An analysis is described of a welded stainless steel box beam that experienced a structural failure during fatigue testing. Cracks initiated at notches caused by partial penetration welds and grew to a length of several centimetres in about 1000 load cycles.
The objective here is to describe the characterization of fracture toughness and fatigue crack initiation for the precipitation-hardening stainless steels used for the welds and parent plate of the beam. Three-point bend specimens were used to measure both fatigue crack initiation life and the J-integral fracture toughness of the parent plate and weld metal in various conditions. The notch fatigue analysis method of Barsom and Rolfe was used to analyze the crack initiation test results. The crack was grown further, side notches were added, and JIc tests were performed using ASTM Test Method for JIc, a Measure of Fracture Toughness (E 813-87) with a modified load-line-displacement unloading-compliance procedure to measure crack growth.
Conclusions drawn from the work include the following: (a) JIc can be accurately determined with a three-point bend test using load-line displacement to measure crack growth by unloading compliance (An accurate expression for a/W in terms of load-line displacement was developed.); and (b) fatigue crack initiation life and JIc fracture toughness of stainless steels in various conditions were characterized. The welded and aged condition, with no intermediate solution treatment, showed unstable, cleavage-type fracture and resulted in a low JIc value and a short initiation life.
Fracture Fatigue Fatigue Life Cylinder 20. ABSTRACT fCotrtfiJue on reverse »M» ff nrncevamry ami Identify by block number) A program of nondestructive inspection, mechanical tests, and fracture mechanics tests was performed on a high pressure air storage bottle. The tests were planned to provide the basis of fracture mechanics life analysis of gas bottles in their service environment. This report describes the procedures and results and gives a preliminary analysis of the results.
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