Arnaud Blouin | AREVA - Academia.edu (original) (raw)
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Papers by Arnaud Blouin
International Journal of Pressure Vessels and Piping, Jun 1, 2019
Volume 6: Materials and Fabrication, 2020
Stainless steel dissimilar metal welds (SS DMW) are widely used within the French nuclear power p... more Stainless steel dissimilar metal welds (SS DMW) are widely used within the French nuclear power plants where they connect the main components (pressure vessel, pressurizer, steam generator) made of low alloy ferritic steel to the primary circuit pipes made of austenitic stainless steel. Because of their heterogeneous microstructure and mechanical properties, these junctions are critical components for the structure integrity and their fracture resistance has to be demonstrated for all the nominal or accidental operating conditions. This work aims at building a model to evaluate the risk of brittle fracture of the SS DMW in the upper shelf of the brittle-to ductile transition range. The observation of the microstructures around the fusion line revealed a martensitic layer and a fully austenitic zone, which undergo an important carbides precipitation during the post-weld heat treatment and form a narrow hard layer of carburized martensite and austenite. Fracture toughness tests were t...
International Journal of Pressure Vessels and Piping, 2019
In this paper, the behavior of large ductile crack propagation in a pipe using the local approach... more In this paper, the behavior of large ductile crack propagation in a pipe using the local approach models of Gurson is predicted. The mock-up presents a narrow gap INCONEL dissimilar weld joining a low alloy ferritic steel pipe and a 316L type stainless austenitic steel pipe. It was performed in the frame of the European Commission (EC) funded STYLE project (2010-2013). During the four points bending test on the mockup, the behavior of the crack growth was highly unexpected, and was not deeply analyzed. The initial crack, located at the interface between the weld and the ferritic Heat-Affected Zone (HAZ), grew in the weld and deviated from it to finally reach the austenitic HAZ. A local approach modeling in order to explain the crack behavior has been performed, using the Gurson-Tvergaard-Needlemann (GTN) model. First, the characterization of the materials composing the weld is made through the experimental program of the STYLE project. Then, GTN parameters are identified using the experimental data from the laboratory specimens. The behavior of Compact Tension (CT) specimens and the pipe are then numerically predicted. It is shown that GTN model is able to catch the mechanical differences between the CT specimens and the pipe, providing a good prediction of the crack propagation during the four points bending test.
This article presents the current status on the effort performed within AREVA in support of the F... more This article presents the current status on the effort performed within AREVA in support of the Fracture Mechanics Assessment approach under development for the justification of Dissimilar Metal Welds. It follows a first step presented in a previous paper and devoted to the validation of the J parameter calculation through a Finite Element (F.E.) modelling for a crack at the interface between two different materials. This paper focuses on the residual stress field consideration within the F.E. modelling: how to define the residual stress field to consider in the model, how to introduce it in the model and how relevant are the calculated values. In a first part, the main obtained results from the previous paper are reminded. Afterwards, the definition of the residual stress field is discussed. It basically relies on residual stress measurements and numerical welding simulation but it has to be specifically adapted for the F.E. modelling purpose. Following this definition step, a protocol for the introduction of those stresses within the model and a parametric study on the residual stress distribution are proposed. Here, the model is 2D and thus allows a fast and accurate sensitive study. As a conclusion, several perspectives are discussed from that parametric study.
International Journal of Pressure Vessels and Piping, Jun 1, 2019
Volume 6: Materials and Fabrication, 2020
Stainless steel dissimilar metal welds (SS DMW) are widely used within the French nuclear power p... more Stainless steel dissimilar metal welds (SS DMW) are widely used within the French nuclear power plants where they connect the main components (pressure vessel, pressurizer, steam generator) made of low alloy ferritic steel to the primary circuit pipes made of austenitic stainless steel. Because of their heterogeneous microstructure and mechanical properties, these junctions are critical components for the structure integrity and their fracture resistance has to be demonstrated for all the nominal or accidental operating conditions. This work aims at building a model to evaluate the risk of brittle fracture of the SS DMW in the upper shelf of the brittle-to ductile transition range. The observation of the microstructures around the fusion line revealed a martensitic layer and a fully austenitic zone, which undergo an important carbides precipitation during the post-weld heat treatment and form a narrow hard layer of carburized martensite and austenite. Fracture toughness tests were t...
International Journal of Pressure Vessels and Piping, 2019
In this paper, the behavior of large ductile crack propagation in a pipe using the local approach... more In this paper, the behavior of large ductile crack propagation in a pipe using the local approach models of Gurson is predicted. The mock-up presents a narrow gap INCONEL dissimilar weld joining a low alloy ferritic steel pipe and a 316L type stainless austenitic steel pipe. It was performed in the frame of the European Commission (EC) funded STYLE project (2010-2013). During the four points bending test on the mockup, the behavior of the crack growth was highly unexpected, and was not deeply analyzed. The initial crack, located at the interface between the weld and the ferritic Heat-Affected Zone (HAZ), grew in the weld and deviated from it to finally reach the austenitic HAZ. A local approach modeling in order to explain the crack behavior has been performed, using the Gurson-Tvergaard-Needlemann (GTN) model. First, the characterization of the materials composing the weld is made through the experimental program of the STYLE project. Then, GTN parameters are identified using the experimental data from the laboratory specimens. The behavior of Compact Tension (CT) specimens and the pipe are then numerically predicted. It is shown that GTN model is able to catch the mechanical differences between the CT specimens and the pipe, providing a good prediction of the crack propagation during the four points bending test.
This article presents the current status on the effort performed within AREVA in support of the F... more This article presents the current status on the effort performed within AREVA in support of the Fracture Mechanics Assessment approach under development for the justification of Dissimilar Metal Welds. It follows a first step presented in a previous paper and devoted to the validation of the J parameter calculation through a Finite Element (F.E.) modelling for a crack at the interface between two different materials. This paper focuses on the residual stress field consideration within the F.E. modelling: how to define the residual stress field to consider in the model, how to introduce it in the model and how relevant are the calculated values. In a first part, the main obtained results from the previous paper are reminded. Afterwards, the definition of the residual stress field is discussed. It basically relies on residual stress measurements and numerical welding simulation but it has to be specifically adapted for the F.E. modelling purpose. Following this definition step, a protocol for the introduction of those stresses within the model and a parametric study on the residual stress distribution are proposed. Here, the model is 2D and thus allows a fast and accurate sensitive study. As a conclusion, several perspectives are discussed from that parametric study.