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  1. dag113

    Vibe "analysis" by natural frequencies only?

    I understand your point about the finitely-rigid mounting structure. Considering the mass and stiffness of the particular vehicle involved, though, I'm not really concerned about significant changes to its natural frequencies due to what we're mounting to it. And the customer spec is vague...
  2. dag113

    Vibe "analysis" by natural frequencies only?

    Thank you for the example. That's a very good point and gives me more backup for saying that this isn't a good idea. I really appreciate your help, WARose. Apart from actually running the vibe profile against the model (which they can't do because they can't have the profile and I can't do...
  3. dag113

    Vibe "analysis" by natural frequencies only?

    WARose, Thank you very much for your response. That's just what I was thinking. Their natural frequency results will just tell me if the applied vibration profile will have a magnification issue like you said. The stresses at other frequencies (steady-state amplitude?) could still be...
  4. dag113

    Vibe "analysis" by natural frequencies only?

    "What are you trying to work out, the worst case deflection?" Normally, I would think I'm working out stresses in the structure caused by the vibrations. If this was my own structure, I'd be running a modal and then a vibration analysis based on the inputs defined in the vibe profile, review...
  5. dag113

    Vibe "analysis" by natural frequencies only?

    I have a situation where a subcontractor is designing a structure to be attached to our system (a moving vehicle). Per the requirements from our customer, their structure needs to withstand a certain vibration profile (broadband with narrow band spikes). However, we are unable to share the...
  6. dag113

    Can you re-use a Keensert?

    Thanks, btrueblood. Your experience and comments on safety, etc., back up my own experience and what I was thinking. My issue is going to end up being a matter of assessing risk, as the bolt cost is high in this particular application. Thanks again.
  7. dag113

    Can you re-use a Keensert?

    Thank you all very much for the information. These are locking inserts, so Mr. Kinney's point is taken. My scenario should not have the inserts being used for more than just a couple of uses, though, so I think I'm still in good shape. Regarding the bolts going in to the Keensert: does anyone...
  8. dag113

    Can you re-use a Keensert?

    I don't mean "re-use" as in install the Keensert, then remove it, then reinstall it. I mean "re-use" as in install the Keensert, then install a bolt into it, then remove the bolt, then install a different bolt into it. (Did that make sense?) What does this do to the Keensert? Are there any...
  9. dag113

    Threaded Inserts - load into member

    Thanks again, Desertfox. That was what I thought (before I started overthinking; very bad habit). Yes, the stresses drop down due to the increased diameter, but my aluminum plate is the weak link in this joint and the bigger diameter doesn't buy me enough to make up for the low material...
  10. dag113

    Threaded Inserts - load into member

    Desertfox and Drawoh, Thank you both very much for your replies, as well as for the fastener links. My issue really isn't the keensert but the threads on the aluminum plate where the insert is installed. When the bolt is installed into this joint (torqued into the insert in the Al plate), do...
  11. dag113

    Threaded Inserts - load into member

    I have a joint comprised of a bolt, a washer, a steel plate, and an aluminum plate. The aluminum plate contains an MS51830 threaded insert; the bolt is threaded into the insert. A specified torque is applied to the bolt to clamp up the joint. I can calculate the preload developed in the bolt...
  12. dag113

    Road test (g vs. time) vs. PSD table (g-rms)

    Thank you both very much for the responses; that's very helpful. I'm glad to see I was at least on the right track. I'm going to go digest all that and try to go from there. (By the way, that PSD was from MIL-STD-810; I apparently had a small aneurysm when typing and listed the wrong spec)...
  13. dag113

    Road test (g vs. time) vs. PSD table (g-rms)

    In the past, we performed a random vibration test on a particular component (PSD from MIL-STD-209). The component has now been installed on a vehicle and that vehicle driven over test courses. The component was instrumented with accelerometers for the test. I've been given the test results...

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