Intrinsic critical speed of a steel circular shaft

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Discussion Overview

The discussion revolves around determining the intrinsic first critical speed of a circular steel shaft supported by two bearings. Participants explore methods for calculating critical speed, including the Rayleigh Method and Dunkerley's equation, while addressing the challenges posed by the shaft's varying regions and the available data.

Discussion Character

  • Homework-related, Technical explanation

Main Points Raised

  • The original poster (OP) expresses confusion about how to determine the critical speed of the shaft, noting that only the modulus of elasticity (E) is provided.
  • One participant asks the OP to clarify their confusion and inquires about their familiarity with critical speed calculations and specific methods like the Rayleigh Method and Dunkerley's equation.
  • The OP mentions uncertainty regarding whether to calculate critical speed for each of the three different regions of the shaft and whether to take the lowest value.
  • Another participant suggests that the OP can look up the density of steel to determine the mass of the shaft, which is necessary for the calculations.
  • This participant also advises starting with a static analysis of the shaft to determine its deflection between the bearings.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the approach to take, as the OP's confusion about the problem remains unresolved and multiple methods are suggested without agreement on a single path forward.

Contextual Notes

The discussion highlights limitations in the provided information, such as the absence of mass and the need to consider the shaft's different regions in the calculations.

Who May Find This Useful

This discussion may be useful for students or individuals studying mechanical engineering, particularly those interested in dynamics and critical speed calculations of shafts.

Mechatroni
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Homework Statement


Determine the intrinsic first critical speed of a circular steel shaft supported by two bearings
E=207GPa

How can i determine it I'm very confused about this question , you can see the question at the attachment. Thanks for the help
 

Attachments

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Specifically, what are you confused about? Do you understand how to calculate the critical speed of a shaft? Have you been exposed to the Rayleigh Method? Dunkerley's equation?
 
i'm not so good at this lecture. The part I'm confused is there is 3 different regions in the shaft so do i have to calculate for each of them and take the lowest one? i know the Rayleigh Method and the Dunkerley's Equation but i need to use m ( mass ) in those equations , the problem is only E is given to me. Where do i have to start to solve this
 
The OP says it is a steel shaft, so you can look up the density of steel and figure the mass of the shaft.

I think your first order of business is to analyze the shaft statically and determine its deflection between the bearings.
 

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