# Deformation

Written by Jerry Ratzlaff on . Posted in Classical Mechanics

Deformation, abbreviated as $$\delta$$  (Greek symbol delta), is measured by how much an object is deformed from its origional dimensions.

## Deformation Formulas

 $$\large{ \epsilon = \frac{ \delta }{ l_i } }$$ $$\large{ \sigma = \lambda \; \epsilon }$$ (linear elastic deformation)

### Where:

 Units English Metric $$\large{ \delta }$$  (Greek symbol delta) = deformation $$in$$ $$mm$$ $$\large{ \lambda }$$  (Greek symbol lambda) = elastic modulus $$\large{\frac{lbf}{in^2}}$$ $$\large{MPa}$$ $$\large{ l_i }$$ = initial length $$\large{ft}$$ $$\large{m}$$ $$\large{ \epsilon }$$  (Greek symbol epsilon) = strain $$\large{\frac{in}{in}}$$ $$\large{\frac{mm}{mm}}$$ $$\large{ \sigma }$$  (Greek symbol sigma) = stress $$\large{\frac{lbf}{in^2}}$$ $$\large{MPa}$$

## Elastic deformation

Elastic deformation is when strain is applied and disappears immediately when the stress is removed.

## Plastic deformation

Plastic deformation is when strain is applied and does not disappear when the strain is removed.  When the load on a material has passed its elastic limits or yield stress the deformation becomes perminent.

## Deformation wear

Deformation wear is a result of repeated plastic deformation at the wearing surface, producing a surrounding structure of cracks that grow and combine to form wear particles.