Measuring and understanding the mechanical response is critical for material research, product development, and process control. Mechanical characterization requires four key factors as fundamental data: load (P), distance (d), area (A) and time (t). These four parameters are necessary regardless of technique.
Hooke's Law schematic of a stress-strain curve with elastic and plastic regions before fracture
Mechanical properties are determined from a stress-strain curve generated by an applied load as described in Traditional Mechanical Testing. Stress (σ) is the instantaneous load applied to a specimen divided by its cross-sectional area before any deformation. Strain (ε) is the change in gauge length of a specimen divided by its original gauge length. Yield stress (σy) is the stress at the point where the material no longer responds elastically, referred to as the yield point.
From fundamental data, mechanical properties are determined:
- Elastic modulus and hardness
- Complex modulus for viscoelastic materials
- Fracture toughness
- Creep and relaxation