Design and Stress Analysis of Artificial Hip Joint

Artificial hip joint, either as a partial or a total replacement, has become a widely accepted solution for natural hip joint damages. To function as a replacement of a natural joint, the artificial one must fulfill the requirements of biocompatibility, stability and mobility. This study was focused on the 3D geometrical design of a total hip joint replacement and finite element analysis to evaluate the mobility and stability of the artificial joint. First, three dimensional model was built and components were assembled. Then, assembly analysis was used to detect geometrical collision during relative movement. Finally, the geometry of joint replacement components was optimized by carrying out finite element analysis for static and dynamic loadings. Results depicted that the joint mobility of hip joint replacement represented by the range of motion, was not equal to the natural one. However the range of motion of the artificial joint was still satisfactory for daily activity. Finite element analysis results indicated that the strength of hip joint replacement was sufficient which is indicated by the value of the factor of safety. The most critical areas were the neck of the femoral stem and the doom of the cup inlay. From the Finite element analysis (FEA) results, it was also predicted that wear failure tend to occur in the upper periphery of the cup inlay

Influences of Draw Forming Process on the Crash Analysis of a Circular Cup

The change of a structural part that occurred after forming process can affect crash response. Current industrial practice only utilizes the geometry in crash analysis. This study investigates the effect of forming histories of a circular cup formed by draw forming process in the crash simulation. Crash analysis at an initial velocity of 50km/h was performed using the explicit finite element code Radioss. The Johnson-Cook constitutive material model was used to characterize the material properties of advanced high strength steel DP600. Crash simulations are conducted in two different cases using a geometrical cup model with case 1 no forming history and case 2 all forming histories obtained from forming process. Results from this study indicate that the mechanical response of steel DP600 in a crash differ by 80.7 % for contact force and 5.87% for energy absorption when forming effects were considered. The contact force tends to increase more with displacement in case 2 compared to case 1. The non-uniform thickness and work hardening from forming process do alter significantly the crashworthiness of a structural part in the subsequent crash event

Static Analysis of a Laminated Rubber-Metal Spring Using Finite Element Method

The laminated rubber-metal spring has been widely applied for earthquake vibration isolation which deals mainly for horizontal motion at a very low frequency input. This article presents the effect of a vertical vibration input, which is also aimed at applying the laminated spring for high frequency excitation. Static analysis is discussed here using the Finite Element Analysis (FEA) to observe the stress and strain distribution as well as the safety factor of the isolator due to the axial force. Solid rubber spring experienced greater deformation while it decreased for the laminated rubber-metal spring as more plates were embedded in the rubber. However, higher stress distributions occurred on spring with multiple plates compared to solid rubber and the stress concentrate on steel plate layers. Strain distribution was observed to be high at solid rubber spring and it was decreasing on the laminated rubber-metal spring. The critical part for the strain distribution in the laminated rubber-metal spring was in the rubber layers