A universal multi-stress field coupling analysis method for connecting rod hole machining

Abstract

The present invention discloses a universal multi-stress field coupling analysis method for connecting rod hole processing. The method focuses on the processing of the connecting rod hole system, analyzes the structure and processing technology of the connecting rod, establishes a finite element simulation model of the connecting rod, and obtains finite element simulation models of the connecting rod cover and the connecting rod body respectively. The cutting edge motion model and the cutting force model are determined according to the boring and milling processing processes respectively, and a processing physical process simulation analysis program is established to convert the complex processing physical process into a dynamic force distribution, thereby simplifying the finite element simulation of the cutting process. By utilizing the processing physical process simulation analysis program, combined with the assembly constraints and boundary constraints in the connecting rod processing process, the process cycle is performed according to the processing technology to realize multi-process superposition and multi-stress field coupling analysis. This method can effectively associate the residual stress field of the entire connecting rod machining process, and more realistically and reasonably analyze the deformation law of the key feature position of the connecting rod.

Description

Technical Field

[0001] The invention belongs to the technical field of mechanical processing, and in particular relates to a universal multi-stress field coupling analysis method for connecting rod hole processing. Background Art

[0002] As a major moving part in marine diesel engines, the connecting rod is one of the most heavily loaded components and must possess sufficient fatigue resistance and structural strength. The connecting rod's operating loads include the gas force transmitted by the piston, the inertial forces of its own reciprocating motion and swinging motion, and other factors. It is subjected to alternating impact dynamic loads such as compression, tension, and bending. These harsh operating conditions place high demands on the connecting rod's structural dimensions and mechanical properties.

[0003] Connecting rod deformation is a common problem during the machining process, especially after milling or boring the large end hole. This shrinkage can significantly impact the assembly accuracy and performance of the connecting rod. The primary cause of this deformation is the release of residual stress within the connecting rod as material is removed during the machining of the connecting rod blank, leading to a redistribution and rebalancing of the residual stress field within the connecting rod. Furthermore, the connecting rod's geometric structure and inherent stiffness contribute to varying degrees of deformation after machining. Improving the connecting rod's machining process can reduce this deformation. However, due to the combined effects of multiple processes and the coupling of multiple stress fields, the relationship between the connecting rod's machining process and the deformation mechanism remains unclear. Summary of the Invention

[0004] Purpose of the invention: The purpose of the present invention is to provide a universal multi-stress field coupling analysis method for connecting rod hole machining.

[0005] Technical Solution: The present invention provides a universal multi-stress field coupling analysis method for connecting rod hole machining, wherein the connecting rod comprises a connecting rod cap and a connecting rod body. The method comprises the following steps:

[0006] (1) Establish a casting simulation model of the connecting rod cap and connecting rod body, and determine the processing procedures, clamping methods, and processing parameters of the connecting rod cap and connecting rod body;

[0007] (2) Simplify boring and milling processes into dynamically distributed forces and write a simulation analysis program for the physical process of boring and milling processes;

[0008] (3) Implement the machining deformation analysis of each process of the connecting rod cap and the connecting rod body in sequence according to the machining process; impose boundary constraints on the simulation model according to each machining process, and call the machining physical process simulation analysis program;

[0009] (4) Apply assembly constraints to the connecting rod cap and the connecting rod body according to the assembly process, apply boundary constraints to the connecting rod simulation model according to each processing process of the connecting rod after assembly, and call the processing physical process simulation analysis program; perform processing deformation analysis of each process of the assembled connecting rod in sequence according to the processing process;

[0010] (5) The assembled connecting rod simulation model is unloaded, boundary constraints and assembly constraints are released, and the strain of the connecting rod target characteristics is extracted.

[0011] Preferably, in step (1), structural features of the connecting rod cap and the connecting rod body are also analyzed to delete model features that have no effect on machining deformation in the connecting rod simulation model.

[0012] Preferably, in step (2), by analyzing the working conditions of boring and milling during the actual processing of the connecting rod, the physical process of boring and milling is converted into the dynamic distribution of cutting force. The specific method is as follows:

[0013] The cutting motion model f(x, y, z) of the cutting edge of the tool is determined according to the tool path during the connecting rod processing; the cutting force model F[n, f z ,a e ,a p ,], where n is the spindle speed; f z is the feed per tooth; a e is the radial cutting width; a p The axial cutting depth is obtained; a machining physical process simulation analysis program for simulating boring and milling is established by combining the cutting motion model and the cutting force model.

[0014] Preferably, in step (3), the clamping methods during the boring and milling processes of the connecting rod cover and the connecting rod shaft are analyzed and the clamping methods during the processing of the connecting rod cover and the connecting rod shaft are converted into boundary constraints in the simulation model.

[0015] Preferably, in step (3), the processing deformation analysis of each process of the connecting rod cover and the connecting rod body is completed on the basis of the processing deformation analysis of the previous process, so as to realize the superposition of the processing processes of the connecting rod cover and the connecting rod body and the effective correlation of the residual stress field. When performing the processing deformation analysis of each process, the parameters of the processing physical process simulation analysis program must be adjusted.

[0016] Preferably, in step (4), the clamping mode of the connecting rod during the boring and milling processes after assembly is analyzed and the clamping mode in the connecting rod processing step after assembly is converted into boundary constraints in the simulation model.

[0017] Preferably, in step (4), the processing deformation analysis of each process of the rear connecting rod is completed on the basis of the processing deformation analysis of the previous process, so as to realize the superposition of the processing processes of the rear connecting rod and the multi-stress field coupling analysis. When performing the processing deformation analysis of each process, the parameters of the processing physical process simulation analysis program must be adjusted.

[0018] Preferably, in step (5), after the connecting rod simulation model is unloaded and the boundary constraints and assembly constraints are released, the strain quantities of the key features of the connecting rod cover and the connecting rod body are extracted to obtain the processing deformation results under the conditions of multi-process superposition and multi-stress field coupling.

[0019] Furthermore, in step (1), a method for establishing a casting simulation model of the connecting rod cover and the connecting rod shaft is provided. The connecting rod casting is divided into two parts: the connecting rod cover and the connecting rod shaft. Model features that have no effect on processing deformation in the simulation model of the connecting rod cover and the connecting rod shaft are analyzed, including chamfers, locating holes, etc. A finite element simulation model is established based on the size and structural information of the connecting rod cover and the connecting rod shaft.

[0020] Furthermore, during the simulation of the connecting rod cap and the connecting rod body, key simulation parameters include density, Young's modulus, Poisson's ratio, shear modulus, yield strength, boring process parameters, milling process parameters, and processing allowance.

[0021] Furthermore, the machining deformation analysis program converts the physical process of boring and milling into the dynamic distribution of cutting force, where the motion model of the tool cutting edge is f(x,y,z)=f[x(t),y(t),z(t)],x(t)=rcos(f z ·t),y(t)=rsin(f z ·t),z(t)=f z ·t; where r is the pore radius, f z is the feed per tooth.

[0022] Empirical equations of cutting force on cutting edge in boring and milling Among them C F is the milling force coefficient, n is the spindle speed, the unit is n / min; f z is the feed per tooth, in mm / z; a e is the radial cutting width, in mm; a p Axial cutting depth, in mm; a, b, c, d are the indexes of each part respectively.

[0023] Through secondary development of ABAQUS, a finite element analysis subroutine was developed to simulate the motion trajectory, cutting force and action form during boring and milling processes, and the physical process of connecting rod processing was converted into the dynamic distribution of cutting force, which simplified the finite element analysis of the physical process of processing and improved the efficiency of finite element analysis.

[0024] Beneficial Effects: By analyzing the deformation patterns of connecting rods under the conditions of multi-process superposition and multi-stress coupling, the authors realized the superposition effect of multiple processes during the connecting rod machining process. This method also took into account the hereditary characteristics of the processes, ensuring the continuity of the analysis. This method effectively correlated the residual stress field throughout the entire connecting rod machining process, and more realistically and reasonably analyzed the deformation patterns of the connecting rod's key feature locations. Furthermore, using finite element simulation data to analyze the deformation patterns of connecting rods eliminates the need for extensive physical experimental data, thus reducing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a workflow diagram of the present invention;

[0026] Figure 2 This is a front view of a three-dimensional model of the connecting rod in the present invention;

[0027] Figure 3 A top view of a three-dimensional model of the connecting rod in the present invention;

[0028] Figure 4 Schematic diagram of the boundary constraint conditions of the connecting rod cover in the present invention;

[0029] Figure 5 This is a schematic diagram of the first boundary constraint condition of the connecting rod shaft in the present invention;

[0030] Figure 6 Schematic diagram of the second boundary constraint condition of the connecting rod shaft in the present invention;

[0031] Figure 7 This is a schematic diagram of the first assembly constraint condition of the connecting rod in the present invention;

[0032] Figure 8 Schematic diagram of the second assembly constraint condition of the connecting rod in the present invention;

[0033] Figure 9 Schematic diagram of the third assembly constraint condition of the connecting rod in the present invention;

[0034] Figure 10 This is the result of the simulation analysis of the deformation of the connecting rod in the present invention. DETAILED DESCRIPTION

[0035] The technical solution of the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0036] A universal multi-stress field coupling analysis method for connecting rod hole machining. This method is applied to Figure 2 and Figure 3 In the connecting rod model shown, the connecting rod includes a connecting rod cap and a connecting rod body. By analyzing the deformation law of the key feature of the connecting rod, the deformation law of the connecting rod's big head hole under the coupling of multiple process superposition and multiple stress fields is obtained. The process of this method is as follows: Figure 1 As shown, the steps include:

[0037] Step 1: Establish a casting simulation model of the connecting rod cap and the connecting rod shaft, and determine the processing procedures, clamping methods, and processing parameters of the connecting rod cap and the connecting rod shaft;

[0038] For the casting simulation model, simplify the connecting rod structure to minimize the impact on the analysis results, such as locating holes and chamfers. Then, determine the finite element simulation model for the connecting rod cap and connecting rod shaft based on the connecting rod's dimensions and structure. During the simulation of the connecting rod cap and connecting rod shaft, key simulation parameters include density, Young's modulus, Poisson's ratio, shear modulus, yield strength, boring process parameters, milling process parameters, and machining process allowances. The relevant material parameters determined based on the simulation model are shown in Table 1:

[0039] Table 1 Simulation model related material parameters

[0040]

[0041] A material model for casting simulation model simulation analysis is established based on the above material parameters.

[0042] Step 2: By analyzing the machining process of the connecting rod, determine the process parameters in the process, and determine the cutting force mode, force magnitude and tool path in the boring and milling processes. It is determined that the machining process allowances can be R1 = 86mm and R2 = 95mm respectively; the cutting forces in boring and milling processes are F t With F x ,According to the process parameters, the magnitude of the forces acting on the two can be estimated to be 300N, 500N and 800N, respectively, which are denoted as F1, F2 and F3.

[0043] The boring and milling processes are simplified into dynamically distributed forces, and a simulation analysis program for simulating the physical process of boring a single tooth and milling multiple teeth is written. The specific method is as follows: the motion model of the tool cutting edge is f(x,y,z)=f[x(t),y(t),z(t)], x(t)=rcos(f z ·t),y(t)=rsin(f z ·t),z(t)=f z ·t; where r is the pore radius, fz is the feed rate per tooth. Empirical equation of cutting force of cutting edge in boring and milling Among them C F is the milling force coefficient, n is the spindle speed, the unit is n / min; f z is the feed per tooth, in mm / z; a e is the radial cutting width, in mm; a p The axial depth of cut is in mm; a, b, c, and d are the indices of each component. Through secondary development of ABAQUS, a finite element analysis subroutine was developed to simulate the motion trajectory, cutting forces, and action forms during boring and milling operations, transforming the physical process of connecting rod machining into the dynamic distribution of cutting forces.

[0044] Step 3: Determine the clamping method of the connecting rod cover and the connecting rod body according to the process, and convert the clamping method into the boundary constraint conditions of the finite element simulation model in ABAQUS; the boundary constraint conditions of the connecting rod cover are as follows: Figure 4 As shown in the figure, the shape of the connecting rod cover is symmetrical, so the six degrees of freedom of the left end face of the connecting rod cover are fully constrained, denoted as GAI-L. Due to the asymmetric structure of the connecting rod body, there are two types of boundary condition constraints, such as Figure 5 、 Figure 6 As shown, Figure 5 The boundary constraint method shown is that the six degrees of freedom of the two end faces of the small hole are completely fixed, and the right end of the large hole of the connecting rod is fixed, which is denoted as GAN-R, where Figure 6 The boundary constraint method shown is that the six degrees of freedom of the two end surfaces of the small hole are completely fixed, and the left end of the large hole of the connecting rod is fixed, which is denoted as GAN-L.

[0045] In step 4, after applying boundary constraints to the simulation models of the connecting rod cap and connecting rod shaft based on the machining procedures, the physical process simulation analysis program established in step 2 is simultaneously invoked to perform deformation analysis for each machining process. The boundary constraints and process parameters in the program are then varied, and the analysis and calculation of the next machining process is performed based on the deformation of the previous machining process. This cycle is repeated until all machining procedures for the connecting rod cap and connecting rod shaft are completed, thereby obtaining the residual stress field of the final state of the connecting rod cap and connecting rod shaft.

[0046] Step 5: In ABAQUS, the assembly constraint conditions are established between the connecting rod cap and the connecting rod body, where the connecting rod cap and the connecting rod body maintain the original residual stress field when they are processed independently, and the connecting rod assembly finite element model is obtained. The machining deformation analysis of each process is carried out in sequence for the assembled connecting rod according to the processing steps. The boundary constraints applied to the assembled connecting rod are divided into three working conditions, such as Figures 7 to 9 As shown, Figure 7 The boundary constraint mode shown is that the left end of the large hole is constrained, and the two end surfaces of the small hole are fully constrained in six degrees of freedom, which is denoted as LG-1; Figure 8 The boundary constraint method shown is full constraint of three points: the two end faces of the small hole, the middle position, and the right side of the large hole, which is denoted as LG-2; Figure 9 The boundary constraint method shown is that the two end faces of the small hole and the two points in the middle are fully constrained, which is recorded as LG-3.

[0047] Step 6: Based on the processing procedures of the assembled connecting rod, finite element simulation calculation is performed on the connecting rod to realize the superposition process of multiple processes and the coupling analysis of multiple stress fields. After all process analysis and calculations are completed, the residual stress field of the connecting rod in the final state is obtained.

[0048] In step 7, after unloading the connecting rod simulation model and releasing the boundary constraints and assembly constraints, the strain variables of the connecting rod cover hole diameter and the connecting rod body big end hole diameter are extracted to obtain the evolution law of the connecting rod processing deformation.

[0049] According to the processing steps of the connecting rod, the relationship between the connecting rod processing deformation and the connecting rod processing technology under the conditions of multi-process superposition and multi-stress field coupling can be obtained. Figure 10 The following is the simulation analysis result, from which the deformation law of the connecting rod processing can be analyzed, which can be described as follows:

[0050] The relationship between machining method and connecting rod deformation: Different deformation patterns were observed when boring and milling were used during the connecting rod machining process. Under the same machining allowance, cutting force, and clamping method, the strain in boring the connecting rod cap was smaller than that in milling. The strain in milling the connecting rod body and the assembled connecting rod was smaller than that in boring.

[0051] The relationship between clamping method and connecting rod deformation: The clamping method serves as the boundary constraint during finite element simulation. When other factors remain constant, the relationship between boundary constraints and connecting rod deformation patterns varies. For the connecting rod shaft, with other machining parameters remaining constant, the deformation tendency for the two clamping methods is: GAN-L > GAN-R.

[0052] After the assembly is completed, when the machining allowance of the connecting rod is φ86mm, the deformation tendency of the three clamping methods is in the order of LG-1>LG-2>LG-3. After the assembly is completed, when the machining allowance of the connecting rod is φ95mm, the deformation tendency of the three clamping methods is in the order of LG-1>LG-3>LG-2.

[0053] The relationship between machining allowance and connecting rod machining deformation: The experimental group with the applied force being F2 was selected, and the experimental group obtained was divided into two groups with machining process allowances of φ86mm and φ95mm. Through data analysis of the φ86mm group and the φ95mm group, it can be seen that the machining deformation trend of the machining process size of φ86mm is smaller than that of the machining process size of φ95mm.

[0054] In summary, this multi-stress field coupling analysis method for connecting rod hole machining focuses on connecting rod hole machining, analyzes the connecting rod structure and machining process, and establishes finite element simulation models for the connecting rod, including those for the connecting rod cap and connecting rod body. The cutting edge motion model and cutting force model are determined based on the boring and milling processes, respectively. A machining physics simulation analysis program is established, transforming the complex machining physics into a dynamic force distribution and simplifying the analysis process. By combining assembly and boundary constraints in the connecting rod machining process and implementing process cycles based on the machining process, multi-process superposition and multi-stress field coupling analysis are achieved. This method effectively correlates the residual stress fields throughout the entire connecting rod machining process, allowing for a realistic and reasonable analysis of the deformation patterns at key connecting rod feature locations.

Claims

1. A universal multi-stress field coupling analysis method for connecting rod hole machining, wherein the connecting rod comprises a connecting rod cap and a connecting rod shaft, characterized in that: The method comprises the following steps: (1) Establish a casting simulation model of the connecting rod cap and connecting rod body, and determine the processing procedures, clamping methods, and processing parameters of the connecting rod cap and connecting rod body; (2) Simplify boring and milling processes into dynamically distributed forces and write a simulation analysis program for the physical process of boring and milling processes; (3) Perform machining deformation analysis of the connecting rod cap and the connecting rod body in each machining process in sequence; apply boundary constraints to the simulation model according to each machining process, and call the machining physical process simulation analysis program; (4) Apply assembly constraints to the connecting rod cap and the connecting rod body according to the assembly process, apply boundary constraints to the connecting rod simulation model according to each processing step of the connecting rod after assembly, and call the processing physical process simulation analysis program; perform processing deformation analysis of each processing step of the assembled connecting rod in sequence according to the processing steps; (5) The assembled connecting rod simulation model is unloaded, boundary constraints and assembly constraints are released, and the strain of the connecting rod target characteristics is extracted.

2. The universal multi-stress field coupling analysis method for connecting rod hole machining according to claim 1 is characterized in that: In the step (1), the structural features of the connecting rod cap and the connecting rod shaft are also analyzed to delete the model features that have no effect on the machining deformation in the simulation model of the connecting rod cap and the connecting rod shaft.

3. The universal multi-stress field coupling analysis method for connecting rod hole machining according to claim 1 is characterized in that: In step (2), the working conditions of boring and milling during the actual machining of the connecting rod are analyzed to convert the physical processes of boring and milling into the dynamic distribution of cutting force. The specific method is as follows: Determine the cutting motion model of the tool cutting edge based on the tool path during connecting rod machining ; Determine the cutting force model of boring or milling according to the position of the action point, the magnitude of the action force and the direction of the action force in boring or milling ,where n is the spindle speed; is the feed per tooth; The radial cutting width; The axial cutting depth is obtained; a machining physical process simulation analysis program for simulating boring and milling is established by combining the cutting motion model and the cutting force model.

4. The universal multi-stress field coupling analysis method for connecting rod hole machining according to claim 1 is characterized in that: In the step (3), the clamping methods in the boring and milling processes of the connecting rod cap and the connecting rod shaft are analyzed and the clamping methods in the machining process of the connecting rod cap and the connecting rod shaft are converted into boundary constraints in the simulation model.

5. The universal multi-stress field coupling analysis method for connecting rod hole machining according to claim 4 is characterized in that: In the step (3), the machining deformation analysis of each process of the connecting rod cap and the connecting rod body is completed on the basis of the machining deformation analysis of the previous process, so as to realize the superposition of the machining processes of the connecting rod cap and the connecting rod body and the effective correlation of the residual stress field. When performing the machining deformation analysis for each process, the parameters of the machining physical process simulation analysis program must be adjusted.

6. The universal multi-stress field coupling analysis method for connecting rod hole machining according to claim 1 is characterized in that: In the step (4), the clamping mode of the connecting rod during the boring and milling processes after assembly is analyzed and the clamping mode in the connecting rod processing process after assembly is converted into boundary constraints in the simulation model.

7. The universal multi-stress field coupling analysis method for connecting rod hole machining according to claim 6 is characterized in that: In the step (4), the processing deformation analysis of each process of the connecting rod after assembly is completed on the basis of the processing deformation analysis of the previous process, which is used to realize the superposition of the processing processes of the connecting rod after assembly and the multi-stress field coupling analysis. When performing the processing deformation analysis of each process, the parameters of the processing physical process simulation analysis program must be adjusted.

8. The universal multi-stress field coupling analysis method for connecting rod hole machining according to claim 1 is characterized in that: In the step (5), after the connecting rod simulation model is unloaded and the boundary constraints and assembly constraints are released, the strain variables of the key features of the connecting rod cover and the connecting rod body are extracted to obtain the processing deformation results under the conditions of multi-process superposition and multi-stress field coupling.

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