Papers by Author: Jiu Hua Xu

Abstract: Effect of the pore size and volume fraction of alumina bubbles on the mechanical properties and microstructure of metal bond for superabrasive grinding wheels were studied by means of single factor test. The results showed that the mechanical strength reduced with the increase of bubble size and volume fraction of alumina bubbles. The morphology of the center section of the binder matrix showed that the higher the volume fraction of alumina bubbles was the less the effective area rate of the matrix was. Additionally, the bigger the bubble size was the more inhomogeneous the bubbles distributed. The pores generated after the fracture of the alumina bubbles had a regular shape and size which satisfied the chip space requirement of the wheels. At last, the failure condition of the bond matrix was established, which indicated that the strength of the bond matrix is mainly related to the effective area rate and the homogeneity of the bubble distribution.

Abstract: This article studies the effect of process parameters on the grindability of Ti-6Al-4V and particulate reinforced titanium matrix composites (PTMCs) comparatively, using the wheels of white alundum (WA) and cubic boron nitride (CBN) respectively. The processing variables, such as grinding force, grinding temperature, specific energy were investigated in detail. The results indicate that the grinding force and temperature with WA wheels were obviously larger than that of CBN wheels. The specific energy of Ti-6Al-4V and PTMCs decreased gradually with the increase in the maximum underformed chip thickness using the two different wheels.

Abstract: Particulate reinforced titanium matrix composites (PTMCs) are attracting increasingly attention in various engineering applications. In this paper, comparative grinding experiments of PTMCs were carried out using WA abrasive wheel and CBN abrasive wheel. The morphology of the ground surface was observed by scanning electron microscope. The main results are summarized as follows: (1) The damage of reinforcements in the PTMCs results from the plowing and shearing during grinding in the form of crater, micron gap, broken, coating and micron crack. (2) The formation of grinding chip is a function of the collaborate removal of reinforcements and matrix material. (3) The surface fracture pattern of PTMCs using WA wheel is to form the grinding chip through severe extrusion. While using CBN wheel, the abrasion due to the formation of the wear debris is the main surface fracture pattern of PTMCs.

Abstract: This paper deals with an investigation of surface integrity of Ti6Al4V alloy with zirconia alumina and SiC belts. The experiments were conducted under dry grinding environments in milling machine XS5040 equipped with belt grinding device. Microcosmic geometry parameters were measured with TALYSURF5 instrument, the surface morphology machined workpiece and the phase structure was analyzed using 3D viewer microscope, surface hardness for ground surface was measured by HXS-1000A instrument. The results show that surface quality maintain better level during a long period, the grinding affected zone was small(≤15μm), zirconia alumina belt has excellent performance than SiC belt during dry grinding Ti6Al4V alloy.

Abstract: This paper was dedicated to elucidate an investigation of abrasive wear and surface topography of Titanium alloy TA15 on dry grinding with zirconia alumina belt. In the investigation, experiments were performed on milling machine XS5040 equipped with assembled belt grinding device. The wear abrasive, surface morphology of machined belt in different phase were analyzed using 3D viewer microscope. The results show that the wear of belt abrasive is mainly steady attritions wear since zirconia alumina belt was stable on dry grinding. At higher grinding force, the abrasive was found to undergo dislodging prior to being gradually worn. So zirconia alumina belt has excellent performance in the dry grinding titanium alloy.

Abstract: Abrasive composite bulks consisting of polycrystalline cubic boron nitride (PCBN) grains, Cu-Sn-Ti alloy and graphite particles were sintered at the heating temperature of 920 °C for the dwell time of 30 min. The bending strength of abrasive composite bulks was measured. The interfacial microstructure and the phases were characterized. In addition, the dressing experiment was carried out to detect the self-sharpening behavior of the composite bulks. Results obtained show that the abrasive composite bulks in this investigation give higher bending strength than that of the vitrified abrasive wheels. The compounds of TiN, TiB₂ were formed and the PCBN grains were embedded firmly. Strong fixing of the bulks to the PCBN grains led to the breakage of the PCBN grains when the abrasive composite bulks fractured. The intergranular fracture mode of the PCBN grains ensured the self-sharpening effect of the grains.