Transient temperature measurement using embedded thermocouples

• Published in: Experimental mechanics Vol. 38; no. 2; pp. 73 - 78
• Main Author: Rittel, D.
• Format: Journal Article
• Language: English
• Published: Heidelberg Springer 01.06.1998
• Subjects: Applied sciences; Exact sciences and technology; Fundamental areas of phenomenology (including applications); Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Measurement and testing methods; Measurement methods and techniques in continuum mechanics of solids; Physics; Polymer industry, paints, wood; Properties and testing; Solid mechanics; Structural and continuum mechanics; Technology of polymers; Testing and control; Thermal instruments, apparatus and techniques; Thermometry; Temperature measurement; Transient response; Testing equipment; Thermomechanical properties; Embedded transducer; Experimental study; Impact test; Dynamic load; Mechanical shock; Dynamic test; Thermocouple; Strain rate
• ISSN: 0014-4851; 1741-2765
• DOI: 10.1007/BF02321647

Transient temperature changes which develop during dynamic straining of materials, adiabatic shear band formation, dynamic fracture and related fields are often investigated using sophisticated noncontact measurement techniques such as IR detectors. In these phenomena, the time scale is of the order of the microsec. We revisit the application of thermocouples to such measurements using small embedded thermocouples (ETC). Experiments with dynamically loaded polymeric disks (characteristic strain rate of 10 exp 3/s) show that the thermocouples record transient temperatures with a short typical rise time of 10 microsecs as a result of the conversion of plastic deformation into heat. This observation is corroborated by the solution of the temperature distribution in a sphere subject to constant surface temperature which predicts the same fast reaction. Specifically, considering a sphere which is representative of the sensing bead, the average temperature rises in a few microsecs. These theoretical results can be used to deconvolve the experimental results with respect to a calculated impulse response of the sensor to recover the actual temperature variations. The results show that small thermocouples can be embedded to yield useful information about the transient temperature evolution in a solid. (Author)