Advanced Materials Research Vol. 952

Abstract: By disrupting the regenerative effect, milling cutters with variable-pitch are usually used to improve stability. Since high interrupted cutting processes, such as low radial immersion case, will result in more nonlinear phenomena and some consequent differences of stability chart, in this paper, an improved semi-discretization algorithm is utilized to predict the stability lobes for variable-pitch milling under low radial immersion ratios, the focus of the current manuscript is to investigate the stability trend caused by tool geometries. In addition, the chart differences in the cases of low and high radial immersion milling are also discussed by comparisons. Under certain combinations of parameters, some phenomena, like bunch of isolated island and flip bifurcation region are described, and some influences of tool geometries on stability trends are shown and explained.

Abstract: Wind turbine blade is an important component to capture wind energy and converse energy. Basing on Wilson optimization method and engineering pratice, 2MW wind turbine blade’s aerodynamic profile is designed. Meanwhile, in order to avoid the resonance damage, top 10 rank modal frequencies and displacement gradient distribution contours are obtained through modal analysis. The results show that blade’s natural frequency does not coincide with the external excitation frequency, which avoids the resonance damage. Blade’s major vibration forms are waving and shimmy, requiring the ability of excellent resisting torsion. Therefore, the design should enhance bending stiffness of the blade. This paper provides an effective method for large wind turbine blades’ design and optimization.

Abstract: The technology of high pressure water jet in radial drilling has currently been used widely at home and abroad. A numerical simulation and analysis of the internal and external flow fields of jet nozzle will 1ay the foundation for the further study of high pressure water jet rock breaking. The physical and mathematical models of axial-symmetrical submerged jet rock breaking with single nozzle were established. And a numerical simulation of the internal and external flow fields of high pressure water jet nozzle in radial drilling was conducted with the Fluent software. The 1aws of the internal and external flow fields were analyzed in different jet distances and inlet flow rates.

Abstract: According to the principle of fluid dynamics, the Fluent software is used for the numerical simulation analysis of three-dimensional single-hole nozzle submerged jet flow field of radial drilling inclined shaft. The results show that when the bottom is tilted, there are two sizes of spiral along the center axis, and the vortices along tilt direction of the wall are stronger. When the jet source closes the bottom, the kinetic energy of jet is converted into the impact for the bottom of well, making the pressure of bottom hole on the wall have a tendency to rise.

Abstract: An equivalent circuit model of the PEM fuel cell is built to study the voltage dynamic response during load change. A mathematical model is built to simulate the voltage response during load change. The simulation results fit the test results very well. Then the model is applied to predict the limiting operation condition of the fuel cell. The model also provides a reference to design PEM fuel cell control modes.

Abstract: In order to simulate and analyze the rolling movement state of motorcycle in collision accidents, the trajectory reconstruction model was studied. The motorcycle’s centroid trajectory model during the process of rolling and the feature point trajectory model during the process of sliding are both constructed. Using the accidents reconstruction and analysis software named PC-Crash and the models constructed in this paper respectively, a real accident case was reconstructed and analyzed. The comparative study between the reconstruction analysis results and the marks remained in the accident scene was conducted. Research showed that, the analysis result reconstructed by the model was consistent with the actual accident scene. This model can be used to reconstruct and analyze the motorcycle’s rolling movement trajectory after collision occurring.

Abstract: the low pressure oil chamber and the high pressure oil chamber act directly on Both sides of the rotary valve. It will be large axial force to the valve body If the system working pressure is greater. The resulting outcome is low vibration frequency of the rotary valve driven hydraulic exciter. How to improve the hydraulic exciter frequencyWe can improve the speed of the rotary valve or increase the number of rotary valve guide groove. But if we increase the tank guided number ,the diameter of the rotary valve spoo must be increased. Design a rotary valve without axial force can solve the problem of the rotary valve spool shaft size restricted. By calculation and analysis of the rotary valve spool suffered axial force . The work of a single rotary valve chamber pressure problems can be solved spool axial force

Abstract: In order to investigate the electromechanical coupling dynamic behaviors of portal crane's hoisting system, the electromechanical coupling model of the system was established by utilizing Lagrange-Maxwell equation. Taking the MQ2535 portal crane as an example, the electromechanical coupling dynamic characteristic curves of the hoisting system was studied based on the MATLAB simulation platform, in addition that the interrelate and interactive characteristics between the electromagnetic system and mechanical system was presented. It is shown that the results have larger difference compared with the results of neglecting the electromechanical coupling effects. This is because of the energy-stored role of the electromagnetic system and the load tracking property of the driving motor that the dynamic load got buffered and then the dynamic load factor became lower. The research results can provide theoretical supports for matching and optimizing the parameters of electromechanical system and improving the portal crane safety.

Abstract: In vibration process, viscoelastic isolators’ temperature will rise due to energy dissipation, especially when the isolators have high damping characteristics. First, for the arbitrary loadings, the thermomechanical coupling model and the corresponding difference form are established based on the five-parameter fractional derivative model. Then, for the steady-state harmonic inputs, which is very common in engineering application, the derived model is significantly simplified by Fourier transformation. Finally, the proposed model is verified by experiments and shows a reasonable agreement with measured data.

Abstract: To realize the lightweight structure, a car body frame conceptual design of a mini electric vehicle was performed with topology optimization and size optimization. Topology optimization was used to search load paths and size optimization was applied to model a simplified structure. Static stiffness, crash safety and free vibration conditions were considered simultaneously in both of the optimization phases. Due to the feature of conceptual design, crashworthiness cases were regarded as static stiffness ones with inertia relief analysis for a linear equivalent. The objective function in multi-objective topology optimization was defined by Compromise Programming Method in OptiStruct. Because of the characteristic of the geometry and the manufacturing constraints of profiles, the design variables in size optimization were defined as both continuous and discrete variables. The resultant structure outperforms the original one in many structure responses and most significantly, it reduces weight by 36%, which demonstrates the efficiency of the proposed method.