Papers by Keyword: KDP

Abstract: Method of processing water-soluble potassium dihydrogen phosphate (KDP, KH₂PO₄) crystal is presented in this article. Diamond wire cutting machine “RTS 440“ was used for cutting. Only one of cutting parameters – vertical feed rate of diamond wire – was varied during experiments. Other cutting parameters (speed and strain of wire, cutting method, cutting angle) were constant. Original kerosene cooling system was designed and produced. Results are presented as graphs of dependence of arithmetic average surface profile deviation Ra of KDP and cutting time on vertical feed rate. Optimal interval of feed rates was obtained.

Abstract: In order to improve the positioning resolution of the tool adapter on ultra-precision machine tool for KDP crystals, this paper presents a new piezo tool actuator. First, a new flexible membrane structure is designed after considering the characteristics of the machine tool for KDP crystals. Then, its detailed structural dimension is determined by finite element method. Finally, the piezo tool actuator is machined based on designs and its performance data is obtained by experiments. Experimental results indicate that its positioning resolution is superior to 0.5μm and its stroke reaches 4.7μm, which can meet the requirements of ultra-precision machine tool for KDP crystals.

Abstract: In order to find and repair surface damage on KDP crystal, an open computer numerical control(CNC) system has been developed. This paper introduces the hardware structure of the control system, explains the development of an open CNC system software, which has friendly human-machine interface (HMI) and can make the finding and repairing process efficiently and conveniently and also expounds the algorithm and related parameters for servo tuning. With the open CNC system, the process of finding surface damage is accomplished in 3 hours and clear images of crystal surface damage is taken by CCD. And also, with the help of the open CNC system, a 600µm-diameter, 25µm-depth Gaussian repair contour with low roughness is obtained. Experimental results prove that the open CNC system for finding and repairing surface damage on KDP crystal meets the requirement of efficient detection and ultra-precision machining.

Abstract: This paper investigates the mechanical properties of potassium dihydrogen phosphate (KDP) crystals with the aid of nanoindentation using a conical diamond indenter. It was found that when unloading is after the first pop-in, the common method of obtaining elastic modulus from the unloading curve of nanoindentation is no longer applicable, because the unloading is inelastic. The study revealed that the pop-in could be due to dislocation nucleation and propagation, and that the first pop-in occurs under a stress below that of the major dislocation burst. Hence, the macroscopic yielding point, which is usually regarded as the onset of plasticity of a material, is nanoscopically not a critical point of the first dislocation in KDP. The study found that the elastic modulus of KDP indenting on its (001) plane is 52.8±3.8GPa. The hardness of the material is 1.89±0.05GPa.

Abstract: The geometry structure, band structure and density of states of KH2PO4 (KDP) and NH4H2PO4 (ADP) single crystals were investigated by using density functional theory (DFT) method. Parameters including the phase velocity, electromechanical coupling factor and power flow angle (PFA) were calculated for KDP and ADP at X, Y, Z cuts, respectively. Our calculated data are in good agreement with the experimental results. Compared with quartz, KDP and ADP crystals are of lower phase velocities. Considering PFA, electromechanical coupling coefficients and phase velocity, it was concluded that the propagation direction of 60 of X-cut and Y-cut possess superior SAW performance for both KDP and ADP crystals.

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: In order to machine high accuracy Potassium Dihydrogen Phosphate (KDP) crystal part, the indentation experiments are carried out with various loads and various orientation angles. The experimental results show that the critical condition of brittle-ductile transition of KDP has strong anisotropy. Therefore, the influence factors on the surface quality of crystal KDP was discussed, it is shown that influences of the tool's geometry parameter, feed rate and Nominal depth of cut etc on the surface quality of KDP are main. Afterwards the cutting experimental study on crystal KDP material is carried out. The experimental results show that the super-smooth surface quality only can be obtained while KDP is ultra-precision machined in ductile mode.