Abstract
The aim of this scientific work was to evaluate the compression instability effects during static and low-cycle fatigue loadings of AA 5083 welded joints, commonly used in marine structures. Low-cycle fatigue assessment in marine structures is of utmost importance since high levels of plastic deformation can arise in the proximity of high-stress concentration areas. Displacement ratios equal to minus one and zero were used to perform experimental low-cycle fatigue tests. The tests were monitored by means of the Digital Image Correlation technique in order to detect the strain patterns, with particular attention paid to stress concentration areas, indicating that a specimen tends to buckle during high compression loads, for tests with a displacement ratio of minus one. The tests at displacement ratios equal to −1 showed a lowering of the strain–life curve revealing a considerable effect on compression instability. A nonlinear finite element modelling procedure, depending only on hardness measurements, was developed. The hardness measurements were used in order to assess the distinct mechanical properties of the different zones that were included in the finite element model. The finite element model results were compared to the data achieved by means of the digital image correlation technique, demonstrating that hardness measurements can help predict the low-cycle fatigue behaviour of welded joints and consider compression instability phenomena.
Highlights
The finite element model results were compared to the data achieved by means of the digital image correlation technique, demonstrating that hardness measurements can help predict the low-cycle fatigue behaviour of welded joints and consider compression instability phenomena
Most marine structures involve tubular or plate details linked by welded joints with longitudinal and transverse elements that are exposed to severe weather conditions, such as storms, loading/unloading operations, and intense wave loads, which cause significant fatigue loads and cracks [1,2,3,4,5,6,7]
Local mechanical properties are assumed to vary from the base material (BM) to the heat-affected zone (HAZ) and the weld metal (WM) [8]
Summary
Most marine structures involve tubular or plate details linked by welded joints with longitudinal and transverse elements that are exposed to severe weather conditions, such as storms, loading/unloading operations, and intense wave loads, which cause significant fatigue loads and cracks [1,2,3,4,5,6,7] Adding these effects to the welding process, which produces variations in local mechanical properties, further complicates the problems. The notch strain approach [24] is mainly used for the low-cycle fatigue (LCF) assessment of welded details to contemplate the effect of elastic-plastic stress/strain on material behaviour. The aim of this study was to assess and comprehend the LCF behaviour of welded joints made of AA 5086, widely used in marine installations and constructions, considering the effects of high values of applied displacements during the compression phase and how these affect the LCF life. The author employed the DIC technique to different kinds of connections [32,33,34]
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