This set of Machine Design Multiple Choice Questions & Answers (MCQs) focuses on “Stress Concentration & Its Factors”.
1. Stress concentration is defined as the localization of high stresses due to irregularities present in the component and no changes of the cross section.
Explanation: The given statement is true apart from the fact that there is no change in the cross section.
2. 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.
Explanation: The stress concentration factor is just the reciprocal of that cited in the question.
3. If a flat plate with a circular hole is subjected to tensile force, then its theoretical stress concentration factor is?
Explanation: For any ellipse, K=1+2 x (semi major axis/semi minor axis).
4. For an elliptical hole on a flat plate, if width of the hole in direction of the load decrease, Stress Concentration Factor will______
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.
5. 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.
6. Is it logical to use fluid analogy to understand the phenomenon of stress concentration?
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.
7. 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.
8. 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.
9. 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.
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.
Sanfoundry Global Education & Learning Series – Machine Design.
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