Residual stress modelling in laser welding marine steel EH36 considering a thermodynamics-based solid phase transformation

Significance 

Low alloy steels are one of the most used materials in structural applications owing to their excellent properties such as ease of manufacturing, good toughness, and high strength. Among the available material joining methods, welding is undoubtfully the most suitable. This has led to significant research amongst scientists over the past years with the aim of improving the manufacturing processes. Generally, there are different types of welding whose application depends on the types of material and the intended application. Consequently, the microstructures and mechanical properties of these welds affect the properties and functionality of the materials and their entire structures in general.

Recent studies have shown significant improvements in the investigation of the joint performance of high strength steels using the residual stress, microstructure and weld pool flow. Unfortunately, considering the different nature of the arc welding and marine welding, the aforementioned criteria are insufficient to assure high-quality welding in marine manufacturing.

To this note, Huazhong University of Science and Technology scientists: Dr. Youmin Rong, Ting Lei, Dr. Jiajun Xu, Professor Yu Huang, Professor Chunming Wang assessed the distribution of residual stresses in laser welding in marine high strength steel EH36. In particular, a finite element model was designed by taking into consideration the solid transformation based on thermodynamics. Their research work is currently published in the journal, International Journal of Mechanical Sciences.

Briefly, the research team assessed the phase transformation and its effects of the residual stress by further taking into account the response of the microstructure to strain in laser welding marine high strength steel. Next, the distribution of the temperature was investigated using a heat source model while on the other hand, thermodynamics of the solid phase transformation was used in determining the microstructure fractions. To actualize their study, the research team experimentally verified the prediction accuracy of the designed model based on the residual stress, microstructure and weld profile.

The authors uncovered the usefulness of the index increment double cone method in fitting the penetration resulting from laser welding. As such, they recorded prediction errors of 11.06%, 10.24% and 6.69% in UW, MW, and BW respectively. On the other hand, a prediction error of 10.372% and 5.6435 were observed in the microstructures of the laser-welded EH36 and in particularly for martensite and ferrites. This was attributed to the influence of the weld microstructures on the strain and residual stresses of the material. However, it was worth noting that the heat affected zone, and not the center of the fusion zone, produced the maximum stress.

Therefore, the Huazhong University scientists successfully proposed a finite element model for not only accurately predicting the residual stresses in laser welded EH36 steels but also providing a basis for minimizing the welding associated stresses. Furthermore, considering the stability if the plastic strain without the need for external forces, the study will advance marine manufacturing through high-quality welds.

Residual stress modelling in laser welding marine steel EH36- Advances in Engineering

About the author

Dr. Youmin Rong, Assistant researcher/Postdoctor, State Key Lab of Digital Manufacturing Equipment and Technology, School of Mechanical Science and Engineering, Huazhong University of Science and Technology, China. His research interesting is laser manufacturing and equipment, mainly including laser welding process, welding deformation and residual stress, seam tracking and equipment development. He has published 17 SCI papers as first or corresponding author in Mar Stuct, J Mat Process Techno, Sci Techno Weld Join and so on, and is a reviewer for some journals (Thin Wall Struct, J Mat Process Techno, J Manuf Process, etc.). He also achieved First Prize of Hubei Science and Technology Progress Award in 2017.

Email: [email protected]; [email protected].

About the author

Prof. Yu Huang, State Key Lab of Digital Manufacturing Equipment and Technology, School of Mechanical Science and Engineering, Huazhong University of Science and Technology, China. Prof. Huang received his PhD, MS and BS in Mechanical Engineering from Huazhong University of Science & Technology in 2004, 1997 and 1993.

Prof. Huang has been engaged in research and teaching in the mechanical design, mechatronics, laser and related special processing, exclusive of special equipment, numerical control technology etc. Prof. Huang research interesting is advanced manufacturing and equipment. Prof. Huang has published more than 50 SCI journal papers, and licensed more than 40 patents in China. Prof. Huang has received 1st/2nd-clase prize of the National Science and Technology Progress Award once/twice, an Outstanding Award of Provincial Science and Technology Progress, four first prize of Provincial Science and Technology Progress Award.

About the author

Ting Lei is a doctor of Mechanical and electrical engineering. He received his MS and BS in Mechanical Engineering from Huazhong University of Science & Technology and Changchun Institute of Technology in 2006 and 2010, respectively. His research area was tracking and detection in welding, monitoring and control of welding process.

He presided over the youth fund of Wuhan donghu University, participated in the tracking and detection in supper narrow gap of thick plates in sub-project of National 973 projects, cooperated with the enterprises in the subject of full position tube-to-tubesheet automatic welding. He has published several papers and one software copyright.

About the author

Jiajun Xu currently is a Ph.D at school of mechanical science and engineering, Huazhong University of Science and Technology. His major research interest is laser welding, particularly in the areas of online detection of dynamic behaviors, and deformation and residual stress simulation during laser welding process.

His work has made a better understanding of the mechanism of keyhole-induced porosity. Current research has been focused on the deformation optimization in laser welding of thin sheets, aiming at light weight of car body especially for new energy vehicle. Jiajun Xu has published 11 journal articles.

Reference

Rong, Y., Lei, T., Xu, J., Huang, Y., & Wang, C. (2018). Residual stress modelling in laser welding marine steel EH36 considering a thermodynamics-based solid phase transformation. International Journal of Mechanical Sciences, 146-147, 180-190.

Go To International Journal of Mechanical Sciences

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