Definitions Flashcards
Stress
External force applied to a material of cross sectional area A.
Elastic Deformation
When a load is applied to a material, the atomic bonds will stretch. When the load is removed, the atoms return to their original position. Deformation is not permanent.
Plastic Deformation
When a load is applied to a material, the atomic bonds slip over each other. When the load is removed, the atoms do no return to their original position. Deformation is permanent.
Strain
Change in length/ Original Length
Hardness
Measure of a materials resistance to localised plastic deformation (eg an indent or scratch)
Toughness
Measure of a materials resistance to fracture. Related to total area under a stress-strain curve
Ductility
Measure of a materials plastic deformation that has been sustained at fracture
Youngs Modulus
Measure of the ease of elastic deformation. Equal to stress/strain
Ulitmate Tensile Strength
Maximum tensile stress supported at any point on the curve. Stress that is applied to fully break the sample.
Yield Strength
Stress at which plastic deformation occurs
Shear Stress
τ=Shear Force/Cross Sectional Area. Sheer stress is in the same direction as the Shear force.
Shear Strain
γ = x/l = tan(θ)
Shear Modulus (rigidity modulus)
G = τ/γ
Βulk Modulus
The resistance of an material to isostatic pressure.
P = -K*(Change in vol/initial volume)
Offset Yield Strength
The stress at which a certain amount of plastic deformation has occurred (0.2%)
