Question

Long-term deformation of a material under sustained constant loading is primarily governed by:

• A. Creep
• B. Modulus of toughness
• C. Modulus of resilience
• D. Yield strength

Hint:

Associate keywords: "long-term," "time-dependent," "constant load" \(\rightarrow\) Creep. "Energy to fracture" \(\rightarrow\) Toughness. "Elastic energy" \(\rightarrow\) Resilience. "Start of plastic deformation" \(\rightarrow\) Yield strength.

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
The question asks for the term that describes the phenomenon of long-term, time-dependent deformation of a material when it is subjected to a constant load or stress, especially at elevated temperatures.
Step 2: Detailed Explanation of Options:

• (a) Creep: This is the precise definition of the tendency of a solid material to move slowly or deform permanently under the influence of persistent mechanical stresses. It is a time-dependent deformation that occurs at stress levels below the yield strength of the material.
  
• (b) Modulus of toughness: This is a measure of the total energy a material can absorb up to the point of fracture. It relates to failure under impact or large deformation, not long-term deformation under constant load.
  
• (c) Modulus of resilience: This is the maximum elastic energy that can be stored per unit volume in a material. It relates to the material's ability to absorb energy without permanent deformation, not time-dependent deformation.
  
• (d) Yield strength: This is the stress at which a material begins to deform plastically (permanently). Creep can and does occur at stresses below the yield strength.

Step 3: Final Answer:
The correct term for long-term deformation under sustained constant loading is creep.