Retain the imposed deformation while reading a changing stress trace; constant strain does not require constant stress in a viscoelastic material.
Identify the Deformation and Model
TA Instruments describes stress relaxation as the stress response after a strain change that is then held. Within the relevant linear regime, stress divided by the imposed strain gives the relaxation modulus. Primary reference: stress relaxation and range.
Review a Hypothetical Comparison
Imagine an invented shear strain of 0.010 is imposed and held. Recorded stress is 100 Pa at one identified time and 40 Pa later. The corresponding apparent relaxation moduli are 10,000 and 4,000 Pa on that strain basis. A constant strain label therefore does not imply that the measured stress remained 100 Pa.
Keep the Evidence with the Decision
Keep the achieved strain trace, rise duration and time origin with stress. Mark the interval over which strain was actually held, and retain temperature and material state. Ask whether the normalization is being interpreted as a linear material property or only as the ratio at a particular nonlinear deformation. A different imposed amplitude needs its own range justification.
A short trace does not supply the full long-time modulus or a unique material model. Creep holds stress and observes deformation; relaxation holds deformation and observes stress, so the experiments cannot be merged just because their axes use time. The fictional values establish no formulation acceptance limit or HM force requirement. Their purpose is a controlled-input record that identifies which changing response was measured.
Which relaxation response follows the stated imposed deformation?
This blank worksheet is for your own project. It contains no H M machine trial result.
| Review field | Reference or result | Responsible person |
|---|---|---|
| Achieved strain and rise duration | To complete | To complete |
| Stress versus time and baseline | To complete | To complete |
| Linear-range/normalization basis | To complete | To complete |
| Temperature and observed horizon | To complete | To complete |
Customer Questions
What is 100 Pa divided by 0.010?
10,000 Pa on the stated ratio basis.
Does held strain guarantee held stress?
No. Stress can relax.
Is this the same imposed quantity as creep?
No. Creep holds stress instead.
Primary References
These references support the technical principles discussed in this guide. The worked examples and review questions are educational.
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