Development of Material Models and Acquisition of Model Parameters for Metal Cutting Simulations

Sampsa Vili Antero Laakso

    Research output: ThesisDoctoral ThesisCollection of Articles

    Abstract

    Metal cutting is a complex physical problem with many interdependent operational parameters. To illustrate this, a graph analysis is performed for the network of relationships between the parameters. In order to systematically develop metal cutting operations, a tool such as finite element simulations, capable of simultaneously calculating the combined effect of the parameters, is required. Metal cutting simulations are a useful tool for optimizing machining parameters and tool design with respect to quality and costs. Wide range of different cutting parameters or tool geometries can be simulated to find conditions to minimize tool wear or residuals stresses on the workpiece and finding appropriate level of cutting temperature, cutting forces, chip geometry or the thermal and mechanical loading of the tool. Simulations are faster and cheaper to perform than cutting experiments especially since simulations do not disrupt the production. Especially with recent interest in digital manufacturing, expert systems and design tools, finite element modeling of cutting is in research focus. The use of the finite element method for metal cutting simulations has been researched for several decades and the method is progressively reaching maturity. The first machining simulations date back to 1970's observed from Mackerle's bibliography from 1998. There are a few commercial software packages available for cutting simulations and the industry has slowly started to take advantage of the method. The major difficulty is that even though the software includes extensive work material libraries, many engineering materials are not included in them. When the material is not included in the library, the process of testing and characterizing the new material for the simulations is expensive, time consuming and requires a high level of expertise. In this dissertation, the state-of-the-art method of traditional materials testing for determining the material model parameters is investigated through practical implementation. A method for using cutting experiments for material characterization instead of tensile testing or other traditional methods is investigated. The approach is to use an analytical cutting model to map the measurable out-puts of cutting experiments to material deformation characteristics. The method is validated with simulations. Additionally, a new material model is investigated for modeling work material thermal softening damping behavior that was observed during the state-of-the-art method. The research is done with cutting experiments, analytical modeling, materials testing, and simulations. The results show that using the cutting experiments as a materials testing method has practical potential. It is also observed that the testing conditions in traditional methods of tensile testing and SHPB testing are not completely compatible with metal cutting conditions.
    Translated title of the contributionMateriaalimallien kehitys ja materiaaliparametrien määrittäminen lastuavan työstön simulointia varten
    Original languageEnglish
    QualificationDoctor's degree
    Awarding Institution
    • Aalto University
    Supervisors/Advisors
    • Niemi, Esko, Supervising Professor
    Publisher
    Print ISBNs978-952-60-6523-6
    Electronic ISBNs978-952-60-6524-3
    Publication statusPublished - 2015
    MoE publication typeG5 Doctoral dissertation (article)

    Keywords

    • finite element method
    • metal cutting
    • Johnson-Cook model
    • inverse analysis
    • graph analysis
    • SHPB
    • turning
    • cutting force
    • Oxley's model
    • parallel sided shear zone model

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