Pedestrian head impact - as per FMVSS 201 for occupant safety

OBJECTIVE:

1. Study the pedestrian head impact with simple head and LSTC pedestrian head form with two scenerios.

• Impact with rigid wall
• Impact with car hood

2. Study the pedestrian head impact for given velocity range and angle.

• Velocity = 20kmph, angle of impact = 35 degrees.
• Velocity = 40kmph, angle of impact = 75 degrees.

DELIVERABLES:

1. The impact simulation of a simple head impact with the Rigid wall.
2. The impact simulation of the Headform provided with the Rigid wall with the Stress / Strain plots and acceleration plot.
3. The impact simulation of the head form with the Hood with the Stress / Strain plots and acceleration plot. For the hood, you can use Aluminium.
4. The Stress / Strain plot from the Rigidwall simulation should be compared with the Stress / Strain plot from the Hood Simulation and there should be a detailed explanation if there is any difference in the plots

KEYWORD FILES TO BE INCLUDED:

A set of input files are provided, which are to be included in the main solver file.

• Keyword file for simple head: Simple_Head_Model.k
• Keyword file for LSTC Pedestrian headform: PEDESTRIAN_HEADFORM.k
• Keyword file for automotive hood: Meshed_Hood.k

NOTE: In case of Meshed_Hood. k import. We define material (Aluminium) and section thickness as per our requirement.

NOTE: The LSTC Headform is imported as it is, without any change, under defined transformation defined in DEFINE_
TRANSFORMATION

DESIGN OF EXPERIMENT:

Load conditions

The load conditions vary in every case. The load varies due to magnitude of velocity and angle of impact assigned to Headform.

Boundary conditions

The boundary conditions are same as Hood is constrained by single point contact in translational x,y and z and rotational x,y and z.

Time step

The time step for this explicit experiment is 0.1ms to get the coarse data and time step is calculated to compensate the flow of stress in aluminium hood. (t = 0.0036ms)

LS PrePost file

The BCs and LCs are in the main solver file, and LSTC headform and hood is imported into main file.

The transformations are defined *DEFINE keyword and *INCLUDE_TRANSFORMATION is used to import headform and hood under transformed conditions.

Post processing:

Resultant acceleration and HIC(d) values are calculated for each case. Results are compared in few cases.

Basically, we need to study the effects of impact on headform and quantify the effect using HIC(d).

We aslo aim to compare results for impact on hood for various thickness.

Comparison for data:

• The stresses for headform in collision with hood and rigid wall is compared at 30kmph and 35 degrees.
• The resultant acceleration are compared in collision with hood and rigid wall is compared at 30kmph and 35 degrees.
• The resultant acceleration and HIC(d) values are compared in collision with hood and rigid wall is compared at 30kmph and 35 degrees.
• The stresses induced in hood when impacted at 30 kmph at 35 degrees, where imported hood differs in thickness. (1.5mm-2mm-2.5mm)

CASES:

CASE1: Simple head at 30kmph with rigid wall.

CASE2: Head form at 30kmph, 35 degrees with rigid wall.

CASE3: Head form at 30kmph, 35 degrees with hood. (1.5 mm thickness)

CASE4: Head form at 40kmph, 75 degrees with rigid wall.

CASE5: Head form at 40kmph, 75degrees with hood. (1.5 mm thickness)

CASE6: Head form at 30kmph, 35 degrees with hood (2 mm thickness)

CASE7: Head form at 30kmph, 35 degrees with hood (2.5 mm thickness)

THEORY:

Pedestrian safety:

Pedestrian Safety is a CAE study by which we determine the effects on the head of human body parts in the event of collision with the automobile.

This helps in making cars safer for pedestrians.

Impact with automobile is at different angles and sides of automobile. Similarly, effects on various sections of body are deduced such as Head, upper legs (thighs), lower leg, and knee at a particular speed range.

Head Impact:

The effects of the impact on head is discussed in this report. The head impact on collision at a certain velocity and angle is studied in pedestrian head impact, results are quantified and effects are studied and tabulated.

The effects are quantified using Head Impact Coefficient (HIC)

A universal expression for HIC is given below, It is called Free Motion Headform HIC:

HIC = max(t1,t2) {[1/(t1-t2)`int`a(t)dt]^2.5 * (t1-t2)} where integration is from t1 to t2`

There are various standards according to which Free Motion Headform HIC can be formulated as a finite value:

As per Federal Motor Vehicle Safety Standard (FMVSS) No. 201,

HIC(d) = 0.75446 * (Free Motion Headform HIC) + 166.40.

There are various levels of consequences and HIC value determine the probability of those levels prevailing:

LEVEL1: Slight damage to brain (headache, dizziness, contusion)

LEVEL2: Detached ratina, 15 mins consiousness, nose fracture, contusion with or without skull fracture.

LEVEL3: Detached ratina, 15 mins consiousness, nose fracture, contusion with or without skull fracture. Multiple skull fracture, loss of vision, multiple facial fracture, and unconsciousness without any neurological damage.

LEVEL4: Multiple skull fracture with neurological damage.

LEVEL5: More than 12 hours of unconsciousness, hemorrage in skull and critical neurological condition.

LEVEL6: Death, cervical fracture with damage to spine.

For Example:

If HIC(d) = 650

Level1: 90% probability

Level2: 55% probability

Level3: 20% probability

Level4: 5% probability

NOTE:

1. Time interval for HIC calculations is < 36ms as injury is not increased or decreased if time is greater than 36 ms.

2. For HIC calculation we only consider acclrn/ deacclrn peaks which last atleast 3ms because such Severity Index values only create damage to pedestrian on impact. sometimes we also consider interval <15 ms.

Type of analysis:

In case of aluminium hood, we need to decide on what kind of simulation we need to run.

We need to study the stress propogation

We need to consider inertia effects.

We need to calculate a proper time step.

Stress propogation in aluminium.

speed of shear stress propogation, c = `root`(G/`rho`)

where G = Shear modulus of rigidity

`G = E/2*(1+ν)`

`time step, t = L/c`

where L is element length.

Computing for Aluminium.

so G = 70/2(1+0.33) = 27 GPa

Now `rho`= 2.77e-6 Kg/mm3

so c = `root`(27/ 2.77e-6) = 3122 mm/ms

`time step, t = 11/3122 = 3.52e-3`` ms

`dt = 0.00352 ms`

Time step should be greater than 0.00352 ms

______________________________________________________________________________________________________________________________________________________________________

CASE1: Simple head at 30kmpl with Rigid wall

KEYWORDS:

*INCLUDE

This keyword helps in importing an external file into the main solver file as:

• It helps in getting data drom read-only files.
• It helps in inter-team collaboration.

Include>>Include>>Enter path>>Insert>>Accept>>OK

Path of file:- ../../Simple_Head_Model.k

Save the Input file 2 steps down from included file.

Load Input file, and input file parameters will be available in loaded input file.

Here, no transformations are entered in included file and it is included as it is in the main solver file.

*SET

1. Set of nodes created to assign velocity to the simple head.

Create Entity>>Set Node>>Create>>select all nodes of head using area selection>>Apply

NSID = 1

*RIGIDWALL

Create Entity>>Rigidwall>>rigidwall>>Planar>>select node>>translate -15mm>>apply.

*CONTACT

As elements of head need not to penetrate eachother so single surface contact need to be defined.

Automatic_single_surface.

SSID = as PID

SSTYP = 3

*INITIAL

To assign velocity to set node NSID =1

Velocity = 30kmpl = 30*1000*1000 mm/ 60*60*1000 ms = 8.333 mm/ms

velocity is in negative x direction.

*CONTROL

1. Energy - To balance the energy as hourglass energy to be included.

2. Termination - 20ms

As 15mm/(8.333 mm/ms) = 1.80 ms is the time of approach.

so impact is studied for 18.20 ms.

*MATERIAL

024_PIECEWISE_LINEAR_PLASTICITY

1. MID =1

2. DENSITY = 7.850e-6

3. YOUNGS MODULUS = 2010

4. POISONS RATIO = 0.3

5. YIELD STRESS = 0.3115

6. ETAN = 1.3

*SECTION

1. Shell elements

2. ELFORM = 2

3. SectionID = 1

*PART

1. SecID =1

2. MatID =1

3. PartID =5

*DATABASE

1. ASCII output files

• GLSTAT, DT = 0.5
• NODOUT, DT = 0.5
• RWFORC, DT = 0.5

2. BINARY.D3PLOT, DT = 0.5

3. EXTENT_BINARY, STGFLAG = 1 to compute the elstic stress and strain in the body.

4. HISTORY_NODE, for Node 69022 to compute the HIC(d) and resultant acceleration.

POST PROCESSING:

Simulation video:

VIDEO 1.1 Simulation of Simple head impact with Rigid wall.

V-m Stress/ Efective plastic Strain with time. and Stress Vs Strain plots (For element #15342)

Element #15342

Figure 1.1 The position of element #15342.

Plot 1.1 Plot of Stress/ Strain with time. Plot of Stress Vs Strain.

Rigidwall forces:

Plot 1.1 Rigid wall forces with time.

Energy Plot:

Plot 1.2 depicting the energies

Acceleration plot:

Plot 1.3 Acceleration with time.

________________________________________________________________________________________________________________________________________________________________________

CASE2: Pedestrian Headform at 30kmph, 35degrees with Rigid wall.

Keywords:

*DEFINE

Transformation 1:

*DEFINE_TRANSFORMATION

TRANID = 1

Title: Headform_y_35degrees

ROTATE: 0 1 0 0 0 0 35

Here, a line inclined at 35 degrees with Y and perpendicular to X and Z is included as transformation

The imported file will be inclined to 35 degrees with Y.

*INCLUDE

The file included is of LSTC Pedestrian headform which contains modelling for headform

LSTC.PEDESTRIAN_HEADFORM_CHILD.180605_V1.03.2BETA.k

Figure 2.1 LSTC Headform. Filename - PEDESTRIAN_HEADFORM.k

*INCLUDE_TRANSFORMATION

TranID = 1

Path: ../../../PEDESTRIAN_HEADFORM.k

As imported files is 2 steps up from the location of main solver file.

Using this file headform is imported at an angle 35 degrees with Y.

Figure 2.2 Pedestrian headform imported into main solver file under above mentioned transformations. (RIGHT SIDE VIEW)

Figure 2.3 Pedestrian headform imported into main solver file under above mentioned transformations. (ISO-METRIC VIEW)

Figure 2.4 Pedestrian headform imported into main solver file under above mentioned transformations. (FRONT VIEW)

*INITIAL

To assign velocity to headform nodes, it is very much necessary to create a set of nodes.

*SET_NODE

Title: Velocity_nodes

NSID = 3

All nodes of headform are selected by area box.

*INITIAL_VELOCITY

NSID = 3

Velocity = 30 kmph = 8.3333 mm/ms

The velocity vector is in X-Z plane.

X componenet of velocity at 35 degrees with X.

Vx = -8.333cos 35 = -6.826 mm/ms

Z componenet of velocity at 35 degrees with X.

Vz = -8.333sin 35 = -4.779 mm/ms

Figure 2.5 Velocity vector for headform. (Right side view)

*CONTACT

Contacts are established to avoid penetration of skull into skin.

Contacts are established to avoid penetration of skin into hood.

Self contacts are established to avoid self penetrations of componenets.

*AUTOMATIC_SURFACE_TO_SURFACE

MSTYP = 3 to define part set id.

SSTYP = 3 to define part set id.

SSID = 2 (skin)

MSID = 1 (skull)

To avoid penetration of skull into skin

*CONTROL

Termination = 40ms

The solution of problem will happen for this time period.

*DATABASE

ASCII

*GLSTAT, dt = 0.5 - To retrieve data for energies.

*NODOUT, dt = 0.5 - To retrieve data for node specified under *History_node

*BINARY.D3PLOT, dt = 0.5 - to retrieve binary file for post processing.

*EXTENT_BINARY, STRFLG = 1 - to retrieve data for stress and strain with time.

Post-Processing:

Simulation Video:

VIDEO 2.1 S

Resultant acceleration for Head_Accelerometer. (Node 25679)

Plot 2.2 Resultant acceleration readings from head_accelerometer

Head Impact Coefficient calculation:

Head_accelerometer data is calculated for peak accleration to quantify the effect of collision.

Plot 2.3 HIC36 and HIC(d) value from resultant acceleration.

`triangle`T = 1.5 ms

Free motion headform HIC = 4405

HIC(d) = 3490

Hand calculation:

Average accleration = 370

a`=int370.dt` for t = 3.5 to 5 = 555

b`= a/(t2-t1) = 555/1.5 = 370`

c`= b^2.5 = 370^2.5 = 2633324.0`

d= c x dt = 2633324.0 x 1.5 = 3949986.117

`HIC = d/1000 = `3949.986`

`HIC(d) = 0.75446*(HIC)+166.40`

HIC(d) = 3146.5064

Table 2.1 Data from LS Prepost and hand calculations for HIC and HIC(d)

_______________________________________________________________________________________________________________________________________________________________________

CASE3: Pedestrian Headform at 30kmph and 35degrees with Meshed hood.

DESIGN OF EXPERIMENT:

The included files are for Hood and LSTC Hadform.

The main solver file contains the boundary conditions and the Load conditions.

The main solver file also contains the output files and termination and time step.

*KEYWORDS

*DEFINE

Transformation 1:

*DEFINE_TRANSFORMATION

TRANID = 1

Title - Hood

SCALE - 0 0 0 0 0 0 0

It is a dummy transformation, and it will import the included file as it is.

Transformation 2:

*DEFINE_TRANSFORMATION

TRANID = 2

Title: Headform_y_35degrees

ROTATE: 0 1 0 0 0 0 35

Here, a line inclined at 35 degrees with Y and perpendicular to X and Z is included as transformation

The imported file will be inclined to 35 degrees with Y.

*INCLUDE

The file included is of LSTC Pedestrian headform which contains modelling for headform

LSTC.PEDESTRIAN_HEADFORM_CHILD.180605_V1.03.2BETA.k

Figure 3.1 LSTC Headform. Filename - PEDESTRIAN_HEADFORM.k

The file included is a meshed hood which comprised of quad-tria shell elements.

Figure 3.2 Meshed hood. File name- Meshed_Hood.k

*INCLUDE_TRANSFORMATION

TranID = 1

Path: ../../../Meshed_Hood.k

As imported file is 2 steps up from the location of main solver file.

Using this file hood is imported as it is into main solver file.

TranID = 2

Path: ../../../PEDESTRIAN_HEADFORM.k

As imported files is 2 steps up from the location of main solver file.

Using this file headform is imported at an angle 35 degrees with Y.

Figure 3.3 Meshed hood and headform imported into main solver file under above mentioned transformations. (ISO-METRIC VIEW)

Figure 3.4 Meshed hood and headform imported into main solver file under above mentioned transformations. (RIGHT SIDE VIEW)

Figure 3.5 Meshed hood and headform imported into main solver file under above mentioned transformations. (FRONT VIEW)

*INITIAL

To assign velocity to headform nodes, it is very much necessary to create a set of nodes.

*SET_NODE

Title: Velocity_nodes

NSID = 3

All nodes of headform are selected by area box.

*INITIAL_VELOCITY

NSID = 3

Velocity = 30 kmph = 8.3333 mm/ms

The velocity vector is in X-Z plane.

X componenet of velocity at 35 degrees with X.

Vx = -8.333cos 35 = -6.826 mm/ms

Z componenet of velocity at 35 degrees with X.

Vz = -8.333sin 35 = -4.779 mm/ms

Figure 3.6 Velocity vector for headform. (Right side view)

*CONTACT

Contacts are established to avoid penetration of skull into skin.

Contacts are established to avoid penetration of skin into hood.

Self contacts are established to avoid self penetrations of componenets.

*AUTOMATIC_SURFACE_TO_SURFACE

MSTYP = 3 to define part set id.

SSTYP = 3 to define part set id.

SSID = 2 (skin)

MSID = 1 (skull)

To avoid penetration of skull into skin

MSTYP = 3

SSTYP = 3

SSID = 2 (Skin)

MSID = 2000300 (Hood)

To avoid penetration of skin into hood.

*AUTOMATIC_SINGLE_SURFACE

SSTYP = 3

SSID = 1,2,3,4,5,2000300

To avoid self penetration or buckling and to study plastic strain and fracture.

*CONTROL

Termination = 50ms

The solution of problem will happen for this time period.

*DATABASE

ASCII

*GLSTAT, dt = 0.5 - To retrieve data for energies.

*NODOUT, dt = 0.5 - To retrieve data for node specified under *History_node

*BINARY.D3PLOT, dt = 0.5 - to retrieve binary file for post processing.

*EXTENT_BINARY, STRFLG = 1 - to retrieve data for stress and strain with time.

*MATERIAL

Material for Hood is to be determined.

Material Card - Piecewise linear plasticity *MAT_024

Material - Aluminium

Density - 2.77e-3 kg/mm3

Modulus of Elasticity - 70 GPa

Yield Stress - 0.115 GPa

Tangent Modulus - 1.082 GPa

*SECTION

A section for shell elements is defined with following properties:

ELFORM - 2

Thickness - 1.5mm

Post-Processing:

Simulation

Element under analysis:

Element: #2692 #2693 #3028 #3029 are under maximum stress on collision.

Figure 3.7 Element under analysis i.e element 3031

Plot 3.1 Effective stress (Von-mises) with time.

Maximum stress (Average of maximum stress for each element) is = 1.76`times``10^-4` Kg/mm.ms2

Resultant acceleration for Head_Accelerometer. (Node 25679)

Plot 3.2 Resultant acceleration readings from head_accelerometer

Head Impact Coefficient calculation:

Head_accelerometer data is calculated for peak accleration to quantify the effect of collision.

Plot 3.3 HIC36 and HIC(d) value from resultant acceleration.

`triangle`T = 15.3 ms`

Free motion headform HIC = 67.34

HIC(d) = 217.2

Hand calculation:

Average accleration = 28

a = `int`28.70dt for t = 3.5 to 18.8 ms

b`= a/(t2-t1) = 43/1.5 = 28.70`

c`= b^2.5 = 28.7^2.5 = 4412.703`

d= c x dt = 4412.703 x 15.3 = 67514.3627

`HIC = d/1000 = 67.514`

`HIC(d) = 0.75446*(HIC)+166.40`

HIC(d) = 217.336

Table 3.1 Data from LS Prepost and hand calculations for HIC and HIC(d).

________________________________________________________________________________________________________________________________________________________________________

CASE4: Pedestrian Headform at 40kmph, 75degrees with Rigid wall.

Keywords:

*DEFINE

Transformation 1:

*DEFINE_TRANSFORMATION

TRANID = 1

Title: Headform_y_75degrees

ROTATE: 0 1 0 0 0 0 75

Here, a line inclined at 35 degrees with Y and perpendicular to X and Z is included as transformation

The imported file will be inclined to 75 degrees with Y.

*INCLUDE

The file included is of LSTC Pedestrian headform which contains modelling for headform

LSTC.PEDESTRIAN_HEADFORM_CHILD.180605_V1.03.2BETA.k

Figure 4.1 LSTC Headform. Filename - PEDESTRIAN_HEADFORM.k

*INCLUDE_TRANSFORMATION

TranID = 1

Path: ../../../PEDESTRIAN_HEADFORM.k

As imported files is 2 steps up from the location of main solver file.

Using this file headform is imported at an angle 35 degrees with Y.

Figure 4.2 Pedestrian headform imported into main solver file under above mentioned transformations. (RIGHT SIDE VIEW)

Figure 4.3 Pedestrian headform imported into main solver file under above mentioned transformations. (ISO-METRIC VIEW)

Figure 4.4 Pedestrian headform imported into main solver file under above mentioned transformations. (FRONT VIEW)

*INITIAL

To assign velocity to headform nodes, it is very much necessary to create a set of nodes.

*SET_NODE

Title: Velocity_nodes

NSID = 3

All nodes of headform are selected by area box.

*INITIAL_VELOCITY

NSID = 3

Velocity = 40 kmph = 11.1111 mm/ms

The velocity vector is in X-Z plane.

X componenet of velocity at 75 degrees with X.

Vx = -11.1111cos 35 = -2.487 mm/ms

Z componenet of velocity at 35 degrees with X.

Vz = -11.1111sin 35 = -10.9725 mm/ms

Figure 4.5 Velocity vector for headform. (Right side view)

*CONTACT

Contacts are established to avoid penetration of skull into skin.

Contacts are established to avoid penetration of skin into hood.

Self contacts are established to avoid self penetrations of componenets.

*AUTOMATIC_SURFACE_TO_SURFACE

MSTYP = 3 to define part set id.

SSTYP = 3 to define part set id.

SSID = 2 (skin)

MSID = 1 (skull)

To avoid penetration of skull into skin

*CONTROL

Termination = 40ms

The solution of problem will happen for this time period.

*DATABASE

ASCII

*GLSTAT, dt = 0.5 - To retrieve data for energies.

*NODOUT, dt = 0.5 - To retrieve data for node specified under *History_node

*BINARY.D3PLOT, dt = 0.5 - to retrieve binary file for post processing.

*EXTENT_BINARY, STRFLG = 1 - to retrieve data for stress and strain with time.

Post-Processing:

Simulation:

VEDIO 4.1 The simulation of headform at 40kmph at 75degrees.

Resultant acceleration for Head_Accelerometer. (Node 25679)

Plot 4.3 Resultant acceleration readings from head_accelerometer

Head Impact Coefficient calculation:

Head_accelerometer data is calculated for peak accleration to quantify the effect of collision.

Plot 4.4 HIC36 and HIC(d) value from resultant acceleration.

`triangle`T = 1.5 ms

Free motion headform HIC = 45270

HIC(d) = 34320

Hand calculation:

Average accleration = 1030

a`=int1030.dt` for t = 3.5 to 5 = 1545

b`= a/(t2-t1) = 1545/1.5 = 1030`

c`= b^2.5 = 1030^2.5 = 34048114.11`

d= c x dt = 34048114.11 x 1.5 = 51072171.16

`HIC = d/1000 = 51072.171`

`HIC(d) = 0.75446*(HIC)+166.40`

HIC(d) = 38698.31025

Table 4.1 Data from LS Prepost and hand calculations for HIC and HIC(d)

________________________________________________________________________________________________________________________________________________________________________

CASE5: Pedestrian Headform at 40kmph and 75 degrees with Meshed hood.

DESIGN OF EXPERIMENT:

The included files are for Hood and LSTC Hadform.

The main solver file contains the boundary conditions and the Load conditions.

The main solver file also contains the output files and termination and time step.

*KEYWORDS

*DEFINE

Transformation 1:

*DEFINE_TRANSFORMATION

TRANID = 1

Title - Hood

SCALE - 0 0 0 0 0 0 0

It is a dummy transformation, and it will import the included file as it is.

Transformation 2:

*DEFINE_TRANSFORMATION

TRANID = 2

Title: Headform_y_35degrees

ROTATE: 0 1 0 0 0 0 75

Here, a line inclined at 35 degrees with Y and perpendicular to X and Z is included as transformation

The imported file will be inclined to 35 degrees with Y.

*INCLUDE

The file included is of LSTC Pedestrian headform which contains modelling for headform

LSTC.PEDESTRIAN_HEADFORM_CHILD.180605_V1.03.2BETA.k

Figure 5.1 LSTC Headform. Filename - PEDESTRIAN_HEADFORM.k

The file included is a meshed hood which comprised of quad-tria shell elements.

Figure 5.2 Meshed hood. File name- Meshed_Hood.k

*INCLUDE_TRANSFORMATION

TranID = 1

Path: ../../../Meshed_Hood.k

As imported file is 2 steps up from the location of main solver file.

Using this file hood is imported as it is into main solver file.

TranID = 2

Path: ../../../PEDESTRIAN_HEADFORM.k

As imported files is 2 steps up from the location of main solver file.

Using this file headform is imported at an angle 35 degrees with Y.

Figure 5.3 Meshed hood and headform imported into main solver file under above mentioned transformations. (ISO-METRIC VIEW)

Figure 5.4 Meshed hood and headform imported into main solver file under above mentioned transformations. (RIGHT SIDE VIEW)

Figure 5.5 Meshed hood and headform imported into main solver file under above mentioned transformations. (FRONT VIEW)

*INITIAL

To assign velocity to headform nodes, it is very much necessary to create a set of nodes.

*SET_NODE

Title: Velocity_nodes

NSID = 3

All nodes of headform are selected by area box.

*INITIAL_VELOCITY

NSID = 3

Velocity = 40 kmph = 11.1111 mm/ms

The velocity vector is in X-Z plane.

X componenet of velocity at 35 degrees with X.

Vx = -11.11cos 35 = -2.8757 mm/ms

Z componenet of velocity at 35 degrees with X.

Vz = -11.11sin 75 = -10.7325 mm/ms

Figure 5.6 Velocity vector for headform. (Right side view)

*CONTACT

Contacts are established to avoid penetration of skull into skin.

Contacts are established to avoid penetration of skin into hood.

Self contacts are established to avoid self penetrations of componenets.

*AUTOMATIC_SURFACE_TO_SURFACE

MSTYP = 3 to define part set id.

SSTYP = 3 to define part set id.

SSID = 2 (skin)

MSID = 1 (skull)

To avoid penetration of skull into skin

MSTYP = 3

SSTYP = 3

SSID = 2 (Skin)

MSID = 2000300 (Hood)

To avoid penetration of skin into hood.

*AUTOMATIC_SINGLE_SURFACE

SSTYP = 3

SSID = 1,2,3,4,5,2000300

To avoid self penetration or buckling and to study plastic strain and fracture.

*CONTROL

Termination = 50ms

The solution of problem will happen for this time period.

*DATABASE

ASCII

*GLSTAT, dt = 0.5 - To retrieve data for energies.

*NODOUT, dt = 0.5 - To retrieve data for node specified under *History_node

*BINARY.D3PLOT, dt = 0.5 - to retrieve binary file for post processing.

*EXTENT_BINARY, STRFLG = 1 - to retrieve data for stress and strain with time.

*MATERIAL

Material for Hood is to be determined.

Material Card - Piecewise linear plasticity *MAT_024

Material - Aluminium

Density - 2.77e-3 kg/mm3

Modulus of Elasticity - 70 GPa

Yield Stress - 0.115 GPa

Tangent Modulus - 1.082 GPa

*SECTION

A section for shell elements is defined with following properties:

ELFORM - 2

Thickness - 1.5mm

Post-Processing:

Element under analysis:

Element: #3291 #2955 and #2958 under analysis.

Figure 5.7 Element under analysis

Effective stress with time for element #3031

Plot 5.1 Effective stress (Von-mises) with time.

Maximum stress (average of maximum stress for each element) = 3.75 `times` `10^-3` Kg/mm.ms2 at time t = 8ms

Resultant acceleration for Head_Accelerometer. (Node 25679)

Plot 5.3 Resultant acceleration readings from head_accelerometer

Head Impact Coefficient calculation:

Head_accelerometer data is calculated for peak accleration to quantify the effect of collision.

Plot 5.4 HIC36 and HIC(d) value from resultant acceleration.

`triangle`T = 13.2 ms`

Free motion headform HIC = 315.3

HIC(d) = 404.3

Hand calculation:

Average accleration = 56.40

a = `int`56.40dt for t = 3.7 to 16.9 ms

b`= a/(t2-t1) = 744.48/13.2 = 56.40`

c`= b^2.5 = 56.40^2.5 = 23888.98`

d= c x dt = 23888.98 x 13.2 = 315334.6472

`HIC = d/1000 = 315.334`

`HIC(d) = 0.75446*(HIC)+166.40`

HIC(d) = 404.307

Table 5.1 Data from LS Prepost and hand calculations for HIC and HIC(d).

________________________________________________________________________________________________________________________________________________________________________

CASE6: Pedestrian Headform at 30kmph and 35degrees with Meshed hood (2mm thickness).

DESIGN OF EXPERIMENT:

The included files are for Hood and LSTC Hadform.

The main solver file contains the boundary conditions and the Load conditions.

The main solver file also contains the output files and termination and time step.

*KEYWORDS

*DEFINE

Transformation 1:

*DEFINE_TRANSFORMATION

TRANID = 1

Title - Hood

SCALE - 0 0 0 0 0 0 0

It is a dummy transformation, and it will import the included file as it is.

Transformation 2:

*DEFINE_TRANSFORMATION

TRANID = 2

Title: Headform_y_35degrees

ROTATE: 0 1 0 0 0 0 35

Here, a line inclined at 35 degrees with Y and perpendicular to X and Z is included as transformation

The imported file will be inclined to 35 degrees with Y.

*INCLUDE

The file included is of LSTC Pedestrian headform which contains modelling for headform

LSTC.PEDESTRIAN_HEADFORM_CHILD.180605_V1.03.2BETA.k

Figure 6.1 LSTC Headform. Filename - PEDESTRIAN_HEADFORM.k

The file included is a meshed hood which comprised of quad-tria shell elements.

Figure 6.2 Meshed hood. File name- Meshed_Hood02.k

*INCLUDE_TRANSFORMATION

TranID = 1

Path: ../../../Meshed_Hood02.k

As imported file is 2 steps up from the location of main solver file.

Using this file hood is imported as it is into main solver file.

TranID = 2

Path: ../../../PEDESTRIAN_HEADFORM.k

As imported files is 2 steps up from the location of main solver file.

Using this file headform is imported at an angle 35 degrees with Y.

Figure 6.3 Meshed hood and headform imported into main solver file under above mentioned transformations. (ISO-METRIC VIEW)

Figure 6.4 Meshed hood and headform imported into main solver file under above mentioned transformations. (RIGHT SIDE VIEW)

Figure 6.5 Meshed hood and headform imported into main solver file under above mentioned transformations. (FRONT VIEW)

*INITIAL

To assign velocity to headform nodes, it is very much necessary to create a set of nodes.

*SET_NODE

Title: Velocity_nodes

NSID = 3

All nodes of headform are selected by area box.

*INITIAL_VELOCITY

NSID = 3

Velocity = 30 kmph = 8.3333 mm/ms

The velocity vector is in X-Z plane.

X componenet of velocity at 35 degrees with X.

Vx = -8.333cos 35 = -6.826 mm/ms

Z componenet of velocity at 35 degrees with X.

Vz = -8.333sin 35 = -4.779 mm/ms

Figure 6.6 Velocity vector for headform. (Right side view)

*CONTACT

Contacts are established to avoid penetration of skull into skin.

Contacts are established to avoid penetration of skin into hood.

Self contacts are established to avoid self penetrations of componenets.

*AUTOMATIC_SURFACE_TO_SURFACE

MSTYP = 3 to define part set id.

SSTYP = 3 to define part set id.

SSID = 2 (skin)

MSID = 1 (skull)

To avoid penetration of skull into skin

MSTYP = 3

SSTYP = 3

SSID = 2 (Skin)

MSID = 2000300 (Hood)

To avoid penetration of skin into hood.

*AUTOMATIC_SINGLE_SURFACE

SSTYP = 3

SSID = 1,2,3,4,5,2000300

To avoid self penetration or buckling and to study plastic strain and fracture.

*CONTROL

Termination = 50ms

The solution of problem will happen for this time period.

*DATABASE

ASCII

*GLSTAT, dt = 0.5 - To retrieve data for energies.

*NODOUT, dt = 0.5 - To retrieve data for node specified under *History_node

*BINARY.D3PLOT, dt = 0.5 - to retrieve binary file for post processing.

*EXTENT_BINARY, STRFLG = 1 - to retrieve data for stress and strain with time.

*MATERIAL

Material for Hood is to be determined.

Material Card - Piecewise linear plasticity *MAT_024

Material - Aluminium

Density - 2.77e-3 kg/mm3

Modulus of Elasticity - 70 GPa

Yield Stress - 0.115 GPa

Tangent Modulus - 1.082 GPa

*SECTION

A section for shell elements is defined with following properties:

ELFORM - 2

Thickness - 2.0mm

Post-Processing:

Element under analysis:

Element: #3029 #2693 #2694 #3030

Figure 6.7 Element under analysis.

Effective stress with time for element #3031

Plot 6.1 Effective stress (Von-mises) with time.

Maximum stress (Average of maximum stress for each element) = 3.690 `times` `10^-3` Kg/mm.ms2

Resultant acceleration for Head_Accelerometer. (Node 25679)

Plot 6.2 Resultant acceleration readings from head_accelerometer

Head Impact Coefficient calculation:

Head_accelerometer data is calculated for peak accleration to quantify the effect of collision.

Plot 6.3 HIC36 and HIC(d) value from resultant acceleration.

`triangle`T = 13.5 ms`

Free motion headform HIC = 141.9

HIC(d) = 273.5

Hand calculation:

Average accleration = 40.6

a = `int`40.6dt for t = 3.6 to 17.1 ms

b`= a/(t2-t1) = 40.6/13.5 = 40.6`

c`= b^2.5 = 40.6^2.5 = 10503.04`

d= c x dt = 10503.04 x 13.5 = 141791.06

`HIC = d/1000 = 141.80`

`HIC(d) = 0.75446*(HIC)+166.40`

HIC(d) = 273.37

Table 6.1 Data from LS Prepost and hand calculations for HIC and HIC(d).

________________________________________________________________________________________________________________________________________________________________________

CASE7: Pedestrian Headform at 30kmph and 35degrees with Meshed hood (2.5mm thickness).

DESIGN OF EXPERIMENT:

The included files are for Hood and LSTC Hadform.

The main solver file contains the boundary conditions and the Load conditions.

The main solver file also contains the output files and termination and time step.

*KEYWORDS

*DEFINE

Transformation 1:

*DEFINE_TRANSFORMATION

TRANID = 1

Title - Hood

SCALE - 0 0 0 0 0 0 0

It is a dummy transformation, and it will import the included file as it is.

Transformation 2:

*DEFINE_TRANSFORMATION

TRANID = 2

Title: Headform_y_35degrees

ROTATE: 0 1 0 0 0 0 35

Here, a line inclined at 35 degrees with Y and perpendicular to X and Z is included as transformation

The imported file will be inclined to 35 degrees with Y.

*INCLUDE

The file included is of LSTC Pedestrian headform which contains modelling for headform

LSTC.PEDESTRIAN_HEADFORM_CHILD.180605_V1.03.2BETA.k

Figure 7.1 LSTC Headform. Filename - PEDESTRIAN_HEADFORM.k

The file included is a meshed hood which comprised of quad-tria shell elements.

Figure 7.2 Meshed hood. File name- Meshed_Hood2.5.k

*INCLUDE_TRANSFORMATION

TranID = 1

Path: ../../../Meshed_Hood2.5mm.k

As imported file is 2 steps up from the location of main solver file.

Using this file hood is imported as it is into main solver file.

TranID = 2

Path: ../../../PEDESTRIAN_HEADFORM.k

As imported files is 2 steps up from the location of main solver file.

Using this file headform is imported at an angle 35 degrees with Y.

Figure 7.3 Meshed hood and headform imported into main solver file under above mentioned transformations. (ISO-METRIC VIEW)

Figure 7.4 Meshed hood and headform imported into main solver file under above mentioned transformations. (RIGHT SIDE VIEW)

Figure 7.5 Meshed hood and headform imported into main solver file under above mentioned transformations. (FRONT VIEW)

*INITIAL

To assign velocity to headform nodes, it is very much necessary to create a set of nodes.

*SET_NODE

Title: Velocity_nodes

NSID = 3

All nodes of headform are selected by area box.

*INITIAL_VELOCITY

NSID = 3

Velocity = 30 kmph = 8.3333 mm/ms

The velocity vector is in X-Z plane.

X componenet of velocity at 35 degrees with X.

Vx = -8.333cos 35 = -6.826 mm/ms

Z componenet of velocity at 35 degrees with X.

Vz = -8.333sin 35 = -4.779 mm/ms

Figure 7.6 Velocity vector for headform. (Right side view)

*CONTACT

Contacts are established to avoid penetration of skull into skin.

Contacts are established to avoid penetration of skin into hood.

Self contacts are established to avoid self penetrations of componenets.

*AUTOMATIC_SURFACE_TO_SURFACE

MSTYP = 3 to define part set id.

SSTYP = 3 to define part set id.

SSID = 2 (skin)

MSID = 1 (skull)

To avoid penetration of skull into skin

MSTYP = 3

SSTYP = 3

SSID = 2 (Skin)

MSID = 2000300 (Hood)

To avoid penetration of skin into hood.

*AUTOMATIC_SINGLE_SURFACE

SSTYP = 3

SSID = 1,2,3,4,5,2000300

To avoid self penetration or buckling and to study plastic strain and fracture.

*CONTROL

Termination = 50ms

The solution of problem will happen for this time period.

*DATABASE

ASCII

*GLSTAT, dt = 0.5 - To retrieve data for energies.

*NODOUT, dt = 0.5 - To retrieve data for node specified under *History_node

*BINARY.D3PLOT, dt = 0.5 - to retrieve binary file for post processing.

*EXTENT_BINARY, STRFLG = 1 - to retrieve data for stress and strain with time.

*MATERIAL

Material for Hood is to be determined.

Material Card - Piecewise linear plasticity *MAT_024

Material - Aluminium

Density - 2.77e-3 kg/mm3

Modulus of Elasticity - 70 GPa

Yield Stress - 0.115 GPa

Tangent Modulus - 1.082 GPa

*SECTION

A section for shell elements is defined with following properties:

ELFORM - 2

Thickness - 2.5mm

Post-Processing:

Element under analysis:

Element: #2692 #2693 #3030 #3029

Figure 7.7 Element under analysis.

Effective stress with time for element.

Plot 7.1 Effective stress (Von-mises) with time.

Maximum stress (Avg of max stress for each element) = 3.7 `times` `10^-3` kg/mm.ms2

Resultant acceleration for Head_Accelerometer. (Node 25679)

Plot 7.2 Resultant acceleration readings from head_accelerometer

Head Impact Coefficient calculation:

Head_accelerometer data is calculated for peak accleration to quantify the effect of collision.

Plot 7.3 HIC36 and HIC(d) value from resultant acceleration.

`triangle`T = 13.5 ms`

Free motion headform HIC = 259.6

HIC(d) = 362.3

Hand calculation:

Average accleration = 51.7

a = `int`51.7dt for t = 2.7 to 16.2 ms

b`= a/(t2-t1) = 697.95/13.5 = 51.7`

c`= b^2.5 = 51.7^2.5 = 19218.80`

d= c x dt = 19218.80 x 13.5 = 259453.85

`HIC = d/1000 = 259.453`

`HIC(d) = 0.75446*(HIC)+166.40`

HIC(d) = 362.1469

Table 7.1 Data from LS Prepost and hand calculations for HIC and HIC(d).

________________________________________________________________________________________________________________________________________________________________________

COMPARISON OF RESULTS:

Comparison 1:

Stress/ Strain comparison for Element #3031 from two cases.

30kmph - 35 degrees collision of LSTC headform with:

1. Rigid wall
2. Hood (1.5 mm thickness)

Table 8.1 V-m stress and effective plastic strain for the two cases.

Plot 8.1 Effective stress for two cases.

Plot 8.2 Effective plastic strain for two cases.

Observation for element #3031:

Von mises stress in case of collision with Rigid wall is greater.

Max stress (Hood) = 2.47 `times` `10^-3 (Kg)/(mm.ms^2)`

Max stress (Rigid wall) = 5.21 `times` `10^-3 (Kg)/(mm.ms^2)`

Effective plastic strain is much greater in case of rigid wall.

Max strain (Hood) = 2182.756 `times` `10^-6`

Max strain (Rigid wall) = 3.736 `times` `10^-6`

Clearly, damage to headform is significantly more in case of impact with rigid wall.

Comparison 2:

Acceleration plots for two cases:

30kmph - 35 degrees collision of LSTC headform with:

1. Rigid wall
2. Hood (1.5 mm thickness)

Table 8.2 Acceleration for two cases.

Observation:

Acceleration in case of hood is gradual.

Acceleration in case of rigid wall is steep.

Comparison 3:

HIC and HIC(d) values for two cases:

30kmph - 35 degrees collision of LSTC headform with:

1. Rigid wall
2. Hood (1.5 mm thickness)

HIC(rigid wall) = 4405

HIC(d) (rigid wall) = 3490

HIC(hood) = 67.34

HIC(d) (Hood) = 217.20

Comparison 4:

Effective stress for 1.5mm, 2mm and 3.5mm hood in 30kmph and 30degrees.

Effective stress for headforms for each case.

HIC(d) values for each case.

Pedestrian head is safest in case of 1.5mm thickness.

Deformation in hood is least in 2.5mm thickness.