# Accession Number:

## AD0698849

# Title:

## CRACK PROPAGATION GENERATED BY AN INCIDENT SHEAR WAVE,

# Descriptive Note:

# Corporate Author:

## NORTHWESTERN UNIV EVANSTON ILL STRUCTURAL MECHANICS LAB

# Personal Author(s):

# Report Date:

## 1969-11-01

# Pagination or Media Count:

## 39.0

# Abstract:

A plane horizontally polarized shear wave propagates into an undisturbed brittle elastic material containing a crack. The paper inquires into the conditions for initiation of crack propagation at a constant velocity upon diffraction of the incident wave by the crack. The investigation consists of two parts. In the first part the particle velocity and the shear stresses are determined for diffraction of a transient wave of arbitrary shape by a semi-infinite crack which extends at a constant speed once the wave front has impinged on the crack tip. In the second part of the investigation a power balance is employed to determine that shape of the incident pulse which is consistent with crack propagation at a constant velocity. It is shown that near the wave front the incident displacement wave must be of the form of a square root of the general argument t-ax-by. For this particular type of incident wave the instantaneous constant velocity of crack propagation is computed as a function of the angle of incidence, the amplitude of the incident wave, and of the material parameters. Curves are presented for the shear stress ahead of the crack tip. Author

# Descriptors:

# Subject Categories:

- Mechanics