

July 12, 2018 at 11:32 amAdisaSubscriber
Hi everybody,
I am trying to do sphere test on the simple . Can anyone has advice for this test. In this example I do not know time and velocity, the height is known, can I calculate velocity from these equations:
From these equations we can get that the velocity is: v = g*sqr(2*h*g);
Whether this can be used that calculates free fall sphere from height of 50 mm. From these equations I can see that the mass has not affect on the magnitude of the velocity. Do I need to use another equation to calculate velocity.
Or can I drop the sphere nearer the another part for reducing time for solving but that the sphere has the same velocity, which would simulate drop of the sphere from 50mm.
Does anyone know how to do this analysis.
Best regards.

July 12, 2018 at 11:58 ampeteroznewmanSubscriber
Hello Adisa,
I have done many simulations of impact due to a sphere being dropped on an object, since it is part of a Safety Standard.
First, measure the drop height, h, from the bottom of the sphere to the surface, not the center.
Second, calculate the impact velocity from an equation with g and h. For h = 0.05 m, v = 0.99 m/s.
Third, use CAD to move the sphere to be tangent to the surface. Check that the initial contact status is closed. Use Adjust to Touch if it isn't.
Fourth, assign the initial velocity calculated in step 2 to the sphere.
In Analysis Settings, select an initial time step to capture the beginning of the compression of the contact area. For example, if the sphere is travelling at 1 m/s and its diameter is 0.005 m, choose 2% of the diameter as the first time step, so a distance of 0.0001 m at 1 m/s takes t = 1e4 seconds.
ANSYS will automatically increase the time step as the Transient Structural analysis solves.
Best regards.

July 12, 2018 at 12:49 pmAdisaSubscriber
Peter, thank you for all. You are the best teacher which I know.
Yes, from the link which you posted use the same equations from the first post, but I am now confused.
OK, For Ansys I understand how to do this analysis, from your steps, but the velocity from these equation will be the same for difference the sphere, for example: If I am using the sphere with 5 or 15 mm diameter the velocity of the sphere will be the same. The mass do not have affect at the speed of the sphere. Maybe the velocity of the sphere with diameter 15mm will be bigger than with 5mm.
Maybe in Transient Structural need to include Standard Earth Gravity. I do not know, maybe I am wrong.
Thank you.

July 12, 2018 at 2:46 pmpeteroznewmanSubscriber
If the 5 and 15 mm start the same distance from the bottom of the sphere to the impact surface, they will have the same velocity. Only if you are talking about a huge height, then mass does make a difference to the terminal velocity where you have to include air resistance.
Yes, you can turn on Standard Earth Gravity. If you simulate for long enough, you can see the sphere rebound, slow down and fall again, but you probably don't care after the sphere has lost contact with the plate after the impact is over.
Best regards.

July 12, 2018 at 10:23 pmAdisaSubscriber
Yes, You are right, so far i though the sphere with bigger the mass has bigger the velocity.
I saw a few video, where It is true.
Thank you.

July 12, 2018 at 11:09 pm

July 13, 2018 at 7:06 amAdisaSubscriber
Thank Peter,
Does your the first post in this discussion can be used and for drop test. Or I need to do other set up.
Peter, one more, thank you!

July 13, 2018 at 11:25 ampeteroznewmanSubscriber
The method in my first post in this discussion applied to any drop test simulation.

 You must be logged in to reply to this topic.
Simulation World 2022
Check out more than 70 different sessions now available on demand. Get inspired as you hear from visionary companies, leading researchers and educators from around the globe on a variety of topics from lifesaving improvements in healthcare, to bold new realities of space travel. Take a leap of certainty and check out a session today here.
Earth Rescue – An Ansys Online Series
The climate crisis is here. But so is the human ingenuity to fight it. Earth Rescue reveals what visionary companies are doing today to engineer radical new ideas in the fight against climate change. Click here to watch the first episode.
Ansys Blog
Subscribe to the Ansys Blog to get great new content about the power of simulation delivered right to your email on a weekly basis. With content from Ansys experts, partners and customers you will learn about product development advances, thought leadership and trends and tips to better use Ansys tools. Sign up here.
 How to calculate the residual stress on a coating by Vickers indentation?
 An Unknown error occurred during solution. Check the Solver Output…..
 Saving & sharing of Working project files in .wbpz format
 Solver Pivot Warning in Beam Element Model
 Understanding Force Convergence Solution Output
 whether have the difference between using contact and target bodies
 Colors and Mesh Display
 The solver engine was unable to converge on a solution for the nonlinear problem as constrained.
 Massive amount of memory (RAM) required for solve
 What is the difference between bonded contact region and fixed joint

1862

1661

913

670

349
© 2022 Copyright ANSYS, Inc. All rights reserved.