Planar Tests
For planar tests for a hyperelastic material consider the following figure:
1. Initial configuration
2. Loaded configuration
3. Stress
4. Strain
In a planar test, the specimen is slowly loaded or pulled in one direction, say the x-direction. No other loads are applied but the specimen is constrained from deforming in a direction orthogonal to the applied load, say the z-direction. For a nearly incompressible hyperelastic material, the stretch ratios are:
Note that in this case
For test data specify engineering stress as:
Specify engineering strain as:
