【作者】 周六如；

【导师】 肖祥芷；

【作者基本信息】 华中科技大学 ， 材料加工工程， 2004， 博士

【摘要】 传统的板料零件通常通过模具的凸、凹模作用获得所需形状。因为制造模具的成本很高,这种制造方法仅仅适合于大批量生产。为了满足用户产品多样化的要求,需要开发适合于小批量产品生产的新工艺。在过去几年开发的多种方法中,应用简单工具的板料数控渐进成形工艺的研究受到极大的关注。板料数控渐进成形工艺不需要专用的模具,是一种柔性的成形工艺,它根据板料零件的成形要求设计数控程序,然后通过数控机床的进给系统,成形工具按照一定的轨迹逐步地成形板料,直到得到需要的零件。可以通过修改产品的数字模型来调节成形工具的成形运动轨迹,达到改变成形零件的形状的目的。因此,它的成形周期短,产品更新快。这种工艺非常适合于小批量、多品种和复杂的板料产品。本文研究了金属板料数控渐进成形工艺的成形机理。通过对成形机理的实验研究,掌握金属板料数控渐进成形的变形规律,并且详细地分析了变形过程中应力、应变以及变形力的情况,得出了求解公式。通过网格实验和金相组织分析等方法验证了数控渐进成形过程主要是剪切变形过程。实验表明,影响数控渐进成形过程的主要工艺参数有:工具头球半径 r、成形半锥角α、减薄率、进给量、芯模和工具头之间的间隙、工具头进给速度和摩擦等等。本文作者全面分析了各种工艺参数的影响,以及这些工艺参数的选择与优化组合,研究表明,这是保证数控渐进成形成功的重要条件。成形机理的研究为指导数控渐进成形工艺用于实际生产提供了有力的理论依据。由于金属板料数控渐进成形工艺的变形是剪切变形,故其板料变形区厚度 t 、板料初始厚度 t0及半锥角α等三者的关系符合正弦定律,即 t = t0 sinα 。根据正弦定律,α接近于零时,板料成形部分的厚度接近于零。因此,难以一次成形直壁件。为了成形直壁件,作者采用多次成形逐次逼近的方法,渐渐地由锥形件加工成直壁件,即,首先,工具头通过斜路径把板料成形为锥形件,然后,通过多次工具头的倾斜角路径,使锥形面逐次逼近直面,最终成形直壁件。 I<WP=5>这种渐进成形过程中通常会出现破裂、起皱和回弹等缺陷,严重影响成形零件的质量。作者针对各种缺陷产生的原因,采取了不同的处理措施,取得了较好的效果。根据上述研究成果,本文作者提出了一种板料数控渐进成形工艺方案,并做了一些覆盖件和直壁件的加工实验,得到了理想的结果。更多还原

【Abstract】 Conventionally, a sheet metal component is manufactured with dies and punches.However, the high cost of dies and punches limits the traditional manufacturing methodonly to mass production. Recently, customer’s demand in product diversification in thisfield calls for new manufacturing processes appropriate for small-lot production. Amongvarious kinds of processes developed over the past few years, the research of the NCincremental sheet forming process which utilizes a simple tool has been paid great attentionto. The NC incremental sheet metal forming process is a flexible forming process withoutdedicated forming dies, in which the NC program is designed according to the formingrequirement of sheet metal components. The sheet metal is formed step by step with aforming tool according to a certain trace prescribed by the feed system of the NC formingmachine until the required shape is obtained. The forming trace of the forming tool can beadjusted by correcting the numerical model of the product. Thus, its forming period is shortand products can be quickly renovated. This process is very suitable for small-lot, variedand complex sheet metal products. In this paper, the forming principle of the NC incremental sheet metal forming processis researched. The deformation law is obtained from the experiments performed on the NCincremental sheet metal forming machine. The stress, strain and deformation force in thedeformation process are analysed in detail and formulas are obtained. It is verified that theNC incremental sheet metal forming process is mainly a shear forming process by gridexperiment and metallurgical analysis. The key process parameters in the NC incremental sheet metal forming processconsist of sphere radius r of the tool head, forming half-apex angleα, ironing ratio, amountof feed, interval between the model and the forming tool, feed speed of the forming tool, III<WP=7>friction, and so on. In this paper, the effect of all the process parameters on the deformationprocess and how to choose suitable process parameters are researched, which is animportant condition of success in the NC incremental sheet metal forming process. Theresearch on the forming principle provides a powerful rationale for the practical production. Because of being shear forming process, the relationship between the thickness (t) ofthe deformed region, the thickness (t0) of the raw sheet, and the angleαbetween sheetmetal forming surface and vertical direction z conforms to the sine law, i.e.,t = t0 sinα .Thesine law indicates that the thickness of the deformed region is close to zero when thehalf-apex angle of the box is close to zero. Therefore, the vertical wall parts can’t beformed in a single process. To settle the problem, a method is given to form vertical wall parts, through which aconical part is gradually formed into vertical a wall part by multi-tool paths. The defects, such as fracture, wrinkle, springback, and so on, seriously affect thequality of formed parts. A good result has been achieved by taking a variety of measures toremove these defects. In this paper, a NC incremental sheet metal forming process is presented according tothe above-mentioned researches. The forming experiments of some panels and vertical wallparts have been made, and good results have been achieved.更多还原