圆筒形件充液拉深皱曲和破裂极限的研究

从充液拉深时零件变形的应力应变状态出发,根据普通拉深成形起皱和破裂的控制和预测,导出了圆筒形件充液拉深防皱曲和防破裂压边力的极限判据,作为其皱曲与破裂极限的预报及控制.同时还给出了圆筒形件充液拉深成形安全区域图,由此可以确定圆筒形件充液拉深成形的极限拉深系数和最小拉深系数,适用于无凸缘圆筒形件拉深、带凸缘圆筒形件拉深和刚性凸模的胀形.另外分析了在4组压边力的条件下液压力对零件成形的影响,为工艺参数确定、模具设计和设备选择提供依据.     

拉深件破裂起因探讨

针对筒形拉深件破裂实例,分析了制件在拉深过程中出现破裂缺陷的原因,从而找到解决和防止各类拉深件破裂的措施,对拉深加工生产,起到了借鉴和指导作用.     

轴对称零件拉深成形中失稳破裂及其承载能力的分析

分析了圆锥形零件拉深过程中 ,毛坯靠模时破裂失稳处的变形特点和受力情况。在拉伸失稳理论的基础上 ,推导出了圆锥形零件拉深成形时的极限承载能力 ,即破裂极限载荷的计算公式 ,并用实验对理论计算公式进行了分析验证。     

一种板料拉深性能的快捷解析预测方法

破裂是板料拉深成形的典型缺陷,板料在变形过程中,可以根据其厚度变化预测破裂,即厚度减薄到一定程度时即视为其破裂.本文以筒形件为例,基于Hill48屈服准则,推导出板料拉深变形的厚度计算公式,进而得出拉深后的最小厚度.比较了解析解与Dynaform数值模拟结果.算例表明:解析方法在预测板料拉深性能时有一定的应用价值.     

拉深筋对板料拉深成形的影响

分析了拉深筋对板料拉深成形的影响机理和作用,提出拉深筋的基本设置原则,阐述设计其几何参数时应考虑的因素。结合汽车挡泥板的成形过程,利用有限元软件Dynaform分别模拟了无拉深筋、有整体拉深筋和局部拉深筋时挡泥板的成形过程。模拟结果证明,合理的拉深筋参数和布局能够有效地解决成形件的起皱和破裂问题,提高板料拉深成形质量。     

AZ31镁合金板材室温拉深破裂行为

为了探索提高AZ31镁合金板材室温冲压性能的途径,通过断口形貌分析,对板材室温拉深变形过程中的破裂机理进行了研究.结果表明,室温下,对于普通轧制板材,在拉深比达到1.2后即在冲头肩部发生破裂;对于等径角轧制板材.其拉深比可达1.6以上;当拉深比达到1.8时,在杯形件凸缘发生破裂,断面光滑平整.为解理断裂.这主要与板材在拉深变形中的应力应变状态和其非基面织构有关.单向拉伸与断口分析表明其冲压性能和破裂行为的差异,主要是因为这两种板材织构不同所致.     

风扇体拉深破裂浅析

通过对风扇体拉深破裂进行简单的机理分析，着重分析研究影响拉深破裂的因素，提出了纠正的预防拉深破裂的措施。     

拉深筋阻力模型在模拟分析中的应用与比较

将<拉深筋约束力模型及试验研究>文中建立的拉深筋阻力模型作为等效拉深筋使用,模拟分析了表盘座某部件的成形.分析结果表明,在分析起皱、破裂等成形问题时,文中建立的拉深筋阻力模型比使用模拟软件Dynaform自带等效拉深筋更接近使用真实拉深筋模拟的结果.     

方形盒制件圆角处拉深破裂的数值模拟

金属薄板成形的数值模拟技术在冲压件生产和模具设计中起着重要的作用。文章借助Dynaform软件对某方形盒制件拉深破裂现象进行数值模拟,分析其产生原因和影响因素,并利用正交实验找出防止该制件圆角破裂的拉深条件组合。结果表明,在冲压速度、凸模圆角半径、摩擦系数和板料厚度4个因素中,凸模圆角半径对盒形件拉深破裂的影响最大。为降低因圆角处板料剧烈减薄而产生破裂的几率,盒形件拉深时应采用较大的凸模圆角半径。     

带凸缘拉深件拉深过程中的超高问题

<正> 本文提出了带凸缘的拉深件在拉深过程中存在瞬间超高现象(即工件总高超过该工序拉深结束时的高度),认为这是导致拉深时压扁筒壁或凸缘卷边的原因。文中分析了瞬间超高的原因,并推荐了相应的解决措施。 一、问题的提出 多工序拉深成形的带凸缘拉深件在拉深过程中常会出现筒壁失稳压扁或凸缘卷边的现象,见图1。前者将导致工件筒壁破裂,     

基于DYNAFORM仿真模拟的拉深工艺方案确定

在对某无凸缘圆筒拉深件进行拉深工艺分析时,以最大拉深高度确定的拉深次数为1次,而以拉深系数确定拉深次数时,发现需多次拉深才可完成,且在多次拉深过程中必须考虑材料硬化对拉深变形的影响。针对该问题,使用DYNAFORM软件分别对两种不同拉深方案进行仿真模拟,获得两种方案下拉深件的成形极限图。对比分析两种成形极限图并最终确定该拉深件的合理拉深方案。     

拉伸筋在盒形件拉伸成形中的应用

用盒形件拉伸成形工艺参数判断油底壳的拉伸成形时,油底壳需要2道拉伸工序成形,拉伸模具增加拉伸筋后,可使油底壳1道工序拉伸成形,并介绍了几种拉伸筋的结构、形状及布置注意事项。     

薄壁铜管固定芯头拉拔和游动芯头拉拔的对比分析

为提高薄壁铜管拉拔后的成形质量,探讨不同拉拔工艺对薄壁铜管成形性能的影响,利用有限元软件MARC分别对两种拉拔成形工艺建立有限元模型,对比分析薄壁铜管固定芯头拉拔和游动芯头拉拔对拉拔力、铜管拉拔后等效应力、应变和残余应力的影响。结果表明:在相同工艺参数下,与固定芯头拉拔相比,游动芯头拉拔所需拉拔力明显更小,等效应力也相对更小,等效应变相等,残余应力在轴向和周向更小,且分布更均匀,在径向都趋近于0。在不考虑其他因素下,游动芯头拉拔更有助于提高薄壁铜管的产品质量。     

管材拉拔模具定径区摩擦力的研究

比较精确地确定管材在拉拔时的拉拔力,对于制定合理的拉拔工艺,充分发挥拉拔机的能力,保证拉拔机在拉拔过程中安全可靠地运行均具有重要意义。研究了在空拉、固定芯头拉拔和游动芯头拉拔三种状况下拉拔模具定径区摩擦力对拉拔力的影响,并推导出合理的拉拔力计算公式。     

Wear behaviors and lubrication medium of TiC/Al2O3 ceramic wire drawing dies

The suitable test equipment for wire-drawing was designed. Wire-drawing tests were carried on with this equipment for TiC/Al2O3 ceramic wire-drawing die. Effect of lubrication medium and drawing velocity on the drawing force was investigated. The wear mechanisms of the ceramic drawing dies were investigated. Worn bore surfaces of the ceramic drawing dies were examined by scanning electron microscopy. The results show that lubricant media have great influence on the drawing force. The drawing force is the smallest when a grease lubricant is used. But alteration of drawing velocity has scarcely any influence on the drawing force. Detailed observations and analyses of the die wear surface reveal that the most common failure of the ceramic drawing die is the wear in the invariable zone and bearing zone owing to the greater press stresses. Abrasive and adhesive wear are found to be the predominant wear mechanisms for ceramic drawing die.     

保证汽车覆盖件具有优良拉深工艺的方法

汽车覆盖件的工艺性关键是拉深工艺性,车身表面质量的好坏也取决于覆盖件拉深的结果,必须认真分析覆盖件的拉深工艺。采用案例分析法,从汽车覆盖件材料的合理选用、冲压工序的合理安排、拉深冲压方向和压料面的正确确定、反拉深成形的合理安排、拉深工艺补充部分、工艺冲孔或切口的合理确定以及拉深筋的合理设置7个方面,对汽车覆盖件的拉深工艺进行了分析。通过这些工艺的合理安排与确定,可有效地抑制汽车覆盖件拉深过程中起皱和裂纹的产生,提高拉深稳定性,保证汽车覆盖件具有良好的拉深工艺。     

翼子板成形工艺分析与数值模拟

根据覆盖件拉深成形工艺补充面、压料面和拉深筋的设计原则和方法,设计出翼子板拉深件,并运用有限元软件Dynaform对拉深成形过程进行分析,然后根据影响拉深成形的因素及模拟结果对拉深型面进行修改、优化,从而得出合理的拉深型面,用于模具加工制造,最终得到合格产品。     

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.     

基于能耗计算的PCD拉丝模压缩角优化设计

分析切割钢丝拉拔过程中压缩变形功、摩擦阻力功及在变径区由于速度突变而消耗的多余变形功,分别推导其相应的功率损耗数学公式,最后得出切割钢丝拉拔过程中总功率损耗表达式。以太阳能硅晶片切割钢丝用PCD拉丝模为例,计算出?0.12 mm切割钢丝用PCD拉丝模具的最佳压缩半角α=3.675°,及其最小平均拉拔力F=2.49 N。      

Simulation of ultrasonic-vibration drawing using the finite element method (FEM)

In ultrasonic-vibration drawing, wires are drawn while ultrasonic vibration is applied to a drawing die. Prior studies provide experimental proof that ultrasonic-vibration drawing reduces drawing resistance, improves lubrication and prevents wire breakage. In the future, ultrasonic-vibration drawing is expected to contribute to the drawing of difficult-to-draw materials and operations, such as shaped wires, ultrafine wires, and the wire drawing operation in semidry or dry condition. However, a detailed analysis and understanding of the mechanism of improvement is not possible on the basis of conventional experimental observations because the ultrasonic-vibration processing phenomenon occurs at high speed. Therefore, we attempted to understand the processing mechanism of ultrasonic-vibration drawing using the finite element method (FEM). ABAQUS was used for the FEM. Drawing force and stress–strain distributions in drawn wires were analyzed. From these studies, we quantitatively clarified the mechanism of improved drawing characteristics, such as decreased drawing force.