Advanced Materials Research Vols. 314-316

Abstract: Numerical simulation on low-speed magnetic flux leakage inspection to heat exchanger pipes is described. Statistics suggest that 90% of defects in ferromagnetic heat exchanger pipes occur under the retaining plate or nearby, making it a key monitoring area. This paper illustrates influence of different velocities, defect depth and position on the characteristic of flux leakage signals. Result of the numerical simulation provides theoretical principle for application of Magnetic flux leakage (MFL) technique to inspection of heat exchanger pipes. It possesses great significance to enhance the possibility for defect inspection as well.

Abstract: A novel silicon-based packaging platform with the electroplated-based reflector and the electrode- guided interconnections is developed for the packaging component of a high-luminosity and high-efficiency multi-chip light-emitting diode (LED) module, which is patterned on a new type of insulating layer that consists of nanoporous anodized aluminum oxide (AAO) layer and plasma- enhanced chemical vapor deposition (PECVD) deposited silicon dioxide (SiO2) on a doped silicon substrate. The reflector and the electrical interconnections are successfully fabricated by using the electroplating method in the same body. In order to obtain the benefits of high efficiency LED modules, the requirements concerning thermal management and photomechanical layout have to be met. In this paper, we will discuss a novel fabrication method in LED module packaging platform, and then describe the thin layer of electroplated Cu/Ni/Au in order to reduce thermal resistance and to increase thermal diffusion efficiency. The heat generated by the LED chips is dissipated directly to the silicon body through the metal-plated platform, and truly excellent heat dissipation characteristics are observed. We demonstrate 987 lm 8 W-level cool-white light (5000 K, 16 V, 110 lm/W, CRI = 77) emission for 570 µm × 230 µm-chip LEDs at 600 mA operation.

Abstract: A three-dimensional incompressible two phase flow model of vertical centrifugal casting is proposed to simulate the fluid flow of mould filling process accurately and effectively. The Projection method is adopted to solve the govern equation of the flow field, and the Level Set method is used to capture the free surface. The mold filling of a complex part with thin-wall is simulated. The numerical result shows that the Projection-Level Set method could simulate centrifugal casting effectively. The present study has a guiding significance to the production of vertical centrifugal casting.

Abstract: A simplified mathematical model for describing the solidification processing of fluid flow, heat and solute transfer in binary alloys is developed. The conservation equations are numerically solved on a staggered grid by using the control volume-based finite difference method. As the interdendritic flow in the mushy zone is governed by Darcy’s law, the Modified Projection Method is presented for solving the momentum and continuity equations. The solidification processing of Fe-C alloy in rectangular domains is simulated and discussed. The numerical result shows that, by using the Modified Projection Method technique, the presented model is able to predict the macrosegregation formation effectively.

Abstract: This paper investigates the output feedback cycle time assignability of the min-max systems which are more complex than the systems studied in recent years. Max-plus projection representation for the closed-loop system with min-max output feedback is introduced. The coloring graph is presented and applied to analyze the structure of systems effectively. The necessary and sufficient criterion for the output feedback cycle time assignability is established which is an extension of the results studied before. The methods are constructive in nature.

Abstract: This paper focuses on the thermal stress and deformation analysis of the support plate of a nuclear reactor during the quenching process. A 3D finite element model of the support plate is incorporated into nonlinear coupling analysis that considers temperature, stress, and deformation. To verify the effect of cooling rate on the thermal stress and deformation of the model, we applied the heat transfer coefficients of water and heat treatment oil, depending on temperature variations, into heat conduction analysis. This analytical method enables the determination of the maximum deformation and residual stresses, so that the strength of the support plate can be identified.

Abstract: It is an important and fundamental work to establish a general mathematical model for the gear tooth surfaces of spiral bevel and hypoid gears. Based on the three-axis CNC bevel gear machine, a mathematical model with the equations of the radial position vector, the normal unit vector and the second order parameters for the generated gear tooth surfaces of spiral bevel and hypoid gears is established. The mathematical model can be used for the gear tooth surfaces generated in different types on both the three-axis CNC bevel gear machine and the cradle bevel gear machine. As an application example of the mathematical model, the generating motions of the cradle bevel gear machine are determined.

Abstract: High-speed milling (HSM) has advantages in high productivity high precision and low production cost. Thus it can be widely used in the manufacture industry. However, when the speed of spindle-tool reaches a higher speed range, the gyroscopic effect will become an important part of its stable milling. In this paper, a dynamics model of HSM system was proposed considering the influence of gyroscopic moment due to high rotating speed of end milling. Finite element model (FEM) is used to model the dynamics of a spindle-milling system. It obtains the trajectory of central point in face milling with considering gyroscopic effects through the dynamics model at high speeds. Then the cutting force model will be corrected by the trajectory of face milling. So it can provide a basis for stability prediction of high speed milling.

Abstract: An unconstrained optimization model is established for assessing roundness errors by the maximum inscribed circle method based on radial deviation measurement. The properties of the objective function in the optimization model are thoroughly researched. On the basis of the modern theory on convex functions, it is strictly proved that the objective function is a continuous and non-differentiable and convex function defined on the two-dimensional Euclidean space. The minimal value of the objective function is unique and any of its minimal point must be its global minimal point. Any existing optimization algorithm, so long as it is convergent, can be used to solve the objective function in order to get the wanted roundness errors by the maximum inscribed circle assessment. One example is given to verify the theoretical results presented.

Abstract: Analyzing the mutil-process manufacturing for nitride piston ring, and construct a multi-criteria decision system with AHP, then the nitride, stereotype and microhoning process are selected as the first, second and third key process of quality control. Further, six principle components are extracted with KPCA, and the nitride temperature, nitride time and activator are selected as the input of the prediction model, while the nitride rigidity is selected as the output of the prediction model. Then the quality prediction model based on an Elman neural network is successfully applied in nitride process, which inspects any odd change and predicts the process characteristics, and the predictive accuracy achieves that ninety-two percent of the actual value.