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I am creating a simulation and am interested in pulling stretchy things and when they break, like taffy. I imagine this is a bit tougher then a simple equation like gravity, but I have no idea.

Is there a general equation for an object's threshold and pulling it apart?

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IMO you'd need a stress-strain graph for taffy. A quick internet search reveals nothing. Would be something nice to investigate, worthy of an Ig Nobel prize. – Manishearth Feb 25 '12 at 11:49
look into elasticity and plasticity , – anna v Feb 25 '12 at 11:54
@annav Elasticity won't help; taffy is nearly perfectly plastic. Plasticity has no fixed equation; only stress-strain curves. – Manishearth Feb 25 '12 at 12:46

1 Answer 1

Like most materials, toffee (UK English) is elastic under low loads and plastic under greater loads. However, its response is highly dependent on both temperature (obviously?) and strain rate. If you load it quickly, it will fracture but, if you load it slowly, it will deform plastically. There's then a different stress-strain curve for each value of strain rate, which makes it difficult to analyse (although there are finite element studies of toffee in the literature). In practical terms, if you want to break a slab of toffee, hit it with a (toffee) hammer or bash it against your elbow.

More info: see Wikipedia Viscoplasticity.

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