ISSN:
1573-4803
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract Fatigue tests were conducted on three linear poly (methyl methacrylate) (PMMA) resins having weight average molecular weights (M w) of 82 000, 205 000 and 390000 and on a fourth, cross-linked sample (M c=3337 g mol−1). Fatigue threshold test conditions included a constant load ratio (R c=0.1) and a constant maximum stress intensity level (K max c =0.52 MPa m1/2). TheR c=0.1 test results demonstrated that fatigue resistance increased with increasingM w, and that the cross-linked sample possessed a higher fatigue threshold than the linear Iow-Mw material. However, the K max c test results revealed the opposite trend, with fatigue resistance decreasing with increasingM w and chemical crosslinking. The marked change in relative fatigue resistance of the PMMA resins investigated under high mean stress conditions is believed to be a consequence of the competition between two molecular deformation mechanisms: chain scission and chain slippage. The presumed shift in operative mechanism as a function of theR level is reflected in differences noted on the fracture surfaces of the PMMA resins studied. Discontinuous growth band formation, which is indicative of large amounts of chain slippage, is favoured by lowM w and lowR ratios, but disappears in association with high-M w and highR-ratio test conditions.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00570057
