EXTENSION SPRING CALCULATION FORMULAS FOR STATIC LOADING

Extension Spring Calculation Formulas including spring index, Wahl factor, correction factor and shear and tensile stress formulas are given below.

Parameter	Formula
Spring outer diameter [OD]
Spring inner diameter [ID]
Spring index [C]
Spring index -1 [C1]
Curvature correction factor for point A [KA ]
Tensile stress at point A [σA]
Spring index -2 [C2+]
Stress correction factor for point B [KB  ]
Shear stress at point B [σB]
Wahl factor [Kw]
Shear stress at spring body [τsb]
Factor of safety at point A [fosA]
Factor of safety at point B [fosB]
Factor of safety at spring body [fossb]

Note 1 : ⁺ Recommended practice is to make C₂ greater than 4.

Reference:

• Budynas.R , Nisbett.K . (2014) . Shigley's Mechanical Engineering Design . 10th edition.  McGraw-Hill
• Shigley J.E. , Mischke C.R. (1996), Standard Handbook of Machine Design , 2nd edition