No cooling was needed. Furthermore, the software averaged 16 acquisitions. The calibration block is made of the same aluminum alloy as the COF external structure, that is, alloy 2219 T6. Relative errors are given in Figure 6. Their calculation took into account theoretical temperature expansion.
Thickness is overevaluated at high temperature and is underevaluated at low temperature.
These differences may be explained by changes in shear waves velocity due to temperature variations. Lift-off has a dramatic influence on signal amplitude. This will cause problem for thickness measurement at the center of deep concave craters unless the probe diameter is minimized. Conclusions Temperature variations are not a problem if EMATs are used for wall thickness measurement purpose on the COF, in space environment. Development should be continued to optimize the probe, particularly regarding the lift-off effect, and to adapt the whole system to space standards and procedures.