Applied Mechanics and Materials Vol. 598

Abstract: Crashworthiness proof is a certification requirement by aviation authorities for new aircraft types. The objective of static design is a sufficiently stiff and strong structure to carry bending and torsion during flight and ground maneuvers. High stiffness, however, is critical for good crashworthiness behavior. Therefore, crashworthiness investigations should be included at early design stages of the overall aircraft design process. This paper introduces the crash analysis tool AC-CRASH and shows an approach of integrating it into the preliminary design phase.

Abstract: An elliptical nozzle of 3:1 aspect ratio (AR) issuing a Mach 1.5 jet has been used to investigate its mixing promoting efficiency under over-expanded and under-expanded conditions at the nozzle exit. Azimuthal asymmetry of the elliptical shape is interpreted as a benefit to the mixing process, which is significantly enhanced in comparison to an equivalent circular jet under identical conditions. The elliptical jet decays faster than its circular counterpart throughout the jet field. It is found that continuous variation in the size of the mixing promoting vortices shed from the nozzle exit, as a result of its azimuthal asymmetry, is responsible for faster decay of elliptical jet. The visualization of elliptic jet corroborates the fact that the waves prevailing in the elliptical jet are significantly weaker than those in the circular jet.

Abstract: A Numerical-Analytical Method (NAM) and Discrete Vortices Method (DVM) are developed for simulating unsteady separated flow around an airfoil with a spoiler. For flow separated at each sharp edge, such as the spoiler tips and the trailing edge of the airfoil, a vortex sheet is used to feed discrete vortices at each time step. The solution is determined under the assumption of fluid being ideal and incompressible. This paper develops modeling behavior of the vortices around the airfoil with the spoiler. The NAM based into the combination of the DVM and TFCV (Theory Function of Complex Variable) that gives to increase the accuracy of the calculation. In this paper the variation of the separation zones for the unsteady separated flow are shown.

Abstract: To meet the need of the automation and intelligence of welding process, it’s very important to extract the edge of weld seam accurately for seam tracking. According to the characteristics of GMAW (gas metal arc welding), an image sensing system of weld pool region based on CCD (Charge-coupled Device) is established. An improved method of weld seam extraction is presented. Firstly, weld pool region localization method using saliency detection is proposed, and weld seam region is obtained from the right edge of weld pool, then Sobel transformation and computation model is used to extract the edge of weld seam. Experimental results show that our method can obtain a more accurate weld seam edge and cost less than other method.

Abstract: Machining the components precisely and accurately on consistent basis is a huge challenge in the aerospace industry. Nowadays, manufacturer's demand to machine the components to tighter tolerances. In this paper, a case study of machining aircraft rib components in CNC milling was selected and tighter tolerances were defined. For this, two factors: cutting speed and feed rate was considered with five levels. Thus, 25 different combination of experiments were conducted for design of experiments. Several different statistical tools such as normality test, DOE and ANOVA were used. The study outcome found that feed rate has more significant effect over the machining of aircraft rib components than cutting speed; and there is no significant effect found when interaction of both cutting speed and feed rate were defined. The hypothesis test was performed to determine the optimum cutting parameters for the given condition using full factorial ANOVA test.

Abstract: On the basic of passive damping control, we do modeling and simulating in another approach to improve the vibration alleviating effect, the piezoelectric layer damping (PLD), which is called active control. The piezoelectric damping patches are under control of PID controller (matlab simulating) in voltage defference. Here, we use the software PRO/ENGINEER to design and model a wind turbine blade before using COMSOL to simulate the dynamic motion of the wind turbine blade and its interaction with aerodynamic force of wind in finite element method. Some different models are built-- the original turbine blade and the turbine blade with damping patches on different location and quantity. Then, according to the simulation results, we compare the effects of passive and active damping control, also the effect of patches locations and quantities under different wind speed. This research can provide a direction for future study about ways to decrease vibration of turbine blades.

Abstract: For a wind energy generator, the most significant factor which decreases the working life of it is the vibration from the rotating turbine blades under wind. In this paper, we do modeling and simulating in the constrained layer damping (CLD) approach, which is called passive control. Here, we use software PRO/ENGINEER to design and model a wind turbine blade before using COMSOL to simulate the dynamic motion of the wind turbine blade and its interaction with aerodynamic force of wind in finite element method. Some different models are built, the original turbine blade and the turbine blade with damping patches on different location and quantity. Then, according to the simulation results, we compare the effects of passive damping control in defferent patches locations and quantities under different wind speed. This research can provide us foundation and comparision with our future study which is related to the piezoelectric layer damping (PLD).

Abstract: Surface roughness is strongly affected by machining parameters. In the past few decades, many researchers have established the relationship between the surface roughness and machining parameters, but less attention has been paid to tool shape and geometry. In addition, the number of tool flutes was ignored, which affects in vibrations and machining system. Therefore, this study first-time includes the tool flutes in addition to cutting speed, depth of cut and feed rate as independent variables. Firstly, a set of machining experiments were conducted using AA6061 as a work piece material to provide original data. Response Surface Model (RSM) adopted to establish the relationship model of surface roughness and machining parameters using Minitab 16. Based on analysis of variance (ANOVA), the results show cutter flutes has higher significant followed by feed rate, depth of cut and cutting speed which has less significant. Finally, machining parameters were optimized to desired surface roughness, and optimization prediction error has limited values between-0.02 and 0.02μm.

Abstract: In this paper, a very detailed process analysis for UAV integral impeller was made. According to the specific processing requirements, the appropriate CNC machine, blank and cutting tools have been choosing. In the rough machining process, various machining strategies have been used for comparing and analyzing, finally a more efficient roughing method with the accurate machining parameters will be obtained. At the same time the machining method have been improved and the processing parameters also have been determined in the semi-finishing process. Through the simulation processing in VERICUT, the possibility of the existence of interference which is usually occurred in the actual processing can be ruled out and the program optimization will be finished in the meantime. Finally, using intelligent three-coordinate measuring machine the consequence will be verified and inspected in the actual machining process.

Abstract: Stress linearization is used to define constant and linear through-thickness FEA (Finite Element Analysis) stress distributions that are used in place of membrane and membrane plus bending stress distributions in pressure vessel Design by Analysis. In this paper, stress linearization procedures are reviewed with reference to the ASME Boiler & Pressure Vessel Code Section VIII Division 2 and EN13445. The basis of the linearization procedure is stated and a new method of stress linearization considering selected stress tensors for linearization is proposed.