Duh! Hi everyone. In this video, I'm going to talk about the maximum normal stress theory. So the max normal stress theory, or MNST, is the first theory that we want to talk about, which is applicable to brittle materials. So the max normal stress theory is pretty simple. Again, if I draw my coordinate axes, which I have sigma 1 and sigma 2 axes, I can plot on these axes four intersecting points, which represent the ultimate tensile strength of my brittle material that I'm looking at. And the max normal stress theory basically says that if I draw a box crossing the axes at these points, I'm safe if I'm inside the box, failure if I'm outside the box, and mathematically what that means is that sigma 1 must be less than this ultimate strength, and sigma 2 must be less than this ultimate strength. Now, we can represent here max tensile, and we could also say max compression. A lot of times for this theory, those would be considered to be the same thing, but I could substitute in sigma sub-UC for compressive strength. Brittle materials sometimes are, or maybe even often, are a little bit stronger in compression, so I could draw that, and then my axes crossings here would be sigma UC, sigma UC, and sigma UT just for completeness. So, if I include that on here, then I just, you know, would check those two criteria, and it's basically that simple, as long as you're less than those strengths, then we'd be predicting that it's safe. If not, then we'd predict failure. Thanks.