Papers by Author: Yu Jing Hu

Abstract: This paper presents a PMAC-based combined CNC machine that integrates technologies of ultrasonic machining, electrical discharge machining and high speed grinding. As a multifunctional machine, it can provide diverse machining methods for different materials. For hard and brittle materials, it can conduct ultrasonic machining and high-speed grinding respectively or in a combined form; for conductive hard and brittle materials, electrical discharge machining with or without ultrasonic vibration could be implemented. Driven by AC servomotors, the mechanical structure of the vertical machine is mainly composed of a cross workbench for work piece handling, and a spindle head for tool feeding or high speed rotating. Besides those mentioned above, the system management program, the pulse power generator as well as the ultrasonic generator are also analyzed in this paper. Experimental results show that this machine has a wide range of application indeed and is suitable for various materials processing.

Abstract: Because the machining of ultrasonic vibration assisted electro-discharge machining (UEDM) is a very complex process and it is too difficult to describe precisely every influencing factor with an accurate mathematics model, the study of parameters selection system is necessary and important for the practical application of machining method, the improvement of machining efficiency and minimizing the tool wear ratio (TWR). In this paper, the model and the corresponding database are built for UEDM based on the back propagation (BP) algorithm artificial neural network (ANN) to optimize machining parameters. Through learning and training, this system realizes the intelligent selection of machining parameters. As shown by the experiment results, the predictions accord with the test results, which shows that the reasonable and reliable project of UEDM can be provided by the system. With the increase of the machining sample, the machining database can be enriched and the application range will be expanded, so this system has the excellent fault-tolerance and extensible quality.

Abstract: In this paper, a new three dimensional FEM model was elucidated on arch dam cracking analysis. Based on the least potential energy method, the stiffness of the interface between two types of mesh is coupled into the whole stiff matrix in this model. By this means, the FEM mesh of local area of arch dam can be easily changed from a coarse mesh to a fine mesh. By changing the density of mesh, the consideration of heterogeneity for the calculating elements is achieved by assigned to the elements random strength and elastic modulus according to a Weibull distribution. This model allows to densify the mesh of a local area and to trace the cracking of this area undertake damage criterion. By applying this new model, the mechanism of vertical cracks opening along the downstream surface of Shuanghe Arch Dam after two years of operation was briefly analyzed. The numerical result is basically agreed with the field investigation.