Recently, the 3D printer which can make products in a short time without cutting or casting has been attracted worldwide attention. It is possible that a customized product which is well suited to the individual is fabricated with low cost and in a short time. On the other hand, in the intelligent materials, shape memory polymer (SMP) has been practically used. In SMP, shape fixity and shape recovery appear based on the difference of properties of molecular motion between above and below the glass transition temperature in temperature variation. The thermomechanical property of SMP is close to that of the human body around glass the transition temperature. Since SMP has these characteristics, it can be applied to the elements coming into contact with body as a nursing-care robot in the medical field. Hence, if we make a product with SMP using the 3D printer, the new device which is well suited to the individual can be developed. In the present paper, the deformation properties of SMP made by the fused deposition modeling 3D printer were investigated.

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 element for the purpose of improving the product's life span. However, shape memory and mechanical characteristics of tape-shaped SMA is deteriorated with increasing number of heating and cooling cycle. This function deterioration leads to variation of transformation temperatures and shape memory characteristics. The output power of SMA heat-engine depends on the transformation temperature and shape memory characteristics of SMA element. Owing to this, the improvement of function deterioration characteristics of SMA element leads to the output stabilization of SMA heat-engine. In this research, the effects of heating and cooling cycle on the shape memory and mechanical characteristics of tape-shaped SMA element is investigated.

The pulley-type heat-engine using shape memory alloy (SMA) system, which is consisted of pulleys and coil or liner shape SMA element, is one of the representative SMA heat-engine for the recovering of low-temperature exhaust heat energy. However, the pulley-type SMA engine tends to reduce of output-power by the cooling insufficiency of SMA element because the main cooling method of this engine is air cooling. For improvement of the cooling efficiency and output power, we invented a new cooling system contained in the pulley and confirmed the availability. It is thought that the cooling position of SMA element for pulley-type heat engine has an effect on the output power of engine. Therefore, we fabricate the idler pulley with cooling system and the effect of cooling position of SMA element on the output power of heat engine is investigated.

Sharp memory alloy (SMA) is one of the functional material which shows the shape memory effect and superelasticities. Since the shape recovery temperature of Ti-Ni system SMA is below at 373K, this alloy is expected the element of heat-engine driven by low-temperature thermal of energy. Previous SMA heat-engines have not became commonplace because of short product life. Last year, we reported the planetary geared type SMA heat-engine using SMA spiral spring actuator. This heat-engine targeted an improvement life cycle of SMA and reduction mechanism. However, spiral spring actuator did not operate by the energy of hot water when this engine was soused a hot water, for this type actuator was low output power. Therefore, we attempt to use SMA coil spring element for improving the planetary geared type SMA heat-engine. In this research, we investigated the operating characteristic of planetary geared type SMA heat-engine using SMA coil spring element.

A constitutive model of shape memory alloys (SMAs) including phase transformation and plastic deformation is proposed. This model is based on the one-dimensional phase transformation model in which the austenite and the martensite phases transform one-dimensionally. A form of the yield function is assumed to the same as the driving energy minus the required transformation energy for the phase transformation. To show the validity of this model, a cyclic twisting test of an SMA shaft is simulated numerically. The result shows that the proposed model can reproduce the stress-strain-temperature relationship during the phase transformation and the plastic deformation qualitatively.

In this paper, the similarity relation between the singular stresses under the tension and the bending is confirmed by performing 3D FE analyses on the bonded cylinders under the tension and the bending which are subdivided by the same mesh pattern. The ratios of the intensity of the singular stress field under the bending to that under the tension are computed changing material combinations variously, the maximum and minimum values of the ratios are shown in the chart according to Dundurs' parameter (α, β) . Because the differences between the maximum and minimum values are small, the ratios can be controlled by Dundurs' parameter. Then, the ratios are larger than 0.7 and smaller than 1.0 in almost all material combinations with α(α - 2β) < 0.

In the present study, singular stress fields at three-dimensional piezoelectric bonded joints are analyzed. The conservative integral is applied for calculated the intensity of singularity at a vertex. The model applied electrical load is considered. In order to investigate the influence of integral area on the accuracy of the results, models with various integral areas are used.

Singular electric displacement fields occur around the vertex of interface in a piezoelectric material joints under loadings. In the previous study, influence of load conditions on singular electric displacement fields in the piezoelectric material joints were investigated to apply for engineering. In this study, some characteristics of singular electric displacement fields in an outside domain of piezoelectric material joints were investigated by using 3-dimensional finite element analysis. Influences of loading conditions on singular electric displacement fields are discussed . Singular electric displacement fields in an outside domain of piezoelectric material joints occur around the vertex of interface in it under loadings. Singular electric displacement fields are infulenced by tme change of the stress to depend on a piezoelectric material joints.

Recently, dissimilar material joints are used in industrial products for improving functionality and strength. In this study, the joining strength of adhesive joints of carbon fiber composite material which is an anisotropic materials are investigated through a conservative integral. The order of singularity and the angular function are calculated using the eigenvalue analysis based on finite element method. Intensity of stress singularity is calculated using a conservative integral. By using these analysis methods, quantitative evaluation of stress singular field at the edge of interface in the adhesive joints of carbon fiber reinforced plastic is conducted.

We proposed new technique to analysis the asymptotic solution around a three dimensional interface corners. We analyzed the scalar parameters of the asymptotic solutions using the H-integral, which is a conservative integral, in conjunction with the finite element analysis. Singular orders of these three-dimensional corners were obtained using the finite element method for the eigen analysis. We discovered that if λ is an eigenvalue of a three dimensional corner, –λ–1 is also an eigenvalue. Complementary eigenvalues and eigenvectors are used for the H-integral analysis to obtain the scalar parameters. If we select eigenvalues as –λ–1 and related eigenvalues for complementary solutions, H-integrals correspond with scalar parameters. We demonstrate that the obtained asymptotic solutions correspond well with the finite element analyses around three-dimensional interface corners.

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.

The geometrical concept of Volterra's disclination is applied to model the inhomogeneous deformation that occurs at the triple junction of grain boundaries in deformed polycrystal. It is shown that even though the deformation is restricted to maintain the strain compatibility on the three grain boundaries meeting at the triple junction, the misfit in the dihedral angles of the three grains would occur. The angular misfit gives the angle of the equivalent disclination that is accompanied by a logarithmic stress singularity at the origin, which is similar to the stress concentration at the triple junction in deformed tricrystals.

Recently, advanced semiconductor products have structures with thickness and width in nanoscale. As the size of the structures reduces to an nanometer level, a ratio of their surface to volume increases.In the present study, three-layered structure is analyzed using molecular dynamics (MD) method and the anisotropic elasticity theory. The analysis of stress and displacement near interface misfit dislocation in a two-phase anisotropic body is considering interface stress and interface elasticity. The stress and displacement distribution at the interface are compared the analysis considering the interface properties and the MD method.

Misfit dislocations appear along the interfaces between dissimilar materials due to the gap of lattice size. Since misfit dislocations affect stress field around the interface greatly, it is important to evaluate stress field around the misfit dislocations. However, the accurate elastic solution has not been obtained. In this study, we obtained the elastic solution around the interface with misfit dislocations by superposing two stress fields, which are derived from coherent elastic strain and misfit dislocations. Then, We assumed periodic misfit dislocations. The elastic solution around a misfit dislocation was obtained from Stroh formalism. We also analyzed stress field around the interface between dissimilar materials using molecular statics method. By comparing the result of molecular statics method with the elastic solution, we investigated the validity of the obtained elastic solution. The comparison was carried out in the case of the combination of ideal materials, and their gap of lattice size were assumed to be 10% and 3.3% in order to investigate the effect of dislocation on the stress field along the interfaces.

This paper deals with the strength evaluation of the dissimilar adhesive butt joint under tension and bending based on the intensity of singular stress field at the interface corner. In this study, the intensity of the singular stress can be analyzed by using the perfectly bonded model and fictitious crack model. The stress intensity factor of the edge interface crack is controlled by the singular stress field at the interface free edge in butt joint without the crack when the crack is very small. By using the experimental strength for carbon steel/epoxy/aluminum butt joint in a variety of the adhesive thicknesses under tension and three-point-bending, the fracture criterion of adhesive butt joint is investigated. The calculation shows that the adhesive strength can be expressed as the critical intensities of singular stress at the interface corner. In the fictitious crack model, the debonding strength is also found to be controlled by the critical interface stress intensity factor of the fictitious crack.

In this study, a suitable evaluation method of adhesive strength is investigated focusing on the intensity of singular stress field appearing at the end of interface. The effect of specimen geometry on the intensity of singular stress is considered by changing tensile force direction and fixed boundary length. It is found that the minimum intensity of singular stress can be obtained when the adherend thickness is large enough, and the deformation angle at the interface corner edge is smallest. The usefulness of the method is discussed focusing on the deformation angle at the interface corner edge.

Strength evaluation for brazed joint between OMC and A286 at high temperature is needed because the combustion chamber of LE-9 engine for H3 rocket is planned to be manufactured by HIP (Hot Isostatic Pressing) brazing for realizing high reliability and low cost. This paper introduces the internal pressure burst test and creep test results of brazed joint specimen connecting OMC and A286, respectively a copper alloy and a nickel-based alloy composing the combustion chamber. Internal pressure burst test results are evaluated by the strength of stress singularity field in brazed joint. Creep test results are evaluated by the stress at fracture origin after stress redistribution due to high creep rate of brazed material.

Recently in many traffic vehicles such as the aircrafts, high speed trains, cars or elevators many light-weight /high strength materials such as CFRP are used. In these cases the developments of new metal/CFRP joint structures are indispensable. Now the most anticipated joint method will be the adhesive joint. This joint structure have merits of high rigidity, but on the other hand have the demerit of large dispersions of strength. So, in this paper we present the bolted/adhesive hybrid joints. Which combines both merit of high rigidity and stable strength. Finally we recommend that this bolted/adhesive hybrid joints exhibit high effect when consist of multi bolt fastenings.

This study provides that effects of interface edge geometrical condition on bonding strength of a ceramic to metal joint system with arc-shaped free surface. An electro-conductive ceramic silicon nitride (Si3N4) and the pure nickel (Ni) were used in this experiment. The interface edge shape was characterized by defining as a configuration angle between the interface plane surface and tangential line at the edge of the bonded interface of the joint system with arc-shaped free surface. The dependency of the bonding strength on the edge angle was experimentally clarified in the silicon nitride to nickel joint with arc-shaped free surfaces. The optimum interface edge angle appears at geometrical conditions which fracture pattern changes. It also shows that optimum geometrical conditions can improve bonding strength. This study contributes to provide useful geometric interface shapes to improve the tensile bonding strength of ceramic-to-metal joint.

Three different resin materials were jointed with an aluminum alloy with surface modified. Strength of the joint depended on groove depth formed at the interface of aluminum alloy. Fracture morphology changed from pull-out mode to base material failure mode with increase in the groove depth. The critical groove depth at the transition point was different in the different joints. A new evaluation method of the interfacial strength was proposed by taking into account the transition behavior of the failure modes.

This paper deals with the cryogenic dynamic fatigue behavior of cracked piezoelectric ceramics under electric fields analytically and experimentally. The crack was created normal to the poling direction. Constant load-rate testing was conducted, using three-point bending technique, with the single-edge precracked-beam (SEPB) specimens at room temperature and liquid nitrogen temperature (77 K). The effects of electric fields and loading-rate on the fracture load were examined. Plain strain finite element analysis (FEA) was also performed, and the energy release rate for the permeable crack model was calculated to discuss the effects of loading-rate and temperature on the critical energy release rate.

In this study, we perform eigenvalue buckling analysis for swelling-induced buckling of porous gel membranes. Swelling process is analyzed by increasing the chemical potential of external solvent in an inhomogeneous field theory. To investigate the point of buckling and the buckling mode, eigenvalue buckling prediction is conducted using a quasi incremental loading pattern instead of using the chemical potential, because the chemical potential is not available in eigenvalue buckling analysis. This approach is verified by analyzing pattern transformation in gel membranes with a square lattice of holes. It is found that diamond plate patterns are successfully predicted.

This paper studies the dielectric and piezoelectric behavior of unpoled and poled barium titanate (BaTiO₃) polycrystals with oxygen vacancies. A phase field model is employed for BaTiO₃ polycrystals, coupled with the time-dependent Ginzburg-Landau theory and the oxygen vacancies diffusion, to demonstrate the interaction between oxygen vacancies and domain evolutions. To generate grain structures, the phase field model for grain growth is also used. The hysteresis loop and butterfly curve are predicted at room and high temperatures. The permittivity, and longitudinal and transverse piezoelectric constants of the BaTiO₃ polycrystals are then examined for various grain sizes and oxygen vacancy densities.

Double layer mattresses (DLM) are used commonly, but the correlation between the mechanical properties and the function of pressure redistribution is not revealed yet. In this study we measured the nonuniform deformation of the DLM with low and high repulsion polyurethane foams, which was compressed with a semicircular tube. We also carried out finite element analysis with a compressible isotropic hyperelastic model to obtain the deformation of the DLM and the pressure on the contact surface of the tube. The results showed the concentration of the strain in the vicinity of the semicircular tube and the concentration of the surface pressure at the most deformed location.

In this work, we developed the simulation method for ductile materials by using damage model and finite cover method(Finite Cover Method: FCM). Estimating the ductile behavior of materials and structures is basic interest in many fields of engineering. In nowadays, a lot of models to predict the ductile fracture have been developed. The damage model, which based on the continuum damage mechanics assumes the microscopic mechanism of the fracture as the damage evolution. However, the proposed simulations by using the damage model are not good at describing the discontinuous surfaces. Hence, the finite cover method(FCM) is one of the candidate for the implementation to generate the discontinuous surfaces. To simulate the process (e.g., crack generation or propagation of the discontinuous surfaces ) of the ductile fracture, we implement the damage model to our FCM codes.

Behaviors of crystal reorientation and twinning during rolling were calculated using the crystal plasticity. The calculations were performed for several Ni alloys with different stacking fault energies. The calculation results were compared with EBSD observation of cold rolled samples of the Ni alloys. Large amount of deformation twinning was observed in the rolled Alloy C22 that has low stacking fault energy. Both the grains with twinning and the grains without twinning were observed in the rolled Alloy C22. These behaviors were successfully simulated by the crystal plasticity.

The effect of morphological change in microstructure called by ‘rafting’ on fatigue crack growth (FCG) behavior of a directionally solidified Ni-base superally has been investigated. The FCG tests have been conducted in the rafted and non-rafted CT specimens. The anisotropic characteristics in the FCG rate were also explored. The crack growth rate of the rafted specimens was lower than that of non-rafted specimens at room temperature. At 600°C, the difference in crack growth behavior got significant. These results were discussed in relation to the crack propagation mode.

The interface strength of adhesive film measured by Peel test is determined by subtracting energy consumed for plastic deformation of substrate film from external work for peeling. The film and adhesive layer are conventionally regarded to be linear elastic for easy calculation, but thinner film of 100 μm may cause plastic deformation during peeling. The film deformation might be also affected by viscoelastic property of adhesive layer since thickness of adhesive layer is no longer negligible. In this study, the interface strength was evaluated by modifying conventional elastic model to consider viscoelastic behavior of adhesive layer. Stress in adhesive layer was calculated as a function of strain and strain rate, and the corresponding deformation of substrate film was computed by finite element method. The film deformation was compared with one obtained from conventional elastic model in terms of film thickness. The interface strength was also obtained from directly observing peel shape using high speed camera to validate the proposed model. As a result, it was found that the film deformations were all similar when the film was thick, but proposed model more accurately reflected the influence of peeling rate in the thin film. Furthermore, decrease in interface strength was confirmed for thinner film at faster peeling rate.

In this study, we analyze swelling-induced inhomogeneous deformation in swollen elastomers using two scaling exponents. Two scaling exponents are introduced into the Flory-Rehner free energy function, and the values are adjusted to fit the swelling dependence on elastic properties of swollen elastomers. A model with two layers is analyzed to reproduce swelling-induced inhomogeneous deformation. It is found that swelling-induced softening results in swelling-induced inhomogeneous deformation.

Much attention has been paid to composites made from biocompatible ceramics and metals in the medical field because the composites are expected to exhibit high mechanical properties and biocompatibility. The interfacial properties between ceramic/metal should be elucidate to evaluate their mechanical properties. In this study, we fabricated square pillar-shaped specimens with an interface made of partially stabilized zirconia (PSZ) and pure titanium (Ti) by the spark plasma sintering (SPS) technique. Then, bending tests were performed to evaluate the strength of the PSZ-Ti interface. As a result, fracture occurred within a reaction layer which was formed around the PSZ-Ti interface, and the bending strength of the PSZ-Ti interface lower than that of the monolithic PSZ and Ti.

Bioabsorbable polymer degrades in the body. Degradation rate of bioabsorbable polymer changes with molecular weight, crystallinity and size. In this study, the degradation of bioabsorbable poly(lactic acid) (PLA) was investigated. PLA is molded into plate shape by hot compression method. Molding temperature was 200°C. The plate was cut into tensile test specimen. Annealing was conducted on the specimen. Annealing temperature was 70°C and 130°C. Three types of specimens were used; non-annealing , 70°C-annealing , 130°C-annealing. Immersion test was conducted to evaluate the change in weight-averaged molecular weight due to hydrolysis and tensile test was conducted to clarify the effect of hydrolysis on mechanical properties. Molecular weight of Ingeo 4.5 mm , Ingeo 1.3 mm and Ecodear 1.3 mm of 130°C-annealed did not change at 8 weeks immersion. Young’s modulus of Ingeo 1.3 mm of 130°C-annealed decreased at 8 weeks immersion. Fracture strength of Ecodear 1.3 mm decreased at 8 weeks immersion.

The miniature specimens made from Sn-3.0Ag-0.5Cu (SAC) solder tend to show larger variation in the tensile strength than the ordinary size specimen. This means that the comparison of the internal structure between high-strength specimens and low-strength specimens will give valuable information to propose a method for giving high strength to solder joints in electronic equipment. Therefore, in this study, the tensile tests using miniature SAC solder specimens made by casting were conducted. The shape and distribution morphology of primary Tin crystal in the specimen after the tensile test were also investigated, and they were compared between the high-strength specimen and the low-strength specimen. The high-strength specimen had the primary Tin crystals which grow in a direction vertical to tensile direction, while the low-strength specimen had the primary Tin crystals which grow in a direction of about 45 degrees.

This paper attempts to quantitatively evaluate Bauschinger effect based on Field Theory of Multiscale Plasticity (FTMP). In FTMP, deformation-induced structures emerge spontaneously during the course of elasto-plastic deformation in a context-dependent manner, where “context-dependent” means that it tends to sensitively capture various pieces of information associated with the crystallography, fluctuating stress/strain fields and prescribed boundary conditions including imperfections. This study deals with FCC single crystal models and dual phase models with 23 grains under tensions followed by load reversal. The 23-grained dual phase models contain hard grains with 50% volume fraction with various strength ratios. What has been revealed first is the critical roles of the dynamic interplay among local/global instabilities caused or controlled by the orientation-dependent substructure evolutions, in terms of strain energy storage and/or release. By looking into the interrelationships among the incompatibility tensor, strain energy fluctuation and the duality coefficient at maximum tension measured right before load reversal, based on the Flow-Evolutionary hypothesis, the transient softening measured by Bauschinger strain is demonstrated to be evaluated quantitatively by the reciprocal of the duality coefficient, capturing governing mechanisms of the inhomogeneity-induced Bauschinger effect.

Modeling fatigue crack initiation process has been one of the long-standing difficult-to-solve problems, since it inevitably involves rational treatments about “transition from deformation to fracture,” i.e., a fatigue crack initiation evolved from a slip band. We tackle this issue by focusing on the critical roles of the PSB ladder structure, i.e., as (a)a carrier of concentrated plastic flow, (b)a generator of vacancies and (c)a provider of the diffusion path of the vacancies. The model is further extended to simulate surface groove formation and the subsequent evolution ultimately into a crack at the edge of the PSB ladder-surface interface.

This study attempts to develop a computational model for hierarchically-organized lath martensitic structures based on Field Theory of Maltiscale Plasticity (FTMP), in view of evolving inhomogeneities and interactions among different scales. To this end, the FTMP-based interaction formalism is introduced for taking account of contributions from high dense dislocations (scale A), and lath block structures (scale B). Creep deformation is demonstrated to be accelerated via the incompatibility for the interaction field from Scales A to B. The contribution of the interaction term becomes greatly enhanced when the applied stress level is low enough, because of highly-localized deformation within a lath block by the pronounced fluctuation in the interaction field of incompatibility.

In order to predict dynamic recrystallization (DRX) texture evolution during the forming processes of aluminum alloy, we propose a hypothesis to predict DRX evolution and develop a comprehensive computational tool for the thermal process metallurgy simulation. It consists of the Multi-scale finite element method based on the thermo-coupled elasto-crystalline plasticity analysis and the dynamic-explicit finite element procedure. The computationally evaluated texture evolution, which includes DRX texture, under the severe compression at high temperature is compared against the experimental results. The results predict the evolution of the cube component which is observed in the experiments. Therefore, our proposed method is approved to have a potential predicting DRX texture evolution.

A new scheme called Di-CAP (Deformation-induced Context-dependent Autonomic Pluripotency) modeling is proposed based on the flow-evolutionary law constructed within FTMP (Field Theory of Multiscale Plasticity). The scheme allows not only appropriate reproductions of deformation-induced inhomogeneities, but also flexible manipulations of them for further extended testing and/or restart analyses. The scheme is applied to a couple of problems to verify the concept. Demonstrated first are FTMP's basic capabilities in reproducing various dislocation patterns under typical loading modes. Secondly, the evolved substructures are shown to be freely manipulated via simple “cut-and-paste” operations. A systematic series of preliminary analyses on the reproduced models identified the critical pieces of information that must be transferred for the above purposes.

In recent years, phase change materials (PCMs) have attracted attention as a temperature regulator for electronic devices. Resin composite materials containing microencapsulated PCM (MPCM) are needed in order to secure the mass of PCM in thin mobile devices. The mechanical properties of resin composite materials containing MPCM have not been clear. In this study, tensile tests and finite element analysis of the MPCM/high density polyethylene (HDPE) composite material are conducted to investigate the effects of MPCM on the mechanical properties of the composite material. Four kinds of the test specimens, such as the mass fraction of MPCM 0% (pure HDPE), 10%, 30% and 50%, were prepared. Young’s modulus, fracture strength and fracture elongation of the specimen are discussed considering the interface strength of HDPE and the melamine resin capsule of MPCM.

In this study, the negative through-the-thickness Poisson's ratio of an angle-ply carbon fiber-reinforced plastic (CFRP) laminate is measured based on a full-field measurement technique using digital images. For this, a [±30] angle-ply CFRP laminate with 11.5 mm thick is prepared. The thickness change of the laminate under tensile loading in the in-plane direction is measured using a digital image correlation (DIC) measurement system and a 3D digital scanner. The through-the-thickness Poisson's ratio of the laminate is then calculated using the observed thickness change. It is shown from the results that the through-the-thickness Poisson's ratio becomes negative, and the negativity becomes stronger with the increase in the inelastic tensile deformation of the laminate.

Effect of temperature on notched off-axis fatigue behavior of CFRP laminates has been studied. Static and fatigue tests are performed at different temperatures on unnotched (UN) and center-hole (CH) coupon specimens of unidirectional CFRP laminates for different fiber orientations as well as for different stress ratios. The notched off-axis fatigue life of the unidirectional CFRP laminate at difference temperatures is predicted using the notched fatigue life prediction method that was started to develop in an earlier study on the notched off-axis fatigue life of unidirectional CFRP laminates at room temperature. The values of fatigue life predicted using the method are compared with the fatigue lives observed in this study. The predicted off-axis notched fatigue life of unidirectional CFRP laminates agrees well with the experimental fatigue life, demonstrating the potential usefulness of the model for prediction of notched fatigue life of unidirectional composites at high temperature.

Development of an engineering method for predicting strain ratcheting in an engineering thermoplastic polyamide 6 (PA6) has been attempted. For this purpose, the ratcheting behavior of PA6 is studied with emphasis on its temperature dependence. First, uniaxial ratcheting tests with different levels of maximum stress are performed on coupon specimens at different temperatures, respectively. The experimental results show that the accumulation of ratcheting strain in PA6 is significantly dependent on temperature as well as the maximum level of stress. The ratcheting behavior is similar to the transient creep behavior under constant stress in all aspects of its stress and time dependence. It is demonstrated that a master curve can be identified for the uniaxial ratcheting data for PA6 over a range of temperature by scaling the time axis with the help of a shift factor that depends on stress.

The static and fatigue behaviors of stampable discontinuous carbon fiber-reinforced polyamide (DCF/PA) composite have been examined. Static tension and compression tests are first performed at different temperatures (RT, 70°C and 130°C), respectively, to quantify the temperature dependence of basic mechanical properties of the composite. Then, constant amplitude fatigue tests are carried out for different stress ratios (0.1, χ, -1 and 10) at different temperatures (RT, 70°C and 130°C), respectively. The fatigue test results demonstrate that the S-N relationship of the discontinuous fiber composite significantly depends on stress ratio, and fatigue degradation occurs most rapidly at the critical stress ratio in line with the observations made thus far for continuous carbon fiber composites. Finally, the anisomorphic constant fatigue life diagram approach developed for continuous carbon fiber composites is applied to the DCF/PA composite, and it is proved that this method can successfully be used to predict the fatigue life values of the discontinuous carbon fiber-reinforced composite at different stress ratios as well.

Surface machined layer may change fatigue strength. In this study, the effect of cutting and grinding on low cycle fatigue strength of steels was investigated. Surface shape was measured using laser micro scope. Microstructure changing was observed by EBSD. There are more scratches and deeper microstructural change on the surface machining under low cutting speed. Fatigue life decreased when specimen was machined under low cutting and grinding speeds. However, fatigue life didn’t change on high speed cutting. From these results, fatigue strength is changed by a scratch configuration including the size, depth and shape under low cycle fatigue condition.Microstructural change has small effect on low cycle fatigue life.

Japan has the special feature that there are a lot of natural disasters compared with other country. Recently, the volcanic explosion at Mt. Fuji has been paid attention. If Mt. Fuji is exploded, it is expected that land-based gas turbines utilized as power generator in Tokyo bay inhales aerosol-like volcanic ash and its ash deposits on the turbine blade, and also all generators are stopped. In this study, high temperature corrosion property of nickel-based superalloy IN738LC deposited by volcanic ash was examined. In order to achieve this purpose, high temperature exposure test and microstructure observation by SEM were conducted. Vickers hardness test and tensile test were also performed.

Purpose of this study is to model statistical characteristics of crack initiation and crack growth in PWR environment and to investigate them. 2-step experiment was conducted, which was composed of periodical strain-controlled fatigue test for 3 kinds of strain range conditions in simulated PWR primary coolant environment with type 316 stainless steel and observation of cracks on specimen surface with 2-step replica method. Statistical dispersion of crack initiation and crack growth were modeled. It was confirmed that environmental effect on fatigue life was caused by reduction of crack initiation life and acceleration of “appeared” crack growth rate by coalescence of cracks and not affected by acceleration of crack growth rate.

Integrity of cracked pipe is assessed by predicting crack growth. In the fitness-for-service (FSS) codes of Japan Society of Mechanical Engineers (JSME), the crack growth prediction is made based on the stress intensity factor at the deepest and surface points. A semi-elliptical crack is assumed not to become deeper than semi-circular. The deep crack is replaced with the semi-circular crack of the same depth. In this study, validity of the current JSME FFS code for predicting the crack growth at weld was discussed. Crack growth was simulated by finite element analysis together with an auto meshing technique. The residual stress distribution and retardation of the crack growth at the fusion line were considered in the simulation. It was demonstrates that the JSME FFS code brings about a conservative growth prediction even if the crack became deeper than semi-circular shape. It was also revealed that, when the growth in the surface direction was restricted, the growth in the depth direction could be predicted conservatively by the current crack growth procedure of JSME.

Fracture toughness tests were performed for borated stainless steel in the present study. Fracture resistance curves were determined by the unloading elastic compliance method based on the ASTME1820 as well as an image processing technique. The latter was applied to investigate the effect of strain rate on the fracture toughness using split Hopkinson bar method.

Charpy impact tests were performed for borated stainless steel in the present study. In order to investigate the effect of strain rate on the fracture toughness, starting position of a hammer was reduced until complete fracture did not occur. Impact strains were measured on the specimen and the fracture mechanisms were studied.

The basket of transport and storage cask must have enough mechanical property to support fuel assembly and play a role of critical control at all assumption phenomena which are being used. One of the basket materials which can be used for the cask is B-SUS304P-1 and this material is registered in the “Rules on Transport / Storage Packagings for Spent Nuclear Fuel (JSME S FA1-2007)” by the Japanese Society of Mechanical Engineers. B-SUS304P-1 shows ductile fracture behavior though Boron addition causes reduction of the elongation and fracture toughness of the material. Elastic-plastic fracture of B-SUS304P-1 was evaluated by using two-parameter approach fracture assessment diagram.

In this paper, mechanical properties of type CF-3M cast austenitic stainless steels (CASSs) aged at 548–673K for up to 30000 h were investigated using hardness test and elastic-plastic fracture toughness test in order to evaluate the thermal aging behavior. Moreover, the fracture toughness values obtained by fracture toughness test were compared with the predicted values by H3T model which is one of the fracture toughness prediction method for CASS. As a result, it was suggested that the H3T model was applicable to type CF-3M CASS.