A simulation method suitable for large and complex hot stamping dies

Abstract

The present invention provides a simulation method suitable for large and complex hot stamping dies, including full-process simulation of hot stamping and simulation of service strength of hot stamping dies. The full-process simulation of hot stamping includes three stages: stamping stage, pressure-holding quenching, and die cooling. Implicit statics analysis is used to obtain the contact pressure existing on the contact surface between the slab and the die calculated at each stage, and the distribution field of each contact pressure is mapped to a pre-established die service strength model. The present invention can simulate the complete process of hot stamping and save production time for enterprises.

Description

Technical Field

[0001] The invention relates to the technical field of fire trucks, and mainly to a simulation method suitable for large and complex hot stamping dies. Background Art

[0002] Since the hot stamping process involves multiple coupling effects of heat, force, and phase, the existing simple simulation cannot adapt to the simulation of large and complex hot stamping dies. Therefore, if there is no professional software that can simulate the service conditions of large and complex hot stamping dies, it is impossible to perform a complete hot stamping simulation of large and complex hot stamping dies.

[0003] Then the manufacturer cannot determine whether there are any problems with the large and complex hot stamping mold during the hot stamping process. If a problem occurs in the actual production process of the large and complex hot stamping mold, resulting in failure of the stamped product without being discovered in time, it will increase the manufacturer's production cost, extend the production time, and delay the manufacturer's production schedule. Summary of the invention

[0004] The purpose of the present invention is to provide a simulation method suitable for large and complex hot stamping dies, which can simulate the complete process of hot stamping and save the production time of the enterprise.

[0005] To this end, a simulation method suitable for large and complex hot stamping dies is provided, including full-process hot stamping simulation and hot stamping die service strength simulation. The full-process hot stamping simulation includes three stages: stamping stage, pressure holding quenching, and die cooling. Implicit statics analysis is used to obtain the contact pressure existing on the contact surface between the slab and the die calculated in each stage, and the distribution field of each contact pressure is mapped to a pre-established die service strength model.

[0006] Furthermore, the simulation method of the stamping stage is: drawing models of the upper die, the lower die and the slab, approximating the upper die and the lower die as rigid bodies, extracting the surfaces of the upper die and the lower die excluding the horizontal projections of their respective cooling water channels as rigid shells, and defining the slab as a deformed entity;

[0007] Define the forming temperature of the slab and the friction coefficient of the contact surface, bind the punch and the edge holder in the "Tie" contact form, define the descent of the upper die in the form of segmented speed, and calculate the contact pressure between the slab and the die surface under the set holding pressure.

[0008] Furthermore, a positioning pin is provided between the upper die and the lower die. The positioning pin is fixed on the mutually facing surface of the upper die and the lower die and is embedded in the positioning hole of the slab to define the surface contact, so that the displacement of the slab meets the actual constraint conditions.

[0009] Furthermore, the models of the upper die and the lower die are drawn, the contact pressure between the die surface and the slab surface in the simulated stamping stage is imported, the holding pressure in the later stage of the stamping stage is applied to the end surfaces of the upper die and the lower die that are away from each other, and the positions of the upper die and the lower die are ensured to be consistent with the original positions before the holding pressure is applied, and the slab that has undergone the stamping stage is embedded in the gap between the upper die and the lower die for assembly.

[0010] The heat transfer coefficient between the slab and the mold, and the heat transfer between the slab and the mold surface are obtained according to the heat transfer outside the surface of the horizontal projection of the cooling water channel. The specific method for calculating the contact pressure is specifically the following steps S1 to S2:

[0011] Step S1: defining the heat transfer coefficient between the slab and the mold excluding the horizontal projection of the cooling water channel on the mold according to the transmission of contact pressure;

[0012] Step S2: define the heat transfer coefficient of the horizontal projection of the cooling water channel on the mold, couple the heat transfer coefficients of the cooling water channel on the mold and the projection of the non-cooling water channel on the mold, and obtain the heat transfer coefficient of the entire mold.

[0013] Furthermore, the step S1 is specifically as follows: when a contact surface with contact pressure is defined and the contact gap of the contact surface is zero, the heat transfer coefficient calculated by the contact pressure between the contact surface and the mold surface is used to replace the heat transfer coefficient when the contact gap is zero. The heat transfer coefficient corresponding to the contact pressure between the unit surface and the mold surface can be obtained by querying the relationship table between the heat transfer coefficient and the contact pressure. Except for the case where the contact gap is zero, the remaining heat transfer coefficients are all obtained by querying the relationship table between the heat transfer coefficient and the contact pressure.

[0014] Furthermore, step S2 is specifically as follows: the heat transfer coefficient of the horizontal projection of the cooling water channel on the mold is defined according to the heat transfer coefficients of the two end faces of the water inlet and the water outlet in the mold cooling water channel, and the heat transfer coefficient generated by the cooling water flow in the cooling water channel is obtained by simulation, that is, the cooling water flow rate distribution in the cooling water channel and the heat transfer coefficient of the inner wall of the cooling water channel are calculated, thereby obtaining the heat transfer coefficient of the horizontal projection of the cooling water channel on the mold.

[0015] Furthermore, the simulation of the die-out cooling stage is similar to that of the press-holding quenching stage. The activation state of the heat exchange definition between the slab and the mold is canceled, that is, only the heat transfer between the cooling water channel and the mold is considered. The simulation lasts for a set time. After the simulation of this stage is completed, the temperature field mapping of the final mold is transferred to the mold as the initial temperature condition for the next stamping stage. The next stamping stage completes the simulation of press-holding quenching and die-out cooling in sequence according to the initial temperature.

[0016] Furthermore, during the whole hot stamping simulation, three-dimensional unit grids are used for grid division to obtain the contact pressure and heat transfer coefficient of each contact surface respectively. The extracted contact pressure and heat transfer coefficient are coupled to serve as the heat transfer coefficient value of the next simulation stage.

[0017] Furthermore, the simulation method of the mold service strength also simulates the three stages of stamping, pressure holding quenching, and die cooling in the full simulation of hot stamping. First, the stamping simulation calculation is performed through explicit dynamics analysis to obtain the contact pressure distribution on the mold surface, and then the distribution field of the contact pressure is mapped to the mold service strength model for implicit statics analysis.

[0018] Furthermore, the stable temperature field in the pressure holding and quenching stage is coupled with the contact pressure of the mold surface in this stage, and then the transient thermal-mechanical coupling calculation is substituted into the mold service strength model corresponding to the pressure holding and quenching stage in the full hot stamping simulation to simulate the mold service strength; the stable temperature field in the demolding cooling stage is coupled with the contact pressure of the mold surface in this stage, and then the steady-state thermal-mechanical coupling calculation is substituted into the mold service strength model corresponding to the demolding cooling stage in the full hot stamping simulation to simulate the mold service strength.

[0019] Beneficial effects:

[0020] The present invention provides a simulation method suitable for large and complex hot stamping dies, including full-process hot stamping simulation and hot stamping die service strength simulation. The full-process hot stamping simulation includes three stages: stamping stage, pressure holding quenching, and die cooling. Implicit statics analysis is used to obtain the contact pressure existing on the contact surface between the slab and the die calculated in each stage, and the distribution field of each contact pressure is mapped to a pre-established die service strength model. The complete process of hot stamping can be simulated, saving the production time of the enterprise.

[0021] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented according to the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0023] Figure 1 It is a flowchart of the simulation method applicable to large and complex hot stamping dies of the present invention;

[0024] Figure 2 It is a schematic diagram of the relationship between the heat transfer coefficient and the contact gap of the present invention;

[0025] Figure 3 It is a schematic diagram of the relationship between the heat transfer coefficient and the contact pressure of the present invention;

[0026] Figure 4 It is a structural schematic diagram of the electronic device of the present invention;

[0027] Figure 5 It is a schematic structural diagram of the medium of the present invention.

[0028] Description of the accompanying drawings: 21 - processor; 22 - memory; 23 - storage space; 24 - program code; 31 - program code. DETAILED DESCRIPTION

[0029] The present invention is further described in conjunction with the following examples.

[0030] See Figure 1 The simulation method of this embodiment applicable to large and complex hot stamping dies (hereinafter referred to as dies, the dies include upper dies and lower dies) includes two parts: full hot stamping simulation and hot stamping die service strength simulation.

[0031] The whole process simulation of hot stamping includes three stages: stamping stage, holding pressure quenching, and die cooling. Among them, the stamping stage adopts dynamic explicit analysis (dynamic explicit analysis is an existing technology and will not be described here). During the stamping process of the slab, the contact pressure between the slab and the mold surface is calculated according to the deformed shape of the slab. Because the duration of the actual stamping process (for example, 0.4s) is extremely short, this process is approximated as a process that only considers the deformation of the slab, without considering the deformation of the mold and the change in temperature. During the holding pressure quenching process, a constant holding pressure is applied to the end faces of the upper and lower dies that are far away from each other. The shape of the slab between the upper and lower dies will not change much. There are cooling water channels in the middle of the upper and lower dies. The external water source continuously transmits cooling water to the cooling water channel to reduce the temperature of the upper and lower die surfaces. The slab exchanges heat by contacting the surfaces of the upper and lower dies. Therefore, during the pressure-holding quenching process, transient heat transfer analysis is used to calculate the temperature changes and distribution of the upper die, lower die and slab, so that the pressure-holding quenching process can be simulated (transient heat transfer analysis is a prior art and will not be described here). During the die-out cooling process, it is necessary to consider the idle time of the upper and lower dies between the slab being out of the die and the next slab entering the stamping stage. At this time, it is only necessary to consider the heat exchange between the upper die, lower die and the cooling water channels in the two, and transient heat transfer is used to calculate the temperature changes of the upper and lower dies.

[0032] The die service strength simulation corresponds to the three stages of stamping, pressure holding quenching, and die cooling in the full hot stamping simulation. The die service strength model is established in ABAQUS software in advance, and then implicit statics analysis is used to obtain the contact pressure between the slab and the die surface calculated in each stage of the full hot stamping simulation, and the distribution field of each contact pressure is mapped to the die service strength model (implicit statics analysis is a prior art and will not be described here).

[0033] The contact pressure of the die contact surface in the stamping stage is simulated by scanning ABAQUS software, and the spatial distribution analytical field of the contact pressure of the die contact surface is extracted. The analytical field is loaded as the pressure load amplitude in the die service strength model, and then the die service strength model in the stamping stage is obtained.

[0034] The relatively stable temperature field in the pressure-holding quenching stage is coupled with the contact pressure of the mold contact surface, wherein the temperature change and distribution become the temperature field, and then the mold service strength model of the mold in the pressure-holding quenching stage is obtained through transient thermal-mechanical coupling calculation (transient thermal-mechanical coupling calculation is a prior art and will not be described here); the stable temperature field in the demolding cooling stage is coupled with the mold surface contact pressure when the stamping stage is completed, and the mold service strength model of the mold in the demolding cooling stage is obtained through steady-state thermal-mechanical coupling calculation (steady-state thermal-mechanical coupling calculation is a prior art and will not be described here).

[0035] In this embodiment, the die service strength model is established through ABAQUS software, and then the temperature field and the contact pressure of the die surface are coupled for the three stages of the hot stamping full simulation, namely the stamping stage, pressure holding quenching, and die cooling, to improve the die service strength model, thereby realizing the service status of large and complex hot stamping dies.

[0036] The specific hot stamping full-process simulation method cycle executes the following steps (i) to (iii):

[0037] (I) Simulation of stamping stage

[0038] After drawing the UG models of the upper die, lower die and slab, they were imported into the ABAQUS software in CATIA format. After scaling, the model size unit was unified to m. Then, the upper die and lower die were approximated as rigid bodies, and the surfaces of the upper die and lower die except the horizontal projection of their respective cooling water channels were extracted as rigid shells. The slab was defined as a deformed entity.

[0039] According to the field data, the slab forming temperature is defined as 750℃. According to the material properties of the slab at this temperature, the friction coefficient of the contact surface is defined as 0.5. The definition of the friction coefficient can truly simulate the stamping process between the upper die and the lower die, and can accurately obtain the contact pressure between the die and the slab. The lower die is constrained to be completely fixed, and the punch and the edge clamping part are defined as "Tie" contact form and the upper die descent is defined in the form of segmented speed. The positioning pin set between the upper die and the lower die is simplified to a cylindrical shell. The positioning pin is fixed on the side of the upper die and the lower die facing each other. The positioning pin and the positioning hole of the slab are defined in surface contact, so that the displacement of the slab meets the actual constraint conditions. In actual production, the speed segmentation of the upper die stamping is shown in Table 2-1 below.

[0040] Table 2-1 Speed ​​segment table

[0041]

[0042]

[0043] In order to save calculation time, in actual calculation, it is necessary to remove the time of the upper mold itself descending (for example, the descending time is 0.6s, and the descending position is 0.48m). Then the timing needs to start from the actual 0.6s position (descending 0.48m), and calculate the contact pressure between the slab and the mold surface under the holding pressure of 5500KN.

[0044] Since the calculation focus area is concentrated on the contact position between the mold surface and the slab, the grid in these key areas needs to be adjusted to be finer than the grid in other positions (for example, the grid size is 3mm). The grid at the key position is adjusted to be finer, and the grid at other less concerned positions is adjusted to be wider. This can shorten the calculation time of the contact pressure between the slab and the mold surface.

[0045] The slab surface and the mold surface are both defined and displayed using a grid, and the contact pressure of the surfaces of the upper and lower molds excluding the horizontal projections of their respective cooling water channels is greater than the contact pressure of the surfaces of the horizontal projections of their cooling water channels.

[0046] (II) Simulation of pressure holding quenching stage

[0047] The UG models of the upper die and the lower die are imported into ABAQUS in CATIA format, and the contact pressure between the die surface and the blank surface in the simulation stamping stage is imported in the form of PART.

[0048] The upper die, lower die and slab are all set as deformed entities. The holding pressure in the late stamping stage is applied to the end faces of the upper die and lower die that are far away from each other, and the positions of the upper die and lower die are adjusted so that the upper die and lower die are kept in the same original position when no holding pressure is applied. The slab that has undergone the stamping stage is embedded in the gap between the upper die and lower die for assembly. The initial temperature of the mold is set to 25°C, the cooling water temperature in the cooling water channel is set to be constant at 8°C, and the initial temperature of the slab is set to 750°C.

[0049] In the heat transfer analysis of the pressure-holding quenching stage, the focus is on the heat transfer of the horizontal projection surface of the cooling water channel to obtain the heat transfer coefficient between the slab and the mold, and the heat transfer between the slab and the mold surface. However, the shapes of these two positions are relatively complex, so it is difficult to obtain their respective heat transfer conditions. Therefore, during the simulation, the area where the mesh is refined needs to be set to the position corresponding to the surface of the horizontal projection of the cooling water channel on the mold surface, and the slab mesh remains consistent with the previous stage. While ensuring that the calculation can converge, the mesh of the mold surface outside the horizontal projection surface of the cooling water channel is enlarged as much as possible to increase the speed of calculating the contact pressure.

[0050] The specific method for calculating the contact pressure is specifically the following steps S1 to S2:

[0051] Step S1: defining the heat transfer coefficient between the slab and the mold according to the transmission of contact pressure;

[0052] Specifically, the slab and the mold are defined as surface-to-surface contact. The ABAQUS software has built-in definitions of heat transfer coefficients related to contact gap, contact pressure, and both. However, in heat transfer analysis, it is impossible to directly obtain or define the contact pressure between contact surfaces. Therefore, calculations can only be performed using the definition of heat transfer coefficients related to contact gap. The relationship between heat transfer coefficient and contact gap is gradually reduced. For details, see Figure 2 The relationship table of heat transfer coefficient and contact pressure (i.e. Figure 3 The contact pressure in the relationship is gradually increased. Figure 3 Relationship table.

[0053] Generally speaking, the heat transfer coefficient is obtained by looking up the relationship table between the heat transfer coefficient and the contact gap. However, when the contact gap is zero, the heat transfer coefficient corresponding to the relationship table between the heat transfer coefficient and the contact gap is unstable and inaccurate. Therefore, directly using the heat transfer coefficient in the relationship table between the heat transfer coefficient and the contact gap will cause deviations in the simulation results.

[0054] To this end, when a unit surface with contact pressure is defined and the contact gap is zero, the heat transfer coefficient calculated by the contact pressure (or contact pressure) between the unit surface and the mold surface is used to replace the heat transfer coefficient when the contact gap is zero. The heat transfer coefficient corresponding to the contact pressure (or contact pressure) between the unit surface and the mold surface can be obtained by querying the relationship table between the heat transfer coefficient and the contact pressure. Except for the case where the contact gap is zero, the remaining heat transfer coefficients are obtained by querying the relationship table between the heat transfer coefficient and the contact pressure.

[0055] Since there are a huge number of unit surfaces on the surface of the slab, even up to tens of thousands, it is obviously unreasonable to input them by manpower. Therefore, secondary development through Python programming is required for batch processing.

[0056] The specific Python programming process is as follows: first, use ABAQUS software to output the contact pressure results of the slab surface in the upper stamping stage. The default output format of ABAQUS software is TXT file. TXT file is not convenient for data extraction and processing. Therefore, the data are pre-processed by writing Python program in conjunction with Excel software.

[0057] Then, by extracting the unit label, unit face label, and contact pressure of each node of the unit face, the average contact pressure of each node of the unit face is taken as the average contact pressure of the unit face. When the average contact pressure of the unit is greater than zero, the heat transfer coefficient with a contact gap of zero is replaced by the heat transfer coefficient calculated by the contact pressure (or contact pressure) between the unit face and the mold surface; in other cases, the heat transfer coefficient corresponding to the relationship table of the heat transfer coefficient and the contact gap is defined. In order to make the calculation feasible and improve the calculation efficiency, the relationship between the contact pressure and the heat transfer coefficient is divided into several linear regions according to the reference data, and the contact pressure intervals of these regions are divided into several small contact pressure domains, and the average contact heat transfer coefficient calculated values ​​of these small domains are used as the calculated contact heat transfer values ​​of these small domains. That is, when the calculated value of the unit heat transfer coefficient falls within a certain contact pressure domain, its heat transfer coefficient calculated value uses the average contact heat transfer coefficient of the domain.

[0058] According to this logic, an ABAQUS operation Python file is generated to define all unit surfaces of the slab. Finally, the file is run in the ABAQUS software to complete the definition of the contact between the slab and the mold.

[0059] Step S2: Definition of heat transfer coefficient between cooling water and mold

[0060] The heat exchange between the cooling water and the mold is defined by the heat transfer coefficient of the two end faces of the water inlet and the water outlet in the cooling water channel of the mold. In order to obtain a more realistic heat transfer coefficient of the cooling water channel at the horizontal projection of the mold, the heat transfer coefficient generated by the flow of cooling water in the cooling water channel is obtained by CFD software simulation, that is, the cooling water flow rate distribution in the cooling water channel and the heat transfer coefficient of the inner wall of the cooling water channel are calculated. Due to the huge amount of calculation, the influence of the flow rate of cooling water in the cooling water channel on the heat transfer coefficient is not considered in the existing simulation. However, this embodiment simplifies the simulation method of the flow rate of cooling water in the cooling water channel, thereby facilitating the influence of the flow rate of cooling water in the cooling water channel on the heat transfer coefficient.

[0061] The three-dimensional model of the cooling water channel is imported into the CFD software for meshing. The meshes at the bends in the cooling water channel are denser, and the meshes at the straight channels are wider. After the cooling water channel is divided into multiple grids, these grids are imported in the form of ".cas" files that can be recognized by Fluent software to perform flow field calculations (flow field calculations are existing technologies and will not be described in detail here).

[0062] In actual production, the outlet water temperature of the cooling water pump is about 8°C, the pump pressure of the cooling water pump is 8 bar, and the cooling water pump is used to supply cooling water to the cooling water channel. Assuming that the initial temperature of the cooling water channel is set to 8°C, the boundaries of the water inlet and outlet of the cooling water channel are defined as pressure boundaries, and the water pressure difference between the water inlet and outlet of the cooling water channel is fixed to 0.8MPa, and the initial temperature of the cooling water channel, the pump pressure of the cooling water pump, and the water pressure difference between the water inlet and outlet of the cooling water channel are substituted into the ke turbulence model. The three data of the initial temperature of the cooling water channel, the pump pressure of the cooling water pump, and the water pressure difference between the water inlet and outlet of the cooling water channel are solved in a steady state by the simple algorithm, and the energy equation is opened to calculate the flow velocity field distribution of the cooling water channel in a steady state, and then the heat transfer coefficient of the inner wall of the cooling water channel is obtained.

[0063] According to the calculated flow velocity field results, the flow velocities in different areas of the cooling water channel are significantly different. Among them, the flow velocity distribution of the cooling water channel in the upper mold is relatively uniform, while the flow velocity difference between each area of ​​the cooling water channel in the lower mold is slightly larger. Such flow velocity differences may be caused by the similar water pressure difference between the water inlet and outlet of each cooling water channel, and the uneven length distribution of each cooling water channel, which causes the problem of obvious differences in flow velocity in different areas of the cooling water channel.

[0064] Based on the above principle, the existing simulation method that directly assumes that the flow rate of each water channel is equal during the pressure holding quenching stage is unreasonable. Therefore, when setting the heat transfer coefficient between the two end faces of the water inlet and outlet in the cooling water channel in ABAQUS software, the cooling water channel is first divided into multiple grids in CFD, and the heat transfer coefficient of each grid is calculated, and the heat transfer coefficient of each grid is output to Fluent. Fluent outputs the heat transfer coefficient of each unit according to the spatial coordinate position and converts it into a format that can be used by ABAQUS software. After that, the heat transfer coefficient of each unit is output to ABAQUS software to construct scanning data points to obtain the analytical field of the heat transfer coefficient of the inner wall of the cooling water channel. Finally, the interface contact definition is used to map the analytical field of the heat transfer coefficient of the inner wall of the cooling water channel to the end faces of the cooling water channels of the upper and lower molds to complete the coupling.

[0065] (III) Simulation of mold cooling stage

[0066] The simulation of this stage is similar to that of the pressure holding and quenching stage. The activation state of the heat exchange definition between the slab and the mold is canceled, that is, only the heat transfer between the cooling water channel and the mold is considered, and the simulation duration is 10s. After the simulation of this stage is completed, the result of the temperature field of the final mold is directly transferred to each part of the mold through the internal mapping of ABAQUS as the initial temperature condition of the next stamping stage. The next stamping stage will complete the simulation of pressure holding and quenching and mold cooling in sequence according to the initial temperature.

[0067] The specific simulation method of mold service strength is as follows:

[0068] The simulation method of the mold service strength is also to simulate the three stages of stamping, pressure holding quenching, and die cooling in the full simulation of hot stamping. First, the stamping simulation is calculated through explicit dynamics analysis to obtain the contact pressure distribution on the mold surface, and then the distribution field of the contact pressure is mapped to the mold service strength model for implicit static analysis.

[0069] In order to facilitate the transmission of contact pressure and temperature field, an approximate three-dimensional unit grid is used for meshing in the die service strength model. The contact pressure of the die contact surface in the stamping stage of the hot stamping simulation is scanned in ABAQUS software, and the spatial distribution analytical field of the contact pressure of the die contact surface is extracted, and the analytical field is loaded as the pressure load amplitude in the die service strength model.

[0070] The stable temperature field in the pressure holding and quenching stage is coupled with the contact pressure of the mold surface in this stage, and then the transient thermal-mechanical coupling calculation is substituted into the mold service strength model corresponding to the pressure holding and quenching stage in the full hot stamping simulation to simulate the mold service strength; the stable temperature field in the demolding cooling stage is coupled with the contact pressure of the mold surface in this stage, and then the steady-state thermal-mechanical coupling calculation is substituted into the mold service strength model corresponding to the demolding cooling stage in the full hot stamping simulation to simulate the mold service strength.

[0071] It should be noted that:

[0072] The method used in this embodiment can be converted into program steps and devices that can be stored in a computer storage medium, and implemented by being called and executed by the processor 21.

[0073] The algorithms and displays provided herein are not inherently related to any particular computer, virtual device, or other apparatus. The descriptions made in specific language are intended to disclose the best mode of carrying out the present invention.

[0074] In the description provided herein, a large number of specific details are described. However, it is understood that embodiments of the present invention can be practiced without these specific details. In some instances, well-known methods, structures and techniques are not shown in detail so as not to obscure the understanding of this description.

[0075] Similarly, it should be understood that in order to streamline the disclosure and aid in understanding one or more of the various inventive aspects, in the above description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together into a single embodiment, figure, or description thereof. However, this disclosed method should not be interpreted as reflecting the intention that the claimed invention requires more features than those expressly recited in each claim. Rather, as reflected in the claims, inventive aspects lie in less than all of the features of the individual embodiments previously disclosed. Therefore, the claims that follow the detailed description are hereby expressly incorporated into the detailed description, with each claim itself serving as a separate embodiment of the invention.

[0076] Those skilled in the art will appreciate that the modules in the devices in the embodiments can be adaptively changed and set in one or more devices different from the embodiments. The modules or units or components in the embodiments can be combined into one module or unit or component, and in addition they can be divided into multiple submodules or subunits or subcomponents. Except that at least some of such features and / or processes or units are mutually exclusive, all features disclosed in this specification (including the accompanying claims, abstracts and drawings) and all processes or units of any method or device disclosed in this manner can be combined in any combination. Unless otherwise explicitly stated, each feature disclosed in this specification (including the accompanying claims, abstracts and drawings) can be replaced by an alternative feature that provides the same, equivalent or similar purpose.

[0077] Furthermore, those skilled in the art will appreciate that although some embodiments described herein include certain features included in other embodiments but not other features, the combination of features from different embodiments is meant to be within the scope of the present invention and to form different embodiments.

[0078] The various component embodiments of the present invention may be implemented in hardware, or in software modules running on one or more processors, or in a combination thereof. It should be understood by those skilled in the art that a microprocessor or a digital signal processor (DSP) may be used in practice to implement some or all of the functions of some or all of the components in the device for detecting the wearing state of an electronic device according to an embodiment of the present invention. The present invention may also be implemented as a device or device program (e.g., a computer program and a computer program product) for executing part or all of the methods described herein. Such a program for implementing the present invention may be stored on a computer-readable medium, or may be in the form of one or more signals. Such a signal may be downloaded from an Internet website, or provided on a carrier signal, or provided in any other form.

[0079] For example, Figure 4A schematic diagram of the structure of an electronic device according to an embodiment of the present invention is shown. The electronic device conventionally includes a processor 21 and a memory 22 arranged to store computer executable instructions (program code). The memory 22 can be an electronic memory such as a flash memory, an EEPROM (electrically erasable programmable read-only memory), an EPROM, a hard disk or a ROM. The memory 22 has a storage space 23 for storing a program code 24 for executing any method steps in the embodiment. For example, the storage space 23 for program code may include individual program codes 24 for implementing various steps in the above method, respectively. These program codes can be read from or written to one or more computer program products. These computer program products include program code carriers such as a hard disk, a compact disk (CD), a memory card or a floppy disk. Such a computer program product is typically, for example Figure 5 The medium may have Figure 4 The memory 22 in the electronic device of the present invention is similarly arranged as a storage segment, storage space, etc. The program code can be compressed, for example, in an appropriate form. Generally, the storage unit stores program code 31 for executing the steps of the method according to the present invention, that is, program code that can be read by a processor such as 21, and when these program codes are run by the electronic device, the electronic device performs the various steps in the method described above.

[0080] It should be noted that the above embodiments illustrate the present invention rather than limit it, and that those skilled in the art may devise alternative embodiments without departing from the scope of the appended claims. In the claims, any reference symbol between brackets shall not be construed as a limitation on the claims. The word "comprising" does not exclude the presence of elements or steps not listed in the claims. The word "one" or "an" preceding an element does not exclude the presence of a plurality of such elements. The present invention may be implemented by means of hardware comprising a number of different elements and by means of a suitably programmed computer. In a unit claim enumerating a number of devices, several of these devices may be embodied by the same hardware item. The use of the words first, second, and third, etc., does not indicate any order. These words may be interpreted as names.

Claims

1. A simulation method suitable for large and complex hot stamping dies, characterized in that: It includes full-process simulation of hot stamping and simulation of service strength of hot stamping die. The full-process simulation of hot stamping includes three stages: stamping stage, pressure holding quenching, and die cooling. Implicit statics analysis is used to obtain the contact pressure existing on the contact surface between the slab and the die calculated at each stage, and the distribution field of each contact pressure is mapped to the pre-established die service strength model. The simulation method of the stamping stage is as follows: draw models of the upper die, the lower die and the slab, approximate the upper die and the lower die as rigid bodies, extract the surfaces of the upper die and the lower die except the horizontal projections of their respective cooling water channels as rigid shells, define the slab as a deformed entity; define the forming temperature of the slab and the friction coefficient of the contact surface, bind the punch and the edge holding part in the "Tie" contact form, define the descent of the upper die in the form of segmented speed, and calculate the contact pressure between the slab and the die surface under the set holding pressure; Draw the models of the upper die and the lower die, import the contact pressure between the die profile and the slab surface in the simulated stamping stage, apply the holding pressure in the later stage of the stamping stage to the end faces of the upper die and the lower die that are away from each other, and ensure that the positions of the upper die and the lower die are consistent with the original positions before the holding pressure is applied, and insert the slab that has undergone the stamping stage into the gap between the upper die and the lower die for assembly. According to the heat exchange outside the surface of the horizontal projection of the cooling water channel, the heat exchange coefficient between the slab and the die, as well as the heat exchange between the slab and the die profile, are obtained. The specific method for calculating the contact pressure is specifically the following steps S1 to S2: Step S1: defining the heat transfer coefficient between the slab and the mold excluding the horizontal projection of the cooling water channel on the mold according to the transmission of contact pressure; Step S2: define the heat transfer coefficient of the horizontal projection of the cooling water channel on the mold, couple the heat transfer coefficients of the cooling water channel on the mold and the projection of the non-cooling water channel on the mold, and obtain the heat transfer coefficient of the entire mold.

2. The simulation method for large and complex hot stamping dies according to claim 1, characterized in that: A positioning pin is arranged between the upper die and the lower die. The positioning pin is fixed on the mutually facing surface of the upper die and the lower die and is embedded in the positioning hole of the slab to define the surface contact so that the displacement of the slab meets the actual constraint conditions.

3. The simulation method for large and complex hot stamping dies according to claim 1, characterized in that: Specifically, step S1 is as follows: when a contact surface with contact pressure is defined and the contact gap of the contact surface is zero, the heat transfer coefficient calculated by the contact pressure between the contact surface and the mold surface is used to replace the heat transfer coefficient when the contact gap is zero. The heat transfer coefficient corresponding to the contact pressure between the unit surface and the mold surface can be obtained by querying the relationship table between the heat transfer coefficient and the contact pressure. Except for the case where the contact gap is zero, the remaining heat transfer coefficients are obtained by querying the relationship table between the heat transfer coefficient and the contact pressure.

4. The simulation method for large and complex hot stamping dies according to claim 1, characterized in that: The specific step S2 is as follows: the heat transfer coefficient of the horizontal projection of the cooling water channel on the mold is defined according to the heat transfer coefficients of the two end faces of the water inlet and the water outlet in the mold cooling water channel, and the heat transfer coefficient generated by the cooling water flow in the cooling water channel is obtained by simulation, that is, the cooling water flow rate distribution in the cooling water channel and the heat transfer coefficient of the inner wall of the cooling water channel are calculated, thereby obtaining the heat transfer coefficient of the horizontal projection of the cooling water channel on the mold.

5. The simulation method for large and complex hot stamping dies according to claim 1, characterized in that: The simulation of the die-out cooling stage is similar to that of the pressure-holding quenching stage. The activation state of the heat exchange definition between the slab and the mold is canceled, that is, only the heat transfer between the cooling water channel and the mold is considered. The simulation lasts for a set time. After the simulation of this stage is completed, the temperature field mapping of the final mold is transferred to the mold as the initial temperature condition for the next stamping stage. The next stamping stage completes the simulation of pressure-holding quenching and die-out cooling in sequence according to the initial temperature.

6. The simulation method for large and complex hot stamping dies according to any one of claims 1 to 5, characterized in that: During the entire hot stamping simulation, three-dimensional unit grids are used for grid division to obtain the contact pressure and heat transfer coefficient of each contact surface. The extracted contact pressure and heat transfer coefficient are coupled to serve as the heat transfer coefficient value for the next simulation stage.

7. The simulation method for large and complex hot stamping dies according to claim 6, characterized in that: The simulation method of the mold service strength also simulates the three stages of stamping, pressure holding quenching, and die cooling in the full simulation of hot stamping. First, the stamping simulation calculation is performed through explicit dynamics analysis to obtain the contact pressure distribution on the mold surface, and then the distribution field of the contact pressure is mapped to the mold service strength model for implicit statics analysis.

8. The simulation method for large and complex hot stamping dies according to claim 7, characterized in that: The stable temperature field in the holding and quenching stage is coupled with the contact pressure of the mold surface in this stage, and then the transient thermal-mechanical coupling calculation is substituted into the mold service strength model corresponding to the holding and quenching stage in the full hot stamping simulation to simulate the mold service strength; The stable temperature field in the demolding cooling stage is coupled with the contact pressure of the mold surface in this stage, and then the steady-state thermal-mechanical coupling calculation is substituted into the mold service strength model to simulate the mold service strength in the demolding cooling stage in the full hot stamping simulation.

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