Xun Sheng Zhu

The Study on Ductile Removal Mechanisms of Ultrasonic Vibration Grinding Nano-ZrO2 Ceramics

On the basis of analyzing the brittleness, ductileity, and the removal mechanisms of the^nano-ZrO2 Ceramics, the critical ductile grinding depth formula of the nano-ceramics was established. Due to superductileity of the nano-ZrO2 ceramics, it couldn’t apply the formula of the common engineering ceramic material according to experimental results. The value of material coefficient ζ has relations with not only the material characteristics but also the processing methods and the processing parameters. It was proved that ζ has great effects on the accuracy of theoretical calculation. Experimental results showed that the critical ductility grinding depth of the nano-ZrO2 ceramics is up to 12 µm in common grinding methods, while in ultrasonic grinding is up to 20µm. The grinding chips with and without ultrasonic vibration assistance were discussed.

Study on Ultrasonic Vibration Grinding Character of Nano ZrO2 Ceramics

Nano ceramics possessed ascendant mechanical property and physical characteristics contrast with engineering ceramics, so it has extensive application prospect in various industries. On the basis of applying the indentation fracture mechanics to analyze the removal mechanics of ceramic material, this paper analyzed the critical ductile grinding depth of the nano ZrO2 ceramics. Adopting ultrasonic composite processing we describe the influence of different processing parameters and grain size of diamond wheel on the grinding forces and surface roughness. Based on the grinding forces and surface roughness the grinding process with and without vibration is analyzed. By means of SEM and AFM the surface character and critical ductile grinding depth of nano ZrO2 ceramics are also discussed. The paper supplied the theoretical and experimental basis for the grinding of the large-sized ultraprecision plate structure of nano ZrO2 ceramics (nm).

Research on the vibration cutting performance of particle reinforced metallic matrix composites SiCp/Al

Abstract The cutting performance of particle reinforced metallic matrix composites (PRMMCs) SiCp/Al in ultrasonic vibration cutting and common cutting (CC) with carbide tools and PCD tools was researched experimentally in this work. The changing rules of chip shape, deformation coefficient, shear angle, surface residual stress and microstructure in ultrasonic vibration cutting are presented. The result shows that when adopting CC, a spiral chip with a smaller curl radius will be obtained. The chip of zig-zag contour, is short and thick. There are numerous sheet cracks both on the face of the chip and on the machined surface. That is to say, the cutting process of metallic matrix composites (MMCs) is not like the cutting process of plastic material, but is similar to the breaking process of brittle material. By comparison, when adopting ultrasonic cutting, the deformation of chip is small, and a loose spiral chip with a larger curl radius that is long and thin is produced. The phenomenon is similar to the vibration cutting of plastic material, but the chip still belongs to the group of plastic or semi-plastic segmental chips due to the structure characteristics of the material itself. Furthermore, the tangential residual compression stress of vibration cutting is larger than that of CC, the axial residual stress has a relationship to the feed rate, and the residual stress does not change obviously with cutting depth and they are of the same order of magnitude on the whole. According to the microstructure, ultrasonic cutting can reduce the influence of tearing, plastic deformation and built-up edge in cutting and can restrain flutter so as to make the cutting process more stable.

Experimental and theoretical research on ‘local resonance’ in an ultrasonic honing system

Abstract Through systematic experimental and theoretical research, this paper reveals the character of ‘local resonance’ in ultrasonic honing system, which has the same essence as the ‘local resonance’ of the ultrasonic machining deep hole system. The experiment and deduction method and the new design method of a ‘local resonance’ tool system have not only important practical usage but also edification for other ultrasonic systems.

Experimental Research on Surface Integrity of Ceramic Nanocomposites in Two-Dimensional Ultrasonic Vibration Grinding

The grain cutting trace of elliptical spiral in workpiece two-dimensional ultrasonic vibration grinding(WTDUVG) is defined, the reason of machining accuracy improvement by applying two-dimensional ultrasonic vibration is discussed. Adopting two-dimensional ultrasonic composite processing, the influences of grinding depth, worktable velocity, wheel granularity on the surface roughness of Al2O3/ZrO2 ceramic nanocomposites were described. Experimental results of AFM microstructure show that the material removal model in WTDUVG is dominated by ductile flow of material, some crystal refinement, the crush powder and grain pull-out are visible and there is almost no fracture. Furthermore, the surface roughness in WTDUVG with coarse grit is about 30 40% less than that in CG under identical grinding condition; the qualitative analysis of X-diffraction results indicated that the surface phases are composed of α-Al2O3, t-ZrO2 and small quality m-ZrO2, there are amorphous phase in the surface both with and without vibration grinding. M-zirconia phase transitions rule in vibration and conventional grinding was found. Under definitive grinding conditions, the material removal mechanism of inelastic deformation is the principal removal mechanism of Al2O3/ZrO2 ceramic nanocomposites, the grit size of diamond wheel and vibration grinding mode have important influence on material removal mechanism of ceramic nanocomposites.

Study on Material Removal Mechanism of Fine-Crystalline ZrO2 Ceramics under Two Dimensional Ultrasonic Grinding

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.

Research on Relationships Between Surface Fracture States and Surface Roughness Dispersion Range in Ultrasonic Grinding ZrO2

On the basis of the relationship between machined surface roughness and cutting parameters of hard-brittle materials, experiments of common and ultrasonic honing ZrO2 engineering ceramics were carried out using coarse diamond grits to discuss the relationship between surface roughness and its dispersion range and surface fracture states. Experimental results show that the machined surface roughness value of hard-brittle materials and the characteristics of its dispersion range can be considered as the criteria of cutting state. Therefore, as the machined surface roughness value and its dispersion range are both rather small, the cutting goes in the ductile cutting state, whilst the machined surface roughness value and its dispersion range are both rather large, the cutting goes in the crack cutting state. When the machined surface roughness value is rather small and its dispersion range is rather large the cutting is in the transition cutting state. Introduction At present with combination to the special machining technology such as ultrasonic, the traditional ultra-precision machining technology for hard-brittle materials has developed a new way to obtain the ductile surface effectively. In 1993, Professor D. Prabhakar put forward a theoretical model of material removal rate for rotating ultrasonic machining engineering ceramics [1] to discuss the theoretical relationship between material removal rate and amplitude, rotating velocity, grit size and machining pressure, and proved that the rotating ultrasonic machining has a relatively lower cutting force and higher material removal rate with the same conditions as common grinding. In 1994, H. Frei and G. Grathwohl studied the microstructure and intensity of advanced ceramics after ultrasonic machining [2], and found out in the process of machining engineering ceramics such as Al2O3, ZrO2 and N4Si3, the material removal process includes both crack and mini-plastic deformation, and the later resulted in higher surface compressive stress and flexural strength. In the same year, Professor X. Ai and D.M. Kim studied the ultrasonic drilling of engineering ceramics [3] and found that ultrasonic machining has smaller cutting force, lower cutting temperature and better surface quality than common way. In 1995, Z.J. Pei investigated the material removal rate of rotating ultrasonic milling MgO and ZrO2 engineering ceramics, and forecasted the relation between removal rate and cutting parameters [4]. A.R Jones worked over the press distributing model of ultrasonic polishing using stamping die [5]. Z.Y. Wang put forward the dynamic model of material removal rate in ultrasonic machining metal accessories [6]. H. Dam studied the productivity, surface quality and dimension tolerance of ultrasonic machining ceramics [7]. In the 48th CIRP annual meeting, B. Varghese and S. Malkin gave a progress report of radial ultrasonic vibration machining, and the results shew contact press, loaded area, working cycle time, ultrasonic vibration and its direction, and slotted wheel have effort on the material removal rate of ZrO2 and Si3N4 [8]. E. Uhlman and G. Spur discussed the surface figuration mechanism of slow-feed grinding advanced ceramics assisted by ultrasonic, reviewed the cut-in mechanism of single grit imposed ultrasonic vibration in the normal direction of workpiece, and forecasted that the axial vibration could get a better machining effect [9]. Obviously these researches focused on the Key Engineering Materials Online: 2004-03-15 ISSN: 1662-9795, Vols. 259-260, pp 239-243 doi:10.4028/www.scientific.net/KEM.259-260.239

Brittle-ductile Transition in the Two-dimensional Ultrasonic Vibration Grinding of Nanocomposite Ceramics

Based on impulse theories and indentation fracture mechanics, the motion model of the contact between abrasive particle and workpiece in workpiece two-dimension ultrasonic vibration grinding (WTDUVG) was analyzed, and the critical condition of ultrasonic vibration grinding brittle-ductile transition was analyzed theoretically, furthermore the critical cutting depths of a grain under different grinding conditions were obtained by Matlab programs. In this work, the ultrasonic vibration and conventional diamond grinding of Al2O3/ZrO2 nanoceramics were performed in order to investigate the effect of workpiece ultrasonic vibration on the brittle-ductile transition mechanism, the effect of grit size, worktable speed and grinding depth on the critical depth of cut were studied by grinding experiments. the micro-topography of the grinding surface was observed by AFM and SEM. Experiment indicated that only when the grinding depth less than critical grinding depth, ductile regime grinding of ceramics can be realized, the appropriate grinding parameter on surface finish are suggested.

Ultrasonic Dressing of Grinding Wheel and Its Influence on Grinding Quality

Being a key step in grinding process, dressing of grinding wheel influences the whole grinding results, especially grinding quality. Because of its good dressing effect, a new dressing method assisted by ultrasonic vibration attracted researchers’ attention. In this paper, on the basis of the researches on dressing with single-point diamond dresser, physical model of ultrasonic dressing of grinding wheel were established. According to the physical model and the SEM photos of grinding wheel’s surface topography, the mechanism of ultrasonic dressing was brought to light. Through contrast experiments, based on roughness and micro-feature of the ground surface, the influence of ultrasonic dressing on grinding quality was researched.

Modeling of Material Removal in Workpiece Lateral Ultrasonic Vibration Grinding of Fine-Crystalline Zirconia Ceramics

Based on the grain movement model of ultrasonic grinding, models representing the grinding force of single abrasive and the material removal rate (MRR) are deduced and verified. Mechanism of high efficiency material removal in work lateral ultrasonic vibration grinding (WLUVG) was analyzed. The MRR of fine-crystalline ZrO2 ceramics in WLUVG and conventional grinding (CG) with diamond wheel were researched experimentally in this work. The effects on the MRR, the surface roughness and microstructure of the process parameters and the size of abrasive are measured. It has been concluded that: (1) the MRR in ultrasonic grinding process is two times as large as that of in CG. (2) any increase in the amount of energy imparted to the workpiece in terms of the average diameter of grains, grinding depth both in with and without ultrasonic grinding, will result in an increase in the MRR and the surfaces roughness. (3) the ultrasonic grinding surface had no spur and build-up edge and its surface roughness was smaller than CG significantly. Surface quality of vibration grinding is superior to that of CG, it is easy for ultrasonic vibration grinding that material removal mechanism is ductile mode grinding.