Vibration, Structural Engineering and Measurement II

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Authors: Jia Rong Zhang, Dong Hu Nie, Can Wang
Abstract: With the accelerated process of urbanization, water pipeline leak problem becomes more and more serious. If this problem dose not solved in a timely manner, water resource waste, even serious geological disasters will be caused. In order to locate the water pipeline leak position, we studied the characters and mechanism of the leakage acoustic signals in this paper, and analyzed the spectrum characters of acoustic signal with different leakage quantity and noise on pipeline diameter sudden change point. Based on this, we designed and implemented a set of software, using wavelet denoising method and cross-correlation time delay estimation method for leak location. Finally, we conducted an experiment based on the cast iron pipeline with a diameter of 1.5 inch using the proposed software, and compared the results obtained by different processing approaches. As a conclusion, the experiment results and the theoretical expectations are basically the same.
Authors: Zhi Jun Dong, Xiao Yi Li, Pei Yu Yan, Feng Xing
Abstract: Corresponding prevention strategies can be put forward by learning the stray current distribution in the metro rebar. In the paper, the stray current intensity of the rebar in the ballast of the power supply area and the 24-hour polarization potential of the rebar in the ballast are obtained through the test of vertical resistance, track-current drainage net resistance and track-earth resistance, and the polarization potential test in the tunnel ballast of metro system in service. The daily leak of the stray current of the rebar in the ballast is also obtained based on the relationship between the polarization potential and current intensity. The test result shows that the vertical resistance of the track has quite good consistency while the track-current drainage net resistance and track-earth resistance have relatively great discreteness. The polarization potential peak of the rebar in the ballast is over 500mV and the 24-hour equivalent and average current intensity of the rebar in the ballast can rise up to 0.26~0.43A/dm2.
Authors: Xin Zhi Zhou, Chao Yu, Yin Qi Xiong, Qian Ning
Abstract: The saturation magnetostriction (λs) for Fe-Ni alloy can only reach 30ppm, leading the magnetostrictive displacement sensor based on the alloy not to be used in the large displacement measurement. Therefore, applying Fe(100-x)Gax alloy, of which maximum λs can reach 400 ppm to giant magnetostrictive displacement sensor is presented. The crystal magnetostrictive model is shown at first; and then the magnetostriction in [100] and [111] directions have the decided advantage over Fe-Ni alloy and Ni alloy is given; besides, the characteristics of high permeability, low coercivity and low hysteresis loss for Fe(100-x)Gax are shown; moreover, the signal of the magnetostrictive displacement sensors made from Fe(100-x)Gax is analyzed. Finally, it is proved that Fe(100-x)Gax (17≤x≤19) is practicable for extending measure range of MDS.
Authors: Jing Lei Zhou, Zeng You Zhu
Abstract: When re-quantize a signal of low levels, serious distortion may occur due to word length reduction. Adding proper dither before re-quantization can improve the quantization error characteristic, while it will increase overall noise. By applying noise shaping, transposing most of the noise power to the band which human ear is less sensitive can reduce audible noise and thus improve auditory sense. This paper firstly discussed the applications of dither and noise shaping in professional digital audio, according to human ear’s psychoacoustic properties, by adopting genetic algorithm, fulfilled the design of psycho-acoustically optimal noise shaping filter. Then it applied the noise shaping technology to upsampling processing, realized the optimal noise shaping filter design under oversampling condition. Finally, it performed algorithm simulation on mat lab platform. Actual listening test confirms that by combining noise shaping technology with upsampling technology, sound quality can be improved significantly.
Authors: Xu Dong Zhang, Ji Fu Guan, Liang Gu
Abstract: System identification, which includes parameter identification and non-parameter identification, is to estimate its mathematical model based on the input and output observation in system. This paper discusses the system identification theory and establishes a transfer function of 1/4 vehicle’s second-order vibration system model. Through the discrete transfer function, the system’s difference equation can be obtained to identify the system in two ways, RLS (recursive least squares) and RELS (extended recursive least squares). Finally, the paper makes a comparative analysis about RLS and RELS in connection with the vehicle model. The results show that RELS method is more accurate and has stronger convergence than RLS method, which provides the basis for the researching of control system’s algorithm, simulation and making control strategy.
Authors: Wei Wang, Wei Yan, Wan Chun Li
Abstract: Electro-mechanical impedance (EMI) analysis is conducted in the paper for a one-dimensional rod. Two identical PZT patches bonded symmetrically onto the top and bottom surfaces of the rod are activated in phase and hence a pure axial excitation is created. Based on the finite element software ANSYS, an electro-mechanical impedance (EMI) model for the coupled structural system consisting of the host rod, bonding layer and the piezoelectric patches is established for structural health monitoring. A comparison study with the mode superposition method usually employed in the conventional EMI model is implemented to validate the effectivity and accuracy of the proposed EMI model. Finally, the numerical results indicate that the cracks appearing in the structures can be detected by using the proposed analysis.
Authors: Xiang Guo Zhao, Si Zhong Zhou, Bo Jiang, Kai Jiang, Chao Mei
Abstract: Abstract. This paper analyzes the relationship between the parameters of CFH (Cosine Flexure Hinge) and the adjustable angle in the measurement and micro-adjustment of yaw, pitch and roll angle in the DCM (Double Crystal Monochromator). We derive the motion equations of CFH during the measurement and adjustment process, and get accurate expression formulas. Then we use ANSYS software to simulate the CFH and compare the simulation value and the theoretical value. It shows that the maximum angular deflection error is less than 3.5 percent. We compare the CFH to the RCFH (Right Circular Flexure Hinge), and get that the maximum angular deflection and the linear displacements of RCFH are all about 1.56 times than the CFH when the parameters are equivalent. Therefore, we provide a simple flexure hinge to improve the stability and accuracy of angular measurement and micro- adjustment in the DCM.
Authors: Hai Tao Sun
Abstract: An indirect radial basis neural network (IRBNN) is proposed for improving the accuracy of the approximated functions. The IRBNN is constructed by new prompted functions generated from the Nth order derivative of the approximated function. In this way, high accuracy derivatives in different order can be obtained, so that more accuracy of the numerical results would be given while the IRBNN is employed for creating approximated functions in numerical methods. Numerical results through applications in elasticity show the effectiveness and accuracy of the IRBNN method.
Authors: Hua Jin Yu, Jia Liu, Yue Ying Wang
Abstract: Leak before break(LBB) is an important analysis method for insuring the structure safety and reliability of nuclear reactor. Now LBB technology is widely used in nuclear power plant design. It has a good development in foreign countries, but domestic research is relatively little. The study of crack propagation is core of LBB analysis. In this paper the Molecular dynamics simulations of crack propagation for material of pipes in China Experimental Fast Reactor(CEFR) were studied. The temperature on the flaw in the top of the model has a significant effect, and the position of the flaw would affect the damage form and the damage position of material analyzing the deformation of models. For the same model, temperature has a significant effect on crack propagation process. The analysis of this paper has a guiding role for the LBB analysis of pipes from microcosmic angle.
Authors: Zhong Liang Yang, Yu Miao Chen, Zheng Liu
Abstract: This paper presents a method of ergonomic design based on subjective rating for the purpose of modeling cushion surface mapped by body pressure distribution (BPD) test data. A sitting comfort evaluation scale was designed to collect subjective comfort perception. Optimal BPD test data were selected by comparing comfort rating after experiments on a trial seat. A data mapping model was established between point clouds in three dimensional coordinate and BPD test data, which can be recognized and transferred in CAD system. In this context, an ergonomic-aided system was developed in practical application to demonstrate the viability of the method. Two designers tried out the system to design a seat cushion, and compared it with conventional method in Rhino software. Results show that the system is more interactive to designers, which can save time of surface modeling by about 50%.

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