【作者】 祝海燕；

【导师】 汪建敏； 姜银方； 袁国定；

【作者基本信息】 江苏大学 ， 材料加工工程， 2009， 硕士

【摘要】 拼焊板具有提高生产效率、降低生产成本、节约能源、适应环保、增加安全性等优势,在汽车工业中受到越来越多的重视,其应用必将促进汽车产业的巨大进步。基于拼焊板基板间存在机械性能、厚度等差异,这就导致拼焊板成形时的应力与应变与传统板材的成形有很大的不同,它更容易引起破裂、起皱、焊缝移动以及回弹等问题。在实际生产过程中,如何控制差厚拼焊板成形时所引起的焊缝移动和成形能力的下降是困扰工程师的两个主要技术难题。目前,国内外对拼焊板成形时所出现的破裂、起皱和焊缝移动等问题的研究多局限于传统工艺,而对于既有拉深成形,又有胀形成形的拼焊板充液拉深技术研究较少。因此,本论文试图通过先进的充液拉深技术来分析拼焊板方盒形件成形时各参数对焊缝移动和成形极限深度的影响规律,为指导和控制焊缝移动提供理论依据。本文在压边力和液体压力作用下,针对差厚拼焊板方盒形件的焊缝移动的问题进行了以下研究:1.理论分析。从理论上分析了差厚拼焊板充液拉深工艺的成形原理及特点。针对成形机理较为复杂的盒形件,分别对凸缘、侧壁、凸模与压边圈之间的自由变形区从力学角度对焊缝移动产生的原因进行了分析。2.拼焊板盒形件的建模。考虑到毛坯形状、焊缝、材料性能对拼焊板成形性能的影响,在建模时,针对这些因素进行了模拟分析,从而确定了盒形件拼焊板有限元分析模型。3.充液拉深中焊缝移动的控制。分析了不同参数条件下压边力对焊缝移动的影响,通过比较看出充液拉深工艺的应用可以减小盒形件底部焊缝移动量,但对侧壁焊缝移动影响不大;同时还对充液拉深工艺中的压边力大小及分布,液体压力大小及加载路径、模具与毛坯之间的摩擦系数和模具间隙等参数进行了模拟分析,结果表明,通过调节压边力大小及分布,液体压力及其加载方式、摩擦系数和模具间隙可以达到控制焊缝移动的目的。4.充液拉深中极限拉深深度的控制。由模拟结果得出,在相同的压边力条件下充液拉深工艺与传统拉深相比可以提高极限拉深深度;但是,在充液拉深成形中,改变液体压力大小及加载路径对极限拉深深度影响不大,而增大模具间隙则可以大大提高极限拉深深度。更多还原

【Abstract】 The tailor-welded blanks(TWBs) become more and more important in the automobile industry and its applications can accelerate the development of the automobile industry,for their advantages such as low manufacturing cost,vehicle weight reduction,environmental protection and safety improvement,etc.Despite of these advantages of TWBs,there are great differences including mechanical properties and thickness between the two sides of TWBs which makes the stress and strain in the forming more complex compared with the traditional blank,so it cause problems mor easily,such as cracking,wrinkling,weld line movement and springback.In the actual production,how to control the weld-line movement and the decline of formability is the two main technical problems puzzling engineers in the different thickness TWBs forming.At present,national researchers have done a great works in traditional TWBs forming problems such as cracking,wrinkling and weld-line movement,but little work has been done in the hydro-forming of TWBs which includes not only drawing,but also bulging. Therefore,this thesis tries to find out the rules of different parameters influencing square cup with TWBs to supply theoretical foundation for directing and controlling weld-line movement.In this thesis,the effects of blank holder force and liquid pressure on the weld-line movement of square cup with different thickness TWBs have been researched.1.Theoretical analysis.The principle and characteristics of hydro-forming of different thickness TWBs were analyzed theoretically.Owing to the complex shaped mechanism of square cup,the effects of flange,wall and the free transfiguration between punch and blank holder on weld-line movement are separately analyzed at the mechanical point.2.The modelling of square car with TWBs.Considering the effects of the blank shape, welding line,material properties on formability,the finite element analyse model is built on the base of analysing these factors’ effects.3.Control the weld-line movement in the hydro-forming.By analysing blank holder force’s effects on weld-line movement in different forming process,the results show that hydro-forming has great advantage in decrease the weld-line movement,especially at the bottom of square cup;at the same time,by simulating these parameters’ effects in hydro-forming,such as blank holder force and its distribution,liquid pressure and its load path,friction coefficient between mould and blank and mould clearance,the results show that weld-line movement can be controlled by adjusting these parameters.4.Control the limit drawing depth of hydro-forming.The simulation results show that hydro-forming process can improve limit drawing depth compared with traditional forming process in the same conditions,however,in hydro-forming,change liquid pressure and its load path don’t have much effect on the limit drawing depth,while increase the mould clearance can improve the limit drawing depth greatly.更多还原