Ansys Learning Forum › Forums › Discuss Simulation › LS Dyna › Explicit Dynamics – Tyre and Wheel Sim – Please help › Reply To: Explicit Dynamics – Tyre and Wheel Sim – Please help
July 26, 2021 at 10:37 pm
peteroznewman
Subscriber
I recommend you start with a much simpler model to learn Explicit Dynamics. For example, don't have so much detail, make a very simple tube shape. This allows you to have larger elements which allow ED to take bigger time steps. There is an example in this discussion: /forum/discussion/22403/can-anyone-help-me-to-do-explicit-dynamics-for-turning-operation
When you have a tyre rolling along the road, do you want to simulate just the tyre with no car as if you were rolling the spare tyre by itself, or do you want to simulate the tyre connected through a suspension spring to the mass of a car?
Do the tyre on its own as a first simulation. I suggest you have an Initial Condition where the tyre spins about its axis. I had problems with a model this simple as you can read about in the links in the discussion above.
For a second simulation, add the road with bump with an initial velocity toward the tyre. Use a velocity constraint to keep the road with bump traveling in the -Z direction at 2.e+4 mm/s which is about 75 km/hour. I don't believe you want an initial velocity of 2.e+7 mm/s which is 75,000 km/hour. Yes, the road will move toward the tyre rather than have the tyre move toward the bump.
If the tyre has a 600 mm diameter, the radius is 300 mm. When the road is traveling at 2e+4 mm/s that means the angular velocity of the tyre is 2e+4/300 = 66.67 radians/sec = 159 RPM so the road speed and tyre surface speed are equal.
Don't use any contact. ED will automatically add Body Interactions. That is all you need. Make the density of the tyre 1000 times larger that reality to make the simulation time step 10 times larger which will reduce the simulation time.
Since you will have the tyre spinning and the road moving as initial conditions, position the bump so it is tangent to the tyre. That way, the simulation can begin at the time of impact and you don't have to waste computations where two bodies move with nothing interesting happening.
When you have a tyre rolling along the road, do you want to simulate just the tyre with no car as if you were rolling the spare tyre by itself, or do you want to simulate the tyre connected through a suspension spring to the mass of a car?
Do the tyre on its own as a first simulation. I suggest you have an Initial Condition where the tyre spins about its axis. I had problems with a model this simple as you can read about in the links in the discussion above.
For a second simulation, add the road with bump with an initial velocity toward the tyre. Use a velocity constraint to keep the road with bump traveling in the -Z direction at 2.e+4 mm/s which is about 75 km/hour. I don't believe you want an initial velocity of 2.e+7 mm/s which is 75,000 km/hour. Yes, the road will move toward the tyre rather than have the tyre move toward the bump.
If the tyre has a 600 mm diameter, the radius is 300 mm. When the road is traveling at 2e+4 mm/s that means the angular velocity of the tyre is 2e+4/300 = 66.67 radians/sec = 159 RPM so the road speed and tyre surface speed are equal.
Don't use any contact. ED will automatically add Body Interactions. That is all you need. Make the density of the tyre 1000 times larger that reality to make the simulation time step 10 times larger which will reduce the simulation time.
Since you will have the tyre spinning and the road moving as initial conditions, position the bump so it is tangent to the tyre. That way, the simulation can begin at the time of impact and you don't have to waste computations where two bodies move with nothing interesting happening.
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