Electromagnetic-based Distributed Blank-holding Optimization Method and Distributed Electromagnetic Blank-holding Die

Abstract

The present invention relates to the technical field of sheet metal stamping forming, in particular to a distributed blank-holding optimization method based on electromagnetism and a distributed electromagnetic blank-holding die. The present invention establishes a stamping simulation model of distributed blank-holders, initializes the stamping simulation model based on the blank-holders and analysis steps, and uses finite element simulation analysis to obtain the optimal blank-holding force matrix, so as to obtain the blank-holding force loading line corresponding to the blank-holders as the control basis for the blank-holding force. The blank-holding operation is divided according to the duration of the analysis step. The division of the analysis step combines the thermal characteristics of the electromagnetic part, and a certain duration is reserved after magnetization or demagnetization to dissipate the heat generated, so as to realize the continuous and stable loading of the blank-holding force during the batch production process.

Description

Technical Field

[0001] The present invention relates to the technical field of sheet metal stamping forming, in particular to a distributed blank-holding optimization method based on electromagnetism and a distributed electromagnetic blank-holding die. Background Art

[0002] The blank-holding force is a very important process parameter in the stamping forming process. An appropriate blank-holding force not only helps to improve the forming quality of the stamping parts, but also can greatly reduce the energy consumption of the process. An excessive blank-holding force easily causes the stamping sheet to crack; an insufficient blank-holding force fails to achieve the blank-holding effect and easily causes the stamping sheet to wrinkle.

[0003] Most sheet metal stamping is carried out with constant and integral blank-holding, that is, the blank-holding force received by the stamping area of the sheet is roughly the same, which easily leads to cracking or wrinkling in some areas. Therefore, a stamping forming method with distributed blank-holding has emerged, that is, relatively independent blank-holding blocks are set for different areas of the sheet to provide different blank-holding forces. Based on the above distributed blank-holding method, at present, the blank-holding force is provided either by a mechanical structure or by an electromagnet (i.e., an electromagnetic part). The blank-holding force provided by the former is generally a fixed value, which is not convenient and cannot be adjusted in a timely manner. Although the latter is adjustable and controllable, the inventor later found that heat is easily accumulated inside the electromagnet during use. Although the influence of this heat accumulation is not significant for short stamping times of sheet metal (for example, less than 5 s), if the stamping time of the sheet metal is long (for example, greater than 10 s), the influence of heat accumulation on the electromagnet should be considered. However, there is little research on this point at present. Summary of the Invention

[0004] Based on this, in view of the problem that the existing electromagnet-based blank-holding force has the influence of heat accumulation, it is necessary to provide a distributed blank-holding optimization method based on electromagnetism and a distributed electromagnetic blank-holding die.

[0005] The present invention is implemented by the following technical solutions:

[0006] In the first aspect

[0007] The present invention provides a distributed blank-holding optimization method based on electromagnetism, which is applicable to a distributed electromagnetic blank-holding die, and the electromagnetic part in the distributed electromagnetic blank-holding die provides a blank-holding force for the blank-holding block. The distributed blank-holding optimization method based on electromagnetism includes the following steps:

[0008] Step 1, establishing a stamping simulation model of the distributed blank-holding block: Among them, the blank-holding blocks are sequentially denoted as B1 to B n , the stamping depth is discretized into m preset analysis steps and denoted as H1 to H m ;

[0009] Step 2, initializing the blank-holding blocks and analysis steps in the stamping simulation model and forming a blank-holding force matrix Among them Indicates the blank-holding force received by the blank-holder B1 in analysis steps H1 to H m ; where Indicates the blank-holding force received by the blank-holders B1 to B n in analysis step H1;

[0010] Step 3: Perform finite element simulation analysis on the stamping simulation model and obtain the optimal blank-holding force matrix

[0011] Step 4: Use the electromagnetic and thermal characteristics to correct the optimal blank-holding force matrix to obtain the corrected blank-holding force loading line, which is used as the final basis for blank-holding force loading;

[0012] Among them, based on the blank-holding force model provided by the electromagnetic part, the duration of the analysis step is obtained, and it is ensured that the blank-holding force loading line is loaded normally and the temperature of the electromagnetic part is in a normal state; the duration of each analysis step includes the magnetization / demagnetization duration, the remanent magnetization duration, and the heat dissipation duration of the electromagnetic part; based on the duration of the analysis step, the corrected number of analysis steps M is obtained, and the optimal blank-holding force matrix is corrected to obtain the corrected blank-holding force matrix For the corrected blank-holding force matrix After being divided into columns in blocks, n groups of corrected blank-holding force sub-matrices are obtained, and then the n groups of corrected blank-holding force sub-matrices are fitted to obtain n corrected blank-holding force loading lines, and the acting force is applied to the corresponding blank-holder according to each corrected blank-holding force loading line.

[0013] The electromagnetic-based distributed blank-holding optimization method implements the method or process according to the embodiments of the present disclosure.

[0014] Second aspect

[0015] The present invention provides a distributed electromagnetic blank-holding die, including a punch and a die that cooperate with each other, a plurality of blank-holders, and the same number of electromagnetic parts as the blank-holders.

[0016] There is a blank-holding area between the punch and the die for placing the stamping blank. The blank-holders are discretely distributed in the blank-holding area according to a certain rule according to the shape of the formed part, and are used to apply blank-holding force to the stamping blank. The electromagnetic parts are arranged in the punch or / and the die and are correspondingly distributed with the blank-holders. The electromagnetic parts are provided with temperature sensors for detecting the real-time temperature of the electromagnetic parts; the electromagnetic parts attract the blank-holders, so that the blank-holders apply blank-holding force to the blank-holding area. The distributed electromagnetic blank-holding die uses the above-mentioned electromagnetic-based distributed blank-holding optimization method.

[0017] The present invention also provides another distributed electromagnetic blank-holding die, including a punch and a die that cooperate with each other, a plurality of blank-holders, the same number of attracted plates as the blank-holders, and the same number of electromagnetic parts as the attracted plates.

[0018] A blank holding area is provided between the punch and the die for placing the stamping blank. The blank holding blocks are discretely distributed in the blank holding area according to a certain rule according to the shape of the formed part, and are used to apply blank holding force to the stamping blank. The blank holding blocks are fixed on the attracted plate. The electromagnetic part is arranged in the punch or / and the die and is correspondingly distributed with the attracted plate. The electromagnetic part is provided with a temperature sensor for detecting the real-time temperature of the electromagnetic part. The electromagnetic part attracts the attracted plate, so that the attracted plate drives the blank holding blocks to apply blank holding force to the blank holding area. This distributed electromagnetic blank holding die uses the above-mentioned electromagnetic-based distributed blank holding optimization method.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. The present invention establishes a stamping simulation model of distributed blank holding blocks, initializes the stamping simulation model based on the blank holding blocks and analysis steps, and uses finite element simulation analysis to obtain the optimal blank holding force matrix, so as to obtain the blank holding force loading line corresponding to the blank holding blocks, which is used as the control basis for the blank holding force; the present invention discretely samples the stamping depth, that is, discretely divides the stamping depth into multiple analysis steps. This method makes continuous blank holding optimizable, and the number of analysis steps and the duration of each analysis step are combined with the electromagnetic thermal characteristics to ensure that the electromagnetic part is still in a normal working state during continuous operation.

[0021] 2. The present invention makes full use of the residual magnetism of the electromagnetic part. This loading process combines the electro-permanent magnet technology and the distributed blank holding technology to control the blank holding force in different regions and at different stamping depths of the formed part, improves the blank holding force loading path, optimizes the forming quality, reduces energy consumption, and enables the electromagnetic distributed blank holding to avoid wrinkling and cracking phenomena, which is of great significance for improving the control accuracy and the forming quality of the stamping parts. Description of the Drawings

[0022] Figure 1 is a structural diagram of an embodiment of the distributed electromagnetic blank holding die in the present invention;

[0023] Figure 2 is a principle flow chart of the electromagnetic-based distributed blank holding optimization method in the present invention;

[0024] Figure 3 is Figure 2 the flow chart for determining the duration of the analysis step in

[0025] Figure 4 is Figure 2 the relationship diagram of the magnetization, residual magnetism of the electromagnetic part and the corresponding blank holding force applied in

[0026] Figure 5 is Figure 2 the schematic diagram of the obtained blank holding force loading line in

[0027] In the drawings, the list of components represented by each reference numeral is as follows:

[0028] 101. Blanking area; 102. Blank holder; 103. Suction plate; 104. Female die; 105. Electromagnetic part; 106. Male die. Detailed implementation manner

[0029] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0030] It should be noted that when a component is referred to as being "installed on" another component, it can be directly on the other component or there may also be an intermediate component. When a component is considered to be "arranged on" another component, it can be directly arranged on the other component or there may be an intermediate component at the same time. When a component is considered to be "fixed to" another component, it can be directly fixed to the other component or there may be an intermediate component at the same time.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the description of the present invention in this specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "or / and" used herein includes any and all combinations of one or more of the related listed items.

[0032] Refer to Figure 1 , Figure 1 It is a structural diagram of an embodiment of the distributed electromagnetic blanking die in the present invention, specifically a partial structural diagram of the die.

[0033] This distributed electromagnetic blanking die includes a male die 106 and a female die 105 that cooperate with each other. The shapes of the male die 106 and the female die 105 are designed according to the characteristics of the required formed part. Taking Figure 1 as an example, the female die 105 is located above the male die 106, and a blanking area 101 is formed between the male die 106 and the female die 105. The blanking area 101 is used to place the stamping blank.

[0034] This distributed electromagnetic blanking die also includes a plurality of blank holders 102, a plurality of suction plates 103 with the same number as the blank holders 102, and a plurality of electromagnetic parts 105 with the same number as the suction plates 103. The plurality of blank holders 102 are discretely distributed in the blanking area according to the shape of the formed part according to a certain rule, and are used to blank the stamping blank. Such as Figure 1As shown, this partial structural diagram only shows the component structure corresponding to a single blank holder 102. The blank holder 102 is arranged at the lower edge of the blank holding area 101. The blank holder 102 can be installed on the suction plate 103 by means of bolt fixation or the like. The electromagnetic part 105 can be installed in the punch 106 or / and the die 105. It should be noted that the electromagnetic part 105 is a component composed of several magnetic pole units, but the number of a single set of electromagnetic parts 105 is regarded as one. Among them, the electromagnetic part 105 is equipped with a temperature sensor for detecting the real-time temperature of the electromagnetic part 105.

[0035] In this embodiment, the punch 106 moves upward to punch the stamping sheet metal, and then the electromagnetic part 105 is installed in the die 105, and the suction plate 103 extends to the electromagnetic part 105, so that the electromagnetic part 105 and the suction plate 103 are correspondingly distributed. The suction plate 103 is made of a magnetically adsorbable material, such as iron or 45# steel. In this way, when punching, the electromagnetic part 105 is energized to attract the suction plate 103, so that the suction plate 103 drives the blank holder 102 to apply a blank holding force to the blank holding area (that is, Figure 1 the direction of the dotted arrow in the figure), ensuring that the formed part after punching the stamping sheet metal does not wrinkle or crack.

[0036] The blank holders 102 distributed in other places also adopt the same design as above, so that each blank holder 102 can be independently stressed in the punching direction during punching, ensuring that different blank holding forces can be applied to the blank holding area 101 of the sheet metal.

[0037] Of course, the structure of this form of distributed electromagnetic blank holding die can be adjusted. For example, the suction plate 103 is discarded, and the blank holder 102 is directly extended to the electromagnetic part 105, so that the electromagnetic part 105 and the blank holder 102 are correspondingly distributed. The blank holder 102 is made of a high-strength material and can be adsorbed by the electromagnetic part 105, such as 45 steel or ferroalloy. In this way, when punching, the electromagnetic part 105 is energized to attract the blank holder 102, so that the blank holder 102 applies a blank holding force to the blank holding area, ensuring that the formed part after punching the stamping sheet metal does not wrinkle or crack.

[0038] Obviously, only the above-mentioned distributed electromagnetic blank holding die is not enough. If direct production experiments are carried out, it is easy to produce waste products, waste materials, and it is easy to cause die wear, resulting in a significant increase in production costs. Therefore, the present invention also provides a distributed blank holding optimization method based on electromagnetism, which optimizes the distributed blank holding force by means of the interaction between intelligent algorithms and finite elements, greatly reducing the production cost.

[0039] The distributed blank holding optimization method based on electromagnetism of the present invention is applied to a distributed electromagnetic blank holding die. The distributed electromagnetic blank holding die can adopt the structures in the above several embodiments or other deformed structures.

[0040] It should be emphasized that although the structure of the distributed electromagnetic blank-holding die is adjustable, there are several commonalities in the basic structure:

[0041] 1. Multiple blank-holding blocks are set in the structure of the distributed electromagnetic blank-holding die, and are discretely distributed in the blank-holding area of the stamping sheet according to a certain rule according to the shape of the formed part, so as to generate different blank-holding forces on the blank-holding area;

[0042] 2. The distributed electromagnetic blank-holding die uses an electromagnetic part based on electromagnetism to control the blank-holding force of the blank-holding block;

[0043] 3. The electromagnetic part is equipped with a temperature sensor for real-time detection of the temperature of the electromagnetic part.

[0044] The following specifically describes the distributed blank-holding optimization method based on electromagnetism. Refer to Figure 2 , the distributed blank-holding optimization method based on electromagnetism includes the following steps:

[0045] Step 1, establish a stamping simulation model of the distributed blank-holding block, for example, use finite element analysis software such as Abaqus to establish the model.

[0046] The blank-holding blocks are sequentially denoted as B1 to B n ;

[0047] The stamping depth is discretized into m preset analysis steps and denoted as H1 to H m : Specifically, the stamping depth of the stamping simulation model is discretely sampled, and the discrete stamping depth is divided into m analysis steps, and the analysis step numbers are H1 to H m .

[0048] Step 2, initialize the blank-holding blocks and analysis steps in the stamping simulation model, and form a blank-holding force matrix

[0049]

[0050] Among them, the initialization is carried out by using an intelligent algorithm (such as the particle swarm optimization algorithm PSO);

[0051] Among them represents the blank-holding force received by the blank-holding block B1 in the analysis steps H1 to H m ; among them represents the blank-holding force received by the blank-holding blocks B1 to B n in the analysis step H1;

[0052] Step 3, perform finite element simulation analysis on the stamping simulation model, and obtain the optimal blank-holding force matrix

[0053] Specifically, a finite element simulation analysis is carried out on the stamping simulation mathematical model for initializing the blank holding force matrix in Abaqus. The simulation result Odb file is read through an intelligent algorithm (such as the particle swarm optimization algorithm PSO) to obtain the average thickness of the stamping sheet metal. The maximum thickness STH max and the minimum thickness STH min are used to calculate the thinning rate of the sheet metal and the thickening rate

[0054] It is judged whether the thinning rate Q and the thickening rate P meet the requirements of sheet metal rupture and wrinkling, that is, Q and P should satisfy the threshold range of Q < λ & P < μ, where λ and μ are judgment coefficients.

[0055] If satisfied, first convert the thinning rate Q and the thickening rate P into an evaluation function J = αQ + βP; where α and β are the proportionality coefficients of the thinning rate Q and the thickening rate P respectively; here, Q and P within the threshold range are converted into J, that is, the multi-objective optimization is converted into a single-objective optimization problem; then, the initialized stamping simulation model is subjected to j iterative calculations until the evaluation function J converges or reaches the maximum number of iterations, so as to obtain the optimal blank holding force matrix corresponding to the minimum value of J. Specifically, based on the intelligent algorithm, the established stamping simulation model is subjected to j iterative calculations until the evaluation function J converges or reaches the maximum number of iterations, in order to find the minimum value of J = αQ + βP and obtain the corresponding optimal blank holding force matrix at this time.

[0056] If not, return to step two; it should be noted that this return to step two actually re-initializes the blank holding force matrix, and the data is different from before.

[0057] Step four, use the electromagnetic thermal characteristics to correct the optimal blank holding force matrix and obtain the corrected blank holding force loading line, which is used as the final basis for blank holding force loading:

[0058] First, based on the blank holding force model provided by the electromagnetic part, obtain the analysis step duration and ensure that the blank holding force loading line is loaded normally and the temperature of the electromagnetic part is in a normal state.

[0059] Specifically, the establishment method of the blank holding force model provided by the electromagnetic part is as follows:

[0060] For any blank holding area b i , i ∈ (1, n), control the electromagnetic part c i corresponding to the blank holding area b i ;

[0061] Among them, the electromagnetic part c i consists of magnetic pole units a1 to a nComposition; the electromagnetic part c i and the attracted plate d i or / and the blank-holder block B i constitute the electromagnetic distributed blank-holder unit e i . All the blank-holder blocks correspond to all the electromagnetic parts, that is, the whole electromagnetic part.

[0062] The electromagnetic part c i generates an electromagnetic force g through a high-frequency pulsed current i to make the electromagnetic part c i attract the corresponding attracted plate d i or the blank-holder block B i (the former acts indirectly on the blank-holder block B i , and the latter acts directly on the blank-holder block B i ), so as to provide a blank-holding force f for the blank-holder block B i , i∈(1,n) i ;

[0063] The electromagnetic part c i realizes the adjustment of the electromagnetic force g by changing the duty cycle of the pulsed current i , thereby realizing the control of the blank-holding force f i .

[0064] Based on the above blank-holding force model provided by the electromagnetic part,

[0065] for the stamping forming to analysis step H v-1 , v∈(1,m), if a certain blank-holding area b w , w∈(1,n) is blank-held, the pulsed current I can be passed through the electromagnetic part c w corresponding to the blank-holding area b w , so as to realize the application of the blank-holding force f to the blank-holder block B e w ; e

[0066] When the stamping forming reaches the analysis step H v stage, pass the pulsed current I through the electromagnetic part c w , and apply the required blank-holding force f to the blank-holder block B f w ; f .

[0067] Specifically, the determination method of the analysis step duration is as follows, which is divided into three forms:

[0068] 1. For the analysis step from stage H v-1 to stage H v , if the required blank-holding force f e < f f , that is, magnetize the electromagnetic part c w , and the magnetization duration ta Apply a pulsed current with a positive voltage direction, an application period of T, and a duty cycle of 50%. The analysis step is from H v-1 to H v During the times of pulsed current are applied.

[0069] If within the u-th, u ∈ (1, k a ) pulsed current period, then the current expression when the current is turned on is:

[0070]

[0071]

[0072] Where: is the current parameter of the u-th period; I u0 is the initial current parameter within the u-th period; The current parameter of the (u - 1)-th period; T is the period of the PWM pulse width modulation signal; V(u) is the voltage value within the u-th period; R is the coil resistance value; L is the coil inductance value; τ is the time constant.

[0073] The analysis step is from H v-1 to H v During the magnetization stage, its energy consumption W a :

[0074]

[0075] The analysis step is from H v-1 to H v During the magnetization stage, its heat generation Q a :

[0076]

[0077] Where: R' is the resistance of the electromagnetic part c w of.

[0078] If the magnetization circuit stops loading and the pulsed current drops to zero, the residual magnetism generation duration is t b , during this process, the electromagnetic part c w energy consumption W b and heat generation Q b :

[0079]

[0080]

[0081] The total heat generated during the analysis step H v during the blank holding force loading process of the electromagnetic part c wIn analysis step H v-1 Normal operating temperature T v-1 , if electromagnetic part c w is to be ensured in analysis step H v to have a normal operating temperature of T v , then electromagnetic group c w in analysis step H v absorbs heat Q x :

[0082]

[0083] where c is the specific heat capacity of electromagnetic part c w and m is the mass of electromagnetic part c w ;

[0084] To ensure the normal operation of electromagnetic part c w , heat dissipation treatment needs to be carried out on it, and its heat dissipation amount:

[0085]

[0086] The thermal conductivity q between the electromagnetic part and the external environment v :

[0087] q v =KA(T v-1 -T w );

[0088] where A is the total heat transfer area of electromagnetic part c w ; T v-1 is the operating temperature of electromagnetic part c w ; T w is the ambient temperature; K is the total heat transfer coefficient;

[0089] It should be noted that electromagnetic part c w uses permanent magnetic materials such as alnico: According to the characteristics of alnico reversible permanent magnets, during the electro-control operation process, pulsed current excites the alnico reversible permanent magnet to generate a magnetic field with a specific direction and magnitude. This magnetic field is stable and will not change the magnitude or direction of the magnetic field due to the disappearance of the pulsed current. Therefore, electromagnetic part c w can use the residual magnetism to apply a blank holding force f w to blank holder B f , then the duration of the blank holding force application is also the heat dissipation duration;

[0090] By following this step, ensure that electromagnetic part c w is in a normal operating state, and determine the total duration t v of analysis step H v =t a +t b +t c .

[0091] See Figure 4 、 Figure 5 , Figure 4 shows the electromagnetic part c w the relationship diagram of magnetization, remanence and the corresponding blank holding force applied Figure 5 then shows the blank holding force corresponding to each analysis step, that is, the blank holding force loading line. It should be noted that t a 、t b is very short compared with the total duration of the H v phase, so it is not shown in detail in Figure 5

[0092] 2. For the analysis step from the H v-1 phase to the H v phase, if the required blank holding force f e >f f , that is, demagnetize the electromagnetic part c w , the demagnetization duration is t d , apply a pulsed current with the voltage direction reversed, the application period is T, and the duty cycle is 50%. The analysis step applies a total of v-1 to v phase times of pulsed current

[0093] If in the u-th, u ∈ (1, k b ) pulse period, the current expression when the current is turned on is:

[0094]

[0095]

[0096] In the formula: is the current parameter of the u-th cycle; I u0 is the initial current parameter in the u-th cycle; the current parameter of the (u - 1)-th cycle; T is the period of the PWM pulse width modulation signal; V(u) is the voltage value in the u-th cycle; R is the coil resistance value; L is the coil inductance value; τ is the time constant

[0097] For the analysis step from H v-1 to v demagnetization phase, its energy consumption W c :

[0098]

[0099] For the analysis step from H v-1 to v demagnetization phase, its heat generation Q c :

[0100] ​

[0101] Where: R' is the resistance of the electromagnetic part c w of.

[0102] If the demagnetization circuit stops loading, the pulsed current drops to zero, and the residual magnetization generation duration is t e , during which the electromagnetic part c w energy consumption W d , heat generation Q d :

[0103]

[0104]

[0105] During the blank holding force loading process, the total heat generated in analysis step H v The electromagnetic part c w At analysis step H v-1 Normal operating temperature T v-1 , if it is ensured that the electromagnetic part c w At analysis step H v Normal operating temperature is T v , then the heat absorbed by the electromagnetic group c w At analysis step H v Q x :

[0106]

[0107] Where c is the specific heat capacity of the electromagnetic part c w , m is the mass of the electromagnetic part c w ;

[0108] In order to ensure that the electromagnetic part c w is at the normal operating temperature, heat dissipation treatment needs to be carried out on it, and its heat dissipation amount:

[0109]

[0110] The formula for the thermal conductivity between the electromagnetic part and the external environment:

[0111] q v = KA(T v-1 - T w );

[0112] Where A is the total heat transfer area of the electromagnetic part c w ; T v-1 is the operating temperature of the electromagnetic part c w ; T w is the ambient temperature; K is the total heat transfer coefficient; ​

[0113] Based on the electromagnetic part c w The residual magnetism applies a blank holding force f w to the blank holder B f , then the blank holding force loading duration is also the heat dissipation duration; the principle of applying a constant blank holding force by the residual magnetism is the same as the above situation and will not be elaborated here.

[0114] Ensure that the electromagnetic part c w is in a normal working state according to this step, and determine the total duration t' v of the analysis step H v = t d + t e + t f .

[0115] 3. For the analysis step from H v-1 stage to H v stage, if the required blank holding force f e = f f , H v-1 and H v are combined together and regarded as one step, and continue to be loaded with the residual magnetism of H v-1 , and the electromagnetic force does not change.

[0116] In summary, the duration of each analysis step consists of the magnetization / demagnetization duration, the residual magnetism duration, and the heat dissipation duration of the electromagnetic part.

[0117] Then, based on the analysis step duration, the optimal blank holding force matrix is corrected to obtain the corrected blank holding force matrix

[0118] Specifically, first obtain the total time t0 consumed by the overall stamping of the distributed electromagnetic blank holder die; for example, calculate according to the overall stamping depth of H0 and the overall stamping speed of V0

[0119] From the above calculation method of the analysis step duration, the total duration of any blank holder B i , i ∈ (1, n) in a certain analysis step H v can be determined as t i , so that the average duration of the electromagnetic part as a whole in a certain analysis step H v stage Furthermore, for all analysis steps H1 to H m , the average analysis step duration of the electromagnetic part as a whole

[0120] Then, calculate the corrected number of analysis steps M according to the average analysis step duration to update the optimal blank holding force matrix in step three m, and obtain the corrected blank-holder force matrix

[0121] For the corrected blank-holder force matrix After partitioning by column, n groups of corrected blank-holder force sub-matrices are obtained. Then, n corrected blank-holder force loading lines are obtained by fitting the n groups of corrected blank-holder force sub-matrices. According to each corrected blank-holder force loading line, a force is applied to the corresponding blank-holder block

[0122] The construction of the above n corrected blank-holder force loading lines is based on the following principle

[0123] For blank-holder blocks B1 to B n , correction analysis steps H1 to H M The corresponding stamping depths h1 to h M . According to the correction analysis step H l , l ∈ (1, M), and the corresponding stamping depth h l , l ∈ (1, M), apply an appropriate blank-holder force to blank-holder block B i , i ∈ (1, n):

[0124] Specifically, obtain The data and partition it by column to obtain n groups of corrected blank-holder force sub-matrices. Each group of corrected blank-holder force sub-matrices includes the blank-holder force received by a single blank-holder block in analysis steps H1 to H M . In this way, the n groups of corrected blank-holder force sub-matrices cover all n blank-holder blocks, namely B1 to B n ;

[0125] Respectively fit the n groups of corrected blank-holder force sub-matrices, that is, n corrected blank-holder force loading lines are generated. The style of the blank-holder force loading line is as Figure 5 shown

[0126] In addition, refer to Figure 2 , which also shows the above process

[0127] Establish a stamping simulation model (finite element model) of the distributed blank-holder blocks, and use Abaqus finite element software to program the simulation modeling. Combine the modeling program with the particle swarm optimization algorithm to form a blank-holder force optimization algorithm

[0128] For the blank-holder block B of the modeling program i , i ∈ (1, n), the blank-holder force i received in analysis step H , i ∈ (1, m) is the optimization variable, then the blank-holder force is the particle of the particle swarm optimization algorithm. That is, a blank-holder force matrix is composed of blank-holder blocks and analysis steps This blank-holder force matrix has a total of nm optimization variables, that is, the spatial dimension of this blank-holder force optimization algorithm is nm

[0129] Initialize through the particle swarm optimization algorithm (initialize the particle swarm parameters, the position and velocity of each particle), use Python to call Abaqus to run the modeled program after assignment, Python reads the Abaqus simulation result Odb file, and extracts the average thickness of the sheet metal from the Odb file The maximum thickness STH max and the minimum thickness STH min . Calculate the thinning rate of the sheet metal and the thickening rate Judge whether the thinning rate Q and the thickening rate P meet the requirements of sheet metal fracture and wrinkling

[0130] If satisfied, convert the thinning rate Q and the thickening rate P into the evaluation function J = αQ + βP

[0131] If the algorithm does not meet the end condition, update the velocity and position of each particle according to the particle swarm optimization algorithm, and select the optimal particle body from all particle individuals generated by the current iteration number

[0132] Assign the selected optimal value to the modeled program and perform simulation analysis in the finite element until the maximum iteration number is reached or the evaluation function J converges, and output the optimal blank holding force matrix

[0133] After that, correct it in combination with the electromagnetic heat characteristics and convert it into the corrected blank holding force loading line. The blank holding force applied to the blank holder is loaded according to the corrected blank holding force loading line

[0134] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification

[0135] The above-described embodiments only represent several implementation manners of the present invention. Their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several deformations and improvements can be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent should be subject to the appended claims

Claims

1. An electromagnetic-based distributed blank-holding optimization method, which is applicable to a distributed electromagnetic blank-holding die. In the distributed electromagnetic blank-holding die, the electromagnetic part provides a blank-holding force to the blank-holder block. It is characterized in that The electromagnetic-based distributed blank-holding optimization method includes the following steps: Step 1, establish a stamping simulation model of the distributed blank-holder block: Among them, the blank holders are sequentially denoted as B1 to B n , the stamping depth is discretized into m preset analysis steps and denoted as H1 to H m ; Step 2: Initialize the binder and analysis steps in the stamping simulation model and form a blank holder force matrix Among them indicates the blank-holder force received by the blank-holder B1 in analysis steps H1 to H m ; among them indicates the blank-holder force received by the blank-holders B1 to B n in analysis step H1 Step 3: Perform finite element simulation analysis on the stamping simulation model and obtain the optimal blank holder force matrix Step 4: Use the electromagnetic heat characteristics to correct the optimal blank-holding force matrix to obtain the corrected blank-holding force loading line, which is used as the final basis for blank-holding force loading; Among them, obtain the analysis step duration based on the blank-holding force model provided by the electromagnetic part, and ensure that the blank-holding force loading line is normally loaded and the temperature of the electromagnetic part is in a normal state; The duration of each analysis step includes the magnetization / demagnetization duration, the remanence duration, and the heat dissipation duration of the electromagnetic part; Based on the analysis step duration, the number of corrected analysis steps M is obtained, and the optimal blank holding force matrix is corrected to obtain the corrected blank holding force matrix For the corrected blank holding force matrix After block partitioning by column, n groups of corrected blank holding force sub-matrices are obtained. Then, n corrected blank holding force loading lines are obtained by fitting the n groups of corrected blank holding force sub-matrices. According to each corrected blank holding force loading line, a force is applied to the corresponding blank holder block.

2. The electromagnetic-based distributed blank holding optimization method according to claim 1, wherein Step 3 includes the following steps: Obtain the average thickness of the stamping sheet metal Maximum thickness STH max , minimum thickness STH min , calculate the sheet metal thinning rate and thickening rate Judge whether the thinning rate Q and the thickening rate P meet the requirements of sheet metal fracture and wrinkling, that is, Q and P should satisfy the threshold range of Q < λ & P < μ, where λ and μ are judgment coefficients; If satisfied, the thinning rate Q and the thickening rate P are converted into a judgment function J = αQ + βP; where α and β are the proportionality coefficients of the thinning rate Q and the thickening rate P respectively; the initialized stamping simulation model is iteratively calculated j times until the judgment function J converges or reaches the maximum number of iterations, and then the optimal blank holder force matrix corresponding to the minimum value of J is obtained If not, return to Step 2.

3. The electromagnetic-based distributed blank holding optimization method according to claim 1, wherein The method for establishing the blank-holding force model provided by the electromagnetic part in Step 4 includes: For any blank-holding area b i , i ∈ (1, n), control the blank-holding area b i corresponding to the electromagnetic part c i ; Electromagnetic part c i Generate electromagnetic force g through high-frequency pulsed current i , causing the electromagnetic part c i To act directly or indirectly on the blank holder B i , achieving the application of blank holding force f i to the blank holder B, i ∈ (1, n) i ; Electromagnetic part c i The electromagnetic force g is adjusted by changing the duty cycle of the pulsed current i so as to realize the blank holding force f i control.

4. The electromagnetic-based distributed blank holding optimization method according to claim 3, wherein In Step 4, the stamping forming proceeds to analysis step H v-1 , for v ∈ (1, m), if for a certain blank-holding area b w , and w ∈ (1, n) for blank holding, that is, by controlling the blank-holding area b w the corresponding electromagnetic part c w to pass a pulsed current I e , so as to apply a blank-holding force f w to the blank-holder B e ; The stamping process proceeds to analysis step H v phase, and a pulsed current I w is applied to the electromagnetic part c f , and the required blank holding force f w is applied to the blank holder B f .

5. The electromagnetic-based distributed blank-holding optimization method according to claim 4, wherein Analysis step from H v-1 phase to H v phase. If the required blank holding force f e <f f , that is, apply a positive pulse current I w to the electromagnetic part c a , magnetize the electromagnetic part c w , and the magnetization duration is t a ; The magnetizing circuit stops loading, and I a drops to zero, and its residual magnetism duration is t b ; Electromagnetic part c w Apply a blank holding force f w to the blank holder B f based on the residual magnetism, and the blank holding force application duration t c ; During the loading process of the blank holding force, for analysis step H v The generated heat Q a Perform heat dissipation treatment, that is, the blank holding force loading duration t c Is also equivalent to the heat dissipation duration until the electromagnetic part c w The temperature T after heat dissipation b Satisfies T b <T a ,T a Is the normal operating temperature of the electromagnetic part c w So as to ensure that the electromagnetic part c w Is in a normal operating state, and determine the total duration t of the analysis step H according to this step v The total duration t of the stage v =t a +t b +t c .

6. The electromagnetic-based distributed blank holding optimization method according to claim 5, characterized in that Analysis step from H v-1 phase to H v phase, if the required blank holding force f e > f f , that is, apply a reverse pulse current I w to the electromagnetic part c b , demagnetize the electromagnetic part c w , and the demagnetization duration t d ; The demagnetization circuit stops loading, and I b drops to zero, and its residual magnetization duration is t e ; Electromagnetic part c w Applying a blank holding force f w to the blank holder B based on the residual magnetism e with a blank holding force application duration t f ; During the loading process of the blank holding force for analysis step H v The generated heat Q b Perform heat dissipation treatment, that is, the blank holding force loading duration t f Is also equivalent to the heat dissipation duration until the electromagnetic part c w The temperature T' after heat dissipation b Satisfies T' b <T a ,T a Is the normal operating temperature of the electromagnetic part c w So as to ensure that the electromagnetic part c w Is in a normal operating state, and determine the total duration t' of the analysis step H according to this step v The total stage duration t' v =t d +t e +t f 。 7. The electromagnetic-based distributed blank holding optimization method according to claim 6, wherein The method for establishing the blank holder force matrix in step four includes: Obtain the total stamping time t0 of the distributed electromagnetic blank-holding die; Obtain the average duration of the analysis step for the entire electromagnetic unit Calculate the number of modified analysis steps M is used to update m in the optimal blank holder force matrix in Step 3 and obtain the modified blank holder force matrix 8. The electromagnetic-based distributed blank holding optimization method according to claim 7, wherein, The method for establishing n groups of corrected blank-holding force sub-matrices in Step 4 includes: Obtain the corrected blank holding force matrix of the data and partition it by columns to obtain n groups of corrected blank holding force sub-matrices; Each set of corrected blank-holding force sub-matrices includes the blank-holding force received by a single blank-holder during analysis steps H1 to H M The blank-holding force received by the blank-holder, and n sets of corrected blank-holding force sub-matrices cover all blank-holders B1 to B n .

9. A distributed electromagnetic blank-holding die, including a punch and a die that cooperate with each other, and a plurality of blank-holder blocks; a blank-holding area is provided between the punch and the die for placing a stamping sheet metal. The blank-holder blocks are discretely distributed in the blank-holding area according to the shape of the formed part to perform blank-holding on the stamping sheet metal. It is characterized in that The distributed electromagnetic blank-holding die further includes: The same number of electromagnetic parts as the blank-holder blocks, which are arranged in the punch or / and the die and are correspondingly distributed with the blank-holder blocks; the electromagnetic parts are provided with temperature sensors for detecting the real-time temperature of the electromagnetic parts; the electromagnetic parts attract the blank-holder blocks to make the blank-holder blocks apply a blank-holding force to the blank-holding area. The distributed electromagnetic blank-holding die uses the electromagnetic-based distributed blank-holding optimization method described in any one of claims 1-8.

10. A distributed electromagnetic blank-holding die, including a punch and a die that cooperate with each other, and a plurality of blank-holder blocks; a blank-holding area is provided between the punch and the die for placing a stamping sheet metal. The blank-holder blocks are discretely distributed in the blank-holding area according to the shape of the formed part to perform blank-holding on the stamping sheet metal. It is characterized in that The distributed electromagnetic blank-holding die further includes: The same number of attracted plates as the blank-holder blocks, and the blank-holder blocks are fixed on the attracted plates; The same number of electromagnetic parts as the attracted plates, which are arranged in the punch or / and the die and are correspondingly distributed with the attracted plates; the electromagnetic parts are provided with temperature sensors for detecting the real-time temperature of the electromagnetic parts; the electromagnetic parts attract the attracted plates to make the attracted plates drive the blank-holder blocks to apply a blank-holding force to the blank-holding area. The distributed electromagnetic blank-holding die uses the electromagnetic-based distributed blank-holding optimization method described in any one of claims 1-8.

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