Effect of applied moment on B10 life?
Effect of applied moment on B10 life?
(OP)
I am working on a small bearing application (20mm shaft) where the load is primarily radial, with a very small amount of overturning moment. There's not much axial space to work with, and the main candidates in my design are currently a deep-groove ball or needle-roller bearing with a thrust washer set.
The ISO and ABMA standard calculations for B10 life include factors for calculating an "effective" radial load for use in the life equation, but say nothing about applied moments.
Does anyone know of a good way to factor those loads into the calculation?
The ISO and ABMA standard calculations for B10 life include factors for calculating an "effective" radial load for use in the life equation, but say nothing about applied moments.
Does anyone know of a good way to factor those loads into the calculation?





RE: Effect of applied moment on B10 life?
thrust and radial components.
RE: Effect of applied moment on B10 life?
To my knowledge, moment loads on single bearings cannot be resolved into purely axial and radial components. I'd be happy to be proven wrong, though.
I know that deep groove ball bearings can support some small moment loading; I want to know how much it will affect the B10 life.
RE: Effect of applied moment on B10 life?
RE: Effect of applied moment on B10 life?
I'm still waiting to hear back from the manufacturer. The problem was too complex for the local applications "engineer"/salesman, so it's been referred to the guys who do the calculations. I just thought I'd ask here and see if anyone had run into a similar problem.
Also, I'm starting to look into codes (software) for bearing analysis (looking at ball loading, hertz stress, internal clearance, effect of bearing fit-up), and was wondering if anyone had any recommendations for a good basic package? I've looked at COBRA-AHS/EHL so far. Can you even buy A.B. Jones anymore? I don't need any rotordynamics stuff; quasi-static is fine for what I'm doing.
Any ideas?
RE: Effect of applied moment on B10 life?
TK solver based - not cheap - used to cost about 5 grand.
RE: Effect of applied moment on B10 life?
RE: Effect of applied moment on B10 life?
It's interesting that FAG/INA has decided to provide their Bearinx software as an online service. It looks like a very capable package, but unfortunately my company doesn't buy direct from INA (you have to be a direct account to access Bearinx.)
I found some moment calculation information in Harris' "Rolling Bearing Analysis." Suffice it to say that the method is not simple. Maybe software is the right way to go with this one.
RE: Effect of applied moment on B10 life?
RE: Effect of applied moment on B10 life?
RE: Effect of applied moment on B10 life?
I am perfectly willing to pay for analysis and related tools, but I don't see that INA/FAG has made any provision for that.
My current supplier will eventually respond (they're a quality manufacturer also), but if I try to iterate the design through them, it could take weeks.
mbensema, there might be room for a double-row angular contact bearing, but I think this is probably overkill. I've also considered a 4-point contact bearing, which should be able to handle more moment due to the increased contact angle.
But again, the moment loading is very small compared to the radial load, and should be well within the performance envelope of even a basic radial ball bearing. The problem is still how do you calculate B10 life on any of these bearings with this loading?
I suppose I could code up the equations from Harris/Jones, but it's probably better to just buy an off-the-shelf program, since they have more capability and have already been debugged and proven.
Arg.
RE: Effect of applied moment on B10 life?
You might want to check out Tedric Harris's
books on Roller Bearing Design Anaylysis.
Even if you have a program, you will need
the basic bearing parameters:
Bearing Diameter
Ball Diameter
Contact Angle
Conformity Radius
Amount of Clearance or Preload
Harris does have equations to determine
the effects of moment and combined loads.
Almost all of the bearing formulas assume
use the most heavily loaded ball or roller
to base their calculations.
If you can resolve the effect of the moment
on the top ball tdc, I think you can use
the basic equation that the b10 life will
decrease by the ratio of the third power
of the loads.
RE: Effect of applied moment on B10 life?
Assume that the ball load increases by 10 percent
1.1 cubed would be 1.331. The reciprocal would
be 75 percent of the b10 life.
RE: Effect of applied moment on B10 life?
If you send me your conact information I will send you a couple of papers on the subject and you can write your own mini-program. Since you have ted's book, you may want to check the section with the moment load. It appears more complicated that it actually is.
RE: Effect of applied moment on B10 life?
RE: Effect of applied moment on B10 life?
Fr=radial load; M=moment; P&Po=equivalent loads (dynamic & static).
Fr=100N; M=1Nm; P=234N Po=222N
Fr=200; M=1; P=320; Po=318
Fr=300; M=1; P=408; Po=414
Fr=500; M=1; P=595; Po=605
Fr=1000; M=1; P=1080; Po=1080
If you change the clearance the equivalent load is affected as well. By doubling the clearance to 0.016mm, the equivalent load decreases as follows:
Fr=100; M=1; P=199; Po=192
Fr=200; M=1; P=296; Po=294
Fr=300; M=1; P=390; Po=390
Fr=500; M=1; P=580; Po=585
Fr=1000' M=1; P=1070; Po=1070
You can draw your own conclusions.