An Experimental Method for Measuring Crack Tip Constraint Under Low-Velocity Impact Loading Conditions

摘要

A novel experimental technique for measuringrncrack tip T-stress ress (or, σ_(0x) )and hence in-plane crack tiprnconstraint in elastic materials has been developed. Thernmethod exploits optimal positioning of stacked strain gagernrosettes near a mode-I crack tip such that the influence ofrndominant singular strains are negated in order torndetermine T-stress accurately. The method isrndemonstrated for low-velocity loading conditions. Byrncoupling this new method with Dally-Sanford's straingagernmethod [1] for measuring mode-I stress intensity factors ( K_I ), crack tip biaxiality parameters β rn=T(πa)~(1/2)/K_I are also measured experimentally. Thernexperimental results are in agreement with those obtainedrnfrom elasto-dynamic finite element computations.