Fatigue limit and crack growth in ultra-fine grain metals produced by severe plastic deformation

Influence of Particulate Reinforcement and Equal-Channel Angular Pressing on Fatigue Crack Growth of an Aluminum Alloy

“…The matrix material shows the highest thresholds and also a strong load ratio dependency. This can be explained by the well-known effect of the grain size on the crack growth at different load ratios [11][12][13]15,35]. The amount of crack deflection is constant for all load ratios, whereas the effect of roughness induced crack closure is minimized by increasing the load ratio.…”

“…Presumably, due to the preferred crack propagation along the shear bands and the finer grains in this area, less crack deflection and closure occurs. Supposedly, also the high dislocation density induced by ECAP inhibits stress relief and, therefore, early damaging at the crack tip takes place [13]. For the reinforced conditions, at low cyclic stress intensities, the crack propagation rates are higher as compared to the matrix material conditions.…”

“…These investigations show the well-known effect of the grain or particle size on the fatigue crack growth. The grain refinement through ECAP leads to a minimized amount of crack deflection and roughness-induced crack closure, which results in higher crack propagation rates and, therefore, in minor thresholds [11][12][13][14][15][16][17][18]. In reinforced materials, particle sizes larger than 2-5 µm have a contrary effect on crack propagation: by increasing crack deflection and roughness-induced crack closure, crack propagation rates are lowered [19][20][21][22][23][24].…”

Fatigue Crack Resistance of Ultrafine-Grained Copper Structures

“…Furthermore, fracture mechanisms and damage evolution have yet to be fully understood. Some relevant works describing studies on nanomaterials are those presented in Meyers et al (2006) and Valiev (1997), while others focused on the investigation of the fatigue and the fatigue crack resistance of UFG-Cu are Lugo et al (2008), Höppel et al (2006), Cavaliere (2009), Lukáš et al (2009), Vinogradov (2007 and Collini (2010aCollini ( , 2010b.…”

Microstructure and Mechanical Properties Affecting Crack Growth Behaviour in AA6060 Produced by Equal-Channel Angular Extrusion

“…In conjunction with fatigue life experiments, characterisation of crack initiation and growth in UFG materials have become a subject of increased interest. Vinogradov et al [5,6] have clearly shown, that an ECAP-processed UFG material generally exhibits the same stages of crack propagation as a conventional coarse grained (CG) material: (I) a near-threshold region of slow crack advance at a low stress intensity factor range ∆K, (II) an intermediate stage which can be described by the well known Paris-Erdogan-equation…”