This paper presents a failure analysis of connecting bolts used for holding streetlights inside the tunnels of a mountain highway. The fracture occurred in correspondence to crevices formed in bolted joints. Fractographic and metallurgical studies indicate that the bolt failure is due to a deep crevice corrosion process that is further aggravated by the presence of chlorides coming from the spray formed inside tunnels during the winter when sodium chloride is spread for de-icing roads. Metallographic studies highlighted also that corrosion affects only bolts, while all the other joints’ components are intact. EDS analyses revealed that the bolt material was a Cu-bearing stainless steel that, in chloride media, has a bad corrosion resistance because Cu destabilises the alloy passive film. Therefore, it is recommended that the bolt material should be changed to prevent similar failures and that in such environment crevices should be avoided in design.

Failure analysis of connecting bolts used for anchoring streetlights of a mountain highway / Pilone, Daniela; Brotzu, Andrea; Felli, Ferdinando. - In: ENGINEERING FAILURE ANALYSIS. - ISSN 1350-6307. - ELETTRONICO. - 48:(2015), pp. 137-143. [10.1016/j.engfailanal.2014.11.006]

Failure analysis of connecting bolts used for anchoring streetlights of a mountain highway

PILONE, Daniela;BROTZU, Andrea;FELLI, Ferdinando
2015

Abstract

This paper presents a failure analysis of connecting bolts used for holding streetlights inside the tunnels of a mountain highway. The fracture occurred in correspondence to crevices formed in bolted joints. Fractographic and metallurgical studies indicate that the bolt failure is due to a deep crevice corrosion process that is further aggravated by the presence of chlorides coming from the spray formed inside tunnels during the winter when sodium chloride is spread for de-icing roads. Metallographic studies highlighted also that corrosion affects only bolts, while all the other joints’ components are intact. EDS analyses revealed that the bolt material was a Cu-bearing stainless steel that, in chloride media, has a bad corrosion resistance because Cu destabilises the alloy passive film. Therefore, it is recommended that the bolt material should be changed to prevent similar failures and that in such environment crevices should be avoided in design.
2015
bolt failure; chloride media; corrosion; stainless steel
01 Pubblicazione su rivista::01a Articolo in rivista
Failure analysis of connecting bolts used for anchoring streetlights of a mountain highway / Pilone, Daniela; Brotzu, Andrea; Felli, Ferdinando. - In: ENGINEERING FAILURE ANALYSIS. - ISSN 1350-6307. - ELETTRONICO. - 48:(2015), pp. 137-143. [10.1016/j.engfailanal.2014.11.006]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11573/759698
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