Choose the correct answer in the following questions (10 x 2)
1. There is always a limiting value of load up to which strain is totally disappeared on the removal of load, the stress corresponding to this load is called as:
(a) Elastic limit
(b) Unit stress
(c) Yield stress
(d) Ultimate stress
2. In a two-dimensional stress system the maximum shear stress occurs on planes inclined with horizontal as:
3. In a cantilever beam with a uniformly distributed load, the shear force varies as
(a) linear laws
(b) parabolic law
(c) cubic law
(d) constant, does not vary
4. The diameter of the kernel of a circular section (no tension) is
5. The amount of deflection of a beam subject to some type of loading depends on :
(a) cross section
(b) bending moment
(c) either (a) or (b)
(d) both (a) and (b)
6. A pipe of 200 mm internal diameter and 50 mm thickness carriers a fluid at a pressure of 5 MN/m². The maximum circumferential stress will be:
(a) 13 MN/m²
(b) 8 MN/m²
(c) 5 MN/m²
(d) none of the above
7. A hollow shaft has an external diameter of 300 mm and an internal diameter of 150 mm. The ratio of strength with that of a solid shaft of the same weight per unit length and materials is:
(d) None of the above
8. In case of plane stress problems
(a) σz = 0
(b) τxz = 0
(c) τyz = 0
(d) All of the above
9. Mild steel is
(a) brittle material
(b) ductile material
(c) neither brittle nor ductile material
10. In the determination of hardness of razor blade the method that can be used is
(a) Brinell hardness
(b) Vicker hardness
(c) Rockwell hardness
(d) scratch test.
1. (a) When an external force acts on a body, the body tends to undergo some deformation. If the external force is removed and the body comes back to its original shape and size (which means the deformation disappears completely), the body is known as an elastic body. This property, by virtue of which certain materials return back to their original position after the removal of the external force, is called elasticity.
The body will regain its previous shape and size only when the deformation caused by the external force, is within a certain limit. Thus there is a limiting value of force up to and within which, the deformation completely disappears on the removal of the force. The value of stress corresponding to this limiting force is known as the elastic limit of the material.
- Principal stresses occur on mutually perpendicular planes.
- Shear stresses are zero on principal planes.
- Planes of maximum shear stress occur at 45° to the principal planes.
- The maximum shear stress is equal to one half the difference of the principal stresses.
9. (b) Mild steel is a type of low carbon steel. Carbon steels are metals that contain a small percentage of carbon (max 2.1%) which enhances the properties of pure iron. The carbon content varies depending on the requirements for the steel. Low carbon steels contain carbon in the range of 0.05 to 0.25 per cent.
10. (c) When looking at knives you will often see a number in the specs with “RC” after it. This number represents the Rockwell Rating. The Rockwell rating is a scale that is used to measure the hardness of a material. The Rockwell hardness test is the industry standard for knives.
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