Search Results (4)

In this paper, the influence of the viscoelasticity of boundary constraints on the forced vibration of the nonlinear forced resonance of a fluid-conveying layered pipe under an external forced excitation is studied. The pipe lays on viscoelastic foundations and is simply supported at both ends, and one end is subject to a viscoelastic boundary constraint. The Kelvin–Voight model was employed to describe the viscoelasticity provided by the foundation and boundary constraint. Hamilton’s variational principle was used to obtain the governing equations, during which geometric nonlinear factors including curvature nonlinearity and inertia nonlinearity were considered. By employing a perturbation-incremental harmonic balance method (IHBM), amplitude–frequency bifurcation diagrams of the pipe were obtained. The results show that the viscoelastic constraints from the boundary and foundation have significant influence on the linear and nonlinear dynamic behavior of the pipe system. Full article

Hollow floors are widely used in structures with a large span that bear a large load. In this study, we propose a hollow floor with built-in corrugated pipes as a filling material that has the advantages of a lighter weight, higher stiffness, and lower cost than traditional floors. We first propose a novel form of stiffness by coupling the anisotropies of the material and the structure. This concept is then used to develop a theoretical formula to compute the deflection of a hollow slab set using corrugated pipes on simply supported and fixed constraints on opposite sides. We then use static loading tests to show that this hollow slab has excellent ductility and load-bearing capacity. Following this, we design a mixed finite element model of the hollow slab to predict its deflection by considering concrete, steel, and corrugated tubes. We then use six reference points on the hollow slab to verify the model in comparison with the results of the static loading test and the theoretical formula. The results show that while the maximum deformation occurred at point a₁ in the middle of the slab, the maximum errors among the results of the theoretical formula, static loading tests, and the finite element model occurred at point a₂. The maximum and minimum errors between the results of the theoretical prediction and the outcomes of the static loading test were 9.09% and 0%, while those between the results of the theoretical prediction and the finite element model were 8.92% and 1.19%, respectively. The proposed hollow slab, set using thin-walled corrugated tubes, can be used in a variety of engineering designs. Full article

In this study, the Kevin–Voigt viscoelastic constitutive relationship is used to investigate the vibration characteristics and stability of a functionally graded viscoelastic(FGV) fluid-conveying pipe with initial geometric defects under thermal–magnetic coupling fields. First, the nonlinear dimensionless differential equations of motion are derived by applying Timoshenko beam theory. Second, by solving the equilibrium position of the system, the nonlinear term in the differential equations of motion is approximated as the sum of the longitudinal displacement at the current time and longitudinal displacement relative to the position, and the equations are linearized. Third, these equations are discretized using the Galerkin method and are numerically solved under simply supported conditions. Finally, the effects of dimensionless temperature field parameters, dimensionless magnetic field parameters, thermal–magnetic coupling, initial geometric defect types, and the power-law exponent on the complex frequency of the pipe are examined. Results show that increasing the magnetic field intensity enhances the critical velocity of first-order mode instability, whereas a heightened temperature variation reduces the critical velocity of first-order diverge instability. Under thermal–magnetic fields, when the magnetic field intensity and temperature difference are simultaneously increased, their effects on the complex frequency can partially offset each other. Increasing the initial geometric defect amplitude increases the imaginary parts of the complex frequencies; however, for different types of initial geometric defect tubes, it exhibits the most distinct influence only on a certain order. Full article

The dynamic responses of simply supported horizontal pipes conveying gas-liquid two-phase slug flow are explored. The intermittent characteristics of slug flow parameters are mainly considered to analyze the dynamic model of the piping system. The results show that the variations of the midpoint transverse displacement could vary from periodic-like motion to a kind of motion whose amplitude increases as time goes on if increasing the superficial gas velocity. Meanwhile, the dynamic responses have certain relations with the vibration acceleration. By analyzing the parameters in the power spectrum densities of vibration acceleration such as the number of predominant frequencies and the amplitude of each peak frequency, the dynamic behaviors of the piping system like periodicity could be calculated expediently. Full article