Papers by Author: Hang Gao

Abstract: The mechanical properties of Potassium Dihydrogen Phosphate (KDP) crystal had been relatively well investigated, and it was reported that mechanical properties of KDP crystal are anisotropic corresponding to crystallography orientation. However, the affect of the crystallography orientation to the critical undeformed chip thickness and cutting force variation in ductile mode cutting of KDP crystal are still not clear, which are important in determining proper cutting parameters to get fine finished surface. This paper investigates the influence of crystallographic orientation to critical undeformed chip thickness by a kind of groove cutting on {001} plane, and the influence to cutting force is also researched by face turning. The experiment results demonstrate that the cutting forces and critical undeformed chip thickness for ductile mode cutting varies greatly according to KDP crystallographic orientation. This paper point out that two slipping plane, {110} and {1__,10}, account for the variation of cutting force and critical undeformed chip thickness in different orientation on {001} plane. A set of cutting parameters for ductile mode cutting are selected based on the derived critical undeformed chip thicknesses at different crystal orientations, and overall sooth surface has been achieved on face turned {001} surface, which the roughness is Ra 2.6nm measured by Veeco white-light interferometer.

Abstract: Microgroove processes are carried out on Potassium Dihydrogen Phosphate (KDP) crystals of different crystalline orientation using diamond tool, the speed of groove is very low in order to avoid the influence of temperature. The main process characteristics are examined including the groove geometry, cutting forces and critical underformed chip thickness at the onset of ductile-to-brittle cutting transition. Additionally, the cutting pressure is calculated from the cutting force and grooving geometry. The experimental results show that as the groove depth increase, the groove geometry clearly revealed that ductile-to-brittle cutting transition occurred, and the transition are well reflected by changing in the cutting pressure. Further, it is shown that the critical undeformed chip thickness varies greatly with the workpiece KDP crystalline orientation.

Abstract: Potassium Dihydrogen Phosphate (KDP) crystals are used for the key components in high power density solid-state laser for Inertial Confinement Fusion. KDP crystals are mainly machined in the dry cutting condition to avoid ‘Fogging’ of the crystals. The main difficulty identified in dry machining of KDP is chip removal from the machined surface. A vacuum sucking device based on venturi vacuum pump is used to suck the chips during cutting, and the relationship between level of vacuum in cutting zone and the comply air pressure was established. An empirical model for chip emission during turning processes is used to analyze the influence of cutting parameters on the chip emission. The influence of cutting parameters on the removal of chips is investigated. Finally, a face turning of KDP crystals is carried out with the turning parameters of feed rate 1um/rev, depth of cut of 0.8 um/rev and the cutting speed from 1.82m/s to 3.9m/s. A super-smooth surface with chips free in the whole sample is achieved, having the surface roughness of 2.994nm (Ra) measured by AFM. The surface quality achieved satisfies the requirements of KDP crystals implemented in high power lasers.

Abstract: Invar 36 alloy is widely used in the field of precision manufacturing owing to its minimal thermal expansion coefficient. Grinding is very important in Invar surface processing, and the thermal characteristics is a key factor to affect the residual stress and deformation of grinding. In this paper, the thermal characteristics of Invar 36 alloy during plane grinding was tested. The thermal characteristics of Invar 36 alloy was found to be between carbon steel and nickel-based superalloy. The lower grinding temperature and better ground surface with lower residual stress can be obtained by using the reasonable grinding parameters.

Abstract: Strong anisotropy of physical and mechanical properties of Potassium Dihydrogen Phosphate (KDP) crystals significantly affects surface quality during processing the samples. Different processing direction, along [100], [110], and [120] crystallographic orientations, are chosen on (001) crystal plane in order to evaluate the anisotropic characterizations on the processed surface. Scanning electronic microscopy (SEM) is employed to observe the machined surface damage, defects and profiles. At the same time, surface quality is measured by Zygo surface profiler to estimate the processed surface quality. The results show that the machined surfaces along three different orientations under the same processing conditions behave quite differently from each other. Strong anisotropy and complex slip system of KDP crystals lead to several different asymmetric damages on the machined surface. Surface roughness (Ra) values along [100] are the smallest, that along [120] are in average, and that along [110] are largest. Moreover, many illustrations are given to understand the anisotropic nature during processing, including slip system, mechanical properties during processing, and technical parameters, etc.

Abstract: According to the demand for internal grinding machine in precise machining of air-conditioner compressor piston hole, a kind of high precise CNC internal grinding machine with CBN wheel is developed by adopting self-adaptive control for grinding process. Meanwhile, grinding precision and stability are achieved by overcoming many problems emerging from high-speed grinding process with CBN wheel. More than 100000 times’ grinding experimental results show that the whole performance of grinding machine developed is the same as that of the same kind of international machine. In order to study grinding mechanism with CBN wheels and then improve machine’s capability, grinding data in several machining cycles is analyzed.

Abstract: Grinding fluid has an important effect in processing work piece, so in view of the new grinding fluid, a large number of tests have been taken in the application of the power ultrasonic vibration honing. The massive experimental study, separated from the work piece’s surface roughness, the work piece’s surface rubbed deterioration layer and the influence to the processing characteristic with different density of the new grinding fluid and so on, discussed the adaptability of the new grinding fluid in power ultrasonic vibration honing processing. The research has been indicated that although the new grinding fluid does not surpass the traditional working fluid, such as emulsion and liquor, in cooling performance, it has a better lubricating property and has the obvious superiority in the working accuracy and the oilstone’s length of life. Therefore the new self-developed grinding fluid is suitable for the power ultrasonic honing processing.

Abstract: Aiming at solving the problems of wheel loading in dry grinding of Carbon/Epoxy composite materials, a novel electroplated grinding wheel with controlled abrasive cluster was developed, in which the diameter of clusters is in Φ0.2 mm to Φ1.0 mm and the interspace between them is about 0.5 mm to 1.0 mm. A conventional electroplated grinding wheel with abrasive grains distributed randomly was fabricated in the same way. The comparison experiments involving C/E composite were conducted on a vertical spindle grinder with the novel and conventional grinding wheels. The results show that the grinding forces of novel wheel developed is more lower though little larger surface roughness, and the wheel loading phenomenon is markedly decreased compared with conventional electroplated wheel.

Abstract: Potassium dihydrogen phosphate (KDP) crystal is widely used in navigates spaceflight, national defenses, energy sources and information technology fields based on its excellent nonlinear optical property. Surface quality of KDP crystal influences the property and life time of the device directly. So detection and analysis of the damage induced during machining process, especially on subsurface, should be solved. In this paper, surface damage of the KDP crystal, which machined from #600 grinding wheel with different feed rate, was detected by optical microscope. Cross section and selective etching were used to analyzing the subsurface damage. Because #600 grinding wheel mainly used in coarse grinding and the removal rate is high, the results shown that there was obvious scratch, crack and crushing on the machining surface. When the feed rate is 10+m and 40+m, the subsurface damage depth is 7.41+m and 8.96+m corresponding. This study is a kind of guide for following precision grinding, polishing machining time and removal amount.

Abstract: On the basis of analysis and summary of the research of the others, we choose the notepad as the carrier of the data file and a code as the expression of the feature information of the products, embedding them in the 3D CAD system like a plug-in unit. In this way, the products’ data accurate transmission between distributed and isomeric CAD systems over the internet is realized. This method can also be used in the real-time collaborative design system.