# Mechanics Use left and right arrows to cycle through stems, and up and down arrows to test yourself.

# Stress

## Stress: force per unit area - The *intensity of internal force* within a material as a result of loading. - Defined by force over cross-sectional area. - It cannot be measured directly. - Stress within a material can be in *tension*, *compression*, or *shear*.

# Strain

## Strain: proportional deformation - Linear deformation under loading. - Defined by change in length over original length.

## Critical strain of repair tissues |Tissue|Critical strain| |------|--------------:| |Granulation tissue|100%| |Dense fibrous tissue|20%| |Cartilage|10%| |Cancellous bone|2%| |Lamellar bone|2%| *Yamada and Evans, 1970*

# Young's Modulus

## Young's Modulus - A material property of stiffness of a material in the *elastic zone* during *uniaxial deformation*. - The ratio of tensile stress (force per unit area) to tensile strain (proportional deformation).