拼焊板成形性能及其在方盒形件拉深成形中的应用研究

发布时间：2018-05-25 16:34

本文选题：拼焊板 + 焊接区力学性能　；参考：《燕山大学》2015年博士论文

【摘要】：拼焊板成形技术是指采用不同厚度、不同材质或不同表面涂层的板材,经下料后焊接成整体预制板坯,再进行冲压成形的工艺方法。拼焊板成形技术在减少车身重量、增强车身结构安全性等方面具有重要作用。近年来,随着社会对环境保护、节能减排等要求越来越高,拼焊板成形技术在汽车制造业中的应用越来越广泛。但是,拼焊板母材或厚度不同或强度不同,且存在焊缝和热影响区,导致拼焊板在成形技术上与常规单一板材相比有很大不同,有很多新的技术问题亟待解决,如拼焊板激光焊接、焊接区对拼焊板成形的影响和成形极限等问题。因此,对拼焊板激光焊接过程、焊缝及热影响区金属力学性能测定、拼焊板成形极限以及拼焊板拉深成形过程控制等问题进行深入研究具有十分重要的意义。本文首先研究了不同焊接功率和不同焊接速度对拼焊板激光焊接接头宏观质量的影响规律,给出了课题研究用拼焊板的合理焊接工艺参数取值范围,并基于显微组织分析、硬度测试等试验对拼焊板激光焊接接头进行了质量检测。通过“小尺寸型”拼焊板试样单向拉伸、混合法则和纳米压痕等技术,分别建立了拼焊板焊缝及热影响区金属的平均和非平均弹塑性力学性能测定模型。采用Erichsen杯突试验对比了忽略和考虑焊缝及热影响区金属弹塑性力学性能对拼焊板成形结果的影响。基于塑性本构关系和Hosford屈服准则,在拼焊板焊缝及热影响区金属的弹塑性力学性能已知条件下,提出了一种能较好预测同材等厚拼焊板成形极限的理论计算方法。对于异厚拼焊板,建立了从细观损伤角度预测拼焊板成形极限的GTN(Gurson-Tvergaard-Needleman)模型,采用有限元软件ABAQUS,耦合基于Mises屈服准则的弹塑性GTN损伤模型,对异厚拼焊板的成形极限进行了预测。设计了拼焊板半球凸模胀形物理试验,试验过程中通过改变试件的宽度得到了不同应变状态下完整的拼焊板成形极限图,并与前面两种预测模型得到的拼焊板成形极限图进行了对比分析。综合考虑焊缝及热影响区金属弹塑性力学性能,以拼焊板成形极限图作为拼焊板方盒形件拉深成形的破裂判据,建立了拼焊板方盒形件拉深成形的有限元数值模拟模型。着重分析了拉深成形过程中压边力这一最重要且易于控制的工艺参数对拼焊板方盒形件拉深成形极限、焊缝移动和侧壁起皱(对于锥壁类方盒形件而言)的影响规律,给出了较优的压边力加载方式。引入人工神经网络模型,分析了拼焊板方盒形件拉深成形过程中的主要影响因素,建立了拼焊板方盒形件拉深成形过程中较优的压边力神经网络预测模型。基于正交试验设计和有限元数值模拟构建了神经网络预测模型所需的训练样本,从而实现了压边力控制规律的准确预测。本文最后建立了拼焊板方盒形件拉深成形实验系统,在拉深过程变量P(拉深力)、Q(压边力)和h(拉深行程)的采集实验中,利用LabVIEW虚拟仪器和技术,建立了拼焊板方盒形件拉深成形实验的数据采集系统。设计了拼焊板方盒形件拉深成形的实验模具,并通过物理实验和有限元数值模拟相结合的方法,探讨了板料厚度比、压边力和模具参数等因素对拼焊板方盒形件拉深成形的影响规律。
[Abstract]:Tailor welded sheet forming technology refers to the process of forming a whole preform with different thickness, different material or different surface coating, and then welded into a whole preform after being under material. The forming technology of tailor welded plate is important in reducing body weight and enhancing the safety of body structure. In recent years, with the society to the environment protection. The requirements for protection, energy saving and emission reduction are becoming more and more high. The application of tailor welded plate forming technology is more and more widely used in automobile manufacturing industry. However, the welding plate has different thickness or thickness or strength, and there is a weld and heat affected zone. The welding plate is different from the conventional single sheet in forming technology, and there are many new technical problems. It is very important to solve the problems such as the laser welding of the tailor welded plate, the influence of the welding zone on the forming of the tailor welded plate and the forming limit. Therefore, it is very important to study the laser welding process of the tailor welded plate, the measurement of the mechanical properties of the metal in the weld and the heat affected zone, the forming limit of the tailor welded plate and the control of the drawing process of the tailor welded plate. First, the influence of different welding power and different welding speed on the macroscopic quality of the laser welded joint of tailor welded plate is studied. The range of the reasonable welding parameters for the study is given, and the quality testing of the welded joint of the tailor welded plate is carried out based on the microstructure analysis and the hardness test. The average and non average elastoplastic mechanical properties of the welded joint and heat affected zone of the tailor welded plate were established by the unidirectional stretching, the mixing rule and the nano indentation. The Erichsen cup process test was used to compare the metal elastic and plastic mechanical properties of the weld and heat affected areas to the forming of the tailor welded plate. Based on the plastic constitutive relation and the Hosford yield criterion, a theoretical calculation method for predicting the forming limit of the same thickness tailor welded plate is proposed under the condition of the known elastoplastic mechanical properties of the weld plate weld and the heat affected zone. For the tailor welded plate, the tailor welded plate is predicted from the meso damage angle. The GTN (Gurson-Tvergaard-Needleman) model of the shape limit, using the finite element software ABAQUS, coupled with the elastoplastic GTN damage model based on the Mises yield criterion, predicts the forming limit of the different thick tailor welded plate, and designs the bulging physical test of the hemispherical punch in the tailor welded plate, and the different strain shapes are obtained by changing the width of the specimen during the test. The whole forming limit diagram of the tailor welded plate is analyzed and compared with the forming limit diagram of the tailor welded plate obtained from the two previous prediction models. Considering the elastic and plastic mechanical properties of the weld and heat affected areas, the forming limit diagram of the tailor welded plate is taken as the fracture criterion of the drawing of the box shaped part of the tailor welded plate, and the box box of the tailor welded plate is established. The finite element numerical simulation model of drawing forming is used to analyze the most important and easy to control process parameters in drawing forming process, which are the most important and easy to control process parameters for the drawing limit of the square box shaped parts of the tailor welded plate, the movement of the weld and the wrinkling of the side wall (for the box shaped box shaped parts), and the superior loading way of the blank holder force is given. In the artificial neural network model, the main influencing factors in the drawing process of the square box shaped parts of the tailor welded plate are analyzed, and the better prediction model of the blank holder force neural network is established. The training samples for the neural network prediction model are constructed based on the orthogonal test design and the finite element numerical simulation. In this paper, an experimental system for the drawing of a square box shaped part of a tailor welded plate is established at the end of this paper. In the acquisition experiment of the drawing process variables P (drawing force), Q (pressing force) and H (deep drawing stroke), the data mining experiment of the square box shaped part of the tailor welded plate is established by using the LabVIEW virtual instrument and technology. The experimental mould for drawing forming of the square box shaped parts of the tailor welded plate is designed, and the influence of the thickness ratio of sheet material, the blank holder force and the parameters of the die on the drawing forming of the box box shaped parts of the tailor welded plate is discussed by combining the physical experiment with the finite element numerical simulation.
【学位授予单位】：燕山大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TG386

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