Maximum bending moment and maximum deflection of the spring?

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Discussion Overview

The discussion revolves around determining the maximum bending moment and maximum deflection of a coil spring under a concentrated load applied in the compression direction. Participants explore the mechanics involved, including the nature of the loading and the appropriate calculations for springs.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant seeks a clear procedure and formula for calculating maximum bending moment and deflection in a spring.
  • Another participant questions the type of spring being discussed.
  • A participant clarifies that the spring in question is a coil spring subjected to a concentrated load in compression, resting on a table.
  • Concerns are raised about the concept of "bending moment," with a participant arguing that the described loading does not produce a bending moment.
  • It is noted that the maximum deflection of a compression coil occurs when the clearance between the coils is zero.
  • A participant mentions that helical springs under compression are analyzed for torsion, suggesting reference to established texts for formulas.
  • Another participant points out a potential misunderstanding regarding the units of bending moment, indicating that springs are typically loaded in pure torsion.

Areas of Agreement / Disagreement

Participants express differing views on the application of bending moment in the context of the spring's loading. There is no consensus on the correct approach to calculating maximum bending moment and deflection, as some participants challenge the relevance of bending moment in this scenario.

Contextual Notes

Participants have not reached an agreement on the definitions and calculations relevant to the spring's behavior under load, particularly regarding the distinction between bending moment and torsion.

metalsunsuccess1
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TL;DR
How do I find the maximum bending moment and maximum deflection of the spring?
How can I find the maximum bending moment and maximum deflection for a spring?

It would be very helpful if you could explain the specific procedure and formula in an easy-to-understand manner.

that's all, thank you very much.
 
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What kind of spring is this?
 
Thank you for your reply.

This assumed mechanical spring is a coil spring, and the lower part is placed on a table (not fixed), and a concentrated load is applied from above in the compression direction.

Thank you.
 
metalsunsuccess1 said:
Thank you for your reply.

This assumed mechanical spring is a coil spring, and the lower part is placed on a table (not fixed), and a concentrated load is applied from above in the compression direction.

Thank you.

So how is there a "bending moment"? The loading you described wouldn't produce one.

The "maximum deflection" of a compression coil is when the clearance between the coils is zero.
 
Helical springs subjected to compression are calculated for torsion. You can find the formulas for example in "Shigley’s Mechanical Engineering Design" or in "Roark’s Formulas for Stress and Strain".
 
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It looks like you saw the units [N.m] or [lbf.ft] somewhere and thought it was bending moment, but springs are usually loaded in pure torsion, which uses the same units, but the meaning is completely different.
 

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