*2.2. Finite Element Modelling*

A computational model is established to analyze metal-on-metal bearings is carried out by analyzing two main components, namely, the acetabular cup and femoral head by adopting a 2D axisymmetric ball-in-socket model as shown in Figure 1. Pelvic bones, fixation system, and femoral stem components were not considered in the current study to simplify the computational process but without significantly affecting the results. The definition of contact was made by configuring the femoral head and acetabular cup contact surfaces as master and slave surfaces, respectively. For contact formulation, discretization method, friction formulation, and threshold are defined as surface to surface, penalty, and nodal, respectively.

**Figure 1.** Metal-on-metal total hip arthroplasty model for finite element analysis.

The contact process also ignores micro separation with the femoral head always concentric with the acetabular cup position. The influence of synovial fluid during contact was ignored in the analysis with only considering surface roughness in dry contact. Temperature changes are not analyzed. Then, the acetabular cup component is made immobile by selecting fix constraint set of nodes in the outer acetabular cup area. In addition, the loading condition is given, being the concentrated load on the femoral head with selecting center node of femoral head.

The selection of the number of elements is obtained through a convergence study to find the optimal number of elements using the H-refinement method by finding the least number of elements but with near-accurate results to provide computational time efficiency. A total of 5500 CAX4 elements have been used with details of 2000 and 3500 CAX4 elements for the femoral head and acetabular, respectively, in analyzing Tresca stress on metal-onmetal using ABAQUS/CAE 6.14-1 software. In the present computational simulation, Tresca stress is analyzed in the bulk area of the acetabular cup.
