Method for calculating fatigue life of working device with bias side load working condition

Abstract

The invention discloses a method for calculating the fatigue life of a working device with an offset side load working condition, and belongs to the technical field of engineering machinery detection, and the method comprises the steps: importing actual operation mining data into a damping calibration multi-rigid body model, and carrying out the calculation to obtain bucket tooth space displacement data; the bucket tooth space displacement data, the oil cylinder driving force and the rotation driving torque are imported into the damping calibration multi-rigid-body model, and the bearing reaction is obtained through calculation; iterating a load spectrum of an action point in the bucket, and simultaneously applying the load spectrum and an oil cylinder displacement rotation speed to the damping calibration multi-rigid-body model to obtain a hinge point force between a movable arm and a bucket rod; and multiplying the stress component result of the key welding seam by the hinge point force to obtain a stress component matrix, obtaining a time-domain stress curve of the key welding seam, and carrying out fatigue damage calculation. According to the method, firstly, the influence of lateral load on the structure can be considered, the load iteration speed is high, solving is accurate, and the fatigue life calculation efficiency is high;

Description

Technical Field

[0001] The invention relates to a method for calculating the fatigue life of a working device under eccentric load conditions, and belongs to the technical field of engineering machinery detection. Background Art

[0002] Excavators are widely used in engineering applications. As the requirements for excavator structures become increasingly stringent, the need for more precise load spectra is also increasing. Load spectra encompass the various load conditions encountered during an excavator's service life. Excavators operate under complex operating conditions, including not only complex normal load conditions but also numerous lateral load conditions. Therefore, accurately identifying these lateral load conditions is crucial.

[0003] Existing methods for identifying eccentric load conditions primarily consider only the iteration of planar loads. Eccentric load acquisition is rarely addressed, and the specific impact of eccentric loads on the structure cannot be considered. Furthermore, load iteration utilizes moment balance or static balance solutions, resulting in inaccurate iterative loads or other slow iteration methods. Finally, fatigue calculations typically employ a global rigid-flexible coupling analysis or transient dynamics analysis, typically calculating stress results for the entire boom and arm before performing fatigue calculations, resulting in low computational efficiency. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the defects of the existing technology and provide a fatigue life calculation method for a working device with eccentric load conditions. First, it can consider the influence of eccentric load on the structure, and the load iteration speed is fast and the solution is accurate. Finally, the fatigue life calculation efficiency is high.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A method for calculating the fatigue life of a working device under eccentric load conditions comprises the following steps: controlling an excavator to perform operations, obtaining actual excavation data, and importing the actual excavation data into a damping calibration multi-rigid body model to calculate bucket tooth spatial displacement data; calculating a cylinder driving force and a rotary driving torque based on the actual excavation data, importing the bucket tooth spatial displacement data, the cylinder driving force, and the rotary driving torque into the damping calibration multi-rigid body model, performing a multi-rigid body dynamics analysis of the model using the bucket tooth spatial displacement data as a drive, and calculating a support reaction force between the bucket and the ground relative to a turntable rotation center coordinate system; iterating a load spectrum of an action point in the bucket based on the support reaction force, applying the load spectrum and the cylinder displacement rotation speed in the actual excavation data to the damping calibration multi-rigid body model simultaneously, and obtaining a hinge force between a boom and a dipper arm; performing a finite element analysis on the boom and dipper arm weld position to obtain a stress component result of unit load inertia release, and obtaining a final fatigue damage value based on the stress component result and the hinge force between the boom and the dipper arm.

[0007] The damping calibration multi-rigid body model is obtained specifically by calibrating the damping coefficients of the motion cylinder and the rotation in the excavator multi-rigid body model to obtain the damping calibration multi-rigid body model.

[0008] The damping coefficients of the motion cylinder and rotation in the multi-rigid body model of the excavator are calibrated to obtain the damping calibrated multi-rigid body model, including: controlling the excavator to perform single action calibration according to the multi-rigid body model, the single action calibration including single cylinder action and single rotation action calibration, obtaining single action experimental data, extracting the experimental cylinder driving force and the experimental rotation driving force from the single action experimental data, and then extracting the action cylinder driving force and the action rotation driving force according to the single action of the multi-rigid body model; subtracting the action cylinder driving force from the experimental cylinder driving force, and The time-drive damping force difference curve S1(t) is obtained by subtracting the rotational driving force from the experimental rotational driving force; the cylinder and rotation time displacement curves in the multi-rigid body model are obtained based on the single-action experimental data, and the cylinder and rotation time displacement curves are derived to obtain the time-velocity curve S2(t); the velocity-damping curve S3(v) is made based on the time-drive damping force difference curve S1(t) and the time-velocity curve S2(t); the velocity-damping curve S3(v) is imported into the initial multi-rigid body model to obtain the damping calibration multi-rigid body model.

[0009] The cylinder driving force and rotary driving torque calculated based on actual excavation data are specifically as follows: Cylinder driving force = boom large chamber pressure * boom large chamber area - boom small chamber pressure * boom small chamber area; rotary driving torque = rotary motor inlet and outlet pressure difference * motor displacement * mechanical efficiency * rotary mechanism transmission ratio / 2 .

[0010] The bucket tooth spatial displacement data includes the bucket tooth's translational X-direction displacement UX, Y-direction displacement UY, Z-direction displacement UZ relative to the vehicle's rotation center coordinate system, and the bucket tooth's rotational displacement UROZ relative to the turntable's rotation center coordinate system.

[0011] The support reaction force includes the translation force Fx of the bucket in the X direction of the plane force system, the translation force Fy of the bucket in the Y direction of the plane force system, the rotation torque Mroz in the plane force system, and the force of the external load on the excavation and rotation during the excavation and rotation actions. .

[0012] The load spectrum of the bucket action point iterated based on the support reaction force includes: calculating the rotation torque generated by the bucket during the excavation process; , , L1 represents the distance from the iterative force position of the bucket to the rotation center of the turntable; calculate the torque of the bucket mid-surface , the torque relative to the iterated position , where the position P of the eccentric load action point of the digging force is calculated as follows: , is a symbolic function, is the bucket tooth width; the rotation torque Torque with iterative position For comparison, if , then the rotary torque generated by the bucket is completely converted into the torque generated by the eccentric tooth excavation. =0, Represents side loading, if , then part of the rotary torque generated by the bucket is converted into the torque generated by the eccentric tooth excavation, and the remaining torque is converted into the side load during excavation , , the load spectrum of the action point in the bucket obtained by the final iteration is Fx, Fy, Fz, Mrox, Mroy and Mroz.

[0013] The method of obtaining a final fatigue damage value based on the stress component results and the hinge force between the boom and the bucket arm includes: multiplying the stress component results with the hinge force between the boom and the bucket arm to obtain a stress component matrix under the time domain load spectrum; then combining the stress components in the stress component matrix into a combined stress to obtain a time domain stress curve for a limited number of weld positions; finally, performing rain flow statistics on the time domain stress curve and performing fatigue damage calculation through the SN curve, performing fatigue accumulation on the data obtained in each section, and calculating the final fatigue damage value.

[0014] The stress component matrix under the time domain load spectrum is specifically: (1); among them, represents the stress component matrix under the time domain load spectrum, is the kth stress component of the jth degree of freedom of any key weld element or node under unit load inertia release analysis, represent The hinge force at the jth degree of freedom of the kth stress component at the time instant.

[0015] The stress components in the stress component matrix are combined into a combined stress, where the combined stress is a signed Mises stress, specifically: (2); is the Mises stress symbol, is the signed Mises stress synthesis method.

[0016] Beneficial effects of the present invention: The present invention provides a fatigue life calculation method for a working device with eccentric load conditions, calibrates the damping coefficients of the moving cylinder and rotation in the multi-rigid body model of the excavator, uses a precise model for iteration, uses the spatial displacement data of the bucket teeth as a drive, performs multi-rigid body dynamics analysis of the model, calculates the support reaction force between the bucket and the earth relative to the turntable rotation center coordinate system, and iterates the load spectrum of the action point in the bucket based on the support reaction force. During the iteration, rigid body kinematics and rigid body dynamics need to be solved, the iteration speed is fast, and the solution is accurate; the eccentric load has a greater impact on the life of the boom and the dipper arm. The present invention multiplies the stress component result with the hinge force between the boom and the dipper arm, which can well consider the influence of the eccentric load working device and make the life result more accurate; the fatigue life calculation only considers a limited number of welds or important positions, and uses matrix multiplication to calculate the time domain stress to avoid rigid-flexible coupling analysis, and the evaluation speed is faster and more targeted. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the sensor and rotation center coordinate system in the present invention;

[0018] Figure 2 Schematic diagram of the load force in the model of the present invention. DETAILED DESCRIPTION

[0019] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention.

[0020] The present invention discloses a method for calculating the fatigue life of a working device under lateral load conditions, comprising the following steps:

[0021] Step 1: calibrate the damping coefficients of the motion cylinder and motor in the excavator multi-rigid body model. Figure 1 As shown, A is the installation position of the inlet and outlet pressure sensors of the rotary motor, B is the installation position of the oil chamber displacement and large and small chamber pressure sensors, and C is the installation position of the rotary angular velocity sensor. First, install 8 pressure sensors, 3 cylinder displacement sensors, and one rotary angular velocity sensor. The above sensors respectively collect the pressure of the boom large and small chambers, the pressure of the dipper arm large and small chambers, the pressure of the bucket large and small chambers, the rotary inlet and outlet pressures, the boom displacement, the dipper arm displacement, the bucket displacement, and the rotary speed. The cylinder driving force can be calculated based on the cylinder pressure and the cylinder cavity area. Specifically, the boom cylinder driving force = boom large chamber pressure * boom large chamber area - boom small chamber pressure * boom small chamber area. The rotary driving torque can be calculated based on the rotary inlet and outlet pressures and the rotary motor parameters. Specifically, the rotary torque = rotary motor inlet and outlet pressure difference * motor displacement * mechanical efficiency * rotary mechanism transmission ratio / 2 The multi-rigid-body model includes a boom, an arm, a connecting rod, a rocker, a bucket, a cylinder, a turntable, an underframe, and the connecting pairs between the rigid bodies. The present invention controls the excavator to perform eight actions: boom raising, boom lowering, arm retraction, arm swinging, bucket retraction, bucket swinging, left rotation, and right rotation. Each of these eight actions is reproduced using a multi-rigid-body model.

[0022] The excavator is controlled to perform single-action calibration according to the multi-rigid-body model. Single-action calibration includes single-cylinder and single-rotation action calibration. Single-action experimental data is obtained, and the collected boom displacement curve is imported into the multi-rigid-body model. The boom displacement is used as the displacement drive of the multi-rigid-body model. The rotation, arm cylinder, and bucket cylinder drives are set to 0. The boom raising or boom lowering action is executed to obtain the time-driving force curve S4(t) and time-velocity curve S2(t) of the displacement drive. The time-boom cylinder driving force curve calculated after the experimental data collection is recorded as S5(t). The calculated displacement driving force curve is subtracted from the cylinder driving force curve to obtain the time-driving damping force difference curve S1(t) = S4(t) - S5(t). Based on the time-driving damping force difference curve S1(t) and the time-velocity curve S2(t), the velocity-damping curve S3(v) is generated. Assume the damping form is: , where C is the damping coefficient, V is the velocity, is the damping force. Finally, the velocity-damping curve S3(v) is imported into the initial multi-rigid body model to obtain the damping calibration multi-rigid body model.

[0023] In the second step, the excavator is operated. The data collected by the sensor in the first step is used to import the actual excavation data (boom displacement, dipper arm displacement, bucket displacement, and rotation speed) into the damping calibration multi-rigid body model for multi-body dynamics calculation. The spatial displacement data of the bucket teeth is calculated. The data includes the translational X-direction displacement UX, the translational Y-direction displacement UY, and the translational Z-direction displacement UZ of the bucket teeth relative to the rotation center coordinate system of the lower frame, and the rotational displacement UROZ of the bucket teeth relative to the rotation center coordinate system of the turntable frame.

[0024] Step 3: Import the collected and calculated cylinder driving force, rotary driving torque and bucket tooth displacement data (UX, UY, UZ, UROZ) into the damping calibrated multi-rigid body model, use the bucket tooth displacement data as the drive, perform model multi-body dynamics analysis, and calculate the bucket support reaction force combination to obtain the forces Fx, Fy, Mroz, and Where Fx and Fy are the translational forces of the bucket in the X direction and the Y direction in the plane force system, respectively, and Mroz is the rotational torque in the plane force system. The load force in the model of the present invention is as follows: Figure 2 shown.

[0025] Step 4: During the excavation process, the rotary torque generated by the bucket in step 2 for , L1 represents the distance from the iterative force position of the bucket to the rotation center of the turntable. The generation of the rotation torque mainly considers the translation force Fx of the bucket in the X direction in the plane force system, which is generated by the eccentric tooth excavation, followed by the side load Fz. The bucket tooth width is , the position of the eccentric load action point of the digging force for , is a sign function. Therefore, the torque on the bucket mid-surface , relative to the iteration position .if The rotary torque generated by the bucket is completely converted into the translation force of the bucket in the X direction in the plane force system. The torque generated by the eccentric tooth excavation, at this time =0( stands for sideloading). If , then part of the rotary torque generated by the bucket is converted into the eccentric tooth excavation The remaining torque is converted into side load during excavation. , so the iterative load spectrum of the action point in the bucket is Fx, Fy, Fz, Mrox, Mroy, Mroz. The bucket load spectrum and the cylinder displacement and rotation speed are simultaneously applied to the damping calibration multi-rigid body model to obtain the hinge force between the boom and the dipper stick During the iteration, the bucket can apply force between teeth or anywhere in the bucket's plane. When the load is at the bucket's center of gravity, the mass of material excavated at each time can be derived from the load Fy. This iterative method is also effective for rotary impacts, where the Fy and Fx values are very small and therefore converted entirely to Fz.

[0026] Step 5: The strain and force of the boom and bucket arm are assumed to be linearly related within the linear elastic range. First, the finite element analysis of the boom and bucket arm is performed to obtain the stress component results of the unit load inertia release at the boom and bucket arm, which are prone to cracking or critical weld positions. The stress component results of the specific weld unit are compared with the hinge force between the boom and bucket arm in step 4. Multiplying them, we can get the stress component matrix under the time domain load spectrum , as shown in Equation 1, and then the stress components are combined into signed Mises stress or other stress, as shown in Equation 2, and finally the time domain stress curves of a finite number of weld positions are obtained.

[0027] (1).

[0028] (2).

[0029] represent The hinge force of the kth stress component under the jth degree of freedom at the time, is the kth stress component of the jth degree of freedom of any key weld element or node under unit load inertia release analysis, j is the degree of freedom of the boom or arm connection point, is the signed Mises stress synthesis method.

[0030] Rainflow statistics are applied to the time-domain stress curve, and fatigue damage is calculated using the SN curve. Fatigue accumulation is performed on the data acquired for each segment, and the final fatigue damage value is calculated. This method avoids the use of rigid-flexible coupling methods to calculate stresses for all nodes or elements, resulting in faster and more targeted calculations.

[0031] The present invention provides a fatigue life calculation method for a working device under eccentric load conditions, calibrates the damping coefficients of the moving cylinder and rotation in the multi-rigid body model of the excavator, uses a precise model for iteration, uses the spatial displacement data of the bucket teeth as a drive, performs multi-rigid body dynamics analysis of the model, calculates the support reaction force between the bucket and the earth relative to the turntable rotation center coordinate system, and obtains the load spectrum of the bucket mid-surface action point based on the support reaction force. The rigid body kinematics solution and the rigid body dynamics solution need to be performed during the iteration, the iteration speed is fast, and the solution is accurate; the eccentric load has a great influence on the life of the boom and the dipper arm, and the present invention multiplies the stress component result with the hinge force between the boom and the dipper arm, which can well consider the influence of the eccentric load working device and make the life result more accurate; the fatigue life calculation only considers a limited number of welds or important positions, and uses matrix multiplication to calculate the time domain stress to avoid rigid-flexible coupling analysis, and the evaluation speed is faster and more targeted.

[0032] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowcharts and / or block diagrams, as well as combinations of processes and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowcharts and / or block diagrams. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0033] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0034] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0035] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for calculating the fatigue life of a working device under eccentric load conditions, characterized by: The following steps are involved: Control the excavator to operate, obtain actual excavation data, and import the actual excavation data into the damping calibration multi-rigid body model to calculate the bucket tooth spatial displacement data; The cylinder driving force and rotary driving torque are calculated based on actual excavation data. The bucket tooth spatial displacement data, cylinder driving force, and rotary driving torque are then imported into a damping calibration multi-rigid body model. Using the bucket tooth spatial displacement data as the driving force, a multi-rigid body dynamics analysis of the model is performed to calculate the support reaction force between the bucket and the ground relative to the turntable's rotation center coordinate system. Based on the load spectrum of the action point in the bucket iterated by the support reaction force, the load spectrum and the cylinder displacement and rotation speed in the actual excavation data are simultaneously applied to the damping calibration multi-rigid body model to obtain the hinge force between the boom and the dipper arm; Finite element analysis was performed on the boom arm weld position to obtain the stress component results of unit load inertia release. The final fatigue damage value was obtained based on the stress component results and the hinge force between the boom and arm.

2. The fatigue life calculation method for a working device under eccentric load conditions according to claim 1 is characterized in that: The damping calibration multi-rigid body model is obtained specifically by calibrating the damping coefficients of the motion cylinder and the rotation in the excavator multi-rigid body model to obtain the damping calibration multi-rigid body model.

3. The fatigue life calculation method for a working device under eccentric load conditions according to claim 2 is characterized in that: The damping coefficients of the moving cylinder and the rotation in the excavator multi-rigid body model are calibrated to obtain the damping calibration multi-rigid body model, including: Control the excavator to perform single-action calibration according to the multi-rigid body model. The single-action calibration includes single-cylinder action and single-rotation action calibration. Obtain single-action experimental data, extract the experimental cylinder driving force and experimental rotation driving force from the single-action experimental data, and then extract the action cylinder driving force and action rotation driving force according to the multi-rigid body model single action. The time-drive damping force difference curve S1(t) is obtained by subtracting the action cylinder driving force from the experimental cylinder driving force, and by subtracting the action rotary driving force from the experimental rotary driving force. The cylinder and rotation time-displacement curves in the multi-rigid body model are obtained based on the single-action experimental data, and the cylinder and rotation time-displacement curves are derived to obtain the time-speed curve S2(t); Draw the velocity-damping curve S3(v) based on the time-driving damping force difference curve S1(t) and the time-velocity curve S2(t); The velocity-damping curve S3(v) is imported into the initial multi-rigid-body model to obtain the damping calibrated multi-rigid-body model.

4. The fatigue life calculation method for a working device under eccentric load conditions according to claim 1 is characterized in that: The cylinder driving force and rotary driving torque calculated based on the actual excavation data are specifically: Cylinder driving force = boom large chamber pressure * boom large chamber area - boom small chamber pressure * boom small chamber area; rotary driving torque = rotary motor inlet and outlet pressure difference * motor displacement * mechanical efficiency * rotary mechanism transmission ratio / 2 .

5. The fatigue life calculation method of a working device under eccentric load conditions according to claim 1 is characterized in that: The bucket tooth spatial displacement data includes the bucket tooth's translational X-direction displacement UX, Y-direction displacement UY, Z-direction displacement UZ relative to the vehicle's rotation center coordinate system, and the bucket tooth's rotational displacement UROZ relative to the turntable's rotation center coordinate system.

6. The fatigue life calculation method for a working device under eccentric load conditions according to claim 5 is characterized in that: The support reaction force includes the translation force Fx of the bucket in the X direction of the plane force system, the translation force Fy of the bucket in the Y direction of the plane force system, the rotation torque Mroz in the plane force system, and the force of the external load on the excavation and rotation during the excavation and rotation actions. .

7. The fatigue life calculation method for a working device under eccentric load conditions according to claim 6 is characterized in that: The load spectrum of the action point in the bucket iterated based on the support reaction force includes: Calculate the rotary torque generated by the bucket during digging , , L1 represents the distance from the iterative force position of the bucket to the rotation center of the turntable; Calculate the torque on the bucket mid-surface , the torque relative to the iterated position , where the position P of the eccentric load action point of the digging force is calculated as follows: , is a symbolic function, is the bucket tooth width; The rotation torque Torque with iterative position For comparison, if , then the rotary torque generated by the bucket is completely converted into the torque generated by the eccentric tooth excavation. =0, Represents side loading, if , then part of the rotary torque generated by the bucket is converted into the torque generated by the eccentric tooth excavation, and the remaining torque is converted into the side load during excavation , , the load spectrum of the action point in the bucket obtained by the final iteration is Fx, Fy, Fz, Mrox, Mroy and Mroz.

8. The fatigue life calculation method for a working device under eccentric load conditions according to claim 7 is characterized in that: The final fatigue damage value obtained based on the stress component results and the hinge force between the boom and the stick includes: Multiply the stress component result with the hinge force between the boom and the stick to obtain the stress component matrix under the time domain load spectrum; Then, the stress components in the stress component matrix are combined into combined stress to obtain the time domain stress curves of a finite number of weld positions; Finally, the time domain stress curve is subjected to rain flow statistics and fatigue damage calculation is performed through the SN curve. The data obtained in each section are fatigue accumulated to calculate the final fatigue damage value.

9. The fatigue life calculation method for a working device under eccentric load conditions according to claim 8 is characterized in that: The stress component matrix under the time domain load spectrum is specifically: （1）； in, represents the stress component matrix under the time domain load spectrum, is the kth stress component of the jth degree of freedom of any key weld element or node under unit load inertia release analysis, represent The hinge force at the jth degree of freedom of the kth stress component at the time instant.

10. The fatigue life calculation method of a working device under eccentric load conditions according to claim 9, characterized in that: The stress components in the stress component matrix are combined into a combined stress, where the combined stress is a signed Mises stress, specifically: （2）； is the Mises stress symbol, is the signed Mises stress synthesis method.

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