# Strain

on . Posted in Classical Mechanics

Strain, abbreviated as $$\epsilon$$ (Greek symbol epsilon), a dimensionless number, also called linear strain or longitudinal strain, is a measure of the deformation or elongation experienced by a material when subjected to an external force or load.  It quantifies the relative change in size or shape of an object compared to its original size or shape.

Engineers and designers use strain data to understand how materials respond to loads, helping them design structures and components with the right level of elasticity and durability.  Additionally, strain measurements are crucial in stress analysis to ensure the safety and performance of various products and systems.

### strain Types

• Elastic Strain  -  A transitory dimensional change that exists only while the initiating stress is applied and disappears immediately upon removal of the stress.
• Plastic Strain  -  A dimensional change that does not go away when the initiating stress is removed.

## strain formula

$$\large{ \epsilon = \frac{ \Delta l }{ l_i } }$$     (Strain)

$$\large{ \Delta l = \epsilon \; l_i }$$

$$\large{ l_i = \frac{ \Delta l }{ \epsilon } }$$

### Solve for ϵ

 length change, Δl initial length, li

### Solve for Δl

 strain, ϵ initial length, li

### Solve for li

 length change, Δl strain, ϵ

Symbol English Metric
$$\large{ \epsilon }$$  (Greek symbol epsilon) = strain $$\large{ dimensionless }$$
$$\large{ \Delta l }$$ = length change $$\large{ ft }$$ $$\large{ m }$$
$$\large{ l_i }$$ = initial length $$\large{ ft }$$ $$\large{ m }$$