Design of Helical Spring

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1. Design Of Mechanical Springs By : SAAD NASEER AWAN ZAID AMAD NAEEM AKHTAR ALI AKBAR MECHANICAL ENGINEERING DEPARTMENT Supervision : Muhammad Zeeshan Ali ISLAM COLLEGE OF ENGINEERING 1

2. INDEX Introduction (What is springs ?) Spring material Applications of springs Disadvantages 0f springs Types of springs Design of helical spring Conclusion 2

3. INTRODUCTION Spring is : a device used to store energy, so that when the energy is needed, it is released. They can return to their original shape when the force is released. It is defined as elastic bodies. 3

4. SPRING MATERIALS The mainly used material for manufacturing the springs are as follows : Hard drawn high carbon steel 06) Inconel Oil tempered high carbon steel 07) Monel Stainless steel 08) Titanium Copper or nickel based alloys 09) Chrome vanadium Phosphor bronze 10) Chrome silicon 4

5. APPLICATIONS OF SPRINGS To apply forces and controlling motion, as in brakes and clutches. Measuring forces, as in the case of a spring balance. Storing energy, as in the case of springs used in watches and toys. Reducing the effect of shocks and vibrations in vehicles and machine foundations. 5

6. DISADVANTAGES OF SPRINGS If the deflection of the spring exceeds some critical value than the spring will buckle . It is difficult to replace the spring Ones the spring is damaged it is difficult to repair 6

7. Helical springs Leaf springs V olute springs Beam springs Belleville springs 7 Classification of springs

8. WHAT IS HELICAL SPRING Helical spring is a spiral wound wire with a constant coil diameter and uniform pitch. FUNCTION OF HELICAL SPRING Used to store energy and subsequently release it To absorb shock To maintain a force between contacting surfaces 8

9. TYPES OF HELICAL SPRINGS 9 Tensional springs Compressional springs Spiral springs Torsional springs

10. EXTENSION HELICAL SPRING 10 It has some means of transferring the load from the support to the body. It stretches apart to create load. 2. The gap between the successive coils is small . 3. The wire is coiled in a sequence that the turn is at right angles to the axis of the spring. 4. The spring is loaded along the axis. 5. By applying load the spring elongates in action

11. COMPRESSION HELICAL SPRING Among the four types, the plain end type is less expensive to manufacture. It tends to bow sideways when applying a compressive load. 11

12. TORSION SPRING It is also a form of helical spring, but it rotates about an axis to create load . It releases the load in an arc around the axis. Mainly used for torque transmission The ends of the spring are attached to other application objects, so that if the object rotates around the center of the spring, it tends to push the spring to retrieve its normal position. 12

13. SPIRAL SPRING It is made of a band of steel wrapped around itself a number of times to create a geometric shape. Its inner end is attached to an arbor and outer end is attached to a retaining drum. It has a few rotations and also contains a thicker band of steel. It releases power when it unwinds. 13

14. LEAF SPRING Sometimes it is also called as a semi-elliptical spring, as it takes the form of a slender arc shaped length of spring steel of rectangular cross section. The center of the arc provides the location for the axle,while the tie holes are provided at either end for attaching to the vehicle body . Heavy vehicles leaves are stacked one upon the other to ensure rigidity and strenth . It provides dampness and springing function. 14

15. Beam spring The beam spring is the name commonly given to an IBM key switch mechanism which was formally referred to in some documents as the combination beam spring and fly spring or beam/fly spring interlock . It was used in almost all of the keyboards that IBM designed during the 1970s 15

16. Belleville washer spring A Belleville washer , also known as a coned-disc spring, conical spring washer , disc spring, Belleville spring is a type of spring shaped like a washer . It has a frusto -conical shape which gives the washer a spring characteristic . 16

17. Volute spring A volute spring is a compression spring in the form of a cone (a volute ). 17

18. SOME PICTURES : 18

19. 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 19

20. NOMENCLATURE OF HELICAL SPRING 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 coils n = Number of active coils p = pitch (m) τ = shear stress (N/m2) τ max = Max shear stress (N/m2) θ = Deflection (radians) 20

21. STRESSES IN HELICAL SPRING A round wire helical compression is subjected to axial force. The effect of axial force is equivalent to: Torsional T=FD/2, acting on the wire cross section Direct shear force F acting on wire cross section So stresses induced in spring wire are, Torsional shear stress Direct shear stress 21

22. 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, 22

23. 3. Resultant Shear Stress: - Hence, the maximum resultant shear stress in the spring wire is given by,

24. CONCLUSION : Spring is made of an elastic material that changes in shape , or deforms when a force is applied to it . There are a number of other spring shapes used in engineering . 24

25. THANK YOU 25