Abstract: In this paper, a comprehensive model is used to describe dynamic behavior of SDA and its components during stepwise motion. In this model, Hamilton’s principle and Newton's method are used to extract dynamic equations of the SDA plate and dynamic equation for the linear motion of SDA. Comparison between the modeling results and available experimental data shows that this model is very effective in predicting some design objectives such as step size and output force for this type of actuators.
Abstract: CFD method is inexpensive method of analysis of flow over aerodynamic structure. It incorporates mathematical relations and algorithms to analyze and solve the problems regarding fluid flow. CFD analysis of an airfoil produces results such as lift and drag forces which determines the ability of an airfoil. Optimization of an airfoil involves improving the design of the airfoil in order to manipulate the lift and drag coefficients according to the requirements. It is a very common method used in all fields of engineering. MATLAB is a numerical computing environment which supports interface with other software. XFoil is airfoil analysis software which calculates the lift and drag characteristics for different Reynolds numbers, Mach numbers and angles of attack. MALAB is interfaced with XFoil and the optimization of NACA 0012 airfoil is done and the results are analyzed. The performance of optimized air foil is analyzed using ANSYS FLUENT software.
Abstract: Laser aided activating TIG welding was called LA-TIG. At first, the surface of weld was melted by the mini power laser protected by oxygen, and then the conventional TIG was used to cover the weld, which achieved the target of the weld with deeper penetration and narrower width. In this article, the weld bead morphology, arc images, microstructures and mechanical properties of laser aided activating TIG welding joint were analyzed. The results shows that the penetration increased significantly, excellent weld appearance and finger shape penetration were gained by laser aided activating TIG welding. It was found that the arc images of the LA-TIG was only the enlarged form compared with which observed in the conventional TIG and the arc constriction was also observed. LA-TIG weld exhibits better mechanical properties than the conventional TIG welding. Thus laser aided activating TIG welding was developed as a novel active welding method.
Abstract: Polishing of core and cavity surfaces after machining is a vital operation in the processing of plastic and metal cast products. It is carried out in order to achieve a certain degreeof surfacefinish-roughness or smoothness-on the machined surface, depending on its application as an end product and also for release from the cavities during ejection of the parts after moulding. Polishing is a high skilled manual time-consuming process in the overall cycle time of mould manufacturing. In this study, a CNC toolpath is generated in order to polish the core and cavity on the same machine where it is machined initially. The machine parameters for the polishing of the surfaces are optimized through a DOE set up. The surface finish achieved through machine polishing is inspected and recorded using a surface roughness tester and toolmaker’s microscope. It is observed, through the study that a combination of higher interference values between the tool face and the surface being polished along with higher feed rates proved to be determining factors in providing better surface finishes as high as 0.5μ Ra in machine polishing.
Abstract: In this work, the shaped charge jet formation depends on different parameters which can has effect on jet behavior such as jet velocity, breakup and penetration. Jet radius or liner thickness, shell thickness, liner material density, α angle and stand-off distance are evaluated in purpose to investigate their effect on performance of shaped charge jet velocity and jet breakup phenomena, also we investigate the effect of stand-off distance on shaped charge jet penetration into steel target. We also studied the performance of some protective shields materials in order to assure more protection for vehicle structure against shaped charge jet penetration. For that, different materials were used as armors such as: kevlar epoxy, polyethylene, glass epoxy, steel-1006 and Al2O3 ceramic. These protective shields were evaluated in order to show their performance against shaped charge penetration into target. To do so, adopted explicit dynamic analyzing program Autodyn basing on finite element were used to simulate shaped charge jet formation and penetration. Autodyn-2D simulationshighlight the efficiency of our work comparing with the experiments done in literature and Birkhoff’s theory. In other terms, increasing in shell thickness, alpha angle and liner densityenhance jet breakup time, protective shields layered armor of steel-1006, steel 1006 with polyethylene and steel-1006 with Al2O3ceramic give more protection for structure against shaped charge jet penetration comparing with others armors.
Abstract: The paper describes the results of analytical investigation on the application of vane-turbine in the propeller slipstream. The vane-turbine is attached on single-and twin-screw ships with total number of investigated ships are 20. Performance of the turbine was analyzed by actuator disc method. The effect of vane-turbine on ship performance is investigated. Discussions are focused on two main topics, namely speed loss and power efficiency gain. Final result finds out that the ratio of the thrust-power producing by vane turbine and thrust-power producing by propeller will influence the efficiency gain.
Abstract: Objective: To study the influence of disc cutter spacing on rock fragmentation efficiency and optimize cutter layout and improve the efficiency of disc cutter. Method: ANSYS, a finite element software was used to simulate double disc cutter cutting process. Result: Find a good corresponding relationship between penetration and cutter spacing. At the process of sandstone, if disc cutter spacing as 54 ~ 55 mm, rock crushing as the largest and rock fragmentation efficiency is the highest; with the penetration of 10 mm. If disc cutter spacing as 66~68.5mm, rock crushing as the largest and rock fragmentation efficiency is the highest with the penetration of 15 mm. Changing the cutter spacing and penetration, rock stress and broken degree will also change. Conclusion: Double disc cutters change within the range of best cutter spacing, cutter spacing is proportional to the rock crushing. If the cutter distance is greater than the best cutter spacing, the ledge will be appeared. For one type of rocks, the penetration would have some effects on the optimal cutter spacing. If the penetration increases, the optimal cutter spacing increases gradually, at the time of other construction parameters unchanged.
Abstract: Constrained independent component analysis (cICA) is a new theory and new method derived from the independent component analysis (ICA).It can extract the desired independent components (ICs) from the data based on some prior information, thus overcoming the uncertainty of the traditional ICA. Early gearbox fault signals is often very weak ,characterized by non-Gaussian,low signal-to-noise ratio (SNR), which make the existing diagnosis methods in the diagnosis of early application restricted. In this paper,cICA algorithm is applied to gear fault diagnosis. Through the case studies verify the feasibility of this method to extract the desired independent components (ICs), indicating the applicability and effectiveness of the method.
Abstract: Recently the demand of sloshing analysis is rising for building FLNG (Floating Liquefied Natural Gas) vessel. This study considers the experimental and numerical observations on strongly nonlinear sloshing flows in ship motion. The FLNG (Floating Liquefied Natural Gas) vessel was considered to be rigid body supported by non-permanent pole with distributed spring damper. Based on the general equation of the ship motion in waves, and various wave amplitude, various heading, wave period and critical fluid level on the cargo tank period governing equation induced by sloshing were derived. Several physical issues are introduced in the analysis of sloshing flows, and the corresponding numerical models are described. To study the sloshing effects on ship motion, a ship motion program based on impulsive response function (IRF) is coupled with the developed numerical models for sloshing analysis. The results show that the nonlinearity of sloshing-induced forces and moments plays a critical role in the coupling effects.
Abstract: To explore effective methods of avoiding POGO instability, this paper starts with a thorough study on influence of parameters on natural frequency of propulsion system in liquid rocket. By adopting the method of critical damping ratio, stability of coupled structure-propulsion system is analyzed. The results show that installing an accumulator in suction line can effectively decrease natural frequency of propulsion system, which can improve the stability of coupled system. When cavitation and inertance of accumulator increases or installation position gets closer to top of pump, the influence of accumulator on the natural frequency becomes more significant.