省力液压成形的原理与途径

Theory and Method of Less-loading Hydroforming

为了适应现代工业对高质量、轻量化以及低成本零件的要求,作为金属成形中重要工艺方法的液压成形获得快速的发展。由于该方法利用液体作为传力介质或模具,因此可以通过对液体介质的实时控制,来实现对工艺参数的精确控制,并且,液体作为传力介质亦可节省成形所需模具。然而,采用液压成形往往需要大吨位的设备,限制了该成形方法的应用。证明对于液压成形所需设备合模载荷等于液体压力乘以在其作用方向的投影面积,它与冲头的形状无关。液压成形中实现省力的途径主要有三种;一是减少投影面积,二是降低材料的流动应力,三是采用合适的预制坯。针对于无模胀球、护环液压胀形及管材内高压成形,介绍省力成形的原理及液压成形用省力柱方法和'以推代胀'等方法的具体省力措施。

In order to obtain the demands of parts with high quality, lightweight and less cost, hydroforming, as an important metal forming process, is developed fast. Because the liquid is used as the pressure transfer medium, the process parameters can be controlled precisely by online real-time controlling the liquid. And also, the need of forming dies can be reduced. However, It restricts the use of hydroforming process that the heavy hydroforming press is required. It is proven that the forming load for hydroforming equals the liquid pressure times projection area along the pressure action direction, and it is irrelevant with punch shape. There are three ways of less-loading hydroforming： Decreasing the projection area, decreasing the material flow stress and adopting appropriate preform. It is also indicated the concrete less-loading method for dieless hydro-bulging spherical vessels, for hydro-bulging protective ring and internal high pressure forming. Some practical application of less loading hydroforming is given too.