Effect of inclusion/matrix interface cavities on internal-fracture-type rolling contact fatigue life

Evaluation of rolling contact fatigue crack path in high strength steel with artificial defects

“…In particular, properties under pure RCF, that is, without macroscopic slip and under oil lubrication, are influenced by a non-metallic inclusion. The detrimental effect of inclusion on the RCF property has been discussed by many researchers [1][2][3][4][5][6]. According to previous researches, size, shape, location and composition of inclusion, interface condition between inclusion and surrounding matrix were considered as factors affecting the RCF life.…”

“…From the point of view of fracture mechanics, smaller inclusions, high interfacial strength, smaller differences of Young's modulus between an inclusion and a surrounding matrix lead to longer RCF life [1]. On the other hand, from the point of view of metallurgy, transformation of a microstructure of the matrix around the inclusion, a so-called WEA, or a white etching area is considered an influencing factor on RCF life [2].…”

A numerical approach to subsurface crack propagation assessment in rolling contact

“…Subsurface crack nucleation and propagation is one of the damage phenomena occurring in components subjected to rolling contact: it is responsible of severe damage such as shelling, spalling and case crushing, especially in hard materials such as those used for bearings or cams. [1][2][3][4][5] This phenomenon has been studied initially by a phenomenological and statistical approach, leading to the well-known Lundberg-Palmgren model for contact fatigue strength. More recently, deeper approaches have put into evidence the role of microstructure defects such as voids, inclusions, dents, etc.…”

“…as stress raisers and preferential sites for crack nucleation, and much work has been carried out upon this topic by means of experiments and numerical calculations. 2,4,6,7 Several experimental evidences show that, especially in hard materials, subsurface micro-cracks usually initiate at the interface between microstructure defects (such as voids or inclusions) and the metallic matrix since the early load cycles: once they have nucleated, they can propagate or arrest, but the propagation phase is prevalent within the total life of the component. 8,9 This fact induced Murakami to state that subsurface micro-cracks can be considered intrinsically existent in materials.…”

Effects of Tube Processing on the Fatigue Life of Nitinol

“…In the case of Nitinol, simulations of hot deformation of damaged inclusion stringers have shown inter-particle void closure with continued plastic deformation under compressive stress states [37]. These numerical simulations are supported as applications of hot deformation at high pressures to re-bond damaged inclusions have demonstrated significant HCF improvements in bearing steels [38]. The observed relations between higher probabilistic fatigue life and smaller inclusion/void length or diameter in the current study confirm that inclusion and void morphology have notable effects on fatigue life of Nitinol.…”