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991.
Hongyang Wang Baoqiang Feng Gang Song Liming Liu 《Materials and Manufacturing Processes》2018,33(7):735-742
The laser–tungsten inert gas hybrid welding method was adopted to realize the welding process between Q460 high-strength steel and 6061 aluminum alloy. The influence of the dual heat source on the mechanical properties and microstructure of the welded joints are discussed. In addition, the effects of including a copper–zinc interlayer on the microstructure, elemental distribution, and mechanical properties of welded joints are also studied. The results show that the mechanical properties of the welded joints are influenced by the relative heat inputs of the two heat sources and the Cu-Zn interlayer. The braze welded joint fabricated without a Cu-Zn interlayer fractured at an Al-Fe intermetallic compound (IMC) layer formed at the interface, whereas the braze welded joint fabricated with a Cu-Zn interlayer fractured at an Al-Cu IMC layer formed at the interface. Comparisons show that the maximum tensile shear load of the brazed welded joint with the Cu-Zn interlayer was increased by about 20% relative to that formed without the interlayer. The formation of Al-Fe IMC layer in the deep penetration joint was inhibited by the combined effect of the dual heating sources and the Cu-Zn interlayer. 相似文献
992.
Antony Jan Benjamin A. Reeves Yoeri van de Burgt Garrett J. Hayes Bruce M. Clemens 《Advanced Engineering Materials》2018,20(1)
993.
Study of DNA Origami Dimerization and Dimer Dissociation Dynamics and of the Factors that Limit Dimerization 下载免费PDF全文
Miran Liber Toma E. Tomov Roman Tsukanov Yaron Berger Mary Popov Dinesh C. Khara Eyal Nir 《Small (Weinheim an der Bergstrasse, Germany)》2018,14(23)
Organizing DNA origami building blocks into higher order structures is essential for fabrication of large structurally and functionally diverse devices and molecular machines. Unfortunately, the yields of origami building block attachment reactions are typically not sufficient to allow programed assembly of DNA devices made from more than a few origami building blocks. To investigate possible reasons for these low yields, a detailed single‐molecule fluorescence study of the dynamics of rectangular origami dimerization and origami dimer dissociation reactions is conducted. Reactions kinetics and yields are investigated at different origami and ion concentrations, for different ion types, for different lengths of bridging strands, and for the “sticky end” and “weaving welding” attachment techniques. Dimerization yields are never higher than 86%, which is typical for such systems. Analysis of the dynamic data shows that the low yield cannot be explained by thermodynamic instability or structural imperfections of the origami constructs. Atomic force microscopy and gel electrophoresis evidence reveal self‐dimerization of the origami monomers, likely via blunt‐end interactions made possible by the presence of bridging strands. It is suggested that this mechanism is the major factor that inhibits correct dimerization and means to overcome it are discussed. 相似文献
994.
Asymmetrical Micro‐Supercapacitors: Laser‐Assisted Large‐Scale Fabrication of All‐Solid‐State Asymmetrical Micro‐Supercapacitor Array (Small 37/2018) 下载免费PDF全文
995.
Laser‐Assisted Large‐Scale Fabrication of All‐Solid‐State Asymmetrical Micro‐Supercapacitor Array 下载免费PDF全文
Jian Gao Changxiang Shao Shengxian Shao Feng Wan Chang Gao Yang Zhao Lan Jiang Liangti Qu 《Small (Weinheim an der Bergstrasse, Germany)》2018,14(37)
The micro‐supercapacitors are of great value for portable, flexible, and integrated electronic equipments. Here, the large‐scale and integrated asymmetrical micro‐supercapacitor (AMSC) array is fabricated in virtue of the laser direct writing and electrodeposition technology. The AMSC shows the ideal flexibility, high areal specific capacitance (21.8 mF cm?2), and good rate capability. Moreover, its energy density reaches 12.16 µW h cm?2, outperforming most micro‐supercapacitors reported previously. Meanwhile, large‐scale series‐connected AMSCs are integrated on the flexible substrates (e.g., indium tin oxide‐polyethylene terephthalate film), which can power a veriety of the commercial electronics. The combination of AMSCs array, solar cell, and electronic device proves the feasibility for practical application in the portable, flexible, and integrated electronic equipments. 相似文献
996.
激光具有加工重复性好、能量精确控制及加工精度高等优点,其加工对象的尺寸可以达到微米甚至是亚微米级,可实现三维空间结构高精度加工。激光因其具备上述优异的性能,被应用于材料加工。激光能量还被用来诱发物质向特定方向转印,此类技术也被称为激光前向转移技术。主要综述了激光前向转移技术的实现过程、原理及微观机制,着重介绍并分析了激光前向转印技术发展的历史及其应用现状,如金属Cu,Cr,Al等金属薄膜的转印、单壁碳纳米管转印键合、微纳米结构的加工、元件异质集成等。最后对激光前向转移技术的温度场仿真的研究现状进行了分析和总结,具体包括仿真的方法、模型的使用等。 相似文献
997.
998.
目的 研究火箭发动机关键部件过滤器壳体的改良加工方案,以替代传统的化学铣切、手工氩弧焊等工艺,提高产品尺寸精度和生产效率。方法 改良加工方案采用激光切割、激光焊接等技术,利用激光切割精度高、成形快的优点,实现镂空区域的一次成形,避免化铣周期长、易于产生飞边且打磨困难的问题;利用激光焊接热输入量低、焊接变形少的特点,使镂空状态下单边宽度3.5 mm的筋条焊接成为可能。结果 通过设置合理的工艺参数,可以有效保证产品尺寸精度并控制焊接变形,提高生产效率。结论 使用该工艺方法已成功制备了产品,并经过了发动机试车考核。 相似文献
999.
ABSTRACTWhile selective laser melting (SLM) offers design freedom of metal parts with much less material consumption, there exist several limitations, including high surface roughness, low-dimensional accuracy, and high tensile residual stresses. To make functional parts with high form accuracy and superior surface integrity, an as-SLM part needs finishing to remove the deposited surface material. The integration of machining and SLM creates a hybrid manufacturing route to overcome the inherited limitations of SLM. However, little study has been done to characterise surface integrity of an as-SLM part followed by machining (e.g. hybrid SLM-milling). In this paper, surface, integrity including surface roughness, microstructure, and microhardness, have been characterised for IN718 samples processed by the hybrid process. It has been found that microhardness varies with the scan direction and the use of coolant in the subsequent milling, and surface integrity can be significantly improved by the hybrid SLM-milling route. 相似文献
1000.
针对现有的机载激光雷达产品测试系统不能模拟特定信噪比,且系统使用复杂的问题,开发了基于USB总线的机载多脉冲激光雷达产品测试系统;测控软件可以设定信噪比、脉冲幅值、脉冲周期等参数,并根据静态测距和动态测距的实际需要,生成静态和动态模拟数据;另外,测试系统还能够采集外场数据,并在测控计算机上存储和分析;采集和生成的数据经过USB总线发送给基于FPGA+高速D/A转换器架构的数据转换器,再输出给激光雷达产品,保证了数据传输的高速性和灵活性;经过测试表明,信噪比在3~9的情况下,产生回波信号的距离误差控制在1%以内,信号幅值误差控制在0.5%以内;测试系统的各项指标都满足实际需要,为激光雷达产品调试提供了良好的模拟仿真平台。 相似文献