chapter_3-_Biomaterials - Biomaterials: Properties, Types...

Info iconThis preview shows pages 1–6. Sign up to view the full content.

View Full Document Right Arrow Icon
1 Biomaterials: Properties, Types and applications MECH 634- SPRING SEMESTER 2008 Prepared by: Nasser-Eddin M., Ph.D
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
2 OUTLINES OUTLINES Biomaterials: Properties, Types, and Applications 3.1 Mechanical Properties and Mechanical Testing 3.2 Metals 3.3 Ceramics and Glasses 3.4 Polymers 3.5 Natural Materials 3.6 Composites
Background image of page 2
3 MECHANICAL TESTING MECHANICAL TESTING • The most common way to determine mechanical properties is to pull a specimen apart and measure the force and deformation. •Materials are also tested by crushing them in compression or by bending them. •Standardized test protocols have been developed to facilitate comparison of data generated from different laboratories. The vast majority of those used in the biomaterials field are from the American Society for Testing and Materials (ASTM). •For example, tensile testing of metals can be done according to ASTM E8, ASTM D412 is for rubber materials, and ASTM D638 is for tensile testing of rigid plastics. These methods describe specimen shapes and dimensions, conditions for testing, and methods for calculating and reporting the results. www.astm.org
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
4 MECHANICAL TESTING EXAMPLE: ASTM E8 MECHANICAL TESTING EXAMPLE: ASTM E8 • Test done with a ‘‘dog bone’’ shaped specimen that has its large ends held in some sort of a grip while its narrow midsection is the ‘‘test’’ section. • The mid portion is marked as the ‘‘gage length’’ where deformation is measured. A mechanical test machine uses rotating screws or hydraulics to stretch the specimen. Force is measured in Newtons (N), and how much the specimen stretches— deformation—is measured in millimeters.
Background image of page 4
5 ASTM E8 ASTM E8 (Cont.) (Cont.) Typical stress–strain curve for a metal that stretches and deforms (yields) before breaking. Stress is measured in N/m2 (Pa) while strain is measured as a percentage of the original length. The minimum stress that results in permanent deformation of the material is called the yield strength (YS). The ultimate strength (UTS) is the maximum stress that is tolerated by the material before rupturing. The stress at which failure occurs is called the failure strength (FS). Region A represents the elastic region since the strain increases in direct proportion to the applied stress. If a small stress is applied (e.g., to point 1), the material will return to its original length when the stress is removed. Region B represents the plastic region in which changes in strain are no longer proportional to changes in stress. Stresses in this region result in permanent deformation of the material. If a stress is
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 6
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 02/07/2011 for the course MECH 633 taught by Professor Mohammadnasserdine during the Spring '10 term at American University of Beirut.

Page1 / 23

chapter_3-_Biomaterials - Biomaterials: Properties, Types...

This preview shows document pages 1 - 6. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online