Engineering Data Processing in MATLAB

Engineering Task

Using MATLAB to process, analyse and visualise engineering data from FEA results, test measurements or load spectra.

Reading FEA Results

• Abaqus: export field output as .rpt (ASCII); parse with textscan and custom format strings
• Nastran: read F06 or OP2 files; use regexp to extract grid point force or stress tables
• ANSYS: export results as CSV or APDL output files; read with readmatrix
• Use readtable for structured CSV exports from any solver

Rainflow Cycle Counting

MATLAB's Signal Processing Toolbox includes the rainflow function for counting fatigue cycles from time histories.

cycles = rainflow(stress_time_history);
ranges = cycles(:,1);
means = cycles(:,2);
counts = cycles(:,3);
amplitudes = ranges / 2;

S-N Curve Implementation

Implement S-N curves as anonymous functions or lookup tables with log-log interpolation.

% Basquin equation:
N_fail = @(Sa) ((Sa / sf_prime) .^ (1/b)) / 2;
% Goodman correction:
Sa_equiv = @(Sa, Sm) Sa ./ (1 - Sm ./ Ftu);

PSD Processing

• Use pwelch for PSD estimation from acceleration time histories
• Use fft for frequency-domain analysis
• Use interp1 for resampling or frequency-domain interpolation
• Verify units: g²/Hz for acceleration PSD; Pa²/Hz for stress PSD

Useful Toolboxes

Related Knowledge

• S-N Fatigue Assessment Checklist
• Random Vibration Analysis Checklist