Void growth at ductile crack initiation of a structural steel

✍ Scribed by Y.W. Shi; J.T. Barnby; A.S. Nadkarni

• Publisher: Elsevier Science
• Year: 1991
• Tongue: English
• Weight: 636 KB
• Volume: 39
• Category: Article
• ISSN: 0013-7944
• DOI: 10.1016/0013-7944(91)90020-2

✦ Synopsis

This investigation deals with the critical void growth in a BS4360 Grade 50D structural steel. The tests are carried out on four variations of the Charpy size specimens, namely a standard geometry; side grooved; fatigue cracked; side grooved and fatigue cracked. The geometry variations are intended to vary the level of hydrostatic stress or constraint in the region of fracture initiation. The void growth is measured on mid-sections of specimens at onset of crack growth. It is known that there are two micromechanistic concepts regarding initiation of the ductile failure processes. One is the critical void volume fraction, and the other is the critical void growth rate. The experimental studies indicate that the critical void volume fraction (f,), at onset of crack growth is not a material constant. The volume fraction is dependent on the geometry constraint. However, the critical void growth rate R,/R, is a material constant within a first approximation. Thus, it is probable in engineering to evaluate the crack initiation in a cracked specimen by using the critical void growth rate measured on smooth tensile specimen with lower constraint to take it easy.