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Lei Chen,Tae Hyun Baek 한국비파괴검사학회 2007 한국비파괴검사학회지 Vol.27 No.6
Stress intensity factor is one of the most important parameters in fracture mechanics. Both the stress field distribution and the crack propagation are closely related to these parameters. Due to the complexity of actual engineering problems, it is difficult to calculate the stress intensity factor by theoretical formulation, so photoelasticity method is a good choice. In this paper, modified twoparameter method is employed to calculate stress intensity factor for opening mode by using data from more than one photoelastic fringe loop. For getting accurate experiment results, the initial fringes are doubled and sharpened by digital image programs from the fringe patterns obtained by a CCD camera. Photoelastic results are compared with those obtained by the use of empirical equation and FEM. Good agreement shows that the methods utilized in experiments are considerably reliable. The photoelastic experiment can be used for bench mark in theoretical study and other experiments.
Chen, Lei,Baek, Tae-Hyun The Korean Society for Nondestructive Testing 2007 한국비파괴검사학회지 Vol.27 No.6
Stress intensity factor is one of the most important parameters in fracture mechanics. Both the stress field distribution and the crack propagation are closely related to these parameters. Due to the complexity of actual engineering problems, it is difficult to calculate the stress intensity factor by theoretical formulation, so photoelasticity method is a good choice. In this paper, modified two parameter method is employed to calculate stress intensity factor for opening mode by using data from more than one photoelastic fringe loop. For getting accurate experiment results, the initial fringes are doubled and sharpened by digital image programs from the fringe patterns obtained by a CCD camera. Photoelastic results are compared with those obtained by the use of empirical equation and FEM. Good agreement shows that the methods utilized in experiments are considerably reliable. The photoelastic experiment can be used for bench mark in theoretical study and other experiments.
Dynamic Magnetostriction Characteristics of an Fe-Based Nanocrystalline FeCuNbSiB Alloy
Lei Chen,Ping Li,Yumei Wen 한국자기학회 2011 Journal of Magnetics Vol.16 No.3
The dynamic magnetostriction characteristics of an Fe-based nanocrystalline FeCuNbSiB alloy are investigated as a function of the dc bias magnetic field. The experimental results show that the piezomagnetic coefficient of FeCuNbSiB is about 2.1 times higher than that of Terfenol-D at the low dc magnetic bias Hdc = 46 Oe. Moreover, FeCuNbSiB has a large resonant dynamic strain coefficient at quite low Hdc due to a high mechanical quality factor, which is 3-5 times greater than that of Terfenol-D at the same low Hdc. Based on such magnetostriction characteristics, we fabricate a new type of transducer with FeCuNbSiB/PZT-8/FeCuNbSiB. Its maximum resonant magnetoelectric voltage coefficient achieves ~10 V/Oe. The ME output power reaches 331.8 ㎼ at an optimum load resistance of 7 ㏀ under 0.4 Oe ac magnetic field, which is 50 times higher than that of the previous ultrasonic-horn-substrate composite transducer and it decreases the size by nearly 86%. The performance indicate that the FeCuNbSiB/PZT-8/FeCuNbSiB transducer is promising for application in highly efficient magnetoelectric energy conversion.
Lei Chen,Yulin Luo 한국자기학회 2015 Journal of Magnetics Vol.20 No.4
The magnetoelectric (ME) characteristics for Terfenol-D/PZT laminate composite dependence on bias magnetic field is investigated. At low frequency, ME response is determined by the piezomagnetic coefficient d33,m and the elastic compliance S<SUP>H</SUP>33 of magnetostrictive material, d33,m and S<SUP>H</SUP>33 for Terfenol-D are inherently nonlinear and dependent on Hdc, leading to the influence of Hdc on low-frequency ME voltage coefficient. At resonance, the mechanical quality factor Qm dependences on Hdc results in the differences between the low-frequency and resonant ME voltage coefficient with Hdc. In terms of ΔE effect, the resonant frequency shift is derived with respect to the bias magnetic field. Considering the nonlinear effect of magnetostrictive material and Qm dependence on Hdc, it predicts the low-frequency and resonant ME voltage coefficients as a function of the dc bias magnetic field. A good agreement between the theoretical results and experimental data is obtained and it is found that ME characteristics dependence on Hdc are mainly influenced by the nonlinear effect of magnetostrictive material.
Design strategies of supported metal-based catalysts for efficient oxidative desulfurization of fuel
Lei Chen,Zhong-Yong Yuan 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.108 No.-
The consumption of fuel oil containing sulfur compounds produces SOx, which inevitably leads to severeenvironmental pollution and even threatens human health. Oxidative desulfurization (ODS) has beenidentified as a promising pathway to produce clean fuel by virtue of its high efficiency and mild reactionconditions. In recent years, supported metal-based catalysts have attracted scientific research interestdue to the high activity and remarkable recyclability for ultra-deep ODS reactions. In this review, the latestresearch progress on the supported metal-based ODS catalysts is summarized. The reaction mechanismof the supported metal-based ODS catalysts is briefly discussed based on the different metalactive components. Notably, we focus on summarizing the design strategies of highly efficient supportedmetal-based ODS catalysts, with special emphasis on the creation of the concentrated microenvironmentof reactants around active sites, construction of highly effective catalytically active sites and improvementof recyclability. These improved strategies are also applicable to the development of the supportedmetal-based catalysts for other green catalytic reactions. In addition, the current issues and future developmenttrends of the supported metal-based ODS catalysts are pointed out.
Dynamic Magneto-mechanical Behavior of Magnetization-graded Ferromagnetic Materials
Lei Chen,Yao Wang 한국자기학회 2014 Journal of Magnetics Vol.19 No.3
This study investigates the dynamic magneto-mechanical behavior of magnetization-graded ferromagnetic materials Terfenol-D/FeCuNbSiB (MF). We measure the dynamic magneto-mechanical properties as a function of the DC bias magnetic field (Hdc). Our experimental results show that these dynamic magneto-mechanical properties are strongly dependent on the DC bias magnetic field. Furthermore, the dynamic strain coefficient, electromechanical resonance frequency, Young’s moduli, and mechanical quality factor of Terfenol-D/FeCuNbSiB are greater than those of Terfenol-D under a lower DC bias magnetic field. The dynamic strain coefficient increases by a factor of between one and three, under the same DC bias magnetic field. In particular, the dynamic strain coefficient of Terfenol-D/FeCuNbSiB at zero bias achieves 48.6 nm/A, which is about 3.05 times larger than that of Terfenol-D. These good performances indicate that magnetization-graded ferromagnetic materials show promise for application in magnetic sensors.