Discussion
A copper wire upon loading instantaneously increases in length to l, and then continues to elongate gradually. Upon unloading, the wire retracts to length l. According to the Maxwell model, which one of the options given correctly relates the total strain E, the applied stress S, the modulus G, the material’s resistance to flow \(\eta\), and the elapsed time t between loading and unloading?
Answer: C
The Maxwell model gives E = (S/G) + (S/\(\eta\))t.
The Maxwell model is a spring (modulus G) and a dashpot (viscosity \(\eta\)) in series. Under a constant stress S, both elements carry the full stress and their strains add. The spring stretches at once by S/G, the instantaneous elongation to l; the dashpot flows at a constant rate S/\(\eta\), so after time t it has added (S/\(\eta\))t, the gradual creep:
\[ E = \frac{S}{G} + \frac{S}{\eta}t \]
On unloading only the spring recovers, which is why the wire retracts by the elastic part and keeps the viscous flow. Subtracting the terms, multiplying them or dividing them has no basis: strains of elements in series simply add.
Post your comment
Please log in or register to post a comment.
Examination Categories
- SSC Exams
- Banking Exams
- Teaching Exams
- Civil Services Exams
- Railways Exams
- Engineering Recruitment Exams
- Defence Exams
- State Government Exams
- Police Exams
- Insurance Exams
- Nursing Exams
- Other Government Exams
- NRA CET
- PG Entrance Exams
- Campus Placement
- MBA Entrance Exams
- CUET and UG Entrance
- Judiciary Exams
- Regulatory Body Exams
- Software Development