In case of materials which are difficult to draw in one step redrawing is performed. Generally during the first stage upto 40 reduction is achieved. Drawing ratios can help determine the maximum amount of deep drawing possible.
limiting drawing ratio formula
Necking crack and shear crack.
Limiting drawing ratio formula. One of the most commonly used procedures to determine drawability is the limiting draw ratio ldr test. The fracture modes of these four types of blanks are then compared and classified into two categories. The drawing ratio is a measure of the severity of the drawing operation and is the ratio of the initial blank diameter to the punch diameter. Due to the geometry forces metal flow and material properties of the work there is a limit to the amount of deep drawing that can be performed on a sheet metal blank in a single operation.
For a given material the limiting drawing ratio ldr is a measure of that materials deep drawability and is calculated from the largest blank that can be completely deep drawn for a given punch diameter. Component mainly depends upon the limiting drawing ratio ldr. Slide 11 of 20. Ldr is defined as the ratio of.
The higher the drawing ratio the more extreme the amount of deep drawing. Ldr is the ratio of the maximum blank diameter to the punch diam eter that can be drawn successfully without failure see figure 1. In the second redrawing stage 16 reduction is set. Been drawn to a certain draw ratio.
Integritypaper presents the theoretical determination of the limiting drawing ratio ldr in dependence on d 0 t 0 ratio and friction coefficient between blank and punchlimiting drawing ratio ldr converges to eulers number e for high test piece depth and final cup diameter ratio values. This paper first conducts limiting drawing ratio ldr experiments to identify the maximum blank diameter of spfc340 dp600 dp800 and dp1000 with onset crack. This can be done with the drawing ratio. Slide 11 of 20.
In the first redrawing after drawing maximum of 30 reduction can be set. In deed ldr is an essential design component to be familiarized by process engineers in minimization of forming steps for multistage deep drawing process in which the forming of finished component cannot be achieved in single stage deep drawing process. Limiting drawing ratioldr is the ratioofthe diameterofthe largestblankthat canbe successfully drawntothe diameterofthe punch.
