Key Engineering Materials Vol. 621

Abstract: Cryogenic MQL is a kind of green machining technology of the combination of cryogenic air and minimal quantity lubrication (MQL). The aim of this research is to determine if the cryogenic MQL technique in turning with Cutting tool with internal cooling structure gives some advantages in terms of tool life, surface roughness and cutting chip breaking. This paper reports the results obtained from turning tests, at one feed rates (0.12mm/r) and one depth of cut (0.4mm) and different cutting speeds (43m/min, 108m/min, 217m/min), and the results obtained show that using cryogenic MQL had some advantages in terms of tool wear, surface roughness and cutting chip breaking compared to using dry cutting and cryogenic air cutting. And the results obtained show that when cryogenic MQL and cryogenic air cutting were applied to high speed cutting, they had more advantages.

Abstract: The finite element model of heavy-duty machine tool’s ram components has a large number of elements, many contact pairs for assembly and a large-scale optimization calculation, which make the optimization difficult to conduct. To solve this problem, a static stiffness optimization method of the large component based on the equivalent elastic modulus is put forward. The proposed method is applied to super-heavy-duty CNC floor-type milling and boring machine of TK6932 as a case study. Based on the principle of the equivalent stiffness, the ram assembly with complex constraints and contacts is equivalent to a ram part without other components, the calculation method of the equivalent elastic modulus is analyzed and the equivalent elastic modulus formula of the ram under the bending load is derived. Taking the four box-walls’ thickness and the three stiffened-plates’ thickness of the ram as the optimization variables, the minimal volume under static loading as the target and the maximal displacement and stress as the constraints, the optimized mathematical model of the ram’s equivalent static stiffness is established. The results of the optimization are rounded according to the sensitivity analysis. Besides, the optimization effect is proved by simulation through the finite element technology. The optimization procedure and results show that the simplified method based on equivalent elastic modulus presented in the paper can control the calculation scale effectively, and ensure the process of the optimization smooth.

Abstract: Laser impact welding (LIW) is a novel welding technique which uses laser induced shock waves to obtain the solid-state and metallurgical bonding between flyer and base plates, and can be applied in welding of dissimilar metal plates in micron level. In this paper, experimental study is conducted with titanium as the flyer plate and aluminum as the base plate under different laser energies and laser spot diameters. Besides, the microstructure and mechanical properties of the welding joints are also investigated. The wavy interface is observed by metallographic investigation which is similar to explosive welding and electromagnetic pulse welding. Moreover, the micro-hardness taken from the interface region shows an obvious improvement compared with the base metal. It is also found that laser shock welding results in fine grained structure of titanium on the weld interface. In conclusion, laser shock welding can not only improve the material microstructure of weld interface, but also avoid the heat affected zone and formation of intermetallic phase during dissimilar metal welding. Therefore, it is a promising welding technology in the field of MEMS.

Abstract: Laser shock micro-adjustment is a precise and noncontact adjustment technique using laser-shock-waves to adjust the curvature of micro-components. The experimental studies have indicated that: when laser shock region is located at the free end of cantilevers, multiple impacts are applied to achieve a large bending degree; meanwhile, different bending directions can be obtained with multiple impacts in the junction position. Efforts should been made to understand the mechanisms of multiple laser shock micro-adjustment. Two mechanisms have been proposed for describing the laser shock micro-adjustment in different laser shock regions, namely shock inertia mechanism and material flow mechanism. The proposed micro-adjustment mechanisms can predict bending angles and directions. To validate the proposed micro-adjustment mechanisms, numerical simulations were carried out based on the FEM method using the ANSYS/LS-DYNA software and the corresponding results demonstrate the proposed mechanisms.

Abstract: Molecular dynamics simulations method is used on the study of material deformation in monocrystal silicon during nanomachining. Both nanoindentation and nanocutting by a diamond tool tip is investigated using LAMMPS. Characterization methods such as coordination number and labeling atoms in different layers have been adopted to study the law of transformation. As the surface atoms are tracked, their transformation law is analyzed and the formation mechanism of the cuttings and finished surface is announced. The impact crystal orientation of silicon on the machining is also studied.

Abstract: The optical detection of the crosslinking degree is very important to the forming quality’s on-line control of the hydrogel fibers and tissue engineering scaffolds in 3D printing process at room temperature. For the feature of small scale object, low contrast ratio and unclear outline of the crosslinked area, we processed the crosslinking image with the dual-threshold enhancement method. Firstly, the color image is decomposed into three two–dimensional RGB signals. Secondly, the RGB signals are processed through wavelet transform respectively, and those wavelet coefficients are amplified or reduced with dual-threshold method for the purpose of enhancement and denoising. Then, the new RGB signals are reconstructed by those wavelet coefficients. At last, the new RGB signals are regrouped to get enhanced crosslinking image. Experimental results show that, after processed with this method, the image has a strong sense of color gradation, the details of image are outstanding, and the distinction of the crosslinked zone of the hydrogel fiber is obvious. Moreover, measurement precision of crosslinking degree is improved by 4.58%. This is helpful to improve the performance of the real-time control of crosslinking process.

Abstract: Integration of approximate model and clonal selection algorithm (CSA) is considered as an effective way to solve complicated optimization design problems in engineering field. The principles of approximate model and of clonal selection algorithm were presented in this paper. A variotherm temperature injection mold used to produce a large-size liquid crystal display (LCD) TV panel was demonstrated and an approximate model for optimizing the layout of heating channels of the mold was established. The clonal selection algorithm program was coded according to its principle in order to solve the established approximate model. The layout of the heating channels was optimized and the optimal solutions were obtained. Finite element simulation and industrial injection production indicated that the integration of the approximate model and clone selection algorithm used in this paper to optimize the layout of the heating channels for the injection mold was very effective.

Abstract: The affecting factor of thread precision was found out through the analysis of the formation of dimension chain when thread hob (cutlery) of double-roller machine rolls thread by axial feed, methods and measures of settlement was presented, which improve the precision of rolling thread, the grade of product and economic benefit of enterprise.

Abstract: Inertial Confinement Fusion (ICF) is an effective method to alleviate the energy crisis . As the key segment in the construction process of laser fusion device, mechanical tiling technology has played an important role in the field of laser pulse compression and final optics assembly. For this reason, grating tiling and off-axis parabolic mirror tiling are discussed primarily in this paper. The primary principle of tiled-grating assembly design is elucidated briefly, the movement adjustment process of 1¡Á3 type tiled-grating and the driving process of 5PTSP-PPS serial-parallel tiling mechanism are reviewed. By analyzing the adjustment method of primary mirror in E-ELT, ideas to realize tiling off-axis parabolic mirror are proposed. Finally, some suggestions for further study on mechanical tiling technology are commented.