Contact mechanics is the study of the behavior of solids when they come into contact at one or more points. Contact mechanics research allows for the investigation of tribology, contact stiffness, electrical contact resistance, and indentation hardness. This understanding is required for the safe and efficient design of technological systems. One of the main interesting research observations is the study of contact mechanics behavior between two brass hemisphere with different diameter ratios and friction coefficients, which subsequently becomes the subject of this study. For this study, seven diameter ratios ranging from one- to seven-folds were compared using friction coefficients of 0.05, 0.1, 0.4, and 0.8. Both experiments and simulations were performed to investigate the behavior of the contact mechanics. The experiments and simulation were designed to investigate the effect of friction coefficient and diameter ratio on Von-Misses in the loading process and deformation. The results of the finite element method simulations µ = 0 and lubricated condition experiments are coherent between each other. As a result, it is proven that the coefficient of friction has influenced the unloading deformation and von Mises stress distribution. However, the impact on the deformation ratio with a coefficient of friction from 0.05 to 0.8 does not show a significant difference. The distribution of von Mises stress on diameter ratio 1 showed similar results between the two specimens. Specimen 2 had a wider von Mises stress distribution than specimen 1 at a higher diameter ratio. From diameter ratio 3 to diameter ratio 7, there is a highly localized stress at the edge of the contact area. This region is caused by shear stress as a result of the middle material pushing the surrounding material sideways. When the friction coefficient is increased, the localized stress area decreases, which indicates that the resultant load given is reduced.

The term “contact area” refers to the total surface area of two entities in direct physical touch. When discussing an artificial hip joint, “contact area” refers to the surface area of contact between the components of the artificial hip joint (ball and cup) positioned inside the patient. Several methods can be used to figure out the contact area of an artificial hip joint, such as finite element analysis and traditional experiments on contact mechanics with hip joint simulators. The contact area in an artificial hip joint ensures load distribution. For optimal and long-term performance, the prosthetic hip joint’s contact area must be well understood for design, fitting, and monitoring. This study presented a novel method to estimate the liner surface contact area due to interaction contact in the artificial hip joint using a computer-aided design (CAD) program. This study also contrasted numerical approaches utilizing computer-aided engineering software and theoretical predictions based on Hertz theory with three-dimensional processes using CAD software to determine the contact area in the inner liner. There were no significant discrepancies in the outcomes of the three approaches.

The running-in process is considered an essential aspect of the comprehensive wear process. The phenomenon of running-in occurs during the initial stages of wear in the prosthetic hip joint. Within the field of tribology, the running-in phenomenon of the hip joint pertains to the mechanism by which the contact surfaces of the artificial hip joint components are adjusted and a suitable lubricating film is formed. During the process of hip joint running-in, there is an interaction between the metal surface of the ball and the joint cup, which results in adjustments being made until a steady state is achieved. The achievement of desirable wear existence and reliable performance of artificial hip joint components are reliant upon the tribological running-in of the hip joint. Despite the establishment of current modeling approaches, there remains a significant lack of understanding concerning running-in wear, particularly the metal-on-polyethylene (MoP) articulations in dual-mobility cups (DMC). An essential aspect to consider is the running-in phase of the dual mobility component. The present study employed finite element analysis to investigate the running-in behavior of dual mobility cups, wherein femoral head components were matched with polyethylene liners of varying thicknesses. The analysis of the running-in phase was conducted during the normal gait cycle. The results of this investigation may be utilized to design a dual-mobility prosthetic hip joint that exhibits minimal running-in wear.

Total hip arthroplasty is a short-term solution for replacing a damaged hip joint with synthetic biomaterials. Total hip arthroplasty comes in two flavors: single and dual mobility. Mechanical and biological factors may degrade the quality of biomaterials over time. This may lead to implant failure and second surgical treatment. Wear is the crucial element leading to damaged bone and debris release throughout the body over time. Running-in is the initial wear phase between two surfaces before the steady-state phase. The stage of running-in is critical for understanding hip joint wear. Running-in and wear behavior have been extensively studied in single-mobility total hip arthroplasty, but aseptic loosening is the leading reason for restoration in arthroplasty registries. This paper seeks to summarize running-in behavior on single mobility hip implants, emphasizing its key aspects and recent developments.

Based on several references, Asians carry out several daily activities that are different from Westerners, which require a greater range of motion. Because of that, a dual mobility (DM) implant was created that was adapted to the activities of Asian people. One of the factors that might shorten the life of a hip implant is wear. Simulations of wear that are based on computation can guide product design to reduce the amount of adhesive and abrasive wear. Even though advanced modeling approaches have been established, a great deal of wear is still not understood, especially regarding the metal-on-polyethylene articulations found on DM cups. It is critical to examine the wear on the DM cup's head-to-liner ratio to determine the proper head diameter and liner thickness for this DM cup. In this work, wear was analyzed using finite-element analysis and compared between three different femoral head diameters matched with different thicknesses of the polyethylene liner on DM cups. Wear was analyzed throughout the regular walking cycle at each head-to-liner ratio. The findings of this study can be used to develop a dual-mobility artificial hip joint for Asians with the slightest wear.