Carrier rocket box bottom and forming method thereof

Abstract

The invention provides a carrier rocket box bottom and a forming method thereof. The forming method comprises the following steps: S1, calculating box bottom stress distribution under the action of internal pressure by adopting a film stress method and a moment-free theory; s2, determining a latitudinal tension-compression stress boundary according to box bottom stress distribution under the action of internal pressure; s3, the top is subjected to forming machining, and the bottom is subjected to forming machining; and S4, the machined top and the machined bottom are subjected to tailor welding according to the latitudinal tension and compression stress boundary, and therefore the finally-formed box bottom is obtained. According to the carrier rocket box bottom forming method, the problems that under the action of internal pressure, the bottom of the box bottom is prone to wrinkling and elastic buckling, and the top of the box bottom is prone to cracking and instability are solved.

Description

Technical Field

[0001] The present invention relates to the field of aerospace technology, and in particular to a launch vehicle tank bottom and a forming method thereof. Background Art

[0002] The diameter of a launch vehicle directly determines its carrying capacity. With the development of space activities, the demand for high-reliability manufacturing of rocket body structures is becoming more and more urgent. As a key component of the rocket body structure, the design of the bottom box structure and its service reliability are of paramount importance for launch vehicles.

[0003] The forming technology and equipment manufacturing technology for rocket box bottom components have always been the focus of rocket manufacturing technology at home and abroad. Since the 1970s, foreign countries have developed the overall forming manufacturing technology and methods of the box bottom. Among them, the ultra-thick plate spinning + machining technology developed by military enterprises represented by Japan's Mitsubishi Heavy Industries, Germany's MT Aerospace Technology Company, and the United States Boeing Company represents the leading level of the last century. Typical products include Japan's H2 full bottom, with a diameter of 5.2 meters; Ariane's full bottom, with a diameter of 5.6 meters; and the bottom of the external tank of the US space shuttle, with a diameter of 5.5 meters. The materials are all 2195 aluminum-lithium alloy and 2219 aluminum alloy. The stir friction welding technology is used for the slab to be welded, and the hot spinning technology is used in the spinning process. The thickness of the slab reaches more than 70mm. The reliability of the weld seam of the welded bottom is still a difficulty that limits the flight application of the 5-meter-level full bottom. Therefore, the 5-meter-level full bottom spinning manufacturing technology has not been applied in batch models. Since the 21st century, my country has also carried out research on spinning technology. Enterprises represented by the 211 Factory, 7102 Factory, 706 Institute, and 800 Institute of the First Academy of China Aerospace Science and Technology Corporation have successively carried out research on the whole bottom forming technology and achieved breakthrough progress. The 2250 diameter box bottom of 5A06 material has passed flight verification. The 3350 aluminum-lithium alloy box bottom and the 3800 whole bottom box bottom developed by the 800 Institute have passed ground tests and are expected to complete their first flight by the end of 2024.

[0004] The above-mentioned spinning technology uses ultra-thick plate materials. The thickness of the slab of the 5-meter-level whole bottom product abroad has reached 70mm, and the material utilization rate is only 5.7%, resulting in extremely high material costs and processing costs. For this reason, China has proposed a thin plate whole bottom liquid filling deep drawing forming technology, which has achieved mass production of 3350 whole bottoms and realized the application verification of various materials. The material utilization rate has been increased to more than 30%, and the processing efficiency has also been greatly improved. However, in the context of the flightization of space activities, high-reliability manufacturing of manned spaceflight, and manned deep space exploration, the whole bottom forming technology can no longer meet the future 4-meter or even 10-meter-level whole bottom manufacturing needs.

[0005] To this end, the present invention proposes a lightweight thin-walled box bottom design and manufacturing method to solve the future large-diameter box bottom components lightweight and high-reliability manufacturing needs, and meet the low-cost, high-quality manufacturing of box bottom structures above 4 meters. Summary of the invention

[0006] In view of the defects in the prior art, an object of the present invention is to provide a launch vehicle box bottom and a forming method thereof.

[0007] A method for forming a carrier rocket bottom provided by the present invention comprises:

[0008] Step S1: using the film stress method and the moment-free theory to calculate the stress distribution of the bottom of the box under the action of internal pressure;

[0009] Step S2: determining the tensile and compressive stress boundary line in the latitudinal direction according to the stress distribution of the box bottom under the action of the internal pressure;

[0010] Step S3: performing forming processing on the top and the bottom respectively;

[0011] Step S4: according to the tensile and compressive stress dividing line in the latitudinal direction, the processed top and bottom are welded together to obtain the final formed box bottom.

[0012] Preferably, the step S1 comprises:

[0013]

[0014]

[0015]

[0016]

[0017]

[0018]

[0019] Among them, a represents the major axis of the ellipse, b represents the minor axis of the ellipse, t represents the shell thickness, and p represents the applied force.

[0020] Preferably, the step S2 comprises:

[0021]

[0022]

[0023] m=a / b

[0024] Among them, y is the direction of the minor axis of the box bottom ellipse, x is the direction of the major axis of the box bottom ellipse; a is the major semi-axis of the ellipsoid equation, and b is the minor semi-axis of the ellipsoid equation.

[0025] Preferably, step S3 comprises:

[0026] The top is an integral thin-wall shell structure, and is an integral seamless curved surface component formed by a whole plate;

[0027] The bottom is a circumferentially welded structure, which is formed by a welding manufacturing method.

[0028] Preferably, the forming process of the top includes: cutting the raw material into circular slabs, annealing or solution treating the circular slabs; processing the processed circular slabs into part blanks by the top forming method, performing artificial aging treatment on the part blanks, and finally obtaining the top by machining.

[0029] Preferably, the forming method of the top comprises: a hydraulic bulging method, a liquid filling deep drawing method, an ultra-low temperature deep drawing method, a spinning forming method or an additive forming method.

[0030] Preferably, the bottom forming process includes: using a flat billet to roll-bend in an annealed state or a solid solution state to obtain a cylindrical section or a conical cylindrical section, and then welding to form a whole ring part through a bottom welding manufacturing method; when the roll-bending forming is carried out in an annealed state, the welded whole ring part is subjected to a solid solution heat treatment; after obtaining the whole ring in the solid solution state, it is subjected to shrinking or expansion forming to obtain a rotating ring shell with a specific generatrix; then the ring shell is subjected to artificial aging treatment, and finally mechanical processing is performed.

[0031] Preferably, the welding manufacturing method of the bottom includes: welding cylinder shrinkage forming, welding cone bottom expansion forming, ring additive manufacturing or welding cylinder spinning forming.

[0032] Preferably, the welding of the processed top and bottom comprises: welding the top and bottom to form the box bottom by any one of friction stir welding, arc welding and laser welding.

[0033] A launch vehicle box bottom provided according to the present invention is prepared by using the launch vehicle box bottom forming method described above.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] 1. The present invention adopts a method of making a combined structural box bottom with a latitudinal tensile and compressive stress boundary circle. The top cover is a thin-walled integral shell and the bottom is a thick-walled annular shell, thereby improving the ability of the large-modulus box bottom to resist wrinkling and cracking defects, and providing a reliable design and manufacturing method for the design and manufacture of box bottoms of 4 meters and above;

[0036] 2. The present invention provides a method for forming the bottom of a launch vehicle box, which solves the problem of wrinkling and elastic buckling of the bottom and cracking and instability of the top of the box bottom under the action of internal pressure;

[0037] 3. The weld of the present invention is located at the internal stress tension-compression conversion point, and the weld area and the bottom adopt a thickened structure, so that the wrinkling resistance of this part under the compressive stress state is enhanced. At the same time, the influence of the weld is eliminated under the conditions of top longitudinal and latitudinal tensile stress, thereby improving the ability of the top to resist cracking and instability under internal pressure;

[0038] 4. The present invention theoretically calculates the stress distribution characteristics under the internal pressure of the tank bottom, calculates the intersection point of the latitudinal tensile and compressive stresses for the tank bottom with a modulus greater than 1, and designs the welds connecting the tank bottom based on this position; the top adopts an integral component and the bottom adopts a circumferential welding structure, thereby realizing a highly reliable manufacturing method for the tank bottom of 4 meters and above. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0040] Figure 1 This is a schematic diagram of the welded box bottom of a traditional launch vehicle.

[0041] Figure 2 It is a schematic diagram of a box bottom structure with anti-wrinkling and cracking instability capabilities provided by an embodiment of the present invention.

[0042] Figure 3 It is a schematic diagram of the force unit analysis of the bottom of the ellipsoid box.

[0043] Figure 4 It is a schematic diagram of the ellipse equation of the meridian section.

[0044] Figure 5 It is a schematic diagram of latitudinal stress distribution.

[0045] Figure 6 It is a structural diagram of the top integral part when the tank bottom diameter is 4200mm and the modulus is 1.6.

[0046] Figure 7 It is a schematic diagram of the structure of the bottom circular ring part when the tank bottom diameter is 4200mm and the modulus is 1.6.

[0047] Figure 8 It is a flow chart of forming a box bottom structure provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0048] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0049] Example 1

[0050] A method for forming a carrier rocket bottom provided by the present invention comprises:

[0051] Step S1: using the film stress method and the moment-free theory to calculate the stress distribution of the bottom of the box under the action of internal pressure;

[0052] Step S2: determining the tensile and compressive stress dividing line in the latitudinal direction according to the stress distribution of the bottom of the box under the action of the internal pressure; in this embodiment, the structure of the bottom of the box is designed based on the tensile and compressive stress dividing line in the latitudinal direction; the bottom of the box is divided into two major parts: a top seamless part and a bottom thick area;

[0053] Step S3: performing forming processing on the top and the bottom respectively;

[0054] Step S4: according to the tensile and compressive stress dividing line in the latitudinal direction, the processed top and bottom are welded together to obtain the final formed box bottom.

[0055] Specifically, the step S1 includes:

[0056]

[0057]

[0058]

[0059]

[0060]

[0061]

[0062] Among them, a represents the major axis of the ellipse, b represents the minor axis of the ellipse, t represents the shell thickness, and p represents the applied force.

[0063] Specifically, in this embodiment, step S2 includes: the tensile and compressive stress dividing line refers to the area where the latitudinal stress is zero, the latitudinal stress of the dividing line toward the opening area is compressive stress, and the latitudinal stress toward the bottom area is tensile stress. The dividing line is related to the modulus of the box bottom. Taking the ellipse equation on the normal section passing through the axis of the box bottom as an example, the position coordinates of the critical line are:

[0064]

[0065]

[0066] m=a / b

[0067] Among them, y is the coordinate of the rotation direction of the bottom of the box, that is, the direction of the minor axis of the bottom ellipse, x is the direction of the major axis of the bottom ellipse; a is the major semi-axis of the ellipsoid equation, b is the minor semi-axis of the ellipsoid equation, and m is the modulus of the ellipsoid equation;

[0068] Specifically, step S3 includes:

[0069] The top is an integral thin-wall shell structure, and is an integral seamless curved surface component formed by a whole plate; wherein, the whole plate forming means that the plate blank has no process restrictions such as welding and material addition.

[0070] The cross-sectional curve of the longitudinal section of the box bottom can be a circle, an ellipse or a cone.

[0071] The bottom is a circumferentially welded structure formed by a welding manufacturing method. The bottom ring is a thick-walled structure, and the wall thickness is larger than that of the top area. In this embodiment, the wall thickness of the bottom ring ranges from 20mm to 35mm; the wall thickness of the bottom area is 5mm to 12mm.

[0072] Specifically, the forming process of the top includes: cutting the raw material into circular slabs, annealing or solution treating the circular slabs; processing the processed circular slabs into part blanks through the top forming method, artificially aging the part blanks, and finally obtaining the top by machining.

[0073] Specifically, the forming method of the top includes: a hydraulic bulging method, a liquid filling deep drawing method, an ultra-low temperature deep drawing method, a spinning forming method or an additive forming method.

[0074] Specifically, the bottom forming process includes: using a flat billet to roll-bend in an annealed state or a solid solution state to obtain a cylindrical section or a conical cylindrical section, and then welding the whole ring part through a bottom welding manufacturing method; when the roll-bending forming is carried out in an annealed state, the welded whole ring part is subjected to solid solution heat treatment; after obtaining the whole ring in the solid solution state, it is then subjected to shrinking or expansion forming to obtain a rotating ring shell with a specific generatrix; then the ring shell is subjected to artificial aging treatment, and finally mechanical processing is performed.

[0075] Specifically, the bottom welding manufacturing method includes: (1) wall panel rolling + welding straight tube + hard mold shrinking forming; (2) wall panel rolling + welding straight tube + spinning shrinking; (3) wall panel rolling + welding cone tube + bulging; (4) stir friction welding additive forming.

[0076] Specifically, the welding of the processed top and bottom includes: welding the top and bottom to form the box bottom by any one of friction stir welding, arc welding and laser welding.

[0077] In this embodiment, for non-strengthenable aluminum alloy or stainless steel and other materials, the above parts (top and bottom components) are bent, rolled, expanded, and shrunken in the annealed state (solid solution treatment state). The forming process takes into account the regulation of uniform deformation to achieve the control of component strength, that is, the forming process needs to control the uniformity of the deformation amount of each area of ​​the part. For example, the top part can adopt the liquid filling deep drawing process method to adjust the deformation amount by regulating the reverse expansion of the slab.

[0078] A launch vehicle box bottom provided according to the present invention is prepared by using the launch vehicle box bottom forming method described above.

[0079] Example 2

[0080] Embodiment 2 is a preferred embodiment of Embodiment 1

[0081] According to the present invention, a design and manufacturing method for a space launch vehicle tank bottom structure with high reliability and service performance is provided, comprising:

[0082] Step S1: Theoretical calculation of the latitudinal stress boundary line of the bottom of the box, such as Figures 3 to 5 As shown;

[0083] The differential equation of the force element is:

[0084]

[0085] Among them, σ 1 is the longitudinal stress; σ 2 is the latitudinal stress; r 1 is the radius of the region in the longitudinal direction; r 2 is the latitudinal area radius; ds 1 is the unit radial arc length; ds 2 is the unit latitudinal arc length; dθ 1 is the radial sweep angle of the unit; dθ 2 is the unit latitudinal sweep angle; t is the shell thickness; and p is the applied force.

[0086] ds 1 =r 1 dθ 1 and ds 2 =r 2 dθ 2 Substituting sinθ=θ into formula (1), when the angle is very small, formula (1) is simplified to

[0087] σ 2 tr 1 +σ 1 tr 2 =pr 1 r 2 (2)

[0088] The formula is further transformed into

[0089]

[0090] r 1 is the radius of the region in the longitudinal direction; r 2 is the latitudinal radius of the region; r is obtained by using the elliptic equation and differential calculation 1 as follows:

[0091]

[0092]

[0093] Among them, x represents the direction of the major axis of the box bottom ellipse, and y represents the direction of the minor axis of the box bottom ellipse. is the first derivative of y with respect to x, is the second derivative of y with respect to x, and a and b are the major and minor axes of the ellipse respectively.

[0094] The equation of an ellipse can be converted to

[0095]

[0096] so

[0097]

[0098]

[0099] The expression of the meridian curvature radius obtained by introducing the above reciprocal into formula (4) is as follows:

[0100]

[0101] The normal of the surface used, define l is r 2 The vertical component of

[0102] r 2 =[l 2 +x 2 ] 1 / 2 (10)

[0103]

[0104]

[0105]

[0106]

[0107] r 1 With r 2 The ratio is

[0108]

[0109] The application equation simplifies to:

[0110] pπx 2 -σ 1 (2πx)tsinθ=0(16)

[0111] because After merging

[0112]

[0113] Substituting the above formula into formula (3), we get

[0114]

[0115] The stress calculation equation for the bottom of the ellipsoidal bottom box is as follows:

[0116]

[0117]

[0118]

[0119]

[0120]

[0121]

[0122]

[0123]

[0124] This embodiment takes the ellipsoid bottom with a tank bottom diameter of 4200mm and a modulus of 1.6 as an example, and its major semi-axis is 2100mm. Substituting into formula (19) and formula (20), the coordinates of its stress boundary circle are: x = 1908mm, y = 556mm. The tank bottom structure forming process diagram provided by the embodiment of the present invention is as follows: Figure 8 As shown in the figure, this figure is a process route for heat-treated strengthened aluminum alloy, in which the top component is formed by a liquid filling deep drawing method and the bottom part is formed by a bulging method.

[0125] S2, top overall part

[0126] Figure 6It is a schematic diagram of the top structure of this embodiment. The top is designed as an integral component, the component opening diameter is 3816mm, the height is 765mm, the wall thickness is designed according to the internal pressure, and the wall thickness is 4.0mm; the top is an ellipsoid crown, the major axis of the generatrix is ​​2100mm, and the minor axis is 1312.5mm. The generatrix of the revolving shell can also be designed as a circle, a cone or an arbitrary curve.

[0127] S3, bottom ring part

[0128] Figure 7 It is a schematic diagram of the bottom circular ring structure. The bottom circular ring is designed to be a welded structural part or an integral structural part. The large diameter of the component is 4200mm, the small diameter is 3816mm, and the height is 549mm. The wall thickness is designed according to the internal pressure. Compared with the top wall thickness, it is thicker. The wall thickness design here is designed according to the loss coefficient of welding reinforcement. It is generally designed according to the strength coefficient of 0.6, and the wall thickness is 1.7 times the thickness of the top area. According to the calculation of 4.0mm wall thickness in the top area of ​​4200mm, the wall thickness is designed to be 7mm. The circular ring part is divided into 3 equal sections in the circumferential direction, or the stirring additive method is used, and it is designed as an integral structure.

[0129] S4. Top member forming process

[0130] The forming process of the top component adopts the thin plate liquid filling deep drawing process method, which can stamp and form the top component in one piece. The diameter of the overall plate blank used is 4000-4500mm, and the plate blank is an integral rolling or integral forging plate blank.

[0131] After the top component is formed by the above process, it is thinned by mirror milling. The initial thickness of the slab is 8 mm, and the thickness of the slab after machining is 4 mm.

[0132] S5. Bottom component forming process

[0133] The forming process of the bottom member adopts a flat sector plate that is rolled and welded into a cone, and then bulged to form an ellipsoidal shell with an elliptical generatrix. The bulging forming can be divided into hydraulic bulging or steel die bulging. The ellipsoidal part formed by the above process is turned to obtain a box bottom with equal wall thickness.

[0134] S6. Welding of top and bottom rings

[0135] The top cover and the bottom ring of the box are welded together by assembling. The welding is carried out by friction stir welding. After the box bottom components are welded, stress relief heat treatment or shape correction is carried out as needed.

[0136] and Figure 1 The diagram shown is a schematic diagram of the welded box bottom of a conventional launch vehicle; Figure 2Shown is a schematic diagram of a box bottom structure with anti-wrinkling and cracking instability capabilities provided by an embodiment of the present invention.

[0137] The launch vehicle box bottom structure design and manufacturing method provided by the present invention is not only applicable to box bottom parts in the aerospace field, but also to other closed or semi-closed structural parts; it is not only applicable to parts after sheet metal forming, but also to components obtained by additive manufacturing, forging, casting, machining and other process methods.

[0138] Those skilled in the art know that, in addition to realizing the system and its various devices, modules, and units provided by the present invention in a purely computer-readable program code, it is entirely possible to realize the same functions in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers by logically programming the method steps. Therefore, the system and its various devices, modules, and units provided by the present invention can be considered as a hardware component, and the devices, modules, and units included therein for realizing various functions can also be regarded as structures within the hardware component; the devices, modules, and units for realizing various functions can also be regarded as both software modules for realizing the method and structures within the hardware component.

[0139] In the description of the present application, it should be understood that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0140] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A method for forming a launch vehicle bottom, characterized in that: include: Step S1: using the film stress method and the moment-free theory to calculate the stress distribution of the bottom of the box under the action of internal pressure; Step S2: determining the tensile and compressive stress boundary line in the latitudinal direction according to the stress distribution of the box bottom under the action of the internal pressure; Step S3: performing forming processing on the top and the bottom respectively; Step S4: according to the tensile and compressive stress dividing line in the latitudinal direction, the processed top and bottom are welded together to obtain the final formed box bottom.

2. The launch vehicle box bottom forming method according to claim 1, characterized in that: The step S1 comprises: Among them, a represents the major axis of the ellipse, b represents the minor axis of the ellipse, t represents the shell thickness, and p represents the applied force.

3. The launch vehicle box bottom forming method according to claim 1, characterized in that: The step S2 comprises: m=a / b Among them, y is the direction of the minor axis of the box bottom ellipse, x is the direction of the major axis of the box bottom ellipse; a is the major semi-axis of the ellipsoid equation, and b is the minor semi-axis of the ellipsoid equation.

4. The method for forming a launch vehicle bottom according to claim 1, characterized in that: The step S3 comprises: The top is an integral thin-wall shell structure, and is an integral seamless curved surface component formed by a whole plate; The bottom is a circumferentially welded structure, which is formed by a welding manufacturing method.

5. The launch vehicle box bottom forming method according to claim 1, characterized in that: The forming process of the top comprises: cutting the raw material into circular slabs, annealing or solution treating the circular slabs; processing the processed circular slabs into part blanks by the top forming method, performing artificial aging treatment on the part blanks, and finally obtaining the top by machining.

6. The method for forming a launch vehicle bottom according to claim 5, characterized in that: The forming method of the top includes: a hydraulic bulging method, a liquid filling deep drawing method, an ultra-low temperature deep drawing forming method, a spinning forming method or an additive forming method.

7. The method for forming a launch vehicle bottom according to claim 1, characterized in that: The bottom forming process includes: using a flat blank to roll-bend in an annealed state or a solid solution state to obtain a cylindrical section or a conical cylinder section, and then welding the whole ring part through a bottom welding manufacturing method; when the roll-bending forming is carried out in an annealed state, the welded whole ring part is subjected to a solid solution heat treatment; after obtaining the whole ring in the solid solution state, it is then subjected to shrinking or expansion forming to obtain a rotating ring shell with a specific generatrix; then the ring shell is subjected to artificial aging treatment, and finally mechanical processing is performed.

8. The method for forming a launch vehicle bottom according to claim 7, characterized in that: The welding manufacturing method of the bottom includes: welding cylinder shrinkage forming, welding cone bottom expansion forming, ring additive manufacturing or welding cylinder spinning forming.

9. The method for forming a launch vehicle bottom according to claim 1, characterized in that: The welding of the processed top and bottom comprises: welding the top and bottom into the box bottom by any one of the welding methods of friction stir welding, arc welding and laser welding.

10. A launch vehicle box bottom, characterized in that: The launch vehicle box bottom is prepared by the launch vehicle box bottom forming method described in any one of claims 1 to 9.

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