Learning Forum

[Mohamed Albordini]

Hi everyone,

I'm running drop test simulations on explicit dynamics in workbench. I'm simulation an apple falling from a drop height of 2 meters under standard earth gravity. I want to simulate the deformation once the apple lands on the rigid surface.


Here are some the challenges I'm facing:

1. An apple is not a perfect sphere. How do I include some physical and mechanical properties of the apple e.g.
~Equatorial diameter
~Polar diameter
~Thickness
~Shape index
~Volume
~Curvature radius

2. I assumed a perfect sphere for the initial simulations. However, the apple bounced off the rigid structural steel surface like a tennis ball would. How can I overcome this and effectively realize a simulation that depicts normal reaction of the apple in such a scenario

3. Change in color depicts change in deformation to a varying extent. However, there is change before the apple hits the surface. What could be the issue and how can I overcome it.

[peteroznewman]

You will need material properties for the apple skin and the apple fruit that is under the skin.  These two materials have very different properties. Do some research on the internet and see if you can find some published mechanical properties for at least these two materials. You might choose to ignore the apple core material in this first model.

If you can't find apple material properties, I suggest you choose to simulate the drop test on an object that you can find material properties for.

 

[Mohamed Albordini]

Thank you. What about changes in color despite the sphere not hitting the ground?

[peteroznewman]

If the apple was 2 m above the ground, and you plot Deformation, the color will change as the apple falls because Deformation measures the distance from the starting point.  If you were to plot Stress, then the color wouldn't change as the apple falls because there is no change in stress as if falls.

Drop Test simulations are usually performed by positioning the object tanget to the ground and assigning the impact velocity to the object. That way no time is wasted simulating the free-fall.  All the simulation effort is on the deformation following the impact which occurs at T=0 seconds.