Second Order work and Strain Energy 1

[Clay1969]

what is the difference bewtween Second Order Work =dEij dSij (Eij is strain tensor and Sij is the Stress tensor)
and Strain Energy

 

[xerf]

1. Strain energy is the amount of energy stored inside the material through elastic deformation and it is recovered when the load is removed.

2. The second order work is typically used to characterize the stability of the material (i.e. work hardening/softening).

 

[Clay1969]

What is the first order work then

 

[cbrn]

the work internally done by the material to create an equilibrated force field (and a compatible displacement field)