What causes stress concentration in materials?

• A. Variation in properties of material
• B. Pitting at load points
• C. Abrupt change of section
• D. All of the above

Answer: (D)

Stress concentration occurs when there are changes in the geometry of a material or variations in its properties, leading to localized increases in stress. An abrupt change of section, such as a notch or a hole in a solid structure, creates areas where stress is significantly higher than in the surrounding material. This is because the load is distributed unevenly, and the geometry causes stress flows to concentrate at these points.

Additionally, variations in the properties of the material can contribute to stress concentration. For example, if a material has different mechanical properties across its sections—such as hardness or ductility—this can lead to uneven stress distribution.

Pitting at load points also contributes to stress concentration because the formation of small pits or voids can alter the surface area and introduce discontinuities. These defects create points of weakness, making the material more susceptible to higher localized stresses.

Therefore, stress concentration can indeed arise from a combination of these factors, which is why the choice indicating that all of the listed causes contribute to stress concentration is correct.