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Homework Help: Safety factor, temperature and torque

  1. Apr 27, 2016 #1
    1. The problem statement, all variables and given/known data

    https://drive.google.com/file/d/0BxPEJS0qVOpeWENSREI1RlNsNDQ/view?usp=sharing [Broken]

    A hub is connected to a shaft with a shrink fit (pressurized oil assembly, grease removed). The material of the hub is quenched and tempered steel (ReH = 450 N/mm2) and the material of the shaft is steel S355. The diameter DF = 30 mm and the length of the D sleeve is l = 30 mm. The outside diameter of the hub is D = 140 mm. Interference fit is

    φ30H7/u6 . Surface roughnesses of the shaft and the hub are according to SFS 5595. The

    load is pulsating: T = 150 Nm and Fa = 9000 N.

    1. a) Calculate the safety factor against sliding.

    2. b) Calculate the safety factor of the hub against the yielding.

    3. c) Calculate the temperature of the hub at assembly.

    4. d) Calculate the transmitted torque, if a parallel key (SFS 2636) is used to connect the

      hub to the shaft. The key length is 30 mm.

    2. Relevant equations
    Maybe from a similar problem and only for d)

    T = (π/2)⋅DF2⋅lF⋅vru(p/Sr)

    3. The attempt at a solution
    Sadly, as with my other homework problems, I do not have any formulas or methods showing me how to solve it since the course material is in Finnish.
    I can't use the Torque formula either since I don't yet have the safety factors...
    Last edited by a moderator: May 7, 2017
  2. jcsd
  3. Apr 28, 2016 #2


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  4. Apr 29, 2016 #3
    @Nidum Thank you, I am pretty busy at the moment but I will get more into it next week and let you know if it works!
  5. May 2, 2016 #4
    @Nidum It seems the links you give me don't have much information on the actual values asked and if they do, they require that I already have calculated some of the other variables (i.e. the calculator). Do you have any information on how I should start the approach?
  6. May 2, 2016 #5


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    To answer all the main parts of the original question you first need to evaluate :

    (a) the interface stress between the shaft and the ring .
    (b) the coefficient of friction effective between the shaft and the ring .

    There is a range of possible values for each of these quantities .
    Decide for yourself which are the safest values to use in further calculations .
  7. May 2, 2016 #6
    Ok, I think I have now found the safety factor against sliding with sum of resisting moments/sum of driving moments = (moment on shaft face + moment by contact pressure)/torque
    Now for the yielding safety factor i found the formula FS=yield strength (of the shaft i guess)/von mises maximum stress however I don't know how to find von mises' maximum stress...
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