ref: Storia.
Ut tensio sic vis. L'allungamento causa la forza elastica.
*k | |||
ΔL | → | F | F=kΔL |
F | =E | A L |
ΔL |
F A |
=E | ΔL L |
σ=Eε |
ε = | ΔL L |
σ = | F A |
it: tensione interna (o sollecitazione interna o sforzo)
en: stress (force per unit area)
E = | σ ε |
scelgo: l'ordine della formula, nel senso
stress in funzione di strain, l'allungamento causa la forza.
schey's equation
Y is the average flow stress of the material
flow stress sforzo di flusso plastico
stres strain related by known constitutive equations.
The applied loads can cause
wp/Stres-strain_analysis | Analisi_delle_sollecitazioni
Stress-strain_curve (Yield curve (physics))
A linear element of a structure is one that is essentially one dimensional and is often subject to axial loading only.
When a structural element is subjected to tension or compression its length will tend to elongate or shorten, and its cross-sectional area changes by an amount that depends on the Poisson's ratio of the material.
In engineering applications, structural members experience small deformations and the reduction in cross-sectional area is very small and can be neglected, i.e., the cross-sectional area is assumed constant during deformation.
For this case, the stress is called engineering stress or nominal stress and is calculated using the original cross section.
σ_{e} = P/A_{o}
P is the applied load
A_{o} is the original cross-sectional area.
In some other cases, e.g., elastomers and plastic materials, the change in cross-sectional area is significant. For the case of materials where the volume is conserved (i.e. Poisson's ratio = 0.5), if the true stress is desired, it must be calculated using the true cross-sectional area instead of the initial cross-sectional area, as:
σ_{true} = ( 1 + ε_{e} ) ( σ_{e} )
ε_{e} nominal (engineering) strain
σ_{e} nominal (engineering) stress.
The relationship between true strain and engineering strain is given by
ε_{true} = ln ( 1 + ε_{e} )
In uniaxial tension, true stress is then greater than nominal stress. The converse holds in compression.