دراسة مقاومة الكلال و حساب نسبة الصلابة الى الوزن لطرف صناعي عبر الركبة

Investigation of fatigue strength and stiffness weight ratio of knee disarticulation prosthetic socket

    Prosthesis is an artificial part that replaces a missing body part, lost due to trauma or congenital defect. People with knee disarticulation (through knee amputation (TKA)) are prone to have their socket failed under different conditions. Various reasons are responsible for that, such as the sort of material used in producing the socket the conditions of load exerted on the prosthetic socket. In this research, composite materials are suggested in order to modify the prosthetic socket for the sake of extending its life and increasing the comfort for its user.
This study included two major parts; experimental and numerical parts. The experimental part included two major types of tests. The first type of tests concerned about performing mechanical tests on the socket materials including available and suggested materials used in socket lamination. The available material consists of laminated (4 perlon 2 fiber glass 4 perlon) layers, and the suggested material consists of (3 perlon 1 carbon fiber 1 perlon 2 carbon fiber 1 perlon 1carbon fiber 3 perlon) layers. Suggested materials provide better physical and mechanical properties, such as improving stability and providing equilibrium for the TKA socket as compared to sockets that are currently available, while nut palm powder does not give any significant effect on the strength of material. The second type of tests dealt with the 27-years old male patient whose weight is 80 kg and height of 180 cm, in order to measure the Ground Reaction Force (GRF), and pressure distribution for both suggested and available prostheses. F-Socket sensor is used to measure the interface pressure between stump and socket. The calculations of the stiffness to weight ratio showed that the suggested socket has a value higher than of the available one for axial (204.5%), bending (189%) and torsion (182.7%).
The second part of this work is the numerical part which involves the analytical and numerical investigations that focus on simulation of through knee prosthesis to calculate the equivalent von-Mises stresses and safety factor by performing finite element analysis conducted through ANSYS 14.5 software. The interface pressure between stump and socket was obtained from, both, analytical and experimental work. F-socket as found experimentally and used in simulation.
For the suggested composite material, the results showed that the maximum equivalent von- Mises stress is equal to 14.43 MPa for the experimental work (F-socket) which is very close to that obtained from the analytical work (15.42 MPa). It was observed that the lamination of the suggested composite material provided better results in terms of high safety factor in experimental and analytically which are 4.83 and 4.93 respectively, low deformation and comfortable feeling gained by the patient during locomotion compared to available materials.