What is "Corrected Stress"?

The wire in a coil spring is primarily loaded in torsion. The stress calculations found in nearly all spring design handbooks are based on bar-in-torsion theory. Because the spring wire is not a straight bar and because the spring is coiled with pitch, there is also a bending component to the total stresses. Wahl, the author of the industry's most common design reference, developed a correction factor based on spring index. This has come to be known as the "Wahl Correction Factor." When the calculated torsional stresses (the "uncorrected stresses") are multiplied by this correction factor, the end result is the "corrected stress." This gives a more accurate representation of the true applied stress state.