A method for calculating fatigue of a drill boom coupling model based on transient impact load

Abstract

This invention discloses a fatigue calculation method for a coupled model of a drill arm based on transient impact loads. This method differs from traditional low-acceleration, small-impact simulations that primarily consider linear analysis and rely heavily on statics instead of dynamics for fatigue calculations. In step S2, this method considers acquiring dynamic data of drilling reaction force under large impacts and strong nonlinear loads. Simultaneously, in step S3, the obtained dynamic data of drilling reaction force is combined with the finite element model of the drill arm to perform transient impact response dynamic analysis. The results of this transient impact response dynamic analysis are then matched with actual vehicle test data to continuously improve the model and simulate the real conditions during the drilling process as closely as possible to calculate the fatigue life of the drill arm. This method improves the fatigue calculation method for drill arms, providing a basis for both early-stage design and later-stage structural fatigue optimization, shortening the development cycle and reducing development costs.

Description

Technical Field

[0001] This invention relates to the field of drill arm structure optimization design, and specifically to a fatigue calculation method for a coupled model of a drill arm based on transient impact load. Background Technology

[0002] With the rapid development of my country's economy, infrastructure construction has become increasingly important. Rock drilling rigs are specialized engineering machinery used in tunnel drilling and blasting construction. They have various advantages such as fast drilling speed, high drilling accuracy, and short positioning time. They are widely used in mountain tunnel projects with various geological conditions and cross-sections. In the research and development of rock drilling rigs, the most important aspect is the structural strength and fatigue design of the rig's drill arm. The fatigue life design of the drill arm is directly related to the reliability and economy of the product.

[0003] With the rapid development of domestic infrastructure construction, the demand for rock drilling rigs is increasing, and the requirements for the drill arms of rock drilling rigs are also becoming more stringent. The reliability, lightweight design, and fatigue life of the drill arms have become crucial aspects of drill arm design. Currently, in the research on rock drilling rigs in the heavy industry, both domestic and foreign companies focus primarily on establishing mathematical models and simulation analysis of the drill arm's kinematics and dynamics, as well as automatic control and lightweight design. Methods for calculating drill arm fatigue damage are less common. Traditional dynamics simulations mainly focus on low acceleration and small impacts, primarily considering linear analysis methods. However, rock drilling rigs experience large impact loads on the drill bit, requiring consideration of nonlinear working conditions in rock or earthwork. The drill arm typically experiences large impacts and strong nonlinear... Working under severe loads, the drill arm operates in harsh conditions. In traditional actual point measurement, due to the limitation of the number of equipment, only the stress-time curves of key points are measured, and the stress-time variation curves of the points of maximum stress are usually not obtained. This makes it impossible to accurately calculate the fatigue life of the drill arm under large impacts and strong nonlinear loads. Consequently, there is no effective method for calculating the overall fatigue of the drill arm. Due to the lack of an effective scheme for calculating the fatigue of the drill arm of a rock drilling rig, the drill arm design is mostly based on experience. In the later optimization design such as lightweighting, there is a lack of effective theoretical data support, resulting in some redundant structures in the drill arm of the rock drill, which increases the weight of the rock drill and thus increases the manufacturing cost, reducing its competitiveness in the market.

[0004] In summary, there is an urgent need for a fatigue calculation method for a coupled drill arm model based on transient impact loads to solve the problem of inaccurate fatigue calculation results caused by the lack of calculation of large impacts and strong nonlinear loads in the existing technology. Summary of the Invention

[0005] The purpose of this invention is to provide a fatigue calculation method for a coupled drill arm model based on transient impact loads, in order to solve the problem of inaccurate fatigue calculation results caused by the lack of calculation for large impacts and strong nonlinear loads in the existing technology. The specific technical solution is as follows:

[0006] A fatigue calculation method for a coupled drill arm model based on transient impact load includes the following steps:

[0007] Step S1: Establish the finite element model of the drill arm and the rock breaking model of the drill bit through the overall model of the drill arm;

[0008] Step S2: Import the meshed drill bit rock breaking model into a nonlinear finite element software for structural analysis, and solve for the dynamic data of the reaction force corresponding to the drill bit rock breaking over time.

[0009] Step S3: The drill arm finite element model is meshed using a Q mm mesh. The dynamic reaction data from step S2 is compared with the meshed drill arm finite element model to perform transient response dynamic analysis, and the analyzed model is obtained.

[0010] Step S4: Select multiple analysis locations in the analyzed model. For each analysis location, compare the simulated value of that location in the transient response dynamics analysis model with the measured value of that location. Determine the result based on the comparison.

[0011] When the comparison results meet the deviation requirements: import the analyzed model into the fatigue analysis software to obtain the fatigue results of the drill arm;

[0012] When the comparison results do not meet the deviation requirements: after remodeling the part at the analysis location, let Q = QM, where M is a constant less than Q, and return to step S3.

[0013] In the preferred embodiment of the above technical solution, step S1 includes:

[0014] Step S1.1: Establish finite element models of the boom and propulsion mechanism, motor, hydraulic mechanism, and drill bit assembly respectively; couple the finite element models of the boom and propulsion mechanism, motor, hydraulic mechanism, and drill bit assembly to obtain the drill arm finite element model;

[0015] Step S1.2: Establish a rock mass model. Based on the finite element model of the drill bit assembly and the rock mass model in step S1.1, obtain the drill bit rock breaking model.

[0016] In the preferred embodiment of the above technical solution, in step S2, for the drill bit rock breaking model, the area in contact between the drill bit and the rock is divided into grids of K millimeters, where K is less than Q.

[0017] In the preferred embodiment of the above technical solution, Q in step S3 is 3-6 mm; M in step S4 is 0.5-1 mm.

[0018] In the preferred embodiment of the above technical solution, the analysis locations selected for data comparison in step S4 include the drill arm propulsion beam, the drill arm lateral joint, the drill arm pitch joint, the connection between the first and second arms, and the connection between the second and third arms.

[0019] In the preferred embodiment of the above technical solution, in step S4, for a single analysis position where data comparison is performed, it is determined whether the deviation requirement is met by Equation 1);

[0020] μ-2σ≤d≤μ+2σ1);

[0021] Where d is the difference between the measured value and the simulated value at a certain time point of the analysis location; μ is the mean of all differences d at the analysis location within the time period T; and σ is the variance of all differences d.

[0022] n is the number of times the measured value and the simulated value are compared within the time period T. When more than 95% of the n comparisons satisfy Equation 1), the comparison result is determined to meet the deviation requirement; otherwise, it is not.

[0023] In the preferred embodiment of the above technical solution, the calculation of μ and σ is shown in Equation 1.1):

[0024]

[0025]

[0026] Where, d i This represents the difference between the measured value and the simulated value at the i-th comparison point in the analysis; i = 1 to n.

[0027] In the preferred embodiment of the above technical solution, in step S4, when the deviation requirement is met, the analyzed model is imported into the fatigue analysis software, and the fatigue results of the drill arm are obtained through the following steps:

[0028] Step 1: Import the stress-time curves obtained from the transient response analysis into the fatigue analysis software;

[0029] Step 2: Set the SN curve of the material in the fatigue analysis software according to the actual material of each part in the finite element model of the drill arm;

[0030] Step 3: Select the time step load mapping method in the fatigue analysis software to perform SN fatigue analysis. In this process, the rainflow counting method is used to simplify the irregular stress-time history into a regular cyclic stress process.

[0031] Step 4: Set the calculation parameters;

[0032] Step 5: Analyze the fatigue results of the drill arm, visualize the fatigue life of each part of the drill arm in the fatigue analysis software, and compare the fatigue life of each part of the drill arm with the specified actual life to see if it can reach the expected life.

[0033] The preferred embodiment of the above technical solution also includes step S5, as follows:

[0034] The fatigue results of the drill arm obtained in step S4 are compared with the actual service life specified for the drill arm. Based on the comparison results, if the fatigue results do not meet the design requirements, the overall model of the drill arm is structurally optimized using the fatigue results obtained in step S4.

[0035] The preferred embodiment of the above technical solution also includes step S6, which involves repeating steps S1 to S5 on the overall drill arm model obtained after optimization in step S5 until the fatigue result of the drill arm meets the actual life specified for the drill arm.

[0036] The application of the technical solution of the present invention has the following beneficial effects:

[0037] (1) The fatigue calculation method of the drill arm coupled model based on transient impact load in this invention is different from the traditional simulation method of low acceleration and small impact, which mainly considers linear analysis and uses a lot of statics to replace dynamics to calculate fatigue. In step S2 of this method, dynamic data of drilling reaction force under large impact and strong nonlinear load are considered. At the same time, in step S3, the obtained dynamic data of drilling reaction force is combined with the finite element model of the drill arm to perform transient impact response dynamic analysis. The results of transient impact response dynamic analysis are matched with actual vehicle test data to continuously improve the model and simulate the real situation in the drilling process as much as possible to calculate the fatigue life of the drill arm. This method improves the fatigue calculation method of the drill arm, so that the drill arm has a basis in the early design and later structural fatigue optimization, shortens the development cycle and reduces the development cost.

[0038] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to the figures. Attached Figure Description

[0039] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0040] In the attached diagram:

[0041] Figure 1 This is a flowchart illustrating the fatigue calculation method of the drill arm coupling model based on transient impact load in this embodiment.

[0042] Figure 2 This is a schematic diagram illustrating the selection of the analysis location in this embodiment;

[0043] Among them, 1. at the drill arm propulsion beam; 2. at the drill arm lateral joint; 3. at the drill arm pitch joint; 4. at the connection between the first and second arms; 5. at the connection between the second and third arms. Detailed Implementation

[0044] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in many different ways as defined and covered by the claims.

[0045] Example:

[0046] A fatigue calculation method for a coupled drill arm model based on transient impact load includes steps S1 to S6, such as... Figure 1 and Figure 2 As shown, the details are as follows:

[0047] Step S1: Establish the finite element model of the drill arm and the rock-breaking model of the drill bit using the overall drill arm model:

[0048] In this embodiment, the overall model of the drill arm includes four main parts: the boom and propulsion mechanism, the motor, the hydraulic mechanism, and the drill bit assembly. The boom and propulsion mechanism mainly consists of a telescopic boom, an auxiliary boom, a slewing boom, a propulsion beam, and a propulsion beam base. The motor includes a rotary motor and a propulsion motor. The hydraulic mechanism mainly includes a boom end swing cylinder for vertical movement, a boom end swing cylinder for horizontal movement, and an auxiliary cylinder for the propulsion mechanism. The drill bit assembly mainly includes a drill bit, a drill bit, a drill rod, a drill shank, and a thread.

[0049] The finite element model of the drill arm and the rock-breaking model of the drill bit are established as follows:

[0050] Step S1.1: In the establishment of the finite element model of the drill arm, the four main parts and other small parts of the drill arm are first established in three dimensions using CAD software. The bolts, pins and other parts are simplified. After assembly, the parts are imported into the finite element preprocessing modeling software. In the finite element preprocessing modeling software, each part is meshed and then combined into an overall finite element model of the drill arm according to the actual situation through various connection methods (the finite element model of the drill arm here is the initial model, which needs to be continuously improved and optimized in subsequent steps S3 and S4).

[0051] Step S1.2: Since the established finite element model of the drill arm has many degrees of freedom, it takes a long time to perform explicit nonlinear finite element calculations. Moreover, in the actual rock drilling process, the drill bit performs rock drilling operations after the propulsion mechanism contacts and fixes with the rock. Therefore, in the process of acquiring dynamic rock drilling data, only the drill bit part of the finite element model of the drill arm is needed. That is, the simplified model of the drill bit breaking rock is established as follows: In numerical simulation technology, the drill bit, drill bit, drill rod, drill tail, thread, connecting sleeve parts are separated from the drill arm to form an overall drill bit model. A rock mass model is established, and the drill bit breaking rock model is obtained through the overall drill bit model and the rock mass model.

[0052] Step S2: Import the meshed drill bit rock-breaking model into a nonlinear finite element software for structural analysis, and solve for the dynamic data of the reaction force corresponding to the drill bit rock breaking over time, as detailed below:

[0053] Step S2.1: Mesh the drill bit rock breaking model. In the drill bit rock breaking model, the area where the drill bit contacts the rock is meshed with a grid of size K mm, where K is a constant. In this embodiment, in order to better simulate the real situation of the rock drilling process, a smaller grid (i.e., K mm, for example 2 mm) is used in the area where the drill bit contacts the rock, while a larger grid (for example 10 mm) is used in other areas of the drill bit rock breaking model.

[0054] Step S2.2: Solve for the dynamic data of the reaction force. The specific steps are as follows:

[0055] The first step is to preprocess the drill bit rock breaking model. Importing the drill bit rock breaking model into the structural analysis nonlinear finite element software requires setting the load curves, model contact type, boundary constraints, and output solution. The specific settings are as follows:

[0056] Load curve: Sets information on drill bit speed, thrust, impact kinetic energy, and propulsion time;

[0057] Model contact type: Set static friction coefficient, dynamic friction coefficient, and contact type between surfaces;

[0058] Boundary constraints: Determine the boundary constraints of the rock based on the actual situation;

[0059] Output Solution: Set the corresponding dynamic solution type in the nonlinear finite element software for structural analysis.

[0060] Step 2: Solve the structure using a nonlinear finite element software solver.

[0061] Step 3: Obtaining Rock Breaking Visualization Data: By using structural analysis nonlinear finite element software for post-processing, dynamic rock breaking visualization data corresponding to time is obtained, and dynamic data of rock drilling reaction force is obtained.

[0062] Among them, the rock breaking of the drill bit of the drill arm needs to take into account the elastic-plastic properties of steel and rock. It is a very complex dynamic process accompanied by large impacts and nonlinear loads. In the past fatigue life analysis, static analysis technology was often used, and a large amount of static analysis was used to replace dynamic analysis. The load spectrum that changes over time was not obtained for dynamic analysis. Therefore, this step S3 is mainly to obtain rock drilling dynamic data to prepare for the next step of transient dynamic response analysis.

[0063] Step S3: The drill arm finite element model is meshed using a Q mm mesh. The dynamic reaction data obtained in step S2 is then compared with the meshed drill arm finite element model to perform transient response dynamic analysis, resulting in the analyzed model (i.e., the model obtained after transient response dynamic analysis), as follows:

[0064] Step S3.1: Mesh the finite element model of the drill arm. A mesh of size Q millimeters is used to mesh the finite element model of the drill arm, where Q is a constant. In this embodiment, the initial Q is 3-6 millimeters, and the aforementioned K is less than the initial Q.

[0065] Step S3.2: In traditional methods, a large amount of static analysis is usually used instead of dynamic analysis to obtain static stress for calculating fatigue life. However, in reality, the drill arm is subjected to large impact nonlinear loads, and the stress condition of the drill arm changes drastically over time. It is difficult to obtain accurate analysis results using traditional static analysis methods instead of dynamic analysis. Moreover, due to the complex structure of the drill arm of the rock drilling rig, it is difficult to measure the location of the stress maximum using actual measurement methods, which leads to low accuracy of fatigue analysis results. Therefore, this embodiment proposes to perform transient response dynamic analysis based on the obtained dynamic data of rock drilling reaction force combined with the overall finite element model of the drill arm to obtain the dynamic stress data of the drill arm under large impact nonlinear loads. The specific steps are as follows:

[0066] 1. Import the finite element model of the drill arm into CAE software;

[0067] II. Define dynamic load curve data and create corresponding cards;

[0068] 3. Set the time step card for transient analysis, and set the analysis time, output time step, and interval time according to the actual vehicle test data;

[0069] IV. Define the type of external load, with the loading point at the center of the drill bit and the direction along the drill bit axis;

[0070] 5. Based on the dynamic data of rock drilling reaction force, establish a load set, loading excitation and dynamic load curve, and consider the influence of gravity to establish a gravity loading condition;

[0071] VI. Create the load step for transient response analysis;

[0072] VII. Define the output response of nodes at the same locations as the test points (i.e., analysis locations): stress and acceleration;

[0073] 8. Damping settings: Damping for metal structures is generally between 0.008 and 0.05, while damping for welded structures is generally between 0.008 and 0.01.

[0074] 9. Submit the solution calculation and output the model after completing the transient impact response dynamic analysis;

[0075] Step S4: Due to the large impacts and strong nonlinear loads experienced by the drill arm during rock drilling, its working conditions are complex, the working environment is harsh, and obtaining real data through experiments under certain extreme working conditions is difficult or costly. Furthermore, the location of the point of maximum stress is difficult to measure. Therefore, this embodiment also conducts point-based test data analysis at key points (i.e., multiple analysis points) of the drill arm under different typical working conditions of the rock drilling rig. Data including acceleration and stress changes over time are obtained. The data from the actual test points (i.e., analysis points) are compared with the CAE software numerical simulation results at those points (i.e., the simulation values ​​obtained after step S3). The consistency between the actual measurement and the simulation is determined based on the deviation. Detailed explanation follows:

[0076] For the model after transient impact response dynamic analysis in step S3 (hereinafter referred to as the analyzed model), multiple analysis locations are selected in the analyzed model. For each analysis location, the simulated value of that analysis location in the analyzed model is compared with the measured value (i.e., test value) of that analysis location. That is, this step involves comparing the simulated values ​​and measured values ​​of multiple key locations. Based on the comparison results, the following judgments are made:

[0077] 1) When the comparison results meet the deviation requirements: import the analyzed model into the fatigue analysis software to obtain the fatigue results of the drill arm, and then perform subsequent structural optimization based on the obtained fatigue results of the drill arm.

[0078] Generally, under constant amplitude stress cycling, the fatigue life of the boom can be estimated using the material SN curve. The SN curve describes the correspondence between the cyclic stress amplitude of the specimen and the number of cycles required for fatigue failure in a fatigue failure test. It is one of the most fundamental bases for fatigue calculation. After the transient impact response dynamic analysis is completed, the stress-time curves at each point are saved in the model. The stress-time history at each point is variable, and the rainflow counting method is needed to simplify the irregular stress-time history into a regular cyclic stress process. These will be automatically generated into a load spectrum after the model after the transient impact response dynamic analysis is input into the fatigue analysis software. The fatigue load spectrum is obtained by using the stress cycle amplitude, mean, and number of cycles at the stress points in the fatigue analysis software. After obtaining the load spectrum, the software will automatically calculate the fatigue life of the boom, as follows:

[0079] Step 1: Model Input - Import the stress-time curves obtained from the transient response analysis into the fatigue analysis software;

[0080] Step 2: Material settings. Based on the actual materials of each part in the finite element model of the drill arm, set the SN curve of the material in the fatigue analysis software.

[0081] Step 3: Stress time history load spectrum setting. The transient impact dynamics analysis result model includes the stress time history of all model elements of the drill arm. In the fatigue analysis software, the time step load mapping method can be directly selected to perform SN fatigue analysis. The SN fatigue analysis engine has embedded rainflow counting statistics, so there is no need to add load spectrum for calculation, simplifying the steps.

[0082] Step 4: Set the calculation parameters, including the stress ratio, analysis engine type, equivalent stress combination method, and mean stress correction method;

[0083] Step 5: Result Analysis. After completing the above four steps, the fatigue results of the drill arm can be analyzed. The fatigue life of each part of the drill arm can be visualized in the fatigue analysis software. The fatigue life of each part of the drill arm is compared with the specified actual life to see if the expected life can be achieved (if it cannot be achieved, the corresponding optimization design is carried out, i.e., step S5).

[0084] 2) When the comparison results do not meet the deviation requirements: After remodeling the part at the analysis location, let Q = QM, where M is a constant less than Q, and M is 0.5-1 mm or 0.1-0.3 mm (selected according to the actual situation); return to step S3. The meaning of this step is: if the data fit at a certain location (i.e., a certain analysis location) is not good, return to the drill arm coupling model establishment point to remodel the part at the analysis location, use a smaller mesh size than before to finely divide the analysis location, change the connection method between the part and the surrounding parts, until the simulation results at the analysis location and the actual vehicle test results (i.e., measured data) have a good trend fit.

[0085] It should be noted that in step S4, if... Figure 2 As shown, the analysis locations selected for data comparison include the drill arm propulsion beam 1, the drill arm lateral joint 2, the drill arm pitch joint 3, the connection between the first and second arms 4, and the connection between the second and third arms 5. That is, the analysis locations are selected within the range of the above five locations.

[0086] In this embodiment, the determination of whether the comparison result meets the deviation requirement is as follows:

[0087] For a single analysis location where data is compared, the judgment is made according to Equation 1):

[0088] μ-2σ≤d≤μ+2σ1);

[0089] Where d is the difference between the measured value and the simulated value at a certain time point of the analysis location; μ is the mean of all differences d at the analysis location within the time period T; and σ is the variance of all differences d.

[0090] n is the number of times the measured value and the simulated value are compared within the time period T (i.e., a single analysis location is compared n times within the time period T). When more than 95% of the n comparisons satisfy Equation 1), the comparison results are judged to meet the deviation requirements; otherwise, they are not.

[0091] Furthermore, the calculations of μ and σ are shown in Equation 1.1):

[0092]

[0093]

[0094] Where, d i This represents the difference between the measured value and the simulated value at the i-th comparison point in the analysis; i = 1 to n;

[0095] Step S5: After the deviation results in step S4 meet the requirements, the fatigue results of the drill arm are compared with the actual service life specified for the drill arm. Based on the comparison results, if the fatigue results do not meet the design requirements, the overall model of the drill arm is structurally optimized using the fatigue results obtained in step S4.

[0096] Step S6: Repeat steps S1 to S6 for the overall drill arm model obtained after optimization in step S5 until the fatigue result of the drill arm meets the actual life specified for the drill arm.

[0097] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A fatigue calculation method for a coupled drill arm model based on transient impact load, characterized in that, Includes the following steps: Step S1: Establish the finite element model of the drill arm and the rock breaking model of the drill bit through the overall model of the drill arm; Step S2: Import the meshed drill bit rock breaking model into a nonlinear finite element software for structural analysis, and solve for the dynamic data of the reaction force corresponding to the drill bit rock breaking over time. Step S3: The drill arm finite element model is meshed using a Q mm mesh. The dynamic reaction data from step S2 is compared with the meshed drill arm finite element model to perform transient response dynamic analysis, and the analyzed model is obtained. Step S4: Select multiple analysis locations in the analyzed model. For each analysis location, compare the simulated value of that location in the transient response dynamics analysis model with the measured value of that location. Determine the result based on the comparison. When the comparison results meet the deviation requirements: import the analyzed model into the fatigue analysis software to obtain the fatigue results of the drill arm; When the comparison results do not meet the deviation requirements: after remodeling the part at the analysis location, let Q = QM, where M is a constant less than Q, and return to step S3.

2. The fatigue calculation method for the coupled drill arm model based on transient impact load according to claim 1, characterized in that, Step S1 includes: Step S1.1: Establish finite element models of the boom and propulsion mechanism, motor, hydraulic mechanism, and drill bit assembly respectively; couple the finite element models of the boom and propulsion mechanism, motor, hydraulic mechanism, and drill bit assembly to obtain the drill arm finite element model; Step S1.2: Establish a rock mass model. Based on the finite element model of the drill bit assembly and the rock mass model in step S1.1, obtain the drill bit rock breaking model.

3. The fatigue calculation method for the coupled drill arm model based on transient impact load according to claim 1, characterized in that, In step S2, for the drill bit rock breaking model, the area where the drill bit contacts the rock is meshed using a grid of K millimeters, where K is less than Q.

4. The fatigue calculation method for the coupled drill arm model based on transient impact load according to claim 3, characterized in that, In step S3, Q is 3-6 mm; in step S4, M is 0.5-1 mm.

5. The fatigue calculation method for the coupled drill arm model based on transient impact load according to claim 1, characterized in that, In step S4, the analysis locations selected for data comparison include the drill arm propulsion beam (1), the drill arm sway joint (2), the drill arm pitch joint (3), the connection between the first and second arms (4), and the connection between the second and third arms (5).

6. The fatigue calculation method for the coupled drill arm model based on transient impact load according to claim 5, characterized in that, In step S4, for a single analysis position where data is compared, it is determined whether the deviation requirement is met by Equation 1). μ-2σ≤d≤μ+2σ1); Where d is the difference between the measured value and the simulated value at a certain time point of the analysis location; μ is the mean of all differences d at the analysis location within the time period T; and σ is the variance of all differences d. n is the number of times the measured value and the simulated value are compared within the time period T. When more than 95% of the n comparisons satisfy Equation 1), the comparison result is determined to meet the deviation requirement; otherwise, it is not.

7. The fatigue calculation method for the coupled drill arm model based on transient impact load according to claim 6, characterized in that, The calculation of μ and σ is shown in Equation 1.1): Where, d i This represents the difference between the measured value and the simulated value at the i-th comparison point in the analysis; i = 1 to n.

8. The fatigue calculation method for a coupled drill arm model based on transient impact load according to claim 6 or 7, characterized in that, In step S4, when the deviation requirement is met, the analyzed model is imported into the fatigue analysis software, and the fatigue results of the drill arm are obtained through the following steps: Step 1: Import the stress-time curves obtained from the transient response analysis into the fatigue analysis software; Step 2: Set the SN curve of the material in the fatigue analysis software according to the actual material of each part in the finite element model of the drill arm; Step 3: Select the time step load mapping method in the fatigue analysis software to perform SN fatigue analysis. In this process, the rainflow counting method is used to simplify the irregular stress-time history into a regular cyclic stress process. Step 4: Set the calculation parameters; Step 5: Analyze the fatigue results of the drill arm, visualize the fatigue life of each part of the drill arm in the fatigue analysis software, and compare the fatigue life of each part of the drill arm with the specified actual life to see if it can reach the expected life.

9. The fatigue calculation method for the coupled drill arm model based on transient impact load according to claim 8, characterized in that, It also includes step S5, as follows: The fatigue results of the drill arm obtained in step S4 are compared with the actual service life specified for the drill arm. Based on the comparison results, if the fatigue results do not meet the design requirements, the overall model of the drill arm is structurally optimized using the fatigue results obtained in step S4.

10. The fatigue calculation method for a coupled drill arm model based on transient impact load according to claim 9, characterized in that, It also includes step S6, which repeats steps S1 to S5 on the overall model of the drill arm obtained after optimization in step S5 until the fatigue result of the drill arm meets the actual life specified by the drill arm.

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