DK141355B - ROTATION SYMMETRIC HOLE FIBER ARMED COMPULSORY AND PROCEDURE FOR PREPARING IT - Google Patents

Description

(®) \ RB / di) SUBMISSION WRITTEN 1 ^ + 1355 DENMARK (ευ intci.3 b 22 d 19/02 § (21) Application No 1864/72 (22) filed on 17 * 8, 1972 (23) Running Day 17 · & 1972 1972 (44) The application submitted and the receipt issued to the public on 3 · 018 ^ · 1 9 ^

DIRECTORATE OF

PATENT AND TRADEMARKETENET (30) The work commits' from it

Apr 19 1971a 2118848, DE

(71) MASCHINENFABRIK AUGSBURG-NUERNBERG AKTIENGESELLSCHAFT, 8000 Muenchen 50, Daohauer Straese 667a DE · (72) Inventor: Hartwin Zechmeieter, Heinrich-Buz-Weg 10, 8000 Muenchen 50, BE.

(74) Plenipotentiary in the proceedings:

The engineering company Budde, Schou & Co.

(54) Rotationally symmetrical, hollow, multi-armed compound body and method of manufacture thereof.

The present invention relates to a rotationally symmetrical, hollow, fiber-reinforced compound body consisting of two equally rotationally symmetrical layers, one of which is disposed within and joints seamlessly of the other, of which the inner layer consists of metal, in particular of nickel alloys. -, titanium, cobalt or aluminum base, and the outer layer consists of a fiber material, in particular tungsten, beryllium, steel, boron, carbon or silicon carbide fibers arranged as wound endless fibers which fiber lengths or as fiber mats wherein the spaces between the fibers are molded with one of the aforementioned metals.

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It is generally known to manufacture tubes, bearings and the like of metal or plastic by centrifugal casting. It is further known in this manner to produce fiber-reinforced plastic cylinders, preferably for stationary use, e.g. as a master. For the production of boilers or rapidly rotating pipes, drums or rollers, the known centrifugal molding methods are not suitable, since the compound bodies thus produced provide insufficient coherence and allow large radial deformations. The relationship between fiber reinforcement and matrix is e.g. insufficient at large peripheral speeds of a rotary centrifuge drum, which has solution respectively. tearing or expansion of the components as a result.

From the German Engineers Association's journal (VDI-Zeitschrift) no.

112, 1970 page 1390/92, it is known to manufacture a material for very large stresses to embed fibers in moldable materials. As fiber materials thereby serve, inter alia, boron and carbon, and as casting materials i.a. titanium, aluminum, nickel or cobalt.

Such high strength material, as disclosed in Swedish Laid-Open Specification No. 311,064, can be used to make a centrifuge rotor by centrifugal casting, elongate particles being added to the molding material due to different angular velocities of the outer centrifugal mold and one disposed therein. the core after solidification is generally perpendicular to the radii of the centrifugal mold and in planes perpendicular to the axis of rotation of the mold.

When rotational bodies of the type initially specified, e.g. a centrifuge drum, brought up to a very high rpm, it responds to interference with precession and nutritional motions, which give rise to intrinsic oscillations in the rotary body, and more particularly to bending oscillations along the rotor axis, leading to alternating tensile and compressive stresses in the axial direction. Due to the large centrifugal forces, very large tensile stresses in the tangential direction occur in the rotating body, which only a fiber-reinforced material can withstand.

Since such a material can only absorb tensile stresses in the fiber direction, the fibers essentially run in the tangential direction, as stated in the Swedish publication specification.

While the embedded fiber sections of the present invention increase the resistance of the rotor to tangential forces, at the same time, the resistance of the wall material is sensitively degraded to axially directed, alternating bending loads occurring by oscillating rotors, as the fibers may form along or rotate along the fibers. destruction of the rotor.

Therefore, it has not hitherto been possible to use fiber-reinforced material in rotary bodies of this kind at very high rpm, since such material has not been able to withstand the tensile stresses acting perpendicular to the fiber direction at axially acting alternating loads.

The object of the present invention is to provide a fiber reinforced rotationally symmetrical compound body, e.g. a centrifuge rotor which, while retaining the advantages of the prior art such as increased resistance to tangential forces, is also capable of absorbing the alternating tensile and compressive stresses caused by the axial bending vibrations.

This object is solved according to the invention for a rotationally symmetrical hollow compound body of the type initially indicated by the fact that the compound body in the region where the layers are interlaced has intertwining crystal formation and that the coefficient of thermal expansion of the outer layer is less than or equal to the inner layer.

When the outer layer consists of fiber-reinforced metal having a smaller coefficient of thermal expansion than the metal in the inner layer, it is obtained that when the rotary body made by centrifugal casting is cooled, the inner layer contracts more strongly than the outer layer. Thus, an axially directed tensile bias occurs in the inner layer and a pressure bias in the outer layer.

Due to the axial pressure bias in the outer layer, the alternating axial tensile and compressive stresses are transformed into varying compressive stresses that a fiber-reinforced rotary body is able to withstand.

While the molded item cools, the centrifugal mold is kept at a high rpm. Below, the inner layer solidifies, after which it deforms plastically in the radial direction and settles so close to the fiber-reinforced layer that a tangential stress state can be established between the two layers. This ensures that the axial stress state can be maintained along the interface between the two layers, especially as the two layers further engage each other through crystal formation upon cooling.

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The aforementioned stress state is obtained according to the invention not only when the coefficient of thermal expansion of the outer layer is less than the inner layer, but also when the coefficient of thermal expansion of the two layers is equal, and more specifically because the inner layer is cooled first during rotation of the centrifugal mold and the outer layer. layers only then self-cool.

Thus, during the use of the rotary body, tensile stresses in the axial direction no longer occur in the fiber-reinforced layer, which in turn holds the inner layer together under the influence of centrifugal forces. Thus, rotary bodies according to the invention can withstand the centrifugal forces and perturbation movements that occur in unreachable rpm ranges.

According to the invention there is also provided a method for producing such a rotationally symmetrical compound body, in which the cast metal, especially nickel, titanium, cobalt and aluminum alloys, is cast by means of a rotary or fixed casting device lying in the axis of a rotating mold. on the endless fibers, fiber lengths or fiber mats lying against the inner wall of the mold, in particular of tungsten, beryllium, boron, steel, carbon or silicon carbide, and in which immediately another layer of saturated fiber reinforced with the matrix metal is cast a metal, especially one of the aforementioned; metal, which is characterized in that the outer layer is kept warm while the inner layer cools and only then cools, and that the rotation of the mold is maintained until the metal in the inner layer has reached its final strength after solidification. Thus, upon cooling of the compound body, axially directed compressive stresses occur in the outer, fiber-reinforced layers and axially directed tensile stresses in the inner metallic layers. Consists of the outer layers e.g. of a carbon fiber reinforced nickel alloy and the inner layers of an (unarmored) aluminum alloy, the coefficient of thermal expansion is less in the outer than in the inner layers. Upon cooling, the inner layer will attempt to contract in the axial direction relative to the outer layer which does not substantially contract. Thereby, an axial intrinsic stress state is built up which gives the compound body particularly favorable properties for alternating bending load, e.g. when used as a centrifuge drum or the like, with a bending of the outer layers which causes a tensile load thereof, 5

U135B

due to the pressure bias does not cause tearing of the outer layers.

The method is further characterized in that the transition between the outer and inner layers proceeds smoothly and that an anchoring of a force and shape is provided. A compound body with this intrinsic stress state exhibits slight radial deformation upon rotation or upon application of an internal pressure. The invention further provides a compound body which is suitable for use at high temperatures and at which the fibers are very firmly incorporated into matrix. Of course, this must be taken into account that the demands on the stability of the fibers when used at high temperatures limit the range of systems for those whose state diagrams do not or only to a limited extent allow the formation of compounds, diffusion reaction with matrix and internal oxidation. Taking these factors into account, e.g. The following systems for the manufacturing process of the invention: Carbon fibers or tungsten fibers in Ni superalloys or beryllium fibers in aluminum alloys. There is further the possibility of optimizing the connection between and compression of the components for various applications by appropriately adjusting the speed of the drum and molding device. A further advantage must be seen in the possibility of adding different matrix material during the casting, so that a compound body with different layers can be prepared with e.g. different sized, specific E-modules. Thus, by using compound bodies for centrifuge drums, the specific E-modulus, which is the ratio of E-module to density, will grow from the inside out. The cohesive properties of such a compound body are substantially better than that of a wound compound body. Compound bodies made in this way are suitable e.g. for centrifuge drums, for containers, for bearings and rollers or for combustion chambers or propellant nozzles in rockets. graphite.

The invention will be described in more detail below with reference to the drawing which shows an apparatus for carrying out the method according to the invention and with a compound body according to the invention.

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A casting device 3 projects in an axial direction into a vertically rotating cylindrical drum 2, which is closed with a bottom 1. The casting device 3 consists of a cylindrical container provided with diametrically opposite nozzles 4 extending longitudinally. In the top of the container is a tubular piece 5, in front of which is inserted a mixing chamber 6, to which the desired metals respectively. alloy components (arrows A, B) are set. In the middle axis of the casting device 31 is a heating means in the form of a heat hose 7. The nozzles or slots 4 are arranged radially or tangentially in the container wall. At the center 1 of the bottom 1 of the drum 2 is arranged an axially directed spindle 8, which serves to operate and store the drum 2. The bearing shown diagrammatically is indicated by 9.

Heating means 10. The drum is enclosed in a ring 11. The whole apparatus is enclosed by a casing 12 (shown punctured), so that it can be cast into vacuum or protective gas as desired.

After this description of the apparatus, the method can be explained in a simple manner. The fibers 13, e.g. beryllium fibers in the form of fiber lengths, are laid against the wall of the drum in several layers substantially in the circumferential direction. Similarly, e.g. fiber mats. The matrix material 14, e.g. an aluminum alloy, is fed in liquid form to the mixing chamber where it is homogenized and, where appropriate, mixed with a wetting agent, e.g. a fluorine-hydrocarbon such that a constant temperature alloy free of inclusions is supplied to the rotary molding apparatus. From here, the matrix material is thrown through the nozzles against the rotating inner wall of the drum, where it immediately surrounds the fibers and, due to the large centrifugal force acting below, forms a dense compound body. The heaters in the wall of the drum keep the compound body at an elevated temperature. During the centrifugal casting, after the fibers are coiled a dense layer of metal, another metal 15, e.g. with a somewhat larger specific E-module but with about the same or somewhat larger coefficient of thermal expansion, such as an aluminum titanium alloy, optionally connected to the pre-cast metal matrix. These conditions must be adapted to the desired use of the compound body.

Eg. the outer layer is made with greater density than the inner, 7 1A1355 when the body is to be used as flywheel. After finishing the casting of the metal through the nozzles, the rotation of the drum is continued until the inner layers are cooled approximately to room temperature. With the continued rotation, the inner layer solidifies. Only then, according to the invention, is the outer, substantially yet plastic layer, cooled to room temperature. As a result of the crystallization, an anchoring of the inner and outer layers is also achieved. The resulting stress conditions can easily be affected, respectively. optimized by changing the temperature of the drum wall. Melting and centrifugal casting in vacuum or protective gas provide the known advantages according to which it is possible to produce materials of the highest purity with certain chemical and physical properties, without the need to fear suction, oxidation * and the like in the compound material.

In the manufacture of larger length compound bodies, it may be advantageous to position the casting axially slidably in the drum such that during casting the casting member moves from one end of the drum to the other. By appropriately selecting the casting material and adjusting the casting tension and the speed of the drum as well as the cooling conditions, a compound doctor can be produced which has the optimum properties desired for the purpose of use. Of course, when using a longer drum to produce longer compound bodies, further storage of the drum is required.