CN110442982B - Unilateral rivet pulling rivet structure for composite material and design method thereof - Google Patents
Unilateral rivet pulling rivet structure for composite material and design method thereof Download PDFInfo
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Abstract
The invention relates to a structure of a single-side rivet pulling rivet special for composite material interference connection and a design method thereof. The unilateral rivet pulling structure comprises an expansion bush, a threaded core rod, a driving nut and a rivet body. The structure has the advantages that: firstly, the composite material connected piece forms interference connection, and the fatigue life of the composite material connected piece is prolonged; secondly, this structure provides certain pretightning force, has improved combined material by the joint strength of connecting piece. According to the connection principle of the structure and the requirement of composite material interference connection, a design method for each part of the unilateral rivet drawing rivet is established.
Description
Technical Field
The invention relates to the technical field of advanced manufacturing, in particular to a single-side rivet and a structural design method thereof.
Background
The composite material has the excellent characteristics of high specific strength, high specific stiffness, good designability, good fatigue fracture resistance, corrosion resistance, convenience for large-size forming and the like, and is widely applied to the fields of aviation, large ships and the like. The cementing is used extensively, but can not be used for transmitting great concentrated load, and the interlaminar intensity of material and adhesive strength difference are very big simultaneously, and the anti peel strength of glue film is very low, and bolted connection bears the weight of the attach fitting form with rivet connection as the combined material structure is big, has following problem: (1) the bolt connection can provide great pretightning force, mostly be the clearance connection, greatly reduce fatigue life, the weight of attach fitting occupies 20% -30% of structure weight simultaneously, and then cause the combined material structure reliability low, it is unobvious to subtract heavy, (2) the riveting can't obtain unanimous clamp force, and installation thickness is limited, some special occasions can't obtain the use, consequently, need urgently to transmit the connecting piece of great load, high reliability, improve combined material attach fitting's performance with this, in view of this, we propose a combined material and use unilateral nail rivet structure of taking out.
Disclosure of Invention
Based on the connection characteristics of composite materials and the defects in the technology, the single-side rivet-drawing rivet for the interference connection composite materials, which can realize large bearing and high pre-tightening load, and the design method for establishing each part of the single-side rivet-drawing rivet based on the thickness of the connected piece and the diameter of the opening is provided.
In order to meet the requirements, the technical scheme of the invention is as follows:
the utility model provides a nail rivet structure is taken out to unilateral for combined material, includes core bar 1, the tip of core bar 1 is equipped with T type head 6, the center department of core bar 1 is seted up threadedly, core bar 1 lateral wall divide into core bar polished rod section 5, core bar screw thread section 7 and centre gripping section 8, core bar 1 overcoat is equipped with the nail body 3, nail body 3 both sides are equipped with bush 2 and drive nut 4 respectively, the bush 2 is equipped with combined material sandwich panel 14 outward.
The core rod 1 is in threaded connection with the driving nut 4.
The inner diameter of the bush 2 is smaller than the outer diameter of the nail body 3.
The nail body 3 is a hollow cylindrical hole structure, nail body convex table surfaces 10 and nail body circular arcs 11 are respectively arranged at two ends of the nail body 3, and nail body chamfers 9 are arranged at positions, close to the nail body circular arcs 11, of the nail body 3.
And the two ends of the lining 2 are respectively provided with a lining convex table surface 12 and an end part conical surface 13.
The center of the composite material sandwich plate is provided with a through hole.
A structural design method of a single-side rivet pulling rivet for connecting based on composite materials comprises the following steps:
the method comprises the following steps: preliminary design of composite laminate joint:
when designing the size structure of the fastener, firstly, the size of the connecting hole diameter needed by the laminated plate is determined, and the hole diameter of the connecting laminated plate is set to be D0The acceptable failure mode for fastener joints is typically crush failure, and thus the laminate end diameter ratio e/D is required to meet the composite design manual requirements0Not less than 3, width-to-diameter ratio w/D0The design size is more than or equal to 4, and the ratio of the aperture to the thickness of the connecting plate is more than or equal to 1 (D)0/t)≤2；
Assuming that the thickness of the single board of the composite board to be connected is t/2, the total thickness of the two boards is t, and the aperture of the composite board is D0(ii) a If the size of the connecting joint is determined, the related size of the bushing can be designed; the amount of fastener connection interference is usually measured by
To define, therefore, the relative interference of the rivet hole of the single-side rivet drawing rivet
Wherein the inner diameter of the expansion bush is D, the outer diameter is D, and the outer diameter of the nail body is D2Meanwhile, the front end of the nail body plays a role of expanding the expansion sleeve, and the chamfer angle is a;
step two: the expansion bush is designed in size:
1) designing the outer diameter of the bushing:
the aperture of the composite material is D0The bushing is conveniently embedded into the hole when being installed, the outer diameter of the expansion bushing is set to be D, the bushing is initially in clearance fit with the hole, and the fit tolerance is +0.1/0 mm;
2) and (3) designing the wall thickness of the bushing:
according to the mechanical research of the interference fit connection damage of the composite material and the evaluation of structural mechanics and material mechanics, selecting a proper interference amount I and setting the wall thickness of the expansion bush as h1The inner diameter of the expansion bush is D-2h1；
3) Designing the size of the folded angle of the end part of the bushing:
the total thickness of the connected plate is t, the total length of the expansion bush is L, and the boss thickness of the left end face of the expansion bush is S and L1Equal to the length of the expansion liner mid-section; in order to form the inward-folded angle of the end part, if the length required by the extension of the connecting section of the expansion sleeve to the plate thickness is f1, f1 is M-S-t, and the length of the folded angle section is longF2, f2 is L-M, and the angle is a1；
Step three: designing the size of a nail body:
1) designing the outer diameter of the nail body;
diameter D of opening0And the inner diameter D of the expansion bush is calculated to obtain the outer diameter D of the nail body according to the selected relative interference quantity of connection as I2；
2) Designing the inner diameter of the nail body:
the wall thickness of the nail taking body is h2Inner diameter D of the nail body1＝D2-2h2(ii) a The length of the transition section part at the front end of the nail body is L2Then L is2＝L3-L4The angle is a;
step four: designing the sizes of the nut and the core rod:
1) the size design of the core rod with the thread:
the core rod is in clearance fit with the nail body, and the diameter D of the head part of the core rod is equal to D0Secondly, according to the requirement of a proper length-diameter ratio, the size of a connecting part is designed to be met, and the total length is set as C;
2) the size design of the driving nut is as follows:
selecting a driving nut matched with the thread at the tail end of the core rod according to the designed thread size of the core rod;
step five: optimizing and determining the structural size of the preliminarily designed single-side rivet
1) Establishing a three-dimensional model by using ABAQUS: solid modeling is adopted for the fiber reinforced composite material, a three-dimensional Hashin loss starting criterion is called to simulate the damage of the composite material, and solid modeling is adopted for each part of the unilateral rivet drawing rivet;
2) the boundary condition of the connecting structure is a preliminarily designed fastener, so that the interference installation completion effect and the stress bearing state of each part are mainly analyzed during simulation;
3) the grid division of the connection structure is used for carrying out grid refinement on the hole periphery area and each part and carrying out grid coarsening away from the connection area in order to reduce the influence of the grid quality on the calculation result;
4) determining optimization parameters, constraints and objective functions
The optimized parameters are the wall thickness h1 of the bushing, the folding angle length f2 and angle of the bushing, and the length and angle of the transition section of the nail body;
the constraint conditions are as follows:
(σ22/YT)2+(σ12/S12)2+(σ23/S23)2<1
(σ22/Yc)2+(σ12/S12)2+(σ23/S23)2<1
(σ11/Xc)2<1
(σ11/YT)2+(σ12/S12)2+(σ13/S13)2<1
(σ11/Yc)2+(σ12/S12)2+(σ13/S13)2<1
(σ33/Zc)2+(σ13/S13)2+(σ23/S23)2<1
the objective function is: pre-tightening force f and the stress-strain state of each part;
wherein XT、Xc、YT、Yc、Zc、S12、S13、S13Respectively representing the tensile ultimate strength of the composite material in the 1 direction, the compressive ultimate strength in the 1 direction, the tensile ultimate strength in the 2 direction, the compressive ultimate strength in the 3 direction, the shear ultimate strength in the 12 plane, the shear ultimate strength in the 13 plane and the shear ultimate strength in the 23 plane;
multiple simulations show that the yield strength sigma of the expansion bush is not exceeded under the condition of meeting the material strength of the selected partsbOn the premise of finding out the appropriate wall thickness h1 of the bushing; and the folded angle of the bush and the connecting section satisfy n1：n2And a better installation effect is obtained in the proportional relation, and a higher pretightening force effect is achieved. The invention relates to a novel single-side rivet pulling rivetStructure and design method adopt interference fit connected mode to carry out reasonable connection design, design out can provide great pretightning force simultaneously, be used for interfering the novel unilateral rivet of taking out of connection, compare in general connection, have following advantage:
firstly, the composite material connected piece forms interference connection, and the fatigue life of the composite material connected piece is prolonged;
secondly, this structure provides certain pretightning force, has improved combined material by the joint strength of connecting piece. According to the connection principle of the structure and the requirement of composite material interference connection, a design method for each part of the unilateral rivet drawing rivet is established.
Thirdly, the expansion bush mainly acts to maintain the whole connection structure to generate a uniform interference amount on the thickness of the interlayer in the whole assembly process, and the material can greatly improve the fatigue service life under the cyclic action.
Fourthly, parts are reduced, the installation is convenient, the universality is strong, and the riveting device has the characteristics of high strength, reliable riveting connection, convenient operation, high installation efficiency and the like, and meanwhile, the damage to the connecting piece and the nail body after the installation is completed is very small, and the subsequent treatment procedures are reduced.
Drawings
For a clearer explanation of the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a schematic view of a riveted installation of the present invention;
FIG. 2 is a schematic illustration of the rivet structure of the present invention;
FIG. 3 is a schematic structural view of a core rod of the present invention;
FIG. 4 is a schematic view of the structure of the nail body of the present invention;
FIG. 5 is a schematic view of the bushing configuration of the present invention;
FIG. 6 is a schematic view of the effect of the drive nut of the present invention;
FIG. 7 is a schematic diagram of the effect of the present invention before installation on a sandwich;
FIG. 8 is a schematic diagram illustrating the effect of the present invention after the clamping process is completed;
in the figure: 1. a core bar; 2. a bushing; 3. a nail body; 4. a drive nut; 5. a core bar T-shaped head; 6. breaking the core rod polished rod; 7. a core rod thread section; 8. a core bar clamping section; 9. chamfering the nail body; 10. the nail body is convex; 11. the nail body is arc-shaped; 12. a bushing boss surface; 13. an end conical surface;
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments of the present invention without any creative effort belong to the protection scope of the present invention, and the embodiments and features of the embodiments of the present invention can be combined with each other without conflict.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, but the present invention may be practiced in other ways than those specifically described and will be readily apparent to those of ordinary skill in the art without departing from the spirit of the present invention and therefore the present invention is not limited to the specific embodiments disclosed below.
Next, the present invention will be described in detail with reference to the drawings, in which the cross-sectional views showing the structure of the device are not partially enlarged in a general scale for convenience of explanation, and the drawings are only examples, and should not limit the scope of the present invention. In addition, the three-dimensional dimensions of length, width and height should be included in the actual fabrication.
In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on the orientations or positional relationships illustrated in the drawings, and are used merely for convenience in describing the present invention and for simplicity in description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed in a particular orientation, and be operated, and thus, are not to be construed as limiting the present invention. Furthermore, the terms "first", "second", etc. are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first," "second," etc. may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless otherwise specified.
In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be interpreted broadly, such as a fixed connection or a detachable connection; can be mechanically or electrically connected; can be directly connected or indirectly connected. The specific meanings of the above terms in the present invention can also be understood by those skilled in the art through specific situations.
Referring to fig. 1 to 8, a single-side rivet pulling rivet for connecting composite materials comprises an expansion bush, a threaded core rod, a driving nut and a rivet body. The core rod consists of a head part and a rod part, and one end of the rod part, which is close to the head part of the core rod, is provided with an external thread and a polished rod part; the expansion bush is of an internal hollow structure, is sleeved outside the core rod, has a large-diameter ring at one end, abuts against the T-shaped head of the core rod at the other end, forms a conical surface with a certain angle, has a slightly smaller inner diameter than the outer diameter of the nail body, and radially deforms under the action of the nail body during installation so as to achieve the purpose of interference fit of the nail hole; the nail body is of a hollow cylindrical hole structure, one end of the nail body similar to the expansion bush is a large-diameter annular end face, the nail body is in contact fit with the driving nut, and the nut is screwed until the end face of the nail body is abutted to drive the nail body to interfere with the expansion bush; the end part of the nail body is provided with a transition chamfer angle at one end matched with the bush, so that the nail body can conveniently enter the expansion bush; the rivet driving nut is in threaded connection with the core rod, and the size of the large diameter of the internal thread of the driving nut is consistent with that of the thread at the tail end of the core rod.
Taking a complete rivet as an example, before installation, the core rod is inserted into the composite material hole, the bushing and the nail body are sequentially sleeved on the rod part of the core rod, the driving nut is screwed in from the tail section of the core rod until the tail section of the core rod abuts against the end face of the nail body, the nut drives the nail body to screw in, and the bushing expands circumferentially to form interference fit, meanwhile, the core rod is pulled, the bent angle at one end of the bushing is turned inwards to form an end face with a diameter larger than the aperture, the end face is buckled on the end face of the composite material, and when a preset clamping torque is reached, the core rod is broken, and the installation is completed.
The structural design and design method of the unilateral rivet pulling rivet based on composite material connection comprises the following steps:
the method comprises the following steps: preliminary design of composite laminate joint:
when designing the size structure of the fastener, firstly, the size of the connecting hole diameter needed by the laminated plate is determined, and the hole diameter of the connecting laminated plate is set to be D0The acceptable failure mode for fastener joints is typically crush failure, and thus the laminate end diameter ratio e/D is required to meet the composite design manual requirements0Not less than 3, width-to-diameter ratio w/D0The design size is more than or equal to 4, and the ratio of the aperture to the thickness of the connecting plate is more than or equal to 1 (D)0/t)≤2。
Assuming that the thickness of the single board of the composite board to be connected is t/2, the total thickness of the two boards is t, and the aperture of the composite board is D0(ii) a The relevant dimensions of the bushing can be designed, given the dimensions of the connection joint. The amount of fastener connection interference is usually measured by
To define, therefore, the relative interference of the rivet hole of the single-side rivet drawing rivet
Wherein the inner diameter of the expansion bush is D, the outer diameter is D, and the outer diameter of the nail body is D2Meanwhile, the front end of the nail body plays a role of expanding the expansion sleeve, and the chamfer angle is a;
step two: the expansion bush is designed in size:
1) designing the outer diameter of the bushing:
the aperture of the composite material is D0And the bush is embedded in the hole when being convenient for to mount, the outer diameter of the expansion bush is D, the bush is in clearance fit with the hole initially, and the fit tolerance is +0.1/0 mm.
2) And (3) designing the wall thickness of the bushing:
according to the mechanical research of the interference fit connection damage of the composite material and the evaluation of structural mechanics and material mechanics, selecting a proper interference amount I and setting the wall thickness of the expansion bush as h1The inner diameter of the expansion bush is D-2h1。
3) Designing the size of the folded angle of the end part of the bushing:
the total thickness of the connected plate is t, the total length of the expansion bush is L, and the boss thickness of the left end face of the expansion bush is S and L1Equal to the length of the intermediate section of the expansion bushing. In order to form the inward-folded end angles, if the length required by the connecting section of the expansion sleeve to extend out of the plate thickness is f1, f1 is M-S-t, the length of the folded angle section is f2, f2 is L-M, and the angle is a1。
Step three: designing the size of a nail body:
1) designing the outer diameter of the nail body:
diameter D of opening0And the inner diameter D of the expansion bush is calculated to obtain the outer diameter D of the nail body according to the selected relative interference quantity of connection as I2；
2) Designing the inner diameter of the nail body:
the wall thickness of the nail taking body is h2Inner diameter D of the nail body1＝D2-2h2(ii) a The length of the transition section part at the front end of the nail body is L2Then L is2＝L3-L4The angle is a.
Step four: designing the sizes of the nut and the core rod:
1) the size design of the core rod with the thread:
the core rod is in clearance fit with the nail body, and the diameter D of the head part of the core rod is equal to D0And secondly, designing to meet the size of the connecting part according to the requirement of a proper length-diameter ratio, and setting the total length as C.
2) The size design of the driving nut is as follows:
and selecting a driving nut matched with the thread at the tail end of the core rod according to the designed thread size of the core rod.
Step five: optimizing and determining the structural size of the preliminarily designed single-side rivet
1) Establishing a three-dimensional model by using ABAQUS: solid modeling is adopted for the fiber reinforced composite material, a three-dimensional Hashin loss starting criterion is called to simulate the damage of the composite material, and solid modeling is adopted for each part of the unilateral rivet drawing rivet;
2) the boundary condition of the connecting structure is a preliminarily designed fastener, so that the interference installation completion effect and the stress bearing state of each part are mainly analyzed during simulation;
3) the grid division of the connection structure is used for carrying out grid refinement on the hole periphery area and each part and carrying out grid coarsening away from the connection area in order to reduce the influence of the grid quality on the calculation result;
4) determining optimization parameters, constraints and objective functions
The optimized parameters are the wall thickness h1 of the bushing, the folding angle length f2 and angle of the bushing, and the length and angle of the transition section of the nail body;
the constraint conditions are as follows:
(σ22/YT)2+(σ12/S12)2+(σ23/S23)2<1
(σ22/Yc)2+(σ12/S12)2+(σ23/S23)2<1
(σ11/Xc)2<1
(σ11/YT)2+(σ12/S12)2+(σ13/S13)2<1
(σ11/Yc)2+(σ12/S12)2+(σ13/S13)2<1
(σ33/Zc)2+(σ13/S13)2+(σ23/S23)2<1
the objective function is: pre-tightening force f and the stress-strain state of each part;
wherein XT、Xc、YT、Yc、Zc、S12、S13、S13Respectively representing the tensile ultimate strength of the composite material in the 1 direction, the compressive ultimate strength in the 1 direction, the tensile ultimate strength in the 2 direction, the compressive ultimate strength in the 3 direction, the shear ultimate strength in the 12 plane, the shear ultimate strength in the 13 plane and the shear ultimate strength in the 23 plane;
multiple simulations show that the yield strength sigma of the expansion bush is not exceeded under the condition of meeting the material strength of the selected partsbOn the premise of finding out the appropriate wall thickness h1 of the bushing; and the folded angle of the bush and the connecting section satisfy n1：n2And a better installation effect is obtained in the proportional relation, and a higher pretightening force effect is achieved.
As shown in figure 1, the invention comprises a core bar 1, and an expansion bush 2, a nail body 3 and a driving nut 4 which are sleeved on the core bar 1 in sequence;
as shown in fig. 2, the core rod 1 is composed of a T-shaped head and a screw, the tail section of the rod is provided with a clamping section 8, the middle section of the rod is divided into a smooth section 5 and a middle section of threads 7, and the external threads of the middle section 7 of the core rod are in threaded fit with the driving nut;
as shown in fig. 3, the nail body 3 is a hollow conical cylinder with an end surface, the right end of the nail body is provided with a chamfer transition section 9, the left end of the nail body is provided with a large-diameter end surface 10, a nut can conveniently abut against a screwing bush, and the nail body is sleeved on a core rod before being installed;
as shown in fig. 4, the bushing 2 is a hollow cylinder, the left end of the bushing is provided with a large-diameter end face 12, the right end of the bushing is a conical surface with a certain angle, the bushing is propped against the inner fold and is expanded into a gasket shape when the core rod generates relative displacement, and meanwhile, the inner diameter of the bushing is smaller than that of the nail body, so that interference connection is formed;
as shown in fig. 5, the internal thread of the driving nut 4 with the hexagonal internal thread structure is matched with the external threads of the middle section and the first section of the core rod 1;
the working principle is as follows: the driving nut is connected with the threaded core rod through the thread pair, the core rod is clamped, the driving nut is rotated, relative motion enables the driving nut to push the nail body to move towards the expansion bush along the threaded core rod, the expansion bush cannot move under the restraint action of the end part of the threaded core rod, and therefore axial motion of the nail body causes radial deformation of the expansion bush, and composite material interference connection is achieved. Meanwhile, one end of the expansion bush close to the head of the core rod is subjected to large radial deformation to clamp the connected piece.
When the rivet is installed and used, the installation process is completed in three stages, firstly, the assembled structure is inserted into a riveting hole of a sandwich plate (to be riveted) which is prepared in advance, the driving nut is screwed to abut against the raised table top 9 of the rivet body, the tail section of the core rod is clamped by an installation tool, the driving nut is rotated, and the nut drives the rivet body to be screwed into the expansion bush, which is a screw body screwing-in stage. Then under the action of a thread pair, the nail body is screwed into an inner hole of the bush, meanwhile, the core rod 1 can generate axial displacement relative to the driving nut 4 and is pulled out, and meanwhile, the bush sleeved on the core rod 1 can synchronously have axial displacement along with the whole core rod and is pulled out; when the nail body 3 starts to be embedded into the bush, one end of the nail body is provided with an end chamfer transition section, so that the nail body is convenient to enter in an interference manner, and damage to the laminated plate and the expansion bush in the initial installation is prevented; the right end of the bushing 2 is a conical surface, the core rod is pulled out to a certain degree and props against one end of the conical surface of the bushing, and the end surface is inverted and deformed, which is a large footing forming stage; finally, due to the simultaneous extrusion effect of the two ends, after the bush forms the flaring, the axial displacement is continued until the T-shaped head abutting against the core rod is finished, after the end face is formed, the core rod continues to be withdrawn, but the end face of the butt foot formed by inwards turning the bush abuts against the riveting component until a gasket is formed, the end face of the sandwich plate is buckled to form a certain pre-tightening, and due to the retraction in place, the core rod 1 reaches a preset twist-off moment, the core rod is broken, so that the riveting is achieved, and the breaking stage is completed for the installation.
The embodiments of the present invention have been described in detail, but the description is only for the preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. But all equivalent changes and modifications made according to the scope of the present invention are within the scope of the present invention.
Claims (1)
1. A structural design method of a single-side rivet pulling rivet for connecting based on composite materials comprises the following steps:
the method comprises the following steps: preliminary design of composite laminate joint:
when designing the size structure of the fastener, firstly, the size of the connecting hole diameter needed by the laminated plate is determined, and the hole diameter of the needed composite material plate is set as D0The acceptable failure mode of fastener connection is extrusion failure, so that the end diameter ratio e/D of the laminated plate is required to be met according to the requirements of a composite material design manual0Not less than 3, width-to-diameter ratio w/D0The design size is more than or equal to 4, and the ratio of the aperture to the thickness of the connecting plate is more than or equal to 1 (D)0/t)≤2；
Assuming that the thickness of the single board of the composite board to be connected is t/2, the total thickness of the two boards is t, and the aperture of the composite board is D0(ii) a If the size of the connecting joint is determined, the related size of the bushing can be designed; fastener attachment interference amount to
To define, therefore, the relative interference of the rivet hole of the single-side rivet drawing rivet
Wherein the inner diameter of the expansion bush is D, the outer diameter is D, and the outer diameter of the nail body is D2Meanwhile, the front end of the nail body plays a role of expanding the expansion sleeve, and the chamfer angle is a;
step two: the expansion bush is designed in size:
1) bushing outer diameter dimension design
The aperture of the composite material plate is D0The bush is conveniently embedded into the hole when being installed, the outer diameter of the expansion bush is set to be d1, the bush is initially in clearance fit with the hole, and the fit tolerance is +0.1/0 mm;
2) and (3) designing the wall thickness of the bushing:
according to the mechanical research of the interference fit connection damage of the composite material and the structural forceThe method comprises the following steps of studying and material mechanics evaluation, selecting a proper interference amount I, and setting the wall thickness of the expansion lining to be h1The inner diameter of the expansion bush is D-2h1；
3) Designing the size of the folded angle of the end part of the bushing:
the total thickness of the connected plate is t, the total length of the expansion bush is L, and the boss thickness of the left end face of the expansion bush is S and L1Equal to the length of the expansion liner mid-section; m is the length from the left end face to the end of the middle section of the expansion bush, i.e. M is S + L1(ii) a In order to form the inward-folded end angles, if the length required by the connecting section of the expansion sleeve to extend out of the plate thickness is f1, f1 is M-S-t, the length of the folded angle section is f2, f2 is L-M, and the angle is a1(ii) a Step three: designing the size of a nail body:
1) designing the outer diameter of the nail body:
the aperture of the composite material plate is D0And the inner diameter D of the expansion bush is calculated to obtain the outer diameter D of the nail body according to the selected relative interference quantity of connection as I2；
2) Designing the inner diameter of the nail body:
the wall thickness of the nail taking body is h2Inner diameter D of the nail body1＝D2-2h2(ii) a The length of the transition section part at the front end of the nail body is L2,L3The total length of the nail body is L4The length from the left end face of the nail body to the tail end of the middle section is L2＝L3-L4The angle is a; step four: designing the sizes of the nut and the core rod:
1) the size design of the core rod with the thread:
the core rod is in clearance fit with the nail body, and the diameter D of the head part of the core rod is equal to D0Secondly, according to the length-diameter ratio requirement, the size of the connecting part is designed to be met, and the total length is set as C;
2) the size design of the driving nut is as follows:
selecting a driving nut matched with the thread at the tail end of the core rod according to the designed thread size of the core rod;
step five: optimizing and determining the structural size of the initially designed unilateral rivet pulling rivet:
1) establishing a three-dimensional model by using ABAQUS: solid modeling is adopted for the fiber reinforced composite material, a three-dimensional Hashin loss starting criterion is called to simulate the damage of the composite material, and solid modeling is adopted for each part of the unilateral rivet drawing rivet;
2) the boundary condition of the connecting structure is a preliminarily designed fastener, so that the interference installation completion effect and the stress bearing state of each part are mainly analyzed during simulation;
3) the grid division of the connection structure is used for carrying out grid refinement on the hole periphery area and each part and carrying out grid coarsening away from the connection area in order to reduce the influence of the grid quality on the calculation result;
4) determining optimization parameters, constraint conditions and an objective function:
the optimized parameters are the wall thickness h1 of the bushing, the folding angle length f2 and angle of the bushing, and the length and angle of the transition section of the nail body;
the constraint conditions are as follows:
(σ22/YT)2+(σ12/S12)2+(σ23/S23)2<1
(σ22/Yc)2+(σ12/S12)2+(σ23/S23)2<1
(σ11/Xc)2<1
(σ11/XT)2+(σ12/S12)2+(σ13/S13)2<1
(σ11/Xc)2+(σ12/S12)2+(σ13/S13)2<1
(σ33/Zc)2+(σ13/S13)2+(σ23/S23)2<1，
the objective function is: pre-tightening force f and the stress-strain state of each part;
wherein σ11、σ12、σ13、σ22、σ23、σ33Respectively 1 direction stress, 12 plane shear stress and 13 plane shear stress of the composite materialForce, 2-direction stress, 23-plane shear stress, 3-direction stress; xT、XC、YT、YC、ZC、S12、S13、S23Respectively representing the tensile ultimate strength of the composite material in the 1 direction, the compressive ultimate strength in the 1 direction, the tensile ultimate strength in the 2 direction, the compressive ultimate strength in the 3 direction, the shear ultimate strength in the 12 plane, the shear ultimate strength in the 13 plane and the shear ultimate strength in the 23 plane;
multiple times of simulation result shows that the yield strength sigma of the expansion bush is not exceeded under the condition of meeting the strength of the selected part materialbOn the premise of finding out the wall thickness h1 of the bushing; and the folded angle of the bush and the connecting section satisfy n1：n2A proportional relationship;
the composite material single-side rivet pulling structure comprises a core rod (1), a T-shaped head (6) is arranged at the end of the core rod (1), threads are formed in the center of the core rod (1), the side wall of the core rod (1) is divided into a core rod polished rod section (5), a core rod threaded section (7) and a clamping section (8), a nail body (3) is sleeved outside the core rod (1), a bushing (2) and a driving nut (4) are respectively arranged on two sides of the nail body (3), and a composite material sandwich plate (14) is arranged outside the bushing (2); the inner diameter of the bushing (2) is smaller than the outer diameter of the nail body (3), and the size difference of the bushing and the nail body satisfies a design interference amount I; the nail body (3) is of a hollow cylindrical hole structure and is in clearance fit with the core rod (1), a nail body convex table surface (10) and a nail body arc (11) are respectively arranged at two ends of the nail body (3), and a nail body chamfer (9) is arranged at the position, close to the nail body arc (11), of the nail body (3); and the two ends of the lining (2) are respectively provided with a lining convex table surface (12) and an end part conical surface (13).
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| CN112693622B (en) * | 2020-12-29 | 2023-09-05 | 中国航空工业集团公司西安飞机设计研究所 | Method for repairing aircraft wing surface screw-pulling loosening |
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