 Compression Spring Force & Stress Design Home Springs Overview Design Considerations Spring Buckling Extension Springs Natural Frequency Calculators Overview Spring Force Deformed Length Spring Rate k Force & Stress Range of Rates k Spring Designer Spring Designer Eqns. Cyclic Loads: Res. Cyclic Loads: Fatigue Fatigue Equations Resources Bibliography  Login   Home Membership Magazines Forum Search Member Calculators  Materials  Design  Processes  Units  Formulas  Math Calculator This calculator computes the force exerted by a compression spring (with a known spring constant k) when given the spring length before and after loading. It also computes the maximum shear stress in the spring from the provided spring geometry. Inputs
 Spring free length, Lfree: m cm mm in ft Spring length when deformed, Ldef: m cm mm in ft Wire diameter, d: cm mm in Outer diameter of spring, Douter: cm mm in Spring constant, k: N/m dyne/cm lbf/in lbf/ft
 Equations Behind the Calculator The force in the compression spring is found from Hooke's Law, The maximum shear stress tmax in the spring occurs on the inside surface of the coils. It is proportional to the spring force F, and is given by the formula, where D is the mean diameter of the spring (measured from the centers of the wire cross-sections), W is the Wahl correction factor to account for the spring curvature stress, and C is the spring index (essentially an aspect ratio of the spring cross-section),   Note that W approaches 1 in the limit as C gets large. In other words, as the spring's diameter increases or as its wire diameter decreases, the effect of curvature on the spring shear stress diminishes.
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