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Evaluating Local Elasticity of the Metal Nano-films Quantitatively Based on Referencing Approach of Atomic Force Acoustic Microscopy

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Chinese Journal of Mechanical Engineering 2012年第6期25卷 1281-1286页

作者： ZHANG Gaimei he cunfu WU Bin CheN Qiang College of Mechanical Engineering and Applied Electronics Technology Beijing University of Technology Beijing 100124 China Laboratory of Plasma Physics and Materials Beijing Institute of Graphic Communication Beijing 102600 China

Traditional technique such nanoindenter（NI） can＇t measure the local elastic modulus at nano-scale（lateral）. Atomic force acoustic microscopy （AFAM） is a dynamic method, which can quantitatively determine indentation modulus by measuring the contact resonance spectra for high order modes of the cantilever. But there are few reports on the effect of experimental factors, such length of cantilever, contact stiffness on measured value. For three different samples, including copper（Cu） film with 110 nm thickness, zinc（Zn） film of 90 nm thickness and glass slides, are prepared and tested, using referencing approach in which measurements are performed on the test and reference samples （it＇s elastic modulus is known）, and their contact resonance spectra are measured used the AFAM system experimentally. According to the vibration theory, from the lowest two contact resonance frequencies, the tip-sample contact stiffness is calculated, and then the values for the elastic properties of test sample, such as the indentation modulus, are determined. Using AFAM system, the measured indentation modulus of copper nano-film, zinc nano-film and glass slides are 113.53 GPa, 87.92 GPa and 57.04 GPa, which are agreement with literature values Mcu--105-130 GPa, Mzn = 88.44 GPa and Molass = 50-90 GPa. Furthermore, the sensitivity of contact resonance frequency to contact stiffness is analyzed theoretically. The results show that for the cantilevers with the length 160 pm, 225 μm and 520 μm respectively, when contact stiffness increases from 400 N/m to 600 N/m, the increments of first contact resonance frequency are 126 kHz, 93 kHz and 0.6 kHz, which show that the sensitivity of the contact resonance frequency to the contact stiffness reduces with the length of cantilever increasing. The novel method presented can characterize elastic modulus of near surface for nano-film and bulk material, and local elasticity of near surface can be evaluated by optimizing the experimental parameters using

关键词： local elasticity atomic force acoustic microscope(AFAM) contact stiffness referencing approach

Numerical Analysis of the Nonlinear Interactions Between Lamb Waves and Microcracks in Plate

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Acta Mechanica Solida Sinica 2019年第6期32卷 767-784页

作者： Hongtao Lv Jingpin Jiao Bin Wu cunfu he Department of Mechanical Engineering and Applied Electronics Technology Beijing University of TechnologyBeijing 100124China

In this paper,three-dimensional finite-element modeling is conducted to investigate the nonlinear interactions between Lamb waves and *** simulation research focuses on the influence of microcrack orientation on the propagation direction of generated sum-frequency Lamb *** simulation results show that the resonant conditions based on classical nonlinear theory are valid for such interactions,leading to the generation of transmitted and reflected sum-frequency SO waves(SFSWs).Moreover,the propagation directions of these two SFSWs exhibit different trends with respect to the orientations of *** transmitted SFSW can be used to detect microcracks,whereas the reflected one can be used to measure their orientations.

关键词： Nonlinear ultrasonic Lamb wave mixing Resonant condition Microcrack Finiteelement method

Temperature Dependence of Ultrasonic Longitudinal Guided Wave Propagation in Long Range Steel Strands

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Chinese Journal of Mechanical Engineering 2011年第3期24卷 487-494页

作者： LIU Zenghua ZHAO Jichen WU Bin he cunfu College of Mechanical Engineering and Applied Electronics Technology Beijing University of Technology Beijing 100124 China

Ultrasonic guided wave inspection is an effective non-destructive testing method which can be used for stress level evaluation in steel *** the propagation velocity of ultrasonic guided waves changes due to temperature shift making the prestress measurement of steel strands inaccurate and even sometimes *** the course of solving the problem,this paper reports on quantitative research on the temperature dependence of ultrasonic longitudinal guided wave propagation in long range steel *** order to achieve the generation and reception of a chosen longitudinal mode in a steel strand with a helical shaped surface,a new type of magnetostrictive transducer was developed,characterized by a group of thin clips and three identical permanent *** and reception of ultrasonic guided waves in a steel strand were performed *** results shows that in the temperature range from-4 ℃ to 34 ℃,the propagation velocity of the L（0,1） mode at 160 kHz linearly decreased with increasing temperature and its temperature dependent coefficient was 0.90（m·s-1 ·（℃）-1） which is very close to the theoretical *** effect of dimension deviation between the helical and center wires and the effect of the thermal expansion of the steel strand on ultrasonic longitudinal guided wave propagation were also *** was found that these effects could be ignored compared with the change in the material mechanical properties of the steel strands due to temperature *** was also observed that the longitudinal guided wave mode was somewhat more sensitive to temperature changes compared with conventional ultrasonic waves ***,it is considered that the temperature effect on ultrasonic longitudinal guided wave propagation in order to improve the accuracy of stress measurement in prestressed steel *** research on the temperature dependence of ultrasonic guided wave propagation in steel strands

关键词： steel strand ultrasonic guided waves mode temperature coefficient magnetostrictive transducer

A Sensitivity Mapping Technique for Tensile Force and Case Depth Characterization Based on Magnetic Minor Hysteresis Loops

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Chinese Journal of Mechanical Engineering 2020年第6期33卷 93-104页

作者： cunfu he Wenqiao Dou Xiucheng Liu Meng Yang Ruifang Zhang Faculty of Materials and Manufacturing Beijing University of TechnologyBeijing 100124China

In the nondestructive testing and evaluation area,magnetic major hysteresis loop measurement technology are widely applied for ferromagnetic material *** the characterization ability of major hysteresis loop measurement technology greatly varies as the evaluated target *** solve this limitation,magnetic minor hysteresis loops,which reflect the responses of ferromagnetic material magnetization in a systematic way,is *** by plenty of information carried by the minor loops,the sensitivity mapping technique was developed to achieve the highest sensitivity of minor-loop parameters to the nondestructively evaluated *** this study,for the first time,the sensitivity mapping technique is used to measure the tensile force in a steel strand and evaluate the effective case depth in induction-hardened steel *** method and procedures for the sensitivity mapping technique are given before experimental *** obtained experimental results indicate that the linear correlation between the induced voltage(or the magnetic induction intensity)and the tensile force(or effective case depth)exists at most of the locations in the cluster of minor *** obtained sensitivity maps can be used to optimize the applied magnetic field(or excitation current)and the analyzed locations at the minor loops for achieving the highest *** the purpose of tensile force measurement,it is suggested that the strand should be firstly magnetized to the near-saturation state and then restored to the remanent *** this way,the highest sensitivity is obtained as about 15.26 mV/*** for the induction-hardened steel rods,the highest sensitivity of magnetic induction intensity to the effective case depth occurs under low magnetic field conditions and the absolute value of the highest sensitivity is about 0.1110 T/*** indicates that if the highest sensitivity is required in the case depth evaluation,the induction-hardened steel rods are

关键词： Sensitivity mapping technique Magnetic minor hysteresis loop Tensile force Case depth

Delamination damage detection of laminated composite beams using air-coupled ultrasonic transducers

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Science China(Physics,Mechanics & Astronomy) 2013年第7期56卷 1269-1279页

作者： LIU ZengHua YU HongTao he cunfu WU Bin College of Mechanical Engineering and Applied Electronics Technology Beijing University of Technology

Air-coupled ultrasonic transducers are used to generate and receive Lamb waves in quasi-isotropic laminated composite beams for delamination detection. The influence of incident angle on the excited mode is studied. Numerical calculation and experimental results show that a pure Lamb wave mode can be generated if the transmitting transducer is oriented at a specific angle, and the receiving transducer can either be oriented to detect the same mode as that generated by the transmitter or to detect another mode generated by mode conversion at a defect. A three-dimensional finite element model is created to predict the interaction of Lamb waves with delamination, and some unique mechanisms of interaction between A0 mode Lamb waves and delamination are revealed in detail. The experimental results obtained on laminated composite beam using air-coupled ultrasonic transducers are well in accordance with finite element simulation results. Research results show that air-coupled ultrasonic guided waves can be used for delamination damage detection effectively in laminated composite beams.

关键词： delamination detection composite beam Lamb wave mode air-coupled ultrasonic transducer three-dimensional finite element simulation

Quantitative Rectangular Notch Detection of Laser-induced Lamb Waves in Aluminium Plates with Wavenumber Analysis

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Transactions of Nanjing University of Aeronautics and Astronautics 2018年第2期35卷 244-255页

作者： Liu Zenghua Feng Xuejian he cunfu Wu Bin College of Mechanical Engineering and Applied Electronics Technology Beijing University of Technology Beijing Engineering Research Center of Precision Measurement Technology and Instruments Beijing University of Technology

It is difficult to quantitatively detect defects by using the time domain or frequency domain features of Lamb wave signals due to their dispersion and multimodal ***,it is important to discover an intrinsical parameter of Lamb waves that could be used as a damage sensitive *** this paper,quantitative defect detection in aluminium plates is carried out by means of wavenumber analysis *** wavenumber of excited Lamb wave mode is a fixed value,given a frequency,a thickness and material properties of the target *** Lamb waves propagate to the structural discontinuity,new wavenumber components are created by abrupt wavefield *** new wavenumber components can be identified in the frequency-wavenumber *** estimate spatially dependent wavenumber values,a short-space two-dimensional Fourier transform(FT)method is presented for processing wavefield data of Lamb *** results can be used to determine the location,size and depth of rectangular *** analysis techniques are demonstrated using simulation examples of an aluminium plate with a rectangular ***,the wavenumber analysis method is applied to simulation data that are obtained through a range of notch depths and *** results are analyzed and rules of the technique with regards to estimating notch depth are *** on simulation results,guidelines for using the technique are ***,experimental wavefield data are obtained in aluminium plates with rectangular notches by a full noncontact transceiving method,i.e.,laser-laser ***-pass filtering combined with continuous wavelet transform is used to extract a certain frequency component from the full laser-induced wavefield with wide *** two-dimensional FT method is used for further processing full wavefield data at a certain frequency to estimate spatially dependent wavenumber *** consistency of simulation and experimental results shows the effectivenes

关键词： wavenumber analysis short space two-dimensional Fourier transform(FT) notch aluminium plate

FOULING DETECTION IN FOOD VESSELS USING INTERDIGITAL LAMB WAVE TRANSDUCER

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Chinese Journal of Mechanical Engineering 2007年第1期20卷 111-114页

作者： JIAO Jingpin GE Haiyan WU Bin he cunfu College of Mechanical Engineenng and Applied Electronic Technology Beijing University of Technology Beijing 100022 China

Lamb waves are used to detect fouling in food vessels. The propagation of the Lamb waves in plates exhibits many modes and dispersion characteristics, which have great influence on fouling detection. The relative distribution of the in-plane and out-of-plane displacement of the mode across the thickness of the plate will determine the sensitivity of the mode to a particular loading condition. By considering the dispersion and multi-mode characteristics of guided waves, an interdigital polyvi- nylidene fluoride （PVDF） transducer is designed to realize the mode selection of gnided waves, and a single a0 mode is used for guided wave detection. Fouling detection experiments are conducted in the laboratory using epoxy adhesive on a thin plate. Using the interdigital PVDF transducer, three fouled areas are detected. Using one of the time-frequency analysis methods, the waveforms are further processed. This also demonstrates the validity of this method of fouling detection.

关键词： Lamb waves Interdigital transducer Fouling detection

Application of Uniform Experimental Design in Optimizing Excitation Parameters for Magnetic Frequency Mixing Measurements

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Chinese Journal of Mechanical Engineering 2020年第1期33卷 197-209页

作者： Yu Chang Jingpin Jiao Xiucheng Liu Guanghai Li cunfu he Bin Wu College of Mechanical Engineering and Applied Electronics Technology Beijing University of TechnologyBeijing 100124China China Special Equipment Inspection and Research Institute Beijing 100013China

Excitation parameter preferences are key factors a ecting the performance of magnetic frequency mixing detection.A uniform experimental design method was used to analyze this *** fuzzy theory,a comprehensive model is established for evaluating the e ect of magnetic frequency mixing.A polynomial is selected as the regression function to express explicitly the correlation between the excitation parameters and the frequency-mixing e *** excitation parameters were then optimized using genetic *** frequency mixing experiments were conducted to measure the surface hardness of some ferromagnetic *** mixing is further enhanced under the optimal settings,resulting in an improvement in the measurement *** results of this study support the application of the magnetic frequency mixing technique in non-destructive testing.

关键词： Magnetic frequency mixing technology Excitation parameters Uniform experimental design Regression statistical method Surface hardness measurement

Application of Nonlinear Lamb Wave Mixing Method for Residual Stress Measurement in Metal Plate

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Chinese Journal of Mechanical Engineering 2023年第1期36卷 211-223页

作者： Jingpin Jiao Li Li Xiang Gao Quan Cheng cunfu he Bin Wu Faculty of Materials and Manufacturing Beijing University of TechnologyBeijing 100124China

Harmonic nonlinear ultrasound can offer high sensitivity for residual stress measurements;however,it cannot be used for local stress measurements at a point in space and exhibits nonlinear distortions in the experimental *** paper presents a feasibility study on the measurement of residual stress in a metal plate using a nonlinear Lamb wave-mixing *** resonant conditions for two Lamb waves to generate a mixing frequency wave are obtained via theoretical *** element simulations are performed to investigate the nonlinear interactions between the two Lamb *** show that two incident A0 waves interact in regions of material nonlinearity and generate a rightward S0 wave at the sum *** stress measurement experiments are conducted on steel plate specimens using the collinear Lamb wave-mixing *** setting different delays for two transmitters,the generated sum-frequency component at different spatial locations is *** results show that the spatial distribution of the amplitude of the sum-frequency component agrees well with the spatial distribution of the residual stress measured using *** proposed collinear Lamb wave-mixing method is effective for measuring the distribution of residual stress in metal plates.

关键词： Residual stress Lamb wave Collinear wave mixing Nondestructive testing Resonant conditions