Young, shear and bulk elastic moduli
Stress and strain need a loading geometry and a constitutive range.
Key knowledge
For small reversible linear deformations, uniaxial stress σ=F_perp/A gives axial strain ε=ΔL/L₀ with σ=E_Yε. Simple shear obeys τ=Gγ, where γ is the engineering shear strain. Isotropic pressure compression has Δp=−K_BΔV/V₀. The moduli characterize different loading responses and are not interchangeable with strength or fracture limits.
Values and equations
σ=F_perp/A=E_Y(ΔL/L₀); τ=Gγ; Δp=−K_BΔV/V₀
- σ,τ,Δp
- Axial stress, shear stress and pressure change Pa
- E_Y,G,K_B
- Young, shear and bulk moduli Pa
- F_perp
- Signed axial force, positive in tension N
- A
- Cross-sectional area m²
- ΔL,L₀
- Length change and initial length m
- γ
- Engineering shear strain Δx/h 1
- ΔV,V₀
- Volume change and initial volume m³
Conditions and scope
- Uniform idealized loading and a valid small-strain linear elastic regime; positive stable moduli. Axial force and stress are signed positive in tension, so compression has negative axial stress and negative length change.
- The scalar formulas are specified loading limits, not the full tensor constitutive law for anisotropic matter. Engineering shear strain is twice the corresponding small-strain tensor component.
Sources · 1
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Read §12.3 scalar stress/strain relations12.33, axial12.34–12.36, bulk12.39–12.40 and shear12.41–12.43. Avoid the statement that shear-stress concepts never apply to flowing fluids; the record concerns reversible solid elasticity.
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Entry details
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- foundation-physics-linear-elastic-moduli
- Revision
- foundations-refresh.1
- Structured reference record
- Foundational reference additions