The Department of Materials Science and Engineering at Ohio State University using methods, tooling, and a testing machine of their design, generally referred to as the OSU Formability Test, were sponsored by the Industrial Perforators Association to evaluate the capacity of various types of perforated carbon steel, stainless steel and aluminum as to their formability. The tests, performed first on carbon steel and then on stainless steel and aluminum, are presented below under Part I and Part II respectively.
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 94 carbon steel and 90 stainless steel and aluminum samples. The average punch height was recorded as the test result.
The OSU testing machine shown here in three steps of the test.
Step 1
The 1" radius-punching tool withdrawn with the test sample above it.
Step 2
The test sample is clamped in position.
Step 3
The punching tool advanced at a rate of 1mm/sec until failure.
Carbon Steel
The goals of the study were to determine how cold rolled perforated steel reacts to drawing operations and develop the following relationships:
1. Effect of the open area on Formability.
2. Effect of the hole size on Formability.
3. Differences between commercial quality and drawing quality cold rolled steel in their Formability.
4. Differences in Formability according to the orientation of the work piece with respect to the punching tool, i.e., when applying drawing forces perpendicular to straight rows of holes or parallel to straight rows of holes.
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View charts 1 through 8 using the above links "next" or "back".
The Effect of Hole Size and Sheet Thickness
In Charts 1 through 4, it can be seen that increasing the hole size has very little effect in the 10 to 20 percent open area range. Looking at Chart 5, in the 30 to 40 percent range, increasing the hole size could slightly increase the formability for the same percent
open area. For a particular hole size and percent open area, the formability actually decreases slightly with increasing thickness. This can be seen in Chart 6.
The Effect of Draw Quality Versus Commercial Quality Steel
A comparison of the formability of draw quality versus commercial quality steel is shown in Chart 7. Generally, draw quality has higher formability. Chart 7 compares four thicknesses of steel with a perforated pattern with a hole size of .1875" and 17.01% open area.
The Effect of Orientation
The effect of orientation changes the formability by about 30%. A perforated pattern that has the straight row of holes parallel to the straight punch (B orientation) has less formability than having the straight row of holes perpendicular to the punch (A orientation).
Stainless Steel & Aluminum
The goals of this study were to measure the formability of perforated sheets of stainless steel and aluminum and develop the following relationships:
1. Effect of the open area on Formability
2. Effect of the thickness and hole size on Formability
3. Differences in the formability of materials-aluminum alloys 3003, 5052, and 6061 as well as stainless steel types 304L, 316L, and 409.
NOTE: Tests conducted on Stainless Steel and Aluminum were performed with the straight row of holes running parallel to the punch because it was determined to be the weaker of the two possible orientations during Part I of the study. Therefore, the results of this study are the worse case scenario.
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View charts 1 through 13 using the above links "next" or "back".
Effect of Thickness and Hole Size
The plots of average of punch heights (averaged over all choices of % open area) versus thickness are shown in Charts 7-12. Each of these has graphs for the two choices of hole size: 4.71 mm and 1.5 mm.
These charts do not show any consistent trend of formability with thickness. However, it can be seen that the formability of the sheets with 1.55 mm holes is consistently less than that of the specimens with 4.72 mm holes.
Material Comparison
The six materials were compared by taking an average formability of all the tests with that material. This average punch height has been compared by means of Chart 13.
It clearly shows that the perforated aluminum sheets have a lower formability than steel sheets. Aluminum, 3003 has the least formability, whereas Stainless Steel 304L has the highest formability.