Revista Migrações

Com este número da Revista Migrações retrata-se de forma aprofundada o papel do movimento associativo imigrante na construção de uma sociedade intercultural onde se aliam os dois objectivos definidos, à primeira vista, como opostos de preservação da identidade cultural de origem e integração na sociedade de acolhimento. A experiência acumulada pelo ACIDI neste domínio comprova a justeza do princípio trabalhar para os imigrantes, com os imigrantes. Esta co-responsabilidade na construção das sociedades democráticas onde todos somos participantes leva-nos a desejar um associativismo imigrante cada vez mais forte, contribuindo para quebrar a solidão daqueles que procuram, longe das suas comunidades de origem, um futuro melhor para si, em troca do trabalho que prestam para o desenvolvimento da comunidade que os acolhe.peerrewie

Effect of Laser Peening on Mechanical Properties of 6082 Aluminum Alloy

为研究激光冲击强化对6082铝合金性能的影响,利用波长为1064 nm、脉宽为15 ns、脉冲能量为08 J的Nd∶YAG激光器对6082铝合金进行工艺试验研究,采用表面粗糙度仪、显微硬度计、X射线应力分析仪和疲劳试验机分别对试件的表面粗糙度、显微硬度、残余应力和疲劳寿命进行测量。实验结果表明:激光能量为7 J,冲击4次时,在试件表面引入了坑穴和褶皱等微结构,使得表面形貌高低不平,粗糙度提高了2倍左右,使得表层材料发生塑性变形以及加工硬化,表面显微硬度提高了43%左右,最大残余压应力达-261 MPa,硬化层深度达700 mm左右,疲劳寿命提高了6.8倍左右,即激光冲击强化能够极大地改善60..

Experimental investigation of laser peening on Ti17 titanium alloy for rotor blade applications

Laser peening is an innovative surface treatment technique, and can significantly improve the mechanical performance of metallic components. To investigate the fatigue life of Ti17 titanium alloy by laser peening, laser peening experiment was undertaken using Nd:YAG laser system with the pulse-width of 15 ns and max pulse-energy of 7 J. Firstly, the mechanical properties and microstructure with different laser peening parameters were investigated, which were measured and observed by Vickers indenter, X-ray diffraction, scanning electron microscope and transmission electron microscope. Micro-hardness and compressive residual stress distribution was remarkably improved. High-density dislocations and fine-grains were observed in the surface layer. Then, several stress levels were chosen to be applied on the tension and compression fatigue specimens. The fatigue life and fracture mechanism of the specimens without- and with-laser peened were compared, and the strengthening mechanism was indicated by analyzing the effects on the microstructure and residual stress evolution. The results demonstrate that laser peening could effectively improve the fatigue life of Ti17 titanium alloy. (C) 2015 Elsevier B.V. All rights reserved

System and method for automatic control over laser shock peening

本发明涉及一种激光冲击强化自动化控制方法，包括以下步骤：根据加工要求在力学分析软件中建立零件的分析模型并得到残余应力分布；将残余应力分布导入CAE分析软件，自动生成作用在零件表面的加工运动轨迹；同时工控机根据激光冲击波压力与激光喷丸工艺参数之间的关系选择激光冲击波压力设定值对应的工艺参数；将加工运动轨迹和工艺参数导入力学分析软件进行仿真得到模拟加工后的应变值；如果应变值在设定范围内，则工控机将工艺参数发送至激光器，并将加工运动轨迹发送至机器人，实现激光的自动加工；本发明能够实现整体叶盘的激光冲击强化，实现残余应力定量的精确控制，有效的提高整体叶盘的使用寿命及抗异物损伤的能力

一种利用激光冲击强化技术在工件表面制备涂层的方法

本发明公开了一种利用激光冲击强化技术在工件表面制备涂层的方法，属于材料改性技术领域。该方法首先在激光冲击强化过程中用的吸收层材料上均匀涂敷涂层粉末；将涂敷涂层粉末的吸收层材料贴敷在待喷涂工件上，采用脉冲纳秒Nd:YAG激光器对吸收层进行激光冲击强化处理，激光经过光束整形后输出，将吸收层表面的涂层粉末冲击嵌入工件表面，从而在工件表面制备所需要涂层；该方法制备的涂层均匀，与基材结合强度高，不受工件形状的限制，适用于在形状复杂工件表面制备涂层

Study of Laser Peening on TiAl Alloy Properties with Different Parameters

Laser peening is a novel surface treatment process that generates deep compressive residual stresses and microstructural changes and thereby dramatically improves fatigue strength of critical metal aircraft engine parts. In order to study the effects of laser peening on properties of TiAl alloy, Surface micro-hardness, microstructural, residual stress and pole figures before and after laser peening were tested. The experimental results showed that surface micro-hardness increased by 23%. The compressive residual stress increased 20 times. The texture in the normal direction of 8J peened sample showed a strong fiber texture components 10o away. In conclusion, the laser peening could improve properties of TiAl alloy

Laser shock life-prolonging method of tungsten electrode of short-arc lamp

本发明公开了一种短弧灯钨电极的激光冲击延寿方法，利用去离子水将工件清洗后用干燥的氮气吹干，然后放入100℃的干燥箱中干燥10min；接着在钨电极工作端面覆盖吸收层吸收激光能量防止激光烁伤钨电极表面；接着将钨电极安装在工作台上并在吸收层上施加一层约束层约束激光冲击波增加冲击力；接着以脉宽为3-40ns、波长为532nm或1064nm、激光能量为0.5-20J、重复频率为0.1-10Hz、光束直径为0.5-10mm的激光束进行预冲击延寿处理和冲击延寿处理；接着去除钨电极工作端面涂覆的吸收层；最后利用去离子水清洗后用干燥的氮气吹干留作短弧灯组装。本发明延寿方法工艺简单，延寿效果显著、效率高、成本低、无污染

Investigation of technical and strengthening mechanism research of TiAl alloy by laser shock peening

主要研究航空常用材料TiAl合金激光冲击强化效果,当激光诱导产生的冲击波大于TiAl合金的动态屈服强度时,材料表面发生塑性变形,并引入大量的位错等晶体缺陷,从而达到表面强化的目的。通过调整激光冲击的次数和激光的能量等因素,得到不同工艺参数下TiAl合金的显微硬度和表面粗糙度。对其微观结构进行透射电镜观察,并与未进行冲击的试样进行对比分析,可以看出激光冲击强化可以有效地提高受冲击表面的位错密度,当位错运动受阻形成位错线的塞积,导致位错缠结;位错受到晶界的阻碍在晶界堆积,形成位错墙,位错墙与位错缠结最终导致亚晶界的形成,为后期晶粒细化做准备,通过分析激光冲击强化机制,揭示了位错密度是材料表面力学性能提高的本质</p

波纹管自动焊接系统的研制

针对波纹管手工焊焊接过程中人工劳动强度高、生产效率低、废品率高的问题，研制了基于激光测量技术的波纹管自动焊接系统，上位机通过激光轮廓仪获得波纹管焊缝的径向坐标点，运动控制系统根据坐标点控制二维平台及回转平台运动。对焊缝跟踪精度和焊接质量进行了试验分析，结果表明，研制的波纹管自动焊接系统稳定可靠，焊枪跟踪焊缝径向的平均误差小于0.02mm，焊缝接头外观美观、强度高、组织优化，满足波纹管自动化焊的要求

铝合金电子束焊接性能及缺陷分析

为了研究铝合金焊接力学性能及焊接缺陷，采用THDW-6 真空电子束焊机对6061 铝合金试样进行焊接试验研究，采用工作距离110mm、工作电用70kV、电子束流40mA、聚焦电流638mA、焊接速度540mm/min进行穿透焊，接头的抗拉强度为母材的92% ，接头的显微硬度有明显的软化，约为母材的79%。并对焊接中常产生的塌陷和顶尖缺陷、裂纹与气孔缺陷、飞溅缺陷进行了分析，提出了铝合金真空电子束焊接时相应的工艺措施，可以获得良好的焊缝形貌和力学性能