The impact welding of aluminum onto copper was carried out using a gas gun and the mechanical properties of Al/Cu joint were investigated by the tension test and a micro hardness indentation test. The results of the tension test suggested that it was necessary to make a microscopic survey of the joining interface. Then, the inverse analysis with FEM analysis was applied to the load and depth curves measured by the indentation technique to identify the mechanical constants in the constitutive equations of aluminum, copper and the compound layer. The nominal stress - strain curve of the compound layer obtained by the numerical simulation showed the typical feature of brittle material. The ultimate tensile stress of the compound layer was about 1.2 GPa and ten times larger than that of aluminum. It was clarified from those results that the bonding strength of Al/Cu joint was dependent on the integrity of the compound layer.

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Due to the strong non-linearity and the difficulty of obtaining data on the behavior of polymers at high strain rates, most crash simulations use materials data based on quasi-static testing. This study therefore attempted to obtain materials data for polypropylene used in the interior and exterior of automobiles at high strain rates. The material data obtained differs from data obtained through the linear extrapolation of stress to model the behavior of polymers at high strain rates. Then, the yield stress is estimated based on the strain rate and glass transition temperature effects. Finally, the estimation method is validated with results obtained using commercial finite element model.

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Pitting damage due to ca vital ion micro-bubble collapse is one of critical issue to realize a MW-scate mercury target for spallation neutron source. Micro-impact analysis was carried out to discuss the pit formation by mercury micro-jet impact. It was confirmed from the comparison between analytical and experimental results that D(depth)/R(radius) of pits is a useful parameter to estimate the impact velocity and surface hardening treatment is effective to suppress the pitting damage.

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Recently, the tailored blanking technique using high tensile strength steels begins to be adopted in car industry to reduce the weight of automotive bodies without any decreases of their stiffness and strength. Therefore, it is important to storage of the fundamental data concerning the technique such as tensile, compressive, shearing and fatigue properties of welded joints. In this research, the effect of pre-fatigue on the impact tensile properties of the welded butt joint of high strength steel plates was investigated by means of the split Hopkinson bar method for tensile test.

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In order to examine the compatibility of improvement of crashworthiness with weight-saving of automobiles by using high strength steel, new prediction model of the fracture strength of spot weld in automobile parts has been established. By using of this model, we can predict exact crush mode and absorbed energy of the crash parts with spot weld fracture. Therefore, we can simulate optimum design of the spot weld of the automobile parts. It was confirmed that stress concentration between the nugget of spot weld and the specimen controls fracture initiation of spot weld. We installed fracture prediction system based on this model to crash analysis solver and confirmed that this system predicts exactly the fracture of spot weld. These prediction systems are applicable to respective high strength steels.

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Dynamic buckling behavior of thin-walled cylindrical shells was studied with focusing on the effects of geometry and material properties. The buckling mode changed from axisymmetric mode to nonaxisymmetric mode with increasing the aspect ratio of the specimen, D/t. The transition point of the buckling mode depended on the elastic modulus of the specimen, E. The energy absorbing capacity of the shells was remarkably improved by filling polyurethane foam. The origami model was applied to study the buckling behavior of the shells.

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To examine axial crushing behavior of thin-walled structures under axial compression, a series of numerical simulations and experiments for circular tubes were conducted. In the estimation of the energy-absorption abilities of those specimens, we especially paid attention to the relation between the absorbed energy per unit volume and the ratio of thickness to diameter, as well as the effect of strain rate dependence of specimen material in these examinations. We also tried to clarify the relation between the buckling modes and the initial imperfection through the numerical simulations.

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This paper presents a method that generates a topological structure under an impulsive load by the extended distinct element method (EDEM). The EDEM model consists of springs, dampers and sliders between two elements in both the normal and tangential directions. According to the local rule using the calculated equivalent stress, elements are generated or eliminated. From numerical results, it demonstrates that various topological structures are generated by the initial shapes.

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Improvement of tensile mechanical properties under dynamic loading has been demonstrated for a commercial magnesium alloy of AZ31. A commercial AZ31 alloy was subjected to simple shear processing through ECAE(equal-channel-angular-extrusion) followed by annealing to develop a different texture compared with the directly-extruded alloy. During the dynamic tensile test, elongation-to-failure was more than twice higher than that of the directly-extruded alloy. Inspection of the fracture surface on the dynamically deformed sample revealed that the ECAE processed alloy followed by annealing fractured with the development of ductile dimples and few macro cracks, which is often observed on the fracture surface of magnesium alloys.

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In order to evaluate a strain rate sensitivity of a dynamic flow stress "dσ/dlogε" of iron at very high strain rates, constant strain rate tests and strain rate reduction tests are conducted for a high purity iron-14ppmC in a strain rate range from about 4×10^3/s to 2×10^4/s. The flow stress depends on strongly on the strain rate and a instantaneous strain rate plays a dominant role in the flow stress. The "dσ/dlogε" in Fe-14ppmC is compared with that obtained in Fe-lOOppmC. An effect of a difference in carbon content to the "dσ/dlogε" is not observed explicitly and an increase in impurity atoms contribute to increasing in an internal stress.

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In this study, the effect of high strain rate on the stress triaxiality is examined. Tensile tests are performed at three kinds of strain rates (ε=7.2×10^<-4>, 1.0×10^2 and 1.0×10^3 s^<-1>). FEM simulations also reveal the effect of stress triaxiality on the mechanical response under dynamic loading condition. The plastic constraint factors of the round-notched specimen under dynamic loading condition are lower than those under static loading condition. Stress triaxiality is decreased by the reflection of the stress wave near the notch root of the round-notched specimen under dynamic loading condition. The decrease of the stress triaxiality under the dynamic loading condition affects the relaxation of the plastic constraint in the round-notched specimens.

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Impact compressive characteristics of carbon/epoxy laminates in through-thickness direction are evaluated using the standard split Hopkinson pressure bar. Three types of carbon/epoxy composites, namely unidirectional carbon/epoxy, cross-ply carbon/epoxy and plain-weave carbon/epoxy with almost the same thickness are tested at room temperature. Cylindrical compression specimens are machined such that the longitudinal direction of each specimen is parallel to the thickness direction of the laminates. The effects of strain rate, and reinforcement geometry on the secant modulus, ultimate compressive strength and strain, and the absorbed energy are examined in detail. It is shown that the cross-ply carbon/epoxy laminated composite exhibits the highest strength characteristics at low and high rates of strain.

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In order to understand fully the restitution performance of two different types of golf balls, high strain-rate compressive characteristics of resin and rubbers used for 2-piece and 3-piece balls were evaluated using the conventional split Hopkinson bar. An aluminum split Hopkinson bar was used to measure the impact compressive stress-strain relations for the resin and rubbers with low acoustic impedance. Compressive stress-strain data at high strain rates are presented and compared with those at quasi-static strain rates obtained on an Instron testing machine. It is shown that the resin exhibits hisher strain rate sensitivity than does the rubbers.

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When a high explosive contacts with a metal plate is detonated, a very high compressive stress wave is originated from the surface contacts with the explosive and a tensile stress wave with the same value of the compressive one is reflected from the rear surface. If the stress produced by the interference of the incident stress wave and the reflected one is over the limit of tensile stress for its fracture, a spalling fracture is occurred there. The experimental investigation was performed on how the state of spalling fracture generated depending on the experimental conditions such as the shape and charge weight of the explosive.

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The speed effect on the high-speed punching in a commercially aluminum sheet is investigated by an impact test machine using the compressed air. The projectile, which is considered as a punch, is accelerated at the air pressure and collides with the specimen fixed in the die. The hole is formed by penetration of the projectile. The shearing force is measured using strain gages mounted on the side surface of the die. From experimental results, it was found that the shearing force was decreased when the impact velocity exceed a critical velocity. It was demonstrated that sheared surfaces changed from the brittle fractured surface to the ductile fractured surface with the increase in impact velocity.

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This investigation deals with the deformation mechanism of a circular metal plate subjected to a uniform shock pressure whose duration is relatively long. The deformation in this case is assumed as two stages. One of them is the deformation produced according to the plastic bending wave propagating from the periphery of the plate to its center, and the other is the bulging deformation of the whole area similar to that generated due to static hydraulic pressure. In this investigation we try to analyze the effect of shock pressure profile on the deformation mechanism using a numerical simulation method which is verified by the experimental result.

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Fretting wear and fatigue properties of an epoxy resin filled with crushed silica particles were examined The three dimensional elastic-contact stress analysis was carried out for predicting the fretting fatigue limits. The fretting wear morphology was three-body abrasive wear accelerated by the silica particles isolated from the matrix surface. The friction coefficient between the specimen and the pad was 0.6-0.65. However it was reduced to 0.1 by inserting a PTFE film. At the contact pressure of 20MPa, the fretting fatigue reduction factor at fatigue limit was 3.0, however by inserting the PTFE film the fretting fatigue strength was extremely improved up to the unfretted fatigue level. The fretting fatigue limits predicted by a surface stress criteria approach possessed relatively large errors especially at high contact pressures, but the prediction values by a fracture mechanics approach successfully maintained reasonable and practical accuracy over the wide range of contact pressure.

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The objective of the present study is to investigate the effect of contact load on the friction and wear characteristics of an Al-Si alloy impregnated graphite composite under fretting. Flat-against-ball type fretting wear tests for the composite (disk) in point contact with a bearing steel (ball) were conducted in moist air at a constant amplitude of relative slip. From the results, there are two types of fretting process. In Type A, the coefficient of kinetic friction and half amplitude of relative slip drastically change at a certain time with process of fretting. In Type B, the kinetic friction coefficient and the slip amplitude are constant throughout the test. The cause for the occurrence of the two types of fretting process may be a difference in portion of Al-Si alloy and graphite in the contact area for each test.

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Fretting fatigue behavior of an extruded AZ61 magnesium alloy was studied. Plain fatigue test and fretting fatigue test had been conducted at relative humidity of 30-65%RH and 80%RH. Fatigue strength under plain fatigue was 140MPa and that under fretting fatigue with contact pressure of lOOMPa was 40MPa at 10^8cycles in humidity of 30-65%RH. Crack initiated at the edge of the contact region due to the singularity stress field near the contact edge. Crack initiation life was only 1.0〜-2.5% of total fretting fatigue life. Fretting fatigue strength at 10^8 cycles decreased to 20MPa under 80%RH. Corrosion pits were found at the fracture origin in the high humidity condition with low stress amplitude.

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The impact pressure of the cavitation jet stream in water jet was evaluated by using brick as a target for water jet peeing. The first peak and the second peak of the impact pressure in cavitation jet could be recognized. Furthermore, the life time of fretting fatigue on compressor dovetail was investigated after performing water jet peening. As a result of reducing the residual tensile stress of contact surface, it was clearly shown that a crack initiation life would be extended.

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Smooth fatigue and fretting fatigue tests of SUS304 and SUS630 were carried out under various mean stress. It is shown that the Modified Goodman's relationship can be applicable under low mean stress. On the other hand, Gerber's relationship is good under high mean stress.

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To clarify the effect of hydrogen gas environment on fatigue strength is important to design and to safely operate hydrogen utilization machines. In this study, fretting fatigue test in hydrogen gas environment was done. Test material was aluminum alloy T6061-T6. In case of relatively low contact pressure, fretting fatigue limit decreased in the order of air, nitrogen gas and hydrogen gas. Tangential force excerted on a pair of contact surfaces increased in the reverse order. Therefore, the difference of fretting fatigue strength was considered to be caused by the difference of tangential force among environments.

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It was shown that fretting fatigue failure occurred in the case of variable amplitude loading even when every stress amplitude was kept below the fretting fatigue limit diagram. The reason why such a phenomenon occurred was examined by repeated two-step loading fretting fatigue test. The first step stress of the repeated two-step loading was chosen as R=-l and the second step stress was with high mean stress. A non-propagating crack was formed by the first step stress even well below the fatigue limit. This crack functioned as a pre-crack for the second step stress with high mean stress. Consequently, fatigue failure did occur even when every stress was kept below the fretting fatigue limit diagram of constant amplitude.

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In recycling of Al alloys, deterioration of mechanical properties occurs by effect of impurities. Reducing of size of impurities by rapid solidification prevents deterioration of mechanical properties. Twin roll caster has high cooling ability. Twin roll caster is suitable for reducing size of impurities. 6111 alloy, to which Fe was added as impurity, was cast at a speed of 60m/min using a high speed twin roll caster. The Fe content ranged from 0.2mass% to 1.5mass%. Cast ability, surface condition, microstructure, and mechanical properties of the strip was investigated.

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Casting of magnesium alloy strip was tried using a vertical type high speed twin roll caster. The process to make magnesium alloy strip of the present study was very simple. Thin strip of magnesium alloy strip could be cast from molten metal directly. The casting speed was up to 150m/min, and thickness was thinner than 2 mm. A high cooling ability of the roll and low superheat enabled the high speed casting. The microstructure of as cast strip was not columnar structure but equiaxed structure. Thickness was reduced down to 0.5 mm by three times of hot rolling. Deep drawing was operated, and 2.0 of LDR value could be attained.

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An unequal diameter twin roll caster was adopted in the strip casting of aluminum alloy. This caster allowed easy start of casting, high speed roll casting, second cooling and casting of hypereutectic Al-Si alloy strip. Al-20%Si alloy, which has wide freezing zone, could be cast into the strip continuously at the speed of 20m/min. Primary Si was very fine by the effect of excellent cooling ability. The diameter of the large roll (lower roll) was 1000mm, and that of smaller roll (upper roll) was 250mm. The nozzle of this caster was assembled from 4 pieces of plates, and the attachment of the nozzle to the caster was very easy.

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In thixocasting it is necessary to keep the fluidity of slurry. Then, in most cases, structure of the ingot for thixocasting was changed from dendrite to granular crystal by stirring method. In this investigation, the ingot was manufactured by cooling slope method in which device was simpler than stirring method. Mechanical properties and microstructure of thixocast product were investigated. As the result, Thixocast product showed higher tensile strength and elongation than that of the diecast. The shape of primary a phase crystal was granular crystal.

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Die casting shrinks due to decrease of volume through the solidification process in mushy state and the following cooling process in solid. As the die set prevents die casting from shirking freely, high thermal stress occurs inside it and sometimes breaks products. Die casting also deforms largely when it is pulled out from die set. In the paper the effect of ununiform temperature distribution, shrinkage of volume and the shape of die set on stress distribution and deformation of die casting during solidification and cooling process is investigated by FEM computer simulation about two typical shapes of products, a cylindrical model with a large step between thick and thin wall and a square model with thin wall and narrow rib at the rim like a case of Mini-Disc player. Especially the analysis on thermal stress in sand casting in which the restriction of deformation is very small is carried out about a same cylindrical model.

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We developed a small casting machine for metallic glasses on the concept of microfactory. The apparatus consists of 0.3mm diameter-nozzle at an end of 2mm-dia silica tube, cylindrical furnace for heating Pt-based metallic glass in the glass tube, pressure Ar-gas for spouting of molten metal to a microdie. Micro-die is cooled in a vacuum chamber with Peltie-cooling module. Die casting was carried out by using micro-gear-die of 50 and 10μm in module and good formability was observed. We performed to cast with 2μm width-V-grooved (100)Si die, and observed submicron-roughness on the surface of the specimen and confirmed the possibility of ultra-precision casting.

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Thermal Barrier Coatings (TBCs) are essential technique for increasing gas temperature on the gas turbines, but evaluation method for Young's modulus of top-coating has not established until now. On the other hand, indentation hardness tests are useful to evaluate materials properties, not only hardness value but also Young's modulus, tensile strength, and so on. In addition, indentation hardness tests have a lot of advantages, compared with another material testing - its simplicity, swiftness, and it is able to experiment with various materials such as composite or coating materials. Therefore, indentation hardness tests are suitable to evaluate Young's modulus of top-coating. In this paper, indentation hardness tests with a truncated conical indenter were carried out to evaluate Young's modulus of top-coating. As the results, effectiveness of the indentation theory for a truncated conical indenter was demonstrated from 4.9 to 9.8 N of testing load. Furthermore, load dependency of calculated Young's modulus was discussed.

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In order to make a product light, the use of aluminum as a material is increasing, and this tendency is thought to continues from now on. However, aluminum has the fault that the hardness is low and that the surface tends to get damaged compared with iron base material. In this study, surface modified layer was formed on the surface of aluminum alloy A5083 by irradiating YAG laser beam, after sticking iron, compound of iron and chromium, and nickel powder to the surface. As a result, the surface modified layer was formed, and the surface hardness improved. About the improvement in surface hardness, it has been understood that the effect of chromium and nickel was larger than that of iron.

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In a flattening behavior of the thermal sprayed powder particles, we have pointed out that the flattening pattern change to a disk type from a splash type due to once heating of the substrate to some elevated temperatures. This drastic change may be associated with the change in the wetting of the substrate by the particles. However, the wetting mechanism change by the substrate heating has not been clearly understood. In this study, substrate surface roughness change due to the heating was precisely investigated by AFM and wetting behavior change was observed by a sessile drop method. The results obtained indicated that an increasing of the substrate surface roughness due to heating induced the improvement in the wetting of the substrate by the droplet. Hence, the substrate heating may bring about the change of the wetting condition essentially, and the change in the flattening pattern can be explained by this hypothesis.

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This paper describes about the surface texture of Japanese oak boards. The arithmetical mean roughness value, Ra, the glossiness, and surface color are the three main elements selected for evaluation the surface texture. The surface of Japanese oak boards were filled by pure aluminum powder of different particle diameter. The surface texture after filling was compared to the texture before filling. As a result, the glossiness and the chroma of the filled surface of the Japanese oak boards decreases compared to the texture before filling. Furthermore, when the surface was filled with pure aluminum powder with smaller particle, the glossiness and the chroma tend to decrease more.

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Lateral compression tests for plasma-sprayed CoNiCrAlY coatings were carried out. In considering the deformation of tubes, the elastic contact with a flat plate and a tube surface was taken into account as well as the bending of the curved beam of the tube. Young's modulus of mild steel tubes obtained from the lateral compression tests agreed well with the true value. In order to examine the effects of spraying processes on mechanical properties of sprayed coatings, coatings were sprayed by both Atmospheric Plasma Spray(APS) and Low Pressure Plasma Spray(LPPS) and three types of spraying powder size were selected. Tube specimens with thickness of 150〜700μm independent of substrates were manufactured by dissolving out the substrate by nitric acid. It was found that Young's modulus and fracture stresses in lateral compression increased with an increase of coating thickness and those also increased by diffusion thermal treatment.

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Continuous strip casting method attracts attention as the integrated production process in wrought Magnesium alloys. In this research, AZ61 sheet was cast from molten metal by twin-roll strip casting and the characteristics were analyzed. Experimental parameters were roll gap, roll speed and molten temperature, and the effects of these parameters on surface aspect and microstructure were investigated. Obtained results are as follows: (1) Wrinkle and crack of sheet surface were improved as roll speed increased. (2) The grain size was fined as roll gap, roll speed and molten temperature decreased, and the finest average grain size was about 20μm. (3) Eutectoid Mg_<17>Al_<12> mainly precipitated in grain boundary and that could be soluble in grain by heat treatment (400T℃/3.6ks).

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Honeycomb core sandwich panels (HSP) are used in many vehicle structures i.e. aircrafts, cars and trains. On the other hand, roll core sandwich panels (RSP) are expected to use in many fields, because RSP are manufactured with easier process and indicate the higher static bending strength than HSP. In this study, the drop weight impact test was carried out for HSP and RSP to compare with each other. It was clear that the relationship between the absorption energy of each panels and their cell size and core height. And the suitable sandwich panel for using in various cases was suggested.

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When extruded billet of AZ61 is compressed in warm temperature range in using grooved tool, mushroom deformation, that is, unstable deformation is generated. This behavior is limited in extruded billet, and this phenomenon has been investigated, but its mechanism is not clarified yet. Here, from view point of observation of microstructure, the effects of initial crystal orientation of billet and distribution of twin appeared in upsetting on mushroom deformation are researched. The mushroom deformation in upper side of upsetted specimen has a close correlation with twin generation.

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The Mg_2Si/Mg composites, which show excellent mechanical properties, have been produced via solid-state synthesis in the previous study. In this report, the reaction behavior of Mg and Si was investigated to evaluate the effects of particle characteristics on the synthesis of Mg_2Si. Mg powder and two sizes of Si powders were employed as initial materials. They were mixed as Mg-5,10,20,30wt%Si and were cold pressed at 500 and 874 MPa. Powder mixtures with same composition were also prepared to compare with each compact. Those compacts and powder mixtures were analyzed by DTA. From a view point of the Mg_2Si formation in solid-state, the suitable temperature ranees of the reaction and its exothermic heat were discussed.

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Fatigue strengths of extruded AZ61 magnesium alloy plate in three different directions were investigated. Specimens were machined that the extrusion direction was parallel, perpendicular or 45-degree to the loading axis direction. Fatigue limit for the longitudinal, transverse and 45-degree specimens were 85, 63 and 67 MPa, respectively. Fatigue crack was nucleated from inclusions in the early stage of fatigue life for all three kinds of specimens. Fatigue crack growth behaviors of short and long cracks vere also investigated by using SECT and CT specimens, respectively. The results for short crack growth behaviors show that, transverse and 45-degree specimens exhibited higher fatigue crack growth rates compare to the longitudinal specimen. Fatigue crack growth curves arranged by effective stress intensity factor of all three directions for short crack coincide with those for long crack.

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The application of the magnesium alloy die casting and rolled magnesium alloy on strength parts is investigated by the mechanical properties which are tensile test, fracture toughness test and fatigue crack propagation test. Especially, the magnesium alloy made by the die casting is compared with the aluminum alloy which is used for the vehicles as the strength parts. In consequence, the magnesium alloy die casting need to surpass the 0.2% proof stress relative of the aluminum alloy. Moreover, the fracture toughness and fatigue crack propagation of magnesium alloy approximate to the aluminum alloy. The rolled magnesium alloy can sustain rather the bending moment than the tensile load. And the joint of rolled magnesium alloy that resist 100N・m on the proof stress of AZ31 and the pipe with 30mm in diameter and 2mm thick is proposed. The joint react to increase the diameter of magnesium alloy.

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The spray forming method is a rapid solidification technique for the deposit of molten metal using inert gas. Adoption of this method enables a reduction in manufacturing steps compared to the conventional powder sintering method, as well as allowing the manufacture of large-sized material. In the context of turbochargers for diesel engines, improved heat resistance for aluminum impellers is an issue under consideration due to requirements for lower energy consumption and higher output, i. e. , higher pressure power ratios. This paper presents the relationship between the strength properties and material structure of a heat-resistant Al-Fe alloy manufactured using the spray forming method, as well as the possibility of application for turbocharger impellers.

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In case of infiltration process with low pressure in the fabrication of aluminum alloy matrix composites, the infiltration of molten aluminum alloy to reinforcement preform was predicted by using Darcy' low and computer simulation. Furthermore, permeability of molten aluminum alloy in preform was examined and then was adapted to the fundamental equation of infiltration.

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Cu-Fe-Cr alloy was severe plastic deformed by multi-directional-forging (MDF) method at room temperature. With increasing strain, microstructure evolved gradually. Though fine precipitates contributed much to strengthening of the material, the fine precipitates delayed the evolution of ultra-fine grain by impediment of recovery. Prolonged deformation by MDF with combination of heat treatment to a cumulative strain of 30, fine grains of 1μm in diameter uniformly evolved.

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Automation of arc welding process is very important to improve weld quality and cost performance. However, arc welding process has not fully understood, because of less knowledge on arc bihavior. The welding process was captured by high-speed video systems to analyze dynamic behavior of molten pool Some surface defects such as under-cut, humping bead, bum through. etc can be detected. Internal defects such as blow holes, cracks, lack of fusion, etc are very difficult to estimate their existences from surface observation. However, dynamic behavior of surface condition changes by their existences. So, it is possible to predict defects by image analysis of surface movie images.

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Hybrid welding combined YAG laser welding process and TIG arc welding process was developed for thin plate welding. It was applied to welding of 2mm thickness SUS304 stainless steel plate and AZ31B magnesium alloy plate. In consequence, sound penetration bead of stainless steel was obtained by hybrid welding process. In case of magnesium alloy hybrid welding, improvement of heat efficiency was remarkable. Moreover, tensile test results of hybrid weld joint shows sufficient joint strength of magnesium alloy.

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This study deals with the resistance spot welding of magnesium alloy thin sheets, In order to obtain the spot welds with large nugget and high tensile-shear strength, the spot welding is performed on lap joint, which is put between two cover plates. It was shown that the application of cover plates enabled the spot welding of magnesium alloy sheets with relative low welding current and short weld time. In addition, large nugget diameter and high tensile-shear strength of spot weld were also obtained from this method.

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