薄壁零件熔融沉积快速成型工艺的研究

对于薄壁零件，其快速原型的成型工艺与一般零件的成型工艺有着很大的不同，通过实验，对这类零件的熔融沉积快速成型工艺进行了研究，得出参数选择的一般原则，提高制件的加工精度和表面质量。     

机械臂3D打印技术及系统的试验研究

3D打印技术多以单材均质为基础,开展金属、塑料等零部件的快速成型制造。在此基础上,发展了激光近净成形、熔融挤出成型、选择性激光烧结(熔化)、立体光刻等3D打印工艺和装备。论文以流体挤出成型和激光烧结为基础,结合工业机械手6自由度的空间特性,初步搭建了机械臂3D打印系统;对该系统构成做出了简要介绍,分析了该系统的数据链与数据模型的坐标转换;对电气性能器件常用材料导线银、树脂基复合材料、硅酮橡胶、碳化硅陶瓷等的成型工艺进行了初步探索,为下一步制造出具备电气性能的功能结构化器件与进行曲面3D打印的研究打下基础。     

复杂曲面薄壁零件手板模型的快速成型研究

针对复杂曲面薄壁零件手板模型制作的问题,对手板模型的3种常用制作方法进行了对比,研究了快速成型过程的关键技术,包括:STL格式文件转换的格式设置参数设置和快速成型关键参数设置,对普通手板模型及复杂曲面薄壁零件手板模型的关键问题进行了讨论和对比。通过壁厚为0.5 mm的曲面零件设计和模型制作,给出了适合普通零件及曲面薄壁零件快速成型零件的合理工艺参数。研究结果表明,只要正确合理的选取关键工艺参数,可以避免曲面薄壁零件快速成型易出现的断壁、多毛刺的问题,能高效、高精度地制造手板模型,能满足手板模型的各项特性需求。     

复杂曲面样件的计算机辅助制造技术

针对具有复杂曲面产品零件的设计成本过高的困难,提出了一种复杂曲面样件的计算机辅助制造技术。以激光选区失效快速成型技术为核心,通过设置辅助分割体的办法对废料进行依次剥离,所获得的样件具有较高的尺寸精度及机械强度,整个制造过程由CAD模型直接驱动,完全实现自动化,可在数个小时之内为产品的设计提供实物验证。大量的实际应用验证了此技术的稳定性及有效性。     

熔融堆积成型系统中结构自动生成算法的研究

在熔融堆积成型系统中，零件原型的制作是靠热喷头挤出热熔丝逐层堆积成型的，因此，在零件原型的成过程中，支撑结构的生成是不可避免的。通过利用截面轮廓区域的自动识别、多边形区域的布尔运算以及多边形轮廓的OFFSET运算等几种关键算法，提出了SW2501快速成型系统中支撑结构的自动生成算法。该算法实际应用效果较好。     

光固化快速成型中零件非水平下表面的支撑设计规则研究

激光固化快速成型制造中,支撑结构设计的优劣极大影响原型的制作精度。首先通过分析非水平下表面的分层制作过程,研究了其翘曲变形的机理。利用可仿真成型过程中层间力学行为的有限元计算模型,对层间悬臂量与翘曲变形量的关系进行了有限元计算仿真与试验验证。针对激光成型过程中零件需要支撑的非水平下表面,从激光固化快速成型制造中支撑结构的作用出发,以成型精度为设计目标,通过有限元计算仿真、试验验证等手段研究提出了针对零件中非水平下表面的支撑结构形式、布局及支撑间距等支撑设计规则。通过试验验证,按该规则对零件的非水平下表面进行支撑结构设计,可有效地保证激光固化快速成型的制作质量。     

金属选区激光熔化成型仿真模拟

选区激光熔化金属零件时,不仅要考虑零件的摆放方式,还需添加支撑结构以增加零件的强度,提高其成型稳定性,降低残余应力,防止翘曲变形等问题。为获得合理的摆放方式及优化支撑结构,借助仿真软件,预先模拟不同摆放角度及相应的支撑结构对金属零件变形的影响,依据模拟结果中变形情况及时修正摆放位置和支撑结构,并与实际成型情况比较分析。结果表明,仿真模拟有效预测了选区激光熔化金属零件的变形量,这一手段大大减少了反复实验试错次数,提高生产效率,避免材料消耗,降低生产成本。     

熔融沉积技术中成型环境温度对质量精度的影响研究

熔融沉积快速成型技术是当代先进的制造技术之一,针对其成型件的成型精度问题,在分析成型工艺参数的基础上研究了成型环境温度对快速成型技术质量精度的影响。通过建立模型及网格划分进行有限元分析,合理地描述出熔融沉积快速成型过程,分析模拟结果并且对比在不同成型环境温度下的成型件的应力分布。实验模拟结果表明:在成型过程中选择合理的成型环境温度可以有效降低成型件的翘曲变形和受力情况,而且成型环境温度因素可以导致试件在结构较为复杂的部位出现应力集中现象。     

熔融挤压快速成型中支撑工艺的研究

针对单喷头的熔融挤压快速成型制作成型件的特点,必须保证能很好地去除支撑才能得到制件的要求,对熔融挤压快速成型中支撑工艺进行了研究。支撑关系到零件的加工成败、加工时间和表面质量等,提出了支撑的一些生成原则和设置辅助支撑的作用。根据挤出丝的截面形状,建立了支撑丝宽的数学模型,对生成支撑的重要工艺参数进行了分析,结果表明:栅格宽度w较出料速度v对支撑间的间隙L0影响要大,但当层高h由0.2 mm变为0.1 mm时,栅格宽度对支撑间间隙的影响基本不变,而出料速度对支撑间间隙的影响成倍增长,并进行了实验验证。     

选择性激光烧结3D打印参数对成型精度影响研究

选择性激光烧结的成型过程中,零件的成型性能主要受激光功率、扫描速度、扫描间距与激光能量密度等多种因素的影响。采用实验方法研究了PS粉选择性激光烧结工艺,通过测量烧结件的尺寸精度,得出不同影响因素对烧结件成型精度影响的变化规律。通过实验结果发现,激光功率、扫描速度、扫描间距分别通过改变激光能量密度影响成型精度,并得到成型件精度与激光能量密度的变化规律,同时选出最佳的加工参数与加工方式,指导实际生产。     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

Quantum Cooperative Robotics and Autonomy

The intersection of Quantum Technologies and Robotics Autonomy is explored in the present paper.The two areas are brought together in establishing an interdisci...     

On the Relation of Load to Average Gap in the Contact Between Surfaces with Longitudinal Roughness

A computer simulation model for the contact between longitudinally-oriented rough surfaces has been formulated. This model closely duplicates the actual surf ace contact deformation behavior by taking into account the elastic interactions between the asperities. There were no assumptions made about the shapes, or any deformation behavior of the asperities, except for their obeying the laws of elasticity. The plastic deformations on the high asperity peaks were taken into account by setting a ceiling on their contact pressures at the material hardness value. The simulations used real surface profiles which were digitized from unworn circumferentially ground steel surfaces. Each pair of these profiles was mathematically combined to form an equivalent rough profile pressing against an infinitely rigid flat and having the appropriately adjusted elastic modulus. A total of 28 different pairs of profiles were used in the simulations. Each contacting pair was subjected to 30 different load levels and the local contact pressures and deformations were calculated. The contact simulations yielded some important mathematical relationships between parameters, such as the real area of contact, average gap, and average asperity load through statistical curve fitting. Two analytical functions were generated to relate the average load to average gap and the real area of contact to load.     

三绕组变压器的双绕组等效建模及在Matpower中的应用

针对实际电网存在着大量的三绕组变压器,但国际上一些著名商业软件,如BPA仿真软件、Matpower这一权威潮流计算开源软件,均只提供双绕组变压器模型,限制了其在具有三绕组变压器的电力系统中的应用的问题,潮流计算是自主开发的电力系统各种应用软件的核心模块,因此依托国际权威开源程序进行二次开发,是一种较好的选择。对Matpower要求的数据格式进行了归纳,对变压器的一般的等值电路及带理想变压器的等值电路和带标幺值的等值电路进行了分析研究,提出了三绕组变压器转换为双绕组等效模型的建模方法,使得原先只适应双绕组变压器的潮流计算软件可以适用于三绕组变压器电网的潮流计算;最后以Matpower软件为例进行了案例计算,并用PSASP仿真软件进行对比验证。研究结果证明,所提出的建模方法是有效的。     

电站锅炉模糊风险评价方法研究与应用

针对电站锅炉风险等级评价问题,将模糊综合评价技术应用到电站锅炉风险等级评价中。开展了电站锅炉失效影响因素及模糊评价因素的重要程度分析,建立了一套科学合理适于在线评价的电站锅炉风险评价体系,提出了模糊综合评价技术与改进的模糊层次分析法相结合的模糊风险评价方法,利用改进的模糊层次分析法计算了指标体系中各层指标权重。对某一台电站锅炉的实际运行工况影响子因素进行了模糊风险评价,采用模糊合成算子进行模糊综合运算得到电了站锅炉运行工况影响子因素的评价向量。研究结果表明:电站锅炉的运行工况影响子因素的风险评价等级为第6级,失效可能性等级为小,该电站锅炉运行工况良好。     

考虑进油孔有限长滑动轴承油膜力的近似解析解

针对具有进油孔的有限长滑动轴承油膜力求解问题,采用变分原理和分离变量法,求得了有限长滑动轴承油膜压力分布的近似解析表达式。将油膜压力分布的近似解析表达式在油膜存在区域上进行积分,即得到了油膜力。将提出的计算有限长滑动轴承油膜力方法与无限长轴承模型、有限元方法的计算结果进行了比较,发现了提出的方法与有限元方法的计算结果很接近。最后,研究了进油孔位置和进油压力对油膜存在区域、油膜力等的影响,研究结果表明进油孔位置和进油压力对油膜存在区域和油膜力有较大的影响。     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

Fifth International Summer School on Screw-Theory Based Methods in Robotics

正3-11 September,2014University of Bologna,Bologna,Italy www.summerscrews.org summerscrews2014.ing.unibo.it SUMMER 20SCREWS 14In 2014,our screw-theory school comes to the world's oldest university.In early September,Summer Screws'14 will gather six experts in the application of screw theory in robotics and up to 40 participants at the University of Bologna,Bologna,Italy.The school will teach attendees how to apply existing methods and empower them to develop new ones in their own research.The basic theoretical notions will be introduced in a rigorous manner,emphasizing examples,applications,and exercises.Scholarships are available.     

交通荷载作用下桥梁结构参数识别方法

应用动力节点加载法,将作用在桥梁上的交通荷载转化为等效节点荷载,再用两步构造法识别结构物理参数.第1步,用Newmark-β方法变换结构运动方程,并用结构的加速度响应求得变换空间内的位移、速度和加速度响应;第2步,基于最小二乘原理,构造出变换空间内求解结构参数的递推式,进行结构物理参数识别.数值模拟结果表明,在交通荷载作用下,该方法能够快速、准确地进行桥梁结构参数识别.     

INDUSTRIAL ENGINEERING AND VISUALISATION-A PRODUCT DEVELOPMENT PERSPECTIVE

Taking the actual project of teaching and researching process for example, the relationship between the industrial engineering and product development is discussed. And use the novel visualization technology to support the industrial engineering and product development. How to use the new computer modeling and simulating technologies to support the product development and industrial engineering, is introduced especially. The support includes both domestic products and industrial systems. The visualization and computer technologies take a very important role in some system or multi-direction modeling, those technologies mentioned above can help the industrial engineers study the effect of design on the whole life circle, including the producing steps. So the engineers can avoid making the wrong decision which may cause bad effects on the whole industrial engineering.