No surface is perfectly flat. Over time, microscopic peaks flatten out under pressure. VDI 2230 accounts for this "embedding" loss ( FZcap F sub cap Z
Focuses on Multi-Bolted Joints (MBJ). It provides guidelines on how to take complex, system-wide loads on a large flange or plate and break them down into the individual loads acting on each single bolt, which can then be calculated using Part 1. Conclusion vdi 2230 2021
: The 2021 version includes refined reference values for metric coarse and fine threads, as well as updated tightening torques for HV (high-strength) bolting and non-metal screws. No surface is perfectly flat