Week-7 Head Impact
OBJECTIVE:-
To perform Head Impact Simulation and calculate the HIC value in Pre-Post.
PROCEDURE:-
Case 1:- Simple Head Impact against Rigid Wall.
A planar Rigid wall was created normal to Z-axis towards which the Head is going to impact.
A *Section_Shell was created with Element Formulation 2 and Thickness 3 mm.
A *MAT_Elastic(001) card was created to assign the Elastic Material for the head.
*INITIAL_VELOCITY card was created to assign the velocity of 40 kmph (11.11 mm/ms) towards -ve Z-direction, for which a node set was created by selecting all the nodes of the sphere using *SET_NODE option under Create Entity.
CONTACT_AUTOMATIC_SINGLE_SURFACE card was used to assign the contact behaviour of the Head. The only parameter which was initialized was the SSID, which was created by selecting the entire part using *SET_PART under Create Entity.
A *CONTROL_TERMINATION card was created to ensure the running time of 2.5 ms.
Under ASCII_option, time interval of 0.1 ms was assigned for GLSTAT, NODOUT, RWFORC and MATSUM. Also, BINARY_D3PLOT card was created with the time interval fo 0.1 ms.
Post-Processing:-
The image above shows the Effective Stress of the simple head which just got collided with the Rigid Wall.
Case 2:- Pedestrian Headfoam imapcting against Rigid Wall.
Unlike previous case, in this case we ll be required to hit the head of the pedestrian at an angle of 45 degrees with respect to the rigid surface.
In order to do that, we will be using the cards DEFINE_TRANSFORMATION. This keyword will let us perform the operation such as Rotate, Scale etc to the part file reference in INCLUDE keyword. But in our case, we ll be rotating the Head of the pedestrian about Y-axis at an angle of 45 degrees, where a1-a3 defines the axis of rotation, a4-a6 defines the point through which the vector passes and a7 defines the angle of rotation in degrees.
Next, we use the keyword *INCLUDE_TRANSFORMATION which will help us make prior transformation to the default model.
A planar Rigid wall was created normal to Z-axis towards which the Head is going to impact.
*INITIAL_VELOCITY card was created to assign the velocity of 40 kmph (11.11 mm/ms) towards -ve Z-direction, for which a node set was created by selecting all the nodes of the sphere using *SET_NODE option under Create Entity.
Since the Headfoam consists of 4 subparts, so 4 material was assigned. For Skull, Accel Block and Backplate MAT_20_RIGID was used and for Skin MAT_77_OGDEN_RUBBER is used.
*CONTACT_AUTOMATIC_SURFACE_TO_SURFACE is used for Contact between Skull as Master and Skin as Slave.
A *CONTROL_TERMINATION card was created to ensure the running time of 5 ms.
Under ASCII_option, time interval of 0.1 ms was assigned for GLSTAT, NODOUT, RWFORC and MATSUM. Also, BINARY_D3PLOT card was created with the time interval fo 0.1 ms.
Post-Processing:-
Effective Stress of the Pedestrian Headfoam after colliding with the Rigid Wall
GLSTAT:-
HIC-36 Plot:-
The value of HIC is resulted to be 6.333e+04 which is almost 10 times that of the HIC value 650 as per the pedestrian test procedure protocols by EURONCAP. This result will obtain very serious injuries which can also include death.
Effective Plastic Strain:-
The effective plastic strain at node 3301 is 0.00221 at 3.70 ms.
Effective Von-Mises Stress:-
The effective Von-Mises Stress at node 3301 is 0.00465 GPA at 3.60 ms.
Case 3:- Pedestrian Headfoam impacting against Hood of the car.
Similar to Case 2, Pedestrian Headfoam was inclined at an angle of 45 degrees with respect to the Car Hood and the very file was saved under new name.
*INCLUDE keyword was used under the Car Hood file where Pedestrian Headfoam file was added and was saved under the new name.
The new file was opened where we assigned the *MAT_PIECEWISE_LINEAR_PLASTICITY(024) to the Hood and also created a *SECTION_SHELL for the same.
*INITIAL_VELOCITY card was created to assign the velocity of 40 kmph (11.11 mm/ms) towards -ve Z-direction and -ve X-direction, for which a node set was created by selecting all the nodes of the sphere using *SET_NODE option under Create Entity.
*CONTACT_AUTOMATIC_SURFACE_TO_SURFACE is used for Contact between entire Headfoam as Master and Hood as Slave.
A *CONTROL_TERMINATION card was created to ensure the running time of 20 ms.
Under ASCII_option, time interval of 0.1 ms was assigned for GLSTAT, NODOUT, RWFORC and MATSUM. Also, BINARY_D3PLOT card was created with the time interval fo 0.1 ms.
Post-Processing:-
Effective Stress contour of Headfoam colliding with Hood of the car.
GLSTAT:-
HIC-36 Plot:-
The value of HIC is resulted to be 721.6.
CONCLUSIONS:-
Case 1:- It gives us the idea of simple simulation. The simple head geometry shows no deform and has negligible strain values. This case has the highest HIC due to the rigid wall and Head.
Case 2:- It gives us an idea of the impact of Pedestrian Head with the Rigid wall. The impact result is severe and shows the plastic deformation in the head. the HIC value in this case is lower than the Case 1 but higher than Case 3 due to the similar properties of Head as in Case 1.
Case 3:- It gives us a brief idea of actual impact of Head on car hood. The hood deforms during impact cause of its elastoplastic behaviour. This impact is less severe as the HIC value as result is lower than Case 1 and Case 2, hence proves that there will be lwss head injury as compared to other two cases.