This paper describes the multi-color microfluidic display with sub-pixels, especially the design strategy of the display. Our display has four primary color sub-pixels in the single pixel, and shows various colors by patterning the ON/OFF of sub-pixels (dyed-fluid show ON, and air show OFF). To show high quality and richly tonal color images on our display, small sub-pixels and large screen are required. However, the driving pressure must be greater than the pressure drop caused by the friction between the fluid and the channel wall, and the driving pressure limits the display design. Therefore, the quantitative design strategy of our display is essential for commercial application. Then, we calculated the driving pressure, and revealed the relationship between the driving pressure and the display resolution (sub-pixel size) and the screen area (the number of the sub-pixels). Finally, we confirmed the smoother color mixing by high resolution and large screen display.

In medical and drug discovery studies, it is necessary to investigate efficacy of drug candidates under development. Conventionally, cell-based assays using human cells are widely carried out as an alternative to animal testing for this purpose in vitro. However, it is difficult to evaluate the effectiveness over time of drugs using conventional methods which are not capable of measuring cell kinetics. Currently, microfluidic devices integrated with a glucose sensor have been proposed for measurement of cell kinetics in the research field of μTAS (Micro Total Analysis Systems). Because cells consume glucose as an energy source, glucose consumption is an important indicator related to their activities. We aim to develop a microfluidic device integrated with a glucose dehydrogenase (GDH) based glucose sensor with a dialysis membrane for long-term online measurement of cell activities. In this study, we evaluated function of a GDH-based glucose sensor with a dialysis membrane that we developed for long-term measurement. The results showed that a dialysis membrane prevent the blood serum protein adheres to the sensing membrane, suggesting that it is possible to measure cell kinetics long-term on-line on chips.

Plastic has become an essential part of modern life. In recent years, microplastics, less than 5mm plastics, have been rising an international environmental issue. Above all, laundry wastewater is considered to be one of the largest sources of microplastics. In this study, we designed the microchannel network to separate microplastics from laundry wastewater based on acoustic focusing. In a microchannel, microplastics focused at the center of the flow channel by acoustic force are drained only from the center channel at the tree-branch channel. When 1/3.2 of the total flow goes into the center channel, microplastic suspension is concentrated 3.2 times. By performing this process four times, microplastic solution will be concentrated over 100 times. The flow model of serial separations was designed with 3D CAD software and was analyzed by COMSOL Multiphysics. The simulation result showed that the designed microchannel combined with acoustic focusing would concentrate the microplastic suspension by over 100 times.

Ultraviolet (UV) rays or radiation impose crucial damages to the intranuclear DNA, causing cell death and carcinogenesis. Therefore, researches focusing on the mechanism of DNA damage generation and repair is important. We previously found that the UV radiation-induced DNA damages were significantly suppressed in the nucleus compressed by using a microfabricated substrate (micropillar substrate) in which fine cylinders with a diameter and height of several μm are arranged. However, the detailed mechanism underlying the UV radiation resistance of DNA in the compressed nucleus has not been clarified yet. In this study, we investigated the detailed mechanism of the promotion of the UV radiation resistance of DNA caused by the nuclear deformation. The nucleus in the cells on the micropillar substrate manifested a significant resistance for UV radiation, especially on the micropillars with circular cross section. Detailed observation with confocal microscope revealed that intranuclear DNA concentration facilitated by the nuclear deformation with the circular micropillars and leads to improve the UV radiation resistance of DNA. Our finding may provide a new concept for improving the radiation resistance of cells.

The effect of multi-step ultrasonic shot peening (M-USP) on the fatigue characteristics of austenitic stainless steel was investigated. It is known that austenitic stainless steels in the atmosphere are hard to rust because they are covered with a passive film. However, the peening effect on stainless steel has not been well investigated. The test materials are four types of commercially available austenitic alloys SUS304, 304L, 316, 316L. The shot used was a bearing steel ball with a hardness of 800 HV and a diameter of 1, 2, and 3 mm. By M-USP, the surface roughness was reduced and the hardness near the surface was increased. Moreover, as the shot diameter increased, a hardened layer was formed deep inside the material. The fatigue limit of M-USP treatment increased by about 87 MPa compared with that of USP treatment. It was found that M-USP treatment was effective for improving fatigue characteristics.

Modified 9Cr-1Mo steel is used for the steam turbine rotors because of its superior high-temperature property. Creep-fatigue damage progresses preferentially at stress concentration portions in the steam turbine rotors. In this study，creep-fatigue tests using round notch bar specimens on a modified 9Cr-1Mo steel have been conducted to clarify effect of multiaxial stress conditions on failure life. The failure life of round notch bar specimen was much shorter than that of plain specimen under the same nominal stress conditions. From observation of notch root of the creep-fatigue damage specimens，it suggested that most of the creep fatigue life was occupied by crack propagation up to 1mm from the notch root surface. A new creep-fatigue life evaluation method of round notch bar specimens，in which concept of a damage evaluation area was introduced，was applied. As a result，creep-fatigue lives of the round notch bar specimens were accurately predicted by applying the new procedure with the nonlinear damage accumulation rule.

The fatigue properties of thin wires, which are micro materials, are different from those of bulk materials, and the fatigue properties vary widely. In this study, the fatigue test and the coaxing effect test were conducted for the purpose of investigating the fatigue properties such as the existence of the fatigue limit and the existence condition of the fatigue limit in the Ti-6Al-4V alloy thin wire in which the fatigue limit exists in the bulk material. In addition, the tensile and hardness tests were conducted to examine the variation in the properties of thin wires. As the result of the fatigue test, two types of fracture behaviors were observed: crack-propagation-dominant fracture and necking-dominant fracture. Since the necking–fractured specimens tended to have a relatively short fatigue life, it is considered that one of the factors in the variation of fatigue life is the difference in fracture mode. As a result of the coaxing effect test, the coaxing effect could exist in the Ti-6Al-4V alloy thin wire, and the possibility of existing of the fatigue limit was shown.

The hot ductility of Al-1.00mol% Mg-0.86mol% Si alloy with an average grain size of approximately 50 μm was investigated. At temperatures of 773 K and above, the hot ductility shows a local maximum value in the low and high strain rate ranges and shows a local minimum value in the intermediate strain rate range. In the low strain rate range, a large elongation of over 300% is obtained owing to grain boundary sliding (GBS), and in the high strain rate region, a high ductility of over 200% is obtained by a deformation mechanism called solute drag creep (SDC). The local minimum value (of the hot ductility in the intermediate strain rate range) is observed in the transition region of the GBS and SDC. In this paper, the hot ductility loss in the intermediate strain-rate range is discussed from the viewpoint of the high-temperature deformation mechanism and observation of the microstructure.

In order to investigate the effect of hydrogen on fracture mechanism of a carbon steel JIS-S25C in tensile tests, the metallurgical structure was observed by microscope and Electron Back Scattered Diffraction (EBSD) in terms of crystal deformation. Tensile tests were conducted using hydrogen charged and uncharged specimens introduced pre-strain (0%, 5% and 10%). The hydrogen content of the hydrogen charged specimens increased in increasing pre-strain, and the reduction of area decreased in increasing the hydrogen content. After tensile tests, the metallurgical structure of longitudinal cross section of tensile specimens near the fracture surface by microscope were observed. Many voids of hydrogen charged specimens were observed compared with uncharged. In order to reveal the mechanism of void initiation, crystal orientation of tensile specimens was observed by EBSD. The crystal orientation of the hydrogen charged specimens changed significantly in one crystal compared with the uncharged. The crystal orientation at any point obtained from EBSD maps was compared to that at the adjacent to the point.

Strength of concrete which is composed of cement paste and aggregates is lower than that of cement paste only because of the formation of a porous layer, called the interfacial transition zone, around the interface between the aggregates and cement. In this study, the strength degradation by aggregates was analyzed by using small glass spheres with a uniform diameter as a simplified aggregate to focus on the effects of interfacial transition zone. The compressive test was conducted using the specimens of plain cement paste and cement paste with glass spheres. The strain distribution on the surface of each specimen was obtained by 3D digital image correlation method to investigate the effect of the inclusion of the glass sphere. The strain distribution on the surface of the specimen revealed that the crack initiation is based on the maximum principal strain in both plain cement paste and cement paste with glass spheres, but the interfacial transition zone accelerates the crack propagation until fracture.

The purpose of this research is to investigate progression of local deformation generated under large deformation by using image analysis based on Natural Strain theory. In our previous research, the different total plastic strain and strain hardening are given in the test specimens by applying shear deformation in the forward and reverse direction alternately. And then, the progression of local deformation generated during tensile deformation after the pre-deformation of cyclic shear has been examined. As a consequence, it has been confirmed from the comparison of image daters at upper and middle positions with the results by displacement mater that local deformation begins to occur in the earlier stage of tensile deformation in the case of the cyclic shear more progress. In the present study, the progress of local deformation generated during tensile deformation after the pre-deformation of cyclic shear is examined under conditions that the strain amplitude and the number of cycle are greater than previous them.

Tensile tests of premium connection for Oil Country Tubular Goods (OCTGs) were conducted in order to study the effect of thread crest width on the ductile failure mode. As a result, it is found that, whereas a connection with a large thread crest width (1.864 mm ) was fractured with a crack penetrating in the radial direction of the pipe body, connections with small thread widths (1.573 mm , 1.283 mm ) were fractured with a crack penetrating in the longitudinal direction of the mating thread. When a tensile load was applied, as female thread crests at the end of mating went over the male thread crests sequentially, the end of mating could shift toward the pipe end side. Consequently, the ductile failure mode would be changed depending on the difference between the tensile strength of the pipe body at the end of mating and the shear strength of the mating thread.

Creep damage preferentially progresses at stress concentration portion, where stress gradient exists under multiaxial stress state, in high temperature components. Therefore, it is necessary to clarify creep damage evolution process and to establish a rupture time prediction method under multiaxial stress state. In this study, creep tests using plane specimens and four kinds of round notch bar specimens with different notch radius (notch tip radius 0.1mm(R0.1), 0.5mm(R0.5), 2.0mm(R2.0) and 4.0mm(R4.0)) on a 2.25Cr-1Mo steel were carried out. Creep rupture times of the notch specimens were longer than those of plane specimens. Greater number of voids were observed at around 0.1 mm from notch root in R0.1, and around 0.5 mm from notch root in R0.5, and around center of the specimen in R2.0 and R4.0. The finite element creep analysis of the notch specimens showed that triaxial tensile stress yields at the notch root sections with different distribution of the triaxiality factor depending on the notch radius. Creep rupture times of four kinds of round notch bar specimens were accurately predicted by the area average creep damage evaluation method.

MSE (Micro Slurry Jet Erosion) test is a new method for evaluating material properties in a micro area. In this method, erosion resistance was measured by colliding fine particles to the material surface with high speed. The erosion characteristics and mechanical properties of pure metallic materials, ceramics, coating material and surface treated material, were evaluated in this study. Mechanical properties and erosion rate has correlation in the metallic material when shape of impact particles was polygonal. On the other hand, relationship between mechanical properties and erosion rate showed correlation in the ceramic material when impact particles were spherical.

This study clarified the evolution of crystal orientation distribution in thickness direction of spun A1050 disk using electron back scatter diffraction pattern analysis. This study defined texture-I, II, and III as follows. The texture-I was rotated 20° around <111> from the Cu texture. The texture II was rotated 5° around its <110> from the Cu texture. The texture III was rotated 10° around its <110> from the texture-I. When the blank disk had a sandwich-type layer structure in thickness direction: Cu-I-Cu, the analysis results indicated the following texture evolution. In early passes, the structure was Cu-I-Cu. In later passes, the structures at wall and in the vicinity of the edge of the workpiece were Cu-II-II and Cu-III-III, respectively. In middle passes, the structure had a complex-type of three structures. These results suggest that the crystal orientation changed in the approximately two thirds in thickness from mandrel side by conventional spinning.

Currently, there is an increasing demand for high precision extra fine wires. In order to manufacture ultrafine wires with high accuracy, it is necessary to clarify the processing behavior inside the wire. Therefore, the purpose of this study is to investigate the change of the mechanical state inside the wire that has been drawn multiple times. However, since it is difficult to observe the wiredrawing process experimentally, the state inside the wire is observed by finite element (FE) analysis. We create two models each of which is a continuous four-passes wiredrawing unit, and in the simulation we transpose the end state of the first model into the beginning state of the second model, which means we conduct a continuous eight-times wiredrawing calculation. From the analyzed results, it is found that the mechanical state inside the wire changes greatly as the number of working passes increases. The plastic strain inside the wire increases as the wiredrawing process continues, and its values differ between the outer (peripheral) and the central portions of the wire. The stress inside the wire increased as wiredrawing continues. However, for the larger area reduction, the stress does not increase so much.

To investigate effects of dislocation density on microscopic stress distribution and macroscopic stress-strain relation, we conducted crystal plastic homogenization finite element analysis of Ti-6242 alloy subjected to in-plane reverse loading with dislocation density calculation. As a result, Statistically Stored (SS) dislocation density increased with occurrence of slip deformation for all conditions. On the other hand, Geometrically Necessary (GN) dislocation density was less likely to accumulate at the interface in the parallel relationship between primary slip systems of hcp and bcc. Although GN dislocations only develop near the interface, a large increase in GN dislocation density affects the macroscopic stress-strain relation.

In recent years, miniaturization of solder joints has progressed as performances of electronic devices advanced. This leads to more sever mechanical conditions on the solder joints than before, and requires an evaluation of their strength reliability with high accuracy. In this study, a simple estimation method for the fragility of solder joints on electric substrates in smartphones against dropping impact is proposed. First, the modal and frequency response analyses of substrates are performed to obtain the mode shapes that are assumed as dominant deformation shapes just after impacts. Then, a fatigue failure analysis of solder joints is conducted with referring to those shapes. The estimated results are compared with experimental results, and both results indicate similar tendency in terms of positions of failed solder joints.

Thermal fatigue assessment is often required for high temperature components such as those in thermal power and chemical plants. The procedures used to evaluate fatigue life consumption of a component subjected to cyclic non-steady thermal loading are rather complicated and, in many cases, difficult to carry out. In addition, experimental validation of a thermal fatigue assessment by using FEM has been rarely carried out due to the high cost and length of time required to perform tests where a specimen is subjected to cyclic thermal loading. This study deals with a test previously performed by JAEA in their sodium flow test facility. The stress-strain history imposed on the specimen was mainly non-proportional. In this study finite element analyses, non-steady-state thermal transient and stress analyses were performed using open source FEA software (Salome-Meca, Code-Aster) to evaluate changes in thermal stress and strain. The simplified assessment methods previously proposed for determining the pair of time steps that define the maximum stress range were applied and subsequently compared.

Although fatigue crack propagation in low cycle fatigue loading can be evaluated by using fatigue J-integral ranges, the elastic-plastic analysis of cracked component needed to estimate those parameters is usually costly and laborsome. The enhanced reference stress method can be employed in estimating elastic-plastic J-integral from stress intensity factor and limit load solutions in order to save costs and labor. However, it has limitations on the shape of the crack. In the study that designed to improve usability by creating a database, open source CAE (Salome-Meca, code_aster, ver. 2018) was used to get stress intensity factor and other necessary solutions such as corrections factor，and the commercial software CAE (Mentat, MSC. Marc, ver. 2019) was used to compared with the results. On the basis of verifying the elastic-plastic analysis results, these solutions were applied to the enhanced reference stress method. In addition, Python script that saves labor was used to perform FEA effectively.

In recent years, a significant amount of studies have been carried out on weight reduction, efficiency and optimization of mechanical structures. For example, car engine developments are directly related to global environmental issues such as global warming. In this field, weight reduction and increase in the efficiency of the engine are especially important factors. It is necessary to investigate the deformation characteristics of aluminum alloys subjected to the thermo-mechanical loading when developing engines. In this paper, a constitutive model explaining the deformation of aluminum alloys subjected to the thermo-mechanical loading is developed. The developed constitutive model separately employs the elastic, plastic and creep models. The effect of parameters used in the constitutive model on the simulation is also discussed. As a result, the constitutive model well explained the stress-strain relations caused by the thermos-mechanical loading except for the stress relaxation at high temperature region. To explain the stress relaxation, the effect of the creep strain on the thermo-mechanical deformation should be increased and the constitutive model should be modified.

The purpose of this study is to make clear the strain behavior obtained under cyclic loads after applying large pre-deformations on the basis of the Natural Strain theory. In our previous study, using the test specimens made of tough pitch copper which is already applied large pre-deformations of tension, shear, and combined load of them, the yield stresses with increase of the number of cycles have been investigated. As for yield phenomena in these studies, the decreasing tendency of yield stress has been mainly investigated under the condition of constant strain amplitude. Hence, detail studies under constant stress amplitude have not been done in our previous study. Therefore, in the present study, focusing on the pre-deformation of simple shear which is applied stress in the reverse direction with various values after large simple shear in the forward direction, the strain phenomena under cyclic loads are examined under constant stress amplitude.

This paper describes the anisotropy for the shape of yield surface generated under a large deformation on the basis of the Natural Strain theory. In the previous report, using the test specimens made of tough pitch copper, the yield stresses which is obtained by applying the pre-deformation of simple shear with alternative one cycle load have been investigated. In the present study, the yield stresses are investigated by using test specimens which are already applied the large simple shear with pulsating loads for two cycles so as to the total plastic strain in this study becomes the same as previous study for alternative one cycle loads. Then, the anisotropy of the shape of yield surface formed during cycle shear is revealed by investigating the yield stress with various sizes of reverse shear.

Next-generation power semiconductors using GaN and SiC are expected to be mounted on the power modules used in high-temperature environments over 200°C. Since ordinary lead-free solders and high-melting point solders containing harmful lead cannot be used for the mounting, some new bonding technique is needed to achieve that. Cu3Sn sinter bonding has attracted attention as the technique. To employ it for the semiconductors mounting, the strength reliability of Cu3Sn must be investigated firstly. Especially, the strength at high temperature must be clarified. In this study, we propose a test method for evaluating the tensile properties of Cu3Sn at high temperature. The method employs a Cu wire specimen having Cu3Sn layer. Using this specimen and normal Cu wire specimen, we conducted tensile tests both at room temperature and 200°C. The stress-strain relations obtained from those tests were applied to rule of mixture to estimate the stress-strain relation of Cu3Sn at each temperature.

In the previous study, we conducted tensile tests using a miniature specimen of Sn-3.0Ag-0.5Cu (SAC) solder and found out that the tensile strength of the specimen showed larger variability in the tensile strength than the ordinary size specimen even though the loading conditions were the same. Having investigated the shape and distribution morphology of primary Tin crystal in the specimen after the tests, it was found that the high-strength specimen had the primary Tin crystals which had grown in directions vertical to or parallel to tensile direction, while the low-strength specimen had the crystals which had grown in directions of about 45-degree. In addition, we found out that the growth direction of the primary Tin crystal also affected the creep resistance of the miniature SAC solder specimen. Since the fatigue lives of solders are affected by both the strength and the creep characteristics, the fatigue life of the miniature SAC solder specimen could be affected by the distribution morphology of primary Tin crystal. Therefore, in this study, we carried out fatigue tests using the miniature SAC solder specimens under multiple load conditions and discuss the correlation between the fatigue life and the distribution morphology of primary Tin crystal.

In next-generation power modules, the mounting of the power semiconductor chip using GaN and SiC, which can work in high-temperature environments over 200°C, is demanded. For the mounting, the lead-free solder with a melting point of around 200°C and high melting point solders containing harmful lead cannot be used. So in late years, the sinter bonding using Cu₃Sn, which is a Cu/Sn intermetallic compound, attracts attention. For the practical use of the bonding, it is necessary to clarify the strength reliability of the Cu₃Sn. Therefore, in this study, to evaluate the deformation properties of the Cu₃Sn, a micro-indentation tests are carried out at temperature from room temperature to 200°C for a bulk sample of Cu₃Sn made using the arc melting method. According to these results, Young's modulus and tensile strength of Cu₃Sn in each temperature are estimated. And it is found that the amount of inelastic deformation increases with a rise in temperature.

Due to global environmental problems and limited petroleum resources, we are interested in bio-based polymers made from renewable natural resources. Natural rubber (NR) is a bio-based natural polymer and it is soft and stretches well. The properties of NR can be tailored by adding fillers. Meanwhile, cellulose nano fiber (CNF) is a biomass material made by crushing wood into nano-order. Since CNF has several advantages of light weight, high strength, renewable and biodegradable, it is attracting attention as a filler to replace conventional natural rubber fillers, such as carbon black and silica. In recent years, several studies on CNF-added NR have been reported. However, most of these studies are related to the microstructure, and there have been no reports on the deformation behavior of the surfaces. The purpose of this study is to understand the reinforcing effect of CNF on the surface deformation of NR. In this paper, we considered the evaluation of mechanical properties (tensile strength, elongation, etc.) of CNF added-NR specimen, and observed the height distribution and microscopic height changes of the material surface by a confocal laser microscope. As a result, it showed different tensile behavior depending on the diameter of CNF. In the observation of height distribution, decreases of height distribution due to the pulling-out of the branching CNF during tensile deformation was observed.

In our previous study, using the method of image analysis based on the Natural Strain theory, the distributions for shear strain in the cross-section have been investigated when a large torsion is applied in the lubber test specimens. As a result, it has been revealed that there is difference between the experimental results based on Saint Venant’s torsion theory and the results based on present image analysis. Moreover, it became clear that the results based on modified Saint Venant’s torsion theory for the gauge length of test specimens approach to the results based on the present image analysis. However, it has not been examined the distribution of shear strain for specimens that have rectangular cross-section other than square cross-section. Therefore, the distribution of shear strain in the rectangular cross-section is compared with the distribution of shear strain in the square cross-section in this study. As consequence, the effect of elongation in the narrow side more increase as compare with wide side.

In recent years, CFRTP, which is being used in many industries, is attracting attention because it has the advantages of shorter molding time and easier processing than CFRP. In addition, 3D printers, which are being used in recent years, use a thermoplastic resin like CFRTP, so it is considered to be an appropriate molding method. Therefore, this study evaluates and compares the fracture toughness values of CFRTP molded by a 3D printer and CFRP of a different molding method. Then, the test speed is changed so that the behavior of unstable fracture of the test piece is not shown. It was possible to prevent unstable fracture by reducing the test speed of the CFRP test piece. CFRTP was found to fluctuate due to the effects of fiber cross-linking and fiber breakage, and a sharp increase and decrease in fracture toughness. However, the fracture toughness value was higher than that of CFRP, indicating that CFRTP has industrial utility.

In this study, the compressive response especially average load P_ave of lattice-cored sandwich tubes has been studied using the nonlinear finite element method. Numerical analyses are undrtaken based on the tubes associated with a variety of micro-architecture of the lattice core. This study shows that lattice sandwich tube has a potential to control the non-axisymmetric deformation of the tube to the axisymmetric deformation and enhance the average load P_ave.

Cellulose nanofiber, which is one of biomass materials, attracts attention as a novel polymer material in recent years. It consists of multiple cellulose microfibril (CMF) forming a hierarchical structure. In this study, we evaluate the mechanical properties of a single CMF and two CMFs as a hierarchical structure, using All-Atom model and molecular dynamics simulation. The effects of existence of water molecules are evaluated for a single CMF model in vacuum as well as the model in which water molecules are arranged. In the structural relaxation simulation in water, CMF shows initial twist larger than in vacuum. This is because hydrogen bonds named H02-O6, which are one kind of intramolecular hydrogen bonds, increase in water, but another intramolecular hydrogen bonds, H03-O5, decrease there, as compared with results in vacuum. In the torsion simulation of a single CMF, it is observed that the initial twist generated during the structural relaxation simulation leads to the anisotropy of rigidity depending on the torsion direction. In addition, the rigidity of a single CMF increases in water. In the simulation of transmission of rotation by a hierarchical structure consisting of two CMFs, it is found that rotation is transferred by breaking the hydrogen bonds at the interface. Also, hydrogen bonds at the interface tends to decrease due to the effect of water molecules existing at the interface. Furthermore, in water, the ratio of transmission of the rotation angle is improved.

The effective lifetime of Ni-base alloy decreased drastically by the frequent change of the output of power plants to assure the stable power supply with various renewable energies. The conventional linear damage rule, however, can no longer explain the accelerated damage of Ni-base alloy under creep-fatigue loading. The main reason for the accelerated damage was the change of fracture mode from transgranular to intergranular. It was also found that the initial intergranular cracking under creep-fatigue loading always appeared at certain grain boundaries. Therefore, in this study, intermittent creep-fatigue test was applied to these two Ni-based alloys at 750oC and the change of their micro texture was continuously monitored by using FE-SEM (Field Emission-Scanning Electron Microscope) and EBSD (Electron Backscattered Diffraction) analysis. Eventually, two completely different degradation modes were found in the two Nick-based alloys, due to their different microstructure.

In the Ni-based superalloy Alloy 625, which has been developed for the next-generation high-efficiency thermal power plant, Nb carbides precipitate at grain boundaries during operation at elevated temperatures under high-load conditions. This growth of precipitates degrades the long-term reliability of the alloy, because the growth of creep voids are accelerated around it, and thus, grain boundary cracking is accelerated. Therefore, continuous monitoring of carbide precipitates near grain boundaries in the material used for pressure vessels, pipes, and turbine blade during operating is an essential issue to prevent accidental fracture. In this study, a new non-destructive detecting method of Nb-base precipitates in the atmosphere was proposed by measuring the spatial element distribution using the reflectance spectrum of visible lights. The growth of the precipitates was observed under creep loading at 750oC.

Ni based superalloy IN 738 LC is used for the first stage blades of power generation gas turbines and aircraft jet engines. Creep damage occurs preferentially in stress concentration portions. In this study, creep tests have been conducted by using smooth and round bar notch specimens on IN 738 LC to clarify relation between creep damage extension and stress conditions, and crystal misorientation parameters. Creep rupture time of the notch specimen was longer than that of the plain specimens showing notch strengthen effect. Significant difference of void growth behavior between the plain and notch specimens was not observed. The maximum void length took the maximum value within 0.5mm from the notch root in the notch specimen. This corresponds to higher axial tensile stress and axial creep strain yielding at around the notch root. The results of the crystal misorientation measurement suggested that GRODave corresponded to axial creep strain because there was not significantly different in the relationship between GRODave and damage in the smooth specimen and near the notch root of the notch specimen, and the creep strain was equivalent at the same area.

The dielectric elastomer generators (DEGs) have the characteristics of high energy density. However, the performance of DEGs is affected by dissipative loss, such as viscoelasticity and current leakage. In this paper, the effect of dissipative loss on the performance of DEGs was investigated by conducting experiments and using the model of dissipative dielectric elastomers. The energy conversion efficiency of DEGs (VHB 4905) was experimentally measured with various stretching rates and maximum stretch ratios. It was shown that both the low stretching rate and large maximum stretch ratio result in remarkable current leakage, and the excessive current leakage even leads to negative efficiency. When the maximum stretch ratio was 5.0 and the stretch rate was reduced from 5.0 s^-1 to 1.5 s^-1, the mechanical to electrical energy conversion efficiency decreased from 11 % to 5%. Both the carbon grease and carbon nanotubes were utilized as compliant electrodes under the same testing conditions. The trade-offs between large power output and poor conversion efficiency were discussed.

In this study, we conduct finite element implementation of a Gent-Gent hyperelastic model for swollen elastomers. To this end, an inhomogeneous field theory for swollen elastomers is extended using the Gent-Gent model, which includes the effects of limiting chain extensibility and the second strain-invariant. The extended theory is implemented into a commercial finite element package using a user-defined material subroutine. The inflation of a spherical balloon made of swollen elastomers is computed and the results are verified with an analytical prediction.

We perform a finite element analysis of gel membrane constrained on a grass substrate to investigate influence factors in a three dimensional structure assembled from a gel film. In-plane compressive stresses cause a three dimensional deformation due to swelling of a gel film. Such a deformation is influenced by attractive force, friction, imperfection and so on. In this study, we, particular, investigate the influence of attractive force by conducting finite element analysis for the Neo-Hookean body. The obtained results are shown to discuss deformation patterns caused in response to different attractive forces.

In this study, the internal structure of auxetic materials was evaluated by finite element analysis. The auxetic materials have periodic voids. Volume of auxetic materials decreases and the density increases under compression. This kind of behavior is referred to as self-contraction. The structure does not necessarily exhibit self-contraction even materials have periodic voids. Finite element analysis showed the deformation behavior of the model on compression displacement. In this paper, the elliptical void model and the dumbbell void model were proposed. Multiple internal structures were created to change the elliptical void angle θ. Self-contractility was improved in the case of placing the elliptical void diagonally to the compression direction. From this results, rotation of internal structure is related to self-contraction. The dumbbell shaped void model composed more rotatable structure. The internal structure made of dumbbell shaped void gave the model high self-contractility. Auxetic materials consisting of periodic voids needs rotational mechanism in its internal structure. The self-contraction occurred stable in the case of rotation angle increases constant.

As for ausforming of medium-carbon steel (Fe-0.56C-0.2Si-0.71Mn-0.017P-0.01 mass%S), it is investigated whether compressive stress during quenching changes the hardness of martensite. The result of hardness measurement indicates that the hardness of martensite is independent of compressive stress. In addition, whether some changes occur in the martensitic microstructure is investigated. There is no change in the size of martensite blocks and no change in the longitudinal direction of the martensite blocks. There is a slight tendency for specific variants to form preferentially in stressed test pieces. It is considered that the hardness does not change because the microstructure does not change significantly.