Axial Deformation -In the linear portion of the stress-strain diagram, the tress is
proportional to strain and is given by σ=Eε
                                         𝑃          𝛿        𝑃    𝛿
                               since 𝜎 = 𝐴 and 𝜀 = 𝐿 , then 𝐴 = 𝐸 𝐿
To use this formula, the load must be axial, the bar must have a uniform cross-
sectional area, and the stress must not exceed the proportional limit.
If however, the cross-sectional area is not uniform, the axial deformation can be
determined by considering a differential length and applying integration.
where A = ty, and y and t if variable, must be expressed in terms of x.
For a rod of unit mass ρ suspended vertically from one end, the total elongation
due to its own weight is
where ρ is in kg/m3, L is the length of the rod in mm, M is the total mass of the rod
in kg, A is the cross-sectional area of the rod in mm2, and g = 9.81 m/s2.
Stiffness, k
Stiffness is the ratio of the steady force acting on an elastic body to the resulting
displacement. It has the unit of N/mm.
Engr MIMD Villalobos