A new dynamic model for bolted joints in heavy machine structures is proposed. The influence of the bolt pretightening force, the interface dimensions and the surface roughness on joint dynamics (i.e. the stiffness ma...
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A new dynamic model for bolted joints in heavy machine structures is proposed. The influence of the bolt pretightening force, the interface dimensions and the surface roughness on joint dynamics (i.e. the stiffness matrix of finite element) were analysed. Each stiffness coefficient in the matrix can be expressed by an exponential function of preload, and a quadratic polynomial function of geometric dimensions. Sixteen specimens were thoroughly designed and analysed. Then, the resulting stiffness matrices were saved as templates, based on which could establish dynamic models of joints with different influence factor values, using curve-fitting and Response Surface Methodology (RSM). The methodology was validated by experiments with a specimen of the new design and a heavy-duty cutting machine.
Magneto-rheological elastomers (MREs) are a new kind of Magneto-rheological materials mainly composed of polymer rubber and micro-sized magnetizable iron particles. In this technical note, a shear-mode semi-active dyn...
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ISBN:
(纸本)9781634392389
Magneto-rheological elastomers (MREs) are a new kind of Magneto-rheological materials mainly composed of polymer rubber and micro-sized magnetizable iron particles. In this technical note, a shear-mode semi-active dynamic vibration absorber (SDVA) based on MREs is proposed and the dynamic design principle of an axial SDVA attached to ship shafting is studied. The material preparation of MREs and their properties under different magnetic fields are introduced. The structure of a single SDVA is designed. Furthermore, the natural frequencies of the single SDVA under different magnetic fields and temperatures are experimentally evaluated. It is found that the natural frequency of SDVA has a decreasing trend with the temperature increasing. However, it has an increasing trend with the excitation current increasing in the same temperature situation. The effect of temperature is more obvious than the excitation current.
ABSTRACT: This paper proposes a method to analyze the geometry and semantic information of 2D vector floor plans, and reconstruct the corresponding 3D building models automatically. First, the Shape-opening graph (SOG...
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Vibration characteristics analysis is important in the design of multi-span pipeline with different support conditions. In order to analyze the natural frequency and the vibration modal of the multi-span pipeline, a m...
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Vibration characteristics analysis is important in the design of multi-span pipeline with different support conditions. In order to analyze the natural frequency and the vibration modal of the multi-span pipeline, a matrix transfer method is proposed in this paper. With the multi-span pipeline divided into single-span pipes, the transmission formulas for the deflection, angle, bending and shear between two adjacent spans are deduced, in combination with the Krylov function solution of the free vibration equation for the single-span pipe, and the constraint condition between the two adjacent spans of the multi-span pipeline. According to the boundary conditions on the starting and ending spans, the natural frequency equation and the vibration modal function between two adjacent spans of the multi-span pipeline are presented. The FORTRAN program based on the above principle is written, and the natural vibration frequencies and the vibration modals of two typical multi-span pipelines are investigated and compared with the results from ABAQUS. It is shown that the model presented in this paper is efficient in the analysis of multi-span pipeline and has the advantages of high computational efficiency and convenience for engineering practice application.
In order to investigate the fluid structure interaction problems occurring in tube bundles, a numerical model is presented. The unsteady three-dimensional Navier-Stokes equation and LES turbulence model are computed w...
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In order to investigate the fluid structure interaction problems occurring in tube bundles, a numerical model is presented. The unsteady three-dimensional Navier-Stokes equation and LES turbulence model are computed with finite volume approach on structured grids combined with the technique of dynamic mesh. The model presents a three dimensional fully coupled approach with solving the fluid flow and the structure vibration simultaneously, for the tube bundles in cross flows. The results show that, the presented model is validated with experimental data and compared with existing models in the literature. Trajectory of single tube is "8" shape at "locked in". The two parallel tubes oscillate in opposite phase and both have the same amplitude. For pitch higher than 1.5D, there is no mutual influence of the tubes and response is close to the case of single tube. The lift force and amplitude of downstream tube of two inline tubes are increasing as the pitch increases. The upstream tube is almost not influenced by the downstream one when the pitch is larger than 2D. The fluid force and response are close to the case of single tube.
There are plentiful and diverse applications of graph data management and mining in the real-world scientific research and business activities. As one of the most basic operations, uniform path pattern query processin...
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ISBN:
(纸本)9781479967209
There are plentiful and diverse applications of graph data management and mining in the real-world scientific research and business activities. As one of the most basic operations, uniform path pattern query processing on graph data faces three big challenges. In this paper, we deal with these challenges by the following points. Firstly, a new query language on graph, called G-Path, is presented, which focuses on complex path pattern query processing on a very large graph. Also, the design of a system called HDGL is proposed, which is based on a BSP-like model as well as MapReduce model, and can effectively handle distributed graph data operations and queries. Secondly, the implementation of HDGL on the de facto cloud platform - Hadoop - is brought forward. Based on the concept of distributed state machine, the query processing of a G-Path statement in HDGL is detailed. In addition, as the query optimization of G-Path queries, several tricks are utilized to improve dramatically the performance of query execution. Finally, extensive experiments on several graph data sets are conducted to show the usability of G-Path query language and the effectiveness of HDGL.
Since many Cascaded H-bridge multilevel (CHBML) inverters that are applied to drive high voltage machines can't transmit electric energy reversely, the electric energy transmitted from the machines may damage the ...
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ISBN:
(纸本)9781479951635
Since many Cascaded H-bridge multilevel (CHBML) inverters that are applied to drive high voltage machines can't transmit electric energy reversely, the electric energy transmitted from the machines may damage the inverters. This paper presents a transfer function to analyze the electromagnetic torque, when the load torque changes suddenly. Based on the achievements, the electric energy that flows between the machine and the inverter can be calculated. And then, a method is proposed to prevent the reversion of the direction of energy flow. Furthermore, the transfer function can be used to guide the design of the control system of induction machine. Simulation results verify the transfer function and the presented method.
The velocity field and pressure field induced by Dielectric-Barrier-Discharge (DBD) plasma actuation (DBD) are accurately measured based on PIV and transient differential pressure sensors. A micro lens is mounted on P...
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ISBN:
(数字)9781624102561
ISBN:
(纸本)9781624102561
The velocity field and pressure field induced by Dielectric-Barrier-Discharge (DBD) plasma actuation (DBD) are accurately measured based on PIV and transient differential pressure sensors. A micro lens is mounted on PIV system to capture the critical region of plasma-induced flow. The transient differential pressure sensors with 0.1 Pa resolutions, respond effectively to the inconspicuous change of pressure gradient in the low speed flow. The neural network model is established, revealing the complex nonlinear mapping of external and internal information, while trained by large numbers of experimental samples. The electrical parameters of the plasma generator, the shape parameters of plasma actuator and coordinate parameters are input into the neural network as external information. On the other hand, the velocity field and pressure field serve as internal information to be output. The obtained velocity field and pressure field through the neural network model are regarded as the source terms and are substituted into momentum equilibrium equations and Navier-Stokes equations to calculate the body force field, thus building the mapping relationship between extrinsic plasma actuator parameters and the body force.
The attitude coordinated tracking problem of multiple spacecraft with control input saturation is studied in this paper. We first construct a decentralized attitude coordinated tracking algorithm with input saturation...
The attitude coordinated tracking problem of multiple spacecraft with control input saturation is studied in this paper. We first construct a decentralized attitude coordinated tracking algorithm with input saturation, such that spacecraft can track a time-varying desired trajectory and align their attitudes. We then introduce a novel auxiliary dynamical systems to present an attitude coordinated tracking algorithm with input saturation and without angular velocity measurements. Throughout this paper, the information flow between spacecraft is assumed to be undirected. Finally, design examples are given to show the effectiveness of the proposed attitude coordinated tracking algorithms.
design is the core of innovation activity, and it aims to establish better and comprehensive qualities of products. It is also a process to explore and enhance the human experience. During decades of exploration and p...
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