Eigenvalues of a string with fixed ends and a mass in the middle

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SUMMARY

The discussion focuses on determining the eigenfrequencies and mode shapes of a taut string with fixed ends and a discrete mass located at the midpoint. The wave equation presented is T * ∂²Y/∂X² = (ρ + m*δ(x-L/2)) * ∂²Y/∂t², where T is tension, ρ is lineal density, m is the mass, δ is the Dirac delta function, and L is the string length. The user seeks guidance on solving this differential equation to find the eigenvalues, as the standard form Y(x,t) = [A*Cos(k*x)+B*Sin(k*x)]*[C*Cos(ω*t)+D*Sin(ω*t)] does not apply directly. A suggested resource for further understanding is a document on single-mass-loaded strings.

PREREQUISITES
  • Understanding of wave equations in mechanical systems
  • Familiarity with eigenvalues and eigenfrequencies
  • Knowledge of Dirac delta functions in physics
  • Basic principles of tension and lineal density in strings
NEXT STEPS
  • Study the derivation of eigenvalues for systems with discrete masses
  • Explore the application of boundary conditions in wave equations
  • Learn about the implications of Dirac delta functions in differential equations
  • Review the provided resource on single-mass-loaded strings for practical examples
USEFUL FOR

Students and professionals in mechanical engineering, physicists studying vibrations, and anyone interested in advanced wave mechanics and eigenvalue problems.

Frank93
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Hi there. First of all, sorry for my bad english. I ´m trying to solve next exercise, from Vibrations and Waves in Continuos Mechanical Systems (Hagedorn, DasGupta): Determine the eigenfrequencies and mode-shapes of transverse vibration of a taut string with fixed ends and a discrete mass in the middle.

I set next wave equation:

T * ∂^2 Y/ ∂^2 X = ( ρ + m*δ(x-L/2) ) * ∂^2 Y/ ∂^2 t

where
T: tension, ρ: lineal density of the string, m: mass of the particle in the middle of the string, δ: Dirac delta, L: length of the string, and the boundary conditions are Y(0,t)=0 and Y(L,t)=0.


I don`t know how to continue this, because to determine the eigenvalues, I need the wave equation, but it isn`t the usual Y(x,t) = [A*Cos(k*x)+B*Sin(k*x)]*[C*Cos(w*t)+D*Sin(w*t)]. How can I solve this differential equation? Or another way to solve this?
 
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Thank you drvrm!
 

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