Tutorial LAOS Application

This short tutorial shows how to load the bundled LAOS examples and inspect raw, filtered, and harmonic-analysis views. It does not require fitting a theory.

Load LAOS Data

  1. Start RepTate and create a new LAOS application.

  2. Open one of the example files in data/LAOS:

    • CPyCL-omega00p30-gam03p1600.laos

    • GiesekusSimulation-omega01p00-gam05p000.laos

    • SlugSlime-omega03p00-Run31.laos

    The LAOS application reads text files with the .laos extension. Each file should contain the angular frequency omega and strain amplitude gamma as file parameters, followed by columns for time, strain, and stress. Extra columns are ignored by the file reader.

Check the Raw Signal

Use the View selector to inspect the raw imported data before using the Fourier-based views:

  • sigma,gamma(t) shows raw stress and raw strain as functions of time.

  • sigma SCA,gamma(t) scales the raw stress by its maximum absolute value so the stress and strain phase can be compared on the same plot.

  • sigma(t) and gamma(t) show each raw signal separately.

  • sigma(gamma) plots the raw stress-strain Lissajous curve.

Use Fourier-Based Views

After checking that the signal is periodic and has a clear oscillatory strain, switch to the Fourier-based views:

  • sigma(gamma) FILT plots reconstructed stress against reconstructed strain.

  • FFT spectrum shows the normalized stress-harmonic spectrum.

  • sigma(gdot) FILT plots reconstructed stress against reconstructed strain-rate, using the file parameter omega.

  • sigma(gamma) ANLS and sigma(gdot) ANLS compare the filtered stress with elastic or viscous harmonic contributions.

  • Cheb elastic and Cheb viscous show the elastic and viscous Chebyshev coefficients from the Fourier coefficients.

When one of these Fourier-based views is selected, RepTate shows two extra view controls. HHSR is the highest harmonic used in stress reconstruction. PPQC is the number of points per quarter cycle used for the Fourier reconstruction; the source code limits it to the range 20 to 500.