Vedenje kratkih razpok, ki nastanejo iz majhnih izvrtin

Specimens with martensitic microstructure were defected by tiny drilled holes with the existing local residual stresses induced by drilling and without them. The objective of this research was to determine the cyclic stress level for the crack initiation and fatigue limit of the defected and smooth specimens\u27 dependence upon the residual-stress field. Compressive residual stresses retarded the crack initiation. Immediately after the crack initiation, residual stresses decelerated the short-crack propagation, but later, when the residual-stress sign was changed, they accelerated it. Non-propagating short-crack size and fatigue limit also depend on the residual-stress field.Pri preizkušancih z martenzitno mikrostrukturo smo naredili majhne izvrtine z obstoječimi lokalnimi zaostalimi napetostmi zaradi vrtanja in brez njih. Namen te raziskave je bilo določiti odvisnost ciklične napetosti, ki je potrebna za nastanek razpoke, in odvisnost trajne dinamične trdnosti z izvrtino oslabljenih in gladkih preizkušancev, od polja zaostalih napetosti. Tlačne zaostale napetosti so zavrle nastanek razpoke. Takoj po nastanku razpoke so zaostale napetosti upočasnile širjenje kratke razpoke, pozneje, ko se je predznak napetosti spremenil, pa so ga pospešile. Velikost kratke razpoke, ki se ne širi več, in trajna dinamična trdnost sta prav tako odvisni od polja zaostalih napetosti