In recent years, particle reinforced metal matrix composites (PRMMCs）has been widely applied because of its excellent mechanical performances. But the machining is very difficult due to the rigidity of reinforced phase in it, thus the popularization of PRMMCs is restricted much. Here, a method of ultrasonic vibration drilling is presented to the hole-making of Aluminum-matrix composites based on cutting force analysis between common and vibration machining. In virtue of the self-developed ultrasonic drilling equipment, experiments of common and ultrasonic vibration drilling are performed on SiC particle reinforced Aluminum-matrix composites with different content of SiC by using two types of tungsten carbide twist drill. Since the tool life can be represented directly by drilling force, especially the torque, the study of drilling force is very important for the surface roughness, the design and life of drill. Drilling force and its variation in the machining process are analyzed by comparison of common and vibration drilling. It shows that the eviction of drilling chips can be meliorated to some extent, and the drilling torque can be reduced about 30% during the ultrasonic vibration drilling process.
The gas velocity and particle velocity in and out of the nozzle have great influence on the coating effect in the process of cold spray. An axis-symmetric two-dimensional mathematical model was presented to study the flow field in and out of cold spray nozzle, and the effect of different pressure, temperature, spraying distance and particle diameter on gas axial velocity and particle velocity were researched. The simulation results showed that the gas axial velocity and particle velocity increased when the gas pressure and temperature were increased, spray distance had little effect on the flow field in the nozzle, and small diameter particle was more easily accelerated.
Orthogonal experiments of ultrasonic deep rolling with Longitudinal-torsional vibration (UDR-LTV) and conventional deep rolling (CDR) 6061-T6 aluminum alloy were carried out. The experimental results were analyzed by orthogonal-response surface methodology to study the effects of processing parameters on surface roughness. The results show that the values of surface roughness obtained by UDR-LTV are smaller than that of CDR with the same processing parameters. Meanwhile, feed-rate has a marked effect on surface roughness, and static pressure has a little effect on surface roughness. The quadratic regression method is used to construct the mathematic model of surface roughness based on the experimental results. The interactions between the processing parameters are analyzed using response surface method. The optimal parameters for the lowest surface roughness are given, which provide technical support for proper parameters in practical processing.
In the paper, the machining characteristics of two dimensional ultrasonic grinding(TDUG) are analyzed, and based on the analysis of the working locus of abrasive particle under TDUG and mechanical performances of fine-crystalline ZrO2 ceramics, a theoretical model of material removal rateMRRis proposed under TDUG with workpiece adhered to ultrasonic vibration respectively from the orthogonal directions. The model shows that any increase of static load, size of grain, work speed, number of effective dynamic abrasive particle, the amplitude and frequency of tool or any decrease of fracture toughness property and hardness will result in the increase of the MRR, and the theoretical model of the MRR is tested, meanwhile the paper draws the conclusion that the surface quality under TDUG is superior to that under common grinding, which is tested by the means of grinding of fine-crystalline ZrO2 ceramics.
With the rapid development of aviation at home, particle reinforced metal matrix composites (PRMMCs) has been widely applied recently. But at the same time, the difficult machining has gradually been one of the most outstanding bottle-necks that restrict the rapid enhancement of productivity. Here, in virtue of the self-developed ultrasonic drilling equipment, hole-making experiments of common and ultrasonic vibration drilling are performed on SiC particle reinforced aluminum-matrix composites （SiCp/Al）with different content of SiC by using two types of tungsten carbide drill. Drilling characteristics of machining composites with ultrasonic vibration are analyzed from such respects as the composites crush, drilling force, drill wear and hole surface quality. Studies show that, during the ultrasonic vibration drilling process, SiC particle in the composites is prone to break along the crystal connection boundary or suffer ductile fracture under the dynamic ultrasonic impulse, in which the cutting resistance could be reduced and the tool edge could be protected. Thereby, drilling locating precision and hole surface quality could be enhanced, wear of the drill chisel edge effectively improved, and the drilling torque reduced about 30%.
Two-dimensional ultrasonic vibration was introduced into common rolled extrusion, effect of the process parameters including tool head radius, feed speed, preload and spindle speed on the 45 steel shaft surface roughness were analyzed through orthogonal experiments. Experimental results show that lower value of surface roughness may be obtained in the process of two-dimensional ultrasonic rolled extrusion than that of common rolled extrusion, and the influence order of process parameters on surface roughness is feed speed, spindle speed, preload and tool head radius; the influence curves of tool head radius and spindle speed on surface roughness are concave curves, and influence curves of feed speed and preload on surface roughness are convex curves, or optimizing process parameters exist. The empirical formula for surface roughness is given using multiple regression analysis based on the experimental results. This study will provide a new technique for finishing precision parts.
Ultrasonic aided high speed lapping with solid abrasive material was put forward aimed at the precision finishing of nano ZTA engineering ceramic. Through theoretical analysis and contrast lapping experiments, the influences of ultrasonic assistance on the surface machining quality were clarified. Research results show that the maximum undeformed chip thickness in ultrasonic aided lapping is smaller than that in conventional lapping under the same conditions; ultrasonic assistance is beneficial to enlarging the range of ductile lapping regime and improving the surface quality of nano ZTA ceramic; with the application of ultrasonic vibration, smaller surface roughness and more regular surface profile can be obtained.
A new ultrasonic aided lapping technology was developed by combining lapping technology and ultrasonic machining technology. The appended special tangential ultrasonic vibration changes the material removal rate (MRR) characteristics. In order to clarify the influence of ultrasonic vibration, in this paper, the MRR models in ultrasonic aided single-point scratch were deduced based on indentation fracture theory. Through contrast scratching and lapping experiments, the MRR characteristics in ultrasonic aided lapping of engineering ceramics were presented. Research result shows that the MMR in ultrasonic aided lapping is larger than that in conventional lapping under the same conditions; with the increase of ultrasonic generator power and lapping pressure, the MMR in lapping increases correspondingly.
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