# Homework Help: The compressive longitudinal strain

1. Jan 6, 2012

### ahmeeeeeeeeee

Hello,

is the strain defined as the absolute deformation to the initial ? i.e is it always positive ??

If Yes , then poission's ration is negative for compression of ordinary materials ?

2. Jan 6, 2012

### LawrenceC

Strain is defined as belowl

e = (a - b)/b

where b is original length and a is the stressed length. So it can be negative for compressive loading. Absolute does not mean |absolute value|.