Osteoporosis is defined as the clinical manifestation of bone atrophy. In most cases, a fracture of a vertebral body is found, which would result in long-term bed care. However, a practically effective technique for the detection of osteoporosis is still not available. In the present report, a method for estimating mechanical reliability of in vivo cancellous bone using ultrasound signals is introduced. The method is based on the two-dimensional bone area fraction (S, bone/ (bone+bone marrow)) calculated from the difference in. the velocity of ultrasound wave propagation through the bone. The technique allows the estimation of in vivo bone mineral density for spine and heel bone as well as Young's modulus and strength from the propagation velocity that could estimate fracture risk of the bone. Further researches from various viewpoints, sport mechanics, image processing, numerical and experimental mechanics, and clinical medicine, are needed to establish the estimation of mechanica1 reliability for in vivo bone as strong diagnostic tool fbr osteoporosis.

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Mechanical properties of ultra high molecular weight polyethylene (UHMWPE) used as a bearing material in total joint replacement system have been investigated under impact compressive load. Ten cylindrical specimens, 8mm in both diameter and length, were machined from compression molded UHMWPE rods. Half of these specimens were gamma-irradiated in air at a dose of 2.9 Mrad without post irradiation treatment. Impact compression tests were performed using the split-Hopkinson pressure-bar technique to evaluate dynamic stress-strain relation up to 8% strain at a strain rate of about 400s-1. For both gamma-irradiated and unirradiated specimens, stress-strain relations exhibited relatively linear portions up to 2% strains and the gradients eventually decreased with increasing strain. Young's modulus determined from the linear portion and 0.5% yield stress were significantly higher for gamma-irradiated specimens than for unirradiated specimens. Two-dimensional elasto-plastic stress and strain analysis of hip prosthesis was performed under impact loading using a finite element method. Results indicated that the increase in mechanical properties induced by gamma irradiation reduced plastic strain within the UHMWPE cup.

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Effects of various initial cure conditions of pulse-delay curing on contraction stress reduction were examined photoelastically. Five different initial cure conditions were considered: P-1) 200mW/cm² for 3s, P-2) 300mW/cm² for 5s, P-3) 300mW/cm² for 10s, P-3′) 300mW/cm² for 10s with no interval, P-4) 600mW/cm² for 10s. Except for P-3′, a three-minute interval was provided between the initial and final light irradiations. All the experimental groups were subjected to the same final light exposure (600mW/cm² for 60s). The control group was light-cured at 600mW/cm² for 60s, with no initial cure and interval. P-2 and 3 developed significantly lower fringe order compared to the control group. P-1 and 4 failed to achieve contraction stress reduction because the light energy from the initial cure was too low and too high respectively. Comparison between P-3 and 3′ indicates that the interval between the initial and final light exposures plays an important role in contraction stress reduction as well as the reduced initial light irradiation. The results of this study indicate that pulse-delay technique can reduce contraction stress, however, both proper initial cure conditions and interval between the two light irradiations are important to attain contraction stress reduction.

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This paper is concerned with a magnetic micro machine driven by the alternating magnetic field. The magnetic micro machine swims like microscopic organisms in water. Frequency dependence of the micro swimming machine is investigated as a basic research for the development of micro robots which work in human blood vessels. The magnetic micro machine is composed of a small neodymium magnet and a polyethyleneterephthalate film. The locomotive behavior of the magnetic micro machine is analyzed by a three-dimensional motion analysis system It is found that the swimming velocity of micro machine depends on the frequency of the alternating magnetic field and the dimensions of the tail.

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The knee joints of a human being, with the assistance of ligaments and muscles, functionally act as the largest load bearing joints in the movements of the human body, and play an important and indispensable role in the movements and exercises performed by the human body. In such conditioned circumstances, we consider the shock waves generated by human beings at the time of running and jumping to be the waves which travel to the knees through the feet bones, tibia, and fibula, and thereby we apply the impact stress to the shitsumin and san-inko of the focal point in acupuncture, namely the tsubo, and clarify the effect of the stress waves upon the knee joints by employing the highspeed photoelastic analysis in researching the behavior of the propagating impact stress waves. We adopt the shitsumin and san-inko as the working points of the impact stress in order to investigate in what way both of these focal points affect the knee joints and grasp the manner in which they are done. Furthermore we clarify that the long bones such as the lower limbs and upper limbs have their shapes and structural formations to protect the bones from the external forces when they are subjected to the impact stress.

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The thickness dependency of the temperature image obtained by an infrared thermography was investigated using specimens with three kinds of materials and four kinds of the thickness of the specimen. Only the sum of the principal stresses which is the first invariant of stress tensor is measured, and it is impossible to measure individual stress components directly. Then, the infrared hybrid method was developed to separate individual stress components. Although the form of the contour line of low stress side differs greatly, the distribution form of high stress side was considerably alike. For thin specimens of 1mm thickness, the stress field obtained from the infrared hybrid method differed from it at the free surface which was obtained from 3-D finite element analysis. For specimens thicker than 3 mm, stress intensity factors were nearly uniform irrespective to thermal conductivity, and remarkable thickness dependency of the specimen could not be observed. The stress intensity factor of material with low thermal conductivity can be estimated with high accuracy by the infrared hybrid method.

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The magnetic diagnosis of iron-based materials was performed by using three kind of tools. Those are a triplefold coil for ac resistivity detections, a small Hall element for leakage flux observations after polarizations of the material and a magnetic Barkhausen noise pick-up coil combined with the excitation yokes. We found the first derivatives of the normal component of the leakage flux along the polarized direction well coincided with intensities of residual strains for ferromagnetic samplcs of A533B and S25C etc. Fur paramagnetic SUS304 samples, the polarity of the derivative was just reversed and was proportional to the induced martensitic transformations. An index derived by the magnetic noises well described the residual stress with its directions. All the parameters obtained by these electromagnetic tools were properly combined to judge the material degradations with high reliability.

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In order to estimate locations of micro-cracks in CFRP-tank during pressurization testing, we developed a source location method for utilizing AE signals. A 4-ch system of 150kHz resonant-type AE sensors was used for the source location. We first investigated the orientation dependence of AE signals in the tank by using artificial sources. Lamb-mode dispersive AE signals were monitored and arrival times to the sensor were defined by the times to maximum 90kHz-wavelet coefficients from each signal. We then investigated the effect of AE signals via liquid in the tank on source location results. Damage monitoring zone was set to the tank, and AE signals from non-monitoring zone were separated from those from monitoring zone by duration. Source location algorithm was proposed in this paper and accuracy of proposed method was discussed using artificial sources at variable points both in the monitoring and non-monitoring zone. Eighty percent of AE signals from non-monitoring zone were correctly separated from AE signals from monitoring zone. Source location of artificial source was estimated by the proposed method. Location of artificial source was identified with average error of 17.8 [mm] except 4 large error points.

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Electroless plating is recently used for electronic industry. But, during the deposition of thin films large internal stresses are frequently built into the films. The internal stress in films has been extensively investigated but its origin has not been clarified yet. In order to determine the origin of stress, measurements of stress are required in the initial stage of film growth. In this study, TV holography, which can capture holographic image at TV frame rates, is used to measure sensitively the change in the internal stress in films by recording the change in deflection of the free end of a cantilever beam. The dependence of internal stress upon film thickness for a Cu plating bath on a Be-Cu substrate was discussed. As the results, large stress variation is generated right after the plating, which occurred simultaneously with the adhesion of the plating particle on the substrate by SEM observation. The stress variation is large different in commercial bath and basic bath which removed small additives. This study shows that present method is useful as “in-situ measurement” of internal stress of electroless plating.

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The authors developed a new approximation algorithm for the construction of a master curve of viscoelastic property with Prony series in high accuracy based on the well-known collocation method. The algorithm enables automatic construction of an approximated master curve for thermosets or thermoplastics irrespectively, with no special experiences in the field and no violation of physical meanings by approximation in which the former algorithm could not avoid oscillation caused by changing. In order to demonstrate the effectiveness of the algorithm, the authors measured a viscoelastic property using a dynamic viscoelastic tester made by Rheometrics Inc. and utilized the data for a Prony series function. In addition, some master curve data of Epoxy resin and Polyisobutylene quoted from references were examined. As a result, the approximated curve fit to experimental data well keeping the sign of coefficient in plus.

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