The mixed mode (I+II) fracture behavior of carbon-fiber/epoxy composite laminates was investigated over a wide range of loading rate to clarify the effects of strain rate and mode mixture on fracture behavior. MMF (Mixed Mode Flexure) and MMB (Mixed Mode Bending) specimens were used to evaluate the mixed mode fracture toughness. The mixed mode fracture toughness clearly showed strain rate dependence regardless of mode ratio; the mixed mode impact fracture toughness was about 10 % lower than the local maximum value under static loading. Local maximum values existed at static loading rate for mixed mode fracture toughness, G_C. The mixed mode fracture toughness conform to the linear criterion for the region of high mode ratio, G_<II>/G_I=13, regardless of loading rates. However, it did not conform to the linear criterion for the region of low mode ratio, G_<II>/G_I&le;3, and high loading rate, G&ge;10^2 J/m^2/s.

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Static FOD characteristics of hybrid composites with non-woven carbon tissue (NWCT) are investigated under contact loading condition with steel ball as the indentor. The hybrid composites are made by stacking NWCT- and CFRP-prepregs. Four kinds of composites are studied; i.e. CFRP composites ([0_5/90_5/0_5] and [0_3/90_3/0_3/90_3/0_3]) and hybrid composites ([0_5//90_5//0_5] and [0_3//90_3//0_3//90_3//0_3]). The symbol " // " means that the NWCT-prepreg is located at an interface between CFRP-layers. The NWCT-prepreg has short fibers, discretely distributed with in-plane random orientation. The objective of this investigation is to study the effect of the NWCT due to indentation loads in order to fundamentally understand the impact damage mechanics of hybrid composites. The fracture surfaces of the specimens observed by deplying process and microscope, and the fracture mechanism was discussed.

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Meso-mechanical material modeling of a super plastic metal alloy is attempted. Multi-crystal grains in the metal that exibit extensive surface sliding is modeled for super-plasticity by employing a nonlinear tangential spring layer between the crystal grain and the matrix. The constitutive law for the domain in which mult-phase crystal grains of the type are dispersed is derived with the use of equivalent inclusion method on the basis of self-consistent shceme. Results of a large deformation finite element analysis on a surface cutting are shown employing Backofen's constitutive law.

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Fundamental study is carried out to investigate accuracy for evaluating the defect size in the circular rods in water by using the ultrasonic caustics. It is shown that the defect can be evaluated by employing not only shear wave but also longitudinal wave and the general relationship between the angle β_0 of receiver and the value of a/D, which is used to determine the crack length, is given. Moreover it is revealed that the minimum defect size which can be evaluated by this technique is approximately 4mm under the experimental condition used in this study.

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Dynamic crack propagation in PMMA was studied using the method of caustics in combination with a Cranz-Schardin type high-speed camera. Three different types of specimen geometries were employed to achieve the crack acceleration, deceleration and/or re-acceleration process in one fracture event. Dynamic stress intensity factor K_<ID> and crack velocity a were evaluated in the course of crack propagation to obtain the relationship between K_<ID> and a. The effect of crack acceleration and deceleration on the K_<ID>-a relations was examined.

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The mechanical consideration of the bimaterial interface is a very important problem on the evaluation of the material. Then, the stress intensity factor K for a crack along the bimaterial interface has been measured by the method of caustics. The effect of initial curve for the measurement accuracy is examined. As a result, it is possible to apply this method to the bimaterial jointed materials when the maximum diameter D of the image is used and the value r_D of initial curve is larger than the value r_D^<min> obtained in this study. And, the value r_D^<min> is about half a value of the specimen thickness when the same materials are jointed, it becomes smaller when the different materials are jointed. There is a close correlation between the size of 3-D stress field and Young's modulus ratio of each specimen.

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Shrink fit is widely used in joining mechanical components and combining prestressed cylinder to increase their elastic strength. However, many serious accidents have occurred because of the fatigue or fracture due to contact pressure between components. In this paper, stress intensity factors were obtained by simulating boss shaped parts with cracks,i.e., inserting a disk into a hollow disk, thus causing contact pressure in the inner surface of the hollow disk. Photoelastic methods were employed to determine the stress intensity factors which could describe the dynamic behavior in the vicinity of crack tips. The effects of shrinkage allowance and crack depth on the stress intensity factorys were examined.

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Out-of-plane deformation and strength of the quench-hardened circular plate glass are studied. First, deformation of plate glass is measured by using reflection of laser beam on the specimen surface and it is revealed that there arises anti-clastic deformation in the plate glass through quench-hardening. Fracture stress is obtained for the plate glass under concentrated load. There is no relationship between the deformation and the fracture stress. Moreover, thermal stress is analyzed for the plate glass by using a light source and strain gage, and it is shown that there arises compressive stress of approximately 300MPa at the central area of the plate.

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The point by point measurement of in-plane displacement was conducted by the pointwise filtering approach of speckle photography. The experiment was conducted on the compact normal and shear (CNS) specimen made of acrylic resin subjected to various kinds of mixed-mode loading. Displacement field inside specimen was measured under various kinds of mixed-mode loading. Then, stress-intensity factors of asymptotic solution derived by Sun and Jih were estimated using the displacement data obtained from speckle photography by the least squares method. The experimental results were compared with the numerical results. The variation of stress-intensity factors with load application angle was discussed on different planes from the free surface to the center of the specimen.

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Speackle interferometry is a wholefield non-contact metrology technique for measuring displacementt, otherwise shearography is one for strain measurement. In order to combine both techniques, we proposed a new system utilized two Michelson interferometers. Phase shifting technique is also used to obtain wholefield information. In this study, the author measures out-of-plane displacement and strain of point loaded aluminium disk and in-plane displacement and strain of tensioned bar with hole is also measured.

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In processing by lathe, the work is processed by experience of craftsman. Also center hole in processing by lathe, this tendency is untill today. If center hole is destructed, it is serious accident. Therefore, this study suggestes standard for safety. This study is formed four kind experimental method. This method is isochromatic line and isoclinic line by photoelasticity, finite element method. In the first, three dimensional model is transformed to two dimensional model. And, it is modeled two dimensional specimen. By this specimen, isochromatic line and isoclinic line by photoelasticity and caustic method is applied. And, finite element method is applied to shape of two dimensional specimen and three dimensional model.

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The frozen strain method has been carried out by long time load under the low temperature or load in the short time over glass transition temperature. The former needs the long time course, the latter causes large deformation by the load, since the Young's modulus changes small and Poisson ratio increases. For the purpose of this experimental study, using the polycarbonate, trying to reduce the days spent for the experiment and to froze the strain under the room temperature. In the industrial product, the polycarbonate used in this study is made by the extruding. Therefore, there is the residual stress. Annealing is effective measures in order to reduce the residual stress. By comparing the polycarbonate with annealing to the polycarbonate without that, the effect of annealing is confirmed.

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The reflection type laser photoelasticity that possesses high detection sensitivity of the birefringence measurement was developed to detect the stress of the film formed on the surfaces. A He-Ne Laser was used as a light source. The magnitudes of principal stress difference and the direction of the principal stress were obtained simultaneously and quantitatively using our equipment. This type of photoelasticity has a problem that the reflected light from film surface give rise to the error of measurement. We had investigated the influence of the reflected light from film surface for measurement value.

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A method for measuring surface strains of real specimens is proposed using the scattering photoviscoplastic analysis with polyester coating. A major advantage of this experimental technique is that interference fringes in the vicinity of the adhesion plane bounding the real specimen and the coating can be observed. The difference in principal strains on the symmetric section of real specimen in two dimensional problems can be calculated using two kinds of scattered-light fringe patterns obtained by two different incidences of polarized light. For the demonstration of effectiveness of this method, surface strains of semicircular notched plate specimen made of aluminum alloy were measured under uniaxial tension. Normal strains on the notched section were estimated and the distributions were consistent with FEM analyses.

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The aim of this study is to construct Jones Matrix Image Fourier Polarimeter for measuring internal stress state of 3-D object. By introducing various methods such as phase shifting and phase unwrapping techniques, this system have been proved to be a possibly available method to measure three optical parameters σ, θ, and ε in 2-D analysis. However, in the case of a 3-D analysis, we have various problems because the rotation of principal axis along light path affects these optical parameters seriously. In this paper, the authors prepare 3-D slice model consist of two thin glass disks and analyze three optical parameters influenced by the rotation of principal axis. As the results, in 3-D analysis, we found that phase difference σ can be treated as integrated value, on the other hand, azimuth angle θ can be treated as average value. And furthermore, ellipticity angle ε increased suddenly in superposed analysis.

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This paper describes an experimental method of stress separation. Thermoelastic stress analysis (TSA) and photoelastic stress analysis (PSA) have been developed as full-field visualization methods of stress distribution. Only the sum of principal stresses can be measured by TSA, while only the difference of principal stresses can be measured by PSA. So it is difficult to separate them into individual stress components by either of the methods. In this study, a hybrid measurement technique using both of these methods was proposed for stress separation. Stress separation of a loaded plate with a circular hole was investigated. The experimental results were compared with results of boundary element method analysis. It was found that the stress components experimentally obtained by the proposed technique coincided with those obtained by the boundary element analysis. Feasibility of the proposed hybrid measurement for stress separation is demonstrated.

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Actual concentrated stress distributions at a notch front in Si_3N_4 were measured by the collimated X-ray sin^2Ψ method and validated by the fracture mechanics. The elliptic model expresses well the features of stress distributions at U and V notch front which is analyzed with their finite length and tip radius. The stress intensity factor, K_I, can be obtained experimentally from the measured stress distribution plotting versus characteristic function in the elliptic model. An apparent stress singularity was observed to be -0.5 in the range 0.05-0.5 mm from the tip, but the elliptic model also provides a similar linear tendency.

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In order to measure 3-D surface deformation in the same site and situation simultaneously, a new optical set-up is constructed by combining Moire interferometry and Twyman-Green interferometry. Phase shifting techniques is applied to obtain 4 fringe image data for estimating u, v and w displacement separately. Furthermore, the phase connecting method using minimum spanning technique is applied to obtained rapping image data. Further improvement of image processing is needed for estimating accurate 3-D deformation.

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Piezoelectric film is a sensing element that generates an electrical charge proportional to a change in mechanical stress. When the piezoelectric film is glued to the surface of a cracked material subjected to varying load, periodic change in distribution of electric potential is observed on the surface of piezoelectric film. Based on this phenomenon, the passive electric potential CT (computed tomography) method was developed for identifying two- and three-dimensional cracks. In the previous study, contact measurement method using electrodes and voltmeter was applied. In the present study, electric potential distribution is measured by non-contact voltmeter, which may be suitable for multi-point measurement, to develop non-contact electric potential CT measurement. It was found that the non-contact electric potential CT measurement had improved resolution and accuracy in crack identification.

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Through-thickness compressive characteristics of laminated composites under impact loading are evaluated using the standard split Hopkinson bar. Compressive stress-strain curves for cross-ply CFRP, plain-weave GFRP and CFRP laminates at high rates of strain up to ε≒1700/s are presented and compared with those at low and medium rates of strain by an Instron testing machine. Comparative assessment of ultimate compressive strength, fracture strain and absorbed energy to fracture for the three different laminated composites are provided. The test results indicate that the compressive properties for cross-ply CFRP laminates decrease greatly with increasing strain rate, whereas those for plain-wave CFRP and GFRP laminates hardly depend on the strain rate.

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Acoustic emission signals were observed when solid target of aluminum alloy, cupper alloy, alumina, fused silica and LiF single crystal were irradiated with fast Ar ions. The projectile beam of 95Me V/u Ar ions was chopped to a pulse shorter than 1 μs. The high sensitive piezoelectric sensors detected the acoustic emission beyond the samples and the irradiated depth could be calculated using onset of acoustic emission and longitudinal wave velocity. The energy of acoustic emission was proportional to the energy of irradiated Ar ions.

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