L5 Notes
Stress
It is a value which describes the amount of applied force F (eg.,tensile, compressive, shear) carried by each unit of cross sectional area of a component. It is presented as "force per unit area".
Normal Stress Expressed as
σ = Fn / A
– σ = normal stress [Pa or N/m^2]
– Fn = normal component force [N]
– A = cross section area of the plane [m^2]
Shear Stress
τ = Fs / A
– τ = shear stress [Pa or N/m^2]
– Fs = Shear force, component force parallel to the surface [N]
– A = area of the plane [m^2]
F = weight (mg)
Strain
ε = x / L
x = Change of length [m]
L = Initial length [m]
Unit for strain ε
ε = ΔL / L
Young Modulas
Stress / Strain = constant
Modulus of Elasticity, E = stress / strain = (P / A) / (x / L) = PL / AX
P = load [N]
L = initial length [m]
A = cross section area [m2]
x = change in length [m]
Safety Factor
SF = Ultimate Stress / Allowable Stress (Design stress)
Ultimate stress = strength of material = strength of material , which is the maximum stress the material can take before it fractures.
• Allowable stress = design stress