TY - JOUR
A1 - Zerbst, Uwe
A1 - Madia, Mauro
A1 - Vormwald, M.
T1 - Fatigue strength and fracture mechanics
T2 - Procedia Structural Integrity
N2 - If fracture mechanics shall be applied to the total lifetime respectively the fatigue limit of components (within the meaning of the S-N curve approach) it has to address four challenges:
(a) It has to adequately describe so-called short crack propagation, which cannot be based on the common long crack concepts for principle reasons. Since the crack size is in the order of the plastic zone size, the modelling of short crack propagation cannot be based on the common linear elastic Delta K concept. Instead, an elastic-plastic parameter such as the cyclic J integral has to be applied. A second point is that the crack closure concept has to be modified in that the crack opening stress is not a constant, crack size- independent parameter but shows a transient behaviour with increasing short crack size.
(b) It has to provide a meaningful definition of the initial crack dimensions as the starting point for an S-N curve relevant (residual) lifetime analysis. This can be based either on the (statistical) size of material defects which can be treated as cracks or by the size of the crack which would arrest subsequent to early crack propagation, whatever is larger.
(c) It has to cope with the problem of multiple cracks for load levels higher than the fatigue limit such as it occurs in many applications in the absence of very large initial defects.
(d) This requires consequent statistical treatment taking into account variations in the local geometry of the area where crack initiation has to be expected as well as the scatter in the initial crack size and in the material data used for the analyses.
T2 - 2nd International Conference on Structural Integrity
CY - Funchal, Madeira, Portugal
DA - 04.09.2017
KW - Fatigue strength
KW - Fracture mechanics
KW - Initial crack size
KW - Short crack propagation
KW - Multiple crack propagation
PY - 2017
UR - https://opus4.kobv.de/opus4-bam/frontdoor/index/index/docId/42545
AN - OPUS4-42545
SN - 2452-3216
VL - 5
SP - 745
EP - 752
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany