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    Wyświetlanie 1-11 z 11
    Tytuł:
    On the behaviour of viscoelastic solids under multiaxial loads
    Autorzy:
    Kolenda, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/259866.pdf
    Data publikacji:
    2008
    Wydawca:
    Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
    Tematy:
    viscoelastic material
    multiaxial stress
    constitutive equations
    static load
    vibratory load
    Opis:
    On the basis of modified Hooke’s law for multiaxial stress in viscoelastic solids, threedimensional constitutive equations for strains have been derived. It is shown that after application or removal of triaxial static load, normal and shear strain components vary in course of time proportionally to each other and that in-phase stress components produce in-phase strain components. Harmonic out-of-phase stress as well as multiaxial periodic and stationary random stresses are also considered. The matrix of dynamical flexibility of viscoelastic materials is determined which depends on three material constants (Young modulus, Poisson’s ratio and coefficient of viscous damping of normal strain) and load circular frequency.
    Źródło:
    Polish Maritime Research; 2008, 3; 12-17
    1233-2585
    Pojawia się w:
    Polish Maritime Research
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Seismic material properties of reinforced concrete and steel casing composite concrete in elevated pile-group foundation
    Autorzy:
    Zhou, M.
    Yuan, W.
    Zhang, Y.
    Powiązania:
    https://bibliotekanauki.pl/articles/963367.pdf
    Data publikacji:
    2015
    Wydawca:
    Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
    Tematy:
    pseudo-static tests
    material properties
    reinforced concrete
    steel composite concrete
    Opis:
    The paper focuses on the material mechanics properties of reinforced concrete and steel casing composite concrete under pseudo-static loads and their application in structure. Although elevated pile-group foundation is widely used in bridge, port and ocean engineering, the seismic performance of this type of foundation still need further study. Four scale-specimens of the elevated pile-group foundation were manufactured by these two kinds of concrete and seismic performance characteristic of each specimen were compared. Meanwhile, the special soil box was designed and built to consider soil-pile-superstructure interaction. According to the test result, the peak strength of strengthening specimens is about 1.77 times of the others and the ultimate displacement is 1.66 times of the RC specimens. Additionally, the dissipated hysteric energy capability of strengthening specimens is more than 2.15 times of the others as the equivalent viscous damping ratio is reduced by 50%. The pinching effect of first two specimens is more obvious than latter two specimens and the hysteretic loops of reinforced specimens are more plumpness. The pseudo-static tests also provided the data to quantitatively assessment the positive effect of steel casing composite concrete in aseismatic design of bridge.
    Źródło:
    Polish Maritime Research; 2015, S 1; 141-148
    1233-2585
    Pojawia się w:
    Polish Maritime Research
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Dissipation energy in viscoelastic solids under multiaxial loads
    Autorzy:
    Kolenda, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/258656.pdf
    Data publikacji:
    2008
    Wydawca:
    Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
    Tematy:
    viscoelastic material
    multiaxial stress
    energy dissipation
    static load
    vibratory load
    Opis:
    On the basis of the three-dimensional constitutive equations for strains resulting from the Kelvin-Voigt’s model and modified Hooke’s law for multiaxial stress in viscoelastic solids, the formulae for the energy dissipated in a given time per unit volume have been derived. It is shown that after application or removal of triaxial static load there is no difference in the time functions governing the dissipation of strain energy of volume change and the dissipation of strain energy of distortion. Harmonic in-phase stress and harmonic out-of-phase stress as well as multiaxial periodic stress are also considered. It is demonstrated that in the process of energy dissipation due to normal and shear stress components the role of the latter is dominant.
    Źródło:
    Polish Maritime Research; 2008, 1; 19-28
    1233-2585
    Pojawia się w:
    Polish Maritime Research
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    New designs of centrifugal magnetic fluid seals for rotating shafts in marine technology
    Autorzy:
    Matuszewski, Leszek
    Powiązania:
    https://bibliotekanauki.pl/articles/260045.pdf
    Data publikacji:
    2019
    Wydawca:
    Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
    Tematy:
    magnetic fluids
    ferrofluids
    lubricants
    magnetic seals
    static seals
    rotational seals
    Opis:
    The centrifugal magnetic fluid seals have important advantage over the conventional centrifugal seals. They maintain very good sealing capacity at static, medium and high speeds of shaft rotation, with the increased seal lifetime, and minimum torque and static friction. These seals are particularly useful in cases when the angular shaft velocity varies and sometimes decreases to nearly or exactly zero, such as in flywheel applications, ship propeller main shafts, etc. Unique properties of the magnetic fluid give rare opportunities for application in marine design, where perfect sealing together with reliable lubrication are required. The paper presents a typical design and operation principle of a centrifugal magnetic fluid shaft seal, along with new design solutions. Not only in ocean technology and underwater robotics. Some cases of application of centrifugal magnetic fluid seals in modern sealing technology are included.
    Źródło:
    Polish Maritime Research; 2019, 2; 33-46
    1233-2585
    Pojawia się w:
    Polish Maritime Research
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Failure criteria of viscoelastic materials under multiaxial loads
    Autorzy:
    Kolenda, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/258612.pdf
    Data publikacji:
    2009
    Wydawca:
    Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
    Tematy:
    viscoelastic material
    multiaxial stress
    fatigue criteria
    yield criterion
    static load
    vibratory load
    Opis:
    The load capacity of homogeneous, isotropic viscoelastic materials subjected to multiaxial stresses is considered. For this purpose uniaxial equivalent stresses in selected load cases are determined and relevant criteria applied. It is shown that in the case of constant load the yield criterion does not differ from that for perfectly elastic materials. Similar conclusion has been drawn for the fatigue and yield criteria at in-phase and out-of-phase stresses. On the contrary, the criteria derived for viscoelastic materials subjected to periodic loads do not coincide with those for perfectly elastic materials.
    Źródło:
    Polish Maritime Research; 2009, 1; 13-21
    1233-2585
    Pojawia się w:
    Polish Maritime Research
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Experimental study of the nonlinear behaviour of deep-sea mooring polyester fibre ropes
    Autorzy:
    Zhang, He
    Zeng, Ji
    Jin, Bowen
    Chou, Chiate
    Li, Hangyu
    Dong, Hailei
    Powiązania:
    https://bibliotekanauki.pl/articles/34611198.pdf
    Data publikacji:
    2023
    Wydawca:
    Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
    Tematy:
    polyester fibre ropes
    static stiffness
    creep coefficient
    long-term cyclic loads
    dynamic stiffness
    Opis:
    Mooring ropes are essential components of ships and offshore floating structures and they are subjected to cyclic axial loads. This study investigates the evolution of the full-cycle stiffness of fibre polyester ropes under long-term static and dynamic loading. First, the static stiffness characteristics of the ropes, including the rope elongation properties at different stages, shrinkage rates, and creep coefficients after an idle period, are examined under static loads; an empirical formula for static stiffness is established. Second, the dynamic stiffness characteristics of the ropes are investigated under cyclic loads that are typical of platform production operations. The stabilities of the structure under different tensions are compared; the effects of mean tension, tension amplitude, and load cycle on the dynamic stiffness of the ropes are analysed and an empirical formula is established to predict the dynamic stiffness during the engineering design phase. The results of this study can be helpful for the rational design of deep-sea taut-leg mooring systems because they present the evolution of the full-cycle stiffness characteristics of mooring ropes.
    Źródło:
    Polish Maritime Research; 2023, 3; 153-162
    1233-2585
    Pojawia się w:
    Polish Maritime Research
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Stiffness characteristics and thermal deformations of the frame of high power marine engine
    Autorzy:
    Murawski, L.
    Szmyt, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/260332.pdf
    Data publikacji:
    2007
    Wydawca:
    Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
    Tematy:
    marine main engine
    main bearing
    static and dynamic stiffness characteristics of bearing
    thermal deformation
    temperature distribution
    Opis:
    In the subject-matter literature detail data on stiffness of the crankshaft foundation connected with the frame of marine main engine are still lacking. Thermal deformation models of the engine’s casing, proposed by engine producers, are excessively simplified. However the parameters are crucial for the shaft-line alignment analysis as well as for the analysis of interactions between the shaft-line and engine crankshaft, especially in the case of high power engines. This paper presents a determination method of the marine engine body characteristics as well as results of example computations performed for a Sulzer 7 RTA 84 C engine installed on a ~3000 TEU container ship. It has been demonstrated that the producer’s assumption about parallel displacement of the crankshaft axis in thermal working conditions is too rough. The thermal deformation of the engine is of hogging character, which results in significant change of the moment load exerted on the crankshaft and shaft line. The stiffness parameters recommended by the producers for the shaft-line alignment are estimated correctly, however they represent only engine’s body flexibility, without taking into account ship’s hull flexibility.
    Źródło:
    Polish Maritime Research; 2007, 1; 16-22
    1233-2585
    Pojawia się w:
    Polish Maritime Research
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Pseudo-static experiment and analysis on seismic behavior of the RC columns strengthened by GHPFRCC
    Autorzy:
    Li, X.
    Wang, J.
    Luo, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/259179.pdf
    Data publikacji:
    2015
    Wydawca:
    Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
    Tematy:
    green high performance fiber reinforced cementitious composites (GHPFRCC)
    pseudo-static test
    reinforced concrete column
    strengthening
    seismic performance
    Opis:
    Green high performance fiber reinforced cementitious composites (GHPFRCC) are a new class of sustainable cementitious composites, employing a high volume of fly ash to replace cement. In addition to increasing the sustainability of the construction environment, GHPFRCC exhibits a high tensile ductility and multiple cracking behaviors in the strainhardening state. These materials can effectively improve the structural energy dissipation capacity and structural durability. In this study, the optimum mixture ratio of GHPFRCC is presented established using an orthogonal experiment for a specific engineering application. The described GHPFRCC sustains the mechanical performance of concrete and is employed as the outer cladding to strengthen concrete columns. The finite element analysis of the material was based on the software ABAQUS and pseudo static experiments were conducted to exhibit retrofitting of GHPFRCC applied in the rehabilitation of seismic-damaged concrete columns. The computed and experimental results showed that GHPFRCC, while incorporating high volume fly ash, can retain significant multiple cracking behaviors. The energy dissipation capacity of the GHPFRCC reinforced concrete (RC) column is better than the comparable unreinforced column.
    Źródło:
    Polish Maritime Research; 2015, S 1; 56-60
    1233-2585
    Pojawia się w:
    Polish Maritime Research
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Position accuracy evaluation of the modernized Polish DGPS
    Autorzy:
    Dziewicki, M.
    Szpecht, C.
    Powiązania:
    https://bibliotekanauki.pl/articles/259101.pdf
    Data publikacji:
    2009
    Wydawca:
    Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
    Tematy:
    radionavigation
    DGPS position
    DGPS transmission;
    accuracy evaluation
    static position measurement
    absolute accuracy
    sccatter plot
    GPS monitoring
    ellipsoid transformation
    Opis:
    Polish Maritime DGPS system has been modernized to meet the requirements set out in IMO resolution for a future GNSS, but also to preserve backward signal compatibility of user equipment. Having finalized installation of the new technology L1, L2 reference equipment performance tests were performed. This paper presents results of the long-term signal measuring campaign of the DGPS reference station Rozewie, which was performed in July 2009. Final results allowed to verify repeatable and absolute accuracy of the system after the modernization. Obtained statistics were compared to past measurements performed in 2005 when previous system infrastructure was in operation.
    Źródło:
    Polish Maritime Research; 2009, 4; 57-61
    1233-2585
    Pojawia się w:
    Polish Maritime Research
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Irregularity of static working states of ship combustion piston engine
    Autorzy:
    Chłopek, Z.
    Piaseczny, L.
    Powiązania:
    https://bibliotekanauki.pl/articles/259660.pdf
    Data publikacji:
    2006
    Wydawca:
    Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
    Tematy:
    silniki spalinowe
    warunki statyczne
    zakłócenia
    hałas
    hałas niewspółzależny
    combustion piston engine
    static conditions
    statistics
    broad-band noise
    uncorrelated noise
    Opis:
    Variability of static working conditions of combustion engine in the range of higher frequencies has character of noise resulting from phenomena not taken directly into account in test program as well as from features of measuring systems. Knowledge of features of the noise contained in observed static signals is important for determining the representative values taken as static and slow-changeable in conditions of unavoidable disturbances. The tests in question were carried out in the static working conditions of a 6AL 20/24 Sulzer diesel engine, determined by the torque Me = 4.33 kNm and the rotational speed n = 660 min-1. The following quantities characterizing emission of pollutants contained in exhaust gas in the conditions described by the engine working point : torque, rotational speed and concentrations of carbon oxide, hydrocarbons and nitrogen oxides, were selected for analyses. The tests were performed in the domains of time, process values and frequency. It was stated that the observed runs of the noise generated by phenomena not directly accounted for in combustion engine static test program and by measuring systems, had mainly the character of uncorrelated broad-band normal noise. The results justify a.o. correctness of averaging the measurement results obtained in static conditions as well as synchronous averaging in steady conditions.
    Źródło:
    Polish Maritime Research; 2006, 2; 9-14
    1233-2585
    Pojawia się w:
    Polish Maritime Research
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Dynamic response analysis of light weight pyramidal sandwich plates subjected to water impact
    Autorzy:
    Wang, Hao
    Zhao,, Fei
    Liu, Jun
    Tian, Yuan
    Powiązania:
    https://bibliotekanauki.pl/articles/259878.pdf
    Data publikacji:
    2012
    Wydawca:
    Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
    Tematy:
    light weight pyramidal sandwich plate structures (LWPSPS)
    multi-physics numerical model
    maximum deformation
    quasi-static
    local air cushion
    Yuan-Sheng Cheng
    Opis:
    The fluid-solid interaction (FSI) dynamic responses for a Light Weight Pyramidal Sandwich Plate Structure (LWPSPS) under different water-entry velocities (1m/s-6m/s) are investigated numerically and theoretically. The characteristics of impact pressure and structure deformation are obtained by using LS-DYNA code based on the proposed 3D multi-physics (air-water-solid) FEM model. Numerical results show that the average water impact pressure of LWPSPS is much lower than that of the monolithic plate with same mass. Moreover, a phenomenon called “local air cushion” is observed for LWPSPS which does not exist for a monolithic plate. Theoretical hydroelasticity analysis demonstrates that the FSI effect of LWPSPS is weak when the ratio of water impact duration time to wet natural vibration period is greater than 4. In the study, an engineering estimation method to predict the maximum deformation of the LWPSPS is proposed, in which the total deformation is divided into two parts, i.e. local field deformation and global field deformation, and they are both computed using analytical model. Good agreement between the numerical results and ones obtained from the proposed engineering estimation method is achieved. Furthermore, the geometric variation sensitiveness analysis is also conducted.
    Źródło:
    Polish Maritime Research; 2012, 4; 31-43
    1233-2585
    Pojawia się w:
    Polish Maritime Research
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
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