Journal of Advanced Research in Ocean Engineering

Korean Society of Ocean Engineers (한국해양공학회)
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A Study on Remaining Efficiency of Thermal Straightening after Block Lifting

  • Ha, Yunsok (Welding Research Part, Central Research Institute, Samsung Heavy Industries, Co., Ltd.) ;
  • Yi, Myungsu (Welding Research Part, Central Research Institute, Samsung Heavy Industries, Co., Ltd.)
  • Received : 2015.06.08
  • Accepted : 2015.08.15
  • Published : 2015.09.30
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Abstract

Deck plates of ships or offshore structures would make out-of-plane distortion for their thin thickness. These distortions are usually straightened by thermal straightening such as flame heating method. After thermal straightening, the blocks are lifted and moved by cranes to assemble it at dry-dock stage. After this lifting process, out-of-plane deformation again happens frequently. And then, they continuously cause quality and accuracy problems in the final dry-dock process. So, it takes more time for repair and correction working. According to preceding research, the lifting process by cranes would offset the effect on thermal straightening. The target of this study is to develop a methodology analyzing the remaining efficiency of thermal straightening after block lifting. The development was based on the assumption of yield state at straightening region. Therefore the remaining efficiency was obtained by different stiffness slope while lifting & relieving. The efficiency formula was designed using inherent strain, and we made a table of zero-efficiency by cooling speed and class rule's steels. As a result, if the stress orthogonal to straightened line is calculated during lifting analysis by FEA, the efficiency can be obtained linearly to the values in the table. Finally, even optimized carling position can be designed by considering the regional data from series project and welding region on deck.

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References

  1. Ha, Y.S., Jang, C.D., Kim, J.T., and Mun, H.S., Analysis of Post-Weld Deformation at the Heat-Affected Zone Using External Forces Based on the Inherent Strain. International Journal of Precision Engineering and Manufacturing, 8(4) (2007) 56-62.
  2. Ha, Y.S., and Jang, C.D., An Improved Inherent Strain Analysis for Plate Bending by Line Heating Considering Phase Transformation of Steel. International Journal of Offshore and Polar Engineering, 17(2) (2007) 139-144.
  3. Ha, Y.S., Development of Thermal Distortion Analysis Method on Large Shell Structure Using Inherent Strain as Boundary Condition. Journal of the Society of Naval Architects of Korea, 45(1) (2008) 93-100 (in Korean). https://doi.org/10.3744/SNAK.2008.45.1.93
  4. Han, M.S., Han, I.S., and Han, Y.S., Prediction of Longitudinal Welding distortion and Mechanical Straightening Parameter of Welded T-section Built-up Beams. International Welding and Joining Conference-Korea 2007, Seoul, (2007) 490-491 (in Korean).
  5. Jang, C.D., Yoon, G.J., Kim, O.H., Yoon, M.C., Kang, J.M. and Yoo, K.H., An Approach to the Analysis of the Large Deformation of Deck Structures of Engine Room Block at Erection Stage. Proc. of Annual Spring Meeting, SNAK, Pusan, (2002) 301-304 (in Korean).
  6. Kim, J.T., Ha, Y.S., and Jang, C.D., Analysis of Post Weld Deformation at HAZ by External Forces Based on Inherent Strain. Society of Naval Architects of Korea, 43(2) (2006) 220-227 (in Korean). https://doi.org/10.3744/SNAK.2006.43.2.220
  7. Seo, S.I., Calculation of Welding Distortions by Simplified Thermal Elasto-plastic Analysis. Journal of Ship and Ocean Technology, 8(3) (2004) 40-49
  8. Shin, S.B., and Lee, D.J., A Structural Design Approach for Controlling Welding Distortion at the Upper Deck of a Hull Structure in the Erection Stage. Metals and Materials International Journal, 17(1) (2011)123-130. https://doi.org/10.1007/s12540-011-0217-x
  9. Ueda, Y., Murakawa, H., Rashwan, A.M., Okumoto, Y., and Kamichika, R., Development of Computer-Aided Process Planning System for Plate Bending by Line Heatnig (Report 1)-Relation Between Final Form of Plate and Inherent Strain. Journal of Ship Production, 10(1) (1994) 59-67.