crush performance of thin walled spot-welded and weld .../media/files/autosteel/great designs...

Crush Performance of Thin Walled

Spot-Welded and

Weld-Bonded Sections

w w w . a u t o s t e e l . o r g

Weld-Bonded Sections

Paul Davidson*, M.S Engineering

Prof. Donald Malen

University of Michigan, Ann Arbor, MI – 48109

*[email protected]

Acknowledgement

This project was sponsored by the Weld Bond Project Team of the

Auto Steel Partnership


Auto Steel Partnership

Objective

• Determine influence of weld

pitch and adhesive on axial

load deflection characteristics

of a hexagonal thin walled

section.


Expected results

• Adhesive improves stability and average crush force for thin metals.

• Adhesive has little effect on thicker, more stable sections.

• Adhesive is more effective for greater spot


• Adhesive is more effective for greater spot weld spacing.

Model Geometry

Rigid Mass

Impacting velocity

- Hex Section column was considered for this drop test simulation. - A 400mm tall column axial impact-loaded with rigid mass of 139kg and 11.15m/s velocity.- Adhesive with uniform thickness of 0.66mm was considered.- Simulation was conducted using LSDYNA® Explicit code.


Impacting velocity

Adhesive Modeling

1. Gurson shell model

2. Gurson solid model

Metal Mid Plane

Metal Mid PlaneAdhesive Mid Plane

• Two modeling methods and 5 Adhesive models benchmarked with physical test.• Gurson shell model was selected for this study.

Shell Model

Physical section

Continuum model


1. Arup solid model

2. Johnson-Cook solid model

Solid Model

Tie Break Contact

Cohesive model

Work Breakdown

Between spot weld buckling

Without adhesive

Planar

flange

Imperfect

flange

With adhesive

Planar

flange

Imperfect

flange


Thickness

(mm)

Pitch (mm)

0.7

2.2

10020 60

1.5

HSLA 350Thickness

(mm)

Pitch (mm)

0.7

2.2

10020 60

1.5

DP 590

IHS140 DP 980

Thickness

(mm)

Pitch (mm)

0.7

2.2

10020 60

1.5

HSLA 350Thickness

(mm)

Pitch (mm)

0.7

2.2

10020 60

1.5

DP 590

IHS140 DP 980Thickness

(mm)

Pitch (mm )

0.7

2.2

10020 60

1.5Thickness

(mm)

Pitch (mm )

0.7

2.2

10020 60

1.5Thickness

(mm)

Pitch (mm )

0.7

2.2

10020 60

1.5Thickness

(mm)

Pitch (mm )

0.7

2.2

10020 60

1.5

Responses

• Response reported are:‒ Fmax – Maximum load.‒ - Average force taken over the entire displacement.‒ Energy absorbed is given by

Fatotal

Fmax

Cripple event

Crush event


Fatotal

0 25 255 Dmax

Forc

e

Displacement (mm)

Data Analysis

Pitch [m

m]

High strength –High thickness

High strength –Low thicknessLow strength –

Low thickness

Low strength –


• Comparison of behavior at the extreme parameters of design.• DP890 and IF140 were characterized with strain rate sensitivity.

Pitch [m

m]

Low strength –High thickness

IF140 No Adhesive

Fmax Fatotal Dmax

10.6 2.53 357.59

Fmax Fatotal Dmax

10.6 2.53 356.5

Fmax Fatotal Dmax

10.6 2.53 357.7

Fmax Fatotal Dmax

25.4 8.09 107.4

Fmax Fatotal Dmax

25.4 7.43 117.1

Fmax Fatotal Dmax

25.5 8.02 108.4

p = 20mm 60mm 100mm

0.7

mm

1.5

mm


25.4 8.09 107.4 25.4 7.43 117.1 25.5 8.02 108.4

Fmax Fatotal Dmax

39.1 15.4 56.01

Fmax Fatotal Dmax

39.0 15.2 56.74

Fmax Fatotal Dmax

39.1 12.8 67.31

1.5

mm

t =

2.2

mm

All forces in x104N

IF140 With Adhesive

Fmax Favg Dmax

13.15 3.11 287.07

Fmax Favg Dmax

12.6 2.84 316.67

Fmax Favg Dmax

12.6 2.50 361.07

Fmax Favg Dmax

27.1 9.97 86.88Fmax Favg Dmax

27.6 9.63 90.07

Fmax Favg Dmax

27.6 9.82 88.24

20mm 60mm 100mm

0.7

mm

1.5

mm


27.1 9.97 86.88 27.6 9.63 90.07 27.6 9.82 88.24

Fmax Favg Dmax

41.4 20.7 41.74

Fmax Favg Dmax

41.4 21.5 40.31

Fmax Favg Dmax

41.4 21.5 40.15

1.5

mm

2.2

mm

All forces in x104N

Qualitative Observations

IF140 p=100mm, t=2.2mm

Pitch [m

m]


Pitch [m

m]

AdhesiveNo Adhesive

IF140 p=100mm, t=2.2mm

time=0.002sec

Cripple Event

Puckering No


Expected difference in flange buckling mode

Puckering No

Puckering

IF140 p=100mm, t=2.2mm

No adhesive case: interweld

buckling initiates crush mode with

low average force level

350,000

400,000

450,000

No adhesive Adhesive

Crush Event


0

50,000

100,000

150,000

200,000

250,000

300,000

350,000

0 0.02 0.04 0.06 0.08

time=0.010s

Deformation (m)

Fo

rce

(N

)no adhesive

with adhesive


IF140 p=100mm, t=0.7mm

Pitch [m

m]


Pitch [m

m]

AdhesiveNo Adhesive

IF140 p=100mm, t=0.7mmtime=0.001sec

Cripple Event

Cripple Event

Puckering No


Expected difference in flange buckling modes

Note: natural buckling wave length does not depend on spot weld spacing for no-adhesive case

Puckering No

Puckering

No adhesive

Adhesive

No adhesive case: Expected

flange buckling mode

-Flange folding.

-Euler buckling of corner

IFS140. t=0.7mm, p=100mm

Crush Event


time=0.016s

0

20,000

40,000

60,000

80,000

100,000

120,000

140,000

0.00 0.10 0.20 0.30 0.40Deformation (m)

Fo

rce

(N

)

no adhesive

with adhesive

Ivv

v

v

v

v

Flange Foldingv

v


Adhesive case: Euler buckling of

corner initiates an unstable crushing mode

IFS140. t=0.7mm, p=100mm

140,000


Unstable Crush


time=0.034s

0

20,000

40,000

60,000

80,000

100,000

120,000

140,000

0.00 0.10 0.20 0.30 0.40Deformation (m)

Fo

rce

(N

)

no adhesive

with adhesive


DP980 p=100mm, t=2.2mm

Pitch [m

m]


Pitch [m

m]

DP980 p=100mm, t=2.2mm

time=0.004s

For this impact energy level, corner crippling dominates average force level


no adhesive with adhesive

Crush Event


time=0.004s

0

200,000

400,000

600,000

800,000

1,000,000

0 0.005 0.010 0.015 0.020 0.025

Fo

rce (

N)

Deformation (m)


DP980 p=100mm, t=0.7mm

Pitch [m

m]


Pitch [m

m]

DP980, t=0.70mm, p=100mm

300,000

350,000

Fo

rce (

N)


Adhesive case: corner initiates an unstable crushing mode

Crush Event


0

50,000

100,000

150,000

200,000

250,000

300,000

0.00 0.05 0.10 0.15 0.20

Fo

rce (

N)

Deformation (m)

time=0.015sno adhesive

with adhesive

Expected v.s Observed

• Adhesive improves

stability and average

crush force for thin

metals.

• Adhesive has little

• Adhesive lowers

stability and average

crush force for thin

metals.

• Adhesive increases

EXPECTED OBSERVED


• Adhesive has little

effect on thicker, more

stable sections.

• Adhesive is more

effective for greater

spot weld spacing.

• Adhesive increases

average crush force for

thicker sections.

• Adhesive is not

always more effective

for greater spot weld

spacing.

Favg: DP980

20mm

60mm

100mm

1.5mm 2.2mm

Pe

rce

nta

ge

Im

pro

ve

me

nt

[%]

0

20

40

60

80

100

SW

Adhesive v/s No adhesive: Favg

0

20

40

60

80

100

0.7 mm 1.5mm 2.2mm

Favg: IF140

20mm

60mm

100mm

Pe

rce

nta

ge

Imp

rove

me

nt

[%]

SW


0.7 mm 1.5mm 2.2mm

Pe

rce

nta

ge

Im

pro

ve

me

nt

[%]

-20

0

t

• Relation of Fatotal improvement is inconsistent with spot weld pitch.• Also there is no clear relationship between thickness and Fatotal

-20

00.7 mm 1.5mm 2.2mmP

erc

en

tag

e Im

pro

vem

en

t [%

]

t

Adhesive v/s No adhesive: Fmax

0

20

40

60

Pe

rce

nta

ge

Im

pro

ve

me

nt

[%]

0.7mm

1.5mm

2.2mm

Fmax: IF140

80

100

20mm

60mm

100mm

SW

Pe

rce

nta

ge

Imp

rove

me

nt

[%]

20mm

60mm

100mm

DP890

0

20

40

60

80

100

SW

Fmax: DP590Fmax: DP980


IF140 shows expected increase in Fmax at low thicknesses.

-20

0

0.7 1.5 2.2

Pe

rce

nta

ge

t

Pe

rce

nta

ge

Imp

rove

me

nt

[%]

-20

0

0.7 1.5 2.2

t

Work done

-20

0

20

40

60

80

100

0.7 mm 1.5mm 2.2mm

Favg: IF140

20mm

60mm

100mm

Pe

rce

nta

ge

Im

pro

ve

me

nt

[%]

t

SW

MODELING SIMULATIONS RESULTS


0.00E+00

5.00E+04

1.00E+05

1.50E+05

2.00E+05

2.50E+05

3.00E+05

3.50E+05

4.00E+05

4.50E+05

5.00E+05

0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00

Fa

vg

[N]

�p

----- : With adhesive

___ : No adhesive

DP980

HSLA350

IF140

2.2mm

1.5mm

0.7mm

σcr-p>σy σcr-p<σy

DP590

F

?

0m

m

~25m

m

>100mm

peak

Axial deformation

Axial force

Thick walled section

Thin walled section

ANALYSISCALCULATIONCORRELATION

• For the fixed energy level used in this DOE (mv2/2), the mean crush force for the thicker and higher strength conditions was dominated by corner crippling behavior

•Spot weld pitch does not have a strong, consistent influence on mean crush force improvement with adhesive

•Plate slenderness is an important indicator for mean crush force. The

Conclusion


•Plate slenderness is an important indicator for mean crush force. The benefit of adhesive bonding is greater for less slender plates (β small)

•An adhesive bonded flange can precipitate an unstable crush mode particularly for sections with slender plates

•Before extending the DOE, it is necessary to understand progressive buckling behavior of the structure (see suggestions for Future Work)

• Theoretical study of:• Buckling Modes• Progression during crush

• Sensitivity study (Robustness)• Pillowing• Imperfection: flange angle, section shape, etc• Strain rate• Crush initiator presence and type

Future work


• Crush initiator presence and type

Thank You!


Thank You!

crush performance of thin walled spot-welded and weld .../media/files/autosteel/great designs...

Documents