design of helical spring against static loading

DESIGN OF HELICAL SPRING AGAINST

STATIC LOADING

BIRLA VISHVAKARMA MAHAVIDHYALYAMECHANICAL ENGINEERING

V.V.NAGARBatch D-6

Created by:-130070119052-Parikh Manir130070119053-Parmar Dinesh130070119054 -Patel Akash130070119057 -Patel HarshGuided By:-Prof. R.G. Jivani

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

DESIGN CONSIDERATION OF HELICAL SPRING

• The design of new helical involves the following consideration. – Space into which the spring must fit and operate– Values of working forces and deflections– Accuracy and reliability needed.– Tolerances and permissible variations in specifications.– Environmental conditions such as temperature, pressure of

corrosive atmosphere.– Cost and qualities needed

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

NOMENCLATURE OF HELICAL SPRING

SPRING MATERIAL1. 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)

STRESSES IN HELICAL SPRING

• A round wire helical compression is subjected to axial force.

• The effect of axial force is equivalent to:1. Torsional T=FD/2, acting on the wire cross section2. Direct shear force F acting on wire cross section

• So stresses induced in spring wire are,1. Torsional shear stress2. Direct shear stress

1. Torsional Shear Stress: - The torsional shear stress induced in a spring wire,due to torsional

moment T=FD/2 is given by,

2. Direct Shear Stress: - The direct shear stress induced in a springwire,due to direct shear

force F is given by,

33

816dFD

dT

t

22

4

4dF

dF

d

3. Resultant Shear Stress: - Hence, the maximum resultant shear stress in the spring

wire is given by,

dt

23

48dF

dFD

Dd

dFD

218

3

CdFD 5.0183

2

8dFCK s

EFFECT OF END TREATMENT

1. Outer Diameter (Do)

2. Spring Index (C)

3. Slenderness ratio

4. Spring Deflection

5. Maximum load

7. Maximum shear stress

6. Corrected maximum stress

8. Wahl correction factor

THE MODULE CALCULATES THE FOLLOWING DESIGN PARAMETERS:

dDD 0

dDDi

DL /

GdnFC 38

maxmax kP

max'max wK

2

8dFcK s

For steel springs

BUCKLING

If free length of helical compression spring is too large as compared to the mean coil dia., the spring act as flexible column and it may buckle under the action of axial force.In order to avoid buckling, the spring must satisfy following condition

21

22

EGGE

DL

63.2

DL

SPRING TESTING MACHINE

REFERENCES

• www.wikipedia.com• A Textbook of Machine Design by R.S.KHURMI AND

J.K.GUPTA, S. Chand publication• https://centroidworks.files.wordpress.com/2008/11/design

-of-helical-spring• http://s3.amazonaws.com/pptdownload/springppt-

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