13 Zentrale Universitätseinrichtungen

Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/14

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Author: search.filters.author.Hossfeld, Max

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    Modeling friction stir welding : on prediction and numerical tool development
    (2022) Hossfeld, Max
    This paper reports on a simulation framework capable of predicting the outcomes of the friction stir welding process. Numerical tool development becomes directly possible without the need for previous calibration to welding experiments. The predictive power of the framework is demonstrated by a case study for numerical tool development and validated experimentally. Different tool geometries with high levels of detail and active material flow features are investigated, and their effect on the process outcomes is quantified. The simulation framework is found to be able to predict forces, material flow, temperature fields, weld formation and welding defects a priori, in detail and precisely. This applies to the outer appearance of the weld as well as the location, shape, and size of inner welding defects. Causes for defects can be identified, analyzed and remedied. Compared to the validation experiment, the simulation showed a slight overestimation of the process impact in the case study. Since the framework relies strictly on analytically describable physics, the efforts for modeling the process are moderate considering the precision of the results.
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    On friction, heat input, and material flow initiation during friction stir welding : tool and process optimization
    (2023) Hossfeld, Max
    The Friction Stir Welding (FSW) process depends entirely upon mechanical contact between the tool and the workpiece. As a result of this, all process phenomena and process outcomes such as weld geometry and mechanical properties are governed by FSW’s frictional system. The following work characterizes this system with a focus on process initialization, heat input and material flow. For this purpose, an experimental program for the isolated investigation of the frictional system was carried out. Short-term effects such as contact initiation, run-in behavior and frictional transitions are considered as well as the influences of process parameters and geometry. The system and its behavior are analyzed quantitatively and qualitatively by experiments altering the normal pressure, relative velocity, and tool geometry. The experiments demonstrate a self-similar behavior of the process, including an important wear transition which initiates the material flow, and a subsequent equilibrium of forces, heat balance, and temperatures. The interaction between the tool and the welded material is described, as is the link between the frictional interface and material flow initialization. Based on these findings, recommendations are provided for process optimization and tool design.
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    A universal framework for skill-based cyber-physical production systems
    (2024) Hossfeld, Max; Wortmann, Andreas
    In the vision of smart manufacturing and Industry 4.0, it is vital to automate production processes. There is a significant gap in current practices, where the derivation of production processes from product data still heavily relies on human expertise, leading to inefficiencies and a shortage of skilled labor. This paper proposes a universal framework for skill-based cyber-physical production systems (CPPS) that formalizes production knowledge into machine-processable formats. Key contributions include a novel conceptual model for skill-based production processes and an automated method to derive production plans from high-level CPPS skills for production planning and execution. This framework aims to enhance smart manufacturing by enabling more efficient, transparent, and automated production planning, thereby addressing the critical gap in current manufacturing practices. The framework’s benefits include making production processes explainable, optimizing multi-criteria systems, and eliminating human biases in process selection. A case study illustrates the framework’s application, demonstrating its current capabilities and potential for modern manufacturing.