Special-shaped tube drawing forming and conformal optimization of die cavity

Aiming at the issues in quick processing and modeling design of drawing special-shaped tube die, by Conformal Mapping Theory and the numerical trigonometry method of interpolation between odd points and even points, the conformal mapping function is obtained. As the result, three-dimension drawing forming were converted into that of two-dimension problems, and the plastic stream function was analyzed, die cavity modeling and its optimized function were set up. Combining with modern processing technology, NC program and CAM of die cavity can be realized. Taking the drawing forming of hexagon tube with arc radii r and ellipse-shaped tube as instances, the drawing die cavity optimization of special-shaped tube was achieved, as well as, the changing principle of wall thickness was analyzed.     

φ114mm直缘成型焊管机组的研制

简介了研制的φ１１４ｍｍ直缘成型焊管机组的技术性能和工艺特点。与普通辊式成型机组相比，该机组工艺先进，焊管精度高。     

板料弯曲回弹的有限元模拟影响因素研究

阐述了板料成形数值模拟中回弹问题的研究历史和发展现状,分析了塑性弯曲加工中工件发生弯曲回弹的原因、特点及有限元模拟过程的影响因素,总结了回弹模拟的算法,从成形过程模拟和回弹计算两方面系统分析了影响回弹模拟准确性和收敛性的主要因素及改进方向,讨论了模具设计中回弹的补偿算法 ,并提出了当前控制回弹的基本方法     

混合室分配板成形工艺及模具设计

对混合室分配板零件介绍了一种落料拉伸成形和立体切沿分割的工艺思路以及模具结构和相关的理论计算 ,在实际应用中获得了好的效果。对同类形状产品 ,尤其是涉及到需要进行立体切沿分割的制件 ,可提供借鉴。     

On a novel press system with six links for precision deep drawing

The objective of this paper is to propose a novel press system with six links for precision deep drawing, and verify its feasibility. First, the system is presented and its advantages are discussed. Then, the kinematic analysis of the system is obtained by examining the geometry of the design. Moreover, kinematic dimensions of the variable coupling are found by using optimization method. Furthermore, the proposed approach is illustrated by a design example, its solid model for the proposed design is established, and then kinematic simulation is performed by ADAMS software. Finally, a prototype and an experimental setup are established, and the experiment is conducted. The results show that the proposed new mechanism is feasible and of reasonable accuracy. In addition, it has the advantages of easy manufacture, lower cost, higher precision, and easy adjustability.     

Optimal blank design based on finite element method for blades of large Francis turbines

Metal pressing process that is widely used in industries has advantages over casting process for producing large Francis turbine blades from thick plates. Prior to the pressing process, blank design is firstly performed to determine flat blanks. The traditional trial and error approach is not applicable to blade design for Francis turbines that are not standard due to hydraulic characteristics of power plant sites. The rapid development of computing technology makes it possible to obtain optimal flat blanks by numerical modelling and simulation. In this paper, inverse finite element approach is investigated for blank design and an elasto-plastic model has been built using the well-known commercial software ANSYS. Numerical simulations for blade unfolding models with thick shell elements, solid elements and shell elements have given results with negligible differences. Unfolding tests with simple geometries have been carried out and the numerical results agree well with the analytical solutions. A large and thick shape of a Francis turbine blade for a hydropower plant has been successfully unfolded by inverse FE model. Sensibility analysis shows that the middle surface of the flat blank is independent of blade thickness. For ensuring the machining of the blade after the pressing process, a new contour is obtained by extending the boundary of the flat blank provided by the numerical model. This research may provide a useful tool for optimal blank design of Francis turbine blades.     

电镀塑料制品对结构设计及成形工艺的要求

为保证电镀塑料制品的质量,提出了符合电镀要求的塑料制品设计原则,并且指出在注塑成形时,对塑料经过充分干燥,采用较高的注塑温度,较低的注射压力和较慢的注射速度,是使镀层获得良好结合强度的先决条件。     

MOLDFLOW在产品注塑分析中的应用研究

由于产品的注塑成型过程非常复杂，而注塑的计算机模拟能比较准确的预测产品的质量和存在的问题。本文介绍了Moldflow软件MPI／Stress中的MPI／Cool、MPI／Flow、MPI／Warpage模块的作用，并以标准齿轮为例进行了冷却、模流和翘曲分析，分析和讨论了影响产品质量的主要原因和问题。     

Process Modeling for Precision Forming of Discrete Parts – State of the Technology and Critical Issues

This paper presents an overview on the application of FE simulation as a virtual manufacturing tool in designing manufacturing processes for precision parts. The processes discussed include forging, sheet metal forming and hydroforming. Determination of reliable input parameters to simulate a process is a key element in successful application of process simulation for process design in all the mentioned areas. These issues are discussed in detail. Practical examples of application of FE simulation are presented for improvement of the existing metal forming process and/or designing new metal forming process for manufacturing discrete precision parts in forging, sheet metal forming and hydroforming.     

Stresses in bent copper tubing: Application to fatigue and stress-corrosion cracking failure mechanisms

The residual and applied stresses in u-bent copper tubing are addressed in the context of both cyclic fatigue and stress-corrosion cracking. Failures as a result of fatigue and stress corrosion cracking in u-bent copper tubing have been observed to initiate at nonintuitive locations when only the applied stresses on the component are considered. This paper presents both qualitative classical and quantitative finite-element stress analysis results for the forming of u-bends. The resulting residual stress distributions are compared to fracture patterns generated by both fatigue and stress-corrosion cracking mechanisms.