Method and system for measuring contact strength of adjustable diameter bolt

Abstract

The application provides a method and system for measuring the contact strength of an adjustable diameter bolt. The test method involves installing a cone sleeve assembly into a test fixture, then fixing and installing it into a torsion testing machine. A rotating torque is applied by the torsion testing machine. The contact surface parameters, including the contact surface strength, are measured and calculated by combining the locking torque and the test complex structure parameters. By controlling a variable, the correlation between the contact surface strength and the variable is analyzed, thereby avoiding the influence of other factors and improving the accuracy of the test. The system involves a test sleeve, a locking nut, an adjusting ring, a guide rod and other simple tools and tooling. The contact surface parameters of the cone sleeve assembly are measured, and the correlation between the contact surface parameters and other factors is analyzed. Standard tools and equipment are used for installation and testing, and the method can be used for comparative testing of various specifications, diameters and different parameters.

Description

Technical Field

[0001] This application relates to the field of adjustable diameter bolt technology, and more particularly to a method and system for measuring the contact strength of adjustable diameter bolts. Background Technology

[0002] Adjustable diameter bolts are a new type of connector designed based on the principle of interference fit of conical surfaces. They consist of one or more pairs of conical sleeve assemblies with inner and outer conical elastic rings. Under axial displacement, the inner elastic ring contracts under pressure, gripping the central core rod, while the outer elastic ring expands under pressure, tightly fitting the mounting hole. This forms a tightly integrated interference fit connection, resisting vibration and transmitting shear force. Because adjustable diameter bolts eliminate gaps between the connector and the structure, reduce or eliminate wear caused by vibration, allow for quick installation and disassembly, and are reusable, they can be applied to: helicopter rotor blade accessories for rapid installation and disassembly of blades; external pylons and other accessories for aircraft / helicopters; rapid installation and disassembly of aircraft engines; positioning and alignment of jet engine components; clamp positioning and alignment; and connection points for aiming devices.

[0003] As adjustable diameter bolts are used more and more widely and in more and more important applications, higher requirements are being placed on the accuracy of their design calculations. Currently, the tightness of the interference fit after the installation of adjustable diameter expansion bolts is theoretically calculated by locking installation force or installation torque. However, due to the influence of multiple factors such as friction coefficient and manufacturing error, the theoretical calculation differs greatly from the actual value, making it difficult to meet the needs of precision assembly connections. Summary of the Invention

[0004] The technical problem to be solved by this application is that the tightness of the interference fit after the installation of adjustable diameter expansion bolts is currently calculated theoretically by locking installation force or installation torque. However, due to the influence of multiple factors such as friction coefficient and manufacturing error, the theoretical calculation differs greatly from the actual value, which is difficult to meet the requirements of precision assembly connection.

[0005] In order to solve the above problems, or at least partially solve the above technical problems, this application provides a method and system for measuring the contact strength of adjustable diameter bolts.

[0006] In a first aspect, the present invention discloses a method for measuring the contact strength of an adjustable diameter bolt, comprising, Obtain the structural parameters of the cone sleeve assembly and the test fixture, install the cone sleeve assembly into the test fixture, and then install the test fixture containing the cone sleeve assembly into the torsion testing machine. The test fixture includes a test sleeve, two locking nuts, and a guide rod. The structural parameters include the diameter of the guide rod, the contact area between the cone sleeve assembly and the guide rod, and the coefficient of friction of the contact surface between the cone sleeve assembly and the guide rod. Start the torsion testing machine and record the torque value displayed by the torsion testing machine and the locking torque of the locking nut to obtain the rotational torque and locking torque. Calculate the relevant parameters of the contact surface based on the rotational torque, locking torque, and structural parameters, and analyze the correlation between the contact surface strength, locking torque, and structural parameters of the test complex. The contact surface parameters include the contact surface friction, contact surface normal force, and contact surface strength.

[0007] Preferably, the process involves obtaining the structural parameters of the cone sleeve assembly and the test fixture, installing the cone sleeve assembly into the test fixture, and then installing the test fixture containing the cone sleeve assembly into a torsion testing machine. Specifically, this includes the following steps: Measure the dimensions of the tapered sleeve assembly, the diameter of the guide rod, and the dimensions of the test sleeve; Based on the dimensional parameters, the contact surface between the tapered sleeve assembly and the guide rod is analyzed, and the contact surface area and friction coefficient are calculated to obtain the structural parameters, including the tapered surface angle of the tapered sleeve assembly, the diameter of the guide rod, the contact surface area between the tapered sleeve assembly and the guide rod, and the friction coefficient of the contact surface between the tapered sleeve assembly and the guide rod. The cone sleeve assembly is installed onto the test fixture, assembled into a test complex, and then the test complex is loaded into the torsion testing machine.

[0008] Preferably, the cone sleeve assembly is mounted onto the test fixture to form a test complex, and the test complex is then loaded into the torsion testing machine, specifically including the following steps: The guide rod is inserted into the tapered sleeve assembly, and the test sleeve is fitted around the outer periphery of the tapered sleeve assembly; An adjusting ring is installed inside each locking nut, and a locking nut is installed at each end of the test sleeve; Install the locking nut using a torque wrench or a torque-controlled installation device to obtain the test assembly. Then, load the test assembly into the torsion testing machine, which holds the two ends of the guide rod. The test sleeve is fixed on the fixed fixture.

[0009] Preferably, the torsion testing machine is started, and the torque value displayed by the torsion testing machine and the locking torque of the locking nut are recorded to obtain the rotational torque and locking torque. Based on the rotational torque, locking torque, and structural parameters, the relevant parameters of the contact surface are calculated, and the correlation between the contact surface strength, locking torque, and structural parameters of the test complex is analyzed. Specifically, this includes the following steps: Tighten the locking nut to the preset installation torque to obtain the locking torque; Start the torsion testing machine. The torsion testing machine applies rotational torque from both ends of the test complex. The rotating guide rod rotates, and the rotational torque applied by the guide rod is recorded to obtain the rotational torque. Calculate the contact surface friction force, contact surface normal force, and contact surface strength based on the locking torque, rotational torque, and structural parameters. The correlations between locking torque, rotational torque and contact surface strength, contact surface area and contact surface strength, contact surface friction coefficient and contact surface strength, and the conical angle of the tapered sleeve assembly and contact surface strength were analyzed.

[0010] Preferably, the analysis includes the correlation between locking torque, rotational torque and contact surface strength, the correlation between contact surface area and contact surface strength, the correlation between contact surface friction coefficient and contact surface strength, and the correlation between the cone angle of the tapered sleeve assembly and contact surface strength, including: Keep the locking torque, contact area, contact friction coefficient, and cone angle of the cone sleeve assembly as one variable, and keep other variables constant, and calculate the change value of the variable; After measuring the contact surface strength value after controlling for the variable, calculate the change in the contact surface strength value, analyze the correlation between the change in the variable and the change in the contact surface strength value, and determine whether the change in the variable and the change in the contact surface strength value are related.

[0011] Secondly, the present invention discloses a system for measuring the contact strength of an adjustable diameter bolt, including the aforementioned method for measuring the contact strength of an adjustable diameter bolt. The system includes a test sleeve, a locking nut, and a guide rod. The locking nut is connected to the test sleeve. The test sleeve is fitted around the outer periphery of a tapered sleeve assembly. The tapered sleeve assembly is fitted around the outer periphery of the guide rod. The locking nut is installed at both ends of the tapered sleeve assembly.

[0012] Preferably, the outer surface of the tapered sleeve assembly contacts the inner surface of the test sleeve, and the inner surface of the tapered sleeve assembly contacts the outer surface of the guide rod.

[0013] Preferably, the assembly includes an adjusting ring, a locking nut with a mounting groove, and the adjusting ring is installed in the mounting groove. When the locking nut is installed at both ends of the tapered sleeve assembly, the adjusting ring abuts against both ends of the tapered sleeve assembly.

[0014] Preferably, the guide rod has internal hexagonal grooves at both ends, the test sleeve has a hexagonal wrench boss, the test sleeve has external thread structure on both ends, and the inner wall of the mounting groove of the locking nut has an internal thread structure that matches the external thread structure.

[0015] Preferably, an opening is made at the center of the locking nut, and the internal hexagonal groove of the guide rod is exposed from the opening.

[0016] The technical solution provided in this application has the following advantages compared with the prior art: The method and system for measuring the contact strength of adjustable diameter bolts provided in this application include a test method in which a tapered sleeve assembly is installed into a test fixture and then fixedly mounted in a torsion testing machine. A rotational torque is applied by the torsion testing machine, and the contact surface parameters, including the contact surface strength, are measured and calculated by combining the locking torque and the structural parameters of the test assembly. By controlling a variable, the correlation between the contact surface strength and the variable is analyzed, thereby avoiding the influence of other factors and improving the accuracy of the test.

[0017] Furthermore, by using the controlled variable method, the correlation between the friction coefficient and the contact surface strength, the correlation between the contact surface strength and the contact surface area, and the correlation between the contact surface strength and the cone angle can be obtained. No expensive special equipment is required; the contact strength calculation and parameter comparison can be completed through simple tooling and conventional calculations, thereby improving the accuracy of the test results. The test results can be used to improve the design and find the optimal solution for the design.

[0018] The system mentions that the testing system consists of simple tools and fixtures such as test sleeves, locking nuts, adjusting rings, and guide rods. It measures the contact surface parameters of the tapered sleeve assembly, analyzes the correlation between the contact surface parameters and other factors, and can be installed and tested using standard tools and equipment. It can be used for comparative testing between various diameters and different parameters. Attached Figure Description

[0019] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 A flowchart illustrating a method for measuring the contact strength of an adjustable diameter bolt provided in this application; Figure 2 A flowchart illustrating step S1 of the method for measuring the contact strength of an adjustable diameter bolt provided in this application; Figure 3 A flowchart illustrating step S2 of the method for measuring the contact strength of an adjustable diameter bolt provided in this application; Figure 4 A schematic diagram of the structure of a contact strength measurement system for an adjustable diameter bolt provided in this application; Figure 5A cross-sectional structural schematic diagram of AA', a measurement system for the contact strength of an adjustable diameter bolt provided in this application; Figure 6 An exploded structural diagram of a contact strength measurement system for an adjustable diameter bolt provided in this application; Figure 7 This is a schematic diagram of the exploded structure of the cone sleeve assembly.

[0022] Explanation of reference numerals in the attached figures: 1. A measurement system for the contact strength of adjustable diameter bolts; 11. Test sleeve; 12. Locking nut; 121. Mounting groove; 13. Guide rod; 14. Adjusting ring; 2. Conical sleeve assembly; 21. Inner conical sleeve; 22. Outer conical sleeve; 23. Semi-inner conical sleeve. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0024] Firstly, see Figures 1-3 This invention discloses a method for measuring the contact strength of an adjustable diameter bolt, comprising: Step S1: Obtain the structural parameters of the cone sleeve assembly and the test fixture, install the cone sleeve assembly into the test fixture, and install the test fixture containing the cone sleeve assembly into the torsion testing machine; the test fixture includes a test sleeve, two locking nuts, and a guide rod, and the structural parameters include the diameter of the guide rod, the contact area between the cone sleeve assembly and the guide rod, and the coefficient of friction of the contact surface between the cone sleeve assembly and the guide rod; Step S2: Start the torsion testing machine, record the torque value displayed by the torsion testing machine and the locking torque of the locking nut, obtain the rotational torque and locking torque, calculate the relevant parameters of the contact surface based on the rotational torque, locking torque and structural parameters, and analyze the correlation between the contact surface strength, locking torque and the structural parameters of the test complex. The contact surface parameters include the contact surface friction, the contact surface normal force and the contact surface strength.

[0025] Specifically, in step S1, the diameter is measured at three different cross-sections (middle and both ends) of the guide rod using measuring tools (such as calipers), and the average value is taken. The contact area S between the tapered sleeve assembly and the guide rod is calculated. The friction coefficient μ is determined by combining the surface condition of the contact surface (roughness, oxide layer / coating), lubrication method, and material friction coefficient manual or standard test data. The test fixture assembly is completed, and then the hexagonal wrench boss of the test sleeve is inserted into the torsion testing machine fixing fixture and locked. The measuring head of the testing machine is embedded into the hexagonal groove inside the guide rod, ensuring a firm connection without slippage. The core basic data necessary for subsequent calculations, such as the guide rod diameter (for the calculation arm L), contact area S, and friction coefficient μ, are obtained to ensure accurate calculation results. By assembling the test fixture in a standardized manner, a stable interference fit is ensured between the tapered sleeve assembly, the guide rod, and the test sleeve, avoiding abnormal contact caused by assembly deviations. At the same time, the firm clamping eliminates additional displacement or slippage during the testing process, reducing torque measurement errors.

[0026] Specifically, in step S2, the target locking torque M1 of the locking nuts is set according to the test requirements. Using a torque wrench or the torque setting function of a torsion testing machine, the locking nuts at both ends are tightened evenly to the set torque, and the actual value is recorded. Then, the torsion testing machine is started, and a steadily increasing torsional force is applied to the guide rod through the measuring head until the guide rod rotates relative to the tapered sleeve assembly. The rotational torque M2 at this time is recorded in real time. The contact surface friction, normal force, and contact strength are calculated sequentially according to the formulas f=M2 / L, N=f / μ, and p=N / S. Using the controlled variable method, other parameters are kept constant while only the target variables (such as locking torque M1, friction coefficient μ, etc.) are changed. The torque test and parameter calculation process is repeated to obtain multiple sets of corresponding data. The correlation and rate of change between each variable and the contact strength are analyzed. By using standardized mechanical formulas, the fuzzy degree of fit is transformed into quantifiable indicators of friction, normal force, and contact strength, achieving accurate characterization of contact strength. Correlation analysis clarifies the inherent laws governing locking torque, structural parameters, and contact strength, providing support for optimizing installation parameters in practical applications and a scientific basis for optimizing product structural design. The process integrates torque testing, parameter calculation, and correlation analysis, creating a coherent and logically closed-loop workflow that eliminates the need for separate operations, resulting in high testing and analysis efficiency. Torque measurement relies on the high-precision sensing technology of a torsion testing machine, calculations are based on classical mechanics formulas, and correlation analysis uses the controlled variable method to eliminate irrelevant interference, ensuring accurate and reliable results. The calculation process is simple and easy to understand, requiring no complex algorithms, and the correlation analysis results can directly guide actual production, installation, and product design, making it suitable for various application scenarios such as aerospace and precision machinery, demonstrating strong practicality. The entire process requires no dedicated computing equipment or complex analysis software, aligning with the original invention's low-cost advantage and offering excellent economic benefits.

[0027] It is understandable that the cone sleeve assembly is installed into the test fixture and then fixedly installed in the torsion testing machine. The torsion testing machine applies a rotational torque, and the contact surface parameters, including the contact surface strength, are measured and calculated by combining the locking torque and the structural parameters of the test complex. By controlling a variable, the correlation between the contact surface strength and the variable is analyzed, thereby avoiding the influence of other factors and improving the accuracy of the test.

[0028] Furthermore, by using the controlled variable method, the correlation between the friction coefficient and the contact surface strength, the correlation between the contact surface strength and the contact surface area, and the correlation between the contact surface strength and the cone angle can be obtained. No expensive special equipment is required; the contact strength calculation and parameter comparison can be completed through simple tooling and conventional calculations, thereby improving the accuracy of the test results. The test results can be used to improve the design and find the optimal solution for the design.

[0029] Step S1 specifically includes the following steps: Step S11: Measure the dimensions of the tapered sleeve assembly, the diameter of the guide rod, and the dimensions of the test sleeve; Step S12: Analyze the contact surface between the tapered sleeve assembly and the guide rod based on the dimensional parameters, calculate the contact surface area and friction coefficient, and obtain the structural parameters, including the tapered surface angle of the tapered sleeve assembly, the diameter of the guide rod, the contact surface area between the tapered sleeve assembly and the guide rod, and the friction coefficient of the contact surface between the tapered sleeve assembly and the guide rod. Step S13: Install the cone sleeve assembly onto the test fixture, assemble it into a test complex, and then load the test complex into the torsion testing machine.

[0030] Specifically, using precision calipers or 3D measuring instruments, key dimensions of the tapered sleeve assembly (such as conical surface dimensions and inner hole dimensions), the diameter of the guide rod (measured at multiple cross-sections at the middle and both ends, and the average value), the inner wall dimensions of the test sleeve, and the thread parameters at both ends are measured. Based on the measured dimensional parameters, a 3D model (software modeling) is calculated using geometric formulas to analyze the actual contact area between the tapered sleeve assembly and the guide rod, thereby determining the contact area. This is combined with the material type of the tapered sleeve assembly and the guide rod, the surface condition of the contact surface (such as roughness, presence of coating or oxide layer), and the preset lubrication method, referencing material friction coefficient manuals or standards for the same operating conditions. Experimental data was used to determine the friction coefficient of the contact surfaces, ultimately integrating the complete structural parameters, including the cone angle of the cone sleeve assembly, the guide rod diameter, the contact surface area, and the contact surface friction coefficient. The cone sleeve assembly was fitted onto the guide rod, with adjusting rings installed at both ends and fitted to the end faces of the cone sleeve assembly. The entire assembly was then inserted into the test sleeve, and two locking nuts were screwed into the threads at both ends of the test sleeve. After assembling the test fixture, a stable test complex was formed. The hexagonal wrench boss of the test sleeve was then inserted into the fixing fixture of the torsion testing machine and locked. The testing machine's adapter measuring head was embedded into the pre-set internal hexagonal groove of the guide rod, ensuring a secure connection between the measuring head and the guide rod without slippage. By using the structural parameters obtained through system measurement and calculation, and completing the assembly of the test fixture and clamping of the test complex according to specifications, it is possible to ensure that the cone sleeve assembly, guide rod, and test sleeve form a contact state that meets the testing requirements, avoiding abnormal contact due to assembly deviations, and eliminating any additional displacement or slippage that may occur during testing, thus reducing torque measurement errors. The assembly process of the test fixture conforms to the tooling design logic, and can be flexibly adapted to different specifications of cone sleeve components, guide rods and test sleeves. Moreover, the connection method with the torsion testing machine is simple and universal, requiring no additional modification and has strong adaptability. The entire operation process effectively controls random errors in parameter acquisition and equipment clamping by measuring dimensions at multiple cross sections, clarifying the standard for measuring the friction coefficient, and standardizing the assembly and clamping process.

[0031] Step S13 specifically includes the following steps: Step S131: The guide rod is inserted into the tapered sleeve assembly, and the test sleeve is fitted around the outer periphery of the tapered sleeve assembly; Step S132: Insert an adjusting ring into each locking nut, and insert a locking nut into each end of the test sleeve; Step S133: Install the locking nut using a torque wrench or a torque-controlled installation device to obtain the test assembly. Place the test assembly into the torsion testing machine, with the torsion testing machine supporting both ends of the guide rod, and the test sleeve fixed on the fixing fixture.

[0032] Specifically, the guide rod is precisely inserted into the preset position inside the tapered sleeve assembly to ensure initial contact between the two. Then, the test sleeve is fitted onto the outer circumference of the tapered sleeve assembly, ensuring that the tapered sleeve assembly is in the center area of ​​the test sleeve without any offset. First, the adjusting ring is embedded into the two locking nuts respectively. Then, the locking nuts with the adjusting rings are screwed into the threads at both ends of the test sleeve. Using a torque wrench or a torque-controlled installation device, the force is smoothly applied according to the test requirements to complete the installation of the locking nuts, ensuring that the guide rod, tapered sleeve assembly, test sleeve, locking nuts, and adjusting ring fit tightly together to form a structurally stable test assembly. Finally, the test assembly is placed in the designated position of the torsion testing machine, allowing the adapter of the testing machine to precisely abut against both ends of the guide rod. At the same time, the test sleeve is firmly clamped onto the fixed fixture of the torsion testing machine, ensuring that the whole assembly is without looseness or gaps. Through a standardized assembly process, the components form a collaborative testing assembly. The torsion testing machine's precise hold on the guide rod and the secure fixation of the test sleeve ensure that the relative positions of the components remain unchanged during testing, preventing axial displacement or radial wobble. This ensures that the tapered sleeve assembly and guide rod maintain a contact state that meets testing requirements, effectively eliminating the interference of clamping deviations on subsequent torque measurements and providing a reliable testing prerequisite for the accurate calculation of contact strength-related parameters. The assembly and clamping process is clear and easy to operate, requiring no complex professional skills or special modified equipment. It is adaptable to tapered sleeve assemblies, guide rods, and test sleeves of different specifications, offering strong versatility. With the help of the constant torque installation equipment and the standardized clamping method of the testing machine, the fit accuracy of each component can be precisely controlled, reducing testing errors caused by manual operation or component loosening. At the same time, it quickly completes the connection from component assembly to testing machine clamping without additional transitional procedures, significantly improving the continuity and efficiency of the testing process.

[0033] Step S2 specifically includes the following steps: Step S21: Tighten the locking nut to the preset installation torque to obtain the locking torque; Step S22: Start the torsion testing machine. The torsion testing machine applies rotational torque from both ends of the test complex. The rotating guide rod rotates and is recorded as the rotational torque applied by the guide rod, thus obtaining the rotational torque. Step S23: Calculate the contact surface friction, contact surface normal force, and contact surface strength based on the locking torque, rotational torque, and structural parameters; Step S24: Analyze the correlation between locking torque, rotational torque and contact surface strength, contact surface area and contact surface strength, contact surface friction coefficient and contact surface strength, and the correlation between the cone angle of the cone sleeve assembly and contact surface strength.

[0034] Specifically, according to the preset installation torque standard, the locking nuts of the test complex are smoothly tightened using a torque wrench or a torque-controlled installation device. The final actual applied locking torque is recorded in real time. The torsion testing machine is started, and a steadily increasing rotational torque is applied to the guide rod from both ends of the test complex through the equipment adapter component until the guide rod rotates relative to the cone sleeve assembly. The applied rotational torque value is recorded simultaneously. The obtained structural parameters (including guide rod diameter, contact surface area, contact surface friction coefficient, and cone surface angle of the cone sleeve assembly) are retrieved. The rotational force arm L of the guide rod is calculated from the guide rod diameter. Combining the recorded locking torque and rotational torque, the rotational force arm L of the guide rod is calculated using the formulas f=M2 / L (f is the contact surface friction force, M2 is the rotational torque, and L is the guide rod rotational force arm), N=f / μ (N is the contact surface normal force, μ is the friction coefficient), and p=N / S (p is the contact surface strength, S is the friction coefficient). The relevant parameters of the contact surface are calculated sequentially (for the contact surface area). Using the controlled variable method, while keeping other parameters constant, the correlations between locking torque and contact surface strength, rotational torque and contact surface strength, contact surface area and contact surface strength, contact surface friction coefficient and contact surface strength, and the cone angle of the cone sleeve assembly and contact surface strength are analyzed one by one to clarify the influence law and trend of each factor on the contact surface strength. By tightening the locking nut to a preset torque, a stable interference fit is formed between the cone sleeve assembly, the guide rod, and the test sleeve. The torsion testing machine applies rotational torque and records the data, providing the core basis for the calculation of contact surface parameters. Through standardized formula calculation, the fuzzy fit tightness is transformed into accurately characterizable contact surface friction, normal force, and contact strength indicators. Multi-dimensional correlation analysis can systematically reveal the intrinsic relationship between each key parameter and contact strength, providing scientific data support for optimizing the installation parameters of adjustable diameter bolts (such as setting the locking torque) and improving structural design (such as adjusting the contact surface area and cone angle), filling the gap in the lack of systematic correlation analysis in the existing technology. Both the application of locking torque and the measurement of rotational torque rely on standardized equipment, ensuring high data acquisition accuracy and effectively reducing human error. The calculation process is based on classical mechanics formulas, with rigorous logic and easy-to-understand principles, requiring no complex algorithms or specialized computing equipment. It balances accuracy and economy. The correlation analysis uses the controlled variable method, which can eliminate interference from irrelevant factors, ensuring the reliability and relevance of the analysis results. It also covers the core parameters affecting contact strength, providing comprehensive analysis dimensions. The entire process, from data acquisition and parameter calculation to correlation analysis, forms a complete closed loop with smooth operation and no need for additional process breakdown, significantly improving testing efficiency. At the same time, the analysis results can directly guide actual production installation and product design, adapting to various application scenarios such as aerospace and precision machinery, making it highly practical and adaptable.

[0035] Step S24 includes: Step S241: Keep the locking torque, contact surface area, contact surface friction coefficient, and cone angle of the cone sleeve assembly as one variable, and keep other variables constant, and calculate the change value of the variable; Step S242: Measure the contact surface strength value after controlling the variable, calculate the change in the contact surface strength value, analyze the correlation between the change in the variable and the change in the contact surface strength value, and determine whether the change in the variable is related to the change in the contact surface strength value.

[0036] Specifically, each time, one of the following is selected as the target variable: locking torque, contact area, contact friction coefficient, and cone angle of the cone sleeve assembly. The other three variables are strictly kept at preset constant values. According to actual test requirements and application scenarios, multiple sets of proportionally increasing or decreasing gradient change values ​​are set for the target variable. For each set of target variable values, the precise measurement of contact surface strength is repeated according to the established test procedure. Then, the specific change values ​​between each set of target variable values ​​and the corresponding change values ​​of contact surface strength are calculated. The correlation coefficient (such as R²) is used to calculate the quantitative analysis method to determine the correlation between the change value of the target variable and the change value of contact surface strength. Then, it is determined whether there is a significant correlation between the change of the target variable and the change of the contact surface strength value. The above process is used to complete the independent analysis of the four core variables one by one. By strictly controlling a single variable while keeping other variables constant, the cross-interference caused by the simultaneous fluctuation of multiple variables is effectively eliminated. The independent impact of each target variable on the contact surface strength is precisely focused. This not only clarifies whether there is a correlation between variable changes and contact surface strength changes, but also quantifies the degree of correlation (strong correlation, weak correlation, or no correlation). This provides a targeted and data-supported analytical basis for subsequent optimization of installation parameters for adjustable diameter bolts (such as setting a reasonable locking torque) and structural design improvements (such as adjusting the contact surface area and cone angle), ensuring the scientific nature and accuracy of optimization directions and improvement measures. The analysis employs the classic controlled variable method, which is logically rigorous and operationally standardized. It minimizes the interference of irrelevant factors on the analysis results, ensuring high reliability and persuasiveness of the conclusions. It comprehensively covers the four core variables affecting the strength of the contact surface, providing complete analytical dimensions and enabling a systematic understanding of the effects of each factor, avoiding the omission of key influencing factors. The operation process is based on existing testing procedures and data foundations, requiring no additional complex equipment, cumbersome steps, or professional algorithms. It is highly practical and has low operating costs. The analysis results can be directly applied to actual production, installation, and product design scenarios, providing clear and actionable guidance for parameter selection and structural optimization, significantly improving the design accuracy and reliability of adjustable diameter bolts.

[0037] As one example, for correlation analysis, the relationship between variables and contact intensity can be obtained and analyzed by linear regression fitting or nonlinear fitting.

[0038] Specifically, based on the controlled variable method, one of the following is selected as a single target variable: locking torque, contact surface area, contact surface friction coefficient, and cone angle of the cone sleeve assembly. The other three variables are kept strictly constant. For the target variable, the linear regression fitting derivation method needs to set at least 5 sets of gradient values ​​that increase or decrease proportionally, and the nonlinear fitting derivation method needs to set at least 6 sets of gradient values ​​that cover the possible nonlinear range. The contact surface strength (p) of each variable is accurately measured according to the standard test procedure to obtain multiple sets of corresponding data between the variable and the contact strength. For linear regression fitting derivation, a scatter plot is drawn with the target variable as the x-axis and contact intensity as the y-axis. The least squares method is used to fit the linear equation p=kX+b (X is the target variable, k is the slope, and b is the intercept). The correlation coefficient R² (0≤R²≤1) is calculated to quantify the degree of linear correlation. For nonlinear fitting derivation, a scatter plot is also drawn, and various types of trend line fittings such as quadratic curves, power functions, and exponential functions are tried in turn. The R² values ​​of each trend line are compared, and the model with the largest R² is selected as the optimal nonlinear fitting model (such as p=aS²+bS+c, p=aμ^b, etc., where a, b, and c are fitting coefficients), thereby clarifying the nonlinear relationship expression between the variable and contact intensity. By using two targeted fitting derivation methods, linear and nonlinear, different types of relationship between the variable and contact intensity can be accurately adapted, breaking the limitations of single linear analysis and achieving a comprehensive quantitative characterization of the correlation between the two. It can not only determine whether the change of variable and the change of contact intensity are related, but also clarify the degree of correlation (strong / weak correlation), the direction of correlation (positive / negative correlation), and the specific change law (such as linear increase, nonlinear decrease). The analysis results provide precise data support for the design optimization and installation parameter setting of adjustable diameter bolts. For example, after clarifying the linear relationship between locking torque and contact strength through linear fitting, the minimum locking torque required to meet the target contact strength can be directly calculated. After mastering the optimal range of the cone angle for contact strength through nonlinear fitting, the structural design of the cone sleeve assembly can be optimized in a targeted manner. Both derivation methods are logically rigorous, based on the control variable method and multiple sets of measured data, effectively eliminating interference from irrelevant factors. The fitting results are highly reliable and persuasive, with comprehensive applicability, covering both common linear correlation scenarios and complex nonlinear correlation cases, avoiding the limitations of a single fitting method. The operation process is simple and easy to perform, requiring no special complex equipment. Fitting calculations can be completed using only conventional data processing tools (such as Excel and Origin). Moreover, the fitting equation and correlation coefficient R² are intuitive and easy to understand, facilitating rapid application by engineering technicians. The quantified fitting results can be directly converted into design parameters and installation standards, significantly improving the design accuracy and installation reliability of adjustable diameter bolts, while reducing trial and error costs, balancing practicality and economy.

[0039] The linear regression fitting derivation method is primarily applicable to scenarios where the variable and contact strength exhibit approximately linear changes. By linearly fitting multiple sets of gradient data, the influence of the variable on the contact strength is transformed into a clear linear relationship. For example, when analyzing the correlation between locking torque (M1) and contact strength (p), five sets of values ​​for M1 are set: 5 N·m, 10 N·m, 15 N·m, 20 N·m, and 25 N·m. After measuring the corresponding p values, a linear equation of p = 10M1 + 5 is obtained through fitting. If R² = 0.98, it indicates a strong positive linear correlation between the two, with p increasing by an average of 10 MPa for every 1 N·m increase in M1.

[0040] The nonlinear fitting derivation method is used for scenarios where the variables and contact intensity change nonlinearly (such as the slowing growth rate of p when the contact area S is too large, or the influence of the cone angle α on p increasing and then decreasing within a specific range). By trying various nonlinear models, the nonlinear variation law of the two can be accurately captured. For example, when analyzing the correlation between the contact area (S) and p, six sets of values ​​for S were set: 80mm², 100mm², 120mm², 150mm², 180mm², and 200mm². After measuring the corresponding p values, it was found that the R² of the quadratic curve fitting was 0.99 (higher than the 0.85 of the linear fitting). Finally, the fitting equation was determined as p = -0.005S² + 2.5S + 30, clarifying the difference in the rate of influence of S on p in different ranges.

[0041] Secondly, see Figures 4-7 The present invention discloses a measurement system 1 for the contact strength of an adjustable diameter bolt, including the above-mentioned measurement method for the contact strength of an adjustable diameter bolt. The system includes a test sleeve 11, a locking nut 12, a guide rod 13, and an adjusting ring 14. The locking nut 12 is connected to the test sleeve 11. The test sleeve 11 is fitted around the outer periphery of the tapered sleeve assembly 2. The tapered sleeve assembly 2 is fitted around the outer periphery of the guide rod 13. The locking nut 12 is installed at both ends of the tapered sleeve assembly 2. The guide rod 13 has internal hexagonal grooves at both ends, the test sleeve 11 has a hexagonal wrench boss, the test sleeve 11 has external thread structure on both ends, the mounting groove 121 of the locking nut 12 has an internal thread structure matching the external thread structure on the inner wall, the locking nut 12 has a mounting groove 121, the locking nut 12 has an opening at the center position, the adjusting ring 14 is installed in the mounting groove 121, when the locking nut 12 is installed at both ends of the tapered sleeve assembly 2, the adjusting ring 14 abuts against both ends of the tapered sleeve assembly 2, the internal hexagonal groove of the guide rod 13 is exposed from the opening, the outer surface of the tapered sleeve assembly 2 contacts the inner surface of the test sleeve 11, and the inner surface of the tapered sleeve assembly 2 contacts the outer surface of the guide rod 13.

[0042] The tapered sleeve assembly 2 includes an inner tapered sleeve 21, an outer tapered sleeve 22, and a semi-inner tapered sleeve 23. The outer tapered sleeves 22 are spaced apart and located at both ends of the assembly. The semi-inner tapered sleeves 23 are mounted on the inner tapered sleeves 21 at both ends. In other words, within the tapered sleeve assembly 2, one outer tapered sleeve 22 and one inner tapered sleeve 21 are arranged adjacently and spaced apart. The outer tapered sleeves 22 at both ends of the assembly are fitted with semi-inner tapered sleeves 23. The number of inner tapered sleeves 21 is one less than the number of outer tapered sleeves 22. A locking torque M1 is preset for the locking nut 12. Under the action of the locking nut 12, the tapered sleeve assembly 2 is subjected to an axial force. Due to the structure of the inner tapered sleeve 21, it exerts a force on the outer tapered sleeve 22, increasing the force exerted by the outer tapered sleeve 22 on the inner wall of the test sleeve 11. The assembly is mounted on a torsion testing machine via a measuring system, with both ends abutting against the hexagonal groove of the guide rod 13. The torsion testing machine can apply a rotational torque M2 to the guide rod 13.

[0043] The system describes a testing system comprised of simple tools and fixtures, including a test sleeve 11, a locking nut 12, an adjusting ring 14, and a guide rod 13. It measures the contact surface parameters of the tapered sleeve assembly 2 and analyzes the correlation between these parameters and other factors. Installation and testing can be performed using standard tools and equipment, and the system can be used for comparative testing of various diameters and parameters. The entire measurement method requires no expensive specialized measuring equipment or tools, nor does it involve complex calculations. Contact strength calculations and comparative analysis of multiple sets of design parameters can be completed using simple measuring fixtures, equipment, and conventional calculation methods.

[0044] When testing the tapered sleeve assembly 2, the test system employs a controlled variable method. By controlling a specific variable to change, the contact surface strength is measured, and the correlation between the variable change and the contact surface strength change is analyzed. For example, keeping the tapered sleeve assembly 2 constant, by proportionally changing the locking torque M1 of the locking nut 12 and measuring the rotational torque M2 of the guide rod 13, the correlation between the locking torque M1, rotational torque M2, and contact surface pressure P can be analyzed. Keeping the locking torque M1 constant, changing the contact surface friction coefficient μ allows for analysis of the relationship between contact surface strength p and the friction coefficient μ. By increasing or decreasing the number of conical surfaces in the tapered sleeve assembly 2, changing the contact surface area S, while keeping the locking torque M1 and friction coefficient μ constant, the relationship between contact surface strength p and contact surface area S can be analyzed. Changing the conical surface angle, while keeping the contact area S, locking torque M1, and friction coefficient μ constant, allows for analysis of the relationship between contact surface strength P and the conical surface angle α.

[0045] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0046] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0047] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0048] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0049] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0050] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. The illustrative expressions of the above terms in this specification should not be construed as necessarily referring to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0051] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Since these modifications and variations fall within the scope of the claims and their equivalents, this invention also intends to include these modifications and variations.

[0052] The above description describes specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for measuring the contact strength of an adjustable diameter bolt, characterized in that, include, Obtain the structural parameters of the cone sleeve assembly and the test fixture, install the cone sleeve assembly into the test fixture, and then install the test fixture containing the cone sleeve assembly into the torsion testing machine. The test fixture includes a test sleeve, two locking nuts, and a guide rod. The structural parameters include the diameter of the guide rod, the contact area between the cone sleeve assembly and the guide rod, and the coefficient of friction of the contact surface between the cone sleeve assembly and the guide rod. Start the torsion testing machine and record the torque value displayed by the torsion testing machine and the locking torque of the locking nut to obtain the rotational torque and locking torque. Calculate the relevant parameters of the contact surface based on the rotational torque, locking torque, and structural parameters, and analyze the correlation between the contact surface strength, locking torque, and structural parameters of the test complex. The contact surface parameters include the contact surface friction, contact surface normal force, and contact surface strength.

2. The method according to claim 1, characterized in that, Obtain the structural parameters of the cone sleeve assembly and the test fixture, install the cone sleeve assembly into the test fixture, and then install the test fixture containing the cone sleeve assembly into the torsion testing machine. The specific steps include: Measure the dimensions of the tapered sleeve assembly, the diameter of the guide rod, and the dimensions of the test sleeve; Based on the dimensional parameters, the contact surface between the tapered sleeve assembly and the guide rod is analyzed, and the contact surface area and friction coefficient are calculated to obtain the structural parameters, including the tapered surface angle of the tapered sleeve assembly, the diameter of the guide rod, the contact surface area between the tapered sleeve assembly and the guide rod, and the friction coefficient of the contact surface between the tapered sleeve assembly and the guide rod. The cone sleeve assembly is installed onto the test fixture, assembled into a test complex, and then the test complex is loaded into the torsion testing machine.

3. The method according to claim 1, characterized in that, The cone sleeve assembly is installed onto the test fixture to form the test complex, which is then placed into the torsion testing machine. The specific steps include: The guide rod is inserted into the tapered sleeve assembly, and the test sleeve is fitted around the outer periphery of the tapered sleeve assembly; An adjusting ring is installed inside each locking nut, and a locking nut is installed at each end of the test sleeve; Install the locking nut using a torque wrench or a torque-controlled installation device to obtain the test assembly. Then, load the test assembly into the torsion testing machine, which holds the two ends of the guide rod. The test sleeve is fixed on the fixed fixture.

4. The method according to claim 1, characterized in that, Start the torsion testing machine and record the torque value displayed by the torsion testing machine and the locking torque of the locking nut to obtain the rotational torque and locking torque. Calculate the relevant parameters of the contact surface based on the rotational torque, locking torque, and structural parameters, and analyze the correlation between the contact surface strength, locking torque, and the structural parameters of the test complex. The specific steps include: Tighten the locking nut to the preset installation torque to obtain the locking torque; Start the torsion testing machine. The torsion testing machine applies rotational torque from both ends of the test complex. The rotating guide rod rotates, and the rotational torque applied by the guide rod is recorded to obtain the rotational torque. Calculate the contact surface friction force, contact surface normal force, and contact surface strength based on the locking torque, rotational torque, and structural parameters. The correlations between locking torque, rotational torque and contact surface strength, contact surface area and contact surface strength, contact surface friction coefficient and contact surface strength, and the conical angle of the tapered sleeve assembly and contact surface strength were analyzed.

5. The method according to claim 1, characterized in that, The correlations between locking torque, rotational torque, and contact surface strength; the correlation between contact surface area and contact surface strength; the correlation between contact surface friction coefficient and contact surface strength; and the correlation between the cone angle of the tapered sleeve assembly and contact surface strength are analyzed, including: Keep the locking torque, contact area, contact friction coefficient, and cone angle of the cone sleeve assembly as one variable, and keep other variables constant, and calculate the change value of the variable; After measuring the contact surface strength value after controlling for the variable, calculate the change in the contact surface strength value, analyze the correlation between the change in the variable and the change in the contact surface strength value, and determine whether the change in the variable and the change in the contact surface strength value are related.

6. A system for measuring the contact strength of an adjustable diameter bolt, comprising the method for measuring the contact strength of an adjustable diameter bolt as described in any one of claims 1-5, characterized in that, It includes a test sleeve, a locking nut, and a guide rod. The locking nut is connected to the test sleeve. The test sleeve is fitted around the outer periphery of the tapered sleeve assembly. The tapered sleeve assembly is fitted around the outer periphery of the guide rod. The locking nut is installed at both ends of the tapered sleeve assembly.

7. The system according to claim 6, characterized in that, The outer surface of the tapered sleeve assembly contacts the inner surface of the test sleeve, and the inner surface of the tapered sleeve assembly contacts the outer surface of the guide rod.

8. The system according to claim 6, characterized in that, The assembly includes an adjusting ring and a locking nut with a mounting groove. The adjusting ring is installed in the mounting groove, and the locking nut is installed at both ends of the tapered sleeve assembly. When the adjusting ring is installed at both ends of the tapered sleeve assembly, the adjusting ring abuts against both ends of the tapered sleeve assembly.

9. The system according to claim 6, characterized in that, The guide rod has internal hexagonal grooves at both ends, the test sleeve has a hexagonal wrench boss, the test sleeve has external thread structure on both ends of the surface, and the inner wall of the mounting groove of the locking nut has an internal thread structure that matches the external thread structure.

10. The system according to claim 6, characterized in that, An opening is made at the center of the locking nut, and the internal hexagonal groove of the guide rod is exposed from the opening.

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