パルスホログラフィ顕微鏡法を用いた高速進展中き裂先端部の撮影技術

抄録

Pulsed holographic microscopy is applied to taking instantaneous photomicrograph of the neighborhood of crack tip which is propagating in a PMMA plate specimen at a speed of several hundred meters per second.
We use two types of holographic recording system with Q-switched ruby laser to record an instant of time of fast propagating crack. One records scattered light from new crack surfaces as object light, the other specularly reflected light from specimen surfaces. Both recording systems are applicable not only to transparent specimen but also to opaque one. Photomicrograph is made with a conventional microscope to magnify the reconstructed image from a hologram of fast propagating crack.
From each photomicrograph obtained, crack opening displacement is measured as a function of distance from crack tip along the crack, and is of the order of ten microns. As a result, it is recognized that crack opening displacement is in proportion to square root of the distance from crack tip. This fact agrees with theoretical prediction of linear elastic fracture mechanics.