Science Buddies: "Ask an Expert"

I am interested in the project on fractography listed at https://www.sciencebuddies.org/mentorin ... ?from=Home
and tried finding some information on St. Venant's principle but don't see how it applies to how brittle materials break. Can you reommend some resources or give me a basic explanation?

Thank you!

Hi esnoke!

A resource is section 3.3 of http://me.queensu.ca/courses/mech422/Notes422.pdf (and you might want to read the intro paragraphs).

Please let us know if you have any questions.

Thanks.

hi!

I hope this sites are helpful:

1.http://personalpages.umist.ac.uk/staff/ ... d/Ch05.pdf (look up St. Venant's)

2.http://mechatools.com/MTSTUDIO/definition.htm (look up saint-venant)

3.http://silver.neep.wisc.edu/~lakes/CossStV.pdf (look in the beginning might be more in the middle and end)

I think I get the basic idea of St. V now - now I'm trying to figure out how it applies to failure or the breaking of brittle materials - specifically in this project. I will be dropping a weight on ceramic, glass and plastic tiles and looking at the resulting pattern of fractures, number of pieces etc. Is the following explanation right?

According to St. V's principle it doesn't matter how the tile is broken (for example, dropping a ball on it or using a hammer) because the differences in the breakage will be localized to near the point of contact as long as the force used to break the tile is the same. This is because outside this area of contact the material (tile) will experience the same internal stresses (which cause it to break).

Also, any other suggestions on relevant terms to look up are welcome. I found this page (http://www.sv.vt.edu/classes/MSE2094_No ... lahan.html) that describes the different types of breaks but most of what I've found seems to apply mostly to bolts and that sort of thing rather than flat surfaces like the tiles.

I am also wondering if I should look more at the fractal nature of the cracks but that may be outside the range of this project.

Thank you for your help!

Hi esnoke!

Thanks for your post.

A few notes:

Help is needed in notes 1 and 2, and note 3 is a comment.

1. I can't verify if you have the explanation of St. V's principle correct. Maybe someone else can help.

2. I also do not have any suggestions on other search terms. Again, maybe someone else can help.

3. Your reference to http://www.sv.vt.edu/classes/MSE2094_No ... lahan.html quickly led to a class photo and some older students. Is the project you have in mind oriented towards older students? At least to this observer, the material in, for example, http://www.sv.vt.edu/classes/MSE2094_No ... lahan.html is fairly complex, and would be best understood by senior high school/college students.