Influence of hot dip galvanizing on fatigue behavior of welded steel joints

Thumbnail Image

Files

master_Behnam_Farah_2019.pdf (3.56 MB)

URL

Journal Title

Journal ISSN

Volume Title

Insinööritieteiden korkeakoulu | Master's thesis
Unless otherwise stated, all rights belong to the author. You may download, display and print this publication for Your own personal use. Commercial use is prohibited.

Authors

Date

2019-12-16

Department

Major/Subject

Mcode

Degree programme

Master's Programme in Mechanical Engineering (MEC)

Language

en

Pages

53

Series

Abstract

This thesis investigates the effect of hot dip galvanizing (HDG) on fatigue strength of fillet welded S355 structural steels. HDG is a surface treatment that allows protecting components from corrosion, but its effect on the fatigue strength of the welded joint is not well understood. In this thesis, a comparative study has been carried out between hot dip galvanized fillet welded cruciform joints made by S355 and non-galvanized welded joints characterized by the same geometry. Microstructures and the fracture surface of fatigue test specimens have been studied macroscopically and microscopically. The effect of galvanizing on microstructure, penetration of zinc to steel and its effects on initiation of crack has been investigated. Based on conducted fatigue tests, reduction of fatigue strength of galvanized samples comparing to bare metal is not considerable in low cycle fatigue regime. Using scanning electron microscopy (SEM), microstructure investigation has both revealed micro cracks on coating and also the notches located close to the welding toe. A few deep cracks were observed close to the weld notches. In high cycle fatigue regime, these cracks have the ability to propagate and lead to reduction of fatigue limit. Debonding and delamination between coating and substrate, which are potential sites for stress concentration and crack initiation, were observed. Based on this study, it has been concluded that HDG can reduce fatigue limit in high cycle load. Further investigation is needed in this subject .

Description

Supervisor

Remes, Heikki

Thesis advisor

Nafar Dastgerdi, Jairan
Hosseiniun, Mir Mostafa

Keywords

hot-dip galvanizing, fatigue strength, crack initiation, debonding, delamination, SEM

Other note

Citation

Permanent link to this item

https://urn.fi/URN:NBN:fi:aalto-201912226719

Collections

[dipl] Insinööritieteiden korkeakoulu / ENG