Abstract
This paper describes the advantages and enhanced accuracy thermography provides to high temperature mechanical testing. This technique is not only used to monitor, but also to control test specimen temperatures where the infra-red technique enables accurate non-invasive control of rapid thermal cycling for non-metallic materials. Isothermal and dynamic waveforms are employed over a 200–800 °C temperature range to pre-oxidised and coated specimens to assess the capability of the technique. This application shows thermography to be accurate to within ±2 °C of thermocouples, a standardised measurement technique. This work demonstrates the superior visibility of test temperatures previously unobtainable by conventional thermocouples or even more modern pyrometers that thermography can deliver. As a result, the speed and accuracy of thermal profiling, thermal gradient measurements and cold/hot spot identification using the technique has increased significantly to the point where temperature can now be controlled by averaging over a specified area. The increased visibility of specimen temperatures has revealed additional unknown effects such as thermocouple shadowing, preferential crack tip heating within an induction coil, and, fundamental response time of individual measurement techniques which are investigated further.
Highlights
Uncertainty still remains with regards to how accurately temperature can be measured and controlled, especially in dynamic circumstances during mechanical testing
This paper demonstrates the inaccuracy of traditional techniques in dynamic temperature testing using thermography
Thermal radiation reflections emitted from reflective metallic surfaces can cause significant complications with temperature accuracy and as such, any reflective surface within a furnace must be covered with a high emissivity black coating
Summary
Uncertainty still remains with regards to how accurately temperature can be measured and controlled, especially in dynamic circumstances during mechanical testing. Significant momentum is building to establish a technique capable of delivering accurate control of complex high temperature waveforms, driven in some instances by the gas turbine sector. The development of new alloys and component designs to further enhance performance and efficiency of the gas turbine engine is becoming increasingly complex, expensive and time consuming. In order to try and maintain the rapid development of gas turbine performance and efficiency existing in-service materials continue to be used and subjected to more extreme thermal environments. Aggressive high temperature damage mechanisms such as thermo-mechanical fatigue (TMF), become more prevalent and require further consideration in advanced component lifing strategies [1]. Fatigue life predictions based only on isothermal testing can potentially be non-conservative
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
