Temperature Control of Pulse Heated Specimens in a Kolsky Bar Apparatus Using Microsecond Time-Resolved Pyrometry: Proceedings of the Fifteenth Symposium on Thermophysical Properties, Part I

Authors: Basak D.¹; Yoon H.W.²; Rhorer R.³; Burns T.J.⁴; Matsumoto T.⁵

Source: International Journal of Thermophysics, Volume 25, Number 2, March 2004 , pp. 561-574(14)

Publisher: Springer

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Abstract:

Analysis of machining processes is important in the understanding and improving of manufacturing methods. The modeling of machining processes relies on high-strain-rate, high-temperature material properties. A Split–Hopkinson (or Kolsky) bar has been developed at NIST for this purpose. By heating the material specimen rapidly with a controlled current pulse prior to the mechanical impact of the bar, structural changes in the specimen are inhibited, thus better simulating conditions during machining. A stress-strain relationship can be determined at various temperatures for a range of materials. For the elevated temperature Kolsky experiments it is essential for the specimen to be maintained at a constant and uniform temperature prior to dynamic loading. The development and implementation of a near-infrared micro-pyrometer (NIMPY) for the precision control of the Kolsky specimen temperature by using a pulse heating system preceding the mechanical impact are described. The pulse-heating system can be operated either in the transient mode, where the current to the specimen is switched off at a preset temperature or time; or in the brief steady-state mode, where the specimen is heated rapidly to achieve the preset temperature (in the range from 400 to 1300 K) in a short time (about 200 ms) and then held isothermally for a brief period (<2s). A brief description of a model of the pulse heating process is provided, and the predicted specimen temperature history is compared with measured temperature data.

Keywords: Kolsky bar apparatus; PID control; pulse heating; pyrometry; temperature control

Document Type: Research article

DOI: 10.1023/B:IJOT.0000028490.97741.4f

Affiliations: 1: Metallurgy Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, U.S.A., Email: debasis.basak@nist.gov 2: Optical Technology Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, U.S.A. 3: Manufacturing Metrology Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, U.S.A. 4: Mathematical and Computational Sciences Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, U.S.A. 5: Metrology Planning Office, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8565, Japan.

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