Deformation of a spring

Mar 2016
37
0
Manchester
I am having a little trouble visualizing what is happening with a specific scenario regarding the full extension of a spring.

The question is as follows:

When the spring reaches an extension of 0.045m, the load on it is gradually reduced to zero. On the graph, sketch how the extension of the spring will vary with load as the load is reduced to zero.

I attached an image of the graph and was hoping someone could help me by showing the sketch.
 

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Apr 2015
1,142
297
Somerset, England
Your unloading curve has to account for the 'permanent set' created by the fact that you have stretched the spring beyond the elastic limit.

Look here, particularly at fig 9

http://www.ce.memphis.edu/1101/notes/concrete/section_1_strength_of_materials.html

I would draw a straight line through B, parallel to the straight (elastic) section of the graph.

The difference between where this intersects the x axis and the origin is the value of the permanenent set.