Applied Mechanics and Materials Vols. 37-38

Abstract: Hydrostatic thrust bearing lubrication is significantly affected by the oil flow state of gap oil film, but it can not be measured by experiment and analysis. For this problem, the oil flow state of gap oil film in sector cavity multi-pad hydrostatic thrust bearing during rotation was simulated by using computational fluid dynamics, lubricating theory, and Finite Element Method. Laminar model and κ-ε turbulence model were adopted to model incompressible steady equations, and the equations were discreted by using Finite Volume Method and Second-order Finite Difference. By comparing the calculated results of numerical simulation and semi-empirical theoretical equation, the numerical simulation is proved feasible in oil film state analysis parameter prediction, which can overcome the deficiency of single model and get good effect. Streamlines and velocity vectors show that the lubricating oil flow in the resistive oil edges and oil cavities are laminar flow under the conditions of speed and flow in less than a certain value, while the flow and speed are more than a certain value, the lubricating oil flow in the resistive oil edges is also laminar flow, but the lubricating oil flow in the oil cavities is turbulent flow, then determines critical flow and critical speed. The critical flow and critical speed were determined, it provides a theoretical basis of the temperature field and thermal field deformation calculation.

Abstract: Volute casing is one of the important components in centrifugal pumps. The strength and stiffness of the volute casing made of PMMA used for PIV measurement were investigated by fluid-structure interaction (FSI) simulation in consideration of the impeller-volute interaction. The distribution of pressure and shear stress on the inner surface of the volute casing was obtained by FLUENT. Pressure, gravity and shear stress were imposed on the volute casing, and its stress and displacement distributions under different working conditions were obtained using ABAQUS. The results indicate that in comparison with pressure, gravity and shear stress have negligible influence on volute casing deformation. The volute casing is structurally safe under design condition, and its maximum rotational speed can reach to 1690r/min. At this rotational speed, the maximum displacement of the volute casing is 4.6mm, and measurement error caused by refraction is about 0.11%. Furthermore, two methods for improving the volute casing structure were put forward in consideration of light decay as well as the strength and stiffness of the volute casing.

Abstract: The latent heat releasing and the criterion for shrinkage porosity in solidification progress of casting are studied. A numerical analysis is presented for solidification progress of the cylinder head casting using finite element method. The temperature distributions of the casting in different solidification phases are solved, and the shrinkage porosity is predicted. Based on this, the solidification progress of casting is evaluated. The simulation results can offer a helpful reference for casting design of cylinder head casting.

Abstract: This article applies the method of formulating those test projects affecting product system properties into a matrix with tabular units. According to the complexity of product system, the complexity in test operation, economical cost for a test, etc., the paper proposes the concept of whole matrix unit, intersection matrix unit and particular matrix unit test plan to test the product properties. The result indicates that there are various complicated factors influencing the properties of the product, aggravating the unstability of products system in operation. By utilizing the unit test matrix method, we can obtain experimental data chain for advancing the product reliability design, optimizing product systematical structure. With the existing scientific and technical results, together with the experiment data analysis, mean value and strategy of reliability design, we can promote product reliability and robustness.

Abstract: This paper applies the method of multi-subject synthetic study for product refinement design and prototype test. Many kinds of limited conditions to product refinement design were researched. It discovered that there are lots of relationships of observation, using, sentimental exchange, research, collection with human. There are also relationships with political and social environment, economical environment, market environment, natural resource environment, technical environment, cultural environment. Product refinement design is based on human vision rule and product intrinsic special function. The paper observed the principle of vision and psychological of gestalt and Berlyne rules, limited by technical manufacture level, facing request of ergonomics and product semantics, examined by fashion symbol in business environment, needs cultural connotation to promote product value, and it needs product identity design to carry on standard operation to product system.

Abstract: This paper adopts the methods of establish matrix list to concept design evaluation, to study the methods of establishing evaluational criteria and the methods of concept design evaluation. It reveals that it is necessary to evaluate the function, use, man-machine interface, physical structure and control, various technology, assembling handicraft, etc. for concept design evaluation. Concept design process exhibits characteristics of diverging, converging, diverging again, converging again, totally converging. The result shows valuation of concept schemes should be carefully chosen by ways of setting up target product model, matrix of standard decision-making, combining perceptual with reason judgement, schemes being improved and chosen. The evaluation should be carried out in such a way that it should take into account the economical value of the scheme and the promotion of the company’s competitiveness during the entire life cycle of the product.

Abstract: Microscale crystalline NiSe₂ porous octahedrons have been solvothermally synthesized from reaction of NiCl₂∙6H₂O with Se powder in ethanol with dodecylbenzene sulfonic acid sodium salt as surfactant at 200°C for 20h. The samples are octahedral crystals with mean size of 2 micron in diameter and the micro-octahedrons present porous morphologies. The octahedral NiSe₂ microcrystals exposed with {111} facets are grown under a thermodynamic process and the porous textures within the octahedrons are resulted from the cooperative effects of the oxidation of selenium in HNO₃ and the coordination of Ni²⁺ with Cl^– under the alcohothermal process. The surfactant increases the monodispersity of the NiSe₂ crystals with octahedral shapes.

Abstract: Grinding is a processing method that involves duplicating shape accuracy, so the shape accuracy of the grinding wheel plays a crucial role in machining accuracy. However, this accuracy is difficult to obtain. This paper describes an on-machine wheel profile measuring method that uses a non-contact displacement sensor to obtain the shape accuracy of an arc grinding wheel in a 3-axis aspheric surface grinding machine. This method involves data processing with object radius confined filtering, as well as evaluation using the methods of fitting residual error, measurement uncertainty, and machining result simulation. To verify the feasibility of this measuring method, experiments were performed using two diamond grinding wheels (FEPA D91 with grit size 75-90 μm, and FEPA D15 with grit size 10-25 μm). The experimental results indicate that the method is accurate enough to give the arc grinding wheel profile measurement, while the measuring uncertainty is of the same order of magnitude as the grit size (that is, tens of μm). Moreover, the simulation of the grinding effect with wheel profile measurement data can derive the relationship between the wheel profile error and the machining form error, and can be used to instruct the truing time determination for precision grinding.

Abstract: Large-scale wind power incorporated into power grid brings new challenges to optimal dispatch of power system. Especially, wind power at different locations may has a significant degree of correlation. A copula function was used to characterize the Joint Probability Distribution (JPD) of wind power from multiple wind farms considering their correlation. An optimal dispatch model based on Chance Constrained Programming (CCP) for power system with multiple wind farms was set up. And Sample Average Approximation (SAA) was proposed to transform the chance constrains. Finally Genetic Algorithm (GA) was employed to solve the optimal model. Simulation results indicate that copula function can well express the correlation of wind power from multiple wind farms and SAA has been a dramatic increase and improvement on the search of solution.

Abstract: In order to achieve the supply of materials on the concrete mixer assembly line timely and accurately, in this paper, the process, production features and actuality of materials supply on the concrete mixer assembly line were analyzed, the stations of the assembly was combined, and function mode of the storage was changed to active distribution. Then the material handling process was optimized using material handling design system. Finally, the effective implementation of material distribution was ensured based on the on-site management.