stress in frame when we put force under the headtube (where fork goes). I used simplification in this simulation because I assumed that seat tube(vertical tube) is rigid. We can see that maximum stress in on welding under the headtube. Frame is made of Aluminium 6061-T6 and force is 500 Newtons (around 50 kilos) going up. Displacement is of course magnificated to show distortion of the frame:)