Wing test bench

We have designed, built and commissioned a wing test bench at Empa for the demonstration of the integrated DIMES measurement system to detect and monitor crack initiation and growth.
From design to reality
Starting from the test article and its load bearing capability, a test bench in the form of an asymmetric three point bend was designed and realized.
Sensor installation
The DIMES system combines image sensors (left, inside a wing bay) with point sensors (right, on the front spar). Visual cameras are used for Digital Image Correlation (DIC) while thermal cameras are monitoring changes in the stress field. Fibre Bragg Gratings (FBG) and Resistance Strain Gauges (RSG) are used for the measurement of the local strains.
Test program
Force and displacement at the onset of constant amplitude cyclic loading as displayed in real-time on the GUI.
wing was exposed to fatigue loading in up- and downbend. It was loaded quasi-statically to a given deflection and then vibrated with a constant amplitude for several thousend cycles. Both the preset deflection and the amplitude were gradually increased to the point that cracks were initiated and grown in the front spar. For an even harder test, a type of flight cycle loading was applied with excursions into up- and downbend, while vibration amplitudes and frequencies were varied according to a prescribed programme.
Crack detection