Solid - solid impact force peak

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Discussion Overview

The discussion revolves around calculating the peak force of an impact between two solid objects, exploring various factors that may complicate this calculation, such as material properties, impact velocity, and potential fracturing of the objects involved. The scope includes theoretical considerations, mathematical reasoning, and implications of high-speed impacts.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant suggests that the peak force calculation is related to how readily the structure compresses, but acknowledges uncertainty about additional complicating factors.
  • Another participant proposes using equations of motion to estimate peak deceleration and force, while noting that this assumes non-elastic impacts and constant deceleration.
  • A third participant emphasizes the importance of impact velocity in determining peak force, contrasting slow and fast impacts.
  • One participant inquires about equations applicable to extremely high-speed impacts (around 3000 meters per second), particularly involving metals and ceramics.
  • Another participant expresses skepticism about finding relevant information for high-speed impacts, suggesting that such scenarios may resemble explosions rather than traditional impacts.
  • A later reply mentions that at high speeds, the stress cannot exceed the crushing stress of the material, and notes the dependence of material properties on strain rate, indicating a lack of readily available data for high-velocity impacts.

Areas of Agreement / Disagreement

Participants express differing views on the factors influencing peak force calculations, particularly regarding the role of impact velocity and the nature of the materials involved. There is no consensus on a definitive method or equation applicable to high-speed impacts.

Contextual Notes

Limitations include the vagueness of the initial question, the dependence on specific material properties, and the challenges in obtaining accurate data for high-velocity impacts. The discussion highlights the complexity of modeling impacts without resolving the various assumptions and conditions involved.

pixelpuffin
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how would i go about calculating the peak force of an impact between two solids
i assume it has to do with the how readily the structure compresses but I am not sure what else might complicate it from there
also what if one of the objects fractures and what about granular impacts
 
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It's very hard unless you make assumptions.. Consider dropping a ball onto something soft like clay...

If the ball comes to a stop making an impression "s" meters deep then you can estimate the peak deceleration "a" using the equations of motion...

V2 = U2 + 2as

where

V=0
U = Impact velocity

Solve for "a"

Then use F = ma to calculate the force.

However this assumes the impact is non-elastic and constant deceleration.

If the situation is more complicated (eg the second object fractures) you could use another method (such as high speed camera) to measure the deceleration of the first object directly.
 
pixelpuffin said:
how would i go about calculating the peak force of an impact between two solids
i assume it has to do with the how readily the structure compresses but I am not sure what else might complicate it from there
also what if one of the objects fractures and what about granular impacts

Your question is extremely vague.

For example, bring two solids slowly together until they finally touch. Now, compare this to slamming those two very, very hard. Do you think there's a difference in "peak force of an impact between two solids"?

You emphasized on the nature of the solid itself when you ignore information on the most important aspect of an impact, the velocity of the collision itself! I've tried to illustrate to you something obvious that you should already be aware of that is a big part of trying to analyze such a situation.

Zz.
 
i need an equation for extremely high speed (3000 meters per second maybe) most of the time involving metals and ceramics
although a high estimate will work to as long as its always a high estimate
 
I suspect you won't find it on a general physics forum although someone might surprise us. At those sort of speeds the energy will be enormous. More like an explosion than impact. Might be meaningless to talk about a "peak force" when everything is turned into a gas?
 
id like to see just how large of a projectile is needed to survive and various angles
 
Your impact speed is the same order of magnitude as the speed of sound in most engineering materials, so you are out of the range of any "simple" approximations to what happens.

Almost by definition, the stress can't exceed the crushing stress of the material, without breaking something. If you don't want to do any modeling of the impact, that is probably as good a "maximum force" estimate as anything else.

But material properties depend on the strain rate, so you won't find good quality good material data for high velocity impacts just lying around on the web.
 

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