阅读说明：本技术 一种基于声发射的切削状态识别方法及系统 (Cutting state identification method and system based on acoustic emission ) 是由 刘志兵 陈洪涛 王西彬 刘书尧 焦黎 解丽静 梁志强 颜培 周天丰 于 2021-08-10 设计创作，主要内容包括：本发明公开了一种基于声发射的切削状态识别方法及系统,涉及声发射检测技术领域,具体步骤包括如下：采集车削加工过程中的声发射信号；对所述声发射信号基于最大熵谱法提取声发射频率分量；基于所述声发射频率分量,识别车削加工过程中的切削状态。本发明中,通过声发射技术对车削加工过程中的信号进行采集并分析,可以识别车削加工过程中的切削状态,获得声发射信号频率分量与切削状态的映射关系,利用最大熵谱法进行声发射信号分析,估计误差小、分辨力高,可以实现弱信号识别与提取。(The invention discloses a cutting state identification method and a system based on acoustic emission, relating to the technical field of acoustic emission detection, and specifically comprising the following steps: collecting acoustic emission signals in the turning process; extracting an acoustic emission frequency component of the acoustic emission signal based on a maximum entropy spectrum method; based on the acoustic emission frequency component, a cutting state in a turning process is identified. According to the invention, signals in the turning process are collected and analyzed through an acoustic emission technology, the cutting state in the turning process can be identified, the mapping relation between the frequency component of the acoustic emission signal and the cutting state is obtained, the acoustic emission signal is analyzed by utilizing a maximum entropy spectrum method, the estimation error is small, the resolution is high, and the weak signal identification and extraction can be realized.)

1. A cutting state identification method based on acoustic emission is characterized by comprising the following specific steps:

collecting acoustic emission signals in the turning process;

extracting an acoustic emission frequency component of the acoustic emission signal based on a maximum entropy spectrum method;

based on the acoustic emission frequency component, a cutting state in a turning process is identified.

2. The method for recognizing a cutting state based on acoustic emission according to claim 1, wherein in the maximum entropy spectrum, a cutting shear process, a tool-to-chip friction process, and a tool-to-workpiece friction process are respectively corresponding to different peaks, i.e. different acoustic emission frequency components, and the acoustic emission frequency components are used for performing cutting state recognition by reversely deducing different cutting processes.

3. The method for recognizing a cutting state based on acoustic emission according to claim 1, wherein a signal source separation process is performed on the acoustic emission signal before the acoustic emission signal is collected.

4. A cutting state identification system based on acoustic emission is characterized by comprising an acoustic emission sensor, a signal amplifier, an acoustic emission signal acquisition and processing system and a display and recording system; the acoustic emission sensor is connected with the signal amplifier, the signal amplifier is connected with the acoustic emission signal acquisition and processing system, and the acoustic emission signal acquisition and processing system is connected with the display and recording system; the acoustic emission sensor is used for receiving an acoustic emission signal and converting the acoustic emission signal into an acoustic emission electric signal; the signal amplifier is used for amplifying the acoustic emission electric signal to obtain a first signal; the acoustic emission signal acquisition and processing system is used for carrying out maximum entropy spectrum analysis on the first signal to obtain an acoustic emission frequency component, and identifying a cutting state through the acoustic emission frequency component; and the display and recording system is used for displaying the acoustic emission frequency component.

5. The cutting state recognition system based on acoustic emission of claim 4, wherein the acoustic emission sensor is SR150M type, the frequency is 6 kHz-400 kHz, and the acoustic emission sensor is fixed on the tool shank through a medium temperature silicone grease coupling agent.

Technical Field

The invention relates to the technical field of acoustic emission detection, in particular to a cutting state identification method and system based on acoustic emission.

Background

The acoustic emission technology is a dynamic nondestructive testing technology and is widely applied to various engineering fields, and the acoustic emission technology has high sensitivity to the change of the microstructure of a material, so that the acoustic emission technology can be used for identifying the cutting state in the turning process.

In metal materials, the acoustic emission phenomenon means that when the material deforms, energy is released rapidly locally inside the material to form elastic waves. The acoustic emission sources of metal materials are many, such as crack propagation, displacement, slip, goldenrain, grain boundary slip and fracture desorption. Many studies have shown that most metal materials cause changes in the stress in the material during processing, handling and use of the material, thereby generating acoustic emission signals, and elastic waves emitted from an emission source eventually propagate to the surface of the material, and particularly, in metal cutting processes, tools and workpieces generate abundant acoustic emission signals. The signals in the turning process are collected and analyzed through an acoustic emission technology, the cutting state in the turning process can be identified, and the mapping relation between the frequency component of the acoustic emission signals and the cutting state is obtained.

There are many methods of acoustic emission signal analysis available today, and ringing, event, and RMS value methods are common in the art. However, the above methods all have the problems of large analysis error and low sensitivity. In order to effectively find out the frequency domain characteristics of the acoustic emission signals so as to separate the frequency domain characteristics from the acoustic emission signals, the extraction of acoustic emission frequency components by maximum entropy spectroscopy for cutting state identification has not been involved in the prior art, which is a problem to be solved by those skilled in the art.

Disclosure of Invention

In view of the above, the invention provides a cutting state identification method and system based on acoustic emission, and when cutting state identification is performed, the estimation error is small, the sensitivity is high, and the state identification is more accurate.

In order to achieve the purpose, the invention adopts the following technical scheme: on the one hand, the cutting state identification method based on acoustic emission is provided, and the specific steps comprise the following steps:

collecting acoustic emission signals in the turning process;

extracting an acoustic emission frequency component of the acoustic emission signal based on a maximum entropy spectrum method;

based on the acoustic emission frequency component, a cutting state in a turning process is identified.

Preferably, in the maximum entropy spectrum method, the cutting shearing process, the tool-to-chip friction process, and the tool-to-workpiece friction process respectively correspond to different wave crests, that is, different acoustic emission frequency components, and different cutting processes are reversely deduced by using the acoustic emission frequency components to identify the cutting state.

By adopting the technical scheme, the method has the following beneficial technical effects: the maximum entropy spectroscopy has the greatest advantage of higher resolution than the classical fourier spectroscopy, and is particularly suitable for power spectrum calculation of short-time sequences. The maximum entropy spectrum method does not need to make any specific assumption on the original time sequence, and the maximum uncertainty of the original signal is ensured at the part outside the time window, so that the obtained power spectrum more reflects the true power spectrum of the signal.

Preferably, before the acoustic emission signal is collected, the acoustic emission signal is subjected to signal source separation processing.

By adopting the technical scheme, the method has the following beneficial technical effects: the acoustic emission signal source separation test is carried out, so that the interference of vibration and background noise in the processing process is avoided.

On the other hand, the cutting state identification system based on acoustic emission is provided and comprises an acoustic emission sensor, a signal amplifier, an acoustic emission signal acquisition and processing system and a display and recording system; the acoustic emission sensor is connected with the signal amplifier, the signal amplifier is connected with the acoustic emission signal acquisition and processing system, and the acoustic emission signal acquisition and processing system is connected with the display and recording system; the acoustic emission sensor is used for receiving an acoustic emission signal and converting the acoustic emission signal into an acoustic emission electric signal; the signal amplifier is used for amplifying the acoustic emission electric signal to obtain a first signal; the acoustic emission signal acquisition and processing system is used for carrying out maximum entropy spectrum analysis on the first signal to obtain an acoustic emission frequency component, and identifying a cutting state through the acoustic emission frequency component; and the display and recording system is used for displaying the acoustic emission frequency component.

Preferably, the acoustic emission sensor is SR150M in model number, the frequency is 6 kHz-400 kHz, and the acoustic emission sensor is fixed on the knife handle through a medium-temperature silicone grease coupling agent.

According to the technical scheme, compared with the prior art, the cutting state identification method and system based on acoustic emission are provided, signals in the turning process are collected and analyzed through the acoustic emission technology, the cutting state in the turning process can be identified, the mapping relation between the frequency component of the acoustic emission signals and the cutting state is obtained, the acoustic emission signals are analyzed through the maximum entropy spectrum method, the estimation error is small, the resolution is high, and weak signal identification and extraction can be achieved.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.

FIG. 1 is a schematic flow diagram of the process of the present invention;

FIGS. 2a-2c are schematic diagrams of the acoustic emission signal source separation experiment of the present invention;

FIG. 3 is a schematic diagram of the principle of maximum entropy spectroscopy of the present invention;

FIG. 4 is a schematic diagram of the system of the present invention;

wherein, 1 is a workpiece, 2 is a cutting chip, 3 is a cutter, 4 is a front angle of the cutter, 5 is a rear angle of the cutter, 6 is an acoustic emission sensor, 7 is a signal amplifier, 8 is an acoustic emission signal acquisition and processing system, and 9 is a display and recording system.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The embodiment of the invention discloses a cutting state identification method based on acoustic emission on the one hand, and as shown in figure 1, the method comprises the following specific steps:

s1, collecting acoustic emission signals in the turning process;

it should be noted that, an acoustic emission signal source separation experiment needs to be performed before an acoustic emission signal is acquired, so as to ensure that an emission source in a shearing process, a tool and chip friction emission source, and a tool and workpiece friction emission source are not interfered by vibration and background noise in a machining process in a turning machining process.

Specifically, studies have shown that: the frequency range of the metal cutting acoustic emission signal is 100KHz-1MHz, mainly comes from plastic deformation and shearing deformation of a workpiece material, and is mainly concentrated on about 100 KHz; the frequency of acoustic emission signals generated by friction is about 200 KHz; the frequency of acoustic emission signals generated by built-up edge and chip shedding is about 500 KHz. Therefore, the frequency range of the acoustic emission signal is not in the range of a low-frequency area (generally, the low-frequency area is caused by vibration and background noise in some machining processes), is not influenced by the change of machining process parameters and cutter parameters, and has strong external influence resistance, high signal frequency and high sensitivity.

According to the cutting principle, if the strip chip is formed, if no built-up edge or scale is generated, the main sound emission source is plastic deformation of the workpiece material and friction in the machining process. When plastic metal materials are machined, strip-shaped chips are generally obtained when the cutting thickness is small, the cutting speed is high, and the front angle of a cutter is large. Therefore, in the present example, as shown in Table 1, experiments were conducted by selecting a cutting speed of 200m/min, a feed amount of 0.1mm/r, and a cutting depth of 0.50mm, and changing the rake angle and the relief angle of the tool, respectively. Fig. 2a-2c show schematic diagrams of the separation experiment of the acoustic emission signal source:

TABLE 1

When the tool relief angle was 15 °, the tools with rake angles of 15 °, 5 ° and 0 ° were selected for the experiments, respectively. When the back angle and the front angle of the cutter are both 15 degrees, the friction between the cutter and the chip and between the cutter and the workpiece is small, and only a shearing sound emission source is generated in the cutting process. Cutting experiments were then carried out with a tool relief angle of 15 ° and a tool rake angle of 5 ° and 0 °, respectively, and due to the reduction in the tool rake angle, friction between the tool and the chip was increased, which is believed to generate shearing and tool-chip frictional acoustic emission sources during the cutting process.

Similarly, when the front angle of the cutter is 15 °, the cutters with the rear angles of 15 ° and 5 ° were selected for the experiment, respectively. From the above, it is believed that the cutting process only produces a source of shear acoustic emissions when the tool rake and relief angles are both 15 °. Then, a cutting experiment that the front angle of the cutter is 15 degrees and the rear angle of the cutter is 5 degrees is carried out, and due to the fact that the rear angle of the cutter is reduced, friction between the cutter and a workpiece is increased, and it can be considered that shearing and a cutter-workpiece friction sound emission source are generated in the cutting process.

S2, extracting acoustic emission frequency components of the acoustic emission signals based on a maximum entropy spectrum method;

as shown in fig. 2c, when the tool relief angle and the tool rake angle are both 15 °, the friction between the tool and the chip and between the tool and the workpiece is small, and only shear sound emission sources are generated during the cutting process. And acquiring the acoustic emission signals, analyzing the acoustic emission signals based on a maximum entropy spectrum method, and obtaining acoustic emission frequency components corresponding to the cutting and shearing process.

As shown in fig. 2b, when the tool back angle is 15 ° and the tool front angle is 0 °, the friction between the tool and the chip is increased due to the decrease of the tool front angle, and the acoustic emission signal is collected and analyzed, so that the acoustic emission frequency component corresponding to the friction process of the cutting tool and the chip can be obtained.

As shown in fig. 2a, when the front angle of the cutting tool is 15 ° and the rear angle of the cutting tool is 5 °, the friction between the cutting tool and the workpiece is increased due to the reduction of the rear angle of the cutting tool, and the acoustic emission signals are collected and analyzed, so that the acoustic emission frequency component corresponding to the friction process between the cutting tool and the workpiece can be obtained.

And S3, identifying the cutting state in the turning process based on the acoustic emission frequency component.

Based on the experiment and the maximum entropy spectrum method, acoustic emission frequency components corresponding to a cutting and shearing process and a tool-chip and tool-workpiece friction process can be extracted, and cutting state identification in a turning process can be carried out by utilizing the acoustic emission frequency components. As shown in fig. 3, the broken line represents the shearing process, the solid line represents the shearing and rubbing process, in the maximum entropy spectrum method, the cutting shearing process and the tool-chip and tool-workpiece rubbing process respectively correspond to different wave crests, i.e. different acoustic emission frequency components, and by using the different acoustic emission frequency components, different cutting processes can be reversely deduced to identify the cutting state.

There are many types of acoustic emission signal analysis methods available today, the most common being ringing, event, and RMS value methods. In order to efficiently find the frequency domain features of the acoustic emission signals in order to separate them, the acoustic emission signal analysis method employed in the embodiment of the present invention is a maximum entropy spectrum method.

The maximum entropy spectrum method is a modern spectrum analysis method, and the basic idea is as follows: and (3) making no deterministic assumption on data except observed limited data, only assuming that the data is random, and recursing an unknown part of correlation function by an iterative method on the premise that the information entropy is maximum so as to obtain the power spectrum. Compared with a classical Fourier analysis method, the maximum entropy spectrum method has the characteristics of small estimation error and high resolution. Therefore, it is quite suitable to study the separation of acoustic emission signals by maximum entropy spectroscopy.

The maximum entropy spectrum method is to extrapolate the autocorrelation function beyond the maximum delay under the condition of maximum entropy, and the corresponding entropy of the autocorrelation function is maximized by each extrapolation. The method of the maximum entropy principle is used for carrying out continuous outward reasoning, which is equivalent to the fact that the length of a signal is continuously increased, and the calculation precision of the power spectrum can be effectively improved after the signal is increased, so that the method of the maximum entropy spectrum is used for obtaining a more accurate power spectrum compared with other methods, the aim of identifying and extracting weak signals is further fulfilled, and the method for calculating the power spectrum by using the maximum entropy principle is the maximum entropy spectrum method.

Another aspect of the embodiment of the present invention provides a cutting state recognition system based on acoustic emission, as shown in fig. 4, including an acoustic emission sensor 6, a signal amplifier 7, an acoustic emission signal acquisition and processing system 8, and a display and recording system 9; the acoustic emission sensor 6 is connected with a signal amplifier 7, the signal amplifier 7 is connected with an acoustic emission signal acquisition and processing system 8, and the acoustic emission signal acquisition and processing system 8 is connected with a display and recording system 9; the acoustic emission sensor 6 is used for receiving an acoustic emission signal and converting the acoustic emission signal into an acoustic emission electric signal; the signal amplifier 7 is used for amplifying the acoustic emission electrical signal to obtain a first signal; the acoustic emission signal acquisition and processing system 8 is used for carrying out maximum entropy spectrum analysis on the first signal to obtain an acoustic emission frequency component, and identifying the cutting state through the acoustic emission frequency component; the display and recording system 9 is used to display the acoustic emission frequency components.

Furthermore, the model of the acoustic emission sensor 6 is SR150M, the frequency is 6 kHz-400 kHz, and the acoustic emission sensor is fixed on the knife handle through a medium-temperature silicone grease coupling agent.

The signal amplifier 7 is used for amplifying weak acoustic emission electric signals, improving the signal-to-noise ratio of the signals and preventing the signals from being attenuated. The signal amplifier 7 is connected with a signal acquisition and processing system 8 through a signal line, the acquisition system adopts a 4-channel acquisition card of the Voronoi Hua science and technology company, the sampling frequency is 10MHz, and the sampling precision is 16 bits.

The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. The device disclosed by the embodiment corresponds to the method disclosed by the embodiment, so that the description is simple, and the relevant points can be referred to the method part for description.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.