Recently, i have read some papers with similar ideas which one piezoelectric layer is laminated to a cantilevered beam with a tip magnet. sometimes they consider an electric enthalpy into the equations of using Hamilton's principle or Euler-Lagrangian to governing equations , sometimes they did not consider it.
example 1: Ts+Tp+Tm-Us-Hp-Um
Here, Ts,Tp,Tm are the kinetic energy of the substrate, piezoelectric and magnet tip mass, respectively; Us and Um are the potential enegry of subtrate and magnet tip mass.
(Ref:Samuel C. Stanton, Clark C. McGehee, Brian P. Mann, Nonlinear dynamics for broadband energy harvesting: Investigation of a bistable piezoelectric inertial generator, Physica D: Nonlinear Phenomena, Volume 239, Issue 10, 15 May 2010, Pages 640-653, ISSN 0167-2789, )
example 2: T-U-UAB-UAC+W
Here, T and U represent the kinetic energy and potential energy for total system, UAB and UAC means magnetic potential energy; W means the work done by the moment produced by voltage V , across the piezoelectric layer.
(Ref:Peyman Firoozy, Siamak E Khadem, S Mehrdad Pourkiaee, Broadband energy harvesting using nonlinear vibrations of a magnetopiezoelastic cantilever beam, International Journal of Engineering Science, Volume 111, February 2017, Pages 113-133, ISSN 0020-7225, )
my questions:
1: The W in example 2 is equal or similar to Hp in example 1? or some kind of transformation?
2. if the W has nothing with the Hp, then how to decide when considering the electric enthalpy with this similar kind of laminated cantilevered structure?