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Virtual experiments by pulse heating techniques: tubular tungsten specimens


G. Bussolino1 and F. Righini2

1CNR Istituto Nazionale Ottica, Pisa, Italy
2INRIM Istituto Nazionale Ricerca Metrologica,Torino, Italy

Keywords: numerical modeling, pulse heating, subsecond experiments
property: temperature
material: tungsten

A research project to evaluate virtual experiments by pulse heating techniques was recently started in collaboration between CNR-INO and INRIM. The work follows similar activities by other research groups, which have developed mathematical models for pulse heating techniques [1] or modelled specific geometries used in subsecond pulse heating experiments [2]. In our case, the experiment is simulated calculating the time dependent behaviour of the relevant quantities by means of a finite-element technique allowing the modelling of different physical processes. In the first stage of the project we have developed a bi-dimensional model for cylindrical tungsten specimens heated by current pulses of subsecond duration [3]. The results indicated that the long thin rod approximation, generally used to computed thermophysical properties from experimental results, must be used with caution in certain cases. In this second stage we present results for the simulation of subsecond experiments performed on tubular tungsten specimens. The bi-dimensional model has been improved with the inclusion of thermal expansion effects and of radiation effects of the inner part of the tube. A comparison of results of typical geometries for cylindrical and tubular tungsten specimens over the entire temperature range up to the melting points will be presented. The optimisation of the specimen requires a careful evaluation of its simulated temperature profile both in the longitudinal and in the radial directions, considering realistic values of the experimental apparatus. The final aim of the project is the establishment of a reliable predictive numerical tool for subsecond current pulse heating methods, as well as the consideration of new measurement techniques. The virtual experiment verifies the feasibility of the proposed measurement technique, in relation to the capabilities of existing instrumentation, and also the accuracy of measurement necessary to reach adequate results, without the necessity of an immediate realization of the experimental apparatus.

References
  1. J. Spisiak, F. Righini, G.C. Bussolino, Int. J. Thermophys. 22, 1241-1251 (2001)

  2. E. Kaschnitz, P. Supancic, Int. J. Thermophys. 26, 957-967 (2005)

  3. G.C. Bussolino, G. Annino, C. Ferrari, F. Righini, paper presented at TEMPMEKO-ISHM 2010, Portorose, Slovenia (June 2010)

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