Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering Conference
Shanghai, China, June 5–10, 2022
Copyright © 2022 by the International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1-880653-81-4; ISSN 1098-6189

www.isope.org

Research on residual stresses distribution of stiffened plate structure after induction heatingbased on SVM
1

Yulong Feng 1, Yujun Liu1,3, Ji Wang 1,2,3*, Rui Li1,3

School of Naval Architecture, Dalian University of Technology, Dalian, China；
Collaborative Innovation Center for Advanced ship and Deep-Sea Exploration, Shanghai, China;
3
State Key Laboratory Of Structural Analysis For Industrial Equipment, Dalian University of Technology, Dalian, China；
2ABSTRACTINTRODUCTION

To accurately predict the stress state of hull stiffened plate structure
after induction heating process, the intelligent algorithm of support
vector machine (SVM) was studied to predict the residual stress
distribution of stiffened plate structure after induction heating. Firstly,
the induction heating experiments of marine stiffened plate structurewith different process parameters and plate specifications were carriedout, then the internal stress-strain data of the structure after induction
heating were measured and the stress-strain distribution characteristics
were analyzed. Secondly, to expand the experimental sample data, thenumerical model of induction heating process of stiffened plate
structure was established by ANSYS finite element software based on
the experimental data, and the influence of induction heating processparameters on the distribution of residual stress in the structure wasanalyzed. Finally, based on the support vector machine algorithm, theinduced current, frequency and heat source moving rate were taken as
the input characteristic parameters of the model, and the width (BS) of
the longitudinal tensile stress concentration area and the maximum
residual tensile stress (S) were taken as the prediction objectives toverify the accuracy of the model. The results show that the width ofstress concentration area increase with the increase of induced current
and induced frequency, and the effect of induced current on
temperature is more obvious than that of frequency, the extreme valueof residual stress is concentrated in the range of 245 MPa – 275 MPa,and the high stress area is concentrated within 30mm of the induction
centerline. In addition, the maximum relative errors of the SVM
algorithm based on radial basis function in predicting the width ofstress concentration zone and maximum stress are less than 5%, whichmeans the established model has high prediction accuracy forpredicting the residual stress distribution of ship stiffened plate
structure after induction heating, this research method has goodengineering practical value in ship manufacturing.

The fillet welding process of thin plate structure is one of the mostimportant process technologies in modern manufacturing industry. It is
widely used in aerospace, automobile, shipbuilding and other industries.
For the shipbuilding industry, residual stress after welding is an importantcause of hull structure deformation and stress corrosion. In order toreduce the welding residual stress and reduce the welding deformation of
the structure, the common welding structures in shipyards still take flame
heating as the main correction means. However, the flame heating
method has the disadvantages of difficult temperature control and poor
automation, and it is not suitable for the curved surface forming andwelding deformation correction of thin plate structure. With thedevelopment and maturity of electromagnetic induction heating
technology, it has been studied and applied to the forming process of hull
curved outer plate and the correction process of welding deformation(Kotani and Okano, et al, 2016). The principle of correcting welding
deformation by electromagnetic induction heating is to produce induced
eddy current in the steel structure. The temperature field generated by
eddy current determines the change of thermal stress in the thin plate
structure, and then affects the forming of the steel structure (Liang andMurakawa, et al, 2015; Okumoto, 2008). By controlling the construction
scheme and process parameters of electromagnetic induction process, thethermal stress distribution in the structure can be effectively adjusted, so
the induction heating process can be used to reduce stress concentrationand eliminate welding deformation. However, in the actual construction,
the temperature distribution and stress distribution caused byelectromagnetic induction are highly nonlinear, which means it isawkward to study, and it is difficult to accurately predict the stress
distribution caused by electromagnetic induction construction by using
the traditional mathematical model (Lim and Bae, 2010; Mathew andMoat, 2017; Arif and Al-Omari, 2012). Therefore, it is necessary toconsider using an intelligent algorithm more suitable for dealing withnonlinear problems to study the law and system of residual stress caused

KEY WORDS:

Stiffened plate structure; Induction heating;Distribution of residual stress; Support vector machines

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