Abstract:
The sole objective of this research thesis is to evaluate the effect of size and load on the wear per cycle in prosthetic knee joints. Prosthetic knee joints are abundantly used in the medical field to cater the deteriorating natural knees and help maintain a better standard of living. The prosthetic knees come in seven universal sizes and each one acts differently under same load conditions. Initially, seven different models developed on SolidWorks constituting the femoral and disk part. The parts were mated so that the femoral component can slide on the disk. Then, the wear analysis was carried out using Abaqus. Firstly, materials were assigned to the two components i.e., Cobalt Chromium Molybdenum Alloy (CoCrMo) to the femoral component and Ultra High Molecular Weight Polyethylene Disk (UHMWPE) to the polyethylene disk. Meshing was done and boundary conditions were defined to execute the whole analysis. The use of this method resulted in the calculation of contact stresses on the area of contact between the two parts. The contact stresses were calculated at 700N, 950N and 1200N for each size. The contact stresses were maximum at the edges due to small area concentration and minimum at the center attributing to the large area. Moreover, the maximum contact stress was utilized to evaluate the wear depth by utilizing Archard’s wear law. The wear depth was calculated for one gait cycle. The wear depths (𝑊d) for size 1 against loads of 700 N, 950 N and 1200 N were 26.131 nm/cycle, 31.706 nm/cycle and 37.253 nm/cycle respectively. The 𝑊d for size 5 against loads of 700 N, 950 N and 1200 N were 140.27 nm/cycle, 156.14 nm/cycle and 171.45 nm/cycle respectively. The 𝑊d for size 6 against loads of 700 N, 950 N and 1200 N were 23.060 nm/cycle, 28.193 nm/cycle and 33.307 nm/cycle respectively. Similarly, the wear depth was calculated for the remaining sizes. The results indicate that the maximum wear occurs in size 5 and the minimum wear occurs in size 6. The incorporation of Cobalt Chromium Molybdenum Alloy (CoCrMo) and Ultra High Molecular Weight Polyethylene Disk (UHMWPE) has greatly reduced the wear debris per cycle and allowed the knee joint to work properly which are quite evident from the results.
