Calculate the mean stress τm, stress amplitude τa and fatigue utilization of a compression spring between two working points s1 and s2. The corrected stresses come unchanged from the validated EN 13906-1 stress core; you supply the permissible stress amplitude.
This is a generic Goodman model, not a DIN EN 13906-1 fatigue diagram: the standard's diagram data is proprietary and neither embedded here nor invented.
Set the inputs and calculate.
Calculate a compression spring's mean stress, stress amplitude and fatigue utilization at two working points, building on the validated EN 13906-1 stress core.
The same spring geometry and material data as the existing EN 13906-1 compression-spring calculator (wire diameter, coil diameter, number of coils, length, two deflections, tensile strength), plus a permissible stress amplitude τkH,perm from your own source.
The corrected lower and upper stresses τku, τko are taken unchanged from the existing EN 13906-1 stress core. From these follow the mean stress τm=(τko+τku)/2 and the stress amplitude τa=(τko−τku)/2. The fatigue utilization is τa/τkH,perm.
With τku≈198 MPa and τko≈396 MPa, τa≈99 MPa; at a permissible stress amplitude of 150 MPa this gives a utilization of 66%.
Sources and limits: Classical Goodman/Haigh diagram principle of fatigue strength assessment; DIN EN 13906-1's own diagram is proprietary and is not reproduced here -- the permissible stress amplitude must come from your own documented source.
Calculate a compression spring's mean stress, stress amplitude and fatigue utilization at two working points, building on the validated EN 13906-1 stress core.
Fatigue utilization under the Goodman principle compares the actual stress amplitude (the stress swing τa) against an amplitude permissible for the given mean stress. It is therefore a general, material-independent fatigue assessment method -- the specific permissible-amplitude numbers for spring wire are usually supplied by a Goodman diagram such as the one in DIN EN 13906-1.
Utilization = τa / τkH,perm
τm = (τko+τku)/2τa = (τko−τku)/2Safety = τkH,perm / τa| Symbol / input | Meaning |
|---|---|
| τku, τko | Corrected lower and upper stress at s1 and s2 respectively, taken unchanged from the EN 13906-1 stress core. |
| τm, τa | Mean stress and stress amplitude of the spring loading. |
| τkH,perm | Permissible stress amplitude at the given mean stress, from your own source (e.g. the DIN EN 13906-1 Goodman diagram or the FKM guideline). |
The same spring geometry and material data as the existing EN 13906-1 compression-spring calculator (wire diameter, coil diameter, number of coils, length, two deflections, tensile strength), plus a permissible stress amplitude τkH,perm from your own source.
Enter the same spring geometry and material data as the existing compression-spring calculator (wire diameter, coil diameter, number of coils, free length, the two deflections s1/s2, tensile strength, end type, bearing coefficient). Add the permissible stress amplitude τkH,perm from your own documented source.
With τku≈198 MPa and τko≈396 MPa, τa≈99 MPa; at a permissible stress amplitude of 150 MPa this gives a utilization of 66%.
τm sets where the working point sits on the Goodman diagram's mean-stress axis; τa is the vertical distance from that axis. A utilization τa/τkH,perm < 1 means the working point sits below the (externally determined) Goodman limit line.
Lengths in mm, tensile strength and permissible stress amplitude in MPa; results in MPa and percent or dimensionless.
Estimating whether a compression spring already sized to EN 13906-1 stays within a known permissible stress amplitude under dynamic loading between two working points (s1, s2), without re-implementing the existing spring calculator's stress formulas.
Classical Goodman/Haigh diagram principle of fatigue strength assessment; DIN EN 13906-1's own diagram is proprietary and is not reproduced here -- the permissible stress amplitude must come from your own documented source.
Common mistake: Don't confuse the permissible stress amplitude τkH,perm with the tensile strength Rm -- Rm is a static material property, τkH,perm comes from a fatigue/Goodman diagram for the specific wire grade and mean stress. Without a documented τkH,perm, the reported utilization is only a plain ratio calculation, not a DIN EN 13906-1 fatigue verification.
Because the Goodman diagrams needed for that in DIN EN 13906-1 are wire-diameter- and material-dependent, copyrighted table data not available in this project without a verified source. Instead, the calculator evaluates the general Goodman relationship using a permissible stress amplitude you supply yourself.
From the DIN EN 13906-1 Goodman diagram for the wire grade used and the calculated mean stress, or from a more current documented source such as the FKM guideline 'Analytical strength assessment of springs and spring elements'.
The existing calculator reports the stress range (corrected_stress_range) and a general warning, but does not assess it against a permissible amplitude. This calculator adds exactly that missing assessment.
The actual stress amplitude τa exceeds the entered permissible stress amplitude τkH,perm -- a calculated fatigue risk suggesting either a spring redesign or a re-check of the permissible stress value.