Mansur Akbari


Last Name

Akbari

First Name

Mansur

ORCID

0000-0002-8970-1246

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2011 - 2019102020 - 20212
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Publications 1 - 10 of 12
  • Inverse material modeling and optimization of free-cutting steel with graphite inclusions
    Item type: Journal Article
    Akbari, Mansur; Smolenicki, Darko; Roelofs, Hans; et al. (2019)
    The International Journal of Advanced Manufacturing Technology
    Graphite inclusions in steel are easing chip breakage and act as in situ lubricants. Therefore, graphitized steels are claimed to perform excellent in machining processes. They are considered as environmentally friendly alternatives to widely used Pb-alloyed steels. However, the effectiveness of graphite inclusions in different machining processes is not well understood. With the support of computer simulation techniques, a deeper understanding about chip formation and the role of internal friction (or lubrication) can be obtained. To enter into numerical analysis of material flow and chip formation, the quality of the applied constitutive law is crucial for close-to-reality simulation. In the present work, a most accurate determination of the Johnson-Cook constitutive law of partially graphitized steel 50SiB8 (hardness 214 HB) is aimed for. Johnson-Cook parameters are identified from dynamical compression tests, performed at strain rates up to 20s−1 and temperatures up to 800 °C. The material parameters are derived from two different numerical methods. The first standard method is based on minimizing the sum of squares of the differences between calculation and measurement. The parameters identified from this method are used as initial values for the second method, an inverse material modeling. The second method is based on a multi-case polynomial metamodel optimization in combination with finite element techniques. By applying inverse material modeling, the maximum discrepancy between measurement and calculation is reduced from 12% (regression with standard method) to 1%. A reliable parameter set for the Johnson-Cook model for graphitic steel 50SiB5 as input for future modeling of the chip formation is now available.
  • Influence of energy fraction in EDM drilling of Inconel 718 by statistical analysis and finite element crater-modelling
    Item type: Journal Article
    Kliuev, Mikhail; Florio, Kevin; Akbari, Mansur; et al. (2019)
    Journal of Manufacturing Processes
  • Thermomechanical analysis of machining and brazing
    Item type: Doctoral Thesis
    Akbari, Mansur (2016)
  • A new value for Johnson Cook damage limit criterion in machining with large negative rake angle as basis for understanding of grinding
    Item type: Journal Article
    Akbari, Mansur; Buhl, Sebastian; Leinenbach, Christian; et al. (2016)
    Journal of Materials Processing Technology
  • Temperature and force measurements in single diamond scratch tests
    Item type: Journal Article
    Akbari, Mansur; Kliuev, Mikhail; Boos, Jens; et al. (2018)
    The International Journal of Advanced Manufacturing Technology
    Analysis of the highest temperature in the machining processes, namely the flash temperature, helps to understand the physics of the process, to improve cutting tool geometry, and to achieve high performance machining. In the present work, the interaction between cutting grain and workpiece material in grinding process is analyzed. Single diamonds are considered for machining, which operates in comparison to other measurements in the range of grinding speed. The highest temperature in the grain-material interaction and cutting forces are measured. In order to measure the flash temperature, an innovative method to measure and analyze the temperature through the diamond grain in the cutting zone by a two-color pyrometer is proposed. Furthermore, cutting forces are measured simultaneously. In order to measure the temperature in the cutting zone, an accurate connection between diamond and pyrometer fiber is required. Thus, the diamond tool holders are manufactured by electrical discharge machining (EDM) milling in deionized water. A 0.5-mm-diameter hole is drilled in each holder to connect the diamond precisely to the pyrometer fiber. Machining processes are performed with 30 μm depth of cut, cutting length of 20 mm, and cutting speed of 65 m/s on Ti6Al4V. The cutting tool is fixed, and the shape of the rotating workpiece is optimized. The diamond holder with the specific shape is designed and manufactured. Quasi-static, dynamic, modal, and harmonic response analyses are performed in order to reduce vibrations and chattering. The measured flash temperature is 1380 °C and cutting normal, tangential, and axial forces are measured.
  • Comparison of Transparent Objects Metrology through Diamond Cutting Edge Radii Measurements
    Item type: Journal Article
    Akbari, Mansur; Knapp, Wolfgang; Wegener, Konrad (2016)
    CIRP Journal of Manufacturing Science and Technology
  • Predicting the Springback of Metal Cutting Operations Using Mesh Free Methods
    Item type: Conference Paper
    Imayasu, Shinya; Rӧthlin, Matthias; Akbari, Mansur; et al. (2015)
    Proceedings of the 8th International Conference on Leading Edge Manufacturing in 21st Century, LEM 2015
  • Thermomechanical analysis of residual stresses in brazed diamond metal joints using Raman spectroscopy and finite element simulation
    Item type: Journal Article
    Akbari, Mansur; Buhl, Sebastian; Leinenbach, Christian; et al. (2012)
    Mechanics of Materials
  • Turning: Autonomous process set-up through Bayesian optimization and Gaussian process models
    Item type: Conference Paper
    Maier, Markus; Rupenyan-Vasileva, Alisa Bohos; Akbari, Mansur; et al. (2020)
    Procedia CRIP
    In turning, process parameters such as feed rate and cutting speed are normally selected by an operator and adapted depending on the process requirements. In this study, autonomous process set-up of the turning process is investigated based on Bayesian optimization and Gaussian process models. Unconstrained Bayesian optimization is compared to an implementation with added constraint with simulated machining parameters. It is shown that constraint Bayesian optimization has a better performance in the turning process set-up. The method is suitable for measurements with uncertainty and typically results in reduced number of experiments.
  • Analysis Of Thermal Residual Stresses In Brazed Diamond-Metal Joints Considering Creep And Plasticity In 316L Stainless Steel And Filler Alloy
    Item type: Other Conference Item
    Akbari, Mansur; Buhl, Sebastian; Leinenbach, Christian; et al. (2011)
Publications 1 - 10 of 12