The invention relates to a laser ultrasonic detection system for quickly positioning faults and a detection method of the laser ultrasonic detection system. The system comprises a laser, wherein the laser is connected with a galvanometer scanning system and a controller; a scanning area is arranged on the lower end of the galvanometer scanning system; an air coupling sensor is arranged on the scanning area, and is connected with a four-way signal conditioning way module; the four-way signal conditioning way module is connected with a four-way high-speed A/D acquisition card; the four-way high-speed A/D acquisition card is connected with an upper computer software system and the controller; the controller is also connected with the upper computer software system and the galvanometer scanning system. According to the laser ultrasonic detection system for quickly positioning faults and the detection method of the laser ultrasonic detection system provided by the invention, the system datamemory space is reduced, the detection speed is improved, and the positions of the faults can be detected accurately.

Laser ultrasonic detection system for quickly positioning faults and detection method of laser ultrasonic detection system

The invention provides an omni-directional A0 mode lamb wave electromagnetic ultrasonic transducer, and solves the issues of poor unicity method, low energy efficiency and low strength lamb wave excitation in current A0 mode lamb wave electromagnetic ultrasonic transducer. The transducer is characterized in that a cylindrical magnet and a first to Nth hollow cylindrical magnets are arranged from the interior to the exterior on the internal of a shell by a back board in an upright, coaxial and isomorph mode. Two adjacent magnets are arranged in opposite polarities. Annular sub-ring coils of equal widths are arranged on the open end of the shell, on the outer edge of the cylindrical magnet and on the inner and outer edges of the hollow cylindrical magnet. Two annular sub-ring coils of the inner and outer edges of the same hollow cylindrical magnet are coil-reeled in the same direction, two annular sub-ring coils of the inner edge of two adjacent hollow cylindrical magnets are coil-reeled in the reverse direction, two annular sub-ring coils of the outer edge of the cylindrical magnets and the inner edge of the first hollow cylindrical magnet are coil-reeled in the reverse direction. The inner diameter of the first annular sub-ring coils is Lambada-W, and the minimum spacing of adjacent annular sub-ring coils is 0.5 Lambada-W.

Omni-directional A0 mode lamb wave electromagnetic ultrasonic transducer

The invention discloses a metal plate defect location method based on laser Lamb wave frequency-wave number analysis and belongs to the field of laser ultrasonic non-destructive testing. The method comprises the following steps: firstly, excitation is performed by a laser excitation probe in a fixed position on a metal plate, a laser receiving probe scans defect lines to receive N groups of Lamb wave data, and a time-space wave field on a scanning path is obtained; secondly, signals under specific center frequency are extracted from the acquired N groups of Lamb wave data with a continuous wavelet transform method, and analyzability of a defect location result is guaranteed; finally, the extracted wave field signals are subjected to space-frequency-wave number imaging with short-space two-dimensional Fourier transform algorithm, and defect location is realized according to characteristics of a wave number spectrum on the scanning path. One completely non-contact type detection method is provided, and action rules between Lamb waves and defects in the wave number field are disclosed.

Metal plate defect location method based on laser Lamb wave frequency-wave number analysis

The invention discloses an acoustic vibration technology-based acoustic emission positioning detection method which comprises the following steps: (1) firstly determining a maximum transmission distance that no obvious signal attenuation occurs during transmission of a knocking signal in a detected material; (2) arranging probes to enable each acoustic vibration point to be spatially connected with a detection point of a detection region in a row where the acoustic vibration point is placed and an adjacent detection point of a detection region in another row to form three parallel-connected triangular regions, and mounting the probe on each detection point; (3) knocking each acoustic vibration point with an acoustic vibration hammer to acquire a signal, and judging whether the detection regions have defects or not through differences of signal indexes according to the comparison of adjacent triangular region signals. According to the acoustic vibration technology-based acoustic emission positioning detection method disclosed by the invention, by the design of the acoustic vibration hammers, the reasonable arrangement mode of sensors is researched; the acoustic vibration hammers areadopted to directly knock parts to be detected to generate exciting signals, and the sensors receive the signals to directly judge whether the defects exist or not and to locate the defects; the acoustic vibration technology-based acoustic emission positioning detection method has the advantages of large detection area and higher convenience in operation.

Acoustic vibration technology-based acoustic emission positioning detection method

The invention discloses an orthogonal vortex detection sensor. A method for increasing a driving exciting coil winding outside a non-directinoal electromagnetic detection sensor is adopted, so that onone hand, the advantages of high anti-jamming capability and capability of detecting 45-degree crack direction are retained, and on the other hand, the effects of improving the detection sensitivityand broadening the frequency band of a probe are achieved.

Orthogonal vortex detection sensor

The invention discloses an acoustic emission source positioning method of a composite material plate of an omnidirectional dual circular array. The method comprises the following steps: adopting a dual acoustic emission sensor circular array and the radius of a known circular array, namely the distance between every two sensors, to solve a wave velocity by using a time difference of arrival of the two sensors; and performing verification on solved multiple groups of wave velocity arrays and an omnidirectional experimental result of a solved 360-degree wave velocity, selecting nearest velocities, matching the nearest velocities with corresponding directions, performing gradual deletion to reduce the range of a detection area, repeating the experiment, and finally achieving accurate regional positioning of an acoustic emission source of a structural damage of the composite material plate.

Acoustic emission source positioning method of composite material plate of omnidirectional dual circular array

The invention discloses a metal plate defect detecting method based on an omni-directional SH0 electromagnetic sound sensor array and belongs to the field of ultrasonic non-destructive detection. Metal plates are wide in application range, are affected by outside factors, easily produce defects affecting normal usage of the plates and can be detected by adopting a non-destructive detection technology. Omni-directional SH0 electromagnetic sound sensors are adopted to form the array, the array is arranged on one side of a metal plate, an experiment system is established for signal acquisition, and an oval imaging algorithm is integrated for achieving the metal plate detection. In the method, an aluminum plate is used as a detection sample, a steel column is adhered to the aluminum plate to simulate a surface defect, and an imaging result proves the feasibility of the method.

Metal plate defect detecting method based on omni-directional SH0 electromagnetic sound sensor array

An electromagnetic acoustic transducer-based nonmetal plate Lamp wave detection method belongs to the field of ultrasonic nondestructive detection. An omnidirectional electromagnetic acoustic transducer is adopted in the method, and the transducer is characterized in that a spiral coil is placed in a flexible circuit board, and a cylindrical neodymium-iron-boron magnet is placed on the spiral coil. The method is combined with a copper foil having a same shape to the transducer coil, the copper foil is pasted to an organic glass plate, the electromagnetic acoustic transducer is placed on the copper foil, and the cylindrical neodymium-iron-boron magnet, the spiral coil and the copper foil are close. When alternating current is applied to the spiral coil, eddy current is generated in the copper foil, and alternating Lorentz force is generated in the copper foil under the action of bias magnetostatic field provided by the cylindrical neodymium-iron-boron magnet. The organic glass plate is closely applied to the copper foil, the Lorentz force causes vibration of particles in the plate, and the vibration s propagated in the plate in a Lamb wave form. An experiment system is established, and the method is used to realize excitation and reception of Lamb wave S0 modulus in the organic glass plate.

Electromagnetic acoustic transducer-based nonmetal plate Lamp wave detection method

The invention relates to an electromagnetic shielding type bidirectional excitation eddy sensor. The electromagnetic shielding type bidirectional excitation eddy sensor comprises a first circular excitation coil, a second circular excitation coil, a circular receiving coil, a cylindrical ferrite magnetic conduction bar, and a tank-shaped magnetic shielding outer casing. The electromagnetic shielding type bidirectional excitation eddy sensor is characterized in that by changing the frequency of an excitation signal, the two excitation coils can produce sensing eddies with different directions in the detected material, and the bidirectional eddy fields in the detected material are mutually superposed; at certain depth h away from the material surface, the near-zero effect is formed in the eddy fields; after beyond the depth h is crossed, the density of the sensing eddy is firstly increased and then reduced; when the detected area of the ferromagnetic material is scanned along a certain direction, the cylindrical receiving coil can receive the impedance and phase angle change of the signal, so as to reflect the depth and position of the defect. The electromagnetic shielding type bidirectional excitation eddy sensor has the advantages that the structure is simple, the size is small, the sensitivity is high, the space resolution is high, and the like; the defection requirement of deeper sub-surface defect of the ferromagnetic material is met.

Electromagnetic shielding type bidirectional excitation eddy sensor

The invention relates to a coaxial double-arc-surface through-type gas baseline focusing air coupling sensor and belongs to the technical field of acoustic transducers. The sensor functions in converting electric signals generated by an excitation end into vibration of a piezoelectric material to generate ultrasonic waves, receiving acoustic wave signals reflected by a detected member and converting the acoustic signals into electric signals. A coaxial double-arc-surface through-type gas-based piezoelectric composite material is adopted as an excitation receiving sensitive element, and the excitation receiving sensitive element, an upper electrode, a lower electrode, a transmission layer, a backing layer, an impedance matching circuit, a metal shell and a BNC form the coaxial double-arc-surface through-type gas baseline focusing air coupling sensor. The sensor has the advantages of low acoustic impedance, high energy transmission efficiency and centralized acoustic energy and completely can meet experimental needs.

Liu Zenghua

Papers

Acoustic emission source positioning method of composite material plate of omnidirectional dual circular array

Metal plate defect detecting method based on omni-directional SH0 electromagnetic sound sensor array

Electromagnetic acoustic transducer-based nonmetal plate Lamp wave detection method

Electromagnetic shielding type bidirectional excitation eddy sensor

Coaxial double-arc-surface through-type gas baseline focusing air coupling sensor