Yukiyoshi Kobayashi

Study on Torsion Property of FW-RP Cylinder with a Side Circular Hole

It is necessary to get a fundamental data of FW-RP cylinder setting up a side circular hole for a design of mechanical structures transmitting torsion load. In this study, the torsion rigidities near the side hole were measured by static torsion tests. Moreover, the properties of FW-RP cylinder with a side circular hole were calculated by an original FEM program that is able to simulate FW-RP cylinder. As a result, the following conclusions were obtained. (1) The partial torsion rigidity of FW-RP cylinder with a side circular hole is remarkably dropped down near the side hole. Especially, the reduction of the partial torsion rigidity is very large in thick FW-RP cylinder. (2) When the diameter of a side circular hole is large, the distribution of the stress around the hole is much influenced by the fiber orientation angle θ. (3) The maximum value of normalized stress around the side circular hole occurred at inside of the FW-RP cylinder in a thin cylinder (t=1mm). The reason of the movement of the maximum normalized stress is based on the difference of the rotation displacement about z-axis along thickness.

Fatigue. Mode III Fatigue Crack Growth Behavior. Transition Condition of the Crack Growth Mode.

Mode III fatigue crack is usually observed at the root of circumferentially notched round bar. As the crack grows in the depth direction of specimen, the growth rate of crack decreases. In this respect, crack mode transition from mode III to mode I is understood responsible. However, quantitative evaluation on crack mode transition has been hardly done. Therefore, values of stress intensity factor KI under mode III fatigue crack growth tests on a low carbon steel were calculated with using principal stress, as crack mode transition began. Then KI values were compared with crack growth rate curve of mode I. As the result, it was observed that the condition of crack mode transition was given by the crack growth rate curve of mode I.

Fatigue Behavior of Solder Joint under Simple Shear Stress.

In order to clarify the simple shear strength of solder joint, we carried out static strength tests, fatigue tests, fatigue crack growth tests and creep crack growth tests on Cu/60Sn·40Pb/Cu joint under simple shear stress. Major conclusions obtained in this study are summarized as follows : 1) The maximum simple shear stress increased with the increase in the simple shear strain rate. 2) The effect of the width of the solder on the fatigue strength were not observed. 3) The fatigue cyclic crack growth rates were governed by neither the stress intensity factor range nor the maximum stress intensity factor. 4) The fatigue and creep loading time crack growth rates were governed by the modified J integral. 5) The fatigue and creep crack growth behaviors depended on the process zone (small scale creep zone) at the crack tip.