Applied Mathematics and Mechanics (English Edition) ›› 2022, Vol. 43 ›› Issue (4): 537-546.doi: https://doi.org/10.1007/s10483-022-2838-5

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On Chien’s question to the Hu-Washizu three-field functional and variational principle

Bohua SUN   

  1. School of Civil Engineering & Institute of Mechanics and Technology, Xi'an University of Architecture and Technology, Xi'an 710055, China
  • 收稿日期:2021-10-31 修回日期:2022-01-27 发布日期:2022-03-29
  • 通讯作者: Bohua SUN, E-mail:sunbohua@xauat.edu.cn
  • 基金资助:
    Xi’an University of Architecture and Technology (No.002/2040221134)

On Chien’s question to the Hu-Washizu three-field functional and variational principle

Bohua SUN   

  1. School of Civil Engineering & Institute of Mechanics and Technology, Xi'an University of Architecture and Technology, Xi'an 710055, China
  • Received:2021-10-31 Revised:2022-01-27 Published:2022-03-29
  • Contact: Bohua SUN, E-mail:sunbohua@xauat.edu.cn
  • Supported by:
    Xi’an University of Architecture and Technology (No.002/2040221134)

摘要: There is an open question, namely Chien’s question, in construction of a generalized functional in elasticity, i.e., why the stress-strain relation can still be derived from the Hu-Washizu generalized variational principle while the Lagrangian multiplier method is applied in vain? This study shows that the generalized variational principle can only be understood and implemented correctly within the framework of thermodynamics. This investigation finds that as long as the functional has one of the combinations (A(εij)-σijεij) or (B(σij)-σijεij), its corresponding variational principle will produce the stress-strain relation without the need to introduce extra constraints by the Lagrangian multiplier method. This research proves that the Hu-Washizu functional ΠHW(uij, εij; σij) is real three-field functional, and resolves the historic academic controversy on the issue of constructing a three-field functional.

关键词: variational principle, elasticity, Lagrangian multiplier, thermodynamics, entropy

Abstract: There is an open question, namely Chien’s question, in construction of a generalized functional in elasticity, i.e., why the stress-strain relation can still be derived from the Hu-Washizu generalized variational principle while the Lagrangian multiplier method is applied in vain? This study shows that the generalized variational principle can only be understood and implemented correctly within the framework of thermodynamics. This investigation finds that as long as the functional has one of the combinations (A(εij)-σijεij) or (B(σij)-σijεij), its corresponding variational principle will produce the stress-strain relation without the need to introduce extra constraints by the Lagrangian multiplier method. This research proves that the Hu-Washizu functional ΠHW(uij, εij; σij) is real three-field functional, and resolves the historic academic controversy on the issue of constructing a three-field functional.

Key words: variational principle, elasticity, Lagrangian multiplier, thermodynamics, entropy

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