Vol.11, No3, 2011, pp.183–187
UDC 620.172.24: 669.15, 620.172.24:66-988-112.81, 621.791.05:539.4.013

DETERMINATION OF FATIGUE CRACK GROWTH PARAMETERS IN WELDED JOINT OF HSLA STEEL

Ljubica Milović 1, Tomaž Vuherer 2, Zoran Radaković 3, Blagoj Petrovski 3, Miodrag Janković 3, Milorad Zrilić 1, Darko Daničić4

1) University of Belgrade, Faculty of Technology and Metallurgy, Belgrade, Serbia, acibulj@tmf.bg.ac.rs

2) Welding Laboratory, University of Maribor, Faculty of Mechanical Engineering, Maribor, Slovenia

3) University of Belgrade, Faculty of Mechanical Engineering, Belgrade, Serbia

4) Kolubara Metal, Vreoci, Serbia

Abstract

The structural integrity and operational safety of welded pressure vessels primarily depends on the behaviour of weldments. In spite of all efforts in material production and improvements in welding techniques, including strict codes, requirements and directives, the crack occurrence in welded structures cannot be completely excluded. This is why fracture mechanics analysis is inevitable in the structural integrity assessment of all welded structures. Examples of practical application of fracture mechanics parameters in cracked pressure vessel structural integrity are considered. This paper shows the determination of parameters of the fatigue crack for constituents of welded joints produced of high strength low alloyed steel Nionikral-70 (yield strength 700 MPa). Results have shown that the position of notch and crack initiation affect the values of the stress intensity range of fatigue threshold ΔKth and parameters in the Paris’ equation.

Keywords: HSLA steel, crack growth rate, fatigue threshold, Paris’ law

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