【作者】 李慧；

【导师】 周杰；

【作者基本信息】 重庆大学 ， 材料加工工程， 2005， 硕士

【摘要】 充液拉深是特种拉深成形中的一种,相对于传统机械拉深工艺来说,可以获得更大的拉深比。在充液拉深过程中,板料在液压介质的压力作用下,紧紧地贴合于凸模,依据库仑摩擦定律可知,板料与凸模贴合面之间的摩擦力将增大,其结果是获得更高的拉深深度;同时,凹模的简化也是该方法经济性的一个重要表现。充液拉深的基本过程如下(坯料为预先下好的板料): 1、将液压油泵入凹模型腔;2、将板料放置在凹模上;3、压边圈下行,将坯料压紧;4、凸模下行,对坯料施加载荷的同时对凹模型腔内的液体形成挤压作用,在密封型腔内压力达到溢流压力时,排出液压油,直到成形结束。本论文介绍了采用Dynaform5.1 对矩形盒形件充液拉深成形进行模拟的过程。重点对型腔内的充液压力的变化路径和压边力的加载方式这两个因素进行了研究。通过研究发现:型腔内液体压力的合理加载是该工艺的一个重要因素;充液压力的加载路径与凸模行程密切相关,合理地控制充液压力的加载是充液拉深成形获得最佳效果的关键。压边力是另一重要因素,在充液拉深工艺中,压边圈不仅被用来防止起皱和拉裂,而且用来密封凹模型腔内的液压油,另外,由于盒形件各部分的成形机理不同,分块控制各部分的压边力是本论文研究的另一个方面。另外,在吸收前人在液压成形方面的知识和借鉴国外先进结构的基础上,分析了充液拉深过程中,盒形件各部分所处的应力-应变状态;设计和制造了充液拉深的成形装置;引入监测系统,实现了对成形过程的实时监控。由于影响盒形件成形的因素较多,定量地研究这些因素对成形结果的影响是全面分析该工艺的关键。模具各个部分结构参数的变化对成形有显著的影响,所以在设计成形装置时,重点考虑了结构的稳定性和部分结构的快换性。本论文的研究对于后续的多参数试验设计和全面分析充液拉深过程奠定了基础。更多还原

【Abstract】 Hydromechanical deep drawing is one of the special deep drawing processes which have been introduced to achieve higher tearing factors compared with those of the conventional deep drawing which used rigid tools. In the hydromechanical deep drawing, the sheet metal is pressed against the punch by the hydrostatic medium. According to the Coulomb’s law of friction, the friction between the sheet metal and punch is increased by this. This makes greater depth possible. The elimination of the female die make the draw die set cost less than a conventional drawing die set does. The paper covers the finite element simulation (FEM) of the complete hydromechanical process for rectangular pieces with symmetrical geometry, performing process using the Dynaform-pc 5.1 of the explicit code LS-DYNA. The study focuses on two factors which are the path of hydraulic load and the path of binder force load. The rectangular pieces hydromechanical process starts with the precut sheet. First, the oil is pumped into the die; Then, the sheet is placed on the die; After that, the blank holder press down on the sheet; Finally, the punch is loaded on the sheet and the counter pressure is generated by penetration of the punch till the forming process finished. The study shows that a rational path of pressure load is a pivotal factor which can improve the forming condition in the process. The pressure load path and the motion path of punch are closely related. In order to get the best forming quality, the pressure load path must be controlled rationally. The blank holder is another vital factor. Not only the blank holder is used to prevent the wrinkling and cracking of the pieces, but also to seal the oil in the die so that higher pressure can be present. In the process of the rectangular box forming, the forming in different parts of the box is in different states of stress and strain. So the control of binder force according to different states is another key point in this study. On the basis of adoption of the knowledge of the hydroforming process and new devices invented recently abroad, the forming states of stress and strain in different parts of the box are analyzed in this study, and the forming device for the experiment is designed and manufactured, and the detector device is used to monitor the forming process. Also, there are many parameters that affect the process. In order to study the whole fact in this process, it is necessary to analyze every factor quantificationally. The tool parameters influence the forming process. So the economically changeable tool is considered in the design process. The study lays an important foundation for the succeeding multi-parameter experiment design and the study of the hydroforming process.更多还原