Finite Element Analysis of Localized Plasticity in Al 2024-T3 Subjected to Fretting Fatigue

Abstract

Fretting fatigue is a combination of two complex mechanical phenomena, namely, fretting and fatigue. Fretting appears between components that are subjected to small relative oscillatory motion. Once these components undergo cyclic fatigue load at the same time, fretting fatigue occurs. Fretting fatigue is an important issue in aerospace structural design. Many studies have investigated fretting fatigue behavior; however, the majority have assumed elastic deformation and very few have considered the effect of plasticity. The main goal of this study is to monitor the effect of different fretting fatigue primary variables on localized plasticity in an aluminum alloy (Al 2024-T3) test specimen. In order to extract the stress distribution at the contact interface under elasto-plastic conditions, a modified finite element contact model was used. The contact model was verified through comparison with an elastic analytical solution. Then, a bilinear elasto-plastic isotropic hardening model with a von Mises yield surface was implemented to simulate the material behavior of the aluminum alloy. The effect of different fretting fatigue primary variables, such as axial stress, contact geometry, and coefficient of friction, on localized plasticity was investigated. Finally, the relationship between the location of maximum localized plasticity and Ruiz fretting damage parameter with the crack initiation site is discussed.

Numerical Modeling of the Effect of Randomly Distributed Inclusions on Fretting Fatigue-Induced Stress in Metals

“…As geometries and loads are symmetric, a simplified model of the structure can be constructed, which is one pad and half of the specimen. In the same way as previous research [8,14,35,38], we can model the load and boundary conditions as shown in Figure 5. As geometries and loads are symmetric, a simplified model of the structure can be constructed, which is one pad and half of the specimen.…”

“…Since inclusion will cause stress concentration [25,30,48,55], and fretting RVE size = 200 μm RVE size = 325 μm RVE size = 100 μm RVE size = 325 μm The fretting fatigue FE model of heterogeneous material can be built in two ways: (a) use the equivalent homogenized material in the whole specimen, or (b) model a small area near the contact region using the heterogeneous material with inclusions and use equivalent homogenized material in the rest of the specimen. Since inclusion will cause stress concentration [25,30,48,55], and fretting fatigue has maximum stress near the contact area [8], the second way is chosen in order to study the effect of inclusion on the stress distribution near the contact area. The partition diagram of the specimen is shown in Figure 9.…”

“…The failure process is generally characterized by two phases, crack nucleation [4,5] and crack propagation [6,7]. Researchers are concerned with contact stresses because it directly affects the initiation of cracks [8]. The contact stresses are affected by various factors, such as loading magnitude, contact geometry, surface imperfections and slip amplitude, which consequently affect the failure process.…”

“…In short, both fretting fatigue and heterogeneity may significantly influence the lifetime and stability of mechanical components. Numerous factors can affect micro stress field, thus affecting the fretting fatigue behavior [8]. The macroscopic fatigue failure occurs due to the distribution of micro-stress.…”

“…For experimental methods, it is difficult to get the details of stress field and initiation of crack. Therefore, numerical modeling is an efficient way to solve the problem of fretting fatigue [8,[32][33][34][35][36][37][38] and fracture [39][40][41][42][43]. However, only few studies have taken into account the heterogeneity of material under fretting fatigue conditions [14,44,45].…”