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  1. PearlRock

    question about spline design

    Tbuelna recommended me to look at Vacuumelt Nitralloy N from Latrobe based on my spline. I've been looking at the vacuumelt; however, I called Latrobe the other day, and they seemed to imply 300M was easier to procure, so I got a quote for that. I've been following a number of shaft and...
  2. PearlRock

    question about spline design

    You guys beat me to it. I think I am looking at improper fatigue properties. I'll post back when I learn more about my material, hopefully in the next day or so. @tbuelna, good points. Yeah, I wish I had more experience with FEA modeling this type of system. I've already noticed that small...
  3. PearlRock

    question about spline design

    Hello everyone, I designed a spline in this thread: http://www.eng-tips.com/viewthread.cfm?qid=373420 Now I'm doing an FEA torsional analysis of my shaft to check for fatigue issues. I modeled the spline along with the shaft. Peak stress is showing to be about 80MPa (12ksi) localized around the...
  4. PearlRock

    Beam188 Stress concentration question

    Dear all, I am simulating a shaft for an electric motor using ANSYS MAPDL rotordynamic tools. I have a shaft with multiple stepped diameters made of Beam188 elements. I was wondering how Beam188 analyzes the stress distribution in this stepped geometry. Are stress concentrations considered? If...
  5. PearlRock

    Questions on Spline Design

    Ok, I'm starting to understand now. These surface measures are more about fatigue/fretting prevention, as opposed to stress/design. I think that clears up most of my confusion. And thank you for the material recommendations. That will keep me going in the right direction. Regards, PR
  6. PearlRock

    Questions on Spline Design

    ...o-ring on the male or female spline? Is my spline a Major Diameter fit????? ANSI B92.2M automatically assumes the major diameter fit requirement, right? Good lord why is this so difficult [sad] This is why I wanted to use a flexible shaft coupling. *shakes fist at dyno engineers* Best...
  7. PearlRock

    Questions on Spline Design

    Terry, It is indeed quite high. For the spline calculations I went with 1million start-stop cycles and 1billion revolutions. The result was about 5ksi compressive stress. If this was for a long lifetime production environment, I'd want more, but the dyno manufacturer and I agreed we believe...
  8. PearlRock

    Questions on Spline Design

    Looks like I'm ok now. I spoke with the dyno manufacturer yesterday. Using the average torque instead of peak torque, the stress goes down considerably. There's still some uncertainty with the factors, but we think with the material selected, we should be in good shape. Thanks for taking the...
  9. PearlRock

    Questions on Spline Design

    @mfgenggear, I'm new to this topic. Machinery guide describes the stresses as different, so I can only assume there may be different solutions to each stress problem. This is a demanding application, so it's critical that I be as precise as possible. @tbuelna Here's the material being used on...
  10. PearlRock

    Questions on Spline Design

    Yes, this is a bi-directional motor, so that will have to be considered. Machinery guide also makes note of a parallelism variation. Would that not give enhanced load capacity bi-directionally? "Regarding your question about modifying the section properties of the area backing the spline...
  11. PearlRock

    Questions on Spline Design

    Hi Terry, thanks for the response! [sad] Lead variation looks complicated. [sad] I'll have to look more into that. The Machinery Handbook doesn't seem to mention too much about that. If you know of any design references for that, I'd appreciate them. Do I need a flexible type joint? You mean...
  12. PearlRock

    Questions on Spline Design

    Dear all, I am designing a flexible spline for an experimental application. I'm looking at ANSI B92.2M in the machinery guide. My root stresses appear to be too high. I am using the maximum effective length and my maximum diameter is restricted. If I could choose a larger diameter, this...
  13. PearlRock

    Mass Assignment

    Hey Guys! Is it possible to directly assign a mass in Creo? I'm making a space model. I don't have all the features or internals of the component. I just want to assign the part mass "4". Do I really have to adjust the density to the part volume to get the right mass? That seems really...
  14. PearlRock

    Dissimilar materials, thermal expansion, and cracking

    Thanks for all the resources everyone, very helpful. Tomwalz, what exactly do you mean by bond line? Thickness of the epoxy section or bond area? Just for an update, I am remaking my samples today. I should have results sometime next week. The plan is to try a roughed bond surface. If that's...
  15. PearlRock

    Dissimilar materials, thermal expansion, and cracking

    That's alright. I think I have the information I need. Now I just need to look at various materials, surface prep and possibly modified geometry.
  16. PearlRock

    Dissimilar materials, thermal expansion, and cracking

    Well, it's not as dramatic as that. A crack formed around the edge is all. Yeah, in most places there will be thinner sections of epoxy, but that's not the part I'm worried about at this time. This test was performed to see if any degradation would happen to the epoxy itself, and so far no...
  17. PearlRock

    Dissimilar materials, thermal expansion, and cracking

    Hi MintJulep, This is a bond failure. I'm doing some R&D on potting of electrical stator cores, so no, the expansion will not be uniform, but full thermal simulation with thermal expansion integration is a bit beyond the project scope at the moment. I may try to break the material later. I'll...
  18. PearlRock

    Dissimilar materials, thermal expansion, and cracking

    Hmmmm, according to that document, I need to determine the max allowable strain. The manufacturer may have that, or I could probably determine it on my own. As long as I use the same prep techniques, and as long as I ensure that thermal strain + elastic strain is less than the allowable...
  19. PearlRock

    Dissimilar materials, thermal expansion, and cracking

    I thought that to at first. MATWEB says 1018 has CTE of 12e-6 in/in-C. Epoxy datasheet says the expansion coefficient is about 31. I've filled a steel cup with epoxy. So I believe both materials experience thermal expansion over the same length. Would that not suggest that they epoxy expanded...
  20. PearlRock

    Dissimilar materials, thermal expansion, and cracking

    I won't be able to mate materials that have precisely equivalent expansion coefficients. Is there a rule of thumb for when the linear expansion coefficient will be close enough? I guess not, because that would depend on the quality of the bond and surface prep as you have suggested. Assuming a...

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