Fraunhofer-Institut für Produktionsanlagen und Konstruktionstechnik IPK

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  • Publication
    Fully coupled wet cylindrical turning simulation using the Finite-Pointset-Method
    ( 2021)
    Uhlmann, Eckart
    ;
    Barth, Enrico
    ;
    Quellhorst, Alexander
    ;
    Seifarth, Tobias
    ;
    Kuhnert, Jörg
    ;
    Nabbout, Kaissar
    ;
    Sommerfeld, Martin
    In industrial machining operations, many turning processes are carried out under wet conditions. In contrast, most simulation tools are only suitable for dry cutting processes due to challenges of modeling fluid-structure-interactions (FSI). In this paper, a wet, fully coupled cutting simulation using the Finite-Pointset-Method (FPM) is presented and validated for industrially relevant cylindrical turning. To facilitate the required reduction of the calculation effort, different routines like adaptive numerical discretization are applied. The results indicate different cutting fluid effects like evaporation areas around the chip.
  • Publication
    Data for a simulation of metal cutting with cutting fluid using the Finite-Pointset-Method
    ( 2021)
    Uhlmann, Eckart
    ;
    Barth, Enrico
    ;
    Seifarth, Tobias
    ;
    Höchel, Maximilian
    ;
    Kuhnert, Jörg
    ;
    Eisenträger, Almut
    The measurement and simulation data, their preparation and the simulation setup published in this co-submission are related to the article ""Simulation of metal cutting with cutting fluid using the Finite-Pointset-Method"". Wet and dry turning experiments were conducted at the Institute for Machine Tools and Factory Management(IWF), Berlin, Germany. Required adaptions of the used software MESHFREE were performed at Fraunhofer ITWM, Kaiserslautern, Germany. Both institutes collaboratively developed and validated the orthogonal cutting simulation model using the Finite-Pointset-Method (FPM). In this paper all measurement and simulation data and their preparation methods are presented in detail. This includes the preparation methods of process forces, analysis of chip morphology images as well as measured contact lengths on tool rake faces. Moreover, the experimental and simulation data are provided at the Mendeley Data repository. Hence the reader can use the data for own validations and analysis. Furthermore, the used simulation model files are completely published at the Mendeley Data repository. It allows the reader to retrace all settings. In addition, this enables to repeat the simulations and to simulate other process parameter combinations according to own interests.
  • Publication
    Optimization with the evolution strategy by example of electrical-discharge drilling
    ( 2020)
    Streckenbach, Jan
    ;
    Koref, Ivan Santibáñez
    ;
    Rechenberg, Ingo
    ;
    Uhlmann, Eckart
    A key challenge in electrical discharge machining (EDM) is to find a suitable combination out of numerous process parameters. Any changes concerning the electrode materials or geometries require newly optimized technologies. These technologies are to be developed from a considerable number of experiments which must be carried out by an experienced operator. This paper presents a new method of finding the optimal set of parameters. Here, the performance of the evolution strategy (ES), a stochastic, metaheuristic optimization method, is investigated. It offers the great advantage of finding solutions, even with little knowledge of system behaviour. The method involved a randomized and a derandomized ES, based on a non-elitist (m,l)-ES with one parent and four children. The two ES were initialized from an unfavourable starting point (A) and from a favourable starting point (B) to investigate their effectiveness. It could be demonstrated that starting from the unfavourable starting point A the erosion duration tero could be reduced by a maximum of 77% with a slightly smaller linear wear of the tool electrode DlE after 40 trials.
  • Publication
    Decision-making support for sustainable product creation
    ( 2012)
    Inoue, Masato
    ;
    Lindow, Kai
    ;
    Stark, Reiner
    ;
    Tanaka, Kenji
    ;
    Nahm, Yoon-Eui
    ;
    Ishikawa, Haruo
    A satisfactory multiobjective design that incorporates physical performance as well as sustainability is necessary from a global environmental protection perspective. For obtaining sustainable lifecycles, decision making in the early phases of the design process, considering multiple sources of uncertainty, is important. Previously, we proposed a preference set-based design (PSD) by Inoue et al. (2010) [16] method, which enables a flexible and robust design under various sources of uncertainty while capturing the designers preference based on his/her knowledge or experience. The present study focuses on a decision-making support for sustainable product creation in the early phases of the design process considering the various design uncertainties. We investigate different officially accepted sustainability indicators and identify the ones that are related to the product development process by considering the physical performance and sustainability of the products concurrently. Thereafter, the proposed method is applied to a multiobjective design problem. This paper discusses the applicability of PSD as a decision-making support method for sustainable development using the design of an alternator as an example.
  • Publication
    Entwicklung der netzfreien Finite-Pointset-Methode für die Zerspansimulation
    ( 2011)
    Uhlmann, E.
    ;
    Gerstenberger, R.
    ;
    Schäfer, M.
    ;
    Kuhnert, J.
    Aktuelle Programme für die Finite-Elemente-Simulation von Zerspanprozessen verwenden Neuvernetzungsprozeduren, um die Trennung von Span und Grundwerkstoff abzubilden und die in den Scherzonen auftretenden großen Elementverzerrungen zu korrigieren. Diese Prozeduren schränken jedoch die Abbildungsgenauigkeit auf Grund von Interpolationsverlusten ein. Eine netzfreie Simulationsmethode ohne Neuvernetzungsprozeduren kann daher für die Zerspansimulation vorteilhaft sein. Im Rahmen der Weiterentwicklung der netzfreien Finite-Pointset-Methode (FPM) für die Zerspansimulation wurden ein Materialmodell für metallische Werkstoffe implementiert, Spanbildungssimulationen mit unterschiedlichen Werkstoffen durchgeführt und erste Schritte zur Darstellung des Kühlschmierstoffs in der Zerspansimulation unternommen.
  • Publication
    Investigating three-dimensional sketching for early conceptual design - results from expert discussions and user studies
    ( 2009)
    Israel, J.H.
    ;
    Wiese, E.
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    Mateescu, M.
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    Zöllner, C.
    ;
    Stark, R.
    As immersive 3D user interfaces reach broader acceptance, their use as sketching media is attracting both commercial and academic interests. So far, little is known about user requirements and cognitive aspects of immersive 3D sketching. Also the latter's integration into the workflow of virtual product development is far from being solved. We present results from two focus group expert discussions, a comparative user study on immersive 3D sketching conducted among professional furniture designers and a qualitative content analysis of user statements. The results of the focus group discussions show a strong interest in using the three-dimensional (3D) space as a medium for conceptual design. Users expect it to provide new means for the sketching process, namely spatiality, one-to-one proportions, associations, and formability. Eight groups of functions required for 3D sketching were outlined during the discussions. The comparative study was intended to find and investigate advantages of immersive three-dimensional space and its additional degrees-of-freedom for creative/reflective externalization processes. We compared a 3D and a 2D baseline condition in the same technical environment, a VR-Cave system. In both conditions, no haptic feedback was provided and the 2D condition was not intended to simulate traditional 2D sketching (on paper). The results from our user study show that both the sketching process and the resulting sketches differ in the 2D and 3D condition, namely in terms of the perceived fluency of sketch creation, in terms of the perceived appropriateness for the task, and in terms of the perceived stimulation by the medium, the movement speed, the sketch sizes, the degree of detail, the functional aspects, and the usage time. In order to validate the results of the focus group discussions, we produced a questionnaire to check for the subjectively perceived advantages and disadvantages in both the 2D and 3D conditions. A qualitative content analysis of the user statements revealed that the biggest advantage of 3D sketching lies in the sketching process itself. In particular, the participants emphasized the system's ability to foster inspiration and to improve the recognition of spatiality and spatial thinking. We argue that both 2D and 3D sketching are relevant for early conceptual design. As we progress towards 3D sketching, new tangible interactive tools are needed, which account for the user's perceptual and cognitive abilities.
  • Publication
    Shape from shading using probability functions and belief propagation
    ( 2009)
    Wilhelmy, J.
    ;
    Krüger, J.
    Shape-from-shading (SFS) aims to reconstruct the three-dimensional shape of an object from a single shaded image. This article proposes an improved framework based on belief propagation for computing SFS. The implementation of the well-known brightness, integrability and smoothness constraints inside this framework is shown. We implement the constraints as probability density functions. For example, the brightness constraint is a two-dimensional probability density function that relates all possible surface gradients at a pixel to their probability given the pixel intensity. A straightforward extension of the framework to photometric stereo is presented, where multiple images of the same scene taken under different lighting conditions are available. The results are promising, especially since the solution is obtained by iteratively applying simple operations on a regular grid of points. The presented framework therefore can be implemented in parallel and is a reasonably likely biological scheme.
  • Publication
    Using codebooks of fragmented connected-component contours in forensic and historic writer identification
    ( 2007)
    Schomaker, L.
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    Franke, K.
    ;
    Bulacu, M.
    Recent advances in "off-line" writer identification allow for new applications in handwritten text retrieval from archives of scanned historical documents. This paper describes new algorithms for forensic or historical writer identification, using the contours of fragmented connected-components in free-style handwriting. The writer is considered to be characterized by a stochastic pattern generator, producing a family of character fragments (fraglets). Using a codebook of such fraglets from an independent training set, the probability distribution of fraglet contours was computed for an independent test set. Results revealed a high sensitivity of the fraglet histogram in identifying individual writers on the basis of a paragraph of text. Large-scale experiments on the optimal size of Kohonen maps of fraglet contours were performed, showing usable classification rates within a non-critical range of Kohonen map dimensions. The proposed automatic approach bridges the gap between image-statistics approaches and purely knowledge-based manual character-based methods.
  • Publication
    Tiny GAs for image processing applications
    ( 2006)
    Köppen, M.
    ;
    Franke, K.
    ;
    Vicente-Garcia, R.
    The expedience of today's image-processing applications is no longer based on the performance of a single algorithm alone. These systems appear to be complex frameworks with a lot of sub-tasks that are solved by specific algorithms, adaptation procedures, data handling, scheduling, and parameter choices. The venture of using computational intelligence (CI) in such a context, thus, is not a matter of a single approach. Among the great choice of techniques to inject CI in an image-processing framework, the primary focus of this presentation will be on the usage of so-called Tiny-GAs. This stands for an evolutionary procedure with low efforts, i.e. small population size (like 10 individuals), little number of generations, and a simple fitness. Obviously, this is not suitable for solving highly complete: optimization tasks, but the primary interest here is not the best individual's fitness, but the fortune of the algorithm and its population, which has just escaped the Monte-Carlo domain after random initialization. That this approach can work in practice will be demonstrated by means of selected image-processing applications, especially in the context of linear regression and line fitting; evolutionary post processing of various clustering results, in order to select a most suitable one by similarity; and classification by the fitness values obtained after a few generations.