FR2593096A1 - Work table for an installation for explosive treatment of materials - Google Patents

Abstract

The invention relates to techniques of explosive treatment of materials. The work table forming the subject of the invention is of the type comprising a body 1 located above a damper and is characterised in that the body 1 forms a closed chamber 2 and includes an oscillation damper 4 which is in the form of an inertial mass placed in the said closed chamber 2 with a clearance delta whose value is smaller than that of the deformation of the damper 3, and having the possibility of moving in this closed chamber 2 along the vertical axis of the table. The invention applies especially to explosive welding of materials.

Description

 The present invention relates to equipment for the impulse treatment of materials and in particular relates to a work table intended for an installation for the treatment of materials by explosion.

 In mechanical constructions, the present invention can be used in devices for welding materials by explosion, hardening of materials by shock waves, compression of powders and stamping of sheets by explosion.

 A work table of an installation for treating materials by explosion is known, produced in the form of a cylindrical envelope placed on the base of the body of a chamber in which are housed a damper and a support plate for the workpiece (see, for example, French invention patent No. 2367532, class B 21D26 / 08, published May 12, 1978).

 In this known work table, the shock absorber consists of steel or cast iron shot. Because shot is a powder material, it absorbs the energy of shock loads. However, this absorption of energy takes place over a short course of deformation of the shot, which generates significant values of the forces transmitted to the base of the body of the chamber. In the work table in question, using such a shock absorber constituted by shot, the oscillations, due to the explosion, of the table top of the work table and, consequently, those of the part which it carries, are practically zero. .

 It should also be noted that the damping properties of the shot deteriorate over time as a result of its compaction and corrosion during operation.

Another work table is also known for an installation for treating materials by explosion, comprising a body disposed above the shock absorber (see, for example, French patent No. 2367540, class
B 210 26/08, published 12 May 1978).

 The shock absorber of this table consists of a number of steel slabs separated by layers of rubber. The use of rubber as a damping medium makes it possible, as a result of the absorption of the energy of the table, to significantly reduce the loads acting on the base of the chamber.

 However, the layers of rubber in deformation after the explosion irreversibly absorb (the rubber heats up) only a small part of the energy transmitted to the table top. Most of the kinetic energy of the table top is converted into potential energy from the compressed layers of rubber.

As a result, the potential energy of the rubber turns back into kinetic energy of the table top, that is to say that the table top and the object are animated by an oscillatory movement characterized by large amplitudes, accelerations and, consequently, such important forces which act on the elements of the table, the elements for fixing the object and on the parts themselves. Due to the small amount of energy dissipated when heating the rubber, the oscillatory process lasts a long time. All this results in frequent breakdowns of the table elements, of the workpiece fixing elements and, consequently, compromises the operating reliability of the work table.

 It has therefore been proposed to create a work table for an explosion processing material installation, the construction of which would reduce the shock loads transmitted to the base of the chamber, to obtain a reduction in the amplitude and of the frequency of the oscillations and, consequently, of the accelerations and the forces acting on the elements of the table, the part and the elements for fixing the latter.

 This problem is solved by the fact that the work table of the explosion material treatment installation, comprising a body arranged above a damper, is characterized, according to the invention, in that the body forms an enclosure closed and includes an oscillation damper in the form of an inertia mass placed in said closed chamber with a clearance whose value is smaller than that of the deformation of the damper, and which can move in this closed enclosure following the vertical axis of the table.

 It is desirable that the work table includes bars connecting, by means of the shock absorber, the body of the table to the frame of the installation for treating materials by explosion.

 It is rational that the oscillation damper of the work table is made of a powdery material of the metallic shot type.

 However, the oscillation damper can consist of a metal slab.

 The described embodiment of the work table of the explosion material treatment installation ensures the reliable operation of the work table by reducing the amplitude and frequency of the oscillations and by reducing the time d damping of the oscillations of the table after the explosion, the forces transmitted from the table to the base of the explosion chamber being of low value.

The invention will be better understood and other objects, details and advantages thereof will appear better in the light of the explanatory description which will follow of different embodiments given only by way of nonlimiting examples with reference to the drawings. nonlimiting annexed in which
- Figure 1 shows, in longitudinal section, a work table of an installation for the treatment of materials by explosion, according to the invention, provided with an oscillation damper constituted by a pulverulent material, in the initial position before the explosion;
- Figure 2 shows, in longitudinal section, the work table according to the invention, with vibration damper constituted by a metal slab, in the initial position before the explosion;
- Figures 3, 4 and 5 show, in longitudinal section, the position of the body of the work table according to the invention, animated by an oscillatory movement following an explosion at the moments of impacts against the shock absorber oscillations;
- Figure 6 shows the oscillation curve of the work table in accordance with that shown in Figure 1 (on the ordinate axis is plotted the amplitude G of the oscillations of the body of the table, in cm; time t oscillations is plotted on the x-axis, in seconds).

 The work table of an installation for the treatment of materials by explosion comprises, according to the invention, a body 1 (FIG. 1) enclosing an enclosed space 2 and mounted on a damper 3.

 In the closed enclosure 2 of the body 1 there is an oscillation damper 4 constituted by a mass of inertia which occupies said enclosure 2 so as to form an interval 87 whose value is smaller than the value of the deformation of l 'damper 3, and which can move in the closed enclosure 2 along the vertical axis of the table.

 In the described embodiment of the work table according to the invention, the oscillation damper 4 consists of a powdery material or the like of the metallic shot type.

 The body 1 is connected via bars 5, 6 and the damper 3 to a support slab 7 of the body 8 of the installation for the treatment of materials by explosion, which is not shown in the drawing of the fact that it is not the subject of the invention.

 To the body 1 of the table are fixed a matrix 9, the material to be shaped 10 and a charge of explosive 11.

The orientation of the vertical movement of the body 1 is provided by guides 12 made on said body and by guides 13 made on the support slab.

 FIG. 2 shows another embodiment of the work table according to the invention.

 This work table is similar to that of FIG. 1, with the only difference that the oscillation damper 4 is constituted by a metal plate or slab.

 The operating principle of the work table of the installation for the treatment of materials by explosion, according to the invention, consists of the following.

 After placing the material to be shaped 10 (FIG. 1) in the matrix 9 located on the body 1, placing the explosive charge 11 and carrying out the operations for preparing the installation for explosion, it is detonated the load 11, that is to say that the desired technological operation is carried out, for example stamping.

During the explosion of the charge 11, half of the energy of the charge is transmitted to the work table (figure 3, arrow A), and the other half, in the form of kinetic energy of the products of explosion, spreads upward relative to the work table.

dans laquelle m1 est la masse de la charge explosive 11; QO est le pouvoir calorifique de l'unité de masse de
la charge explosive 11.Half the energy of the explosive charge 11 constitutes a pulse I defined by the expression

in which m1 is the mass of the explosive charge 11; QO is the calorific value of the unit of mass of
the explosive charge 11.

(mouvement dans le sens de la flèche B sur la figure 3). L'énergie cinétique du corps 1 de la table en déplacement se transforme en énergie potentielle de déformation (de compression) de l'amortisseur 3. Au premier moment qui suit l'explosion, le mouvement n'est imprimé qu'au corps 1 de la table et l'amortisseur d'oscillations 4 reste au repos grâce au jeu s et à son pouvoir d'inertie.Vu que la valeur du jeu & est plus faible que celle de la déformation de l'amortisseur 3 pour l'arrêt complet du corps, le corps se déplaçant à une grande vitesse rencontre, après avoir parcouru l'espace correspondant au jeu J , l'amortisseur d'oscillations 4, de masse m3, qui reste au repos, ce qui s'explique par le temps très réduit de déplacement du corps 1 avant le moment du choc.In practice, this energy is instantly transmitted to the body 1 of the work table having a mass m2 and communicates an acceleration to it at speed.

(movement in the direction of arrow B in Figure 3). The kinetic energy of the body 1 of the moving table is transformed into potential energy of deformation (compression) of the shock absorber 3. At the first moment following the explosion, the movement is only impressed on the body 1 of the table and the oscillation damper 4 remains at rest thanks to the clearance s and its power of inertia. As the value of the clearance & is lower than that of the deformation of the damper 3 for the complete stop of the body, the body moving at a high speed meets, after having traversed the space corresponding to the clearance J, the vibration damper 4, of mass m3, which remains at rest, which is explained by time very reduced movement of the body 1 before the moment of impact.

 Since the shock absorber 4 is made of a pulverulent material, an inelastic shock occurs between the body 1 and the oscillation damper 4 (FIG. 3).

The speed V2 of common displacement of the body 1 and of the damper 4 can be determined using the pulse conservation equation:
m2. V1 = (m3 + m2) V2 'hence

ce qui veut dire que l'énergie cinétique du corps 1 et de l'amortisseur 4 est égale à l'énergie initiale du corps 1 multipliée par le coefficient k du rapport entre la masse du corps 1 et celle de l'amortisseur 4:

The kinetic energy K1 of the body 1 and of the shock absorber 4 in displacement is defined by ltexpres-

which means that the kinetic energy of the body 1 and of the shock absorber 4 is equal to the initial energy of the body 1 multiplied by the coefficient k of the ratio between the mass of the body 1 and that of the shock absorber 4:

This relationship is an expression of the theorem of
Carnot stating that the kinetic energy lost during the inelastic shock is equal to the kinetic energy corresponding to the loss of speed.

The descent of the body 1 and of the shock absorber 4 continuing1 the kinetic energy of the body 1 is transformed into potential energy K2 of compression of the shock absorber 3:

 The body 1 stops and begins to rise: there is a transformation of the potential energy of the damper 3 into kinetic energy of the body 1.

The oscillation damper 4 drops from the value of the clearance r relative to the body 1 and strikes the lower surface of the body (Figure 4, arrows C and D). Again, there is an inelastic shock and therefore an energy loss of k times.

 Then the body 1 and the oscillation damper 4 perform a climb stroke, and the process begins again. The kinetic energy of the upward movement of the body 1 is transformed by the bars 5, 6 into potential energy of decompression of the shock absorber 3, the body 1 stops and begins to descend.

The oscillation damper 4 moves upwards by a value equal to the value of the clearance with respect to the body 1 and collides with the upper wall of the body 1 (FIG. 5, arrows E and F).

Again an inelastic shock occurs and therefore an energy loss of k times.

 Thus, during the first cycle of oscillations of the body 1, there occurs at the shock absorber three inelastic shocks of the body 1 and of the oscillation damper 4, and during each subsequent cycle, there occurs two shocks inelastic. With each shock, the energy decreases according to the value of the coefficient of ratio between the mass of the body 1 and that of the vibration damper 4. This ensures a reduction in the amplitude of the oscillations of the body 1, an increase in the period of the oscillations, a decrease in the accelerations and the forces generated and a very rapid damping of the oscillations of the body 1 (Figure 6, curve 14).

 It is obvious that the greater the mass of the damper 4 (FIG. 1), the more effective the damping of the oscillations.

 The operating principle of the work table shown in Figure 2 is similar to that of the work table shown in Figure 1.

 The only difference is that the energy losses (dissipation) during inelastic shocks of the body 1 and of the vibration damper 4 constituted by a metal slab, are slightly less (slightly less effective) than in the case of the shock absorber consisting of a pulverulent material.

 The work table of the explosion material treatment installation, in accordance with the invention, makes it possible to significantly increase the operating reliability of the work table thanks to an effective reduction in the amplitude and frequency of the oscillations. , the value of the accelerations and the forces acting on the elements of the table, the workpiece and the fastening elements thereof, and greatly reducing the loads transmitted from the work table to the body of said installation.

Claims (4)

 1. Work table of an installation for the treatment of materials by explosion, of the type comprising a body (1) located above a damper, characterized in that the body (1) forms a closed enclosure (2) and comprises an oscillation damper (4) in the form of a mass of inertia placed in said closed enclosure (2) with a clearance .r whose value is smaller than that of the deformation of the damper ( 3), and having the possibility of moving in this closed enclosure (2) along the vertical axis of the table.  2. Work table according to claim 1, characterized in that it comprises bars (5, 6) which connect via the damper (3) the body (1) of the table to the body (8) of the explosion materials processing facility.  3. Work table according to one of claims 1 and 2, characterized in that the oscillation damper (4) consists of a powdery material or the like of the metallic shot type.  4. Work table according to one of claims 1 and 2, characterized in that the oscillation damper (4) consists of a metal slab or plate.