Applied Mechanics and Materials Vol. 696

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Abstract: The airflow velocity over blunt sphere is used to calculate ball-nose vehicle's atmospheric parameters about angle of attack, angle of sideslip and flight speed. A final model satisfying compressible flow is developed, and the expressions for atmospheric parameters is derived from three strategically selected sensors' velocity. The expressions of atmospheric parameters are verified through Fluent stimulation. The result of stimulation demonstrates a good accuracy of angles and flight speed, and the system has a good real-time performance.
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Abstract: The tension distribution of high-strength bolted extended endplate connections does not have unified regulations in china, the assuming tension distribution between the "Code for Design of Steel Structure"(GB50017-2003) and the "Specification of High Strength Bolt Connection of Steel Structures"(JGJ82-2011) are different, it may lead some problems in practical engineering. "Specification of High Strength Bolt Connection of Steel Structures"(JGJ82-2011) has given the assumed tension distribution ,but has not given formula .But its distribution assumption is the same as the British Standard ,so the calculation is given below reference to British Standard. Comparing their calculation methods and referencing to the British Standard ,the latter distribution is more reasonable.
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Abstract: This paper selects a load-bearing stage of an aeroengine compressor stator as study object to describe the model simplification method. Based on the criterion of cross section equivalence, the stator vanes are simplified into three versions of rectangular beams with variable cross section, using eight sections, four sections, and two sections respectively, to set up finite element model of the structure. Natural frequencies of the three simplified models are calculated and the results are compared with that of the original model. Comparison results show that the largest calculation errors of the first 10 natural frequencies using the three simplified models are-3.22%, -4.97% and-5.38%, respectively, but with this method, the model scale and computing time reduce significantly down to 3-4%, and 1-2% of the original model. The result shows that, the proposed method is applicable to relevant practical engineering.
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Abstract: The surface protection systems of aerospace and aircraft are often constructed from discretely stiffened panels to support high thermal acoustic loadings. In actual use, the stiffened panels are often subject to compression, shear and combination of compression and shear loads, bucking instability is the most common failure mode. The analysis of the snap-through process of stiffened panel is always a challenge in the word. This paper studied mainly about the non-liner response of the steel stiffened-plates under combined loads of thermal and acoustic. Firstly, the nonlinear balance equation of bucking process is analysised and a improved arc-length method is introduced . Than the FEM numerical method is used to analysis the nonlinear response of a simply supported stiffened panel under different thermal acoustic loadings. The modal frequency and the vibration displacement and stress are calculated. The displacement power spectrum density is analyzed emphatically. Base on the calculated resulted results, the relationship of the fundamental response frequencies versus temperatures is analyzed comparatively, furthermore, the bucking and snap through response characteristics are discussed as well.
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Abstract: Future missions for aircraft will expose structures to severe thermal and acoustic loads. Efficient analysis methods for predicting nonlinear random response and fatigue life are urgently important. This paper presents a finite element model for analyzing nonlinear random dynamic behaviors of Carbon-Carbon composite panels under temperature gradients and Guassian excitations. The temperature distribution over the plate follows double sine curve. A finite element formulation combined with the equivalent linearization approach and normal mode method is established. The global system of equations is reduced to a set of nonlinear, coupled modal equations. Examples are given for an orthotropic C/C composite laminated panel at various combinations of temperatures gradients and sound pressure levels. Numerical results include RMS values of maximum deflection, time histories of deflection response and stress response, power spectrum densities, probability distribution functions and higher statistical moments. Numerical results verified all three types of panel motions for a simply supported orthotropic laminated plate: small-deflection random vibration about the initial equilibrium positions, snap-through motions between the two buckled positions, and nonlinear random response about new equilibrium positions after post-buckling. Numerical results will provide the important reference basis to aero engine structural integrity design and improving the structure dynamic strength and working life.
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Abstract: The dynamical system of ODEs is about closed-form researches into the field of ODEs from the perspective of dynamical systems. This paper, starting with the research of path in autonomous differential equations and discussion on Poincaré’s viewpoints, probes into the complicated topological dynamic system of ODEs.
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Abstract: Combined with the special structure of mortar shell empennage, a one-dimension projectile trajectory corrector positioned at the empennage is proposed. Flow field simulation is taken in Fluent and the drag coefficient of mortar shell is calculated. The drag coefficient is fitted to get the fitting curves by using Logistic function and polynomial function. Trajectory model is established and solved, the correction capability is evaluated and the correction precision is analyzed. The simulation analysis indicates that this trajectory corrector is feasible and has obvious correction capability.
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Abstract: The anti-rust mechanism of T704 is mainly studied in this paper.T704 was resolute in kinds of base oils to make anti-rust oils, and the effect of which were tested through some experiments, which indicated the humid heat test was good and the salt water immersion was bad. So it is concluded the protective film of T704 on the metal is main Chemisorption film.
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Abstract: The low-temperature viscosity of anhydrous coolant is reduced by adding ethylene glycol to the propylene glycol base fluid, and the evaluation method of low-temperature fluidity is also studied. The experimental results show that the low-temperature fluidity of anhydrous coolant can be greatly improved by the participating of ethylene glycol. Freezing point method is usually used for measuring the low temperature performance of coolant, but for “long icing process” anhydrous coolant, beginning-crystal point shows more practical reference value. Therefore, freezing point, beginning-crystal point and low-temperature fluidity should be considered at the same time when evaluation the low temperature performance of anhydrous coolant.
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