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Design of

Helical spring

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Helical spring is a spiral wound wire with a constant coil diameter and uniform pitch.

What is helical spring

Function of Helical spring

Used to store energy and subsequently release it To absorb shock To maintain a force between contacting surfaces

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Design consideration of helical spring

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C = Spring Index D/d d = wire diameter (m)D = Spring diameter (m)Di = Spring inside diameter (m)Dil = Spring inside diameter (loaded ) (m)E = Young's Modulus (N/m2)F = Axial Force (N)G = Modulus of Rigidity (N/m2)K W = Wahl Factor = [(4C-1)/(4C+5)}]+ (0,615/C)L 0 = Free Length (m)L s = Solid Length (m)n t = Total number of coilsn = Number of active coilsp = pitch (m)y = distance from neutral axis to outer fibre of wire (m)τ = shear stress (N/m2)τ max = Max shear stress (N/m2)θ = Deflection (radians)

Nomenclature of Helical spring

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Spring material

1. High carbon steel

• Music Wire (ASTM A228) • Hard Drawn (ASTM A227) • High Tensile Hard Drawn (ASTM A679) • Oil Tempered (ASTM A229) • Carbon Valve (ASTM A230)

2. Alloy spring steel

• Chrome Vanadium (ASTM A231) • Chrome Silicon (ASTM A401)

3. Stainless steel

• AISI 302/304 - ASTM A313 • AISI 316 - ASTM A313 • 17-7 PH - ASTM A313(631)

4. Copper based alloy

Phosphor Bronze (Grade A) - ASTM B159

Beryllium Copper - ASTM B197 Monel 400 (AMS 7233) Monel K500 (QQ-N-286

5. Nickel based alloy

A286 Alloy Inconel 600 (QQ-W-390) Inconel 718 Inconel X-750 (AMS 5698, 5699)

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Effect of End treatment.

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1. Outer Diameter (Do)

2. Spring Index (C)

3. Slenderness ratio

4. Spring rate (k)

5. Maximum load

7. Uncorrect maximum stress

6. Corrected maximum stress

8. Wahl correction factor

The module calculates the following design parameters:

index range is 4 to 12

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9. Maximum deflection

11. Wire length

10. Spring mass

14. Natural frequency

12. Shear stress

13. uncorrected Shear stress

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1. Stability of spring (buckling)

2. Fatigue loading

CHECKING

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Spring testing machine

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