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  1. IKBrunel

    Shock Mechanics Calculations for Rotor Failures

    Thanks gwolf2, In your example the plastic deformation has elongated the work distance and so the peak force should be lower. I have a known stopping angle and a known angular momentum which leads to the purile result that I should have a known average torque. As you'll know, your average...
  2. IKBrunel

    Shock Mechanics Calculations for Rotor Failures

    Zekeman, Thanks for your thoughts. From your questions I can see how much it would help to explain this: Inducing Failure The rotor hub is drilled axially to weaken it. Experience tells us how much to drill. We spin the rotor to 60krpm, run it some hours and if it doesn't fail we take it off...
  3. IKBrunel

    Shock Mechanics Calculations for Rotor Failures

    Hi, Thanks for the responses. I did mean angular momentum rather than velocity (which is what you get from the acceleration/time graph), sorry for the confusion. Corypad, I haven't got useful pics at hand right now but I'll look for them. Simply imagine a cyclindrical product with four tapped...
  4. IKBrunel

    Shock Mechanics Calculations for Rotor Failures

    Hi rb1957: we calibrated the strain gauge by applying a large torque (dead weight on a lever) to give a KN/V value then zero'd
  5. IKBrunel

    Shock Mechanics Calculations for Rotor Failures

    gwolf2, I misunderstood your point. The loads must still be there though, however the energy is dissipated. Because we measured the failure torque at the mouting interface for the product we should read the net torque correctly, however the loads are distributed. This is becasue angular...
  6. IKBrunel

    Shock Mechanics Calculations for Rotor Failures

    Thanks, Greg, I am using 1.4 as a dynamic friction coefficient, it's an aluminium flange on an aluminium interface. A simple calc shows that if the flange slips round, say, 2mm then only 124J of work has been done. I was surprised by how small this was. I have found fleeting references to...
  7. IKBrunel

    Shock Mechanics Calculations for Rotor Failures

    Thanks for the replies, to answer then: The strain energy is an interesting element but I am happy that it is a negligible effect here. I calculated the strain energy of a few components and it was quickly apparent that strain energy is a few decades lower than rotational kinetic energy. It...
  8. IKBrunel

    Shock Mechanics Calculations for Rotor Failures

    Hi, I am studying the rapid deceleration of a turbo rotor during a catastrophic failure and I need to develop a hand-calc analysis method to help assess the results from tests. The turbo product is about 150mm dia by 200mm tall. The 1.2Kg rotor spins at 60,000rpm and when it fails it stops in...
  9. IKBrunel

    Twice running speed frequency

    Hi all, I am measuring bearing vibration and I have been told by a colleague that twice running speed responses are indicative of a bearing fault, particularly due to misalignment or inadequate preload. The bearing is a deep groove ball bearing with a predominant axial load and runs at a very...
  10. IKBrunel

    Small gap measurement techniques

    Thanks, CoryPad, they've a 2D displacement sensor that is a good option. I've asked what the cost is. It's non-destructive and measurements are taken within a controlled inspection room. Matt
  11. IKBrunel

    Small gap measurement techniques

    Hi, I have a precision shrink-fit rotor assembly that features a shaft with a stack of heated aluminium hub discs (~150mm dia) that are press-fitted onto a LN2-cooled shaft. We are left with small gaps remaining between the discs (shrink-back) and the measurement of these is critical for our...
  12. IKBrunel

    Rotating beam stress calculation

    rB1957, Thanks for the comment, I should have said, it's for a vacuum pump so the rotor isn't started until the system has been pumped down such that aero lift is negigible. That said, we still consider abuse states where a fault or misuse results in atmospheric air being dumped into the pump...
  13. IKBrunel

    Rotating beam stress calculation

    Thanks to all for the responses. Thanks for the formula, Zekeman, I'm new at my company and on this problem so I'm kicking myself a bit for not seeing how to derive it. I've unneccessarily and pedantically checked it with Quickfield ... it checks fine. My problem involves turbo rotor blades...
  14. IKBrunel

    Rotating beam stress calculation

    I'm struggling go to find the formula to calculate the stress & strain developed along a beam that is rotating around one end (simple rotor blade). Roarks give a simplified calc for max stress/strain in a pinned beam, I need to know the stress as it develops from the tip inwards. Does anyone...
  15. IKBrunel

    Determining failure temp from SS colouration

    I came across this page: http://www.mcnallyinstitute.com/05-html/5-3.html Giving the following statement: "The metal will become discolored and soften as it anneals. Annealing can occur any time the temperature exceeds 300°F (150°C): Straw yellow 600° F. 315° C. Brown 700° F. 370° C. Blue...
  16. IKBrunel

    Determining failure temp from SS colouration

    We have a bearing failure and this has led to one adjacent component becoming coloured - straw colour with some blue hue. Does anyone know the correlation of different stainless steel colours with temperature. I tried checking my annealing literature but could not find anything. Thanks

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