damage-tolerance-concept What must be considered with the concept ofdamage tolerance:Sequenceof conceptstepsInciting weak point Sub-critical crack growth FractureAssume that every weakpoint below the non-destructive testing limit is actually present in the partCrack growth dependenton environmental influencesunder cyclical and static loads *)Crack growth until criticalstress /crack size is reachedand fracture occurs NecessaryinformationLimits of NDT and/or limitsthat ensure a safe load cyclenumberAssumed operating loadsand external influencesInfluence of the load progression and the environment on the ultimatefracture Necessary dataProbability of detecting thegrowth-capable weak points,depending on size and shapeKIc, KIc, KIscc, KIb, KIIc,JIc, Stu, or static fracturecriteriada/dN = f( K), determine Kth , da/dt = f(Kmax)under operating influences Steps in order to prevent afractureSpecifying the non-destructive testing demandsSelecting material and finishing control methodsDetermining the inspectionintervals necessary to prevent fractures or cracks before critical size is reachedSpecifying the estimated operating life span*) This includes determining the damage-relevant crack growth mechanismEnvironmental influencesNaClAirInert:e.g. vacuumThreshold value of safe, non-destructive detectibility Crack length "a" Load cyclesDamage (e.g.pitting corrosion)Initiation of the crackstart of crack growthInfluence of surrounding atmosphere on crack growth:Example: steel in a marine environment