Home Forums General Discussion Media, Shot, Beads, etc. AMS 2431/4C - Shape

Sections 3.7.2 3 & 4 all refer to Table 2 - Shape Requirements. I would like some clarification on what is required. AWS17 has a nominal size of 0.43mm +/-0.025 (0.405/0.455mm) the table indicates an area of field of 1.588mm2 is to be used allowing a maximum of 2 of unacceptable particles.

Am I reading this correctly as this would mean that if the wire was at the top end of the spec you could only fit 9 pieces into that area?

Also does the 'Number of Fields Viewed' mean that I take 11 samples of this size to conduct the tests of which on 2 can be unacceptable?

Thanks for your help

The area of field for AWS 17 is 0.0625 inch or 40mm. Although it's not real clear this actually means 40x40mm. At the high end of the sizes you could theoretically fit 9x9 particles or 81 pieces in each field.
Since 11 fields are required you would prepare 11 sample cards with cut-out of 40x40mm and count the number of marginal particles and unacceptable particles. You could have as many as 2 unacceptable particles (total) from all 11 fields.

The nominal size of AWS 17 is 0.43mm which means you could get 93x93 pieces into a 40mm x 40mm area

You would normally expect more than 93 x 93 pieces in a 40mm x 40mm square. That is because you assume "square-packing" - which is the exception rather than the rule. "Close-packing" gives more pieces than "square-packing" for a given area.

If using a recess apposed to tape, dose the sampling area have to be square or can is be say circular? Obviously the area contained with in the shape would be the same.

I must disagree with Jack's interpretation of Table 2 of SAE AMS 2431/4C. The area of field is clearly stated to be in units of a square inch - with the equivalent of 1 square inch being given, correctly, as 645 square millimeters. For AWS 17 the required field of view is 0.0625 of a square inch - which corresponds to 40 square millimeters. 40 square millimeters is the area of a square that has sides of 6.32 mm. Using "square packing", spheres with a diameter of 0.43 mm could be arranged 15 by 15 giving a total of 225 spheres in each of the 11 field areas to be viewed.

For consistency, the field area tested should be square - a spherical field area of the same area as a square field area would accommodate a slightly different number of spheres.

Socrates is correct.

645mm sq = 25.4 X 25.4 mm
151mm sq = 12.7 X 12.7 mm
40 mm sq = 6.32 X 6.32 mm

I was president of math club in high school. Fortunately my math teacher is deceased.

Not all of the spheres will be the same size or shape, by using a square and the 'square packing' method surly that biased and unscientific.
By square pack when forming a single layer in a recess, only conforming media would fit to achieve the neat row formation.
Your basing the square packing idea on that all the media is already of the same diameter and shape.
Is not taking a percentage of fails in an area where alignment of particles is not forced fair, by expecting that a predetermined amount will fit neatly in the sample area you are not testing accurately but predetermining that all media in the sample are already conforming to the required size and shape.
I thought that the media was to be poured into the recess and excess removed, how can they be poor into rows again this is biased and not accurate or fair in my opinion.

Referring to table 2 of AMS2431/4c
It states that the area of a quarter of an inch squared is 161mm and that one sixteenth of an inch has an area in millimeters of 40mm. Both are wrong and contradicts table 2B of AMS2430 rev.S and the analysis procedure.

Inch mm Area mm
1 25.4 645.16
0.5 12.7 161.29
0.25 6.35 40.3225
0.0625 1.588 2.521744