Strain Based Compliance Method for Determining Crack Length for a C(T) Compact(Type) Specimen
Abstract
This report describes the estimation of crack length values based on back-surface strain measurements in a compact-type, C(T), specimen. The method of crack length determination is well suited for use with closed-loop computer controlled test systems. A finite element analysis is used to determine the theoretical back-face strain values for crack length (a) to width (w) ratios from 0.2 to 0.8 and a mathematical relationship for back-face strain compliance as a function of a/W is derived. The a/W values calculated from measured strain compliance are compared with those calculated from crack-mouth-opening- displacement, CMOD. compliance. The variation in a/W predicted from measured strain compliance as compared to a/W predicted from CMOD compliance is approximately + 2 percent at a/W = 0.2 to - 2 percent at a/W = 0.8. A second strain measurement location is determined which enhances the sensitivity of the back-face strain compliance for a/W values from 0.2 to 0.5 and a mathematical relationship of dual-location strain compliance to crack length ratios is derived. Keywords: Crack length ratio, Finite element, Strain compliance, Compact type specimen, Crack opening displacement, Strain gage.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 1987
- Accession Number
- ADA183455
Entities
People
- D. C. Maxwell
Organizations
- Wright Laboratory