ISSN:
0032-3888
Keywords:
Chemistry
;
Chemical Engineering
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
Ultrasonic fractography studies were performed on poly(methyl methacrylate) of high molecular weight. The transient fracture velocity change at the slow-to-fast transition during discontinuous propagation has been measured precisely. Fast fracture starts with a characteristic velocity which falls in a narrow range between 90 to 150 m/s, nearly independent of the loading speeds and the specimen temperature from -50 to 40°C. Parallel double-cantilever-beam specimens exhibited stick-slip type propagation whose velocity change was also evaluated. In these specimens, the fast fracture abruptly slows down to speeds on the order of 10° m/s. These intermediate velocities have never been obtained in the slow-to-fast transition. Velocity measurements under hydrostatic pressure have shown that fracture velocities decrease significantly with increasing pressure, and that the slow-to-fast transition tends to disappear at a pressure between 5 and 10 MPa. Models have been presented concerning the mechanism of the slow-to-fast transition, crazing and cracking under superposed cyclic stress field, and the relationship between dynamic toughness and fracture velocity in this material.
Additional Material:
14 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pen.760270105
Permalink
