Abstract
The use of high strength steel allows the design of lighter, more slender and simpler structures due to high strength and favorable ductility. Nevertheless, the increase of yield strength does not guarantee the corresponding improvement of fatigue resistance, which becomes a major concern for engineering structure design, especially for the welded joints. The paper presents a comparison of the low cycle fatigue behaviors between 10CrNi3MoV high strength steel and its undermatched weldments. Uniaxial tension tests, Push-pull, strain-controlled fatigue tests were conducted on base metal and weldments in the strain range of 0.2–1.2%. The monotonic and cyclic stress-strain curves, stress-life, strain-life and energy-life in terms of these materials were analyzed for fatigue assessment of materials discrepancy. The stress-life results of base metal and undermatched weld metal exhibit cyclic softening behaviors. Furthermore, the shapes of 10CrNi3MoV steel hysteresis loops show a satisfactory Masing-type behavior, while the weld metal shows a non-Masing type behavior. Strain, plastic and total strain energy density amplitudes against the number of reversals to failure results demonstrate that the undermatched weld metal presents a higher resistance to fatigue crack initiation than 10CrNi3MoV high strength steel. Finally, fatigue fracture surfaces of specimens were compared by scanning electron microscopy to identify the differences of crack initiation and the propagation between them.
Highlights
Modern steel manufacturing techniques make it easier to produce high strength steel for various fields of engineering structure applications, such as shipbuilding, marine structures, engineering machinery, bridges, and so on [1,2]
The results found that the high strength steel had superior resistance of fatigue crack initiation, while the crack propagation rates increased with the increases of yield strength
Due tocomputed the discrepancy the chemical composition microstructures the base metal density is by theofsum of the plastic and the and tension elastic strainbetween energy densities of the and undermatched weld metal, loop, it is necessary to confirmEquation the fracture half-life stress-strain hysteresis from the following
Summary
Modern steel manufacturing techniques make it easier to produce high strength steel for various fields of engineering structure applications, such as shipbuilding, marine structures, engineering machinery, bridges, and so on [1,2]. The studies from Westerbaan et al [23] and Xu et al [24] showed that High Strength Low Alloy (HSLA) steel laser welds had lower fatigue resistance than base metal under load-controlled at high stress amplitudes. Sowards et al [25] conducted low cycle fatigue experiments for butt welds of HSLA It revealed that weld fatigue susceptibility was higher than base metal at higher strain amplitudes, weld cyclic strength was greater than that of base metal resulting in lower plastic strains. The paper aims to study the effect of yield strengths of base metal and weld metal on the LCF properties based on the energy method It mainly provides experimental assessment of the LCF behaviors of 10CrNi3MoV high strength steel and corresponding undermatched weldments. The fatigue fractographic of these materials were examined to understand the failure phenomena by scanning electron microscopy (SEM)
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