Hardness testing of Ceramic Fibre Shapes

[Brian Dowsett]

Folks.
Has anyone found a way to measure hardness of ceramic fibre shapes?. We buy crucibles for high temperature melting, which we would like to control for hardness. However, checking with a standard durometer gives a lot of measurement system variation and certainly would not meet normal gauge variation requirements. Obviously checking repeatability is difficult because each time the gauge is used in an area, it makes an indentation - meaning that the reading in that area cannot be repeated. However, meeting the requirements for doing the study is not my major concern- i'd just like a better way to measure product quality.

For info, the shape is cylindrical, about 3 inches in diameter.

Thanks

brian

 

[Jerry Eldred]

I will have to defer this one, as I am not an expert in this area. The only minor point I noted is that perhaps on a particular sample, you could take multiple readings, and for each reading, use an untouched surface area of the sample. Perhaps you could establish a minimum number of readings that would provide you with acceptable measurement variability. I do recall from my limited exposures to Rockwell Hardness standards, that they are not very stable. My recommendation would be to seek out some industry experts. It may be that you could refine measurement methodology, and add some metrology engineering to the measurement (i.e.: devise some details to how you perform the reading such as sample placement, penetration depth, variations on probe tip used and other such details - not being an expert on this, I won't make any specific recommendations). Is there a hardness standard available with a similar hardness rating that you could use to develop methodology.

Just a bit of rambling to try to add something. Apologies that I can not be of much use in this matter.

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