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    Wyświetlanie 1-7 z 7
    Tytuł:
    Determination of crack initiation and propagation in two disc shaped specimens using the improved maximum tangential stress criterion
    Autorzy:
    Eftekhari, M.
    Baghbanan, A.
    Mohtarami, E.
    Hashemolhosseini, H.
    Powiązania:
    https://bibliotekanauki.pl/articles/949128.pdf
    Data publikacji:
    2017
    Wydawca:
    Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
    Tematy:
    Extended Finite Element Method (XFEM)
    maximum tangential stress (MTS) criterion
    improved maximum tangential stress (IMTS) criterion
    crack propagation
    stress intensity factor
    Opis:
    The crack initiation angle and propagation path for two different disc shaped test specimens (i.e., SCB and CBD specimen) are investigated experimentally and theoretically. The Maximum Tangential Stress (MTS) criterion does not calculate the crack initiation angle in SCB and CBD specimens correctly. Moreover, at the angles after occurrence of pure mode II, where the stress intensity factor of mode I becomes negative, this criterion is not applicable. Therefore, in this research work, Improved MTS (IMTS) criterion which has been implemented in the extended finite element method and is applicable under tensile and compressive loading conditions to examine the crack propagation path in the aforementioned disc shaped specimens. Furthermore, an experimental study on a cracked Brazilian disc specimen has been conducted at different angles. Results of IMTS criterion in these specimens show that the crack propagation path and the crack initiation angle can be predicted theoretically by using IMTS criterion.
    Źródło:
    Journal of Theoretical and Applied Mechanics; 2017, 55, 2; 469-480
    1429-2955
    Pojawia się w:
    Journal of Theoretical and Applied Mechanics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Thermoelastic strongly nonlinear vibration of rotating functionally graded ring plate
    Autorzy:
    Hu, Yu Da
    Bao, Hai Jun
    XU, Hao Ran
    Powiązania:
    https://bibliotekanauki.pl/articles/1839696.pdf
    Data publikacji:
    2021
    Wydawca:
    Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
    Tematy:
    functionally graded ring plate
    natural vibration
    rotational motion
    strong nonlinearity
    improved L-P method
    Opis:
    For a metal ceramic functionally graded (FGM) ring plate, considering variations in physical properties with temperature and a power-law distribution of material components along the thickness direction, thermoelastic coupled nonlinear vibration equation in thermal environment is derived by means of Kirchhoff’s thin plate theory and the Hamiltonian principle. The transverse nonlinear vibration differential equation of the inner and outside-clamped ring plate under static load is obtained by using the Galerkin method; moreover, perturbation solution of static deflection is carried out. An improved L-P method is employed to solve the strongly nonlinear vibration equation. The vibration response and nonlinear natural frequency expression are developed. Through numerical examples, natural frequency characteristic curves of the rotating FGM ring plate are plotted. The Runge Kutta method is applied to obtain vibration response, phase and power spectrum diagrams. The influence of different parameters on natural vibration characteristics is analyzed. The results show that analytical solutions are consistent with numerical solutions, and the natural frequency decreases with an increase in the metal content and surface temperature, but grows with an increase in the rotational speed.
    Źródło:
    Journal of Theoretical and Applied Mechanics; 2021, 59, 1; 157-171
    1429-2955
    Pojawia się w:
    Journal of Theoretical and Applied Mechanics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Numerical Simulations for Solving Fuzzy Fractional Differential Equations by max-min Improved Euler Methods
    Autorzy:
    Khan, N. A.
    Razzaq, O. A.
    Riaz, F.
    Powiązania:
    https://bibliotekanauki.pl/articles/108688.pdf
    Data publikacji:
    2015
    Wydawca:
    Społeczna Akademia Nauk w Łodzi
    Tematy:
    fuzzy
    improved Euler method
    numerical solution
    Mathematica 10
    Opis:
    In this paper, an extension is introduced into Max-Min Improved Euler methods for solving initial value problems of fuzzy fractional differential equations (FFDEs). Two modified fractional Euler type methods have been proposed and investigated to obtain numerical solutions of linear and nonlinear FFDEs. The proposed algorithms are tested on various illustrative examples. Exact values are also simulated to compare and discuss the closeness and accuracy of approximations so obtained. Comparatively, tables and graphs results reveal the complete reliability, efficiency and accuracy of the proposed methods.
    Źródło:
    Journal of Applied Computer Science Methods; 2015, 7 No. 1; 53-83
    1689-9636
    Pojawia się w:
    Journal of Applied Computer Science Methods
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Path following control of the underactuated USV based on the improved line-of-sight guidance algorithm
    Autorzy:
    Liu, T.
    Dong, Z.
    Du, H.
    Song, L.
    Mao, Y.
    Powiązania:
    https://bibliotekanauki.pl/articles/259559.pdf
    Data publikacji:
    2017
    Wydawca:
    Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
    Tematy:
    unmanned surface vessel (USV)
    path following control
    Serret-Frenet coordinate frame
    underactuated system
    improved lineof-sight guidance algorithm
    nonlinear backstepping method
    Opis:
    The path following control problem of the underactuated unmanned surface vessel (USV) is studied in this paper. An improved line-of-sight (LOS) guidance algorithm is proposed which can adjust adaptively based on the path following error. The global asymptotically stable path following controller is designed based on the nonlinear backstepping method and the Lyapunov stability theory. Firstly, the USV path following error model is established in the Serret-Frenet (SF) coordinate frame. The path following error in the inertial coordinate frame is transformed into the SF coordinate frame, which is used to define the path following control problem. Secondly, inspired by the traditional LOS guidance algorithm, the longitudinal path following error in the SF coordinate frame is introduced into the improved LOS guidance algorithm. This allows the algorithm to adjust adaptively to the desired path. Thirdly, in order to solve the underactuated problem of the USV path following control system, the tangential velocity of the desired path is designed as a virtual input. The underactuated problem is converted to a virtual fully actuated problem by designing the virtual control law for the tangential velocity. Finally, by combining backstepping design principles and the Lyapunov stability theory, the longitudinal thrust control law and the yaw torque control law are designed for the underactuated USV. Meanwhile, the global asymptotic stability of the path following error is proved. Simulation experiments demonstrate the effectiveness and reliability of the improved LOS guidance algorithm and the path following controller.
    Źródło:
    Polish Maritime Research; 2017, 1; 3-11
    1233-2585
    Pojawia się w:
    Polish Maritime Research
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Smart Substation Network Fault Classification Based on a Hybrid Optimization Algorithm
    Autorzy:
    Xia, Xin
    Liu, Xiaofeng
    Lou, Jichao
    Powiązania:
    https://bibliotekanauki.pl/articles/227220.pdf
    Data publikacji:
    2019
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    smart substation
    network fault classification
    improved separation interval method (ISIM)
    support vector
    machine (SVM)
    Anti-noise processing (ANP)
    Opis:
    Accurate network fault diagnosis in smart substations is key to strengthening grid security. To solve fault classification problems and enhance classification accuracy, we propose a hybrid optimization algorithm consisting of three parts: anti-noise processing (ANP), an improved separation interval method (ISIM), and a genetic algorithm-particle swarm optimization (GA-PSO) method. ANP cleans out the outliers and noise in the dataset. ISIM uses a support vector machine (SVM) architecture to optimize SVM kernel parameters. Finally, we propose the GA-PSO algorithm, which combines the advantages of both genetic and particle swarm optimization algorithms to optimize the penalty parameter. The experimental results show that our proposed hybrid optimization algorithm enhances the classification accuracy of smart substation network faults and shows stronger performance compared with existing methods.
    Źródło:
    International Journal of Electronics and Telecommunications; 2019, 65, 4; 657-663
    2300-1933
    Pojawia się w:
    International Journal of Electronics and Telecommunications
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    An improved feature extraction method for rolling bearing fault diagnosis based on MEMD and PE
    Autorzy:
    Zhang, H.
    Zhao, L.
    Liu, Q.
    Luo, J.
    Wei, Q.
    Zhou, Z.
    Qu, Y.
    Powiązania:
    https://bibliotekanauki.pl/articles/259770.pdf
    Data publikacji:
    2018
    Wydawca:
    Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
    Tematy:
    improved feature extraction method
    rolling bearing fault diagnosis
    MEMD
    PE
    Opis:
    The health condition of rolling bearing can directly influence to the efficiency and lifecycle of rotating machinery, thus monitoring and diagnosing the faults of rolling bearing is of great importance. Unfortunately, vibration signals of rolling bearing are usually overwhelmed by external noise, so the fault frequencies of rolling bearing cannot be readily obtained. In this paper, an improved feature extraction method called IMFs_PE, which combines the multivariate empirical mode decomposition with the permutation entropy, is proposed to extract fault frequencies from the noisy bearing vibration signals. First, the raw bearing vibration signals are filtered by an optimal band-pass filter determined by SK to remove the irrelative noise which is not in the same frequency band of fault frequencies. Then the filtered signals are processed by the IMFs_PE to get rid of the relative noise which is in the same frequency band of fault frequencies. Finally, a frequency domain condition indicator FFR(Fault Frequency Ratio), which measures the magnitude of fault frequencies in frequency domain, is calculated to compare the effectiveness of the feature extraction methods. The feature extraction method proposed in this paper has advantages of removing both irrelative noise and relative noise over other feature extraction methods. The effectiveness of the proposed method is validated by simulated and experimental bearing signals. And the results are shown that the proposed method outperforms other state of the art algorithms with regards to fault feature extraction of rolling bearing.
    Źródło:
    Polish Maritime Research; 2018, S 2; 98-106
    1233-2585
    Pojawia się w:
    Polish Maritime Research
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Improvement of Cauchy integral method for the stresses and displacements around the deeply-buried non-circular tunnel
    Autorzy:
    Zhou, Yulin
    Lu, Aizhong
    Cai, Hui
    Ma, Yaocai
    Powiązania:
    https://bibliotekanauki.pl/articles/2086948.pdf
    Data publikacji:
    2022
    Wydawca:
    Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
    Tematy:
    non-circular tunnel
    Cauchy integral method
    stress and displacement
    abnormal calculations
    improved method
    Opis:
    For a deeply-buried non-circular tunnel, abnormal stress and displacement arise in the region far away from the excavation boundary when the Cauchy integral method is applied. It is found that the calculation error is induced by a polynomial in the analytical function. An improved method is proposed by expanding the polynomial as a power series. The improved method is suitable for calculating the stress and displacement in the whole surrounding rock. The results obtained by the improved method are in good agreement with the numerical results of ANSYS, which proves the effectiveness of the proposed method.
    Źródło:
    Journal of Theoretical and Applied Mechanics; 2022, 60, 1; 153--166
    1429-2955
    Pojawia się w:
    Journal of Theoretical and Applied Mechanics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-7 z 7

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