用Nd:YAG激光焊接殷钢薄板材料

用Nd:YAG脉冲激光作为焊接热源,对殷钢材料Invar36分别进行了平板单道焊接试验和对焊试验,分析了工艺参数(激光功率、焊接速度、脉冲宽度和离焦量)变化对焊缝的表面形貌、熔宽以及熔透性的影响.检测了0.85 mm厚的殷钢薄板对焊接头的硬度、成分以及拉伸强度.结果表明:激光功率和脉宽是影响焊缝熔深、熔宽和热影响区面积的主要因素;扫描速度对焊缝表面的鱼鳞状条纹间距影响尤为明显;离焦量主要影响焊缝的宽度和熔透性;合理匹配工艺参数能够实现0.85 mm厚度薄板的对焊,并且获得形貌良好的焊缝.焊缝的组织成分没有发生明显变化,拉伸强度和基体强度相当,显微硬度略低于基体硬度.     

毫秒激光金属打孔的解析和实验

研究了用毫秒脉宽的长脉冲激光单个脉冲打深孔的成形过程和打孔速率.首先,由切割法得到了1 ms脉宽的Nd:YAG高斯激光对厚铝板打孔时孔的形貌,激光能量为7.9和28.9 J时,对应的孔深分别为1.849和2.975 mm.根据实验建立了轴对称模型,通过热传导方程得到了固相温度的解析解.然后,假设物质一旦熔融就离开孔,由...     

Nd:YAG激光焊接殷钢薄板材料的工艺研究

利用Nd:YAG脉冲激光作为焊接热源,对殷钢材料Invar36分别进行了平板单道焊接试验和对焊试验,分析了工艺参数（激光功率、焊接速度、脉冲宽度和离焦量）变化对焊缝的表面形貌、熔宽以及熔透性的影响。对0.85mm厚度的殷钢薄板对焊接头的硬度和成分的变化以及拉伸强度进行了检测。结果表明：激光功率和脉宽是影响焊缝熔深、熔宽和热影响区大小的主要因素;扫描速度对焊缝表面的鱼鳞状条纹间距影响尤为明显;离焦量主要影响焊缝的宽度和熔透性;合理匹配工艺参数能够实现0.85mm厚度薄板对焊,并且获得形貌良好的焊缝。焊缝的组织成分没有发生明显变化,拉伸强度和基体的相当,显微硬度略低于基体硬度。     

使用长脉冲高能激光对石英玻璃打孔

为了实现玻璃上的高效快速打孔,研究了使用长脉冲激光在石英玻璃上打孔的方法.通过在玻璃表面镀制ZrO2,解决了石英玻璃对1 064 nm激光吸收弱的问题.使用脉宽为1 ms,波长为1 064 nm的Nd:YAG激光在石英玻璃上打出了深为1.55 mm的锥形孔.研究了激光打孔的能效比,结果显示,当激光的能量密度为6.8 k...     

基于遗传算法的激光打孔路径优化

针对目前激光打孔过程中存在的问题,采用遗传算法对激光打孔路径进行优化.建立了路径优化目标函数模型,对激光打孔路径优化总体设计,遗传算法的实现所需要的适应度函数、选择算子、交叉算子、变异算子等遗传操作进行了说明,并通过实例说明,采用遗传算法对激光打孔路径进行优化,可以显著地提高激光打孔加工效率.     

Ejection of molten material produced by pulsed electron and laser beams

Crater formation in electron and laser beam drilling is mainly due to molten material removal. In this process, there are two different modes of removal: ejection outside the target and transport of material which remains around the crater on the target surface. Measurement of these removal modes was carried out. The diameters of molten particles ejected from the targets were obtained. Characteristic particle diameters were determined for each material and each drilling condition. The volume of solidified material remaining around the crater was also obtained. From these results, the proportion of molten material ejected from the target was determined. Most of the molten material remained around the crater for iron and tungsten, but was ejected outside the target for aluminium and alumina ceramics.     

因瓦合金发展现状及应用前景

简要介绍典型的因瓦合金主要特点及应用,介绍膨胀合金的重要品种,传统的典型因瓦合金及应用,以及在新技术发展情况下,因瓦合金作为老材料的新应用发展。     

TA15钛合金深孔钻削试验研究

以难加工材料TA15钛合金为研究对象,采用正交试验设计方法,研究内排屑深孔钻削钻头断屑槽圆弧半径、机床主轴转速和进给量在钻削过程中对切屑形态的影响规律。试验表明:钻头断屑槽的圆弧半径是影响切屑形态的主要因素,机床主轴转速和进给量为次要因素;优化后的工艺参数选取断屑槽圆弧半径为0.8 mm,主轴转速为255 r/min,进给量为0.45 mm/r时,切削过程平稳,排屑顺畅。     

铝合金表面激光沉积Al0.8FeCoNiCrCux高熵合金组织与耐蚀性能

为增强5XXX系铝合金表面的耐蚀性能,利用脉冲激光沉积技术制备了Al0.8FeCoNiCrCux高熵合金(HEA)涂层。利用XRD,SEM和电化学工作站分析了Al0.8FeCoNiCrCux高熵合金的相结构、微观组织和耐腐蚀性能。结果表明随着Cu含量增加,合金的相结构由BCC1和BCC2相转变为BCC1,BCC2和FCC相;当=0时,Al0.8FeCoNiCrCux涂层沿晶间出现裂纹,x=0.25时,涂层裂纹消失,并且在晶间出现了浅色组织,随着x增加,浅色组织由点状分布转变为连续生长;Al0.8FeCoNiCrCux(x=0.25,0.5,0.75,1.0)高熵合金涂层耐蚀性随Cu增加而降低,Al0.8FeCoNiCrCu0.25的腐蚀电流密为7.94×10^-8 A/cm^2,仅为基材的0.17%,腐蚀形式为点蚀,当x增加至1时,腐蚀电流密度增至8.21×10^-7 A/cm^2,为基材的1.99%,腐蚀形式转变为晶间腐蚀,但仍优于基材。显然,当0.25≤x≤1时,采用Al0.8FeCoNiCrCux涂层可显著改善铝合金的耐腐蚀性能。同时,其具有的高熵效应可抑制涂层中由基材的稀释行为引起的金属间化合物形成,解决了传统涂层材料应用在铝合金表面易产生裂纹的问题。     

Numerical prediction of hole shape in energy beam drilling of metals

A procedure for the prediction of energy beam drilling in metals is described. This procedure is based on appropriate zoning of the region to be drilled and on the assumption that as metal is melted it is forced out of the hole by forces exerted by vaporizing metal. Calculations of drilling in several metals and alloys have been made for different conditions of pulse duration, power, and number of pulses. Data were obtained for mild steel, copper, aluminium, and molybdenum. The depths, diameters and shapes of the drilled holes predicted by the proposed procedure are in close agreement with experimental results. During drilling by multiple pulses there is normally a fixed time interval between pulses. Because of heat diffusion during this time, molten metal removal does not begin immediately at the start of the next pulse. The lag time, defined as the time required to initiate molten metal removal from the hole at the beginning of each pulse, can be predicted by the proposed method. When a hole is drilled by multiple pulses, the lag time increases as the hole becomes deeper.     

长脉冲激光与硅相互作用气化过程的数值模拟

为了研究毫秒量级脉宽激光与半导体材料的相互作用机理,建立了一维有限元模型,对长脉冲激光与硅相互作用的气化现象进行了数值模拟.在计算中,利用热焓法处理了固一液相变过程,并根据热流方程考虑了气化产生的能量损失.在人射激光功率密度相同的条件下,定量地描绘了不同脉宽激光辐照材料的温度分布,前表面的温度历史,以及气化速度和气化深...     

Parameter prediction in laser bending of aluminum alloy sheet

Based on the basic platform of BP neural networks, a BP network model is established to predict the bending angle in the laser bending process of an aluminum alloy sheet (1–2 mm in thickness) and to optimize laser bending parameters for bending control. The sample experimental data is used to train the BP network. The nonlinear regularities of sample data are fitted through the trained BP network; the predicted results include laser bending angles and parameters. Experimental results indicate that the prediction allowance is controlled less than 5%–8% and can provide a theoretical and experimental basis for industry purpose. __________ Translated from Optics and Precision Engineering, 2007, 15(6): 915–921 [译自: 光学精密工程     

TiNi形状记忆合金/钛合金异种材料激光焊

由于TiNi合金与钛合金的物理和化学性能差异较大,故其焊接性较差,焊缝区易形成大量的金属间化合物并产生裂纹。为实现上述材料的良好连接、提高接头性能,本文对采用激光焊连接0.2mm厚TiNi形状记忆合金和TC4钛合金异种材料进行了探索。分别采用直接对接焊和手工填丝焊的方法,研究了焊接接头的微观组织和力学性能。结果表明,直接对接焊时焊缝中心产生了纵向裂纹;手工填丝焊则通过合适的焊接工艺,改善了焊缝成形,避免了裂纹的产生。较优的焊接工艺参数为功率百分比18%、脉冲宽度3ms、脉冲频率3Hz;在界面区,Ni与TC4形成的过渡层宽度约为2μm,Ni与TiNi形成的过渡层宽度约为0.5μm。接头最大抗拉强度为332MPa,断裂位置发生在靠近TiNi侧的熔合线附近。     

飞秒激光进给速度对TiC陶瓷微孔加工的影响

采用螺旋打孔技术,在不同的激光进给速度下在TiC陶瓷上加工了微孔。用扫描电子显微镜分析了微孔形貌,利用能量色散谱仪研究了激光加工前后材料化学成分的变化,并结合X射线光电子能谱术(XPS)讨论了材料化学键的变化,探讨了利用飞秒激光加工TiC陶瓷过程中材料的去除机理。结果表明:所得到的微孔具有较好的形貌特征,孔边缘没有出现明显的微裂纹。微孔入口圆度达98%以上,入口直径略小于出口直径。激光进给速度对入口处孔边缘的微观形貌影响较大。进给速度较低时,激光切蚀区域出现平行的条纹状周期结构,随着进给速度的增加,表面以混沌的颗粒状结构为主。在较低或较高的进给速度下,重铸层都会出现更为剧烈的氧化现象,实验显示最佳的进给速率应在6.4μm/s左右。XPS分析显示材料的去除主要是通过多光子吸收,在加工过程中发生Ti-C键的断裂产生的Ti离子被氧化后会生成TiO2和Ti2O3。     

Numerical simulation of metal removal in laser drilling using symmetric smoothed particle hydrodynamics

A simple numerical model is proposed for predicting the penetration depth of metal laser drilling. A simplified 2D axisymmetric model for transient metal laser drilling is introduced. Strong-form of Symmetric Smoothed Particle Hydrodynamics (SSPH) method is used to harness its significant reduction in computational time. The 2D axisymmetric domain is discretized, then SSPH formulation is used to obtain shape functions. Collocation method is used to discretize governing and boundary conditions equations to construct the global stiffness matrix. Laser beam is assumed to be continuous wave with Gaussian distribution. MATLAB code is constructed for numerical simulation, and the results are compared with published work. A good agreement is shown, and thus the proposed numerical model is found to be computationally efficient and accurate standalone platform for predicting the penetration depth of metal laser drilling process.     

A study of the characteristics for electrochemical micromachining with ultrashort voltage pulses

Electrochemical micromachining (EMM) has traditionally been used in highly specialized fields, such as those of the aerospace and defense industries. It is now increasingly being applied in other industries, where parts with difficult-to-cut material, complex geometry and tribology, and devices of microscopic-scale are required. EMM, which is not normally considered as a precision process, is presented in this paper. The application of voltage pulses between a tool electrode and a workpiece in an electrochemical environment allows the three-dimensional machining of conducting materials with micrometer precision. In this paper, tool electrodes (5 μm in diameter, 1 mm in length) are developed by EMM and microholes are manufactured using these tool electrodes. Microholes with a size of below 50 μm in diameter can be accurately achieved by using ultrashort voltage pulses (1–5 μs).     

铝合金MIG+激光复合焊接工艺研究

研究轻量化轿车用3A21铝合金M IG 激光复合焊接工艺,探讨工艺参数对焊缝成型的影响规律及激光与电弧的复合作用。试验结果表明,采用M IG 激光复合焊接工艺可以显著提高熔深和焊速,达到采用小功率激光焊机实现铝合金的激光焊接。在比较宽的工艺参数范围内M IG YAG激光复合焊接铝合金具有焊缝成型美观等优点,熔深和焊速均显著提高,大大提高生产率。     

铝合金板快速加热弯曲的参数预测

基于BP神经网络平台,建立了铝合金板快速加热弯曲的角度预测BP网络模型,实现了脉冲激光加工工艺的参数控制与优化。通过试验获得样本数据,将试验样本数据用于BP网络的训练,利用训练好的BP网络对非线性的样本数据规律进行拟合,对脉冲激光弯曲角度和工艺参数进行准确的预测,预测误差范围可控制在＜5~8%,研究结果为实际生产中精密成形提供了有效的理论与试验依据。     

激光冲击强化对TiAl合金组织和性能的影响

为研究激光冲击强化对TiAl合金组织和性能的影响,利用波长为1 064nm、脉宽为20ns、单脉冲能量为0～22J的Nd:YAG激光器对TiAl合金试件进行了实验研究。采用显微硬度计、表面粗糙度仪和扫描电镜分别测量了激光冲击强化前后的表面显微硬度、粗糙度和表面微观形貌,利用X射线应力分析仪测量了激光冲击强化表面残余应力和晶面极性,并分析了其高温稳定性。实验结果表明:当单脉冲能量增加到9J时,表面显微硬度增加了33.4%,粗糙度由0.042μm增大到了0.285μm,表面残余压应力由20MPa增加到了297MPa,表面微观形貌出现了凸凹不平,局部纹理和层状微结构。将9J激光冲击强化后的试件在650℃下保温4h后,残余压应力值从297MPa降到230MPa,显微硬度值从377HV0.2降到345HV0.2,(002)晶面取向有向中心移回的趋势。得到的数据显示,激光冲击强化能够极大地改善TiAl合金的组织和性能,且具有一定的高温稳定性。