Laplace Boundary Value Problem

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SUMMARY

The discussion focuses on solving the Laplace Boundary Value Problem for a cantilever beam subjected to a uniform load, represented by the equation EI y'''' = -w with boundary conditions y(0) = y'(0) = 0 and y''(L) = y'''(L) = 0. Participants explore the application of Laplace transforms, specifically the equation L[y^4] = S^4*Y(s) - S^3*Y(0) - S^2*Y'(0) - s*Y''(0) - Y'''(0), to derive the solution. The challenge lies in the boundary conditions, particularly the presence of Y''(0) instead of Y''(L), leading to discussions on integrating the equation multiple times to apply the boundary conditions effectively. The conversation emphasizes the necessity of understanding Laplace transforms in solving such boundary value problems.

PREREQUISITES
  • Understanding of Laplace transforms and their applications in differential equations.
  • Familiarity with boundary value problems in structural mechanics.
  • Knowledge of cantilever beam theory and uniform loading conditions.
  • Proficiency in calculus, particularly in integrating higher-order derivatives.
NEXT STEPS
  • Study the application of Laplace transforms in solving ordinary differential equations.
  • Learn about boundary value problems and their significance in engineering mechanics.
  • Explore the theory of cantilever beams under various loading conditions.
  • Investigate methods for integrating higher-order differential equations and applying boundary conditions.
USEFUL FOR

Students and professionals in engineering, particularly those specializing in structural analysis, mechanics, and applied mathematics, will benefit from this discussion. It is particularly relevant for those tackling boundary value problems and utilizing Laplace transforms in their studies or work.

lax1113
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Homework Statement


A cantilever beam has uniform load w over a length of L as described by the eq.

EI y'''' = -w y(0) = y'(0) = 0 y''(L) = y'''(L) = 0

EI are constants

find y(x)

Homework Equations


L[y^4] = S^4*Y(s) - S^3*Y(0) - S^2*Y'(0) - s*Y''(0) - Y'''(0)



The Attempt at a Solution


We really didn't do anything similar to this at all in class. All I could think of doing was simply take the transformation of the equation, and we can see that two fo the terms will go to zero, but we are still left with

S^4*Y(s) - s*Y''(0) - Y'''(0) = -w/S

From here what can we really do? I don't see how we can use the boundary conditions because we have Y''(0) not Y''(L) and i don't see how we would ever get to a point that we could use that.
 
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You could solve for Y(s) leaving the two boundary conditions in there as unknowns. Then take the inverse transform and use the two conditions in the answer to determine the constants.

But why use LaPlace transforms on this problem anyway? You have an equation of the form

y'''' = constant. Just integrate four times and use the BC's.
 

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