Abstract: Friction and wear are very important in mechanical design. This paper studies the friction and wear characteristics of 45 steel under oil lubrication. The sliding friction and wear experiment was carried out with the pin plate friction pairs on the MMW-1A friction and wear test machine. Researching the influence of velocity on friction factor under the same load, the relation between wear and load and wear analysis under the same speed different loads. The results showed that under the same load and with the increase of velocity, the friction factor had a gradually decreasing trend. When some of the parameters were certain, the wear volume and the loading force was roughly linear relation. Pitting occurred when the load increased.
Abstract: Prepared the nanoZrO2 reinforced Cu-matrix composite by pulse electroforming. The effects of the content of nanoZrO2 particle in the casting solution, average cathodic current density, duty cycle, pulse frequency and ultrasonic power on the content of nanoZrO2 in the electroforming Cu-matrix composite have been studied. The microhardness and surface morphology of Cu-ZrO2 composite were analyzed. The experimental results demonstrate that the maximum content of nanoZrO2 in the electroforming Cu-ZrO2 composite is 2.94%, microhardness is 492 HV, which is significantly improved compared with pulse pure copper’s 337 HV, when the content of nanoZrO2 is 40 g/L, average cathodic current density is 4A/dm2, duty cycle is 0.2 , pulse frequency is 1100 Hz and ultrasonic power is 20w .The surface of composite prepared by pulse electroforming is more smooth, organization is denser, grain is finer and agglomeration of nanoZrO2 particles is fewer compared with Direct-current electroforming nanoZrO2 reinforced Cu-ZrO2 composite.
Abstract: The choice of abrasive particle size is crucial to improve the lapping efficiency and surface quality in lapping of sapphire wafer by fixed abrasive (FA) pad. A model for the penetration depth of a single abrasive is developed with fixed abrasive pad. A serious of lapping tests were carried out using FA pads embedded with different size of diamond particles to verify the validity of the developed model. Results show that the penetration depth of abrasive is related not only to the particle size, but to the hardness ratio of the work-piece to the pad as well. The material removal rate of sapphire is proportional to the square of abrasive particle size, while the average surface roughness is proportional to the abrasive particle size.
Abstract: The paper mainly simulates the effects of layer thickness and deposition velocity on thermal stress in fused deposition modelling (FDM). Different values of these variables are considered in this process. The simulation results show the trends of thermal stress with the two variables and the simulation results provide a guidance for the practical fabrication.
Abstract: To improve the material removal rate (MRR), the effects of electrode rotational speed, gap voltage and pulse width on the MRR of PCD EDM grinding process were studied. By adding pre-experiments, the optimization process is more rapid. A second-order regression model of MRR is established by using response surface method based on Composite Circumscribed design (CCC). And the influence of each parameter on the response is analyzed. The results show that the optimal removal rate is after optimized, which is 11.8% higher than that of the pre-experiment.
Abstract: The process parameters of fundamental electroforming solution were optimized firstly. Furthermore, some pure copper electroforming samples were prepared in the condition of different nana La2O3 addition quantity. Three main material properties evaluated. In addition, the EDM machining experiments were conducted to verify the characteristics of electrical corrosion resistance resulting from the prepared copper tube electroforming samples for cooling hole of Inconel718 nickel alloy. EDM experimental results demonstrate that copper electroforming layer with grain size 15.9μm, microhardness 98.2HV, with 1.2g/L addition quantity of nana La2O3, and its electrode loss rate decrease 13.29% and 7.26% than pure copper and copper electroforming layer without nana La2O3 addition respectively.
Abstract: In this paper, the effect of deposition velocity on bonding degree is studied in the aspects of experiment and theory. The experimental results show that the bonding quality of the adjacent filaments is weakened with increasing of deposition velocity. In addition, on the premise of guaranteeing every point in the building process to remain at the optimal temperature, the quantitative relationships between interval and filled area, deposition velocity are investigated by using the technique of deactivate and reactivate element of finite element. On the base of the quantitative relationships, the variable deposition velocity printing method is proposed for the first time. Namely, to reap the best bonding quality of filaments the time of completing one layer can be determined according to the filled area, and then, the optimal deposition velocity can be obtained according to the quantitative relationship between the interval and the deposition velocity. Printing the model at this speed can obtain the part with the best bonding quality between adjacent layers.
Abstract: In this paper, based on micro wear form, an approach that using protrusion height, average tool angle, blunt area ratio and coated density to describe the wear of abrasive belt is put forward. The method for calculating the above parameters are also introduced. In experiments, we use the profilometer to collect the abrasive belt surface data and draw figures of the above parameters under service time, which indicates that using topography parameters can describe the degree of belt wear. According to parameters changing slope, the abrasive belt service time is roughly divided into two stages, initial wear stage and stable wear stage but no abrupt wear stage. Initial worn stage grains suffer more stress, patterns of wear are mainly severe wear and pull-off, while stable wear stage grains bear less stress and pattern of worn is dominated by mild wear. In addition to that, the other parameters changing trend is agreed and synchronous with protrusion height.
Abstract: Jet electrodeposition process is a very promising method in fabricating metal matrix composites reinforced with ceramic particles. In use of this method, insoluble particles suspended in an electrolytic bath are impinged onto and embedded in a growing metal layer. This paper is focused on the investigations of the copper matrix nanocomposite coatings with hard Al2O3 nanoparticles, electrochemically deposited from jet-circulated baths on 304 stainless steel substrate. The Cu-Al2O3 composite coating was characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. The effects of electrolyte jet velocity, current density, addition amount of Al2O3 in the electrolyte were analyzed on the microstructure change, surface morphology change as well as codeposited content of Al2O3 particles in the composite coating. It was found that increasing content of Al2O3 particles in electrolyte may improve composite coating surface morphology and increase the practical current density by exerting impingement effect on the cathode deposit surface, till excessive Al2O3 e.g.20g/L particles was added. Besides, appropriate amount of nanoparticles in the electrolyte also could offer grain refinement by providing nanocrystalline sized between 30~60 nm with current density in the range of 100~500 A/dm2.
Abstract: The hard machinability of titanium alloy material and the poor stiffness of thin-walled parts hindered the extensive application of titanium alloy thin-walled components in aerospace engineering. In order to heighten the geometric accuracy in the processing, the ultrasonic vibration assisted (UVA) end milling technology with workpiece vibrating in feed direction was put forward in this paper, and characteristics of the milling deformation in UVA milling of titanium alloy TC4 thin-walled workpieces were researched. Through the theoretical analysis, the cutting force and deformation characteristics in UVA milling were clarified. Based on the range analysis of orthogonal experiment, the effects of milling parameters and ultrasonic amplitude on the deflection displacement and the milling deformation of workpieces are obtained. Research results show that the deflection displacement in the process of UVA milling affects the thickness error of the thin wall. Ultrasonic parameters as well as milling parameters should be optimized to obtain higher machining accuracy. The research provides a certain reference for the precision milling of titanium alloy thin-walled parts.