Pedestrian Head Impact
Objective:
In this report, I will conduct a head impact simulation. To assess the safety of a child head after impact, the HIC and acceleration values need to be taken care of. A high value of HIC indicates a more probability to more injury.
There are 3 cases in this simulation:
Case 1: A Simple Head Impacting a Rigid Wall
- Model Set-up:
- Simple Head is simulated by shell elements with Elastic material density 1.088e-06 kg/mm^3, E = 14 GPa, Poisson’s ratio = 0.493.
- Simple Head has an initial velocity of 50 km/h = 11.11 m/s --> divided into 2 directions: Vx = 7.86 m/s and Vz = -7.86 m/s.
- A rigid wall is created normal to z axis just below the simple head.
- The self contact of the simple head is used by setting CONTACT_AUTOMATIC_SINGLE_SURFACE.
- Additional Control cards to be set up are:
- CONTACT
- ENERGY
- SHELL
- HOURGLASS
- TERMINATION: endtime = 40 ms
- TIMESTEP
- Output Database cards to be set up are:
- ASCII_option: GLSTAT, MATSUM, NODOUT, RCFORC, RWFORC, SLEOUT.
- BINARY_D3PLOT
- EXTENT_BINARY
- HISTORY_NODE_SET
- Result:
Maximum von Mises stress of the head is 318 MPa.
The peak acceleration is around 31000 G’s and HIC = 9.402e+7.
Energy conservation:
Case 2: Pedestrian Head-Form Impacting a Rigid Wall
- Model Set-up:
- A Pedestrian Head Form is used. The Head is imported into Main.dyn by using *INCLUDE_TRANSFORM with rotational angle -90 degrees about y-axis.
- Head Form has an initial velocity of 50 km/h = 11.11 m/s --> divided into 2 directions: Vx = 7.86 m/s and Vz = -7.86 m/s.
- A rigid wall is created normal to z axis just below the simple head.
- Additional Control cards to be set up are:
- TERMINATION: endtime = 10 ms
- TIMESTEP
- Output Database cards to be set up are:
- ASCII_option: GLSTAT, MATSUM, NODOUT, RCFORC, RWFORC, SLEOUT.
- BINARY_D3PLOT
- EXTENT_BINARY
- HISTORY_NODE_ID
- Result:
Maximum von Mises stress of the head is 6.4 MPa.
The peak acceleration is around 4700 G’s and HIC = 2.297e+5.
Energy conservation:
Case 3: Pedestrian Head-Form Impacting a Hood
- Model Set-up:
- A Pedestrian Head Form and a Car Hood are used. The Head is imported into Main.dyn by using *INCLUDE_TRANSFORM with rotational angle -90 degrees about y-axis. The Hood is imported into Main.dyn by using *INCLUDE.
- Head Form has an initial velocity of 50 km/h = 11.11 m/s --> divided into 2 directions: Vx = 7.86 m/s and Vz = -7.86 m/s.
- The contact between the Head Form and the Hood is set by CONTACT_AUTOMATIC_SURFACE_TO_SURFACE
- Additional Control cards to be set up are:
- SHELL
- TERMINATION: endtime = 40 ms
- TIMESTEP
- Output Database cards to be set up are:
- ASCII_option: GLSTAT, MATSUM, NODOUT, RCFORC, SLEOUT.
- BINARY_D3PLOT
- EXTENT_BINARY
- HISTORY_NODE_ID
- Result:
Maximum von Mises stress of the head is 3.9 MPa.
The peak acceleration is around 98 G’s and HIC = 519.7.
Energy conservation:
Comment:
| Simple Head vs Rigid Wall | Head Form vs Rigid Wall | Head Form vs Car Hood | |
| Peak Acceleration | 31000 Gs | 4700 Gs | 98 Gs |
| HIC Value | 9.40E+07 | 2.30E+05 | 519.7 |
- From the previous results, we can see that the rigid wall adds more deceleration rate to the head models, whereas the hood induces less deceleration due to its deformable material property.
- The HIC value of the Head Form against Car Hood case therefore is less than those against the rigid wall --> hitting the head with a rigid wall increases the probability to fatality.