize muscle strength. However, the measurement results of subjects with long thigh tended to decrease. This result may be due to the lack of fixation of the knee if the subject is a long thigh. Therefore, to measure muscle strength accurately, it was suggested that it is necessary to design a measurement instrument that takes the subject's thigh length into account.

In recent years, bone diseases such as osteoporosis, which tend to cause fractures due to a decrease in bone strength accompanying aging, are becoming a problem. Evaluating bone microscopic mechanical properties and evaluating bone strength is an important research leading to the treatment of bone diseases. Using the component analysis method called Raman spectroscopy, the change in Raman shift was measured while applying load to bone tissue, and the relationship between stress and Raman shift was investigated. In addition, the Raman shifts were measured by statistical process based on the Raman images. The specimens with the sizes of 10 × 2 × 0.5 mm were cut out from bovine femoral diaphysis (Age: 1 m.o., 23 m.o. and 7 y.o.), where the longer edges of specimens are aligned to the parallel to the femoral axis. Strain gauges were attached to bovine cortical bone specimens, and Raman spectrum was measured while applying tensile stress. The Raman shifts were calculated by averaging obtained peak shifts at all measurements point. As the results, a negative correlation was found between tensile load and Raman shift in ν₂PO₃^4－ , ν₄PO₃^4－ and ν₁PO₃^4－. In addition, at 23 months of age, there was a tendency of the increase of changes in Raman shifts.

We investigated a microstructure and mechanical properties of a claw of Japanese fresh water crab (Geothelphusa dehaani) using X-ray diffraction (XRD), scanning electron microscope (SEM) and scanning acoustic microscope (SAM). It was observed using SEM that the microstructure of the claw consists of epicuticle (outermost layer), exocuticle (outer layer) and endocuticle (inner layer). Evaluations of Young's modulus, density and Poisson's ratio performed by using SAM. As a result, Young's modulus and density of exocuticle (outer layer) tend to increase gradually toward the inside and those properties of endocuticle (inner layer) tend to decrease gradually towards the inside. In the area of the exocuticle to the endocuticle, the maximum value of Young's modulus was 42.0 GPa and the minimum value was 12.5 GPa. The maximum value of density was 1.05 g/cm³ and the minimum value was 0.25 g/cm³. It was observed that the tendency for the mechanical properties of the crab hard tissue to change from the exocuticle continuously toward the endocuticle. By changing mechanical properties continuously, it was expected that hardness and toughness are ensured for the whole structure of crab claw.

Spinal implants used for treatment of spinal diseases are required to have high strength and rigidity, and high mating force to fix rods. On the other hand, there is no report on the mechanisms of these fittings and discussions on the breakage of implants. Also, in recent years, the problem of deterioration in quality of life (QOL) such as compression of the skin of the treated patient due to the use of a large implant made abroad has also been reported. While miniaturization of the implant device is required, on the other hand, reduction in strength due to miniaturization is concerned, and the mechanism of low profile is still unknown. Therefore, in this study, we examined the low profile of the spinal implant device. As a result of the experiment, it was found that the reduction of the height and the securing of the number of threads as well as the suppression of the opening by increasing the stiffness of the screw socket are effective for low profile. From observation results, it was found that the cause of decrease in fitting force is wear and plastic deformation of thread surface as well as reduction of contact area due to incomplete contact between threads.

To thoroughly manage information such as medical accident and Product Liability Act, medical products are obliged to display product number directly. Main indication methods are marking using laser. However, fracture with the laser marking part as a starting point has been reported. Laser marking parts which are subjected to thermal influences can be inferred to locally change the surface texture, microstructure, and mechanical properties, but their investigation has not been done sufficiently. In this study, continuous laser irradiation was applied to medical titanium alloys. The laser irradiated surface and cross section was observed in detail using a scanning electron microscope (SEM). With respect to the cross section, polishing was sequentially performed from emery paper #800 to #4000, then mirror-finished using Al₂O₃ particles (0.3μm) and subjected to etching treatment. The quantitative ratio of α phase and β phase in the heat affected zone of the laser irradiated part was analyzed by electron backscatter diffraction (EBSD) method. As a result, the height of the laser-irradiated surface was reduced by dissolution. On the other hand, the end of the irradiation trace width was raised by solidification. Also, the amount of oxygen on the surface oxidized at high temperature by laser irradiation increased and the hardness increased. In addition, the crystal structure (α+β) was changed by laser irradiation from the observation of the microstructure of the cross section of the laser irradiation part.

This research studied the mechanical property and behavior of maxillary sinus membrane experimentally and numerically, in order to discuss about its breakage when elevated during sinus lift surgery for dental implant in upper jaw bone. An experimental apparatus for sinus membrane of fresh cadaver was developed, and the relation between load and elevation height was obtained. In the numerical analysis by finite element method, both geometrical nonlinearity and material nonlinearity were considered by means of Mooney-Rivlin model. This paper describes the outline of the testing machine, experimental results and strain distribution at elevation height of 0.8 mm. High tensile strains were observed in both radial and circumferential directions.

In order to prevent the accidental case of giving damage to nerve system in the mandibular canal in oral implant surgery, the drilling force for mandibular trabecular bone and cortical bone was quantified as a function of drilling depth with the help of stochastic multiscale finite element method (FEM). The surgeons' feeling during drilling was realized in the newly developed force sensing apparatus. The computational method allows us to consider the microarchitecture of the trabecular bone and provides its anisotropic properties, which contributes to the analysis of different drilling forces depending on the drilling angle. The numerical results were implemented in the developed apparatus and evaluated by clinicians. Finally, the developed apparatus was successfully used in the education for dental college students.

Articular cartilages are composed of extracellular matrix, interstitial water and negatively charged proteoglycan aggregates. Furthermore, the articular cartilages have anisotropic and inhomogeneous structure which contains three zones with different collagen content and fibrils orientation. On the other hand, contact phenomenon is a mechanical characteristic of articular cartilages since the diarthrodial joint functions as a load transfer mechanism by contact between cartilage surfaces. In this work, the anisotropic and inhomogeneous structure of the articular cartilages was introduced into the mechano-electrochemical coupling contact analysis algorithm. By taking into account the distribution of the collagen content and fibrils orientation in the cartilage layers, the sliding contact analysis was carried out to investigate the effects of the anisotropy and inhomogeneity of cartilage on the mechano-electrochemical behaviors.

The purpose of this study was to determine whether natural variations in the bone structure of ostensibly identical rat specimens might affect their fracture behavior and mechanism. This was done by scanning four Wistar rat vertebrae samples with a micro-CT scanner, which takes layered two-dimensional images and layers them together to create a three-dimensional representation at a resolution of 30μm3. From this, a finite element model was created and analysed using simulated standard mechanical tests. The finite element models were used to visualize bone density distribution and see how this related to performance under severe loads. It was found that lower overall bone density correlated to an increase in overall fracture rate, as well as a decrease in load to fracture. Bones with stiff outer cortical bone which was thick and dense performed the best, as strain energy density analysis showed it protected the softer internal cancellous bone from damage. vertebrae with isolated regions of stiff bone performed worst, as the mismatch in stiffness caused fractures. These results are expected, however the study shows that although every possible factor to control rat genetics and growth can be accounted for in an animal experiment, variations in bone structure still resulted in large variations in bone mineral density, and therefore large variations in fracture point, fracture severity and stress distribution.

The deformation of soft tissues determines a microvascular closure under loading on the skin surface, which may lead to pressure ulcer. The load has two components, i.e., pressure and shear force. We measured the deformation of skin, subcutaneous tissue (ST) and skeletal muscle (SM) with shear of skin surface for twelve side surfaces in six porcine hind feet in a previous study. In this study we referred to a Cartesian coordinate system with an axis parallel to the path of a point on the side surface of the skin and analyzed the shear deformation of ST to obtain the relationships between the shear strain of ST and the displacement of skin and the relationships of displacements between two points. The results agreed with the three categorized cases, i.e., a case in which the ST followed the skin but the SM did not, a case in which ST and SM followed the skin to a certain degree, and a case in which the ST had a large shear deformation and followed the skin but the SM did not. The results suggest that the shear deformation of ST depends on the connectivity of ST with the skin and the SM. The deformation of the ST may govern the blood circulation under external loading.

Creep damage assessment of steam turbines in ultra-super critical power plants is necessary to maintain reliable operation. The destructive assessment method gives accurate creep damage assessment results, but it is difficult to cut a standard size specimen from steam turbines. Therefore, it is desired to develop a test method and a damage assessment method using a miniature specimen. In this study, creep damaged materials were made by creep tests on round bar notch specimens of the modified 9Cr-1Mo steel (notched tip radius 0.5 mm (R0.5) and 2.0 mm (R2.0)). Large number of voids was observed around 0.5 mm from notch root in R0.5, and it was observed around center of the specimen in R2.0. Creep tests in argon gas were conducted by using a solid bar tensile type miniature specimen with 1 mm diameter taken from the vicinity of the notch root of the creep damaged materials. For miniature specimens collected from the creep damaged materials of R0.5 and R2.0, the rupture time of the miniature specimen became shorter as creep damage increased. It might be possible to apply the miniature specimen for creep damage assessment of damaged materials.

Mod.9Cr-1Mo steels are being used for boiler pipes in ultra-super critical power plants. It is known that the creep strength of the welded joint of the steel is significantly lower than that of the base metal. In this study, miniature test specimens with 1mm diameter and 5mm parallel length were machined from a base metal, weld metal and heat affected zone (HAZ) of a long term used welded joint. Using these test specimens, the creep tests were performed by the special designed creep testing machine. Creep strengths of the base metal and HAZ were similar to unused materials, but remarkable reduction of the creep strength was observed in the weld metal in comparison with the unused materials. Material constants of the Norton's law were determined from creep data obtained by the miniature creep test specimens. Creep tests were also conducted with the miniature and standard size welded joint specimens. The rupture time of the miniature test specimens was shorter than that of the standard specimens. From the results of the finite element elastic creep analysis, the reason why the rupture time of the miniature specimen is shorter than that of the standard specimen, is that triaxiality in the HAZ of the standard specimen is higher than that of the miniature specimen.

All atomic power plants in Japan have stopped its generation after the seismic East-Japan earthquake. Many aged thermal power plants restarted to supply sufficient electricity for the Japanese industry and daily activities. Reasonable guidelines for assessment of its integrity and estimation of remaining life have been required to operate them with a safety margin. Miniature Creep (MC) test is recognized as a semi-destructive technique to examine the degradation level of aged high temperature components. In this study, the MC thin plate specimen of 2.25Cr-1Mo steel and the similar one welded by Electron beam (EB) only for gauge part were employed to evaluate the validity of the EB welded MC specimen. A series of creep tests were conducted in vacuum at 600°C. After the comparison of these test results with those using the conventional uniaxial specimens, following conclusions were obtained: (1) Creep rupture lives of the MC thin plate specimens including the EB welded ones were nearly the same as those of conventional uniaxial ones. (2) Vickers hardness on the surface of the EB welded MC thin plate before/after the creep tests were measured. The HV in the welded zone rapidly decreased in a short time and reached to almost as the mother material or below it. (3) Rupture lives of the welded MC thin plate specimens were longer than that of the monolithic MC thin plate specimen at higher stress levels, because the HV in the welded part was a bit larger than those of mother materials.

In order to ensure the integrity of high temperature components, it is important to evaluate the creep damage of them. Destructive tests are more reliable methods for evaluation than non-destructive and/or numerical ones. However, in some circumstances, conventional uniaxial specimen is too large to sample from some limited areas, e.g. , Heat Affected Zone. Small Punch (SP) creep test has been recognized as a small sample testing method and to solve problems mentioned above. SP creep test employs a small and thin disk, and its volume is smaller than that of conventional uniaxial specimen. In this study, applicability of cumulative damage evaluation by ductility exhaustion rule was examined employing pre-crept ferritic stainless steel. SP creep specimens were prepared from conventional uniaxial creep specimens that were interrupted at life time ratio of 0.27 - 0.98. A series of SP creep test were conducted at three load levels. The thickness strain in SP creep specimen at rupture was calculated by measuring the thickness of fracture edge of ruptured specimen, and the circumference strain in the SP creep specimen was calculated by Finite Element Analysis. Combining the thickness and the circumference strains, equivalent creep strain at rupture was introduced, and ductility exhaustion rule was applied. Test results show that the ductility exhaustion rule can be applied to estimate residual creep life except just before rupture, but that it would underestimate damage of severely pre-crept specimen.

In high Cr ferritic heat resistant steels, the creep strength of welded joint is closely associated with the strength of base metal itself. The creep property of base metal can be good indicator for ranking the strength level of welded joint or assessing its remaining-life, considering that it is not very difficult to scoop a small amount of material from the base metal part of pipings. In this study, the small punch (SP) testing technique was applied to five different heats of Gr.91 steel, which had been actually used for boiler pipings in 600 °C class USC power plants for long periods of time. The SP creep test was carried out at the temperature of 650 °C and under the load levels of 190, 230 and 300 N. Experimental results revealed that the rupture time was varied depending on the heat and there was maximum of one order difference even at same load condition. This difference in creep strength was qualitatively in good agreement with that determined by the conventional uniaxial creep test. Additionally, the correlation between the results of SP creep test and uniaxial one was also investigated using the load/stress conversion coefficients reported before.

This paper describes a development of multiaxial creep testing techniques with a small size cruciform specimen. Structural components such as thermal power plant pipe and turbine blade of airplane engine undergo multiaxial loading at high temperature. Although studies of multiaxial loading at high temperature are essential for commercial product development and designing, there is little experimental research on multiaxial creep. Since there is no commercial multiaxial creep testing apparatus, we are trying to develop a biaxial tensile multiaxial loading testing apparatus with a small size specimen. A small size cruciform type specimen was designed for high temperature multiaxial loading by using finite elements analysis. The specimen has 5mmx5mm size square gage area which is designed as stress distribution of the area to be constant. The specimen also has four loading arms for tensile loading. Changing the applied load value to the loading arm, various principal stress ratio λ, which is used for expressing a stress multiaxiality, can be conduct in the range from λ=0 to λ=1. This study also develops a non-contact strain measuring method which uses a conventional optical observation tools. The method can trace a movement path of some small target marks which are painted on the gage area and calculates the strain of the specimen. The strain value obtained from the non-contact method corresponds with the strain gage value.

Creep remaining life assessment is one of important issues to maintain high-temperature components of aged thermal power plant. Our research group has developed the high-temperature indentation test to evaluate creep constitutive equation known as Norton's law. The creep coefficient k and creep exponent n in the creep constitutive equation can be accurately identified from the relationship between time and impression size marked on the specimen surface. In addition, a possibility of creep life prediction using the indentation test is expected. It has been thus reported that the creep exponent of an aged material increases monotonically with the operating time. In this study, alternative life assessment method is proposed based upon creep exponent n which was identified by the developed indentation test. First of all, uniaxial creep tests were conducted under two test temperatures in order to prepare each five specimens with different creep damage ratios, which are 0, 0.25, 0.50, 0.75 and 1, respectively. Subsequently, the indentation tests were conducted to identify the creep exponent n for each specimen. As a result, it was recognized that the creep exponent n increases monotonically with the creep damage ratio. These results provide us that the creep life can be appropriately predicted using relationship between the creep exponent n and the creep damage ratio φ.

Impression creep (IC) studies were conducted on different heats of 316LN stainless steel (SS) base materials and welded joint in the temperature range 898-923 K, in the punching stress range 472-760 MPa, using specimens of nominal size 10x10x10 mm. The IC curves showed a primary and steady-state creep stages. The stress and temperature dependence of the steady-state impression velocity followed Norton power-law and Arrhenius rate equation, respectively, and indicated dislocation creep mechanism. The heat-affected zone (HAZ), weld metal (WM) and base metal (BM) of the welded joint revealed distinct creep behaviour owing to their different microstuctures. Equivalence between the IC test and uniaxial creep (UC) test parameters was established. The paper discusses the results of IC studies and highlights the potential applications of the IC test technique.

In the analytical life assessment of creep strength enhanced ferritic (CSEF) steels, average creep properties are generally assumed, although there is a large amount of scatter in the creep properties of welded joints of the steels. It is important to estimate the individual creep properties of welded joints of materials used at power stations if analytical life assessment is quantitatively applied to the components of power stations. Thus, author has developed a new method of assessing the individual creep properties of welded portions of actual piping using small samples. This paper describes the concept of the assessment method for modified 9Cr steel, which has been used worldwide as a CSEF steel.

In the evaluation of the creep property of piping base metals, an important consideration is from which region in the thickness direction small specimens are taken. We conducted microstructural observation, composition analysis, hardness measurement and the creep test to evaluate creep properties in the thickness direction of Gr.91 boiler piping base metals used for a long time in three ultra-supercritical (USC) power plants. In the microstructure near the outer surface, no affected layer was observed. Regarding the composition near the outer surface, carbon concentration fluctuations were observed in the region of about 1 mm at maximum from the outer surface, but a region beyond that showed no fluctuations in carbon and chromium concentrations. Regarding hardness, a change in hardness was observed in the region of about 0.1 mm to 0.2 mm from the outer surface, but in all other regions, the hardness in the thickness direction was almost constant. Regarding the creep test, except for some pipings, no significant difference in creep rupture time was observed in the thickness direction. Therefore, the creep property of Gr.91 boiler piping base metals is considered to be constant in the thickness direction, except for the region about 1 mm from the outer surface.

This paper discusses a newly developed tensile testing, low cycle fatigue testing and creep testing technique for electronic materials solder. A investigate working group in Society of Materials Science, Japan established a making procedure for a small size specimen which has 3mm-diameter gage part and developed a testing technique for the small size specimen. Cooling rate of the melted solder for the small size specimen is controlled as under 10K/s by using cooling rate calculation equation developed in this study. The developed testing technique made it possible to conduct not only static tensile testing or creep rupture testing but also low cycle fatigue testing under strain control mode with the small size specimen. This paper also discusses the specimen size influence on static tensile strength, cyclic fatigue and creep properties of solders. There was no specimen size influence on the tensile strength for Sn-3.0Ag-0.5Cu. Although there was stress amplitude difference between the small size specimen and the bulk type specimen which has 10mm in diameter, there was no low cycle fatigue lives difference for Sn-3.0Ag-0.5Cu. Creep rupture time of Sn-3.0Ag-0.5Cu with small size specimen was almost same as that of the bulk type specimen.

In recent years, materials used in automobile engines are required to be used in harsh environments, and there is concern that the material strength will be lowered due to corrosion caused by deteriorated fuel and increase in pressure. Therefore, this study conducts the fatigue test in the same environment as actual condition. The test uses type 440C martensitic stainless steel under corrosive atmospheric environment which is used as a part of automobile engine. However, this type of testing machine had not been available in past. Therefore, a small sized tension and compression fatigue testing machine for fatigue tests under corrosive and air environments were developed. In addition, this study established tension and compression fatigue testing method. This machine can also carry out the tests using a small sized specimen in flammable liquid, and allows testing at high frequencies. Then, the fatigue strengths in air, regular petrol, and inferior petrol conditions were compared to examine the effect of corrosion. From the test result, it was found that the fatigue life in the regular petrol was almost equivalent to that in the air environment regardless of the stress amplitude. However, in the deteriorated petrol environment, the fatigue life was largely reduced compared to former two conditions which will be discussed from the fracture surface morphology.

A new fatigue test apparatus with a small disk-type specimen, in which a cyclic oil pressure could be alternatively applied to both specimen surfaces at the frequency of 10 Hz was developed in this study. This testing technique was termed “Small Bulge Fatigue (SBF) Test”. Unlike the conventional small punch test, a hydraulic bulging method was adopted for avoiding problems attributable to the contact and/or the friction between ball and specimen. Additionally, in order to prevent cracking at the edge of specimen, the specimen thickness of central region was relatively reduced, and the small disk-type specimen with flat and concave surfaces was employed considering machinability and/or handleability. After some verification tests for the displacement and strain measurements, austenitic stainless steel SUS316 was subjected to the preliminary test using this newly developed testing technique. Experimental results revealed that crack was initiated on the vicinity of center of flat surface as expected by finite element analysis, and the oil pressure was abruptly dropped when a part of gauge area was broken. The SBF test result was in good agreement with those of conventional fatigue tests by defining a fatigue life as the number of cycles to sudden drop in pressure due to fracture.

Indentation technique is one of the evaluation methods of material on microscopic region. However, size effect of hardness becomes a problem. Geometrically necessary (GN) dislocations are thought as one of the cause of this effect. The purpose of this study is to investigate the cause of size effect of hardness by evaluating density of GN dislocations. This study used Ni single crystal, having the surface crystal orientation of (0 0 1) and (1 1 1). Indentation test was performed to these planes on various indentation depths by indenters with different ridge angles, and measured density of GN dislocations around the impression. The hardness was same, but high GN dislocation area was different by (0 0 1) and (1 1 1). There was high GN dislocation area around the impression on (0 0 1), but high density area of GN dislocation was made below the impression on (1 1 1). Furthermore, the angle of indenter varied the value of size effect on (0 0 1). Smaller angled indenter made high GN dislocation area, so the angle of indenter affected the size effect. By measuring GN dislocation area, it was clarified that hardness had relation to density of GN dislocation on (0 0 1), while not on (1 1 1). Therefore, it is conceivable that the cause of size effect is storing GN dislocations around impression on (0 0 1), and relation of position between high density area and indenter on (1 1 1).

In order to examine the adaptability of small punch (SP) test to the evaluation of aging degradation of 12%Cr heat resistant steels used for the USC steam turbine, the rotor and casing steels, which had been thermally aged and stress aged at 610, 630 and 650°C, were subjected to the SP test at the temperature range from -196°C to 80°C. The changes in tensile and ductile-brittle transition properties due to aging were investigated based on the SP test results. Experimental results revealed that the tensile strength decreased with increasing aging temperature and aging time, and this decrease in strength level (softening) was more pronounced in the rotor steel. It was also found that the ductile-brittle transition region shifted to higher temperature side and the upper shelf energy decreased with aging at 610°C. This embrittlement tended to recover by the higher temperature aging at 630 and 650°C. There was no significant influence of stress aging (creep) on the abovementioned material deteriorations, that is, softening and embrittlement.

With Gr. 91 boiler piping base metals used for a long time in ultra-supercritical (USC) power plant as target, a small sample was taken using the electric discharge sampling equipment, and we investigated the affected layer thickness by the electric discharge processing method, the dimensional accuracy of the small sample , and processing after sampling of small samples. As a result, it was confirmed that the thickness of the processing influence layer by the electric discharge processing method is within about 30 μm for both the sample and the pipe side, the sampling accuracy in the thickness direction of the sample is about ± 0.2 mm. In addition, almost no processing influence layer after grinder molding was found.

In this study, we enhanced the corrosion fatigue life of a TiNi shape memory alloy wire using a thermal nitridation treatment technique that can generated a passive film on the wire surface. We performed the following procedure for thermal nitridation treatment. First, the as-received material with an oxide film was mechanically polished to remove the film using an abrasive paper and a buffing compound. Second, the material was heat-treated in a furnace filled with a pure nitrogen gas for 1 h at 673 K. Subsequently, the material was allowed to cool in the furnace. The results obtained by this study are summarized as follows: (1) The corrosion resistance of the thermal nitrided material is much better than those of the normal heat treated and the polished material. (2) The fatigue life of the thermal nitrided material is not influenced by environment especially in the low-strain region.

The fatigue property of shape memory alloy (SMA) is one of the most important subjects in view of evaluating functional characteristics of SMA elements. In the present paper, the ultrasonic shot peening (USP) was applied to induce the compressive residual stress on full surfaces of TiNi SMA wire. The influence of USP on the bending fatigue life was investigated. The results obtained are summarrized as follows: (1) Stress level in the tensile test increases slightly by USP. (2) If SMA was treated by the USP, the fatigue life becomes longer. The larger the bending strain amplitude, the shorter the fatigue life is. (3) The surface hardness of SMA wire becomes harder by USP. (4) The fatigue crack nucleates at the internal specimen near the surface of the USP-treated layer.

Nickel Titanium shape memory alloy exhibits shape memory effect and superelasticity. In general, the superelasticity of commercial NiTi wire is around 7% in elongation and the superelastic strain becomes less than the original value after the repetition of superelasticity cycles. Eggeler et al. (2004) called the decrease “functional fatigue”. In this paper superelasticity was repeated for more than 100 times in a wide range of temperature and load. We found that the plateau stress of the stress-induced transformation decreased but that of strain reversal did not change. We also found that the superelasticity strain decreased faster as the temperature was higher. It is suggested that the change is a typical autocatalytic process.

Spherical indentation of an equiatomic nickel titanium shape memory alloy was conducted. The depth profile measured with a laser confocal microscope revealed that the indentation is accompanied with “sink-in” volume, which can exhibit nearly perfect shape memory effect. The depth of sink-in is as large as the half or the depth of indentation and thus cannot be ignored.

A heat-engine using Ti-Ni shape memory alloy (SMA) driven by low-temperature waste heat energy has been investigated for waste heat recovery potential system. In order to improve the cooling efficiency of the SMA element, we proposed the use of a tape-shaped SMA element instead of a wire-shaped SMA element. However the manufacturing cost of the tape-shaped SMA fabricated by arc melting method is higher than that of a wire or coil shaped SMA. To reduce the manufacturing cost, we fabricated a tape-shaped SMA element by the centrifugal casting method using an alloy fabricated by the powder metallurgy method, and investigated the effect of aging-treatment temperature at 573 to 673 K for 72 ksec on shape memory characteristics of this tape-shaped Ti-Ni SMA specimen fabricated by the centrifugal casting method.

Transformation temperatures decrease with increase of aging treatment temperature rises up to 623K, above which they increase. This tendency is thought to be due to variations of Ni-rich precipitations and dislocation density by the variation of aging treatment temperature.

In addition, mechanical properties deteriorate as aging treatment temperature increase, because the precipitations and dislocation density decrease with increase of aging treatment temperature. From these results, it is thought that optimum aging treatment temperature of tape-shaped Ti-Ni SMA specimen fabricated by the centrifugal casting method is below 573K.

Since Ti-Ni shape memory alloys(SMAs) work well at temperature less than 373K ,SMAs are expect to apply the heat-engine which recovers low temperature thermal energy .The pulley-type SMA heat-engine, which is one of the SMA heat-engine, is driven by heating and cooling of the liner or coil shape SMA element. We fabricated tape-shaped SMA elements for the purpose of improving the product's life span. However, shape memory and mechanical characteristics of tape-shaped SMA are deteriorated with increasing number of heating/cooling cycle. In this study, the effects of heating/cooling cycle on the shape memory and mechanical characteristics of tape-shaped SMA element are investigated. The chemical composition of the specimen is Ti-45.0Ni-5.0Cu(at%), heat treatment condition is 673K for 3.6ks and the specimen is memorized two kinds of curvature shape φ10 and φ15. The thermal cycles vary from 0 to 105 times. Recovery bending force of each specimens tend to decrease with increase in the number of thermal cycles. This tendency is caused by increase of the volume fraction of residual martensite with increase in the number of thermal cycles. However, recovery bending force of φ10 curvature-shaped specimen decrease faster than that of φ15 curvature-shaped specimen because φ10 curvature-shaped specimen is applied more bending deformation.

A sintered compact of a near equi-atomic Zr-Cu alloy was fabricated by gas atomization and spark plasma sintering. The properties of the powder were investigated by means of scanning electron microscopy, a laser diffraction technique and X-ray diffraction (XRD). Furthermore, density and microstructure of the sintered compact were investigated by Archimedes’ method and XRD. As the result, it was found that the fabricated powder particles possess a spherical shape. The average values of the particle diameter and standard deviation are about 51.3 μm and 26.4, respectively. In addition, the powder consists of both parent phase and martensitic phase of the intermetallic compound CuZr. Furthermore, it was found that the density and microstructure of the sintered compacts vary with sintering temperature.

Because Fe-based shape memory alloy (Fe-SMA), is attempted to be applied to many engineering fields under different working environment loaded at various strain rates, it is necessary to evaluate stress-induced martensitic transformation which can control such excellent performances, at various strain rate. In this study, tensile tests of Fe-28Mn-6Si-5Cr alloy, which is one of Fe-SMA, are conducted under impact deformation. During impact deformation, it is attempted to evaluate the stress-induced martensitic transformation by measuring the volume resistivity as well as temperature for increasing a reliability of the alloy. The volume resistivity and temperature in the Fe-SMA is estimated experimentally by using the past-established circuit based on the Kelvin double bridge with a higher precision and an extremely-thin thermocouple as well as a laser Doppler vibrometer during impact tensile tests.

In order to reveal the mechanism of negative rate-sensitivity in tensile deformation behavior of Fe-28Mn-6Si-5Cr shape memory alloy, the forward and reverse transformation kinetics models has already been proposed. The sensitivity can be modelled by not only direct-introduction of strain rate into the model but also introduction of temperature change depending on the strain rate. Then, only the forward kinetics model is focused upon and the heat conduction equation is derived based on the weak formulation to include the heat transfer boundary condition. However, the identification of the parameter in the past-proposed forward kinetics model is insufficient to express the experimental results. According to the experimental results, temperature rises and stress decreases nonlinearly during unloading. These features cannot be expressed by the past-proposed reverse kinetics model. In this study, a reverse kinetics model is newly-proposed to reflect the modifications of the forward kinetics model. In addition, the identification of the parameters for the forward kinetics model is improved.

The development of applications using shape memory polymer (SMP) is currently of great interest. The mechanical properties of SMP are different above and below the glass transition temperature T_g. Based on this characteristic, shape recovery and shape fixity appear in SMP. If laminate the SMP with various T_g, we can develop the functionally-graded shape memory polymer (FGSMP) . In the FGSMP, the multistep recovery force can be obtained. In this paper, SMP foams with various T_g were laminated and the compressive properties of FGSMP foam (FGSMPF) were investigated. The results obtained are summarized as follows. (1) FGSMPF was fabricated with two different T_g. The fabricated FGSMPF shows two stepwise deformation behavior corresponding to two different T_g. (2) Deformation property of FGSMPF consist of T_g = 298 K and T_g = 321 K with density of 70 kg/m³ was almost same in the cyclic compression test with heating and cooling. (3) The value of the density of the bottom SMPF have an effect on the value of stress plateau occurring second time in the cyclic with heating and cooling compression test.

This study developed the position/load control system of shape memory alloy (SMA) actuator with electrical resistance feedback which can prevent the overload of the SMA wire by the restriction of the SMA actuator. The SMA wire used in this study is Ti-Ni-Cu alloy with 0.15mm diameter. The variation of measured resistance value and the applied stress after the restriction of the SMA actuator was investigated. The large resistance deviation between the setting resistance value and the measured resistance value occurred by the restriction of the SMA actuator and the applied stress larger than the allowable stress of 165 MPa also occurred. Hence, this study developed the newly position control program which adjusts the setting resistance value automatically so that the resistance deviation do not exceed the limiting resistance deviation. In case of the limiting resistance deviation of 25 mΩ, the applied stress was 133 MPa less than the allowable stress of 165 MPa. Namely, the newly developed position control program could prevent the overload of the SMA wire`. Furthermore, the relationship between the limiting resistance deviation and the applied stress was investigated. There was the linear relation between the limiting resistance deviation and the applied stress. Therefore, the newly developed position control program can control position and load without using position and load sensors.

In recent years, the popularity of cameras (photographs) has increased as a hobby after retirement, and single lens reflex cameras with high image quality are popular. However, single lens reflex cameras are heavy for elderly people and it may be difficult to photograph for a long time. Ti-Ni superelastic alloy is a functional material that can obtain large strain with small load even though it is metal, it is a metal attracting attention in recent years, and waist working aid applying this alloy has been put into practical use There. The aim of this study is to develop a camera holding aid that attaches to clothes, reduces the burden on the body by supporting the arm during camera shooting, and clarifies its effect.

Non-ferrous metals are used in automobile parts for making automobiles lighter and improving fuel efficiency. Braze welding is one of the techniques which can be used to join steel and other different metal. For dissimilar metal joint, the heating during welding process generates intermetallic compounds (IMC) which may cause stress concentration in the interface. For this reason, a dissimilar metal joint could result in weak strength of joint, especially under fatigue loading. As fatigue life is an important parameter for selecting materials in machine or structure, therefore a method for evaluating the fatigue life of dissimilar metal joint is needed. In the previous study done by Fukazawa et al. (2015), fatigue life evaluation of a newly developed FCW (Flux-Cored Wire) braze-welding of Fe-Al joint had been evaluated and several patterns of fatigue failure were reported. However, the mechanism that decides the failure patterns was not investigated. With respect to this, the present work aims to reveal the failure mechanism of the Fe-Al braze-welded specimen due to fatigue loading. The effect of IMC is discussed in detailed by conducting Scanning Electron Microscopy (SEM) analyses. As the results, the existence of IMC containing some voids was revealed. Moreover, crack generated in the interface is observed by SEM image in order to clarify the propagation mechanism.

The aim of this study is to investigate effect of plunging depth of welding tool on tensile shear strength of Al alloy/ CFRP friction lap spot joint. In this study, thermoplastic sheet was set between Al alloy and CFRP in order to join carbon fiber reinforced thermoset to Al alloy. In welding process, frictional heat is generated by contact between rotating welding tool and Al alloy. Generated heat is transferred from Al alloy to thermoplastic sheet. The thermoplastic sheet is melted and bonded to both Al alloy and CFRP. From results of tensile shear test and observation of welding part, in case of shallow plunging depth of welding tool, generated heat was not sufficient to form welding part. On the other hand, in case of more deeper plunging depth of welding than thickness of thermoplastic sheet, Al alloy was directly contacted to CFRP, as a result, decrease in welding area and tensile shear strength was induced. From result of measurement of axial load applied to the welding tool during the process, It is considered that higher axial load was generated to higher interfacial strength of CFRP/thermoplastic sheet and also tensile shear strength of Al alloy/ CFRP friction lap spot joint.

Honeycomb sandwich panels constructed with thin surfaces and honeycomb cores have characteristics like light-weight, higher stiffness and shock absorbency etc. Therefor they are usually developed for large-scale structure applications in various industrial fields. There is no existed standard testing method suitable to evaluate the fatigue strength of thick adhesive bonded structures like honeycomb sandwich panels. Fatigue strengths of adhesive-bonded sandwich panels constructed with aluminum honeycomb cores and CFRP (Carbon Fiber Reinforced Plastics) laminate faces were interested in this study. Fatigue experiments on sample cantilever beams of such honeycomb sandwich panels were carried out to validate the experimental method by improving the configurations of specimens, testing fixtures and instruments etc. From experimental results, proportional relationship between bending deflection and measured maximum strain could be used to validate the proposed testing method. Inner deformation or breakage of honeycomb core are considered to be occurred due to repeated compressive loads caused by large bending deflections. The destruction phenomenon can be confirmed from the decreased loading cyclic numbers with increased bending deflections. Based on the improved testing method, influences of design parameters, such as specimen length and height, foil thickness and cell size of honeycomb cores, on the fatigue strength of adhesive-bonded sandwich panels will be investigated in further experimental study.

Recently, lightening and high strengthening of the structural materials have been expected in the world. Carbon Fiber Reinforced Plastic, i.e. “CFRP” has superior material properties which is lighter and stronger than aluminum alloy, steel and so on. The purpose of this study is to clarify the flexural strength of adhesively bonded single-lap joints with Quasi-isotropic CFRP as both adherends. In this study, we used two ways. First, 3-points bending load tests were carried out to measure the failure loads for sixteen joint types. Second, we analyzed to investigate the stress and deformation state of sixteen joint types subjected to 3-points bending moment by finite element method. From these approaches, the failure loads of various joint specimens and then maximum crosshead displacements were obtained. The effects of lay-up patterns of quasi-isotropic CFRP on the joint strengths were discussed by reference to analytical and experimental results.

Solder has been used for the conventional bonding technology in electronic assembly for a long time. However, the traditional reflow soldering technique is characterized by high heating temperatures. Moreover, due to the progress of power devices, the working temperature in the electrical packages is increased. Therefore, we have proposed nanowire surface fastener (NSF) based on Cu nanowire arrays by which cold bonding for electrical packaging can be realized. Since copper is a high thermal conductive material, a satisfactory heat transfer characteristic is expected. In this paper, we investigated the improvements of the strength and thermal properties by changing the connecting load. The template method was used for fabricating Cu nanowire arrays, and the bonding strength of Cu NSF was evaluated by a tensile test. The highest bonding strength (205.06 N/cm²) was recorded when two nanowire arrays were connected by the connecting load of 125 N. Simultaneously, we measured the electrical resistance of Cu NSF by a four－terminal method. The electrical resistance showed the opposite behaviour to the bonding strength. Specifically, the larger connecting load we applied, the lower electrical resistance it showed. In metallic materials, since free electrons are carriers of the electric current and heat transfer, the electric conductivity and the thermal conductivity are closely related. Therefore, improvements of the electric and thermal conductivity are expected when electrical resistance decreases.

We analyzed the stress distribution around the interface between Ge and Si using the molecular statics with the MEAM and SW potentials. The lattice constants of Ge and Si are different of 4%, and the difference of lattice constant caused misfit dislocations along the interface. We also analyzed the stress distribution using the anisotropic linear elastic theory superposing the coherent stress field and the stress around the dislocation. Stress distributions obtained by the molecular simulation and the anisotropic elasticity are in good agreement.

In order to evaluate interfacial strength of a small size dissimilar materials direct joint between resin and metallic materials, application of indentation test by using a wedge shape indenter was investigated. Groove was machined at the interface of a joint and a wedge shape indenter was inserted into the groove to avoid that an indenter preferentially penetrates into soft material of resin. An adhesive joint between PET and A5052 was prepared for pre-test. Delamination at the interface occurred by the indentation test proposed in the present study. Interfacial strength evaluated by the present method showed good agreement with interfacial strength obtained by bending test. It is concluded that the indentation method proposed can evaluate the interfacial strength in dissimilar materials joint between resin and metallic materials. A dissimilar material joint between Ni alloy and PPS was then tested as a model joint of an actual small component. According to the result of the indentation test, delamination successfully occurred at the interface with the present testing method. However, the interfacial crack was propagated continuously during the indentation test. Therefore, in case of the model joint of actual component, indentation method proposed can evaluate the interfacial strength qualitatively by critical load for the delamination.

The tailor welded blanks between aluminum (Al) alloy, A6061-T6, and stainless steel, SUS304, had been fabricated by a friction stir welding (FSW) technique. The FSW tool was offset to the Al side and the probe was inserted only into Al plate. Hardness, tensile and X-ray CT of Al similar and Al/Steel dissimilar welds had been conducted. Based on the microstructural observation, small steel fragments were recognized in Al side due to the scratching of steel side surface by the probe. The hardness of stir zone (SZ) in Al side was lower than the base metal due to the dissolution of hardening precipitates during welding, where the lowest hardness located near the interface and thermo-mechanically affected zone (TMAZ) in Al side. The tensile strength of the dissimilar weld was about 40% lower than that of the aluminum alloy base metal.

Singular stress and electric displacement fields occur at the vertex of interface in piezoelectric joints under an external loading. It can be expected that concentrated electric displacements causes large electric fields in an adjacent space and electric potential will be induced on the surface of electrode when the electrode approaches to the electric field. In the present paper, a piezoelectric joint which four blocks of piezoelectric material are bonded using a resin is analyzed. In this joint, a singular field occurs at a center gathering four vertexes in blocks and the intensity of singularity in electric displacements around the center of cross section in the joint may be four times larger. The intensity of singularity is numerically investigated using several methods for analysis to pursue the possibility of application of the singular fields. It is shown that when piezoelectric materials with large piezoelectric constant are used, amplified electric displacements are obtained.

We proposed a new method to analyze the scalar parameter of the asymptotic solution around a three-dimensional corner of jointed dissimilar materials under thermal stress using H-integral method with the finite element method. We performed eigenvalue analysis of the singular stress field using finite element method analysis for eigenvalue analyses. Then, we analyzed scalar parameters of the singular stress using the H-integral and the usual finite element analysis for the linear thermal elastic problem. Obtained asymptotic solution corresponds with the singular stress around a three-dimensional interface corner directly obtained by the finite element method.

The materials with property of piezoelectric and piezomagnetic are often seen in high function or high performance sensor. And, dissimilar joints using the material property are used for such sensor much. When external force, electricity and magnetic are acted on the piezoelectric-piezomagnetic joints material, singular stress field is generated in the corner junction of the body junction, causing a decrease in the strength of the material, there is reliability may be lost.

Therefore, analysis of the order of singularity which indicates the strength of the singularity is needed. In the present study, the order of singularity in the interface of piezoelectric-piezomagnetic material joints is analyzed by an eigenvalue analysis based on a three-dimensional finite element method. And, the influence to the order of singularity of the material properties is considered.

Our previous study showed that the debonding condition of butt joints can be expressed as a constant value of the intensity of singular stress field (ISSF) by using 2D FEM model. To consider the real state of stress, in this paper, the ISSF distributions along the interface are shown for 3D butt joint model by varying the adhesive thicknesses. Here, the mesh-independent technique proposed in the previous study is applied to evaluate the ISSF of 3D FEM model. Then, the ISSF is found to be constant along about 90% of the middle region of the side interface. The ISSF increases rapidly in the vicinity of the vertex region. It is found that the critical ISSF values are almost the same independent of the adhesive thickness at the middle region of the side interface and at the vertex in 3D butt joint.