Third Harmonic Generation of Shear Horizontal Guided Waves Propagation in Plate-like Structures

Li, Weibin,Xu, Chunguang,Cho, Younho The Korean Society for Nondestructive Testing 2016 한국비파괴검사학회지 Vol.36 No.2

The use of nonlinear ultrasonics wave has been accepted as a promising tool for monitoring material states related to microstructural changes, as it has improved sensitivity compared to conventional non-destructive testing approaches. In this paper, third harmonic generation of shear horizontal guided waves propagating in an isotropic plate is investigated using the perturbation method and modal analysis approach. An experimental procedure is proposed to detect the third harmonics of shear horizontal guided waves by electromagnetic transducers. The strongly nonlinear response of shear horizontal guided waves is measured. The accumulative growth of relative acoustic nonlinear response with an increase of propagation distance is detected in this investigation. The experimental results agree with the theoretical prediction, and thus providing another indication of the feasibility of using higher harmonic generation of electromagnetic shear horizontal guided waves for material characterization.

Third Harmonic Generation of Shear Horizontal Guided Waves Propagation in Plate-like Structures

Weibin Li,Chunguang Xu,Younho Cho 한국비파괴검사학회 2016 한국비파괴검사학회지 Vol.36 No.2

The use of nonlinear ultrasonics wave has been accepted as a promising tool for monitoring material states related to microstructural changes, as it has improved sensitivity compared to conventional non-destructive testing approaches. In this paper, third harmonic generation of shear horizontal guided waves propagating in an isotropic plate is investigated using the perturbation method and modal analysis approach. An experimental procedure is proposed to detect the third harmonics of shear horizontal guided waves by electromagnetic transducers. The strongly nonlinear response of shear horizontal guided waves is measured. The accumulative growth of relative acoustic nonlinear response with an increase of propagation distance is detected in this investigation. The experimental results agree with the theoretical prediction, and thus providing another indication of the feasibility of using higher harmonic generation of electromagnetic shear horizontal guided waves for material characterization.

Characteristics of Ultrasonic Nonlinearity by Thermal Fatigue

Weibin Li,조윤호,현승호 한국정밀공학회 2012 International Journal of Precision Engineering and Vol. No.

The deterioration conditions of nuclear power plants and chemical plants have raised deep concerns about the safety of high-risk structures. The safety of a structure can be secured by evaluations of breakages and lifespan in the early stage. Therefore, the material condition of a structure needs to be estimated. A nonlinear ultrasonic evaluation method is reportedly more sensitive on microscopic changes of a material than a linear evaluation method. Therefore, the nonlinear ultrasonic technique based on ultrasonic nonlinearity is considered a promising method of evaluation for breakages and lifespan. This study measured the changes in nonlinear parameters by using a nonlinear ultrasonic method, observed the microstructure of a heated material, and analyzed the relation between the size of the microstructure and the changes in the nonlinear parameters.

Comparative Study of Linear and Nonlinear Ultrasonic Techniques for Evaluation Thermal Damage of Tube-Like Structures

Weibin Li,Younho Cho,Xianqiang Li 한국비파괴검사학회 2013 한국비파괴검사학회지 Vol.33 No.1

Ultrasonic guided wave techniques have been widely used for long range nondestructive detection in tube-like structures. The present paper investigates the ultrasonic linear and nonlinear parameters for evaluating the thermal damage in aluminum pipe. Specimens were subjected to thermal loading. Flexible polyvinylidene fluoride (PVDF) comb transducers were used to generate and receive the ultrasonic waves. The second harmonic wave generation technique was used to check the material nonlinearity change after different heat loadings. The conventional linear ultrasonic approach based on attenuation was also used to evaluate the thermal damages in specimens. The results show that the proposed experimental setup is viable to assess the thermal damage in an aluminum pipe. The ultrasonic nonlinear parameter is a promising candidate for the prediction of micro-damages in a tube-like structure.

열처리된 재료의 초음파 비선형성에 관한 연구

Weibin Li,이재선(Jaesun Lee),조윤호(Younho Cho) 대한기계학회 2010 大韓機械學會論文集A Vol.34 No.6

비선형 초음파는 선형 초음파와 비교하였을 때 재료의 물성 변화에 민감하게 반응한다. 이 연구의 목표는 비선형 요소를 포함하여 열처리 조건과 초음파 비선형성의 상관관계를 알아내는 것이다. 본 연구에서 기존의 방법과는 다른 수정된 초음파속도계산 식이 새롭게 제안되었다. 이것은 열처리된 재질에서 초음파 속도변화가 재료의 비선형성 때문에 발생하는 것을 찾아내었다. 실험을 통하여 수정된 초음파 속도와 1차 조화 및 2차 조화파의 진폭 비율이 서로 동일한 경향을 보이는 것을 알아냈다. 그리고 수정된 초음파속도식을 통해 계산된 상대적인 비선형계수는 기존의 방법을 이용하였을 때보다 더 민감함을 알아냈다. Ultrasonic nonlinearity is very sensitive to changes in material properties. This paper describes the study of the correlation between heat treatment and ultrasonic nonlinearity by taking nonlinear factors into consideration. A modified formula was proposed for ultrasonic velocity. This formula indicated that the changes occurring in nonlinearity during heat treatments cause changes in the ultrasonic velocity. The experimental results show that the relative nonlinearity parameters calculated from the modified ultrasonic velocities and the ratio of amplitudes of the second harmonic and fundamental wave are in good agreement. The experimental results prove that heat treatment can result in changes in material nonlinearity. Moreover, the relative nonlinearity parameter calculated from the modified velocity formula is has a large value. Since this parameter has high sensitivity to changes in nonlinearity, it can be used to represent the relative nonlinearity change calculated in this study by using the modified formula for ultrasonic velocity.

Characteristics of Ultrasonic Nonlinearity by Thermal Fatigue

Li, Weibin,Hyun, Seung-Ho,Cho, Youn-Ho 한국정밀공학회 2012 International Journal of Precision Engineering and Vol.13 No.6

The deterioration conditions of nuclear power plants and chemical plants have raised deep concerns about the safety of high-risk structures. The safety of a structure can be secured by evaluations of breakages and lifespan in the early stage. Therefore, the material condition of a structure needs to be estimated. A nonlinear ultrasonic evaluation method is reportedly more sensitive on microscopic changes of a material than a linear evaluation method. Therefore, the nonlinear ultrasonic technique based on ultrasonic nonlinearity is considered a promising method of evaluation for breakages and lifespan. This study measured the changes in nonlinear parameters by using a nonlinear ultrasonic method, observed the microstructure of a heated material, and analyzed the relation between the size of the microstructure and the changes in the nonlinear parameters.

The Study of Ultrasonic Nonlinearity in Heat Treatment Material

Weibin Li(이위빈),Jaesun Lee(이재선),Younho Cho(조윤호) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11

Nonlinear ultarsonic is very senstive to material property change. This paper attempts to study the correlation between heat treatment and ultrasonic nonlinearity by taking the nonlinearity factors into account. The modified ultrasonic velocity formula was deriven. It turns out that nonlinearity varies with ultrasonic velocity change in the material heat treatment, the experimental results show that relative nonlinearity parameters obtained from the modified ultrasonic velocity and the rai\tio of amplitudes(second harmonic and fundamental wave)have a good agreement. Both of them prove that the heat treatment can change the material nonlinearity. Furthermore, then relative nonlinearity calculated from the modified velocity is much more sensitive, representing the relative nonlinearity change based on the modified ultrasonic velocity in this case.

Comparative Study of Linear and Nonlinear Ultrasonic Techniques for Evaluation Thermal Damage of Tube-Like Structures

Li, Weibin,Cho, Younho,Li, Xianqiang The Korean Society for Nondestructive Testing 2013 한국비파괴검사학회지 Vol.33 No.1

Ultrasonic guided wave techniques have been widely used for long range nondestructive detection in tube-like structures. The present paper investigates the ultrasonic linear and nonlinear parameters for evaluating the thermal damage in aluminum pipe. Specimens were subjected to thermal loading. Flexible polyvinylidene fluoride (PVDF) comb transducers were used to generate and receive the ultrasonic waves. The second harmonic wave generation technique was used to check the material nonlinearity change after different heat loadings. The conventional linear ultrasonic approach based on attenuation was also used to evaluate the thermal damages in specimens. The results show that the proposed experimental setup is viable to assess the thermal damage in an aluminum pipe. The ultrasonic nonlinear parameter is a promising candidate for the prediction of micro-damages in a tube-like structure.

Seismic Performance of Welded Steel Beam-to-Column Connections with Initial Weld Defects

Jiaming Li,Haoran Yu,Weibin Li,Weijia Cheng 한국강구조학회 2022 International Journal of Steel Structures Vol.22 No.2

Based on the research of steel structures destroyed in earthquakes, it is often found that brittle fractures of the bottom beam fl anges of welded beam-to-column connections are caused by welding defects. In this study, artifi cial surface notches in the welds of single beam fl anges were prepared, and four experimental specimens of welded steel beam-to-column connections were tested to explore the eff ects of the initial crack and three diff erent connection types on the seismic performance of the connections. Through extended fi nite element methods, the factor of the depth of the initial crack was discussed. The results showed that the fracture mode and the rate and location of crack propagation are signifi cantly changed, and the seismic performance of the connections is reduced when there is an initial crack existing in the weld of a single beam fl ange. The fracture in box beam to box column connections shows brittle failure regardless of the initial crack, but the depth of the initial crack has the least infl uence on their seismic performance among the three connection types. The seismic performance of H-shaped beam to H-shaped column connections is the most sensitive to the depth of the initial crack. It should be noted that the weld quality of steel beam-to-column connections, especially the connections with H-shaped columns, should be carefully checked and monitored during the welding construction process and after earthquakes to ensure the bearing and deformation capacities meeting the requirements.

Numerical study on transient hydraulic excitation force characteristics of a water jet mixed-flow pump during rapid startup period

Guitao Zeng,Weibin Chen,Juanhong Li,Peng Wu,Bin Huang,Dazhuan Wu 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.10

Mixed-flow pumps have been widely used in water jet propulsion field. To ensure reliability and operation efficiency, it is necessary to investigate the characteristics of hydraulic excitation force during transient operations. In this paper, the radial force of a water jet mixed-flow pump during rapid startup period was investigated numerically based on improved delayed detached eddy simulation (IDDES) and siding mesh method, the external characteristics were verified by test results. The spatial-temporal evolution of radial force was analyzed. The radial force during rapid startup presents transient and delay phenomenon, which shows disparity compared with quasi-steady state. The flow analysis and blade strip analysis show inlet recirculation significantly affects the radial force’s evolution, the radial force is quite different from blade root to tip and the blade tip contributes most to the radial force delay phenomenon. By applying boundary vorticity flux (BVF) theory and separation vortex formation diagnosis, separation regions caused by the dissipation of inlet recirculation were effectively identified and the change trend is in line with the change of radial force, which explains how inlet recirculation results the delay of radial force on blade tip strip and the whole impeller blade.