Correct Answer - Option 3 : stress concentration
Explanation:
Stress concentration:
- Stress concentration is defined as the localization of high stresses due to irregularities present in the component and abrupt changes in the cross-section.
Causes of stress concentration:
Variation in properties of the material:
In general, the material is no homogenous throughout, there are some variations in the material properties due to the following factors:
- Internal cracks and flaws like blowholes.
- Cavities in welds.
- Air holes in steel components.
- Non-metallic inclusions.
These variations act as discontinuities in the component and cause stress concentration.
Load application: The machine components are subjected to forces. These forces act either at a small or point area on the component. Since the area is small, the pressure at these points is excessive. This results in stress concentration.
Abrupt changes in section: The abrupt changes are due to steps cut on the shafts to accommodate the bearings, pulleys sprockets. These create change in the cross-section of the shaft ad results in the stress concentration.
Discontinuities in the component: There are some features of machine components such as oil holes, keyways, and splines, and screw threads result in a discontinuity in the cross-section of the component. There is stress concentration in the vicinity of these discontinuities.
Machining Scratches: Machining scratches stamp marks or inspection marks are surface irregularities that cause stress concentration.
