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Stéphane Claudinon
Abstract
Contribution to the study of distortion due to thermal treatment: continuous monitoring by artificial vision and numerical simulation by finite elements
Stéphane Claudinon - 7 february 2000.
Heat treatment of steel is used to change the metallurgical structure and the mechanical properties of the steels. However, during quenching, internal stresses develop in the part and lead to changes in shape of the specimen. As a consequence, one more manufacturing step is often necessary to obtain the right shape of the part, together with the required properties of the material. Finite element softwares have been developed in order to predict these distortions, and thus reduce this final step. However, these softwares require a lot of data such as phase transformation curves, mechanical properties of each constituant, etc. It turns out that they are not systematically used by the industries involved in the heat treatment of metallic parts.
The aim of this work is to study distortions during treatment in order to optimize or even simplify predictive models and data. For this purpose, non intrusive optical measurement methods are used to follow the kinetics of distortions during the treatment itself. A heat treatment vacuum furnace was equiped with CCD cameras. Two experimental techniques were developed : a contour detection system, specialy fitted for the study of axisymetrical parts, and a stereovision measurement system, designed for more complex shape, which give access to tridimensional displacement field.
The contour detection system was used with different steel grades and a special test specimen. Distortion kinetics results are compared with theoretical predictions obtained by the finite element technique. Stereovision was used with a second geometry and one steel grade. The results are promising and confirm the valuable contribution of full field optical methods in this area.
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