Flow Through Defects
In addition to laps, there are other types of the defects that may appear during the forging of complex parts. Flow through defects occur when material is trapped in some cavity of the die while material is still flowing past this trapped material or it can happen because of chilling. The moving material pulls the trapped material away from the die surface into the interior of the part causing a defect that looks like a lap, but the process of formation is different; with flow through defects there is no collapse of the free surface.
The program has special facilities to detect defects that may appear just under the surface. For this purpose special under-surface flow lines are used. Normally these lines remain on the surface of the forging however if undersurface defects occur, clearly visible loops are pulled into the forging that identify these flow-through defects.
Cross section of forging with a flow through defect
Another example of a flow through defect and how it is indicated in QForm by under surface lines
The following example shows a hammer forging of a hook.
The simulation does not show laps and the die is completely filled (Fig. 1).
However looking more thoroughly at how the die is filled
we can see some peculiarities that may cause a defect in fig.2.
In Fig. 3 we see some of the under-surface lines deviate from the surface making loops in the completed forging.
To make the picture more distinctive these lines can be displayed layer-by-layer as in Fig. 4.
Here the defect formation can be clearly seen.