Designing Vibration Fixtures
Designing Vibration Fixtures
(OP)
We are designing fixtures for ESS and qualification testing. We keep hitting a wall with management over the design. The engineers say "build a cube, and bolt directly to the test shaker." How common is a cube structure in vibration testing? Why not bolt directly to the shaker table?





RE: Designing Vibration Fixtures
For high performance, mass and inertia are your enemies. You'll have to look at the tradeoffs between fixturing ease and performance. Every system I worked on bolted as direct as possible right to the table.
RE: Designing Vibration Fixtures
RE: Designing Vibration Fixtures
RE: Designing Vibration Fixtures
As BobM3 said "mass and interia". Think of how the UUT will respond on the set-up.
RE: Designing Vibration Fixtures
> as an adaptor to the shaker head, since it's usually undesirable for everyone to drill their own holes into the head; you wind up with Swiss cheese that no longer can hold anything.
> as a means of altering orientation of the UUT. As mentioned above, vibration tests often require running with different orientations, so it's usually easier to have a single fixture that can orient the UUT as required.
What the fixture looks like depends on the vibration profiles, etc., but the requirement is that the fixture not introduce anomalies into the test. Obviously, if it needs to support different UUT orientations, it needs to be awfully stiff, so a cube might be a plausible solution.
One caveat is that slip tables don't like top-heavy configurations, as that potentially can cause the slip table to rock on its oil film, resulting in unintended resonances.
TTFN
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RE: Designing Vibration Fixtures