Analysis of the failure mechanism of a gripping tool steel component operated in an industrial tube draw bench

摘要

Gripping assemblies are sophisticated machine elements, served as clamping mechanisms in draw benches, pulling the metallic rod or tube through a die. They manufactured from special alloy tool steel and subjected to high axial and repeated stresses due to successive loading and un-loading conditions. In-service failures of gripping tools, occurred in an industrial tube draw bench, led to increased maintenance costs and machine downtime, resulting in low productivity. Samples from fractured components and their connections, namely the arm, the expansion guide and the threaded rod, were brought from a metal working industry for a failure analysis investigation. Failure analysis findings suggest strongly that the failure occurred due to fatigue under high stress amplitude, initiated at the sharp corner of the arm jaw and followed by brittle quasi-cleavage overload fracture. Review of the service history (operating loads, lubrication, etc.), in combination to the examination of a potential improvement of the steel cleanliness and surface condition are mostly recommended as further fatigue failure preventive actions.