【JWS-2012-Spring-Revised】Study on Tendon Force For ...

STUDY ON TENDON FORCE FOR BUCKLING WELIDNG DISTORTION

◯Jiangchao Wang1, Xianqing Yin2, Ninshu Ma1 and Hidekazu Murakawa1 1 Joining and Welding Research Institute, Osaka University, Japan

2 School of Material Science and Engineering, Xi’an Jiaotong University, China

Keywords: Tendon Force, Buckling Behavior, Welding Distortion, Thermal Elastic Plastic FEM

INTRODUCTION In order to improve fuel economy and enhance

the carrying capacity, thin plates are widely used to minimize the weigh of modern vehicle such as ship, car, train and aircraft. When thin plates are assembled by welding, the buckling type welding distortion will occur. In this study, deformation of a thin plate under bead on plate welding is measured by digital camera, and then the inherent deformation method is introduced to reproduce this buckling behavior under welding. THEORY OF TENDON FORCE

According to the welding mechanics, the longitudinal shrinkage and buckling welding distortion are considered as the result of tendon force. In 1980, White et al [1] introduced the concept of tendon force and proposed a formula based on experimental measurement given by Eq. (1)

QFtendon 2.0 (1)

Where, Q means the heat input per unit length. Later, the heat conduction during the welding

process and the inherent strain produced by thermal cycle are investigated and an equation for tendon force given by Eq. (2) is presented [2].

Qc

EFtendon

335.0 (2)

Where, E, α,ρand c mean the young’s modules, thermal expansion coefficient, density and specific heat of material, respectively.

The relation between the tendon force and the inherent deformation is presented given by Eq. (3)

dxdyEEhF LLtendon** (3)

Where, *L , *

L mean the inherent deformation and

inherent strain in the longitudinal direction, x and y denote the coordinate in longitudinal and transverse directions, respectively. EXPERIMENT AND MEASUREMENT

A thin steel plate is selected as a test specimen, the size of which is 300×200×2.28 (mm) and its yield stress is 235MPa. Bead on plate welding is performed using MIG and the welding condition is shown in Table. 1. Figure 1 shows the thin plate after bead on plate welding and buckling distortion measured by digital camera is shown in Fig. 2.

COMPUTATION AND DISCUSSION The in-house code JWRIAN (Joining and

Welding Research Institute ANalysis) consists of a 3D thermal elastic plastic finite element code based on the iterative substructure method and a 2D elastic finite element code using the inherent deformation. The buckling type welding distortion can be reproduced by the large deformation theory in which the initial deflection is considered. 1) Prediction of Welding Distortion and Evaluation of Inherent Deformation by TEP Analysis

Using same welding condition, a 3D thin plate model shown in Fig. 3 is analyzed to predict the welding distortion and evaluate the inherent deformation. Computed welding distortion is shown in Fig.4.

Table 1 welding condition Current Voltage Velocity 100 (A) 13.5(V) 6.25(mm/sec)

Fig. 1 thin plate after bead on plate

3.0

2.01.0

0.0

-1.0

-2.0

-3.0-4.0

-5.0

-6.0

-7.0-8.0

-9.0

-10.0

-11.0

Max: 2.8626 (mm) Min: -10.1544 (mm)

X

Z

Y Fig.2 measured buckling welding distortion

X

Z

YNode: 22445Element: 17600

Fig. 3 solid computational model for TEP analysis

6.05.04.03.02.01.00.0-1.0-2.0-3.0-4.0-5.0-6.0-7.0

Z Direction Max Min Displacement 5.3181 -6.6018

X

Z

Y

Fig. 4 computed welding distortion by TEP method

-0.4

-0.3

-0.2

-0.1

0

0.1

0 50 100 150 200 250 300

Longitudinal ShrinkageTransverse ShrinkageTransverse BendingLongitudinal Bending

Inh

eren

t D

efor

mat

ion

Wedling Line (mm) Fig. 5 evaluated inherent deformation by TEP method

Table 2 the value of inherent deformation

Long Shrinkage

Trans Shrinkage

Trans Bending

Long Bending

0.1034 0.3730 0.0479 -0.0205 According to the definition of inherent

deformation, plastic strain computed by TEP analysis is integrated to obtain the inherent deformation. Figure 5 shows the distribution of inherent deformation and the average value of inherent deformation is shown in Table.2.

2) Prediction of Buckling Welding Distortion

When the inherent deformation produced by welding is known, elastic analysis can be used to investigate the welding distortion problem. Meanwhile, tendon force is considered as the reason of buckling type welding distortion and it can be obtained from the inherent deformation through Eq. (3).

Figure 6 shows the shell model for elastic analysis and line 1 is selected to compare the experimental and computed welding distortion. The computed buckling distortion is shown in Fig. 7 when the initial deflection is considered. A good agreement compared with the measurement is observed in Fig. 8.

X

Z

YNode: 2562Element: 2400

Line 1

Fig. 6 shell model for elastic analysis

Z Direction Max Min Displacement 4.0584 -7.5750

X

Z

Y

5.0

4.0

3.0

2.0

1.0

0.0

-1.0

-2.0

-3.0

-4.0

-5.0

-6.0

-7.0

-8.0

Fig. 7 buckling welding distortion predicted by

inherent deformation method

-12

-10

-8

-6

-4

-2

0

2

4

0 50 100 150 200

Initial DeflectionMeasured DisplacementComputed Displacement

Z D

irec

tion

Dis

pla

cem

ent

(mm

)

Transverse Direction (mm) Fig. 8 comparison between measurement and computation by elastic analysis along line 1

CONCLUSION

When the initial deflection is considered and the large deformation theory is used in inherent deformation method, the buckling welding distortion was accurately predicted compared with measurement. REFERENCE J. D. White, et al. Weld Shrinkage Prediction. Welding and Metal Fabrication, 1980(11), 587-596 Y. Ueda, et al. Computational Approach to Welding Deformation and Residual Stress. 2007