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...     

激光打孔过程的数值模拟

为描述Nd：YAG脉冲激光打孔过程中孔的形貌及温度场的变化规律,建立了三维激光打孔的物理模型,利用APDL语言进行编程,对激光作用区域施加高斯激光热流密度载荷,模拟打孔过程中的温度场分布,并利用单元生死技术模拟激光打孔形貌的变化过程。模拟结果：孔的形貌为圆锥形,光斑中心温度瞬间达到5．6×10^3℃,并以光斑为中心逐渐降低,等温线近似圆形.通过与实际打孔结果对比,发现模拟结果与试验结果相吻合。     

激光打孔温度场的数值分析与仿真

根据激光打孔的特点及实际加工环境建立其数学模型,对激光打孔过程的温度场利用有限元法和有限差分法进行了数值计算,并通过ANSYS进行仿真得到小孔的孔深、孔径的时间特性以及随激光能量的变化曲线,为激光打孔参数的选取提供了依据。     

毫秒脉冲激光辐照光学镜片的热力效应

K9光学镜片是坚硬的脆性材料,对其进行切割、打孔等加工时容易产生裂纹甚至碎裂,而毫秒脉冲激光加工技术具有非接触、精度高、效率高等优点,逐渐被用于切割、打孔领域。为了将毫秒脉冲激光对K9光学镜片进行切割和打孔技术进一步的加强,利用脉宽为1 ms、功率为3 W且重复频率分别为900 Hz、500 Hz、100 Hz的毫秒脉冲激光辐照K9光学镜片,通过构建毫秒脉冲激光辐照光学镜片的热、力效应测量系统,记录K9光学镜片的表面温度演化过程以及镜片表面的实时应变,获得了不同频率毫秒脉冲激光辐照K9光学镜片的温度时程曲线和径向、环向应力时程曲线。得到如下结论：脉宽相同时,随着激光频率的增大,占空比增大,进而导致镜片吸收能量产生的温升增大,对K9光学镜片损伤也越大,得到最高温度与激光频率的2阶多项式拟合函数y=289.03213+0.02698x+4.19812×10^-4x²;脉宽相同时,随着激光频率的增大,占空比增大,镜片温度升高,温度梯度增大,加剧镜片内部单元的涨缩,从而使得径向、环向应力均增大,对K9光学镜片损伤也越大,得到径向、环向应力与激光频率的2...     

水松纸激光打孔控制系统设计

对水松纸激光打孔控制系统进行了研究,其主要由触摸屏和PLC、激光控制、多棱镜控制、张力控制、水松纸卷绕控制等5部分组成.采用触摸屏完成各种操作、参数设置、参数和状态显示等;PLC完成对各种I/O信号的处理、故障自诊断和联锁保护;多棱镜控制用于将连续激光转换成脉冲激光束;张力控制主要用于根据不同型号的水松纸预置一个合适的张力;水松纸卷绕控制主要用于打孔过程中线速度和张力恒定.讨论了各控制部份的详细实施方案,并对有些方案作了分析和对比.经多年实际应用,本控制系统完全能满足线速度600 m/min以下水松纸激光打孔要求.     

陶瓷喷嘴Nd:YAG激光精密打孔应用研究

通过在陶瓷喷嘴上进行激光打孔的多种工艺参数试验，分析了激光能量、脉冲宽度和激光频率等对打孔质量的影响，摸索出了一套切实有效的激光打孔工艺参数，较好地解决了小孔锥度问题，加工出了合格的陶瓷小孔样品。并对激光加工工艺参数进行了多因素分析，探讨了多种加工工艺参数对加工小孔锥度的影响。     

毫秒脉冲激光倒置打孔数值模拟

针对微孔加工中常出现的喷溅物附着在工件表面的问题,开展脉冲激光倒置打孔的研究。基于流体力学和热传导理论建立一个二维瞬态非等温层流模型,模拟倒置情况下毫秒脉冲激光在304L不锈钢上打孔的过程。采用显热容法处理材料相变潜热和非线性的热物性,提高了模型的准确性和收敛性。模拟结果表明,倒置打孔不仅能够帮助排出熔融物,还能够充分利用激光能量将材料加热至熔融和汽化。     

皮秒激光CVD金刚石膜打孔温度场仿真

建立了皮秒激光在CVD金刚石膜打孔时的瞬态热传导三维物理模型并利用ANSYS对过程进行了仿真,分析了温度场的空间变化规律以及温度场随时间变化趋势,将仿真值和实验结果进行了对比,在此基础上研究了激光能量,脉冲宽度,重复频率等对打孔品质的影响。     

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.     

基于ARM及CPLD的烟支在线打孔控制系统设计

基于现阶段烟支激光打孔系统打孔精度差、监控能力欠缺等问题,设计一种新型的烟支在线打孔控制系统。该控制系统采用ARM与CPLD相结合的方式,搭配外围的一套PLC电控模块来完成对整个系统的控制以及状态的监测。ARM的主要功能是数据传输及通讯,CPLD完成一系列的时序逻辑处理、数据运算及存储等功能。运行调试表明,本系统运行稳定可靠,抗干扰能力强,脉冲打孔频率最高可达200 MHz,脉冲打孔时间精度提升至0.1μs。     

Ablation drilling of invar alloy using ultrashort pulsed laser

Drilling a hole in Invar alloy is accomplished by using a nanosecond pulsed Nd:YAG laser. However, this process has a few problems, such as heat effect and poor edge quality. Therefore, the ablation properties of the Invar alloy were investigated by using an ultrashort pulsed laser, which is a regenerative amplifier Ti:sapphire laser with a 1 kHz repetition rate, a 184 fs pulse duration, and a 785 nm wavelength. To study the ablation characteristics of the Invar alloy, we measured the ablation shape, width, and ablated depth at the energy fluence of a single pulse. The optimal condition for hole drilling is a z-axis transfer depth of 4 μm, a circular feed rate of 0.2 mm/s, and a pulse energy of 26.4 μJ. A fine circular hole without burrs and thermal damage were obtained under the optimal processing conditions. The ultrashort pulsed laser system is an excellent tool for micro-hole drilling in Invar alloys without heat effects and poor edge quality.     

钬激光碎石术中结石位移的影响因素

为了减小钬激光碎石术中结石产生的位移,研究了钬激光脉冲峰值功率、激光烧灼尺寸和工作距离对于结石位移的影响。分析了影响结石位移的因素,搭建了一个体外模型装置以此来模拟输尿管内钬激光碎石的过程,实验使用0.25 g的正方体石膏模型来代替人体结石,钬激光功率选择12 W(0.6 J×20 Hz,0.8 J×15 Hz,1.2 J×10 Hz)和20 W(0.8 J×25 Hz、1.0 J×20 Hz、2.0 J×10 Hz),脉冲持续时间为200μs和800μs,光纤使用272μm以及550μm,工作距离从0~5 mm。最后,将体外模型置于水中,在室温进行实验。实验结果表明,结石位移随着脉冲峰值功率的增大而增大;较长的脉冲持续时间可以减小16.95%~27.27%的结石位移;272μm的光纤相比于550μm的光纤能够减少35.59%~54.17%的结石位移;增大工作距离可以减小结石位移,同时降低消融效率,但当结石模型与光纤顶端接触时,会产生吸附挣扎的现象。上述结论为改进国产钬激光器设计以及钬激光参数精细化设置提供了参考,对于临床手术有借鉴意义。     

激光冲击金属板料变形的 最小激光能量估算及其实验研究

介绍了激光冲击板料变形的机理和冲击波产生的原因,提出了激光冲击板料变形中激光－能量转换体－靶材系统的爆轰波压力估算式。根据此压力估算式和材料的动态屈服强度,对激光冲击板料变形中所需的最小激光能量进行了估算,板料厚度为0.5 mm,约束凹模孔径Φ20 mm,在光斑直径6 mm,脉宽25 ns条件下的不锈钢靶材变形所需的最低脉冲能量大约为11 J。实验结果表明估算的最小激光能量与板料变形所需的能量阈值基本一致,且板料变形量随激光能量的增加呈非线性增大。最小激光能量的估算以及能量与板料变形的实验研究为板料变形的精确控制和预测提供了理论依据。     

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.     

Statistical analysis of repeatability in laser percussion drilling

This study investigates the effect of six parameters in the repeatability of drilled holes in laser percussion drilling process by means of statistical techniques. Peak power, pulse width, pulse frequency, number of pulses, gas pressure and focal plane position were considered as independent process parameters. Experiments were designed with the aim of reducing the number of required experiments. The response surface method was used to develop the models for required responses. The significant factors in the process were selected based on the analysis of the variance (ANOVA). The experiments were conducted in mild steel sheet with a thickness of 2 mm. Each experiment was repeated 35 times in order to investigate the repeatability of the process. The equivalent entrance diameter, percentage of standard deviation of entrance diameter (%STD Eq Dia), circularity (ratio of minimum to maximum Feret’s diameter) and its standard deviation (STD circularity) were selected as process characteristics. The %STD Eq Dia and STD circularity, respectively, show the repeatability of equivalent diameter and circularity in the process. The results show that the process of drilling smaller hole diameters is more repeatable than drilling larger holes. Pulse width, gas pressure, focal plane position, peak power and number of pulses, respectively, have significant effect on the repeatability of hole diameter and circularity. Pulse frequency has no significant effect on the repeatability of the process.     

Ceramic to metal joining by using 1064 nm pulsed and CW laser energy source

A novel joining method for ceramic and metallic layers is proposed using laser drilling and surface tension driven liquid metal filling. A high intensity laser beam irradiated a 500 μm thick ceramic filter, and the irradiated laser drilled the ceramic layer. The pulsed or CW laser transmitted through the ceramic layer irradiated the bottom metallic layer; the molten metallic layer then filled the drilled ceramic holes by the capillary force between the liquid metal and ceramic layer. As process variables, average laser power, pulse duration, and the number of pulses were used. The scattering optical properties were also studied for both green and red lasers. There was no significant difference between the colors and the estimated extinction coefficients were ?26.94 1/mm and ?28.42 1/mm for the green and red lasers, respectively.     

内置标准具光栅腔XeF(C-A)准分子激光器的线宽压缩

为了避免阳光背景干扰,针对XeF(C-A)蓝绿激光水下应用需求开展了激光线宽压缩实验以提高信噪比。采用内置标准具的光栅谐振腔开展相关实验。利用光栅腔实现亚纳米级的激光线宽输出,然后在此基础上,通过插入标准具进行更精细的激光线宽压缩实验。利用光栅腔,采用1 200线/mm光栅并提高光栅辐照面积可以实现0.14nm的激光线宽输出。腔内插入反射率为50%的标准具,可以进一步将激光线宽压缩至39pm,激光单脉冲能量约为65mJ,脉冲宽度为1μs。实验结果表明:尽管XeF(C-A)蓝绿激光器的增益系数较低,但是通过优化光栅和标准具的工作参数,对谐振腔光学损耗进行合理的控制,激光器可以实现10pm量级的激光线宽输出。     

引信激光装定用脉冲半导体激光器电源设计

在引信激光装定系统中，针对引信装定信息时脉冲半导体激光器，电源激光频率可调（PFM）、功率可调（PPM）的要求，结合半导体激光器的工作特性，设计一种以单片机（MCU）为控制芯片，以晶体三极管与场效应管为窄脉冲驱动电路的大功率半导体激光器电源。同时为电源驱动电路设计了DC-DC变换器。其中，激光频率设置为连续可调，激光器的驱动电流6～30A连续可调。该电源已应用于引信激光装定系统中，通过仿真与实验验证，该激光器电源工作正常、性能稳定。     

Enhanced processing speed in laser drilling of stainless steel by spatially and temporally superposed pulsed Nd:YAG laser radiation

Percussion drilling through holes in stainless steel (1.4301, 5, 8, and 10 mm in thickness) was performed with the superposed radiation of two pulsed Nd:YAG lasers. Holes were drilled with flash lamp pumped Nd:YAG slab-laser radiation with a pulse duration of 0.5 ms superposed with diode-pumped solid-state (DPSS) laser radiation with a pulse duration of 17 ns. The drilling efficiency is improved by the spatially and temporally superposed radiation of the two lasers. With the superposed laser radiation, drilling through stainless-steel samples at a maximum aspect ratio of 60 is performed up to four times faster with the reproducibility of the drilling time improved by a factor of six in standard deviation.     

双面超薄不锈钢复合板激光焊接接头组织及耐腐蚀性能

采用同步送粉填充焊的方法,利用Nd:YAG固体脉冲激光对0.1mm+0.8mm+0.1mm不锈钢复合板进行了双面焊双面成形的实验研究。确定了激光焊接双面超薄不锈钢复合板的最佳工艺参数,利用金相显微镜观察分析了焊缝区各区的微观组织特征。结果表明,双面超薄不锈钢复合板填充粉末后激光焊接接头表面成形好,热影响区窄,焊接变形小;焊缝中心为细小的等轴晶,熔合线附近有细晶区,其他区域为柱状晶区,焊缝为残余奥氏体+马氏体+碳化物组织;在硫酸-硫酸铜腐蚀溶液中腐蚀16h后,焊缝表面与腐蚀前没有明显变化,对试板进行180°弯曲试验,未产生晶间腐蚀裂纹。