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Specimen Thickness and Crack Depth Effects on J Testing and Crack Tip Constraint for Non-standard Specimen

시편두께 및 균열깊이 영향을 고려한 비표준시편의 J 시험법 및 구속효과의 정량화

  • 김진수 (성균관대학교 기계공학부) ;
  • 조수만 (성균관대학교 기계공학부) ;
  • 김윤재 (성균관대학교 기계공학부) ;
  • 김영진 (성균관대학교 기계공학부)
  • Published : 2003.09.01

Abstract

This paper compiles solutions of plastic $\eta$ factors and crack tip stress triaxialites for standard and nonstandard fracture toughness testing specimens, via detailed three-dimensional (3-D) finite element (FE) analyses. Fracture toughness testing specimens include a middle cracked tension (M(T)) specimen, SE(B), single-edge cracked bar in tension (SE(T)) and C(T) specimen. The ligament-to-thickness ratio of the specimen is systematically varied. It is found that the use of the CMOD overall provides more robust experimental J estimation than that of the LLD, for all cases considered in the present work. Moreover, the J estimation based on the load-CMOD record is shown to be insensitive to the specimen thickness, and thus can be used for testing specimen with any thickness. The effects of in-plane and out-of-plane constraint on the crack tip stress triaxiality are also quantified, so that when experimental J value is estimated according to the procedure recommended in this paper, the corresponding crack tip stress triaxiality can be estimated. Moreover, it is found that the out-of-plane constraint effect is related to the in-plane constraint effect.

Keywords

Crack Tip Constraint;Finite Element Analysis;J-Integral;Plastic $\eta$ Factor;Thickness Effect

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