| Due to aerodynamic heating on the surface of hypersonic vehicles, the temperatureof it can be thousands of degrees Celsius. Thermal stress and change of samples’ stiffnesscaused by high temperature can both influence structures’ vibration performance.Therefore, studies on structures’ thermal modal analysis make contributions to dynamicmodeling and flutter analysis. Traditional way of acquire vibration signals in thermalenvironment is contact measurement, for example, high temperature acceleration sensoror extension poles which lead signals into normal air. The availability of thismeasurement can be restricted by the working temperature of sensors and its measuringaccuracy can be influenced by the change of poles’ Transmissibility caused by elevatingtemperature.In this paper, we use a SDOF oscillator which is excited on the base to develop testmethods of thermal modal analysis based on laser non-contact measurement. The maintasks are:(1)Theories about thermal radiation and laser vibrometer are studied. The motiontransmissibility between velocity and acceleration are derived, and the way to identify thenatural frequency from the motion transmissibility function is discussed.(2) The scheme of thermal modal test based on laser non-contact measurement is setforth. High temperature cabinet designed by utilizing quartz lamp radiant heating canmake the temperature environment vary from room temperature to1200degrees Celsius.By acquiring the motion transmissibility of fixture, the availability of the thermal modaltest scheme is verified.(3) The accuracy of laser signal measurement is concerned which influenced by thesurface condition of test articles, thermal radiation light and hot air. Improvement waysare also proposed along with that.In short, the laser non-contact measurement has advantages as non-contact,conveniences, high dynamic range and precision. In this paper, we apply thismeasurement in thermal modal test which is very valuable in engineering. |
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