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With the development of (electrical discharge machining) EDM technology, composite tools with special features gradually replace the traditional single-material tools and have become widely used in specific processing conditions. In order to predict the wear of composite tool effectively, in this paper, a material removal model of single-pulse EDM with composite tools was established by using the finite element method. The surface temperature distribution of the composite tool was obtained by taking the copper-die steel tool as the analysis object. And the shape of discharge crater as well as the removal volume was obtained by the element birth and death method. The influences of discharge parameters and tool materials on the removal volume were analyzed respectively. The EDM experiments were carried out by using copper-die steel as the composite tool to verify the simulation results. It shows that the errors between actual machining results and the simulation results are less than 10%, which proves the accuracy of the simulation model.

Structure analysis of the long tunnel is difficult due to the lack of available computing power. Water hammer simulation in the water conveyance tunnel is also complicated because of strong fluid structure interactions (FSIs). In this paper, the multi-scale modeling method is used to simulate water hammer impacts in the long tunnel. The method can not only yield water hammer simulations along the full tunnel length, but also the detailed structural responses of the segment linings. In the proposed partitioned approach, the structural field is solved with the finite-element program LS-DYNA. The fluid field is solved with the CFD software package FLUENT. The interaction between two physical fields is realized using ALE description. A practical case study is presented and the results are discussed in detail. The results provide us with a better understanding of water hammers and their effects on tunnel linings.

SUMMARY Shanghai Center Tower, which is 632 m in height with 126 stories, will be the tallest building in China at the end of 2014. The extreme height of the building combined with the exterior shrink-constructed and torsion-constructed curtain wall imposes a great challenge on the seismic design of the curtain wall. This paper establishes a finite element (FE) model of the real-scale building by considering the combination of the curtain wall and the main structure. The lower order modes of the building's vibration have been predicted, and good agreement has been observed between the numerical and experimental data, which validates the FE model of the building. Seismic response of the curtain wall was then investigated under three earthquake levels, including frequent, moderate and severe earthquakes. The acceleration magnification factors, the inter-story drift ratios and the interior forces of the curtain wall met the requirements of the Chinese Design Code, which indicates that the structure is a good solution to withstand earthquakes. The present study provides an important database for the seismic design of curtain wall structure in Shanghai Center Tower, and it can be used as a seismic design reference for similar projects. Copyright © 2011 John Wiley & Sons, Ltd.

Parallel analyses about the dynamic responses of a large-scale water conveyance tunnel under seismic excitation are presented in this paper. A full three-dimensional numerical model considering the water-tunnel-soil coupling is established and adopted to investigate the tunnel’s dynamic responses. The movement and sloshing of the internal water are simulated using the multi-material Arbitrary Lagrangian Eulerian (ALE) method. Nonlinear fluid–structure interaction (FSI) between tunnel and inner water is treated by using the penalty method. Nonlinear soil-structure interaction (SSI) between soil and tunnel is dealt with by using the surface to surface contact algorithm. To overcome computing power limitations and to deal with such a large-scale calculation, a parallel algorithm based on the modified recursive coordinate bisection (MRCB) considering the balance of SSI and FSI loads is proposed and used. The whole simulation is accomplished on Dawning 5000 A using the proposed MRCB based parallel algorithm optimized to run on supercomputers. The simulation model and the proposed approaches are validated by comparison with the added mass method. Dynamic responses of the tunnel are analyzed and the parallelism is discussed. Besides, factors affecting the dynamic responses are investigated. Better speedup and parallel efficiency show the scalability of the parallel method and the analysis results can be used to aid in the design of water conveyance tunnels.

In EDM, especially in small holes EDM machining, there will be a lot of debris produced which is difficult to remove from narrow gap. If the debris can't be removed in time, it will affect the machining accuracy and efficiency, and sometimes even unable to complete the processing. In this paper, the debris movement and escaping process in gap flow between electrodes in the case of Ti alloy small hole EDM machining were studied by combining the means of simulation analysis and experiment study. The perturbation generated by the movement of self-adaptive tool in the gap flow were taken into consideration and the methods of smoothing and remeshing were also applied in order to build a model for the debris movement in the gap flow. And then, the law of debris movement under different depths was analyzed and the distribution rules about pressure field and velocity vector were summarized. Finally, the model was verified by the experiment result showing that the appearances of uneven wear at the bottom of hole and the taper wall are both in accordance with simulating conclusions.