Article
Version 1
Preserved in Portico This version is not peer-reviewed
Thermodynamic Foundation of Generalized Variational Principle
Version 1
: Received: 3 November 2020 / Approved: 3 November 2020 / Online: 3 November 2020 (15:28:25 CET)
Version 2 : Received: 2 August 2021 / Approved: 3 August 2021 / Online: 3 August 2021 (13:01:53 CEST)
Version 2 : Received: 2 August 2021 / Approved: 3 August 2021 / Online: 3 August 2021 (13:01:53 CEST)
How to cite: Sun, B. Thermodynamic Foundation of Generalized Variational Principle. Preprints 2020, 2020110168. https://doi.org/10.20944/preprints202011.0168.v1 Sun, B. Thermodynamic Foundation of Generalized Variational Principle. Preprints 2020, 2020110168. https://doi.org/10.20944/preprints202011.0168.v1
Abstract
One long-standing open question remains regarding the theory of the generalized variational principle, that is, why can the stress-strain relation still be derived from the generalized variational principle while the method of 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. As long as the functional has one of the combination $A(\epsilon_{ij})-\sigma_{ij}\epsilon_{ij}$ or $B(\sigma_{ij})-\sigma_{ij}\epsilon_{ij}$, its corresponding variational principle will produce the stress-strain relation without the need to introduce extra constraints by the Lagrangian multiplier method. It is proved herein that the Hu-Washizu functional $\Pi_{HW}[u_i,\epsilon_{ij},\sigma_{ij}]$ and Hu-Washizu variational principle comprise a real three-field functional. In addition, that Chien's functional $\Pi_{Q}[u_i,\epsilon_{ij},\sigma_{ij},\lambda]$ is a much more general four-field functional and that the Hu-Washizu functional is its special case as $\lambda=0$ are confirmed.
Keywords
variational principle; elasticity; Lagrangian multipliers; thermodynamics; entropy
Subject
Physical Sciences, Acoustics
Copyright: This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Comments (0)
We encourage comments and feedback from a broad range of readers. See criteria for comments and our Diversity statement.
Leave a public commentSend a private comment to the author(s)
* All users must log in before leaving a comment