Papers by Author: Yan Chen

Abstract: Carbon fiber reinforced plastics (CFRP) laminates with different top/bottom fiber direction angle (stacking sequences of each ply) are trimmed at various workpiece inclined angles. Four types of delamination are studied and discussed. The results indicate that fiber direction has great influence on the type of delamination and the workpiece inclined angle determines the proportion of each type of delamination expect a special cast that the delamination form turns into type I/II when the workpiece inclined angle is 58.6o. Stacking sequences of each ply have great influence on the numbers of damaged plies and the 0o fiber direction ply has the ability to prevent the development of damaged ply.

Abstract: The shear strength samples of brazed single crystal diamond with the (72Ag–28Cu)–xTi (x=2, 4, 7wt.%) active filler metal were prepared, using vacuum brazing methods. Microstructure evolution of interfacial reaction product and shear strength of the brazed diamond and Ag based filler alloy were studied. The results show that there exits a layer of TiC on the surface diamond in different Ti additions, and the thickness of TiC layer increases with the increase of Ti addition. With the increase of Ti addition, the shear strength of the brazed joint decreases due to the increase of TiC layer thickness and amount of intermetallics. From the results, it was seen that mutual diffusion of C and Ti was effective on the morphology of the interface zone that affected the shear strength of the bonds. To achieve a reliable brazed joint, the Ti content must be controlled under 4wt.%.

Abstract: In the application of brazed diamond tools, residual stress caused by differences in materials properties is an important factor in obtaining good brazing quality. The residual stress in diamond/steel brazed joint is studied by means of finite element method and Raman spectroscopy in this paper. The comparison between the results from the simulations and the measurements shows that a good agreement has been reached. Tensile stress concentration at the diamond edge near interface was observed. High residual stress concentration may cause cracks in diamond. Actually, cracks in diamond caused by brazing residual stress after were observed. The stress concentration of the joint must be reduced to obtain good brazed joint. The change of brazing atmosphere or to adopt the soft brazing alloy will reduce the stress concentration.

Abstract: The wear resistance samples of brazed single crystal diamond with Ni-Cr filler alloy were prepared, using high frequency induction brazing and vacuum brazing methods. By wear test of brazed single crystal diamond, the wear performance of the samples with different brazing processes was studied. The test result indicates that the wear performance of the high frequency induction brazed diamond samples is better than that of the vacuum brazed diamond samples. Because of different brazing processes, the wearing pattern of diamond varied; the wear course of the vacuum brazed diamond samples in the initial wear period were abnormal and the failure modes is different.