DEFINITION OF A DYNAMIC OPTICAL SENSOR FOR MEASURING UNSTEADY PRESSURES

This study presents our contribution to define an optical dynamic sens or. Given that the studies carried out are of an exploratory nature, t he first task was to validate the mechanical behavior of the specimen body in the sensor and to check that the signals recorded were reprodu cible. To subject the sensor to deformation rates of 10 to 10(2) per s econd, tests were carried out using the KOLSKY-HOPKINSON apparatus. Th e results show that specimen body responds in a satisfactory manner. I t remains within the elastic zone for the loads exerted and this is co nsistent with the results of the sizing calculations carried out. It w as also possible to verify complete reproducibility of the interferome tric signals on the basis of several tests conducted on the same senso r located between two polyurethane sheets. It is also shown that the s ensitivity of the standard monomode fiber used in the MACH-ZENDER appa ratus is highly dependent on deformation rates. This result leads us t o opt for the use of a polarimetric apparatus using birefrigent shapin g fibers in order to limit the intrinsic sensitivity of the two-arm ap paratus. The fact that the fiber is sensitive to deformation rates doe s not appear in the bibliographical references. We identified it on th e basis of tests on the traction/compression machine by varying the lo ad climb rate and on the basis of HOPKINSON bar dynamic tests.