SEDL / STP / STP711-EB / STP27442S

Influence of Specimen Geometry on Crack Propagation and Arrest Toughness

Dahlberg, L
Research assistant, research associate, and research assistant, The Royal Institute of Technology, Stockholm,

Nilsson, F
Research assistant, research associate, and research assistant, The Royal Institute of Technology, Stockholm,

Brickstad, B
Research assistant, research associate, and research assistant, The Royal Institute of Technology, Stockholm,

Pages: 20    Published: Jan 1980

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Abstract

A number of crack propagation experiments on four different specimen geometries were performed in order to investigate the existence of a unique relationship between crack propagation toughness and crack-tip velocity. For one geometry, dynamic finite-element method (FEM) calculations were found to be necessary in order to obtain proper stress-intensity factors, whereas quasi-static FEM-calculations were found to be sufficient for the other geometries. Crack-tip velocities were determined from continuous recordings of crack length versus time, which was measured by an impedance method. The stress-intensity factor and the instantaneous crack-tip velocity were obtained for a number of crack lengths for each experiment. The experimental results do not contradict the hypothesis of a unique relationship between these two quantities at low load levels; neither do they contradict the hypothesis of a geometry-independent crack arrest toughness. At high load levels a deviation from the uniqueness was observed. The height of the specimens was found to influence the crack propagation toughness level at the beginning of deviation from the unique relationship.