Workflows

A project is of a kind, and its kind is what the application knows. Each workflow below carries the shape of its own test: what a project of that kind expects you to bring, which figures its report is built from, and how the result is judged.

Modal analysis

Measure frequency response functions from a hammer or shaker survey, fit modes to them, and animate the shapes on the test geometry. Coherence and drive-point checks come with it, so a doubtful channel is visible before it reaches a fit.

Finite element model correlation

Pair the test modes against a model's, by modal assurance criterion, and show where the two disagree — which pairs, by how much in frequency, and where on the structure the shapes part company.

Random vibration test analysis

Averaged spectra against a specification, with the bands, the tolerance lines and the exceedances marked — and the averaging itself shown rather than assumed, so the number of averages and the window are part of what the report says.

Shock test analysis

Find the events in a record, filter and integrate it into velocity and displacement, compute shock response spectra on log axes, and judge them against the required band.

Transient environment analysis

A measured waveform against the one it was controlled to, aligned and compared over the interval that matters rather than over whatever the file happens to contain.

Sine sweep test analysis

One or more tones swept across a frequency range at a controlled amplitude, so the article sees each frequency in turn. The level each tone actually reached is extracted from the recording and judged against the level it was required to reach, tone by tone and channel by channel, with the difference in decibels.

System identification

The plant a later test will be controlled through: the frequency response of every control channel to every drive, measured from an ambient recording and a driven one. The report carries the plant and the three readings that say whether to believe it — the coherence map, the signal-to-noise against the ambient floor, and the complex mode indicator that reads the whole matrix at a glance.

The signal-to-noise follows the standard definition, signal power over noise power, as IEEE Std 1241 states it and as Bendat and Piersol use it in Random Data. The driven recording holds the signal and the same noise the ambient one recorded, so the signal's power is the driven power less the ambient power, and the ratio is that over the ambient. The report draws it line by line for every channel and once per channel over the whole band, as bars against a 10 dB threshold, the margin at which the coherence the same noise allows reaches 0.91. How it is computed.

Supported data formats

Each one reads into the same objects, so what happens next does not depend on where the data came from. Most of them are written as well as read — where a format is read-only the table says so, rather than leaving you to find out at the export dialog.

A universal file comes in two encodings — dataset 58 as text and dataset 58b as raw floats — and both are read and written. The binary one is about a third the size and exact, where five decimal places of text are not.

The ones that do not write back: a Rattlesnake .nc4 is a controller's own record of a run and writing one would be claiming to have run it, and a STEP or IGES file is the CAD tool's own — both stay read-only on purpose. The punch and Femap writers are simply not written yet — anything read here is meant to be writable, and those two are the outstanding exceptions.

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