Temperature field simulation of laser-TIG hybrid welding

The three dimensional transient temperature distribution of laser TIG hybrid welding was analyzed and simulated numerically. Calculations were based on a finite element model, in which the physical process of hybrid welding was studied and the coupling effect of the laser and arc in the hybrid process was fully considered. The temperature fields and weld cross sections of the typical welding parameters are obtained using present model. The calculation results show that the model can indicate the relationship of energy match between laser and arc to joints cross sections objectively, and the simulation results are well agreed with the experimental results.

Droplet-targeting laser hybrid indirect arc for additive manufacturing technology-A preliminary study

The contradiction between manufacturing accuracy and manufacturing efficiency is discussed in this paper.In order to solve this problem,a novel droplet-targeting laser hybrid indirect arc for additive manufacturing technology is proposed in which a couple of wires are melted using the alternating current with interwire indirect arc to achieve high deposition rate.On the other hand,droplets actively target the laser beam and detach from wire tip under the recoil pressure subjected to pulsed laser irradiating at desired position and with controlled mass for a precise bead forming.The process of alternative droplet growing at desired position are mathematically analyzed and then preliminary verified by experiment.By precisely controlling the wire feed speed and current frequency,the melting process at desired position and mass of wire is successfully obtained which is the fundamental for next-step for the droplet actively targeting laser.

Effect of Fe content on microstructure and mechanical properties of Cu-Fe-based composite coatings by laser induction hybrid rapid cladding

To select the proper composition and obtain an overall material?microstructure?property relationship for Cu?Fe alloy, theeffect of Fe content on microstructure and properties of Cu?Fe-based composite coatings by laser induction hybrid rapid claddingwas investigated. Microstructure characterization of the composite coatings was tested utilizing SEM, XRD and EDS. Microhardnessmeasurement was executed to evaluate the mechanical properties of the composite coatings. The results show that for low Fe content,the composite coating presents a feature that Fe-rich equiaxed dendrites are embedded in the Cu-rich matrix. With increasing Fecontent, the Fe-rich particles are dispersed in the Cu-rich matrix. With further increasing Fe content, large amounts of Cu-richparticles are homogeneously dispersed in the interdendrite of the Fe-rich matrix. Correspondingly, the average microhardness of thecomposite coatings increases gradually with the increase of Fe content and the microhardness of Cu14.5Fe83Si2C0.5 coating is muchtwice higher than that of the substrate.

Three thermal analysis models for laser, GMAW-P and Iaser＋GMAW-P hybrid welding

The temperature fields and the weld pool geometries for laser ＋ GMAW-P hybrid welding, laser welding and pulsed gas metal arc welding （GMAW-P） are numerically simulated in quasi-steady state by using the developed heat source models, respectively. The calculated weld cross-sectious of the three types of welding processes agree well with their respective measured results. Through comparison, it is found that the temperature distribution of laser＋GMAW-P hybrid welding possesses the advantages of those in both laser and GMAW-P welding processes so that the improvement of welding productivity and weld quality are ensured.

Low fabrication cost wavelength tunable WG-FP hybrid-cavity laser working over 1.7μm

A wide wavelength tuning range and single-mode hybrid cavity laser consists of a square Whispering-Gallery(WG)microcavity and a Fabry–Pérot(FP)was introduced and demonstrated.A wavelength tuning range over 12.5 nm from 1760.87 to 1773.39 nm which was single-mode emitting was obtained with the side-mode suppression ratio over 30 dB.The hybrid cavity laser does not need grating etching and special epitaxial structure,which reduces the fabrication difficulty and cost,and shows the potential for gas sensing with absorption lines in this range.

Low-power YAG laser/arc hybrid welding of AZ-based Mg alloy

The results of recent researches on the weldability of laser/arc hybrid welding of AZ-based Mg alloy was presented.Experiments were conducted with a low-power(500 W) Nd:YAG laser and a TIG arc.The synergic effects and mechanical properties of the Mg joints by laser/arc hybrid welding were investigated,and the interaction mechanism of laser to arc was also discussed.The results show that Mg alloys can be easily welded in similar and dissimilar joints by laser/arc hybrid welding technique.With the arc power increasing,a higher weld depth is obtained,and the weld depths for laser and arc acting in combination(laser/arc) are two times higher than that of the total of laser and arc acting separately(laser+arc) in optimal conditions.The tensile strength and fatigue strength of the AZ31B joints welded by laser/arc hybrid process are equivalent to that of the based metal.Besides,the laser-induced plume/plasma images captured by high speed camera were used to study the interaction between laser beam and arc.

Hybrid Laser Technology for Creation of Doped Biomedical Layers

Hybrid laser technologies for deposition of thin films and basic schemes of combination of pulsed laser deposition (PLD) with magnetron sputtering and RF discharges or two lasers or three laser deposition systems are presented. Experiences with deposition of chromium doped diamond-like carbon (DLC) films for coating of prostheses are described. Layers of different chromium concentrations were prepared using hybrid systems (PLD + magnetron sputtering or by double PLD). Results of physical and mechanical characterization of film properties and biomedical tests of trivalent and toxic hexavalent chromium are given. Experiences with double laser deposition of DLC layers doped with silver are also mentioned.

Low temperature impact toughness of laser hybrid welded joint of high strength low alloy steel

High strength low alloy steel with 16 mm thickness was welded by using high power laser hybrid welding. Microstrueture was characterized by using optical microscopy, scanning electron microscopy （ SEM ） , transmission electron microscopy （TEM） and selected area electron diffraction （SAED）. Low temperature impact toughness was estimated by using Charpy V-notch impact samples selected from the upper part and the lower part at the same heterogeneous joint. Results show that the low temperature impact absorbed energies of weld metal are （202,180,165 J） of upper samples and （178,145,160 J） of lower samples, respectively. All of them increase compared to base metal. The embrittlement of HAZ does not occur. Weld metal primarily consists of refined carbide free bainite and a little granular bainite since laser hybrid welding owns the character of low heat input. Retained austenite constituent film ＂locates among the lath structure of bainitie ferrite. Refined bainitic ferrite lath and retained austenite constituent film provide better low temperature impact toughness compared to base metal.

All-fiber laser seeded femtosecond Yb:KGW solid state regenerative amplifier

A high efficiency compact Yb:KGW regenerative amplifier using an all-fiber laser seed source was comprehensively studied.With thermal lensing effect compensated by the cavity design,the compressed pulses with energy of 1 mJ at 1 kHz and 0.4 mJ at 10 kHz in sub-400-fs pulse duration using chirped fiber Bragg grating(CFBG)stretcher were demonstrated.A modified Frantz-Nodvik equation was developed to emulate the dynamic behavior of the regenerative amplifier.The simulation results were in good agreement with the experiment.Numerical simulations and experimental results show that the scheme can be scalable to higher energy of multi-mJ,sub-300 fs pulses.

红外折/衍混杂f-theta镜研究

根据现代红外激光扫描系统的需求,分别设计了工作于808nm～1064nm波段和1064nm～1500nm波段的折/衍混杂f-theta系统。系统分别由三片镜和四片镜组成,激光扫描范围分别为100mm×100mm和60mm×60mm。此二系统相配合,可以完成在808nm～1500nm波长范围的激光扫描工作。点列图分析表明,输出光斑质量优良均匀,在0视场、0.7视场、和全视场光斑均接近衍射极限。像差分析表明,系统最大色差为26μm,最大场曲小于0.3mm,最大f-theta误差小于0.03%。满足现代多工作波长、高精度激光打标机的实际需求。

基于激光结构光的管道激光/电弧复合焊焊道跟踪与能量控制系统

利用650 nm激光结构光发射器与CM0S光电传感器结合获取焊道图像信息,应用数字图像处理技术提取纵向偏差、横向偏差、错边量和对口间隙信息,激光结构光焊道跟踪系统跟据纵向偏差、横向偏差实时调整焊炬位置,保证激光焊点准确对中。能量控制系统依据错边量和对口间隙信息实时调节激光输出功率,提高了管道激光/电弧复合焊对错边量和对口间隙的适应范围,为其工程应用打下了技术基础。

基于Labview的脉冲激光-电弧复合焊接相位匹配触发控制系统

介绍了基于NI Labview开发的脉冲激光-电弧复合焊接相位匹配触发控制系统.应用NI PCI6221数据采集卡对交流电弧信号进行采集,通过上位机对数据进行实时处理并捕获电弧特征点,从而精确识别电弧相位,实现在特定电弧相位对单脉冲激光的连续触发.提出了加锁触发思想,消除了激光的误触发,并实现了脉冲激光与电弧间的倍频关系及激光器的触发频率保护功能.结果表明,该系统实现了电弧特定相位与激光脉冲的精确触发控制,为脉冲激光与交流电弧能量的柔性复合以及两种热源相互作用机理研究提供了技术支持.

计算机存贮技术发展趋势及其展望

依据存储技术领域目前的国内外进展 ,讨论了促进存储技术与设备发展的几个主要因素 ,评述了存储技术与设备的研发现状与发展趋势 ,并展望了存储技术未来的发展趋势。

空间近距离非合作目标的光学主被动复合探测

以天基空间目标探测研究为背景,提出了一种空间近距离非合作目标的光学主被动复合探测系统。该系统由扫描和凝视两套被动成像子系统和一套主动激光雷达子系统组成。两套成像子系统的配合能实现大范围搜索,高精度定向及目标的识别、跟踪,克服了以往空间探测器在设计中存在的大视场与高分辨率的矛盾。激光雷达子系统具有对目标精确测距、测速的能力,再配合被动成像子系统给出的目标方位信息,使整套系统可对空间目标进行球坐标定位,计算其轨道参数。在假定条件下进行了系统设计举例,分析了设计中的各个关键技术,给出了系统相应的关键设计参数。为星载光学探测系统设计提供了一种新思路、新途径。

高精度激光跟踪系统的综合设计

1.前言 激光跟踪系统是航空航天工程中的重要设备之一。要想建造高精度激光跟踪系统,除了提高有关部件的精度之外,系统的综合设计是一个关键步骤。对于这类系统的综合设计,目前都采用全连续或全离散控制方案,而且不考虑对象未建模动态和子系统间的耦合问题。

Hybrid laser/arc welding of thick high-strength steel in different configurations

In this investigation, hybrid laser/arc welding （HLAW） was employed to join 8-mm-thick high-strength quenched and tempered steel （HSQTS） plates in the butt- and T-joint configurations. The influences of welding parame- ters, such as laser power, welding speed, stand-off distance （SD） between the arc of gas metal arc welding, and the laser heat source on the weld quality and mechanical properties of joints, were studied to obtain non-porous and crack-free fully-penetrated welds. The weld microstructure, cross- section, and mechanical properties were evaluated by an optical microscope, and microhardness and tensile tests. In addition, a finite element model was developed to investigate the thermal history and molten pool geometry of the HLAW process to join the HSQTS. The numerical study demon- strated that the SD had a paramount role in good synergy between the heat sources and the stability of the keyhole. For the butt-joint configuration, the results showed that, at a higher welding speed （35 mm/s） and optimum SD between the arc and laser, a fully-penetrated sound weld could be achieved. A non-porous weld in the T-joint configuration was obtained at a lower welding speed （10 mm/s）. Microstructural evaluations indicated that the formation of residual austenite and the continuous network of martensitic structure along the grain boundary through the heat affected zone were the primary reasons of the softening behavior of this area. This was confirmed by the sharp hardness reduction and failure behavior of the tensile coupons in this area.

Relative intensity noise in high-speed hybrid square-rectangular lasers

Relative intensity noise(RIN) and high-speed modulation characteristics are investigated for an Al Ga In As/In P hybrid square-rectangular laser(HSRL) with square side length, rectangular length, and width of 15,300, and 2 μm, respectively. Single-mode operation with side-mode suppression larger than 40 dB has been realized for the HSRL over wide variation of the injection currents. In addition, the HSRL exhibits a 3 dB modulation bandwidth of 15.5 GHz, and an RIN nearly approaches standard quantum shot-noise limit 2 hv∕P=-164 dB∕Hz at high bias currents due to the strong mode selection of the square microcavity. With the increase of the DC bias current of the Fabry–Perot section, significantly enhanced modulation bandwidth and decreased RIN are observed.Furthermore, intrinsic parameters such as resonance frequency, damping factor, and modified Schawlow–Townes linewidth are extracted from the noise spectra.

Investigation of hybrid microring lasers adhesively bonded on silicon wafer

Thermal characteristics are numerically investigated for the hybrid AlGaInAs/InP on silicon microring lasers with different ring radii and widths. Low threshold current and low active region temperature rise are expected for a microring laser with a narrow ring width. Based on the thermal analysis and the 3D simulation for mode characteristics, a hybrid AlGaInAs/InP on silicon microring lasers with an inner n-electrode laterally confined by the p-electrode metallic layer is fabricated using an adhesive bonding technique. A threshold current of 4 mA is achieved for a hybrid microring laser with a radius of 20 μm and a ring width of 3.5 μm at 12°C, and the corresponding threshold current density is as low as 1 kA∕cm^2. The influence of the location of silicon waveguide on output performance is studied experimentally for improving the output coupling efficiency. Furthermore,continuous-wave electrically injected lasing up to 55°C is realized for a hybrid microring laser with a radiusof 30 μm and a ring width of 3 μm.

基于XeF(C-A)放大器的混合(固态/气态)超高功率飞秒激光系统(英文)

提出了基于前端发生器和终端放大器,使用光泵浦XeF（C-A）激活介质的太瓦级混合激光器（THL-100）系统。前端发生器由长532 nm的连续激光泵浦的钛宝石飞秒脉冲振荡器,脉冲展宽机构,532 nm的脉冲激光泵浦的再生多通道放大器,衍射光栅压缩器和二次谐波发生器（KDP）组成。其光束输出参数为：脉冲持续时间50 fs,二次谐波（475 nm）辐射能量5 mJ。前端发生器以10 Hz的单脉冲模式工作。XeF（C-A）放大器由双高压脉冲发生器（线性变压器）,爆炸式阴极发射真空二极管,电子束注入系统,充满Xe的气室转换器和激光单元组成。高压发生器包括12个变压器,每个变压器有8个电容（40 nF）和火花隙,电容可以充电至100 kV。真空二极管中的电子束参数为：总电流300 kA,峰值电压550kV,脉冲持续时间约150 ns。穿透金属箔片到达Xe转换器的6个100 cm×12 cm电子束的总能量为67 kJ。激光系统通过泵浦能量的级联处理导致Xe2＊的快速形成,并在（172±5）nm连续辐射。真空紫外辐射通过CaF2窗口辐射到含有XeF2蒸汽和氮气缓冲气体的激光单元中,使XeF2光解,形成XeF＊准分子。由真空紫外辐射泵浦的放大器激活介质长110 cm,直径为24 cm。文中通过数值模拟给出了输出参数和第一实验结果,根据XeF（C-A）放大器参数模型和增益测量结果,得到的输出能量高达23 J,这意味着50 fs脉冲的峰值功率高达4060 TW。

A novel hybrid Ⅲ–Ⅴ/silicon deformed micro-disk single-mode laser

A novel hybrid III-V/silicon deformed micro-disk single-mode laser connecting to a Si output wave- guide is designed, and fabricated through BCB bonding technology and standard i-line photolithography. Com- pared to a traditional circular micro-disk in multi-longitudinal-mode operation, unidirectional emission and single longitudinal-mode output from a Si waveguide are realized. In the experiments, an output power of 0.31 mW and a side-mode suppression ratio of 27 dB in the continuous-wave regime are obtained.