## LS Dyna

#### Helmet ball dynamic impact- major help required

• Balistic028
Subscriber

hello all

I would like to simulate a cricket ball striking a cricket helmet. the purpose of the simulation is to study the energy absorption characteristics of different materials used in the helmet. The setup below includes, a helmet, a ball and a rigid body inside the helmet that acts as the skull(very crude representation of skull). I have defined the skull as a rigid body, however, it still meshes although rigid bodies aren't supposed to mesh. Now to the contact regions. I'm quite confused when to define these as frictionless or bonded between the helmet and the skull, the ball is frictionless obviously. Furthermore, would I need to 2 body interactions, one between the helmet and skull and one between the helmet and ball. Now when setting up the BC's ive given the ball a velocity in the -Y direction(45m/s) and the rigid body a fixed support. once again, I'm confused as to how the rigid body allows the fixed support, I thought ANSYS doesn't allow to fix rigid bodies. now onto the results. The stress values obtained for the same BC's on two different material were way off each other, isn't stress supposed to be very similar since its not material dependent? lastly, I tried extracting the energy dissipated per unit volume but ANSYS throws an error.

I would be really grateful if anyone could help me in detail! :)

• Ram Gopisetti
Ansys Employee
i dont see that the part is rigid?, an single body interaction might be ok with this model. you need an initial velocity not velocity, what do you mean by "different materials" and stress is response by an material and indeed there is an strict mutual relation. what is the error ?
Cheers, Ram
• Balistic028
Subscriber
hello
I've got the model working now, so my job is a feasibility study of structural behaviour of cricket helmets made using different materials(materials- ABS plastic, carbon fibre, glass fibre). What parameters would you recommend I look into, I was told to looking into how each material attenuates the impact energy across its geometry. I tried getting the Energy dissipated per unit volume but this option is greyed out for some reason.