An improved online dimensional measurement method of large hot cylindrical forging

The dimensional measurement of large forgings under high temperature plays an important role in product control. Cylindrical forgings belong to the important products in the forging workshop. In this paper, an improved online measurement method based on binocular vision for the dimensions of hot cylindrical forgings is proposed. Firstly, images of hot cylindrical forgings are captured by two CCD cameras, and the distorted light stripes projected onto hot cylindrical forgings can be resolved from the image by the deviated stripe model. Then, an accurate sub-pixel extraction algorithm of center points of the light stripes is developed for making the extraction of center points of the lights stripes more accurate. Moreover, for changing the field of view of cameras to measure different sections of forgings in the process of manufacturing, the fundamental matrix F is automatically calculated by matching the intersecting points of the projected light stripes in different images, without interrupting the forging process. Finally, experiments on measuring the diameters of hot cylindrical forgings in the workshop are conducted, and the experimental results indicate that the proposed measurement method is effective. Besides, an additional experiment in the laboratory verifies that the relative error of measuring diameters by the presented method is less than 0.7%.     

刚性粒子流法模拟自由锻造工艺的探索

基于网格的数值计算方法在处理自由锻造、冲压成形、高速碰撞、裂纹动态扩展等大塑性变形问题时,往往会因网格畸变和网格重构困难使得计算精度丢失甚至无法计算。针对该问题,基于连续介质力学理论和分子动力学基本原理,采用一种求解金属大塑性变形的数值模拟方法--刚性粒子流法,建立了刚性粒子流法的数学模型并探讨了初始粒子配置、粒子搜索算法、数值积分和边界条件等关键数值技术。将该方法应用到核电饼类锻件高温镦粗和大型核电封头终锻成形两个数值算例中,计算结果表明：模拟大塑性变形问题时,刚性粒子流法与实验结果能够较好地吻合,有效地解释了大型饼类锻件夹层裂纹和封头锻件层状撕裂的形成机制。研究结果为进一步采用该方法模拟变形更加复杂的自由锻造工艺提供了参考。     

大型轴类锻件切削性及粗加工增效措施研究

大型轴类零件毛坯经直接锻造成形,其粗加工难度很大。本文通过分析大型轴类锻件加工难点,结合目前中国一重大型轴类锻件粗加工的经验,总结出提高大型轴类零件粗加工效率的有效方法,为大型轴类锻件的加工以及强力切削刀具的改进提供了技术指导。     

基于红外测温的筒形锻件内外径在线测量

针对目前筒形锻件外形尺寸无法实现在线测量的现状,提出一种新的基于红外测温技术和激光扫描技术相结合的筒形锻件内外径在线测量方法,该方法中温度信息由红外双色测温系统测得,外径尺寸信息由激光扫描技术测得。对红外测温原理进行研究,根据测量现场的情况构建红外双色测温系统,减小现场恶劣环境和锻造过程中锻件表面氧化皮对测温造成的影响,提高了测量精度。在传热学的基础上推导筒形锻件导热微分方程,建立筒形锻件温度与尺寸的关系,结合锻件内外表面的温度信息和外径尺寸信息求得内径尺寸的大小,从而实现筒形锻件内外径尺寸的在线测量。通过试验验证该方法的可行性,同时可以满足现场测量的精度要求,从而解决筒形锻件内外径测量的瓶颈问题,在筒形锻件锻造现场有一定的应用前景。     

Dimension measurement of hot large forgings with a novel time-of-flight system

The dimension measurement of hot large forgings is necessary for process control and product quality. However, the conventional technique in forging plants leads to a high scrap rate of raw materials. In order to reduce the waste and increase the productivity, this paper presents a novel measurement technique based on the pulsed time-of-flight (TOF) laser radar to measure the dimensions of hot large forgings. The system consists of a TOF, a scanning device of the two-degree-of-freedom (2-dof) spherical parallel mechanism (SPM), and two motors. Then, its measuring principle and the SPM are described. A special data-processing method is developed to extract the dimensions and the shape of a large forging by scanning for a few times. The laboratory experiments indicate that the shape and dimensions such as the diameter and length can be achieved by virtue of the TOF system. The dimension measurement in a forging plant is also conducted to verify the effectiveness of the presented system.     

Image-based measurement of the dimensions and of the axis straightness of hot forgings

Non-contact measurement of shapes and dimensions is currently quite a common issue. A lot of systems with different speeds and accuracies are in the market. Measurement of high temperature objects is, however, a very special task which ensures a specific solution. This paper presents a measurement system composed of two high resolution single-lens reflex cameras and a software application, which is designed for the fast measurement of shapes and dimensions of rotationally symmetric forgings. The software computes the length, diameter, and straightness of the axis, based on a 3D model constructed from four boundary curves of the forging captured in two images. Experimental measurements have shown an error of up to 2% for the length measurement and 1% for the diameter measurement. Results are available in a few seconds. The proposed measurement approach based on boundary curves shows a great potential for practical use in forging plants.     

锻合钢锭内部缺陷的最小锻比研究

本文从大型锻造发展趋势和质量控制、节约能源的要求出发,提出了用最小锻比或有效锻比作为制定大锻件工艺的综合性准则。用模拟试验方法确定了FM锻造法的最小锻比,并介绍了大型支承辊的锻造实例,将100t重大钢锭仅以2.25的小锻比成功地锻造出合格大锻件,节约了大量能源。     

钛合金复杂件等温锻造研究

针对TC4钛合金非对称变截面复杂件在加工过程中锻造温度范围窄、充型能力差、容易产生皱褶等问题,研究了TC4钛合金等温锻造的工艺过程,并采用DEFORM 3D有限元软件进行了数值模拟。结果表明:采用等温锻造工艺,成功的锻造出了某钛合金复杂件,且该锻件轮廓清晰,表面光洁,尺寸精度高;该锻件金属流线分布合理,组织性能超过了常规锻件;该锻件材料用量相对普通锻件材料用量可减少60%。通过软件模拟,了解锻件成形的应力应变及行程载荷等情况。     

汽轮机低压转子锻件锻造的关键技术

介绍了一种新FM法。由于低压转子锻件的尺寸大,容量相同的汽车轮机低压转子锻悠扬要比高中压转子锻件的制造难度大。大型汽轮低压转子锻件常规生产工艺,在镦粗体（h/d＞1）中心区域存在两向拉应力,在WHF法的拔长体中存在一向或两向拉应力。如果不区分锻造作用的阶段性,前道工序的作用很可能被后续工序消除或减弱,所以应用最新发展的新工艺方法、优化组合进行锻造,才有可能使得各阶段的变形机制得到最佳配合。     

A stitching method of radial section line of scanned point cloud data for ring forgings

The dimensions of ring forgings can be analyzed by the point cloud data of ring forgings scanned by laser. The dimensions are the key to evaluating the parameters of ring forgings. Due to the limitation of the scanning angle of the laser scanner, the complete data of the radial section line for the ring forging cannot be obtained through one scan. So the point cloud data of multiple scans are stitched to get the complete data of radial section line. In response to the stitching question, a point cloud data stitching method for ring forgings is proposed in this study. Firstly, the coarse stitching is carried out by using the relationship between the center coordinates of the two data sets. Then, the repeated region is found by the improved Beetle Antennae Search Algorithm (BASA). The repeated region is divided into three parts to find corresponding points in the process of precise stitching. The complete radial section line data can be obtained. Finally, the stitched radial section line is transformed into a complete 3D ring forging model. The comparison experiment results show that the algorithm proposed in this study is simple and fast. The accuracy of this algorithm is verified by extracting the dimensions of the complete model for ring forging.     

RIGID-PLASTIC MECHANICAL MODEL FOR THE FORGING METHOD WITH HORIZONTAL V-SHAPED ANVIL

In order to decrease the anisotropy of mechanical properties, the rigid-plastic mechanical model for the forging method with horizontal V-shaped anvil is presented. The forging method, through the change of anvils shape, is able to control fibrous tissue direction, to improve the anisotropy of mechanical properties of axial forgings, to realize uniform forging. Therefore, the forging method can overcome the defect that conventional forging methods produce. The mechanism of the forging method with horizontal V-shaped anvil and the process of metal deformation are analyzed. The agreement of theoretical analysis with experimental study verifies the fact that the forging method with horizontal V-shaped anvil can control effectively the mechanical properties of axial forgings.     

大型饼类锻件预镦粗工序的数值模拟研究

为了解决镦粗变形缺陷,将饼类锻件的预镦粗工序分为锥台砧镦粗和平砧端面整平两个阶段,利用DEFORM-3D计算平台建立锻造过程的有限元模型并进行仿真分析;分别从锻件内部的应力场和应变场等方面研究了锥台砧锥角和压下率对镦粗过程的影响,平砧旋转锻造方式和下砧砧形对端面整平过程的影响,以获得合理的预镦粗锻造工艺参数,指导实际生产过程.     

计算机辅助辊锻模具设计通用系统的研究

本文研究了制坯辊锻模具的计算机辅助设计通用软件系统,实现了辊锻过程的全部设计计算与绘制图纸的自动化。对于欲用辊锻工艺制坯的任意形状与尺寸的模锻件,只要输入相应的描述锻件几何形状用原始数据及某些必要的参数,电子计算机就可以快速、精确地完成从工步方案选择到模具尺寸计算的全部设计任务,并自动绘制出可供生产用的辊锻工步图与模具图。本文在描述锻件几何状形时采用了等截面体、变截面体、旋转体等三种形状体的组合法,使得能够用较少的原始数据描述各种不同形状的锻件。在简化锻件截面图时,本文提出了自动简化数学模型,明显地提高了设计效率。     

基于瞬态传热的含裂缝环形锻件传热模型

针对目前热态锻件存在的裂缝问题,提出了一种基于传热理论的含裂缝锻件传热模型。首先,基于微元体的传热特性,推导满足微元体热平衡关系的导热微分方程,并以瞬时热流量为中介变量,对传热系数、热导率进行了修正。其次,设定环形锻件内外环境边界条件、裂缝有限空间自然对流边界条件,进而建立了多边界条件下含裂缝的热态环形锻件传热模型,利用分离变量法求解该传热模型。最后,应用有限元软件对含不同尺寸裂缝的环形锻件传热模型进行模拟,通过试验验证了仿真分析及传热模型的可行性。     

A new approach of preform design based on 3D electrostatic field simulation and geometric transformation

Preform design is an important aspect of the research and development of the forging processes, which plays a key role in improving product quality, such as improving material filling capacity and reducing forming loads. In industry, preforms are generally designed by the iterative trial-and-error approach. This approach, however, leads not only to the increase of tool cost but also to prolonged production time. On the basis of the minimum energy principle and the minimum resistance law, a new approach by means of 3D electrostatic field simulation and geometric transformation is proposed in this paper to design the preform shape. Two axisymmetric (a disk and a blind-hole) forgings and a long-axis part are used to demonstrate this method, and finite element package DEFORM 3D is used to simulate the forming process for the purpose of verifying the validity and effectiveness of this approach.     

Study on Modeling Technique and Internal Quality Control for Heavy Forgings

模拟技术是研究大型锻件控制锻造理论的有效方法,在缩短试验周期等方面具有无可比拟的优越性,为此研制了以高温云纹法为代表的物理和数值模拟技术。针对大型锻件中存在的质量问题,研究了内部缺陷的形成过程及影响因素,发现了变形体中存在剪切带、夹杂性裂纹聚合、损伤与修复等新现象,并对其规律进行了深入研究。制定了大型锻件锻造工艺规范,对提高产品质量起到了重要的作用。     

大型轴类锻件的特殊锻造法

利用水平V形砧锻造法，通过有效控制锻件的纤维流向，改善轴类锻件力学性能的异向性。实现轴类锻件的等向锻造，创造普通锻造法无法达到的特殊锻造效果。定性物理模拟实验证明了水平V形砧锻造法是控制轴类锻件力学性能的有效工艺手段。     

基于变形均匀性的锻造过程微观组织优化方法及其应用

在中国国家自然科学基金项目《锻造成形微观组织优化方法研究及应用》资助下，为提供一种控制锻造成形制品微观晶粒尺寸的理论方法和途径，开展基于变形均匀性的锻造过程微观组织优化研究。 锻造生产除保证产品的基本形状要求外，更重要的是通过材料的塑性变形提高产品的综合机械性能。因此，金属塑性成形过程微观组织模拟与优化研究具有应用价值。 在描述金属在高温塑性变形中组织变化机制基础上，提出材料在热锻成形过程中动态再结晶、静态再结晶，以及晶粒长大等微观组织演变机理。金属塑性变形是以位错运动实现的。随着变形的进行，位错密度不断增加，高位错密度聚集的能量使材料处于不稳定状态。对于低层错能金属(碳钢)的热塑性变形，因其动态恢复缓慢而不能充分消除高密度层错能，动态恢复之后紧接着会出现动态再结晶现象。未能经过动态恢复和动态再结晶充分软化的金属停止变形后，其组织将发生静态再结晶。再结晶过程完成后的新组织是亚稳定的，为获得更稳定的组织，需要释放晶粒内部的潜能。因此，再结晶完成后，要发生进一步的晶粒长大来减少单位体积内的晶界面积。     

电力驱动回转台的设计

回转台是大型锻造过程中的重要辅具,主要用于饼形锻件镦粗和圈类锻件的平头.本文通过对各种结构的回转台进行分析,设计出一个适合本单位使用的回转台     

基于质量控制函数的锻造工艺适用性的评估方法

介绍应用模糊数学方法建立的表征锻件晶粒度的隶属函数，根据近代质量控制理论提出了质量控制函数及其计算方法，将表征晶粒度的隶属函数和质量控制函数引入有限元变形－传热耦合分析方法，首次提出了锻造工艺适用性的定量评估方法。所应用所提出的方法对各种锻造工艺的评估结果与生产实践表明，所提出的方法能揭示锻造工艺参数对锻件质量的影响，对合理制定难变形材料锻造工艺和控制锻件质量具有指导作用。