Applied Mechanics and Materials Vol. 775

Abstract: Space nets is one of most promising conceptions that designed for the space debris removal. A critical issue in the design and analysis of space net system is the deployment modeling technology. The dynamic behavior of space net system in different ejection modes is investigated based on finite segment approach. The simulation results show that the model and the evaluation index developed in this paper provide a valid method to evaluate the deployment property of different ejection modes.

Abstract: A semi-analytical method was proposed to analyze the vibration characteristics of an elastic cavity. Combining the precise integration method and bent theory of the beam, the transfer relationship of the ends of the beam was derived. Based on the displacement continuity conditions and equilibrium equations of the junction, the conversion relation of the beams was also established. Then, the dynamics control equations of an elastic cavity were assembled by the above relationship and boundary conditions. The comparison with the FEM had verified the accuracy of the present method. This method avoids the shortage that the calculation accuracy over-depends on the element types and the mesh dividing methods, which is existed in the finite element method. In addition to this, the process of this method is efficient, so it is a useful method to the structural design and optimization of the cavity.

Abstract: In this article, a direct numerical method is developed to solve two-dimensional interaction problems of wave and floating body with ADINA software. Motion’s equation of the floating body and hydrodynamic parameters are expressed based on potential flow theory. The force and response on the floating body boundary is described in terms of linear minor wave theory. The numerical test is carried out. The result intuitively shows the dynamic response and the stability of floating body under incident waves.

Abstract: Flutter, a dynamic and severe self-excited vibration, easily produced in power ultrasonic honing, is one of the important factors, which affects the processing quality of the workpiece, the efficiency of the machine tool. Based on the study of power ultrasonic honing mechanism, choosing single abrasive and workpiece as research objects, respectively establishe the physical and mathematical coupled flutter model of power ultrasonic honing nonlinear system, with two degrees of freedom, determine the differential expression of the model, and simulate the boundry of flutter condition. It is proved flutter is produced in ultrasonic vibration honing, then the way is proposed to restrain. The study provide a theoretical basis for deeply seeking the strategy to repress and eliminate the flutter.

Abstract: This paper presents theoretical investigations of vibration and sound radiation responses of laminated plates in thermal environments. Static thermal stresses are taken into account to describe the stress state of the vibrating plate. First-order shear deformation theory and von Karman nonlinear strain displacement relationship are used to represent the dynamic deformation. And then, governing equations are obtained with Hamilton’s principle. Response characters are studied in both the pre and post-buckling ranges. Results show that the bending stiffness of the heated plate drops in the pre-buckling range and increases after thermal buckling occurs. Thermal environment preforms as two opposite effects before and after buckling. Amplitudes of vibration and radiated sound of the thermal post-buckled plates show opposite variation trends.

Abstract: The purpose of this study was to evaluate changes in kinematic and kinetic gait characteristics due to outsole structure of the shoe. In this experiment, cushioning shoe having cushion for heel (BOSS Corps., Korea) which is designed as a lever, MBT having an unstable rounded shoe (Masai Barefoot Technology, MBT, Swiss) and normal running shoe (Adidas, Germany) were compared. The experiment was performed walking on the straight walkway (10m x 3m) five times with preferred walking speed. 3D motion capture system was used to acquire kinematic and kinetic data using six infrared cameras and two force plates. For comparison among shoes, walking velocity, hip, knee and ankle joint angles (range of motion, trajectory), ground reaction force (loading rate, the decay rate, maximal vertical ground reaction force), and center of mass - center of pressure inclination angle (COM-COP angle) were used. The results showed that there were different effects of types of shoe on lower extremities. Joint angle trajectory of ankle, joint range of motion (ROM) of the hip, and peak force were significantly different among shoe types. MBT provided a decreased impact force. Cushioning shoe provided increased progressive force, decreased loading rate, and decreased COM-COP angle. For further study, it is necessary to analyze additional subjects (i.e., elderly) and long-term effects.

Abstract: Vertical rolling is a vital method for width control in rolling, which has its own deformation characteristic. During the processing, plastic deformation does not go further into center of slab, only in edge where the deformation will be occurred. In this paper, an anti-symmetric parabola is creatively used to describe dog-bone shape and innovatively applied to establish a knematically admissible continuous velocity field for vertical rolling. Based on this field, an analytical form of total deformation power is obtained which is a function of reduction geometric parameters, and friction factor m, as well as parameter of A which is to be determined. With minimization of total power results in rolling forces and torque calculated by this new method is obtained. Copper and aluminum experiments conducted by S.-E.Lundberg are used to verified the results calculated by formula in present paper and compared with those by Lundberg and Duckjoongs’ models. The error is no more than 13%, (average error 7%).

Abstract: A water heating system which utilized biogas energy as a heat source in farrowing house of pig farm was developed in this study. The hot water which was heated by the biogas-burners flowed through the delivery pipeline to heat the metal panel made of aluminum alloy in the piglet’s incubator. The ambient air temperature in the piglets incubator could be raised by way of the thermal radiation of the aluminum panel and then kept the piglets warm. The simulation tests of the hot-water heating system was aimed to find out the reference conditions of the field tests by measuring the temperature of the hot water under different flow rate of the hot water and investigating the air temperature change rate in piglets incubator. The results of simulation tests showed that the ambient air temperature of the piglets incubator can achieve above 28 °C within 30 minutes in the conditions of 90 °C hot water and 45.3 L/min water flow rate. The influence of flow rate to the ambient air temperature in the piglet’s incubator was not significant. The results of the field tests obtained that the heating panel surface temperature increased significantly with the rising hot water temperature. Under the condition of 85 °C hot water and 45.3 L/min flow rate, the raised air temperature was 5.2 °C within 25 minutes in the piglets incubator where 13-day-age eight piglets stayed. This hot-water heating system can switch by hand to the electric-auxiliary heating device when there is no enough biogas to use. The hot-water heating system can achieve the purpose of saving electric energy and reducing the emissions of the greenhouse gas. It is feasible to operate and adjust the suitable temperature for the growth environment of piglets.

Abstract: The study analyzed the thermal performance of a sensible heat recovery system in an office building in Beijing area. Based on proposing the basic evaluation index of the thermal performance, the study analyzed the effect of outdoor temperature and wind speed on the heat recovery efficiency and the reduction of fresh air load. The analysis results show that, the operation effect of the sensible heat recovery device in winter is better. In winter, the sensible heat efficiency η is higher than 60%, the system has higher EER, and the fresh air load can be reduced more than 50%. While the sensible heat efficiency η is lower than 60% in most time in summer. And in a hot, humid climate, the recovery effect of sensible heat recovery device is significantly reduced.