In the sheet stamping of strain-rate-sensitive materials, the forming limit is governed by punch speed (SPD) as well as blank holding force (BHF). In previous research, a combination control algorithm for simultaneously varying SPD and BHF was proposed to achieve high-speed deep-drawing. In this study, finite element (FE) simulation is conducted for circular-cup deep-drawing with combination SPD/BHF control in order to reveal the deformation mechanism of the improvement of deep-drawability. The numerical results demonstrate that even though the blank material has a low strain-rate dependence at room temperature, the drawability and production rate can be improved by properly varying SPD/BHF. It is found, from the simulation results, that a relatively low SPD with a low BHF in the early forming stage causes less thickness reduction at the punch shoulder. In the middle-to-last stage, therefore, the remaining blank can be successfully drawn into the die cavity with SPD and BHF higher than the critical constant SPD and BHF.

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Ultrasonic health monitoring of structures under realistic operating conditions is very difficult because ultrasonic waves are influenced by not only structural defects but also environmental disturbances. We examined a method of ultrasonic spectroscopy in this investigation to classify signal changes as either structural or experimental. We used aluminum plates to investigate the ultrasonic propagation characteristics with respect to the growth of defects (fatigue cracks, slits, and drilled holes) and the change in environmental disturbances (water drops, temperature, and load). The frequency dependency of the propagation delays and amplitudes of tone-burst waves differed for defects and environmental disturbances. Defects could be distinguished from environmental disturbances by monitoring the delay-amplitude plot lines of the tone-burst waves with increasing frequency.

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We propose a generation laser scanning method for imaging of the propagation of ultrasounds. By scanning a pulsed-laser beam on an object for the generation of ultrasounds, the propagated ultrasounds were detected by a fixed PZT transducer. Although the detected waves were ultrasounds generated from different irradiation points, we could, by means of simple data processing, produce the dynamic images of the ultrasounds generated from the reception transducer position. Since this method requires no adjustment of the beam incident angle or beam focus, we can easily visualize the ultrasound propagating on a solid media having a complicated shape. The distinguishing feature of this method is its applicability in the field of inspection work.

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This study was performed as a part of the research on the ultrasonic measurement of bone porosity, bone density, and Young's modulus. It was found that the bone porosity estimated by Biot's theory agrees within 5% of the actual porosity. The bone's structure factor involved in the Biot's theory was determined experimentally to have a value of 2. It was also found that the use of the propagation velocity of the fast wave is more advantageous than using the slow wave in estimating bone porosity. The estimated bone density obtained by the use of Biot's theory is within ±5% of the measured value obtained by the use of Archimedes' principle. Bone density as well as Young's modulus can be estimated precisely by using the proposed ultrasonic wave method.

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Efficient interatomic potentials for Pb(Zr,Ti)O₃ (PZT) crystals, which are intensively applied to ferroelectric devices, are required for the atomic-scale study of the mechanical and electronic behavior of the materials with the increasing demand of further improvement of the devices. In this study, we develop parameters of empirical shell-model potential functions, with which large-scale atomic simulations will be feasible, for the equilibrium lattice parameters and atomic displacements of ferroelectric state and the elastic constants of tetragonal PbTiO₃, PbZrO₃ and PbZr_0.5Ti_0.5O₃ based on first principles calculations. The potentials individually optimized for PbTiO₃, PbZrO₃ and PbZr_0.5Ti_0.5O₃, respectively, reproduce both the structures and the elastic constants of each crystal in good accuracy. The potential simultaneously fitted for all the crystals yields the structural parameters successfully, whereas some components of the elastic constants are poorly reproduced.

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