Accession Number:

ADA183455

Title:

Strain Based Compliance Method for Determining Crack Length for a C(T) Compact(Type) Specimen

Descriptive Note:

Interim rept. Aug 1983-May 1985

Corporate Author:

AIR FORCE WRIGHT AERONAUTICAL LABS WRIGHT-PATTERSON AFB OH

Personal Author(s):

• Maxwell, D. C.

Report Date:

1987-07-01

Pagination or Media Count:

32.0

Abstract:

This report describes the estimation of crack length values based on back-surface strain measurements in a compact-type, CT, 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 aW is derived. The aW values calculated from measured strain compliance are compared with those calculated from crack-mouth-opening- displacement, CMOD. compliance. The variation in aW predicted from measured strain compliance as compared to aW predicted from CMOD compliance is approximately 2 percent at aW 0.2 to - 2 percent at aW 0.8. A second strain measurement location is determined which enhances the sensitivity of the back-face strain compliance for aW 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.

Descriptors:

• *CRACKS
• *STRAIN(MECHANICS)
• RATIOS
• HIGH FREQUENCY
• OPENING(PROCESS)
• HIGH TEMPERATURE
• FINITE ELEMENT ANALYSIS
• DEFORMATION
• TENSILE STRESS
• DISPLACEMENT
• CORRELATION
• MATHEMATICAL PREDICTION
• LENGTH
• STRAIN GAGES
• DATA ACQUISITION
• COMPUTER APPLICATIONS
• MATHEMATICS
• DETERMINATION

Subject Categories:

• Test Facilities, Equipment and Methods
• Mechanics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE