The document compares residual stress in equal matching and undermatching weld joints of high strength steel thick plates through numerical simulation. The simulation found that equivalent stress and longitudinal stress were significantly lower in undermatching welds compared to equal matching welds, while transverse stresses were similar. Stress maximums in equal matching welds occurred in both the weld and heat affected zone, while undermatching welds only showed stress maximums in the heat affected zone. The undermatching weld configuration is an effective way to reduce residual stress and avoid cold cracking in high strength steel thick plate welding.

1. IOSR Journal of Engineering (IOSRJEN) www.iosrjen.org
ISSN (e): 2250-3021, ISSN (p): 2278-8719
Vol. 05, Issue 05 (May. 2015), ||V2|| PP 09-13
International organization of Scientific Research 9 | P a g e
Comparison of residual stress in equal matching and undermatching weld joints of the
high strength steel thick plate
Xu Dongxia, Li Dayong, Yang Dongqing, Zhang Guangjun*
State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin, China
Abstract：- In this paper, numerical simulation by finite element software MARC was used to study the residual
stress in equal matching and undermatching weld joints of the high strength steel thick plate. Equal matching
weld selected ferritic welding consumables and the undermatching weld consisted of austenitic welding
consumables. 3D finite element model of thermal-force coupling was developed and the distribution of
residual stress in equal matching and undermatching weld was acquired. The simulation results were analyzed
and compared. The results showed that the equivalent stress and longitudinal stress in undermatching weld joint
are significantly smaller than those in equal matching weld joint, two transverse stresses are not very different.
The stress maximum in equal matching case occurs in the weld and heat affected zone, and stress maximum in
undermatching case appears only in the heat affected zone.
Keywords: - equal matching weld, undermatching weld, residual stress, numerical simulation
I. INTRODUCTION
Due to its high strength, good ductility, toughness and good weldability, low alloy high strength steel
thick plate is widely used in pressure vessels, ships, construction machinery, bridges, buildings, etc. [1]
. Cold
cracking is one of the main problems in welding [2]
. Residual stress due to local heating and strong binding of
thick plate, hardened microstructure and hydrogen content in weld are the three factors to cause cold cracking
[3]
.
An effective measure to avoid cold cracking for the welding of high strength steel thick plate is the use
of undermatching welding joint [4]
. That is the strength of filler metal is lower than the base metal of high
strength steel. For undermatching welding joint, plastic deformation of the weld of good plasticity and
toughness can lower its three-restraint stress, reduce cold cracking tendency [5]
.
In this paper, finite element software Marc was used to simulate welding and later cooling process of
high strength steel thick plate with equal matching and undermatching filler metal. Calculation and analysis of
the distribution of residual stress in two cases were the research focus.
II. THREE-DIMENSIONAL FINITE ELEMENT MODEL
The model of high strength steel thick plate in the simulation is 50 mm thick, 120mm in width and 300mm in
length.
The mesh model is shown in Figure1. The model is established by using the simulation software MARC.MSC.
In order to balance computing accuracy and efficiency, fine mesh is used around weld, but coarse mesh has to
be used far from the weld. There are 30400 elements and 34542 nodes in the model.

2. Comparison of residual stress in equal matching and undermatching weld joints of the high strength
International organization of Scientific Research 10 | P a g e
Fig.1 Three-dimensional finite element model
2.1 The thermal physical and mechanical properties of used materials
Carbon content of high strength steel thick plate adopted in this paper is 0.1%. At the situation of
ambient temperature, the melting point is 1450℃,the Poisson’s ratio is 0.285, the density is 7.8kg/m3
. The
specific heat is 434J·kg-1
·℃-1
, yield strength 850MPa, heat conductivity 30.7k·℃·W·m-1
, thermal expansion
coefficient 1.06×10-5
℃-1
, and Young’s modulus 2.08×105
MPa.
0 500 1000 1500 2000 2500 3000 3500
30
40
50
60
70
80
90
100
Thermomechanicalproperties
Temperature/℃
Thermal-conductive coefficient（ W/m*℃）
Specific heat（ ×10J/kg*℃）
0 500 1000 1500 2000 2500 3000 3500
0
5
10
15
20
Mechanicalproperties
Temperature/℃
Young's modulus（ ×104Mpa）
Yield stress（ ×102Mpa）
Heat expansion coefficient（ 10-6/℃）
(a) Base matal
0 500 1000 1500 2000 2500 3000
10
15
20
25
30
35
40
45
50
55
60
65
Thermomechanicalproperties
Temperature/℃
Thermal-conductive coefficient（ W/m*℃）
Specific heat（ ×10J*kg/℃）
0 500 1000 1500 2000 2500 3000
0
5
10
15
20
7.644 (13.54%)
Mechanicalproperties
Temperature/℃
Young's modulus（ ×104MPa）
Heat expansion coefficient（ 10-6/℃）
Yield stress（ ×102MPa）
(b) Austenitic welding consumables
Fig.2 Thermomechanical properties
At room temperature, the used austenitic welding consumables have 0.3 Poisson’s ratio, and its density is
7.93kg/m3
.
Figure 2 shows the thermodynamic properties of used materials.

3. Comparison of residual stress in equal matching and undermatching weld joints of the high strength
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III. RESULTS AND DISCUSSIONS
3.1 Stress nephogram
It can be seen from stress nephogram in Figure 3 that the maximal equivalent stress in equal
matching case occurs in weld and heat affected zone, which value is 780Mpa. The maximal equivalent stress in
undermatching case exists only in heat affected zone, which value is 734Mpa, 6% less than that in equal
matching joint.
(a) Equal matching (b) Undermatching
Fig.3 Equivalent Von Mises Stress
The transverse stress and longitudinal stress distributions are shown in Figure 4 and Figure 5
respectively. The maximal transverse stress in equal matching joint is 458Mpa，434Mpa in undermatching case.
The two values are roughly same.
(a) Equal matching (b) Undermatching
Fig.4 Transverse stress nephogram
(b) Equal matching (b) Undermatching
Fig.5 Longitudinal stress nephogram
For equal matching joint, maximal longitudinal stress is 922Mpa, which occurs in weld and
heat-affected zone; For undermatching joint, maximal longitudinal stress is 780Mpa, which exists only in
heat-affected zone. It also can be seen that stress distribution in undermatching case is more uniform than that in

4. Comparison of residual stress in equal matching and undermatching weld joints of the high strength
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equal matching joint.
3.2 Stress distribution curves
0 25 50 75 100 125 150 175 200
0
100
200
300
400
500
600
700
800
900
Longitudinalstress/Mpa
Distance/mm
Matching
Undermatching
the welding direction
0 25 50 75 100 125 150 175 200
-200
-100
0
100
200
300
400
Transversestress/Mpa
Distance/mm
Matching
Undermatching
the welding direction
(a) Longitudinal stress (b) Transverse stress
0 25 50 75 100 125 150 175 200
300
400
500
600
700
800
EquivalentVonMisesStress/Mpa
Distance/mm
Matching
Undermatching
the welding direction
(c) Equivalent stress
Fig.6 Distribution of residual stress on weld toe along weld direction in two cases
Residual stress distribution on weld toe along welding direction is shown in Figure 6. There exists a
stable zone in the middle part of weld for the transverse stress, longitudinal stress and equivalent stress. Stresses
on two ends of weld vary quickly. The equivalent stress and longitudinal stress on weld toe of undermatching
weld joint are significantly smaller than those in equal matching weld joint. The maximal equivalent stress on
weld toe in equal matching joint is 773Mpa, the maximal longitudinal stress is 801Mpa. For undermatching
joint, maximal equivalent stress on weld toe is 601Mpa, 22% smaller than equal matching joint, and the
maximal longitudinal stress is 653Mpa, 18% smaller than equal matching joint. The transverse stresses in tow
cases are roughly same.
Figure 7 shows stress distribution on top surface of the middle section with different filling materials. It
can be seen that the trend of stress distribution is roughly same in equal matching and undermatching joint. The
difference is that the stress in undermatching weld is significantly less than stress in equal matching joint.

5. Comparison of residual stress in equal matching and undermatching weld joints of the high strength
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0 10 20 30 40 50 60 70 80 90 100
-200
0
200
400
600
800
Longitudinalstress/Mpa
Distance/mm
Matching
Undermatching
0 10 20 30 40 50 60 70 80 90 100
-300
-200
-100
0
100
200
300
400
500
Transversestress/Mpa
Distance/mm
Matching
Undermatching
(a) Longitudinal stress (b) Transverse stress
0 10 20 30 40 50 60 70 80 90 100
0
100
200
300
400
500
600
700
800
EquivalentVonMisesStress/Mpa
Distance/mm
Matching
Undermatching
(c) Equivalent stress
Fig.7 Distribution of residual stress perpendicular to weld direction in two cases
IV. CONCLUSIONS
(1) Temperature field and stress field of high strength low alloy steel weldment with different filling materials
were successfully simulated by Marc finite element simulation software.
(2)The equivalent stress and longitudinal stress in undermatching weld joint are significantly smaller than those
in equal matching weld joint, two transverse stresses are not very different.
(3) The stress maximum in equal matching case occurs in the weld and heat affected zone, and stress maximum
in undermatching case appears only in the heat affected zone.
V. ACKNOWLEDGMENTS
The authors gratefully acknowledge the financial support provided by the National Natural Science Foundation
of China under grant No. 51175119.
REFERENCES
[1] Fang Hongyuan. Welding structure. Beijing: Machinery Industry Press (in Chinese),2008.
[2] Leggatt R H. Residual stresses in welded structures [J]. International Journal of Pressure Vessels and
Piping, 2008, 85:144-151.
[3] Xu G , Burdekin F M. Effects of residual stresses on constrain and fracture behavior of wide plates [J].
Mathematical, Physical and Engineering Sciences, 1998,454:2505-2528.
[4] Deb P, Challenger K D, Therrien A E. Structure-property correlation of submerged-arc and gas-metal-arc
weldments in HY-100 steel[J]. Metallurgical Transactions A, 1991, 18(6): 987-999.
[5] Duane K. Miller, P.E. Use Undermatching Weld Metal Where Advantageous. Welding Innovation Vol.
XIV, NO.1,1997.