轴类件拔长V型砧和四砧径向锻造锻透性研究

轴类大锻件拔长可以采用V型砧、四砧径向锻造等。为了解这些拔长方式对锻件芯部变形的影响,应用有限元软件Super Form模拟了拔长锻造过程,对比分析了V型砧和四砧径向锻造两种工艺方法的锻透性。研究表明:V型砧拔长,锻后锻件内部等效应变分布不均匀,各处变形差异较大,经3道次拔长后,锻件芯部锻透性较好,给定条件下的累积等效应变约为1.6;四砧径向锻造,锻后锻件内部等效应变分布比较均匀,但锻件芯部锻透性较差,给定条件下芯部等效应变小于0.2,且端部一定长度范围内,芯部等效应变更小,经4道次拔长后,芯部累积等效应变为0.8左右。     

水平V型锥面砧改善轴类锻件异向性的研究

水平V型锥面砧为横向性能有要求的轴类锻件提供了一种拔长锻造方法,通过改变工具形状、控制纤维流向的方法,来提高轴类锻件横向力学性能,改善异向性.本文进行了水平V型锥面砧与上平砧-下V砧拔长矩形截面坯料锻造的对比试验,通过对比两种锻造方法拔长锻件的纵向、横向力学性能,证实了水平V型锥面砧锻造法达到了普通锻造方法难以实现的锻造效果--轴类锻件力学性能的异向性明显改善,即水平V型锥面砧拔长的锻件同部位屈服强度、抗拉强度和延伸率的横向与纵向之比均在1.0附近变化.     

大锻件锻造拔长砧型

利用有限元软件模拟了V型砧的锻造拔长过程,并对不同夹角的V型砧压下后锻坯塑性变形区内应力、应变的状态进行比较。结果显示,在117°～153°温度范围内,V型角越大,锻坯心部金属获得的变形量越大,但同时锻坯次表层金属的变形程度减小。为此,将V型砧夹角处的V型砧面改为凸型平砧面,提出了梯型砧锻造拔长工艺。结果表明,梯型砧工艺提高了锻坯内部的压应力水平,使锻坯心部和次表层金属同时获得了较大且均匀的变形,有助于扩大锻坯内部孔洞的锻合范围,改善大锻件的内部质量。     

弧形砧砧型参数对车轴锻件拔长效率的影响

以不同砧型的弧形砧为研究对象,利用Deform-3D有限元模拟软件对车轴锻件的拔长过程进行了数值模拟研究,分析了不同砧型的弧形砧对拔长效率的影响。研究表明:随着弧形砧的圆弧半径R减小、圆弧所对应的圆心角θ增大,拔长效率增加,所需的最大锻造力也增大。相同工况下,使用带预成形段型弧形砧比使用普通弧形砧对设备的吨位要求更低,且能保持较高的拔长效率,适用范围更广。     

砧宽对磨辊轴拔长时孔洞闭合的影响研究

孔洞是大型锻件生产时常见的缺陷,严重影响锻件的质量,需要通过在锻造过程中合理控制工艺参数进行消除.砧宽比是影响着孔洞闭合效果的一个重要参数.通过运用不同砧宽对磨辊轴拔长时孔洞闭合的研究,得出了合理的砧宽,为实际生产提供了理论参考.     

轴类大锻件倒棱滚圆后内部质量及尺寸精度研究

轴类大锻件的锻造过程分为压方、拔长和倒棱滚圆三大步骤。为制定准确的倒棱滚圆工艺参数以提高锻件质量并指导实际生产,应用有限元软件Deform-3D建立相应的分析模型,对倒棱滚圆过程进行模拟。从锻件的尺寸精度和锻件内部应力应变状态两个方面对比分析了平砧、90°V型砧和120°V型砧3种工艺方法。模拟结果表明,运用120°V型砧倒棱滚圆可以得到质量更佳的轴类大锻件。     

DN1800整锻管模拔长及空收成形技术北大核心CSCD

DN1800特大整锻管模锻件相对壁厚极小、规格大、吨位重、火次多、拔长效率低、技术要求高,且现有生产工装辅具不匹配,在工艺设计、质量控制和生产组织方面难度极大。通过研究锻造拔长机理及过程,提出控拔控压工艺方案、拔长效率提升控制方案和Φ1900 mm芯轴拔长+上平下V形砧空收+Φ2200 mm上圆弧下V形砧复合空收成形工艺方案,并结合工艺性分析,建立了塑性变形有限元分析模型,不断优化工艺参数,通过提出生产操作关键点,细化空收工艺参数,严格进砧量、压下量、温度和旋转角度的匹配控制,成功完成特大整锻管模的试制生产,验证了工艺参数及成形工艺的合理性,积累了特大整锻管模特殊锻造成形经验。     

凹面砧方坯拔长研究

以 ANSYS软件为平台 ,分别利用凹面砧、平砧两种砧型对方坯拔长进行三维数值模拟。当坯料心部获得相同等效应变时 ,比较中心部位沿轴向的变形区大小和静水应力分布情况 ,发现用凹面砧拔长较平砧拔长更有利于消除锻造缺陷 ,提高生产率     

大锻件不同砧型拔长工艺的研究进展

阐述了大锻件拔长工艺的研究进展,重点阐述了不同砧型拔长工艺的研究现状及取得的成果,展望了拔长工艺未来的研究方向和发展趋势。     

平砧拔长矩形截面毛坯的理论

从理论上分析与论证了平砧拔长矩形截面毛坯只有砧宽比(W/H)一个工艺参数是不足的,认为应增加,个工艺参数料宽比(B/H),才能正确描述拔长毛坯中心区域的应力状态与有效控制锻件质量。该理论已被实验验证。     

核电压力壳锻件芯轴拔长工艺V砧砧角的常温模拟研究

根据核电压力壳筒体锻件拔长工艺的变形特点 ,本文提出衡量其变形优劣的定量化指标 :内部变形均匀度、端面变形率、内孔畸变率和拔长效率。采用密栅云纹法和刚 -粘塑性有限元法研究了核电筒体锻件上平下 V砧芯轴拔长 V砧砧角对变形的影响 ,综合上述各定量指标 ,较合理的 V砧砧角为 110°     

Experimental and numerical investigation on development of new incremental forming process

The main subject of the present work is to present the new and innovative manufacturing technology based on the incremental forming approach. The idea is to develop a deformation process that is strictly based on small incremental deformations realized by a series of thin anvils. To realise this idea in practise this idea, a proper geometry of the upper die has to be designed. In the present work it is a set of several rolls (pressure rollers) that moves down towards a series of small anvils and performs rotational movement at the same time. As a result, the pressure is not transferred by the upper die directly to the material. The pressure is transferred to the sample through the series of thin anvils. To incrementally transfer the desired final shape to the forging a series of anvils with various lengths has to be used. Due to the complexity and novelty of the proposed approach, a set of questions has to addressed. These are related to appropriate depth of anvil indentation, material flow under a single anvil, material interaction with anvils and interaction between subsequent anvils. This basic research is done in the present work with the use of simple laboratory tests. Then detailed experimental analysis of material flow in the developed new process is presented. At this stage of the research the prototype of the proposed device is created on the basis of the orbital Marciniak forging press (Marciniak, 1970). All the obtained results are presented, and conclusions related to the effectiveness of the process are highlighted. The experimental part of the research is also supported by numerical analysis. The commercial finite element (FE) Forge2005 software was used in the present work to evaluate the forging process parameters and analyze the character of material deformation. The obtained numerical results are compared with the experimental analysis performed on the developed prototype press.     

新型复合曲面型砧的设计

以大型钢锭锻造过程为研究对象,创新设计一种新型复合曲面型砧对锻件进行锻造;采用非线性有限元和物理模拟实验方法,通过理论建模和数值模拟,对大锻件内部组织变形的均匀性进行研究,以求找出在用不同形状砧子进行锻造时,锻件内部的应力、应变状态。以DEFORM软件为平台,对新型复合曲面型砧的锻造过程进行有限元模拟;根据影响锻造效果的主要因素砧宽比、型砧角度和设计复合曲面型砧所需的镜像线高度,特设计几种不同几何参数的工况,以求解出复合曲面型砧的最佳几何参数。     

水平V型砧锻造大型轴类锻件的数值模拟和实验

水平V型砧锻造法,可以通过控制锻件金属的流动方向减少轴类锻件力学性能的异向性,在锻件内部应力状态、金属纤维组织、锻件的整体性能、宏观几何形状等方面都优于普通平砧锻造法。采用有限元分析方法,对水平V型砧锻造法进行了数值模拟,结果显示,采用水平V型砧锻造法时,在砧宽比为1.0和料宽比为0.5的条件下,锻件心部的横向应力都处于压应力状态,而采用普通平砧锻造法使用相同工艺参数时,则会出现不利的拉应力状态。这表明水平V型砧锻造法比普通平砧锻造法在控制轴类锻件的横向应力上更有利,有更广泛的工艺参数范围。     

大型圆柱锻件深冲孔最大孔径比的数值模拟研究

本文以内接于大型斜三通锻件的圆柱体为例,基于Deform-3D有限元软件,对高径比H/D=2.5大型圆柱锻件深冲孔工艺过程进行了数值模拟。通过对不同直径坯料冲制多种规格内孔,研究了不同孔径比对坯料形变的影响。模拟分析表明,选择合理孔径比上限,可获得形状规则的目标锻件,研究结果可以为大型圆柱锻件深冲孔工艺的制定提供理论依据。     

Tool design in a multi-stage drawing and ironing process of a rectangular cup with a large aspect ratio using finite element analysis

Tool design is carried out for a multi-stage deep drawing and ironing process of a rectangular cup with the large aspect ratio using the result of the finite element analysis. The analysis incorporates three-dimensional continuum elements for an elasto-plastic finite element method with the explicit time integration scheme using LS-DYNA3D. The analysis simulates the five-stage deep drawing and ironing process with the thickness control of the cup wall. Simulation is performed in order to investigate the failure by tearing during the forming process at the initial state of tool design. The analysis reveals that the difference of the drawing ratio within the cross section induces non-uniform metal flow which causes severe local extension. The irregular contact condition between the blank and the die also induces non-uniform metal flow which causes local wrinkling. This paper identifies such unfavorable mechanism in the rectangular cup drawing with ironing and proposes a new tool design with the guideline for modification in the design of the process and the sequential tool shape. The finite element analysis result with the improved tool design confirms that the proposed design not only reduces the possibility of failure but also improves the quality of a deep-drawn product. The numerical result shows fair coincidence with the experimental result.     

Friction aided deep drawing of sheet metals using polyurethane ring and auxiliary metal punch. Part 2: analysis of the drawing mechanism and process parameters

Friction aided deep drawing using a polyurethane ring as a pressure medium has been analyzed by the slab and the energy methods to understand the main features of the process and to find the optimum conditions to achieve successful drawing. The effect of an auxiliary metal punch on the stress distribution of the deformed blank and the increase in height of the drawn cup is also discussed. From these studies, the reason why the unusual circumferential crack occurs at the flange of the deformed blank has been clarified, based on the radial stress distribution of the deformed blank. A process parameter, which denotes the drawing characteristics of the friction aided deep drawing, has been proposed. In addition, the drawing region diagram has been presented to facilitate the drawing pressure control with the progress of the drawing process. It is shown that the successful drawing region is narrow at the early stage of drawing, although it becomes wide as the drawing proceeds. Therefore, in the early stage of drawing, special care should be paid to the drawing pressure control to avoid the flange crack.     

Numerical study on the evolution of surface defects in wire drawing

In this study, a three-dimensional finite element analysis for multi- or single-pass wire drawing was carried out in order to evaluate the deformation behavior of various surface defects, such as longitudinal, transverse, oblique, and round, introduced during the manufacturing processes. For numerical simulations, a free surface contact treatment algorithm was employed to suppress node penetration by applying a penalty method. Simulation results were compared with the experimental data obtained by optical microscopy for multi-pass drawing samples of the medium carbon steel wire with a longitudinal round-type defect in terms of variation of the load requirement and evolution of the cross-sectional shape of the surface defect. Additional numerical studies were carried out to investigate changes of cross-sectional shapes of various surface defects depending on stress distributions in the single-pass wire drawing. It was found that the radial and circumferential stress components determined the final shape and aspect ratio of the defect. The current numerical approach can be helpful in determining a guideline to assess the acceptability of the surface quality of the drawn wire for the secondary manufacturing process based on the available data in the literature.     

大锻件锻造的新中心压实法--一维温差锻造法

针对大型锻件锻造的特点，综合了普通平砧拔发和中心压实法的优点，提出了一种新的中心压实方法。此法只使锻坯上下表面强制冷却，建立一维不均匀温度场后，采用上下平砧锻造。模拟试验结果表明，新方法不仅在压实效果上达到或超过了中心压实法，而且能避免采用中心压实法时，担任过程复杂、锻件表面压伤、折叠等不足。     

Friction aided deep drawing of sheet metals using polyurethane ring and auxiliary metal punch. Part 1: experimental observations on the deep drawing of aluminium thin sheets and foils

Friction aided deep drawing based on the Maslennikov process is investigated as a method to facilitate the deep drawing of sheet metals with poor drawability. Aluminium foils and thin sheets of 0.1–0.4 mm in thickness are used as a model for the material with poor drawability. An auxiliary metal punch is used together with a polyurethane ring to increase the drawing efficiency and to improve the dimensional accuracy of the drawn cup. The effect of drawing conditions such as thickness, hole diameter and the hardness of the polyurethane ring on the cup height are mainly investigated. Also, the optimum number of drawing operations required to achieve a given drawing ratio is examined by repeating compression and unloading the polyurethane ring. The experimental results show that even for foil and thin sheets, deep cups with drawing ratios of 2.25 and with good shape and dimensional accuracy can be obtained by repeating the drawing operation about ten times. The achievable drawing ratio is appreciably larger when compared with that obtained by the conventional deep drawing process.