Research And Design Of High Sensitivity Array Sensor For Weld-guided Waves

Weld structure is the main means of connecting metal structures,especially in the industrial manufacturing fields such as deep-sea ships.The health of the weld structure is also closely related to the safety of the service site.If the welds in the service site are not regularly inspected for defects and solve the potential hazards,serious costs may be incurred.Among various detection methods,ultrasonic guided wave inspection technology stands out because it has the advantage of being able to detect internal and external defects of long-distance components with one scan.The core part of realizing defect detection based on ultrasonic guided waves is the successful excitation and reception of ultrasonic guided waves by the sensor in the components.However,most of the existing sensors are monolithic sensors,combined with the unevenness and irregularity of the weld structure surface,resulting in a low degree of adhesion between the sensor and the weld surface and low signal transmission efficiency.In order to improve the detection effect of the sensor in the welding seam,this paper uses a combination of finite element analysis method and experimental test to study and design the array sensor,in order to develop a high-precision and high-sensitivity array sensor suitable for welding seam defect detection.sensor.The main research content and effective conclusions of this paper are as follows:(1)Based on the three-dimensional simulation model of the butt weld,combined with the finite element analysis method,the excitation mode and propagation characteristics of the SH wave in the weld are studied,and the vibration mode of the piezoelectric element in the array sensor is further determined.Combined with the finite element analysis model,the wave structure loading method is used to explore the welding seam characteristic guided wave forming conditions formed by the SH wave in the weld structure,as well as the dispersion and attenuation characteristics of its propagation in the weld seam.The research shows that the SH_W0 modal guided wave has the advantages of small dispersion and weak attenuation in the weld,which is suitable for long-distance and large-scale weld inspection;On this basis,the SH_W0 mode vibration form is further studied to determine the vibration mode of the piezoelectric element in the array sensor,which lays the foundation for the research of the array sensor in this paper.(2)Based on the piezoelectric theory,combined with finite element simulation,the design of the relevant parameters and arrangement of the piezoelectric element of the array sensor is completed.Considering the piezoelectric performance and the manufacturing cost of the sensor,the piezoelectric material is determined to be PZT-5H;Through the finite element analysis method,based on the PZT-5H piezoelectric material on the surface of the welding seam of the butt-welded plate,the circumferential and axial array element spacing and the number of circumferential and axial array elements on the sensor signal energy excitation effect are based on the PZT-5H piezoelectric material.Carry out simulation research to obtain the array parameters that can maximize the energy of the excitation signal;At the same time,optimize the selection of backing material,backing thickness,matching layer material,and matching layer thickness to improve the sensitivity of the sensor.The optimization shows that when X is 0.1?(?is the wavelength of the surface wave at the corresponding frequency),Y is 0.25?,and the array parameter M×N is 4×4,the sensor excitation signal has high energy and high concentration.(3)Complete the overall design and packaging of the weld detection array sensor,and complete the performance evaluation of the array sensor through experiments on the attenuation rate,echo reflectivity,defect detection capability and positioning accuracy transmitted from the weld.Experiments have proved that the average location accuracy of the sensor designed in this paper for weld defects is 1.47%,while the average defect location detection accuracy of the traditional single-chip piezoelectric sensor and the 3×3 piezoelectric chip array sensor are 5.32%and 1.58%,respectively.It can be seen that the detection accuracy of 4×4 array sensors is higher than that of existing sensors;At the same time,when the 4×4 array sensor is used for detection,the average reflectivity of the end face and defect echo is 52.4%and 23.6%,which are respectively 23.7%and 9.6%higher than that of the monolithic sensor and higher than the 3×3 piezoelectric chip array sensor.It is 1.02%,1.2%higher,and the excitation signal energy amplitude is close to twice the excitation energy of the 3×3 piezoelectric chip array sensor,which has more obvious advantages in long-distance weld inspection.The experimental verification shows that the array-type flexible sensor developed in this paper can realize the effective excitation of a single-mode guided wave in the weld structure in the welding seam defect detection experiment,and can ensure the accurate positioning of the defect by the excited characteristic guided wave The sensitivity and sensitivity of defect recognition have opened up a new way for the practical application of ultrasonic guided wave nondestructive testing technology in the field of weld defect detection.