Study on Manufacturing Process of Hollow Main Shaft by Open Die Forging

자유단조공법을 통한 중공형 메인샤프트 제조공정에 관한 연구

Kwon, Yong Chul;Kang, Jong Hun;Kim, Sang Sik

  • Received : 2015.07.24
  • Accepted : 2015.12.07
  • Published : 2016.02.01


The main shaft is one of the key components connecting the rotor hub and gear box of a wind power generator. Typically, main shafts are manufactured by open die forging method. However, the main shaft for large MW class wind generators is designed to be hollow in order to reduce the weight. Additionally, the main shafts are manufactured by a casting process. This study aims to develop a manufacturing process for hollow main shafts by the open die forging method. The design of a forging process for a solid main shaft and hollow shaft was prepared by an open die forging process design scheme. Finite element analyses were performed to obtain the flow stress by a hot compression test at different temperature and strain rates. The control parameters of each forging process, such as temperature and effective strain, were obtained and compared to predict the suitability of the hollow main shaft forging process. Finally, high productivity reflecting material utilization ratio, internal quality, shape, and dimension was verified by the prototypes manufactured by the proposed forging process for hollow main shafts.


Hollow Main Shaft;Open Die Forging;Flow Stress;Wind Power Generator;Finite Element Analysis


  1. Manwell, J.F. and Rogers, A.L., 2002, Wind Energy Explained : Theory, Design and Application, John Wiley & Sons LTD, 308-313.
  2. Dudra, S.P. and Im, Y.T., 1990, "Investigation of Metal Flow in Open-Die Forging with Different Die and Billet Geometries," J. Mater. Process. Technol., Vol. 21,No. 2, pp. 143-154.
  3. Choi, S.K., Chun, M.S. and Van Tyne, C.J., 2006, "Optimization of Open Die Forging of Round Shapes Using FEM Analysis," J. Mater. Process. Technol., Vol. 172, No. 1, pp. 88-95.
  4. Kim, D.Y., Kim, Y.D., Kim, D.K. and Kim, J.D., 2003, "A Study on the Open Die Forging Preform Shape of Crank Throw for Large Ship Engines," Proc. Kor. Soc. Tech. Plast. Conf., pp. 191-194.
  5. Choi, S.K., Kim, W.T., Chun, M.S. and Moon, Y.H., 2003, "Effect of Process Parameters on Cylindrical Open Die Forging," Proc. Kor. Soc. Tech. Plast. Conf., pp. 221-224.
  6. Knap, M., Kugler, G. and Palkowski, H., 2004, "Prediction of Material Spreading in Hot Open-Die Forging," Steelres. Int., Vol. 75, No. 6, pp. 405-410.
  7. Tamura, K., Akiyama, M. and Tajima, J., 2005, "Optimization of Anvil Design for Ensuring Dimensional Precision of Forged Round Billet Without Forging Defects by Three-Dimensional Rigid-Plastic Finite Element Analysis," J. Eng. Sci., Vol. 219, pp. 461-475.
  8. Tamura, K. and Tajima, J., 2004, "Optimization of Open-Die Forging Process Design to Ensure Homogeneous Grain Size Refinement of Cast Structures by Three-Dimensional Rigid-Plastic Finite Element Analysis," J. Mech. Eng. Sci., Vol 218, No. 9, pp. 931-946.
  9. Lee, Y.S. and Kwon, Y.C., 2007, "Analysis on Void Closure Behavior During Hot Open Die Forging," Advanced Mat. Research, Vol. 26-28, pp. 69-72.
  10. Kwon, Y.C. and Lee, Y.S., 2007, "A Study on Cavity Closure Behavior During Hot Open Die Forging Process," Trans of the Materials Processing, Vol. 16, No. 4, pp. 293-298
  11. Hatta, T. and Yoshida, H., 2011, "Application of Numerical Simulation Technology to Microstructure Control in Opendieforging," J. Jpn. Soc. Technol. Plast., Vol. 52, pp. 970-974.
  12. Shivpuri, R. and Eruc, E., 1993, "Planning and Simulation of the Ring Rolling Process for Improved Productivity," Int. J. Mach. Tools and Manuf., Vol. 33, No. 2, pp. 153-173.
  13. Johnson, W. and Needham, G., 1968, "Experiments on Ring Rolling," Int. J. Mech. Sci., Vol. 10, pp. 95-113.
  14. Kim, N.S., Machida, S. and Kobayashi, S., 1990, "Ring Rolling Simulation by the Three Dimensional Finite Element Method," Int. J. Mech. Sci., Vol. 30, No. 4, pp. 569-577.
  15. Kim, K.H., Suk, H.G. and Huh, M.Y., 2007, "Development of the Profile Ring Rolling Process for Large Slewing Rings of Alloy Steels," J. Mater. Process. Technol., Vol. 187-188, pp. 730-733.
  16. Cho, J.R. and Bae, W.B., 1998, "Analysis of the Cogging Process for Heavy Ingots by Finite Element Method and Physical Modelling Method," J. of Materials Processing Technol, Vol. 80-81, pp. 161-165.
  17. Aksakal, B. and Osman, F.H., 2008, "Determination of Experimental Axial and Sideways Metal Flow in Open Die Forging," Materials & Design, Vol. 29, pp. 576-583.