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For each rubber ball named selection, LS-DYNA will create a Simple_Pressure_Volume airbag model keycard to
provide instructions on modeling the air pressure inside the rubber ball as it hits the floor.
By telling the program the amount of pressure that should be inside the ball before it hits the ground, we
correlate the relationship between the pressure and volume based on a single parameter called CN. As the value
of the CN number increases, the pressure increases and the volume decreases.
Step 6 – Create Dynamic Relaxation
Dynamic Relaxation is essentially a way of generating a preload, which is necessary because, before the ball hits
the floor, the program has to have instructions on how to inflate the ball. Because load is being introduced into
the system, kinetic energy needs to be minimized.
1. As the value of CN increases, pressure increases more as volume decreases
2. A high CN makes the rubber ball less flat as it hits the floor
3. Dynamic relaxation (Preload) is required to pressurize the airbag, or rubber ball.
Ansys LS-DYNA Simulation Software – An Example Workflow
