 In this problem we have this screw clamp, which is this structure that you can see here in the figure. We generate a combined bending tension stress at this section xx. Then we have to plot the resultant normal stress distribution at this section in terms of the clamping force F. This is the piece of material that we are holding and we can simplify this structure as this. We can substitute here the clamping force F. Then, as I said, we have to calculate what is the stress field distribution here at this section. As you can see, this force here first is creating stress due to tension, so this segment, which I will call AB, is in tension due to this force F, and at the same time this force F is creating here up in the moment, because it is a force applied at a certain distance L. Then we have to combine those stresses, the normal stress and the bending stress, in order to plot what is the total stress distribution at this point. We can start with the stress due to tension. You already know that the normal stress due to axial forces is equal to the force divided by the area. This is F divided by A. Then, if this is my cross-section here, this is why the stress distribution here is constant and it is positive because the whole section is in tension, so this is the magnitude F divided by A. Now, we can calculate the stress due to bending, which, using the flexural formula, the stress due to bending is equal to the moment times Y divided by the moment of inertia. We know that if this is the cross-section, this direction is Y. We have from the side that the stress distribution is something like this. It is zero at the neutral axis, since this is a double symmetric section, the neutral axis is at the center, so it is symmetrical. This upper part is in tension and this lower part is in compression, so this is tension as well and this is compression. You can see this or you can try to understand this from the formation shape of AB. We have that this is the shape of AB deformed, so you can see here that this part is in tension and that the lower part is compressed. Then, in order to plot the resultant normal stress, we have to combine these two stresses and we get the formula that we already know, that the total stress is equal to the force divided by A plus the moment times Y divided by the moment of inertia. Again, this is the cross-section, this direction is Y. We have to sum both contributions. Here the tensile stress is contributing in the same direction and here the compressive stress is being subtracted, so the final expression is this one. Of course, depending on these parameters, on the area of this cross-section, the moment of inertia, this distance, we could have here a distribution like this. We don't know if we have here some compression or not, but in this case we have decided to give this result that is also possible, so we have tension in both parts, but here the magnitude of the stress is larger.