Temperature Calibration Techniques for TMF Testing

One of the methods to control the rapid temperature changes during a thermomechanical fatigue (TMF) test involves the use of an infrared pyrometer for temperature measurement. The infrared pyrometer relies on the emissivity of the test coupon. One way to determine this emissivity is to use a disappearing filament pyrometer. This paper presents two emissivity calibration techniques: Strain measurement and application of non-permanent thermocouples. Both techniques were applied for TMF testing, and the advantages and disadvantages of these techniques are described. The results show that the temperature indicated by these methods can significantly differ when compared to the actual temperature of the test specimen measured by thermocouples. However, these variances can be mitigated by calibration.