Structural Integrity Unit

DESCRIPTION

The unit combines a complete testing equipment for the mechanical characterization of materials and components and the expertise to extract meaningful information from the tests. Testing includes dynamic loadings from very small strain rates (1 µm/hour, typical of creep at elevated temperatures), up to 14 m/s (impact tests). Testing frequencies range from 1 cycle in several minutes (thermo-mechanical fatigue tests) to 200 Hz (in resonant fatigue testing machines).

Loading can be uniaxial (tension-compression) or biaxial (tension-compression plus torsion), within a temperature ranging from liquid nitrogen (77 K) up to 1200 °C. Strains are measured (measuring hysteresis loops) at all temperatures and environments. Fatigue limit and complete S-N (stress vs. number of cycles or time) curves can be determined for real materials, components and structures.

Artificial micro-defects can be introduced by Focused Ion Beam (FIB) milling, when required on testing samples. Interfaces between different materials (surface depositions, coatings) can be characterized determining bonding energy and interface toughness. Early crack detection is available through Infrared Thermography with a resolution of 10 µm.

Residual and total life assessment are deduced, including effects of local residual stresses. Residual stresses are obtained by x-ray diffraction. Local residual stresses are measured -by FIB and Digital Image Correlation (DIC)- at the microscale level.