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The meaning of the phrase “constraint effect in fracture” has changed in thepast two decades from “contained plasticity” to a broader description of“dependence of fracture toughness value on geometry of test specimen orstructure.” This paper will first elucidate the fundamental mechanics reasonsfor the apparent “constraint effects in fracture”, followed by outlining astraightforward approach to overcoming this problem in both brittle (elastic)and ductile (elastic-plastic) fracture. It is concluded by discussing the majordifference in constraint effect on fracture event in elastic and elastic-plasticmaterials.