1. Lecture 9 – Deformation and Damage
Review of terms:
Normal stress, σ: Force per unit area applied perpendicular to the plane
Normal strain, ε: Change in length per unit of length in the direction of the applied normal stress.
Plastic strain: the strain not recovered during unloading
Elastic strain: the strain recovered during unloading
Degree of plasticity: (plastic strain)/(total strain)
Degree of elasticity: (elastic strain)/(total strain)
1/26/07
BAE2022/BAE4400 Physical Properties of Biological Materials

2. Lecture 9 – Deformation and Damage
Review of terms:
Modulus of elasticity, E: E = σ/ ε
Tangent Definition: slope; Et = (σx + Δx - σ x - Δx )/ (ε x + Δx - ε x - Δx )
Poisson’s Ratio, μ: ratio of strain perpendicular to the applied force to the strain in the direction of the applied force... εz = σz/E ; εy = - μ εz ; εx = - μ εz
Shear stress: F/A parallel to surface of the plane, τ
Shear strain: change in angle, δ
Shear Modulus, G: G = τ/δ
1/26/07
BAE2022/BAE4400 Physical Properties of Biological Materials