1. Stress Concentration Factor is the ratio of nominal stress obtained by elementary equations for minimum cross-section and highest value of actual stress near discontinuity.
a) True
b) False
Explanation: The stress concentration factor is just the reciprocal of that cited in the question.
2. If a flat plate with a circular hole is subjected to tensile force, then its theoretical stress concentration factor is?
a) 2
b) 3
c) 4
d) 1
Explanation: For any ellipse, K=1+2 x (semi major axis/semi minor axis).
3. For an elliptical hole on a flat plate, if width of the hole in direction of the load decrease, Stress Concentration Factor will______
a) Increase
b) Decrease
c) Remains constant
d) Can’t be determined. Varies from material to material
Explanation: K=1+2 x (semi major axis/semi minor axis. Hence K is inversely proportional to the semi minor axis.
4. In which of the following case stress concentration factor is ignored?
a) Ductile material under static load
b) Ductile material under fluctuating load
c) Brittle material under static load
d) Brittle material under fluctuating load
Explanation: In ductile materials under static load, there is plastic deformation near yielding point and hence redistribution of stresses take place. The plastic deformation is restricted to a smaller area and hence no perceptible damage take place.
5. Is it logical to use fluid analogy to understand the phenomenon of stress concentration?
a) True
b) False
Explanation: There is a similarity between velocity distribution in fluid flow in a channel and the stress distribution in an axially loaded plate. The equations for flow potential and in fluid mechanics and stress potential in solid mechanics are same.
6. Use of multiple notches in a V shaped flat plate will
a) Reduce the stress concentration
b) Increase the stress concentration
c) No effect
d) Cannot be determined
Explanation: The sharp bending of a force flow line is reduced due to multiple notches.
7. Which of the following reduces the stress concentration?
a) Use of multiple notches
b) Drilling additional holes
c) Removal of undesired material
d) Each of the mentioned
Explanation: All the mentioned options reduce the sharp bending of a force flow line.
8. A flat plate 30mm wide and “t”mm wide is subjected to a tensile force of 5kN. The plate has a circular hole of diameter 15mm with the centre coinciding with the diagonal intersection point of the rectangle. If stress concentration factor=2.16, find the thickness of the plate if maximum allowable tensile stress is 80N/mm².
a) 8mm
b) 9mm
c) 10mm
d) 12mm
Explanation: σ=P/ (w-d) x t or σ=5000/(30-15)xt ; σ(max)=K x σ or σ(max)=2.16 x σ or σ(max)=720/t; Also σ(max)=80.
9. The stress represented by sin (t) + 1 belongs to which category?
a) Fluctuating Stresses
b) Alternating stresses
c) Repeated Stresses
d) Reversed Stresses
Explanation: The minimum stress value is zero and hence is belongs to Repeated Stress category.
10. The stress represented by sin (t) + 2 belongs to which category?
a) Fluctuating Stresses
b) None of the mentioned
c) Repeated Stresses
d) Reversed Stresses
Explanation: The mean as well as the amplitude value is non zero hence it belongs to Fluctuation Stress Category.