CN115952597A - Wear simulation method for sharp edge forming die of automobile fender - Google Patents

Abstract

The invention discloses a method for simulating abrasion of an automobile fender sharp edge forming die, which comprises the following steps of: s1, constructing a finite element model for forming sharp edges of a fender; s2, carrying out grid division on the die and the plate; s3, setting forming simulation conditions and starting simulation; s4, calculating and recording the abrasion loss; s5, determining whether grid degradation is carried out or not according to the wear result and the setting, and updating the forming simulation conditions after degradation; and S6, circulating S2-S5 until the abrasion setting condition is reached and ending the simulation. The method analyzes the workpiece forming process by means of an automatic form forming tool, obtains the position of each node and the contact pressure and speed required by the calculated abrasion in each forming step, utilizes an Archard abrasion calculation formula to compare and analyze the maximum abrasion amount obtained by calculation and the abrasion ridge definition failure evaluation index of the covering part mold, and when the accumulated abrasion amount reaches the failure evaluation index, the accumulated abrasion amount is the mold life value, so that the prediction of the mold life is realized.

Description

Wear simulation method for sharp edge forming die of automobile fender

Technical Field

The invention relates to a simulation method, in particular to a method for simulating abrasion of an automobile fender sharp edge forming die.

Background

With the rapid and vigorous development of new energy automobile industry in China and the rise of various new forces for vehicle construction, the traditional vehicle enterprises can turn to the electric vehicle market, so that the competition of the automobile industry is vigorous. In order to satisfy the market, the product quality is continuously improved, and the reduction of the production cost is one of the most important works of the current automobile enterprises. For passenger cars, the production cost mainly consists of research and development cost, equipment tooling cost, part purchasing cost, labor cost and other expenses, and the equipment tooling cost and the part purchasing cost account for the highest cost. The whole vehicle is often composed of tens of thousands of parts, more than 80% of the parts are metal thin plates, and the production and processing mode mainly adopts stamping forming, namely, a stamping die is needed for production and manufacturing. According to enterprise statistical data, a brand-new developed automobile model can be provided with thousands of stamping dies for producing metal sheet parts, and the design, manufacture, installation and debugging cost is about 2-3 million yuan.

In recent years, the motorization process of the automobile industry is accelerated, more and more automobile enterprises adopt the architectural design to gradually replace the traditional platform design and the modular design, and parts, especially metal sheet parts, shared by different automobile models derived based on the same architecture are increased. Generally, the service limit of a stamping die for producing sheet metal parts can maintain stable production is 50-60 ten thousand punching times. Because the framework shared part needs to meet the production work pieces of a plurality of vehicle types, the stamping die probably needs to produce millions of strokes within the life cycle of the vehicle type and is far beyond the limit service life under the normal working condition. In response to the over-life service of the stamping die, the prior method is to copy the stamping die before the service life limit is met, and the vehicle type development and manufacturing cost are high. Therefore, while the shared architecture is increased, the service limit and the working condition quality of the stamping die are continuously improved, the service life of the stamping die is prolonged, and the method is one of important ways for reducing the development and manufacturing cost of automobiles.

The quality of the stamping die mainly comprises three aspects of structural strength, machining precision and fatigue life, and the former two aspects are mainly determined by a die structure design scheme, machine tool machining precision, a machining process and a research and debugging method. In terms of fatigue life, many factors are determined, and the factors are influenced by factors such as mold material selection, mold structure layout, mold loading mode, stress distribution state and the like, and are also related to factors such as mold surface treatment method, lubricating conditions, periodic maintenance frequency, material strength of produced parts and the like.

In actual production, once the working part of the stamping die is subjected to plastic deformation, the surface roughness and the lubricating condition of the die are deteriorated, and excessive abrasion is caused in the stamping production process, the quality and the service life of the stamping die can be directly reduced, and even the stamping die is scrapped and fails. This, in turn, has the greatest effect on the service life of the stamping die as a result of wear. In the case of an outer cover having a sharp design language for the side lines of the vehicle body, the sharp edge forming mold is more worn due to the higher contact stress. Local abrasion of the sharp edge forming die can not only lead to the irreproducible sharp characteristic edge line, but also cause surface scratch of a stamping part, thereby being incapable of meeting the requirements of automobile production quality. According to research and development and manufacturing experience, a large amount of time and capital cost are required to be invested for designing, processing, installing and debugging the sharp edge forming die, and with the maturity of a finite element simulation technology, finite element simulation analysis is carried out on the die before the die is designed and manufactured to predict the forming of a plate and the abrasion state of the die, so that the method has important significance for reducing the manufacturing cost of the sharp edge forming die and shortening the design and manufacturing cycle of the die. At present, the research on sharp edge forming dies in the industry is mainly focused on steel plates, and the research on the abrasion of the sharp edge forming dies is relatively less for aluminum plate automobile covering parts designed by adopting double sharp edge shapes.

The automobile industry develops rapidly, competition is increasingly violent, cost is reduced on the premise of pursuing high quality, and the pursuit of the automobile industry is constant. In the development and manufacturing cost of automobiles, the cost of automobile molds can account for more than 30% of the development cost, and more than 90% of automobile parts are produced by molding the molds. A new vehicle type needs to develop thousands of molds, and the design and manufacturing cost is about 2 hundred million yuan generally. With the development direction of automobile platform, more and more enterprises consider how to increase the proportion of platform parts, increase the shared quantity of platform part molds and prolong the service life of the molds, so as to reduce the development cost of automobiles.

The quality of the die mainly comprises three aspects of the precision, the structural strength and the fatigue life of the die, and the first two aspects are mainly determined by structural design and machining. The determining factors of the service life are numerous, and the main points are the material, the structure, the local stress distribution state, the surface treatment, the operation, the maintenance and the like of the die.

The automobile stamping die is often scrapped due to the die failure caused by the factors of die plastic deformation, frictional wear and fatigue fracture, wherein the wear is particularly prominent, and for the outer covering part adopting a sharp design language for the side line of the automobile body, the sharp edge forming die is more severely worn due to higher contact stress. Local abrasion of the sharp edge forming die can not only lead to the irreproducible sharp characteristic edge line, but also cause surface scratch of a stamping part, thereby being incapable of meeting the requirements of automobile production quality. In the actual production and manufacturing process, the design and processing of the sharp edge forming die generally need higher time cost and capital cost investment, and with the maturity of a finite element simulation technology, the finite element simulation analysis is carried out on the die before the die is designed and manufactured to predict the forming of a plate and the abrasion state of the die, so that the method has important significance for reducing the manufacturing cost of the sharp edge forming die and shortening the die design and manufacturing and processing period.

At present, finite element analysis software is widely adopted in the industry to analyze the abrasion loss of a solid unit of a die so as to predict the service life of the die. However, the method has the disadvantages of low calculation speed, low calculation precision and high calculation cost, and is not beneficial to adjusting the forming parameters for many times, so that the die cannot be optimized in process or structure. In addition, the Archard theoretical wear model commonly used in finite element analysis ignores the influence of the wear process on the contact stress and the relative slip speed of the die, so that the prediction accuracy is not high.

The existing wear analysis of sharp edge forming dies generally adopts an experimental test method, and experimental data and a simulation model are combined for predicting and researching the wear of the sharp edge forming dies. Due to the fact that continuous structural changes exist in the abrasion process, the finite element model needs to be updated and iterated in real time, the grid of the model is subjected to subdivision operation to capture changes of contact pressure in structural analysis, the abrasion simulation process has extremely high requirements on software and hardware, meanwhile, a single analysis period is very long, and the method cannot be suitable for the requirement of rapid development of stamping dies in the automobile industry. Therefore, the traditional acute edge forming die abrasion simulation method based on the Archard abrasion model needs to be improved urgently.

Disclosure of Invention

Aiming at the problems described in the background art, the invention aims to provide a wear simulation method for an automobile fender sharp edge forming die, which can quickly and accurately predict the wear condition of the fender sharp edge forming die.

In order to achieve the aim, the invention designs a method for simulating the abrasion of an automobile fender sharp edge forming die, which comprises the following steps of:

s1, constructing a finite element model for forming sharp edges of a fender;

s2, carrying out grid division on the die and the plate;

s3, setting forming simulation conditions and starting simulation;

s4, calculating and recording the abrasion loss;

s5, determining whether grid degradation is carried out or not according to the wear result and the setting, and updating the forming simulation conditions after degradation;

and S6, circulating S2-S5 until the abrasion setting condition is reached and ending the simulation.

Preferably, in S1, the three-dimensional model of the stamping die is simplified, unnecessary structures are removed, only the working parts of the male die, the female die and the blank holder of the stamping die are reserved to obtain the simplified model, and the fender sharp edge forming finite element model is constructed based on the simplified model.

Further preferably, the simplifying the three-dimensional model of the press mold includes: the structure of the sharp edge testing trial-manufacturing die and the upper sliding block of the press are simplified, and broken surfaces need to be sewn and smoothened in a surface contact area.

Preferably, the Archard wear model is used to simulate and calculate the amount of wear.

Preferably, the wear process is simulated by using a finite element method: and dispersing the continuous wear area into a group of finite element unit assemblies which are connected with each other in a certain mode, performing mechanical analysis on each unit, and finally performing overall analysis.

Preferably, the amount of wear is evaluated by the depth of die wear.

Further preferably, the calculation formula of the wear depth is:

k is a wear coefficient, namely the probability of generating wear, and is obtained through tests; p is the normal stress of the contact surface, v is the relative slip velocity of the contact surface, dt is the slip time, and H is the hardness of the abraded material, namely the hardness of the die.

Still further preferably, the information of p and v is expressed by performing discretization analysis on the contact surface by a finite element method to obtain a discretization expression as follows:

in the formula, i represents a node position, and j represents an analysis step number; h is _i,j Showing the abrasion depth of the i node area after abrasion occurs at the j step in single stamping forming; k (i, j) represents the value of the wear coefficient corresponding to the Kd diagram under the conditions of contact pressure and hardness to which the i-node region is subjected at step j in a single press forming, H _i,j And the surface hardness value of the die at step j in the i node area in single stamping forming is shown.

The beneficial effects of the invention are: the method comprises the steps of analyzing a workpiece forming flow by means of an automatic form forming tool, obtaining the position of each node and the contact pressure and speed required by abrasion calculation in each forming step, compiling a die abrasion calculation subprogram by means of an Archard abrasion calculation formula and Python language, obtaining abrasion loss of a die after 5-ten-thousand, 50-ten-thousand and 80-ten-thousand punch forming, carrying out comparative analysis on the maximum abrasion loss obtained by calculation and an abrasion ridge definition failure evaluation index of a covering piece die, and obtaining a die service life value when the accumulated abrasion loss reaches the failure evaluation index, thereby realizing the prediction of the die service life.

The method can be used for rapidly and accurately predicting the abrasion condition of the fender sharp edge forming die, carrying out targeted surface strengthening treatment on the sharp edge forming die based on an abrasion simulation result, improving the abrasion resistance of the fender sharp edge forming die, and through mass production verification, the fender sharp edge forming die has no excessive abrasion, can meet the continuous production requirement, and saves the cost of repairing sharp edge lines and improving the surface hardness of the sharp edge forming die by more than 60 ten thousand yuan per vehicle type. The fender sharp edge forming die is used for continuous batch production, so that qualified parts without obvious cracking, wrinkling and large face product defects are obtained, the forming quality of two sharp edges is good, and the defect of slip lines is avoided.

After 80 ten thousand punching times of production of the fender sharp edge forming die, profile scanning is carried out on a male die of the sharp edge forming die, and the characteristic edge line and the abrasion condition of the profile are confirmed. Through comparison and analysis of the scanning data, the fact that the edge line and the molded surface abrasion loss of the fender sharp edge forming die are small is found, and the fact that the sharp edge forming die is subjected to targeted surface strengthening based on an abrasion simulation result is demonstrated, and the abrasion resistance of the sharp edge forming die can be improved.

Drawings

FIG. 1 is a finite element model of the present invention for forming sharp edges of a fender;

FIG. 2 is a pressure cloud chart of the contact surface of the sharp-edged fender forming simulation of the present invention;

FIG. 3 is a cloud chart of simulated tangential slip velocity for shaping sharp-edged fender according to the present invention;

FIG. 4 is an inventive logic block diagram;

FIG. 5 is a flowchart of the present invention for iterative wear calculation based on number of punches;

FIG. 6 shows the amount of wear of the die after 5 ten thousand stamping cycles in accordance with the present invention;

FIG. 7 shows the amount of die wear after 50 ten thousand strokes in accordance with the present invention;

fig. 8 shows the die wear after 80 ten thousand punches in accordance with the present invention.

In the figure: the device comprises a male die 1, a female die 2, a blank holder 3 and a plate 4.

Detailed Description

The invention will now be described in further detail, including the preferred embodiments, with reference to the accompanying drawings and by way of illustration of some alternative embodiments of the invention. It is to be understood that the described embodiments are merely a few embodiments of the invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without any inventive step, are within the scope of the present invention.

As shown in fig. 1 to 8, the method for simulating the abrasion of the sharp edge forming die of the automobile fender panel, which is provided by the invention, comprises the following steps:

s1, constructing a finite element model for forming sharp edges of a fender;

the finite element analysis of the stamping of automobile panels needs to consider various factors. The concrete expression is as follows: (1) the plate 4 is subjected to a large load in the stamping and forming process, usually between 100 kN and 1000kN, so that the material generates large plastic deformation, and the relative displacement between the material and the surface of a die changes along with the large plastic deformation, so that the traditional linear equation cannot accurately represent the complex change; (2) in the stamping and forming process of the plate, once the material is subjected to plastic deformation, the plate is difficult to recover to the initial state, which means that the plate does not change along with the change of time; (3) the contact stress between the stamping die and the sheet is a nonlinear stress, and the characterization of such nonlinear force is extremely complex.

The adopted stamping forming analysis software is Autoform, and the Autoform does not support modeling and drawing of a three-dimensional model. Therefore, the male die, the female die, the blank holder and other non-standard structures of the fender sharp edge forming die are required to be drawn, guided and finally assembled with the standard parts by using CAD software. The CAD software used in the invention is CATIA, the CATIA is used for completing the drawing of the 3D structure diagram of the fender sharp edge forming die, the drawing is converted into an IGS format file and is led into an Autoform R8 finite element simulation platform, and after the model is led in, the assembly relation among all parts of the stamping die is kept unchanged, namely, the 3D structure diagram model does not need to be adjusted in the Autoform software. The model in this embodiment is for modeling the fender mould and keeping its structural characteristics.

The model is simplified, unnecessary structures are removed, the simplified model is obtained, only the working parts of a male die, a female die and a blank holder of a stamping die are reserved, namely the male die 1, the female die 2 and the blank holder 3 are all reserved with the wall thickness of a casting of 60mm, the height of a main supporting rib at the periphery of a forming part and the height of a general reinforcing rib at the inner part are reserved with 120mm, all the other structures are removed, meanwhile, standard parts such as a material positioner, a guide plate, a balance block, a nitrogen spring and the like are required to be removed, and the guidance among all parts of the die is expressed in a friction pair mode. Simplifying the three-dimensional model of the stamping die includes: the structure of the sharp edge testing trial-manufacturing die and the upper sliding block of the press are simplified, and broken surfaces need to be sewn and smoothened in a surface contact area.

And (3) introducing the simplified model of the simplified acute fender drawing die into an Autoform software, dividing the sheet forming into two stages, namely a closing stage and a forming stage, and arranging female dies as active dies in the closing stage and the forming stage. The relative positions of a female die, a male die and a blank holder are set, the moving direction of the die is set to be a-Z direction movement in the closing stage, the male die and the blank holder are fixed, the friction factor between the die and a sheet is set to be 0.13, the working temperature is set to be the default normal-temperature environment temperature, the sheet is 6014-T2 aluminum alloy, the thickness of the sheet is 0.9mm, and the male die, the female die and the blank holder of the sharp edge forming die are all KSCD800I. The finished fender sharp edge forming finite element model is shown in fig. 1.

S2, carrying out grid division on the die and the plate;

and carrying out finite element mesh division on the simplified sharp edge test trial-manufacture die structure and the upper sliding block of the press.

S3, setting forming simulation conditions and starting simulation;

setting of a stamping process and simulation parameters:

and (3) introducing the analog simulation mould model into an Autoform software, dividing plate forming into two stages, namely a closing stage and a forming stage, and arranging female moulds as active moulds in the closing stage and the forming stage. The relative positions of the female die, the male die and the blank holder are set, the moving direction of the die is set to be-Z direction movement in the closing stage, the male die and the blank holder are fixed, the female die stops moving until the clearance between the female die and the blank holder is 0.9mm, the friction factor between the die and the plate is set to be 0.13, and the working temperature is set to be the default normal-temperature environment temperature.

The stamping speed of the die is generally determined by the requirements of a forming process and the capability of a press, and is generally set between 300 and 3000mm/s, and the stamping speed matched with the stamping speed is selected by combining the characteristics of the die, so that the service limit of the die can be effectively prolonged. The stamping speed is too high, so that the load borne by the die in the forming process is obviously changed, the forming quality of a plate is influenced, and the surface abrasion of the die is aggravated; if the stamping speed is too low, the production efficiency is low, and the single-piece stamping production cost is increased. The process conditions of a production workshop and the forming simulation experience of similar parts are comprehensively considered, the stamping speed of the fender sharp edge forming die in the no-load stage is set to be 1500mm/s, the stamping speed of the fender sharp edge forming die in the load stage is set to be 500mm/s, the movement direction of a female die is set to be-Z direction movement, the blank holder force of a blank holder is set to be 1200kN, the movement direction is + Z direction, and the blank holder movement stroke is 125mm.

The method has the advantages that the set step number in the stamping forming simulation process directly determines the efficiency of numerical simulation and the iterative computation process, and in order to improve the simulation efficiency, a dynamic display computation method which does not need to directly solve the tangential stiffness, does not need to carry out balanced iteration and has high computation speed is selected. For the press forming problem of automobile panels, a simulation method of controlling the stroke of a die is generally adopted, and the iteration step size takes 1/3 of the minimum cell size in a finite element model as a reference. When the control mode is time increment, the total time increment is calculated by taking the total stroke of the die as a calculation basis. The pressure between the plate and the working surface of the die is in a nonlinear relation in the deformation stage and is constantly changed in the whole stamping and forming process, so that the contact relation between the plate and the working surface of the die is complex, and the boundary relation between contact and friction cannot be accurately defined by taking time as a unit. Thereby indirectly increasing the workload of finite element analysis and invisibly increasing the complexity of numerical simulation. Therefore, the reasonable definition of the contact relation and the boundary condition is a precondition and a key element for ensuring the simulation accuracy of the stamping forming.

Defining contact relationships and boundary conditions:

the contact relation between the sheet and the die has certain complexity, which is mainly shown in that the pressure action of the sheet and the die is nonlinear in the deformation stage and is continuously changed in the stamping forming process, and the boundary relation of contact and friction cannot be defined by taking time as a unit, so that the calculation work and the complexity of finite element simulation are increased, and therefore, the reasonable definition of the contact relation and the boundary condition is one of the key elements for ensuring that a reliable and accurate analysis result can be obtained in the sheet stamping forming process.

In the stamping forming process of the automobile covering part, the contact form and the stress state between the plate and the die are complex, and among numerous contact forms, the surface-surface contact is the most important contact form, and other complex contact forms such as point-surface contact and line-surface contact are additionally arranged. The fender sharp edge forming die researched by the invention defines five contact surfaces, namely the upper surface of a plate, the lower surface of the plate, the outer surface of a male die, the outer surface of a female die and the outer surface of a blank holder according to the contact relationship between a stamping forming mechanism and the die motion. The contact relation is set as three groups, namely the contact between the upper surface of the plate and the outer surface of the female die, the contact between the lower surface of the plate and the outer surface of the male die, and the contact between the lower surface of the plate and the outer surface of the blank holder. And (4) setting the stamping simulation parameters in detail according to the contact form and the contact condition of the three contact relations. Where the coefficient of friction between the slab and the working surface of the die was set to 0.13. For the temperature setting, because the sharp-edged fender is formed in a cold stamping processing mode, the influence of the temperature change on the process parameters in the stamping forming process is small, and in order to improve the finite element analysis efficiency, the environment temperature is set to be a constant mode, namely, the heat transmission between the plate and the die does not need to be considered. Therefore, the working temperature at the time of press forming was set to 20 ℃ in combination with practical engineering experience.

After the parameters are set, the calculation is submitted to obtain a contact surface pressure cloud chart and a tangential slip speed cloud chart of the sharp-edged fender, as shown in fig. 2 and 3.

S4, calculating and recording the abrasion loss;

the difficulty in obtaining the wear depth of the contact surfaces is the acquisition of the stresses on the contact surfaces, for which purpose finite element methods are introduced to simulate the wear process. The continuous solving area of the research object is dispersed into a group of finite element unit assemblies which are connected with each other in a certain mode, each unit is subjected to mechanical analysis, and finally, the whole analysis is carried out. The surface state of the contact surface changes in the stamping abrasion, the abrasion loss is different, the die grid needs to be reprocessed by a grid dividing method, and the stress value on the contact point can be calculated for calculating the abrasion depth.

For the die wear research, the problems of calculation speed and precision are considered, and the contact surface node wear amount is calculated based on the auto form forming calculation and secondary development is carried out by using python language.

In the formula, dV is the material wear volume; dP is the normal load; dL is the relative slip length; h is the hardness of the abraded material, namely the hardness of the die. k is the wear coefficient, i.e. the probability of wear, obtained by experiment, generally in the range of 10 ^-3 ～10 ^-8 In the meantime. The wear coefficient is related to factors such as contact materials, lubrication conditions and working environment.

Three laws of wear can be derived from the above equation: the longer the friction stroke, the greater the wear loss; the larger the normal load borne by the contact surface is, the larger the abrasion loss is; the greater the surface hardness of the material to be abraded, the smaller the amount of abrasion.

The evaluation of the wear depth is actually more focused on the wear of the overlay part die, and dV in the above formula can be expressed as follows:

dV＝dh·dA

where dh is the wear depth and dA is the contact surface area. Then the user can use the device to make a visual display,

the dP and dL conversions in the above formula were then expressed as:

dP＝p·dA,dL＝v·dt

in the formula, p is the normal stress of the contact surface, v is the relative slip velocity of the contact surface, and dt is the slip time. After finishing:

in the formula, the information of p and v is obtained by carrying out discretization analysis on the contact surface by a finite element method, and the discretized expression is as follows:

in the formula, i represents a node position, and j represents an analysis step number; h is _i,j Showing the abrasion depth of the i-node area after abrasion occurs at the j step in single stamping forming; k (i, j) represents the value of the wear coefficient corresponding to the Kd diagram under the conditions of contact pressure and hardness to which the i-node region is subjected at step j in a single press forming, H _i,j And the surface hardness value of the die at step j in the i node area in single stamping forming is shown.

When the abrasion of the fender sharp edge forming die is calculated, autoform software and python language are needed, so that parallel simulation of sheet stamping forming and die abrasion, process condition setting, material library establishment, abrasion requirement setting and abrasion result reading are achieved.

S5, determining whether grid degradation is carried out or not according to the wear result and the setting, and updating the forming simulation conditions after degradation;

because the actual single-time punching abrasion loss of the covering part die is very small, the punching forming simulation and the die abrasion simulation can not be carried out again after grid degradation is carried out after the abrasion calculation is finished every time. The method includes the steps of simulating micro abrasion in the stamping process of a die, setting the number of grid degradation operations of the die abrasion in order to reduce calculation time and cost, performing the grid degradation operation once every time, and taking 5 ten thousand times as a default grid degradation operation span value in the embodiment. At that time, calculateAnd (4) obtaining a wear loss value h on each node, and performing degradation treatment on the grid model every 5 ten thousand times for a common outer covering piece mold in consideration of calculation time cost (the set value of the degradation treatment can be modified according to the actual part forming state and the forming stress state). In the iterative calculation process, the abrasion loss h is considered to be in a linear relation with the times between every 5 ten thousand times, so that the single abrasion loss h is amplified by 50000 times and is used as the abrasion loss h after 5 ten thousand stamping ₅₀₀₀₀ 。

And S6, circulating S2-S5 until the abrasion setting condition is reached and ending the simulation.

The abrasion loss h of 5 ten thousand times of stamping ₅₀₀₀₀ And corresponding node numbers are in one-to-one correspondence, and grid degradation operation is automatically carried out to obtain a model file after grid degradation. And under the condition that the information of the grid model file, the material, the working condition and the like is not changed, returning to the Autoform again to submit the stamping forming calculation, and obtaining a new round of stamping calculation result file. And performing abrasion calculation again, and obtaining the hardness value of each node in the period according to the abrasion quantity value of each node in the first round. The method is the same as the first wheel abrasion calculation method, and the contact pressure CPRESS, the speed V and the time interval delta T of each node of the mold model are obtained. And the abrasion amount of each node can be obtained by reintroducing the abrasion calculation formula.

The wear cloud charts of the die after stamping for 5 ten thousand, 50 ten thousand and 80 ten thousand are obtained by calculation, and are respectively shown in fig. 6, 7 and 8.

The invention mainly comprises the following steps: (1) And dividing the die grids and the plate grids, setting forming simulation conditions and forming simulation calculation in the Autoform. (2) The position of each node and the contact pressure and velocity required to calculate wear in each forming step are obtained. (3) And determining whether to perform grid degradation according to the wear result and the setting, and simultaneously completing the setting of the reshaping simulation condition to perform circular reshaping simulation calculation and wear calculation until the wear setting condition is reached, and outputting the result.

Simplifying a sharp edge testing trial-manufacturing die structure and a slide block on a press in CAD software, and sewing and smoothing broken surfaces in a surface contact area;

carrying out finite element mesh division on the simplified sharp edge test trial-manufacture die structure and the upper slide block of the press in CAD software, and setting constraints on a fixing area and a guiding area;

outputting the processed finite element model as an INP format file, and importing the file into CAE software;

setting corresponding boundary constraint conditions and loads in CAE software according to actual production conditions of the sharp edge test trial-manufacturing mold; and submitting solution calculation in CAE software to obtain the stress and strain borne by the sharp edge test trial-manufacture mould, and checking whether the stress exceeds the allowable fatigue strength or tensile strength of the mould material.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and any modification, combination, replacement, or improvement made within the spirit and principle of the present invention is included in the scope of the present invention.

Claims (9)

1. The method for simulating the abrasion of the sharp edge forming die of the automobile fender is characterized by comprising the following steps of:

s1, constructing a finite element model for forming sharp edges of a fender;

s2, carrying out grid division on the die and the plate;

s3, setting forming simulation conditions and starting simulation;

s4, calculating and recording the abrasion loss;

s5, determining whether grid degradation is carried out or not according to the wear result and the setting, and updating the forming simulation conditions after degradation;

and S6, circulating S2-S5 until the abrasion setting condition is reached and ending the simulation.

2. The method for simulating the abrasion of the sharp edge forming die of an automobile fender according to claim 1, wherein the method comprises the following steps: and S1, simplifying the three-dimensional model of the stamping die, removing unnecessary structures, only keeping the working parts of a male die, a female die and a blank holder of the stamping die to obtain a simplified model, and constructing a finite element model for the formation of the sharp edges of the fender based on the simplified model.

3. The method for simulating wear of a mold for forming sharp edges of wheel fender of an automobile according to claim 2, wherein: simplifying the three-dimensional model of the stamping die includes: the structure of the sharp edge testing trial-manufacturing die and the upper sliding block of the press are simplified, and broken surfaces need to be sewn and smoothened in a surface contact area.

4. The method for simulating the abrasion of the sharp edge forming die of an automobile fender according to claim 1, wherein the method comprises the following steps: and simulating and calculating the abrasion loss by using an Archard abrasion model.

5. The method for simulating the abrasion of the sharp edge forming die of the automobile fender according to claim 1 or 4, wherein the method comprises the following steps: simulating the abrasion process by adopting a finite element method: the continuous wear area is discretized into a group of finite element unit assemblies which are connected with each other in a certain mode, mechanical analysis is carried out on each unit, and finally, integral analysis is carried out.

6. The method for simulating the abrasion of the sharp edge forming die of the automobile fender according to claim 4, wherein the method comprises the following steps: the amount of wear was evaluated by the depth of die wear.

7. The method for simulating the abrasion of the sharp edge forming die of an automobile fender according to claim 5, wherein the method comprises the following steps: the amount of wear was evaluated by the depth of die wear.

8. The method for simulating the abrasion of the sharp edge forming die of the automobile fender according to claim 6 or 7, wherein: the wear depth is calculated as:

k is a wear coefficient, namely the probability of generating wear, and is obtained through tests; p is the normal stress of the contact surface, v is the relative slip velocity of the contact surface, dt is the slip time, and H is the hardness of the abraded material, namely the hardness of the die.

9. The method of simulating wear of an automobile fender sharp edge forming die of claim 8, wherein: p and v information discrete analysis is carried out on the contact surface by a finite element method to obtain a discrete expression as follows:

in the formula, i represents a node position, and j represents an analysis step number; h is _i,j Showing the abrasion depth of the i-node area after abrasion occurs at the j step in single stamping forming; k (i, j) represents the value of the wear coefficient corresponding to the Kd diagram under the conditions of contact pressure and hardness to which the i-node region is subjected at step j in a single press forming, H _i,j And the surface hardness value of the die at step j in the i node area in single stamping forming is shown.

Images