Discussion Overview
The discussion revolves around the method of obtaining nominal stress and nominal strain, particularly in the context of testing a rubber sample assumed to be hyperelastic. Participants explore the definitions and calculations involved in engineering stress and strain, especially during a tensile test leading to material failure.
Discussion Character
- Homework-related
- Technical explanation
- Debate/contested
Main Points Raised
- One participant inquires whether nominal stress and strain can be calculated using simple equations, referencing the common identification of nominal stress/strain with engineering strain.
- Another participant suggests that nominal stress/strain can be used when the material is uniformly loaded.
- A follow-up question is posed about the appropriateness of using stress and strain values obtained from the test, considering the decrease in cross-sectional area due to elongation.
- A different participant clarifies that engineering stress is calculated using the original cross-sectional area, even if the area decreases during the test, and notes that true stress is calculated using the actual cross-sectional area at the elongation point, leading to different stress-strain curves based on the definition used.
Areas of Agreement / Disagreement
Participants express differing views on the implications of using nominal stress and strain in the context of changing cross-sectional area during testing. There is no consensus on the best approach to take regarding the definitions and calculations of stress and strain in this scenario.
Contextual Notes
Participants acknowledge the complexity of defining stress and strain based on the conditions of the test, particularly regarding the effects of necking in materials under load. The discussion highlights the dependence on definitions and the assumptions made about uniform loading.