New 561-line test file for deformation gradient computation:
- Tests F = ∂x/∂X = I + ∂u/∂X for finite strain mechanics
- Tests identity case (u = 0 → F = I)
- Tests pure translation (rigid body motion)
- Tests pure stretch and simple shear cases
- Tests small vs finite strain difference
- Validates physical constraints (det(F) > 0)
- Tests Hex8 and Tet10 elements
- Validates zero-allocation performance
Comprehensive test for deformation gradient computation essential
for finite strain analysis and hyperelastic materials.
Jukka Aho