Abstract: The transducer comprises a membrane that is deformable under the effect of a magnitude to be measured, a beam joined to the membrane to detect stresses transmitted by the membrane, and strain gauges affixed to the beam to produce a signal indicative of strains suffered by the beam. According to the invention both the beam and the membrane are formed as one element, with the part forming the beam having a thickness substantially greater than the part forming the membrane. The beam portion extends between two oppositely lying peripheral zones of the membrane, and comprises grooves. The bottom portions of the grooves constitute strain concentration zones in the vicinity of which the strain gauges are affixed. Preferably, the grooves are configured in two pairs, each pair being mutually symmetrical about the center of said beam.

Abstract: The clamping tool comprises two plates (1,2) held together by sets of nuts and bolts (4,5) with a precise spacing therebetween determined by spacers (6). In order to obviate the need to machine the tool elements after each infiltration operation due to deposit of infiltrating material on the exposed surfaces, the plate is provided with channels (9) extending along a contour of the contact zones of the spacers. The width of the channels is such that irrespective of a tolerance in the positioning of said blocking elements resulting from some play in assembling the elements forming the clamping tool, the edges delimiting the contacting surfaces of the spacers are always located entirely between an inner edge and an outer edge of their corresponding channel portion.

Abstract: The system for stabilizing a support to be stabilized comprises a working rotor mounted on the support via bearings and fixed to a working member having at least one parameter associated with the rotation of the working rotor and which is variable as a function of time. A servo-controlled first electric motor is interposed between the support and the working rotor and serves to rotate the working rotor in a first direction. A reaction rotor is mounted on the support by means of bearings and independently from the working rotor, while being coaxial therewith.

Abstract: The apparatus comprises a waveguide having one end with an outside rim in the form of a test flange having a plane front surface defining a calibration plane and intended to be applied against a plane surface of a sample of material to be tested, a generator coupled to the waveguide to inject microwaves therein, and means for detecting the waves reflected by the material. At least the terminal portion of the waveguide including the test flange for application against the material to be tested at very high temperature is made of an electrically conductive refractory composite material, such as a carbon/carbon or a carbon/ceramic composite material.

Abstract: The accumulator comprises a vessel which is in communication with a hydraulic circuit and which contains a liquid occupying a portion of the space inside the vessel. The level of the liquid contained in the vessel is regulated by controlling the volume of gas overlying the liquid. The regulation apparatus essentially comprise a calibrated injector device for injecting gas under pressure into a first cavity, and a mechanically controlled gas bleeder device in a second cavity separated from the first cavity by a partition having at least one calibrated orifice situtated in a zone which is safe from being submerged in the liquid, and an opening situated in the liquid level control zone and extending on either side of the level of the interface between the liquid and the gas.

Abstract: A process relating to the manufacture of a composite component comprising a web and a reinforcement structure. The process includes providing a profiled section constituting a fibrous structure that is rigidified by impregnation with a thermoformable binder. The profiled section provided has a cross-section corresponding to the dimensions of a non-compacted blank of the component to be formed in a single unit with the web and the reinforcement structure. A blank of the component to be produced is machined from a length of the profiled section. The blank is press formed to obtain a preform having a shape and dimensions approximating those of the component to be produced and the preform is densified by chemical vapor infiltration of a material constituting a matrix within the fibrous structure, after elimination of the thermoformable binder.

Abstract: Sectors of tubes are adhesively fixed around a prefabricated propellant, the sectors being juxtaposed edge to edge to constitute a cylindrical tube, and a winding is formed around the tube at least in circumferential direction. The front and rear walls which are equipped with a seating and a tuyere, can be joined to the tubular structure formed by the tube sectors, by adhesive means on the inside of that structure, or as a variant, by means of a helical winding formed simultaneously on the wall and on the tubular structure.

Abstract: A composite structure having a fibrous reinforcing body formed from fibers of a refractory material, a ceramic matrix surrounding the fibers of the reinforcing body and an intermediate layer of a refractory material having a laminar structure disposed between the fibers of the refractory material having a laminar structure disposed between the fibers of the refractory material and the ceramic matrix and adherent to both. The intermediate layer has a thickness sufficient to reduce the susceptibility of the structure to crack propagation and to increase impact strength but not exceeding 3.0 microns. The intermediate layer is also elastically deformable in shear and has an elongation at break greater than the matrix.

Abstract: The material is formed by a fibrous reinforcement constituted by a texture of carbon or silicon carbide fibers and a matrix deposited by chemical vapor infiltration through the porosity of the fibrous fabric and containing free carbon co-deposited with the zirconia, the weight proportion of free carbon co-deposited with the zirconia in the matrix being preferably between 0.1 and 10%. In comparison with pure or partly stabilized fritted zirconias, the composite zirconia according to the invention exhibits an improved tenacity, preservation of the mechanical strength and dimensional stability under high temperatures, as well as an improved density, without the introduction of the fibrous reinforcement reducing too excessively the properties of heat insulation and resistance to oxidation.

Abstract: The mechanical stabilization system for a support comprises a working rotor mounted on the support by means of bearings and fixed to a working member having at least one parameter associated with the rotation of the working member and which is variable as a function of time. A reaction rotor is concentric with the working rotor and is mounted on the working rotor by means of bearings and is fixed to a reaction inertia member. A first servo-controlled electric motor is interposed between the working rotor and the reaction rotor and serves to drive the working rotor and the reaction rotor in opposite directions of rotation. A low power second electric motor is interposed between the working rotor and the support and is servo-controlled in such a manner as to reposition the reaction rotor and correct for drift in the correcting motion of the reaction rotor, due in particular to friction in the bearings.

Abstract: A friction system comprising at least two frictionally coupled elements produced of refractory composite materials, wherein one of the friction elements is a carbon-carbon composite material whereas the second friction element is a composite material constituted of a fibrous reinforcement in which the fibers are selected from carbon fibers and silicon carbide fibers, and of a two-phased matrix of which the principal phase is constituted by silicon carbide.

Abstract: The present invention relates to copolymers containing --Si--N-- and --Si--Si-- bonds, which are obtained by the polycondensation ofat least one silane of the formula RR.sub.1 SiCl.sub.2and at least one disilazane of the formula ##STR1## in which formulae: R.sub.2 is a halogen atom, preferably Br and Cl, andR, R.sub.1 and R.sub.3, which are identical or different, represent a hydrogen atom or an alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, aryl, alkylaryl or alkenylaryl hydrocarbon radical which may be functional,to a process for the preparation of the said copolymers,to the polycarbosilazanes obtained by thermolysis of the said copolymers and to the silicon carbonitrides obtained by heating the said polycarbosilazanes.

Abstract: A laminated tubular fibrous structure is produced using a tubular braid and folding over its wall in order to form corrugations or wrinkles superposed in axial direction. The tubular braid is brought over a mandrel of which the inner diameter corresponds to that of the structure to be produced, by causing the braid to pass around a forming head which is mounted on the mandrel and of which the outer diameter corresponds to that of the structure to be produced, and at least one yarn is wound following a helicoidal path on the braid, around the mandrel and at the front of the forming head, between said head and a counter-piece of which the faces in facing relationship have shapes corresponding to the shape of the wrinkles to be produced, the winding of the yarn being performed while the forming head is moving away from the counter-piece progressively with the formation of the wrinkles.

Abstract: The workpiece-carrier spindle assembly comprises a stator (10) mounted on a slide (202), a spindle (50) supported by active magnetic bearings and rotated by an external electric motor (2) connected to the stator via a coupling (3) which filters the mechanical disturbances due to the excentricity of the motor, and a chuck (5) fixed to the spindle (50). Additional means for detecting movements of the spindle assembly slide (202) include, in the servo-control plane of each of the radial beraings, two position detectors (216, 218: 215, 217) fixed to the stator (10) and facing two plane reference surfaces (211, 212) disposed parallel to the direction of slide displacement and delivering signals which are applied to means for selectively modifying the electric reference voltages applied to the servo-control loops of the magnetic bearings. The spindle assembly is applicable to machine tools for providing optical-quality machining.

Abstract: The present invention relates to a mechanical and insulating connection between, on the one hand, a filament-wound casing, constituting a wall for the combustion chamber of a solid propellant rocket motor, and on the other hand, a hot nozzle made from a heat-conducting refractory material wherein said connection consists of a single connecting ring fixed to the nozzle and resiliently connected to the wound casing, which ring is made from a low density insulating material, resistant to mechanical forces, as well as to mechanical shocks and thermal stresses, preferably a composite material with multidirectional reinforcements and a ceramic matrix.

Abstract: The diverging portion of discontinuous curvature is fitted with a controlled injection device for controlled injection of an additional jet of gas into the diverging portion in the same direction as the main flow of gas ejected by the nozzle, and said controlled injection device is disposed outside the diverging portion in the vicinity of the join zone between the first and second lengths in order to inject a determined flow of said additional gas into the diverging portion along a direction which is not tangential to the wall of the diverging portion.

Abstract: A tubular preform (10), fins (30), and fin supports (20) are made independently, with the fins and the fin supports being made by laying fibrous cloth impregnated with polymerizable binder to take up the appropriate shapes, and then polymerizing the binder, whereas the tubular preform is made by winding a thread impregnated with a polymerizable binder. Each fin support has a base integrated with the periphery of the tubular preform, and has fin attachment portions projecting from its base, with the bases of the fin supports and the periphery of the tubular preform being shaped in such a manner as to ensure circumferential continuity of the structure. The fin supports are integrated with the tubular preform by gluing together with at least one position of localized overwinding at the gaps in the fin supports between the fin attachment portions, thereby providing a perform which is smooth in structure both inside and outside.

Abstract: A turbopump with active magnetic suspension comprises at least two back-up bearings, each constituted by a first ring fast with a rotary shaft and a second ring fast with a casing, the rings being concentric and defining a free space whose length in the radial direction is about half the length of the means air gap of the radial magnetic bearings. The first and second rings are preferably anchored, respectively, in the rotor laminated ferromagnetic armature and in the stator laminated ferromagnetic core of a radial active magnetic bearing which may also provide hydrodynamic effects by pumping fluid into the air gap of the bearing.

Abstract: According to the method of machining on ultra-precise surface of revolution (240) on a workpiece (204) held in position by means of a workpiece-carrier spindle assembly (1) whose spindle is mounted on a spindle slide (202) by means of active magnetic bearings, the natural frequencies of the bearing servo-control are adjusted to values which are less than about 80 Hz, and the speed of spindle rotation is adjusted to a value of about 20 Hz to about 75 Hz, the radial and axial positions of the spindle are selectively modified about a nominal position by applying variable reference voltages to the circuits controlling the magnetic bearings, said voltages being varied as a function of control signals which are delivered as a function of the position of the tool (207), and displacement of the spindle slide (202) is inhibited so long as the control signals are less than predetermined values lying within the dynamic range of the magnetic bearings.

Abstract: An arrangement for mounting two bearings supporting a shaft within a housing, each bearing having an inner race secured to the shaft and an outer race, the arrangement comprising two annular membrane-shaped spacer members having a high radial stiffness and a predetermined axial flexibility, the spacer members having an outer edge and an inner edge, the inner edge of each spacer member being secured to the outer race of a respective bearing and the outer edge of each spacer member being secured within the housing, both spacer members being subjected to a predetermined amount of axial deformation with respect to their unstressed condition, whereby the spacer members exert a precisely determined axial preload onto said outer races of the bearings.