CN112541226B - Machining method of double-curved-surface forming equipment - Google Patents
Machining method of double-curved-surface forming equipment Download PDFInfo
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- CN112541226B CN112541226B CN202011406689.XA CN202011406689A CN112541226B CN 112541226 B CN112541226 B CN 112541226B CN 202011406689 A CN202011406689 A CN 202011406689A CN 112541226 B CN112541226 B CN 112541226B
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F30/00—Computer-aided design [CAD]
- G06F30/10—Geometric CAD
- G06F30/15—Vehicle, aircraft or watercraft design
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D37/00—Tools as parts of machines covered by this subclass
- B21D37/10—Die sets; Pillar guides
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D5/00—Bending sheet metal along straight lines, e.g. to form simple curves
- B21D5/02—Bending sheet metal along straight lines, e.g. to form simple curves on press brakes without making use of clamping means
- B21D5/0209—Tools therefor
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F30/00—Computer-aided design [CAD]
- G06F30/20—Design optimisation, verification or simulation
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F2119/00—Details relating to the type or aim of the analysis or the optimisation
- G06F2119/14—Force analysis or force optimisation, e.g. static or dynamic forces
Abstract
The invention discloses a processing technology of hyperboloid forming equipment, which comprises the following steps: establishing a mechanical model for cold forming, researching the mechanical property of the special plate, and deducing the rebound radius of the material for cold forming: fitting the curved surface of the double-curvature plate and performing mathematical characterization on the curved surface: determining the springback value of the shape of the double-curvature forming pressing die by finite element numerical simulation: processing and manufacturing a bent plate pressing die outer plate: and (3) performing fire trimming on the part with insufficient curvature processing of the outer plate part: mounting and storing the base surface spliced plate on a special die, assembling the base surface spliced plate in a partitioning manner according to the number of the base surface spliced plate, and fixing the base surface spliced plate by spot welding; reconstructing the hyperboloid shape after each bending by using an optical surface scanning measurement technology: the invention can accurately control the springback compensation amount, ensure the quality of products, better ensure the precision of curved surfaces, obviously improve the efficiency of bending and forming, reduce the workload of manpower, greatly shorten the working time, save the cost and improve the quality of products.
Description
Technical Field
The invention relates to the ship manufacturing industry, in particular to a processing method of cold-pressed double-curved-surface plate forming equipment used for ship body connection transition.
Background
In the aspects of environmental protection, laws and regulations, marine environmental protection is the starting point for platform disassembly, and the disassembly of old and idle platforms has important significance for guaranteeing marine environment, navigation, fishery production and the like of a working area.
The semi-submersible type hoisting and disassembling platform is complex in structure, different from a conventional semi-submersible type platform, is of an asymmetric structure, is provided with different lower floating bodies and stand columns, has no cross brace in the middle and is only connected by an upper ship body, so that the construction difficulty is high and the precision requirement is high. In order to avoid structural stress concentration, the connection of the semi-submersible hoisting dismantling platform upright post and the upper hull as well as the connection of the upright post and the lower floating body adopt a double-curved-surface large-arc plate structure for transition. The double curved surface plate forming method is usually a water-fire plate bending method, and when the batch size is large, a special pressing die can be arranged on a press machine for pressing and forming. At present, the design method of hyperboloid design forming equipment mainly comprises the steps of manufacturing an upper wood mould and a lower wood mould, then manufacturing a sand mould and pouring a cast steel mould, processing, finally clamping a steel plate between the upper mould and the lower mould by using a large-scale oil press, and forming the bent plate by using the extrusion of the upper mould and the lower mould.
Disclosure of Invention
The invention aims to provide a processing method of double-curved-surface forming equipment.
The technical scheme adopted by the invention is as follows:
a processing method of double-curved-surface forming equipment is characterized by comprising the following steps: the method comprises the following steps:
step 1: establishing a cold-forming mechanical model and researching the mechanical properties of the special plate: solving a mechanical equation of cold forming by combining a yield criterion of a plate material and a constitutive equation of an elastic-plastic finite element method, and deducing to obtain a rebound radius of the material processing forming;
step 2: fitting the curved surface of the double-curvature plate and performing mathematical representation on the curved surface;
and step 3: determining the springback quantity of the shape of the double-curvature forming pressing die by finite element numerical simulation; and 4, step 4: processing and manufacturing a curved plate pressing die outer plate, manufacturing a set of upper dies consistent with the radian of the outer plate at intervals of 500mm according to the change of the curvature of a fitted double curved surface, manufacturing different upper dies according to different curvatures, manufacturing a saddle-shaped lower tire die with the same curvature as that of the outer plate in the width direction and the length direction according to the change of the curvature of the outer plate, and processing a lower die;
and 5: performing fire edge folding on the part with insufficient curvature processing of the outer plate part;
step 6: installing and storing the special die on a storage rack, assembling and fixing the special die in a spot welding mode according to the serial number of the base plane jointed boards and the partition, placing the peripheral boards, placing the upper die and the lower die according to the working state, and starting to weld and fix the die after ensuring that the lines are matched and have no dislocation or unevenness;
and 7: gradually pressing and forming a double-curved-surface plate;
and 8: reconstructing the shape of the hyperboloid after each bending by using an optical surface scanning measurement technology;
and step 9: and (3) manufacturing a sample plate box to measure the shape precision of the formed control plate in real time, and realizing the control of the quality of the technological process.
The specific method of the step 1 comprises the following steps:
a. introducing Mises yielding criterion, describing a mechanical condition for transition from an elastic deformation state to a plastic deformation state through an equation, and determining a fixed value sigma, wherein when the elastic deformation of unit volume in the material can reach the fixed value, the material can yield;
b. describing the relation of stress strain of the material in an elastic stage and an elastic-plastic stage in the processing process through a constitutive equation of an elastic-plastic finite element method;
c. based on the hypothesis that the sheet material keeps a plane in the cold bending deformation process and the rebound process, the magnitude of the shear stress received by the cross section of the sheet material is ignored, the neutral layer of the sheet material is of a beam structure, and all the surfaces are overlapped in the bending process, the mechanical equation of cold forming is deduced, and the micro unit of the sheet material subjected to bending deformation is analyzed and described, so that the rebound radius in the material pressing process is determined.
The specific method of the step 2 comprises the following steps:
a. making a proper specific function by using the function values of a plurality of known points of the function f (x) in the sail board and the saddle board, and taking the values of the specific function as approximate values of the function f (x) at other points of the sail board and the saddle board to obtain the variance and mean square root of the sail board and the saddle board;
b. the Gaussian curvature is used for mathematical representation, so that the curvature of the plate can be visually represented by using one parameter Q, namely the Gaussian curvature, and the rules among the curved plates with different shapes can be conveniently found.
The specific method of the step 3 comprises the following steps:
a. setting performance parameters of the pressing die and the plate in ANSYS/LS-DYNA according to actual conditions, setting the upper pressing die and the lower pressing die as rigid bodies which do not deform, setting parameters, and establishing a numerical model of the double-curvature pressing die;
b. simulating the press forming process according to the real situation, setting a reasonable time-displacement pressing function for the upper pressing die, constraining the displacement of the upper pressing die in the X.Y direction and the corner of the upper pressing die in the X.Y.Z direction, applying a full constraint to the lower pressing die, only adding one displacement constraint to the periphery of the middle plate for fixing, setting the friction coefficient between the pressing die and the plate, and then performing simulation calculation on the model in LS/DYNA to obtain the stress condition of the plate in the press forming process;
c. performing data extraction and analysis by using LS/Prepost post-processing software, extracting coordinates of each point, fitting the coordinates into a curve in the software, and comparing the coordinates of each point and the curvature of the curve with a shape to be formed to obtain an error generated by press forming;
d. the curvature of the upper and lower pressing dies is changed according to the curvature of the required forming, the maximum deflection closest to the curvature of the plate after the pressing forming and the required forming can be obtained according to the fitted curve chart, and the nearby groups of data are compared in detail.
The specific method of the step 4 comprises the following steps:
a. after the steel plate is well placed, firstly, scribing an outer plate to be processed: comprises a central line, a check line, a processing line and a margin line;
b. firstly, pressing a flat die into a curvature in one direction along the length direction of a steel plate, wherein the rebound allowance of 15mm needs to be increased;
c. the manufactured saddle-shaped lower forming die is matched with upper dies with different radians to be rolled for multiple times by a step-by-step pressing method, so that the steel plate is formed in the length direction, and the radian in the width direction is unchanged;
d. after cold forming, the joint degree of the steel plate and the sample box is required to be within +/-15 mm.
The specific method of the step 5 comprises the following steps:
a. the method is characterized in that firer is not allowed to be used in the cold working forming process, and the firer adjustment is carried out on the individually formed regions when the cold working forming process is installed on site, but the firer temperature needs to be controlled below 650 ℃, and a temperature measuring gun is used for monitoring and recording in real time;
b. installing an IACS (International Association of Circuit Board) and requiring the flame correction;
c. after the hot working is finished, the attaching degree of the sample box is within +/-5 mm.
The specific method of the step 7 comprises the following steps:
a. selecting a set of upper and lower die units, horizontally contacting the plane part of the upper die with a 1000T oil press, and waiting for the oil press to press; the plane part of the lower die is placed on a horizontal working platform, the upper die and the lower die are aligned until the curved surface parts of the upper die and the lower die can be superposed, and the upper die is lifted to leave a space for placing the double curved surface plate;
b. placing the curved plate to be pressed between a group of upper and lower die units, starting a 1000T oil press to press the upper die, and plastically deforming the double-sided plate to be pressed at a temperature lower than the crystallization temperature;
c. the upper die unit and the lower die unit are arranged at intervals of 500mm according to the change of the processing curvature; and (4) replacing the next set of upper and lower die units after the 500mm double-curved-surface plate is pressed, and repeating the steps a and b to continue pressing the double-curved-surface plate.
The specific method of the step 8 is as follows:
a. cleaning the surface of the bent plate, preparing scattered spots, and adjusting the height of a platform or the height of a camera according to the distance requirement of DIC shooting to ensure that an image shot by the DIC is clearest;
b. using a three-dimensional optical surface scanning measurement system, firstly calibrating to find out relevant parameters, and then carrying out measurement and data acquisition to obtain speckle point measurement data;
c. opening DIC software for data engineering obtained by testing, firstly creating a speckle domain, covering the whole hyperboloid plate as much as possible, then selecting a seed point on the speckle domain, observing and confirming that images of the seed point in a left camera and a right camera are at the same position, after the seed point is selected, performing speckle point matching in four directions, namely up, down, left and right directions by taking the seed point as a starting point, thereby completing the matching of all scattered spots in the speckle domain, finally executing operation and extracting the coordinates of a required point;
d. and (3) carrying out post-processing on the coordinates of the acquisition points in MATLAB software to obtain point cloud coordinate distribution and a reconstructed hyperboloid surface, and ensuring that the final hyperboloid plate can meet the required shape requirement.
The specific method of the step 9 is as follows:
a. 1:1 producing and manufacturing a triangular sample plate according to the real shape of the formed plate, detecting and adjusting a cold-bending forming process in real time through the triangular sample plate, and realizing cold-bending forming of the curvature plate in a successive approximation mode;
b. and after each bending forming, obtaining a real-time bending deformation numerical value through comparison of the triangular sample plates, and providing a subsequent bending process until the bending precision meets the shape requirement of the target curvature plate.
The forming die comprises an upper die and a lower die which are matched in an arc shape.
The invention has the advantages that: according to the invention, the mechanical properties of the platform special plate are researched by a finite element technology, the materials Mises yield criterion is introduced, the stress-strain relationship of the plate in the elastic stage and the elastic-plastic stage is described by a constitutive equation of an elastic-plastic finite element method, and finally a cold-formed mechanical model is deduced, so that the characteristics of the plate material are accurately mastered; in order to fit a series of points on a curved surface into a smooth curve, various fitting methods are researched and summarized, the interpolation method with the best effect is selected to be linearly fitted into a spline curve finally through comparison of the various fitting methods, and the double-curvature panel is represented more accurately through a mathematical model; by comparing the forming results of cold bending forming and linear heating forming, the double-curved-surface forming processing of the plate is realized by selecting and using the cold bending with better precision and lower cost, so that the bending forming efficiency of the plate is improved, and the deterioration caused by high temperature of the material is avoided; in order to solve the problem that the springback compensation value made by theoretical analysis is often greatly different from the actual springback compensation strategy of the mold process scheme design to be invalid in the prior art, the springback amount of cold machining is used as a parameter to be added into finite element analysis in the process of carrying out numerical simulation on single-curvature and double-curvature plate compression, refrigeration and bending forming, and compared with the parameter model drawn by traditional three-dimensional software, the accuracy of the springback compensation value can be better ensured, and the quality of the processed product is better; by adopting the optical scanning technology, the curved surface after the primary pressing forming is subjected to laser scanning, a mathematical model is established, and the mathematical model is compared with the final forming shape of the plate, so that the error is better confirmed, and the precision of the process is ensured; the problem of low working efficiency of the cold bending forming of the double-curvature plate is solved, precision detection is often required in the cold machining forming process, and a real-time control technology is used; the sample plate boxes with the same shape are manufactured according to the shape required to be formed by the plate, and are continuously compared with the sample plate boxes until the sample plate boxes are completely matched in the plate forming process, the use of the sample plate boxes can realize edge pressing measurement in the plate forming process, the purpose of performing precision detection and real-time control on the plate forming process is achieved, and the curvature precision of the double-curvature plate is improved; the special die is always heavy, the use frequency is low and the like, if the special die is improperly stored and placed, the damage to the die and the waste of resources are caused, and the device for placing and storing the die is designed and manufactured while the double-curved-surface forming equipment is designed and manufactured.
Drawings
The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
FIG. 1 is a final formed double-curved sheet of the present invention;
FIG. 2 is a sectional view of a double-curved-surface forming mold, where A to G denote upper mold sections and H to J denote lower mold sections;
FIG. 3 is a cross-section of a section of an upper die A of the hyperboloid forming die of the present invention;
FIG. 4 is a sectional view of a partition of an upper mold B of the hyperboloid molding mold of the present invention;
FIG. 5 is a sectional view of the upper mold section C of the hyperboloid forming mold of the present invention;
FIG. 6 is a cross-section of a section of an upper die D of the hyperboloid forming die of the present invention;
FIG. 7 is a sectional view of the upper mold section E of the hyperboloid forming mold of the present invention;
FIG. 8 is a sectional view of the upper mold section F of the hyperboloid forming mold of the present invention;
FIG. 9 is a sectional view of the upper mold G section of the hyperboloid forming mold of the present invention;
FIG. 10 is a cross-section of a lower mold section H of the hyperboloid molding mold of the present invention;
FIG. 11 is a cross-section of a lower die section I of the hyperboloid forming die of the present invention;
FIG. 12 is a cross-section of a lower die J section of the hyperboloid forming die of the present invention;
fig. 13 is a schematic view of a hyperboloid forming die of the present invention.
Wherein: 1. an upper die; 2. And (5) a lower die.
Detailed Description
As shown in fig. 1 to 13, a method for processing a hyperboloid forming equipment comprises the following steps:
step 1: establishing a cold-forming mechanical model and researching the mechanical properties of the special plate: solving a mechanical equation of cold forming by combining a yield criterion of a plate material and a constitutive equation of an elastic-plastic finite element method, and deducing to obtain a rebound radius of the material processing forming;
step 2: fitting the curved surface of the double-curvature plate and performing mathematical representation on the curved surface;
and step 3: determining the springback quantity of the shape of the double-curvature forming pressing die by finite element numerical simulation; and 4, step 4: processing and manufacturing a curved plate pressing die outer plate, manufacturing a set of upper dies consistent with the radian of the outer plate at intervals of 500mm according to the change of the curvature of a fitted double curved surface, manufacturing different upper dies according to different curvatures, manufacturing a saddle-shaped lower tire die with the same curvature as that of the outer plate in the width direction and the length direction according to the change of the curvature of the outer plate, and processing a lower die;
and 5: performing fire edge folding on the part with insufficient curvature processing of the outer plate part;
step 6: installing and storing the special die on a storage rack, assembling and fixing the special die in a spot welding mode according to the serial number of the base plane jointed boards and the partition, placing the peripheral boards, placing the upper die and the lower die according to the working state, and starting to weld and fix the die after ensuring that the lines are matched and have no dislocation or unevenness;
and 7: gradually pressing and forming a double-curved-surface plate;
and 8: reconstructing the shape of the hyperboloid after each bending by using an optical surface scanning measurement technology;
and step 9: and (3) manufacturing a sample plate box to measure the shape precision of the formed control plate in real time, and realizing the control of the quality of the technological process.
The specific method of the step 1 comprises the following steps:
a. introducing Mises yielding criterion, describing a mechanical condition for transition from an elastic deformation state to a plastic deformation state through an equation, and determining a fixed value sigma, wherein when the elastic deformation of unit volume in the material can reach the fixed value, the material can yield;
b. describing the relation of stress strain of the material in an elastic stage and an elastic-plastic stage in the processing process through a constitutive equation of an elastic-plastic finite element method;
c. based on the hypothesis that the sheet material keeps a plane in the cold bending deformation process and the rebound process, the magnitude of the shear stress received by the cross section of the sheet material is ignored, the neutral layer of the sheet material is of a beam structure, and all the surfaces are overlapped in the bending process, the mechanical equation of cold forming is deduced, and the micro unit of the sheet material subjected to bending deformation is analyzed and described, so that the rebound radius in the material pressing process is determined.
The specific method of the step 2 comprises the following steps:
a. making a proper specific function by using the function values of a plurality of known points of the function f (x) in the sail board and the saddle board, and taking the values of the specific function as approximate values of the function f (x) at other points of the sail board and the saddle board to obtain the variance and mean square root of the sail board and the saddle board;
b. the Gaussian curvature is used for mathematical representation, so that the curvature of the plate can be visually represented by using one parameter Q, namely the Gaussian curvature, and the rules among the curved plates with different shapes can be conveniently found.
The specific method of the step 3 comprises the following steps:
a. setting performance parameters of the pressing die and the plate in ANSYS/LS-DYNA according to actual conditions, setting the upper pressing die and the lower pressing die as rigid bodies which do not deform, setting parameters, and establishing a numerical model of the double-curvature pressing die;
b. simulating the press forming process according to the real situation, setting a reasonable time-displacement pressing function for the upper pressing die, constraining the displacement of the upper pressing die in the X.Y direction and the corner of the upper pressing die in the X.Y.Z direction, applying a full constraint to the lower pressing die, only adding one displacement constraint to the periphery of the middle plate for fixing, setting the friction coefficient between the pressing die and the plate, and then performing simulation calculation on the model in LS/DYNA to obtain the stress condition of the plate in the press forming process;
c. performing data extraction and analysis by using LS/Prepost post-processing software, extracting coordinates of each point, fitting the coordinates into a curve in the software, and comparing the coordinates of each point and the curvature of the curve with a shape to be formed to obtain an error generated by press forming;
d. the curvature of the upper and lower pressing dies is changed according to the curvature of the required forming, the maximum deflection closest to the curvature of the plate after the pressing forming and the required forming can be obtained according to the fitted curve chart, and the nearby groups of data are compared in detail.
The specific method of the step 4 comprises the following steps:
a. after the steel plate is well placed, firstly, scribing an outer plate to be processed: comprises a central line, a check line, a processing line and a margin line;
b. firstly, pressing a flat die into a curvature in one direction along the length direction of a steel plate, wherein the rebound allowance of 15mm needs to be increased;
c. the manufactured saddle-shaped lower forming die is matched with upper dies with different radians to be rolled for multiple times by a step-by-step pressing method, so that the steel plate is formed in the length direction, and the radian in the width direction is unchanged;
d. after cold forming, the joint degree of the steel plate and the sample box is required to be within +/-15 mm.
The specific method of the step 5 comprises the following steps:
a. the method is characterized in that firer is not allowed to be used in the cold working forming process, and the firer adjustment is carried out on the individually formed regions when the cold working forming process is installed on site, but the firer temperature needs to be controlled below 650 ℃, and a temperature measuring gun is used for monitoring and recording in real time;
b. installing an IACS (International Association of Circuit Board) and requiring the flame correction;
c. after the hot working is finished, the attaching degree of the sample box is within +/-5 mm.
The specific method of the step 7 comprises the following steps:
a. selecting a set of upper and lower die units, horizontally contacting the plane part of the upper die with a 1000T oil press, and waiting for the oil press to press; the plane part of the lower die is placed on a horizontal working platform, the upper die and the lower die are aligned until the curved surface parts of the upper die and the lower die can be superposed, and the upper die is lifted to leave a space for placing the double curved surface plate;
b. placing the curved plate to be pressed between a group of upper and lower die units, starting a 1000T oil press to press the upper die, and plastically deforming the double-sided plate to be pressed at a temperature lower than the crystallization temperature;
c. the upper die unit and the lower die unit are arranged at intervals of 500mm according to the change of the processing curvature; and (4) replacing the next set of upper and lower die units after the 500mm double-curved-surface plate is pressed, and repeating the steps a and b to continue pressing the double-curved-surface plate.
The specific method of the step 8 is as follows:
a. cleaning the surface of the bent plate, preparing scattered spots, and adjusting the height of a platform or the height of a camera according to the distance requirement of DIC shooting to ensure that an image shot by the DIC is clearest;
b. using a three-dimensional optical surface scanning measurement system, firstly calibrating to find out relevant parameters, and then carrying out measurement and data acquisition to obtain speckle point measurement data;
c. opening DIC software for data engineering obtained by testing, firstly creating a speckle domain, covering the whole hyperboloid plate as much as possible, then selecting a seed point on the speckle domain, observing and confirming that images of the seed point in a left camera and a right camera are at the same position, after the seed point is selected, performing speckle point matching in four directions, namely up, down, left and right directions by taking the seed point as a starting point, thereby completing the matching of all scattered spots in the speckle domain, finally executing operation and extracting the coordinates of a required point;
d. and (3) carrying out post-processing on the coordinates of the acquisition points in MATLAB software to obtain point cloud coordinate distribution and a reconstructed hyperboloid surface, and ensuring that the final hyperboloid plate can meet the required shape requirement.
The specific method of the step 9 comprises the following steps:
a. 1:1 producing and manufacturing a triangular sample plate according to the real shape of the formed plate, detecting and adjusting a cold-bending forming process in real time through the triangular sample plate, and realizing cold-bending forming of the curvature plate in a successive approximation mode;
b. and after each bending forming, obtaining a real-time bending deformation numerical value through comparison of the triangular sample plates, and providing a subsequent bending process until the bending precision meets the shape requirement of the target curvature plate.
The forming die comprises an upper die 1 and a lower die 2 which are matched in an arc shape.
According to the invention, the mechanical properties of the platform special plate are researched by a finite element technology, the materials Mises yield criterion is introduced, the stress-strain relationship of the plate in the elastic stage and the elastic-plastic stage is described by a constitutive equation of an elastic-plastic finite element method, and finally a cold-formed mechanical model is deduced, so that the characteristics of the plate material are accurately mastered; in order to fit a series of points on a curved surface into a smooth curve, various fitting methods are researched and summarized, the interpolation method with the best effect is selected to be linearly fitted into a spline curve finally through comparison of the various fitting methods, and the double-curvature panel is represented more accurately through a mathematical model; by comparing the forming results of cold bending forming and linear heating forming, the double-curved-surface forming processing of the plate is realized by selecting and using the cold bending with better precision and lower cost, so that the bending forming efficiency of the plate is improved, and the deterioration caused by high temperature of the material is avoided; in order to solve the problem that the springback compensation value made by theoretical analysis is often greatly different from the actual springback compensation strategy of the mold process scheme design to be invalid in the prior art, the springback amount of cold machining is used as a parameter to be added into finite element analysis in the process of carrying out numerical simulation on single-curvature and double-curvature plate compression, refrigeration and bending forming, and compared with the parameter model drawn by traditional three-dimensional software, the accuracy of the springback compensation value can be better ensured, and the quality of the processed product is better; by adopting the optical scanning technology, the curved surface after the primary pressing forming is subjected to laser scanning, a mathematical model is established, and the mathematical model is compared with the final forming shape of the plate, so that the error is better confirmed, and the precision of the process is ensured; the problem of low working efficiency of the cold bending forming of the double-curvature plate is solved, precision detection is often required in the cold machining forming process, and a real-time control technology is used; the sample plate boxes with the same shape are manufactured according to the shape required to be formed by the plate, and are continuously compared with the sample plate boxes until the sample plate boxes are completely matched in the plate forming process, the use of the sample plate boxes can realize edge pressing measurement in the plate forming process, the purpose of performing precision detection and real-time control on the plate forming process is achieved, and the curvature precision of the double-curvature plate is improved; the special die is always heavy, the use frequency is low and the like, if the special die is improperly stored and placed, the damage to the die and the waste of resources are caused, and the device for placing and storing the die is designed and manufactured while the double-curved-surface forming equipment is designed and manufactured.
Claims (10)
1. A processing method of double-curved-surface forming equipment is characterized by comprising the following steps: the method comprises the following steps:
step 1: establishing a cold-forming mechanical model and researching the mechanical properties of the special plate: solving a mechanical equation of cold forming by combining a yield criterion of a plate material and a constitutive equation of an elastic-plastic finite element method, and deducing to obtain a rebound radius of the material processing forming;
step 2: fitting the curved surface of the double-curvature plate and performing mathematical representation on the curved surface;
and step 3: determining the springback quantity of the shape of the double-curvature forming pressing die by finite element numerical simulation; and 4, step 4: processing and manufacturing a curved plate pressing die outer plate, manufacturing a set of upper dies consistent with the radian of the outer plate at intervals of 500mm according to the change of the curvature of a fitted double curved surface, manufacturing different upper dies according to different curvatures, manufacturing a saddle-shaped lower tire die with the same curvature as that of the outer plate in the width direction and the length direction according to the change of the curvature of the outer plate, and processing a lower die;
and 5: performing fire edge folding on the part with insufficient curvature processing of the outer plate part;
step 6: installing and storing the special die on a storage rack, assembling and fixing the special die in a spot welding mode according to the serial number of the base plane jointed boards and the partition, placing the peripheral boards, placing the upper die and the lower die according to the working state, and starting to weld and fix the die after ensuring that the lines are matched and have no dislocation or unevenness;
and 7: gradually pressing and forming a double-curved-surface plate;
and 8: reconstructing the shape of the hyperboloid after each bending by using an optical surface scanning measurement technology;
and step 9: and (3) manufacturing a sample plate box to measure the shape precision of the formed control plate in real time, and realizing the control of the quality of the technological process.
2. The method for processing the hyperboloid forming equipment according to claim 1, wherein: the specific method of the step 1 comprises the following steps:
a. introducing Mises yielding criterion, describing a mechanical condition for transition from an elastic deformation state to a plastic deformation state through an equation, and determining a fixed value sigma, wherein when the elastic deformation of unit volume in the material can reach the fixed value, the material can yield;
b. describing the relation of stress strain of the material in an elastic stage and an elastic-plastic stage in the processing process through a constitutive equation of an elastic-plastic finite element method;
c. based on the hypothesis that the sheet material keeps a plane in the cold bending deformation process and the rebound process, the magnitude of the shear stress received by the cross section of the sheet material is ignored, the neutral layer of the sheet material is of a beam structure, and all the surfaces are overlapped in the bending process, the mechanical equation of cold forming is deduced, and the micro unit of the sheet material subjected to bending deformation is analyzed and described, so that the rebound radius in the material pressing process is determined.
3. The method for processing the hyperboloid forming equipment according to claim 1, wherein: the specific method of the step 2 comprises the following steps:
a. making a proper specific function by using the function values of a plurality of known points of the function f (x) in the sail board and the saddle board, and taking the values of the specific function as approximate values of the function f (x) at other points of the sail board and the saddle board to obtain the variance and mean square root of the sail board and the saddle board;
b. the Gaussian curvature is used for mathematical representation, so that the curvature of the plate can be visually represented by using one parameter Q, namely the Gaussian curvature, and the rules among the curved plates with different shapes can be conveniently found.
4. The method for processing the hyperboloid forming equipment according to claim 1, wherein: the specific method of the step 3 comprises the following steps:
a. setting performance parameters of the pressing die and the plate in ANSYS/LS-DYNA according to actual conditions, setting the upper pressing die and the lower pressing die as rigid bodies which do not deform, setting parameters, and establishing a numerical model of the double-curvature pressing die;
b. simulating the press forming process according to the real situation, setting a reasonable time-displacement pressing function for the upper pressing die, constraining the displacement of the upper pressing die in the X.Y direction and the corner of the upper pressing die in the X.Y.Z direction, applying a full constraint to the lower pressing die, only adding one displacement constraint to the periphery of the middle plate for fixing, setting the friction coefficient between the pressing die and the plate, and then performing simulation calculation on the model in LS/DYNA to obtain the stress condition of the plate in the press forming process;
c. performing data extraction and analysis by using LS/Prepost post-processing software, extracting coordinates of each point, fitting the coordinates into a curve in the software, and comparing the coordinates of each point and the curvature of the curve with a shape to be formed to obtain an error generated by press forming;
d. the curvature of the upper and lower pressing dies is changed according to the curvature of the required forming, the maximum deflection closest to the curvature of the plate after the pressing forming and the required forming can be obtained according to the fitted curve chart, and the nearby groups of data are compared in detail.
5. The method for processing the hyperboloid forming equipment according to claim 1, wherein: the specific method of the step 4 comprises the following steps:
a. after the steel plate is well placed, firstly, scribing an outer plate to be processed: comprises a central line, a check line, a processing line and a margin line;
b. firstly, pressing a flat die into a curvature in one direction along the length direction of a steel plate, wherein the rebound allowance of 15mm needs to be increased;
c. the manufactured saddle-shaped lower forming die is matched with upper dies with different radians to be rolled for multiple times by a step-by-step pressing method, so that the steel plate is formed in the length direction, and the radian in the width direction is unchanged;
d. after cold forming, the joint degree of the steel plate and the sample box is required to be within +/-15 mm.
6. The method for processing the hyperboloid forming equipment according to claim 1, wherein: the specific method of the step 5 comprises the following steps:
a. the method is characterized in that firer is not allowed to be used in the cold working forming process, and the firer adjustment is carried out on the individually formed regions when the cold working forming process is installed on site, but the firer temperature needs to be controlled below 650 ℃, and a temperature measuring gun is used for monitoring and recording in real time;
b. installing an IACS (International Association of Circuit Board) and requiring the flame correction;
c. after the hot working is finished, the attaching degree of the sample box is within +/-5 mm.
7. The method for processing the hyperboloid forming equipment according to claim 1, wherein: the specific method of the step 7 comprises the following steps:
a. selecting a set of upper and lower die units, horizontally contacting the plane part of the upper die with a 1000T oil press, and waiting for the oil press to press; the plane part of the lower die is placed on a horizontal working platform, the upper die and the lower die are aligned until the curved surface parts of the upper die and the lower die can be superposed, and the upper die is lifted to leave a space for placing the double curved surface plate;
b. placing the curved plate to be pressed between a group of upper and lower die units, starting a 1000T oil press to press the upper die, and plastically deforming the double-sided plate to be pressed at a temperature lower than the crystallization temperature;
c. the upper die unit and the lower die unit are arranged at intervals of 500mm according to the change of the processing curvature; and (4) replacing the next set of upper and lower die units after the 500mm double-curved-surface plate is pressed, and repeating the steps a and b to continue pressing the double-curved-surface plate.
8. The method for processing the hyperboloid forming equipment according to claim 1, wherein: the specific method of the step 8 is as follows:
a. cleaning the surface of the bent plate, preparing scattered spots, and adjusting the height of a platform or the height of a camera according to the distance requirement of DIC shooting to ensure that an image shot by the DIC is clearest;
b. using a three-dimensional optical surface scanning measurement system, firstly calibrating to find out relevant parameters, and then carrying out measurement and data acquisition to obtain speckle point measurement data;
c. opening DIC software for data engineering obtained by testing, firstly creating a speckle domain, covering the whole hyperboloid plate as much as possible, then selecting a seed point on the speckle domain, observing and confirming that images of the seed point in a left camera and a right camera are at the same position, after the seed point is selected, performing speckle point matching in four directions, namely up, down, left and right directions by taking the seed point as a starting point, thereby completing the matching of all scattered spots in the speckle domain, finally executing operation and extracting the coordinates of a required point;
d. and (3) carrying out post-processing on the coordinates of the acquisition points in MATLAB software to obtain point cloud coordinate distribution and a reconstructed hyperboloid surface, and ensuring that the final hyperboloid plate can meet the required shape requirement.
9. The method for processing the hyperboloid forming equipment according to claim 1, wherein: the specific method of the step 9 is as follows:
a. 1:1 producing and manufacturing a triangular sample plate according to the real shape of the formed plate, detecting and adjusting a cold-bending forming process in real time through the triangular sample plate, and realizing cold-bending forming of the curvature plate in a successive approximation mode;
b. and after each bending forming, obtaining a real-time bending deformation numerical value through comparison of the triangular sample plates, and providing a subsequent bending process until the bending precision meets the shape requirement of the target curvature plate.
10. The method for processing the hyperboloid forming equipment according to claim 1, wherein: the forming die comprises an upper die and a lower die which are matched in an arc shape.
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| CN114309261B (en) * | 2021-12-24 | 2023-05-16 | 广东工贸职业技术学院 | Progressive forming bending method for hyperboloid metal plate |
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| CN114535430A (en) * | 2022-02-18 | 2022-05-27 | 上海庆华蜂巢科技发展股份有限公司 | Multi-curved surface honeycomb board forming process and multi-curved surface honeycomb board |
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| CN114603321B (en) * | 2022-03-07 | 2023-05-05 | 中交路桥建设有限公司 | Machining method for hyperboloid template of variable-section cylindrical pier |
| CN114798902A (en) * | 2022-03-15 | 2022-07-29 | 上海建工（江苏）钢结构有限公司 | Method for processing special-shaped curved surface medium plate based on multi-point flexible bending |
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