Strong Steel wire but an elastic spring? Why?

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Discussion Overview

The discussion revolves around the mechanical properties of steel wire when it is coiled into a spring, specifically addressing its tensile strength and elastic behavior. Participants explore the relationship between the wire's resistance to twisting and its performance as a spring under axial loads.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions why a strong steel wire can act as an elastic spring when coiled, suggesting a need for mathematical proof.
  • Another participant inquires about the resistance of the steel wire against twisting motions and the effects of applied torques on the wire's deformation when used as a spring.
  • A third participant requests clarification on the previous responses, indicating uncertainty about the topic.
  • A later reply explains that a straight rod experiences stress and strain when twisted and that a coiled spring can be analyzed similarly, emphasizing that shear and bending can be neglected under pure axial loads.

Areas of Agreement / Disagreement

Participants express varying levels of understanding and clarity regarding the mechanical behavior of coiled steel wire, with some points being contested and others requiring further explanation. No consensus is reached on the initial question of why the wire behaves elastically when coiled.

Contextual Notes

There are limitations in the discussion regarding assumptions about the mechanical properties of materials, the definitions of stress and strain in different configurations, and the mathematical steps needed to support claims.

Who May Find This Useful

This discussion may be of interest to students and professionals in materials science, mechanical engineering, and physics, particularly those exploring the properties of materials under different loading conditions.

tlfx1996
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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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