A bolt preload evaluation method and dynamic parameter measurement device

Abstract

The present invention discloses a bolt preload evaluation method and a dynamic parameter measurement device thereof, the method comprising: considering constant and dynamic parameters, establishing a bolt preload evaluation model based on the energy method; obtaining the geometric dimensions of the bolted structure, the warping displacement of the measuring point and the parameter data of the physical properties of the material; determining the angular displacement of the thin plate according to the warping displacement of the measuring point and its distance from the axis of the tightening bolt; determining the bolt preload based on the parameter data, the angular displacement and the evaluation model. In addition, the device comprises a measuring point warping displacement and a bolt preload measurement system. The technical solution provided by the present invention can improve the level of structural reliability design by effectively evaluating the bolt preload, provide a theoretical basis for the high-performance assembly of mechanical equipment and the improvement of service performance, and reduce maintenance costs.

Description

Technical Field

[0001] The present invention belongs to the technical field of high-performance assembly of mechanical equipment, and in particular relates to a bolt preload evaluation method and a dynamic parameter measurement device thereof. Background Art

[0002] Bolts are the main connection form in the field of mechanical equipment manufacturing. The accurate assessment of their preload has become a key bottleneck restricting the assembly quality and service performance of mechanical equipment (especially high-end equipment such as aerospace, rail transportation, marine engineering and intelligent manufacturing). In addition, safety accidents caused by poor bolt preload have occurred frequently in recent years, making the importance of bolt preload assessment methods increasingly prominent.

[0003] The existing bolt preload assessment methods are mainly divided into two categories: one is the empirical model considering the actual working conditions, and the other is the iterative adjustment model based on finite elements. Studies have found that the accuracy of the former depends on the ratio of prestress to yield limit, while the accuracy and efficiency of the latter depend on the quality of the solid model mesh and boundary conditions. In addition, both methods usually ignore the influence of parameters such as the geometric dimensions and physical properties of the connectors, and fail to establish a more comprehensive bolt preload assessment model in theory. Therefore, it is particularly important to propose a preload assessment method using advanced mathematics and mechanics theory. Summary of the invention

[0004] In view of the shortcomings of the above-mentioned existing methods, the present invention provides a bolt preload evaluation method and a dynamic parameter measurement device, which are used to realize accurate preload evaluation and real-time measurement of dynamic parameters in the design stage, avoiding the difficulty of prestress and boundary condition detection, and can improve the assembly quality and service performance of mechanical equipment.

[0005] In order to achieve the above object, the present invention provides a method for evaluating bolt preload force, and its technical solution is as follows:

[0006] Based on the equivalent method of bolt tightening physical process and mathematical spectrum problem, the following bolt preload evaluation model is established by taking energy as the medium, considering constant parameters such as structural geometric dimensions and material physical properties and dynamic parameters such as warping displacement and angular displacement.

[0007]

[0008] Among them, F is the bolt preload, E is the elastic modulus, I is the moment of inertia, α is the angular displacement, d is the distance between the measuring point and the axis of the tightening bolt, l1 is the length of the thin plate, l2 is the width of the thin plate, and l3 is the thickness of the thin plate;

[0009] Obtaining the geometric dimensions of the bolted structure, the warping displacement of the measuring point and the parameter data of the physical properties of the material. Furthermore, the warping displacement of the measuring point is approximately equal to the elongation of the bolt, and the warping displacement data is used for correction;

[0010] Determine the angular displacement of the thin plate according to the warping displacement of the measuring point and the distance data between the measuring point and the axis of the tightening bolt;

[0011] The bolt preload force is determined based on the parameter data, the angular displacement and the evaluation model.

[0012] Another aspect of the present invention provides a device for measuring dynamic parameters of bolt preload force, and its technical solution is as follows:

[0013] A bolt preload dynamic parameter measuring device comprises a workbench, a digital torque wrench, a fixing fixture, a bolt connection structure, and a measuring point warping displacement and bolt preload measuring system; the bolt connection structure is placed in the fixing fixture fixedly connected to the workbench.

[0014] Furthermore, the measuring point warping displacement measurement system includes a flexible bracket, an eddy current displacement sensor, an LMS system, a power supply device and a displacement acquisition software; the flexible bracket is used to clamp the eddy current displacement sensor, the eddy current displacement sensor and the power supply device are connected to the LMS system, and the LMS system inputs the signal into the displacement acquisition software.

[0015] Furthermore, the bolt preload force measurement system includes an annular pressure sensor, a signal amplifier, a data acquisition card and a preload force acquisition software; the annular pressure sensor is placed between the bolt and the connector, connected to the signal amplifier, and the signal is input into the preload force acquisition software through the data acquisition card.

[0016] Compared with the existing methods, the present invention has the following advantages:

[0017] (1) A bolt preload evaluation model based on the energy method was established. It can quantify the coupling relationship between the bolt preload and constant parameters such as structural geometric dimensions and material physical properties, as well as dynamic parameters such as warping displacement and angular displacement, and provide relatively accurate theoretical calculation results, which provides an effective method for evaluating the bolt preload in the design stage and improving the reliability of mechanical equipment.

[0018] (2) The proposed dynamic parameter measurement device for bolt preload can simultaneously and continuously measure the preload and warping displacement of the measuring point during bolt tightening, thus avoiding the difficulties and high costs of prestress and boundary condition detection. In addition, the device can also be used to verify the bolt preload evaluation method. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a flow chart of the bolt preload assessment method.

[0020] Figure 2 It is a schematic diagram of the device for measuring the warping displacement of thin plates and the preload force of bolts.

[0021] The accompanying drawings are marked as follows: 1-displacement acquisition software; 2-bolt preload acquisition software; 3-data acquisition card; 4-eddy current displacement sensor; 5-signal amplifier; 6-digital torque wrench; 7-LMS system; 8-power supply device; 9-fixing fixture; 10-bolt connection structure; 11-annular pressure sensor; 12-flexible bracket; 13-workbench.

[0022] Figure 3 This is a comparison chart between the bolt preload evaluation results and the measured data. DETAILED DESCRIPTION

[0023] In order to enable technicians in the field of high-performance assembly of mechanical equipment to better understand the technical solutions and advantages of the present invention, the present invention will be further described in conjunction with the drawings in specific embodiments.

[0024] The existing bolt preload force evaluation method is limited to the bolt's own parameters, ignoring the influence of structural geometric dimensions, material physical properties and thin plate deformation. The embodiment of the present invention provides a bolt preload force evaluation method, and its implementation process is as follows: Figure 1 As shown, including:

[0025] Step 1: Establish a bolt preload evaluation model based on the energy method.

[0026] Specifically, a double-bolt connection structure is used as an implementation object, and its tightening physical process is equivalent to a mathematical spectrum problem; a characterization model of the elastic potential energy of the bolts to be tightened and the gravitational potential energy of the thin plate during bolt tightening is constructed based on the energy equation; referring to the law of conservation of energy, considering constant parameters such as structural geometric dimensions and material physical properties and dynamic parameters such as warping displacement and angular displacement, the following preload evaluation model is established

[0027]

[0028] Among them, F is the bolt preload, E is the elastic modulus, I is the moment of inertia, α is the angular displacement, d is the distance between the measuring point and the axis of the tightening bolt, l1 is the length of the thin plate, l2 is the width of the thin plate, and l3 is the thickness of the thin plate.

[0029] Step 2: Obtain the geometric dimensions of the bolted structure, warping displacement of the measuring points, and parameter data of the material physical properties.

[0030] Specifically, the bolt specification is M16, a vernier caliper is used to measure the geometric dimensions of the thin plate and the distance between the axis of the bolt hole, an annular pressure sensor is used to measure the bolt preload, and an eddy current displacement sensor is used to measure the warping displacement of the thin plate measuring point.

[0031] Furthermore, the maximum distance between the measuring point and the axis of the tightened bolt is equal to the distance between the axis of the bolt hole.

[0032] Furthermore, the true value of the warping displacement of the measuring point is equal to the sum of the elongation of the bolt to be tightened and the warping displacement measurement value, and the bolt elongation is the ratio of the preload force of the bolt to be tightened to its stiffness.

[0033] Step 3: Calculate the warping angle displacement of the thin plate based on the displacement data.

[0034] Specifically, the ratio of the true value of the warping displacement of the measuring point to the data of the distance between the axis of the bolt hole is calculated, and the warping angular displacement of the thin plate is obtained based on the trigonometric function relationship.

[0035] Furthermore, the parameter data involved in the bolt preload evaluation model are shown in the following table.

[0036] parameter E / GPa <![CDATA[ρ / g / cm 3 ]]> <![CDATA[l1 / mm]]> <![CDATA[l2 / mm]]> <![CDATA[l3 / mm]]> d / mm value 206 7.82 92 50 20 48

[0037] Step 4: determining the bolt preload based on the parameter data, the angular displacement and the evaluation model.

[0038] The preload force of the bolt to be tightened and the warping displacement of the measuring point are time-varying. In order to achieve real-time measurement, the present invention provides a device for measuring the dynamic parameters of the bolt preload force. Figure 2 As shown, including:

[0039] A workbench, a digital torque wrench, a fixing fixture, a bolt connection structure, and a measuring point warpage displacement and bolt preload force measuring system; the bolt connection structure is placed in a fixing fixture fixed to the workbench.

[0040] Furthermore, the measuring point warping displacement measurement system includes a flexible bracket, an eddy current displacement sensor, an LMS system, a power supply device and a displacement acquisition software; the flexible bracket is used to clamp the eddy current displacement sensor, the eddy current displacement sensor and the power supply device are connected to the LMS system, and the LMS system inputs the signal into the displacement acquisition software.

[0041] Furthermore, the bolt preload force measurement system includes an annular pressure sensor, a signal amplifier, a data acquisition card and a preload force acquisition software; the annular pressure sensor is placed between the bolt and the connector, connected to the signal amplifier, and the signal is input into the preload force acquisition software through the data acquisition card.

[0042] The bolt tightening torque is set to 120 Nm, and the bolt preload evaluation method proposed in the present invention is verified based on 6 bolt tightening experiments. The comparison between the evaluation results and the measured data is shown in the figure below. Figure 3 As shown, the effectiveness of the preload force evaluation method of the present invention is proved.

[0043] The above embodiments and terms are merely examples of the concept of the present invention and should not be construed as any additional limitations. Personnel skilled in the art may modify, supplement, or replace the specific embodiments described, but should not deviate from the concept of the present invention or exceed the scope defined in the appended claims.

Claims

1. A method for evaluating bolt preload, characterized in that: include: A bolt preload evaluation model based on the energy method is established; the evaluation model considers constant parameters such as geometric dimensions and physical properties and dynamic parameters of warpage displacement and angular displacement: Among them, F is the bolt preload, E is the elastic modulus, I is the moment of inertia, α is the angular displacement of the thin plate, d is the distance between the measuring point and the axis of the tightening bolt, l1 is the length of the thin plate, l2 is the width of the thin plate, and l3 is the thickness of the thin plate; Obtain the geometric dimensions of the bolted structure, the warping displacement of the measuring point, and the parameter data of the material physical properties; use a vernier caliper to measure the geometric dimensions of the thin plate and the distance between the bolt hole axis, use an annular pressure sensor to measure the bolt preload, and use an eddy current displacement sensor to measure the warping displacement of the thin plate measuring point; Determine the angular displacement of the thin plate according to the warping displacement of the measuring point and the distance between the measuring point and the axis of the tightened bolt; calculate the ratio of the true value of the warping displacement of the measuring point and the distance data of the axis of the bolt hole, and obtain the warping angular displacement of the thin plate based on the trigonometric function relationship; Determining the bolt preload based on the material physical property parameter data, the thin plate angular displacement and the bolt preload evaluation model; The true value of the warping displacement of the measuring point is equal to the sum of the elongation of the bolt to be tightened and the measured value of the warping displacement, and the elongation of the bolt is the ratio of the preload force of the bolt to be tightened to its stiffness; The parameter data involved in the bolt preload evaluation model are E = 206, ρ = 7.82, l 1＝ 92;l 2＝ 50,l 3＝ 20, d=48.

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