Kindness (material)

The kindness , in Sciences of the materials, is a size often used in calculations.

A kindness of elasticity is defined like the reverse of a modulus of elasticity, and is thus expressed in Pa ^-1.

It intervenes for example in the mechanical Essais following. __TOC

Creep

Concerning a quasi-static test of creep, the function of creep F (T) relating to the deformation of a viscoelastic material has as an expression:

F \ text {(T)}  = \ frac {\ varepsilon \ text {(T)}} {\sigma_0}

and has by consequence the dimensions of a complaisance.
The symbols ε (T) and σ ₀ respectively represents the deformation at time T and the constant Contrainte appliquée.
Concerning this Mechanical test, two cases arise.

Traction

For a creep test in traction, a Poids is imposed on a test-tube (use of a suspended mass).
The kindness of creep in traction is equal to:

D \ text {(T)}  = \ frac {\ varepsilon \ text {(T)}} {\sigma_0}

Note: for an elastic solid , kindness in traction D is the reverse of the Modulus Young E, that is to say:

D = {1 \ over E}

Shearing

For a creep test in shearing, a couple is imposé.
The kindness of creep in shearing is equal to:

J \ text {(T)}  = \ frac {\ varepsilon \ text {(T)}} {\sigma_0}

Note: for an elastic solid, kindness in shearing J is the reverse of the modulus of rigidity G:

J = {1 \ over G}

Pressing

This test corresponds to the application of a pressure Hydrostatique. The kindness of Compressibilité B is the reverse of the module of compressibility K:

B = {1 \ over K}

See too

Elastic strain
Resistance of the materials
Viscoanalyseur