Applied Mechanics and Materials Vols. 543-547

Abstract: The velocity and concentration of sand/dust particles contained in the air flow are the key factors which affect the quality of sand/dust test. In order to obtain the anticipated sand/dust concentration and uniformity in the test segment, numerical simulation methods are adopted to study the characters of different sand/dust inject approaches. Research results indicated that the gravity sand/dust inject approach is not suitable for the large sand/dust test system, upstream spray approach is appropriate to be adopted in dust test, the uniformity of upstream sand spray method is better than downstream sand spray approach, but its diffusivity is not as good as the latter. In a certain range, the velocity difference between sand/dust spray flow and air flow affects the concentration distribution uniformity slightly. The numerical simulation results applied in the optimal design of particles inject system in some large sand/dust test system get a favorable progress. All results provide reference for the design of similar system and sand/dust environment test.

Abstract: When an electromagnetic field propagates through a linear but dispersive medium, the front edge (the launching fringe of the waveform where the field is first turned on) propagates precisely at the speed of light in vacuum by first timing on t₁=t_front =（z/c）and the main signal (the main part of the field) follows up with group velocity which is characterized by the frequency-dependent refractive index of medium by second timing on t₂=t_group=(z/v_group)=[n(φ)z/c] .The distinct wave-packets progress from t_front to t_group (i.e. from the front-edge-timing to the main-signal-starting timing) are well known as optical precursors. It was believed that precursors are an ultra-fast phenomena, persisting only for a few optical cycles, and that they have an exceedingly small amplitude and two different kinds of spike-type wave-packet (i.e. Sommerfeld precursor and Brillouin forerunner). Both exact wave shape for electromagnetic wave while it goes into a linear time-invariant, lossless plasma system is reported.

Abstract: Taking HYPERMESH as pre-processor, the modeling methods for a frame of the cab-over-engine medium bus in crash is expounded. Based on software LS-DYNA, the crash process is simulated with the crash regulations on M1 type bus. The deformations and energy absorbing for the parts and whole frame are analysised, especially for the invade distance and acceleration in crash. Based on these, the crash worthiness is estimated further for the medium bus.

Abstract: Due to the air cushion and splash the slamming into the water of Trimaran connecting bridge are highly nonlinear, this paper discusses the problem of typical Trimaran sections slamming into the water by use of general finite element software MSC.Dytran. Through secondary development program implemented the initialization of water pressure, considered the coupling structural-air-water, a simulation method for connecting bridge slamming into the water has developed. The results show that the method meets the engineering precision and can give reference for Trimaran construction and operation.

Abstract: Aiming at the characteristics of the production in low permeability oil field, the pump efficiency mathematic model is built. Then the factors of affecting the pump efficiency are analyzed, which include the liquid production, diameter of pump, pump depth, immerse depth of pump, stroke and stroke per time, gas oil ratio, inclined angle of pump and discontinuous production efficiency. Through the theoretical calculation, the main factors of affecting the pump efficiency is determined, which are the liquid production, diameter of pump, stroke per minute, pump depth, inclined angle and discontinuous production efficiency. According to the calculation results, it can supply the theoretical foundation for the oil production.

Abstract: In the paper firstly analyzes the engine combustion theory, for the numerical analysis for engine cylinder pressure to provide the basis. This paper makes use of the FIRE simulation software to analyze the shrinkage mouth combustion engine under different working condition of the fuel injection advance Angle of the characteristics of the combustion process and exhaust process, after got the mixture combustion in cylinder gas pressure range and emissions, for the next step muffler simulation model is established by applying the method of finite element and acoustical noise analysis provides the basis of the parameters, shorten product development cycle.

Abstract: By comparative testing and studying and analyzing on the area and range of flow regime influenced during the uniform water flow with free surface and definite depth flowing around varied pile clusters, The author had found and summarized and concluded many scientific laws, which of flowing around pile cluster effect on the uniform water flow, the natural and extents disparity of varied pile cluster effect on the same uniform water flow, the area and range of flow regime influenced during flowing around varied pile clusters. And had found that the influenced extent and scope of flowing around square pile cluster effecting on the uniform water flow more than that of cylinder pile cluster. For a pile cluster, in the way of influenced extent and scope of flowing around the pile cluster, the ratio of obstruct the water flow more than the density of pile lines, and Reynolds number influence the extent and scope of flowing around pile cluster in big degree. It is even more superiority that people adopt the small size pile than the big size pile about pile cluster on water conservancy project.

Abstract: Based on fully structured grids parallel numerical simulations of flow around a cylinder under different Reynolds number are carried out. Two-dimensional and three-dimensional models are established at the same time under specific Reynolds number, and further analyze of three-dimensional flow characteristics as well as the generated influence to overall physical quantities are presented. In order to explore efficient high Reynolds number turbulence models, a comparative research of the LES model without wall functions and the Spalart-Allmaras turbulence model is carried out. In order to improve the computational efficiency, a domain decomposition parallel computing strategy is used, and a calculation strategy that results of coarse grid was assigned to fine grid as initial field value by 3D linear interpolation is presented. Simulation results show that: Drag coefficient and Strouhal number have very good consistency with the experimental data, which verifies the correctness of the calculation method; Even if at low Reynolds number (200≤Re≤300), using a three-dimensional model is still necessary; While in the high Reynolds number stage, compared to LES model without wall functions, Spalart-Allmaras model is more applicable and more efficient.

Abstract: In order to get further understanding of the performance of bar and plate cooler used in the heavy-duty diesel engine, simulation method was employed to study the key parameters and their relationships of the typical bar and plate EGR cooler. It was found that the turning point number of the plate was 13. In addition, an EGR cooler test and analysis system was built to verify the parameters of the modified cooler. It was found that the experimental values of outlet temperatures were about1.17% smaller than the calculated values averagely, while the overall heat transfer coefficient were 3.1% larger.

Abstract: This paper analyzed the failure modes of single layer electroplated uperabrasive products. The bonding force is the primary factor that dominates the grinding quality and tool life. So the understanding of bonding mechanism is of great importance for improving efficiency and quality in the applications of these abrasive products. In this paper, the experimental setup similar to an inclined micro-threading process is designed to observe and measure the failure mode and maximum bonding force respectively. The relationship between maximum bonding force and bonding layer thickness is established through the experiment. In addition, failure modes are analyzed by comparing the morphology before and after the high speed bonding force test for electroplated layer.