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.

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

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

在薄膜电加热的保温技术中,要求保温结构的隔热效果好,但这会使保温结构的制作成本提高.为了解决隔热效果好和制造成本低两者之间相互矛盾的问题,针对3种常用的保温材料,设计了4种不同的保温结构,并根据传热学理论,推导了保温结构的厚度计算方法.使用组合赋权法将保温结构的隔热性能与制作成本相关联,提出并验证了一种综合了隔热性能与制作成本的结构优化方法.测试结果显示,该保温结构优化设计方法既能满足保温需求又能降低制造成本.

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.

The project aim is to demonstrate the simulation analysis of articulated bearing（UC6-GJB269-87/5） based on finite element environment.Using controlled variable methods to study the process parameters of the bearing closing tool with the best closing effect.The result shows the joint bearing can take the stress which is significantly less than the required stress to close the bearing.Furthermore,the axial displacement of the tested bearing matches the finite element simulation result which verifies the correctness of the theoretical analysis,Providing an important theoretical support for the closing of the joint bearing in engineering.

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.

针对蚁群算法存在的收敛速度慢、易陷入局部最优和容易死锁等问题,提出了一种用于自动引导车(AGV,automa-ted guided vehicle)路径规划的双种群蚁群算法;该算法引入差异化信息素初始值,修改启发函数并在信息素更新时对最优及最差路径进行奖惩;以改进策略为基础,引入自适应步长搜索策略,通过具有差异化步长的两个种群相互协作加强算法寻优能力和搜索效率;针对死锁问题,提出了将符合条件的单元格视为障碍物的"填充陷阱"策略;分别进行仿真实验和车间现场实验,结果表明,该算法可以为AGV规划出一条安全且综合性能较好的路径,为AGV路径规划提供了一种可行的方案.

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

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.

针对电热丝加热具有的热惯性、时变性等特点,提出一种基于CARMIA模型的模糊广义预测控制方法,对系统参数进行辨识.将模糊广义预测控制应用到加热过程,进行Matlab仿真和实际加热实验对比.结果表明:该方法在不同条件下的加热响应均可获得更快的调整速度和更好的控制精度,有较强的鲁棒性.

微细超声加工系统的控制过程复杂,当前控制方法均忽略了其动力学属性,因为动力学属性特征较为模糊,过于复杂的约束条件会降低切割控制速度,造成能耗高、切割精度低等问题,基于自校正模糊控制理论,设计了一种考虑微细超声加工系统动力属性的切割自校正控制方法.通过对微细超声加工系统展开详细的动力学分析,获取系统的加速度向量.根据分析结果,结合微细超声加工系统的理想运动变换条件,建立割刀误差数学模型,并计算割刀末端位置误差,再通过自校正模糊控制方法校正该误差,实现对切割过的高精度控制.实验结果表明:该方法提高了微细超声加工系统的切割速度,提高切割误差的控制精度,切割能耗也在承受范围内.

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.

The electrochemical jet machining usually applies a very small standoff distance (SOD) between nozzle and workpiece in order to achieve a high anode dissolution rate. However, this small machining gap can cause intensive stray corrosion and secondary dissolution during the process, and consequently result in worse machining localization. This study investigated machining localization in abrasive-assisted electrochemical jet machining of SiCp/Al composites using large SOD. The analysis shows that using large SOD is expected to reduce stray corrosion of the matrix in the initial phase of the machining, and thereafter avoid secondary dissolution due to preventing the nozzle from re-contacting with reflected jet flow in the further phases. The experimental results agreed well with the analysis in processing 20%-SiCp/Al and 45%-SiCp/Al composites using the SOD ranged between 2 and 8 mm. It was found that the achieved entrance size significantly reduced with increases of the SOD, regardless of electrolyte type, processing time and abrasive concentration. The achieved aspect ratio due to relatively larger SOD will exceed that due to smaller SOD after a longer processing time. The investigation suggests that better machining localization can be obtained using relatively larger SOD and longer processing time compared to using usual narrow SOD.

This paper has investigated the mechanism of over-erosion in WEDM of PCD composite. The result reveals that the over-erosion phenomenon cannot be avoided in the WEDM of PCD composite during fabrication of micro cutter. The reason of that is due to the different erosion rate of different elements in the composite. The discharge voltage, single-pulse energy and machining gap have influences on the size of overerosion groove. A set of optimal parameters for minimum erosion groove were obtained through experiments.

对SiCp/Al复合材料进行了电化学射流加工试验,探讨材料去除机理,分析加工电压、加工时间对加工形貌及材料去除率的影响.研究发现,材料的去除过程主要包括铝基体的阳极溶解与SiC颗粒的冲刷脱落,SiC颗粒脱落在加工表面形成微凹坑,微凹坑的几何尺寸及数量对加工表面粗糙度具有较大影响;材料去除速率随加工电压的增加而增大,这与电化学射流加工单一金属材料相似.

Determining quantity of vehicles in an interior trim assembly line is a key problem for a car manufacturing workshop. This paper presents a work to optimize quantity of vehicles for designing car assembly lines. A simulation model of the car interior trim assembly workshop was established using Siemens Plant Simulation system. Based on the entropy weight method and the TOPSIS method, the effect of various quantity vehicles was evaluated. An optimized solution for the number of vehicles was obtained accordingly. Compared to original design, the optimal solution can reduce the total cost of vehicles up to 6.96%. The calculation of variance for utilization rate of equipment has been reduced approximate 30%, which means the equipment utilization is more balanced than original design.