SPRINGS 06112023.pptx If the material is ductile, failure is usually specified by the initiation of yielding, whereas if the material is brittle it is specified by fracture.

If the material is ductile, failure is usually specified by the initiation of yielding, whereas if the material is brittle it is specified by fracture.

1. SPRINGS Definition : A spring is a device consisting of an elastic but largely rigid body bent or molded in to a coil form that can return into a shape when e xtended or compressed. Largely springs Are made from steel.

2. Functions of spring Absorb shocks and vibrations Store energy Measure force Apply force and control motion

3. Types of Springs Tension / Extension spring Compression spring Conical Spring Torsion spring Leaf Spring Disc or Belleville spring

4. Helical spring Made up of a wire coiled in the form of Helix Can be Circular, Square and rectangular cross section Primarily intended to tensile and compressive loads

5. Helical Spring

6. TERMINOLOGY OF HELICAL SPRING Solid length Free length Diameter of coil Pitch Spring index Number of coils Wire diameter

7. Spring Index The spring index is defined as the ratio of mean coil diameter to wire diameter . C>15 Index spring is high (Buckling) C<3 Index spring is low (Cracking) Spring Index varies 4 to 12 C= 6 to 9 for close tolerances springs

8. Solid length Solid length is the total length of the spring when the spring is compressed and there is no gap between coils.

9. FREE LENGTH The free length of the helical spring is the length of the spring in an unloaded or free condition. 

10. DIAMETER OF COIL It is the diameter of the coil of the spring

11. PITCH The pitch of the spring is defined as the axial distance between two adjacent coils in unloaded condition.

12. SPRING INDEX (C) Spring index of helical spring is defined as the ratio of the mean diameter of spring (D) to the spring wire diameter (d)   Mathematically we can say, Spring Index (C) = D / d

13. Spring terminology

14. PROBLEM Design a Helical spring to carry a load of 550 N with a deflection of 25 mm. Spring index may be taken as 8. Assume the following values for the spring material. Shear stress = 360 Mpa Modulus of rigidity = 85 GPa