TY - JOUR A1 - Schรถnherr, J. A. A1 - Duarte, Larissa A1 - Madia, Mauro A1 - Zerbst, Uwe A1 - Geilen, M. B. A1 - Klein, M. A1 - Oechsner, M. T1 - Robust determination of fatigue crack propagation thresholds from crack growth data JF - Materials N2 - The robust determination of the threshold against fatigue crack propagation DKth is of paramount importance in fracture mechanics based fatigue assessment procedures. The standards ASTM E647 and ISO 12108 introduce operational definitions of DKth based on the crack propagation rate da/dN and suggest linear fits of logarithmic DKโ€“ da/dN test data to calculate DKth. Since these fits typically suffer from a poor representation of the actual curvature of the crack propagation curve, a method for evaluating DKth using a nonlinear function is proposed. It is shown that the proposed method reduces the artificial conservativeness induced by the evaluation method as well as the susceptibility to scatter in test data and the influence of test data density. KW - Fatigue crack propagation threshold KW - ISO 12108 KW - ASTM E647 KW - Data evaluation methods KW - Experimental determination PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-552153 DO - https://doi.org/10.3390/ma15144737 SN - 1996-1944 VL - 15 IS - 14 SP - 1 EP - 21 PB - MDPI CY - Basel AN - OPUS4-55215 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Duarte, Larissa A1 - Madia, Mauro A1 - Zerbst, Uwe A1 - Schรถnherr, J. A. A1 - Geilen, M. B. A1 - Klein, M. A1 - Oechsner, M. T1 - Recent developments in the determination of fatigue crack propagation thresholds JF - International Journal of Fatigue N2 - The impact of crack closure and environmental effects on the experimental determination of the fatigue crack propagation threshold is a major problem for the assessment of cyclically loaded components, especially at low stress ratios ๐‘…. In this work, the influence of the experimental procedure and air humidity on d๐‘Žโˆ•d๐‘ โˆ’ ๐›ฅ๐พ data at different ๐‘… is discussed. Unlike the results at ๐‘… = โˆ’1, the threshold values obtained at ๐‘… โ‰ˆ 0.8, i.e. under negligible crack closure levels, show a very small scatter band regardless of the variation of the test parameters and environmental conditions. KW - Fatigue crack propagation threshold KW - Component assessment KW - Crack closure KW - Environmental effects KW - Testing parameters PY - 2022 DO - https://doi.org/10.1016/j.ijfatigue.2022.107131 SN - 0142-1123 VL - 164 SP - 1 EP - 15 PB - Elsevier Ltd. AN - OPUS4-55403 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -