Multi-process hot forging simulation system for automobile diesel engine fuel rail

Abstract

The multi-step hot forging simulation system of the fuel rail of the automobile diesel engine of the present application establishes a finite element simulation model of the multi-step forging process of the high-pressure fuel rail parts, analyzes the parameter requirements of the finite element numerical simulation FORGE of the screw press, and obtains general conclusions for important characteristic factors including initial energy, machine tool stiffness, and efficiency; based on the research conclusions of the forging machine tool and the software template, the finite element simulation of the rough machining and finishing forging process of the high-pressure fuel rail in the high-pressure common rail fuel system of the diesel engine is realized. It helps to predict the final state, performance and quality of the material under the actual processing environment, so as to achieve the ultimate goal of optimizing the design of plastic forming. It can provide a reference for actual production, and plays an important role in reducing the production cost of the fuel rail, improving product quality, optimizing process design, and improving production efficiency. It helps to improve the stability, reliability, safety and dynamic performance of the fuel rail.

Description

Technical Field

[0001] The present application relates to a diesel engine fuel rail hot forging simulation system, and in particular to a multi-process hot forging simulation system for a fuel rail of an automobile diesel engine, and belongs to the technical field of diesel engine fuel rail simulation. Background Art

[0002] After years of technological development and transformation, the forging industry has made great progress in process design, forging technology, heat treatment technology and product testing. Forging can effectively improve the internal structure of metals and improve the mechanical and physical properties of the technology. Therefore, forging is generally used to process important mechanical parts with high stress and high requirements, such as internal combustion engine crankshafts, connecting rods, bearings, diesel engine high-pressure fuel rails, etc.

[0003] The original diesel engine used a mechanical oil pump, which relied on the plunger to build pressure, and the fuel supply pressure changed with the engine speed. At low speeds, the injection pressure was low, the diesel atomization was poor, the combustion efficiency was low, and the pollution was serious. It was not until the high-pressure common rail fuel system was applied to automotive diesel engines that the fuel supply pressure was independent of the engine speed or the fuel injection process, thereby improving the mechanical and economic performance of the diesel engine. As one of the core components of the system, the high-pressure fuel rail is often manufactured using a forging process due to its complex structural shape, which not only improves production efficiency, but also ensures that the parts have sufficient mechanical properties under complex working conditions. However, due to the complex structural shape of the high-pressure fuel rail, some defects (such as cavities, wrinkles, etc.) are easily generated during the hot forging process, and its surface quality and precision are difficult to control, which in turn leads to increased production costs and reduced production efficiency.

[0004] With the continuous development of computer technology and the deepening of plasticity theory, the research method of material plastic forming process has also changed to scientific informationization. Numerical simulation technology represented by finite element has been widely used in the plastic forming process of materials. Finite element software such as FORGE and DEFORM can be used to simulate the dynamic process of material plastic forming. By controlling various environmental parameters such as temperature, pressure, friction coefficient, thermal conductivity coefficient, etc., the final state, performance and quality of the material under the actual processing environment can be predicted to achieve the ultimate goal of optimizing the design of plastic forming. The results of finite element simulation analysis can provide reference for actual production, and have important reference significance for reducing production costs, improving product quality, optimizing process design, and improving production efficiency.

[0005] The problems that need to be solved in the existing diesel engine fuel rail hot forging simulation and the key technical difficulties of this application include:

[0006] (1) Due to the complex structure and appearance of the high-pressure fuel rail, some defects (such as voids, wrinkles, etc.) are easily generated during the hot forging process, and its surface quality and precision are difficult to control, which in turn leads to increased production costs and reduced production efficiency. As one of the core components of the high-pressure common rail fuel system, the high-pressure fuel rail is manufactured using hot forging processing technology in industrial production, and the forging machinery mostly uses a screw press. In the simulation design of the high-pressure fuel rail by SETFORGE, due to the lack of previous understanding of the working characteristics of the screw press template and the experience of simulating the forging process based on this type of machine tool, in the actual design process, the model of the mechanical press is often used to simulate the forging process of the forging. As a result, there is a certain error in the simulation results compared with the actual finished product. The prior art lacks research on the template features of the screw press in the FORGE software, and is unable to determine the influence of various parameters in the template on the simulation results. It is unable to simulate the multi-step forging process of manufacturing high-pressure fuel rails by a screw press, resulting in insufficient knowledge and understanding of the simulation of the hot forging process using a screw press, a lack of simulation methods for the forging process of parts with different forging equipment, and a lack of technical support for the finite element simulation process of forging equipment or similar forgings.

[0007] (2) High-pressure fuel rail is an indispensable part of the high-pressure common rail fuel system of diesel engines. Hot forging technology is mostly used in industrial production. However, there are also surface quality defects such as voids and wrinkles in the hot forging process, which leads to increased production costs and low efficiency, affecting the economic benefits of the design unit. The existing technology is unable to perform numerical simulation of the hot forging forming process of high-pressure fuel rail forgings in different forging steps, unable to analyze the influence of different parameters on the surface quality and contour accuracy of forgings, and unable to derive a general method suitable for simulating the hot forging parts of such forging machines based on the obtained results; there is a lack of a finite element simulation model for the multi-step forging process of high-pressure fuel rail parts, and it is impossible to analyze the working characteristics of such forging machines based on the parameter requirements of the finite element numerical simulation FORGE of the screw press, and there is a lack of general conclusions on important characteristic factors including initial energy, machine tool stiffness, and efficiency; there is a lack of research conclusions based on forging machines and software templates, and it is impossible to perform finite element simulation of the rough machining and finishing forging processes of the high-pressure fuel rail in the high-pressure common rail fuel system of diesel engines, resulting in poor accuracy and reliability of diesel engine fuel rail simulation, which is not conducive to the improvement and enhancement of diesel engine fuel rail hot forging technology.

[0008] (3) The existing finite element simulation of the diesel engine fuel rail forging process is more based on the use of mechanical presses as forging mechanical templates, which has large errors. First, it is impossible to analyze the characteristic factors of the screw press, and it is impossible to analyze the characteristics of the screw press simulation template formed based on the numerical simulation FORGE, and the conclusions obtained are not applied to the hot forging of high-pressure fuel rails; second, it is impossible to simulate the hot forging process of high-pressure fuel rail parts in multiple steps, and it is impossible to analyze the influence of different variable parameters on the simulation results, and it is impossible to obtain the use conditions of each parameter when the simulation results are closest to the actual parts; third, it is impossible to combine the three stations of rough machining, fine machining, and deburring of the screw press machine tool, and optimize and adjust the simulation plan in combination with the actual production situation, and it is impossible to establish a synchronous simulation of the two steps of rough machining and fine machining, and it is impossible to obtain the conditions of each parameter under the optimal simulation results. It is not possible to predict the final state, performance and quality of the material under the actual processing environment by controlling various environmental parameters such as temperature, pressure, friction coefficient, thermal conductivity coefficient, etc., and it is impossible to optimize the design of plastic forming. It is difficult to provide a reference for actual production, which is not conducive to reducing the production cost, improving product quality, optimizing process design, and improving production efficiency of diesel engine fuel rails. Summary of the invention

[0009] The finite element simulation of the forging process of forgings needs to consider the type of forging machinery. Based on the experience of SETFORGE, a forging production supplier, in simulating the forging process of forgings using finite element simulation technology, this application takes high-pressure fuel rail forgings as a research example, establishes a finite element simulation model of the multi-step forging process of high-pressure fuel rail parts, and analyzes the working characteristics of this type of forging machine based on the parameter requirements of the screw press finite element numerical simulation FORGE. For important characteristic factors including initial energy, machine tool stiffness, and efficiency, general conclusions are obtained; based on the research conclusions of forging machines and software templates, the finite element simulation of the rough machining and finishing forging process of the high-pressure fuel rail in the high-pressure common rail fuel system of diesel engines is realized. It helps to predict the final state, performance and quality of the material under the actual processing environment by controlling various environmental parameters such as temperature, pressure, friction coefficient, thermal conductivity coefficient, etc., so as to achieve the ultimate goal of optimizing the design of plastic forming. It can provide a reference for actual production and play an important role in reducing production costs, improving product quality, optimizing process design, and improving production efficiency. It helps to improve the stability, reliability, safety and dynamic performance of the fuel rail, ensuring its smooth, safe and reliable operation.

[0010] In order to achieve the above technical effects, the technical solutions adopted in this application are as follows:

[0011] The multi-step hot forging simulation system of the fuel rail of the automobile diesel engine is used to establish a finite element simulation model of the multi-step forging process of the high-pressure fuel rail parts. Based on the parameter requirements of the finite element numerical simulation FORGE of the screw press, the working characteristics of this type of forging machine are analyzed, and general conclusions are obtained for important characteristic factors including initial energy, machine tool stiffness, and efficiency; based on the research conclusions of the forging machine and software template, the finite element simulation of the rough machining and finishing forging process of the high-pressure fuel rail in the high-pressure common rail fuel system of the diesel engine is carried out; the hot forging forming process of the high-pressure fuel rail forging is numerically simulated by the forging step, and the influence of different parameters on the surface quality and contour accuracy of the forging is analyzed. According to the results obtained, a general method suitable for simulating the hot forging parts of this type of forging machine is obtained;

[0012] 1) Analyze the characteristic factors of the screw press, analyze the characteristics of the screw press simulation template formed based on the numerical simulation FORGE, and apply the conclusions to the hot forging of high-pressure fuel rails;

[0013] 2) Perform multi-step simulation on the hot forging process of high-pressure fuel rail parts, analyze the influence of different variable parameters on the simulation results, including lubrication conditions, heat conductivity, and temperature between the forging and the forging die, and obtain the use conditions of each parameter when the simulation results are closest to the actual parts;

[0014] 3) Combined with the three stations of rough machining, fine machining and deburring of the screw press machine tool, and combined with the actual production situation, the simulation plan is optimized and adjusted, and the simultaneous simulation of the rough machining and fine machining steps is established to obtain the conditions of each parameter under the optimal simulation results.

[0015] Preferably, the final forging model design method of the high-pressure fuel rail is as follows: first, the complex structure of the high-pressure fuel rail is disassembled into many parts with relatively simple geometric structures as different volume elements, and then the above volume elements are modeled separately, and finally all the above parts are assembled. The high-pressure fuel rail is regarded as consisting of 6 volume elements, and the 6 volume elements are independently modeled in turn, and finally they are assembled into a complete part; each volume element has a simple enough structure relative to the overall part, but is further disassembled and regarded as a number of simple geometric bodies, including cubes, cylinders, spheres, obtained after basic chamfering, filleting, and drafting operations.

[0016] Preferably, the preform model design method: relying on the existing final forging model, modifying its overall structure parameters, thereby obtaining a three-dimensional model of the preform, based on the rule that the model has approximately equal volumes before and after modification, along the forging direction, the preform model has a higher height and a smaller thickness than the final forging model;

[0017] For the geometric structure and geometric elements in the forging model, the following rules are used when transitioning from the final forging model to the preform model:

[0018] 1) Parallel hexahedron structure: For the surface parallel to the forging direction, the thickness is reduced relative to the final forging; for the surface perpendicular to the forging direction, the height is increased to ensure that the model before and after the modification has approximately the same volume;

[0019] 2) Cylindrical surface structure: reduce the thickness of the plane parallel to the forging direction and the cylindrical surface; appropriately translate the changed new geometric body in the opposite direction of forging by a certain height; add a parallelepiped with the translation value as the height and the bottom surface of the geometric body as the length and width on the lower surface of the translated geometric body, so that the final new geometric body has the same reference plane as the original one, and the two have roughly the same volume;

[0020] 3) Plane inclined relative to the reference plane: Based on the actual geometric structure, assuming that the structure has no inclined surface features, reduce the thickness of the plane parallel to the forging direction; increase the height of the plane perpendicular to the forging direction; finally, create an inclined surface feature and keep the inclined angle consistent with the original one. The volume of the newly obtained geometry remains roughly the same as the original one.

[0021] Preferably, the characteristic construction of WEINGARTEN screw press is: the screw press uses screw and nut as transmission mechanism, converts the forward and reverse rotation of the flywheel into the up and down reciprocating motion of the slider, and the flywheel stores the engine energy in the form of rotation. The energy is transmitted to the slider by the screw-nut structure to make it reciprocate up and down to hit the workpiece and forge the workpiece, and the energy supply time of the engine to the flywheel is controlled;

[0022] The energy of a screw press can be divided into several different forms: the total energy provided by the motor (Enet); the energy consumed by the friction of the machine parts (Efriction); the maximum kinetic energy transmitted to the flywheel (Emax); the elastic potential energy consumed by the machine due to vibration (Eelastic); the energy used to forge the workpiece (Eforging), which is derived from the relationship between the energy of each part:

[0023] E net =E max +E friction

[0024] E max =E forgirng +E elastic Formula 1

[0025] The rotation of the flywheel of the screw press is achieved by the motor driving the flywheel rim through the friction disk. Part of the energy is consumed due to friction. It is defined in an indirect way and the energy transfer efficiency n is introduced to avoid directly calculating the energy consumed by friction. The relationship satisfies the following formula:

[0026] Based on energy saving and quality protection of forgings, the energy required for forging is obtained by simulation with FORGE software. The initial kinetic energy of the forging slide is artificially set by parameter R. The machine tool model is simplified into a simple harmonic vibration system with great stiffness. The elastic potential energy loss during operation is related to the working pressure and the numerical value of the machine tool stiffness, and the relationship satisfies:

[0027]

[0028] Simplify the total kinetic energy expression of the system and introduce the equivalent mass Me, so the kinetic energy is expressed as:

[0029]

[0030] Where J represents the moment of inertia of the flywheel and Ms represents the mass of the slider;

[0031] The maximum kinetic energy E of this system max , the corresponding maximum movement speed of the slider is:

[0032]

[0033] The stiffness value of the machine tool is also one of the necessary parameters for finite element simulation. For a vibration system, the greater the stiffness, the smaller the elastic potential energy generated, and vice versa. Its definition is expressed as:

[0034]

[0035] Motor power, energy transfer efficiency, maximum operating speed of the slider, and machine tool stiffness are the necessary characteristic factors for finite element simulation.

[0036] Preferably, the characteristic factors of WEINGARTEN screw press are analyzed: the rotational motion of the flywheel in the screw press is changed into the linear motion of the slider through the screw-nut structure, and the connection and disconnection of its state are controlled by the clutch;

[0037] This application is based on ignoring the situation where the clutch slips, assuming that the two strictly follow the following mathematical relationship, and obtains:

[0038]

[0039] The energy consumed by forging a workpiece is a quadratic function of the working pressure. When the working pressure F is the maximum, the energy E used to forge the workpiece forging is 0, the kinetic energy E of the entire systemmax All converted into elastic potential energy E consumed by the machine tool elastic , Formula 5 is expressed as:

[0040]

[0041] Quantitatively obtain the value of machine tool stiffness K: first determine the maximum working pressure F of the machine tool, and obtain the maximum working pressure value of the machine tool on the forging energy consumption Eforging and working pressure F curve;

[0042] The energy-pressure curve is redrawn and extended. By taking points on the curve and redrawing the curve, and combining the mathematical relationship between the two, the trend line equation coefficient is fine-tuned to obtain the result of the screw press machine tool; by solving the trend line equation, the maximum working pressure F is obtained, and then combined with the total kinetic energy E of the system max , obtain the stiffness value K of the machine tool;

[0043] As for the energy transfer efficiency n, its value reflects the degree of loss caused by friction during the energy transfer from the motor to the flywheel, and is calculated on the basis of being able to directly obtain the values ​​of the two parts of energy;

[0044] It is assumed that the efficiency value n is related to the size of the flywheel, that is, the diameter, and the E net 、E max Value, get the efficiency value of this series of screw press machine tools;

[0045] When the flywheel diameter of the screw press is greater than about 250mm, its energy transfer efficiency is stable at 83%, and the following calculations are made:

[0046] E max =208333J Formula 9

[0047] K = 2.45 × 10 9 NN / m Formula 10

[0048] Get the energy portion E used by the machine tool to forge the workpiece forging Functional relationship with working pressure F:

[0049] E forging =-4.1×10 10 F 2 +208333 Formula 11

[0050] The maximum working speed of the slider is calculated by measuring multiple sets of machine tool working parameters, and the solution is obtained using formula 12:

[0051]

[0052] The preset values ​​before the machine tool works and the measured values ​​during work are calculated respectively, and the equivalent mass value is approximately:

[0053] M e =1.715×10 6 kg Formula 13

[0054] The maximum operating speed of the slider is:

[0055] v max =540mm / s Formula 14

[0056] The above are the parameter characteristics of the screw press machine, as well as the parameter analysis results of the machine tool applying the conclusions to actual processing.

[0057] Preferably, the effect of two parameters that can adjust the energy of the slider on the simulation results: There are two parameters for adjusting the kinetic energy of the forging slider in the simulation template: energy transfer efficiency n and parameter R that can adjust the percentage of the actual kinetic energy of the slider compared to the maximum kinetic energy at each forging strike. For a specific screw press machine, its efficiency value n is determined, and the actual energy of the forging slider is adjusted according to the energy required for each forging strike;

[0058] When the efficiency n and R are not set, the forging slide ends at the position of 93.31 mm, the energy set in the simulation is completely exhausted, and the maximum speed simulation value of the slide in the whole process is consistent with the set value;

[0059] When both efficiency n and R are set to 60%, the real energy consumed by the simulation becomes 60% of the set value; and compared with R, efficiency n does not change the maximum working speed of the slider;

[0060] The simulation calculation process of the template is in good agreement with the theoretical analysis results, and the entire simulation process stops after the energy is completely consumed, which is consistent with the actual situation.

[0061] Preferably, the simulation of the rough machining step: in actual machining, the rough machining forging process of the blank by the machine tool is set to 55% of the energy, the set value is verified by the simulation calculation result, and the calculation result of the working stress changing with the forging stroke is plotted into a curve;

[0062] The upper and lower surfaces of the modified 3D model are extracted as new forging dies respectively, and the simulation parameters are kept consistent with the above. The forging flash of the simulation results still has a trend of gradually decreasing and fitting the actual part contour as the friction coefficient between the die and the blank increases. When the friction coefficient increases to f = 0.35 to f = 0.4, the simulation results completely overlap with the actual forging contour.

[0063] Based on the comparison of simulation results with the actual part contour and the filling degree of the part surface, when the friction condition between the forging die and the metal blank forging is f=0.35, the finite element simulation results are closest to the actual state of the actual forging;

[0064] For the cylindrical blank model, when the maximum mesh size is 3 mm, the volume loss rate is about 0.8%; when the maximum mesh size is 2.5 mm, the value is about 0.7%;

[0065] The selection of the maximum grid size has no effect on the flash contour of the simulation results. When the friction condition is between 0.3 and 0.4, the flash contours of the two sets of simulation results are close enough to the actual parts.

[0066] This application uses 2.5mm as the maximum grid size. Under this parameter condition, a good balance is achieved in terms of result accuracy, computational efficiency, and storage space.

[0067] Based on the simulation results, it is determined that when the friction condition between the forging die and the metal blank is f=0.35 and 2.5mm is used as the maximum grid size for dividing the model into grids, the result is closest to the actual rough-machined part state.

[0068] Preferably, simulation of the finishing step: 25% of the energy is used for the subsequent finishing forging, and the results of the simulation of the finishing forging process are compared with the changes in the machine tool working stress with the forging stroke. For the simulation results of the finishing forging process, the 25% machine tool energy-working stress curve is much greater than the working stress generated and the energy consumed in the forging process;

[0069] When the friction condition between the forging die and the metal blank is between 0.3 and 0.4, the simulation results are better. At the same time, for the finished molded part, the flash thickness is 2 mm, and this value is selected as the maximum mesh size when dividing the model into meshes;

[0070] Comprehensive simulation results show that for the simulation of the finishing forging process of the part, when the friction coefficient used is between 0.3 and 0.4, the finite element simulation results obtained are exactly the same as the contour shape and surface quality of the actual part. It is determined that in the FORGE software, when the friction coefficient between the forging and the die is selected as 0.35, the simulation results are closest to the actual situation.

[0071] When the feature template of the mechanical press is used in FORGE to simulate the forging process, when the friction condition between the forging and the die is set to 0.2, the simulation result is the same as the actual state of the part obtained by processing. Correspondingly, for the parts simulated by screw press forging, when the machine tool feature template is used for finite element simulation, when the friction condition value is taken as 0.35, the simulation result is closest to the actual state of the forging.

[0072] Preferably, the simulation of the forging process of the high-pressure fuel rail parts is optimized: referring to the arrangement of different stations on the forging die, two stations for rough machining and finishing forging are set at the same time when designing the die model. The specific simulation method is: placing a metal blank at the rough machining station, placing a preformed part after rough machining at the finishing station, and when the upper die descends to the specified position, a preformed part and a final part are forged at the same time by one strike;

[0073] When designing the forging die for the finishing step, the absolute position of the preform in space after rough machining is considered, and the finishing forging die is translated downward to finally form the two-station forging die model shown in the figure above;

[0074] In industrial production, when rough machining and finishing steps are performed simultaneously, the machine tool is set to use 60% of the energy. First, this value is verified, and the finite element simulation results of the process are compared with the working characteristic curve of the forging machine. The 60% machine tool energy-working stress curve meets the energy consumption generated in the multi-step synchronous forging process, thereby ensuring the smooth progress of the forging process.

[0075] Preferably, in the optimization simulation of the finished parts: the simulation results when the friction condition is 0.35 are compared with the results of the single simulation of the multi-step forging process. For the working pressure generated in the forging process and the energy parameters consumed, the results of the two simulation schemes are not much different; for the finite element simulation of the multi-step forging process of the same forging, both the single simulation of each step and the simultaneous simulation of multiple steps are feasible, and the simultaneous simulation of the multi-step forging process is more suitable. The verification and optimization of certain results obtained after the single simulation of the multi-step forging process are carried out.

[0076] Compared with the prior art, the innovations and advantages of this application are:

[0077] (1) The prior art lacks knowledge of the working characteristics of the template for the screw press, and based on the experience of simulating the forging process of this type of machine tool, the model of the mechanical press is mostly used to simulate the forging process of the forging, so the simulation results have certain errors compared with the actual finished products. Based on this, the present application studies the template characteristics of the screw press in the FORGE software, models the multi-step high-pressure fuel rail 3D model that meets the industrial processing standards based on CATIA design, and constructs a modeling method that meets industrial production conditions. For the necessary parameters required for simulation, the characteristics of the German WEINGARTEN series screw press are studied, and the simulation template of this type of equipment in the FORGE software is studied to determine its simulation principle. The multi-step (rough machining, fine machining) forging process simulation of the high-pressure fuel rail parts is realized, and the simulation parameters are set and corrected according to the actual parts, and finally a more realistic multi-step simultaneous forging process is realized. The influence of each parameter in the template on the simulation results is determined, and finally the multi-step forging process of the high-pressure fuel rail manufactured by the screw press is successfully simulated. It has deepened the understanding of the hot forging process simulation using screw press, enriched the simulation methods of forging parts for different forging equipment, and provided valuable reference for the finite element simulation process of similar forging equipment or similar forgings in the future.

[0078] (2) This application successfully achieved the numerical simulation of the hot forging process of the high-pressure fuel rail forgings by forging steps, analyzed the characteristic factors of the screw press, and analyzed the characteristics of the screw press simulation template formed based on the numerical simulation FORGE, and applied the obtained conclusions to the hot forging of the high-pressure fuel rail; the hot forging process of the high-pressure fuel rail parts was simulated in multiple steps, and the influence of different variable parameters on the simulation results was analyzed, including the lubrication conditions, heat conductivity, and temperature between the forgings and the forging dies, to obtain the use conditions of each parameter when the simulation results are closest to the actual parts; combined with the three stations of rough machining, fine machining, and deburring of the screw press machine tool, and combined with the actual production situation to optimize and adjust the simulation plan, a simultaneous simulation of the two steps of rough machining and fine machining was established to obtain the conditions of each parameter under the optimal simulation results. This application analyzes the influence of different parameters on the surface quality and contour accuracy of forgings, and based on the results obtained, derives a general method suitable for simulating the hot forging of parts by such forging machines; it is of great help in solving the problem of surface quality defects such as voids and wrinkles that also exist in the hot forging process of high-pressure fuel rails, which lead to increased production costs, low efficiency, and affect the economic benefits of the design unit.

[0079] (3) The finite element simulation of the forging process needs to consider the type of forging machinery. Based on the experience of the forging manufacturer SETFORGE in simulating the forging process of forgings using finite element simulation technology, this application takes the high-pressure fuel rail forging as a research example to establish a finite element simulation model of the multi-step forging process of high-pressure fuel rail parts. Based on the parameter requirements of the screw press finite element numerical simulation FORGE, the working characteristics of this type of forging machine are analyzed, and general conclusions are obtained for important characteristic factors including initial energy, machine tool stiffness, and efficiency; based on the research conclusions of the forging machine and software template, the finite element simulation of the rough machining and finishing forging process of the high-pressure fuel rail in the high-pressure common rail fuel system of the diesel engine is realized. It helps to predict the final state, performance and quality of the material under the actual processing environment by controlling various environmental parameters such as temperature, pressure, friction coefficient, thermal conductivity coefficient, etc., so as to achieve the ultimate goal of optimizing the design of plastic forming. It can provide a reference for actual production and play an important role in reducing production costs, improving product quality, optimizing process design, and improving production efficiency. It helps to improve the stability, reliability, safety and dynamic performance of the fuel rail, ensuring its smooth, safe and reliable operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0080] Figure 1 It is a disassembly diagram of a diesel engine fuel rail forging model.

[0081] Figure 2 It is a tree diagram of diesel engine fuel rail forging modeling method.

[0082] Figure 3 It is a schematic diagram of the relationship between different energy concepts.

[0083] Figure 4 It is the overlap diagram of the results obtained from the initial simulation and the forging.

[0084] Figure 5 It is a schematic diagram of the parameters used for simulation of the rough machining step.

[0085] Figure 6 This is a comparison chart between the simulation results and the actual part profile.

[0086] Figure 7 It is a schematic diagram of the parameters used in the finishing simulation program.

[0087] Figure 8 It is the surface quality filling diagram of the finishing finite element simulation results.

[0088] Fig. 9 It is a schematic diagram of the finite element simulation results of the two-step forging process.

[0089] Fig.10It is a schematic diagram of the parameters used in the multi-step finite element simulation scheme. Fig.11 This is a comparison chart between the finite element simulation results of the preform and the actual contour. DETAILED DESCRIPTION

[0090] The following is a further description of the technical solution of the multi-process hot forging simulation system for the fuel rail of an automobile diesel engine provided by the present application in conjunction with the accompanying drawings, so that those skilled in the art can better understand the present application and implement it.

[0091] As an indispensable component of the high-pressure common rail fuel system of diesel engines, the high-pressure fuel rail plays an important role in accumulating fuel and eliminating fuel pressure fluctuations. Hot forging technology is often used in industrial production. However, there are also surface quality defects such as voids and wrinkles during the hot forging process, which leads to increased production costs, low efficiency, and affects the economic benefits of the design unit.

[0092] The hot forging process of the high-pressure fuel rail forging is numerically simulated in each forging step, and the influence of different parameters on the surface quality and contour accuracy of the forging is analyzed. Based on the results obtained, a general method suitable for simulating the hot forging of such forging machine parts is obtained;

[0093] (1) Analyze the characteristic factors of the screw press and analyze the characteristics of the screw press simulation template formed based on the numerical simulation FORGE, and apply the obtained conclusions to the hot forging of high-pressure fuel rails;

[0094] (2) Perform multi-step simulation on the hot forging process of the high-pressure fuel rail parts, analyze the influence of different variable parameters on the simulation results, including the lubrication conditions, heat conductivity, and temperature between the forging and the forging die, and obtain the use conditions of each parameter when the simulation results are closest to the actual parts;

[0095] (3) Combined with the three workstations of the screw press, namely rough machining, fine machining, and deburring, and in combination with the actual production situation, the simulation scheme is optimized and adjusted, and a simultaneous simulation of the rough machining and fine machining steps is established to obtain the conditions of each parameter under the optimal simulation results.

[0096] 1. High-pressure fuel rail model construction

[0097] (I) Final forging model design method

[0098] First, the complex structure of the high-pressure fuel rail is disassembled into many parts with relatively simple geometric structures as different volume elements, and then the above volume elements are modeled separately, and finally all the above parts are assembled. Figure 1As shown in the figure, the high-pressure fuel rail is considered to be composed of 6 volume elements, which are modeled independently in turn and finally assembled into a complete part; each volume element is simple enough in structure compared to the overall part, but it can also be disassembled and considered as a number of simple geometric bodies, including cubes, cylinders, and spheres, after basic chamfering, rounding, and drafting operations. This modeling idea can be summarized as follows: Figure 2 The tree diagram shown.

[0099] (II) Preform model design method

[0100] The characteristic of the preform is that the structure is very close to the final forging, but its geometric features are different from those of the final forging. Therefore, the design of the preform model is: relying on the existing final forging model, modifying its overall structure parameters to obtain a three-dimensional model of the preform. Based on the rule that the model has roughly equal volume before and after modification, along the forging direction, the preform model has a higher height and a smaller thickness than the final forging model.

[0101] For the geometric structure and geometric elements in the forging model, the following rules are used when transitioning from the final forging model to the preform model:

[0102] (1) Parallel hexahedron structure: For the surface parallel to the forging direction, the thickness is reduced relative to the final forging; for the surface perpendicular to the forging direction, the height is increased to ensure that the model before and after the modification has approximately the same volume;

[0103] (2) Cylindrical surface structure: reduce the thickness of the plane parallel to the forging direction and the cylindrical surface; appropriately translate the changed new geometric body by a certain height in the opposite direction of forging; add a parallelepiped with the translation value as the height and the bottom surface of the geometric body as the length and width to the lower surface of the translated geometric body, so that the final new geometric body has the same reference plane as the original one, and the two have roughly the same volume;

[0104] (3) Plane inclined relative to the reference plane: Based on the actual geometric structure, assuming that the structure has no inclined surface features, reduce the thickness of the plane parallel to the forging direction; increase the height of the plane perpendicular to the forging direction; finally, create an inclined surface feature and keep the inclined angle the same as the original. The volume of the newly obtained geometric body remains roughly the same as the original.

[0105] 2. Characteristics of screw press and simulation template

[0106] With the increasing application of computer finite element simulation in industrial production, forging design and production has also transformed from the previous "empirical design" mode to "simulation design". In order to simulate the processing process as accurately as possible, it is necessary to measure and record various parameters in the actual production environment, such as friction, temperature, lubrication conditions, etc. FORGE software can take some characteristic factors of forging machinery into consideration in the simulation. Therefore, before the simulation design begins, in addition to measuring and recording various environmental parameters, it is necessary to study or measure the characteristic factors of the machine tool required for the simulation.

[0107] At present, SETFORGE has rich experience in hot forging simulation of mechanical presses, and has also conducted in-depth research on the characteristic factors of mechanical presses required for simulation. However, for another type of screw press, not only is there little understanding of the necessary characteristic factors required for simulation, but also the related simulation design is also lacking. Mechanical presses are often used roughly to replace simulations, and their simulation results are often different from actual parts. In order to solve the above problems, it is necessary to study some characteristic factors of screw presses, and then gradually perform simulation design in FORGE software.

[0108] The research on the characteristic factors of the screw press is based on the requirements of the forging machine simulation template of the FORGE software. Based on the finite element simulation of the hot forging process of the screw press, the following important parameters are needed to describe the working characteristics of the machine tool: forging stroke (determined by the initial height and end height of the slider), total motor energy, maximum slider speed, energy transfer efficiency, machine tool stiffness and adjustable actual energy ratio of the slider at each forging strike. For the above required parameters, the mathematical and physical relationships between the parameters are first constructed, and then the results are introduced into the simulation template in the FORGE software to explore the influence of different parameters on the simulation results.

[0109] (I) WEINGARTEN screw press feature construction

[0110] The screw press uses a screw and a nut as a transmission mechanism to convert the forward and reverse rotation of the flywheel into a forging machine with an up and down reciprocating motion of the slider. The flywheel stores the engine energy in the form of rotation, and the energy is transmitted to the slider by the screw-nut structure to make it reciprocate up and down to hit the workpiece and forge the workpiece. By controlling the energy supply time of the engine to the flywheel, the initial kinetic energy of the slider before hitting the workpiece each time can be changed. The working pressure required for different work steps is different, which effectively improves the economic benefits.

[0111] The energy of a screw press can be divided into several different forms: the total energy provided by the motor (Enet); the energy consumed by the friction of the machine parts (Efriction); the maximum kinetic energy transmitted to the flywheel (Emax); the elastic potential energy consumed by the machine due to vibration (Eelastic); the energy used to forge the workpiece (Eforging). The relationship between the energy of each part is as follows: Figure 3 shown.

[0112] From the mutual relationship of the energies of each part, we can conclude that:

[0113] E net =E max +E friction

[0114] E max =E forging +E elastic Formula 1

[0115] The rotation of the flywheel of the screw press is achieved by the motor driving the flywheel rim through the friction disk. Part of the energy is consumed due to friction. It is defined in an indirect way and the energy transfer efficiency n is introduced to avoid directly calculating the energy consumed by friction. The relationship satisfies the following formula:

[0116] Based on energy saving and quality protection of forgings, the energy required for forging is obtained by simulation with FORGE software. The initial kinetic energy of the forging slide is artificially set by parameter R. The machine tool model is simplified into a simple harmonic vibration system with great stiffness. The elastic potential energy loss during operation is related to the working pressure and the numerical value of the machine tool stiffness, and the relationship satisfies:

[0117]

[0118] Simplify the total kinetic energy expression of the system and introduce the equivalent mass Me, so the kinetic energy is expressed as:

[0119]

[0120] Where J represents the moment of inertia of the flywheel and Ms represents the mass of the slider;

[0121] The maximum kinetic energy E of this system max , the corresponding maximum movement speed of the slider is:

[0122]

[0123] The stiffness value of the machine tool is also one of the necessary parameters for finite element simulation. For a vibration system, the greater the stiffness, the smaller the elastic potential energy generated, and vice versa. Its definition is expressed as:

[0124]

[0125] Motor power, energy transfer efficiency, maximum operating speed of the slider, and machine tool stiffness are the necessary characteristic factors for finite element simulation.

[0126] (II) Analysis of characteristic factors of WEINGARTEN screw press

[0127] The rotation of the flywheel in the screw press is changed into the linear motion of the slider through the screw-nut structure, and the connection and disconnection of its state are controlled by the clutch. In actual work, as the working pressure of the machine tool gradually increases and reaches a certain value, "slip" phenomenon will occur; however, in theoretical analysis, the slip factor of the clutch is ignored.

[0128] This application is based on ignoring the situation where the clutch slips, assuming that the two strictly follow the following mathematical relationship, and obtains:

[0129]

[0130] The energy consumed by forging a workpiece is a quadratic function of the working pressure. When the working pressure F is the maximum, the energy E used to forge the workpiece forging is 0, the kinetic energy E of the entire system max All converted into elastic potential energy E consumed by the machine tool elastic , Formula 5 is expressed as:

[0131]

[0132] Quantitatively obtain the value of machine tool stiffness K: first determine the maximum working pressure F of the machine tool, and obtain the maximum working pressure value of the machine tool on the forging energy consumption Eforging and working pressure F curve;

[0133] The energy-pressure curve is redrawn and extended. By taking points on the curve and redrawing the curve, and combining the mathematical relationship between the two, the trend line equation coefficient is fine-tuned to obtain the result of the screw press machine tool; by solving the trend line equation, the maximum working pressure F is obtained, and then combined with the total kinetic energy E of the system max , obtain the stiffness value K of the machine tool;

[0134] As for the energy transfer efficiency n, its value reflects the degree of loss caused by friction in the process of energy transfer from the motor to the flywheel, and is calculated on the basis of directly obtaining the values ​​of the two parts of energy.

[0135] It is assumed that the efficiency value n is related to the size of the flywheel, that is, the diameter, and the E net 、E max Value, get the efficiency value of this series of screw press machine tools;

[0136] When the flywheel diameter of the screw press is greater than about 250mm, its energy transfer efficiency is stable at 83%, and the following calculations are made:

[0137] E max =208333J Formula 9

[0138] K = 2.45 × 10 9 N / / m Formula 10

[0139] Get the energy portion E used by the machine tool to forge the workpiece forging Functional relationship with working pressure F:

[0140] E forging =-4.1×10 -10 F 2 +208333 Formula 11

[0141] The maximum working speed of the slider is calculated by measuring multiple sets of machine tool working parameters, and the solution is obtained using formula 12:

[0142]

[0143] The preset values ​​before the machine tool works and the measured values ​​during work are calculated respectively, and the equivalent mass value is approximately:

[0144] M e =1.715×10 6 kg Formula 13

[0145] The maximum operating speed of the slider is:

[0146] v max =540mm / s Formula 14

[0147] The above are the parameter characteristics of the screw press machine, as well as the parameter analysis results of the machine tool applying the conclusions to actual processing.

[0148] (III) FORGE software simulation template features see analysis

[0149] 1. The effect of two parameters that can adjust the slider energy on the simulation results

[0150] There are two parameters for adjusting the kinetic energy of the forging slider in the simulation template: the energy transfer efficiency n and the parameter R that can adjust the percentage of the actual kinetic energy of the slider compared to the maximum kinetic energy at each forging blow. For a specific screw press, its efficiency value n is fixed. The actual energy of the forging slider is adjusted according to the energy required for each forging blow. The advantage is not only the economy of saving energy, but also can be used to protect parts from quality damage caused by excessive striking, and can also extend the service life of the forging die.

[0151] Without setting any efficiency n and R, the forging slider ends at the position of 93.31mm, and the energy set in the simulation is completely consumed (208.14kJ compared to 208.3kJ). The maximum slider speed simulation value of the whole process is consistent with the set value.

[0152] When the efficiency n and R are both set to 60%, the real energy consumed by the simulation becomes 60% of the set value; while compared with R, the efficiency n does not change the maximum working speed of the slider.

[0153] The simulation calculation process of the template is in good agreement with the theoretical analysis results, and the entire simulation process stops after the energy is completely consumed, which is consistent with the actual situation.

[0154] 2. Effect of machine tool stiffness on simulation results

[0155] During the forging process of metal blanks, the machine tool will generate corresponding vibrations due to the collision between the die and the blank, and the strength of the vibration is related to the stiffness value of the machine tool itself. The greater the stiffness of the machine tool, the smaller the vibration phenomenon and the less elastic potential energy is lost, and vice versa.

[0156] When simulating two groups of models with different sizes, control groups with and without stiffness values ​​were set up respectively, in order to highlight the influence of stiffness parameters on the simulation results.

[0157] Under the same parameter conditions, the two groups of simulations with stiffness setting have the characteristics of shorter forging stroke, relatively less energy available for forging, and smaller maximum working pressure than the simulation group without stiffness setting.

[0158] By obtaining the instantaneous data of simulation calculation in the post-processor and drawing it into E forging The F curve is shown in the figure below. Compared with the characteristic factor curve of the machine tool, it is concluded that the simulation calculation results should follow the characteristic curve conclusion obtained from the theoretical analysis of the machine tool. When the stiffness is not set in the simulation, the result curve obviously does not follow the characteristic law of the machine tool, while the simulation group with the stiffness value set, its result is consistent with the theoretical conclusion.

[0159] 3. Effects of different initial energy values ​​on simulation results

[0160] When it is known that a certain energy value can successfully realize the forging process, the initial energy of the forging process is changed by setting different R values ​​to explore its impact on the simulation results. It is known that under this initial condition, the maximum forging stroke allowed is 39.9mm. Now the forging stroke is set to 35mm, and the proportion of initial energy provided is increased successively.

[0161] For simulating the same forging process, when a certain energy value is sufficient, continuing to increase the initial energy supplied will increase the actual working stress and the actual energy consumed in the forging process.

[0162] It can be concluded that for a forging process, the results of finite element simulation can effectively guide researchers to determine the energy value provided for the process, which can not only effectively reduce its working stress but also appropriately improve the economy of energy consumption.

[0163] 4. Effect of grid size on simulation results

[0164] For the simulation of the same forging process, the energy consumed and the required working stress value increase as the maximum grid parameter value decreases (relative to the minimum simulation result, the maximum working stress increases by about 2%; the actual energy consumption is about 1%). The maximum grid size used in the simulation has a certain influence on the simulation results of the working pressure, and the working pressure value gradually increases as the maximum grid size parameter value decreases.

[0165] 3. Simulation of the forging process of high-pressure fuel rail parts

[0166] The forging process of the diesel engine high-pressure fuel rail can be divided into two steps: rough machining and finishing, as well as the subsequent process of removing the forging flash. According to the parameter measurement results, the forging process simulation of the rough machining and finishing steps of the part is realized separately. Based on the determination and selection conclusions of each parameter, the multi-step forging process of the part is simulated simultaneously.

[0167] The requirements for finite element simulation of a forging process are: while ensuring that the actual working stress meets the normal working range of the machine tool, strive to fully fill the metal material in the mold without wrinkles, defects, or incomplete filling, and strive to make the contour of the simulation result (including the forging flash) consistent with the actual processed parts as much as possible.

[0168] (I) Simulation of rough machining steps

[0169] In actual processing, the machine tool sets the energy of the rough forging process of the blank to 55%. The set value is verified by the simulation calculation results. The above parameters are used for simulation, and the calculation results of the working stress changing with the forging stroke are plotted into a curve.

[0170] When using the WEINGARTEN screw press to forge such blanks, setting its initial total energy to 55% can ensure the smooth progress of the roughing forging process. Combined with the impact of different initial energies on the forging process, this value (55%) can not only ensure the smooth progress of the roughing forging process, but also avoid blindly selecting a larger initial energy, which will increase the actual working stress of the machine tool and the actual energy consumption.

[0171] When using FORGE software to perform finite element simulation on the forging process of forgings, the temperature distribution of the simulation results is not used as a factor in judging the simulation results unless there is any obvious abnormality. The factors to be considered in measuring the quality of the simulation results include: the filling of the metal material in the mold in the simulation results is as consistent as possible with the actual rough-machined parts, and there are no defects, wrinkles, or overlaps on the surface. In particular, from the actual rough-machined part drawings, it can be seen that there are defects on one side where the metal material is not fully filled; the simulated parts, including their flash, have the same outline contour as the actual production and processing parts, and whether the overlap is high.

[0172] Figure 4 This is the overlap diagram of the results obtained from the initial simulation and the forging. It is concluded that the parts of the simulation results coincide well with the forging, but the flash contour is quite different from that of the forging. From the perspective of the flow direction of the metal material, the simulated forging is not completely filled on one side and there are defects on the surface, which is similar to the actual situation. However, the surface defects of the simulation results are obviously more serious than the actual situation.

[0173] In the subsequent simulation, the other parameters were kept unchanged, and the friction conditions between the die and the metal blank were changed. By adding different lubricants, the flash contour of the finite element simulation results gradually decreased as the friction coefficient between the die and the metal blank increased, and it was closer to the actual forged rough-machined parts. However, although the flash of the simulation results gradually fit the actual parts, there are still obvious differences between the two.

[0174] In order to eliminate the influence of the above factors on the finite element simulation results, especially to avoid the result differences caused by different simulation templates of the software itself, the model size is modified accordingly in CATIA according to the measured value of the actual part, so that when the die forging stroke (35mm) is not changed during the finite element simulation, the actual size of the part should be consistent with the design value of the three-dimensional model. Under this condition, the difference between the finite element simulation results and the actual parts can be compared more accurately.

[0175] The upper and lower surfaces of the modified three-dimensional model are extracted as new forging dies respectively, and the simulation parameters are kept consistent with the above. The forging flash of the simulation results still tends to gradually decrease and fit the actual part contour as the friction coefficient between the die and the blank increases. When the friction coefficient increases to f=0.35 to f=0.4, the simulation results almost completely overlap with the actual forging contour.

[0176] Considering the comparison between the simulation results and the actual part contour and the filling degree of the part surface, when the friction condition between the forging die and the metal blank forging is f=0.35, the finite element simulation results are closest to the actual state of the actual forging.

[0177] For the same simulation process, using different maximum mesh size parameters will have a certain impact on the simulation results. 2.5mm, which is slightly smaller than the maximum mesh size of 3mm in the above simulation, is selected as the parameter value for the following simulation to observe the influence of the maximum mesh size on the finite element simulation process of the forging. When the friction condition f<0.3, the simulation results are significantly different from the actual rough-machined parts, and the simulation results for the friction coefficient f<0.3 are omitted.

[0178] The parameters of the new simulation are arranged as follows Figure 5 As shown, for the cylindrical blank model studied in this application, when the maximum grid size is 3 mm, the volume loss rate is about 0.8%; when the maximum grid size is 2.5 mm, the value is about 0.7%.

[0179] Figure 6 (a)-(c) are the contour comparison diagrams of this group of simulation results and the actual parts, as well as the surface filling degree of the parts. This result is compared horizontally with the simulation result with a maximum grid size of 3mm. It is found that the selection of the maximum grid size has no effect on the flash contour of the simulation results. When the friction condition is between 0.3 and 0.4, the flash contours of the two groups of simulation results are close enough to the actual parts.

[0180] The maximum mesh size has a great influence on the surface filling degree of the simulation results. Under the same conditions, the simulation results using 2.5 mm have better surface filling degree than those using 3 mm.

[0181] This application uses 2.5 mm as the maximum grid size. Under this parameter condition, a good balance is achieved in the three aspects of result accuracy, calculation efficiency and storage space.

[0182] Combining the above simulation results, it is determined that when the friction condition between the forging die and the metal blank is f=0.35 and 2.5mm is used as the maximum grid size for dividing the model into grids, the result is closest to the actual state of the rough-machined parts. Based on this, the result is used to simulate the finishing forging process.

[0183] (II) Simulation of finishing steps

[0184] For parts manufactured by multi-step forging, the purpose of the rough machining step is to make the metal blank produce a large deformation and absorb most of the working stress; the finishing step is to complete the forging of the preformed parts obtained after rough machining according to the design size of the parts. For forgings with complex appearance and structure that require large deformation of the metal, multi-step forging can better ensure the quality of the parts, avoid poor surface quality of parts caused by working stress and impact, and the problem of large working stress on the machine tool.

[0185] For the preforms obtained after rough forging, 25% of the energy is used for subsequent finishing forging in actual processing. First, this value is verified. Combined with the working characteristic curve of the forging machine, the results of the simulation of the finishing forging process are compared with the changes in the machine tool working stress with the forging stroke. For the simulation results of the finishing forging process, the 25% machine tool energy-working stress curve is much greater than the working stress generated and the energy consumed in the forging process. Therefore, this value can well ensure the smooth progress of the finishing forging process.

[0186] The conclusion drawn from the simulation of the rough forging process of the part is that when the friction condition between the forging die and the metal blank is between 0.3 and 0.4, the simulation result is better. At the same time, for the finished molded part, the flash thickness is 2mm, and this value is selected as the maximum mesh size when the model is divided into meshes.

[0187] Based on the preform obtained after simulating the rough forging process, the application Figure 7 The simulation results obtained by using the parameters in the simulation result are very similar to the final molded part obtained after actual forging in terms of contour, while the friction condition, which is the parameter with the greatest impact on the simulation result of the rough forging process, has limited impact on the simulation result of the fine forging process. In addition, the surface of the simulation result has no metal material filling and wrinkle defects, which is consistent with the forging requirements of the actual molded part. The results are shown in Figure 8 .

[0188] Based on the above simulation results, for the simulation of the finishing forging process of the part, when the friction coefficient used is between 0.3 and 0.4, the finite element simulation results obtained are almost exactly the same as the contour shape and surface quality of the actual part, that is, the finite element simulation of the forging process of the part is well realized. Combined with the simulation of the rough forging process, it is determined that in the FORGE software, when the friction coefficient between the forging and the die is selected as 0.35, the simulation results are most similar to the actual situation. The optimal simulation results of the above two-step forging process are shown as follows: Fig. 9 .

[0189] When the feature template of the mechanical press is used in FORGE to simulate the forging process, when the friction condition between the forging and the die is set to 0.2, the simulation result is the same as the actual state of the part obtained by processing. Correspondingly, for the parts simulated by screw press forging, when the machine tool feature template is used for finite element simulation, when the friction condition value is taken as 0.35, the simulation result is closest to the actual state of the forging.

[0190] 4. Optimization of forging process simulation of high-pressure fuel rail parts

[0191] The above finite element simulation of the rough machining and finishing forging process of the high-pressure fuel rail parts is realized respectively. The simulation results are highly similar to the actual forgings in terms of both the contour and the surface material filling state. However, the above finite element simulation results are obtained by simulating the rough machining and finishing steps respectively. In the actual machining process, the two steps (and the flash removal process) are carried out simultaneously at each strike of the upper and lower forging dies. Therefore, in order to continue to optimize the simulation of the forging process of the part, combined with the conclusions of the completed simulation, the two-step forging process is now simulated simultaneously;

[0192] Referring to the arrangement of different stations on the forging die in actual processing, two stations for rough machining and finishing forging are set up at the same time when designing the die model. The specific simulation method is: place the metal blank at the rough machining station, and place the rough-machined preform at the finishing station. When the upper die descends to the specified position, the forging of a preform and a final part is completed at the same time with one strike.

[0193] When designing the forging die for the finishing step, the absolute position of the preform in space after rough machining is taken into consideration, so that the finishing forging die is appropriately translated downward, and finally the two-station forging die model shown in the figure above is formed.

[0194] In industrial production, when roughing and finishing are performed simultaneously, the machine tool is set to use 60% of the energy. First, this value needs to be verified. The finite element simulation results of the process are compared with the working characteristic curve of the forging machine. The 60% machine tool energy-working stress curve can meet the energy consumption generated in the multi-step synchronous forging process, thereby ensuring the smooth progress of the forging process.

[0195] The parameters used in this finite element simulation are as follows: Fig.10 .

[0196] (I) Simulation results of rough machining preforms

[0197] In the above finite element simulation process, the structural profile of the preform obtained at the rough processing station is compared with the actual part, such as Fig.11 (a)-(c) are the simulation results of f=0.3, f=0.35 and f=0.4 respectively;

[0198] Comparing the above figure with the results obtained by rough machining simulation alone, it can be seen that under the same parameter conditions, the simulation results of the preforms obtained by the two simulation schemes are almost the same, and this slight difference can be ignored.

[0199] (II) Simulation results of fine-machined parts

[0200] The preform initially located at the finishing station, after the finishing forging step simulation, the final part contour results are f = 0.3, f = 0.35 and f = 0.4 simulations, respectively. From the above figure, it can be seen that whether the method of simulating each forging step separately or the idea of ​​simulating multiple steps simultaneously is adopted, for the final forging, the finite element simulation results are highly similar to the actual situation.

[0201] The simulation results when the friction condition is 0.35 are compared with the results of the single simulation of the multi-step forging process. For the working pressure and energy parameters generated during the forging process, the results of the two simulation schemes are not much different. For the finite element simulation of the multi-step forging process of the same forging, both the single simulation of each step and the simultaneous simulation of multiple steps are feasible. However, in the first simulation, due to the lack of knowledge of the correctness and accuracy of the simulation results, the direct use of the simultaneous simulation of multiple steps may result in a longer time and difficulty in accurately analyzing the impact of a certain factor on the simulation results. On the contrary, the simultaneous simulation of the multi-step forging process is more suitable for verification and optimization of certain results obtained after a single simulation of the multi-step forging process.

[0202] According to the actual processing conditions of the forgings, the finite element simulation of the forging process is adjusted and optimized. Based on the conclusions obtained from the individual simulations of each forging step, the scheme of synchronous finite element simulation of the roughing and finishing steps is adopted. Compared with the idea of ​​simulating each forging step separately, the synchronous simulation of the multi-step forging process is closer to reality. For the preforms obtained after roughing forging, the contour error of the results obtained by the multi-step synchronous simulation is slightly larger than that of the results obtained by the individual simulation of the roughing step, but it is also determined that the result is good enough; accordingly, for the final parts obtained after the finishing forging process, the results obtained by the two simulation schemes are extremely consistent with the actual parts in terms of shape contour and surface material filling.

Claims

1. Multi-process hot forging simulation system for automobile diesel engine fuel rail, characterized by: A finite element simulation model of the multi-step forging process of high-pressure fuel rail parts is established. Based on the parameter requirements of the screw press finite element numerical simulation FORGE, the working characteristics of this type of forging machine are analyzed, and general conclusions are obtained for important characteristic factors including initial energy, machine tool stiffness, and efficiency. Based on the research conclusions of forging machine tools and software templates, a finite element simulation of the rough machining and finishing forging process of the high-pressure fuel rail in the high-pressure common rail fuel system of diesel engines is performed. The hot forging forming process of the high-pressure fuel rail forging is numerically simulated by the forging step, and the influence of different parameters on the surface quality and contour accuracy of the forging is analyzed. Based on the results obtained, a general method suitable for simulating the hot forging parts of this type of forging machine is obtained. 1) Analyze the characteristic factors of the screw press, analyze the characteristics of the screw press simulation template formed based on the numerical simulation FORGE, and apply the conclusions to the hot forging of high-pressure fuel rails; 2) Perform multi-step simulation on the hot forging process of high-pressure fuel rail parts, analyze the influence of different variable parameters on the simulation results, including lubrication conditions, heat conductivity, and temperature between the forging and the forging die, and obtain the use conditions of each parameter when the simulation results are closest to the actual parts; 3) Combined with the three stations of rough machining, fine machining and deburring of the screw press machine tool, and combined with the actual production situation, the simulation plan is optimized and adjusted, and the simultaneous simulation of the rough machining and fine machining steps is established to obtain the conditions of each parameter under the optimal simulation results.

2. According to claim 1, the multi-process hot forging simulation system for fuel rail of automobile diesel engine is characterized in that: Design method of the final forging model of the high-pressure fuel rail: First, the complex structure of the high-pressure fuel rail is disassembled into many parts with relatively simple geometric structures as different volume elements, and then the above volume elements are modeled separately, and finally all the above parts are assembled. The high-pressure fuel rail is regarded as consisting of 6 volume elements, and the 6 volume elements are independently modeled in turn, and finally they are assembled into a complete part; each volume element has a simple enough structure relative to the overall part, but it is further disassembled and regarded as a number of simple geometric bodies, including cubes, cylinders, and spheres after basic chamfering, filleting, and drafting operations.

3. According to claim 1, the multi-process hot forging simulation system for fuel rail of automobile diesel engine is characterized in that: Preform model design method: Based on the existing final forging model, the overall structure is modified in terms of parameters to obtain a three-dimensional model of the preform. Based on the rule that the model has roughly equal volumes before and after modification, along the forging direction, the preform model has a higher height and a smaller thickness than the final forging model. For the geometric structure and geometric elements in the forging model, the following rules are used when transitioning from the final forging model to the preform model: 1) Parallel hexahedron structure: For the surface parallel to the forging direction, the thickness is reduced relative to the final forging; For the faces perpendicular to the forging direction, increase their height to ensure that the model before and after the modification has approximately the same volume; 2) Cylindrical surface structure: reduce the thickness of the plane parallel to the forging direction and the cylindrical surface; appropriately translate the changed new geometric body in the opposite direction of forging by a certain height; add a parallelepiped with the translation value as the height and the bottom surface of the geometric body as the length and width on the lower surface of the translated geometric body, so that the final new geometric body has the same reference plane as the original one, and the two have roughly the same volume; 3) Plane inclined relative to the reference plane: Based on the actual geometric structure, assuming that the structure has no inclined surface features, reduce the thickness of the plane parallel to the forging direction; increase the height of the plane perpendicular to the forging direction; finally, create an inclined surface feature and keep the inclined angle consistent with the original one. The volume of the newly obtained geometry remains roughly the same as the original one.

4. According to claim 1, the multi-process hot forging simulation system for fuel rail of automobile diesel engine is characterized in that: WEINGARTEN screw press features: The screw press uses screw and nut as transmission mechanism, converting the forward and reverse rotation of the flywheel into a forging machine with reciprocating motion of the slider. The flywheel stores the engine energy in the form of rotation, and the energy is transferred from the screw-nut structure to the slider to make it reciprocate up and down to hit the workpiece and forge the workpiece. The energy supply time of the engine to the flywheel is controlled; The energy of a screw press can be divided into several different forms: the total energy provided by the motor (Enet); the energy consumed by the friction of the machine parts (Efriction); the maximum kinetic energy transmitted to the flywheel (Emax); the elastic potential energy consumed by the machine due to vibration (Eelastic); the energy used to forge the workpiece (Eforging), which is derived from the relationship between the energy of each part: AND net =And max +E friction E max = E forging +E elasstic formula 1 The rotation of the flywheel of the screw press is achieved by the motor driving the flywheel rim through the friction disk. Part of the energy is consumed due to friction. It is defined in an indirect way and the energy transfer efficiency n is introduced to avoid directly calculating the energy consumed by friction. The relationship satisfies the following formula: Based on energy saving and quality protection of forgings, the energy required for forging is obtained by simulation with FORGE software. The initial kinetic energy of the forging slide is artificially set by parameter R. The machine tool model is simplified into a simple harmonic vibration system with great stiffness. The elastic potential energy loss during operation is related to the working pressure and the numerical value of the machine tool stiffness, and the relationship satisfies: Simplify the total kinetic energy expression of the system and introduce the equivalent mass Me, so the kinetic energy is expressed as: Where J represents the moment of inertia of the flywheel and Ms represents the mass of the slider; The maximum kinetic energy E of this system max , the corresponding maximum movement speed of the slider is: The stiffness value of the machine tool is also one of the necessary parameters for finite element simulation. For a vibration system, the greater the stiffness, the smaller the elastic potential energy generated, and vice versa. Its definition is expressed as: Motor power, energy transfer efficiency, maximum operating speed of the slider, and machine tool stiffness are the necessary characteristic factors for finite element simulation.

5. According to claim 1, the multi-process hot forging simulation system for fuel rail of automobile diesel engine is characterized in that: Analysis of the characteristic factors of WEINGARTEN screw press: The rotational motion of the flywheel in the screw press is changed into the linear motion of the slider through the screw-nut structure, and the connection and disconnection of its state are controlled by the clutch; This application is based on ignoring the situation where the clutch slips, assuming that the two strictly follow the following mathematical relationship, and obtains: The energy consumed by forging a workpiece is a quadratic function of the working pressure. When the working pressure F is the maximum, the energy E used to forge the workpiece forging is 0, the kinetic energy E of the entire system max All converted into elastic potential energy E consumed by the machine tool elastic , Formula 5 is expressed as: Quantitatively obtain the value of machine tool stiffness K: first determine the maximum working pressure F of the machine tool, and obtain the maximum working pressure value of the machine tool on the forging energy consumption Eforging and working pressure F curve; The energy-pressure curve is redrawn and extended. By taking points on the curve and redrawing the curve, and combining the mathematical relationship between the two, the trend line equation coefficient is fine-tuned to obtain the result of the screw press machine tool; by solving the trend line equation, the maximum working pressure F is obtained, and then combined with the total kinetic energy E of the system max , obtain the stiffness value K of the machine tool; As for the energy transfer efficiency n, its value reflects the degree of loss caused by friction during the energy transfer from the motor to the flywheel, and is calculated on the basis of being able to directly obtain the values ​​of the two parts of energy; It is assumed that the efficiency value n is related to the size of the flywheel, that is, the diameter, and the E net 、E max Value, get the efficiency value of this series of screw press machine tools; When the flywheel diameter of the screw press is greater than about 250mm, its energy transfer efficiency is stable at 83%, and the following calculations are made: E max =208333J Formula 9 K = 2.45 × 10 9 N / m Formula 10 Get the energy portion E used by the machine tool to forge the workpiece forging Functional relationship with working pressure F: E forging =-4.1×10 -10 F 2 +208333 Formula 11 The maximum working speed of the slider is calculated by measuring multiple sets of machine tool working parameters, and the solution is obtained using formula 12: The preset values ​​before the machine tool works and the measured values ​​during work are calculated respectively, and the equivalent mass value is approximately: M e =1.715×10 6 kg Formula 13 The maximum operating speed of the slider is: v max =540mm / s Formula 14 The above are the parameter characteristics of the screw press machine, as well as the parameter analysis results of the machine tool applying the conclusions to actual processing.

6. The multi-process hot forging simulation system for fuel rail of automobile diesel engine according to claim 1 is characterized in that: Effects of two parameters that can adjust the energy of the slider on the simulation results: There are two parameters in the simulation template that adjust the kinetic energy of the forging slider: energy transfer efficiency n and parameter R that can adjust the percentage of the actual kinetic energy of the slider compared to the maximum kinetic energy at each forging stroke. For a specific screw press machine, its efficiency value n is determined, and the actual energy of the forging slider is adjusted according to the energy required for each forging stroke. When the efficiency n and R are not set, the forging slide ends at the position of 93.31 mm, the energy set in the simulation is completely exhausted, and the maximum speed simulation value of the slide in the whole process is consistent with the set value; When both efficiency n and R are set to 60%, the real energy consumed by the simulation becomes 60% of the set value; and compared with R, efficiency n does not change the maximum working speed of the slider; The simulation calculation process of the template is in good agreement with the theoretical analysis results, and the entire simulation process stops after the energy is completely consumed, which is consistent with the actual situation.

7. The multi-process hot forging simulation system for fuel rail of automobile diesel engine according to claim 1 is characterized in that: Simulation of roughing process: In actual processing, the roughing forging process of the blank is set to 55% energy by the machine tool. The set value is verified by the simulation calculation results, and the calculation results of the working stress changing with the forging stroke are plotted into a curve; The upper and lower surfaces of the modified 3D model are extracted as new forging dies respectively, and the simulation parameters are kept consistent with the above. The forging flash of the simulation results still has a trend of gradually decreasing and fitting the actual part contour as the friction coefficient between the die and the blank increases. When the friction coefficient increases to f = 0.35 to f = 0.4, the simulation results completely overlap with the actual forging contour. Based on the comparison of simulation results with the actual part contour and the filling degree of the part surface, when the friction condition between the forging die and the metal blank forging is f=0.35, the finite element simulation results are closest to the actual state of the actual forging; For the cylindrical blank model, when the maximum mesh size is 3 mm, the volume loss rate is about 0.8%; when the maximum mesh size is 2.5 mm, the value is about 0.7%; The selection of the maximum grid size has no effect on the flash contour of the simulation results. When the friction condition is between 0.3 and 0.4, the flash contours of the two sets of simulation results are close enough to the actual parts. This application uses 2.5mm as the maximum grid size. Under this parameter condition, a good balance is achieved in terms of result accuracy, computational efficiency, and storage space. Based on the simulation results, it is determined that when the friction condition between the forging die and the metal blank is f=0.35 and 2.5mm is used as the maximum grid size for dividing the model into grids, the result is closest to the actual rough-machined part state.

8. The multi-process hot forging simulation system for fuel rail of automobile diesel engine according to claim 1 is characterized in that: Simulation of finishing process: 25% energy is used for subsequent finishing forging, and the results of finishing forging process simulation are compared with the changes of machine tool working stress with forging stroke. For the simulation results of finishing forging process, the 25% machine tool energy-working stress curve is much larger than the working stress and energy consumed in the forging process; When the friction condition between the forging die and the metal blank is between 0.3 and 0.4, the simulation results are better. At the same time, for the finished molded part, the flash thickness is 2 mm, and this value is selected as the maximum mesh size when dividing the model into meshes; Comprehensive simulation results show that for the simulation of the finishing forging process of the part, when the friction coefficient used is between 0.3 and 0.4, the finite element simulation results obtained are exactly the same as the contour shape and surface quality of the actual part. It is determined that in the FORGE software, when the friction coefficient between the forging and the die is selected as 0.35, the simulation results are closest to the actual situation. When the feature template of the mechanical press is used in FORGE to simulate the forging process, when the friction condition between the forging and the die is set to 0.2, the simulation result is the same as the actual state of the part obtained by processing. Correspondingly, for the parts simulated by screw press forging, when the machine tool feature template is used for finite element simulation, when the friction condition value is taken as 0.35, the simulation result is closest to the actual state of the forging.

9. The multi-process hot forging simulation system for fuel rail of automobile diesel engine according to claim 1 is characterized in that: Optimization of the simulation of the forging process of high-pressure fuel rail parts: Referring to the arrangement of different stations on the forging die, two stations for rough machining and finishing forging are set at the same time when designing the die model. The specific simulation method is: place the metal blank at the rough machining station, and place the preformed part after rough machining at the finishing station. When the upper die descends to the specified position, the forging of a preform and a final part is completed at one strike. When designing the forging die for the finishing step, the absolute position of the preform in space after rough machining is considered, and the finishing forging die is translated downward to finally form the two-station forging die model shown in the figure above; In industrial production, when rough machining and finishing steps are performed simultaneously, the machine tool is set to use 60% of the energy. First, this value is verified, and the finite element simulation results of the process are compared with the working characteristic curve of the forging machine. The 60% machine tool energy-working stress curve meets the energy consumption generated in the multi-step synchronous forging process, thereby ensuring the smooth progress of the forging process.

10. The multi-process hot forging simulation system for fuel rail of automobile diesel engine according to claim 9 is characterized in that: Optimization simulation of finished parts: The simulation results when the friction condition is 0.35 are compared with the results of the single simulation of the multi-step forging process. For the working pressure and energy parameters generated during the forging process, the results of the two simulation schemes are not much different. For the finite element simulation of the multi-step forging process of the same forging, both the single simulation of each step and the simultaneous simulation of multiple steps are feasible. The simultaneous simulation of the multi-step forging process is more suitable. The verification and optimization of certain results are obtained after the single simulation of the multi-step forging process.

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