Failure Analysis of High Strength Galvanized Bolts Used in Steel Towers

• Main Authors: Jose Alberto Álvarez, Roberto Lacalle, Borja Arroyo, Sergio Cicero, Federico Gutiérrez-Solana
• Format: Article
• Language: English
• Published: MDPI AG 2016-07-01
• Series: Metals
• Subjects: bolt; crack; hydrogen induced cracking; FAD
• Online Access: http://www.mdpi.com/2075-4701/6/7/163

This paper analyses the failure of three bolts used in the structural connections of a number of steel towers located in northern Europe. The analysis comprises optical and scanning electron microscopy, microstructural and hardness analysis, mechanical testing and structural integrity assessments. The three bolts present very similar failure processes, with a circumferential external crack that led to the final failure. The morphology of the crack propagation is typical of Hydrogen-Induced Stress Corrosion Cracking (HISCC), with mixed intergranular-transgranular micromechanisms, tearing processes and secondary cracking. The cracks then grew subcritically until they reached their critical size. Quench cracking or fatigue processes have been ruled out.