Aiming at the complex and difficult problem of multi-branch cable harness layout optimization, a mathematical model of multi-branch cable layout optimization problem is established based on Steiner tree theory. A path search method based on Theta* algorithm is proposed to improve the smoothness of cable harness routing. Then a pattern search improved particle swarm optimization algorithm is proposed for the multi-branch cable layout optimization problem. The strong local search ability of pattern search algorithm is used to provide better optimization direction for the particle's population. Finally, the example of a routing requirement for an aircraft cabin shows that the proposed method has good optimization ability.

目的:提出一种数据采集优化算法,提高小型伽马射线采集系统的性能指标和成像质量.方法:利用重心法将原始数据解析成图像和能谱,并选取合适的位置权重系数匹配小型伽马射线采集系统的光电倍增管阵列和晶体形状;将解析好的数据进一步做非线性校准、均匀性校准和能量校准,利用插值重建校准表的方式减少校准时间;通过时间补偿来消除核素衰变所造成的感兴趣区域变化对药物代谢数据的影响.对算法优化后的小型伽马射线采集系统进行性能验证和动物实验验证.结果:性能验证结果表明,算法优化后小型伽马射线采集系统采集的图像固有空间分辨力的半高宽(full width at half maximum,FWHM)指标达到1.9 mm,固有空间非线性的微分线性指标达到0.3 mm;动物实验表明,算法优化后小型伽马射线采集系统能够对小鼠进行清晰的实时动态成像,获得详细的药物随时间分布的数据.结论:提出的数据采集优化算法提高了小型伽马射线采集系统的性能指标,可满足小动物体内药物代谢数据半定量分析的需求.

介绍了"新工科"提出的背景及南京航空航天大学机械工程专业的发展历程.探讨了"新工科"背景下的机械工程专业的发展要求,提出了在"新工科"背景下,机械工程专业的阶梯式模块化知识体系和"三个结合"多元化的制造技术人才能力培养机制,为培养出具有较高科学素养、创新能力、社会担当能力的机械工程专业高质量人才奠定了基础.

以多分支电缆的总质量作为优化目标,考虑电缆敷设相关的工艺约束,基于Steiner最小树建立多分支电缆自动布线的优化数学模型.提出了电缆布局优化的改进粒子群优化算法,采用一维定长度数组对多分支电缆布局进行粒子编码,在电缆分支点处引入引力算子,指导粒子的运动方向,并通过飞机舱段布线实例验证了所提方法的有效性.

阐述了增强现实的内涵,总结了基于增强现实的装配引导技术的国内外现状.并对其中关键技术进行了分析总结,指出基于深度学习的增强现实装配引导技术是未来的发展趋势.增强现实技术通过将虚拟信息叠加到真实环境中与用户进行交互,显著提升装配效率,为制造业向精密化、复杂化发展提供技术支持.

3D物体识别与位姿估计是AR辅助维修信息增强的基础,目前的3D物体识别技术在识别准确率、运行实时性和位姿估计准确度上仍然存在不足.以物体识别的实时性和位姿估计的准确性为要求,研究基于纹理点云的局部参考系估计技术和点云全局特征描述符生成与匹配技术,提出融合形状与纹理信息的全局正交对象描述符及其3D物体识别算法,基于蜗轮蜗杆减速器的拆装维修场景进行实例验证.验证结果表明,3D物体识别算法在AR辅助维修场景中具备实际可行性和真实有效性.

针对面向布线优化求解的空间模型的性能评价研究不足,目前的空间模型仍然广泛存在影响布线算法求解效率和质量的问题,首先建立了布线空间模型性能评价模型;然后分析了布线规划对空间模型的需求,提出了基于八叉树的空间信息模型及其空间预处理技术;最后通过实例验证了基于八叉树的空间预处理技术的有效性,以及布线空间模型评价模型的可行性.

变幅杆是超声辅助加工中的重要零部件之一,用于辅助加工的变幅杆通常带有工具头负载,研制存在一定难度.通过对带负载的用于超声辅助磨料射流的变幅杆研究分析,在使用解析法设计其初始结构尺寸的基础上,借助有限元软件选择节点耦合方式进行仿真,采用控制变量的原则获得各结构参数对系统频率的影响,修整变幅杆装配体模型,经过试验测定,发现该种处理方式及修整方法获得的仿真结果与实际测定相比,谐振频率误差在1％以内,振幅测定误差在2％以内,为研制带有复杂工具头的变幅杆提供了参考.

对于一个制造企业如果存在两个相似度很高的壳体类零件,则它们的工艺流程以及工时定额也基本一致.将推理技术应用于壳体类零件的工时定额,首先建立壳体类零件工时信息模型,研究零件工时实例的表达方法、相似度检索算法以及实例重用阶段的数控加工工时计算方法,并通过实例验证了该方法的可行性,将定额结果与查表法定额结果比较,误差控制在5％以下,工时定额效率得到了很大的提高.

针对柔性电缆装配仿真时模型受重力作用真实性不足,以及电缆束多分支结构的形态仿真问题。建立了柔性电缆连续性力学模型,并用于多分支结构的柔性电缆束形态仿真。通过建立四个坐标系来描述单根电缆的几何形态,通过增加电缆分支点处的约束建立了多分支电缆的物理模型,对理想约束电缆的物理模型进行了解析求解,及对考虑电缆自重的物理模型进行了数值求解。通过实例表明带重力作用的电缆形态变化更加真实,多分支电缆物理模型能够有效进行形态仿真,可用于交互装配仿真。

An externally applied magnetic field has been proved effective in controlling the molten flow behavior during the laser beam welding. This paper reveals how a magnetic field applied in different orientations influences the weld pool dynamics during the full-penetration laser butt welding of thick aluminum alloy plates. A multi-physics coupling model was developed and numerically solved by considering the electromagnetic interaction between static magnetic field and magnetofluid. The dynamic and electromagnetic information within the weld pool were predicted and comparatively analyzed. The results show that Lorentz force and Hartmann effect induced in magnet-assisted weld pool are quite sensitive to magnetic field direction. The horizontally directed magnetic field leads to limited Hartmann effect by inddcing additional molten vortexes, while the field aligned vertically to aluminum surface can obviously reduce the molten flow velocity and weaken the Marangoni convection. The work can provide a reference in optimizing the operating parameters when an electromagnetic system is employed to improve the welding quality. (C) 2018 Elsevier Ltd. All rights reserved.

机电产品的全三维设计要求对全部线缆组件进行几何建模,然而CAD环境下基于交互的线缆组件的三维几何建模过程十分耗时,影响产品设计周期.为了提高线缆组件的几何建模效率,研究了基于Pro/Toolkit的线缆组件快速几何建模技术.首先给出了线缆组件快速几何建模的流程,建立了线缆组件的信息模型.分析了Creo环境下线缆组件的几何建模需求,提出了基于Pro/Toolkit的线缆组件自动几何建模方法.最后通过某机电产品的布线三维模型,快速建立了线缆组件几何模型,验证了所提方法的有效性.

Purpose This paper aims to describe a three-dimensional mathematical and numerical model based on finite volume method to simulate the fluid dynamics in weld pool, droplet transfer and keyhole behaviors in the laser-MIG hybrid welding process of Fe36Ni Invar alloy. Design/methodology/approach Double-ellipsoidal heat source model and adaptive Gauss rotary body heat source model were used to describe electric arc and laser beam heat source, respectively. Besides, recoil pressure, electromagnetic force, Marangoni force, buoyancy as well as liquid material flow through a porous medium and the heat, mass, momentum transfer because of droplets were taken into consideration in the computational model. Findings The results of computer simulation, including temperature field in welded plate and velocity field in the fusion zone were presented in this article on the basis of the solution of mass, momentum and energy conservation equations. The correctness of elaborated models was validated by experimental results and this proposed model exhibited close correspondence with the experimental results with respect to weld geometry. Originality/value It lays foundation for understanding the physical phenomena accompanying hybrid welding and optimizing the process parameters for laser-MIG hybrid welding of Invar alloy.

为了快速计算线缆装配的工时定额,利用工作研究的方法,开发了计算机辅助工时定额系统.在工作研究方法中,首先将线缆装配整个过程按先后顺序分成几个工步,然后将线缆进行分类,并建立各线缆的计算模型.根据规则关联计算模型,实现机柜线缆装配工时的智能计算.经过实践验证,该方法可以快速、高效、准确的估算机柜线缆装配工时,为生产管理提供了可靠的基础数据.

针对航空薄壁多腔类结构件加工特征数量多、加工易变形导致工艺规划困难的问题,提出基于知识与遗传算法混合的薄壁多腔件加工元排序方法.通过知识规则在遗传算法中加入对染色体的重组步骤,增加染色体的有效性,通过建立分隔面关系矩阵与腔关系矩阵表达薄壁多腔件的阶梯对称铣削工艺,以加工质量、加工效率为优化目标进行遗传操作,最后通过实例验证了算法的有效性.

The welding technology of weave bead welding (WBW) and multi-layer multi-pass welding (MLMPW) are considered to offer advantages over fusion welding in terms of thick plate. The present paper employs a 19.05-mm thick Invar steel plate as the research object to compare the quality of welded joints using WBW and MLMPW. A temperature field model of WBW is established using finite element method; transient temperature field and welding thermal cycle curves of WBW are compared with the ones of MLMPW, which indicates that the characteristic of WBW molten pool periodically changes over time and its temperature distribution is uneven. Moreover, the examinations and analyses of macro/microstructures of WBW and MLMPW are conducted. The results indicate that the inter-layer of Invar steel using WBW is fused better than the one using MLMPW. Perfect weld seam with no defects and a grain growth mechanism of epitaxial solidification of WBW are clearly exposed. The width of heat affected zone (HAZ) using WBW is roughly narrower than that of MLMPW. In addition, the tensile test is conducted to demonstrate that the WBW welded joint has the higher quality.

As the only basis for the manufacturing process,MBD model has gradually become the development trend of the aviation manufacturing industry,and it has been applied to the CAD/CAM system.However,MBD technology has not been used in the CAPP,which results in the poor information flow of the MBD data set during the integration of CAD/CAPP/CAM.In this paper,according to the requirements of NC machining of the aviation structure,the MBD NC machining process model is built based on layers.The work flow of NC machining process based on MBD is proposed.The CAPP system of NC machining based on MBD is researched and developed.The MBD application of integrated design and manufacture on UG platform is realized finally.

In order to solve the problem of large deformation, low production efficiency and high tendency of hot cracking in welding 19.05 mm thick plates of Fe36Ni Invar alloy, laser-MIG hybrid multi-layer welding technique (LMHMW) has been developed. To investigate the influence of different welding parameters on the joint properties, optical microscope observation, SEM, EDS and microhardness measurement were conducted. Experimental results illustrated that different matching of welding parameters significantly affected the depth-to-width ratio, formation of defects and HAZ width. Besides, weld zone were consisted of two regions according to the different grain shape. The region near center of weld seam (region 1) was columnar dendrite induced by laser, while the region far away from weld seam center (region 2) was cellular dendrite which was mainly caused by MIG arc. The peak value of microhardness appeared at the center of weld seam since the grains in region 1 were relatively fine, and the lowest hardness value was obtained in HAZ. In addition, results showed that the sheets can be welded at optimum process parameters, with few defects such as, surface oxidation, porosity, cracks and lack of penetration in the welding seam: laser power of backing weld P = 5500 W, welding current I = 240 A, welding speed v =1 m/min. laser power of filling weld P = 2000 W, welding current I = 220 A, welding speed v = 0.35 m/min. laser power of cosmetic weld P = 2000 W, welding current I = 300 A, welding speed v = 0.35 m/min. (C) 2017 Elsevier Ltd. All rights reserved.

2060 Al–Cu–Li alloy plates with 2- and 1-mm thickness were welded by a fiber laser beam. The weld microstructure features and the mechanical properties such as microhardness and tensile strength of 2060 Al–Cu–Li alloy laser beam-welded joint were investigated to study the influence of welding parameters on the weld bead. By microstructure and mechanical property analysis, it is found that weld width as well as penetration depth increases with the increase of laser power when the welding speed is constant. The microstructures of the fusion line and fusion zone show similar dendrite morphologies with traditional cast structure under the thermal cycling. Fine grain zone can be observed near the fusion line. Welding porosities exist in the microstructure of 2060 Al–Cu–Li laser beam-welded joint. Porosity ratio increases at first, and then declines, and then increases again with the increase of laser power. The larger heat input causes the lower microhardness distribution of the corresponding joint. The optimized welding parameters of fiber laser beam welding of 2- and 1-mm-thick 2060 Al–Cu–Li alloys are 2500 W and 3 m/min and 2300 W and 4 m/min, respectively.

Aiming at the inefficiency of machining feature recognition and the difficulty of recognizing intersecting features for thin-walled and multi-cavity structural parts,a hybrid and parallel recognition method based on rules,layer and feature suppression was put forward.Machining features could be recognized concurrently by every cavity to improve recognition efficiency based on idea of grouping cavities and classifying machining features.The features were suppressed in time after recognizing to simplify the recognition of intersecting features.The method of grouping cavities and classification of machining features were discussed.The process of recognition was elaborated:rules and property of edges were used to recognize complete boles,independent ribs and intersecting ribs firstly;layer and intersecting holes were recognized by using layer and feature suppression technology;the left features were recognized back to the main thread at last.An instance part was used to analyze the efficiency of algorithm and verify the effectiveness of the proposed method.