Of the six typical failure modes of a bolted joint, only one is the bolt being pulled apart. This article starts from how a bolted joint works and gives a checklist: which joints need the systematic VDI 2230 calculation, which can do with simplified preselection, and what the standard covers and does not cover.
The upper half of the VDI 2230 calculation chain R1–R6 explained: the tightening factor αA, the three sources of the minimum clamping force FKerf, the choice of force-ratio Φ formula, preload loss (embedding + thermal expansion), and the derivation of the minimum and maximum assembly preload.
For a given working load, how large should the bolt be? This article covers the preliminary design and pre-selection of bolts: first read the nominal diameter and property class from a quick pre-selection table by load range, then use the Kübler equation to back out the thread stress cross-section from the axial working load and the required clamping force, combined with the tightening factor, reduction factor and simplified fatigue and bearing-pressure checks, to help engineers quickly size a bolt in the early design stage.