Question

Permanent dimension changes due to loading is termed as:

• A. Strain
• B. Extent
• C. Creep
• D. Ambit

Hint:

Creep is significant in materials like concrete and metals at high temperatures or under long-term loading.

Answer 1

The Correct Option is C

A simple everyday picture helps here: think of a shelf that sags a little more every year under the same constant load, or a suspended cable that stretches slowly over months even though the load on it never increases.

1. Strain: only measures deformation at an instant; doesn't capture the slow, ongoing increase over time seen in this picture.
2. Extent: a generic word, not a defined engineering term for this behavior.
3. Creep: exactly names this slow, permanent, time-dependent deformation under sustained constant load, matching the sagging-shelf picture.
4. Ambit: another generic word, not an engineering term either.

So permanent dimension change due to sustained loading over time is called creep.

Answer 2

A third useful check is to compare this phenomenon against a commonly confused neighboring term, fatigue, since both involve damage accumulating slowly under repeated or sustained conditions, but for different reasons.

1. Strain: a snapshot quantity describing deformation at one instant of loading; it does not, by itself, distinguish between a load applied once versus one sustained for years, so it cannot be the specific term for a slow, permanent change.
2. Extent: not an engineering term at all, so it does not describe any specific mechanical behavior, sustained or otherwise.
3. Creep: unlike fatigue (which is caused by many cycles of repeated, varying load causing microscopic cracking), this phenomenon is caused by one constant, unchanging load acting continuously over a long time, gradually stretching the material further and further — this steady, non-cyclic, time-based permanent deformation is precisely what "creep" refers to.
4. Ambit: again a general word with no defined mechanical meaning, so it cannot describe either creep or fatigue-type behavior.

Separating this steady single-load, time-based permanent deformation from the cyclic-loading case of fatigue confirms the specific term being asked for.

Therefore, the correct answer is creep.