# Wave Spring Design Theory

There are 4 critical factors when considering a wave spring –

1. Constraints of the application: Bore/shaft, ID/OD etc.
3. Working height at which the load is applied
4. Material desired

# Wave Spring Design General Considerations

• If a spring is designed for static application, make sure that the % stress at working height is less than 100%. Spring will take a set if subjected to a higher stress.
• If a spring is designed for dynamic application, make sure that the % stress at working height is less than 80%. Spring will take a set if subjected to a higher stress.
• Few things to remember:
• If the work height per turn is less than (2 * Wire Thickness), the spring will operate in a 'non-linear' range and actual loads may be higher than calculated
• Number of turns must be between 2 and 20
• Number of waves per turn (N) must be in ½ increments
• Min. Radial wall = (3 * Wire Thickness)
•  Max. Radial Wall = (10 * Wire Thickness)
• It is NOT recommended to compress a wave spring to solid

OD expansion and OD tolerance must be taken into account while designing a spring to fit in a bore and/or over a shaft

# Formulas:

Operating Stress,

 Design stresses for wave springs: Static/Low Cycles No preset : 100% of tensile strength Preset springs : 150% of tensile strength Dynamic Service 104 cycle life : 80% of tensile strength 105 cycle life : 53% of tensile strength 106 cycle life : 50% of tensile strength 107 cycle life : 48% of tensile strength

Fatigue Stress Ratio,

Where:
s = Material tensile strength
S1 = Calculated operating stress at lower working height (must be less than s)
S2 = Calculated operating stress at upper working height

 X Estimated Cycle Life < .40 : Under 30,000 .40 - .49 : 30,000 – 50,000 .50 - .55 : 50,000 – 75,000 .56 - .60 : 75,000 – 100,000 .61 - .67 : 100,000 – 200,000 .68 - .70 : 200,000 – 1,000,000 > .70 : Over 1,000,000

Deflection,                   Spring Rate,

 Multiple Wave Factor (K): N 2.0-4.0 4.5-6.5 7.0-9.5 10.0 & Over K 3.88 2.9 2.3 2.13

OD Expansion = (0.02222 Rw N T) + b

Where: