Thermal measuring and testing – Thermal testing of a nonthermal quantity – With loading of specimen
Patent
1996-11-21
1999-11-30
Hirshfeld, Andrew
Thermal measuring and testing
Thermal testing of a nonthermal quantity
With loading of specimen
374 46, 219632, 219634, 373139, G01N 318
Patent
active
059930586
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Field of the Invention
The purpose of this invention is to develop a thermomechanical characterization system for a material sample subject to dynamic heating generated by an induction heating device.
It has many applications in aeronautical and automotive fields, and in all fields using new materials.
2. Background of the Invention
In order to characterize new materials, it is usually necessary to know their thermomechanical behavior, i.e. to be familiar with the deformation values of a material simultaneously subjected to dynamic heating and to a constraining force.
There are many conventional devices used to determine the thermomechanical properties of materials. However, most of these devices allow only a relatively slow temperature rise, which is not really representative of thermal stresses in a material in its "normal" usage.
Thus, different types of heating may be considered to enable a fast temperature rise: Symposium support document entitled "Ultra High Temperature Mechanical Testing" and particularly in the chapter entitled "Measurement of High Temperature Emissivity on Opaque Materials using a Temperature controlled solar furnace". This type of heating is capable of generating a thermal flux of about 6.4 MW/cm.sup.2, which is capable of increasing the temperature of a sample to about 2800.degree. C. However, use of this type of heating has the disadvantage that an integration sphere has to be used; system can provide a maximum power of 6 kW and therefore a maximum temperature of 2000.degree. C. on the sample. This type of heating cannot increase the temperature quickly enough; furthermore, it cannot be used without an integration sphere; is capable of generating sufficient power to bring the sample temperature up to 3300.degree. C., but a large number of lamps have to be used at a very high price. Nevertheless, like the previous two types of heating by light radiation mentioned above, this type of heating is difficult to include in a thermomechanical characterization system; current in a material sample. This type of heating is difficult to combine with a means used to generate mechanical forces, due to high thermal losses of these means and radiation losses from the sample surface; Company (in U.S.A.). This system uses a graphite resistor and caulking screens made of graphite felt. This heating can bring the sample temperature up to 3000.degree. C., but the rate of increase is slow at about 1500.degree. C./h. Furthermore, this type of heating has the disadvantage that the resistor deteriorates with time by sublimation.
SUMMARY OF THE INVENTION
The purpose of this invention is to overcome the above-noted disadvantages. Consequently, it disposed a thermomechanical characterization system using an induction heating device capable of increasing the temperature of the sample up to 3300.degree. C. in not more than 20 seconds.
This type of induction heating is achieved by a susceptor placed in a variable magnetic field which induces an electromotive force. Induced currents (or eddy currents) that pass through this susceptor are then transformed into heat. Therefore the sample is heated by radiation emitted by the susceptor.
More precisely, the invention relates to a thermomechanical characterization system for a material, comprising: shaped material sample; the chamber and between which the sample is positioned, these pressure means being capable of applying a compression force to the sample;
This system is characterized in that it comprises a fast induction heating means placed in the chamber and which comprises: induced currents; induced currents into heat radiation; and means to protect said induction means from heat radiation emitted by the susceptor means.
The induction means comprises at least one induction coil with a square cross-section and one side facing the thermal protection means and separated from the thermal protection means by an air gap 26. This coil may include an internal rib placed inside said coil to give a larger heat exchange area.
According to the inventio
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Azzolini Raymond
Rochard Pierre
Commissariat a l''Energie Atomique
Hirshfeld Andrew
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