激光表面硬化处理活塞环槽

320、230活塞材料为QT600-3,球化级别为≤3级,石墨大小级别为5～7级.原是为燃烧轻油设计的,由于轻油燃烧较充分,活塞使用寿命可达到我厂的设计要求.但在燃烧重油时,由于重油燃烧不充分,积碳较多,且重油含硫较多,有酸性腐蚀,造成活塞环槽磨损过快.在对上述磨损形式、环槽结构、工况进行分析后,决定采用激光表面硬化处理活塞环槽表面.     

激光加工机主光路调光方法探讨

JHM-1XY-500B多功能激光加工机的YAG激光器发出的激光束因光电转换效率只有3%左右,大量的电能都转换成热能.所以,主光路调光尤为重要,激光束与He-Ne管激光指示红光同轴性越好,激光输出功率越大.激光光斑越圆,能量分布越均匀,加工效果越好,能充分发挥激光加工优势.这就对激光器主光路调光方法有严格要求,掌握调光方法是保证激光加工的重要条件.     

多零件选区激光熔化成型效率的优化

对多零件选区激光熔化的成型效率进行了优化.首先,分析了多零件选区激光熔化成型过程的时间消耗,并以减少时间消耗为目标建立了3维零件在3维成型空间中的2.5维排料优化规则.然后,研究了2.5维自动排料,提出利用3维零件模型在2维平面区域的投影将2.5维排料转化为2维排料的简化方法和一种利用切片数据进行投影生成的算法.最后,为验证所述方法的有效性,以手术模板模型为例,在虚拟选区激光熔化系统VDemetal280上进行了优化实验.与优化前相比,优化后的成型次数从4次降为3次,在扫描速度为600 mm/s、切片层厚为0.035 mm、扫描间距为0.08mm的工艺参数下,总铺粉次数从3 892次降为2 231次,预计加工时间从约91 276 s降为69 918 s,时间消耗有明显减少.     

High laser damage threshold coatings and damage testing technology

1Introduction Thelaser induceddamagethreshold(LIDT)ofopticalcoatingsisalimitedfactorfordevelop mentofahighpeakpowerlaser.Theoutput fluencesthatcanbeattainedontheNationalIg nitionFacility(NIF)whichcontains192beam linesbuiltbytheUniteStatesareultimatlylim itedbyopticalcoatingswithinthechain.These opticalcoatingsneedtosatisfythefluencere quest,22J/cm2forreflectivemirrorsand11J/cm2forpolarizers(1064nm,3nspulselength).Becausethedamagemechanismofthecoatings understronglaserirradiationisverycom…     

双波长线斑激光诱导荧光检测器的研制

采用正交型结构,研制了一种实用型高效液相色谱激光诱导荧光检测器(HPLC-LIFD),光源为532nm和405nm的线型光斑双波长半导体泵浦固体激光器.设计了一种用于LIFD的柱形石英荧光检测池,池体积为8μL.以罗丹明B和荧光素为样品评价体系的性能.罗丹明B的检出限为5.0×106g/L (S/N＞3),峰高RSD为5.1％;荧光素的检出限为8.0×10-6g/L(S/N＞3),峰高RSD为3.4％.测试结果表明该检测器达到设计要求,有良好的实用性.     

12CrNi3A凸轮轴渗碳激光强化复合处理工艺

对12CrNi3A凸轮轴渗碳激光强化复合处理进行了研究.研究结果表明,采取表面渗碳工艺增加表层的碳浓度,并通过采用合理有效的激光淬火处理工艺,获得理想的淬硬层分布,提高了表层的硬度,是开发和应用激光表面热处理术的一个新的尝试.     

Experimental investigation of laser-produced-plasma EUV source based on liquid target

1Introduction LPPsourcesholdgreatpromiseasbright sourcesofextreme ultraviolet(EUV)andsoft X rayradiationforapplicationssuchasprojec tionlithography[12],microscopy[3].However,withLPPsource,theapplicabilityisrestricted duetotheemissionsofdebris,whichmaydam agesensitivemetrologycomponentsclosetoLPP source.Toreducethedebris,methodsconcen tratingontwoaspectshavebeenappliedbefore theappearanceofgasandliquidtargets.Oneas pectistoreducetheamountofdebris,theother istointerdictthedebrisfromreaching…     

反可见、中红外、透10.6 μm高能激光分色镜的研制

介绍了利用离子辅助在ZnSe基底上沉积YbF3和ZnSe制作反可见、中红外、透10.6 μm高能激光分色镜的理论和工艺方法.采用红外优秀的镀膜材料YbF3替代传统的有放射性红外镀膜材料ThF4用于制作反可见、中红外、透10.6μm高能激光分色镜取得了较好的效果.同时所研制的分色镜在透射率、反射率,吸收等光学性质,应力硬度牢固度等力学性质,和抗高能激光损伤阈值等方面进行了一系列的测试,基本达到理想的指标.     

激光热处理与激光焊接

激光是一种在机械工业中应用前景十分广泛的新型热源.近年来,国外在零件热处理、焊接以及切割等各方面应用得很广,同时越来越显示出独特的优越性.目前,我国机械工业对激光热处理、激光焊接以及切割等方面也进行了大量的研究,并且开始推广应用,取得可喜的成果.本文就激光热处理、激光焊接在机械工业中的应用作一些介绍.     

双光束扫描激光电视系统设计

阐述了双光束扫描激光电视系统的设计,系统采用两束激光(每束都由红、绿、蓝三基色配比而成)通过一个扫描头同时扫描,扫描头的行偏转采用多面转镜、场偏转采用电流计偏转实现,与单束扫描方式相比较有如下优点:1.多面转镜的转速可降至1/2,提高了扫描装置的性能,同时降低了光学扫描系统制作难度;其转镜镜面尺寸和出射光束直径可以相应加大,扫描光斑在屏幕上聚焦更好,图像显示更清晰;2.两组调制器同时工作,屏幕水平分辨率可提高2倍;3.在相同的屏幕亮度下,单点功率密度相应降低,提高了安全性。     

热释电系数自动测试系统的研究

介绍了铁电薄膜材料热释电系数的测量原理和电路,着重设计了PA级前置放大电路,并对PLT铁电薄膜样品进行了测试。     

稳定的窄带干涉滤光片

滤光片通带中心波长λ０ 的稳定性,是使用过程中最重要的性能参数。该文从薄膜材料的“微孔度”出发,实验筛选出两种“微孔度”最小的膜料,用以组成窄带干涉滤光片。研配一种新的完全中性的光学胶,它不与滤光片膜层发生任何化学反应。再辅以其它工艺措施,成功制作出高稳定度的滤光片。滤光片存放３ 年,其λ０ 未发生漂移。这些滤光片已用于激光测距等多种军事工程,它们的长期稳定性在战备环境中得到了进一步验证。此外,该文还提出了一种新的膜厚监控方法。     

基于单板加强筋的焊接夹具设计与仿真

针对充气柜单板加强筋焊接变形问题,设计了焊接专用夹具,并对焊接过程进行了热固耦合数值求解,得到了两种不同焊接顺序下,气体保护焊和激光焊两种焊接方式的温度场和变形。结果表明,两种方案的焊接变形相差不大,激光焊接能明显减小变形,最大可减小达67.09%。充气柜以其优良的性能适用于环境恶劣的场所,在工矿企业变电所广泛安装使用。     

Gap-free lap welding of zinc-coated steel using pulsed CO2 laser

CO₂ laser welding of zinc-coated steel sheets in the lap configuration has been a major research effort for the automotive industry for many years. The introduction of a gap between the sheets is one way of solving the zinc gas explosion problem. However, this requires sophisticated clamping devices and spacer materials. A homogeneous gap is therefore difficult to realise in high volume production. This paper describes a simple but useful approach for CO₂ laser welding of zinc-coated steel sheets in the lap configuration. By using a gated pulse mode, a seam welding process is developed that allows zinc-coated materials to be welded in a gap-free, overlap configuration. Laser seam welds in the lap configuration were produced in 0.7 mm-thick steel sheet with 7 μm zinc coating on both sides. A number of pulsed CO₂ laser welding parameters, including peak power, duty cycle, travel speed, pulse repetition rate, and pulse energy, were identified. Furthermore, the effects of pulsed CO₂ laser welding parameters on weldability were also investigated. The study shows that through the proper selection of welding parameters, it is possible to produce visually sound welds where porosity is still unavoidably formed. It was observed that decreasing the welding speed could reduce the porosity within the visually sound welds.     

片式微波组件激光软钎焊气密封装技术研究

文中对片式微波组件激光软钎焊气密封装工艺开展研究,优化了影响焊缝成形的焊接结构、热台温度、助焊剂、离焦量、激光功率、焊接速度等工艺参数,分析了激光软钎焊密封接头微观组织,测试了激光软钎焊密封组件的气密性。结果表明:激光软钎焊封盖过程是一个温度场不断变化的动态过程,因此激光功率和焊接速度两参数也应在一定范围内通过程序设计动态调节。钎料可完全填充壳体与盖板之间形成的间隙,钎料中无空洞和裂纹,钎料未溢流到壳体内部。钎料与镀Ni 层接触并润湿良好,在钎料与壳体和盖板界面未形成粗大脆性的金锡金属间化合物。接头上部钎料基本保持(Sn)+(Pb)共晶组织状态,接头下部镀Ni层与钎料之间形成薄且均匀连续的金属间化合物层AuSn和AuSn₂。采用优化后的工艺参数激光软钎焊密封的组件气密性满足机载有源天线阵面应用要求。     

薄壁不锈钢换热管与管板焊接工艺

不锈钢薄壁管与管板的焊接有其明显的特点，文中介绍了辅助给水除氧器管一管板自动TIG焊工艺。通过调整焊接参数和使用适当的钨极形状，从而控制熔池形状和焊缝成型，采用胀接方法定位，并使用工装，消除了管口与管板的间隙，解决了薄壁管与管板焊的难题，取得了满意的结果。     

脉冲激光溅射沉积技术的发展及其应用研究

薄膜材料已经在半导体材料、超导材料、生物材料等方面得到广泛应用.为了得到高质量的薄膜材料,脉冲激光溅射沉积(PLD)技术受到了广泛的关注.文中介绍了脉冲激光溅射沉积薄膜的基本原理及特点,分析了脉冲激光溅射沉积技术在制备高温超导膜、铁电薄膜、生物陶瓷薄膜等功能薄膜方面的应用研究.大量研究表明,脉冲激光溅射沉积是目前最好的...     

Three-temperature modeling of carrier-phonon interactions in thin GaAs film structures irradiated by picosecond pulse lasers

This article investigates numerically the carrier-phonon interactions in thin gallium arsenide (GaAs) film structures irradiated by subpicosecond laser pulses to figure out the role of several recombination processes on the energy transport during laser pulses and to examine the effects of laser fluences and pulses on non-equilibrium energy transfer characteristics in thin film structures. The self-consistent hydrodynamic equations derived from the Boltzmann transport equations are established for carriers and two different types of phonons, i.e., acoustic phonons and longitudinal optical (LO) phonons. From the results, it is found that the two-peak structure of carrier temperatures depends mainly on the pulse durations, laser fluences, and nonradiative recombination processes, two different phonons are in nonequilibrium state within such lagging times, and this lagging effect can be neglected for longer pulses. Finally, at the initial stage of laser irradiation, SRH recombination rates increases sufficiently because the abrupt increase in carrier number density no longer permits Auger recombination to be activated. For thin GaAs film structures, it is thus seen that Auger recombination is negligible even at high temperature during laser irradiation.     

Mechanical and microstructural investigation of dissimilar joints of Al-Cu and Cu-Al metals using nanosecond laser

Laser beam welding (LBW) has found wide applications in several fields, including electronics, aerospace, and automobile industries, owing to its inherent capabilities over existing welding techniques. Dissimilar laser welding is one of the challenging fabrication processes. However, joining of different materials poses challenging issues because material properties of each material interacts to give rise to hybrid system performance. In present study weld of Al-Cu and Cu-Al has been performed using Ytterbium pulsed fibre laser with a maximum laser power of 300 W. The scanning electron microscope (SEM), and energy dispersive x-ray spectroscopy (EDS) has been employed to investigate the microstructural and chemical composition of the welded joints. The EDS analysis showed the presence of possible intermetallic compounds (IMCs) like AlCu and Cu2Al in the fusion zone. The Al-Cu and Cu-Al welded joints had maximum shear strength of 295 N and 84 N, respectively. The results showed the efficacy of Al-Cu joints over Cu-Al joints. The study further demonstrated that the Al-Cu weld had a better microstructure with fewer pores and cracks than the Cu-Al welds by varying the laser powers.

     

低功率脉冲激光-电弧复合热源高效焊接过程中的“匙孔”行为研究

激光-电弧复合热源焊接技术由于具有焊接熔深大、效率高、质量好等优点而受到广泛关注。采用低功率脉冲激光-钨极惰性气体保护(Tungsten inert gas,TIG)焊电弧复合热源技术进行镁合金板材的焊接,研究激光脉冲作用消失之后的等离子体行为和激光"匙孔"行为。在上述试验结果的指导下优化工艺参数,对比研究采用单独激光焊、TIG电弧焊和复合热源焊这三种方法实现镁合金板材对接焊相同效果时焊接效率的差异。研究结果表明,激光"匙孔"和"匙孔"等离子体的形成是实现复合热源高效焊接的前提条件,恰当的工艺参数可以使得激光"匙孔"维持稳定的开口状态,这种状态提高了电弧的稳定性和能量密度,延长了镁等离子体的恢复时间,因此能够提高复合热源的焊接效率。达到相同焊接效果时复合热源的焊接效率分别达到单独激光焊接效率的7.14倍和单独TIG电弧焊接效率的4.29倍。