Extension Spring Hook Stress Calculator

Inputs

View results
Total load carried by the spring at the checked extension, including initial tension.
N
Spring wire diameter.
mm
Mean body coil diameter, typically outside diameter minus wire diameter.
mm
Inside bend radius at the hook/loop section checked in bending.
mm
Inside bend radius at the side/transition section checked in torsion.
mm
Entered allowable normal stress for the hook/end loop. Replace the default with material and supplier data.
MPa
Entered allowable torsional shear stress for the hook side and body. Replace the default with material and supplier data.
MPa

Results

Default result
Edit inputs
Hook bending stress(sigma_A)
679.1MPa
Pass

Normal bending stress at the hook/loop radius.

sigma_A = KA*16*F*D/(pi*d^3).

Also computed

Hook side torsion stress(tau_B)Pass350.1MPa

Torsional shear stress at the side/transition radius.

tau_B = KB*8*F*D/(pi*d^3).

Body-coil shear stress(tau_body)301.5MPa

Wahl-corrected body-coil stress at the same load.

Governing utilization(U)Pass0.7989

Hook stress is below the entered allowables for this static screen.

Max of bending and torsion utilization.

Screen safety factor(SF)Pass1.252

Hook stress is below the entered allowables for this static screen.

1 / governing utilization.

Hook bending factor(KA)1.333

Hook torsion factor(KB)1.375

Method notes 3 notes
  • Use the total working force in the spring at the checked extension, including initial tension.
  • Hook geometry is simplified to bend radii r1 and r2. Machine hooks, crossover loops, swivel loops, open gaps and residual forming stress can change the real peak stress.
  • This is a static screening calculation. Fatigue life, shot peening, set, relaxation, supplier catalog limits and drawing approval remain separate checks.

Powered by MachineCalcs ↗