This preview shows pages 1–2. Sign up to view the full content.
This preview has intentionally blurred sections. Sign up to view the full version.View Full Document
Unformatted text preview: ME 382 Lecture 02 7/ix/07 1 T HREE I MPORTANT TERMS FOR MECHANICAL DESIGN Stiffness: Ability of an object to resist deformation A stiff object can support large loads with little deformation A compliant object has large deformations under low loads Strength: Ability of an object to resist failure A strong object can support large loads without failing A weak object fails under low loads Toughness: Ability of an object to dissipate energy A tough object can absorb a large amount of energy before fracture A brittle object fails with little dissipation of energy Stiffness: applied load / resultant deformation (N.m-1 ) Compliance: resultant deformation / applied load (m.N-1 ) Strength: applied force to cause failure (N) The term toughness is used differently in different contexts Energy absorbed has units of (N.m) = (J) Strength and stiffness depend on material , geometry , and dimensions of object Need to separate material properties from geometrical properties Elastic modulus - stiffness of a material (Nm-2 = Pa) Typically resistance to changing bond length between atoms or molecules Atomic / molecular bonding modulus of 1-1000GPa Foams and elastomers are special cases (1 MPa - 1 GPa) Yield strength - resistance of atoms / molecules sliding over each other (Nm...
View Full Document
This note was uploaded on 10/12/2008 for the course MECHENG 382 taught by Professor Thouless during the Spring '08 term at University of Michigan.
- Spring '08