Accession Number : AD0810659

Title :   AN EXPERIMENTAL INVESTIGATION OF DYNAMIC CRACK PROPAGATION IN PLASTIC AND METALS.

Descriptive Note : Final rept. 1 Apr 65-28 Feb 66,

Corporate Author : CALIFORNIA INST OF TECH PASADENA

Personal Author(s) : Beebe, Wayne Metcalf

Report Date : NOV 1966

Pagination or Media Count : 187

Abstract : Crack propagation experiments were conducted in polyester resin sheets containing a central crack. Uniaxial tension loading at several loading rates was applied perpendicular to the crack direction. Two types of experiments were conducted: (1) High loading rate test at 24C and -45C, with a constant loading rate to study the acceleration characteristics of cracks running in a glassy material, and (2) high temperature-low loading rate tests to study slow crack propagation when appreciable viscous dissipation could occur. During crack propagation, full frame photographs were taken of the photoviscoelastic isochromatic patterns and crack tip position at framing rates from 250 to 100,000 frames per second. The principal conclusions were as follows: (1) Even at loading rates exceeding 10 to the 5th power psi per sec, isochromatic patterns prior to crack propagation compare closely with static patterns. (2) Constant crack velocities were achieved in the high loading rate tests and it was found that the isochromatic patterns compare closely with the theoretical solution of Broberg. (3) During the crack acceleration period, the experimental data could not be represented adequately by the Berry elastic theory. (4) For the early phase of the slow (viscous) crack growth period, the crack length could be predicted using a simple theory proposed by Schapery and Williams. Several tests were conducted on silicon-iron metal sheets; it was concluded that the same testing technique can be applied to the study of crack growth in metals. (Author)

Descriptors :   *CRACK PROPAGATION), (*POLYESTER PLASTICS, METALS, SILICON, LOADS(FORCES), TEST EQUIPMENT, VISCOELASTICITY, TENSILE PROPERTIES, HIGH TEMPERATURE, IRON, HIGH SPEED PHOTOGRAPHY, EMBRITTLEMENT, THICKNESS, STRAIN(MECHANICS), FRACTURE(MECHANICS), HIGH SPEED CAMERAS, EXPERIMENTAL DATA.

Subject Categories : Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE