1. The properties of surgical implant materials are given below. The materials a
ID: 81728 • Letter: 1
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1. The properties of surgical implant materials are given below. The materials are selected based on following limit values of criteria listed below. a) Can you identify alternative materials (different from what is specified in the table given under part c of this problem) for hip implants using criteria given below, especially mechanical properties? 1. Tissue tolerance, lower limit, Y-7 2. Corrosion resistance, lower limit. Y :-7 3. Tensile strength, lower limit, Y 95 MPa 4. Fatigue strength, lower limit, Yi 33.25 MPa 5. Toughness, lower limit, 2 6. Wear resistance, lower limit, Y 7. Elastic modulus, target value Y 14 GPa 8. Specific gravity, target value, 2.1 9. Relative total cost, upper limit, Y 10 b) Using the table of properties given below, decide the relative importance of criteria utilizing AHP Property Corrosion resistance (lower-limit property) Tensile strength (lower-limit property Fatigue strength (ower-limit property) Toughness (lower-limit property) Wear resistance (lower-limit property) Elastic modulus (target-value property) Specific gravity (target-value property) Cost (upper-limit property) c) Using the table of material properties, AHP and weight factor of criteria from AHP process of part b, identify the best materials that can be used for hip implants Corrosion Resistance This is because body fluids are aqueous salt solutions with concentrations roughly comparable to seawater and with a pH value of 7.4. This environment is hostile and could cause corrosion of many metallic materials. Corrosion resistance is rated according to a scale of 10-1 Tissue Tolerance In general, biological requirements represent the major constraints in selecting implant materials. The action of the implant material on the body tissues can range from toxicity, in which case the implant material is totally rejected, to inertness. This requirement is usually called tissue tolerance and is difficult to quantify. For the sake of comparison, materials are given a rating of 10 forthe best material and 1 for the worst Only materials with tissue tolerance of 7 or more will be consideredExplanation / Answer
low tissu tolarance value and low corrosion resitance value indicates that it is a composite alloe of Titanium. In general, Ti alloys may be classified as Alpha (), near-,Alpha-Beta (-), metastable , and stable depending upon the microstructure at room temperature. So alloying elements for Ti fall into three categories: (1) -stabilizers, such as Al, O, N, C; (2) -stabilizers, such as V, Nb, Ta, Mo (isomorphous), Fe, W,Cr, Ni, Si, Co, Mn, H (eutectoid); (3) neutrals, such as Zr and Sn. The and near- Ti alloys exhibit superior corrosion resistance.
The alloys also offer the unique characteristic of low elastic modulus and superior corrosion resistance.
the + alloys exhibit higher strength due to the presence of both the and phases.
The elastic modulus of described alloy is 14 GPa and it shows good corosive resistance. So the alloy is Near type Ti-19Nb-14Zr.
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