ISSN: 1945-7553
CODEN: JTEVAB
Page Count: 7

The Use of Small Punch (Bulge) Tests to Estimate Fracture Stress in the Lower Shelf Regime

Joo, Y-H
Graduate student, associate professor, and professor, Research Institute for Fracture Technology, Tohoku University, Aza Aoba Aramaki Aobaku, Sendai,

Hashida, T
Graduate student, associate professor, and professor, Research Institute for Fracture Technology, Tohoku University, Aza Aoba Aramaki Aobaku, Sendai,

Takahashi, H
Graduate student, associate professor, and professor, Research Institute for Fracture Technology, Tohoku University, Aza Aoba Aramaki Aobaku, Sendai,

Shimomura, K
Research staff, Tohoku Electric Power Company, Inc., Sendai,

(Received 7 October 1991; accepted 5 March 1992)

Abstract

The small punch fracture stress σ_f(SP) and fracture toughness K_Ic of embrittled turbine rotor steels have been evaluated at temperatures corresponding to the lower shelf regime. The lower bound values of σ_f(SP), determined by statistically analyzing the data, are found to be relatively independent of test temperature range from −196 to −170°C for rotor M steel and from −196 to −150°C for rotor T steel. The relationship of σ_f(SP) to fractographic features was also investigated. The lower bound values of σ_f(SP) were found to be comparable with values of the microscopic fracture stress σ*_f. This result indicates that small punch tests might be used successfully to measure σ*_f of materials at lower shelf temperatures.

Keywords:
small punch (bulge) tests, small punch fracture stress σf(SP), fracture toughness, lower bound value, statistical analysis, microscopic fracture stress

Paper ID: JTE11918J
DOI: 10.1520/JTE11918J
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