Metrological Objective
Direct quantification of mechanical deformation in structural components operating at temperatures exceeding five hundred degrees Celsius provides critical data for life assessment and design validation. Performing high temperature strain measurement requires specialized instrumentation that resists thermal drift and oxidation. This metrological activity is essential for validating the performance of turbine blades and exhaust systems.
Sensor Selection
Thin film sensors are applied directly to the surface of the component to minimize aerodynamic disturbance and mass loading. These devices rely on platinum or palladium chromium alloys that maintain a stable electrical response under severe thermal loads. The strain is transmitted from the component surface through the thin film to the data acquisition system.
Signal Degradation
Thermal drift and parasitic resistance changes represent major challenges during the sensing process. As the temperature rises, the electrical resistance of the strain gauge changes independently of the applied mechanical load. This phenomenon, known as apparent strain, must be mathematically subtracted from the raw measurement to extract the true strain signal.
Calibration Requirement
Precision calibration is required to characterize the apparent strain profile of the sensor before it is deployed on an operating component. This profile is determined by heating the sensor under zero load conditions to map the resistance change against temperature. The resulting calibration curve is used to correct the sensor output during active testing, ensuring that the final data reflects only the mechanical strain.
This compensation process is executed using digital signal processing algorithms that integrate real time temperature measurements from an adjacent thermocouple to adjust the strain readings dynamically.
