FlowCurveJbyF - Standardization of Flow Curve Determination for Joining by Forming
1st Edition
Published on 20. August 2020
Book
Paperback/Softback
116 pages
978-3-86776-590-9 (ISBN)
Description
The demands for joining techniques increased significantly in the last decade. Today, structures are highly optimized to meet stringent requirements with respect to a variety of performance metrics such as weight, safety and environmental impact. Given that FE modules dedicated to simulating joining by forming process reached a sufficiently high level of maturity, simulation is increasingly used by SMEs for numerical process development, and, through the increasing digitization, also for datamining.
In important caveat, however, is that the predictive accuracy of these FE simulations strongly depends on, amongst others, the adopted material model. For an accurate calculation of the joint geometry and its mechanical strength, accurate large strain flow curves are required. A myriad of experimental techniques have been developed to determine the large strain flow curve of sheet metal. In this regard, there are two issues.
Firstly, these material tests are typically dominated by a certain stress state and yield different results depending on the degree of plastic anisotropy exhibited by the sheet metal. Secondly, due to the small dimensions of the forming tools (e.g. punch or rivet) compared to the nominal sheet thickness, joining by forming processes of sheet metal must be regarded as a bulk forming problem in which the through-thickness stress cannot be ignored. The crux of the problem here is that the plastic material behaviour of sheet metal is conventionally determined using material tests, which are confined to homogeneous plane stress conditions in the plane of the sheet.
Due to a multitude of methods for determining flow curves and the variety of phenomenological hardenings laws models to describe them, problems arise with respect to reproducibility and accuracy in joining by forming simulations. The latter threatens the advantages of numerical process development.
The aim of this research project is to devise a process-informed selection strategy for the selection of flow curves determination methods tailored for FE simulations in mechanical joining. The key point of the method is the identification of the dominating stress state in the joining by forming process at hand, which is then used to select the most appropriate material test to identify the large strain flow curve.
Several material tests are conducted in collaboration with research labs and institutes across the globe. The developed selection strategy is applied to two representative joining by forming techniques, namely clinching and self-pierce riveting. The experimental validation enabled to derive guidelines to identify accurate flow curves for simulating joining by forming processes.
The framework presented in this report enables to arrive at industrial relevant guidelines for the selecting the most appropriate method to identify the large strain flow curve, and, consequently, increase the accuracy of numerical process development in joining by forming.
https://ble-x.de/mydocs/1613
In important caveat, however, is that the predictive accuracy of these FE simulations strongly depends on, amongst others, the adopted material model. For an accurate calculation of the joint geometry and its mechanical strength, accurate large strain flow curves are required. A myriad of experimental techniques have been developed to determine the large strain flow curve of sheet metal. In this regard, there are two issues.
Firstly, these material tests are typically dominated by a certain stress state and yield different results depending on the degree of plastic anisotropy exhibited by the sheet metal. Secondly, due to the small dimensions of the forming tools (e.g. punch or rivet) compared to the nominal sheet thickness, joining by forming processes of sheet metal must be regarded as a bulk forming problem in which the through-thickness stress cannot be ignored. The crux of the problem here is that the plastic material behaviour of sheet metal is conventionally determined using material tests, which are confined to homogeneous plane stress conditions in the plane of the sheet.
Due to a multitude of methods for determining flow curves and the variety of phenomenological hardenings laws models to describe them, problems arise with respect to reproducibility and accuracy in joining by forming simulations. The latter threatens the advantages of numerical process development.
The aim of this research project is to devise a process-informed selection strategy for the selection of flow curves determination methods tailored for FE simulations in mechanical joining. The key point of the method is the identification of the dominating stress state in the joining by forming process at hand, which is then used to select the most appropriate material test to identify the large strain flow curve.
Several material tests are conducted in collaboration with research labs and institutes across the globe. The developed selection strategy is applied to two representative joining by forming techniques, namely clinching and self-pierce riveting. The experimental validation enabled to derive guidelines to identify accurate flow curves for simulating joining by forming processes.
The framework presented in this report enables to arrive at industrial relevant guidelines for the selecting the most appropriate method to identify the large strain flow curve, and, consequently, increase the accuracy of numerical process development in joining by forming.
https://ble-x.de/mydocs/1613