Question

Creep rate decreasing with time is observed during

• A. Viscous creep
• B. Primary creep
• C. Transient creep
• D. Initial stages of creep test

Hint:

Visualize the creep curve (strain vs. time). Stage I has a decreasing slope (rate). Stage II has a constant slope. Stage III has an increasing slope. "Transient" and "Primary" refer to Stage I.

Answer 1

The Correct Option is C

Step 1: Sketch the shape of a typical creep curve.
When strain is plotted against time under a constant load at high temperature, the curve generally passes through three recognisable regions before the specimen finally breaks.
Step 2: Think about the competition happening inside the material in the first region.
Early on, as the material deforms, dislocations multiply and tangle up faster than they can recover, so the material work hardens as it creeps. This growing resistance means the strain rate keeps falling even though the load stays fixed, giving a curve that is steep at first and gradually flattens.
Step 3: Name this stage and compare with the others.
This falling rate stage is called primary creep, also known as transient creep because the rate is still changing rather than settled. It is different from the middle stage, secondary or steady state creep, where hardening and recovery balance out to give a nearly constant rate, and from the final tertiary stage, where the rate accelerates toward failure due to internal damage.
\[ \boxed{\text{Transient creep}} \]