Design and Analysis of a Modified BK Prosthetic Socket

Abstract

ABSTRACT The terrorist operations, the wars and the incidents led to an increase in the number of amputations in Iraq. Prosthetic limbs are manufactured to compensate for the missing parts of the human body. However, the most common type of lower limb is Trans-tibial (Below Knee). In this work, design and analysis of below knee BK Prosthetic Socket is discussed with the aim of selection of material, and manufacturing of socket. Four groups Composite materials used for manufacturing BK prosthetic socket by using vacuum molding technique with various volume fractions are studied. The first group consists of eight layers (2-layers of carbon and 6-layers of perlon with Vf=0.409) with acrylic resin, the second group consists of eight layers (2-layers of carbon and 6-layers of perlon with Vf=0.24) with acrylic resin, The third group consists of twelve layers (4-layres of carbon and 8-layers of perlon) with acrylic resin, and four group consists of acrylic resin only. The study was conducted experimentally, analytically, and numerically. The experimental work involves determination of physical, mechanical and fatigue properties of composite material used for manufacturing below knee prosthetic sockets. Two models Trans-Tibial prosthetic sockets with (3) mm thickness were manufactured from Composite material (12-Layers) and subjected to Force Plate testing and F-socket testing to determine ground reaction force and pressure interface at socket/stump region. The analytical work discusses the friction effect on normal stress at interface. A simplified lower limb model was applied to analyze the effect of frication. MATLAB Program was utilized to calculate the pre-pressure, pressure and shear stress at stump/socket region by solving the equations.The finite element method (ANSYS-15) w s utilized for the analyzing and evaluating of the fatigue properties by observing the, maximum principal stress, the total deformation and safety factor. The results showed the mechanical properties (ultimate strength and Young s modulus) are increasing with the increasing volume frication at constant perlon and carbon fiber layers. The results showed that the composite materials achieve a large increment in mechanical properties such as (ultimate strength, Young s modulus, Flexural strength and flexural modulus ) which were increased to a percentage of (124%), (7.2%), (95.9%), and (83.87%), in composite material (12-Layers) as compared with composite material(8-Layers with volume fraction=0.409). However, The ultimate tensile strength and the modulus of elasticity of composite materials (12-Layers) are higher than those of the composite materials (8-Layers with volume fraction=024) by 100% and 185% respectively, and by 444% and 274% for pure acrylic lamination. The fatigue limit for 12-Layers (perlon and carbon) is 63 MPa. Result of F-socket apparatus, four specific areas of the BK prosthetic socket which experienced pressures in excess of 100 kPa were identified. The highest pressure at socket/stump region was 200 kPa in patella tendon area for long socket. The results show that the maximum principal stress, deformation and safety factor are equal to 37 MPa, 8.48 mm and 1.7 respectively for long socket and 26 MPa, 4.59 mm and 1.83 respectively for standard socket. .