A ring groove rivet for ultrasonic preload detection and in-service detection method

Abstract

The present invention discloses a ring groove rivet for ultrasonic preload detection and an in-service detection method. The ring groove rivet is composed of a head, a polished rod, a locking groove and a short tail; the top surface of the ring groove rivet head is fixed with an ultrasonic piezoelectric chip by bonding, and a reflector is arranged at the junction of the polished rod and the locking groove; the detection method comprises: calibrating the ring groove rivet, obtaining the polished rod diameter, the thickness of the rivet head, the distance from the end face of the rivet head to the reflection hole, the ultrasonic transit time and the temperature of the initial state of the calibration rivet, calibrating the riveting of the ring groove rivet, obtaining the preload after riveting, the ultrasonic transit time, establishing a preload-transit time difference model, determining the calibration coefficient, and using the relational model to obtain the in-service preload of the ring groove rivet. The present invention can be used for in-service detection of ultrasonic preload, and by prefabricating the reflection hole, the calibration and measurement process is simplified, while the influence of the collar on the measurement accuracy is eliminated, thereby improving the measurement accuracy.

Description

Technical Field

[0001] The invention relates to the technical field of ultrasonic detection, and in particular to a ring groove rivet for ultrasonic preload detection and an in-service detection method. Background Art

[0002] As a special fastener, ring groove rivets have been widely used in industrial applications. Preload is an important performance indicator of ring groove rivets. In industrial structure design and testing, in order to ensure the rationality and reliability of the connection design, it is necessary to accurately measure the size of the preload in the connection structure. The most commonly used method of existing detection technology is the strain gauge test method, that is, testing the stress by sticking a strain gauge on the rod of the ring groove rivet. The measurement result of this method is only the stress on the surface of the rivet, and it is impossible to detect the internal stress of the rivet body. It is easily affected by external factors, and the measurement error and limitations are large.

[0003] Ultrasonic detection of bolt preload is a method that has been developed in recent years and has been widely used in practical work. Its principle uses the acoustic elasticity principle of ultrasound to characterize the size of the preload by the difference in the transit time of ultrasound in the bolt body under stress or non-stress conditions. Ultrasonic detection of bolt preload has the following advantages: (1) Ultrasonic detection does not damage the sample being tested and can achieve the goal of not reducing the performance of the bolt. (2) Ultrasonic detection technology can realize the preload detection and monitoring of multiple bolts in one channel. (3) Ultrasonic waves have good penetration and can meet the general needs of bolt preload detection. (4) Ultrasonic preload detection is fast and suitable for the detection of large quantities of similar products.

[0004] Chinese patent application CN108572040B "A detection method, detection system and detection device for the axial force of an in-service bolt" discloses a detection method, detection system and detection device for the axial force of an in-service bolt. The detection method includes: obtaining the bolt diameter, thread diameter, sound velocity before force, nut axial length, screw length, bolt force zone length, measured axial force of the bolt sample under different loads, ultrasonic transit time corresponding to the measured axial force, and ultrasonic transit time-axial force model; determining a soft measurement expression based on the bolt diameter, thread diameter, sound velocity before force, nut axial length, screw length, each measured axial force, ultrasonic transit time and ultrasonic transit time-axial force model; using the soft measurement expression to calculate the axial force of the in-service bolt to be measured. The method used in this application has a complex calibration and measurement process. The measurement accuracy of the ring groove rivet with a collar attachment structure cannot meet the requirements and cannot be applied to more complex ring groove rivet measurements. Summary of the invention

[0005] The object of the present invention is to provide a ring groove rivet and an in-service detection method for ultrasonic preload detection. The ring groove rivet and the detection method of the present invention can be used for in-service detection of ring groove rivets for ultrasonic preload detection, and have the advantages of simple operation and high measurement accuracy.

[0006] The present invention is achieved through the following technical solutions:

[0007] The present invention firstly discloses a ring groove rivet for ultrasonic preload force detection, which is characterized in that the ring groove rivet consists of a head, a polished rod, a locking groove and a short tail tooth; an ultrasonic piezoelectric chip is fixed to the top surface of the ring groove rivet head by bonding, and a reflector is arranged at the junction of the polished rod and the locking groove.

[0008] The reflector is a blind hole or a through hole; the shape is a round hole, an elliptical hole, or a square hole, and the diameter of the round hole is ≥1mm.

[0009] The present invention also discloses an in-service ultrasonic preload force detection method for the annular groove rivet, which is characterized by comprising the following steps:

[0010] (1) The calibration ring groove rivet and the ring groove rivet to be tested have the same specifications and are made of the same material;

[0011] (2) Obtain the polished rod diameter, rivet head thickness, distance from the rivet head end face to the reflection hole, ultrasonic transit time and initial temperature of the calibration ring groove rivet;

[0012] (3) The ring groove rivet is subjected to a riveting calibration test on a pressure sensor at the same temperature to obtain the preload force and ultrasonic transit time after riveting; a relationship model between the rivet preload force and ultrasonic transit time difference is established, and the calibration coefficient is determined by curve fitting; that is, F = AΔs, where F is the preload force of the rivet, A is the calibration coefficient, and Δs is the transit time difference of the ultrasonic wave from the head to the reflector in the ring groove rivet before and after riveting;

[0013] (4) The preload force of the ring groove rivet is measured, and the transit time of the ultrasonic wave in the ring groove rivet before and after the installation of the in-service ring groove rivet is obtained. Then, the in-service preload force of the ring groove rivet can be obtained by using the relationship model: F = AΔs.

[0014] The relationship model F=AΔs is derived as follows.

[0015] According to the principle of acoustic elasticity, the rivet is subjected to the preload after riveting, and its sound velocity is: C1 = (1-kσ) C0. At the same time, the force-bearing section of the rivet is elongated, and its length is: After riveting, the transit time of ultrasonic wave in the rivet is: The transit time of ultrasonic wave in the rivet before riveting is: The ultrasonic transit time difference before and after rivet riveting is: Where kσ<<1, the simplified expression is: C0 is the sound velocity of the ultrasonic wave without preload before riveting, L is the distance between the rivet head and the reflection hole, H is the thickness of the rivet head, E is the elastic modulus of the rivet, K is the length related to the material, and σ is the stress generated by the preload after the rivet is riveted. F is the preload force after rivet connection, and D is the diameter of the rivet rod. make Then we have: F = AΔs.

[0016] In order to make the measurement results more accurate, the calibration coefficient is corrected by establishing an ultrasonic sound velocity-temperature relationship model. According to the ultrasonic propagation principle, the ultrasonic sound velocity and temperature are in a first-order linear relationship, that is: C(t) = C0(1-αΔt). Where C(t) is the ultrasonic sound velocity at temperature t, and α is the coefficient of ultrasonic sound velocity variation with temperature. By measuring the sound velocity of rivets with the same specifications, the same material, and the same stress at different temperatures, the coefficient α is determined, and the relationship between ultrasonic sound velocity and temperature is established, and then the test results are corrected.

[0017] The corrected preload force-ultrasonic transit time difference relationship model is: F=AΔs+BΔt, where A is the coefficient related to the ultrasonic wave and the rivet body, B is the coefficient related to the ultrasonic wave and the temperature, and parameter B is the inherent characteristic of the ultrasonic wave. This module can be preset in advance in the ultrasonic data processing for automatic compensation to reduce the calibration link before detection. BΔt is the temperature difference of the rivet relative to the initial state.

[0018] The benefit of the invention: The invention realizes the ultrasonic measurement of the preload force of the ring groove rivet. For the ring groove rivets of the same specification, an ultrasonic reflection hole is set on the ring groove rivet, and the ultrasonic detection force section of the products with the same diameter and length specifications is the same, eliminating the measurement error caused by different connection thickness during calibration and detection; the reflection hole is set at the intersection of the ring groove rivet polished rod and the locking groove, eliminating the measurement error caused by the rivet being squeezed by the ring and the short tail being stretched by the riveting tool during installation.

[0019] Compared with the existing ultrasonic measurement method, the present invention can be used for in-service detection of ultrasonic preload force. By prefabricating the reflection hole, the calibration and measurement process is simplified, and the influence of the collar on the measurement accuracy is eliminated, thereby improving the measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a connection schematic diagram of the detection device of the present invention;

[0021] Figure 2 It is a schematic diagram of the structure of the ring groove rivet of the present invention;

[0022] Figure 3It is a schematic diagram of the dimensions of the ring groove rivet of the present invention.

[0023] In the figure, 1 is a ring groove rivet, 101 is a head, 102 is a smooth rod, 103 is a locking groove, 104 is a short tail tooth, 105 is an ultrasonic piezoelectric chip, 106 is a reflection hole, 2 is an ultrasonic preload force measuring instrument, 201 is an ultrasonic data processor, 202 is an ultrasonic probe, 203 is a temperature sensor, D is the diameter of the smooth rod, H is the head thickness, and L is the distance from the end face of the head to the reflection hole. DETAILED DESCRIPTION

[0024] The present invention is further described below in conjunction with specific implementation methods. The specific implementation methods are further descriptions of the principles of the present invention and do not limit the present invention in any way. Technologies that are the same or similar to the present invention do not exceed the scope of protection of the present invention.

[0025] Combined with the attached pictures.

[0026] like Figure 1 , Figure 2 and Figure 3 shown.

[0027] The ring groove rivet 1 for ultrasonic preload detection of the present invention is composed of a head 101, a polished rod 102, a locking groove 103 and a short tail end tooth 104; the top surface of the ring groove rivet head 101 is fixed with an ultrasonic piezoelectric chip 105 by bonding, and a reflector is arranged at the junction of the polished rod and the locking groove. In this example, the reflector is a reflection hole 106.

[0028] The reflector of the present invention can be a blind hole or a through hole; the shape is a circular hole, an elliptical hole, a square hole or any structure capable of reflecting ultrasonic waves, and the diameter of the circular hole is ≥1mm.

[0029] The ultrasonic preload force measuring instrument 2 comprises an ultrasonic data processor 201 , an ultrasonic probe 202 , and a temperature sensor 203 , wherein the ultrasonic probe and the temperature sensor are preferably provided with magnets on the outside for fixing with the ring groove rivet 1 .

[0030] During detection, the ultrasonic probe 202 is placed on the ultrasonic piezoelectric ceramic chip 105, and a high voltage is applied to the ultrasonic piezoelectric chip 105 through the ultrasonic probe 202, thereby generating ultrasonic longitudinal waves. The ultrasonic longitudinal waves are transmitted to the reflection hole 106 through the optical rod 102, and the ultrasonic echo reflected by the reflection hole 106 is transmitted to the ultrasonic piezoelectric chip 105 through the optical rod again. The ultrasonic piezoelectric chip 105 converts the ultrasonic echo into an electrical signal, which is received by the ultrasonic probe 202 and then transmitted back to the ultrasonic data processor 201. The temperature sensor 203 is placed near the rivet for temperature compensation. By recording the transit time before and after the rivet is riveted, the preload force of the rivet can be obtained through the change of the transit time difference.

[0031] The ultrasonic in-service detection method for the preload force of the ring groove rivet is performed by using the above-mentioned ring groove rivet, and the specific steps are as follows:

[0032] (1) Before installing the rivet, obtain the polished rod diameter D, rivet head thickness H, distance L from the rivet head end face to the reflection hole, and ultrasonic transit time before riveting of the ring groove rivet sample;

[0033] (2) Install the rivet on the force sensor and record the rivet preload and ultrasonic transit time at this time;

[0034] (3) According to the rivet rod diameter D, the rivet head thickness H, the distance L from the rivet head end face to the reflection hole, the ultrasonic transit time before riveting, the ultrasonic transit time after riveting, and the preload after riveting, a relationship model between the rivet preload and the ultrasonic transit time difference is established to determine the calibration coefficient, that is, F = AΔs, where F is the preload of the rivet, A is the calibration coefficient, and Δs is the ultrasonic transit time difference from the head 101 to the reflection hole 106 in the annular groove rivet before and after riveting;

[0035] The coefficient K calibrated in step (3) can be used to perform in-service testing of the preload force of rivets of the same specification.

[0036] The detection method of the present invention is described below with a specific example:

[0037] (1) Measurement of rivet size parameters. Figure 3 The example diagram of measuring the size parameters of the ring groove rivet described in the present invention respectively measures the distance L from the rivet head to the reflective hole, the thickness H of the rivet head, and the diameter D of the rivet polished rod. Take a short-tail ring groove rivet with a nominal diameter of 24mm and a grade of 10.9 and a marked riveting thickness of 75mm as an example: L = 90mm, H = 15.5mm, D = 23.8mm.

[0038] (2) Calibration of the coefficient to be measured. A ring groove rivet with the same specification and material as the ring groove rivet to be measured is selected as the calibration of the coefficient to be measured. The ultrasonic transit time s0 before riveting, the preload force F after riveting and the transit time s1 after riveting are recorded respectively. In this example, the ultrasonic transit time before riveting is s0 = 33350ns, the ultrasonic transit time after riveting is s1 = 33445ns, the preload force is 278kN, and the calibration coefficient A≈2.926.

[0039] (3) Test verification. In addition, three ring groove rivets with the same specifications and materials as the calibration ring groove rivet were tested on the pressure sensor to verify the test. The transit time of the ultrasonic wave in the rivet before and after riveting and the actual value of the preload force of the ring groove rivet were recorded. The ultrasonic preload force measurement value was calculated according to the formula F = AΔs. The relative error between the actual value and the measured value of the preload force was calculated. The results are shown in Table 1. For the three ring groove rivets, the relative error of the ultrasonic preload force measurement value was 3%.

[0040] Table 1

[0041] Ring groove rivet number Sensor measurement value kN Ultrasonic calculation value kN Relative error % 1 281 278.2 0.9 2 276 273.8 0.8 3 278 272.3 2.1

Claims

1. An in-service ultrasonic preload force detection method for a ring groove rivet, characterized in that: The ring groove rivet is composed of a head, a polished rod, a locking groove and a short tail end tooth; the top surface of the ring groove rivet head is fixed with an ultrasonic piezoelectric chip by bonding, and a reflector is arranged at the junction of the polished rod and the locking groove; The following steps are involved: (1) The calibration ring groove rivet and the ring groove rivet to be tested have the same specifications and are made of the same material; (2) Obtain the polished rod diameter, rivet head thickness, distance from the rivet head end face to the reflection hole, ultrasonic transit time and initial temperature of the calibration ring groove rivet; (3) The ring groove rivet is subjected to a riveting calibration test on a pressure sensor at the same temperature to obtain the preload force and ultrasonic transit time after riveting; a relationship model between the rivet preload force and ultrasonic transit time difference is established, and the calibration coefficient is determined by curve fitting; that is, F = AΔs, where F is the preload force of the rivet, A is the calibration coefficient, and Δs is the transit time difference of the ultrasonic wave from the head to the reflector in the ring groove rivet before and after riveting; (4) The preload force of the ring groove rivet is measured, and the transit time of the ultrasonic wave in the ring groove rivet before and after the installation of the in-service ring groove rivet is obtained. Then, the in-service preload force of the ring groove rivet can be obtained by using the relationship model: F = AΔs.

2. The ultrasonic preload force in-service detection method of the ring groove rivet according to claim 1 is characterized in that: The reflector is a blind hole or a through hole.

3. The ultrasonic preload force in-service detection method of the ring groove rivet according to claim 2 is characterized in that: The reflector is a circular hole, an elliptical hole or a square hole, and the diameter of the circular hole is ≥1mm.

4. The ultrasonic preload force in-service detection method of the ring groove rivet according to claim 1 is characterized in that: The relationship model F=AΔs is corrected by establishing an ultrasonic sound velocity-temperature relationship model. The corrected preload force-ultrasonic transit time difference relationship model is: F=AΔs+BΔt, where A is the calibration coefficient, B is the calibration coefficient related to the ultrasonic wave and temperature, and BΔt is the temperature difference of the rivet relative to the initial state.

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