Learning Forum

[prasannaah.hadagali]

Hello,

We are currently using the Hybrid III 50th percentile Fast Standing model to simulate a fall scenario in LS-DYNA.

In our setup, the ATD is initially positioned at a height above the ground and subjected to an impact from an impactor with a prescribed initial velocity. Gravity is included in the simulation. Following the initial impact, the ATD falls and subsequently frontal pelvis contacts a rigid rail structure.

Physically, we expect the ATD to fall and settle after interacting with the rail. However, in our simulations, the model exhibits significant non-physical behavior—specifically, it rebounds excessively and remains airborne forever (even after 7000 ms of simulation time).

We suspect that this behavior may be related to contact definitions, material properties, damping, or numerical settings. While we acknowledge that the model itself is not fully validated against experimental data, the observed response appears unrealistic.

In other similar cases, the Hybrid III pelvis is not contacting the pelvis region and falling down thereby not making us feel suspicious about the issue.

We would appreciate any guidance on potential causes or troubleshooting steps to address this issue.

Thank you for your time and assistance.

[Imtiaz Gandikota]

Hello, could you please share some pictures showing the behavior? What happens if you remove the initial velocity? Does the ATD fall and settle? How is the contact between ATD and rigid rail defined?