What term describes stresses that are independent of load?

The term that describes stresses independent of load is residual stress. Residual stresses are internal forces that remain in a material after the original cause of the stresses has been removed. These stresses can develop due to various factors such as manufacturing processes (like welding, casting, or machining), phase changes in materials, or temperature gradients.

These stresses are critical to understand because they can significantly affect the performance and failure of components. For example, they can lead to unexpected failure modes, influence fatigue life, and affect the material's strength. In applications where precision and performance are key, such as in aerospace or structural applications, understanding and managing residual stresses can help in predicting how a component will behave under service loads.

Options related to working stress, simple stress, and combined stress refer to stresses that are directly associated with applied loads or forces which affect the material when subjected to external conditions. Thus, they do not encompass the intrinsic stresses present within the material regardless of any load.