When processing SiC/SiC composites using nanosecond-pulsed lasers, thermal effects such as molten deposition and heat-affected zones (HAZs) will occur. In this study, an annulus-conical water jet (ACWJ) was introduced to assist nanosecond laser machining of SiC/SiC composites, aiming to suppress thermal damage. A comparative investigation between laser processing in air and under ACWJ assistance was conducted. The results demonstrated that ACWJ assistance effectively eliminated molten material deposition and HAZs, significantly improving surface quality. However, despite a short beam path in the water (approximately 2.5-3 mm), turbulence in the water stream during ACWJ processing caused beam divergence and focus drift, leading to a substantial reduction in laser energy density on the target surface, and thus a lower material removal efficiency compared to laser machining in air. Moreover, the beam focal position drifted within the turbulent water stream, resulting in broader and shallower machined features. The material removal rate during ACWJ-assisted laser processing was only approximately 3%-10% of that achieved in air. In groove ablation, achieving the same depth as that in air-based processing required a significantly larger number of scan passes under ACWJ conditions. In hole machining, the resulting hole diameters were approximately 240% greater than those achieved in air.

Flexible heating elements consisting of metal circuits and resin layers are widely used in semiconductor, medical, and food service equipment. Laser fabrication of the metal circuit on the resin layer is more efficient and environmentally friendly than traditional chemical etching processes. This study assessed thermal damage on a polyethylene terephthalate (PET) layer while ablating a stainless steel 304 (SS304) circuit on SS304/PET composite films using a nanosecond pulsed laser. The effects of the laser power, scan speed, and scan pass on the damaged width and depth of the PET film were explored. The results showed that the pulsed laser radiation on the upper SS304 foil has a low risk of causing thermal damage to the PET film. The PET thermal damage occurred mainly owing to direct laser radiation after the upper SS304 material was removed. The damage depth developed significantly faster than did the damage width, as the tapered SS304 cutting slit obstructed the periphery of the laser beam. In addition, adding a 35 μm-thick polyethylene vinyl acetated adhesion layer between the SS304 and PET can reduce approximately 80% of the damaged depth. This research provides a reference for the laser cutting of metal circuits/resin films for heating elements.

Inclined holes on superalloys have important functions in aeroengines. These inclined holes need to be polished to improve surface quality before service. This study investigates the effects of time-division bidirectional flow of abrasive water on the polishing results of inclined holes on superalloys. It reveals that there is a significant imbalance in abrasive dynamic pressure and density distribution between the obtuse and acute edges inside the inclined hole during single-directional abrasive water flow polishing (AWFP). This imbalance normally leads to a non-uniform material removal on the hole wall and consequently results in a roughness variation of 50–60

This study investigates the influence of different heat treatment processes on the microstructure and mechanical properties of cold spraying coatings deposited on TIG joints of 2219 Al alloy. The results indicate that there were no significant changes in the microstructure of the joint before and after cold spraying. However, there was noticeable plastic deformation at the interface between the joint and the coating. The porosity rates of coatings subjected to room temperature, direct aging, and solution aging are 1.94

Inclined hole arrays on superalloys have important applications in aeroengines. However, defects occur during fabrication of inclined holes using thermal drilling methods, i.e. electrical discharge drilling (EDD), including a recast layer and microcracks on the hole wall. Therefore, abrasive water flow polishing (AWFP) of a superalloy inclined hole array machined via EDD was investigated in this study. Two types of specimens were designed: a hole array of identical size and a hole array with an identical inclination angle. The fluid simulation revealed that the fluid velocity and pressure on the lower edge of the inclined hole were significantly higher than those on the upper edge when the fluid flowed forward. The fluid characteristics exhibited opposite trends when backward flow was implemented. Time-division bidirectional flow can effectively compensate for flow field nonuniformity and improve material removal consistency during polishing. The experimental results show that for inclined holes with identical inclination angles, the size expansion decreases with an increase in the hole diameter owing to the lower fluid velocity and material removal volume in the relatively larger holes. Consequently, surface roughness Ra increases with hole size. For inclined holes with identical diameters, the size expansions of the entrance and exit approach the same level; whereas, Ra decreased with an increase in the inclination angle. The hole taper slightly reduced in all cases. Using garnet abrasives with 1300 mesh size, 1.5 wt.% abrasive concentration, and 3 MPa fluid pressure, the surface roughness Ra of target holes was reduced from pre-polishing [Formula: see text] 5.0 [Formula: see text]m to approximately post-polishing 1.0 [Formula: see text]m. The recast layer on the hole wall caused by EDD was completely removed.

Micro-inclined holes in nickel-based alloys have important functions in hot-section components of aero-engine. Hole-wall surface defects occur during electrical discharge drilling (EDD) or laser drilling (LD) of these inclined holes. Abrasive water flow polishing (AWFP) is a promising method for finishing inclined holes after EDD or LD processes. However, the abrasives tend to gather at the obtuse edge of the inclined hole during regular AWFP and cause remarkably nonuniform finishing. Fluid field vibration-assisted AWFP has been studied to solve this problem. A comparison between the absence and presence of low-frequency flow field vibrations in AWFP of inclined holes was made. Subsequently, the effects of vibration amplitude and frequency on the polishing results were investigated. The results show that the radial vibration of the fluid field can significantly improve the abrasive dispersion inside the inclined hole and, consequently, enhance the kinetic energy and collision frequency of the abrasives impinging the hole wall. This results in a better material removal uniformity. With the fluid field vibration, the hole-wall finishing nonuniformity inside the target hole can be decreased by 78

The inclined cooling holes on turbine blades needs to be polished to remove thermal barrier coating (TBC) blockage before service. So far, no effective methods have been developed to remove this blockage except manual polishing with grinding needles. In this study, polishing of inclined small holes with TBC blockage on GH4169 superalloys was investigated using a low-pressure abrasive water jet with an optimized nozzle. The results show that the abrasive distribution inside the jet resulting from the five types of commonly used nozzles presented Gaussian-like distribution. The nozzle with 14° convergence angle and 1.5 mm straight section was selected for the subsequent polishing experiment for the consideration of the abrasives divergence and boundary. The hole entrance was shaped as a cone after polishing, and the entrance diameter increased with processing time, standoff distance (SOD) and abrasive concentration. The hole-blocked material at the entrance was cleaned rapidly, while those at the trailing edge was removed slowly because of the greater length of blockage. Increasing the abrasive concentration achieved higher blockage removal rate than increasing the SOD. For the 30° inclined holes with a 200 μm thick TBC, approximate 60

陶瓷基板电热组件具有加热均匀性好、电热转换效率高等优点,广泛应用于需低温加热场合,然而传统金属-陶瓷共烧技术因成本高、效率低而制约发展.通过采用电铸工艺在陶瓷基板上制备镍铜合金电热组件,研究发现镍铜合金电铸层的平均晶粒尺寸随着电铸液温度的升高而增大,电阻率随晶粒尺寸的增大而减小,同时电流密度会显著影响镍铜合金电铸层中镍的含量,进而影响镍铜合金电铸层的线膨胀系数.

Superalloy microholes resulting from electrical discharge drilling (EDD) can have recast layers and microcracks on the machined surfaces. In this study, the abrasive water flow polishing (AWFP) of superalloy microholes machined by EDD was investigated. The recast layer and surface roughness resulting from the EDD process were evaluated through orthogonal experiments. The machining mechanism of AWFP was analyzed. The effects of AWFP parameters were investigated experimentally. The results show that the material removal rate and surface roughness at the hole exit were better than those at the entrance for one-directional fluid flow during the process. Garnet abrasives achieved better polished roughness and a lower material removal rate than alumina abrasives. The taper angle of the target holes changed slightly from positive to negative after AWFP. The corner edge was slightly rounded on the fluid inlet side. Using a bidirectional fluid resulted in better dimensional uniformity and surface roughness at the entrance and exit. This study verified that AWFP can remove the recast layer and microcracks on the hole wall caused by EDD and reduce the surface roughness from an initial Ra of 5.7 & mu;m to an Ra of 0.6 & mu;m.

采用飞秒激光对SiC/SiC复合材料进行环形扫描刻蚀去除试验,分析脉冲能量、光斑重合度及线重合度对加工区域材料残留及环形凹槽外轮廓的影响.结果表明:光斑重合度、线重合度和脉冲能量显著影响光束扫描面积内的能量密度,材料去除量随扫描能量密度的增大而增大.在较小光斑重合度和线重合度条件下,即能量密度较小时,刻蚀槽外轮廓呈现锯齿状,且扫描轨迹间有较多材料残留.随着光斑重合度和线重合度的增大,外轮廓及底面趋于光滑.

由于广泛应用在航空发动机上的热障涂层工作环境恶劣,使用一段时间后会产生脱落现象,为提高磨料水射流去除热障涂层的加工效率,在原基础上引入超声振动并搭建超声振动辅助加工系统,并在不同超声功率下对APS热障涂层进行冲蚀加工试验.试验结果表明:施加超声振动后,热障涂层的材料去除率明显提升.

Ceramic materials will get deposited inside pre-drilled cooling holes and partially or completely block during thermal barrier coating (TBC). In this study, the hole blockage produced by atmosphere plasma spraying (APS) was investigated using industrial computed tomography. The results show that the geometric features of the blockage owing to APS coating are significantly affected by the inclination angle of the pre-drilled holes. The coating deposition in the vertical holes is rotationally symmetric and mainly concentrates at the entrance. For the inclined holes, the deposition on the trailing edge is much more than that on the leading edge. The deposition height and length on the trailing edge increase with the inclination angle; however, they are little disturbed by the hole size. Therefore, the blockage ratio decreases with the increase of the hole size. In addition, greater TBC thickness causes larger deposition height and length and subsequently results in a larger blockage ratio.

电动汽车动力电池在温度过高或过低时,均需要通过换热板进行热交换,以确保动力电池的工作性能.基于此,设计了 3 种不同流道结构的液流换热板,采用计算流体力学方法分析了流道横截面积和流道长度对动力电池散热和加热效果的影响.结果表明:增加内流道横截面面积可以增强换热板与流体之间的传热效果;在横截面面积不变的情况下,增加流道长度可使换热板表面温度分布更均匀.

The micro- and small-sized cooling holes of turbine blades must be polished to remove the thermal barrier coating (TBC) blockage before service. To date, no effective methods have been developed to remove this blockage, except for manual polishing using grinding needles. In this study, the removal of hole blockages from a superalloy material is investigated using a low-pressure abrasive water jet (AWJ) process for the first time. Based on an analysis of the processing mechanism, the kinetic energy threshold for a particle-to-crack TBC is approximate 3.55 nJ. Garnet particles with size of 10 μm and speed of ≥ 60 m/s can theoretically damage the TBC material. For vertical holes, the hole-blocked material near the entrance can be eroded rapidly. For inclined holes, the hole-blocked material at the trailing edge has a much greater volume and length and requires a longer time to remove. Using relatively larger jet size increases the material removal rate of the blockage, however, resulting in a broader hole entrance. When applying a relatively larger standoff distance, the capability of the AWJ in removing the blockage was enhanced owing to the more dispersed distribution of abrasives in the jet. The blockage ratio can be reduced from 60

为实现半导体工艺气体管道加热器装配车间物料的自动化输送,解决动态复杂场景下传统AGV导航精度低、柔性和稳定性差等问题,文章对激光雷达导航AGV在生产车间的地图构建与定位导航技术进行了分析研究.通过建立AGV控制系统框架及数学模型,将里程计与惯性导航传感器数据融合进Cartographer算法,解决了建图时的高漂移问题,提高了建图和导航的精度.在生产车间中验证了优化后的建图与定位导航算法的稳定性、有效性.

目前,一些航空产品零件在返修时报废数据较高,随之越来越多的修复技术受到行业的广泛关注.其中,激光修复是目前修复领域中的重要技术,因其具有独特的技术特性,所以应用前景非常广阔.主要针对报废率高、价值高、加工周期长的铝合金零件,分析激光修复方案和可行性,并开展零件激光修复技术研究.

采用磨料冲蚀-电火花组合加工方法对带TBC高温合金进行 30°斜孔加工试验.在形成TBC冲蚀孔形之后,采用不同尺寸管电极加工高温合金基体,研究管电极尺寸对TBC冲蚀孔形及金属孔形的影响.结果发现:随着管电极尺寸增大,重熔堆积物厚度随之增大,且堆积物生成区域扩大;选用较小尺寸电极进行加工时,会严重影响两孔形的匹配程度;虽然采用较大尺寸电极可以提高孔形匹配,但容易出现TBC裂纹、剥落等缺陷.

飞秒激光有着极窄的脉宽、极高的峰值能量,因此具有加工范围广、加工质量好等优势.利用飞秒激光对CFRP复合材料进行小孔加工试验,研究了光斑局部填充和全填充两种方式对 φ3 mm小孔加工的影响.通过光学显微镜、工业CT等检测手段对试件的小孔加工进行检测,分析小孔进出口形貌以及内壁锥度,对比讨论了不同填充方式对材料去除的影响.试验结果表明,全填充的排屑条件好于局部填充,因此更容易加工出通孔;局部填充易导致光束向底部反射以及热量聚集所致的材料去除,因此加工出的通孔锥度较小.扫描速度越小,孔的锥度越小,反之扫描速度越大,孔的锥度越大.填充间距影响着激光的输入能量密度,因此填充间距对小孔加工的深度有直接影响,对小孔入口直径以及小孔锥度的影响较小.

飞秒激光加工具有脉冲作用时间短、峰值功率高、热影响区小的特点,但在材料去除过程中仍然存在热累积效应.脉冲间的热累积效应对加工质量及热影响区均有直接影响.采用飞秒脉冲激光对碳纤维增强树脂基复合材料(CFRP)进行扫描刻蚀试验,运用三维传热模型对脉冲光斑作用区域温度场进行研究,进而对飞秒激光的热累积效应进行探讨.结果 表明:脉冲能量及重复频率对热累积的影响较为显著;三维传热模型的计算结果与试验结果基本吻合,对飞秒激光加工CFRP材料中的热累积效应控制具有指导意义.

在实际生产过程中,为了保证薄膜电加热器的加热温度达到设定温度,需要实时测量被加热物体温度来控制加热过程.传统温度测量方法通过布置大量温度传感器来实现,但对于某些空间范围狭小的场合,则没有足够空间位置安放温度传感器.针对此难题,该文对基于电加热丝材料正温度特性(PTC)的温控方法开展研究,设计了温度控制总体方案,研究了 3种典型电热丝材料的PTC特性,搭建了一种基于电热丝PTC特性的测温装置,试验结果显示温度测量误差在3％以内.