Week-7 Head Impact

AIM: To perform the head impact simulation from a simple ball and rigid wall to head foam and Hood, check the stresses that are developed on the hood and head foam, also calculate the Head Injury Coefficient (HIC).

PROCEDURE:

CASE1:

• First open the keyword file of simple head model and apply material properties as by selecting the MAT_024 PIECEWISE LINEAR PLASTICITY and section to be assigned with thickness of 1.5.

• Create the Rigid wall from create entity module along X direction with a distance of 15. Make sure that the rigid wall normal pointing towards the simple head model otherwise the it wil go through the rigid wall.

• Create the initial velocity keyword with 40KMPH (-11.11mm/ms) along the X direction. Then create the AUTOMATIC SINGLE SURFACE CONTACT to all the nodes of the simple head model
• Then give the CONTROL TERMINATION CARD with time as 3 ms, and in the DATABASE card ASCII and d3plot is selected with time interval as 0.1ms.

CASE2:

• Here in CASE2 the we need to create a respective folder and copy and paste the head foam into that.
• Then open a new file and give the DEFINE TRANSFORMATION card to rotate along X direction 45deg as shown in the figure.

• Then use the INCLUDE_TRANSFORM keyword and select the head form file and trans ID as DEFINE_TRANSFORMATION ID.

• Then this file in the same folder with different name, close the file and reopen the file.
• Then one can see the transformation of head foam is happened. Then create the rigid wall, initial velocity, Control termination, database cards are similar to case1.
• The only change is that we need to introduce the CONTACT SURFACE TO SURFACE to Head foam parts.

CASE3:

• In case3 create a seperate folder for this as well and copy and paste the head foam file and meshed hood file into the folder.
• Now open a new file and Create the define transformation Y direction 45 deg, and use the include transformation card and save it as seperate file.
• Again open a new file and INCLUDE_INCLUDE to add the both new file which is created after transformation and meshed hood file.

• Fix the perimeter points of the hood along Z DIR to restrict it while impact.

• The rermaining procedure is same as the case 2 like Contact, Initial velocity, control termination, Database files.

RESULTS:

The energy plots, vonmises stresses and HIC are shown in the figures below.

ENERGY PLOTS:

As one can observe from the energy plots that the there is a change in plots is due to change in the material properties in the head foam and hood.

VONMISES STRESS VARIATION:

The maximum effective stress is attained at the time of impact and decreases. In Case 1 the maximum stress 240MPa and in Case 2 the maximum stress 23.6MPa and in the case 3 the maximum stress 283.1MPa.

HIC:

As we can see from the HIC plots the HIC36 value for Case 1 is 3.656e6, in Case 2 is 8.099e4 and in Case 3 is 132.4. The HIC value is decreasing as we go on introducing the material properties of actual case to the model.

CONCLUSION:

For the given model simulation of head impact is done and got the results accordingly.