In situ monitoring methods for selective laser melting additive manufacturing process based on images-A review

Selective laser melting(SLM)has been widely used in the fields of aviation,aerospace and die manufacturing due to its ability to produce metal components with arbitrarily complex shapes.However,the instability of SLM process often leads to quality fluctuation of the formed component,which hinders the further development and application of SLM.In situ quality control during SLM process is an effective solution to the quality fluctuation of formed components.However,the basic premise of feedback control during SLM process is the rapid and accurate diagnosis of the quality.Therefore,an in situ monitoring method of SLM process,which provides quality diagnosis information for feedback control,became one of the research hotspots in this field in recent years.In this paper,the research progress of in situ monitoring during SLM process based on images is reviewed.Firstly,the significance of in situ monitoring during SLM process is analyzed.Then,the image information source of SLM process,the image acquisition systems for different detection objects(the molten pool region,the scanned layer and the powder spread layer)and the methods of the image information analysis,detection and recognition are reviewed and analyzed.Through review and analysis,it is found that the existing image analysis and detection methods during SLM process are mainly based on traditional image processing methods combined with traditional machine learning models.Finally,the main development direction of in situ monitoring during SLM process is proposed by combining with the frontier technology of image-based computer vision.

Statistical Analysis of Process Monitoring Data for Software Process Improvement and Its Application

Software projects influenced by many human factors generate various risks. In order to develop highly quality software, it is important to respond to these risks reasonably and promptly. In addition, it is not easy for project managers to deal with these risks completely. Therefore, it is essential to manage the process quality by promoting activities of process monitoring and design quality assessment. In this paper, we discuss statistical data analysis for actual project management activities in process monitoring and design quality assessment, and analyze the effects for these software process improvement quantitatively by applying the methods of multivariate analysis. Then, we show how process factors affect the management measures of QCD (Quality, Cost, Delivery) by applying the multiple regression analyses to observed process monitoring data. Further, we quantitatively evaluate the effect by performing design quality assessment based on the principal component analysis and the factor analysis. As a result of analysis, we show that the design quality assessment activities are so effective for software process improvement. Further, based on the result of quantitative project assessment, we discuss the usefulness of process monitoring progress assessment by using a software reliability growth model. This result may enable us to give a useful quantitative measure of product release determination.

Mechanical Properties of Remote-Laser Cut CFRP and Thermographic Laser-Process Monitoring

Remote-laser beam cutting is a productive technology without tool wear. Especially when cutting carbon fiber reinforced polymers (CFRP), it offers constant manufacturing quality. Since it is a thermal process, a heat-affected zone (HAZ) is formed at the edge of the cut. Based on quasi-static and cyclic mechanical tests on open-hole specimens, the influence of the process on the mechanical properties of CFRP is shown. The quasi-static tests are in good correlation with results from other researchers by indicating an increase in the maximum tensile stress of the test specimens, cut by remote-laser. The reason is the rearrangement of the shear stresses and a reduction of the notch stress concentration. However, the results of the present study show that excessive expansion of the HAZ leads to a reduction in the maximum tensile stress compared to milled test specimens. Under cyclic load conditions, remote-laser beam cutting does not lead to a more pronounced degradation than milling. The mechanical properties of the notched test pieces are sensitive to the expansion of the HAZ. For the production of components it is therefore necessary that the remote-laser beam cutting is carried out under controlled and documentable conditions. For this purpose, process thermography was tested as a tool for quality assurance. The results show that the technology is basically suitable for this task.

激光测距机在线能量监测系统设计

本文基于无人值守条件下对激光测距机发射能量进行直接人工测量较为困难,为了防止激光器能量下降影响激光测距机性能,需要对测距机工作状态进行实时监控这一需求设计了激光测距机在线能量监测系统。对能量探头的结构与检测位置进行了研究,并设计硬件电路实现能量测量。本文设计的在线能量监测系统可以在不影响测距机测距能力的情况下实现kHz量级重频激光测距机的宽量程实时能量监测,并满足小型化、集成化设计要求。

TC17钛合金激光熔覆熔池实时监测算法研究

航空发动机钛合金压气机叶片工作时,由于长时间高强度服役和异物损伤,叶片会发生变形、凹痕、磨损、裂纹甚至断裂。激光熔覆技术因其热影响区小、沉积性能好、成形精度和自动化程度高,已经成为叶片修复的重要方法之一。熔池几何特征是影响熔覆质量的关键因素,因此本文针对熔池实时监测,提出了一种基于图像处理的识别测量算法。首先,通过图像掩膜提取ROI区域,再对ROI区域进行伽马变换、阈值二值化实现熔池区域的分割;然后计算轮廓面积特征进行去噪;最后采用AABB包围盒对熔池的几何特征进行提取,实现了熔覆过程中熔池长宽的实时监测。最终通过多参数正交试验,验证算法平均识别误差为0.24 mm。

离线并行软件加载技术的研究

文章基于离线型并行软件加载技术的研究,从功能、性能架构,硬件需求,硬件设计方案,软件设计方案等方面为切入点,介绍了离线型并行软件加载技术的实现方案。通过多端口适配技术、多路路由技术、上位机软件开发,实现3种模块、7个接口、19个通道、20余种程序的并行加载。该研究对于其他集成化电子装备在大规模的软件加载环节建立适合自身产品特点的软件加载提供了一定借鉴。

Multi-sensor measurement and data fusion technology for manufacturing process monitoring:a literature review

Due to the rapid development of precision manufacturing technology,much research has been conducted in the field of multisensor measurement and data fusion technology with a goal of enhancing monitoring capabilities in terms of measurement accuracy and information richness,thereby improving the efficiency and precision of manufacturing.In a multisensor system,each sensor independently measures certain parameters.Then,the system uses a relevant signalprocessing algorithm to combine all of the independent measurements into a comprehensive set of measurement results.The purpose of this paper is to describe multisensor measurement and data fusion technology and its applications in precision monitoring systems.The architecture of multisensor measurement systems is reviewed,and some implementations in manufacturing systems are presented.In addition to the multisensor measurement system,related data fusion methods and algorithms are summarized.Further perspectives on multisensor monitoring and data fusion technology are included at the end of this paper.

Laser Surface Hardening of Tool Steels—Experimental and Numerical Analysis

This research work is focused on both experimental and numerical analysis of laser surface hardening of AISI M2 high speed tool steel. Experimental analysis aims at clarifying effect of different laser processing parameters on properties and performance of laser surface treated specimens. Numerical analysis is concerned with analytical approaches that provide efficient tools for estimation of surface temperature, surface hardness and hardened depth as a function of laser surface hardening parameters. Results indicated that optimization of laser processing parameters including laser power, laser spot size and processing speed combination is of considerable importance for achieving maximum surface hardness and deepest hardened zone. In this concern, higher laser power, larger spot size and lower processing speed are more efficient. Hardened zone with 1.25 mm depth and 996 HV surface hardness was obtained using 1800 W laser power, 4 mm laser spot size and 0.5 m/min laser processing speed. The obtained maximum hardness of laser surface treated specimen is 23% higher than that of conventionally heat treated specimen. This in turn has resulted in 30% increase in wear resistance of laser surface treated specimen. Numerical analysis has been carried out for calculation of temperature gradient and cooling rate based on Ashby and Easterling equations. Then, surface hardness and hardened depth have been numerically estimated based on available Design-Expert software. Numerical results indicated that cooling rate of laser surface treated specimen is high enough to be beyond the nose of the CCT diagram of the used steel that in turn resulted in a hard/martensitic structure. Numerically estimated values of surface temperature, surface hardness and hardened depth as a function of laser processing parameters are in a good agreement with experimental results. Laser processing charts indicating expected values of surface temperature, surface hardness and hardened depth as a function of different wider range of laser processing parameters are proposed.

激光冲击强化过程监测及其质量在线评估:现状与挑战

激光冲击强化(Laser shock peening,LSP)是一种新型抗疲劳延寿制造技术,可应用于航空发动机关键零部件。现有LSP离线检测方法存在“质量盲区”的问题,为提高LSP加工质量的一致性、可靠性和稳定性,有必要开展LSP过程多源信息的精确感知和靶材表面完整性在线评估研究。从LSP瞬态高能过程所释放的两类重要物理信息入手,即激光诱导等离子体冲击波(Laser induced plasma shock wave,LIPSW)和激光诱导等离子体光谱(Laser induced plasma spectroscopy,LIPS),分别综述了LSP动态过程两类信息监测感知的研究现状,以及多源信息融合(Multi-source information fusion,MSIF)技术在LSP领域的研究进展。最后探讨了亟待解决的科学问题和现存的挑战。

粮仓粮食数量监测技术研究现状与展望

数量真实是保障国家粮食安全的重要组成部分,对粮食库存数量的监管也影响着国家粮食安全。但是,由于粮食存储点多、面广,监管难度较大,“转圈粮”、擅自动用、未轮报轮等涉及粮食库存数量的违法违规案件时有发生,因此需要加强粮食监管,以避免此类事件发生。近年来,随着科技快速发展,粮仓粮食数量监测的相关技术不断涌现,并在保障国家粮食安全方面发挥了显著作用。文章主要针对压力传感器、三维激光扫描、超声波、雷达、图像处理等技术,阐述了这几种粮仓粮食数量监测技术的主要原理和优缺点,并对粮仓粮食数量监测技术领域存在的问题和未来应用研究趋势进行了展望。

基于SLAM的井筒倾斜变形监测方法研究

针对传统矿山井筒安全监测方法中存在效率低(需停产监测)、数据量少、误差大等问题,提出利用激光SLAM(Simultaneous Localization and Mapping实时定位与建图)技术监测井筒倾斜变形的方法。以峰峰集团牛儿庄矿主井为研究对象,设计监测方案并利用激光SLAM技术感知井筒的内部信息,采用K′-means算法提取井筒边界点云,建立马尔可夫数学模型得到点云切片的中心,进而建立井筒中心基准线,根据整体和分段的方法分析了井筒倾斜变形。结果表明:井筒整体竖向倾斜1.99‰,上部井筒(距井口0~100 m)竖向倾斜3.06‰,下部井筒(距井口150~205 m)竖向倾斜1.85‰;相对于传统监测方法,激光SLAM工作时长由1 d甚至更长时间缩短至1 h,在井筒罐笼检修时间内即可完成监测工作,不需要停产的同时工作效率显著提高。

激光增材制造过程监测与控制研究进展及展望

激光增材制造(Laser additive manufacturing,LAM)以激光为载能束逐层熔化堆积金属材料的方式成形构件,因其兼顾制造效率与成形精度,在国防工程、航空航天领域受到广泛关注。提高制造过程稳定性、改善成形精度、消除内部缺陷是推进LAM高效、高质量发展与应用必须解决的关键科学与技术难题,对LAM过程实施在线监测与控制是解决这些难题的必经之路。分析了LAM成形缺陷的产生机制及相应的抑制措施,阐述了LAM过程信号的监测方法与研究现状,讨论了LAM成形质量的闭环控制策略,指出了未来LAM过程监测与控制的主要研究方向。

基于结构光的井下输送带煤流量监测研究

为了监测井下带式输送机煤流量,进一步调控输送带速度,减少带式输送机能量损耗和设备磨损,提出了一种基于结构光扫描的煤流量监测技术。搭建实验平台,采用直射式激光三角测量法采集输送带上煤流轮廓信息,首先对图像进行导向滤波处理,其次将灰度值梯度作为阈值提取光斑区域,利用Steger算法求取亚像素精度的激光中心线,最后在软件Halcon中重建煤流三维点云模型,计算煤流体积。系统静态测量平均误差率为0.6%,基于速度、体积双变量的原煤体积测量偏差可控制在6%以内,验证了激光扫描法在井下带式输送机高速运行时煤流量监测的可行性,对减少带式输送机能耗有一定意义。

隧道结构变形监测中三维激光扫描技术的应用研究

为提高隧道施工和运营阶段的结构变形监测技术水平,满足日益高要求的信息化、高效率监测要求,文章对三维激光扫描技术在隧道施工和运营期结构变形监测中的应用进行研究,详述了隧道结构变形监测中三维激光扫描所得点云数据的拼接和建模方法,依托实际工程设计验证试验,探究不同空间坐标系转换算法,并对比测量机器人和三维激光扫描技术测量结果,验证了三维激光扫描技术的测量精度能够满足隧道结构变形监测需求。

高灰度级高分辨率激光散斑血流实时成像研究

激光散斑对比成像是一种大测量范围、实时、高分辨率的光学成像方法.现有研究表明,低灰度级(8位)低分辨率(752像素×480像素)照相机可以有效监测血液等散射介质流动,但散粒噪声大、有效成像区域小等缺点难以通过软件弥补,严重影响成像质量.使用高灰度级(16位)高分辨率(2 048像素×2 048像素)照相机监测血液流动会减慢单帧成像速度,并行计算能使图像处理时间减少1/3.研究借助动物血液流动实验,以成像速度与成像质量为评价标准,对比分析高灰度级高分辨率空间激光散斑对比成像与空间近似激光散斑对比成像(sLSCIa)、时间激光散斑对比成像(tLSCI)的结果.结果表明,高灰度级高分辨率空间激光散斑对比成像并行计算兼顾成像质量与成像速度,可以达到临床实时监测血液流动要求.

大型船舶靠泊监测系统设计

大型船舶靠泊监测系统将激光检测技术、互联网技术、手机APP等相关技术有机结合,实时监测靠泊过程中港口环境变化、船舶靠泊速度、角度及距离等数据信息,建立一套船舶靠泊过程安全实时监测及数据实时发布平台,可辅助靠泊指挥人员科学指挥和管理人员有效监管。

双面激光冲击次序对小孔件强化效果影响研究

小孔构件是典型的应力集中细节,其易在疲劳载荷下产生裂纹,影响关键结构的使用性能和服役寿命。为了研究双面冲击次序对小孔件强化效果的影响,对双面激光同时冲击强化(双面对冲)和依次冲击强化的TC4-DT小孔构件进行了疲劳拉伸试验,并利用ABAQUS有限元软件,对两种冲击次序强化后的残余应力分布进行了仿真。结果表明,双面对冲的试样疲劳增益是双面激光依次冲击强化后的2倍以上;双面对冲后小孔件的应力分布更均匀,其疲劳源明显偏离厚度中点处,而双面激光依次冲击时,两激光冲击表面的残余应力差较大。仿真结果与试验有较好的一致性。

使用WinCC在机电一体化系统中实现过程监控

WinCC(WindowsControlCenter,窗口控制中心)是西门子公司(SIMENS)实现PLC与上位机之间的通讯及上位机监控画面的制作的组态软件。主要介绍如何利用WinCC建立监控画面,并使监控画面根据现场实际情况动态显示。并以机电一体化粗纱机的控制系统为例,介绍了使用WinCC系统的硬件配置,并介绍通过WinCC组态监控系统,创建动态人机界面,实现过程监控的具体步骤。最后结合自身经验,总结了一些功能实现的编程技巧与相关源程序。

井下压裂实时监测技术及其应用

采用传统的压裂监测技术测得的井口压力和温度很难反映井底的真实情况。鉴于此,研究了井下压裂实时监测技术,并配套研制了实时监测系统和压裂实时解释处理软件。实时监测系统将承载着监测仪的监测管柱下入目的层,在井底直接测得压力和温度数据,避免了通过井口数据折算至井底时由于井筒摩阻系数、井筒液体密度变化和泵压不稳定等因素产生的误差,因此分析的准确性大大提高;解释处理软件可对测量数据进行解释评价,以此来反映目的层真实信息及压裂效果。井下压裂监测技术在中原油田得到了广泛应用,分别在濮城老区和内蒙探区监测施工50余井次,测试成功率100%。

基于图像识别的水下地形冲刷过程监测

针对水下地形冲刷过程发展的特点,引进医学领域图像处理与分析技术,提出了以波长635 nm的红色线状激光为辅助光源、以MATLAB图像识别处理技术为基础的水下地形冲刷监测方法.该方法具有非接触性测量、实时同步监测等特点.同时基于MATLAB的图像识别原理,提出了重现水下地形的数字化方法.通过在河工模型局部冲刷发展研究中的实际应用及误差分析,结果表明监测系统十分有效,可以实现水下地形冲刷过程的实时精细监测及动态分析.