A fretting fatigue test machine to investigate the fretting fatigue properties of ceramic materials under cyclic loading condition was designed and fabricated. In the test machine, piezo electric bimorphs were used as actuators for cyclic loading and fretting motion. Fretting fatigue tests under static and cyclic loading conditions were carried out using HIP-sintered silicon nitride. From the experimental results, it was found that the effect of cyclic loading on fretting fatigue strength of silicon nitride was almost negligible, and fretting fatigue strengths under two test conditions were identical. A fretting crack was initiated at the very early stage of fatigue life at the position where the friction force is maximum, in accordance to Mindlin's theory. Fretting fatigue life prediction based on fracture mechanics was successfully carried out.

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To clarify the effect of a ceramic coating film on the fatigue strength of metal, a strain-controlled low-cycle fatigue test was conducted in air, using a specimen of 0.37% carbon steel coated with TiN by chemical vapor deposition (CVD). An increase in fatigue strength of the coated specimen was observed in the region of low total strain amplitude, as compared with an uncoated specimen. On the other hand, fatigue strength of the coated specimen decreased in the region of high strain amplitude. This behavior was explained in terms of the fracture of the thin film during the fatigue process, which is affected by the strength of the film itself and the deposition method. Cracks were induced at the substrate due to flaws in the coating film which act as notches. The notch effect of flaws in the film depends on the thickness of the film and adhesion between the film and substrate, which is obtained in a scratch test.

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In order to investigate the scatter characteristics of growth rate for small cracks, rotating bending fatigue tests of smooth specimens were carried out using 0.21% carbon steel with different ferrite grain sizes. Fifteen to eighteen specimens were fatigued at each stress range, and the growth rate of a crack which led to the fracture was measured for all the specimens. The growth data were analyzed statistically. The results show that the growth rate for each crack length can be expressed by a three-or two-parameter Weibull distribution. The CV, coefficient of variance, for crack growth rate distribution was calculated, and using the CV the relations between the scatter in growth rate and the ferrite grain size and stress level were investigated.

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Crack growth analyses of inhomogeneous CT (Compact Type) specimens are carried out by means of the two-dimensional finite-element method. The CT specimen is made of a welded plate of A533B-and HT80-type steel. The fusion line exists perpendicular to the crack direction. By changing the ratio of the widths of the two metals, the three specimens are analyzed. Based on the experimental results, generation phase analyses are conducted. The J-integral is evaluated using several conventional equations, and their availabilities for inhomogeneous material are discussed. The results show that the effect of the fusion line is strong when it is located in front of the crack tip. The crack tip fields are compared with HRR (Hutchinson-Rice-Rosengren) solutions and their deviations from the HRR solutions are measured by the Q-factor. The change of the stable crack growth condition is discussed using Q-factor.

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Stable crack growth tests are conducted using CT specimens and surface-cracked specimens welded of A533B steel and HT80 steel. The distribution patterns of SZW and Δa values along the crack front are measured, and the effects of welding and fusion line are considered. The results show that the effects of fusion line appear clearly in Δa distribution along the crack front. Δa is much larger in HT80 steel than in A533B steel. Three dimensional finite element analyses are then conducted. The J-integral distribution along the crack front is obtained and the crack tip fields are compared with HRR (Huthcinson, Rice and Rosengren) solutions. The Q-factor is also evaluated along the three-dimensional crack front. It is found that the Q-factor controls the local crack growth behavior near the fusion line.

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In this study, a method to analyze an interface crack under both residual stresses and applied loadings is proposed, and some BEM analysis results are presented. Fracture toughness tests of metal/ceramics bonded joints with an interface crack are carried out, and the stress intensity factors of these joints are analyzed by BEM. In all tests, the interface crack kinks into the ceramics out of the interface under rather low applied loadings because of the residual stress. The fracture angle and loadings are well predicted based on the interfacial fracture mechanics and the fracture criterion for an interface crack, which was proposed by the authors in a previous paper. The effect of the residual stress on the fracture toughness of metal/ceramics joints are clarified quantitatively. Moreover, a simulation analysis of the fracture path is presented and the results are compared with those of the experiment.

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A reliability analysis of the Shinkansen vehicle axle using probabilistic fracture mechanics is presented. Failures of the axles are assumed to occur as the result of the growth of cracks originating from fretting corrosion in a wheel seat. Cracks are considered to be randomly distributed in size, and cyclic stresses induced during train operation are used in conjunction with the crack growth characteristics of the material to predict the variation of the crack size with the distance travelled. The probability of failure is considered to equal the probability of having a crack larger than the corresponding critical size. The effects of in-service inspections are evaluated for two different induction- hardened axles. Finally, a series of calculations are performed in order to assess the influence of various factors on these probabilities.

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Quasi-static bending tests of single-crystalline silicon microelements fabricated by dicing and photoetching were performed. The microelements fabricated by photoetching (specimen width : 65-200 μm, thickness : 45-60μm) were subjected to three-point bending, with two-support roll length of l.5 mm. For this purpose, the authors have developed a specially designed testing machine (load range : 0.1 mN-5 N, accuracy : 0.02 mN), which enables mechanical testing including fatigue of microelements. Loads were applied to a specimen by means of an electromagnetic actuator, and the displacement was measured with a differential transformer (measuring accuracy : 0.1 μm) . Mechanical testing of microelements could be thereby performed with sufficient precision. Single-crystalline silicon microelements deformed elastically until final catastrophic failure, showing a brittle nature. The influences of the fabrication process and specimen width on fracture strength were investigated, and the dominating factor on the strength was discussed.

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Effect of a single thermal cycle on residual stresses of Si₃N₄/SUS 304 joints with an insert layer of copper was analyzed using the thermo-elastic-plastic finite-element method (FEM). The residual stress was found to increase after a single thermal cycle, which was consistent with the result of residual stress measurement by the X-ray diffraction method. The exponent and intensity coefficient of stress singularity at the interface edge on the ceramic side were also found to increase with the increase of thermal cycle temperature. The increase of residual stresses was thought to be caused by the elastic-plastic behaviour and strain hardening of the copper insert layer. The temperature dependence of the yield stress of copper was also considered. It was shown that the residual stresses at room temperature were controlled only by the yield stress of copper at room temperature. By applying the isotropic hardening rule and kinematic hardening rule in the analysis, it was found that the constitutive (stress-strain) relation of copper was a problem which must be solved in predicting residual stresses under multiple thermal cycles.

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Bending tests were performed for Si₃N₄-S45C(a carbon steel) joints with a copper sheet as the interlayer and with Ti-Ag-Cu as the brazing filler. To examine the size effects, some various-sized as-jointed specimens were cut into smaller specimens. Test results were interpreted in terms of residual stress due to jointing measured by the X-ray method. Redistributed residual stress after cutting is essentially similar to those of as-jointed specimens with the same dimensions. A stable crack tends to initiate at the interface between Si₃N₄ and brazing filler metal. After some growth, it advanced into Si₃N₄, which resulted in unstable fracture. With broader specimen width, the initiation site shifts to the interface at the specimen edge and this results in the higher bending strength. In this typical type of failure, the bending strength can be successfully evaluated from the stable crack length, the fracture toughness of monolithic Si₃N₄, and the residual stresses.

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Nonlinear fracture behavior of stepped-lap bonded joints is studied. The joints used have adherends of eight kinds of metals : three types of carbon steel, and four types of aluminum alloy and brass. The joints also have various thicknesses, lap lengths and step numbers. The effect of Young's modulus and yield strength of adherend material on the joint strength is calculated by means of elasto-plastic finite element method analysis. It is found that the strength of the joint which yields at an adherend corner is nearly equal to the yield strength of the adherend material, because the displacement of the adhesive layer increases abruptly after the adherend yield, and exceeds the layer's deformation capacity. The joint strength diagrams obtained by the strength prediction method applying our adhesion criteria show good agreement with the experimental results for all the present joins having various dimensions and materials.

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Torsional rigidity of adhesive bonded box beams with a longitudinal partition was analyzed by elastic theory. Theoretical results of the torsional rigidity of bonded beams agreed well with experimental results. Torsional rigidity ratios of bonded beams were independent of plate thickness and partition. The flexural rigidity of the bonded beams in the plane of the partition can increase without decrease of torsional rigidity, if the partition is jointed with adhesive bonding instead of spot welding. We can decrease the plate thickness of bonded beams, with the same torsional rigidity as spot welding.

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Fatigue strength of adhesive bonded box beams with a longitudinal partition was investigated. From the results of the fatigue tests, it was found that the fatigue strength of bonded beams was higher than that of spot-welded beams. Fatigue strength of bonded beams was independent of plate thickness and partition. The flexural rigidity of the box beams in the plane of partition can increase without decrease of torsional fatigue strength, if the partition is jointed with adhesive bonding instead of spot welding.

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A practical numerical method was proposed to analyze the foreign object damage of ceramics for gas turbine components. In this paper, the authors extended the previous damage model developed by Kipp et al. to a general 3-dimensional fracture analysis taking strain rate dependence into account. Moreover, the dynamic fracture toughness of ceramics was measured according to the impact response curve method in the instrumented Charpy impact test. According to the numerical simulation regarding impact tests using ceramic plates and spherical particles, this method was found to be effective to simulate the formation of median cracks and lateral cracks.

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Tensile and torsional tests were carried out on the plain specimens of rolled round carbon steel bars (S15C, S35C, S45C). Each specimen is regarded as an anisotropic material because it has a banded structure of ferrites and pearlites which were produced by rolling. Fine grid lines were drawn on the surface of specimen with a diamond-point needle. The lines were fine enough not to influence the structure of the slip bands. The local strains were measured from the elongated or distorted grids. The local deformations were not uniform in both tension and torsion, and most of the local strains were not the same as the given macroscopic strain. That is, there existed various local strains which were from near zero to several times the given macroscopic strain. The variety of local strains in torsion was greater than that in tension. The banded structure affected the local strain greatly in torsion, but hardly affected that in tension. Strain concentration in tension was small ; however, in torsion, this was large within the ferrite sandwiched between pearlite bands. When the materials had a clear banded structure and large binding force due to pearlites, the banded structure greatly influenced the local strain in torsion. The result of this study is important to the understanding of the fatigue of plain specimens of rolled round carbon steel bars.

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Fatigue tests of graphite/epoxy laminate tubes [ ± 45°]₄ were performed under tension-compression loading. The effects of stress ratio on the inelastic deformation under cyclic tension-compression are discussed. Cyclic stress-strain curves show viscoelastic-plastic behavior with cyclic hardening and softening, and are highly affected by the evolution of internal damage such as matrix cracking, delamination and fiber breakage. Development of matrix cracking and delamination causes an increase of the hysteresis loop width as the result of the decrease in the elastic modulus and the global stiffness. In particular, in the case of stress ratio R ( =σ_min/σ_max) < 0, salient and complex inelastic deformations were observed mainly due to the delamination and the resulting macroscopic buckling of the tubular specimens. The changes of energy dissipation per cycle and Young's modulus are found to reflect the change of the internal damage.

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The recovery stress associated with the martensitic transformation (MT) and the rhombohedral phase transformation(RPT) in TiNi shape memory alloy was investigated experimentally with respect to cyclic heating and cooling under constant residual strain. The results are summarized as follows. ( 1 )The recovery stress in the heating process increases along the reverse transformation lines of RPT and MT. Therefore the recovery stress increases in two stages for the maximum strain in the region of MT. ( 2 ) The stress at high temperature takes an almost constant value for the maximum strain in the region of MT. The recovery stress induced by heating and cooling takes a maximum value for the maximum strain in the region of RPT completion. ( 3 )The recovery stress varies slightly with cycling.

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The recovery stress associated with the martensitic transformation (MT) and the rhombohedral phase transformation (RPT) in TiNi shape memory alloy was invstigated experimentally with respect to cyclic heating and cooling under constant maximum strain. The results are summarized as follows. ( 1 )The recovery stress in the heating or cooling process increases or decreases, respectively, along the reverse transformation line of RPT. ( 2 ) The stress at high temperature takes a maximum value for the maximum strain in the completion region of RPT and just after the starting point of MT. ( 3 )The recovery stress induced by heating and cooling takes a maximum value for the maximum strain in the completion region of RPT. The recovery stress under constant maximum strain almost coincides with that under constant residual strain. ( 4 )The recovery stress varies slightly with cycling.

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In TiNi shape memory alloy, the shape memory effect and pseudoelasticity appear due to the martensitic transformation and the R-phase transformation, and the recovery stress associated with both transformations is utilized in many practical applications. In order to describe these properties of the material, a thermomechanical constitutive equation considering the volume fractions of induced phases associated with both transformations is developed. The proposed constituve equation expresses well the properties of the shape memory effect, pseudoelasticity and recovery stress. The proposed theory is useful for design of shape memory alloy elements in which the working stroke, the working force and the working start and completion temperatures are specified.

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This paper is concerned with the estimation of contact stress between a rolling circular plate and powder. Uniaxial compression tests of limestone powder are carried out to investigate the effect of particle size on the compressive stress. During the compression of powder by a rolling circular plate, the inner stress of the plate is analyzed using the two-dimensional boundary element method and photoelastic analysis. Calculated values, which are evaluated under the assumption that shearing deformation of the powder does not take place under compression, display good agreement with the experimental resusts on the inner stress of the rolling circular plate.

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The low-pressure plasma spray coating process has been established in the field of gas turbines and is used for hot parts (turbine blades, duct segments, etc. ) which are exposed to corrosive gases at high temperatures. Overlay coating is based on the MCrAlY alloy system(M is Ni, Fe or Co) is employed commonly as an oxidation-and corrosion-resistant coating. Of particular importance is the control of residual stress in coating if useful lifetimes are to be achieved. Thermal and mechanical properties were measured for five of MCrAlY alloy coating, which were sprayed by a low-pressure plasma spray system and heat-treated at 1393 K for 2h in Ar atmosphere. The residual stress characteristics of coated materials were analyzed using the finite-element method. A calculation technique for the determination of residual stresses was investigated using the numerical results. It was also confirmed that the estimated residual stress showed good agreement with the results measured by the X-ray technique in the of low aluminum content.

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A magnesium oxide single crystal has simple characteristics with regard to a slip system and reveals clear dislocation etch pits. The (100) surface of this single crystal was exposed to vibratory cavitation to study the erosion behavior produced by bubble collapse. Dislocation rows were observed in [010] and [001] directions on the specimen surface and in the direction 45 degrees to the surface on the cross section. Cracks initiate in these directions to a depth of about 1 percent of the thickness of the deformed layer. Intensity of impact loads in cavitation bubble collapse is widely distributed from low to high, and many cyclic impact loads with low intensities are responsible for the material removal. It was concluded that the volume loss rate has a linear relationship with an increasing rate of dislocation-row density under various cavitation conditions.

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Metal matrix fiber composites are promising candidate material systems for high-temperature applications. The deformation behavior of the composites at elevated temperatures is very complex owing to a number of factors, including the residual stress caused by high processing temperature and interfacial property degradation. A homogenization theory with multiscale asymptotic expansions is introduced as a suitable method to analyze nonlinear behavior of a metal matrix composite. The final formulation of the homogenized constitutive equations is described in the solution for perturbed displacements in the composite. To solve for the perturbed displacement field in the composite, a boundary integral equation method is introduced with an eigenstrain concept for thermal and applied strains. The fiber-matrix interface is modeled as a spring layer where discontinuity of displacements on the interface is assumed to be proportional to the associated tractions. Residual thermal stress and nonlinear behavior for transverse deformations are determined by the present method.

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Fracture toughness tests of glass-fiber-reinforced plastics under high loading rates were performed to clarify the dynamic effects on volume fractions and directions of glass fibers in plastic materials. The results are summarized as follows : (1)Linear elastic fractures occurred under both static and dynamic loading conditions when the crack propagates parallel to the plane of the glass fiber cloth (edge direction). On the other hand, nonlinear fractures are observed when the crack grows perpendicular to the plane of the fiber cloth (flat direction). However, the nonlinearity decreases with increasing loading rate. (2)In both directions, the dynamic fracture toughness decreases with increasing loading rate when the volume fractions are below 20%. (3) With volume fractions above 40%, dynamic effects on fracture toughness become negligibly small in both directions.

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ABS-resin is broadly used in the fabrication of general-purpose plastics. The potential for trouble exists if the molding process control is not sufficient. This paper reports the relation between heat degradation during the molding process and impact strength. The results show that the degradation of ABS-resin is due to the crosslinking of butadiene rubber in this resin and breaking of acrylonitrile-styrene copolymer bonds which are graft-copolymerized with butadiene rubber. The former factor, especially, has a strong influence over impact strength decrease.

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This paper presents a unified analysis of isotropic out-of-plane shear problems containing an arbitrary-shaped hole or an arbitrary rigid inclusion, and shows the closed-form analytical solutions. The applied forces considered in this paper are longitudinal shear stresses at infinity, point force, screw dislocation, dipole force, and dipole dislocation at an arbitrary point. The analysis is based on the complex-variable method using the conformal mapping technique. Using the results, the stress intensity factors (or singularity coefficients) for the tip of the cusp on the boundary L are given. Numerical examples of stress and displacement distributions are shown in graphical representations. The previous results published by several authors can be included as special cases of our solutions.

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This paper presents the experimental data and the analytical explanation of the yielding of a mild steel cylinder with a radial hole under compression. In the experiment, the relationship between, not only the yield stress and the various ratios of the hole diameter to the external diameter of cylinders with variable sizes, but also the yield stress and the various ratios of the internal to the external diameter of the cylinder, were examined under compression. In order to analyze the experimental data, the maximum point of stress occurring in the cylinder was determined in the experiment, and then the yield stress of the cylinder was analyzed in relation to two kinds of problems. One, in the case of thick-walled cylinders, is a strip perpendicular to the radial hole of the cylinder with a hole at the maximum point of stress. The other, in the case of the intermediate-walled cylinders, is an infinite plate with a hole. From the analytical results, it was found that the yield stress of the cylinder could be accounted for by considering the effect of the surface layer near the hole.

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Characteristics of crack initiation and propagation in tensile tests were investigated for Ti-6Al-4V and S45C. Successive observations were made in a SEM servopulser to clarify the relationship between tensile deformation and crack initiation. The main results are summarized as follows. (1)Microcracks appear in a large deformed area in Ti-6Al-4V and in a strongly shear-deformed area in S45C. (2)Net stressσ_net in both materials is nearly equal to σ_B of plain specimens. This means that the most of minimum section deformed plastically under the stress nearly equal to σ_B. (3)The coalesence of two holes occurred through the process of crack initiation and propagation in the strongly deformed area between the two holes in Ti-6Al-4V. (4)With decreasingρ, the hole deformation parameter h_c/d of crack initiation increases. When ρis constant, h_c/d is almost constant, independent of the notch depth(ρ : notch radius, d : initial diameter of hole, h : height of hole, h_c : h at crack initiation).

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To clarify the influence of microstructures on the apparent mechanical properties and the influence of the macroscopic mechanical condition on the microstructural stress and strain, a finite element method for the elastic Cosserat continuum has been developed. For materials obeying micropolar theory and couple stress theory, the validity of the proposed method has been verified through comparison with the exact solution for the case of a circular hole in a uniform tension field. For materials with microstructures which are modeled as a lattice continuum that consists of rigidly interconnected elastic beams, it has been clarified that the characteristic parameters that represent microstructural dimensions and properties are reflected in the apparent mechanical properties as a Cosserat continuum. Furthermore, it has been confirmed that the proposed methods enable us to evaluate the relationship between microscopic and macroscopic deformation behavior.

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A series of monotonous, cyclic and creep tests is performed to elucidate the inelastic behavior of modified 9Cr-1Mo steel. The monotonous tests show that the flow stress does not depend on the strain rate at R. T. and 350°C, but does depend on it at 450°C and 550°C. Cyclic experiments, on the other hand, reveal that the stress amplitude at lower temperatures is significantly influenced by the preceding cycles at 550°C, but is slightly affected by those at the temperatures lower than 450°C. Furthermore, the stress amplitude is not influenced by the preceding cycles at lower temperatures.

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This paper is concerned with a new boundary element method for two-dimensional orthotropic thermoelasticity in steady heat conduction. The governing differential equations of the displacement and temperature fields are transformed into a set of boundary integral equations including the unknown quantities of displacement, temperature, traction, and heat flux on the boundary. They are discretized by means of the standard boundary element method, and solved under the given boundary conditions. The necessary fundamental solutions are derived by the Hormander method. The mathematical formulation is presented in detail for two-dimensional thermoelasticity in orthotropic bodies. The proposed solution is applied to some examples, whereby its usefulness is demonstrated.

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It has been found by one of the authors that the boundary integral equations for the field functions such as potential and displacement can be regularized by introduction of their relative quantity. This technique not only provides a powerful device for accurate calculation of their internal gradients but also makes it easy to derive the integral equations for their gradients on the boundary. We attempt to apply this technique to the thermal-elastic problems. The basic reqularized boundary integral equation for thermal displacement can be obtained by superposing two kinds of special solutions simultaneously into the usual boundary integral equations. Regularized internal integral equation for thermal stress, which has a different form from the known one given by Bui [1978], is also deduced. In addition to that, this approach has succeed, for the first time, in deducing the boundary integral equations for the boundary thermal stress. Some numerical analyses for two-and three-dimensional problems are shown to verify the validity of this method.

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This paper is concerned with an analytical formulation and a numerical solution of the elasto/visco-plastic deformation of the multi-layered shells of revolution subjected to thermal loads due to fluid. Firstly, the temperature distribution through the thickness in each layer is assumed to be linear, and the temperature field in the shell is determined using the equations of heat conduction and heat transfer. Secondly, the stresses and deformations are analyzed by the thermal stress equations. The equations of equilibrium and the relations between the strains and displacements are derived from the Sanders shell theory. For the constitutive relations, Perzyna's equations are employed. As a numerical example, a two-layered cylindrical shell composed of mild steel and titaniuim subjected to locally distributed thermal loads due to fluid is analyzed. Numerical computations have been carried out for three cases of the ratio of the thickness of the titanium layer to the shell thickness. It is found from the computations that the temperature and stress distribuitions and the deformation are significantly varied depending on the ratio.

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An analysis is presented for the elastic buckling problem of angle-ply laminated circular cylindrical shells subjected to axial compressive load. Based upon the Flugge-type shell theory and the classical lamination theory, the total potential energy of the shell is evaluated analytically, and the buckling equation is formulated by minimizing the functional with respect to unknown coefficients in displacement functions. These displacement functions are introduced in the power series form which automatically satisfy any combination of the geometrical boundary conditions. In numerical examples, the critical buckling loads of the angle-ply laminated shells are calculated, and the effects of varying the boundary conditions, lamination parameters and aspect ratio upon the buckling characteristics are studied. Moreover, the optimum layer stacking conditions which attain the highest critical buckling loads are discussed.

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In the present paper, a new method is suggested for the nondestructive measurement of elastic moduli in a local area (100-400 μm in diameter) by the scanning acoustic microscope (SAM). The complex V(z) curve which denotes the amplitude and phase of reflected ultrasonic waves from a specimen is measured for the variable distance through liquid occupying the space between the acoustic lens and the specimen. After inverse Fourier transform of the complex V(z), the reflectance function of the liquid-specimen interface is computed. The velocities of the longitudinal, transverse and Rayleigh waves in the specimen can be estimated from the reflectance function. Then, Young's modulus, shear modulus and Poisson's ratio of the specimen can be determined from the measured wave velocities and the density, according to the elastodynamic theory. The experimental results of six kinds of materials including alloy and ceramics agree with the elastic moduli obtained by other methods. It is shown that the present method is very useful in determining the elastic moduli in local areas.

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Acoustoelasticity is expected to be a powerful method for nondestructive evaluation of the internal stress of materials. The technique is based on the speed shift of ultrasonic waves due to nonlinearity of the elastic coefficients. If the viscocity of the material is high, such as in high polymers, the speed of an ultrasonic wave depends on the frequency of the wave. In general, the nonlinearity of elastic coefficients of such materials is also significant, so that the relation between the speed shift and the stress becomes nonlinear. A theoretical foundation is given for the acoustoelastic laws of viscoelastic material with higher-order nonlinearity. This paper also presents a technique for determination of the speed and the nonlinear acoustoelastic coefficients by spectral analysis of the waveforms. For longitudinal waves propagating in acryl under uniaxial stress, the dependence of the speed and the acoustoelastic coefficients on the frequency and the uniaxial stress is discussed.

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Ultrasonic resonance frequency is measured using noncontacting electromagnetic acoustic transducers (EMATs) for acoustoelastic stress determination. An EMAT consists of a permanent magnet and a coil, which is dynamically driven by high-power rf bursts. It generates bulk waves through Lorentz forces arising from the static magnetic field and the induced eddy current, and detects them with the inversed process. The low efficiency of EMATs is well compensated by bringing the object into resonance. Longitudinal and shear resonance frequencies up to 20 MHz are determined by sweeping the operating frequency and processing the reverberation signals with a superheterodyne receiver linked to a computer. Slight frequency shift with stress application is available with the improved sensitivity on the order of l0⁶ fractional changes. The main features of the measurement system are demonstrated in an experiment utillizing the uniaxial and plane stress field in 1. 2-mm-thick steel and aluminum sheets.

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Grain size in carbon steel exerts a great influence on its mechanical properties. The average grain size was evaluated from the frequency dependence of ultrasonic attenuation using a noncontacting electromagnetic acoustic transducer(EMAT). The present measurement is composed two steps. First, the resonance frequencies of plate samples were determined using an EMAT to excite and receive thickness-shear oscillation. The resonance frequencies are measured at a regular interval in the 0.5-20 MHz range to be on the order of l0⁶ accuracy by sweeping the operating frequency and obtaining its amplitude spectrum. The ringing signals were processed with a superheterodyne phase-sensitive detector. Second, the attenuation coefficient was determined as a function of resonance frequency. At each resonance frequency, the output signal from the detector decreases exponentially with time, and the coefficient is obtained by fitting this ring down curve to an exponential function. Using a suitably chosen scattering coefficient, the average grain size was obtainable from the fourth power term in the frequency dependence. The final results were favorably compared with the average of the 3D distribution of grain size estimated from the photomicrographs of the exposed cross sections.

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Quantitative nondestructive evaluation (QNDE) has become increasingly important in various engineering fields. This paper describes an application of the hierarchical neural network to defect identification with the ultrasonic method. The present method consists of three subprocesses. First, sample data of identification parameters vs dynamic responses of displacements at several monitoring points on surface are calculated by the dynamic finite-element method. Second, the errorbackpropagation neural network is trained using the sample data. Finally, the trained network is utilized for defect identification. The present method is successfully applied to the identification of size and location of a surface defect in a solid. The dependence of network performance on the distribution of learning data is also discussed.

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It is well known that high-frequency a. c. current flows along a surface due to the skin effect. A method for applying the a. c. potential drop technique is proposed to nondestructively evaluate the thickness and the electromagnetic properties of a thin layer on a material surface. First, Maxwell's equations are solved to obtain the potential drop on the surface of a layer for a cylindrical material. Next, a. c. potential drop is measured for a specimen with a thin layer of electroplating on its surface·Finally, the inverse problem is analyzed to determine the thickness and the electromagnetic properties of the electroplated layer, where measurements of the potential drop are compared with theoretical computations. It is verified that the present method can be used for the nondestructive evaluation of the thin layer.

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Artificial hip joint replacement is an effective treatment for serious forms of osteoarthritis and for disabling effects, for example, rheumatoid arthritis etc. Although a vast amount of biomechanics research has been devoted to developing a prosthetic device, the precise mechanism of loosening at the bone-stem interface has not been entirely solved. In this work, to confirm the load transfer between bone and stem following total hip replacement with a noncemented artificial joint of the Harris type, three-dimensional finite element analysis of the femur and hip was carried out before and after total hip replacement. A modeling method was also represented for the complicated three-dimensional geometry of the femur and pelvic bone. Young's modulus of each element in the osseous tissue was estimated from the distribution of mineral content obtained from an X-ray photograph. As a result, the effect of the three-dimensional shapes of an artificial hip joint on the fixation between bone and stem was confirmed from the stress distribution in the interface.

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Tomography is clinically useful in the diagnosis of the temporomandibular joint (TMJ) syndrome. The TMJ is formed by the condyle and the glenoid fossa, and there exists TMJ space between them. Image processing was employed in the present study, and the reference points of the condyle and the glenoid fossa were determined from the tomogram. Subsequently, the TMJ space and the shape factors of the condyle and the glenoid fossa were measured automatically in the image analysis. The TMJs of four patients were examined practically and the characteristics of each result were studied. There is a possibility of distinguishing an abnormal sample from a normal one by making use of the TMJ space and the distance between two reference points. The shape factor is also applicable and it can be used to detect deformation of the condyle.

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