Right, let's pick this up where we left off — Page 1, Lesson 12

Right, let's pick this up where we left off. We've just dealt with the elastic limit — the point beyond which a material won't return to its original dimension once the deforming load is removed. Now, the key consequence: if any load takes the structure beyond that elastic limit, the deformation becomes permanent. That permanent change is what we call plastic deformation. So remember the contrast: within the elastic limit, the material springs back; beyond it, it's permanently bent or stretched, and that's plastic deformation. Now let's move on to how we actually classify these loads in service. We split them into two broad families: dynamic loads and static loads. Dynamic loads are the ones that tend to build up quickly, and they're driven by changes in flight conditions. Think about what happens when an aircraft is manoeuvred — a pull-up, a turn, a sudden control input. Those manoeuvres produce dynamic loads. And here's the important part: they may induce additional loads on other parts of the aircraft, not just the part you're directly loading. They can often be quite severe, which is why they get so much attention in structural design. On the other side, we have static loads. These are generally constant and build slowly. The classic example is an aircraft sitting on the ground. It experiences static loads. The weight of the aircraft acts downwards, and that produces an opposing force coming up from the landing gear. That upward reaction has to be carried by the wing structure. So the wing isn't just carrying lift in flight — on the ground it's carrying the aircraft's weight against the landing gear reaction. So the takeaway: dynamic loads are quick, severe, and can spread to other parts of the structure; static loads are steady, slow-building, and you see them in the parked aircraft on the ramp.