Whoever has ever wanted to size a screw must have met the term VDI, which is the association of German engineers (Verein Deutscher Ingenieure) and their guidelines for sizing bolted joints is the VDI2230. It is not just an enjoyable read, but it is worth taking the trouble and solving some sample exercises from it. We did it with the crank of an internal combustion engine, what’s more, in parallel we analysed it also using FE, because we were interested how simulation and analytical results correlate. In our experience, the simplified analytical method works well in the case of the complex geometry of a bolted screw as well. The load diagrams of the joint determined in analytical way and using FE technique as well as the changes in the graphs due to external loading were similar to each other. Our blog post about the joint diagram can be found here. Please note that in the fatigue of the bolting the stress amplitude, caused by the cyclic external load, is of vital importance. Although on the joint diagram the FEM and analytical results seem to be almost the same, the fatigue causing stress amplitude in simulation can differ with 100% from the result calculated on paper. We could decide which method provides more reliable estimation after series of experiments. The engineer’s intuition tells us that the simulation is the closest to the real practice.

The VDI 2230 Guideline