Applied Mechanics and Materials Vols. 427-429

Abstract: The problem of low accuracy for classic guidance law is considered in this paper. Based on the mature theory used in missiles, this paper presents an integrated guidance law for reentry vehicles. At the initial stage of reentry flight, standard trajectory guidance law is employed, and then converts to 3dof proportional guidance law when this vehicle is close to the target. Simulation results are provided to demonstrate the accuracy of the proposed integrated guidance law.

Abstract: Many different control methods for Anti-lock Braking System (ABS) have been developed. In this paper, a new control algorithm is proposed for ABS based on sliding mode control algorithm, which represents the nonlinear characteristics of external interferences. The proposed sliding mode controller guarantees a highly robust performance against large variations in the system parameters and disturbances. Simulation results show that the proposed method has advantages compared with conventional linear controllers.

Abstract: Based on the principle of orthogonal test, the optimization model of sunflower shaped arch bridge scheme was set up. The five key design parameters were selected as the main factors. The four computation index, which reflect mechanical performance, were selected as analytical objects. The 16 orthogonal experiment schemes were arranged with four levels orthogonal table . The curves of the factors to the index were obtained from the mechanical response under dead load and live load through the finite element analysis model. By the range analysis method, the influential levels of the factors to the index were obtained from the result of the test , and the factor optimizatuion level of the factors was determined to further optimize the layout scheme of the sunfloawer shaped arch bridge.

Abstract: The flexural behavior of non-holomorphic circular pile and cylindrical pile is respectively evaluated based on the results of finite element analysis with ABAQUS. It is presented that the ultimate bearing capacities of non-holomorphic circular pile and cylindrical pile have little difference. The displacement ductility ratio of non-holomorphic circular pile lies between 3.38 and 3.64, indicating that the NHC pile has better ductility.

Abstract: An innovational structure with auxetic effect was designed from inspiration of a re-entrant honeycomb structure firstly proposed by Gibson et.al. In the newly designed structure, yarns were used to replace the straight and tilted ribs of re-entrant honeycomb structure in order to achieve negative Poissons ratio. The compression testing was carried out in the vertical direction of the structure using an INSTRON 5566 tester to understand its deformation behavior. The results show that the difference in bending stiffness between the warp and weft yarns is the main reason for getting negative Poissons ratio of the structure.

Abstract: The foundation slab is the key structure of a pumping station. For such a hydraulic structure cracking is not permitted because it will cause heavily seepage and other disaster. Temperature control is an important way to prevent cracking. With the aid of finite element method for temperature field and stress field simulation, research is carried out for a 43.5m long mass concrete foundation slab of a pumping station poured in different seasons. Different measures, such as pipe cooling, surface preservation and pouring temperature control, are tried to control the temperature and stress. This research gets some useful results, and the measures proposed have a significant reference to similar projects.

Abstract: Double-wall fabricated steel insulation silo with multiple bolted joints is a new structure form of silo. The number of bolt studs used in the1000-ton silo is 12240 which take too much time and money. In order to cut down the cost and shorten the construction period, 6 alternative schemes are put forward to optimize the bolt arrangement. By comparison, Schemes 6 is adopted. The model which uses the original bolt arrangement is defined as Model 1. The optimized model is defined as Model 2. The stress and deformation of these two models were comparatively analyzed. The results show that the maximum stress and the maximum displacement of Model 2 are both smaller than the specified values. Furthermore, the number of bolt studs used in Model 2 is 6600 which is 5640 less than the original number. The bolt studs are saved 46.1%.

Abstract: To break through the drawbacks of the one-mass vibrating screen like plugging screen, high noise and etc., a new vibration screen with two-mass and high energy which could generate transient high vibration intensity was analyzed. To meet the requirements of energy-saving and system stability, a spring with nonlinear and hard features was used in the main vibration system. In this case, the springs stiffness could change along with the vibration intensity. The stiffness of the vibration isolation spring could be determined by analyzing the vibration isolation coefficient, and then the hollow cylindrical rubber spring with internal damping was adopted in the vibration isolation system. On the one hand, this vibration isolation spring could effectively absorb transient high vibration intensity which passed from main vibrating spring to the lower mass. On the other hand, it could achieve good effect of vibration isolation between the lower mass and the foundation. Base on field testing, the vibration intensity was increased by 28%, meanwhile, the noise was reduced by 4% and the impact vibration to foundation was reduced by 24% , which successfully solved the plugging screen problem and also verified the validity of the vibration isolation system.

Abstract: Two different dynamic models have been presented to investigate the transient mechanical response of a RF MEMS switch under the effects of squeeze-film damping based on a modified Reynolds equation. Both the perforated and non-perforated structures are built for comparison. The models include realistic dimensions. The surface pressure, the damping force, and the tip displacement are simulated in three different ambient pressures, such as 500Pa, 5kPa, and 0.05MPa. The result shows that the increased damping leads to a substantial decrease in oscillation with increasing pressure for the non-perforated structure. Compared with the perforated pad, there is a much larger damping force acts on the non-perforated surface, and an obvious decrease in damping force with increasing pressure.

Abstract: For MEMS devices actuated by electrostatic force, unexpected failure modes can be hardly predicted when the electrostatic force coupled with the shock. A response model is established when a micro cantilever subjected to electrostatic force and mechanical shock. First, based on the theory of transverse forced vibration in vibration mechanics, the equation of motion under shock and electrostatic fore is presented. Then the reduced order model is gained after simplifying by mode superposition method. The computing results indicate that: the shock amplitude and duration are the key factors to affect the reliability of the device; the shock load and electrostatic forces make the threshold voltage much lower than the anticipated value. The micro cantilever may collapse to the substrate even at a voltage far lower than the pull-in voltage. This early dynamic pull-in instability may cause some failures such as short circuit, adhesion or collision damage.