Mechanical Properties of Materials

 

mechanical behavior

how a material (or structure) responds to loads

Load-Deformation Diagram	Stress-Strain Diagram

 

stress-strain diagrams

• modulus of elasticity, E = slope of intial linear part of the stress-strain curve

• proportional limit stress, σ_pl = stress value at which the stress-strain curve goes nonlinear

• yield point stress, σ_y = stress value at which the stress-strain curve goes horizontal (for many steels)

• 0.2%-offset yield stress, σ_{0.2% yp} = the stress value at which a line drawn with slope E starting at 0.002 strain intersects the stress-strain curve

• ultimate tensile stress, σ_ult = largest stress on the stress-strain curve (top of the curve)

• engineering fracture stress = fracture load / original area

• true fracture stress = fracture load / fracture area

• energy at yield = area under the elastic portion of the load-deformation curve

• energy at break = area under the entire load-deformation curve

• modulus of resilience, U_r = area under the elastic portion of the stress-strain curve = σ_pl² / 2E = the amount of energy (or work) stored per unit volume at the elastic limit

• modulus of toughness, U_t = area under the entire stress-strain curve = the amount of energy absorbed per unit volume at fracture -- a measure of the material ductility

• percent elongation = (L_f - L_o) / L_o x 100%

  • Percent Elongation of 2" Gage Length = ΔL₂ / 2" x 100%

  • Percent Elongation of 8" Gage Length = ΔL₈ / 8" x 100%

• percent reduction in area = (A_f - A_o) / A_o x 100%