Research About Mechanicalanalysis And Optimization Design Of The Hip Prosthesis

When the body hip joint was not participated in normal activities, doctors often usedartificial hip in replacement. The patients’ condition was relieved and the function ofjoint was recovered if suitable artificial hip joints were replaced. The mathematicalmodel for optimization was established in this thesis, so as to obtain design parameters ofthe best products for hip prosthesis.Firstly, the stress distribution was considered between the acetabulum and femoralhead, referring to the biomechanics characteristics of a hip joint. Then the actual productof hip joint was simplified in order to establish the model of finite element. According tomechanical model applied loads for finite element analysis model of artificial hip joint,the reslut maximum equivalent stress of40.603MPa was got in the medial edge of theacetabular prosthesis by using ANSYS software for static analysis. Then, the constrainedmodal analysis of artificial hip joint was executed. It was showed that fake body insidethe outer edge of the acetabulum was weak. The thicknesses of hip acetabular prosthesisas well as its materials were considered to be improved to increase abrasion resistance.Secondly, the geometric relationship between the size of the hip and the placement ofartificial hip joint replacement requirements were analyzed for static analysis of theparametric model, through the use of ANSYS parametric design language (APDL)established log files. Mathematical model optimization in ANSYS was comprised of thedesign variables, the state variables and the objective function composition. Theacetabular inclination, the acetabular anteversion, the supplementary angle of femoralneck-shaft angle, the length of femoral neck, the radius of the femoral head, the distancebetween femoral head and the acetabular lining and the acetabular thickness of geometricdimension were regarded as design variables. The flexion angle, the extension angle, theexternal angle, the internal angle, the abduction angle, the adduction angle of artificialtotal hip replacement and the femoral offset were chosen as design variables. Theobjective function was to reduce integrated stress. The best design parameters of artificialhip joint were obtained from the use of ANSYS optimization method for first-orderiterative solution. Finally, Based on Hertz elastic theory combination of ANSYS designvariables and state variables, the optimization mathematical model was established inMATLAB. At the same time, FMINCON optimization method being belonged toMATLAB Optimization Toolbox was chosen to solve this model. By contrast, theoptimization results of MATLAB and ANSYS, it was showed ultimately determined thebest design parameters for artificial hip joint such as the acetabular inclination of50 degrees; the acetabular anteversion of8degrees; femoral neck-shaft angle of58degrees;the length of femoral neck is31mm;15mm radius of the femoral head; the distancebetween the femoral head and acetabular liner is0.1mm; acetabular thickness10mm.The reslut of integrated stress was22.676MPa. It was indicated that the optimizingmodel of the hip joint was40percentages lower than the original model.