RESEARCH ON CALIBRATION METHOD OF SAPCE-BORNE HIGH TEMPERATURE STRAIN SENSOR

摘要

High temperature strain sensors are extensively used in astronautic vehicles to monitor the distribution and variation of the strain. During the re-entry capsule backing to the earth, complex thermal conditions of the outer space generate considerable unwanted thermal output, thermal sensitivity coefficient variation, creep and null shift, which greatly reduce the measurement accuracy. Therefore, thermal parameters calibration in various experiment conditions is a key technique for application of space-borne high temperature strain sensors. In this paper, a thermal parameters calibration method and device for space-borne high temperature strain sensors is proposed and demonstrated. The calibration device consists of a bidirectional strain generation mechanism, a high temperature furnace and an optical speckle measurement system. The bidirectional strain field generation mechanism is designed in the way that a equal-strength strain beam is implemented by bidirectional pulling and pressure loading using a torque motor, a force screw and a lever structure, so that the positive and negative strains are generated on the same side of the equal-strain regions on the equal-strength strain beam. The strain beam is placed in a high temperature furnace to realize temperature loading and control from room temperature to 1200 °C . The surface deformations of the linear working zone as well as the strain sensors on the strain beam surface are measured by the optical speckle measurement system through the optical window on the high temperature furnace. And the all-field strain is derived as the standard strain value according to the speckle interference map. Then the thermal parameters of the high temperature strain sensor can be calibrated under different temperature regions. During high temperature application, thermal output is much larger than null shift and creep, so the research is focused on calibration method of the thermal output and thermal sensitivity coefficient in thi