Elucidating the Mechanism of Fatigue Crack Acceleration Following the Occurrence of an Underload

Abstract

Fatigue Crack Growth Rate (FCGR) is altered by a single anomalous load exceeding cyclic maximum (Overload) or compressive load below cyclic minimum (Underload). The authors study fatigue crack acceleration due to a single compressive Underload using residual stress mapping (by synchrotron XRD) and crack closure analysis (by DIC). The relative influence and duration of these two principal causes of FCGR alteration are revealed. Validated FEA model is used for parametric analysis of the effect of baseline cyclic loading ratio and magnitude of Underload on the cyclic J-integral.

Multiscale analysis of bamboo deformation mechanisms following NaOH treatment using X-ray and correlative microscopy

“…These patterns show the typical Debye-Scherrer rings, which are associated to certain crystalline plane reflections; the relevant planes were identified and labelled in Figure . Amongst the number of information that can be extracted from the analysis of these patters, we focus our effort in the analysis of strains. It is well known that the radial position of rings is associated with the interplanar distance and therefore, under loading condition, variation of this distance can be correlated to the strain occurring at the crystalline scale [38][39][40][41][42][43][44]. For a given Miller index hkl, the conversion between the interplanar distance (lattice parameter ℎ ) and the estimated lattice strain ℎ is given by:…”

An analysis of macro- and micro-scale residual stresses of Type I, II and III using FIB-DIC micro-ring-core milling and crystal plasticity FE modelling

“…the evaluation of interplanar atomic lattice spacing by diffraction, or changes in molecular bond stiffness by spectroscopy. The wide range of experimental methods includes high resolution optical techniques, Raman spectroscopy analysis of diamond-like coatings [19,20] and a multitude of X-ray diffraction techniques for the analysis of intergranular stresses [21][22][23][24][25][26][27]. High resolution Electron Back Scatter Diffraction (HR-EBSD) has also made significant advances, and provides a powerful means of determining the lattice strains at resolutions ranging from sub-micron scale in backscattered geometry to a few nm in transmission.…”

Vibration Fatigue Damage Accumulation of Ti–6Al–4V under Constant and Sequenced Variable Loading Conditions

“…Salvati et al [17] studied the fatigue crack acceleration due to a single compressive underload through residual stress mapping and crack closure analysis. It is found the main contributions to crack acceleration are the crack tip blunting, crack closure, and the crack tip residual stress variation.…”