 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 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 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 would check those two criteria and it's it's basically that simple as long as you're less than those those strengths then then we'd be predicting that it's safe. If not then we'd predict failure. Thanks.