Fracture Toughness Comparison between a Semielliptical Surface Crack in a 4PBPlate and a Through-Thickness Crack in a 3PB Fracture Toughness Test Specimen

摘要

Finite-element analyses were conducted for two 4PB plates with different sizesemielliptical surface cracks. The results of the analyses were compared to the results of a previously published analysis of a 3PB specimen by Nevalainen and Dodds (1995). Differences in the small-scale yielding, the J-Q behavior and the effective crack-front length were found between the plates and the 3PB specimen. Two methods were proposed to be used to calculate the fracture toughness of the plate. Experimental verification of the analysis results was carried out by testing plate specimens with the larger surface crack and 3PB specimens. The experimental results seemed to support the results of the finite-element analyses, although the test material properties did not match those of the analyses exactly. The ductile-to-brittle transition curve of the test material was determined, and a transition shift of 29 deg C was found between the specimen types. A combined thickness and constraint correction was applied to the results. The correction seemed very promising and brought the test results to the same level. (Copyright (c) Valtion teknillinen tutkimusk eskus 1997.)