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Hoop residual stress at 180° central angle on the inner surface, AISI304 pipe, against axial distance.
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Experimental tests of multi-pass lined pipe welding are reported and a computational procedure for the determination of the history of temperature, strains and residual stresses is presented in this paper and validated against the experimental test results. The effect of the manufacturing process of the lined pipe on the thermo-mechanical analysis...
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Citations
... Results showed that the longitudinal weld resulted in high tensile stress and was not applicable to the manufacture of cylindrical components. Obeid et al. [27] carried out a 3-D FE model to evaluate the lap-weld and butt-weld in the circumferential welding process of lined pipe. The numerical results show a good correlation with the experimental. ...
The inner tank is the core weldment of the electric water heater (EWH). During service, leakage often occurs at the welds of the inner tank due to stress concentration. Reducing the welding residual stress and deformation is crucial to improve its service life. In this paper, the welding process optimization of the inner tank was investigated by numerical simulation and experimental validation. The influence of the welding sequence and welding start location of the circumferential welds (C-Welds) on the welding residual stress and deformation have been fully analyzed. The results show that the welding sequence has little effect on decreasing the welding residual stress and deformation. The peak welding residual stress and deformation reach a minimum of 170.06 MPa and 0.897 mm when the welding start location of the C-Welds was adjusted from 180° to 270° clockwise from the longitudinal weld (L-Weld), a reduction of 15.17 % and 12.98 %, respectively. The welding start location of the C-Welds is the determining factor of welding residual stress and deformation. To verify the effectiveness of the proposed welding process, full-scale welding and pulse pressure experiments were carried out. The pulse number of the inner tank has reached over 100,000 times, which satisfies the requirements of welding quality of the enterprise. This article is valuable for guiding the service life improvement of the inner tank, which results in economic efficiency growth.
... The actual pipeline welding layer has a certain radian in the welding process due to various reasons. Such as concave, convex, and hump [20][21][22][23][24][25], as shown in Figure 4. To facilitate the study of the filling strategy of the weld filling layer, simplified processing is carried out, and the actual filling layer is treated as an isosceles trapezoid. The schematic diagram of the filling is shown in Figure 5. ...
With the increase in transmission pressure and pipe diameter of long-distance oil and gas pipelines, automatic welding of the pipeline has become the mainstream welding method. The multi-layer and multi-pass welding path planning of large-diameter pipelines with typical narrow gap grooves are studied, and a welding strategy for pipeline external welding robot is proposed. By analyzing the shape of the weld bead section of the narrow gap groove and comparing the advantages and disadvantages of the equal-height method and the equal-area method, the mathematical model of the filling layer is established. Through the test and analysis in the workshop, the predicted lifting value meets the actual welding requirements. The microstructure of the weld was analyzed by SEM. The main structure of the weld was fine acicular ferrite, which could improve the mechanical properties of the welded joint. After multi-layer filling, the filling layer is flush with the edge of the groove. The establishment of this model lays a foundation for the formulation of welding process parameters for large-diameter pipes and the off-line programming of welding procedures.
... In this case, the inner layer (the liner) protects the outer pipe 36 (backing steel) from corrosion. The liner is made of a corrosion resistant alloy (CRA) such as 37 austenitic stainless steel, whilst the thicker outer pipe is made of low carbon steel, such as C- 38 Mn steel, to maintain the mechanical strength of the lined pipes [3]. 39 For several years, great efforts of Karlsson and Josefson [4] had been devoted to develop full 40 3D thermo-mechanical models for a circumferential single-pass butt welding in a C-Mn pipe. ...
An experimental and numerical investigation on the thermal and mechanical response of a lined pipe (compound pipe) under welding is presented. The welding process consists of a single-pass overlay welding (inner lap-weld) and a two-pass girth welding (outer butt-weld). The influence of the filler material of the girth welding has been examined thermally and mechanically as it is a key factor that can affect the quality of lined pipe welding. To this end, a three-dimensional non-linear finite element model based on the ABAQUS code has been developed and successfully validated against small-scale experimental results. This study was conducted on two specimens of lined pipe joined together by a girth welding deposited either by mild steel or by austenitic stainless steel. Furthermore, in this study, a pre-heat treatment required to produce lined pipe specimens has been taken into account. Strains and residual stresses have been measured by means of high temperature strain gauges, residual stress gauges and the X-ray diffraction technique along the inner and outer surfaces of the welded lined pipe whereas the thermal history has been recorded by thermocouples. The findings point out that replacing the girth welding mild steel by austenitic stainless steel has a significant effect on the residual stress results but no influence on the thermal history results.
... D'Ostuni et al. [13] developed a FE model to simulate dissimilar aluminum-titanium fiber-lased welds employing two-dimensional and three-dimensional Gaussian heat sources. Finally, Obeid et al. [14] developed a 3D FE model to simulate a circumferential single-pass weld overlay and two-pass girth welding and validated the results coming from the model with experimental measurements. In general, numerical methods provide useful and accurate information, but they need a great computational effort and can be relatively time-consuming, depending on the dimension of the joint and the number of welding runs to be simulated. ...
An analytical model is proposed to rapidly capture the thermal and residual stresses values induced by the hybrid metal extrusion and bonding (HYB) process on dissimilar-metal butt-welded joints. The power input for two welding velocities is first assessed using a thermal–mechanical model solved by a heat generation routine written in MATLAB code. Subsequently, the obtained temperature history is used as input to solve the equilibrium and compatibility equations formulated to calculate the thermal and residual stresses. To verify the soundness of the analytical approach, a Finite Element numerical model of the entire process is carried out and results are compared with those coming from the proposed rapid method. It is found that the degree of accuracy reached by the analytical model is excellent, especially considering the tremendous time reduction when compared to that characterizing the standard numerical approach.
... Therefore, according to Equations (2)-(4), mechanical, thermal, and creep loads are updated automatically at each time step. In the viscoplastic model, the plastic element is inactive for stress lesser than the yielding stress of the material [30]. As the transient progresses, the properties of 304L degrade, and the implemented creep model describes the primary and secondary stage. ...
Combining global experience, comprehensive aging knowledge, and predictive methodologies provides ideal prerequisites for the long-term operation strategy (LTO) of a nuclear power plant (NPP). Applying management strategies with an understanding of the ways in which structures relevant for the plant safety perform and interact in their operating environments is of meaningful importance for operating the plant beyond its originally licensed service life. In performing aging studies on the nuclear systems, structure, and components (SSCs), the results are crucial for demonstrating the safety and reliability of the NPP beyond 30 years of nominal operation. In this study, the synergistic effect of a creep mechanism with the alteration suffered by piping material is analyzed by means of MSC©MARC finite element code. Nonlinear analyses were performed to calculate the effects of the long operational period on a primary pipe, assess its degradation, and determine its residual functionality. In these analyses, both homogeneous and inhomogeneous pipe wall thinning are considered, as well as the operating or expected thermal–mechanical loads. The obtained results indicate that thermo–mechanical loads are responsible for pipe deformation, which develops and increases as the transient progresses. Furthermore, an excessive (general or local) wall thinning may determine a dimensional change of the pipe, even causing bending or buckling.
... Experimental measurement of residual stresses in lined pipes (as stated in section-3) is extremely time-consuming and expensive, making computer modeling an alternative and effective technique for the experimental method [11]. In this research, a stainless CRA inner tube with specifications of ASTM A213 TP316L, nominal 3-inch diameter, and thickness of 3.2-mm, a carbon steel outer pipe with specifications of SA106-GrB, nominal 4inch diameter, and 13.49-mm thickness were utilized. ...
... A nonlinear kinematic hardening component, which describes the translation of the yield surface in stress space through the back stress (Fig. 9b). Through omitting any temperature or field variable dependencies, the kinematic hardening law is then defined as [11,17]: ...
For transmission of high-pressure corrosive fluids, it is required to pipe that with both anti-corrosive and high strength material. One of the economical and reliable approaches is the use of Tight Fit Pipe (TFP). Tight Fit Pipe is a double-walled pipe, where a corrosion-resistant alloy liner is fitted inside a carbon steel outer pipe through a thermal-hydraulic manufacturing process. TFP is manufactured under specified conditions for conducting this research. The most influential parameter to improve these pipes' structural response is the residual stress between the inner and outer pipes. In this study, finite element analysis and experimental method were utilized to calculate residual stress between the inner and outer pipes. A 2D finite-element model was performed in ABAQUS software to simulate the lined pipe with considering the effects of heat on the mechanical properties of the pipes and nonlinear isotropic/kinematic hardening material model. Analytical and experimental (Saw cut) methods were applied to measure residual stresses of two pipes to validate the numerical method's results. By comparing the simulation results with the experimental results, an appropriate agreement has been observed.
... The results showed that the maximum tensile residual stresses had happened in the interface of the weld and heat affected zone. Obeid et al. evaluated the parametric of thermal and residual stress and the effect of welding process in the lined pipe recently [10][11]. The investigation of in service behavior of the gas pipeline in the weld induced large residual stress zone requires comprehensive identification of the distribution of these stresses. ...
In order to achieve integrated condition in the girth welding of high pressure natural gas transmission pipelines, the weld zones and its surrounding area should have homogeneous mechanical properties as possible. Residual stresses are an important defect specially in the girth welding of pipeline. In this paper, two API X70 steel pipes (with spiral seam weld) of 56 inches outside diameter and 0.780 inch wall thickness were girth welded first. Hole drilling tests were conducted for residual stress measurement on the surfaces of the pipes. Hoop tensile residual stress on the external surface of the pipe with maximum value equal to 318-MPa was measured on the weld centerline. Hoop residual stress distributions in the internal and external surface of the pipe were approximately similar. The maximum axial residual stress was observed in the heat affected zone (a distance of approximately 30 mm from weld centerline). The maximum axial residual stress on the external surface of the pipe was tensile, equal to 137 MPa and on the internal surface of the pipe was compressive equal to 135-MPa. Axial residual stress magnitudes in the weld centerline on the internal and external surfaces of the pipe were close together. Away from the weld centerline, axial residual stresses on the internal and external surface shown opposite behavior. Thus, in the girth welding of natural gas transmission pipelines, peripheral direction on the internal surface of the pipe is the critical zone and have the highest tensile residual stresses.
