Selecting Materials for Prosthesis - Report Example

Material Engineering Selecting Materials for Prosthesis Name: Institution: Date: Contents Summary 1 1.0 Introduction 1 2.0 Report Analysis and Discussion 3 2.1 Task 1 3 2.1.1 Service requirements 3 2.1.2 Manufacturing Requirements 5 2.1.3 Material Grading Criteria 6 2.2 Task 2 15 2.2.1 Service limitations, environmental impact of processing the materials, and recyclability 15 Service limitation 15 2.2.2 Environmental impact of processing materials used in prosthetic 15 2.2.3 Recyclability 16 3.0 Conclusion 17 References 18 Summary From the findings of in the report, polar expedition leg should be made from aluminium by extrusion process. For the day leg, titanium is the suitable material and can be made by injection moulding. 1.0 Introduction A prosthesis is an artificially manufactured limb for substituting a natural limb that has been lost through congenital defect, illness, accident, or wartime injury. They are intended to restore the normal function to amputees to some degree as they cannot function as the natural limbs. A cosmetics is a type of prosthesis that is designed to be cosmetic with no or little function on the body. Artificial hands are often put in this category (Wills, 1995). Other types of prosthesis have no or little cosmetic and are highly functional. Artificial legs fall in this category and are sometimes designed with more than just metal rods and wires. In practice, four types of prosthetic limb that can be used to replace partial or complete loss exist. These are: i. Below the knee (BK), transtibial – A prosthetic lower leg that is usually attached to an intact upper part of the leg. ii. Above the knee (AK), transfemoral – A prosthetic upper and lower leg, includes a prosthetic knee. iii. Below the elbow (BE), transradial – A prosthetic forearm. iv. Above the elbow (AE), transhumeral – A prosthetic upper and lower arm, includes a prosthetic elbow. This report is a study of prosthetic limbs. It focuses on the below the knee prosthesis for use on a polar expedition and realistic looking BK prosthesis for everyday use. The report seeks to establish the service requirements in terms of load, strength, appearance, manufacturing methods etc., as well as environmental conditions. In addition to above, environmental impact assessment of the materials selected in the manufacture of prosthetic limbs. 2.0 Report Analysis and Discussion 2.1 Task 1 Service and manufacturing requirements for selection of suitable materials for a realistic looking BK prosthetic leg and an endurance walking leg for a polar expedition. Materials used in the design of prosthetic leg differ by the level of activity. Plastic, foam and wood are usually found in leg designed for people with low level of activity and require stability, while prosthetic leg design using carbon fiber meets the functional requirements for energy efficiency, lightweight and shock absorption. The service and manufacturing requirements for these materials are discussed in this section. 2.1.1 Service requirements Compressive strength – As much of the patient’s weight will be supported by the limbs, it is necessary to ensure that the materials used can support the patient’s weight by having sufficient compressive strength. Steel and aluminum have a compressive strength of about 250 MPa, while that of plastics range between 65 and 130 MPa depending on the type of plastic. A composite material of polyimide and glass fiber provides a polymer material with a compressive strength of about 220 MPa. Thus, these materials have high compressive strength and suitable for the design of prosthetic limbs. Fatigue resistance – The materials used in the design of prosthetic limbs are required to have good fatigue resistance as the limps are subjected to repeated or cyclic stresses. Generally, fatigue is not a limiting factor for selection of the material in structural use. However, aluminum is subject to failure due to fatigue after reaching its endurance limit more readily compared to steel. The fatigue limit of alloyed aluminum is considered more carefully especially where vibrations and high stresses are encountered more frequently. The high-cycle fatigue strength of Titanium and its alloys is generally good, with a fatigue limit of 40-60% of tensile strength (Mariana & Ion, 2007). Rigidity – The rigidity of prosthetic limbs should be designed to replace the loss of tendons and muscles of the biological limb. The prosthetic limb does not have the capability to vary the joint stiffness, and thus, depends on the fixed rigidity of the material used (Klute, Kallfelz and Czerniecki). The modulus of rigidity of aluminum and its alloys range between 24 and 28 GPa, while that of steel is about 77 GPa and that of titanium is 41 GPa. Polyethylene and rubber have the lowest modulus of rigidity ( Read More