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    Wyświetlanie 1-5 z 5
    Tytuł:
    Investigation of biomechanics of skull structures damages caused by dynamic loads
    Autorzy:
    Ptak, M.
    Ratajczak, M.
    Kwiatkowski, A.
    Sawicki, M.
    Wilhelm, J.
    Fernandes, F. A. O.
    Druszcz, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/306216.pdf
    Data publikacji:
    2018
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    czaszka
    urazy
    biomechanika
    FEM
    skull fracture
    biomechanics
    cranial sutures
    vulnerable road user
    finite element method
    Opis:
    The aim of the study was to examine the influence of cranial sutures on the crack behaviour of a human skull after the impact. The authors focused on the assessment of skull breaking nature, based on a real-world vehicle-to-bicyclist accident. In the state of the art, there is still no consensus about sutures mechanical properties. Currently, most of the numerical head models do not have distinguished cranial sutures. Methods: The authors compared different elastic properties for cranial sutures and their influence on the nature of the skull fracture. The mathematical and numerical modelling have been applied to mimic the nature of the skull fracture. The LS-DYNA explicit code with material models featuring the erosion of finite elements was used. The models of the skull with different cranial sutures properties were impacted against a validated front-end of a vehicle. Results: Various fracture patterns were obtained for different material properties of the sutures and the results were compared to a model without the cranial sutures. Based on the results, a graph was plotted to indicate differences in sutures energy absorption capabilities. The numerical results were supported by the mathematical modelling. The developed diagram may enable better understanding of the complex mechanical phenomena on the suture interface. Conclusions: Biomechanical evidence was provided for the important role of the sutures in numerical models as well as their significant influence on the biomechanics of skull fractures caused by dynamic loads.
    Źródło:
    Acta of Bioengineering and Biomechanics; 2018, 20, 4; 143-150
    1509-409X
    2450-6303
    Pojawia się w:
    Acta of Bioengineering and Biomechanics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Assessment of susceptibility to liquefaction of saturated road embankment subjected to dynamic loads
    Autorzy:
    Borowiec, A.
    Maciejewski, K.
    Powiązania:
    https://bibliotekanauki.pl/articles/178526.pdf
    Data publikacji:
    2014
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    liquefaction susceptibility
    soil dynamic
    seismic lads
    vibrations propagation in soil
    dynamika gruntów
    propagacja drgań w gruncie
    Opis:
    Liquefaction has always been intensely studied in parts of the world where earthquakes occur. However, the seismic activity is not the only possible cause of this phenomenon. It may in fact be triggered by some human activities, such as constructing and mining or by rail and road transport. In the paper a road embankment built across a shallow water reservoir is analyzed in terms of susceptibility to liquefaction. Two types of dynamic loadings are considered: first corresponding to an operation of a vibratory roller and second to an earthquake. In order to evaluate a susceptibility of soil to liquefaction, a factor of safety against triggering of liquefaction is used (FSTriggering). It is defined as a ratio of vertical effective stresses to the shear stresses both varying with time. For the structure considered both stresses are obtained using finite element method program, here Plaxis 2D. The plastic behavior of the cohesionless soils is modeled by means of Hardening Soil (HS) constitutive relationship, implemented in Plaxis software. As the stress tensor varies with time during dynamic excitation, the FSTriggering has to be calculated for some particular moment of time when liquefaction is most likely to occur. For the purposes of this paper it is named a critical time and established for reference point at which the pore pressures were traced in time. As a result a factor of safety distribution throughout embankment is generated. For the modeled structure, cyclic point loads (i.e., vibrating roller) present higher risk than earthquake of magnitude 5.4. Explanation why considered structure is less susceptible to earthquake than typical dam could lay in stabilizing and damping influence of water, acting here on both sides of the slope. Analogical procedure is applied to assess liquefaction susceptibility of the road embankment considered but under earthquake excitation. Only the higher water table is considered as it is the most unfavorable. Additionally the modified factor of safety is introduced, where the dynamic shear stress component is obtained at a time step when its magnitude is the highest – not necessarily at the same time step when the pore pressure reaches its peak (i.e., critical time). This procedure provides a greater margin of safety as the computed factors of safety are smaller. Method introduced in the paper presents a clear and easy way to locate liquefied zones and estimate liquefaction susceptibility of the subsoil – not only in the road embankment.
    Źródło:
    Studia Geotechnica et Mechanica; 2014, 36, 1; 15-22
    0137-6365
    2083-831X
    Pojawia się w:
    Studia Geotechnica et Mechanica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Problems of modelling of dynamic loads acting on cranes caused by driving over uneven rails
    Autorzy:
    Jasiński, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/1189966.pdf
    Data publikacji:
    2018
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    dźwignice
    modelowanie obciążeń dynamicznych
    jazda po nierównościach
    cranes
    modeling of dynamic loads
    driving over uneven surfaces
    Opis:
    The article reviews the standards and literature describing the issue of determining dynamic loads acting on crane caused by travelling on uneven surfaces, the knowledge of which is essential for proper dimensioning of the supporting structures of cranes, in particular cranes for working at high movement speeds. It presents the factors significantly affecting the value of these dynamic loads. The article also demonstrates selected dynamic models of cranes and methodology of their building. Presented are the similarities and differences in the modeling of dynamic loads. Calculated values of the dynamic coefficients as well as discussion of the results are presented.
    Źródło:
    Interdisciplinary Journal of Engineering Sciences; 2018, 6, 1; 6--11
    2300-5874
    Pojawia się w:
    Interdisciplinary Journal of Engineering Sciences
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Wybrane problemy obliczania oddziaływań dynamicznych obiektów posadowionych na terenach szkód górnyczych
    SELECTED ISSUES OF COMPUTING DYNAMIC LOADS OF OBJECTS SITUATED ON MINING DAMAGE AREAS
    Autorzy:
    Bońkowski, Piotr
    Powiązania:
    https://bibliotekanauki.pl/chapters/39783065.pdf
    Data publikacji:
    2015
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    szkody górnicze
    oddziaływania parasejsmiczne
    Eurokody
    Opis:
    Artykuł porusza problemy związane z obliczaniem oddziaływań dynamicznych obiektów posadowionych na terenach szkód górniczych pochodzących od wstrząsu górotworu. W artykule zostały przedstawione zalecenia Eurokodu 8 co do projektowania konstrukcji, z uwzględnieniem praktyki krajowej obliczania konstrukcji poddanych oddziaływaniom parasejsmicznym.
    The article discusses problems associated with computing dynamic loads of objects situated on mining damage areas which come from earth shake. The article shows Eurocode 8 recommendations for designing, considering polish experience of designing buildings, which are being subject of paraseismic influences.
    Źródło:
    Konferencja Studentów i Doktorantów Wydziałów Budownictwa KONstruktor2015; 275-283
    9788374938815
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Dynamic load indicators for take-off–landing sequence in blocks and attacks of elite female volleyball players
    Autorzy:
    Kabaciński, J.
    Dworak, L. B.
    Murawa, M.
    Rzepnicka, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/307295.pdf
    Data publikacji:
    2016
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    siła reakcji podłoża
    obciążenie dynamiczne
    start
    atak
    biomechanika
    ground reaction forces
    take-off–landing
    dynamic loads
    blocks
    attacks
    volleyball
    biomechanics
    Opis:
    Purpose: Dynamic loads during landings determined by the ground reaction forces (GRFs) may elaborate internal loads and increase the risk of overload knee injuries as a result of performing volleyball jumps many times. The study dealt with a biomechanical assessment of dynamic load indicators in female volleyball players for the motion sequence of take-off–landing in blocks and attacks. Methods: Twelve professional female volleyball players participated in the study. Blocks and attacks were filmed by two cameras. GRFs vs. time graphs were recorded with the use of a force platform. Values of dynamic load indicators in terms of the relations of peak of vertical component of GRF, build-up index of this force (BIF), and power output (P) during landing to the vGRF, BIF and P during take-off (L/T) were calculated. Results: The statistically significant ( p < 0.05) highest values of L/T indicators were found for back row attack spikes: 2.4 (vGRF), 12.2 (BIF) and 3.1 (P). In the case of blocks, slide attack spikes and attack line spikes, results of these variables were in range: 1.8÷2.1, 5.9÷7.6 and 2.1÷2.9, respectively. Conclusions: The reduction of GRFs during landings contributes to decreasing the level of the load indicators L/T which should minimize the incidence of anterior cruciate ligament and patellar tendon injuries in female volleyball players.
    Źródło:
    Acta of Bioengineering and Biomechanics; 2016, 18, 1; 41-46
    1509-409X
    2450-6303
    Pojawia się w:
    Acta of Bioengineering and Biomechanics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-5 z 5

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