Kübler Equation

🧮 在线计算器：Bolt Pre-selection Calculator — Fast sizing with the Kübler equation; supports a design mode and a check mode. The reduction factor $\kappa$ explained: the “invisible tax” of tightening a bolt 📎 Prerequisite reading: this article is a deeper supplement to Bolt Pre-selection (001) — From Load to Size , focusing on the physical nature and derivation of the $\kappa$ parameter in the denominator of the Kübler equation. In the design and installation of a bolted joint, the reduction factor $\kappa$ (Reduktionsfaktor) is a very central parameter. It answers a key question: while the bolt is being tightened, how much strength is still “available” for axial load carrying? Below we break down its definition, derivation and formula, based on the public technical standard VDI 2230. ...

🧮 在线计算器：Bolt Pre-selection Calculator — Fast sizing with the Kübler equation; supports a design mode and a check mode. Preliminary sizing of a bolted joint: from load to size, fast Before getting into complex system-level bolted-joint calculations, the first challenge an engineer faces is often: “for a given working load, how large should the bolt be? Is M8 enough, or M12?” A sound preliminary design / pre-selection (German: Vorauslegung) quickly fixes a suitable nominal diameter and does an early “sweep” for common failure modes (such as fatigue fracture, or loss of preload from crushing of the bearing surface). This article shows how to do a quick pre-selection from the working load, and how to check the feasibility of the design with simplified formulas. ...