A strain gage method for determination of fracture parameters in bimaterial systems

A simple technique for complex stress intensity factor (SIF) determination in a bimaterial crack using electrical strain gages is developed. The asymp totic radial and hoop strain equations are used to compute the SIF by linea r transformation. The location of the strain gage relative to the crack tip is chosen through parametric study of the asymptotic fields. The need for higher order terms of the series solution to describe the strain distributi on at the gage location is discussed, and a correction procedure using high er order terms is introduced. Static and dynamic experiments are conducted on epoxy/glass-filled epoxy bimaterial specimens in three point bend config uration. Under static loading conditions, the complex SIF estimated from th e measured strains is in good agreement with the finite element results obt ained by extrapolation of crack flank displacements. The applicability of t he present method for dynamic loading conditions is demonstrated by conduct ing impact tests in a drop-tower system and comparing the measured data wit h dynamic finite element analysis. The measured dynamic SIF-time history ma tches favorably with the numerical simulation. (C) 1999 Elsevier Science Lt d. All rights reserved.