Strength of Materials viva Question and Answers

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1. Define Hooke’s Law. 
Ans. It states that when the material is loaded within the elastic limit the stress is directly proportional to strain.
i.e. Stress α strain. or Stress = constant x Strain

2. Define Strength of materials.
 Ans. The strength of a material is its ability to withstand an applied stress without failure.

3. What is stress? 
Ans. When load is applied on any object then a resisting force is induced, that resisting or reacting per unit area of cross-section is called stress.

4. What is strain?
Ans. Stress is change in dimensions upon original dimentions.

5. What is deformation? 
Ans. Deformation is change in dimensions of any object due to applied load.

6. On which steel you have performed tension test. What is its carbon content? 
Ans. On mild steel (0.3 to 0.6% carbon).

7. What kind of fracture has occurred in tensile specimen. 
Ans. Ductile fracture.

8. Define temperature stress.
Ans. Stress introduced by uniform or nonuniform temperature change in a structure or material which is constrained against expansion or contraction.

9. What is hardness? 
Ans. Hardness is the resistance of a material to localized deformation.

Or 

Hardness is the mechanical resistance which a material asserts against the mechanical penetration of a harder test body.

10. What is toughness?
 Ans. Toughness is the amount of energy per volume that a material can absorb before rupturing. It is also defined as the resistance to fracture of a material when stressed.

11. Types of stresses. 
Ans. Normal stresses(tensile & compressive), shear stresses

12. Types of strains.
 Ans. Longitudinal strain(tensile & compressive), shear strain, volumetric strain.

13. What is volumetric strain? 
Ans. Volumetric strain is change in volume upon original volume.

14. What is poisson’s ratio? 
Ans. It is the ratio of lateral(or transverse) strain to longitudinal strain.

15. Define longitudinal strain and lateral (transverse) strain. 
Ans. Longitudinal strain is change in length upon original length. Lateral strain is change in lateral dimensions (i.e. dimensions perpendicular to length) upon original lateral dimensions.

16. Differentiate Shear Strain and Shear stress. 
Ans. Stress is a measure of how much force is taken by an object of particular size. shear stress is therefore shear force divided by area under shear. Clearly, increasing the force and/or decreasing the size or cross sectional area will result in larger stresses. Shear strain is a measure of the deflection caused by a shear stress, and is related via the Shear modulus of elasticity or modulus of rigidity(C or G) is the ratio of shear stress to shear strain. modulus (or modulus of rigidity) G, where G= shear stress/shear strain.

17. What is factor of safety? 
Ans. The ratio of the breaking stress of a structure to the estimated maximum stress.

18. What is Ultimate strength? 
Ans. Absolute maximum compressive, shear, or tensile stress a material can bear without failure is called ultimate strength.

19. Define elastic constants E,K & G. 
Ans. Young’s modulus of elasticity(E) is the ratio of normal stress to normal strain. Bulk modulus of elasticity(K) is the ratio of normal stress to volumetric strain.Shear modulus of elasticity or modulus of rigidity(C or G) is the ratio of shear stress to shear strain

20. What is Yield Strength? 
Ans. The ability of a metal to tolerate gradual progressive force without permanent deformation. Yield strength is the stress at which a specified amount of permanent deformation of a material occurs.

21. Define impact strength.
Ans. The ability of a material to withstand shock loading.

22. What is beam. 
Ans. A beam is a horizontal structural element in which longitudinal dimensions are very large in comparison of lateral dimensions and that is capable of withstanding load primarily by resisting bending.

23. What is difference between force and load.
 Ans: Force is a push or pull applied on a body to change its state. Load is the combined effect of external applied forces at any point.

24. Types of Loads. 
Ans: Point load, uniformly distributed load, uniformly varying load.

25. What is torque? 
Ans. Torque is the tendency of a force to cause or change rotational motion of a body. A force applied at a right angle to a lever multiplied by its distance from the lever's fulcrum (the length of the lever arm) is its torque.

26. What is Torsional force? 
Ans. A force acting on a body that tends to twist the body.

27. What is torsional rigidity? 
Ans. The applied torque needed to produce a unit angle of twist in a circular elastic material, it is a measure of a body's resistance to torsion.

28. Types of beams. 
Ans. Simply supported beam, over hanging beam, Cantilever beam, continuous beam, fixed beam.

29. Define shear force and bending moment. 
Ans. Shear force is the algebraic sum of all the vertical forces acting on either side of the section. Bending moment is the algebraic sum of all the moments of the forces acting on either side of the section.

30. What is point of inflection. 
Ans. The point on beam at which the moment is zero is called point of inflection or point of contraflexure.

31. What are sagging and hogging moments? 
Ans. If clockwise bending moments are taken as negative, then a negative bending moment within an element will cause "sagging", and a positive moment will cause "hogging". It is therefore clear that a point of zero bending moment within a beam is a point of contraflexure that is the point of transition from hogging to sagging or vice versa.

32. When bending moment will be maximum? 
Ans. Bending moment is maximum when shear force is zero.

33. What is Moment of inertia? 
Ans. Moment of inertia is second moment of area or second moment of mass.

34. What is Polar moment of inertia? 
Ans. The Polar Moment of Inertia is a geometric property of a cross section. Physically, it is a measure of how difficult it is to turn a cross-section about an axis perpendicular to it.

35. Define slope and deflection. 
Ans. The deflection at any point on the axis of the beam is the distance between its position before and after loading. Slope at any section in a deflected beam is defined as the angle in radians which the tangent at the section makes with the original position.

36. Explain about Principal plane. 
Ans. The planes on which shearing stresses are zero are called principal planes.

37. Explain about Principal stresses. 
Ans. The stresses normal to principal planes are known as principal stresses

38. Units of force, deflection, stress, strain, E, K, G. 
Ans. SI Unit of force is Newton, SI unit of deflection is meter, SI unit of stress,E,K&G is N/m2 , Strain is unitless quantity.

39. Purpose of UTM.
Ans. UTM is used to test the tensile stress and compressive strength of materials.

40. What are lifting machines? 
Ans. Lifting machines are devices which are used to lift heavy load by applying less effort.

41. What is torsion equation? 
Ans. T/J = τ/R = Gθ/L

42. What is flexural rigidity? 
Ans. The product EI is called flexural rigidity.

43. Define Mechanical Advantage,velocity ratio & efficiency. 
Ans. M.A. is the ratio of load lifted to effort applied. V.R. is the ratio of distance moved by effort to distance moved by load. Efficiency is the ratio of mechanical advantage to velocity ratio.

44. Define Section modulus. 
Ans. The elastic section modulus is defined as S = I / y, where I is the second moment of area (or moment of inertia) and y is the distance from the neutral axis to any given fibre.

45. What is a composite beam? 
Ans. A structural member composed of two or more dissimilar materials joined together to act as a unit in which the resulting system is stronger than the sum of its parts.