How to Calculate Spring Design
What is Spring Design?
Spring design calculates stress and deflection under load. Springs store and release energy, used in many mechanical systems.
Formula
Calculate stress: τ = (16×D×F) / (π×d³) for compression spring
- D
- D value — Variable used in the calculation
- F
- F value — Variable used in the calculation
Step-by-Step Guide
- 1Calculate stress: τ = (16×D×F) / (π×d³) for compression spring
- 2Deflection: δ = (64×N×F×D³) / (G×d⁴)
- 3Verify safety margin and fatigue life
Worked Examples
Input
Spring wire d=5mm, mean dia D=40mm, N=10 coils, F=100N
Result
Deflection ≈ 3.4 mm, stress ≈ 82 MPa
Typical mild steel spring
Common Mistakes to Avoid
- ✕Neglecting stress concentration factor
- ✕Using wrong wire properties (modulus G)
Frequently Asked Questions
Why does mean diameter matter more than wire diameter?
Spring stiffness proportional to d⁴ but stress uses d³; larger diameter dominates stiffness.
What causes spring failure?
Fatigue from cyclic loading, stress concentration at coils, corrosion.
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