Design Optimization of B-Pillar for Sustaining Roof Crush Test … · · 2016-09-14load is...

Innovation Intelligence®

Design Optimization of B-Pillar for Sustaining

Roof Crush Test

Prof Tae Hee Lee

Sung Sik Choi (Masters Program)

Amalnerkar Eshan(Masters Program)

Hanyang University

Department of Automotive Engineering

Sensitivity Analysis and Design Innovation

(SANDI)

Copyright © 2012 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.

Contents

Study Overview

Aim of Research

B-Pillar : Design Inspiration

B-Pillar : FEM Model

B-Pillar : Analysis Condition

Concept Design : Topology Optimization

Morphing using Hypermorph

Batch Job

Optimization (High fidelity)

Screening & Metamodel

Optimization (Metamodel)

Summary

Conclusion


Study overview- Accidents due to rollovers

Accidents due to rollovers constitutes one of the large proportions of injury producing collisions for vehicles.

According to

latest NHTSA

data, nearly 35%

of all deaths

from passenger

vehicle crashes

are cause due to

rollovers.

Source:

*) Advanced Technologies: the Pathway to Total Safety. International Technical conference On Enhanced Safety of Vehicle, May 19,2003

Retrieved from: http://www-nrd.nhtsa.dot.gov/departments/esv/18th/discussions/JK_ESVAdv.htm

Vehicle damage in rollover crashes include:

- deformation of the roof and its supporting structures

- head and neck injuries to the occupants.

Relevant regulation for roof strength is based on

US Federal Motor Vehicle Safety Standard (FMVSS)

216,Roof Crush Resistance, Passenger Cars.

*) Dummy inside a car undergoing roof crush test


Study overview- Test regulation & B-Pillar

Statement

- Force applied is 1.5 times unloaded vehicle weight ,but should not exceed 22,240 N for passenger cars.

- Deformation of test device must not move more than 127mm.

FMVSS 216, Roof Crush Resistance, Passenger Cars

**) Test Device Orientation

*) Actual Test Device

Source:

*) Standard No. 216;Roof Crush Resistance

Retrieved from http://www.fmcsa.dot.gov/rules-regulations/administration/fmcsr/fmcsrruletext.aspx?reg=571.216

**) Insurance Institute For Highway Safety [IIHS] performing Rollover Test Procedure.

Retrieved from: http://wot.motortrend.com/watch-iihs-perform-rollover-crash-test-on-mkz-335i-372031.html#axzz2a8iF5gDp

***) General example of B-Pillar of Ford Mondeo. Retrieved from; http://boronextrication.com/tag/ford/

B-Pillars are safety-relevant parts and essential load carrying elements for achieving roof strength

B-Pillar - Vertical support between a car’s front door window and rear side window

***) Typical car B-Pillar

http://wot.motortrend.com/watch-iihs-perform-rollover-crash-test-on-mkz-335i-372031.html





















Aim of Research

The current styling trend towards slimmer B-Pillar results in numerous conflicting

requirements to be met with new concepts, innovative materials and manufacturing

processes.

Thus our aim is to..

Check B-Pillar strength by given analysis condition.

[Tool used- Radioss]

Use reinforced materials [Aluminum foam] to dampen the intensity of load.

[Tool used- Radioss]

Conduct topology optimization to reduce volume of the reinforced material.

[Tool used - Optistruct]

Use morphing process to achieve improved designs with minimum element distortion. [Tool used - Hypermorph]

Conduct high fidelity optimization using batch job technique to obtain better results. [Tool used - Radioss & Matlab]

Perform optimization using Kriging metamodel for comparison.

[Tool used - Radioss & Matlab]

Obtain, an optimized design for B-Pillar using the above process


B-pillar : Design Inspiration

*) outer hat section of B-pillar **) Inner hat section of B-Pillar Designed CAD model

Source;

*) **)Thor Fraser, Darren Goldenberg, Muhammad Yazid Mat Isa, Alex Steinhauser, “Design of Automotive Center

Pillar Reinforcement to Resist Roof Crush in F-Series Crew Cab”, Final Report ME 450: Design and Manufacturing III ,Fall 2007

Ford F-150 SUV


B-Pillar : FEM Model

Color Part Material

Properties

Element Type Number Of

Elements Young’s

Modulus [

N/mm2]

Poisson’s

Ratio

Density

[kg/mm3]

Outer Pillar

[Shell] Steel 2.1e5 0.3 7.9e-9

Mixed

[Quad4 +Tria3]

8753

[8716+37] Inner Pillar

[Shell] Steel 2.1e5 0.3 7.9e-9

Foam

[Solid] AA 6063 8e4 0.33 2.7e-9 Tetra 10997

Weld - - - - Hexa 18

Exploded view of designed B-Pillar

The Aluminum Foam is

connected to the inner and

outer surface using weld

joints at specific locations

Weld joints

Total number of elements = 19768 < 20000 [Required condition is satisfied]

Total=19768


B-Pillar : Analysis Condition

Assumptions:

1. Point of application of force is

fixed.

2. Maximum displacement is at the

bend of B-Pillar structure.

Z-axis Fixed

Reasons for considering the displacement at the bend of B-Pillar-

1. Instead of assuming the full structure of roof and related parts

connected to it, our focus is mainly on B-Pillar. So, the point at which the

load is applied is fixed unlike in the actual roof crush test where it is not

fixed.

2. Also, in the test, the deformation is restricted up to 127mm for whole

roof and adjoining pillar structure. Whereas, in our case, impact is on the

B-Pillar only, so ideal deformation assumed is of 38mm.

Hypermesh Model with

applied load and Boundary

Conditions

*) Thor Fraser, Darren Goldenberg, Muhammad Yazid Mat Isa, Alex Steinhauser, “Design of Automotive Center

Pillar Reinforcement to Resist Roof Crush in F-Series Crew Cab”, Final Report ME 450: Design and Manufacturing III ,Fall 2007

Load

Condition Value Direction

Force [FMVSS 216]

*) 22500 N

(Negative) Y-axis

25° Roll in Z-axis

5° Pitch in X-axis

Boundary

conditions Fixed

Upper : Z-axis

Lower : X,Y and Z-axis


B-Pillar : Analysis Results

Deformation of the B-Pillar with Foam Deformation of B-Pillar without Foam

Maximum Displacement

at Bend of B-Pillar

Without Foam With Foam

[Full reinforced]

68 mm 12 mm


Concept Design : Topology Optimization

Design Region Foam (Design Space)

Pillars (Non-Design Space)

Constraints on

Design Variables Draw and Pattern Grouping

Element Density contour plot

after topology optimization

Remodeled foam

Fit new foam design

Displacement contour plot

Topology Optimization- Process for optimum

material distribution in a given design domain.

Parameters

Result Comparison

Before Topology After Topology

Design

Volume 1.173*e7 mm3 3.63*e6 mm3

Displacement 12mm 42mm

69% ↓


Morphing using Hypermorph

Variable Position Parameter Range

(mm)

X1 Pos1, Pos2,

Pos3 Translate_X [-50,+50]

X2 Pos2 Width_X [-50,+50]




X6 Pos4, Pos5,

Pos6 Translate_X [-30,+30]

X7 Pos7 Width_Z [-20,+20]

X8 Pos8 Width_Z [-20,+20]

Hypermorph:

- easy to use mesh

manipulation tool

- quickly stretch any finite

element mesh while keeping

mesh distortion at minimum.

- It only changes the nodal

location.

- Nodal id or element id remain

unchanged.

Handles and positions of inner pillar Handles and positions of outer pillar


Morphing using Hypermorph - Example

For variable X1(Pos 1/2/3 translation of X axis, morphing process is undertaken

Magnitude of translation= +50

Displacement = 41.315 mm Magnitude of translation= -50

Displacement = 44.987 mm

Magnitude of translation= 0

Displacement = 43.003 mm

Response

- Displacement : Magnitude of displacement vector at no.223705 node


Batch Job

MATLAB

Batch command

HyperMesh

Original model

Applied loads and BCs

1cycle of batch job

Purpose- Combine Hyperworks and Matlab processes to achieve automatically

about the responses obtained from the morphing process

Load original

FE model from

HyperMesh

Define input

variables using

Hypermorph

Save modified

FE model

Achieve responses

(volume, stress,

displacement)

Run RADIOSS

for FE analysis


Optimization (High fidelity)

Optimization [High fidelity]

Formulation

Optimizer – fmincon (SQP)

F - calls 760 calls

Running Time 4.2 hours

Unit time 20 sec

127mm) of (30% 38mm Disp

MPa1202

240

factorsafety

S S

MPa2852

570

factorsafety

S SWhere,

38mmDisp

MPa120S

MPa285S Subject to

Volume Minimize

aluminium ultimate,

foam critical,

steel ultimate,

pillar critical,

foammax,

pillarmax,


Responses

Designs

Improvement Initial

topology model

Optimization

[High fidelity]

Displacement (mm)

[Node ID=223705] 42 [NG] 38 9.5%

Maximum stress (N/mm²): Pillar 293.5 [NG] 285 4.6%

Maximum stress (N/mm²): Foam 4.8 7.2 -

Volume (mm³) 5.15*e6 5.093*e6 1.1%

Optimization Results( High fidelity )

Variable

Magnitude

Initial topology model Optimization

[High fidelity]

X1 [mm] 0 -0.515

X2 [mm] 0 50.000

X3 [mm] 0 -23.908

X4 [mm] 0 -29.998

X5 [mm] 0 -29.995

X6 [mm] 0 2.985

X7 [mm] 0 20.000

X8 [mm] 0 -14.487 Optimized Model


Screening & Metamodel

ANOVA from DOE by

orthogonal array

(8 variables, 27 sample point)

Response: Displacement Response: Max stress Response: Volume

DOE for building Kriging metamodel

by Full Factorial Design

(5 variables, 4 levels,

1024 sample point)

ex) 2 variables 4 levels FFD

Validation for evaluating the accuracy

of Kriging metamodel

(50 points by random sampling)

RMSE [%] R²

Displacement 1.462 0.979

Max stress 0.406 0.948

Volume 0.342 0.998

8 variables → 5 variables


Optimization (Metamodeling)

Optimization using Kriging Metamodel

Hypermesh model after

metamodeling

Validation Result

High

Fidelity

Meta

model

X1 (mm) -8.774

X2 (mm) -46.917

X4 (mm) -30

X7 (mm) 20.000

X8 (mm) 0.131

Displacement

(mm) 37.671 38(0.76%)

Max Stress

[Pillar] (N/mm²) 287.2 285(0.87%)

Max Stress

[Foam] (N/mm²) 7.2 -

Volume (mm³) 4.796 x e6 4.833 x e6

(0.77%)

※ ( %) : Relative Error

F - calls 148 calls

Running

Time 33 sec

Unit time 0.22 sec

38mmDisp

MPa120S

MPa285S Subject to

Volume Minimize

foammax,

pillarmax,


Metamodel

for calculating

responses

-6 -4 -2 0 2 4 6 8 10 12 140

0.05

0.1

0.15

0.2

0.25

PDF of MCS

Reliability

Reliability

analysis

Why metamodel?

Fast

Reliability Analysis is possible !

Optimization result High Fidelity

Model Metamodel

F - calls 750 calls 148 calls

Running Time 4.16 hours 33 sec

Unit time 20 sec 0.22 sec

Reliability Based Design Optimization is possible !

Design variables

Reliability

constraint

Probability of Failure

Response

]/[stressMax 285)(

][ntdisplacemeMax 38)(

95.0,3,2,1,)0)((toSubject

VolumenimizemiTo

)5,4,3,2,1(Find

2

2

1

mmNXG

mmXG

RjRXGR

ix

gettargettar

j

i


Summary

Responses

Designs

Without foam With foam

[Full reinforced] Initial topology

Optimization

[High fidelity]

Optimization

[Metamodel]

Displacement (mm)

(node id = 223705) 68 12 42 38 37.7

Maximum stress

(N/mm²) 390 Very stiff 293.5 285 287.2

Volume (mm³) 1.525*e6 1.326*e7 5.15*e6 5.093*e6 4.796*e6

Model Designs

Efficient use of the material of Aluminum Foam to dampen the intensity of load

Improved Roof Crush Strength by achieving less deformation in the new design

Maximum Stress levels are maintained within the limits

Volume reduced considerably when compared to full foam B-Pillar


Conclusion

At the condition for roof crush test regarding B-Pillar, we checked the

tendency of topology optimization using Optistruct

We used Hypermorph function in Hyperworks for utilizing a parametric

design variable

For obtaining the results from high fidelity model optimization for

minimizing volume subject to limited displacement and maximum stress,

we practiced batch job between Hyperworks and Matlab

Using low fidelity metamodel through computational DOE, we compared

cost and accuracy between two optimal results

Our Special Job


Q & A


Back data


Literature Review

Since the 1970s, a large body of technical literature on association and/or causation of occupant injury

In rollover crashes, focusing on roof deformation.

Narrowing down to impact of rollover crash onto roof and more specifically on B-Pillar a few analysis have been

done, like “Using CAE to evaluate a structural foam design for increasing roof strength” by Sameer Gupta,2011;

“Design optimization of a vehicle B-Pillar subjected to roof crush using mixed reactive taboo search” by Hamza

et al,2003 etc.

More recent studies like “Occupant Injury Experience In Rollover Crashes: An In-Depth Review Of NASS/CDS

Data” by Padmanaban et all,2005, researchers have examined—through testing, engineering, and statistical

analysis—whether a relationship exists between roof crush and rollover

From the earliest analyses, “The Use Of Accident Data in Studying Vehicle Handling Performance“ by Mackay

and Tampen; “Injury Frequency And Severity In Rollover Crashes As Related To occupant Ejection, Contacts

And Roof Damage” by Huelke and Compton, 1983; etc.


References

1) Altair Engineering, Inc., Altair Hyperworks Manual, Altair Engineering, Inc.

2) Altair Engineering, Inc., Optistruct Optimization Manual, Altair Engineering, Inc.

3) Thor Fraser, Darren Goldenberg, Muhammad Yazid Mat Isa, Alex Steinhauser, “Design of Automotive Center

Pillar Reinforcement to Resist Roof Crush in F-Series Crew Cab”, Final Report ME 450: Design and

Manufacturing III ,Fall 2007.

4) J. Christensen, C. Bastien and M.V. Blundell(2012), ‘Effects of roof crush loading scenario upon body in

white using topology optimization’, Coventry University, International Journal of Crashworthiness,

17:1, 29-38,2013.

5) Sameer Gupta, ‘Using CAE to evaluate a structural foam design for increasing roof strength’, Honda R&D,

Americas, Inc., 21001 State Route 739, Raymond, OH 43067-9705, 8th European LS-DYNA Users

Conference,2011.

6) Marco Danti, Maurizio Meneguzzo, Raffaele Saponaro, Izabela Kowarska, ‘Multi-objective Optimization in

Vehicle Concept Modeling’ , Italy, Proceedings of ISMA2010 including USD2010,2010.


Background

Vehicle damage in rollover crashes include:

- deformation of the roof and its supporting structures

- head and neck injuries to the occupants.

Hence, strengthening of the roof is suggested as

an appropriate countermeasure for such fatalities.

Relevant regulation for roof strength is based on

US Federal Motor Vehicle Safety Standard (FMVSS)

216,Roof Crush Resistance, Passenger Cars.

Figure 1. Dummy inside a car undergoing roof crush test

Figure 2. Common rollover crash

Source: Figure 1. Insurance Institute For Highway Safety [IIHS] performing Rollover Test Procedure.

Retrieved from: http://wot.motortrend.com/watch-iihs-perform-rollover-crash-test-on-mkz-335i-372031.html#axzz2a8iF5gDp


Introduction of Car B-Pillar

B-Pillars are safety-relevant parts and load carrying elements of the

passenger compartments

Location - Vertical support between a car’s front door window and

rear side window

Purpose of B-Pillar:

• Legal requirements for crash safety place high demands on the

structural mechanical properties of B-Pillars.

• Integrating the seat belt retractor and belt height adjustment

system.

• Holding the lock of the front door and also the hinge of the rear

door

Figure 1. Typical car B-Pillar

Belt height adjustment system

Seat belt retractor system

Figure 2. Internal structure of B-Pillar

Source; Figure 1. General example of B-Pillar of Ford Mondeo.

Retrieved from; http://boronextrication.com/tag/ford/

Figure 2. Chrysler B-Pillar Components details

Retrieved from: http://www.factorychryslerparts.com/showAssembly.aspx?ukey_assembly=573875


Batch Job

MATLAB

Batch command

Define input variables

Arrange output

responses

Hypermesh

Modify model

Apply loads and BCs

Modify the finite element model

Save the modified model

Radioss

Finite element analysis

Run analysis

Export results

Variable Design Range

X1 [-50,+50]

X2 [-50,+50]

X3 [-30,+30]

X4 [-30,+30]

X5 [-30,+30]

X6 [-30,+30]

X7 [-20,+20]

X8 [-20,+20]

Batch

Response

Volume

Displacement

Max stress

Purpose- Combine Hyperworks and Matlab processes to find the Optimal

values for the responses obtained from the morphing process

Design Optimization of B-Pillar for Sustaining Roof Crush Test … · · 2016-09-14load is...

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