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    Wyświetlanie 1-3 z 3
    Tytuł:
    Micromechanical models of ductile fracture of metals
    Mikromechaniczne modele ciągliwego pękania metali
    Autorzy:
    Wciślik, W.
    Powiązania:
    https://bibliotekanauki.pl/articles/402155.pdf
    Data publikacji:
    2010
    Wydawca:
    Politechnika Świętokrzyska w Kielcach. Wydawnictwo PŚw
    Tematy:
    model pękania żeliwa sferoidalnego
    pustki
    ductile fracture models
    voids
    Opis:
    In the present paper a few models of ductile fracture were presented. Alloys used in civil engineering most often crack due to void nucleation and growth. Voids are created on the border between matrix and inclusions (made of sulphur and manganese compounds). The majority of described models can be used for modelling of ductile fracture in micro scale. The Gurson Tvergaard Needleman (GTN) material model was found to be the most useful in modelling of plastic deformation of existing steel elements and structures in civil engineering. This paper was presented at seminar for Ph.D. candidates at Kielce University of Technology.
    Źródło:
    Structure and Environment; 2010, 2. no. 4; 16-22
    2081-1500
    Pojawia się w:
    Structure and Environment
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Geometryzacja form zjawisk krasowych na podstawie badań metodą georadarową
    Geometrization of karst phenomena based on GPR research
    Autorzy:
    Ortyl, Łukasz
    Powiązania:
    https://bibliotekanauki.pl/articles/2075956.pdf
    Data publikacji:
    2019
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    metoda georadarowa
    kras
    wapienie
    jaskinia
    pustki
    modelowanie danych
    naziemne skanowanie laserowe
    ground penetrating radar
    GPR
    karst
    limestones
    cave
    voids
    finite differential time domain
    FDTD
    terrestrial laser scanning
    TLS
    Opis:
    Recognition of subsoil in areas threatened with discontinuous deformation associated with the existence of natural and mining voids can be implemented by various geophysical methods. The purpose of such research, apart from confirming the existence of voids, is to determine their spatial extent. This is not a simple issue, regardless of the geophysical method used. This paper discusses the possibilities of geometrization of karst phenomenon localization using the ground penetrating radar (GPR) method by the example of a karst cave as a natural void. The area of data acquisition is located on limestone formations with numerous karstforms. The study object is the main hall of the karst cave with a height of up to 3 m, located at a depth of 3 to 7 m below the surface. Such location and shape of the subsurface structure made it possible for the author to perform a wide range of research. Their original aspects are presented in this paper. The shape of the hall was obtained using terrestrial laser scanning (TLS). The GPR data were obtained employing the 250 MHz shielded antenna that was directly positioned using a robotized total station with the option of automatic target tracking. Thus, the GPR and geodetic data were immediately achieved in a uniform coordinate system. The accuracy of the data obtained in this way is discussed in this paper. The author’s original algorithm for processing of GPR data into a point cloud is presented. Based on the results obtained, it was possible to compare the GPR signal, which represents the shape of the cave hall, in relation to its image in the form of a point cloud from terrestrial laser scanning. A unique part of this paper is the selection of filtration procedures and their parameters in optimal GPR data processing, which were widely discussed and documented in a way beyond the standard filtration procedures. A significant contribution is the analysis that was carried out on the data obtained in the field and on the model data generated using the finite difference method. Modeling was carried out for two wave sources: exploding reflector and point. The presented methodology and discrimination between the actual shape of the cave, GPR field data and model data made it possible for the author to draw many conclusions related to the possibilities of shape geometrization of the subsurface voids determined by the GPR method.
    Źródło:
    Przegląd Geologiczny; 2019, 67, 4; 252--269
    0033-2151
    Pojawia się w:
    Przegląd Geologiczny
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Effect of initial porosity on material response under multi-axial stress state for S235JR steel
    Autorzy:
    Kossakowski, P. G.
    Powiązania:
    https://bibliotekanauki.pl/articles/230606.pdf
    Data publikacji:
    2012
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    porowatość początkowa
    objętość pustek początkowa
    model materiałowy Gurson-Tvergaard-Needleman
    stany naprężeń wieloosiowe
    naprężenie trójosiowe duże
    pustki
    obliczenia numeryczne
    stal S235JR
    initial porosity
    initial void volume fraction
    Gurson-Tvergaard-Needleman material model
    multi-axial stress states
    high stress triaxiality
    voids
    numerical calculations
    S235JR steel
    Opis:
    The effect of the initial porosity on the material response under multi-axial stress state for S235JR steel using the Gurson-Tvergaard-Needleman (GTN) material model was examined. Three levels of initial porosity, defined by the void volume fraction f0, were considered: zero porosity for fully dense material without pores, average and maximum porosity according to the metallurgical requirements for S235JR steel. The effect of the initial porosity on the material response was noticed for tensile elements under multi-axial stress state defined by high stress triaxiality sigma m/sigma e = 1.345. This effect was especially noticeable at the range of the material failure. In terms of the load-bearing capacity of the elements, the conservative results were obtained when maximum value of f0 = 0.0024 was used for S235JR steel under multi-axial stress state, and this value is recommended to use in the calculations in order to preserve the highest safety level of the structure. In usual engineering calculations, the average porosity defined by f0 = 0.001 may be applied for S235JR.
    Źródło:
    Archives of Civil Engineering; 2012, 58, 4; 445-462
    1230-2945
    Pojawia się w:
    Archives of Civil Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-3 z 3

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