Which of the following is not a type of mechanical stress?

Which of the following is not a type of mechanical stress?

• A. Shear
• B. Torsion
• C. Compression
• D. Vibration

Answer: (D)

Mechanical stress is the internal force per unit area inside a material caused by external loads. Compression shortens the material, shear makes layers slide past each other, and torsion twists the material, producing shear stresses on cross-sections. Vibration is an oscillatory motion, not a specific internal stress state. It can cause stresses to vary over time, but it isn’t a type of mechanical stress itself.

Mechanical stress is the internal force per unit area inside a material caused by external loads. Compression shortens the material, shear makes layers slide past each other, and torsion twists the material, producing shear stresses on cross-sections. Vibration is an oscillatory motion, not a specific internal stress state. It can cause stresses to vary over time, but it isn’t a type of mechanical stress itself.