Papers by Author: Wei Zhao

Abstract: The comparison of the hyperbolic perturbation method and the hyperbolic Lindstedt-Poincaré method for homoclinic solutions of self-excited systems is studied in this paper. The homoclinic solution of a generalized Van del Pol system with strongly quadratic nonlinearity is analytically derived by both of the methods. The critical value of the bifurcation parameter under which homoclinic trajectory forms can be determined by the both of the perturbation procedures. Typical numerical examples are studied in detail and compared to illustrate the accuracy and the efficiency.

Abstract: It is commonly believed that the white layer formed during hard machining of steels is caused primarily by a thermally induced phase transformation resulting from rapid heating and quenching. The focus of this study is to investigate the white layers produced on the machined surfaces and on the inner side part of the chips in dry hard turning GCr15 with PCBN tools. Samples of machined workpiece and chips were metallographically processed and observed under a microscope to determine whether white layers were present or not. Some properties of white layers were deduced in order to verify some of the prevalent theories. More specifically, chip shapes were studied to determine how they developed during machining with potential appearance of white layers, with a view to correlating the chip shapes with the white layer formation.