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 Fatigue is an issue in springs subjected to cyclic loading, where the force on the spring varies between a maximum and minimum value. For example, the springs in a car's shock absorption system would be subject to fatigue loading. Over time, excessive cyclic stresses from fatigue can cause the spring to fail. Use this calculator to predict if a known spring subjected to a known range of loading forces will be in danger of failing from fatigue. The calculator outputs a GO / NO-GO assessment after checking the maximum shear stresses in the spring against Soderberg's criterion.
Inputs
 Spring free length, Lfree: mm cm in ft Spring constant, k: N/m dyne/cm lbf/in Maximum force on spring, Fmax: N dyne gf kgf lbf Minimum force on spring, Fmin: N dyne gf kgf lbf Wire diameter, d: mm cm in Outer diameter of spring, Douter: mm cm in Material's limiting fatigue stress: kPa psi ksi Pa Mpa Material's yield stress: psi ksi Pa Mpa kPa Factor of safety:
 Minimum length of spring (under Fmax): 3.85  in mm cm in ft Mean component of shear, tmean: 13.4  ksi Pa kPa Mpa psi ksi Alternating component of shear, talt: 2.68  ksi Soderberg limit for talt: 3.91  ksi

 Fatigue Check:  Your spring is safe from fatigue.
Equations Behind the Calculator
 See the companion page to view the equations for this calculator.
Essentials of Manufacturing

Information, coverage of important developments and expert commentary in manufacturing.

Salary Expectation

8 things to know about the interview question "What's your salary expectation"?

Mechanical Engineers Outlook

Guide for those interested in becoming a mechanical engineer. Includes qualifications, pay, and job duties.

Metal 3D Printing Design Guide

Direct Metal Laser Sintering (DMLS) 3D printing for parts with reduced cost and little waste.