Advanced Materials Research Vol. 629

Abstract: Use similar material and system of caustics to simulate the characteristics of fissure distribution and dynamic vacation regulations of fissure generation and expansion, whose fissure is made by plexiglass jet slotting and blasting under the condition of explosion. We have analyzed and compared the expanding length and velocity of main fissure’s point and dynamic intensity factors between the holes of ordinary blasting and water-jet slotting; and discussed the dynamic effects of slotting blasting. The study shows that, with the same explosive quantity, the fissures of common blasting hole distribute randomly around the hole with large quantity but with short fissures and the caustic spots have small diameter and distribute with fissures; while the fissures of jet slotting hole blasting are longer and distribute mainly along the fissure’s direction, the caustic spots are clear and mainly concentrate among the fissures with lager diameter. That is to say, the jet cutting blasting energy concentration can improve the effect of rock damage. The existence of jet seam has a guidance quality to rock breakage. Main fissures take place and expand from the direction of slotting seam while the distension along other directions is heavily weakened in the process.

Abstract: With the convective heat transfer theory, numerical analysis of fluid-solid-heat coupling is implemented for the engine combustion chamber cooling structure based on finite element method and computational fluid dynamic method, thus to obtain valuable simulation results. Different components of the mesh generation method used which have different influences on the computational results are thought over during this analysis process, including different grid type, grid density and boundary layer meshes. Moreover, MPI parallel technique is also used to resolve the computation demands. The temperature distributions of the key parts in the cooling structure are investigated, which can be used as a significant reference for the thermal protection design of the engine combustion chamber.

Abstract: Ultrasonic guided wave detection technology has mangy special characteristics. It can spread very far along the components in the distance and it can throughout the whole thickness of components, so we can make use of ultrasonic guided wave to test component of internal and surface defects. The rotating shafts are the organizations widely used in the modern production but they are very easy to be dangerous faults. If we can realize the rotating shaft in time, it can reduce the danger. It is significant to design an affordable generator which produces signals to drive magnetostrictive probe that produces ultrasonic guided wave. In this paper, we choose the torsional wave as example to design signal generator. We will introduce the way to select the appropriate guided wave mode and frequency of excitation. Design signal generator with ATmega32, AD9851 and DAC0832.

Abstract: Due to large planar scale and small lateral scale of plastic drawing board, it was easy to cause warpage problem in injection molding. Optimization of injection molding process was taken to reduce residual stress and improve quality. Combining orthogonal experimental method and software Moldflow, analyzed the effect of mold temperature, melt temperature, hold pressure and injection velocity on warpage deformation. It changed multi-objective optimization to single-objective optimization by weighted method. Through range analysis obtained the influence trend between parameters and comprehensive optimal object. Lastly got the optimal combination of injection molding process parameters.

Abstract: Underwater towed systems have the many applications in exploitation of underwater environments. While in the research exists which is about the numerical models of towed system, the relatively simple model of the towed body is used and the dynamic of the towing ship is neglected. The towing ship as part of towed system, its heave and pitch motion are coupled and highly non-linear. Considering the dynamic of three parts of towed system is important. In the paper, a newly couple model is developed to predict the behaviors of underwater towed systems under effect of the heave and pitch motion of towing ship. We use a finite difference method as the towed cable and is coupled with the non-linear numerical models of a towing ship and a towed body. Illustrative application of the coupling model is presented. The numerical results show the heave and pitch motion of towing ship affect the motion of towed body.

Abstract: According to energy conservation law, the functional of quasi-variational principle of rigid-elastic coupled dynamics is established. Quasi-stationary value conditions of quasi-variational principle of rigid-elastic coupled dynamics are derived. The governing equations of rigid-elastic coupled dynamics are obtained. As an application of rigid-elastic coupled dynamics, an approach of coupled vibration mode determined of unrestrained beam is established. The coupled vibration mode and coupled frequency are studied by the approach.

Abstract: An improved K-ω model, which allows for compressible corrections, is proposed in this paper. Numerical scheme was established utilizing the improved Total Variation Diminishing (TVD) scheme and applying implicit scheme to the negative source terms of the turbulence model. Hypersonic flat-plate boundary-layer flows and hypersonic compression ramp flows marked with separation, reattachment and shock/boundary layer interactions are then computed. Comparisons between the computational results, the experimental results and the semi-empirical formulations show that the compressible correction term of the K-ω turbulence model is a pressure-dilatation correlation. In addition, for flow with separation and without separation, calculation results of wall pressures, friction coefficients and wall heat transfer rate distributions using the improved model and established scheme agree better with the experimental results than that using the original K-ω model.

Abstract: At present the concept of instantaneous equilibrium is often adopted for simulating the wellbore pressure and temperature distribution in heavy oil wells. In this paper, the mathematical model was built and the diffusion of gas in the oil phase was researched. It proves that the non-equilibrium phenomenon is not obvious in convenient oil wells and it could be overlooked, while in heavy oil wells the non-equilibrium phenomenon is too prominent to be overlooked. Basing on the mass conservation principle, the momentum conservation principle and the energy conservation principle, the calculated model for wellbore pressure and temperature in heavy oil wells considering of the non-equilibrium effect was established. One example shows that the model can accurately reflect the flowing laws in heavy oil wells, which has a relative value for engineering.

Abstract: The main draw back of the Moving Least Squares (MLS) approximate used in element free Galerkin method (EFGM) is its lack the property of the delta function. To alleviate difficulties in the treatment of essential boundary conditions in EFGM, the local transformation method and the boundary singular weight method, which are used in the reproducing kernel particle method, is combined with the element free Galerkin method. The computational method is given to analyze the stress intensity factors and the numerical simulation of crack propagation of two-dimentional problems of the elastic fracture analysis. The application examples reveal the effectiveness and feasibility of the present methods.

Abstract: With the development of Micro Electro Mechanism System, the linear slip boundary of liquid flow has been often used. In this paper, some flows in different wettability boundaries were researched by Non-Equilibrium Molecular Dynamics (NEMD) simulation, and the characteristics of the slip length were discussed. The results show that: when liquid flow on the hydrophobic boundary, the slip length decreases with the external force increasing and the shear rate increasing near boundaries, the width of channel and the external force are not independent variables of the slip length, and the shear rate and the surface wettability are independent variables of the slip length. The slip length can be reduced by increasing the driving force for liquid flow in a channel. Finally, a new power law model of the slip boundary of liquid flow was derived.