habraste materjalide sitkenemismehhanism, mida iseloomustavad struktuursed muutused prao tipu alas, vähendades prao levikut põhjustavaid pingeid; pingeid prao tipu ümbruses vähendavad mikropragude moodustumine, plastse tsooni või faasimuutustest tingitud survepingete tekkimine, a stress induced microstructural change that results in a reduction in stress at the crack tip; the effect occurs in a zone around the crack tip and extending back along the crack; several types of crack shielding have been identified: microcracking, ductile zone, and transformation zone