Fatigue crack propagation behaviour in thick steel weldments

Abstract

If you would like to write for this, or any other Emerald publication, then please use our Emerald for Authors service information about how to choose which publication to write for and submission guidelines are available for all. Please visit www.emeraldinsight.com/authors for more information. About Emerald www.emeraldinsight.comEmerald is a global publisher linking research and practice to the benefit of society. The company manages a portfolio of more than 290 journals and over 2,350 books and book series volumes, as well as providing an extensive range of online products and additional customer resources and services.Emerald is both COUNTER 4 and TRANSFER compliant. The organization is a partner of the Committee on Publication Ethics (COPE) and also works with Portico and the LOCKSS initiative for digital archive preservation. AbstractPurpose -The purpose of this paper is to study the fatigue crack growth (FCG) behaviour of the steel and weldments of a railway bridge. Design/methodology/approach -Tests were carried out on compact tension (CT) specimens using the thickness (B ¼ 32 mm) of a structural detail. The test matrix included three R values and three material conditions: base material (BM), heat affected zone (HAZ) and weld metal (WM). An evaluation of opening load behavior was carried out. The full field measurement of the residual stress perpendicular to the crack plane was performed using the contour technique. A simplified finite element analysis supported the interpretation of the results. Scanning electron microscopy (SEM) observation of the fracture surface of BM and HAZ specimens was carried out. Findings -Extensive crack closure effects were found in the welded specimens. Important through-the-thickness variation of residual stress was found using the contour technique. The residual stress fields of HAZ and WM specimens led to slowing down the FCG rate in the initial stages of crack propagation and to uncommon fracture surfaces. When the opening load effect was taken into consideration it was found that the da/dN vs DK of the different types of specimens are approximately identical. The ratio (striation spacing)/(da/dN) decreases up to approximately unity as a/W increases. In the specimens analyzed, FCG rates below approximately 2E-7 to 3E-7 m/cycle are associated with approximately constant striation spacing values, which could be considered a conservative upper bound of the real crack growth rate. Originality/value -Fatigue crack growth behavior of thick welded steel CT specimens was analyzed on the basis of tests including full field residual stress measurements, crack closure behavior and striation spacing, allowing for the simultaneous consideration of all those aspects. It is shown that the striations spacing provides no more than a conservative upper bond of the real crack propagation rate.

Fatigue crack propagation behavior in railway steels

“…No striation spacing vs da/dN correlation was found, as in other studies, e.g. Albuquerque et al (2012) and Roven and Nes (1991), since striation spacing was found to be approximately constant for values of da/dN between 10 2 5 and 10 2 4 mm/cycle. It was also observed a random behavior in the striation orientation, as sugested in Figure 14(b).…”

Microstructural and fatigue crack growth behavior inhomogeneity of trace Sc added 7085 alloy friction stir welded joint

“…Previous works have proved that the present of residual stress could reduce the FCG rate, especially at a low ΔK levels (near‐threshold regime) 39,40 . And its effect on FCG rates is most pronounced in thick plate 41,42 . Considering that the thickness of CT sample is only 4.5 mm, and the initial values of ΔK is higher than the threshold regime, the effect of residual stress on FCG behavior would not be a major factor in this work, relative to the microstructure.…”

An efficient methodology for fatigue damage assessment of bridge details using modal superposition of stress intensity factors

“…The Paris Law material constants, C and m, were determined by fatigue crack propagation tests conducted using compact tension (CT) specimens built on the same material used in the bridge and with similar thickness. Results were published in reference [38].…”