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Engineering Materials 2E VOLUME2 Episode 8

Tham khảo tài liệu 'engineering materials 2e volume2 episode 8', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 166 Engineering Materials 2 Data for ceramics Ceramics without exception are hard brittle solids. When designing with metals failure by plastic collapse and by fatigue are the primary considerations. For ceramics plastic collapse and fatigue are seldom problems it is brittle failure caused by direct loading or by thermal stresses that is the overriding consideration. Because of this the data listed in Table 15.7 for ceramic materials differ in emphasis from those listed for metals. In particular the Table shows the modulus of rupture the maximum surface stress when a beam breaks in bending and the thermal shock resistance the ability of the solid to withstand sudden changes in temperature . These rather than the yield strength tend to be the critical properties in any design exercise. As before the data presented here are approximate intended for the first phase of design. When the choice has narrowed sufficiently it is important to consult more exhaustive data compilations see Further Reading and then to obtain detailed specifications from the supplier of the material you intend to use. Finally if the component is a critical one you should conduct your own tests. The properties of ceramics are more variable than those of metals the same material from two different suppliers could differ in toughness and strength by a factor of two. There are of course many more ceramics available than those listed here alumina is available in many densities silicon carbide in many qualities. As before the structureinsensitive properties density modulus and melting point depend little on quality -they do not vary by more than 10 . But the structure-sensitive properties fracture toughness modulus of rupture and some thermal properties including expansion are much more variable. For these it is essential to consult manufacturers data sheets or conduct your own tests. Further reading D. W. Richardson Modern Ceramic Engineering Marcel Dekker 1982. R. W. Davidge Mechanical Behaviour of