Voids as stress relievers and a palliative in fretting

Abstract

There are several procedures used to increase fatigue life of components suffering from fretting, certain of which involve the modification of the surface material properties or the generation of compressive residual stresses near the surfaces in contact. Moreover, relatively little attention has been paid to the situation in which the contact pair stiffness is modified by changing the geometry of the components. The present paper describes an analysis of the possible beneficial effects on the fretting life of introducing voids inside the material of the components under fretting conditions. From a 3D perspective, this manufacturing characteristic is difficult to achieve using conventional techniques, although additive manufacturing could achieve this easily. A numerical analysis of a typical cylindrical contact configuration in fretting is simulated, with the novelty of introducing circular holes beneath the half‐plane surface. These holes change the contact pair stiffness, leading to a decrease in the surface contact stress field.

Numerical analysis of the influence of micro-voids on fretting fatigue crack initiation lifetime

“…This slight change in the contact pressure distribution is due to the loss of stiffness caused by the particular micro-void distribution and results in the increase of the crack initiation lifetime. This result is in line with the results obtained by Erena et al [24], where the introduction of voids beneath the contact surface in a fretting wear numerical model decreases the damage severity for crack initiation.…”

“…These material constants are measured using smooth specimens. Although, Al2024-T3 has a low percentage of voids in comparison with other metals, such as those produced in castings or with metal additive manufacturing, voids can appear involuntarily as defects during manufacturing or intentionally through perforation and acting as a possible palliative [24].…”

“…They conclude that the heterogeneity has a relevant effect in the shear stress state, being more critical than the homogeneous case. Erena et al [24] studied numerically the influence of the introduction of voids in plain fretting on the damage severity using a critical plane approach and a multiaxial damage criterion. The authors showed a decrease in the damage parameter for certain configurations of the micro-voids and suggest its employment as a palliative.…”

Lifetime estimation of mechanical assemblies under constant amplitude fretting fatigue loading

“…[18][19][20] Therefore, fretting fatigue has attracted the interest of many researchers, and various aspects of this phenomenon have been investigated during the last decades, such as life prediction, influential factors, mechanisms, new fretting test set-ups, and possible palliatives. 10,[21][22][23][24][25][26] In particular, many damage models and approaches related to both crack nucleation and propagation phase have been applied to assess the fatigue life of frettingaffected components. However, since crack nucleation life is around 90% of the total fretting fatigue life for all kinds of tests, 27 damage models concerning the crack nucleation phase are mainly employed in fretting fatigue assessment.…”

“…Fretting fatigue has been recognised as a primary failure mode across a wide range of structural components, such as dovetail joints, bolt and riveted joints, spline coupling, running cables, and overhead conductors . Therefore, fretting fatigue has attracted the interest of many researchers, and various aspects of this phenomenon have been investigated during the last decades, such as life prediction, influential factors, mechanisms, new fretting test set‐ups, and possible palliatives …”