Procedure
Each sample was cleaned with acetone followed by methanol and drying. The sample was lubricated with oil in the region of punch contact. The sample was placed in the OSU formability tooling and clampled. The punch was then advanced at a rate of 1 mm/sec until failure occured.
For each test the measure of formability was the punch height at which the material sustained a maximum load was obtained from the recorded load versus displacement data. Three tests were performed on each of the 90 test conditions requested and the punch heights recorded for each were averaged.
Test Results
Table 1 summarizes the materials and perforation spacing tested. For each hole diameter, different hole spacing giving rise to different percent open areas which have been summarized.
Table 2 summarizes formability measurements for the 90 tests performed. The results are grouped by the pattern and size of holes, then ordered by material and gauge. The mode of failure (either single failure,.S, or multiple failure, M) and the places where failure was observed (near die, D, near punch, P, or center, C). A blank in these columns means that the failure was not uniquely located. The effect of each of the variables on how they affect formability has been considered and explained with the help of plots and charts in the following sections.
Effect of percent open area
The % open area was plotted against the punch height at maximum load. Charts 1-6 show this variation for each of the materials. Each plot contains a series of curves for various hole sizes and thickness, as noted in the legend of the plot. The hole size is given in mm and the thickness is given as the gauge number.
The results show that there is a drop in formability as the % open area increases. However for aluminum 3003, the trends were not very clear. The reason for this could be that the punch height at which these were failing was too small and the specimen failed in a very short time. Hence the scatter in the values is expected to be high and the test may not be sufficiently accurate to deduce a trend.
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