# Theories of Elastic Failure - Mechanical Engineering (MCQ) questions and answers

1)   A circular bar is subjected to an axial force and shear force, the difference between two principle stresses is 120 Mpa. Based on maximum shear stress theory what is the factor of safety, if elastic limit of the bar is 300 Mpa?

a. .5
b. 2
c. 2.5
d. 3
 Answer  Explanation ANSWER: 2.5 Explanation: No explanation is available for this question!

2)   According to maximum strain energy theory, failure of material due to complex stresses occurs when total stored energy per unit volume at a point ___________

a. reaches the value of yield point
b. reaches the value of strain energy stored per unit volume at yield point
c. reaches the value of strain energy stored per unit volume at elastic limit
d. exceeds total strain energy caused by uniaxial stress at elastic point
 Answer  Explanation ANSWER: reaches the value of strain energy stored per unit volume at elastic limit Explanation: No explanation is available for this question!

3)   For designing ductile materials, which of the following theories is/are used?

a. Maximum shear stress theory
b. Shear strain energy theory
c. Both a. and b.
d. None of the above
 Answer  Explanation ANSWER: Both a. and b. Explanation: No explanation is available for this question!

4)   St. Venant's theory is also known as maximum  _________

a. principle stress theory
b. shear stress theory
c. principle strain theory
d. strain energy theory
 Answer  Explanation ANSWER: principle strain theory Explanation: No explanation is available for this question!

5)   According to Coulomb's theory, material subjected to complex stresses fails, if ________ shear stress induced in the material exceeds _______ shear stress at the yield point.

a. minimum, maximum
b. maximum, minimum
c. maximum, maximum
d. minimum, minimum
 Answer  Explanation ANSWER: maximum, maximum Explanation: No explanation is available for this question!

6)   In simple tensile test, when maximum principle stress reaches the value of yield point, the material subjected to complex stresses fail. This theory is called as ________.

a. Coulumb's theory
b. Rankine's theory
c. Venant's theory
d. Von Mises theory
 Answer  Explanation ANSWER: Rankine's theory Explanation: No explanation is available for this question!

7)   Which theory gives satisfactory results for brittle materials?

a. Maximum shear stress theory
b. Maximum principle stress theory
c. Shear strain energy theory
d. None of the above
 Answer  Explanation ANSWER: Maximum principle stress theory Explanation: No explanation is available for this question!

8)   In maximum principle strain theory, maximum principal strain for no failure condition is ________

a. e = (σx - σy )/ E +τ2
b. e = qmax ≥ qyp
c. e = σyp / E
d. none of the above
 Answer  Explanation ANSWER: e = σyp / E Explanation: No explanation is available for this question!

9)   Principal stress of 30 Mpa and -70 Mpa acts on a material which has elastic limit stress in simple tension and compression as 60 Mpa and 200 Mpa respectively. Specify the reason for failure of the material assuming maximum principle stress theory.

a. Compression
b. Tension
c. Unpredictable

 Answer  Explanation ANSWER: Tension Explanation: No explanation is available for this question!

10)   Shear stress energy theory is called as ______

a. distortion theory
b. Von Mises theory
c. both a. and b.
d. none of the above
 Answer  Explanation ANSWER: both a. and b. Explanation: No explanation is available for this question!