SURFACE INTEGRAL OF THREE－DIMENSIONAL VELOCITY FIELD FOR SQUARE BAR DRAWING THROUGH CONICAL DIE

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Three-dimensional experimental study of loose top-coal drawing law for longwall top-coal caving mining technology

Based on the loose medium flow field theory, the loose top-coal drawing law of longwall top-coal caving（LTCC） mining technology is studied by using self-developed three-dimensional（3D） test device. The loose top-coal drawing test with shields and the controlled test without shields are performed in the condition without any boundary effect. Test results show that shields will cause reduction in drawing volume of coal in the LTCC mining. The deflection phenomenon of drawing body is also observed in the controlled test, which is verified that the deflection of drawing body is caused by shield. It is found that the deflection angle decreases with increasing caving height, with the maximum value of atailand the minimum value of 0. In addition, the formula to calculate the drawing volume is proposed subsequently.The deflection of drawing body is numerically simulated using particle flow code PFC3 Dand the proposed formula to calculate drawing volume in LTCC is also verified.

TURBULENT SEPARATED REATTACHED FLOW IN A TWO-DIMENSIONAL CURVED-WALL DIFFUSER

A turbulent separation-rcattachment flow in a two-dimensional asymmetrical curved-wall diffuser is studied by a two-dimensional laser doppler velocimeter.The turbulent boundary layer separates on the lower curved wall under strong pressure gradient and then reattaches on a parallel channel.At the inlet of the diffuser,Reynolds number based on the diffuser height is 1.2×10~5 and the velocity is 25.2m/s.The re- sults of experiments are presented and analyzed in new defined streamline-aligned coordinates.The experiment shows that after Transitory Detachment Reynolds shear stress is negative in the near-wall backflow region. Their characteristics are approximately the same as in simple turbulent shear layers near the maximum Reynolds shear stress.A scale is formed using the maximum Reynolds shear stresses.It is found that a Reynolds shear stress similarity exists from separation to reattachment and the Schofield-Perry velocity law ex- ists in the forward shear flow.Both profiles are used in the experimental work that leads to the design of a new eddy-viscosity model.The length scale is taken from that developed by Schofield and Perry.The composite velocity scale is formed by the maximum Reynolds shear stress and the Schofield Perry velocity scale as well as the edge velocity of the boundary layer.The results of these experiments are presented in this paper

Effect of die cavity dimension on micro U deep drawing behaviour with T2 foil

The strips U deep drawing experiments were carried out to study the effect of die cavity dimension with an extension machine manufactured by SANS company. The effects of parameters were analyzed in deep drawing process under different experimental conditions, such as punch load, reduction of thickness, angle of U part and surface quality. The experiment results show that the punch load increases with the decrease of female radius, and larger blank holder force enlarges the range of increasing. With the increasing of blank holder force, the angle of U part increases, and the reduction of foil thickness at the corner becomes larger. Obvious scratch and accumulation at the die cavity corner were observed by SEM. The investigation results indicate that micro U deep drawing of foil is affected by micro die cavity dimension.

Teaching Reform and Practice in Engineering Drawing Based on 3D Modeling with Computer

Based on the necessity of three dimensional modeling with computer in teaching reform, this paper is the summarization of reform practice of teaching engineering drawing in our institute. The teaching reform begins with three dimensional modeling that used computer instead of board. On the basis of target of teaching reform, set of teaching content, arrangement of class hour and teaching method, the research of teaching practice have been done, and very good effects in teaching of engineering drawing have been achieved.

Introduction and Analysis of Three-Dimensional Modern Modeling and Design Method

In order to overcome many problems and shortcomings of our three-dimensional design education in mechanical drawing, make the students master the modem design method and technology easily, modem modeling method and shaping method are introduced, and the shaping designing methods of assembled-body are analyzed including basic requirements for shaping design, common principles of shaping and shaping design method. It will be helpful to improve the spatial imagination and modelling ability of student.

A fractal-based model for the microstructure evolution of silicon bronze wires fabricated by dieless drawing

The back-propagation neural （BPN） network was proposed to model the relationship between the parameters of the dieless draw- ing process and the microstrecmres of the QSi3-1 silicon bronze alloy. Combined with image processing techniques, grain sizes and grain-boundary morphologies were respectively determined by the quantitative metallographic method and the flactal theory. The outcomes obtained show that the deformed microstructures exhibit typical fractal features, and the boundaries can be characterized quantitatively by ffactal dimensions. With the temperature of 600-800℃ and the drawing speed of 0.67-1.00 mm-s-1, either a lower temperature or a higher speed will cause a smaller grain size together with an elevated fractal dimension. The developed model can be capable for forecasting the microstructure evolution with a minimum error. The average relative errors between the predicted results and the experimental values of grain size and fractal dimension are 3.9% and 0.9%, respectively.

高速拉拔ER70S-6焊丝钢生产工艺优化

通过总结分析ER70S-6焊丝钢存在的质量问题,提出了有针对性的优化改进措施,重点对ER70S-6焊丝钢的化学成分范围、气体氮含量、尺寸精度、显微组织等关键指标严格控制,攻关后C、Si、Mn、N含量内控达标率提高,尺寸偏差C级精度得到改善,而且消除了混晶异常组织。用户拉拔使用结果表明,优化后的焊丝钢质量得到进一步的提高,可满足用户拉拔速度28 m/s以上高速拉拔的要求。

一种基于CATIA V6的轴系三维设计方法

本文基于CATIA V6软件平台,设计针对船舶轴系的三维建模方法。文章将船舶轴系设计需求和三维参数化建模相结合,考虑技术实现难点,利用多级骨架,实体建模,二次开发等多种CATIA软件功能,逐步提高船舶轴系设计过程中建模效率,模型关联性,三维出图质量。在实际建模应用中体现出此方法在模型迭代更新,建模效率、质量等方面有显著优越性。此设计建模方法可结合实际工程需求,适用于除船舶轴系的其它回转体结构机械乃至更多种复杂机械设备的设计。

OPM三维软件在工艺管道设计中的应用

目前,三维设计软件大都是国外产品,其自身对于工程设计及出图往往不能满足国内要求,所以项目设计前期及设计完成后出图的软件二次开发工作显得至关重要。研究BIM软件之一OPM软件绘制工艺管道的二次开发工作,并将其应用到具体的项目施工图中。应用结果表明,软件二次开发工作得当,三维出图的管道轴测图、主要设备及材料表、保温油漆清册和阀门清册满足工程标准要求,给设计者带来极大的设计便利,在保证图纸质量的同时,提高出图的效率和准确性,对后续研究数字化交付具有重要意义。

WPS电子表格在等值电位图绘制中的应用

曲线图通常用于显示检测数据的变化规律,如地基静载试验中的s-lgt曲线和钢筋锈蚀电位检测中的等值电位图。使用WPS sheet能实现编程方法在等值线点坐标的计算、数据分析的应用,同时X-Y散点图可用于等值电位图的绘制。等值电位图上的等值线,本质上是密集的等值电位线点。WPS电子表格,能实现设定的等值线点坐标计算,再绘制密布的等值点即可完成绘制等值电位图。进而,WPS电子表格可用于绘制简单的、二维的图纸。

应用无人机倾斜测量技术的不动产测量研究

维护农民合法权益,促进“三农”发展是我国的重要国策,而不动产地籍测量工作的质量高低将直接影响农村社会稳定,切实关系着农民的自身利益。近年来,无人机技术随着科学技术的发展突飞猛进,随之而来的是倾斜摄影测量凭借着无人机作业也不断地在测绘行业内广泛应用,人们越来越熟练和频繁地使用该技术创建真实场景的三维模型。采用无人机倾斜摄影测量的方式对农村不动产进行测量,详细探讨了航摄的实施、像控点布设与测量、数据处理与模型构建以及制作数字线划图,为无人机倾斜测量技术的完善提供了经验和参考。

组合体尺寸标注完整性的立体思维法

针对组合体尺寸标注的传统形体分析法因忽略孔、槽、楔角等局部切割结构细分,导致完整尺寸标注实操性差的问题,提出一种立体思维法,将组合体视为具有正负体积的基本体叠加,按照“先定形后定位再总体”的顺序,从长宽高3个维度逐个标出尺寸,剔除重复、受控以及零值尺寸。以轴承座组合体为例标注的结果表明,所提方法能够有效避免三视图尺寸标注的漏标和冗标,确保尺寸标注的完整性。

基于三维模型的铁路工程车空气制动系统管路设计

为了高效、准确设计空气制动系统管路,以采用JZ-7型空气制动机的工程车用空气制动系统为例,介绍空气制动系统组成和工作原理。依据空气制动系统原理图,采用基于三维布管模型的布管设计方法,设计空气制动系统三维图,生成布管工程图,并在JJC型接触网检修作业车上装车验证。验证结果表明,采用基于三维布管模型的布管设计方法设计的布管工程图准确,利用布管工程图进行管路装配施工,能提高现场装配效率,减少管路干涉。

变电站图纸物理回路建模方法及实现

目前变电站原始图纸信息保存单一、数字化解析程度不高,人工解析变电站原始图纸工作量庞大。为了解决该问题,提出基于可携带文档格式(portable document format,PDF)图纸智能化提取变电站设备及其连接关系信息、构建物理回路模型的方法,并根据智能变电站物理配置描述(substation physical configuration description,SPCD)文件对该方法进行具体实现。首先,对图纸中提取的图元信息进行处理;然后,通过字符串相似度匹配结合KR的贪心串覆盖(running Karp-Rabin greedy string tiling,RKR-GST)算法实现电气符号的识别,使用梯度提升决策树和逻辑回归(gradient boosting decision tree-logistics regression,GBDT-LR)混合算法进行变电站图像分类;最后,根据SPCD文件完成从原始图纸到物理回路模型的数字化描述。实验结果表明,在图元存在误差的情况下,电气符号匹配正确率达到93%,物理回路识别正确率超过90%。

线上教学资源构建及教学质量反馈评价——以《土木工程制图基础》课程为例

工程教育中,传统的线下授课教学模式单一,考核方式也有局限,而线上教学又存在教学资源匮乏的问题,同时还存在缺少教学活动记录和考核方式不客观的问题,导致难以实现教育部提出的课程“高阶性、创新性、挑战度”要求。该文以《土木工程制图基础》课程为例,分析线上教学资源库构建和多维差异化权重考核体系建设问题,并对实施效果进行了讨论,结果表明,近三年的课程教学目标达成度,统计证实了所提出的方法提高了课程教学目标的达成度,并促进了学生土木工程制图能力的培养。

5056铝合金丝材表面缺陷产生的原因及改善措施

由于航空航天紧固件对5056铝合金铆钉丝材的表面质量和尺寸精度提出了更高的要求,丝材表面存在的缺陷会导致产品镦制时出现开裂,尺寸精度低导致产品组装时出现装配不上等问题。因此,本试验采用目视、扫描、荧光等检测方法对5056铝合金丝材尺寸及其产品表面质量进行了检测,通过对检测效果的比较和分析,采取了提高丝材表面质量和尺寸精度的措施,满足了产品的使用要求。

工程教育专业认证背景下建筑工程制图课程教学质量管理探讨

工程教育专业认证对土木类专业的建筑工程制图课程的教学质量提出了更高要求,该文分析目前建筑工程制图课程教学过程中存在的问题,并提出了建筑工程制图PDCA质量管理体系。其中,着重分析了成果导向下的教学目标和需要达成的能力项,设计了线上线下资源库建设和“以学生为中心”的混合教学模式,并通过多维加权教学评价体系,实现教学质量的综合客观评价,可供参考。

三维数字化设计智能翻模及审图研究与应用

为了提高三维数字化设计中智能翻模及审图智能化水平,提出基于三维模型尺寸标注检查的三维数字化设计智能翻模研究。构建三维数字化设计智能翻模图像特征检测,结合重叠点过滤方法,构建三维数字化设计智能翻模的尺寸标注模型。分析尺寸冗余及缺失参数,实现智能翻模尺寸校核。完成三维数字化设计智能翻模审图,实现三维数字化设计智能翻模审图过程中的点、线、面间位形参数分析,并检查孤立标注面的尺寸缺失,实现三维数字化设计智能翻模审图重组。实验测试结果表明方法大幅度降低了翻模和审图的误差。

BIM在建筑设计中的有效应用研究——软件工作效率对比与分析

本文提出BIM因具备“集成式”信息组成结构与“多维度”信息处理能力,使得建筑设计在应用BIM后工作效率将得到较大提升。首先,明确了BIM“集成式”信息组成结构本身将助力效率的提升。为量化显示效率提升程度,研究选用天正建筑(T)、AutoCAD(C)以及BIM软件ArchiCAD(A)分别创建同一模型,并统计整个过程中的鼠标点击次数。结果显示:(1)三款软件创建模型的鼠标点击次数比例为T:C:A≈12:16:1;(2)创建图纸的比例为T:C:A≈1.71:1.90:1;(3)对比方案设计阶段和施工图设计阶段,初步设计阶段制图应用BIM的效率最高;(4)通过计算鼠标点击次数的增幅,可知使用BIM进行设计修改更加便捷。其次,依据前期对单一维度单一专业的研究结果,预判因具备“多维度”信息处理能力,BIM工作效率将随应用维度的增加而不断提升。