The three types of stress are:

• A. Tensile, Compressive, Shear
• B. Normal, Thermal, Residual
• C. Bending, Torsional, Shear
• D. Tensile, Compressive, Torsional

Answer: (A)

Stress is classified by how it acts on a plane inside a material: normal stresses act perpendicular to the plane, while shear stresses act parallel to the plane. The three basic stress types typically used to describe a simple state are tensile, compressive, and shear. Tensile stress pulls the material apart, increasing length; compressive stress pushes it together, decreasing length; and shear stress causes adjacent layers to slide past one another along the plane.

The other options mix in concepts that aren’t the fundamental stress types. Normal is a broad category that includes tensile and compressive, while thermal and residual refer to causes or history of stress rather than distinct stress types. Bending and torsional describe loading modes, not a basic set of stress categories, and torsional stress is really a form of shear stress encountered under twisting.