Multivariate Analysis to Relate CTOD Values with Material Properties in Steel Welded Joints for the Offshore Wind Power Industry

[EN] The increasingly mechanical requirements of offshore structures have established the relevance of fracture mechanics-based quality control in welded joints. For this purpose, crack tip opening displacement (CTOD) at a given distance from the crack tip has been considered one of the most suited parameters for modeling and control of crack growth, and it is broadly used at the industrial level. We have modeled, through multivariate analysis techniques, the relationships among CTOD values and other material properties (such as hardness, chemical composition, toughness, and microstructural morphology) in high-thickness offshore steel welded joints. In order to create this model, hundreds of tests were done on 72 real samples, which were welded with a wide range of real industrial parameters. The obtained results were processed and evaluated with different multivariate techniques, and we established the significance of all the chosen explanatory variables and the good predictive capability of the CTOD tests within the limits of the experimental variation. By establishing the use of this model, significant savings can be achieved in the manufacturing of wind generators, as CTOD tests are more expensive and complex than the proposed alternatives. Additionally, this model allows for some technical conclusions.S

Material Behavior and Fatigue Assessment of Old Steel Bridges of the Spanish Conventional Rail Network

[EN] This work presented salient features of the steel behavior of seven metallic bridges close to, or over, 100 years old, among the Spanish conventional rail network as well as the results of a fatigue life expectancy study. A preliminary study of the properties of the constituent materials obtained from the bridges samples was carried out followed by dynamic fatigue tests under service representative loads. Due to the steelmaking techniques in the late 19th and early 20th centuries, disperse fatigue behavior results were obtained. However, the wide safety margins with which these bridges were designed, as well as the mechanical properties of the steel (relatively good mechanical resistance but with low ductility), seem to guarantee a long fatigue life. This estimate decreases sharply with increasing loads.S

Modelo matemático multivariante para estimar el valor CTOD en función de propiedades mecánicas, químicas y microestructurales aplicado a uniones soldadas para la industria Offshore = Multivariate analysis to relate CTOD values with material properties in steel welded joints for the Offshore industry

159 p.A través de técnicas de análisis multivariante, se ha modelado la relación entre el valor CTOD y otras propiedades del material (tales como dureza, composición química, tenacidad o morfología microestructural) aplicadas a uniones soldadas de acero de alta resistencia para estructuras en alta mar. Para crear este modelo, se realizaron cientos de pruebas en 72 muestras reales soldadas con una amplia gama de parámetros industriales reales. Los resultados obtenidos han sido procesados y evaluados con diferentes técnicas matemáticas, y se ha podido establecer la importancia de todas las variables explicativas elegidas y la buena capacidad predictiva del modelo dentro de los límites del conjunto experimental. Al establecer el uso de este modelo, se podrían lograr ahorros significativos en la fabricación de estas estructuras ya que las pruebas CTOD son más caras y complejas que las alternativas propuestas. Además, este modelo permite algunas conclusiones técnicas importantes para la industria fabricante de estructuras Offshore. = The increasingly mechanical requirements of the offshore structures have established the relevance of fracture mechanics-based quality control in welded joints. For this purpose, CrackTip Opening Displacement (CTOD) at a given distance from Crack-tip has been considered one of the most suited parameters for modelling and control of crack growth and is it broadly used at the industrial level. We have modelled through multivariate analysis techniques the relationship among CTOD values and other material properties (as hardness, chemical composition, toughness or microstructural morphology) in high-thickness offshore steel welded joints. In order to create this model, hundreds of tests were done in 72 real samples welded with a wide range of real industrial parameters. The results obtained have been processed and evaluated with different multivariate techniques, and we have established the significance of all the chosen explanatory variables and the good predictive capability of the CTOD value within the limits of the experimental set variation. By establishing the use of this model, significant savings are achieved in the manufacturing of wind generator as CTOD tests are more expensive and complex than the proposed alternatives. Besides, this model allows for some technical conclusions

Multivariate Analysis to Relate CTOD Values with Material Properties in Steel Welded Joints for the Offshore Wind Power Industry

The increasingly mechanical requirements of offshore structures have established the relevance of fracture mechanics-based quality control in welded joints. For this purpose, crack tip opening displacement (CTOD) at a given distance from the crack tip has been considered one of the most suited parameters for modeling and control of crack growth, and it is broadly used at the industrial level. We have modeled, through multivariate analysis techniques, the relationships among CTOD values and other material properties (such as hardness, chemical composition, toughness, and microstructural morphology) in high-thickness offshore steel welded joints. In order to create this model, hundreds of tests were done on 72 real samples, which were welded with a wide range of real industrial parameters. The obtained results were processed and evaluated with different multivariate techniques, and we established the significance of all the chosen explanatory variables and the good predictive capability of the CTOD tests within the limits of the experimental variation. By establishing the use of this model, significant savings can be achieved in the manufacturing of wind generators, as CTOD tests are more expensive and complex than the proposed alternatives. Additionally, this model allows for some technical conclusions

Material Behavior and Fatigue Assessment of Old Steel Bridges of the Spanish Conventional Rail Network

This work presented salient features of the steel behavior of seven metallic bridges close to, or over, 100 years old, among the Spanish conventional rail network as well as the results of a fatigue life expectancy study. A preliminary study of the properties of the constituent materials obtained from the bridges samples was carried out followed by dynamic fatigue tests under service representative loads. Due to the steelmaking techniques in the late 19th and early 20th centuries, disperse fatigue behavior results were obtained. However, the wide safety margins with which these bridges were designed, as well as the mechanical properties of the steel (relatively good mechanical resistance but with low ductility), seem to guarantee a long fatigue life. This estimate decreases sharply with increasing loads

Tantalum Alloy Welding: Does the Thermal Cycle Influence the Microstructure?

The aim of the present work is to verify the microstructural behavior of a B 521 tantalum alloy UNS Grade R05200 after welding, in relation to the welding thermal cycle. The joint design was a 1.5 mm thickness circumferential butt welding, on a 32 mm outside diameter pipe, welded in 1 G position (horizontal, flat, and rotating). The chosen welding process was gas tungsten arc welding (GTAW). The microstructural analysis showed the presence of coarse, dendritic-columnar structures, as well as a hexagonal cell, with no cracks noted. Hardness tests showed an increase in hardness, from 120 HV to 425 HV, in the heat-affected zone. Through finite element methods, the behavior of the temperature field was estimated and compared

Tantalum Alloy Welding: Does the Thermal Cycle Influence the Microstructure?

The aim of the present work is to verify the microstructural behavior of a B 521 tantalum alloy UNS Grade R05200 after welding, in relation to the welding thermal cycle. The joint design was a 1.5 mm thickness circumferential butt welding, on a 32 mm outside diameter pipe, welded in 1 G position (horizontal, flat, and rotating). The chosen welding process was gas tungsten arc welding (GTAW). The microstructural analysis showed the presence of coarse, dendritic-columnar structures, as well as a hexagonal cell, with no cracks noted. Hardness tests showed an increase in hardness, from 120 HV to 425 HV, in the heat-affected zone. Through finite element methods, the behavior of the temperature field was estimated and compared

Tantalum Alloy Welding: Does the Thermal Cycle Influence the Microstructure?

[EN] The aim of the present work is to verify the microstructural behavior of a B 521 tantalum alloy UNS Grade R05200 after welding, in relation to the welding thermal cycle. The joint design was a 1.5 mm thickness circumferential butt welding, on a 32 mm outside diameter pipe, welded in 1 G position (horizontal, flat, and rotating). The chosen welding process was gas tungsten arc welding (GTAW). The microstructural analysis showed the presence of coarse, dendritic-columnar structures, as well as a hexagonal cell, with no cracks noted. Hardness tests showed an increase in hardness, from 120 HV to 425 HV, in the heat-affected zone. Through finite element methods, the behavior of the temperature field was estimated and compared.S