Applied Mechanics and Materials Vols. 201-202

Abstract: The purpose of this article is to study and devise pulse signal source of electrical discharge machining(EDM). The technology of EDM is the necessary key technology in various processing methods. Electrical discharge machining pulse power aims to convert the industrial frequency alternating current into certain frequencies pulse current to supply energy for electrode discharging to removal metal. Pulse power generator, controlled by an embedded MCU, can produce high voltage or low voltage discharge pulse waveform. After the research on characteristics and principles of many pulse powers, a novel, intelligent, high frequency pulse power supply with adjustable amplitude, frequency and duty is developed which has a favorable foreground in engineering application and a great theoretical significance. This paper is to realize the design of EDM pulse signal source based on the method of combining single-chip computer and complex programmable logic devices (CPLD), to satisfy the technical requirement of periodic variable and machining efficiency improving.

Abstract: A new weld seam detection based on the genetic algorithm has been presented. Firstly, the experimental platform has been setup, and the welding images can be captured by the CCD camera in real time. On this basis, the process region, which is in front of the weld pool, has been determined. Then the median filter has been applied to reduce the disturbance of the noise producing during the welding period. Moreover, the GA has been deeply researched and applied to the weld seam detection. In the end, some experiments have been caught out, and the results show that compared with the traditional Ostu process method, the weld seam images, which are processed by the genetic algorithm, are more clearer and have less noise, which can meet the satisfy of auto welding system.

Abstract: There is seriously temperature coupling affection in the traditional fiber acceleration sensor, which affects the measurement accuracy. In order to improve anti-interference ability of the sensor, the structural characteristics of the dual-FP cavity is adapted to realize temperature decoupling. Based on the double-beam interference theory, the optimal film thickness requirements, and the output spectrum change of FP cavity caused by the vibration and temperature change is analyzed. Acceleration sensor with structure of the dual-FP cavity and three-bridge is designed. The structure of sensor is analyzed by ANSYS software, such as the thickness of the bridges and the mass size of sensor, and cavity length change caused by equivalent force. Based on the analysis, it can be concluded that the corresponding bridge thickness is 100μm and mass diameter is 0.5mm for the sensor with external diameter of 2 mm and inner diameter of 1.6mm. The resonant frequency of the system is 6.6kHz, and measuring range is 0 ~ 10g.

Abstract: The technique of electromagnetic expansion ring was widely used to study the material uniaxial dynamic tensile properties and fracture characteristics. In this paper, the ANSYS Multi-physical FEM code was used to analyze the electromagnetic expansion process of metal ring. The distribution of the inductive magnetic field, the transient electromagnetic force and the deformation act on metal ring were discussed. The results show that the radial and axial magnetic pressure are existent in early stage of excitation current. The tensil strain of the ring could be approximately assumed as uniform. The plastic strain of the ring almost achieved maximum value after one cycle excitation current and then the deformation remains under subsequent attenuating excitation.

Abstract: Researchers and engineers around the globe are striving to improve green energy technologies. Among green energy technologies, diffuser augmented tidal turbines are attracting focus due to enormous potential for producing energy. The power output by a tidal turbine is directly proportional to the cube of velocity of incoming fluid flow. Thus, even a minor increase in velocity considerably increases the power output. The diffuser helps accelerate the velocity of incoming fluid flow. Hence, the efficiency of the turbine is significantly increased by using a diffuser. It is challenging to to accelerate the incoming flow by a diffuser due to its shape, geometry and fabrication limitations. The diffuser design requires great deal of innovation and time investment. The research community is investing considerable time and financial resources in this arena. However, limited reserach results are available for diffuser augmented tidal turbines due to their emerging nature, large and costly research & development setup, startup cost and proprietary issues. The purpose of this paper is to present the numerical simulation of 2D model of diffuser for tidal turbine. Numerical simulation results of velocity profile for fifteen models with different mesh sizes is presented in detail. The effect of mesh density on coefficient of velocity is discussed. Predicted results are then compared to experimental results and found in reasonable agreement. The research is essential for utilizing CFD tools for diffuser design for tidal turbine.

Abstract: In some metamaterial such as the chiral negative refraction medium, the lateral shift is analyzed in theory. When total internal reflection occurs, the lateral shift curves as the incident angle have been figured out for a linearly polarized incident wave. The shift directions of the TM and TE components in the reflected wave are opposite when the incident angle is between the two critical angles of the eigen-waves. Both TM and TE waves will have positive lateral shift once the incident angle is larger than the total internal reflection angle. By contrast with the common medium and normal chiral medium, we have found that the lateral shift character in the chiral negative refraction medium is distinctive.

Abstract: Dynamic symbolic execution is a promising approach for software analyzing and testing. However, it fails to scale to large programs due to the exponential number of paths to be explored. This paper focus on tackling loop caused path explosion problems and proposes a new approach to reduce paths that produce the same effects. We present a loop transparency strategy that makes use of the decision graph of under test program to discard constraints that produce paths with only a different number of iterations. A dynamic software testing tool LTDse based on loop transparency is designed and evaluated on three benchmarks. The experimental results show that our approach is effective since it can achieve better code coverage or require fewer program executions than traditional strategies.

Abstract: It is difficult to obtain exact solutions of the nonlinear partial differential equations (PDEs) due to the complexity and nonlinearity, especially for non-integrable systems. In this case, some reasonable approximations of real physics are considered, by means of the standard truncated expansion approach to solve real nonlinear system is proposed. In this paper, a simple standard truncated expansion approach with a quite universal pseudopotential is used for generalized fifth-order Korteweg-de Vries (KdV) equation, we can get two kinds of approximate solutions of the above equation, in some special cases, the approximate solutions may become exact. The same idea can also used to find approximate solutions of other well known nonlinear equations. We find a quite universal expansion approach which is valid for various nonlinear partial differential equations (PDEs).

Abstract: The error of the three-dimensional structure light measurement is analyzed in the paper. The experiment is done to verify the presence of measurement error. The error of data is analyzed and some conclusions are gotten. The three-dimensional structure light measurement is based on the triangulation principle. The error distribution is different because of the view angle of measurement equipment relative to the part to be inspected, the effect of the external environment light and the effect of the data processing software system. Finally, the corresponding compensation measures are put forward in the paper according to different errors.

Abstract: In the paper, a fault feature extraction method for rotor system is proposed based on Hilbert marginal spectrum. Compared with the spectrum analysis method via Fourier transformation, it is more effective for the rotating machinery vibrating signal analysis. Extracting the rotor system fault feature frequency from Hilbert marginal spectrum can not only enhance the frequency resolution, but also remove other unrelated frequency component, so as to make the spectrum peak of the fault feature frequency more obviously, and the analysis diagnosis results more accurately. This method result is applied to the fault feature extraction and diagnosis of the rotor system, and the analysis results of the experiment signal verify the validity of this method.