新川 和夫

ZrO2/Ni複合材料の変形・破壊挙動に及ぼす分散状態の影響

Six different types of ZrO2/Ni composite materials were fabricated by means of the slip casting method to study the effects of composition and dispersiveness on their deformation and fracture properties. The result of three-point bend testing indicated that the composition had significant influence on the bend strength and absorbed fracture energy with sufficient dispersiveness, whereas there was little effect on these properties with insufficient dispersiveness. The result of mode I fracture testing also exhibited that the critical mode I energy release rate, GIc, depended upon the composition, and the sufficient dispersiveness resulted in better GIc than the insufficient dispersiveness. The microstructures and fracture behaviors of the composites were examined using a laser microscope, an optical microscope with an image analysis technique and a scanning electron microscope (SEM). The result of the image analysis showed that the compositions of the sintered materials were different from those of the compacts. The SEM observation also exhibited that in the materials with insufficient dispersiveness, cracks tended to propagate along the interfaces of Ni aggregations, resulting in the degradation of the fracture properties.

動的き裂進展を伴う高分子材料の除荷挙動 : 第1報, エポキシ樹脂の場合

The method of caustics in combination with a Cranz Schardin high-speed camera was utilized to study dynamic crack propagation in epoxy specimens. Single-edge-cracked tensile specimens were fractured under pin-loading conditions so that cracks could undergo acceleration and deceleration stages in one fracture process. Dynamic stress intensity factor Km and crack velocity a were evaluated in the course of crack propagation. Caustic patterns at the loading points were also recorded to estimate the dynamic load P applied to the specimen. Unloading rate P, i.e. the time derivative of P, was determined as a function of time t, and its correlations with Km and a were examined.