The split Hopkinson pressure bar (SHPB) technique has been often used for determining dynamic stress?strain behavior of materials. Nevertheless, some specific problems still remain regarding effects of specimen size and diameter ratio between the specimen and pressure bars. In our previous study, a model was established by neglecting the kinetic energy from the energy balance and expressing the radial inertia in terms of the time derivative of strain rate and frictional forces acting on both ends of the specimen. From the established model, the actual stress can be expressed by taking sum of the evaluated stress and stress decrement as a function of friction coefficient, Poisson’s ratio and the slenderness ratio of the specimen. The proposed model shows good correspondence with the computed results obtained from the FE model. However, the reliability of the computed results is not high enough, since the assumed constitutive parameters used in the previous study were quoted from literatures. In order to confirm the higher reliability of the model, the constitutive parameters are identified from the experimental results for an Al alloy 7075-T6 by one of the authors. The FE simulations are then performed to investigate the effects of specimen slenderness ratio and diameter ratio between the specimen and the pressure bars on the evaluated stress.

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   The effect of mechanical impedance of loading bars in the Split-Hopkinson pressure bar testing system is numerically clarified based on the one-dimensional elastic stress wave theory. Uniformity of the stress distribution in a specimen depends on difference of mechanical impedances between the loading bars and the specimen. From a practical point of view, almost uniform stress distribution in the specimen is obtained after several reverberations of stress waves even in the case of the high mechanical impedance loading bars. Applying ramp incident wave is a useful method to realize uniform stress distribution at relatively low stress level and consequently, it is available to high strain rate deformation. For soft materials with low mechanical impedance a flanged loading bar system is proposed to measure the flow stress accurately under a uniform stress distribution in the specimen. The effect of mechanical impedance of loading bar on the strain rate is also discussed.

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   In order to evaluate the crash safety of automobiles, various collision tests have been performed. In the offset frontal collision test and the side collision test, which simulate car-to-car crashes, the deformable target is a honeycomb material made of aluminum sheets. The impact absorption property of the honeycomb material depends on various parameters. In this study, these influential parameters (the collapsing velocity, the air pressure inside hexagonal cells, the honeycomb geometrical shapes and the delamination force of cell walls) were investigated with the falling weight tests and the finite element simulations. The obtained results are shown as follows; High collapsing velocity increases the impact collapsing load in large deformed region. In more than 40% deforming ratio, the air pressure change inside the hexagonal cell influences the impact collapsing load. The specimen height does not affect the impact collapsing load directly. The experimental static/dynamic ratio of honeycomb collapsing load was 1.5.

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   In-plane dynamic compressive properties of aluminum alloy honeycombs were examined experimentally. Six types of cell patterns filled with epoxy resin were proposed in order to increase plateau stresses and absorbed energies of honeycombs. Three cell patterns of them increased the plateau stresses and absorbed energies, but the others did not affect them. The main reason for showing such difference was discussed using images captured by a high speed video camera. It was important for deformation modes of honeycombs to increase the plateau stresses and absorbed energies. Only when the restricted compressive (RC) modes were formed, the plateau stresses and absorbed energies could be increased slightly. However, it was difficult to increase significantly the plateau stresses and absorbed energies using the specified filled cell patterns used.

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   The use of viscoelastic materials has been increasing in various industries such as automotive and electronic industries because of their excellent impact resistance or damping capability. Precise knowledge of their dynamic properties are needed to further widen the applicability of viscoelastic materials. In the present study, attenuation and the dispersion properties of a polymethyl methacrylate (PMMA) bar were examined using both ultrasonic wave propagation experiments in the higher frequency range of 25 - 200kHz and longitudinal wave propagation experiments in the lower frequency range of up to 15kHz. Since the geometrical dispersion due to three-dimensional deformation was caused by higher frequency components involved in the ultrasonic waves, the three-dimensional wave theory was employed to analyze experimental data of wave propagation. Consequently, it was found that the dynamic properties in the lower frequency range can be identified as a 3-element viscoelastic model based on the elementary one-dimensional wave theory, while those in the higher frequency range must be identified as a 5-element viscoelastic model based on the three-dimensional wave theory.

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   A simple and cost effective experimental method is developed to reconstruct the complete 3D shapes of different objects outer perimeter. In this paper, a mannequin’s head, a cube and a cylinder are used as subjects. A safe and practical method to apply a random speckle pattern on a human’s face is also established, by using an air brush make up set. The apparatus for the proposed method is environmentally friendly and consists of basic camera equipment. The experimental method requires a single camera and a double sided calibration board, with check marks on both sides that are aligned with each other. In order to get multi-view stereo images, rotational and translational movements of the subject are executed using a pan head and a slider. The alteration of the rotational and translational displacement error between the overlaying sets of the 3D point clouds and alignment is executed using the iterative closet point algorithm method. Finally, accuracy evaluations of the 3D models are performed.

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   Development of ultrasonic velocity profile (UVP) method for two-phase flow using spike signals is executed. Multiwave transducer (TDX) which can emit two different ultrasonic frequencies, i.e. 2MHz and 8MHz for liquid/bubble two-phase flow, has been developed. The spike signal is frequently used for ultrasonic inspection as non-destructive test discipline, and it has less number of waves and time to pass than conventionally used burst signals. A pulser/receiver (P/R) for spike and a flexible unit as the analog to digital converter (ADC) are applied to this system. The measurement method which is based on ultrasonic Doppler method (UDM) and autocorrelation method based on Wiener-Khinchine's theorem is applied instead of conventional FFT based technique. Multiwave method has been developed for the measurement of two-phase bubbly flows. Furthermore, a phase separation method has been proposed, which leads to obtain instantaneous velocity profiles of both liquid and bubble. Practical application of the new method has been conducted, and the results show the robustness of the method. In addition, the instantaneous local void fraction profiles can be calculated along the measurement line using this method. Further investigation of two-phase flows in a vertical pipe with varied flow configurations will be conducted.

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   A force plate and motion analysis system are commonly used to measure the function of prosthetic foot-ankle units while walking. It is difficult, however, to use a force plate to measure gait on slopes and stairs while side-step walking with prosthetic foot-ankle units. Side-step walking involves two possible walking conditions, an actual leg or prosthetic leg that supports the body for ascending or descending a slope and stairs. Therefore, side-step walking is an important part of rehabilitation training for ascending or descending a slope and stairs. To measure the function of prosthetic foot-ankle units while subjects walked on a slope, a prosthetic lower leg was fitted with a compact, six-component force transducer, and an ambulatory gait-monitoring system was developed. The developed system is capable of calculating the load line. We report on the function of prosthetic foot-ankle units using the load line while side-step walking on a slope.

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   There are many prosthetic foot-ankle units with various functions. A postheist selects a prosthetic foot to match the life style and activity of each prosthetic user. One of the methods to evaluate the prosthetic foot function is the roll-over shape of foot-sole. This paper describes new method to get the rollover shape in walking. A measuring system is constructed from a six-component force transducer installed in upper position of the prosthetic foot and a three dimensional coordinates measuring device (Mac3D), and the roll-over shape while in walking is calculated. In this paper, we propose a new calculation method to get the locus of the fcp ( force contact point ), instead of the cop ( center of pressure ).

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   The copper electroplating stress measurement method utilizes the grain growth in the copper on a machine element that has been subjected to repeated loads. Since the grain growth is also caused by thermal energy, an effect of ambient temperature on grown grain density and grain orientation was investigated. Cyclic torsion tests were carried out at temperatures from 293K to 353K. The relationship among grown grain density, maximum shearing stress, number of cycles and ambient temperature was formulated to measure the maximum shearing stress occurring on the machine element. Moreover, the cyclic bending-torsion tests were also performed and the orientation of grown grain was analyzed by EBSD. The slip direction of grown grain corresponded closely with the direction of shearing stress in spite of ambient temperatures. This means that principal stresses can be measured using the pole figure and the inverse pole figure map of grown grain at temperatures up to 353K.

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