Numerical and experimental impact analysis of square crash box structure with holes

Numerical and Experimental Impact Analysis of Square Crash Box Structure with Holes

Thesis Defence

By:

Sahril Afandi Sitompul23611004

Supervisors:

Dr. Tatacipta DirgantaraDr. Leonardo GunawanProf. Dr. Ichsan S. Putra

Lightweight Structure Research GroupFaculty of Mechanical and Aerospace Engineering

Institut Teknologi BandungJl. Ganesha 10 Bandung 40132, INDONESIA

Structural Impact EngineeringLightweight Structure Laboratory

Presentation Outline Introduction• Research Background

• Research Objectives

• Scope of works

• Methodology

Axial Crushing• Theoretical Analysis

Finite Element Methods

• Computational Mechanics

•Explicit Finite Element Method

• Structural Model

• Modeling Procedure

Experimental Tests

• Tensile Testing

• Dynamic Axial Crushing Testing

Result and Analysis

• Numerical and Experimental Results

Conclusions and Future Works


Introduction

Research Background

Auto Motor und Sport spezial 1992, photo H.P. Seufert


Introduction

Research Background

T. Frank and K. Gruber. Numerical simulation of frontal impact and offset

collisions.Cray Research Inc., CRAY Channels: 2–6, 1992.

J. Marsolek and H. G. Reimerdes. Energy absorption of metallic cylindrical shells with induced non-

axisymmetric folding patterns. International Journal of Impact Engineering 30 (2004) 1209-1223.


Research Background

Introduction

Concentrating on one of

research areas: STRUCTURAL

IMPACT ENGINEERING

Lightweight Structure Research Group

Crashworthiness

PRESERVES SUFFICIENT SURVIVAL SPACE around the

occupants to limit bodily injury during an accident.

CONTROLLING THE DECELERATION within an

acceptable safety level to prevent the injury to the

passenger.

Safety


Research Objectives

Introduction

To study the behavior of extruded aluminum thin-walled columns with square cross-section and to examine the EFFECT OF INSERTING OF CIRCULAR HOLE(S) as a crush initiator subjected to impact loading

Crashworthy Performance

Crushing Parameters

Peak Crushing Load

Mean Crushing

Force

Crushing Force Efficiency

Meet acceptable safety level

Light-weight vehicle structure

Reduce fuel consumption

Reduce CO2

emissions

Crash box design


Scope of Works

Introduction

• The numerical and experimental analysis are limited to a square column with cross section 38 x 38 mm and thickness 1.15 mm subjected to axial impact load with initial velocity below 4.5 m/s.

• In parametric study, the column width is varied from 40 to 80 mm with uniform thickness of 1.2 mm. The impact velocity is 4.5 m/s.

• The material used in this work was the aluminum extrusion AA 6063-T1.

•The holes inserted on the column have the diameter to column width ratios ranged from 0 – 0.8.


Methodology

Introduction

Axial Crushing of Square Crash Box

Experimental Numerical

Tensile Testing

Axial Crushing Testing

Numerical and Experimental Analysis


Parametric Study


Theoretical Analysis

Axial Crushing

High Velocity

Low Velocity (up to 10 m/s)

Axial Crushing Column

Material Loading Thin-Walled Structures

Independent of Strain Rate

Dependent of Strain Rate

Static Progressive Buckling

Dynamic Progressive Buckling

Dynamic Plastic Buckling

N Jones. Structural Impact. 2003.Ly Hung Anh. 2007.



Axial Crushing

Folding Mechanism of Square Column

Super folding Element.Inextensional mode plastic deformation.

Annisa Jusuf. 2012.



Axial Crushing

0

20

40

60

0 20 40 60 80 100

Inst

anta

neo

us

Cru

shin

g F

orc

e, P

(kN

)

Crushing Length, (mm)

Instantaneous Crushing Force Curve

Mean Crushing Force Curve

Pm

MEAN CRUSHING FORCE

CRUSHING FORCE EFFICIENCY

Pmax

MAXIMUMPEAK CRUSHING

FORCE


Computational Mechanics


NANOMECHANICS & MICROMECHANICS

CONTINUUM MECHANICS

SYSTEMS

FLUID MECHANICS (CFD)

SOLID MECHANICS

FLUID-STRUCTURE INTERACTION (FSI)

DISCRETIZATION

SPATIAL

FINITE ELEMENT METHOD (FEM)

BOUNDARY ELEMENT METHOD (BEM)

FINITE DIFFERENCE METHOD (FDM)

FINITE VOLUME METHOD (FVM)

SMOOTHED PARTICLE HYDRODYNAMICS (SPH)

EXPLICIT

IMPLICIT

TIME

EXPLICITFINITE ELEMENT

METHODS


Explicit Finite Element Methods


Used in LS-DYNA commercial code

Formulations

Increment 1 Increment 2

Finite Element Steps

Non-iterative

Small time step (conditional stability)


Structural Model


b (mm) t (mm) D/bNumber of Holes

Impact Velocity

(m/s)

Impact Mass

(kg)

Set 1 (Experimental and Numerical )

38 1.15

0

1

4.3684

45.50.3 4.3751

0.5 4.4538

0.7 4.3824

Set 2 (Experimental and Numerical )

38 1.15

0.2

2

4.3812

45.50.3 4.3602

0.5 4.4024

Set 3 (Numerical )

40, 50,…,80

0,0.1,…,0.8

1 & 2 4.5 80


Modeling Procedure


4

1

2

3

5

HOLE location

The hole was introduced in the column model to achieve a stable deformation mode and reduce initial peak load during loading

BOUNDARY condition

The column was fixed in all directions, the constraints are located on every nodes from the lower end of the

columns to 12 mm above to simulate the lower jig in the experiment

The impactor was constrained in all direction except along the vertical axis which coincides with the direction of the impact in order to ensure the impacting mass did

not rotate during impact

VELOCITY

Impact Velocity direction

IMPACTING mass

The impactor was modeled as a rigid body using

hexahedral eight-node solid rigid element

FINITE ELEMENT MODEL OF THE COLUMN

COLUMN wall

The column was fully modeled using quadrilateral Belytscko-Tsay four-nodes shell

elements with size 1 mm x 1 mm


Tensile Testing

Experimental Tests

Engineering Stress – Strain Curve

High Speed Material Testing Machine for INTERMEDIATE STRAIN RATE TENSILE TEST

(strain rate 1/s, 10/s, 100/s)

INSTRON 5585 for QUASI-STATIC TENSILE TEST(strain rate 0.001/s, 0.1/s)

Mechanical Properties of AA 6063 T1

AA 6063-T1

Young’s modulus, E (MPa) 7.32.104

Yield stress, y (MPa) 83.81

Tensile stress, u (MPa) 154

Poisson’s ratio, 0.3

Density, (kg/mm3) 2.7×10–6 0

40

80

120

160

0 0.02 0.04 0.06 0.08 0.1 0.12

Stre

ss,

σ (

MP

a)

Strain, ε

The behavior of AA 6063-T1

is

INDEPENDENT OF THE STRAIN

RATE


Dynamic Axial Crushing Testing

Experimental Tests

DAQ Data acquisition

equipment

Computer

Speed sensor

Specimen

Load cell

Guide column

Steel plate

Concrete base

Hoist

Clamp

Impactor head

Weightening mass

WheelFrame

Schematic drawing and picture of

dropped weight impact testing machine in the

Lightweight Structure Laboratory,

Faculty of Mechanical and Aerospace Engineering

Institut Teknologi Bandung

DROP WEIGHT IMPACT TESTINGMACHINE SPECIFICATIONS :

Max. Impact Mass 150 kg

Max. Impact Height 5 m

Max. Impact Velocity 9.8 m/s



Experimental Tests

Strain Gage

Adjust the signal type and range of the

output

Provide the output signal representing

the measurement in a digital code

Convert a physical property change into

an electrical signal DAQ NI USB-

6211, Sampling Rate 250 kHz

Wheatstone Bridge

Crushing Force History



Experimental Tests

Displacement History

Trapezoidal Integration rule applied


Square Tubes with One Hole

Result and Analysis

square crash box with D/b = 0 (without hole)

COLLAPSE DEFORMATION MODES INSTANTANEOUS CRUSHING FORCE

0

5

10

15

20

25

0 10 20 30 40 50 60 70

Cru

shin

g F

orc

e, P

(kN

)


Experimental

Experimental (smoothing)

Numerical

square crash box with D/b = 0.3

0

5

10

15

20

25

0 10 20 30 40 50 60

Cru

shin

g F

orc

e, P

(kN

)


Experimental


Numerical

Hole

location


Square Tubes with One Hole

Result and Analysis

0

2

4

6

8

10

0 0.2 0.4 0.6 0.8Mea

n C

rush

ing F

orc

e, P

m (

kN

)

D/b

Experimental

Numerical

0

5

10

15

20

25

30

0 0.2 0.4 0.6 0.8

Pea

k C

rush

ing F

orc

e, P

Max

(kN

)

D/b

Experimental

Numerical

0

0.1

0.2

0.3

0.4

0.5

0 0.2 0.4 0.6 0.8

Cru

shin

g F

orc

e E

ffic

ien

cy, C

FE

D/b

Experimental


D/b Pm

(kN)

Pmax

(kN)

CFE Pm

(kN)

Pmax

(kN)

CFE

0 8.09 24.45 0.33 6.78 18.62 0.36

0.3 8.24 22.60 0.36 6.62 17.76 0.37

0.5 7.63 21.55 0.35 6.76 16.39 0.41

0.7 7.84 22.88 0.34 6.19 14.67 0.420

0.1

0.2

0.3

0.4

0.5

0 0.2 0.4 0.6 0.8

Cru

shin

g F

orc

e E

ffic

ien

cy, C

FE

D/b

Experimental

Numerical

0

5

10

15

20

25

30

0 0.2 0.4 0.6 0.8

Pea

k C

rush

ing F

orc

e, P

Max

(kN

)

D/b

Experimental

Numerical

0

2

4

6

8

10

0 0.2 0.4 0.6 0.8Mea

n C

rush

ing F

orc

e, P

m (

kN

)

D/b

Experimental

Numerical


Square Tubes with Two Holes

Result and Analysis

0

5

10

15

20

25

0 10 20 30 40 50 60 70C

rush

ing F

orc

e, P

(kN

)


Experimental


Numerical

square crash box with D/b = 0.2

COLLAPSE DEFORMATION MODES INSTANTANEOUS CRUSHING FORCE

Hole

location


Square Tubes with Two Holes

Result and Analysis

0

2

4

6

8

10

0 0.1 0.2 0.3 0.4 0.5 0.6Mea

n C

rush

ing F

orc

e, P

m (

kN

)

D/b

Experimental

Numerical

0

5

10

15

20

25

30

0 0.1 0.2 0.3 0.4 0.5 0.6Pea

k C

rush

ing F

orc

e, P

Max

(kN

)

D/b

Experimental

Numerical

0

0.1

0.2

0.3

0.4

0.5

0 0.1 0.2 0.3 0.4 0.5 0.6Cru

shin

g F

orc

e E

ffic

ien

cy, C

FE

D/b

Experimental

Numerical


D/b Pm

(kN)

Pmax

(kN)

CFE Pm

(kN)

Pmax

(kN)

CFE

0 8.09 24.45 0.33 6.78 18.62 0.36

0.2 7.71 22.63 0.34 6.29 17.79 0.35

0.3 7.72 21.43 0.36 6.34 17.21 0.37

0.5 7.59 19.55 0.39 6.40 15.29 0.42


Parametric Study

Result and Analysis

0

5

10

15

20

25

0 20 40 60 80 100 120 140

Inst

anta

neo

us

Cru

shin

g F

orc

e, P

(kN

)

Displacement, mm

D/b = 0

D/b = 0.2

D/b = 0.3

D/b = 0.4

D/b = 0.5

D/b = 0.6

D/b = 0.7

D/b = 0.8

Deformation modes of square crash box with b = 40: (a) D/b = 0.3; (b) D/b = 0.4.

Square Columns with One Hole


Parametric Study

Result and Analysis

Square Columns with One Hole

0

2

4

6

8

10

12

0 0.2 0.4 0.6 0.8 1Mea

n C

rush

ing F

orc

e, P

m (

kN

)

D/b

b = 40

b = 50

b = 60

b = 70

b = 800

10

20

30

40

50

60

0 0.2 0.4 0.6 0.8 1

Pea

k C

rush

ing F

orc

e, P

Max

(kN

)

D/b

b = 40b = 50b = 60b = 70b = 80

0

0.1

0.2

0.3

0.4

0.5

0 0.2 0.4 0.6 0.8 1Cru

shin

g F

orc

e E

ffic

ien

cy, C

FE

D/b

b = 40

b = 50

b = 60

b = 70

b = 80


Parametric Study

Result and Analysis

Deformation modes of square crash box with b = 50: (a) D/b = 0.3; (b) D/b = 0.5.

Square Columns with Two Holes

0

5

10

15

20

25

0 20 40 60 80 100 120 140

Inst

anta

neo

us

Cru

shin

g F

orc

e, P

(kN

)

Displacement, mm

D/b = 0

D/b = 0.2

D/b = 0.3

D/b = 0.4

D/b = 0.5

D/b = 0.6

D/b = 0.7

D/b = 0.8


Parametric Study

Result and Analysis

Square Columns with Two Holes

0

0.1

0.2

0.3

0.4

0.5

0 0.2 0.4 0.6 0.8 1

Cru

shin

g F

orc

e E

ffic

ien

cy, C

FE

D/b

b = 40b = 50b = 60b = 70b = 80

0

10

20

30

40

50

60

0 0.2 0.4 0.6 0.8 1Pea

k C

rush

ing F

orc

e, P

Max

(kN

)

D/b

b = 40b = 50b = 60b = 70b = 80

0

2

4

6

8

10

12

0 0.2 0.4 0.6 0.8 1Mea

n C

rush

ing F

orc

e, P

m (

kN

)

D/b

b = 40b = 50b = 60b = 70b = 80


Conclusions


• The numerical simulation can predict the deformation mode compared to the experiment results.

• It is found that inserting holes in a square box column will decrease the peak crushing force and increase the CFE of the column.


Future Works


• Perform numerical and experimental analysis to obtain a higher value of CFE with different geometrical configurations and location of the discontinuities.

• Perform numerical and experimental analysis to study the effect of discontinuities for different material properties.


Thank You

Numerical and experimental impact analysis of square crash box structure with holes

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