基于PC-DMIS的三坐标测量机测量距离评价的探讨

介绍了PC-DMIS软件中常用的三种距离评价方式以及实际测量中的选用原则,结合实例,简述了三坐标测量距离的不确定度评定。     

Uncertainty analysis and variation reduction of three dimensional coordinate metrology. Part 1: geometric error decomposition

In this paper our study focuses on the uncertainty analysis and variation reduction of coordinate system estimation using discrete measurement data and is associated with the applications that deal with parts produced by end-milling processes and having complex geometry. This paper consists of three parts. Since the uncertainty of the estimated coordinate transformation arises from the geometric errors on a part surface, Part 1 is devoted to the study of surface geometric errors. In this study, according to the characteristics of end-milling processes the sampled geometric error is divided into two components, and a decomposition procedure is developed for geometric error decomposition. The results of surface geometric error decomposition will be used in Part 2 for uncertainty analysis and in Part 3 for variation reduction.     

2A14合金的连续冷却转变动力学曲线及其应用

测定2A14合金连续冷却转变动力学曲线(CCT图),并对该曲线进行应用研究.通过DSC分析和SEM组织观察确定2A14合金合理的固溶温度,采用动态电阻法测得固溶后合金连续冷却过程的电阻-温度曲线,根据曲线斜率变化判断相变信息,绘制2A14合金的CCT图,利用透射电镜(TEM)观察连续冷却过程中合金的组织转变.结果表明:2A14合金适宜的固溶温度为505℃;随着冷却速度的增加,相变开始温度先降低,在达到某冷却速度时骤升,然后持续增加;相变主要集中在140～380℃的温度区间发生,抑制相变发生的临界冷却速度稍大于3.8.5℃/s;在实验范围内,20 mm厚的2A14合金板适宜采用60℃或100℃水淬,参考所测CCT图制定分级淬火工艺,可以在最大限度减小淬火应力的同时,抑制第二相的析出.     

有限元模型转换及其在金属板料成形数值模拟中的应用

本文根据CAD和CAE软件各自的功能和特点 ,探讨了板料成形数值模拟中CAD模型向CAE模型转换的方法 ;并针对有限元分析软件ANSYS与ABAQUS的实际特点 ,编写了有限元模型转换接口程序 ,用实例验证了所编接口转换程序的可行性与正确性。     

焊管纵缝实时焊缝跟踪的机器视觉方法

介绍了一个大直径不锈钢等离子弧焊管纵缝焊缝跟踪系统。该系统利用视觉传感器将熔池与接缝拍摄在一幅图像中，检测出接缝偏差然后驱动工件运动使接缝对准焊枪。提出了一种新颖的基于机器视觉的熔池区域图像处理算法。该算法以20帧／s的速度实时处理图像并提取出三个特征量用来计算接缝偏差。试验证明这种算法是有效的，并且能够满足系统的实时响应要求。     

手工氩弧焊机半自动改造电控方案

在不改变传统手工送丝钨极氩弧焊机(TIG)基本构造的前提下,对其电气控制部分进行改造为半自动氩弧焊机。改造后进行了通电试验,在热待机状态,即焊机高频引弧系统未工作时,新增的送丝控制电路工作很正常,达到预期的效果。一旦高频引弧系统工作,直流调速模块便失去原有的控制功能——调速模块损坏。     

A machine vision approach to seam tracking in real-time in PAW of large-diameter stainless steel tube

Manual monitoring and seam tracking through watching weld pool images in real-time, by naked eyes or by industrial TV, are experience-depended, subjective, labor intensive, and sometimes biased. So it is necessary to realize the automation of computer-aided seam tracking. A PAW (plasma arc welding) seam tracking system was developed, which senses the molten pool and the seam in one frame by a vision sensor, and then detects the seam deviation to adjust the work piece motion adaptively to the seam position sensed by vision sensor. A novel molten pool area image-processing algorithm based on machine vision was proposed. The algorithm processes each image at the speed of 20 frames/second in real-time to extract three feature variables to get the seam deviation. It is proved experimentally that the algorithm is very fast and effective. Issues related to the algorithm are also discussed.     

三维计算机视觉及其在焊接中的应用

随着视觉传感、图像处理和人工智能等技术的发展,计算机视觉以其信息量大、精度高、通用性好、检测范围大等特点,在焊接领域得到了广泛的应用。简要地介绍了目前出现的三堆计算机视觉技术和方法,综述了该技术在焊接中的典型应用,并在此基础上提出了目前存在的问题和未来的发展趋势。     

Calculation of phase transformation latent heat based on cooling curves in end-quench test and its application in nickel-based superalloy

To obtain the phase transformation latent heat corresponding to different cooling rates with low test workload and cost, the Newton thermal analysis method and the improved Newtonian thermal analysis method were discussed based on the cooling curve obtained in the end-quench test. The validity of two methods was given by the latent heat calculation of 45^# steel. The results show that the relative error of latent heat is 5.20% through the improved Newtonian thermal analysis method, which is more accurate than the Newtonian thermal analysis method. Furthermore, the latent heat release of phase transformation of the self-designed CSU-A1 powder metallurgy nickel-based superalloy increases from 4.3 to 12.29 J/g when the cooling rate decreases from 50.15 to 33.40 °C/min, because there is more sufficient time for the alloy microstructure to complete the phase transformation process when the cooling rate is smaller.     

3Cr2Mo钢马氏体相变塑性及应力对其相变动力学的影响

通过不同单轴拉/压应力载荷作用下的膨胀试验研究了3Cr2Mo钢中马氏体相变的相变塑性和应力对马氏体相变动力学的影响。结果表明:所测定的Greenwood-Johnson相变塑性模型中参数K随等效应力增加而增加,表征马氏体相变动力学的Koistinen-Marburger方程中系数α约为0.0236,应力状态对其没有明显影响。马氏体点(MS)范围在410～438℃之间,且随等效应力值的增加而升高。     

低碳钢压缩变形时的形变不均匀性及其对铁素体转变的影响

宏观的形变不均匀性会导致相变和再结晶的差异 ,从而造成最终组织和性能的变化。本文观察并测量了单向压缩的低碳钢形变强化相变、铁素体热、冷形变时样品中心与边缘的铁素体形貌、珠光体或渗碳体分布和织构的差异。分析了不同区域相变及再结晶时的组织演变特点。讨论了形变储存能、渗碳体粒子及形变温度对铁素体相变及再结晶的影响。     

Feature extraction of machine sound using wavelet and its application in fault diagnosis

Machine sound always carries information about the working of the machine. But in many cases, the sound has a very low SNR. To obtain correct information, the background noise has to be removed or the sound must be purified. A de-noising method is given in this paper and is successfully used in feature sound extraction. We can easily diagnose a machine using the purified sound. This de-noising method is based on the wavelet technique and uses the Morlet wavelet as the mother wavelet, because its time–frequency resolution can be adjusted to adapt to the signal to be analyzed. The method is used for extracting the sound of some vehicle engines with different types of failure. The feature sound is extracted successfully.     

A die forging design approach for controlling metal flow way and its application in practice

In this paper a novel idea about die forging process design in relation to metal flow is presented. The purpose is to almost completely fill a die cavity before flash starts to form. The paper shows that preform design is the way to realize this situation. The paper describes a method in which metal flow is simulated using UBET in reverse sequence to that occurring in practice. The successful application of the method in production is shown.     

Inverse finite element approach and its application in sheet metal forming

The inverse finite element approach (IFEA) was derived from ideal forming to predict the development blank of sheet metal and the thickness strain distribution according to the geometry of final product. The flange portion of stamping product under blank-holder is a free parameter that is mostly dependent on the shape of the initial flat blank. Based on the IFEA, this paper proposed a node relocation technique to estimate the influence of flange shape and evaluate the final geometry and thickness strain distribution from the prescribed flat blank. The applications of the IFEA cover the backward and forward evaluations: from given product to initial blank and from given initial blank to final product. Those applications make the design of sheet metal forming easy and fast. A door-like product experiment confirmed that the precision of the IFEA satisfied the manufacturing requirement.     

基于单片机的交流电机软启动器及其在机床电力拖动中的应用

0 引言。众所周知，三相异步电动机以其低成本、高可靠性和易维护等特点，被广泛应用在各个行业。特别是机床设备中，它作为一种主要的动力设备，常常用来拖动主轴、工作台、冷却泵、油泵等装置。但是它在直接启动时，由于启动电流高达额定电流的5～7倍，所以会对电网及负载造成很大的冲击，影响了周边电器的工作，增加了机械传动部件的磨损，降低了设备的寿命。     

Design of a six-axis high precision machine tool and its application in machining aspherical optical mirrors

The paper presents the design of a six-axis machining system and its application in fabricating large off-axis aspherical mirrors with sub-aperture lapping techniques. The new system is based on computer-controlled optical surfacing (CCOS), which combines the faculties of grinding, polishing, and on-machine profile measuring, has the features of conventional loose abrasive machining with the characteristics of a tool having multiple degrees of freedom moving in planar model. And a novel dual touch-trigger probe profiler is designed, which is composed of a probe, model METRO-MT60 made by HEIDENHAIN Co., is integrated into the system for measuring the shape accuracy of the tested aspherical surface, another probe modeled METRO-MT12 is designed as a calibrating device for minimizing the cosine error caused by assembly inaccuracy. The new CNC machining system with two kinds of moving coordinate systems, dual tool activities and on-machine measuring is presently developed based on the new concept. The general material removal function during machining is analyzed on the basis of the Preston hypothesis. Further, an alignment test of the measuring profiler is carried out using a leveling rule as a specimen. The accuracy of the optical surfaces measured by the dual probe profiler is found to be within 1 μm PV after removing cosine error and error compensating, achieves to the resolving power of the profiler is about 0.2–0.5 μm, so the developed system can be applied to the shape accuracy measuring of aspheric fabrication with micro precision during fine grinding process according to the calibrating results. Finally, the manufacturing experiments are carried out by virtue of an off-axis oblate ellipsoid mirror with rectangular aperture as 770 mm×210 mm and centered 127 mm. The accuracy of the aspherical mirror improved from the initial form error of 17.648 μm rms to the final one of 0.728 μm rms after grinding for 200 h.     

A machining test to calibrate rotary axis error motions of five-axis machine tools and its application to thermal deformation test

This paper proposes a machining test to parameterize error motions, or position-dependent geometric errors, of rotary axes in a five-axis machine tool. At the given set of angular positions of rotary axes, a square-shaped step is machined by a straight end mill. By measuring geometric errors of the finished test piece, the position and the orientation of rotary axis average lines (location errors), as well as position-dependent geometric errors of rotary axes, can be numerically identified based on the machine׳s kinematic model. Furthermore, by consequently performing the proposed machining test, one can quantitatively observe how error motions of rotary axes change due to thermal deformation induced mainly by spindle rotation. Experimental demonstration is presented.     

内时塑性一致切线刚度法及在胀形中的应用

介绍了位移基有限元方法 ,并在位移基有限元中嵌入了无屈服面内时本构理论 ,并提出了相应于平面应力问题的直接代入法。在求解所得到的非线性方程中 ,由于得到的非线性方程在解的邻域内高度病态 ,Newton方法收敛性得不到保证 ,采用全局收敛的二分法可以得到很好的解。利用推导出的位移基内时本构有限元模拟了半球形冲头胀形问题 ,并把它的解与Mises屈服模型的解进行了比较 ,两者吻合较好 ,表明了本文方法是正确与可靠的。本文在位移基有限元中成功地嵌入了内时本构模型 ,并成功地模拟了半球形冲头胀形问题。同已有的本构模型相比 ,本文模型非常简明 ,并且易于应用。     

Effect of isothermal transformation temperature on amount of retained austenite and its thermal stability in a bainitic Fe–3%Si–0.45%C–X steel

Film-like morphology of retained austenite is observed at low isothermal temperatures, whereas blocky morphology of retained austenite appears at high temperatures in a bainitic Fe–3%Si–0.45%C–X steel. Amount of retained austenite increases with increasing temperature, exhibiting a peak at around 350 °C, above which it decreases with increasing temperature.     

超高强度帘线钢LX92A连续和等温冷却下的相变行为

通过热模拟试验研究了超高强度帘线钢LX92A在920 ℃压缩变形60%后的动态连续冷却转变和等温转变行为。连续冷却转变时,当冷速为0.5 K/s及以下时,在晶界位置存在明显网状结构渗碳体;当冷速达到1 K/s及以上时,渗碳体变为线条状,并随冷速增大,渗碳体逐渐减少;当冷速达到15 K/s以上时,组织中出现马氏体。等温转变时,珠光体转变的温度区间为550~700 ℃,鼻尖温度约为604 ℃,随温度降低,转变后的显微组织由粗大片层状珠光体向片状珠光体、索氏体、屈氏体转变,当转变温度降低到525 ℃时,组织中出现贝氏体。研究了珠光体片层间距与过冷度和冷速的关系,并采用回归分析法得到了片层间距模型,拟合优度分别达到0.99和0.97以上。