The mechanical properties of a biomaterial can best be described by its modulus of elasticity, ultimate tensile strength, elongation to failure, and fracture toughness.
• Modulus of elasticity describes the stiffness of the material and is usually obtained from the slope of a stress-strain diagram.
• Ultimate tensile strength describes the ability of the material to withstand a load before it fails.
• Elongation to failure describes how much strain the material can bear before it fails.
• Fracture toughness is an important measurement of the material s resistance to crack propagation.
Figures 1 (a) to (d) show the comparisons amongst different classes of biomaterial with respect to the four properties mentioned above. It can be seen that metals are generally very stiff and have high fracture toughness. In sharp contrast to the metals are the polymers, which have low stiffness and fracture toughness. However the polymers have high elongation to failure. The high stiffness of metals, on the other hand, can be a disadvantage since this can give rise to "stress shielding" in bone fracture repair. Stress shielding is a phenomenon where bone loss occurs when a stiffer material is placed over the bone. Bone responds to stresses during the healing process. Since the stress is practically shielded from the bone, the density of the bone underneath the stiffer material decreases as a result.
المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .
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