Strength of Materials

How parts stretch, bend, twist, buckle and eventually fail. Turn loads into stresses and deformations. Learn stress and strain, elastic behaviour, shear, bending, torsion, beam deflection, column buckling and fatigue — the tools used to size every shaft, beam, bolt and bracket safely.

• Stress — Stress is internal force per unit area. Learn normal (tensile/compressive) stress, bearing stress, allowable stress and factor of safety, stress concentrations, and thin-walled pressure vessels.
• Strain — Strain is deformation per unit length. Learn normal and shear strain, microstrain, the stress–strain curve, ductility, lateral strain and Poisson's ratio, and how strain gauges measure it.
• Elasticity — Elasticity is a material's ability to spring back. Learn Hooke's law, Young's, shear and bulk moduli, axial deformation δ = PL/AE, stiffness, thermal stress and composite bars.
• Shear — Shear stress acts parallel to a surface. Learn direct shear in pins and bolts (single and double shear), punching, shear strain and modulus, and the shear-stress distribution in beams (VQ/Ib).
• Bending — Bending creates tension on one side of a beam and compression on the other. Learn the flexure formula σ = My/I, neutral axis, section modulus, beam selection and combined bending and axial load.
• Torsion — Torsion is twisting. Learn shear stress τ = Tr/J, angle of twist θ = TL/GJ, power transmission P = Tω, solid vs hollow shafts, and designing shafts for strength and stiffness.
• Deflection — Deflection is how far a beam moves under load. Learn the elastic curve EI·y″ = M, standard formulas for cantilevers and simply supported beams, superposition, and serviceability limits.
• Buckling — Slender members in compression can suddenly bow sideways at loads far below their crushing strength. Learn Euler's critical load, effective length, slenderness ratio, Johnson's formula and design against instability.
• Fatigue — Fatigue is failure under repeated loading at stresses below yield. Learn S–N curves, endurance limit, mean-stress effects (Goodman), Marin factors, crack growth and how to design for millions of cycles.