带热障涂层镍基单晶高温合金的激光制孔研究

采用毫秒激光和皮秒激光在带热障涂层的镍基单晶合金上加工了气膜孔,对比研究了长脉冲与超短脉冲加工对热障涂层及金属基体孔壁形貌的影响。实验发现,波长1064 nm的毫秒激光在试样表面产生的能量密度直接影响到陶瓷层的加工。以2866 J/cm2的能量密度从陶瓷面加工,陶瓷面的熔化所需要的热积累时间长,热量会传导至高温金属,产生类似熔池的热影响;而从金属面加工则由于陶瓷是最后加工的材料,有足够的热积累时间熔化陶瓷涂层,从而直接打通小孔。当毫秒激光的能量密度提高至6369 J/cm2时,热量在涂层中的积累速度加快,陶瓷材料能够快速熔化,从而避免了金属基体先于陶瓷熔化的现象,同时,加工过程中熔化后的陶瓷会经过孔通道,从而出现附着在孔壁上的现象。采用皮秒激光加工陶瓷涂层仅需要能量密度达到32 J/cm2,皮秒激光旋切制孔是将小孔圆周上的材料全部剥蚀掉,直至孔打通,而孔内的材料会从孔中掉出。皮秒激光加工中产生的等离子体冲击力会引起涂层的开裂,由于热障涂层制备方法不同引起涂层中的裂纹方向有所不同,等离子喷涂制备的涂层为层状结构,裂纹易沿平行于表面方向生长,而EB-PVD制备的涂层为柱状晶结构,裂纹多出现在柱状晶的间隙。     

人造单晶金刚石激光微孔加工技术研究

人造单晶金刚石传统的激光打孔方法采用"轮廓法".该方法的缺点是越靠近孔的中心剥去的材料越多,精确的孔型难以得到.本文在理论和实践的基础上,提出了一种新的激光数控打孔自适应模型.在模具的压缩区,通过控制工件的转速实现材料的均匀去除,并且使激光脉冲能量随着孔径的减小而递减,以提高孔型精度.结果表明,该模型可以有效提高微孔的加工精度,最小加工孔径达到3.5 μm.理论和实践证明,本文提出的激光打孔数控模型是人造单晶金刚石激光打孔的有效方法.     

电火花打孔对单晶高温合金损伤的多角度表征方法及损伤机理

本文旨在研究多种工艺参数下电火花打孔对新一代单晶高温合金的损伤行为,通过进行加工电流、脉冲宽度与脉冲间隔3种参数变化的25组正交试验,采用激光共聚焦显微镜、扫描电子显微镜（SEM）、能谱仪（EDS）、电子背散射仪（EBSD）等表征手段对打孔形成的不同损伤的影响规律进行研究。结果表明:加工电流对孔壁粗糙度和重熔层厚度影响最明显,脉冲宽度其次,脉冲间隔影响最弱。基于试验结果形成从圆度、锥度、孔内壁粗糙度、孔内壁形貌、重熔层厚度分布、重熔层组织结构、重熔层成分等多角度表征气膜孔损伤的方法。利用多处测量正交计算和极差的方法,以及面积方法评价不同打孔工艺重熔层厚度,剖析重熔层的形成过程,分析出电火花打孔对先进单晶高温合金的损伤机理。     

飞秒激光微加工技术在航空发动机高压单晶涡轮叶片的应用

飞秒激光加工工艺是一种国际领先的新型超精细"冷加工"工艺,可实现无材料选择性的微米级刻蚀、切割、制孔等应用,其加工件无热应力、无再铸层、无微裂纹。国产某型发动机高压涡轮工作叶片的工作环境要求极为苛刻,这已成为其发动机性能和使用寿命提升的短板。从高压涡轮单晶叶片制孔要求出发,阐述了飞秒激光"冷加工"技术、基于曲面特征点迭代逼近算法的叶片自适应定位技术和实时穿透感知技术等三项关键技术,依托Micro Drill100五轴飞秒激光微加工装备实现了单晶叶片的高质量批量加工。经金相检查、工业CT等多项检测验证,满足设计要求。     

激光加工模式变换及其在硬质合金打孔中的应用

在复制法激光打孔中 ,激光束的横向模式决定着加工孔的形状和尺寸精度。本文从理论上分析了金属材料对激光的热吸收效应 ,进而通过预热加工工艺来改善激光束模式在材料表面上的热作用效果 ,使 JG- 2型固体激光器加工精度从设计给定的±0 .0 3mm ,提高到± 0 .0 1m m。实验证明 ,通过对激光模式的变换 ,能进一步提高激光加工硬质合金材料的质量     

钣金工艺中的激光加工技术

激光材料加工是高能束流加工技术的重要组成部分,已广泛用于材料的打孔、切割、成形、焊接汲表面处理,主要综述了各种激光材料加工技术在钣金工艺中的应用情况。     

钣金工艺中的激光加工技术

激光材料加工是高能束流加工技术的重要组成部分,已广泛用于材料的打孔,切割,成形,焊接及表面处理。本文主要综述了各种激光材料加工技术在钣金工艺中的应用情况。     

金属材料超快激光制孔研究进展

超快激光作为一种先进加工手段，因具有高柔性、高峰值功率密度、热影响小等特点可满足任意材料的精密加工，在航空航天、电子信息、新能源等领域的金属材料精密制孔中具有显著优势，故针对金属材料的超快激光冲击制孔、铣削制孔、螺旋制孔、环切制孔以及复合工艺制孔等工艺进行综述，总结了各制孔工艺的优势和面临的挑战。     

DD6单晶带气膜孔平板试件高周疲劳性能研究

利用电液束、激光、电火花三种不同制孔工艺制备了DD6镍基单晶高温合金气膜孔平板试验件,在980℃下对试件的高周疲劳性能进行了测试,并对疲劳极限与断口形貌进行了分析比较.结果表明:不同制孔工艺对试件的高周疲劳性能影响显著,电液束制孔工艺的疲劳极限较高速电火花制孔、毫秒激光制孔工艺提升约5.3％和7.1％.不同制孔工艺的试...     

液体辅助激光微孔加工研究进展

随着微孔加工技术的逐渐成熟,激光微孔加工的应用越来越广泛,但依靠单一激光束进行微孔加工仍存在一些问题,尤其是在深孔加工方面,出现了以激光束为主、多能量场辅助的复合打孔技术,并逐渐成为了热点。针对液体辅助激光微孔加工研究领域,总结了水基辅助激光打孔、水基超声振动辅助激光打孔、水基超声?磁场辅助激光打孔和电解液/水射流辅助激光打孔等方法。在水基的基础上,加入了超声、磁场和温度场,使得辅助场变得多元化,在多层面上进行复合加工。介绍了不同辅助加工方法的去除材料机理及加工后材料特性的变化,水起到冷却的作用,但在水层下会形成空化气泡,超声振动可以击溃气泡,磁场和温度场为材料残渣提供了能量,具体表现在热效应、材料去除速率、打孔深度、重铸层及裂纹等方面。影响微孔质量的因素有微孔锥度、深径比、孔的圆度、重铸层厚度、热影响区、微裂纹和粗糙度等,主要对微孔锥度、深径比及其他指标进行了分析,总结了加工方法对微孔质量的影响。     

The infrared thermography control of the laser welding of amorphous polymers

In laser welding technique, a real-time control of temperature distribution inside the irradiated materials is essential when attempting to optimize the process. For all laser welding methods that operate by the transmission principle, the difficulty of recording the developed temperature at the interface derives from the fact that materials to be welded are in contact throughout the entire process. In the present study, in order to overcome this issue, a contact-free method such the infrared thermography is used for surface temperature measurement. Corroborating this data with a numerical simulation of the temperature field evolution inside the components, an assessment of optimal process parameters is possible. The experimental investigations are made on amorphous polymers, in a typical configuration for through-transmission laser welding. The fine agreement obtained between the experimentally and calculated data, validate the infrared thermography as a non-destructive method for real-time monitoring of the welding process.     

超声红外热像技术检测激光焊缝质量

超声红外热像技术是一种新兴的无损检测技术。使用超声作为热激励源,可以实现对缺陷部位选择性热激励,同时用红外热像仪捕捉材料表面温度变化。介绍了超声红外热像技术的基本原理,对两类激光焊接试件进行了检测。试验结果可用以分析激光功率和焊接速度对焊接质量的影响。     

Diagnosis of the leakage point on a structure surface using infrared thermography in near ambient conditions

It is important to check for leakage points of fluids on a surface to maintain and manage various structures satisfactorily. In particular, it is necessary that the leaking walls of a bank, dam, tunnel, pipeline and so on are diagnosed appropriately using some remote sensing technique and that they should be repaired immediately. Recently, infrared thermography for measuring temperature has become attractive in a wide variety of engineering applications. Infrared thermography in near ambient conditions is introduced to check the leakage point and its applicability is estimated by visualizing the temperature field generated around the point. The generated temperature around the leakage point is not usually consistent with the surrounding temperature. When using infrared thermography, we can detect the leakage point at the location where a marked temperature difference occurs.     

Comparison between thermographic techniques for frescoes NDT

The use of infrared thermography in the architectural restoration field is examined. Three samples, made of a support of marble, brick, or tuff, covered with a layer of plaster with inclusions to simulate detachments or cracks in frescoes, are considered. Different techniques: pulse thermography, lateral heating thermography, lock-in or modulated thermography and pulse phase thermography are employed to detect the flaws artificially created; advantages and disadvantages of each technique are discussed. It is found that pulse thermography is easy and fast to use for information about the state of the art treasures, but data may be affected by non-uniform heating and local variation of thermal emission; the lateral heating can help to overcome interference effects due to non-uniform heating but it is more troublesome to use. When the evaluation regards rare art treasures the lock-in technique seems to be the only response since it is able to operate within very low increase of surface temperature; this technique is also able to give information about the material composition. The pulse phase thermography may be used to detect more in depth flaws but it needs higher temperature increase with respect to the ambient temperature and so it is recommended to control, before testing, the temperature sensitivity of the artefact.     

直升机旋翼桨叶的红外检测

采用便携式红外无损检测系统对直升机旋翼桨叶的不锈钢前缘包片、桨叶前“Z”形梁和后缘条等部位进行了红外检测研究。在主动热激励方式下,由于内部材料的阻热与吸热特性不同将导致表面温度场分布不均,使红外热图像能够清晰显示出桨叶漆层下的内部结构特征或损伤情况。检测结果表明,主动红外检测技术完全可用于直升机复合材料结构的内部分层、脱粘和漆层下腐蚀等的快速检查,在直升机日常和应急维护保障中的应用前景广阔。     

SIMULATION-MEASUREMENT INVERSION OF ENVIRONMENT PARAMETERS DURING WELDING

The manual selection of environment parameters during welding simulation will bring a significant error to the simulation result of welding temperature field. By a combination of finite element method （FEM） and infrared thermography, these environment parameters were inversed mathematically in place of previous manual selection. First, FEM model of the welding process was constructed, and the temperature field was computed with initial environment parameters. Then, a real welding process was conducted and the temperature field was measured by infrared thermography. Last, the simulation and measurement results were compared, and the environment parameters were adjusted continuously with the genetic algorithm （ GA ） until the simulation matched the measurement best. Parameters according to the best-matched simulation results were considered as the most appropriate parameters.     

基于红外热像的激光微细丝成形过程热累积研究

激光微细丝增材制造技术是一种能快速成形小型零件的制造技术,但由于受制造过程中热累积效应的影响,往往无法保证对成形零件的精准控形控性。针对这一问题,本文利用标定后的红外热像仪采集单道多层薄壁零件的表面温度,研究其制造过程温度场特征变化规律及热累积效应,为成形工艺的优化提供依据。结果表明：利用红外热像仪可实现对薄壁堆积过程温度场演化规律的研究,随着熔覆高度的增加,高温区域面积逐渐增大,热累积效应明显增强。熔覆过程中,热量向下传导,散热条件逐渐变差,各层冷却速率随层数增大而减小,直至趋于平稳。此外,当熔覆层数大于15层时,热累积效应不再对15层以下熔覆层产生影响。     

Laser heating mechanism including evaporation process initiating laser drilling

A laser heating mechanism initiating the drilling process is examined. The study includes conduction and convection effects and assumes a steady-state evaporation process. This enables estimation of the limits of the Fourier theory in laser drilling applications. Using the model described in the analysis, maximum temperature attained inside the material, nucleation, explosion process and drilling efficiency are predicted. The results obtained from the present work for the vapor front velocity are compared to those obtained from previous experiments. In addition, a laser drilling experiment is carried out while monitoring the surface evaporation process. This enables correlation of the theoretical results with the experiments.     

超声热成像检测应用实例

简要介绍了超声热成像检测方法的基本原理和特点。该方法利用激励超声波在缺陷处产生机械振动,使缺陷处因热弹效应和滞后效应等原因释放出热量,用红外热像仪对此局部发热过程进行监测,最后对图像进行分析。由于激励信号的频率调制和特殊的图像处理方法,超声热成像检测法优势独特。对某航空碳纤维增强复合材料的检测表明,该方法能有效检测出裂纹、分层或破裂等缺陷,应用前景广阔。     

TEMPERATURE FIELD THERMOGRAPHY ON FRICTION FACING OF CERTAIN WEAR-RESISTANT ALLOYS

The change of temperature field on the friction facing during contact wearing for 3wear-resistant alloys:Co-Cr-Ni-Si,Co-Cr-Mo and Co-Cr-W has been monitored bythe infrared sensing thermography.Their flash temperature of the wearing area wasmeasured.