Papers by Author: Yu Can Fu

Abstract: A numerical investigation was conducted to apply cold expansion methods on composites structures under the guidance of cold expansion techniques of metal materials and interference-fit techniques of composites structures. Finite element expansion models with sleeves or without sleeves are established to study the stress distributions and failure conditions around cold expanded holes with different expansion values (0.5%, 1% and 1.5%). Results show that no damage occurs with expansion value 0.5% and using a sleeve in the expansion process can cause uniform stress distributions.

Abstract: Milling tests were undertaken to analyze and compare the machinability of hydrogenated titanium alloy Ti6Al4V. Uncoated WC-Co tool inserts were used in the study. The feed and the depth of milling were maintained constant, and only the milling speed was varied because it is the most affecting parameter. Results showed that cutting force and tool life were greatly influenced by the contents of hydrogen. Tool life decreased at first and then increased gradually with the increase of hydrogen content, and the maximum magnitude decrease of tool life is about 0.2%H, meanwhile, the maximum tool life is about 0.5%H. However, with the increase of cutting speed, the favorable effect of hydrogen on the titanium alloy machinability would be weakened even disappear, therefore, 50-100m/min would be a suitable choice of cutting speed.

Abstract: High temperature in grinding can cause thermal damage to the workpiece. In order to reduce the grinding zone temperature, a method about enhancing heat transfer based on the rotation heat pipe technology is proposed. In this paper, the heat transfer effect of heat pipe grinding wheel (HPGW) under different conditions such as the rotating speed of grinding wheel, the kinds of working fluid and the film thickness are analyzed. The results show that the HPGW has great superiority of heat transfer under certain conditions.

Abstract: In this paper, plunge grinding experiment was conducted on 20CrMnTi with monolayer brazed cubic boron nitride (CBN) wheel. Surface integrity was evaluated through morphology observing and roughness testing. It is found that surface roughness Ra is lower than 0.8μm. Grinding forces were measured and the effects of process parameters (i.e. workpiece speed and depth of cut) on grinding forces were studied. The changing regulation of specific grinding energy with the increase of equivalent chip thickness was revealed. The result shows that both grinding force and specific energy are lower comparing with white fused alumina (WA) wheels. In general, monolayer brazed CBN wheels perform better in grinding of 20CrMnTi than WA wheels.

Abstract: High-speed turning tests were performed on vol.10%(TiC_p+TiB_w)/TC4 composite (TMC) in the speed range of 60-120m/min using PCD and carbide tools to investigate the tool life, tool wear, cutting temperatures and cutting forces. The results showed that the carbide tool was not suit for the machining of TMC. Tool life of PCD was confined to 12 min for all the cutting conditions. Flank wear increased obviously with the increasing cutting speed especially when the cutting speed surpassed 80m/min. PCD tool mainly took place chipping, peeling, abrasive wear and adhesive wear at the rake face and flank. The cutting temperatures of carbide were about 1.5-2.0 times higher than that of the PCD. Under the same cutting condition, cutting temperature of TMC was nearly 100°C higher than that of the TC4 matrix. The cutting forces were confined to 130N and 150N for the PCD and carbide tool respectively. For the carbide the cutting forces slightly decreased when the cutting speed increased from 60m/min to 120m/min. When using the worn tool, the cutting forces significantly decreased with the increasing cutting speed especially for the peripheral force component.

Abstract: Heat pipe grinding wheel (HPGW) is a new grinding wheel which can improves heat transfer enhancement with the contact zone by means of the heat pipe technology. In this paper, the heat transfer principle and making process about heat pipe grinding wheel is illustrated. After then, grinding experiments with HPGW were carried out to verify the effect of heat transfer in the grinding titanium alloy Ti-6Al-4V. Results showed that using HPGW could significantly reduce grinding temperature and prevent the burnout in the grinding.

Abstract: This article studies the performance of ceramic grinding wheel made of micro-crystalline alumina in the creep feed grinding of nickel-based superalloy Inconel 718. The effects of abrasives and specific pore volume on the performance of wheels are experimentally discussed. Grinding force and temperature were measured and analyzed during grinding tests. The surface roughness was used to describe the quality of ground surfaces. The results indicate that the micro-crystalline alumina SG abrasive wheel with large specific volume has good grinding properties when grinding Inconel 718 in comparison of the wheels with PA abrasives or SG abrasives of small specific pore volume.

Abstract: High speed grinding technology has great help about high speed grinding in application to the grinding of titanium alloy. In order to search the efficiency way to grinding the difficult to grinding material, the high speed grinding tests of titanium alloy Ti6Al4V were systematically conducted by using three wheels: brazed CBN wheel, ceramic bond CBN wheel and electroplated CBN wheel. Different equations of the maximum undeformed chip thickness a_gmax are adopted for different wheels based on their topography. The experiment results revealed that the grinding forces are increasing following the increasing of a_gmax, and the forces decrease slightly while the grinding speed v_s rise, the specific energy decrease with an increase in undeformed chip thickness firstly then reduce slightly. Particllarly, the removal rate is highest for brazed CBN wheel when the same specific energy is consumed. These phenomena indicate that with adopting the reasonable a_gmax, high speed grinding with brazed CBN grinding wheel can improve the grinding efficiency and reduce the energy.

Abstract: Ti-6Al-4V alloy was hydrogenated at 800°C by thermohydrogen treatment technology. Sliding friction and wear tests were carried out in a special device assembled on CA6140 turning lathe to investigate the friction and wear mechanism between hydrogenated titanium alloys and WC-Co cemented carbide. The morphological analyses of the worn surface were made by scanning electron microscope (SEM) and the diffusion and chemical reaction behavior of elements were analyzed by X-ray energy dispersive spectrometer (EDS). It was found that the main wear mechanisms of the unhydrogenated alloys were abrasion and adhesion and surface fatigue, while the main wear mechanisms of the hydrogenated alloys were abrasion and adhesion. The main wear mechanisms of the cemented carbide were all serious adhesion and spalling, and the specific wear forms were closed related to hydrogen contents. There are all not the chemical reaction wear and element diffusion wear in the friction region of whether the unhydrogenated alloys or the hydrogenated alloys or cemented carbide.

Abstract: Carbon fiber reinforced plastics (CFRP) use in many industries applications has seen a dramatic increase over the last decade. Milling is the most practical machining operation for removing excess material. The work presented details the effect of different cutting parameters on the surface roughness and integrity of machined multidirectional CFRP laminates. The results indicate that the surface morphology mainly relates to the fiber orientation. Increasing cutting speed leads to severe softening, degradation and burning of the matrix material that binds fibers together. The feed speed has little effect on the surface morphology. And the roughness value Ra increases with the feed rate, and decreases with the cutting speed.