大口径直缝焊管O成形过程的有限元分析

采用有限元分析方法,研究了焊管UOE成形工艺O成形过程模具载荷、板料变形模式和曲率分布变化,揭示了板料O成形过程变形的机理.结果表明,O成形过程是一个悬弧分段细分弯曲的过程,板料横截面形状曲率峰由单一峰向多峰演变,曲率峰峰间距离均匀.载荷在成形过程产生相应的阶段性交化,各段位移载荷曲线具有相似性,并且载荷随悬弧的细分明显增加.O成形过程分为4个阶段:U形口合扰、直边弯曲、悬弧二次弯曲和悬弧多次弯曲过程.     

渐进成形A3003铝板减薄带分析及数值模拟研究

研究渐进成形过程中板料减薄带的变化,可以提供合理的加工参数,提高板料的成形性能和加工利用率,减少零件破裂失效.基于渐进成形过程中金属板料轮廓的变化与理想情况下轮廓的区别,对渐进成形初始成形阶段A3003铝板减薄带的产生原因和剪切力的变化过程进行了理论分析,并通过有限元模拟分别从未变形区金属板料的长度和强度两个角度对板料渐进成形过程中未变形区下沉的影响,以及成形角度和杨氏模量对变形区回弹的影响两个方面,对减薄带的产生原因进行研究.结果表明:板料未变形区的下沉和变形区的回弹使板料在初始加工阶段形成一段平缓区域,工具头在平缓区域的变形性质发生了变化,平缓区域发生剪切变形导致了板料在初始加工阶段形成了减薄带;渐进成形时减小板料未变形区的长度,增大板料与垂直方向的角度可以一定程度上阻碍减薄带的产生,模拟结果与理论分析相符合.     

BT20钛合金筒形件的UOE热成形

阐述了用UOE热成形BT20钛合金筒形件的特点.通过对BT20筒形件UOE热成形的实验研究,确定了BT20钛合金筒形件UOE热成形工艺过程,得到了一系列成形工艺参数及在成形过程中控制产品质量的措施.     

电磁成形放电频率对板料变形的影响

目的研究电磁成形放电频率对板料变形的影响规律。方法以商用有限元软件ANSYS为平台,建立板料电磁成形有限元模型。通过数值模拟方法,研究不同厚度的1040铝合金板在不同放电频率下的变形过程,得到不同板厚对应的最优放电频率。对比板料自由胀形试验结果,验证数值模拟的可靠性。结果放电频率对线圈放电电流、板料内电流分布、磁场力分布以及变形影响较大,并且存在最优放电频率使得板料的变形量最大。结论最优相对放电频率随着板厚的增加而减小,其变化规律呈幂指数函数变化。     

板料冲压成形和回弹分析过程的三维动态模拟

利用ANSYS/LS-DYNA非线性动力有限元程序的显式-隐式连续求解功能,模拟了板料成形过程与卸载后板料回弹变形的全过程,得到了成形过程中任一时刻各处的应力和应变值及卸载后板料的回弹结果.     

板料V形弯曲回弹的动力显式有限元分析

板料成形后的回弹对精度影响较大,在数值模拟时对回弹进行精确预测显得非常重要.基于连续介质力学及有限变形理论,建立了适合于三维板料成形分析的显式算法的有限元数学模型,采取集中质量矩阵,用动力显式积分的方法,使位移计算显式化,避免了由材料、几何、边界条件等高度非线性因素引起的计算收敛问题.根据该模型开发了动力显式算法的板料成形过程模拟的有限元分析程序DESSFORM3D,应用该软件模拟了包括回弹在内的整个板料V形弯曲的成形过程.通过3个不同凸模行程时计算与实验的板料几何形状对比以及计算结果与实验结果对比,验证了软件计算结果的准确性.     

板料V形弯曲回弹的动力烛式有限元分析

板料成形后的回弹对精度影响较大，在数值模拟时对回弹进行精确预测显得非常重要。基于连续介质力学及有限变形理论，建立了适合于三给板料成形分析的显式算法的有限元数学模型，采取集中质量矩阵，用动力显式积分的方法，使位移计算显式化，避免了由材料、几何、边界条件等高度非线性因素引起的计算收敛问题。根据该模型开发了动力显式算法的板料成形过程模拟的有限元分析程序DESSFORM3D，应用该软件模拟了包括回弹在内的整个板料V形弯曲的成形过程。通过3个不同凸模行程时计算与实验的板料几何形状对比以及计算结果与实验结果对比，验证了软件计算结果的准确性。     

研究单位压边力值对板料成形性能的影响

主要介绍板料在拉深成形过程中单位压边力值对板料成形性能的影响。研究方法采用仿真技术,指出板料在成形过程中如按最初设定的单位压边力值进行成形,那么,板料成形过程中单位压边力值将逐渐增大,严重影响板料成形极限。如果采用控制板料在成形过程中压边圈下坯料的单位压边力值,将提高板料成形极限。其结论为生产现场提高板料成形性能和表面质量提供了一种可实施的方法。     

三维曲面零件连续柔性成形技术的理论分析与回弹控制

对三维曲面零件连续柔性成形(CFF)新技术中的成形件形状控制、柔性辊轴线形状描述以及回弹等理论问题进行了研究.基于对连续成形过程中板料纵向与横向变形的分析,建立了成形纵向形状控制的理论与方法;结合多点控制的特点,给出了描述柔性辊辊形的样条插值公式;针对板料连续成形中的回弹补偿问题,基于对材料及变形方面的简化与假设,推导...     

板料渐进成形数值模拟与实验研究

为提高渐进成形的成形效率和成形质量,了解板料渐进成形的变形规律及工艺参数对成形的影响,采用有限元方法对板料渐进成形过程进行了数值模拟研究,分析了斜壁盒形件渐进成形过程应力分布和厚度变化趋势,通过对不同进给量和不同成形路径进行数值模拟,分析了工艺参数对成形的影响.结果表明,斜壁盒形件最大应力和最大厚度减薄发生在底面拐角处;成形过程中工具头运动轨迹应尽量采用走螺旋线的方式,可以提高成形件的成形能力和成形质量.渐进成形实验表明,数值模拟结果与实验结果基本吻合.     

Dynamic energy release rate evaluation of rapid crack propagation in discrete element analysis

A non-associated/associated flow rule coupled with an anisotropic/isotropic quadratic yield function is presented to describe the mechanical responses of two distinct X65 pipeline steels. The first as a product of the cold-rolling forming (UOE) process also known as seam weld pipes and the second as a result of high temperature piercing process called seamless tube manufacturing. The experimental settings consist of a wide range of sample types, whose geometric characteristics represent different state of stresses and loading modes. For low to intermediate stress triaxiality levels, flat specimens are extracted at different material orientations along with notched round bar samples for high stress triaxialities. The results indicate that despite the existing differences in plasticity between materials due to anisotropy induced processes, material failure can be characterized by an isotropic weighting function based on the modified Mohr–Coulomb (MMC) criterion. The non-associated flow rule allows for inclusion of strain directional dependence in the definition of equivalent plastic strain by means of scalar anisotropy (Lankford) coefficients and thus keeping the original capabilities of the MMC model.     

Effect of microalloying additions on steel plate to pipe property variations during UOE linepipe processing

Abstract

Composition variations have been used to generate three steels, developing plate strengths in the range 350-530 MPa for the same rolling schedules. The tensile properties of the plate have been determined and compared with those of first, pipe formed by the UOE process and second, specimens from the same pipe after flattening. It has been shown that the difference between plate and pipe strength levels for the specific pipe geometry investigated is related to the steel grade. In particular, changes have been related to the Bauschinger stress parameter, optical microstructure, fine particle distribution (from TEM replicas) and stored energy (measured using differential scanning calorimetry) differences between the steels. The trends in property variation result from the balance of work hardening behaviour and Bauschinger effect, and have been related to the presence of fine microalloying element precipitates in higher strength grades, increasing the Bauschinger effect and forming a more highly ordered dislocation structure during the various deformation stages.     

UOE直缝埋弧焊管横向屈服强度测定的影响因素

针对UOE直缝埋弧焊管横向屈服强度测定的3个重要影响因素,分别讨论了钢管横向板拉伸试样的压平影响和钢管横向圆棒拉伸试验的应变时效现象,并分析了拉伸试验速率的影响。得出了横向板拉伸试样的屈服强度低于圆棒拉伸的结果是由于试样的不平直原因引起的结论,同时对UOE钢管圆棒拉伸应变时效的防止和不同实验室拉伸速率的统一提出了建议。     

A Comparative Study on the Production of a Hat Profile by Roll Forming and Stamping

Lightweight design using high-strength aluminum alloys has gained importance due to the continuing need for weight reduction and increasing crash safety requirements in the automotive industry. There are various manufacturing processes available for processing high-strength aluminum alloys. Herein, the production of high-strength aluminum parts by roll forming and stamping based on the example of an AA7075-T6 hat profile is compared. Roll forming represents a continuous manufacturing process, while stamping is a discontinuous process. Different process routes (T6, W-Temper and O) for roll forming as well as for stamping (T6, W-Temper, O and hot forming) are in focus of the investigation. Fundamental differences of the forming processes and the tempering condition are observed and criteria for the choice of the manufacturing process and process route are presented. The temperature-supported process routes improve the poor cold formability of AA7075 alloy and thus enhance the process window. Potential is offered for both manufacturing processes by applying tailored properties achieved through targeted quenching.     

连轴体成形工艺模拟分析

根据连轴体件凸缘较宽、凸台较高且直径较小、壁厚不均匀等结构特点及成形难点,制定了拉深和挤压2种工艺方案。采用有限元数值模拟,对2种成形工艺的模拟结果分析表明：采用拉深工艺时,成形力小,成形质量差;采用挤压工艺时,成形力大,成形质量好。通过对挤压工艺坯料形状的改进,降低了成形载荷并提高成形质量。     

7A04铝合金等温正挤压制坯工艺技术

通过对铝合金轴杆件毛坯零件的成形工艺技术研究分析,提出采用正挤压最佳成形制坯方法取代原粗车工艺。介绍了7A04铝合金等温正挤压成形工艺主要工艺条件的选择和工艺参数的确定,模具控温装置的选择和控温原理,模具结构和工作过程,以及生产中出现的质量问题和解决方法,正挤压制成的毛坯质量满足要求。     

铝合金汽车顶盖充液成形的数值模拟

目的研究铝合金汽车顶盖拉延工序的充液成形工艺。方法基于有限元分析软件Dynaform,利用带局部刚性凹模整形的被动式充液成形工艺,通过建立有限元分析模型,优化成形过程中的关键工艺参数,分析变形规律并进行质量控制。结果成形过程中的液室压力加载路径、压边力、拉延筋,以及坯料形状等工艺参数对成形影响较大。液室压力不宜过早加载。液室压力过大或压边力过小不利于顶部产生充分塑性变形。压边力过大极易造成顶盖圆角处的破裂。结论该成形工艺可行,且数值模拟的准确性及适用性较高,采用该成形工艺可得到表面质量良好,未出现起皱、破裂缺陷的合格零件。     

塑性有限元在金属体积成形过程中应用的进展

塑性有限元法已经成为研究金属体积成形的重要方法。介绍了刚塑性有限元和弹塑性有限元的原理;综述了金属体积成形过程中锻造、挤压和轧制工艺有限元模拟的国内外最新应用进展,并分析了有限元法在不同工艺中应用的未来发展方向。最后总结了塑性有限元法在金属体积成形领域未来发展的难点和趋势。     

Feasibility of underwater laser forming of laminated metal composites

Laminated metal composites are of great interest in various industries. Previous studies demonstrate undesired mechanical or microstructural changes in these composites during the laser forming process due to rapid temperature gradient. In this research, underwater laser forming is proposed to minimize this effect. This process could also be an effective method for on-site forming or repairing of large metal/composite sheets used in underwater applications, such as marine equipment, ships, and lake/sea-based offshore oil platforms. The underwater laser forming process is performed experimentally on a three-layered stainless steel/copper/stainless steel composite and compared with the results of in-air tests. Total forming time, bending rate, and microstructural changes are compared for both underwater and in-air conditions. The effects of forming parameters, such as the number of irradiations, laser beam velocity, diameter, and power, are also compared and discussed. It is shown that the bending angle per irradiation in underwater forming is significantly lower in comparison with in-air condition, but the production time is less due to the elimination of cooling time. Also, the microstructure of stainless steel at heat-affected zone was unchanged, and the hardness of upper layer experienced smaller changes when formed under water. The underwater laser forming process is demonstrated to be feasible and can be applied for underwater applications with a high degree of reliability.     

圆柱体压扭锻造的有限元分析与模拟试验研究

根据塑性理论分析了压扭工艺省力的原理及预期效果，用塑性有限元预测了该工艺的应变分布，用塑性泥模拟了圆柱体的微粗和压扭工艺，观察了工件内部孔洞性缺陷的演变过程，理论分析与试验结果吻合。