Atsushi Oguchi

A Magnetostrictive Load Cell for Use under High Hydrostatic Pressures

A load cell utilizing magnetostrictive strain gauges which is suitable for measuring loads up to 300 kg in tensile testing of materials under high hydrostatic pressures up to 15000 kg/cm2 is described. Temperature and pressure variations during tensile testing can be completely compensated by the use of a dummy gauge. The calibration of the load cell under pressure is performed by a coil spring which is calibrated at atmospheric pressure. The calibration curves under pressures up to 13400 kg/cm2 and 200 kg agree with the atmospheric calibration curve within 2%.

Strain-induced transformation and plastic deformation behaviour of a 17Cr-7Ni-1Al steel at high hydrostatic pressure

Tensile tests of a 17Cr-7Ni-1Al steel were carried out at 0.1, 300 and 600 MPa hydrostatic pressure, and the mechanical properties of the material were found to be considerably changed by the pressure. The martensitic transition temperatureMsγ→α′ decreased under pressure. The volume fraction ofα-martensite induced by tensile deformation increased with strain, but was suppressed by hydrostatic pressure. The yield stress increased with pressure. The yield surface became a nonlinear cone with a pointed apex. The stress-strain curve was considerably changed by pressure, and was expressed by a modified identical-strain model (law of mixture) as a quantitative function. Uniform-strain limit increased with pressure. It was found that these changes were not caused by the mechanical effect of hydrostatic pressure, but by its thermodynamic effects.

Characterization of Cu/Ti Multi-Layered Structure by Improved Sputter Crater Method

Layered Cu/Ti superlattice structures have been studied by an improved sputter crater method. A low-energy and large-area rastering Ar-ion beam was intensitionally used to produce a shallow and homogeneously etched crater. The Cu and Ti layers 10-20 A thick could be observed as concentric circles with a magnification factor (lateral/depth) of 104~105.