Act perpendicular to a surface.
Tension and compression stretch or shorten material along a direction.
Side 153
Solid Mechanics
How solid bodies carry load, deform, store elastic energy, yield and fail under forces distributed through geometry and material structure.
load→stress→strain→deformation→failure
04lenses
16working concepts
V0content
SS-1.0standard
External loads become internal stress and deformation.
Stress describes force intensity; strain describes geometric change.
Act tangentially across a surface.
Shear distorts shape and is central in torsion and many failure modes.
Measure relative length change.
Strain is dimensionless and can vary throughout a body.
Measure angular distortion.
Small-angle approximations connect shear strain to displacement gradients.
Elastic models relate stress to recoverable deformation.
Linear elasticity is powerful within a limited range of strain and material behavior.
Relate stress and strain linearly in simple cases.
Young's modulus measures axial stiffness in a linear elastic regime.
Couple axial extension to transverse contraction.
Poisson's ratio captures one part of multiaxial elastic response.
Store reversible strain energy.
Energy methods can simplify deflection and stability calculations.
Generalize loading in three dimensions.
Stress at a point requires directional components rather than one scalar value.
Geometry converts material stiffness into structural behavior.
Beams, columns and shafts respond differently because load path and cross-section matter.
Create tension and compression across a cross-section.
Curvature depends on bending moment and flexural rigidity.
Twist shafts under torque.
Shear stress distribution depends on cross-sectional geometry.
Lose stability before material strength is reached.
Slender compression members can fail through geometric instability.
Amplify stress near notches and discontinuities.
Local geometry can control failure despite moderate nominal stress.
Real materials leave the elastic regime and eventually fail.
Strength depends on loading mode, defects, repetition and environment.
Begin permanent plastic deformation.
Yield criteria generalize uniaxial test results to multiaxial stress states.
Propagate cracks through stored energy and material resistance.
Crack geometry can dominate failure even when average stress is low.
Accumulate damage under repeated loading.
Cyclic failure can occur below monotonic strength limits.
Separate expected demand from allowable capacity.
A safety factor is a design margin, not a substitute for understanding uncertainty and failure modes.
Structures fail through fields, not isolated forces. Loads create internal stress and strain patterns whose distribution depends on geometry, support conditions and constitutive behavior.