What type of stress occurs under compressive forces?

When a material is subjected to compressive forces, it experiences compressive stress, which is the internal reaction of the material to externally applied loads that tend to compress or shorten it. Compressive stress is defined as the force applied per unit area and is measured in units such as Pascals or megapascals.

In engineering applications, understanding compressive stress is crucial because it helps determine how a material will behave under loading conditions. It affects the stability and integrity of structures and components, particularly in columns, beams, and other load-bearing elements that are designed to withstand compressive forces. Proper knowledge of compressive stress allows engineers to select appropriate materials and design structures with the necessary strength and reliability.

The other choices refer to different types of stress or limitations in material mechanics or engineering standards. Ultimate stress typically refers to the maximum stress a material can withstand before failure, shear stress relates to forces that cause parts of a material to slide past each other, and allowable stress is the maximum stress a material can safely carry under given conditions, incorporating factors of safety.