Advanced Materials Research Vols. 452-453

Abstract: In order to research dynamic characters of CNC machine tools, the finite element method is always adopted to model the system, and its dynamic characters are analyzed based on the modeling. The large dimension of the model for CNC machine and its key system become a problem to be solved. In this paper, the model reduce methods are compared and analyzed in order to clarify this problem. The transmission system of CNC machine tool is modeled by FEM firstly, then, the model reduction methods of reduce method, subspace method and Block Lanzcos method are applied for its modal analysis. The reduced method have to search a set of master DoF, the subspace is used for calculating partial mode in a relative large scale system with simple geometries;. Block-Lanczos method is adopted when the system with large scale dimension, but it needs good computer storage capacity and performance

Abstract: “CPOE62”platform is a self-elevating workover platform. Under the construction and service process，because of the particularity of work environment，Not only does it bear its own weight and variable load, but also bears the role of environmental load all the time. Sometimes this environment load will have an enormous destruction. Based on the analysis of environmental load, the author checks the bottom stability and verifies it through ANSYS. These will provide some useful information for the deep sea platform research in Bohai Sea deep-water oil and gas development, which achieves higher security and economic efficiency.

Abstract: Vortex-induced vibration (VIV) was largely investigated by experiments. However, with the improvements in computing capabilities, the numerical method is becoming more and more popular. This paper reviews the literature on the numerical simulation of VIV and focuses on the advances in the last decade.

Abstract: As direct connection of a floor and the cylindrical shell would reduce sound stealth performance of underwater vehicles, an indirect connection mode is proposed. To compare the effect of connection mode on vibration transmission characteristics, two models, directly-connected model and indirectly-connected model, are designed and manufactured to take experiments. Experimental result shows that indirect connection can reduce the vibration energy transmitted from the floor to the shell when these two models have the same structural parameters. Thus indirect connection is more useful to improve the sound stealth performance of underwater vehicles.

Abstract: Previously, for the case of fixed or steady state rotation rate, spectrum analysis can be used to extract the frequency features as the basis for the gearbox fault detection of machine center. However, the gearbox of machine center for increasingly instant speed variations mostly generate non-stationary signals, and the signal features must be averaged with analysis time which makes it difficult to identify the causes of failures. This study proposes a time frequency order spectrum method combining the short-time Fourier transform (STFT) and speed frequency order method to capture the order features of non-stationary signals. Such signal features do not change with speed, and are thus effective in identifying faults in mechanical components under non-stationary conditions. In this study, back propagation neural networks (BPNN) and time frequency order spectrum methods were used to verify faults diagnosis and obtained superior diagnosis results in non-stationary signals of gear-rotor systems in machine center.

Abstract: The numerical simulation, based on computational fluid dynamics methodology, has been performed to study the two-phase turbulent combustion flow in rocket engine using non-metallized multicomponent propellant. A reduced reaction mechanism is developed for modelling combustion of fuel droplets in the absence of metal. Gas governing equations are two dimensional axisymmetric N-S equations in Eulerian coordinates. The trajectory model is adopted to analyse the droplet-phase including the droplet collision, breakup and evaporation. The gas flow is influenced by the droplets by adding source term to N-S equations. The reliability of the simulation programme is validated by comparing numerical simulation result with engine test data.

Abstract: To describe detailedly the flowing process and field of gel propellants in the round pipe, the experiments of the gel flowing in the tubes were conducted and the governing equations of the steady, incompressible, isothermal, laminar flow of a power-law, shear-thinning gel propellants in 3D pipe were formulated, discretized and solved. The results indicate that pressure drop per unit length increases with decreasing the tube diameter as well as increasing the mass flow rate, and the liquidity of gel is more difficultly than water, and the wall-slip effect of the tube flowing for gel propellants must be considered. The results indicate also that the velocity increases as the flow moves downstream as well as with decreasing the tube diameter, and the apparent viscosity decreases as the flow moves downstream, and the apparent viscosity on the radial center is the maximum. For the same tube geometry, the apparent viscosity at the exit plane decreases with increasing the mass flow rate. For the same tube length and the same mass flow rate, increasing the tube diameter results in an increase of the apparent viscosity at the exit plane.

Abstract: The coupled influence between structure and internal flow field will make the pressure oscillation during working process of the solid rocket motor. This coupled effect will bring the dynamic press on the payload and extremely destroyed the payload. For researching the influence of internal flow field by the deformation of inhibitor, the parallel fluid structure interaction method with the large eddy simulation model was used to analyze the solid rocket motor with segments. The results show that the deformation of inhibitor will influence the internal flow field parameter’s distribution and enhance the pressure frequency and amplitude remarkably. The partitioned method could solution the fluid structure interaction problems in the segmented solid rocket motor properly.

Abstract: The aim of this paper is to demonstrate a possibility to optimize a shock absorber design to minimize level of vibrations with the use of model-based approach. The paper introduces a proposal of an optimization method that allows to choose the optimal values of the design parameters using a shock absorber model to minimize the level of vibrations. A model-based approach is considered to obtain the optimal pressure-flow characteristic by simulations conducted with the use of coupled models, including the damper and the servo-hydraulic tester model. The presence of the tester model is required due to high non-linear coupling of the tested object (damper) and the tester itself to be used for noise evaluation. This kind of evaluation is used in the automotive industry to investigate dampers, as an alternative to vehicle-level tests. The paper provides numerical experimental case studies to show application scope of the proposed method

Abstract: The aim of this paper is to develop a method for optimizing the design of a spring valve system by reducing the aeration and cavitation effect which negatively influences the performance of a shock absorber. A fluid-structure interaction (FSI) model is used in order to modify the geometry of the valve interior and, in turn, to achieve better performance in shock absorbers. The paper analyzes the pressure distribution along the flow paths inside the valve cavity to reduce the risk of aeration and cavitation, while other important engineering aspects are omitted, e.g. durability of disc-spring valve systems as discussed in [1]. The objective of this work is to show key steps of the simulation process focusing on interactions between fluid and structure domain and to review relevant simulation results.