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  1. cbk14

    No boundary conditions listed in PSD G Accel load in Random Vib (Ansys Mechanical)

    OK I'm an idiot. I was using body to ground joints above. Even though they were 6-DOF fixed joints, Ansys won't use those for a PSD G Acceleration boundary condition. Even though I was able to run the modal no problem. I needed to define Fixed Supports in Modal using right click > Insert > Fixed...
  2. cbk14

    No boundary conditions listed in PSD G Accel load in Random Vib (Ansys Mechanical)

    I'm having a strange issue where I can't select any boundary condition for my PSD G acceleration load in a random vibration study. I have the prerequisite modal analysis linked properly, with fixed boundary conditions defined therein, but the PSD G acceleration definition doesn't list them, nor...
  3. cbk14

    Is it reasonable to average von Mises stress plots at discontinuities?

    Suppose I have a FEM with two bodies. One body represents the washer underneath a bolt head; it is circular and small relative to the other body, which is a large, thick, flat plate. The washer is bonded to the plate in a circular region with compatible meshes. The edge of the bonded contact is...
  4. cbk14

    Circuit Card Strength

    Thanks for the replies, all. I guess my primary question was something like "what is a reasonable yield/ultimate strength for typical FR-4 PCBs?" but that question now seems moot. PCB construction (# of layers, copper thicknesses, etc) varies widely so there's probably not a convenient figure...
  5. cbk14

    Circuit Card Strength

    Hi all, I have tasks to analyze some mechanical assemblies which include circuit cards (PCB / PCA / CCA whichever terminology you prefer) under particular load conditions. For the purposes of this discussion, let's stick with common FR-4. What are the recommended best practices for mechanical...
  6. cbk14

    Studs sheared and magnetic particles found

    To clarify, we replaced the studs and lug nuts after the stud failures. My friend decided it would be wise to replace all the studs and lug nuts at the same time rather than just the two broken studs. My findings posted above are all post-breakage and were all during the replacement of the...
  7. cbk14

    Studs sheared and magnetic particles found

    Hello all, A friend of mine had two (out of twenty) OEM wheel studs shear off. One sheared while installing wheels and the other sheared while taking the wheels off (about a week later). Both stud failures occurred while tightening or loosening the lug nuts (also OEM). Being curious, I...
  8. cbk14

    ASME Membership Perks?

    Hi everyone, I'm looking at becoming an ASME member, but I want to make sure I understand what's offered before I drop the quid. I basically just want access to the ASME journals with no per-article fees or anything. As an ASME member, is that possible? Or do you still have to buy articles even...
  9. cbk14

    Vibration of a Retaining Ring / E-Clip

    3DDave: yes that is the exact idea. We actually adapted the jack screw idea (with E-clips) from TE, the manufacturer of the connectors. I think the solution has been converged on. The E-clip was changed to be a "heavy duty" version which has a larger OD and higher spring force keeping it in...
  10. cbk14

    Vibration of a Retaining Ring / E-Clip

    Corypad: The overall purpose of this design is to pull two PCBs together and accurately mate their connectors without cocking one in the other. The clips enable the screws to also act to unmate the PCBs. The screw is inserted through the PCB (green) and secured in place with an e-clip. The PCB...
  11. cbk14

    Vibration of a Retaining Ring / E-Clip

    tbuelna: I've attached a cut-away image of the design. Thrust washers are used on both sides to protect the PCB and to prevent moments being exerted on the E-clip during unscrewing...
  12. cbk14

    Vibration of a Retaining Ring / E-Clip

    Jboggs: That would be great if you looked up their phone numbers for me. Better yet, would you mind calling them for me and just post what they tell you? Actually, I might just upload my model and you could finish it up for me. That would be super! [smile] Why the crappy attitude? Nobody...
  13. cbk14

    Vibration of a Retaining Ring / E-Clip

    So I did call up McMaster earlier today and explained the concern. They got back to me by email, with the response essentially "the manufacturer doesn't have shock or vibe test data." McMaster said that the manufacturer claimed a circlip style ring would be more likely to vibrate off a shaft...
  14. cbk14

    Vibration of a Retaining Ring / E-Clip

    Jboggs, good thinking. I always forget to just call the vendor directly. Only problem is the vendor is McMaster (for ease of obtaining 3D models) and I don't think they design/test/manufacture.
  15. cbk14

    Vibration of a Retaining Ring / E-Clip

    I am working a design that has jack screws - basically a grooved screw with an E-clip retaining ring for captive purposes. The design will undergo pyro shock and random vibe, so there is some worry that the E-clip will vibrate out of the groove on the screw. Has anyone experienced E-clips...
  16. cbk14

    Thermal analysis of a PCA

    Hi all, I'm trying to conduct a thermal analysis of an FPGA on a PCA. According to the data sheet the FPGA can be roughly modeled as a two-resistor network, with one resistor being the IC-junction to case thermal resistance and the other resistor being the IC-junction to board thermal...
  17. cbk14

    Thermal Analysis of a PCA

    Hi all, I'm trying to conduct a thermal analysis of an FPGA on a PCA. According to the data sheet the FPGA can be roughly modeled as a two-resistor network, with one resistor being the IC-junction to case thermal resistance and the other resistor being the IC-junction to board thermal...

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