Vibrating reed machine to thin plate fatigue test is a kind of resonance type, invented by Hirata 1995 as the method of a speaker unit was used as the vibrator. In the case of the fatigue evaluation of thin plate plane bending stress as typified by bellows are needed, it was expected as the effectual method. There are little research papers that made adequacy evaluations about absolute level of fatigue data. Furthermore, even though the test method is high-speed and simple, it doesn't become universal. And so, this paper is appeared to make adequacy evaluations of thin plate vibrating reed fatigue test with testing thin test pieces actually. In this time, adding the determined points of the displacement, and using a vibration exciter, accuracy is increased. Vibrating reed fatigue tests were carried out for Inconel 718 in ambient air using 5 mil and 8 mil notched specimens with 64 Hz and 110 Hz. Fatigue results appeared that the fatigue strength in vibration reed method was higher than that in rotating bending fatigue tests with 55 Hz reported by Kawagoishi et al. 2006. Then pointing out the stress field of crack tip in the difference of thickness, the calculations of each stress intensity factor conduced to the effect of thickness. The increase in fatigue strength of thin plate was caused by the reduction of stress intensity factor in the crack tip with early crack growth.

It is important to manage the growth of fatigue cracks for a long time. These cracks are growing due to vibration or welding heat, generally. When a crack length runs into the limit, it becomes unstable fracture state. Then, it cannot be managed. In this study, fatigue crack from the stress distribution at the crack tip is to clarify the process until the limit crack length, to perform the development of stress relaxation and the remaining life extension using elasticity. The results of this study, it is possible to release stress concentration by utilizing the piezoelectric actuator and to prolonging a life of steel materials under cyclic loading.

More than ten years, an author has been developing a study for diagraming and formulating fatigue strength of notched and un-notched specimens. As a result, two fundamental and important concepts have been proposed; a hypothesis of cyclic plastic adaptation and a size effect criterion of a yield-zone-partitioning type. The former describes microscopic actual cyclic stress behavior at a fatigue slip band. From this concept, an equivalent cyclic stress ratio R_EQ and equivalent mean stress σ_meanEQ are derived as a parameter correlating a cyclic stress condition of the notched specimen with that of the un-notched specimen, and as a result a fatigue strength diagram is formulated with a consistent equation for a large-sized notch type and un-notch type specimen. The latter concept of the size effect is formulated based on a normalized yield zone growth curve drawn from a notch root yield zone model (NRYZ model) that has been devised/constructed based on Dugdale model, and as a result a subordinate parameter that concretely quantify the size effect and inserted in the equation of the fatigue strength diagram has been derived. In the present paper, background, significance and perspective of the study are described with reviewing the outline of approach.

In this study, the effect of residual stress on indentation load-depth curves, which were obtained through the instrumented indentation techniques, was numerically investigated. Three-dimensional finite element models of the instrumented indentation techniques using the Vickers and Knoop indenters were developed, respectively, based on the comparison with indentation load-depth curves measured. On the basis of the developed simulation models, the uniaxial and equi-biaxial stress conditions were achieved by applying thermal strain as initial conditions, respectively, to demonstrate the effect of residual stress on indentation load-depth curves. From the calculation results, the penetration depth-dependence of the conversion factor between the residual stress and the change in indentation load due to existing residual stress was discussed. Then, it was concluded that the conversion factors between the residual stress and the change in indentation load due to existing residual stress were approximately expressed as a quadratic function of penetration depth for each residual stress condition and indenter shape.

In this study, fatigue strength of high-modulus type PBO (Poly-p-Phenylene Benzobisoxazole) fiber with kinking damage was investigated in monofilament fatigue tests. PBO fiber is high polymer material and has the highest tensile strength and tensile modulus of elasticity in any polymeric fiber. Kinking damages was created on surface of virgin fiber by winding bundle fibers to steel rod. Diameter of steel rod was set to 0.625 mm. Average value of compressive strain on surface of fiber determined based on the diameter of steel rod was -1.71 %. Load-controlled fatigue tests were carried out using a sinusoidal load with frequency 10 Hz and stress ratio of R = 0.5, and the load cell capacity was 10 N. It was found that fatigue strength of PBO fiber with kinking damage was lower than that of PBO fiber without kinking damage. Fatigue strength decrease of PBO fiber with kinking damage in a low cycle area was larger than that in a high cycle area.

The purpose of this study is to investigate the effect of wood particle size on mechanical properties of wood plastic composites (WPC). The target of this study was wood flour of 100 μm or less. Wood chips which were manufactured from cedars and cypresses were employed as the feedstocks. Wood flour was finally prepared by wet milling. Then the average size of wood flour was adjusted to three types (approximately 30 μm, 60 μm and 140 μm) by changing the milling time. Their wood flour was kneaded with polypropylene and maleic anhydride grafted polypropylene (MAPP). Then weight fraction of wood flour and MAPP was 10%. The tensile test specimens were prepared by injection molding. Mechanical properties of the composites were evaluated with the uni-axial tensile test. The results indicated that elastic modulus and strength decrease as the wood particle size becomes smaller. We employed multiscale finite element method based on homogenization in order to understand the influence of microstructural factors on elastic modulus of the WPC. The computation indicated that the wood particle size dependence of elastic modulus is caused by mechanical property change of matrix.

In this study, thermal deformation of Carbon Fiber Reinforced Plastic (CFRP) heated rapidly by JAXA/ISAS arc wind tunnel is measured by using digital image correlation. The specimen of CFRP is exposed to plasma flow. Then, the specimen is heated rapidly to approximately 2300°C. Stereo digital image correlation is used to measure in-plane and out-of-plane displacement of the specimen. Ceramic bond is applied on the specimen surface as high-temperature resistance random pattern. An infrared ray cut filter is used for cutting strong infrared radiation from the specimen. Reference images are updated to correlate rapid change of random pattern in deformed images. As the result, the expansive of CFRP by high-temperature airflow is observed by using digital image correlation.

It's important for industry products to keep enough adhesive strength between inorganic materials and organic materials. Therefore silane coupling agent is employed to improve adhesive strength. Silane coupling agent consists of the hydrolyzable group which reacts to an inorganic material and the organic functional group which reacts to organic material. Although the combination of hydrolyzable group and organic functional group should be designed, its variation is many and huge. Influence of B to A and influence of D to C are investigated. However, influence of D to A and influence of B to C aren't investigated. In this paper, we investigate the influence of molecular structure of the silane coupling agent on adhesive strength with the metal layers using first-principle calculation. Especially, we investigated adhesive strength of γ-mercapto propyl trimethoxysilane (MPS) and γ-aminopropyltrimethoxysilane (APS) with the chromium layer by comparing the cohesion energy.

This study examined the through-thickness residual stress in multi-pass welding joint via a coupled experimental/numerical approach. For a numerical approach, an integrated welding simulation model between arc plasma process and thermo-mechanical behavior during welding was developed. Then, the iterative substructure method was adopted for a fast simulation to solve welding thermo-mechanical problems. Using the developed modeling and simulation techniques, the through-thickness residual stress in multi-pass welding joint was estimated from welding process and heat input conditions, without preliminarily observed weld bead morphology and measured temperature profiles obtained by welding experiments. Meanwhile, the experimental measurements were conducted using stress relief method and deep hole drilling techniques. Through the comparisons of weld bead morphology, temperature profiles and through-thickness residual stress, the usefulness of developed modeling and simulation technique was discussed. As the results, we concluded that the developed modeling and simulation techniques have great potential to be efficient residual stress analysis with a high degree of accuracy.

The purpose of this study is to investigate the effect of flaw shape and microstructure on stress field of cracks initiated from small flaws. First, we investigated the effect of flaw shape on stress field of cracks initiated from small flaws using the previous data. Secondly, to investigate the effect of microstructure on stress field of cracks initiated from small flaws, the finite element analysis was conducted using the polycrystalline model. In this study, a single-phase ferrite steel was employed as the polycrystalline model. It is found that the increase of local stress due to the grain anisotropy is less than 10% in the single-phase ferrite model. Moreover, it is suggested that the effect of the microstructure on stress field of cracks was relatively small in the case of the single-phase ferrite model.

Slip deformation in tricrystal models subjected to cyclic deformation is investigated by a finite element crystal plasticity analysis code. Accumulation of geometrically necessary dislocations (GNDs) are studied in detail. Results of the analysis shown that non-uniform deformation and the high density of GNDs accumulated in the form of band around the grain boundary triple junction, this dislocation pattern formation shown that develop during increase of number of cyclic deformation and extend of development of dislocation pattern depend on the strain amplitude. Mechanism of dislocation pattern formation and extend of development of dislocation pattern are discussed from the viewpoint of influence of compressive deformation and strain amplitude on dislocation interaction of primary and secondary slip systems.

This paper describes the progress of the local deformation generated under large deformation, which is measured by using the image analysis based on the Natural strain theory. In our previous studies, the experiments of local deformations, i.e., the simple shear to the reversed direction after the forward direction, have been conducted. And as the results, it has been confirmed that the progress of the local deformation is almost the same if the sums of the strain is the same value even if the deformation path is different. In the present study, the developments of local deformation are examined under the uniaxial tension by using the specimen which is preliminarily applied the simple shear in the reversed direction after forward direction. Then, the effect of the pre-deformation of simple shear on the developments of local deformation generated under large uniaxial tension is revealed by changing the value of the pre-deformation of simple shear.

The purpose of this study is to elucidate the development of anisotropy in the yield surface by investigating the shape of yield surface which is generated under large deformation. In a series of our studies, focusing on the three types of different pre-deformation, namely, proportional loading of tension and torsion, shear after uniaxial tension and tension after simple shear, the experiments for examining the shape of yield surface have been conducted. From the results of these experiments, it was revealed that the anisotropy of the yield surface is closely related to the pre-deformation that is applied in the latter stage of deformation path. In the present study, the shape of yield surface, which is generated after applying the pre-deformation of simple shear in the reverse direction after forward direction, is examined. Then, the effect of the deformation history in the pre-deformation on the development of anisotropy in yield surface is revealed.

This study describes an efficient application of Rackwitz Fiessler algorithm to search out all of design points, utilized in the importance sampling simulation to estimate structural failure probabilities. Specify several initial points to execute Rackwitz Fiessler algorithm in respective quadrants of the basic random variables space and all of possible design points are determined. Numerical example to estimate the failure probability of structural system with nonlinear limit state function by the multimodal importance sampling simulation utilizing all of design points determined by the proposed method is presented to illustrate the proposed method contribute to give accurate estimation effectively.

Super-pressure balloons have been developed for scientific observation at high altitude. The strength of net that covers balloon's surface is important to utilize the balloon in safety. The purpose of this study is to evaluate the practicable condition by determining fracture strength and elastic modulus. Net of balloon have mesh of rope to cover the whole balloon. Polyarylate rope for our super-pressure balloon is formed by two strands which is consists of many thin fibers. Tensile test of a single fiber, a rope and a rope with a point of intersection were carried out. Rope is made of Polyarylate which is used for super-pressure balloons. The tensile strength of a single fiber is 80% of bulk specimen, and that of a rope is 45%. Following reasons are considered for the decrease of the strength; 1. a twisted rope has a torque which makes twist back force, 2. friction between piled fibers due to loading on piled fibers. Moreover, the strength of rope containing a point of intersection is 40% of bulk specimen. This is because friction is generated at a point of intersection where rope contact each other. Although the fracture strength of the Polyarylate rope is smaller than that of the bulk, it is well higher than that of the strength required for pressurized balloons. It is shown that the rope is practicable as a net of super-pressure balloons.

The lattice structure has possibility for making weight lighter. This is applicable for jet engine also. By utilizing 3D-printer, anyone can make lattice easier and cheaper. This paper report that tension tests are conducted with lattice specimen made by 3D-printer with orthogonal pattern. It is already known that those specimens have large surface roughness, therefore this paper shows the comparison between FEM result and tension test result to investigate this problem, and describe some notice for estimation of roughness.

Many threaded fasteners are used for joining of machine structures. Therefore, development of the bolt and nut excellent in fatigue and fracture is very important. It is necessary to get to know the load distribution on the screw thread for the se researches. There are many researches which used an experiment, theory, and FEM analysis among the researches about the load distribution of the screw thread. However, since there are few examples of research about nut height, it solves about maximum load and its position for the difference in nut length. In this report, the method of measuring the load distribution using strain gauge was proposed, and it compared with the theory of Sopwith and the FEM analysis. The thread type compared with a triangle tooth thread about a case of a buttress tooth thread.

In this study, quasi-static axial crushing behavior of hollow spheres is investigated by using finite element method. The effects of material and geometrical parameters on the crushing response have been calculated systematically. Based on our numerical results, an approximation equation for evaluating the axial-load versus displacement curve was proposed. This equation can be used for spheres with various combinations of radius and thickness.

In case structures form some boundary and are expected to keep some liquid or gas inside its boundary, it is very important to maintain the integrity of its boundary even if the external load becomes severe beyond the design basis level which prohibits buckling of structures. In this study we focused on the head plate structures subjected to external pressure. Pressure loading tests of some head plate test specimens by using hydraulic pressure loading unit were conducted. Also, detailed non-linear FEM analyses were implemented. Buckling behaviors and post-buckling behaviors of head plates, especially the influence of different thickness of test specimens were examined based on the test results and the numerical analysis results.

Small Punch (SP) tests were carried out for the ceramics thin plates for use in Solid Oxide Fuel Cell. As a result of SP tests, the fracture strength decreases with decreasing crosshead speed. The reason for decreasing fracture strength is the delayed fracture. Also, the fracture strength slightly increases with decreasing dimension of specimen. The specimen size almost has no effect on the fracture strength. Next, it was possible to measure a Young's modulus of the ceramics thin plates except for that with the small deflection. Three-dimensional SP model which introduced the semicircle crack as a preexistence defect was made, and the FEM analysis was carried out. In the case of φ10mm × 10mm specimen, there is a case in which stress intensity factor of semicircle crack on the indentation plane is larger than that on the back side. Therefore, there is a high probability that the specimen is fractured from preexistence defect in the indentation plane side of specimen. For that, it is necessary to decrease the thickness of specimen.

Piezoelectric materials are widely used as sensors, actuators, etc. Determination of stress intensity factor is important for piezoelectric materials with defects like a crack or inclusion. Analytical research of piezoelectric materials has been conducted enough. However, experimental research of piezoelectric materials is scarce because of difficulty of mechanical handling. Therefore, determination method of stress intensity factor for piezoelectric materials is not fully-established. In this study, we focused on the similarity of analytical theory between piezoelectric materials and anisotropic materials. Based on the similarity, stress distribution around a crack and an elliptical inclusion are shown. Furthermore, methods that estimate stress intensity factor for piezoelectric materials from each physical quantity of anisotropic materials are discussed.

The conservative integral formulation is developed for calculating the intensities of singularities at a vertex of an interface in three-dimensional piezoelectric bonded joint. The model with three-real singularities is considered. The intensities of singularities of each term of stress singularity are calculated. Various integral areas, which located at various distances from the singular point, are used to investigate an influence of an integral area on an accuracy of results.

In press forming, pure titanium sheet has sufficient ductility. However, the seizure tends to occur during the deep drawing due to high reactivity with die materials. The authors reported that the heat oxided sheets were treated by oxide coating so as to get oxide surface layer effective for preventing the seizing. In the current study, the square titanium cups were formed by multistage deep drawing using oxided titanium sheets for preventing seizing. The sheets were employed and a flat sheet blank is formed into a square by a punch. Various cups were drawn by exchanging the punch and die. The die was a funnel shape without a blankholder in the subsequent stages. The effects of the oxide layer and die shape on the occurrence of seizure in multistage deep drawing were examined. The square cups were successfully drawn by oxide coating. As the number of drawn cups increases, the thickness strain increases at the corner of cups. However, the seizure did not cause even for cups of the 12th stage. It was found that the oxide titanium sheets have sufficient ability in preventing the seizure in multistage deep drawing processes.

In press forming, pure titanium sheet has sufficient ductility. However, the seizure tends to occur during the deep drawing due to high reactivity with die materials. In the current study, by using the resin composite die, the titanium cups were formed by deep drawing for preventing seizing. In the experiment, the material was pure titanium sheet TP340. The initial thickness of the sheet was 0.5 mm in thickness. The sheets were employed and a flat sheet blank is formed into a cylindrical by a punch. The effect of the die shape on the deep drawability was examined. The cups were successfully drawn by the resin composite die. Even if the number of drawn cups increased, the thickness strain hardly changed. The seizure did not cause in the case of 100 times of processing number of times. It was found that the resin composite die has sufficient ability in preventing the seizure in deep drawing processes.

To reduce axial forming load in upsetting process, upsetting process with cyclic torsion die motion was proposed. In the proposed upsetting process, cyclic torsion of torsional moment was simultaneously superposed with axial forming load during upsetting process. In this study, a cylindrical workpiece was twisted around the z-axis with an alternating amplitude angle of π/8 rad (22.5°) and a maximum rate of 0.05 rad/s (0.5 rpm) during upsetting with an axial compression speed of 0.1 mm/s. The maximum torsion frequency was 0.03 Hz. It was found that the axial forming load of the workpiece was reduced by approximately 5-40% in the forming conditions where torsion angle/axial stroke were larger than approximately 0.26 rad/mm.

Carbon nanotube (CNT) is attracted a lot of attention for new conductors because of its high current capacity, comparing with copper. In past study, carbon nanotube-copper (CNT-Cu) composite sheet was developed, which exhibiting similar conductivity as copper, but with a 100-times higher current capacity. However, since the length of CNT-Cu conductors was limited to several hundred μm long, the problem that using CNT with high electrical properties macroscopically remains to be solved. Therefore, in this study, untwisted CNT yarn was prepared by drawing multiwall carbon nanotube through die and was electroplated to realize metal CNT composite yarn with high electric conductivity and current capacity. For the influence of copper oxide layer, the electrical property of copper CNT composite yarn (CNT-Cu) showed a poor improvement from the untreated CNT yarn. On the other hand, both conductivity and current capacity of gold CNT composite yarn (CNT-Au) showed a higher value by the heat treating at 800°C, comparing with that of untreated CNT-Au.

This paper presents a proposal of the developed incremental forming method with optical heating system for CFRTP blank sheets. The blank sheet is fixed to a blank holder and is locally heated by a halogen lamp set under the sheet. The heated region of the blank sheet is formed by a spherical punch with reciprocating motion by a hammering unit, which is set opposite to the halogen lamp through the sheet. Discontinuous fiber sheet, which thickness is 0.5 mm, was used as blank sheets. The temperature distribution around the heated region was measured, and the temperature of the heated region, the same as punch diameter of φ5 mm, reached approximately 200 °C, at which the matrix of the blank sheet can deform plastically. The convex formed shape followed the punch shape can be obtained by the single point hammering without the sheet feed as simple forming conditions, and the superiority of the developed forming method was verified.

Cladding is the bonding together of dissimilar metals. One of clad products is the titanium clad steel sheet. It is effective to cover with pure titanium sheet to improve the corrosion resistance of the steel sheet. Titanium clad steel sheets are often achieved by rolling sheets together under high pressure. In the current study, the formability of pure titanium clad sheet by multistage deep drawing was investigated to enhance corrosion resistance of steel cup. In the experiment, the materials were pure titanium sheets TP270, ultralow-carbon steel SPCC, and stainless steel SUS316L. The initial thickness of the sheet was 0.2 to 0.5 mm in thickness. A total plate thickness of the blank was 1.0 mm. In the deep drawing process, the blank was employed and a flat sheet blank was formed into a circle by a punch. Various cups were drawn by exchanging the punch and die. The die was a conical shape without a blankholder in the subsequent stages. For the prevention, pure titanium blank was treated by oxide coating. By oxide coating, the titanium sheet has sufficient ability in preventing the seizure in multistage deep drawing. It was found that the titanium clad cups were successfully drawn.

Casting of a clad strip consisting of AM60 and AZ121 magnesium alloy was tried using an equal diameter twin roll caster with a scraper. The casting speed was 30 m/min and casting was conducted in the oxidizing atmosphere. The AM60 strip was cast using a scraper, and the molten metal of the AZ121 was poured on the scribed AM60 surface. The two-layer clad strip could be cast by one caster. The two layers were bonded strongly at the interface. The interface was clear. It was estimated that the AM60 was not melted by the molten metal of the AZ121.

In friction stir incremental forming, formed shape becomes a little smaller than objective one due to springback. To improve forming accuracy, tool path was modified by experimentally obtained calibration equation. A5052 aluminum alloy sheets which size was 150 mm x 150 mm x 0.5 mm were employed for specimen. A hemispherical tool with a diameter of 6 mm was used. The tool was rotated at 10000 rpm and moved at 3000 mm/min and sheets were formed into a frustum of conical shape which height of 20 mm and wall angle of 25 °. Distance from the edge of blank holder to start position of forming was changed and errors of initial diameter of a frustum of cone, forming height and bottom diameter were measured. Errors of wall angle and overall shape were measured due to springback. By modification of tool path, errors of initial diameter, forming height, bottom diameter and wall angle were improved from 7.62 mm to 0.23 mm, 4.76 mm to 0.16 mm, 2.27 mm to 0.27 mm and 1.09 ° to 0.12 °, respectively.

Carbon fiber reinforced plastic (CFRP) is increasingly used as a structural material in the aircraft industry due to its superior properties such as low weight, high strength, good toughness and so on. Drilling of CFRP is the most common post process of structural parts of aircraft. Recently, gyro-driving grinding wheel system has been developed as a new drilling system for CFRP. This system provides holes with high precision on CFRP without delamination and burr formation. In the gyro-driving grinding wheel system, a grinding wheel was used, instead of drill bits for drilling. In our previous study, Cu-bonded grinding wheel with diamond abrasive grains was fabricated by centrifugal mixed-powder method, which is an application of centrifugal casting. However, designed distribution of diamond grains in the grinding wheel cannot be obtained because of the influence of gravity on the mixed-powder set in the caster. In this study, Al-based grinding wheel with designed distribution of the diamond grains has been fabricated by the centrifugal mixed-powder method with preform.

Magnesium alloys are widely used in the automotive and aircraft fields. They have excellent physical and mechanical properties, such as low density and high strength-to-weight ratio. However, their poor corrosion resistance has been the main impediment in their applications. Surface modification is the main methods to control the degradation rate of magnesium alloys. This problem has been studied by many researchers. The authors have proposed a lining process of metals with thin aluminium foils using shot peening. In this method, the foil can be bonded to the workpiece surface bringing about large plastic deformation. The pressure generated by the hit of many shots is utilized for the bonding. In the present study, to improve the surface characteristics of magnesium alloy, the formation of an Fe-Al intermetallic compound film on magnesium alloy by compound treatment combining shot lining method and heat treatment was investigated. Shot peening was performed with a centrifugal-type machine using cast steel ball. The lined sheet is aluminum foil with pure iron powders, and the workpiece was the commercial magnesium alloy AZ31. The lining experiment was performed at 573 K in air. The lined workpieces are heat treated by laser in air. The Vickers hardness test was performed with a microhardness tester. It was confirmed that the present method could be used for the formation of functional films on magnesium alloy.

The effect of microshot peening on the surface hardness and fatigue strength of titanium alloy was investigated. Shot peening is a widely used surface treatment method for improving fatigue life. This process imparts compressive residual stresses on the surface, thus improving the fatigue life of the machine parts. In the peening process, the equipment were used an air-type machine and ultrasonic peening machine. The microshot used were high-carbon cast steel with an average diameter of 0.1mm. The surface hardness data showed that, in the case of microshot peening, work hardening extended deeper than the mean diameter of the media. In addition, in the case of ultrasonic peening, the surface hardness increased slowly with the projection time. The rotary bending fatigue tests were carried at a frequency of 3150 cycles/min. Improvement of the fatigue strength was observed by both treatments. The higher effect was found in the ultrasonic peening treatment, because a work-hardened layer was formed deeper in the material.

Fatigue property in gigacycle regime is focused as an important subject in recent years. In such a long life region, a tremendous long period is required to perform fatigue tests. In order to overcome this difficulty, a multi-type rotating bending fatigue testing machine of cantilever type has been developed. It is known that this type of fatigue machine can be performed much quickly comparing with the tension and compression fatigue testing machines, and the fatigue dates are matched with many experimental dates in the past though the dates of an ultrasonic fatigue testing machine are unclear. Researchers would like to carry out fatigue tests at the rotating speed as fast as possible, but the maximum speed of a rotating bending fatigue test are limited because of the heat generation caused by the cyclic plasticity work and the clamping area of a specimen. Each maximum loading frequency may as well be limited by each raised temperature to affect the fatigue properties of base materials. However each appropriate limited loading frequency is unclear because it is very difficult to measure the temperature of the fracture portion of a specimen precisely during the rotating bending fatigue test. The measuring technique of the temperature near the fracture portion in a specimen during the rotating bending fatigue test of cantilever type is proposed, and the maximum speed of a rotating bending fatigue testing machine is discussed about the validity in this study.

The effects of projection conditions on the surface hardness and fatigue strength of stainless steel was investigated. In the peening process, the equipment were used an air-type machine and ultrasonic peening machine. The microshot media used were high-carbon cast with an average diameter of 0.1mm. The surface hardness data showed that, in the case of microshot peening, work hardening extended deeper than the mean diameter of the media. In addition, in the case of ultrasonic peening, the surface hardness increased slowly with the projection time. The rotary bending fatigue tests were carried at a frequency of 3150 cycles/min. Improvement of the fatigue strength was observed by both treatments. The higher effect was found in the ultrasonic peening treatment, because a work-hardened layer was formed deeper in the material.

The electron backscatter diffraction (EBSD) and positron annihilation methods applied to analysis of low-cycle fatigue damage in an austenitic stainless steel (SUS316L) which is mostly used in primary water line of power reactor. Samples of various degrees of low-cycle fatigue with strain control from room temperature to high temperature were prepared for the above measurement methods. The average of misorientation obtained by KAM (Kernel Average Misorientation) showed a proportional increase with the fatigue damage to cycle to fatigue, Nf. As compared with the sample of room temperature fatigue damage, the that of high temperature fatigue damage decreased slightly the average of misorientation at each cycles. It was considered to be due to the recovery of the dislocation. Positron annihilation lifetime measurements showed an increase in the positron lifetime for fatigued SUS316L samples compared to the as-received sample.

In order to enhance mechanical properties of metallic materials by surface improvement, laser peening using a pulse laser has been developed. There is two types of laser peening. One of them is that target with water film is exposed to the pulse laser, and the other method is that target in a water chamber is treated by the pulse laser. The latter laser peening method is called as “submerged laser peening”. For both laser peening, it was believed that impact induced by laser abrasion caused plastic deformation. However, in the case of submerged laser peening, bubble is developed after laser abrasion, and it produces severe impact at bubble collapse. In the present paper, impact induced by laser abrasion and impact at bubble collapse were evaluated by a handmade PVDF sensor which was placed in the target. It was revealed that the impact at bubble collapse was about 1.5 times larger than that of impact induced by laser abrasion.

In large-scale structural tests, displacement transducers and potentiometers have been commonly used to measure specimen displacements. Due to the restriction of device installment, however, large and/or multi-point displacements cannot be measured with those devices. In this study, a motion capture system (MSC) is applied to a large-scale structural test for non-contract, multi-point and three dimensional (3D) displacement measurements. The motion capture is a technology to record 3D movements of objects by tracking the markers installed on the measurement target with special cameras. The displacement measurement for a tensile test of an elbow pipe specimen was carried out by using MSC with 127 target markers. The measured values were verified by comparing with those by conventional displacement transducers and total-station. Finite element analysis was also conducted to compare the displacement distributions. The verified results show that the displacement by motion capture system can be measured with 1mm of difference compared to previous conventional displacement measurements, and provided comparable displacement distributions with the finite element analysis result.