The Experts: The making or breaking of bolted joints

What is Hooke’s Law and why is it crucial to bolted joints?

Hooke’s Law relates to the accurate tightening of bolted joints.

When examining a bolt’s behaviour, the axial force is plotted against the extension. During tightening, these two properties increase simultaneously.

Hooke’s Law states that, up to its yield point, the bolt acts elastically, meaning that the extension is directly proportional to the axial force. This relationship is essential for safely securing bolted joints.

Within this range, the bolt will return to its original length upon disassembly. This predictable behaviour is essential to the bolt’s integrity. However, if the safe working range (the elastic limit) is exceeded, permanent deformation will occur, eventually leading to bolt failure.

The law was discovered by the 17th century physicist Robert Hooke. It assures the reliable operation of many components, including springs, beams and bearings – not just bolts. In fact, its applicability to all elastic materials makes it an essential part of the design of numerous engineering applications.