Scholarly article on topic 'Thermal Stress Analysis of dissimilar welding joints by Finite Element Method'

Thermal Stress Analysis of dissimilar welding joints by Finite Element Method Academic research paper on "Mechanical engineering"

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Abstract of research paper on Mechanical engineering, author of scientific article — Shu Xu

Abstract his paper relates to the dissimilar welding joints of 45, 0Cr18Ni9 and 1Cr9Mo steel using the different welding metal A302 or Inconel182. The thermal stress numerical simulation is carried out to the dissimilar welding joints. The thermal stresses of dissimilar welding joints generated in the heating to 450°C from the ambient temperature for 45/1Cr9Mo and 45/0Cr18Ni9 and 500°C for 1Cr9Mo/0Cr18Ni9 are calculated by finite element method. It is shown that large tensile stress is generated in the weld metal, fusion line and heat affected zone (HAZ) when the welding metal is A302, while the compressive or low tensile stress is shown in the HAZ and fusion line of 1Cr9Mo or 45 steel. The maximum circumferential stress is presented in 1Cr9Mo or 45 steel, while the large compressive or low tensile stress is shown in 0Cr18Ni9. The stress is decreased when the A302 is changed to Inconel182. It is concluded that the replacement of A302 by Inconel182 can decrease the thermal stress and increase the life of the welding joint.

Academic research paper on topic "Thermal Stress Analysis of dissimilar welding joints by Finite Element Method"

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W70 ELSEVIER

Procedía Engineering

Procedía Engineering 155 (2011) 3860 - 3864

www.elsevier.com/Iocate/procedia

Advanced in Control Engineering and Information Science

Thermal Stress Analysis of dissimilar welding joints by Finite

Element Method

Shu Xua a*

Abstract:This paper relates to the dissimilar welding joints of 45, 0Cr18Ni9 and 1Cr9Mo steel using the different welding metal A302 or Inconel182. The thermal stress numerical simulation is carried out to the dissimilar welding joints. The thermal stresses of dissimilar welding joints generated in the heating to 450 °C from the ambient temperature for 45/1Cr9Mo and 45/0Cr18Ni9 and 500 °C for 1Cr9Mo/0Cr18Ni9 are calculated by finite element method. It is shown that large tensile stress is generated in the weld metal, fusion line and heat affected zone (HAZ) when the welding metal is A302, while the compressive or low tensile stress is shown in the HAZ and fusion line of 1Cr9Mo or 45 steel. The maximum circumferential stress is presented in 1Cr9Mo or 45 steel, while the large compressive or low tensile stress is shown in 0Cr18Ni9. The stress is decreased when the A302 is changed to Inconel182. It is concluded that the replacement of A302 by Inconel182 can decrease the thermal stress and increase the life of the welding joint.

© 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of [CEIS 2011]

Keywords; dissimilar welding joints, finite element method, thermal stress analysis

1 Introduction

Dissimilar welding joints causes joint parts produce complex thermal stress, which makes the welding joint become a relatively weak link[1-3], mainly because coefficient of thermal expansion between

* Corresponding author. Tel.:+115298615182; E-mail address: gladxushu@163.com.

aSchool of Mechanical Engineering, Huaihai Institute of Technology, Lianyungang , China

1877-7058 © 2011 Published by Elsevier Ltd. doi:10.1016/j.proeng.2011.08.722

Uhu Xu / Procedia Engineering 15 (22011) 0860 - 3864

materials or between material and the welding materials has large difference[4-6]. Under the working conditions of alternating temperatures or temperature fluctuations, thermal stress can lead to joints craze early[7-10]. So predicting and analysis distribution of dissimilar welding joints thermal stress only in temperature variation by the numerical simulation has important significance.

This paper proposed finite element simulation of dissimilar steel welding joint involved in six different kinds ( 45+A302+1 Cr9Mo , 45+ A302 +0Cr18Ni9 , 1Cr9Mo+A302+0Cr18Ni9 , 45+Inconel182+1Cr9Mo, 45+Inconel182+ 0Cr18Ni9 fP 1Cr9Mo+Inconel182+0Cr18Ni9) and welding joint thermal stress in variable temperature conditions, the stress distribution of six joints is analyzed, then mechanical properties are tested on .

2. The finite element analysis of the dissimilar welding joints thermal stress

Using ABAQUS6.5, a followed coupled the thermal stress calculation program to simulate the welding residual stress is studied. Firstly, the thermal analysis in calculating is made, calculation results files of each node temperature field will be as mechanics analysis of predefined field, in the process of mechanics analysis, each point of temperature from the predefined games is read, and interpolation is calculated , the same unit and the node is adopted in thermal analysis and force analysis .

2.1Establish the finite element model

Figure 1 shows the geometrical structure schematic drawing of the weld joint. Materials respectively are 1Cr9Mo/45, 0Cr18Ni9/45 and 1Cr9Mo / 0Cr18Ni9; welding materials are A302 or Incone182. According to the requirement of GB985-88 "the basic form and size of the welding seam groove about gas welding, manual arc welding and gas shielded ", V type groove is adopted.

Ax symmetric unit is used in model uses. Considering the stress concentration parts in the welding parts and heat affected zone, so meshing of the welding joint is divided carefully in welding parts, and is divided roughly far away welding parts. Meshing of welding and heat affected zone is shown in figure 2.

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Fig 1 Geometric model of the welding joint

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Fig. 2 Meshing of the welding joint

2.2 Lord rnd boundary conditions

Considering the six joint application temperature in the projects, heterogeneous steel 45/1Cr9Mo and 45/0Cr18Ni9 welding joint heated from ambient temperature (25 °C) to 400 °C, 1Cr9Mo / 0Cr18Ni9 heated from ambient temperature (25 C) to 500 C are analoged. Temperature load is applied on directly;

3862 Shu Xu/Procedia Eengineering 15 (2011) 3860 - 3864

residual stress distribution of six joints in only the temperature rises is analoged. During the heating process, the temperature field and stress field adopt direct coupling. Due to whole heating in the joint, so we don't consider the thermal radiation and the convection in the heating process .In addition, its axial movement is limited.

3 The results of the finite element analysis

Thermal stress convective distributions of six dissimilar welding joints are shown in Figure 3 ~ figure 8.

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Fig. 3 thermal stress of the joint lCr9Mo (left) +A302+45 (right) at 450°C

Fig. 4 Thermal stress of the joint lCr9Mo (left) +Inconel 182+45 (right) at 450°C

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Fig. 5 Thermal stress of the joint 0Crl8Ni9 (left ) +A302+45 (right ) at 450°C

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Fig. 6 Thermal stress of the joint 0Cr18Ni9 (left) +Inconel182+45 (right) at 450 °C

Fig. 7 Thermal stress of the joint lCr9Mo (left) +A302+0Crl8Ni9 (right) at 500°C

Fig. 8 Thermal stress of the joint 1Cr5Mo (left) +Inconel182+0Cr18Ni9 (right) at 500 C

Shu Xu / Procndia Engineering 15 (22011) 3860 - 3864

The left diagrams in figure 3 ~ figures 8 are distribution of axial stress and the right diagrams in figure 3 ~ figures 8 are distribution of circumferential stress .From figure 3 ~ figure 8, we can see: due to the difference of thermal expansion coefficients, six dissimilar welding joints produced the larger axial thermal stress in the fusion line. When 1Cr9Mo + A302 + 45 joints is heated to 450 °C, the larger axial compressive stress in the sides of 1Cr9Mo and 45 steel is produced, and the larger tensile stress in the welding line is produced; When welding materials are nickel-based Inconel182, axial compressive stress will be decreased gradually, eventually, compressive stress is still existed in 1Cr9Mo side, while pressure stress is transformed into tensile stress in 45 steel side. When 0Cr18Ni9 + A302 + 45 joints is heated to 400 C, the larger axial tensile stress is produced in the welding line of the side of 0Cr18Ni9, larger axial compressive stress is produced in the 45 steel side; When the welding material is nickel-based Inconel182, although axial stress has been increased, distribution has greatly been improved, and it is mainly distributed on welding fusion line. when 1Cr9Mo + A302 + 0Cr18Ni9 is heated up to 500 C, the larger axial tensile stress is also produced in the side and beside of 0Cr18Ni9, and larger axial compressive stress is produced in 1Cr9Mo side; When the welding material is nickel-based Inconel182, the thermal stress has not large changes in values, but stress distribution has greatly been improved, and transferred to welding fusion line.

And this larger thermal circumferential stress of six kinds of dissimilar welding joint mainly is distributed in the materials near the welding line and austenitic welding line. When 1Cr9Mo + A302 + 45 joints is heated to 450 C, larger circumferential tensile stress and tensile stress are produced in 1Cr5Mo and 20 steel , the larger compressive stress is produced in welding line; When the welding materials are nickel-based Inconel182, annular compressive stress is reduced. When 0Cr18Ni9 + A302 + 45joint are heated to 400Cand 1Cr9Mo + A302 + 0Cr18Ni9 are heated to 500C, all the larger axial compressive stress are produced in 0Cr18Ni9, larger axial tensile stress are produced in 45 steel and 1Cr5Mo steel side, and the more larger compressive stress are also produced in austenitic welding line; When the welding materials are nickel-based Inconel182, circumferential stress decreased in some degree in values , compressive stress transform to tensile stress in the welding line, the distribution of stress has greatly been improved.

Generally we can see from the comparison and analysis: when perform austenitic welding, due to the larger axial thermal stress, there is greater tensile stress exists in austenite weld or austenitic materials (0Cr18Ni9) fusion line or heat affected zone; And in ferritic materials (1Cr9Mo or 45 steel), near the fusion line and heat affected zone materials is kept in compressive stress state or low tensile stress state. And the larger tensile stress of circumferential stress is appeared in ferrite materials (1Cr9Mo or 45 steel), while the larger compressive stress or low tensile stress is existed in austenitic materials. This mainly because thermal expansion coefficient of austenite materials is larger than ferrite materials, after heated , the expansion obstruction in ferrite leads larger compressive stress or smaller tensile stress existing in ferrite side, and there is larger tensile stress in austenitic. Because of the influence of weld groove, the compressive or tensile stress location of the circumferential stress is not existed in surface fusion welding line. And Ni-based Inconel182 is adopted; the distribution of thermal stress has been improved. The value of thermal expansion coefficient of Inconel182 is stayed among ferrite materials and austenitic. Materials expanding differences of the heterogeneous steel have better been coordinated.

4. Conclusion

From six kinds of thermal stress of dissimilar welding steel welded joint by FEM simulation results, we can have some below conclusions:

1. When the welding of austenitic electrodes A302 is used, large axial tensile stress exists in austenite or austenite weld fusion line of base metal 0Cr18Ni9 and heat-affected zone; and 1Cr5Mo or 45 steel near the fusion line of base metal and heat affected zone stays in a state of compressive stress or low tensile stress. This was mainly because thermal expansion coefficient of austenite materials than ferrite materials

SUu Xu / Procedia Engineering 35 (2033) 3860 - 3864

larger, after heated, the obstruction of expansion in ferrite leads to ferrite side has compressive stress or smaller tensile stress, and austenitic side has larger tensile stress, due to the influence of welding breach Angle, the location of tensile or compressive stress in circumference is not on the fusion line of welding seams surface.

2. When soldering by nickel-based electrode Inconel182 instead of austenitic electrode A302, the distribution of thermal stress has great improved, stress in values has a certain degree of decline. Visibly, adopting Inconel182 to replace A302, this can effectively change the joint distribution of thermal stresses, and improve the life of the joint.

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