An official website of the United States government
In-service welding simulations were carried out using a multiphysics finite element analysis (FEA). Calculated data as temperature and thermal cycles were validated by comparing them with experimental welding results carried out in a carbon steel pipe attached to a water loop. Two in-service welding cases were tested using the GMAW-P process with and without the assistance of induction preheating. The molten zone of weld macrographs and the simulated models were matched with excellent accuracy. The great agreement between the simulation and experimental molten zone generated a maximum error in the peak temperature of 1%, while in the cooling curve, the error was about 10% at lower temperatures. A higher hardness zone appeared in the weld’s toe within the CGHAZ, where the maximum induction preheating temperature achieved was 90°C with a power of 35 kW. Induction preheating reduced the maximum hardness from 390 HV to 339 HV.
more »
« less
Multiphysics Simulation of In-Service Welding and Induction Preheating: Part 1
In most cases, in-service welding is susceptible to a higher using a multiphysics finite element analysis (FEA) coupling heat transfer, fluid flow, and electromagnetic heating. Part 1 presents the software implementation and model equations beside the mesh setting and modeling approach to simulate circumferential welding of Type B sleeve repair. The simulation was divided into four steps running sequentially for each physic solved in the model. Induction preheating was simulated and validated by comparing simulated temperature with experimental measurements. The multiphysics model differs from the usual simulations present in the literature, expressing more reliability in the results and making way for more-complete modeling for in-service applications.
more »
« less
- Award ID(s):
- 2052747
- PAR ID:
- 10506246
- Publisher / Repository:
- AWS
- Date Published:
- Journal Name:
- Welding Journal
- Volume:
- 103
- Issue:
- 02
- ISSN:
- 0043-2296
- Page Range / eLocation ID:
- 48 to 61
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Dissimilar metal welds (DMWs) are routinely used in the oil and gas industries for structural joining of high-strength steels to eliminate the need for post-weld heat treatment (PWHT) in field welding. Hydrogen-assisted cracking (HAC) can occur in DMWs during subsea service under cathodic protection. DMWs of two material combinations, 8630 steel/FM 625 and F22 steel/FM 625, produced with two welding procedures, non-temper bead (BS1) and temper bead (BS3), in the as-welded and PWHT conditions were investigated in this study. These DMWs were subjected to metallurgical characterization and testing with the delayed hydrogen cracking test (DHCT) to identify the effects of base metal composition, welding and PWHT procedures on their HAC susceptibility. The HAC susceptibility was ranked using the time to failure in the DHCT at loads equivalent to 90% of the base metal yield strength (YS) and the apparent stress threshold for HAC. A criterion for resistance to HAC in the testing conditions of DHCT was also established. The results of this study showed that 8630/FM 625 DMWs were more susceptible to HAC than the F22/FM 625 DMWs. PWHT did not sufficiently reduce the HAC susceptibility of the 8630/FM 625 and F22/FM 625 BS1 welds. DMWs produced using BS3 performed better than BS1 DMWs. The post-weld heat-treated F22/FM 625 BS3 DMW passed the HAC resistance criterion.more » « less
-
The Hyper Duplex Stainless Steel HDSS enhanced corrosion resistance and toughness relies upon high alloying to obtain a balanced ferrite and austenite volume and pitting resistance equivalent number PREn. However, during welding, sigma phase precipitates might form, hindering corrosion and mechanical performance. Therefore, a kinetics model is developed to avoid the sigma phase's formation during welding and validated using physical simulation, finite element analysis (FEA), welding, and SEM characterisation. The sigma phase kinetics model produced calculated and validated temperature-time-transformation (TTT) and continuous-cooling-transformation (CCT) curves from which a 4°C/s cooling rate was found as a cooling rate threshold for sigma phase formation in this new material. Three-layered gas tungsten arc welding GTAW cladded mockup with 53 beads produced 24°C/s minimum cooling rate. Moreover, microscopy, mechanical, and corrosion testing attested it as a sigma-free weld.more » « less
-
This paper presents a 3D model of a photoconductive antenna (PCA) on semiconductor substrate. The simulations were conducted using the COMSOL Multiphysics package. The model considers the laser excitation and the carrier generation acceleration in the semiconductor layer. The computational work was achieved using the frequency-domain RF module and the semiconductor module. The results demonstrate that simulating the active area alone produces sufficient accuracy ~ 0.01% in the RF module solution (solution of the electric and magnetic fields) and ~ 0.23% in the semiconductor solution (photocurrent solution). The reduction in the simulated area helps minimizing the required CPU time and memory requirement in the 3D model at THz frequencies. The largest case in this study was simulated at the National XSEDE Supercomputing with ~ 0.3 billion unknowns and memory requirement of ~ 3.2TB in the RF module.more » « less
-
This study aims to extract critical scenes/continents in the weld pool region during gas metal arc welding (GMAW). The scenes considered include the wire, arc, and weld pool, while other secondary ones such as oxides are temporarily excluded. They are critical to understanding, analyzing, monitoring and controlling the welding process, in particular the critical correlation how the welding parameter, arc and weld pool are dynamically correlated. Unfortunately, such fundamental correlation has not been studied and lack of effective ways to simultaneously monitor/extract these scenes is responsible. With the development of optoelectronic devices, weld pool regions can be better imaged. However, because of the nature of the scenes in particular the arc which is formed by ionized gas without a clear boundary and highly dynamic, detecting them using computer vision is challenging. Deep learning is an effective method, but model training usually needs a large number of labels. As manually labeling is expensive, we propose an approach to address this challenge that can train a model from a small, inaccurately labeled dataset. This approach is designed, per the characteristics of the scenes and their dynamics All-in-One Network (AOD-Net) was deployed first for defogging, and then the YOLOX network was utilized to identify regions of interest to reduce the impact of molten metal splashes on image sharpness. Subsequently, we developed a timed segmentation network incorporating the Long Short-Term Memory (LSTM) mechanism into U-Net, which can be used to extract more accurate information about the weld pool by combining the temporal and spatial information in the continuous process of welding at a low cost because our scene of interest is in a continuous and dynamic evolutionary process. After defogging and removing the effects of molten metal spatter, we can obtain information on the dynamics of the weld pool and the weld arc at the same time. Experimental results verified that the trained network could extract the critical boundaries accurately under various welding conditions despite the highly dynamic changes and fuzziness of the views.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.29391/2024.103.005
