Flexural Waves: Kelvin-Voigt Solid Questions

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Discussion Overview

The discussion centers around the nature of flexural waves in Kelvin-Voigt solids, particularly in relation to the governing equations and how they differ from traditional wave equations. Participants explore the implications of non-linear restoring forces and the treatment of bending moments in continuum mechanics.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether flexural waves in a Kelvin-Voigt solid are solutions to the standard continuum mechanics equations or if they require separate consideration due to their governing fourth-order differential equation.
  • Another participant suggests that assuming a non-linear restoring force allows for higher-order solutions to the wave equation.
  • Several participants express a need for resources, such as links or papers, to better understand the topic, indicating a lack of accessible information on the subject.
  • One participant reflects on their confusion regarding the relationship between linear forces and bending moments, indicating a struggle to integrate these concepts within the framework of elasticity.
  • A participant explains that non-linear restoring forces can be expressed as polynomials, and that the wave equation is linear, allowing for separate solutions for each term in the polynomial, which can lead to distinct physical manifestations.

Areas of Agreement / Disagreement

Participants express varying levels of understanding and confusion regarding the treatment of flexural waves and non-linear forces. There is no consensus on whether flexural waves should be treated as part of the standard equations or separately, and the discussion remains unresolved.

Contextual Notes

Participants note limitations in available literature and resources on the topic, indicating that existing textbooks may treat elastic equations and those governing flexure separately, which contributes to the confusion.

psv
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Whenever I've seen solutions to elastic or viscoelastic stress strain relations and resulting wave equations, the solutions are only acoustic, shear, love, reyleigh waves etc. Recently I saw that flexural waves are governed not by the 2nd order wave equation I'm used to seeing, but by a 4th order different one derived from bending moments. So my question then is when you say that some object is a kelvin-voigt solid and assume the corresponding continumm mechanics equations, are flexural waves a solution or do they need to be considerred somewhat seperatly?
 
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If you assume a non-linear restoring force, then this permits higher order solutions to the wave equation.

Claude.
 
Do you, or anyone else happen to know any good links or books/papers concerning this, my searches have so far come up with little.

Thnx
 
Sorry to be off topic here, what is this about? Is this for an advanced material science class? Is it theory of elasticity?
 
psv said:
Do you, or anyone else happen to know any good links or books/papers concerning this, my searches have so far come up with little.

Thnx

Do you have access to research journals?

Claude.
 
Sorry if bumping such an old thread is bad manners,and that I took so long to reply, but I recently got back to wondering about this.

cyrusabdollahi: no, this was just my own interest mostly, although since I should know more about elasticity maybe you could say that area :smile:

Claude: yes, I have access to journals and books, and I was mostly interested in anything where it is put in terms as plain as you did about higher order solutions resulting from non-linear restoring forces. Sorry I didn't mean for people to go do journal searches for me, I was just hoping someone might know a better book. I looked in some classic engineering books by timoshenko and fung, but they seemed to present there elastic equations and those governing flexure seperatly.

I guess my main confusion lies in the the fact that I usually think forces, u, v in a continuum as linear, so bending moments sort of throw me for a loop when I am trying to tie everything together. (there has to be a pun in there)
 
The non-linear restoring force is usually experessed as a polynomial of some description. Since the wave equation is linear, you can solve each term in the polynomial separately - this is why some solutions are labelled 'second-order' or 'fourth-order', for example, because those solutions correspond to the inclusion of the second and fourth terms in the polynomial.

Textbooks solve each part separately because it is much simpler (and far less confusing) than tackling the whole solution at once. In addition, each set of solutions (first, second, third order etc) often have a distinct physical manifestation, so it is advantageous to obtain an distinct, separate equation for each physical effect, rather than have them all conglomerated into one super-equation.

Claude.
 

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