造纸烘缸用灰铸铁力学性能试验研究

为对超长年限服役的灰铸铁造纸烘缸的力学性能状况进行更准确判断，采用不同方法对一台连续服役62年的烘缸灰铸铁材料进行硬度试验和拉伸试验，并对试验结果进行了比对分析。试验结果表明：D型冲击装置里氏硬度计的试验结果与实验室台式布氏硬度计的试验结果存在较大偏差，不宜采用D型冲击装置里氏硬度计进行灰铸铁造纸烘缸的现场检验；G型冲击装置里氏硬度计试验结果与实验室台式布氏硬度计的试验结果相对接近，不同部件的试验结果偏差也存在较大差异；灰铸铁材料的硬度和强度之间并没有明显的线性对应关系，建议可结合显微组织检验等方法对材料性能状况进行综合判断。     

造纸烘缸用灰铸铁力学性能试验研究

为对超长年限服役的灰铸铁造纸烘缸的力学性能状况进行更准确判断，采用不同方法对一台连续服役62年的烘缸灰铸铁材料进行硬度试验和拉伸试验，并对试验结果进行了比对分析。试验结果表明：D型冲击装置里氏硬度计的试验结果与实验室台式布氏硬度计的试验结果存在较大偏差，不宜采用D型冲击装置里氏硬度计进行灰铸铁造纸烘缸的现场检验；G型冲击装置里氏硬度计试验结果与实验室台式布氏硬度计的试验结果相对接近，不同部件的试验结果偏差也存在较大差异；灰铸铁材料的硬度和强度之间并没有明显的线性对应关系，建议可结合显微组织检验等方法对材料性能状况进行综合判断。     

Tool path adaption based on optical measurement data for milling with industrial robots

Industrial robots are used in a great variety of applications for handling, welding and milling operations. They represent a cost-saving and flexible alternative for machining applications. A reduced pose and path accuracy, especially under process force load due to the high mechanical compliance, restrict the use of industrial robots for further machining applications. Test results showed that these deviations range up to 0.6?mm. In this paper, a method is presented to determine the resulting path deviation of the robot under process force by using a structured light scanner. The obtained data is compared with the CAD (Computer Aided Design) data of the machined part within a developed software module. Additionally, the developed module provides functions for manipulation, registration of STL (Surface Tessellation Language) surface point clouds and a postprocessor for program translation. The comparison is performed using a dexel discretization of each data set. Based on this comparison the robot path is adapted to improve the machining quality. This method can be applied to 3- and 5-axis machining operations. The results show that the deviation can be reduced to 0.1?mm.     

Concept of an offline correction method based on historical data for milling operations using industrial robots

Industrial robots for machining applications have been researched to achieve an alternative, flexible and less expensive machining technology against conventional machine tools. The previous work on industrial robots indicates that industrial robots are only applicable without requirement of high accuracy. The low accuracy and instability under various configurations of industry robot are still major barriers for deploying robots for machining in industries. In this paper, a new method, namely historical data based correction (HDC), is presented to improve the accuracy of industrial robots for milling operations. First, the HDC method is able to calculate the corrected values to compensate the systematical errors during milling operations. Consequently, new tool paths of robots with corrected values are generated. In addition, the HDC method is able to fulfill the requirement of large-scale production. With the proposed method, the surface quality of the machined parts can be improved by more than 60 % without using any additional measuring systems.     

工业机器人多目标拓扑优化设计

为了综合提高工业机器人的结构刚度、振动频率,降低结构质量,从而提高机器人整体的静动态性能,提出了一种基于多目标拓扑优化的机器人结构优化方法。该方法首先对机器人整机和部件进行分析,寻找机器人薄弱的零部件;然后对其进行多目标拓扑优化和模型重建,从而获得最佳的结构。将该方法成功应用于一款3 kg装配、搬运等多功能机器人的分析优化中,结果验证了该分析优化方法的可用性和有效性。     

Retesting thermal-spray powders

Advances in the plasma-spraying process have resulted from the reproducibility of torch and substrate movements by use of robots and handling systems, from constant energy levels by use of thyristor power sources, microprocessor controls and mass flow gas systems, and from constant powder feed rates (±1%) using volumetric systems. Further improvements are to be expected by accurately controlling the powder used in the process. Variations in powder shape and particle size distribution range can alter the deposition efficiency and affect the coating properties.In this paper a scheme designed to ensure constant powder quality for powders used to produce plasma-sprayed coatings for various applications is described. The variety of procedures used to characterize and assess the individual properties of powders relevant to their uses are described and discussed.     

高压输电线路巡检机器人机械结构研究现状及发展趋势

随着国家电网的发展,高压输电线路的人工巡检任务日趋繁重,因此利用智能机器人技术代替传统的巡检方法已经是国内外研究的热点。结合目前国内外巡检机器人的研究现状,对其机械结构研究现状进行了分析,并归纳了其类型以及行走机构、越障机构的结构特征,提出了电力巡检机器人的发展趋势。     

Development of auto defect classification system on porosity powder metallurgy products

Automatic optical inspection (AOI) has been applied to many manufacturing fields for defect inspection of mass production parts, such as PCB and TFT-LCD, but it has never been applied to the production line of porous powder metallurgy. By its nature, the powder-formed part has inherent non-uniform porosity pattern on the metal substrate. The defect’s images are not easily separated from the substrate surface using the conventional binarization technique. This study develops a new image processing methodology and employs optical system design to build up an on-line surface defect inspection system for powder metallurgy parts. An analysis algorithm is also developed for the auto defect classification technique. It removes the noise signals from the porous image, detects the object edge and uses the hybrid-based method to sort out defects on the surface, such as crevice, scratch, broken corner and dent. Experimental tests show the maximum miss rate can be controlled to less than 5.65%.     

Manufacturing of WC–Co moulds using SLS machine

Tungsten carbide–cobalt composite is widely used as a wear-resistant material for cutting tools, molds and other applications. Its production by Selective Laser Sintering (SLS) technique promises to combine the material properties of a composite with the flexibility of a production process. The present paper deals with SLS of a powder mixture of tungsten carbide and cobalt with an aim to make functional parts using a modified Rapid Prototyping (RP) machine (100 W DTM Sinterstation 2000). The associated manufacturing problems and their solutions are discussed. Various compositions of powders have been tried before being settled to a particular composition of WC–9 wt.% Co for making final parts. Bronze infiltration is done on laser sintered parts to enhance their mechanical properties. Fretting wear test is taken as a main characterizing test which is used for estimating the wear resistance of samples.     

50钢汽车前轴开裂原因分析

50钢是一种中碳高强度碳素结构钢,主要用于制造动负载、冲击载荷不大以及要求耐磨性好的机械零件。针对50钢在加工成汽车前轴过程中发生开裂问题,取开裂缺陷试样进行成分、金相等理化性能检测分析。分析结果表明：加热过程中过热产生魏氏组织,导致样件塑性、韧性下降,从而造成开裂。     

Evaluation of the structural integrity of timber bridges

Timber bridges are used on all types of rail lines including important main transcontinental rail lines. A combined structural dynamic and ultrasonic inspection approach is proposed for testing these bridges. This paper presents results of preliminary field tests. Dynamic excitation of the system is used to identify suspect elements in the bridge. Ultrasonic inspection is used to evaluate the suspect elements identified from global testing. The potential for on-site evaluation based on two different dynamic excitations is investigated. Testing of a bridge member using dry coupled ultrasonics is shown to demonstrate this technique on aged timber.     

基于机器视觉的机械零件直线边缘精确检测

本文以计算机视觉在机械零件几何参数检测的实际应用为例，给出了一种使用高斯拉普拉斯(LOG)函数检测斜坡状边缘的像素级位置，在已知目标为直线边缘的情况下，使用最小二乘线性回归方法，把二维的边缘拟合降为一维边缘定位，从而使直线边缘定位达到亚像素级的精度。     

Integrated visual nanometric three-dimensional positioning and inspection in the automated assembly of AFM probe arrays

This paper presents the design of a monocular three-dimensional artificial vision system attached to a 20× microscope lens for precision and microsystems applications. Possible uses in assembly include: positioner calibration, sensor-based part handling, positioning, and inspection in the nanometric range. The developed image acquisition method - along one direction (in steps of 100 nm), the depth-from-focus algorithm and subpixel interpolation (of 5 acquisitions for concurrent localization and inspection), allow to overcome the physical optics limitation achieving a resolution under 200 nm. The vision strategy and algorithms, described in the paper, have been validated by handling an AFM probe array by a micropositioner.     

在役缆索自动检测

缆索检测是保证斜拉桥等大型斜拉结构安全的关键。在缆索机器人基础上，对缆索表面检查、内部检测和维护等进行了讨论。系统采用电磁检测方法，巳在徐浦大桥缆索机器人现场试验中成功进行了实践。     

Evaluation of thermal sprayed coating using ultrasonic inspection by means of bottom echo back reflection

Thermal spraying technique is widely used in various mechanical parts as a surface reforming technique. However, as demand to maintain superior mechanical performance in harsh operating environment increases, the need for non-destructive evaluation method for thermal spray coating becomes more important. For this purpose, we thinned the thickness of the thermal sprayed coating by abrasion with blasting and used ultrasonic inspection by means of bottom echo reflection for effective measurement of abrasion quantity in thermal sprayed coating. The results obtained are summarized as follows. When the thickness of thermal sprayed coating becomes thin, the echo height increases. This is because thermal sprayed coatings absorb ultrasonic energy. Ultrasonic energy absorbed by Al₂O₃ is smaller compared with Fe-13Cr coating. Thermal sprayed coatings submerged in water have a lower echo height compared with air. As mentioned above, the thermal sprayed coating thickness can be estimated using ultrasonic inspection by means of bottom echo back reflection.     

Effect of Thermomechanical Processing on the Microstructure and Mechanical Properties of Nb-Ti-V Microalloyed Steel

The paper presents the results of thermomechanical treatment via forging on the microstructure and mechanical properties of newly obtained microalloyed steel containing 0.28% C, 1.41% Mn, 0.027% Nb, 0.028% Ti, and 0.019% V. The investigated steel is assigned to the production of forged elements for the automotive industry. Conditions of forging using the thermomechanical processing method were developed based on plastometric tests. Continuous and double-hit compression tests were conducted using the Gleeble 3800 thermomechanical simulator. The samples were investigated in a temperature range from 900 to 1100 °C and a strain rate of 1 and 10 s^?1. To determine the recrystallization kinetics of plastically deformed austenite, discontinuous compression tests of samples using the applied deformation were conducted in a temperature range from 900 to 1100 °C with isothermal holding of the specimens between successive deformations for 2-100 s. Observations of the microstructures of thin foils were conducted using a TITAN80-300 FEI transmission electron microscope. The applied thermomechanical treatment allows to obtain a fine-grained microstructure of the austenite during hot-working and production of forged parts. These acquire advantageous mechanical properties and guaranteed crack resistance after controlled cooling from the end plastic deformation temperature and successive tempering. Forgings produced using the thermomechanical treatment method, consecutively subjected to tempering in a temperature range from 550 to 650 °C, reveal values of YS_0.2 which equal from 994 to 892 MPa, UTS from 1084 to 958 MPa, KV from 69 to 109 J, KV^?40 from 55 to 83 J, and a hardness ranging from 360 to 300 HBW.     

A contribution to collision free trajectory planning for 6r robots in varying environments

In flexible und complex handling systems trajectory planning becomes increasingly demanding. As an example, the geometry of the work pieces tends to vary more than it used to. Therefore, the planned trajectory of the handling robot has to either be adjusted for each piece individually or the trajectory has to allow general geometry. This leads to performance loss for smaller work pieces since they are less sensitive to obstacles and can therefore be moved on shorter (faster) trajectories. In both cases, time and costs could be reduced. Another characteristic of handling systems is that several handling robots share the same workspace. Again the positions of these obstacles are only known at runtime. This places great demands on the planning tools. In this paper, it is shown that both problems can be treated with a hybrid method called curve flow method. This method combines a gradient flow which comes from a variational principle and a potential field method. The variational principle makes the planned trajectories short, the potential field prevents collision.     

Creation of helicopter dynamic systems digital twin using multibody simulations

This paper presents a new approach to develop digital twins of helicopter dynamic systems. Helicopter industries attach growing attention to the development of digital twins to be more predictive of mechanical parts lifetime. The number of sensors available to measure loads during flights is limited. Complementary simulations are necessary to compute all the loads that the mechanical parts undergo.A new process is described to build these simulations fed with flights data records. Complexity of helicopters dynamics systems leads to create several local models of subsystems using a multibody dynamic formalism. A study focused on a swashplate rotor assembly is presented to illustrate this approach, including a new model of bearing and its validation based on bench tests.     

桥梁检测机器人运动分析与运动规划研究

针对桥梁检测机器人对于高墩、高厚度桥梁不同部位的便捷检测需求,开展五自由度桥检机器人运动分析与运动规划研究。采用改进型D-H方法进行正向运动学建模,通过解析方法求解两种形式的运动学逆解,推导雅可比矩阵,分析机器人的奇异位型;通过蒙特卡洛方法得到机器人工作空间,确定工作空间可覆盖待检测区域;由连杆力与力矩平衡方程推导各关节受力关系,基于关节负载能力开展运动规划研究。仿真分析结果证明了方法的可行性,说明机器人能够完成预定的工作任务需求。     

激光功率与扫描速度对选区激光熔化钴铬合金组织性能的影响

目的 明确选区激光熔化钴铬合金中激光线能量密度、激光功率和激光扫描速度对成形件组织、性能的影响,探究优化工艺参数的方法。方法 基于ANSYS有限元软件模拟选区激光熔化过程中熔池尺寸的基础上,通过金相显微镜分析了熔池尺寸和显微组织,电子背散射衍射分析了晶粒尺寸,使用力学试验机和洛氏硬度计研究了试样的力学性能。结果 随着线能量密度降低,成形件的熔池尺寸、晶粒大小、冷却速度和力学性能降低。但在激光线线能量密度为0.242 J/mm的条件下,扫描速度为1 200 mm/s时成形试样的致密度为98.7%,抗拉强度为867 MPa,延伸率为6.5%,其力学性能均高于扫描速度为950 mm/s时成形的试样,与线能量密度更高的0.263 J/mm成形条件下250 W+950 mm/s的成形试样力学性能相近。结论 激光线能量密度是影响选区激光熔化钴铬合金熔池尺寸和组织性能的关键因素,但熔池尺寸与激光线能量密度没有线性关系。相同的线能量密度下,增加激光扫描速度,有利于获得大的熔池尺寸和冷却速度,提高成形件的致密度和降低晶粒尺寸,最终使成形件力学性能提高。