# What's the difference between Strain tensor and deformation gradient tensor?

Why do we need to define the strain tensor if we already have a tensor that describes the deformation between relative particles in the continuum which is the deformation gradient tensor?

• You don't need to. The deformation gradient is enough to calculate stresses etc. However, the deformation gradient is a two-point tensor with one foot in the reference configuration and the other in the current configuration. It's easier to measure quantities either completely in the reference or completely in the current configuration. Hence the popularity of "strain" measures. – Biswajit Banerjee Mar 19 at 5:04
• can you please give an example? – user134613 Mar 19 at 9:34
• en.wikipedia.org/wiki/… – Biswajit Banerjee Mar 19 at 17:59