Abstract (EN):
J integral and COD measurements were made simultaneously on three-point bend specimens of 50D structural steel (specification BS4360). Tests were performed at temperatures over the range -100°C up to room temperature, and at each temperature a series of specimens with a/W ranging from 0.2 to 0.8 were tested. Using a value of J derived from the equation J=-(1/B)(d U/d a), it was shown that Jc (where the subscript c denotes the critical value for unstable crack propagation) was a function of a/W at -80°C, decreasing with the increase in crack length, whereas at lower temperatures Jc was found to be insensitive to a/W. Measurements of Jmax at temperatures corresponding to the upper shelf regime of the material also presented the trend of decreasing Jmax with increasing value of a/W. A study of the range of applicability of the commonly used approximate expression J=2 U/B(W-a) was carried out, and it was found to agree well with theoretical values for 0.4<a/W<0.6. At each test temperature, a constant relationship between Jc and ¿c (critical value of the crack opening displacement) was determined which was independent of a/W, showing that COD and J are subject to the same limitations in specimen dimensions. This work supports the suggestion that Jc values should be obtained on material of the full thickness of interest, as is accepted practice for COD. The value of m in the relationship J=m¿y¿ was shown to depend upon test temperature with values varying from m¿1.8 at -10° to 1.3 at -100°C. © 1981 Sijthoff & Noordhoff International Publishers.
Language:
English
Type (Professor's evaluation):
Scientific