True stress

True stress is a measure of the intensity of internal forces within a material when it is stretched or compressed. Unlike the average stress (engineering stress), which is calculated based on the original cross-sectional area, true stress considers the actual small area at every stage of deformation as the material changes shape. This provides a more accurate understanding of how the material responds under load, especially during significant stretching or thinning, by reflecting the instantaneous force per current area rather than the initial one.