The breakage of a pulley shaft in a cable car could have been a catastrophe. Forensic analysis using 3D scanning revealed that the fracture was not a random accident, but the direct consequence of a previous faulty repair. The use of the Artec Space Spider and Ansys Mechanical allowed engineers to uncover how an alteration in the steel's microstructure created the exact point of fatigue failure.
Forensic workflow: from scanning to finite element simulation 🔍
The process began with digitizing the fractured surface using the Artec Space Spider scanner, capturing the geometry with submillimeter precision. This model was imported into GOM Inspect to align the parts and detect plastic deformations. Subsequently, the mesh was transferred to Ansys Mechanical, where the cable car's operational loads were applied. The finite element method (FEM) simulation revealed that, in the area of the poorly executed repair, the Von Mises equivalent stresses exceeded the base material's yield strength by 340%. Microstructural analysis confirmed that the heat applied during the repair had transformed the steel's pearlite into brittle martensite, generating a lethal stress concentrator.
Fatigue lessons: the microstructure does not forgive ⚙️
This case demonstrates that material fatigue depends not only on cyclic loading, but also on the component's thermomechanical history. A repair without temperature control or without proper subsequent heat treatment can nullify the fatigue resistance of any steel. 3D scanning and simulation not only identify the culprit, but also allow for establishing new non-destructive inspection protocols to prevent a poorly done repair from becoming a death sentence for the structure.
How can forensic 3D scanning differentiate between a natural material fatigue failure and one induced by defects in a previous repair on a cable car pulley shaft
(PS: Material fatigue is like yours after 10 hours of simulation.)