100 Strength of Materials (SOM) Interview Questions (With Answers) – 2025 Guide
Strength of Materials (SOM) is a core subject in Mechanical, Civil, Aerospace, and Structural engineering interviews. Whether you are preparing for PSU, MNC, or academic interviews, this list of 100+ SOM interview questions with short, crisp answers will help you revise quickly and confidently.
Table of Contents
- Introduction
- Basic Strength of Materials Questions
- Stress–Strain Concepts
- Beams, Shear Force & Bending
- Torsion
- Columns & Struts
- Springs
- Deflection
- Mohr’s Circle
- Theories of Failure
- Miscellaneous & Advanced Questions
- Conclusion
1. Introduction
Strength of Materials deals with how different materials behave under external loads. It includes concepts like stress, strain, bending, torsion, elasticity, failure theories, and more. Interviewers often check concept clarity through short and application-based questions.
This article provides 100 interview questions with simple explanations, suitable for job interviews, viva, and placement exams.
2. Basic Strength of Materials Interview Questions
1. What is Strength of Materials?
It is the study of how solid materials behave under stresses and strains.
2. Define stress.
Stress = Force / Area (σ = F/A).
3. Define strain.
Strain is the deformation per unit length (ε = δL/L).
4. What is elasticity?
The property of a material to regain its original shape after removing the load.
5. What is plasticity?
The ability of a material to undergo permanent deformation.
6. What is Hooke’s law?
Stress is directly proportional to strain within the elastic limit.
7. What is modulus of elasticity?
Ratio of stress to strain in the elastic region (E = σ/ε).
8. What is Poisson’s ratio?
Ratio of lateral strain to longitudinal strain.
9. What is shear stress?
Stress acting tangentially to a surface (τ = F/A).
10. Define factor of safety.
FOS = Ultimate stress / Working stress.
3. Stress–Strain Interview Questions
11. What is yield point?
Point where material begins to deform permanently.
12. What is ultimate tensile strength?
Maximum stress a material can withstand before failure.
13. Define necking.
Local reduction in diameter of a tensile specimen after UTS.
14. What is resilience?
Ability to absorb energy within elastic limit.
15. What is toughness?
Ability to absorb energy before fracture.
16. What is creep?
Time-dependent deformation under constant load.
17. What is fatigue?
Failure due to repeated cyclic stresses.
18. What is brittle material?
Material with little plastic deformation before fracture (e.g., glass).
19. What is ductile material?
Material that undergoes significant plastic deformation (e.g., steel).
20. What is hardness?
Resistance to indentation or scratching.
4. Beams, Shear Force & Bending
21. What is a beam?
Structural member resisting bending.
22. Define shear force in a beam.
Internal force acting perpendicular to the beam axis.
23. Define bending moment.
Internal moment causing bending.
24. What is SFD and BMD?
Shear Force Diagram and Bending Moment Diagram.
25. What is point of contra-flexure?
Point where bending moment changes sign.
26. What is neutral axis?
Axis in a beam where stress is zero.
27. What is the bending equation?
M/I = σ/y = E/R.
28. What is section modulus?
Z = I/y.
29. Where is maximum bending stress in a beam?
At extreme fiber (top or bottom).
30. What is pure bending?
Bending without shear force.
5. Torsion Interview Questions
31. What is torsion?
Twisting of a shaft due to torque.
32. Write the torsion equation.
T/J = τ/R = Gθ/L.
33. What is polar moment of inertia?
J = πd⁴/32 for circular shaft.
34. What causes shear stress in shafts?
Torque.
35. What is angle of twist?
Angular deformation of a shaft under torque.
6. Columns & Struts
36. Define a column.
Long vertical member subjected to axial compressive load.
37. What is buckling?
Sudden lateral bending of column before crushing.
38. State Euler’s formula for buckling load.
Pcr = π²EI / (Le²).
39. What is slenderness ratio?
L/r, where r = √(I/A).
40. What is Rankine’s formula?
Hybrid of crushing and buckling strengths.
7. Springs Interview Questions
41. What is a spring?
Elastic member that stores energy.
42. What is stiffness of a spring?
k = load/deflection.
43. Which stress acts in helical spring?
Torsional shear stress.
44. What is surge in springs?
Vibration of spring under load.
45. What is spring index?
C = D/d.
8. Deflection of Beams
46. What is beam deflection?
Vertical displacement under bending.
47. What is the double-integration method?
Method using EI d²y/dx² = M.
48. What is Macaulay’s method?
Advanced form of double integration for multiple loads.
49. What is moment area theorem?
Used to find slope and deflection.
50. What is Castigliano’s theorem?
Strain energy method for deflection.
9. Mohr’s Circle Interview Questions
51. What is Mohr’s circle?
Graphical method to find stresses on inclined plane.
52. What is principal stress?
Maximum normal stress at a point.
53. Define principal plane.
Plane on which shear stress is zero.
54. What is maximum shear stress?
τmax = (σ₁ – σ₂)/2.
55. What is radius of Mohr’s circle?
R = √[(σx – σy)²/4 + τxy²].
10. Theories of Failure
56. What is maximum principal stress theory?
Failure occurs when σmax ≥ σyield.
57. What is maximum shear stress theory?
Failure occurs when τmax ≥ τyield.
58. What is maximum strain energy theory?
Total strain energy reaches critical value.
59. What is distortion energy theory (von Mises)?
Failure occurs when distortion energy reaches yield value.
60. Which theory is best for ductile materials?
Von Mises theory.
11. Miscellaneous & Advanced SOM Questions
61. What is thermal stress?
Stress due to temperature change.
62. Define composite bar.
Bar made of more than one material.
63. What is stress concentration?
Increase in stress at notches/holes.
64. What is notch sensitivity?
Sensitivity of material to stress concentration.
65. What are statically indeterminate structures?
Structures with more unknowns than equilibrium equations.
66. What is shear modulus?
G = E / 2(1 + μ).
67. What is bulk modulus?
K = volumetric stress / volumetric strain.
68. What is thin cylinder stress?
Hoop stress = pd/2t.
69. What is thick cylinder stress?
Lame’s equations used.
70. What is strain energy?
Energy stored due to deformation.
30 More Frequently Asked SOM Questions (Short)
71. Define permissible stress.
72. What is impact loading?
73. Define torsional rigidity.
74. What is eccentric loading?
75. Define flexural rigidity.
76. What is neutral layer?
77. What is bending stress formula?
78. What is end-fixity for columns?
79. Define Creep curve.
80. Name brittle fracture types.
81. Define Young’s modulus.
82. What is volumetric strain?
83. What are thin pressure vessels?
84. What is principal strain?
85. Define hoop stress.
86. What is modulus of rigidity?
87. What is working stress?
88. What is unit load method?
89. What is torsional shear stress formula?
90. Define crippling load.
91. What is complementary shear?
92. Define shear centre.
93. What is moment of inertia?
94. What is parallel axis theorem?
95. What is torsional stiffness?
96. What is load eccentricity?
97. What is shear lag?
98. What is yield stress?
99. Define ultimate load.
100. What is modulus of toughness?
Conclusion
These 100 Strength of Materials interview questions help you prepare for academic, technical, and job-related interviews. Revise concepts like stress, strain, bending, torsion, and failure theories thoroughly for guaranteed confidence.
Comments