Applied Mechanics and Materials Vols. 138-139

Abstract: In order to solve centralized installation and cooling problems of airborne electronic equipment with big power and high heat flow density in aircraft, the paper put forward an innovative closed-loop forced ventilation cooling system, expatiated system compositions and operation principles, and also took a cabinet system for example to introduce new cooling system design method and simulation results.

Abstract: An experiment of a single particle movement in vertical spiral rectangular duct has investigated with the aim to study the rotational Coriolis force based on kinetic model of single granular. The results indicate that: the dominant forces upon the particle are the centrifugal force, rotational Coriolis force, effectual gravity and drag force. There is exponential relation between λ and ζ, where λ stand for the ratio of tangential velocity of particle and water velocity, ζ stand for the ratio of rotational the Coriolis force and the centrifugal force. The probability of rotational Coriolis force and centrifugal force in the same order of magnitude is three-quarter. Therefore, the rotational Coriolis force should not be ignored on force analysis of a particle in small-scale rotational flow.

Abstract: In this paper, we study the attitude control problems based on model of the 3D axially symmetric rigid pendulum. Three degrees of freedom pendulum (3D pendulum) is a rigid body supported by a frictionless pivot. According to relative position of the center of mass and the fixed pivot without friction, the 3D rigid pendulum can be divided into two balanced attitudes, Hanging equilibrium and inverted equilibrium. When the 3D rigid pendulum in axis symmetric case, the axis of symmetry is equivalent to axis of inertia of rigid body, and angular velocity around the axis of symmetry is constant that not equal to zero, as a result, the 3D rigid pendulum equal to the axisymmetric rigid pendulum. According to the motion attitude of the axially symmetric 3D pendulum, this article proposes a control method based on passivity, By analyzing the dynamic characteristics, and demonstrate the dynamic characteristics to meet the passive condition. Firstly, we use the passivity theory, from total energy of the system, to research the equilibrium stability of the axially symmetric 3D pendulum in the inverted position. Secondly, to utilize the passivity theory and the Lyapunov function that we proposed to deduce the control law based on the energy method, so that the axially symmetric 3D pendulum to reach asymptotically stable in equilibrium position, and the simulation results verify the availability of the method.

Abstract: Taking a structure of single-degree freedom as analyzed object, the problem of structural dynamic response to blasting vibration loads was transformed into the problem of that to a series of simple harmonic loads with wavelet packet method. A safety criterion of structural response to blasting vibration has been put forward, which is more detailed, reasonable and scientific than others in use with involving parameters related to structural characteristics, blasting energy, blasting amplitude, blasting frequency and blasting duration.

Abstract: Ice accretion on aircraft components is an enormous threat to flight safety. In this paper, ice accretions on the leading edge of the NACA 0012 airfoil and the NLR 7301 multi-element airfoil with flap are predicted using the icing code developed by us. This code mainly contains five modules which are grid module, airflow module, droplet module, heat module, and boundary reconstruction module. The effectiveness and robustness of this code are tested by executing the five modules orderly and repeatedly. The Spalart-Allmaras one-equation turbulence model is adopt to calculate the viscous airflow field and the four-order Runge-Kutta method is used to solve the droplet trajectory equations. In order to enhance the efficiency of the icing calculations, the multi-block grid technique is integrated into the grid module. Based on the above methods, numerical results in both two cases are presented and the necessary comparisons with the experimental data are given in corresponding chapters. The computational results show that performance of the icing code is very good for the wide range of icing conditions.

Abstract: Based on the significant destructive effect of heavy vehicle on uneven roads, two simplified models of pavement unevenness and vehicle dynamic load were established in accordance with D'A lembert principle, and Matlab software was used to analyze the changing law of dynamic load under the conditions of different road unevenness, vehicle speed and load. The results show that vehicles running on uneven road may produce more cumulative damages than static load, and DLC (dynamic load coefficient) changes in wide range, maximum up to 2.0 or more; the effect of speed and load on dynamic load is complex, and due to multi-factor interaction, DLC doesn’t consistently increase or decrease with speed and load increasing. Although the dynamic load level caused by high-speed heavy vehicle is not necessarily too high, its impact on the road can not be ignored.

Abstract: In this study, we present the effects of design parameters on the performance of a hopping robot. In particular, we focus on the effects of torsional stiffness and preload on a hopping model with two-segment legs having passive knee joints with torsional stiffness. One of the objectives for a field robot is the ability to travel quickly with energy efficiency [1]. Therefore, it is important to determine what range of each design variable is proper to realize not only the high forward speed for great mobility, but also the low torque consumption for energy efficiency. Accordingly, we describe both the analogy simulation of a hopping gait with two-segment legs and the results of this simulation.

Abstract: Fuel efficiency necessitates the use of light weight vehicle parts. Conventional researches have shown that an electro wedge brake (EWB) can provide good braking efficiency such as the generation of a large braking force with a small power motor. To further reduce the weight of a brake system, it is necessary to reduce the weight of the structural parts. The braking force is proportional to the clamping force with the coefficient of friction between the brake pad and disc. The clamping force in a brake system is the caliper's stiffness multiplied by the displacement. Therefore, if the caliper has a high stiffness, the EWB size can be compact, with small displacement. Toward this goal, in this paper, we provide a simple design review of the wedge profile related to the caliper stiffness, and design of caliper stiffness for reducing the weight of an electro wedge brake.

Abstract: This paper studies the relations of the homeomorphisms in the contact dynamical systems on compact regular contact manifolds. Using some improved approximation lemmas and techniques of inequalities, this paper finally proves the coincidence of the topological strictly contact homeomorphisms and the modified continuous strictly contact homeomorphisms.

Abstract: In this study, a finite element method was used to study force transducer anti-deviated load characteristics. Through the changes produced by different sizes of force transducer finite element models, modal analyses in linear static analyses of different biased loadings were applied to perform cross-validation. The results indicate that force transducers with same strain output but with high torsional stiffness have better anti-deviated load capacity. Increasing the torsional stiffness of the force transducer could reduce the loss of precision due to biased loading.