Applied Mechanics and Materials Vol. 470

Abstract: Dedicated TestBed (DTB) for detecting the sealing performance of Metal Rubber (MR) was designed and manufactured based on Siemens S7-200 PLC. The experiments, such as high temperature and large temperature difference experiment, could be conducted with real-time monitoring by DTB. The general design including mechanical and control part of DTB is introduced in detail.

Abstract: Tolerance analysis plays an important role at the stage of product design and has great influences on the assembly quality and manufacturing costs. A positioning mechanism composed of two parts with cylindrical and planar junction is chosen for studying the influences of datum precedence on functional tolerance analysis. For different cases, the tolerance specification is specified with ISO tolerance language and the analysis line method is applied to obtain the analytical expression between the possible displacement on functional feature and geometric deviation on each part. The results for different datum precedence are summarized in this paper.

Abstract: The concept of reverse engineering, reverse design process and reverse analysis were introduced in this paper, and has been used in teaching practice of mechanical design specialized curriculum, the students will be guided to apply method of reverse design to the innovation design of product by motorcycle as an example. Through the reverse design and analysis of motorcycle, students have a comprehensive understanding about computer integrated manufacturing system, which will cultivate technology talents who can adapt to the advanced manufacturing technology development and meet the requirement of the society.

Abstract: In this paper, a novel nonlinear magnetic vibration isolator is developed. The developed isolators possess the characteristic of quasi-zero stiffness (QZS). It is obtained by connecting a vertical coil spring with two permanent magnet springs in couple with three permanent magnets. Firstly, the permanent magnet spring is introduced, and approximate expression of repulsive force in the permanent magnet spring is proposed. Secondly, characteristic analysis of system is investigated. It is shown that there is a unique relationship between the stiffness of vertical spring and parameters of system that yields a QZS system. The approximate stiffness of QZS system can be used instead of the analytical stiffness in dynamic analysis.

Abstract: The five double layer cylinder reticulated shells (single diagonal rod cylinder reticulated shell, Foeppl cylinder reticulated shell, double diagonal rod cylinder reticulated shell, lamella cylinder reticulated shell and three way grid of cylinder reticulated shell) are developed by adopting the upper and lower translation method. Five connection forms of web member (cross truss, positive four pyramidal, upend four pyramidal, evacuated positive four pyramidal, evacuated upend four pyramidal) and the methods of the node generation and element connection are established in the cylindrical coordinate system. By using the ANSYS parametric design language APDL, the corresponding parametric design macro program is developed so that the five double-layer cylindrical shells can be parametrically modeled under the given parameters such as shell type, shell span D, rise high t, thickness h, length L and number of grids m and n, etc. Examples prove that this method is simple, efficient and pragmatic, which provides great convenience for the force analysis and the optimization scheme comparison.

Abstract: The coating and drying process of Li-ion power battery plays an important role in performance of battery. Its drying system is composed of an air inlet and return pipe, heat exchanger, air nozzle and so on. The air nozzle is a key component of drying system. Whether its design is reasonable or not, it will directly affect the distribution of the velocity, pressure and other factors in the dryer. In this paper, the simulation research of the key parameters of slit air nozzle on the coating and drying of Li-ion power battery will be achieved by using fluid simulation software. And then we determine the slit width of the air nozzle with 3mm, slit angle of air nozzle with 60° on the basis of the simulation results.

Abstract: The aerodynamic force and pressure distribution on a cantilevered cylinder with aspect ratio of 5 mounted in smooth uniform oncoming flow and turbulent boundary layer have been experimentally investigated. The tested Reynolds number ranges from 0.64×10⁵ to 5.81×10⁵, covering subcritical, critical and supercritical regimes. The results indicate that the aerodynamic drag of a cantilevered cylinder is smaller that that of 2D cylinder. The drag differs significantly along cylinder span because of the three dimensionality of the flow. The presence of turbulent boundary layer makes cylinder back pressure more uniform along cylinder span relative to that in uniform flow. Transition from subcritical to critical regime occurs earlier near cylinder free end in uniform flow, while this behavior disappears with the presence of turbulent boundary layer.

Abstract: As commonly supporting parts of the spindle and the feed systems on the high-end grade CNC machine tool, the dynamic characteristics of angular contact ball bearings had been a research hot spot in the current. Aiming at solving the problem that obtained dynamic stiffness and damping of angular contact ball bearings, an approach to investigate dynamic parameters of bearings joint surfaces was proposed based on the single degree of freedom (SDOF) system, and several groups of modal testing were carried out. The dynamic characteristics of bearings joint surfaces were viewed as several viscoelastic units of spring and damper. Then, models of bearings dynamic parameters in the axial and radial directions were established, and several groups of modal simulation were carried out. The comparison of experiment and simulation results showed that the proposed approach could accurately identify dynamic stiffness and damping of bearings under different load conditions, and the errors were controlled within 7.6%.

Abstract: Composite tube is one new kind of multi-material shell structures. It has both of metal and composite energy absorption advantage. In order to find the energy absorption characteristic of composite tube and put it into use, the Drop-Weight Tear Test (DWTT) was carried out. The LD2Y aluminum was chosen as the inner metal material which was wrapped fiberglass epoxy composite outside. During the test, the displacement signal and velocity signal, acceleration signal were got by piezoelectric acceleration transducer. Furthermore, the DWTT test of the composite tube was simulated in LS-DYNA, and proved the validity of the model by comparing the simulation results with the experiment results. We established the vehicle front longitudinal beam model with the material type of the composite tube, and carried out the simulations of whole car collisions in LS-DYNA according to FMVSS 208. Through the analysis of occupant head injury got from the simulations, we got the result that using the composite tube material could not only elevate the cars safety but also reduce front longitudinal beam weight effectively.

Abstract: This paper aims to establish a thermal analysis model for stratospheric airships. Mixed convective heat transfer between envelope and air has been specially considered. Thermal analysis of HAB on the summer solstice was carried out in this paper, results show that forced convective heat transfer coefficient increases obviously as the air speed decreasing, which will enhance the heat transfer between envelope and atmospheric. The pressure difference decreases obviously as air speed increasing during the whole day. Therefore HAB(high altitude balloon) should increase the air speed to reduce the pressure difference, which will enhance the safety of HAB.