Materials Science 101
03 Mechanical Behavior
Chapter 06

Mechanical Properties

Explore the five fundamental load types and the full anatomy of a tensile test — from elastic stretch to plastic flow, necking, and fracture.

Tension

Tensile Load

σ = F / A₀

Two equal and opposite forces pull the specimen apart along its axis. The bar elongates and its cross-section shrinks (Poisson contraction).

Compression

Compressive Load

σ = −F / A₀

Forces push the specimen together along its axis. The bar shortens and bulges outward. Sign convention: compressive stress is negative.

Shear

Shear Load

τ = F / A₀

Parallel forces act on opposite faces in opposite directions. The body distorts into a parallelogram; the shear angle γ measures the strain.

Torsion

Torsional Load

τ = T·r / J

Equal and opposite twisting moments are applied to the ends of a shaft. Cross-sections rotate relative to each other, producing pure shear stress.

Bending (Flexure)

Bending Load

σ = M·c / I

A transverse load makes a beam curve. Tension on one side, compression on the other, with a neutral axis at the centroid where σ = 0.

Elastic σ = 0 MPa ε = 0.000

Stress is proportional to strain. Atomic bonds stretch but return to their original length when the load is released — fully recoverable deformation.