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Solid body of lined pipe model Apart from the yield points, the parent and weld materials have similar thermal and
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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 ther...
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This paper deals with a non-destructive analysis of residual stress through the visualization of deformation behaviors induced by a local spot heating. Deformation was applied to the surface of an aluminum alloy with an infrared spot laser. The heating process is non-contact, and the applied strain is reversible in the range of room temperature to...
Citations
... With the increasing complexity of modern welding techniques and the ongoing development of high-strength low-alloy (HSLA) steels, engineers and researchers are adopting a variety of design strategies to control and enhance welding performance [6][7][8]. For instance, in pipeline steels, the demand for thicker plates has led to the widespread use of a two-pass welding process, typically comprising an inner pass followed by an outer pass [9,10]. Among these, the outer pass welding significantly impacts the post-weld properties, as final performance evaluations largely depend on it. ...
In this study, a novel hybrid heat source model was developed to simulate the welding temperature field in the heat-affected zone (HAZ) of X80 pipeline steel. This model replicates welding conditions with high accuracy and allows flexible three-dimensional adjustments to suit various scenarios. Its development involved the innovative integration of microstructural crystallography information with a multi-scale calibration and validation methodology. The methodology focused on three critical aspects: the weld interface morphology, the location of the Ac1 temperature, and the size of prior austenite grains (PAG). The morphology of the weld interface was calibrated to align closely with experimental observations. The model’s prediction of the Ac1 location in actual welded joints exhibited a deviation of less than ±0.3 mm. Furthermore, comparisons of reconstructed PAG sizes between thermal simulation samples and actual HAZ samples revealed minimal discrepancies (5 μm). Validation results confirmed that the calibrated model accurately describes the welding temperature field, with reconstructed PAG size differences between simulation and experimental results being less than 9 μm. These findings validate the accuracy of the calibrated model in predicting welding temperature fields. This research introduces a novel framework for the development of heat source models, offering a robust foundation for improving welding performance and controlling microstructure in different regions during the welding process of high-strength low-alloy (HSLA) steel.
... 2020, Dassault Systems Simulia Corp, Johnston, RI, USA) was used as the finite element analysis program for heat transfer analysis. Considering the previously reported high reliability of Fortran user subroutines [31][32][33][34][35], they were used to implement the moving heat source (Fortan Ver. 17.0, Intel, San Jose, CA, USA). ...
... Materials 2023, 16, x FOR PEER REVIEW 6 of 21 USA) was used as the finite element analysis program for heat transfer analysis. Considering the previously reported high reliability of Fortran user subroutines [31][32][33][34][35], they were used to implement the moving heat source (Fortan Ver. 17.0, Intel, San Jose, CA, USA). ...
The International Maritime Organization (IMO) is tightening regulations on air pollutants. Consequently, more LNG-powered ships are being used to adhere to the sulfur oxide regulations. Among the tank materials for storing LNG, 9% nickel steel is widely used for cryogenic tanks and containers due to its high cryogenic impact toughness and high yield strength. Hence, numerous studies have sought to predict 9% nickel steel welding distortion. Previously, a methodology to derive the optimal parameters constituting the Goldak welding heat source for arc welding was developed. This was achieved by integrating heat transfer finite element analysis and optimization algorithms. However, this process is time-consuming, and the resulting shape of the weld differs by ~15% from its actual size. Therefore, this study proposes a simplified model to reduce the analysis time required for the arc welding process. Moreover, a new objective function and temperature constraints are presented to derive a more sophisticated heat source model for arc welding. As a result, the analysis time was reduced by ~70% compared to that previously reported, and the error rates of the weld geometry and HAZ size were within 10% and 15% of the actual weld, respectively. The findings of this study provide a strategy to rapidly predict welding distortion in the field, which can inform the revision of welding guidelines and overall welded structure designs.
... To increase the reliability of the welded connection and to understand the welding process itself, it is necessary to use suitable experimental methods for the evaluation of the mechanical properties of the welding structure (weld, affected zone, etc.). Here, contact (e.g., strain measurements using strain gauges [6]) and non-contact methods (e.g., optical strain measurements using thermal imaging, laser triangulation inspection [7]) can be used for the observation and evaluation of the welding process [8]. In addition to these macro-level methods, micro-level methods, such as the hardness method or the scanning electron microscopy technique can be performed to evaluate the weld-basic material interface quality or to view changes in the material properties in the affected zone [9,10]. ...
The article presents a study of the mechanical processes occurring during the aluminothermic reaction using experimental methods (strain gauges, digital image correlation, thermography, scanning electron microscopy, profilometry). The aluminothermic reaction is a highly efficient welding method due to its exothermic behaviour, however, it places considerable demands not only on the welding technique, but also on the capabilities of the experimental methods used; these limitations are also discussed in the article. The aluminothermic reaction is associated with the formation of a localised heat source with a time evolution dictated by the technological procedure, which manifests itself in heat propagation to the surrounding weld material. The unequal evolution of the temperature field is the fundamental cause of the appearance of the heat affected zone or local deformations or surface curvature, which was the focus of the experimental methods deployed above and the results of which are shown in the article.
... Some papers also discuss topics of weld overlay and girth welding in detail. Focusing on the influence of the fil ler material of the girth welding, Obeid et al. presents an experimental and numerical investigation on the thermal and mechanical response of a lined pipe under welding [ 15 ]. Furthermore, they took into account a new procedure of pre-heat treatment, so called Tight Fit Pipe ( TFP ) process, to produce lined pipe specimens. ...
This present paper summarizes applying weld overlay repair on the feedwater nozzle in a boiling water reactor, and evaluates the influence on the structure and fracture mechanics of the component. The requirements for utilizing a full structural weld overlay, including the weld overlay design, effects of welding residual stresses, impacts of weld shrinkage, prediction of potential flaw growth, and influence on ASME Code Section III design evaluations, are further defined in ASME Code Case N-504–2. In order to confirm the effectiveness of the weld overlay design of the nozzle, the welding residual stresses following overlay installation were determined using engineering simulation software. The impacts of weld shrinkage form overlay welding are also addressed. The shrinkage stresses were evaluated via a numerical model of the attached piping system to ensure the design margins of the pipe structure. Since the weld overlay technique is well known to be effective in mitigating crack initiation or cracking to leakage, a fatigue crack growth prediction under ASME Code Section XI must be conducted to address the fatigue qualification of the affected component. The ASME Code Section III construction qualification of the whole nozzle region must consider the applicable thermal transient stresses, structural discontinuities, and bimetallic effects that are caused by the weld overlay. This investigation proves that the current stress analyses of the nozzle and the pipe structure are not significantly affected by the added overlay mass, so the structural integrity of the component can be ensured, meeting the requirements of ASME Code Case N-504–2.
... According to statistics, majority of pipeline failures occur at the girth weld [7][8][9][10]. This is because the girth weld can greatly reduce the load-bearing capacity of the pipe [11], and the welding process can produce cracks, porosity, inclusions and other welding defects as well as welding residual stresses [12][13][14][15] and other unfavorable factors, all of which greatly reduce the fracture resistance of the pipe. Therefore, the study of X80 pipe girth welds is of great significance. ...
The girth weld is the weakest region of the entire pipeline. When the pipeline crosses areas with complex terrain or where natural disasters are frequent, the pipeline may be subjected to large displacement effects and large plastic deformations. In these scenarios, the traditional stress-based assessment methods will no longer be applicable. Therefore, it is of great importance to develop strain-based assessment methods for pipelines. This paper investigates the effects of crack size, strength mismatch, heat affected zone (HAZ) width and HAZ softening/hardening coefficient on the crack driving force (CDF) of weld center crack (WCC) and HAZ center crack (HAZCC) on the inner surface of X80 pipes using finite element method. The results show that the CDF is significantly affected by crack size, crack location, strength mismatch, HAZ softening coefficient but slightly affected by HAZ width when HAZ width is greater than 2 mm. The CDF of WCC is greater than that of HAZCC under large strain conditions with HAZ width of 2 mm. The distribution of the J-integral at the crack tip is then investigated and the results show that the maximum value of the J-integral does not necessarily occur at the deepest point of the crack tip. Finally, the factors influencing the failure assessment curve (FAC) of WCC are investigated and the lower bound strain-based failure assessment diagram (SB-FAD) considering strength mismatch and HAZ softening coefficient is developed with varying crack depths. This study can provide a reference for the safety assessment of crack-like defects on the inner surface of X80 pipeline girth welds.
