In order to investigate the effect of corrosion damage like as corrosion pits on high cycle fatigue strength of SUS316NG which was used for nuclear power generation plant, rotating bending fatigue tests were carried out using the specimen which has a few artificial corrosion pits. As a result, the fatigue strength at (10)^8 cycle of specimen having corrosion pits was much lower than that specimen without pits. The decrease of fatigue strength at (10)^8 cycles was explained by treating a stress concentration factor from shapes of each corrosion pits as fatigue strength reduction factor.

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High temperature fatigue (R=0) damage and deformation behaviors of SUS304 steel thermally sprayed with Al_2O_3/NiCr coating were investigated using an electronic speckle pattern interferometry (ESPI) method. Surface cracks and delamination occurred after 1×(10)^5 cycles test when σ_<max> was 202Mpa at 873K. The lengths and number of cracks or delamination largely decreased when σ_<max> or temperature decreased to 115MPa or 573K, respectively. Strain values along cracks measured with the ESPI method were much larger than other areas due to crack opening under the tensile load. The positions of strain concentration zones on strain distribution figures by ESPI method were well corresponded to those of cracks on sprayed coatings. Strain values decreased largely where local delamination occurred.

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It can be said that it also exists the relationship of Hall-Petch which it is possible to increase proof stress by decreasing a grain diameter about austenitic stainless steel SUS304. In order to make grain diameter of SUS304 small, it must make use of the recrystallization after it is done hot roll and cold roll since phase transformation does not happen in heating and cooling processes. On the other hand, in order to increase the fatigue strength of HIP device or automobile parts, authors were clear the process of fatigue fracture and defensive factors, and was proposed the new improvement method on fatigue strength. By decreasing grain diameter, it can be expected effects such as, (1) proof stress become high (2) it can obtain a greater compressive residual stress (3) it is possible to be short fatigue crack length of stage I. In this study, in order to investigate the relationship between grain diameter and fatigue strength, it was carried out experiment by using the metal bellows of SUS304,and grain diameter was adjusted by changing BA temperature after cold roll. It could be obtained the results that fatigue strength was improved in proportion with decreasing grain diameter.

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Ultrafine-grained specimens with the average grain size of less than 2μm and medium-grained specimens were prepared from steel plates produced by an advanced thermo-mechanical control process. The smooth specimens were fatigued under cyclic axial tension compression at room temperature and the crack initiation and early propagation behaviors were investigated by atomic force microscopy. In the medium-grained specimens, the fatigue cracks initiated from the simple slip lines. On the other hand, in the ultrafine-grained specimens, complex slip deformation was formed in the vicinity of grain boundaries prior to the initiation of fatigue cracks. The fatigue cracks were nucleated at the grain boundary between the grains with the complex slip deformation. The crack propagation rate in the early stage decreases because of the grain-boundary blocking and crack deflection in the ultrafine-grained specimens.

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As for initial fatigue crack, quantitative evaluation was considered to be difficulty for reasons of both sides of metallurgical factor and mechanics factor influence behavior and crack growth mode change. In this study, paid its attention to initial fatigue crack growth to a depth direction, and examined an influence of mechanics factor which gave an influence to mode transition. As a result the various kinds of influences that mechanics factor gave initial fatigue crack became clear.

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Fatigue crack growth test under constant amplitude loading was carried out on α-brass. Successive observation of small fatigue crack growth behavior was performed by means of an atomic force microscope (AFM) equipped with small in-plane bending fatigue testing machine. Crack deflection and crack branching were observed frequently. They were resulted from the constraint of slip deformation due to strain hardening. Those intervals were found to be affected by the difference of mobility between slip systems and cross slip.

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In the past decade, threshold stress intensity factor range : △K_<th> obtained by K_<max> = const. method, has become to be recognized as the intrinsic △K_<th>. However, some up-to-date show that when K_<max> becomes large, threshold will decrease or disappear. We therefore made K_<max> = const △K_<th> test with mild steel S55C as a first step, and made a study on the mechanism of this decrease.

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It is important to detect cracks in the primary phase because cracks extend both in length and depth with increasing fatigue cycles. This paper proposes an index of homogeneity based on the spatio-temporal gradient analysis of Lamb wave field. The index is the normalized dimensionless number based on the rank of the covariance matrix which is composed of the vertical surface displacement, its vertical particle velocity, and the corresponding pair of shear strains. Consequently, the proposed index has the property which is independent of wave number and its velocity.

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In the present study a detection method of an overload application during stress cycles under a constant stress amplitude was investigated. Also, the effect of a tensile overload was shown at three R values ; R=0,-1 and -1.5,in order to understand the effects of R on crack propagation after an overload. At a baseline of R=0,after an overload retardation in the crack propagation was observed. However, in the case of R=-1.5,the fatigue crack growth rate actually accelerated after a tensile overload. These behaviors of crack propagation can be monitored by the information of strain waveform, and an overload application can be detected by it.

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The requirement of the high processing high strength light steel sheet recently rises in the car from the global environmental problems and so on from the body lightening because of fuel expenses and the view point of the safety improvement at the time of the collision. In the present paper, fatigue properties of extra-low carbon steels with different tin contents, varied from 0.002 to 0.22% mass, are investigated. The results show that the fatigue strength by (10)^7 cycles increases with increasing Sn content.The fatigue strength of annealing specimens at 750℃ is higher than that at 650℃. The cracks initiated from the surface of specimen and propagated mainly in intergranular modes for all materials.

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Small defect gives a substantial effect on the fatigue limit. The effects of mean stress and hardness on the fatigue limit of a small defect are quite different from those of a long crack nor a plain specimen. Fatigue tests with a small defect were performed under a wide range of mean stress for three kinds of steels with different hardness. The crack closure of a short crack was measured. It was shown that the crack closure was strongly dependent on the material hardness at low stress ratio. This behavior of crack closure resulted in peculiar fatigue limit properties of a small defect.

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As parameter for correspondence between notched and unnotched fatigue data, Equivalent Stress Ratio R_<EQ> was previously proposed based on a hypothesis of Fatigue Plastic Adaptation and its availability was confirmed by authors' experimental data as well as some published experimental ones. In the present study, a basic concept and inductive process on the Equivalent Stress Ratio R_<EQ> was reconsidered.

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Fatigue properties of double notched specimens have been eraluated using Ono-type rotating bending fatigue testing machine. In this test, the double notch is consisted of the combination of V notch and a drill hole. The fatigue limit of the single-notched specimen with a V notch and that with a drill hole is estimated using the fatigue notch factor K proposed by JSME. According to the result of this study, the fatigue limit of a double-notched specimen could be practically estimated by applying the product of fatigue notch factor for each relative single notch. The detailed analysis by from now on, limited element law is necessary and need to examine and to compare with the experiment result.

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To ensure long life reliability of the machine parts made of thin sheet metals, ultrasonic plain bending fatigue test method for thin sheet metals was developed. One end of the sheet specimen is fixed at a loop point of the bar oscillating at a frequency of 20kHz and the other end is set free. As a result, resonance occurs in the specimen due to vibration at the fixed end and long life fatigue strengths (e. g., fatigue strength at (10)^9 cycles) can be obtained in a short time. This method can be applied to the sheet specimens up to 1.0 mm thick.

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In the back-up roll using iron and steel rolling, establishment of evaluation technique for the rolling contact fatigue damage has been longed for. Thus far, fatigued zone below the surface of rolls has been evaluated using half value breadth of X-ray diffraction line profile analysis. However, the quantitative evaluation of the rolling contact fatigue damage is moreover expected. Therefore, in this study, we estimated the density of movable dislocation under the rolling contact fatigue process by measuring ultrasonic surface wave velocities with three-different propagating frequencies via Granato-Lucke's dislocation string theory. The comparison of changes of the density of movable dislocation with changes of half value breadth of X-ray diffraction line profile analysis under the rolling contact fatigue process suggests promising availability of the proposed method. As a result, the ultrasonic surface wave velocities with three-different propagating frequencies (5,10 and 15 MHz) decreased due to increasing of the rolling number of rolling contact fatigue. And, the density of movable dislocation estimated by Granato-Lucke's model increased in the fatigue damage progress.

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A convenient method for predicting mechanical properties of solder materials was proposed in this study. Indentation method was used to obtain mechanical properties including elastic, plastic and creep deformations. Elastic-plastic finite element method (FEM) correlated Young's modulus, E, and yield stress, σ_<ys>, with unloading portion of load-displacement curve and Vickers hardness, HV, respectively. Tensile creep properties were lead by measured indentation creep properties, where the creep properties were evaluated by the Norton's law. The above prediction methods established in our previous work are based on elastic-plastic-creep analysis of FEM for a indenter with rotational symmetry, whereas the Vickers indenter is a 3-dimentional configuration of quadrangular pyramid. The agreement of the prediction methods was confirmed by 3-dimentional analysis of FEM. Some other factors, which influence the prediction methods, were investigated by 2-dimentional analysis of FEM. Using the proposed method, mechanical properties of lead-free solders such as Sn-3.5Ag and Sn-3Ag-0.5Cu-0&acd;3Bi alloy systems were determined for the temperature between -20℃ and 160℃.

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Viscoplastic deformation of solder alloys was experimentally observed. Pure tensile tests with several strain rates, creep tests, and stress relaxation tests were conducted using both Sn-37Pb and Sn-3.5Ag-0.75Cu solder alloys at several temperatures. The test results showed that the Sn-3.5Ag-0.75Cu solder alloy has lower viscosity than Sn-37Pb. The lower viscosity of the solder alloys causes larger bending of electronic devises due to temperature chang during the reflow process. Then FEM analysis was also conducted to clear the difference of the bending of the electronic devises using Sn-3.5Ag-0.75Cu and Sn-37Pb solder alloys.

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Recently, environmental pollution caused by lead liquation from the solder in wasted electronic machines has become matter of serious concern. Therefore, a great variety of chemical compositions for the 'lead free solder' have been proposed. To use these 'lead free solder' in electronic packaging, the reliability of the solder joints by those solders to the fatigue failure has to be estimated by the FEM analysis. For the accurate analysis, a constitutive model for the lead free solder alloys has been required. The requirement is not only the precision of simulation but also the reduction of the number of experiments to determine the material parameters because the analysis has to be conducted on the proposed various composites of lead free solder joints. In this study, we show the constitutive model that can divide the inelastic deformation into the plastic and creep parts and its numerical determination method for the material constants by only pure tensile tests under several strain rates. The simulations of the creep and cyclic tension-compression loading using Sn/Ag, Sn/Zn and Sn/Bi solder alloys are conducted to verify the applicability of the model and method to the lead free solder alloys.

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Isothermal axial strain controlled creep-fatigue testing of a eutectic alloy Sn-37Pb was carried out at room temperature. Four kinds of triangular strain waveform, so called fast-fast, fast-slow, slow-fast and slow-slow, were used in order to obtain the creep-fatigue properties of the material as the partitioned inelastic strainrange versus life relationships, that is, &lrtri;_<εij>-N_<ij> (ij=pp, pc, cp and cc) relationships. The fast and slow strain rates adopted were 0.01/s and 0.0001/s respectively. The obtained &lrtri;_<εij>-N_<ij> relationships were converted to the partitioned inelastic shear strainrange versus life relationships, that is, the &lrtri;_<γij>-N_<ij> relationships which can be used in order to estimate the creep-fatigue life under cyclic pure torsion. The results are compared with the literature data.

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Recently, an environment problem has been treated as important. So many studies on a Pb-free material instead of a Pb/Sn alloy have been done actively in microelectronics packaging. Most of them focused on the thermal fatigue of solder joints. On the other hand, there is very little research done to understand the effect of frequency on solder joints when microelectronics devices are subjected to vibrations. In this study, the effect of frequency due to a vibration on a Pb-free IC package and Pb-Sn IC package which are used as BGA interconnecters was researched. The effects of a normal stress, a shear stress and a frequency to a fatigue life was studied. although the normal stress and the shear stress reduce a fatigue life, the shear stress is a dominant factor. The Pb IC package is more sensitive than the Pb-free IC package against a frequency in a range 15&acd;25Hz.

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This paper describes low cycle fatigue (LCF) lives of Sn-37Pb and Sn-3.5Ag solders at lower temperatures. Push-Pull LCF test were carried out at 253K and 273K to examine the effect of temperature on fatigue life. Tension stress increased with decreasing temperature for Sn-37Pb. There was a slight effect of temperature on tension stress for Sn-3.5Ag. Plastic strain range was a suitable parameter for correlate the LCF lives. All of the data correlated with plastic strain range within a factor of 2 band based on the 313K data independent of temperature for Sn-37Pb. Plastic strain gave a proper life prediction, within a factor of 2 for Sn-37Pb, but gave an unconservative prediction for Sn-3.5Ag data at a lower temperature. Main cracks propagated in the principal strain direction for both solders.

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Three different sizes of BGA (Ball Grid Array) solder joints were subjected to mechanical fatigue testing. It was found that the fatigue life of these joints strongly depends on their size and can be expressed by Coffin-Manson's law. In addition, Sn-3Ag-0.5Cu, Sn-1Ag-0.7Cu, and conventional Sn-37Pb BGA solder joints were also subjected to mechanical fatigue testing. It was found that the Sn-3Ag-0.5Cu joints had a fatigue life close to that of the Sn-37Pb joints. In contrast, the Sn-1Ag-0.7Cu joints had a fatigue life half as long as that of the Sn-37Pb joints.

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This paper describes a new miniature creep tester and the size effect of creep and creep rupture lives for solders. The new miniature creep tester was developed and creep rupture tests were carried out using five types of Sn-37Pb specimens with different diameters. Creep rupture times of miniature specimens were longer than those of bulk specimens. Creep rates of miniature specimens were slower than those of bulk specimens but the unique relationship held between the strain rate and rupture time in all types of specimens.

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To investigate the mechanical characteristics of veins in butterbut (Petasites japonicus) leaves, the angle of veins, their length and diameter, the thickness of lamina etc. were measured A series of static tensile tests for veins and lamina were also carried out to obtain their mechanical properties. It was found that the vein volume including in an unit area of lamina is almost constant over a butterbur leaf. From the tensile tests, it was obtained that tensile strength and Young's modulus of the vein were 2.24 MPa and 63.6 MPa, respectively, and they are much greater than those of lamina.

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The fracture modes, i.e., brittle fracture and ductile fracture are studied comparing the criteria in macroscopic and microscopic aspects. As the macroscopic criterion, the critical stress intensity factor is used. As the microscopic criterion, the idea of fractal is applied to the profile of fracture surfaces. In this study, the three points bending fracture tests of cracked specimens were carried out using S45C, S55C and FC20. The relationship between the fracture modes and the fractal dimension of the fracture surfaces is discussed.

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Porous silicon was examined as a material for micromachining. A micro resonator was fabricated with porous silicon membrane formed by anisotropic etching of a silicon wafer. The resonator was excited using a laser beam irradiation and the vibration was detected by measuring intensity fluctuation of He-Ne laser beam reflected on the resonator mass. The resonant frequency was determined from the resonant characteristics. Young's modulus was calculated using measured value of the resonant frequency.

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Impact fracture tests of laminated glass were performed using an instrumented drop weight testing apparatus. Different types of fracture mode were obtained by changing input energy and fracture absorbed energy was evaluated for each of the fracture modes. The experimental results clearly exhibited that large amount of energy absorbed through the deformation and fracture of the middle polymeric layer results in higher impact resistance of laminated glass than that of single glass. The result of strain measurement on the glass surfaces showed that the free glass layer fractured prior to the impact layer under this impact condition.

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It is known that the behavior of crack propagation in an internally pressurized tube is much different from that in a flat plate. For example, a sinusoidal crack may propagate in an internally pressurized tube under some conditions. On this phenomenon, experiments were carried out using glass tubes pressurized internally by water, As a result, it has been found out that the velocity of the sinusoidal crack tip is very small comparing with the elastic wave velocity in glass; therefore, the effect of inertia can be ignored in this case, When the crack velocity was not small, no sinusoidal crack was observed.

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In this paper, chirped fiber Bragg grating (FBG) sensors were applied for the detection of crack locations in CFRP laminates since the reflection spectrum from a chirped FBG was expressed as a function of the position along the grating. Two types of chirped FBG sensors were embedded in CFRP cross-ply laminate, and reflection spectra from the sensors were measured during loading-unloading tests. When transverse cracks appeared, the spectrum had dips at the wavelengths that corresponded to the locations of the transverse cracks. These results have revealed that chirped FBG sensors have a potential to detect the locations of transverse cracks through the changes in form of the reflection spectrum.

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The present paper investigates the relationship between crack phenomena and electric resistance of an ITO thin film on polymer film. The electrical conductivity of ITO film was decreases due to the multiple film cracking. In order to predict the variation of electrical conductivity of ITO film with applied strain, we conducted the Monte Carlo simulation with a finite element analysis. This numerical procedure can easily and accurately calculate the stress distribution in the film on the elastic-plastic substrate. The predictions are found to have good agreements with the experimental results.

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In the present study, the electrical resistance change behavior of CFRP laminate [±25/±25/90]s under re/unload loading condition is investigated experimentally. Especially, the effect of the delamination on the electrical characteristics is evaluated using the internal and the surface electrical voltage distrbution. From the experimental results, we identified that the residual resistance reduces along with the increase of the previously applied maximum strain and the internal voltage distribution in thickness direction does not change despite of the delamination. Voltage distribution of the bottom and the top surface indicates that the electrical current can flow through the region that has no delamiation and this can explain the constant internal voltage distribution in thickness direction. For the reason of the decrease in the residual resistance, further theoretical and experimental investigations are needed

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Ti50Ni50-xCux (x=0,5,10,15at%) fine fibers (diameter= φ 80 μ m, length=20cm&acd;1m) were successfully developed by the arc-melted rapid-solidification method. It has been very difficult to do the conventional melt-work processing from the bulk material of this alloy to very fine fiber because of the brittleness from metallic compounds especially in the range of Cu≧8at%. The fibers showed good shape memory effect. As Cu content increased, the temperature hysteresis (=Af-Mf) of recovery strain-temperature curves as well as DSC curves became smaller and the tensile strength showed more than 1000MPa in Ti50Ni40Cu10at%. Therefore, the developed rapid-solidified, thermoelastic fine fiber actuator/sensor materials have high potentiality of applications for micro-machines and the fillers of smart composites.

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Fe-15at%Ga ribbon whose thickness was about 100μm with improvement of ductility. The Fe-15at%Ga ribbon sample showed a very large magnetostriction of ε_<max>=-400×(10)^<-6>in comparison with ε_<max>=-40×(10)^<-6> for the conventionally melt-worked bulk material at applied magnetic field, 955kA/m. In the bulk material with random crystal orientation, the dependence of magnetostriction on magnetization direction (θ) to the surface of ribbon was scarcely recognized. On the contrary, in rapid-solidified ribbon, that dependence was extraordinarily enhanced and large magnetostriction was obtained in the thickness direction of ribbon (θ≒90°) where coercive force showed the maximum value. Based on these experimental results, it is considered that the large magnetostriction is be strongly correlated with special metallic microstructures in the rapid-solidified Fe-15at%Ga ribbon with very strong magnetic anisotropy. Fe-Ga rapid-solidified ribbon has the promising possibility as a new magnetostrictive material as it has large magnetostriction, ductility and very small magnetostriction hysteresis.

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Six kinds of new actuator materials such as the Fe-Pd alloy film, the hydrogen storage alloy film, the hydrogen storage bi-polymer, the polymer-metal bi-metal, the glass-crystal bi-metal and the bi-ceramics glass were developed. In order to apply practical articles, load dependence is important facor. Thus, we were examined load dependence measurement each bimorph materials, which developed. As a result, large power has been found in the Fe-Pd magnetostrictive film and the hydrogen storage alloy bimorph.

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A laminated piezoelectric bimorph actuator with a graded compositional distribution of PZT was fabricated, and its deflection characteristics were evaluated. Using experimentally determined compositional dependency of elastic and piezoelectric properties in the PZT/Pt composites, the modified classical lamination theory and the finite element method were applied to find the optimum compositional profile that will give a lager deflection and smaller stress, simultaneously. The miniature bimorph-type graded actuator that consists of a composite internal-electrode (PZT/30vol%Pt) and three piezoelectric layers of different composition (PZT/0-20vol%Pt) were fabricated by powder stacking and sintering. The deflection was found to strongly depend on the composition distribution profile. Under an applied electric field of 100Vm^<-1>, the actuator with an optimum composition profile exhibited a curvature of up to 0.03m^<-1>, which is satisfactory performance for this kind of actuators. The stress generated on actuation was estimated to be as low as 0.4MPa, which is much smaller than those of conventional directly bonded actuators and will assure a long actuation life.

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From an engineering point of view, it is important to know the surface condition of materials. Sheet electron beam irradiation (SEBI) generates the dangling bond without the residual impurity atoms. The electron beam irradiation improved the hardness, ductility and fracture toughness.

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This paper describes temperature dependency of electric resistance of metal nano-composite DLC (Diamond-like Carbon) film considering its application to temperature sensors. DLC has many attractive properties such as low friction, low wear resistivity, chemical inertness etc. Few reports have shown the application for the temperature sensors of DLC film. We fabricated metal (Chromium) containing DLC (Metal nanocomposite DLC : Me-DLC) film and measured the temperature dependency of electric resistivity. After measuring temperature dependency we evaluated relation between the composite atomic concentration (C, O, Si, Cr) and resistivity of Me-DLC film.

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Long time creep fracture of austenite stainless steels is caused by the initiation and growth of creep voids at grain boundaries during creep. Present work was intended to propose a healing process for the creep voids and improve the creep rupture properties. Addition of B, N and Ti and also removal of S in a 304 stainless steel promoted the precipitation of BN at surface of creep voids. The modified steel showed high rupture strength and high rupture ductilities, and it was confirmed that boronnitride precipitates at creep void surface in the steel. It was thought that the boronnitride at creep void surface suppresses creep void growth and improvecreep upture properties by the self-healing effect on creep voids.

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Powder particles of polystyrene coated with nickel-phosphorus alloy layers using electroless plating were pressed into pellets by isostatic pressing and sintered in vacuum at high temperature. A metallic closed cellular material was then fabricated. The compressive and damping tests of this metallic closed cellular material were performed. The obtained results show that this material has the different stress-strain curves among the specimens that have different thickness of the cell walls, and this closed cellular material has a long plateau region in the curves and high energy absorption. In addition, Young's modulus and compressive strength of this material depend on the thickness of the cell walls. The loss factor of this material also depends on the sintering temperature.

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A pulsed current hot pressing (PCHP) technique was used to fabricate Ti/intermetallics layered composites, in which a combustion synthesis reaction was initiated at the interface between Ti and Al foils, resulting in the formation of multi-layered aluminides between Ti foils and the aluminides were densified and bonded to the Ti layers. Microstructure of the composite fabricated was an alternatively-laminated structure composed of Ti and layered aluminides, and the layered aluminides was composed of four layers : Al_3Ti, Al-rich, TiAl and Ti_3Al layers. The tensile strength and the elongation of the composite attained about 700MPa and 3.5%, respectively.

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This paper describes development of an active and sensitive composite based on a simple metal composite. To realize this material system, continuous titanium fiber was embedded in aluminum matrix of which surface was oxidized to be insulated from matrix to form a heater and a temperature/strain sensor. It successfully actuated and worked as sensors of temperature and deformation.

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From an engineering point of view, it is important to know the magnetic field around a variable reluctance hybrid magnet. To occur a technology revolution, a variable reluctance hybrid magnet has been studied to obtain a new type of high torque motor. Thus, we studied the surface magnetic field of strong hybrid magnet in high torque motor.

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Using an equipment which could apply arbitrary relative slip, fretting fatigue tests were performed in order to clarify the reason why the location of fretting fatigue crack changes depending on relative slip amount. The influence of the location of cracking on fatigue limit was also investigated. When relative slip amount was less than 5μm, cracks were observed in both edge and center of contact part. Fracture positions changed depending on the relative slip amount, but fatigue limit was not affected. In order to explain these behaviors, it is necessary to clarify the local condition of each cracking site.

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Fretting fatigue strength with contiguous contact edges are analyzed using fracture mechanics. Stress intensity factors of fretting cracks are calculated using stress distributions near the crack tip. Crack propagation and arrest behaviors are estimated using threshold stress intensity factor range ΔK_<th>. AS a results it was clarified that the fretting fatigue limit decrease about 40 or 50% by the contiguity of the contact edges.

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A technique to determine stress intensity factors, K_I and K_<II>, of an oblique crack initiated under fretting fatigue conditions was proposed in this report. Firstly, the database for contact stress distributions has been established through a series of boundary element analyses of contact pressure and friction stress of the contact interface. Secondary, the computer program to interpolate pad load distribution and calculate the stress intensity factors has been developed. The calculation method of stress intensity factors is based on the Green's functions method and the principle of superposition. Finally, the wide range of variation in stress intensity factors has been obtained. This program is applicable to crack propagation mechanism, growth rate, etc.

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In order to investigate the effect of the contact pad geometry on fretting fatigue strength, the fretting fatigue tests and interrupted fretting fatigue test by using two types bridge pad with the contact edge chamfered and non-chamfered were carried out for Ni-Cr-Mo steel. In this paper, the fretting fatigue test was conducted with; a stress ratio R=0.05,a contact pressure P=200Mpa. The main features in this study are as follows : the fretting fatigue strength increased by using bridge pad with the contact edge chamfered, and the interrupted fretting fatigue tests showed that crack initiation behavior was affected by the shape of contact edge in the fretting fatigue.

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Deformation mode at the contact edge depends on stress ratio as well as other geometrical and mechanical parameters. In the present study, fretting fatigue tests with high stress ratios as well as FEM analysis were carried out to investigate the effect of stress ratio on crack initiation point. The crack initiation point become inside of the contact region at the high stress ratio, where the deformation mode at the edge is Gapping even under the minimum stress. The crack initiation point is found to be the maximum stress range point.

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Fretting fatigue tests with various contact pressures were carried out using a fatigue testing machine with SEM for in-situ observation of relative slip amplitude distribution. The fretting fatigue life and the relative slip amplitude decreased with increasing contact pressure. The reduction of the life is mainly because the tangential force coefficient increased with increasing contact pressure.

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Significant wear damage of the rim flange at the contact region with the rubber tire is one of serious problems in an aluminum wheel. In the present study, the fretting wear tests between aluminum alloy and rubber were carried out in order to understand the mechanism of this wear behavior. The fretting wear test in air atmosphere indicated almost no damage on the aluminum surface. The wear test with a 0.5%H_2SO_4 solution also showed no recognizable damage on the aluminum surface. However, the test with a 10% CaCl_2 solution, which is used as an antifreezing agent on roads, exhibited significant wear damage on the surface. This damage looked similar to that observed in the practical wheel. Though the dissolving ability of H_2SO_4 solution is further stronger than that of CaCl_2 Solution, CaCl_2 solution induced more significant damage under wear condition. It is considered that the wear damage of the aluminum wheel dramatically promoted due to mechano-chemical reaction.

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