Wahl Factor
Definition
A stress correction factor for helical springs that accounts for wire curvature and direct shear effects. Calculated as K = (4C-1)/(4C-4) + 0.615/C, where C is the spring index (D/d).
Practical Note
The Wahl factor is always greater than 1 and increases stress prediction by 10-50% compared to simple torsion theory. Essential for accurate fatigue analysis.