Assessment of the cause of cracking of hydraulic hose clamps

The aim of this study was to determine the cause of failure of the shells of hydraulic hose crimped fittings. For the purpose of examination the damaged crimped shells, undamaged crimped shells and shells prior to crimping were used. Fractographic and metallographic analysis, including chemical microanalysis of inclusions, were performed to determine the cause of failure. For this investigation, optical and scanning electron microscopes and hardness measurement were used. Damaged crimped shells contained higher amount of inclusions compared to undamaged crimped shells and substantially differed in microstructure and hardness. Furthermore, different geometry of the cross section at outer edge containing more effective stress concentrators was observed on failed crimped shells. Based on microstructural observation in cross section, hardness measurements and analysis of inclusions, the conclusion is that cracking of the shells occurred mainly due to deviations in the manufacturing process, combined with lower quality of shell material. Modifications to the technology were suggested to prevent this kind of failure.