The SPR process can be described in four steps, as shown in Figure 1 : (1) the blank holder
clamps the sheets against the die; (2) a semi-tubular rivet is driven into the first sheet; (3) a mechanical interlock is formed, where part of the bottom plate flows into the die cavity and the rivet shank begins to flare outward; (4) the punch and blank-holder are released and the joint is created.
In Figure 2, the blank holder
and die are heated, and the punch is cooled by cyclic cold water.
In this process, many parameters such as friction, drawing ratio, quality and type of die and sheet, blank holder
force, drawing speed, mandrel head radius, and matrix edge is involved.
The first one is based on controlling the blank holder
In , the sheet forming simulation of rectangular box was conducted and the method of determining VBHF (variable blank holder
force) were proposed based on the displacement in the Z direction of blank holder
The u-bending or in some cases name as deep drawing (depth larger than width) process requires at least a blank, blank holder
, punch, and die as shown in Figure 4.
force optimization of hemispherical product using numerical simulation.
This pressurized fluid is directed to the peripheral surface of the blank through the bypass holes and also this high pressure fluid leak out between the blank and both the blank holder
For the direct analysis method that was employed, it was necessary to model the die, the punch and the blank holder
and to introduce the contacts and frictions between the active elements and the blank.
Techniques must be developed to properly design the blank holder
to avoid the leakage.
The blank holder
can be improved substantially by equipping the knuckle-joint press with a servo-acting draw cushion.