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6283 |
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Tuesday, May 04, 2021, Hall 1 2:15 PM Process & Quality Control |
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Brazing cycle influence on the brazing joint microstructure and nanohardness - Behaviour law of the header-joint tube assembly for thermal shock heat exchanger simulation optimization |
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Anne-Gaelle Villemiane* / VALEO Thermal System, France Laurent Pasquet / VALEO Thermal System, France Dassidi Douksouna/ Laboratoire d'Etude des Microstructures et de Mécanique des Matériaux LEM3, Université de Lorraine, CNRS, Arts et Métiers ParisTech, France Jean-Sebastien Lecomte/ Laboratoire d'Etude des Microstructures et de Mécanique des Matériaux LEM3, Université de Lorraine, CNRS, Arts et Métiers ParisTech, France Eric Fleury/ Laboratoire d'Etude des Microstructures et de Mécanique des Matériaux LEM3, Université de Lorraine, CNRS, Arts et Métiers ParisTech, France Christophe Schuman/ Laboratoire d'Etude des Microstructures et de Mécanique des Matériaux LEM3, Université de Lorraine, CNRS, Arts et Métiers ParisTech, France |
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Economic and environmental drivers are leading to exchanger weight reduction for automotive applications. The consequence is material downgauging and some robustness limit reached for automotive exchangers. Parallel to that, exchangers are brazed with specific temperatures and timing to optimize bonding reliability. Finally, one of the main failure modes of the exchanger, occurs at the level of tube-header junction next to the brazing joint, as a result of thermal shock which is induced by transient differential thermal expansion between the exchanger components of different designs. Five different brazing cycles have been processed in this study from cold temperature and short timing to hot temperature and long duration to understand the consequence of these two parameters thanks to a design of experiment on the brazing joint microstructure and nanohardness. In this work, different nano and ultrananoindentation tests have been performed after SEM-EBSD microstructure observation of the tube header junction to choose the most suitable brazing cycle conditions from the five cycles. This paper will focus on the implementation of representative behavior law for tube/joint/header to define simulation models to better represent the stress undergone during a thermal shock test. |