Limit analysis of flow through conical converging dies

A variety of mathematical models may be used to analyse plastic deformation during a metal-forming process. One of these methods—limit analysis—places the estimate of required power between an upper bound and a lower bound. The upper and lower bound analyses are designed so that the actual power or forming stress requirement is less than that predicted by the upper bound and greater than that predicted by the lower bound. Finding a lower upper bound and a higher lower bound reduces the uncertainty of the actual power requirement. Upper and lower bounds will permit the determination of such quantities as required forces, limitations on the process, optimal die design, flow patterns, and prediction and prevention of defects.Fundamental to the development of both upper bound and lower bound solutions is the division of the body into zones. For each of the zones there is written either a velocity field (upper bound) or a stress field (lower bound). A better choice of zones and fields brings the calculated values closer to actual values.In the present work, both upper and lower bound solutions are presented for axisymmetric flow through conical converging dies. For the upper bound triangular velocity fields have been solved and compared to previously published work on spherical velocity fields. It is found that each type provides a lower solution over a part of the range of process variables. A previously published lower bound solution for axisymmetric flow is refined.     

The analytical determination of friction for flow through conical converging dies

The effects of friction upon the intermediate and final distorted grids for wire drawing and/or extrusion were analytically studied for an assumed triangular velocity field. An upper-bound solution for the process was used. This solution predicted that the shape of the final and intermediate distorted grids were functions of the process geometry and of friction. Initially, combinations of reduction and semi-cone angle (α) were found for which the triangular velocity field was energetically preferred over an existing spherical velocity field. The analytical final distorted grids were then compared to experimentally obtained final distorted grids to determine the experimental friction. This was done by plotting calibration curves for distortion where friction served as the parameter and by comparing the actual distortion with the family of calibration curves.     

用图看世界——建筑制图课程思政建设的探索

党的十八大以来,习近平总书记围绕“培养社会主义建设者和接班人”做出一系列重要讲话,指出教育工作的根本任务是培养德智体美劳全面发展的社会主义建设者和接班人。须将建筑制图教学与祖国需求联系起来,激发学生的学习兴趣;结合社会热点和历史重要事件,在建筑制图课程教学中融入思政教育元素,在培养学生工程制图能力的同时,对学生的价值观进行培育,在课堂教学中检验思政教育效果,以培养更多优秀的社会主义建设者和接班人。     

用图看世界——建筑制图课程思政建设的探索

党的十八大以来,习近平总书记围绕“培养社会主义建设者和接班人”做出一系列重要讲话,指出教育工作的根本任务是培养德智体美劳全面发展的社会主义建设者和接班人。须将建筑制图教学与祖国需求联系起来,激发学生的学习兴趣;结合社会热点和历史重要事件,在建筑制图课程教学中融入思政教育元素,在培养学生工程制图能力的同时,对学生的价值观进行培育,在课堂教学中检验思政教育效果,以培养更多优秀的社会主义建设者和接班人。     

The potential of microfluidics-enhanced extrusion bioprinting

Microfluidics-enhanced bioprinting holds great promise in the field of biofabrication as it enables the fabrication of complex constructs with high shape fidelity and utilization of a broad range of bioinks with varying viscosities. Microfluidic systems contain channels on the micrometer-scale, causing a change in fluid behaviors, enabling unconventional bioprinting applications such as facilitating the precise spatial positioning and switching between bioinks with higher accuracy compared to traditional approaches. These systems can roughly be divided into three groups: microfluidic chips, co- and triaxial printheads, and printheads combining both. Although several aspects and parameters remain to be improved, this technology is promising as it is a step toward recapitulating the complex native histoarchitecture of human tissues more precisely. In this Perspective, key research on these different systems will be discussed before moving onto the limitations and outlook of microfluidics-enhanced bioprinting as a whole.     

景观手绘表现之我见

景观手绘表现是一种古老而质朴的设计表现手段。在现代设计中,在计算机铺天盖地的时代里,依然以它最独到的特点在设计界保持着自己应有的地位。我们用一张张图纸捕捉创意灵感,与他人沟通自己的意图,彰显自己的个性,描绘生活的意境。     

高校制图课程教学的探索

本文将制图课程与应用型高等院校的人才培养目标以及专业能力有机地结合,体现了应用型院校培养学生的职业能力这一主题。     

用CorelDRAW制作科技期刊插图全攻略

介绍了用CorelDRAW软件制作科技期刊插图的全过程,包括参数的设置、图素库的建立,以及处理其他软件制作的插图的方法。提出了用CorelDRAW软件作图时应该注意的几个重要问题。用CorelDRAW软件制作EPS格式的图片文件,既有矢量图形输出的高质量,又节省了存储空间,是以方正软件排版的科技期刊实现图文混排的极佳工具。     

浅议用Matlab绘制Bode图及频率特性分析

在工程实践中,要求能比较简单迅速地分析出系统各参数对暂态特性的影响以及系统稳态性能的好坏。频率法是应用频率特性研究控制系统的一种重要方法,采用这种方法可直观地表达出系统的频率特性。根据系统的频率特性能间接地揭示系统某些环节或者参数对系统稳态特性和暂态特性的影响,并能指明改进系统的方向。而Matlab的介入,使得利用计算机来精确地绘制系统的各种频率特性成为现实。