Date : 2016-06-23 12:24:21

Classification of helical springs:

Helical spring

The figures below show the schematic representation of a helical spring acted upon by a tensile load F and compressive load F. The circles denote the cross section of the spring wire.

The cut section, i.e. from the entire coil somewhere we make a cut, is indicated as a circle with shade.

If we look at the free body diagram of the shaded region only (the cut section) then we shall see that at the cut section, vertical equilibrium of forces will give us force, F as indicated in the figure.

This F is the shear force. The torque T, at the cut section and its direction is also marked in the figure.

There is no horizontal force coming into the picture because externally there is no horizontal force present. So from the fundamental understanding of the free body diagram one can see that any section of the spring is experiencing a torque and a force.

Shear force will always be associated with a bending moment.

However, in an ideal situation, when force is acting at the centre of the circular spring and the coils of spring are almost parallel to each other, no bending moment would result at any section of the spring ( no moment arm), except torsion and shear force.

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