Deformation

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.