Strong Steel wire but an elastic spring? Why?

AI Thread Summary
Steel wire exhibits strong tensile strength, allowing it to function as an elastic spring when coiled. The coiling process enables the wire to withstand twisting motions and opposing torques, similar to how a straight rod would resist such forces. Stress and strain can be analyzed in both the straight and coiled forms under torque applications. When loaded axially, the coiled spring's resistance to shear and bending can be neglected, focusing solely on the axial load. Understanding these principles can clarify the mechanical behavior of steel wire in spring applications.
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The steel wire can withstand strong tensile stress, but when the steel wire is being coiled into a spring it can be an elastic spring. Why is this? Can this be proven mathematically?
 
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How much resistance will that strong steel wire provide against a twisting motion, opposing torques applied to opposite ends of the wire, which is most of the relative deformation in the case of a spring?
 
I'm sorry, can you explain your answer straight away. Ii'm not sure of the answer. thx
 
A straight rod will have some resistance to being twisted or having a torque applied to it. There will be a stress and strain asscociated with the amount of twist.

Now coil up the rod into the shape of a coiled spring. If a force is put on the spring, the rod, or rather a cross section through a part of the coiled rod, even though coiled up, can be analyzed for the stress and strain in the same manner as the straight rod experiences a torque.

For a coiled spring loaded axially,
http://www.codecogs.com/library/engineering/materials/springs.php
http://nptel.iitm.ac.in/courses/Web...ials/lects & picts/image/lect20/lecture20.htm

When they say shear and bending can be neglected, they mean a pure axial load, so no sideways force or a moment is to be applied to the spring.
 
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