Strain

Written by Jerry Ratzlaff on . Posted in Classical Mechanics

strain 3Strain, abbreviated as \(\epsilon\) (Greek symbol epsilon), a dimensionless number, also known as linear strain or longitudinal strain, is the deformation, stretched or compressed, of a material compared to its original length.

 

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

\(\large{ \epsilon = \frac{ \Delta l }{ l_i }  }\) 
\(\large{ \epsilon = \frac{ l_f \;-\; l_i }{ l_i }  }\) 

Where:

 Units English Metric
\(\large{ \epsilon }\)  (Greek symbol epsilon) = strain \(\large{\frac{in}{in}}\) \(\large{\frac{mm}{mm}}\)
\(\large{ \Delta l }\) = length change \(\large{ ft }\) \(\large{ m }\)
\(\large{ l_f }\) = final length \(\large{ ft }\) \(\large{ m }\)
\(\large{ l_i }\) = initial length \(\large{ ft }\) \(\large{ m }\)

 

Related formulas

\(\large{ \epsilon = \frac { \sigma } { \lambda } }\)  (elastic modulus
\(\large{ \epsilon = \frac { \sigma } { E } }\)  (Young's modulus

Where:

\(\large{ \epsilon }\)  (Greek symbol epsilon) = strain

\(\large{ \lambda }\)  (Greek symbol lambda) = elastic modulus

\(\large{ \sigma }\)  (Greek symbol sigma) = stress

\(\large{ E }\) = Young's modulus

 

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Tags: Strain and Stress Equations Soil Equations Hoop Stress Equations