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PublicationKnowledge-Based Adaptation of Product and Process Design in Blisk Manufacturing( 2022)Early and efficient harmonization between product design and manufacturing represents one of the most challenging tasks in engineering. Concepts such as simultaneous engineering aim for a product creation process, which addresses both, functional requirements as well as requirements from production. However, existing concepts mostly focus on organizational tasks and heavily rely on the human factor for the exchange of complex information across different domains, organizations, or systems. Nowadays product and process design make use of advanced software tools such as computer-aided design, manufacturing, and engineering systems (CAD/CAM/CAE). Modern systems already provide seamless integration of both worlds in a single digital environment to ensure a continuous workflow. Yet, for the holistic harmonization between product and process design, the following aspects are missing: (i) the digital environment does not provide a complete and data consistent digital twin of the component; this applies especially to the process design and analysis environment, (ii) due to the lack of process and part condition data in the manufacturing environment, an adaptation of product and process design for a balanced functionality and manufacturability is hindered, and (iii) systematic long-term data analytics across different product and process designs with the ultimate goal to transfer knowledge from one product to the next and to accelerate the entire product development process is not considered. This paper presents an exploration concept which couples product design (CAD), process design (CAM), process simulation (CAE), and process adaptation in a single software system. The approach provides insights into correlations and dependencies between input parameters of product/process design and the process output. The insights potentially allow for a knowledge-based adaptation, tackling well-known optimization issues such as parameter choice or operation sequencing. First results are demonstrated using the example of a blade integrated disk (blisk). Early and efficient harmonization between product design and manufacturing represents one of the most challenging tasks in engineering. Concepts such as simultaneous engineering aim for a product creation process, which addresses both, functional requirements as well as requirements from production. However, existing concepts mostly focus on organizational tasks and heavily rely on the human factor for the exchange of complex information across different domains, organizations, or systems. Nowadays product and process design make use of advanced software tools such as computer-aided design, manufacturing, and engineering systems (CAD/CAM/CAE). Modern systems already provide seamless integration of both worlds in a single digital environment to ensure a continuous workflow. Yet, for the holistic harmonization between product and process design, the following aspects are missing: (i) the digital environment does not provide a complete and data consistent digital twin of the component; this applies especially to the process design and analysis environment, (ii) due to the lack of process and part condition data in the manufacturing environment, an adaptation of product and process design for a balanced functionality and manufacturability is hindered, and (iii) systematic long-term data analytics across different product and process designs with the ultimate goal to transfer knowledge from one product to the next and to accelerate the entire product development process is not considered. This paper presents an exploration concept which couples product design (CAD), process design (CAM), process simulation (CAE), and process adaptation in a single software system. The approach provides insights into correlations and dependencies between input parameters of product/process design and the process output. The insights potentially allow for a knowledge-based adaptation, tackling well-known optimization issues such as parameter choice or operation sequencing. First results are demonstrated using the example of a blade integrated disk (blisk).
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PublicationDpart - A digital twin framework for the machining domain( 2021)
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PublicationSpatially Resolved Tool Wear Prediction in Finish Milling( 2021)Tool wear is a cost driver in the metal cutting industry. The development of tool wear is mostly unknown during process planning of a finish milling operation. This study investigates a tool wear prediction method based on a dexel-based engagement simulation and cutting experiments. With this modelling approach, progression of tool wear is spatially resolved along the cutting edge of the tool. This paper contributes to the perspective of transparent process planning in milling. In particular, the ability to plan tool changes and to distribute wear uniformly along the cutting edge helps to improve surface quality and reduce tool cost.
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PublicationInfluence of heat treatment on the residual stress-related machining distortion of Ti-6Al-4V alloy monolithic parts( 2021)Machining distortion caused by residual stresses is one of the major challenges in the production of thin-walled monolithic parts. One reason for the distortion is the relaxation of the initial residual stresses within the raw part due to the material removal during the machining process. The initial residual stresses mainly depend on the manufacturing process of the raw part and the subsequent heat treatment. This paper presents the results from a set of experimental and computational studies of the influence of heat treatment on residual stress-related machining distortion of Ti-6Al-4V alloy monolithic parts. A thermo-mechanical simulation of the heat treatment process is developed for the prediction of the initial residual stresses. For experimental validation, the contour method is use d to quantify the initial residual stresses. Finally, machining tests are conducted to measure the final part distortion for two different residual stress states.
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PublicationLife cycle assessment for milling of Ti- and Ni-based alloy aero engine components( 2021)Motivation: Aero engine optimization focuses on reducing emissions during operation. Resource extraction and manufacturing are considered insufficiently. An LCA of resource extraction and machining for aero engine components comparing a Ti-alloy and a Ni-alloy was conducted. Method: Aero engine components were manufactured comparing a Ti-alloy and a Ni-alloy. Results: Machining mostly affects climate change, water use, resource depletion and human toxicity. The Ni-alloy showed an overall higher environmental impact than the Ti-alloy. Conclusion: Raw material, tool life and energy usage significantly contribute to environmental impacts. Further investigation should focus on tool life travel path optimization and reducing raw material.
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PublicationThe finite cell method for the prediction of machining distortion caused by initial residual stresses in milling( 2021)Machining distortion caused by residual stresses is one of the major challenges in the production of thin-walled monolithic parts, which are widely used in the aerospace industry. This distortion often results in large deviations in form and position outside the tolerance requirements of the part. Time-consuming and cost-intensive running-in processes or manual reworking are therefore necessary to meet the tolerances of the parts. Current research mainly uses the finite element method (FEM) to predict machining distortion caused by residual stresses. However, the disadvantage of the FEM is the high manual effort required to generate a computational mesh of the in-process workpiece (IPW). Moreover, the FEM demands a very fine mesh, which has to be frequently updated by remeshing, to be in good agreement with the IPW. This leads to high computation times overall. In this paper, a novel machining distortion prediction method based on the Finite Cell Method (FCM) is presented. A major advantage of FCM compared to the established FEM in the context of milling simulation is the decoupling of the computational mesh and the IPW geometry, which allows for analysis updates of the modified IPW due to material removal, without the need for expensive re-meshing. Thus, the time complexity of the simulation can be reduced significantly. The milling process of a thin-walled part made of Ti-6Al-4V was considered to demonstrate the overall simulation approach.
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PublicationPreparation of symmetrical and asymmetrical cutting edges on solid cutting tools using brushing tools with filament-integrated diamond grits( 2020)The manufacturing of asymmetric cutting edges is crucial for tool life and performance of cutting tools. For rotationally symmetric cutting tools with a complex profile of the cutting edges, such as milling or drilling tools, no suitable preparation methods exist so far. This paper presents a model that describes the targeted preparation of symmetrical and asymmetrical cutting edges using abrasive brushing tools with filament-integrated diamond grits in dependence of various process parameters. The selected process parameters and dimensions of the brushing tool ensure the accessibility of real cutting tools. In addition, the results of investigations on brushing tool wear are presented.
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PublicationImproving dynamic process stability in milling of thin-walled workpieces by optimization of spindle speed based on a linear parameter-varying model( 2020)In milling of thin-walled workpieces, like aero engine blades, the reduction of vibrations is of central importance to reach a more economical and reliable process as well as an improved workpiece surface quality. However, the dynamic behavior of the workpiece continuously varies due to changes in workpiece stiffness and mass, caused by the moving position of the excitation force as well as the material removal. In this paper, the simulation of the changing workpiece dynamics for a simplified blade geometry using FE-modal analysis is demonstrated. All extracted workpiece dynamic states are combined in a reduced LPV-model (Linear Parameter-Varying model). The LPV-model is able to describe the varying process dynamic behavior and makes the selection of advantageous spindle speeds possible.
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PublicationOrthogonal cutting of cortical bone: Temperature elevation and fracture toughness( 2017)During surgical procedures, the heat development of bone cutting can lead to thermal cell necrosis and secondary implant instability. Therefore, fundamental knowledge on heat development and temperature control is crucial. This paper investigates the basic principles of the machining of cortical bone in an orthogonal cutting process. Cutting forces, temperature elevation and chip formation were measured in real time for two different rake angles and six different cuffing depths. A non-linear relationship between cutting depth and cutting forces as well as temperature elevation was found. The cutting behavior changed from a ductile to two distinguishable fracture cutting modes with increasing cutting depth. A linear correlation between cutting forces and temperature elevation of both bone chip and workpiece was determined (R-2 = 0.8697). An increasing rake angle lowered cutting forces and temperature elevations significantly and was explained using a fracture mechanics approach. Additionally, a new method to calculate the fracture toughness of (quasi-)brittle materials from orthogonal cutting tests was introduced.
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PublicationComparison of rotational turning and hard turning regarding surface generation( 2014)In this paper, two different turning processes namely rotational turning and hard turning are compared to each other regarding surface generation aspects. By experiments it is shown that, with higher feed rates, rotational turning yields same surface quality as hard turning. Feed rates can be chosen six times higher in rotational turning than in conventional hard turning without losses in the surface roughness quality. Also experiments reveal that the tool wear in rotational turning has a beneficial effect on the surface roughness. A corresponding explanation model is thereby presented which takes the specific tool/work piece engagement in rotational turning into account. Furthermore, it is shown that rotational turning has negative effects on the surface integrity. The phase transformation zones (""white layers"") are thicker in rotational turned parts than in hard turned parts. Also the level of tensile residual stress in rotational turning is higher than in hard turning. Both effects are probably caused by high thermal material loads in rotational turning due to increased friction. However, the results of this paper show that rotational turning has a high potential to become an efficient alternative to hard turning, especially when it comes to large scale production of simple shaped parts.
