A method for detecting cracks in the top hammer of a six-sided top press based on electromagnetic ultrasonic surface waves.

Abstract

This invention relates to a method for detecting cracks in the top hammer of a six-sided press based on electromagnetic ultrasonic surface waves (EMAT). The method includes: providing a pulsed current to a folding coil according to the EMAT transduction principle; generating surface waves on the surface of the object under test due to the coupling of multiple physical fields (electric, magnetic, and acoustic fields) under the influence of a permanent magnet bias magnetic field; placing four arrayed electromagnetic ultrasonic transducers on the four working inclined surfaces of the top hammer; sequentially using one of the four transducers as the excitation source and the remaining three as receivers; acquiring non-destructive and destructive ultrasonic surface wave signals received by the transducers on the top hammer from different channels; processing and analyzing the received signals; and determining the degree of damage to the top hammer by calculating and comparing the difference coefficients. This invention can effectively and promptly detect surface cracks in the top hammer, improving detection accuracy and efficiency, and can be widely applied in the field of surface crack detection.

Description

Technical Field

[0001] This invention relates to the field of nondestructive testing technology, and in particular to a method for detecting cracks in the top hammer of a six-sided top press based on electromagnetic ultrasonic surface waves. Background Technology

[0002] Currently, the detection of surface cracks in top hammers is mostly done manually. However, manual inspection is cumbersome and has low accuracy. Electromagnetic ultrasonic testing technology, as a newly developed non-destructive testing technology, mainly uses the Lorentz magnetic mechanism and magnetostriction mechanism to excite ultrasonic waves in ferromagnetic materials. Electromagnetic ultrasonic testing technology can complete the inspection of the specimen without coupling agent and without contact. When magnets of different shapes and coils with different winding methods are combined, specific waveforms, such as surface waves and Lamb waves, can be excited. Therefore, how to use electromagnetic ultrasonic surface waves to detect surface cracks in top hammers is a problem that needs to be considered.

[0003] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for detecting cracks in the top hammer of a six-sided top press based on electromagnetic ultrasonic surface waves, thus solving the deficiencies of existing detection methods.

[0005] The objective of this invention is achieved through the following technical solution: a method for detecting cracks in the top hammer of a six-sided top press based on electromagnetic ultrasonic surface waves, the detection method comprising:

[0006] S1. According to the EMAT transduction principle, pulse current is provided to the folding coil. Under the action of the bias magnetic field of the permanent magnet, surface waves are excited on the surface of the object when multiple physical fields such as electric field, magnetic field and sound field are coupled together.

[0007] S2. In sequence, one of the four electromagnetic ultrasonic transducers is used as the excitation transducer, and the remaining three transducers are used as receivers. The non-destructive and destructive ultrasonic surface wave signals received by the electromagnetic ultrasonic transducer on the top hammer of the six-sided top press are acquired in different channels. The received signals are processed and differentially analyzed. The degree of damage to the top hammer is determined by calculating and comparing the difference coefficients.

[0008] The S1 step specifically includes: according to the EMAT transduction principle, a pulse current is provided to the folding coil, and a permanent magnet provides a vertical bias magnetic field. When a high-power high-frequency excitation current is passed through the coil, according to Lafarge's law of electromagnetic induction, an alternating magnetic field is generated around the current, causing vortices with the same frequency but opposite directions to be generated on the surface or near the surface of the workpiece close to the coil. Under the action of the bias magnetic field, the particles on the surface of the top hammer vibrate at high frequency under the action of the Lorentz force, thereby exciting and propagating surface waves on the surface of the top hammer.

[0009] The S2 step specifically includes the following:

[0010] S21. All four electromagnetic ultrasonic transducers are used as excitation and reception. When one of the transducers on the inclined plane of the working section is used as excitation, a high-power high-frequency excitation current is applied to it, which excites surface waves to propagate on the surface of the top hammer. After the incident surface wave encounters the surface defect, it is scattered and projected. The surface wave waveform that finally reaches the receiving electromagnetic ultrasonic transducer includes the direct wave that passes through the defect and the scattered wave that passes through the defect.

[0011] S22. Sequentially, one of the four electromagnetic ultrasonic transducers is used as the excitation transducer, and the other three transducers are used as receivers to collect signals. Surface waves are excited on the undamaged top hammer surface, and waveform information of the undamaged top hammer surface is collected. Then, on the top hammer surface to be tested, the excitation and receiving ultrasonic transducers are set with the same channel, and the waveform information of the corresponding channel is collected. By calculating the degree of difference between the signal received by the undamaged top hammer on the corresponding channel and the signal received in the top hammer to be tested, the degree of damage on the top hammer is determined.

[0012] In step S22, the loss index is calculated using the formula... The degree of difference between the signal received by the defect-free hammer and the signal received by the hammer under test in the same channel is calculated. Here, D is the damage index, I(t) is the signal received by the crack-free hammer, and V(t) is the signal received by the cracked hammer. The closer the damage index D is to 0, the more similar the signal received by the hammer under test is to the signal received by the defect-free hammer, and the smaller the difference. The closer it is to 1, the greater the difference between the signal received by the hammer under test and the signal received by the crack-free hammer, and the greater the probability that the hammer has a defect. The presence of a defect in the hammer can be determined by analyzing the damage index.

[0013] In step S22, one of the four electromagnetic ultrasonic transducers is used as the excitation source, and the other three are used as receivers for signal acquisition, including:

[0014] like Figure 3 The example, Figure 3This is a schematic diagram of the detection principle of the present invention. When transducer A excites surface waves on the surface of the hammer, the signal from the non-destructive test piece is directly transmitted to transducer B for reception, while transducers C and D do not receive the detection signal. When a crack appears on the surface of the hammer, the presence of the crack causes the surface waves to refract and scatter, thereby allowing transducers C and D to receive the detection signal containing the defect, and the received signal from transducer B will also be affected and attenuated.

[0015] Transducers B, C, and D act as receivers, and can respectively receive the signal data B, which is used by A to excite the transducer. A C A D A Similarly, when transducers A, C, and D act as receivers, they can respectively receive signal data A from transducer B, which is used as the excitation transducer. B C B D B When transducers A, B, and D are used as receivers, they can respectively receive signal data A from transducer C, which is used as the excitation transducer. C B C D C When transducers A, B, and C are used as receivers, they can respectively receive signal data A from transducer D, which is used to excite the transducer. D B D C D ;

[0016] This process is repeated. Each transducer, acting as a receiver, can acquire signal data from three different channels. If the signal of the tested hammer received by the transducer is from the same channel as the signal of the undamaged hammer, and the larger and closer the difference coefficient of the acquired signals is to 1, the greater the probability that there is a crack around the installation location of this transducer. Assume that when transducer A acts as a receiver, it acquires the excitation signals from transducers B, C, and D, respectively. B A C A D Determine whether the difference coefficient of the signal in each channel is close to 1 or 0. If A B The difference coefficient of the signal within the channel is close to 1, A C A D If the difference coefficient is close to 0, then there is a high probability that defects exist near the working surfaces where transducers A and B are installed. By processing and analyzing the difference coefficients of the three channels of each electromagnetic ultrasonic transducer, a preliminary assessment can be made based on the data to determine whether cracks appear and their location around the working surfaces where the transducers are installed.

[0017] The detection method also includes an electromagnetic ultrasonic transducer installation step performed before step S1. The electromagnetic ultrasonic transducer installation step includes: the working section of the six-sided top press hammer consists of a working plane and four working inclined planes. Four electromagnetic ultrasonic transducers are respectively installed at the four working inclined planes of the six-sided top press hammer. Each electromagnetic ultrasonic transducer consists of a neodymium iron boron square permanent magnet and a folding coil. The coil is made of a flexible printed circuit board. The permanent magnet is protected by an aluminum alloy shell and fixed and sealed with epoxy resin.

[0018] The present invention has the following advantages: a method for detecting cracks in the top hammer of a six-sided top press based on electromagnetic ultrasonic surface waves can effectively and timely detect surface cracks in the top hammer, improve detection accuracy and speed up detection efficiency, and can be widely used in the field of surface crack detection. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the process of the present invention;

[0020] Figure 2 This is a schematic diagram of the installation of the ultrasonic transducer in this invention.

[0021] Figure 3 This is a schematic diagram of the detection principle of the present invention. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the detailed description of the embodiments of this application provided below with reference to the accompanying drawings is not intended to limit the scope of protection of the claimed application, but merely represents selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application. The present invention will be further described below with reference to the accompanying drawings.

[0023] like Figure 1As shown, a crack detection method for the top hammer of a six-sided top press based on electromagnetic ultrasonic surface waves can achieve excellent crack detection accuracy even after the working surface of the top hammer of a six-sided top press has been damaged and cracks have formed. The main content involves placing electromagnetic ultrasonic transducers on the four working inclined surfaces of the top hammer. Four electromagnetic ultrasonic transducers on different working planes are used sequentially as excitation transducers to generate ultrasonic waves on the top hammer surface. After the ultrasonic waves propagate along the top hammer surface, they undergo mode conversion, generating transverse and longitudinal waves. These two waves superimpose to form surface waves. After propagating a certain distance on the top hammer surface, the signals are collected by three other receiving transducer probes. Each receiving transducer collects signals corresponding to a different acquisition channel. By processing and differential analysis of the detection signals in different channels, the presence of cracks on the top hammer surface is evaluated and determined. Specifically, the method includes the following:

[0024] S1. According to the EMAT transduction principle, pulse current is provided to the folding coil. Under the action of the bias magnetic field of the permanent magnet, surface waves are excited on the surface of the object when multiple physical fields such as electric field, magnetic field and sound field are coupled together.

[0025] S2. In sequence, one of the four electromagnetic ultrasonic transducers is used as the excitation transducer, and the remaining three transducers are used as receivers. The non-destructive and destructive ultrasonic surface wave signals received by the electromagnetic ultrasonic transducer on the top hammer of the six-sided top press are acquired in different channels. The received signals are processed and differentially analyzed. The degree of damage to the top hammer is determined by calculating and comparing the difference coefficients.

[0026] like Figure 2 As shown, the process also includes an electromagnetic ultrasonic transducer installation step performed before step S1. The electromagnetic ultrasonic transducer installation step includes: the working section of the six-sided top press hammer consists of a working plane and four working inclined planes. Four electromagnetic ultrasonic transducers are installed on the four working inclined planes of the six-sided top press hammer. Each electromagnetic ultrasonic transducer consists of a neodymium iron boron square permanent magnet and a folding coil. The coil is made of a flexible printed circuit board. The permanent magnet is protected by an aluminum alloy shell and fixed and sealed with epoxy resin.

[0027] Furthermore, step S1 specifically includes: according to the EMAT transduction principle, a pulse current is provided to the folding coil, and a permanent magnet provides a vertical bias magnetic field. When a high-power high-frequency excitation current is passed through the coil, according to Lafarge's law of electromagnetic induction, an alternating magnetic field is generated around the current, causing vortices with the same frequency but opposite directions to be generated on the surface or near the surface of the workpiece close to the coil. Under the action of the bias magnetic field, the particles on the surface of the hammer vibrate at high frequency under the action of the Lorentz force, thereby exciting and propagating surface waves on the surface of the hammer.

[0028] Furthermore, step S2 specifically includes the following:

[0029] S21. All four electromagnetic ultrasonic transducers are used as excitation and reception. When one of the transducers on the inclined plane of the working section is used as excitation, a high-power high-frequency excitation current is applied to it, which excites surface waves to propagate on the surface of the top hammer. After the incident surface wave encounters the surface defect, it is scattered and projected. The surface wave waveform that finally reaches the receiving transducer includes the direct wave that passes through the defect and the scattered wave that passes through the defect.

[0030] S22. Sequentially, one of the four electromagnetic ultrasonic transducers is used as the excitation source, and the other three are used as receivers to collect signals. Surface waves are excited on the undamaged top hammer surface, and waveform information of the undamaged top hammer surface is collected. Then, excitation and receiving transducers are set up with the same channel on the top hammer surface to be tested, and waveform information of the corresponding channel is collected. By calculating the degree of difference between the signal received by the undamaged top hammer on the corresponding channel and the signal received by the top hammer to be tested, the degree of damage on the top hammer is determined.

[0031] Furthermore, in step S22, the loss index is calculated using the formula... The degree of difference between the signal received by the defect-free hammer and the signal received by the hammer under test in the same channel is calculated. Here, D is the damage index, I(t) is the signal received by the crack-free hammer, and V(t) is the signal received by the cracked hammer. The closer the damage index D is to 0, the more similar the signal received by the hammer under test is to the signal received by the defect-free hammer, and the smaller the difference. The closer it is to 1, the greater the difference between the signal received by the hammer under test and the signal received by the crack-free hammer, and the greater the probability that the hammer has a defect. The presence of a defect in the hammer can be determined by analyzing the damage index.

[0032] Furthermore, in step S22, one of the four electromagnetic ultrasonic transducers is used as the excitation source, and the other three transducers are used as receivers to acquire signals, including:

[0033] like Figure 3 The example, Figure 3 This is a schematic diagram of the detection principle of the present invention. When transducer A excites surface waves on the surface of the hammer, the signal from the non-destructive test piece is directly transmitted to transducer B for reception, while transducers C and D do not receive the detection signal. When a crack appears on the surface of the hammer, the presence of the crack causes the surface waves to refract and scatter, thereby allowing transducers C and D to receive the detection signal containing the defect, and the received signal from transducer B will also be affected and attenuated.

[0034] Transducers B, C, and D act as receivers, and can respectively receive the signal data B, which is used by A to excite the transducer. A C A D A Similarly, when transducers A, C, and D act as receivers, they can respectively receive signal data A from transducer B, which is used as the excitation transducer.B C B D B When transducers A, B, and D are used as receivers, they can respectively receive signal data A from transducer C, which is used as the excitation transducer. C B C D C When transducers A, B, and C are used as receivers, they can respectively receive signal data A from transducer D, which is used to excite the transducer. D B D C D ;

[0035] This process is repeated. Each transducer, acting as a receiver, can acquire signal data from three different channels. If the signal of the tested hammer received by the transducer is from the same channel as the signal of the undamaged hammer, and the larger and closer the difference coefficient of the acquired signals is to 1, the greater the probability that there is a crack around the installation location of this transducer. Assume that when transducer A acts as a receiver, it acquires the excitation signals from transducers B, C, and D, respectively. B A C A D Determine whether the difference coefficient of the signal in each channel is close to 1 or 0. If A B The difference coefficient of the signal within the channel is close to 1, A C A D If the difference coefficient is close to 0, then there is a high probability that defects exist near the working surfaces where transducers A and B are installed. By processing and analyzing the difference coefficients of the three channels of each electromagnetic ultrasonic transducer, a preliminary assessment can be made based on the data to determine whether cracks appear and their location around the working surfaces where the transducers are installed.

[0036] The above description is merely a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the concept described herein through the above teachings or related technologies or knowledge. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.

Claims

1. A method for detecting cracks in the top hammer of a six-sided top press based on electromagnetic ultrasonic surface waves, characterized in that: The detection method includes: S1. According to the EMAT transduction principle, pulse current is provided to the folding coil. Under the action of the bias magnetic field of the permanent magnet, surface waves are excited on the surface of the object when multiple physical fields such as electric field, magnetic field and sound field are coupled together. S2. In sequence, one of the four electromagnetic ultrasonic transducers is used as the excitation, and the remaining three transducers are used as the receivers. The non-destructive and damaged ultrasonic surface wave signals received by the electromagnetic ultrasonic transducers on the top hammer of the six-sided top press are obtained in different channels. The received signals are processed and the difference analysis is performed. The degree of damage to the top hammer is determined by calculating and comparing the difference coefficients. The S2 step specifically includes the following: S21. All four electromagnetic ultrasonic transducers are used as excitation and reception. When one of the transducers on the inclined plane of the working section is used as excitation, a high-power high-frequency excitation current is applied to it, which excites surface waves to propagate on the surface of the top hammer. After the incident surface wave encounters the surface defect, it is scattered and projected. The surface wave waveform that finally reaches the receiving transducer includes the direct wave that passes through the defect and the scattered wave that passes through the defect. S22. One of the four electromagnetic ultrasonic transducers is used as the excitation source, and the other three transducers are used as receivers to collect signals. Surface waves are excited on the undamaged top hammer surface, and waveform information of the undamaged top hammer surface is collected. Then, the excitation and receiving transducers are set up with the same channel on the top hammer surface to be tested, and waveform information of the corresponding channel is collected. The degree of damage on the top hammer is determined by calculating the difference between the signal received by the undamaged top hammer on the corresponding channel and the signal received in the top hammer to be tested. In step S22, the loss index is calculated using the formula... Calculate the degree of difference between the signal received by the defect-free hammer in the same channel and the signal received by the hammer under test. The damage index, The signal received from the crack-free top hammer. The signal received in the cracked hammer; loss index The closer the value is to 0, the more similar the signal received by the hammer under test is to the signal received by the hammer without defects, and the smaller the difference. The closer the value is to 1, the greater the difference between the signal received by the hammer under test and the signal received by the hammer without cracks, and the greater the probability that the hammer has defects. By analyzing the damage index, it can be determined whether the hammer has defects. The detection method also includes an ultrasonic transducer installation step performed before step S1. The electromagnetic ultrasonic transducer installation step includes: the working section of the six-sided top press hammer consists of a working plane and four working inclined planes. Four electromagnetic ultrasonic transducers are installed at the four working inclined planes of the six-sided top press hammer. Each electromagnetic ultrasonic transducer consists of a neodymium iron boron square permanent magnet and a folding coil. The coil is made of a flexible printed circuit board. The permanent magnet is protected by an aluminum alloy shell and fixed and sealed with epoxy resin.

2. The method for detecting cracks in the top hammer of a six-sided top press based on electromagnetic ultrasonic surface waves according to claim 1, characterized in that: The S1 step specifically includes: according to the EMAT transduction principle, a pulse current is provided to the folding coil, and a permanent magnet provides a vertical bias magnetic field. When a high-power high-frequency excitation current is passed through the coil, according to Lafarge's law of electromagnetic induction, an alternating magnetic field is generated around the current, causing vortices with the same frequency but opposite directions to be generated on the surface or near the surface of the workpiece close to the coil. Under the action of the bias magnetic field, the particles on the surface of the top hammer vibrate at high frequency under the action of the Lorentz force, thereby exciting and propagating surface waves on the surface of the top hammer.

3. The method for detecting cracks in the top hammer of a six-sided top press based on electromagnetic ultrasonic surface waves according to claim 1, characterized in that: In step S22, the sequential use of one of the four electromagnetic ultrasonic transducers as the excitation source and the other three as the receivers for signal acquisition includes: Transducers B, C, and D, acting as receivers, can respectively receive signal data from transducer A, which is used as the excitation transducer. , , Similarly, when transducers A, C, and D act as receivers, they can respectively receive the signal data from transducer B, which acts as the excitation transducer. , , When transducers A, B, and D are used as receivers, they can respectively receive the signal data from transducer C, which is used as the excitation transducer. , , When transducers A, B, and C are used as receivers, they can respectively receive the signal data from transducer D, which is used as the excitation transducer. , , ; This process is repeated, and each transducer, acting as a receiver, can acquire signal data from three different channels. If the signal of the hammer under test received by the transducer is from the same channel as the signal of the undamaged hammer, and the larger the difference coefficient of the acquired signals and the closer it is to 1, the greater the probability that there is a crack around the installation location of this transducer. For example, suppose that when transducer A acts as a receiver, it acquires the excitation signals from transducers B, C, and D as follows: , , Determine whether the difference coefficient of the signal in each channel is close to 1 or 0. The difference coefficient of the signal within the channel is close to 1. , If the difference coefficient is close to 0, there is a high probability that there are defects near the working surface where transducers A and B are installed. By processing and analyzing the difference coefficient of the three channels of each electromagnetic ultrasonic transducer, a preliminary assessment can be made based on the data to determine whether cracks and their location appear around the working surface where the transducer is installed.

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