Experimental observations of “reversible” transformation toughening

Materials with the propensity to undergo irreversible deformation display an increasing resistance progressive crack advance, i.e., stable growth. A one-parameter description of growth by a fracture toughness vs. advance (resistance) curve is possible under specific conditions. Here, experimental observations are reported (i) demonstrate that enhancement due in hysteretic materials may be “reversed” partial unloading, which has implications on evaluation and its validity conditions, (ii) provide verification theoretical insight into mechanics