An ultrasonic synchronous detection method for film thickness and deformation distribution of a plastic tile thrust bearing

Abstract

The present invention discloses an ultrasonic synchronous detection method for the film thickness and deformation distribution of a plastic tile thrust bearing. By utilizing the characteristics that the thickness information of the lubricating film layer and the deformation information of the coating layer of the plastic tile thrust bearing are reflected in different characteristics of the ultrasonic reflection signals at the interface between the plastic tile thrust bearing and the lubricating layer, the ultrasonic phase film thickness measurement method and the ultrasonic time-of-flight deformation measurement method are respectively used to obtain the film thickness and deformation information at the measuring points of the plastic tile thrust bearing, realizing the synchronous measurement of the film thickness and deformation distribution of the plastic tile thrust bearing, which can provide an effective detection means for revealing the lubrication mechanism of the plastic tile thrust bearing, and at the same time provide an excellent on-line monitoring means for monitoring the operating state of large plastic tile thrust bearings.

Description

Technical Field

[0001] The present invention belongs to the technical field of lubrication state detection, and particularly relates to an ultrasonic synchronous detection method for film thickness and deformation distribution of a plastic tile thrust bearing. Background Art

[0002] The thrust bearing has the characteristics of high running accuracy, large impact load bearing capacity, long service life, etc., and is particularly suitable for high-speed, precision, heavy-load and other occasions, so it is widely used. Especially in important equipment such as large thermal power and hydropower generating units, and the main circulation pump of nuclear power plants, it has become one of the key core components. For a thrust bearing, in order to improve its friction performance, a layer of wear-resistant material is usually cast on the surface of the bearing bush. New type of high molecular composite materials such as polytetrafluoroethylene (PTFE) and polyetheretherketone (PEEK) have gradually replaced traditional Babbitt alloy as the surface coating material of the thrust bearing due to their high allowable unit pressure, small friction coefficient, good wear resistance and corrosion resistance, and have obtained good engineering application effects in large hydro-generating units.

[0003] The special elastic structure of the plastic tile and the high molecular tile surface material different from metal materials not only bring many advantages to the engineering application of this type of plastic tile bearing, but also bring many new problems to its lubrication theory and application. For example, the surface slip phenomenon caused by the weak surface adhesion of high molecular polymer materials, the complex elastic deformation caused by the low elastic modulus, and the irregular thermal deformation caused by the very poor thermal conductivity. These characteristics make the lubricating film mechanism of the plastic tile bearing very different from that of traditional metal bearings and become very complex. Although this new type of plastic tile bearing has a history of nearly fifty years since it first appeared in 1969, its lubrication mechanism has not been truly mastered, and malignant accidents caused by plastic tile burning in engineering applications still occur from time to time. Malignant accidents of plastic tile burning have occurred during the start-up process of units in power stations such as Gezhouba and Dahua, and unit vibration accidents caused by plastic tiles have occurred during the start-up of the Yellow River Xiaolangdi Water Control Project.

[0004] The limitations of the theoretical research on the lubrication mechanism of plastic tile thrust bearings call for the supplementation and verification of experimental detection. At present, the research on the lubrication mechanism of plastic tile thrust bearings mainly focuses on theoretical simulation. There are already many theoretical models at home and abroad for analyzing the lubrication performance of this type of new thrust bearing under different structures and working conditions, and some very interesting results have been obtained. For example, when the thrust bearing bears a large pressure, the key parameter characterizing the lubrication performance of the thrust bearing - the lubricating film thickness distribution shows a "necking" phenomenon similar to that in the classical elastohydrodynamic lubrication case at the oil outlet. However, due to the lack of effective detection means, these interesting phenomena have not been experimentally verified yet. In addition, there are usually some assumptions in the theoretical research and partial simplifications of the actual situation, which will undoubtedly introduce deviations, and the accuracy of the theoretical model still needs to be verified by experimental detection. Therefore, the significance of developing an on-line detection method that can be used to experimentally verify and supplement the lubrication theory research of plastic tile bearings is very obvious.

[0005] The complexity of the lubrication mechanism requires experimental detection to provide multi-dimensional information. Traditional babbit alloy tile thrust bearings have a large elastic modulus and can be considered rigid or have slight elastic deformation during actual operation. However, plastic tile thrust bearings, due to their bronze wire mesh layer and plastic coating layer, are a special elastic structure. The biggest difference between them and traditional babbit alloy tile thrust bearings during actual operation is that obvious elastic deformation will occur, and the film thickness distribution during operation is the result of the combined action of hydrodynamic pressure and the elastic deformation of the bearing bush. In order to accurately reveal the lubrication mechanism of this plastic tile thrust bearing, information on both the film thickness distribution and the elastic deformation distribution needs to be provided simultaneously.

[0006] In order to make up for the deficiencies of the existing technology, the present invention aims to provide a detection technology that can synchronously and real-time detect the surface elastic deformation amount and the lubricating film thickness distribution during the operation of plastic tile thrust bearings. The present invention can not only provide an excellent detection means for the empirical verification and correction of the lubrication mechanism theory research of plastic tile thrust bearings, but also the developed related detection technology can be used for the real-time monitoring of the lubrication state of large rotating equipment to ensure the safe and reliable operation of the equipment. Summary of the Invention

[0007] The purpose of the present invention is to provide an ultrasonic synchronous detection method for the lubricating film thickness distribution and elastic deformation distribution of plastic tile thrust bearings, to provide an excellent detection means for the empirical verification and correction of the lubrication mechanism theory research of plastic tile thrust bearings, and at the same time can be used for the real-time monitoring of the lubrication state of large rotating equipment to ensure the safe and reliable operation of the equipment.

[0008] In order to achieve the above purpose, an ultrasonic synchronous detection method for the lubricating film thickness distribution and elastic deformation distribution of plastic tile thrust bearings includes the following steps:

[0009] Step 1: Embedded install ultrasonic sensors at the optimized measuring point positions on the back of the plastic thrust bearing tile.

[0010] Step 2: Synchronously obtain the film thickness and deformation of the plastic thrust bearing by using the reflection signals of ultrasonic waves at each interface of the plastic thrust bearing.

[0011] Step 3: Obtain the film thickness and deformation distribution of the plastic thrust bearing through the film thickness and deformation information obtained at each measuring point by using the interpolation algorithm.

[0012] The determination method of the optimized measuring point positions on the back of the plastic thrust bearing tile in Step 1 is as follows: Solve the three-dimensional energy equation, Reynolds equation considering slip, bearing bush heat conduction equation, and bearing bush thermoelastic deformation equation of the plastic thrust bearing to obtain the theoretical pressure, film thickness, temperature, and deformation distribution information of the plastic thrust bearing under different working conditions. Determine the number and positions of the optimized measuring points according to the theoretical pressure, film thickness, temperature, and deformation distribution information.

[0013] In Step 2, synchronously obtain the film thickness and deformation of the plastic thrust bearing by using the reflection signals of ultrasonic waves at each interface of the plastic thrust bearing. Specifically: Obtain the film thickness value of the plastic thrust bearing through the phase spectrum of the reflection signal of ultrasonic waves at the interface between the plastic thrust bearing and the lubricating layer; Obtain the deformation of the measuring point of the plastic thrust bearing through the change amount of the flight time of ultrasonic waves in the plastic coating layer under loaded and unloaded conditions.

[0014] The method for obtaining the film thickness of the plastic thrust bearing by using the reflection signal of ultrasonic waves at the interface between the plastic thrust bearing and the lubricating layer in Step 2 is as follows: The complex metal wire mesh structure of the plastic thrust bearing causes the reflection signals of ultrasonic waves in the plastic thrust bearing to be very complex, and each reflection signal will overlap. Equivalent the overlapping ultrasonic reflection signals to the superposition of multiple Gaussian echo signals, use the matching pursuit algorithm to separate each overlapping ultrasonic signal, obtain the reflection signal of ultrasonic waves at the interface between the plastic thrust bearing and the lubricating layer, and through the phase spectrum of the reflection signal at the interface between the plastic thrust bearing and the lubricating layer, use the existing ultrasonic film thickness measurement method to obtain the thickness value of the lubricating film at this measuring point.

[0015] The method for obtaining the deformation of the plastic tile by using the reflection signals of ultrasonic waves at each interface of the plastic thrust bearing in Step 2 is as follows: Perform Hilbert transform on the reflection signals of ultrasonic waves at the interface between the plastic thrust bearing and the lubricating film under loaded and unloaded conditions to construct an analytic signal, and find the modulus of this analytic signal to obtain the envelope signal of the reflection signal, so as to remove the change amount of the flight time caused by the phase change of the reflection signal on the lubricating film layer. Perform cross-correlation analysis on the envelope signals of the loaded and unloaded reflection signals to obtain the change amount of the flight time of ultrasonic waves in the coating layer under loaded and unloaded conditions, and obtain the elastic deformation amount at the measuring point according to the relationship between the deformation and the change amount of the flight time.

[0016] The measurement method for improving the measurement accuracy of the elastic deformation amount in the second step is as follows: the obtained reflected signal is used to obtain its envelope signal by means of Hilbert transform, and 100-point linear interpolation is performed for every two points of the envelope signal data to obtain a higher-precision envelope signal;

[0017] The method for obtaining the film thickness distribution of the plastic tile thrust bearing in the third step is as follows: the measured film thickness values of each measuring point are used to obtain the film thickness and deformation distribution of the plastic tile thrust bearing through an interpolation fitting algorithm.

[0018] Compared with the prior art, in the present invention, an ultrasonic sensor is embedded on the back of the plastic tile thrust bearing. Under the excitation of an ultrasonic pulse transmitting and receiving instrument, complex reflected signals of ultrasonic waves at each interface of the plastic tile thrust bearing are collected. The obtained complex reflected signals are equivalent to the superposition of multiple Gaussian echoes. The matching pursuit algorithm is used to obtain the reflected signal of ultrasonic waves at the interface between the plastic tile thrust bearing and the lubricating film. The film thickness value at the measuring point is obtained through the phase information of the reflected signal, and the deformation value of the measuring point is obtained through the time difference of flight between the reflected signals under the loaded and unloaded conditions of the reflected signal, realizing the ultrasonic synchronous detection of the film thickness and deformation of the plastic tile thrust bearing.

[0019] The present invention cleverly utilizes the characteristics that the thickness information of the lubricating film layer and the deformation information of the coating layer of the plastic tile thrust bearing are reflected in different characteristics of the reflected signal of ultrasonic waves at the interface between the plastic tile thrust bearing and the lubricating layer. The lubricating film thickness information is reflected in the phase change of the reflected signal, while the deformation information is reflected in the change amount of the flight time of the reflected signal. The ultrasonic phase film thickness measurement method and the ultrasonic flight time deformation measurement method are respectively used to obtain the film thickness and deformation information at the measuring points of the plastic tile thrust bearing, realizing the synchronous measurement of the film thickness and deformation distribution of the plastic tile thrust bearing, which can provide an effective detection means for revealing the lubrication mechanism of the plastic tile thrust bearing, and at the same time provide an excellent on-line monitoring means for monitoring the operating state of large plastic tile thrust bearings. Description of the Drawings

[0020] Figure 1 It is a schematic diagram of the ultrasonic synchronous detection principle of the film thickness and deformation distribution of a plastic tile thrust bearing

[0021] Figure 2 It is a schematic diagram of the distribution of the ultrasonic sensors used

[0022] Figure 3 It is the overlapping reflected signal of ultrasonic waves on the plastic tile thrust bearing on the lubricating layer

[0023] Figure 4 Plastic tile thrust bearing test bench Detailed Embodiments

[0024] The present invention will be further described below in conjunction with the accompanying drawings.

[0025] Refer to Figure 1 , the specific implementation method of an ultrasonic synchronous detection method for the lubricating film thickness and deformation distribution of a plastic tile thrust bearing is as follows: An ultrasonic sensor is embedded at the optimized measuring point position on the back of the plastic tile thrust bearing (see Figure 2 ), and the complex reflection signal of ultrasonic waves on the plastic tile thrust bearing is collected (see Figure 3 ), and then transmitted to a PC for post-processing; the overlapping reflection signals are equivalent to the superposition of multiple Gaussian echoes, and the reflection signal of ultrasonic waves at the interface between the plastic tile thrust bearing and the lubricating layer is obtained through the matching pursuit algorithm. Using the phase information of the reflection signal of ultrasonic waves at the interface between the plastic tile thrust bearing and the lubricating film, the film thickness value of the lubricating layer is obtained according to the ultrasonic phase film thickness measurement method. According to the change amount of the flight time of ultrasonic waves in the coating layer of the plastic tile thrust bearing when it is loaded and unloaded, the deformation information of the measuring point is obtained; using the film thickness and deformation information of each optimized measuring point, the film thickness and deformation distribution of the plastic tile thrust bearing under different working conditions are obtained through interpolation fitting.

[0026] Example:

[0027] Taking a polymer thrust bearing with an inner diameter of 70 mm and an outer diameter of 150 mm as an example, an ultrasonic sensor is embedded at the optimized measuring point position on the back of the base, and this bearing is used on a thrust bearing simulation test bench (such as Figure 4 ), and the film thickness and deformation values of each measuring point are synchronously obtained through the reflection signal of ultrasonic waves in the plastic tile thrust bearing. Through the three-dimensional imaging interpolation technology, the film thickness and deformation distribution information of the plastic tile thrust bearing under different working conditions are obtained.

Claims

1. An ultrasonic synchronous detection method for film thickness and deformation distribution of a plastic tile thrust bearing, comprising the following steps: Step 1: Embeddedly install ultrasonic sensors at the optimized measuring point positions on the back of the plastic tile thrust bearing; Step 2: Synchronously obtain the film thickness and deformation of the plastic tile thrust bearing by using the reflection signals of ultrasonic waves at each interface of the plastic tile thrust bearing; The specific methods for obtaining the film thickness and deformation are as follows: Equivalent the overlapping ultrasonic reflection signals obtained on the coating layer of the plastic tile thrust bearing to the superposition of multiple Gaussian echo signals, use the matching pursuit algorithm to separate each overlapping ultrasonic signal, obtain the reflection signal of the ultrasonic wave at the interface between the plastic tile thrust bearing and the lubricating layer, and use the existing ultrasonic phase film thickness measurement method through the phase information of the reflection signal at the interface between the plastic tile thrust bearing and the lubricating layer to obtain the thickness value of the lubricating film at this measuring point; Perform Hilbert transform on the reflection signals of the ultrasonic wave at the interface between the plastic tile thrust bearing and the lubricating film under the loaded and unloaded conditions to obtain its envelope signal, so as to remove the change in flight time caused by the phase change of the reflection signal on the lubricating film layer. Perform cross-correlation analysis on the analytical signals obtained by Hilbert transform of the loaded and unloaded reflection signals to obtain the change in flight time of the ultrasonic wave in the coating layer under the loaded and unloaded conditions, and obtain the elastic deformation amount at the measuring point according to the relationship between the deformation and the change in flight time; Step 3: Obtain the film thickness and deformation distribution of the plastic tile thrust bearing by using the interpolation algorithm for the film thickness and deformation information obtained at each measuring point.

2. The ultrasonic synchronous detection method for the film thickness and deformation distribution of a plastic tile thrust bearing according to claim 1, wherein The determination method of the optimized measuring point positions on the back of the plastic tile thrust bearing in Step 1 is as follows: Solve the three-dimensional energy equation, Reynolds equation considering slip, bearing bush heat conduction equation, and bearing bush thermoelastic deformation equation of the plastic tile thrust bearing to obtain the theoretical pressure, film thickness, temperature, and deformation distribution information of the plastic tile thrust bearing under different working conditions; Determine the number and positions of the optimized measuring points according to the theoretical pressure, film thickness, temperature, and deformation distribution information.

3. The ultrasonic synchronous detection method for the film thickness and deformation distribution of a plastic tile thrust bearing according to claim 1, characterized in that The method for obtaining the film thickness distribution of the plastic tile thrust bearing in Step 3 is as follows: The measured film thickness values and deformation values at each measuring point are obtained by interpolation fitting to obtain the film thickness and deformation distribution of the plastic tile thrust bearing.

Images