CN111112528A

CN111112528A - Manufacturing method of containing type node

Info

Publication number: CN111112528A
Application number: CN201911227306.XA
Authority: CN
Inventors: 孙远韬; 陈凯歌; 张氢; 秦仙蓉; 翟金金
Original assignee: Tongji University
Current assignee: Tongji University
Priority date: 2019-12-04
Filing date: 2019-12-04
Publication date: 2020-05-08
Anticipated expiration: 2039-12-04
Also published as: CN111112528B

Abstract

A manufacturing method of a containing node comprises the following steps: (1) selecting a plate parent metal according to design requirements, and determining the basic size of the plate parent metal; (2) determining the basic size and shape of the upper die and the lower die according to the node shape; (3) forming the nodes by adopting a hot forging process; (4) cutting off the flash of the blank obtained in the step (3); (5) and (4) carrying out numerical control hole opening on the node obtained in the step (4). The invention has simple process and convenient operation, fully considers the molding defects while ensuring the external dimension of the node, adopts an optimized design method to design the die and the hot forging parameters, and ensures the molding quality and reliability; in addition, the groove is cut once when the flash is cut off, the processing efficiency is high, the cost is saved, and the method can be widely applied to the field of sheet forming.

Description

Manufacturing method of containing type node

Technical Field

The invention belongs to the field of mechanical manufacturing processes, and relates to a manufacturing method of a containing node.

Background

Compared with a box type structure, the truss structure is lighter by more than 25% -30%, and the truss structure is small in windward area, small in wind resistance, light in weight and low in cost. However, the node of the truss structure is complex in stress and serious in stress concentration, and the containing node can simplify the structure, reduce the stress concentration and improve the strength and reliability of the node.

At present, the traditional manufacturing method of the containing type node is hydraulic forming, namely, a tube blank is used as a raw material, the tube blank is subjected to plastic deformation in a given mold cavity by applying liquid pressure in the tube cavity and applying load action in the axial direction, and the tube wall is attached to the inner surface of the mold, so that the forming technology of the part with the required shape is obtained. The fillet size is small, and products difficult to form are often formed by sectional type pressurization, namely, the pipe expansion is completed by using small pressure to form a large fillet, the wall thickness is kept uniform at the moment, then the pressure is increased to force the pipe fitting to be attached to the die, the material at the fillet generates tensile deformation, the pipe wall is thinned, and the required shape is finally obtained.

The method has relatively complex molding process and complex design of the molding die. Therefore, there is a need to develop a manufacturing process of a contained node, which simplifies the forming process and ensures the forming quality and reliability while ensuring the overall dimension of the node.

Disclosure of Invention

In order to overcome the defects in the prior art, the invention provides a manufacturing method of a containing node, which has simple process flow and is easy to operate.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

a manufacturing method of a containing node comprises the following steps:

(1) selecting a plate parent metal according to design requirements, and determining the basic dimensions (length, width and thickness) of the parent metal according to the maximum longitudinal and transverse circumferences of a designed node. And reasonably selecting the base material according to the requirements of node strength and rigidity and according to the material yield limit and safety coefficient selection criteria given in mechanical design manual.

(2) The initial design of the containing type special die for the nodes is carried out according to the node appearance, the basic sizes and the shapes of the upper die and the lower die (a female die and a male die) are determined, the die is matched with the node shape, and in order to facilitate the welding of the nodes and the main chord members, the shapes of two ends of the die are matched with the shapes of the member members so as to ensure that the formed nodes can wrap the main chord members. On the basis of the basic design, in order to prevent the occurrence of fracture defects in the sheet forming process, the maximum thinning rate after the node forming is taken as an optimization target, the upper and lower bounds of the die design parameters are taken as constraint conditions, the important design parameters (die fillet and friction coefficient) of the die are optimally designed, so that the quality of the formed node is ensured to be reliable, the probability of occurrence of defects is minimum, and the final manufacturing of the die adopts a forging process.

Aiming at the optimal design of the die, relevant researches at home and abroad are sufficient at present. For problems (defects) possibly occurring in the sheet metal forming process, experts and scholars have already set up corresponding optimized mathematical models from failure mechanisms, the researches can provide sufficient reference for the current mold optimization design, and practitioners can construct models to optimize according to engineering practice. This is not described in detail.

(3) And forming the node by adopting a hot forging process. The forging temperature and the forging speed influence the forming quality of the nodes in the hot forging process, the maximum reduction rate after the nodes are formed is taken as an optimization target before the hot forging, the upper and lower limits of the hot forging temperature and the speed are taken as constraint conditions, the hot forging parameters are designed by adopting an optimization design method, and the optimal hot forging parameters are finally obtained.

And (3) mounting the special die designed in the step (2) on a proper forging machine, applying forging force according to the forming requirement, controlling the forging temperature and speed, and finally completing the forging of the node blank, wherein the forged blank adopts a reasonable heat treatment mode according to the hardness requirement, the node function and the use requirement of the material hardness and heat treatment relation comparison chart given in a mechanical design manual.

(4) And (4) cutting off the flash of the blank obtained in the step (3) according to the design drawing of the containing type node, and simultaneously cutting into a welding groove at one time according to the welding requirement, so that the subsequent welding of the node and the truss is facilitated.

(5) And (3) generally, the node shapes of the truss structures are the same, the number of web members connected with each node is determined according to the different positions of the nodes on the truss, and the nodes obtained in the step (4) are subjected to numerical control hole opening according to the determined number of web members and based on a three-dimensional model.

The manufacturing process of the containing type node provided by the invention requires that the forming base material is a plate, the pressure in the vertical direction is mainly applied as the load in the forging process, and the loading mode is simple. The node described by the invention is tile-shaped and comprises a gently-transitional edge part and a bulge-shaped raised part, the shape of the die designed by the invention is matched with the shape of the node, one-time forming can be realized, sectional type pressure forming is not needed, and the manufacturing efficiency is greatly improved. The design of the die adopts an optimized design method, parameters such as die fillets, friction coefficients and the like are optimally designed, the molding quality is ensured, the molding reliability is improved, and the molding defects are reduced. The hot forging forming process carries out optimization design on forging temperature and speed in the hot forging process, optimal hot forging parameters are optimized, and forming quality is guaranteed. The deburring process can simultaneously cut the welding groove, and the processing flow is simplified. According to the characteristics of the truss structure, the forging and pressing of the nodes can be performed in batch operation and then numerical control tapping is performed on the basis of the three-dimensional model, so that the time cost is saved. The manufacturing process adopts a reliability design and an optimization design method while ensuring the overall dimension of the node, controls the defects of cracking, wrinkling and resilience in the forming process, improves the forming quality of the node, reduces the rejection rate and saves the cost.

Drawings

Fig. 1 is a schematic combination of a three-dimensional shape and a three-dimensional plane of an inclusive node according to an embodiment of the present invention.

Fig. 2a is a schematic combination of a three-dimensional shape and a three-dimensional plane of a lower die (concave die) of the die according to the embodiment of the invention.

Fig. 2b is a schematic combination of the three-dimensional shape and three-dimensional plane of the upper die (male die) of the die according to the embodiment of the invention.

Fig. 3a is a schematic combination of a three-dimensional shape and a three-dimensional plane of an open hole of an accommodation node a according to an embodiment of the present invention.

Fig. 3B is a schematic combination of a three-dimensional shape and a three-dimensional plane of an inclusive node B aperture according to an embodiment of the invention.

Fig. 3C is a schematic combination of a three-dimensional shape and a three-dimensional plane of an open hole of an inclusive node C according to an embodiment of the present invention.

Fig. 3D is a schematic combination of a three-dimensional shape and a three-dimensional plane of an open hole of an inclusive node D according to an embodiment of the present invention.

Fig. 3E is a schematic combination of the three-dimensional shape and the three-dimensional plane of the containing node E opening according to the embodiment of the invention.

Fig. 3F is a schematic combination of a three-dimensional shape and a three-dimensional plane of an open hole of an accommodation node F according to an embodiment of the present invention.

Fig. 3G is a schematic combination of a three-dimensional shape and a three-dimensional plane of an opening of an accommodation node G according to an embodiment of the present invention.

Detailed description of the preferred embodiments

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the present invention is further described below with reference to the embodiments shown in the drawings.

The containing type node is integrally tile-shaped, two ends of the containing type node are straight semicircular pipes, the middle of the containing type node is of an arc bulge structure, and arc transition is adopted between the bulge and the semicircular pipes. The containing type node is formed by hot forging a Q355 steel plate with the thickness of 12mm, the length of 910mm and the width of 918mm on a 8000t friction press, annealing treatment is carried out after forging, rough edges and oxygen cutting are carried out on a blank formed by forging according to the designed overall dimension, and a welding groove is cut into the containing type node at one time. The die required in the forging process is a special die, the die is designed by adopting an optimal design method, important design parameters are optimized, the obtained blank has the minimum defect and the most reliable quality, and the die is a forging piece. The containing type node is used for connecting a main chord member and a web member of a truss with a pipe structure, the number of holes is determined according to the position difference of the node on the truss, three-dimensional modeling is carried out, holes penetrating through the node are opened in a numerical control mode according to the three-dimensional model, and finally the required containing type node is formed.

The overall appearance of the contained node is shown in fig. 1. FIG. 2 shows a mold layout, wherein FIG. 2a is a schematic view of the lower mold (female mold) and FIG. 2b is a schematic view of the upper mold (male mold); fig. 3a to 3g are schematic views illustrating the positions of the holes of the contained node.

The manufacturing method of the containing node comprises the following steps:

(1) a simple method for calculating the size of a base material is provided, in which the thickness of a contained node shown in FIG. 1 is 12mm and the maximum longitudinal circumference (width direction)

l_zmax＝l_zsmooth+l_zbulge＝2×(343-213)+π·201＝891.14mm

The node bulge is designed by adopting a spline curve in the transverse direction, and the maximum perimeter (length direction) of the node bulge can be counted by means of CAD (computer aided design)

l_hmax＝l_hsmooth+l_hbulge＝80+822＝902mm

In the formula I_zsmooth,l_zbulgeRespectively, longitudinal flattish and bulge circumferential lengths,/_hsmooth,l_hbulgeThe girth of the transverse gentle section and the girth of the bulge section are respectively, the elastic-plastic deformation in the sheet forming process is considered according to the design parameters, and the thickness of a base material of the sheet of the containing node is 12mm, the length is 900mm-910mm, and the width is 910mm-930 mm. And selecting a plate material as Q355 according to the static strength theory according to the bearing condition of the designed truss structure and the bearing condition of the containing type node.

For the sheet thickness, it should be equal to the thickness of the final formed part. The length and width of the plate, the invention provides a simple selection method, as step (1), the size of the parent metal is slightly larger than the calculated theoretical value. If the specific parent metal size needs to be obtained, the reverse calculation can be performed according to commercial software (Dynaform, auto), and the accurate parent metal size is finally determined.

(2) The containing node shown in fig. 1 is tile-shaped as a whole, and comprises a gently-transitional edge part and a bulge part protruding in a bulge shape, and a large arc is adopted between the bulge and the edge for transition. According to the above requirements, the containing type node mold is designed, as shown in fig. 2a and fig. 2b, the edges of the upper mold and the lower mold both adopt a gentle transition structure, and the middle part is a convex (concave) bulge structure, so that the one-step forging molding of the node is realized. In the initial stage of mold design, in order to avoid molding defects, failure mechanisms and failure criteria of fracture defects are analyzed, it is considered in the industry that when the maximum thinning rate reaches 20%, the fracture defects occur in molding, the maximum thinning rate of nodes is controlled, and the reliability of molding is ensured while the minimum maximum thinning rate is ensured by combining an optimization design method, the optimization result shows that the radius of the optimal mold fillet is 7mm-8mm, the friction coefficient of the mold is about 0.15, and accordingly, the mold is designed. The thickness of the plate is reduced in a sub-area after forging and pressing, as shown in figure 2a, the radius of a smooth transition area at the edge of the upper die is 202mm-205mm, the radius of a bulge part of the middle bulge is 212mm-215mm, and the two parts are in large arc transition with the arc radius of 220mm-222 mm; as shown in FIG. 2b, the radius of the gentle transition area of the whole dimension edge of the lower die is 218mm-221mm, the radius of the middle concave bulge part is 219mm-222mm, and the two parts are in large arc transition, wherein the radius of the arc is 210mm-213 mm. The final die size can be designed according to 80% of the predicted maximum reduction. And finally, forging the die according to the obtained design parameters.

(3) And forming the node by adopting a hot forging process. And (3) in the same step (2), considering the influence of the hot forging temperature and speed on the forming quality, and optimally designing the maximum thinning rate after forming to avoid the occurrence of fracture defects, so as to finally obtain the optimal value of the parameters. The results show that the hot forging temperature is 920-940 ℃ and the stamping speed is about 205mm/s under the condition of ensuring the maximum reduction rate to be the lowest. And (3) fixedly mounting the lower die designed in the step (2) on a forging platform, mounting the upper die on a 8000t friction press, fixedly placing the plate material in the step (1) on the lower die, applying forging pressure by a forging machine to form a node blank, and annealing the forged blank according to the hardness requirement to meet the hardness of the design requirement.

(4) And (3) cutting off the flash of the blank obtained in the step (3) according to the outline diagram shown in fig. 1, wherein the flash cutting is carried out in an oxygen cutting mode, and as shown in fig. 1, the flash is cut off and simultaneously a welding groove of 6 multiplied by 45 degrees is cut at one time, so that the containing node to be drilled is formed.

(5) As shown in fig. 3a to 3g, in the embodiment, there are 7 different opening modes for the contained node in the truss structure, and the opening is performed based on the three-dimensional model of the contained node, and a mode of numerically controlling the opening of the intersecting node hole is adopted. All the opening diameters are phi 159 according to the diameters of the web members, and all the opening directions form 30-degree included angles with the x axis of the node symmetry axis shown in the figures according to the connecting angles of the web members and the main chord members. FIG. 3a is a contained node A with 2 holes; FIG. 3b shows a contained node C with 5 holes; FIG. 3C is a view of a contained node C with 3 holes; FIG. 3D is a view of a contained node D with 2 holes; FIG. 3E is a view of a contained node E with 3 holes; FIG. 3F is a view of a contained node F with 3 holes; fig. 3G shows a contained node G with 5 holes. The number of the holes of the nodes shown in fig. 3a and fig. 3d is the same, and the two nodes are respectively used at the two ends of the truss and cannot be used alternatively; the number of the holes of the nodes shown in fig. 3c, fig. 3e and fig. 3f is the same, the nodes shown in fig. 3c are located in the middle of the truss, and the nodes shown in fig. 3e and fig. 3f are located at two ends of the truss respectively, so that the nodes cannot be used alternatively.

The optimization design result shows that under the design parameters, the forming process can control the maximum reduction rate to be smaller after forming, and meanwhile, the reliability of the forming quality of the node is ensured.

After the implementation process is completed, the following characteristics of the invention can be embodied:

the manufacturing process of the containing type node provided by the invention requires that the base material of the node is a plate, the pressure with the load in the vertical direction is mainly applied in the forging process, and the loading mode is simple. The shape of the die designed by the invention is matched with the shape of the node, one-time forming can be realized, sectional type pressure forming is not needed, and the manufacturing efficiency is greatly simplified. The mold is designed by adopting an optimized design method, so that the molding quality is ensured, the molding reliability is high, and the molding defects are reduced. The forging temperature and speed in the hot forging process are optimally designed, and the forming quality and reliability are also ensured. The deburring process can simultaneously cut the welding groove, and simplifies the processing flow. According to the characteristics of the truss structure, the forging and pressing of the nodes can be performed with batch operation and then the holes are opened, so that the time cost is greatly saved. The manufacturing process adopts an optimized design method to control the fracture defect in the forming process while ensuring the overall dimension of the node, improves the forming quality of the node, reduces the rejection rate and saves the cost.

In conclusion, the invention provides the manufacturing process of the containing type node, the process is simple, the operation is convenient, the molding defects are fully considered while the external dimension of the node is ensured, the mold and the hot forging parameters are designed by adopting an optimized design method, and the molding quality and the reliability are ensured.

The embodiments described above are intended to facilitate one of ordinary skill in the art in understanding and using the present invention. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.

Claims

1. A manufacturing method of a containing node is characterized by comprising the following steps:

(1) selecting a plate parent metal according to design requirements, and determining the basic size of the plate parent metal;

(2) determining the basic size and shape of the upper die and the lower die according to the node shape;

(3) forming the nodes by adopting a hot forging process;

(4) cutting off the flash of the blank obtained in the step (3);

(5) and (4) carrying out numerical control hole opening on the node obtained in the step (4).

2. The method of claim 1, wherein:

determining the basic size of the parent metal according to the maximum longitudinal and transverse girth of the designed node in the step (1);

wherein, the maximum circumference in the longitudinal/width direction:

l_zmax＝l_zsmooth+l_zbulge；

the node bulge is designed by adopting a spline curve in the transverse direction, and the maximum perimeter in the length direction can be counted by means of CAD:

l_hmax＝l_hsmooth+l_hbulge；

in the formula I_zsmooth,l_zbulgeRespectively, longitudinal flattish and bulge circumferential lengths,/_hsmooth,l_hbulgeRespectively the circumferences of the transverse gentle section and the bulge section.

3. The method of claim 1, wherein:

in the step (1), according to the requirements of node strength and rigidity, corresponding base material materials are adopted according to the material yield limit and safety coefficient selection criteria given by a mechanical design manual.

4. The method of claim 1, wherein:

in the step (2), the shape of the mould is matched with that of the node, and in order to facilitate the welding of the node and the main chord member, the shapes of two ends of the mould are matched with the shape of the member so as to ensure that the formed node can wrap the main chord member.

5. The method of claim 4, wherein:

in order to prevent the occurrence of fracture defects in the sheet forming process, the maximum thinning rate after the nodes are formed is taken as an optimization target, the upper and lower bounds of the design parameters of the die are taken as constraint conditions, and the important design parameters of the die are optimally designed so as to ensure the reliable quality of the formed nodes and the minimum probability of occurrence of defects.

6. The method of claim 1, wherein:

in the step (3), before hot forging, the maximum reduction rate after node forming is taken as an optimization target, the upper and lower limits of hot forging temperature and speed are taken as constraint conditions, and the hot forging parameters are designed by adopting an optimization design method, so that the optimal hot forging parameters are finally obtained.

7. The method of claim 1, wherein:

and (3) mounting the special die designed in the step (2) on a proper forging machine, applying forging force according to the forming requirement, controlling the forging temperature and speed, and finally completing the forging of the node blank.

8. The method of claim 7, wherein:

and (3) according to the hardness requirement, the function of the node and the use requirement of the forged blank, referring to a material hardness and heat treatment relation comparison chart given in a mechanical design manual, and adopting a corresponding heat treatment mode.

9. The method of claim 1, wherein:

and (4) cutting the joint into a welding groove at one time according to the welding requirement, so that the subsequent welding of the joint and the truss is facilitated.

10. The method of claim 1, wherein:

and (5) determining the number of web members connected with each node according to the difference of positions of the nodes on the truss, and performing numerical control hole opening on the nodes obtained in the step (4) based on the three-dimensional model according to the determined number of web members.