FR2688300A1 - Thermal treatment device making it possible to subject a charge to thermal (heat) shocks - Google Patents

Abstract

The invention relates to a thermal treatment device comprising an insulation element in which a heating element is arranged placed facing the charge to be tested. According to the invention, the device comprises a movable thermal insulation member (106), arranged between the heating element (105) and the charge (E), said member being displaceable so as to be capable of passing from an interposition position, in which it constitutes a thermal well, into a moved-away position, in which the charge (E) suddenly receives the totality of the thermal flow emitted by the heating element (105). Very great thermal shocks can thus be simulated.

Description

 The invention relates to the field of high temperature thermal tests, and more particularly a device for subjecting a load to thermal shock.

 Devices are known comprising a thermal insulation element in which is disposed a heating element placed facing the load to be tested.

 The thermal insulation means is generally placed in a confinement enclosure, which makes it possible to control the atmosphere to which the load is subjected.

The internal equipment of this containment is generally made up of two complementary parts, one of which is then mounted on the door of the enclosure, so that when it opens, the volume of the the enclosure is fully accessible for easy installation of test loads. The heating element is generally an electrical resistance (often called a "resistor" by specialists in this technical field), in graphite or in refractory metal, in the form of adjacent plates or a flat or round element with a crenellated outline. The electrical resistance can be replaced by a conductive part which is heated by induction (this is called a "susceptor"). In the following text, the general term "heating element" will be used, it being understood that it may in particular be a resistor or a susceptor.

 Such devices are perfectly satisfactory for subjecting loads to tests in a high temperature environment, that is to say reaching 1 0000C at 3 2000 C in steady state.

 However, these devices do not make it possible to carry out treatments comprising thermal shocks, that is to say by which the load to be tested is subjected for a very short time, for example a few seconds at most, to a very high thermal flux. . Indeed, the rise curve of the heating element de facto limits the possible thermal variations.

 Such tests are however very interesting, because they make it possible to simulate thermal shocks that one could encounter for nozzles or attack faces of aircraft control surfaces (during the re-entry into the atmosphere of spacecraft), or even in blast situations.

 We could certainly use direct induction heating techniques, but these techniques generate constraints of thermal origin due to the fact that the dissipation in the thickness of the load is poorly controlled. In addition, such techniques remain limited to certain materials, and they involve installation that is both bulky and expensive.

 The object of the invention is precisely to solve this problem, by designing a device capable of simulating very intense thermal shocks, with in particular temperatures between 1 0000C and 3 0000C.

The object of the invention is therefore to provide a thermal treatment device which is capable of very quickly subjecting a load to a very high thermal flux, in accordance with a situation of athermal shock;
I1 more particularly of a heat treatment device making it possible to subject a load to thermal shocks, comprising a thermal insulation element which surrounds a heating element placed opposite the load to be tested, characterized in that it comprises in addition a movable thermal insulation member, arranged between the heating element and the load to be tested, said thermal insulation member being movable so as to be able to pass from an interposition position in which it constitutes a thermal sink, to an erasing position in which the load suddenly receives all of the heat flux emitted by the heating element.

 In the particular case where the heating element is organized essentially cylindrical, it is advantageous for the movable thermal insulation member to be movable in a direction parallel to the axis of said heating element.

 Preferably, when the axis of the heating element is vertical, it is advantageous for the movable thermal insulation member to be displaceable by an actuating means associated between a high position of interposition and a low position of erasure. . In particular, the actuating means can be a movable retaining member between a locking position in which it maintains the movable thermal insulation member in its high position of interposition, and a release position in which this movable member falls by gravity to its low erasure position.

 As a variant, the movable thermal insulation member is displaceable by an actuating means associated between a low position of interposition and a high position of erasure.

 Also preferably, the device comprises a guide means associated with the movable thermal insulation member. In particular, the guide means essentially consists of parallel rods on which the movable thermal insulation member slides freely.

 Advantageously again, one movable thermal insulation member is constituted by an inner cylindrical screen serving as a heat sink, and an outer cylindrical screen, between which is placed a thermally insulating or reflective filling material.

 Preferably then, the interior screen is a metal wall cooled by any known means, for example by circulation of fluids, or by vaporization of a material, or also by Peltier effect, and the exterior screen is made of rigid graphite. According to an advantageous example, the interior screen is a wall made of steel or copper, which is cooled by circulation of water.

 The filling material may be a thermally insulating material made of graphite or alumina fibers, or else a reflective material, for example made in the form of polished metal screens.

Other characteristics and advantages of the invention will appear more clearly in the light of the description which follows and of the appended drawing, relating to a particular embodiment, with reference to the figures or
- Figure 1 illustrates in section a heat treatment device according to the invention, the movable thermal insulation member is in the position of interposition constituting a heat sink;
- Figure 2 illustrates the same device with the movable thermal insulation member which has passed into the erasing position, in which the load to be tested is suddenly subjected to the thermal flux emitted by the heating element.

 Figures 1 and 2 make it possible to distinguish a heat treatment device 100 according to the invention, a device which is capable of subjecting a load E to very intense thermal shocks, with in particular temperatures between 1 0000C and 3 0000C.

 In this case, the load E is a cylindrical bar, of which a predetermined portion, which may be of smaller cross section, constitutes the useful area for the test concerned. It could be mechanical tests in compression and / or in tension and / or in torsion, using a test bench not shown here. The treatment device also makes it possible to subject a load to mechanical bending tests, the load then being placed inside the enclosure of the device on an associated support. It will thus be understood that the embodiment represented here, with a load in the form of a bar passing through the insulating element of the treatment device should in no way be considered as a limitation within the scope of the invention. It also goes without saying that the treatment device makes it possible to carry out non-mechanical tests (resistance to corrosion, etc.) in a high temperature environment, with exposure of the load to thermal shocks.

 The device 100 includes a thermal insulation element or "insulation" 101, which here has passages 102 and 103 associated with the load E, said passages being here arranged along an axis X. The material constituting this insulation element may be of the traditional type, with a double-walled structure whose internal space is occupied by a thermally insulating material which may be graphite or alumina fiber. Inside this insulation 101 is housed a heating element 105 which is held by associated supports 104.

 The heating element 105 is here cylindrically organized around the aforementioned axis X, opposite the load to be tested E. When using, as is illustrated here, a through bar, this bar is preferably arranged in such a way that its axis merges with the X axis, but if these are bending tests or other types of tests in which the load rests on a support inside the insulation, the load is then centered on the 'aforementioned X axis.

 The heating element 105 can be made of graphite or of refractory metal, being organized cylindrically around the aforementioned axis X (in the form for example of adjacent plates, or of a flat or round element with crenellated outline). As a variant, it is naturally possible to use an element made of stranded wires, tantalum, molybdenum, or even tungsten, or else a susceptor heated by induction.

 In practice, the thermal insulation element will be placed in a containment enclosure 140 (shown in dashed lines in the figures), comprising bushings 141 for the passage of the load E, the insulation element 101 and l heating element 105 then preferably being produced in two complementary parts, one of which is fixed to the bottom of the confinement enclosure, and the other of which is mounted on the door of this enclosure, so that at the opening of it, the volume of the enclosure is fully accessible for easy installation of the loads to be tested.

 Such a heating element can be a "resistor", and specialists already use such heating elements to produce heating by radiation. The heat flux emitted by the heating element 105 is here symbolized by arrows directed towards the axis X around which said heating element is arranged.

 According to an essential aspect of the invention, the device further comprises a movable thermal insulation member 106, here of generally cylindrical shape, which is disposed between the heating element 105 and the load E by surrounding said load: the mobile thermal insulation member is movable so as to be able to pass from an interposition position (illustrated in FIG. 1) in which it constitutes a thermal sink for the axial zone in which the load to be tested is placed, to a position erasure (Figure 2) in which the load E suddenly receives all of the heat flux emitted by the heating element 105 (and of course also by the inner screen of the insulating element 101 which is fixed).

 The mobile thermal insulation member 106 thus constitutes a real mobile thermal well, arranged in the central space 130 of the heating element 105, being here displaceable in a direction essentially parallel to the axis X.

 The erasure of this movable thermal insulation member 106 can be organized in many ways. It suffices for this to provide a suitable actuation means which is both capable of very quickly moving the movable member of thermal insulation 106, while being able to withstand the very high temperatures prevailing in the direct vicinity of the element. heated 105.

 In practice, the X axis of the heating element 105 will be vertical, and we can then take advantage of the possibility of erasing the movable thermal insulation member 106 by a simple fall by gravity.

In this case, the movable thermal insulation member 106 is displaceable by an associated actuation means 107 between a high position of interposition (FIG. 1) and a low position of erasure (FIG. 2), this means d actuation being here carried out in the form of a retaining member 109 which slides in a small suitable housing 108 fixed on the insulating element 101, this retaining member having the shape of a rod whose end is arranged to penetrate into a bore 111 of the movable thermal insulation member 106, possibly supported by an associated stop 109.1, said member being for example subjected to the action of a spring 110 tending to maintain the locking as is illustrated in FIG. 1. Unlocking can be carried out by an electromagnet or by any equivalent system. The retaining member 109 is thus movable between a locking position in which it maintains the movable member of thermal insulation 106 d in its high position of interposition, and a release position in which said movable member 106 falls by gravity to its low position of erasure, as shown by the arrow 200 in FIG. 2.

 It will naturally be possible, as a variant, to provide for a retraction of the movable thermal insulation member 106 upward, while then releasing the upper part of the insulation element 101, and by providing an adequate actuation means, by example an articulated system or a control jack, for very quickly moving the movable member 106 between a low position of interposition and a high position of erasure.

 It is naturally appropriate to ensure that, when it falls, the movable member 106 does not touch the heating element 105, which would have the effect of short-circuiting the two current leads of said heating element. I1 is then advantageous to provide for this purpose a guide means associated with the movable thermal insulation member 106. In this case, the treatment device 100 includes a guide means 112 which is essentially constituted by parallel rods 113 on which the movable member 106 freely slides. These rods are naturally parallel to the axis X of the heating element, and are for example fixed on a base 114. It may prove advantageous to provide small springs 115 in part bottom of the guide rods 113, in order to avoid too sudden a fall of the movable member 106 when the latter suddenly passes to its erasing position.

 I1 may possibly be provided to move the movable member 106 in a predetermined sequence, said member alternately passing from its position of interposition to its erasing position.

 The movable thermal insulation member 106 is preferably constituted by an inner cylindrical screen 118 serving as a heat sink, and an outer screen 119, between which is placed a thermally insulating or reflective filling material 120. These two screens 118 and 119 are preferably held by bottoms 126 and 127, which have holes 116 and 117 for the passage of the guide rods 113.

 The internal screen 118 serving as a heat sink is advantageously, as illustrated here, a metal wall cooled by any known means, for example by circulation of fluids (or by vaporization of a material, or also by Peltier effect). There is thus a double wall 121, 122 between which are defined passages 123 which can borrow a cooling fluid arriving by a supply pipe 124, and leaving by an associated pipe 125. Preferably, this double wall will be made of steel or copper, and will be cooled by circulating water. Naturally, nitrogen gas or a chlorine and fluorine-based refrigerant can be used for cooling this double wall, but the technology is then more difficult to control. The outer screen 119 will preferably be made of rigid graphite, or refractory metal suitable for high temperatures. The filling material 120 occupying the intermediate space between the two screens 118 and 119 may be a thermally insulating material, for example graphite or alumina fiber, or else a reflective material, for example produced in the form of a set of polished metal screens.

 We have thus succeeded in designing a treatment device capable of simulating very intense thermal shocks, with in particular temperatures between 1,000 ° C. and 3,000 ° C. This device is in fact capable of very quickly subjecting a load to be tested to a very high thermal flux, in accordance with a thermal shock situation.

 The device of the invention is also compact, and the manufacturing cost remains very reasonable. In addition, it is quite certain to avoid local overheating, since one cannot exceed the temperature of the heating element, which is not the case with induction heating techniques due to the skin effect.

 The invention is not limited to the embodiment which has just been described, but on the contrary encompasses any variant incorporating, with equivalent means, the essential characteristics set out above.

Claims (12)

 1. A heat treatment device making it possible to subject a load to thermal shocks, comprising a thermal insulation element which surrounds a heating element arranged facing the load to be tested, characterized in that it also comprises a movable member of thermal insulation (106) disposed between the heating element (105) and the load (E) to be tested, said thermal insulation member being movable so as to be able to pass from a position of interposition in which it constitutes a heat sink, in an erasing position in which the load (E) suddenly receives all of the heat flux emitted by the heating element (105).  2. Device according to claim 1, wherein the heating element (105) is organized essentially cylindrical, characterized in that the movable member of thermal insulation (106) is movable in a direction parallel to the axis (X ) of said heating element.  3. Device according to claim 2, wherein the axis (X) of the heating element (105) is vertical, characterized in that the movable member of thermal insulation (106) is displaceable by means of associated actuation (107) between a high position of interposition and a low position of erasure.  4. Device according to claim 3, characterized in that the actuating means is a retaining member (109) movable between a locking position in which it maintains the movable member of thermal insulation (106) in its position high interposition, and a release position in which this movable member (106) falls by gravity to its low position of erasure.  5. Device according to claim 2, wherein the axis (X) of the heating element (105) is vertical, characterized in that the movable member of thermal insulation (106) is displaceable by means of actuation associated between a low position of interposition and a high position of erasure.  6. Device according to one of claims 1 to 5, characterized in that it comprises a guide means (112) associated with the movable member of thermal insulation (106).  7. Device according to claim 6, characterized in that the guide means (112) consists essentially of parallel rods (113) on which the movable member of thermal insulation (106) slides freely.  8. Device according to one of claims 1 to 7, characterized in that the movable thermal insulation member (106) is constituted by an internal cylindrical screen (118), serving as a heat sink, and an external cylindrical screen (119), between which is placed a thermally insulating or reflective filling material (120).  9. Device according to claim 8, characterized in that the interior screen (118) is a metal wall cooled by any known means, for example by circulation of fluids, by vaporization of a material, or by Peltier effect, and that the outer screen (119) is made of rigid graphite or of refractory metal suitable for high temperatures.  10. Device according to claim 9, characterized in that the interior screen (118) is a wall made of steel or copper, and is cooled by circulation of water.  11. Device according to claim 8, characterized in that the filling material (120) is a thermally insulating material made of graphite or alumina fibers.  12. Device according to claim 8, characterized in that the filling material (120) is a set of polished metal screens.