• 期刊

Engineering Analysis of Super Elliptic Plates on Nonlinear Elastic Foundation

A new combined numerical algorithm is introduced in this paper to analyze the structural behavior of super elliptic plates on nonlinear foundation. The objectives are two folds, one is to investigate the behavior of elliptic plates of different sizes residing on nonlinear foundation in terms of different power orders, and the other is to obtain approximate solutions by using genetic algorithms for comparison. Detailed description of nonlinear structural behaviors of elliptical plates of different geometric shapes are elaborated. Especially, as the power becomes large enough to have the shape turned into a rectangular one, or on the other hand, as the power equals to one, the shape of the ellipse goes to the other extremity of a circle. In either case, differential equations are derived based upon the maximum principle, and the residual solutions of monotony are presented with rigor validation. The problem solving of differential equations is further converted into a mathematical programming problem with practical constraints. By combining with optimization algorithms the solutions are obtained from bilateral sides and the solutions of minimal upper and maximal lower bounds are obtained. The weighted residual and collocation methods are also used to solve for the differential equations in combination with genetic algorithms (GA) to obtain satisfactory bounds that comply with specific optimization rules.

• 期刊

Dynamic Flow Behaviour and Microstructural Evolution of Pure Titanium during Hot Deformation

The dynamic flow behaviour and microstructural evolution of pure titanium are investigated at strain rates of 1x10^3 s^(-1), 3x10^3 s^(-1) and 5x10^3 s^(-1) and temperatures of 25℃, 400℃, 800℃ and 1000℃ using a compressive split-Hopkinson pressure bar (SHPB) system. The results show that the flow stress, strain rate sensitivity, temperature sensitivity and work hardening coefficient increase with increasing strain rate or decreasing temperature. In addition, it is shown that the flow behaviour of pure titanium can be adequately described using the Zerilli-Armstrong hcp constitutive equation. Transmission electron microscopy observations reveal that the dislocation density decreases with increasing temperature or decreasing strain rate. The loss of flow resistance under elevated deformation temperatures can be attributed to a greater annihilation rate of the dislocations. Finally, the flow stress increases linearly with the square root of the dislocation density and obeys the Bailey-Hirsch relationship.

• 期刊

Analysis of Downward Depth at the Junction of T shape Nanochannel

The paper uses atomic force microscopy (AFM) and the concept of specific down force energy (SDFE) to establish a method for fabricating T shape nanochannel grooves on silicon (Si) substrate. For fabricating T shape nanochannel, it is set that cutting is firstly carried out for one horizontal cutting and the vertical cutting on each cutting layer at a fixed down force. Then the probe carries out cutting for repeated above two cutting passes for next cutting layer. Using this cutting way by AFM and SDFE theory, the cutting depth and width of each cutting pass can be predicted. The results of simulation and experiment of fabricating method for T shape nanochannel is further compared. Besides, the paper explores the T shape nanochannel at a cutting depth of around 20nm at a fixed down force. This paper innovatively proposes a method pf calculating downward depth at the junction between horizontal cutting path and vertical cutting path. This method uses the same fixed down force in the middle of horizontal cutting path, then downpresses and cuts the workpiece material in the direction of vertical cutting path. SDFE equation and CAD software are used to simulate the cutting and cutting depth of each horizontal cutting layer and the downward depths at the junction of T shape nanochannels on different horizontal cutting layers. As observed from the simulation results, the downward depth at the junction between horizontal cutting layer and vertical cutting layer of T shape nanochannel is almost equivalent to an increased cutting depth on an additional horizontal cutting layer. The paper also compares the experimental result and simulation result of the downward depth measured at the junction of T shape nanochannel being cutted to the 5th cutting layer. Hence, the paper's proposal of using SDFE method to simulate and calculate the downward depth produced at the junction between horizontal and vertical cutting junction between horizontal and vertical cutting passes on each cutting layer of T shape nanochannel, is proved to be feasible.

• 期刊

Electrical Modeling of a Plated-Through-Hole Microstructure in Multilayered Circuit Boards

The purpose of the research presented in this paper is to examine the relationship between return path discontinuity and power dissipation. Firstly, we identify the major causes of power dissipation when signals are transmitted by Plated-Through-Hole (PTH). Secondly, we create a finite element model of a PTH and extract the S-parameters. Finally, a decoupling capacitor and a shorting via are used to improve return path discontinuity. The simulation results show that the decoupling capacitance can improve return path discontinuity and decrease power dissipation. A five-layer board is proposed to solve power and ground planes that cannot be shorted in four-layer boards. The simulation results show that a five-layer board with shorting vias can perfectly prevent power attenuation at the response frequency. The simulation results show that the small radius of a PTH improves the insertion loss. Using these models, we can improve and predict the electrical performance of a PTH.

• 期刊

Mechanism and Performance of a Novel Supersonic Atomizer for Metal Powder Production

Gas atomization is a widely used process for the production of metal powders, typically at high gas pressure (generally ＞2 MPa). In the present study, a novel internal-mixing atomizer was designed to produce metal powder at lower gas pressure (up to 4 bar), with a convergent-divergent configuration that enables the gas to achieve supersonic speed. The atomization mechanisms at the initial and stable stages were investigated by high speed photography. An upstream extension of the recirculation zone was observed owing to the existence and movement of internal shock at the divergent section. The performance was characterized by atomization of water and melt of copper for a parametric study. The size of the water droplets can be reduced by increasing gas pressure and decreasing the inner diameter of the delivery tube. Copper powders with median mean particle size of 64.83 μm were obtained with a spherical shape.

• 期刊

Numerical Study and Modeling of The Solar Radiation Measurement on Tilted Surface for The Local Behavior Database

This study experimentally investigates the performance of isotropic and anisotropic diffuse sky models to measure solar radiation characteristics on the tilted surface based on the local behavior database under different weather conditions. Experiments will be tested, including an effective absorbed radiation performance and solar radiation components of tilted surface using three models of diffused sky. Three models were used to test the performance of the solar radiation is as follows isotropic diffuse sky by Liu and Jordan (as model #1), anisotropic diffuse sky by HDKR (as model #2), and anisotropic diffuse sky by Perez et al. (as model #3). The analysis results showed that the measurements and analyses of solar radiation by isotropic model #1 and anisotropic model #2 have the results apparently better than anisotropic model #3 on a sunny day and partially cloudy weather conditions.

• 期刊

Mechanical and Metallurgical Properties of Dissimilar Friction Welded Aluminum Alloys Under Sub-Zero Temperature

Joining of dissimilar metals by continuous direct drive friction welding produces high quality weld joints. This study explores the joint properties of two dissimilar aluminum alloys, namely AA7075 and AA6061in tempered (T6) condition under shallow cryogenic treatment (-80℃). Experiments were designed by Taguchi method with L9 orthogonal array and carried out with the selected process parameters. Radiography test was performed to detect the defects in the weld joints like voids and lack of fusion. The welded specimen was treated at the specified temperature for two different time periods. The quality of welded joints has been evaluated by tensile strength, hardness, and micro structure. The microstructure shows ultrafine grains of Mg_2Si eutectic particles with traces of MgAl_2, Cu-Al_2, Mg_2 Zn and other inter metallic phases. The friction pressure plays a major role in enhancing the tensile strength, which is confirmed with the aid of Taguchi's parametric optimization analysis.

• 期刊

On the Global Optimum Cylindrical Counterweight Balancing of RSCR Mechanisms

Proposing appropriate balancing designs on high speed machinery to reduce the shaking effects is one of the most important subjects of mechanism designs. It is the main concern, to investigate the designs of installing cylindrical counterweights on moving links with fixed revolute joints of spatial RSCR four-bar mechanisms, to minimize (1) the shaking force only with no size limitations on the counterweights, (2) the sum of its root-mean-squared (rms) shaking force, shaking moment and driving torque without size constraints, and (3) the sum of its rms shaking force, shaking moment and driving torque with constraints, whose counterweight contours need be tangential to the fixed pivot axes. Applying the proposed inertial parametrization, the models for the kinematic and kinetostatic analyses are developed. Based on them, the models of the optimum balancing designs of the above problems are proposed. Additionally, for each problem, the necessary and sufficient conditions of the optimal solution are also derived; the necessary conditions are then applied for solving all optimum candidates, and then the sufficient condition is used to check which of these candidates are the local optimums; consequently, the global optimum can be found among them. An example for each problem is included, to demonstrate the usage of each model and to show the balancing effects of the optimum designs. According to the result of each problem, only one solution satisfies both of the necessary and sufficient conditions, which is also the same as that searched by using the proposed optimal balancing design model. Thus, the proposed models can be applied to find the global optimums of the balancing design problems, respectively

• 期刊

Topographic Measurement for Bevel Gears Using a One-Dimensional Scanning Probe Based on a Five-Axis CNC Machine

The majority of commercialized gear measuring machines, such as the Klingelnberg P and Gleason GMS series, are based on four-axis structures. Gear accuracy on such machines is assessed using gear measurement software and the 3D scanning probe systems that, because of their high speed precision, are installed as preliminary measurement tools on many highly accurate gear grinding and cutting machines. The key technology for these gear machines is online scanning measurement. However, although domestic manufacturers have some experience building online measurement systems for cylindrical gear machines, they lack the ability to do so for bevel gear machines. This paper therefore develops an online measurement system for bevel gears on a five-axis CNC machine, but one that uses the cheaper 1D scanning probe instead of the expensive 3D model. Specifically, after first developing a mathematical model of bevel gear measurement as a foundation for the online measurement, we use Visual C# to establish an online scanning measurement system that can communicate with the Siemens 840D controller and the probe sensor. Then, adopting the five-axis CNC as our experimental machine, a spiral bevel gear is inspected and evaluated by measuring the pitch and topographic errors. The proposed mathematical model is verified by comparing our results with the accuracy report for the Klingelnberg P40 gear measurement machine.

• 期刊

Quality Evaluation and Prediction of PV Modules by Utilizing LM-Based Back Propagation Neural Network

This paper presents quality evaluation of PV modules using back propagation neural networks (BPNN) with one hidden layer and four neurons, four inputs and three outputs. The key input parameters were adopted on internationally verified standards for silicon modules (International Electro-technical Commission, IEC61215). Firstly, the correlation mechanism between the module quality and defects in solar cell modules is investigated. Then, the key factors affecting quality evaluations of photovoltaic modules for classifications were developed. An estimated model is then constructed using artificial neural networks technology and the weight values between defect factors were automatically allocated by giving several learning data. Four key input parameters were the attenuation ratio of maximum output power and the EL image quantitative indicators, insulation resistance and wet leakage resistance regularization indicators. The output qualities were assigned evaluation classifications of A, B, and C. By using 30 set of simulated Training data, a best neural networks model with 4 internal nodes is obtained. From validation evaluation results for another 15 set of test simulated data, the successful rate is about 93.3%.