Nonlinear rubberband type thing - "k" dropping fast as it is stretched

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SUMMARY

The discussion focuses on achieving a specific displacement versus force curve using materials that can withstand at least 100 stretch cycles without messiness. Participants suggest exploring silicone-based materials with additives, as well as mechanical solutions like springs and cams for reliable performance. The conversation also clarifies the axes of the graph, confirming that displacement is on the x-axis and force on the y-axis. The variability in rubber band behavior is noted, emphasizing the need for precise material selection.

PREREQUISITES
  • Understanding of stress-strain relationships in materials
  • Familiarity with silicone materials and their properties
  • Knowledge of mechanical components like springs and cams
  • Basic graph interpretation skills for displacement versus force curves
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  • Research silicone additives for enhanced elasticity and durability
  • Explore the design and application of mechanical springs in force-displacement systems
  • Investigate the properties of various rubber materials for consistent performance
  • Learn about hysteresis effects in materials under cyclic loading
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Engineers, material scientists, and product designers interested in developing reliable elastic systems and understanding the mechanics of displacement versus force relationships.

Swamp Thing
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What materials can I try in order to get a curve of displacement versus force that looks somewhat like this..
(of course, there would be a small kink around the origin where the ends of the rubberband are closer together than its length, which is not shown here).

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I am looking for something that will last at least 100 stretch cycles and is not messy, so for example liquid based colloidal stuff won't be suitable. Is there something one can whip up using silicone and some additive, say? Or something that exists commonly or is available on Amazon?
 
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Swamp Thing said:
What materials can I try in order to get a curve of displacement versus force that looks somewhat like this..
A piston in a cylinder, like a bicycle pump, that is connected to a balloon. As the piston moves, high pressure is needed to begin inflating the balloon, then the pressure falls rapidly as the balloon volume rises.
 
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Swamp Thing said:
a curve of displacement versus force
the graph is not labelled.
Is stress ( force ) along the y-axis, and strain ( displacement ) along the x-axis ?
 
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Sorry... X is displacement and Y is force.

(If it was the other way round, there would be some interesting hystereses type things going on I guess)
 
That response is like a symmetrical over-centre latch.
Are the units mg, g, kg, tonne or N ?
 
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Baluncore said:
That response is like a symmetrical over-centre latch.
Are the units mg, g, kg, tonne or N ?
I just arrived here and was wanting to put your comment in. You'd done it already!

Rubber bands will not all behave the same. I would say that a spring and cam would do what you want - very reliably. As in the above, the magnitudes of force and displacement will determine how you actually realise the design.
 

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