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#876 - 02/29/12 12:03 PM AMS2431/6 Glass Beads
AdamC
Unregistered


Hi,

I was just looking at AMS2431/6 and it says that the hardness of the glassbeads under this spec should be between HRC48-52. This is the same for for normal hardness steel shots under AMS2431/1. Did I interpret this incorrectly? I find it kind of puzzling: how can glass beads be of same hardness as steel shots? I would think that glassbeads definitely fractures much faster than steel shots.

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#878 - 02/29/12 02:56 PM Re: AMS2431/6 Glass Beads [Re: ]
Socrates Offline


Registered: 02/20/06
Posts: 108
There are two questions to answer.
Firstly: it is not surprising that glass beads have the same hardness as steel shot. Glass is a pseudo-ceramic material with strong molecular bonds. Diamond, the hardest of materials, is also a ceramic with even stronger bonds. Different types of glass have different hardnesses.
Secondly: steel is tougher than glass. As a rough guide, toughness is hardness multiplied by ductility. Glass has a much lower ductility than has steel. It therefore follows that steel is tougher than glass of the same hardness and is therefore much more resistant to fracture.

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#882 - 03/07/12 01:04 PM Re: AMS2431/6 Glass Beads [Re: ]
AdamC
Unregistered


Hi socrates,

Thanks for your input. Ductility is something new to me, i don't see any tests required under the ams specs for glassbeads, but it seems to be something that affects intensity quite a bit, is there anything in the spec that specifies anything for this? I ve tried using some glassbeads that s very brittle and there seems to be a limit to how high an intensity.(ie even when I increase the air pressure, there doesn't seem to increase the intensity by much). Do you think it s possible there are other factors which could have caused this?

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#883 - 03/07/12 02:52 PM Re: AMS2431/6 Glass Beads [Re: ]
Socrates Offline


Registered: 02/20/06
Posts: 108
Intensity is controlled by a combination of bead size and velocity. Glass is a brittle material when compared to steel. Hitting a glass ball with a hammer will fracture it but that wouldn't happen with a steel ball. Glass beads are useful for softer target materials such as aluminum alloys. Have you read article 1990149? This can be accessed from the Shotpeener.com library, enter "glass beads" in the Search box and this article is the fourth one down. The article provides an excellent background of knowledge.

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