Failure Analysis on a Broken Lifting Device

Broken suspension devices for concrete slabs, which originated from an accident at a construction site, were subjected to a damage analysis. Here, fractographic methods made it possible to demonstrate that the suspension devices presented brittle spontaneous fractures in the area of the welds. Hardness increases and cracks in the heat-affected zone were proved to exist by means of metallography. A check by calculation on the components has shown that inadmissibly high stresses arose during work at the construction site and were caused by an unfavorable way of construction. If the material condition had been intact excessive stresses would make themselves felt by plastic deformations which, however, resulted in a cleavage fracture in the present case because of the notch effect and the multi-axial stress conditions which were involved. The result of the examination was that the construction failed because of a welding defect. A wrong selection of the materials caused hardness increases, crack formations and associated brittle points in the heat-affected areas of the welded seams.