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1
Content available remote Nonlinear forced vibration analysis of micro-rotating shaft-disk systems through a formulation based on the nonlocal strain gradient theory
Panahi Ramin, Asghari Mohsen, Borjalilou Vahid
Archives of Civil and Mechanical Engineering
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2023
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Vol. 23, no. 2
art. no. e85, 2023
EN
The paper presents an upgraded size-dependent formulation for micro-rotating shaft-disks system to study their nonlinear forced vibration behavior. The novel formulation is based on the nonlocal strain gradient theory (NSGT). To achieve this goal, first of all, by incorporating the geometrical nonlinearity within the Rayleigh beam theory, the governing equations of the lateral motion of the system are derived by the Hamilton principle and then converted into a complex form. By defning some dimensionless parameters, the normalized form of the complex governing equation is also extracted. In the next step, the Galerkin method is implemented to establish an infinite set of ordinary differential equations (ODEs). Then, with the help of the method of multiple scales, the nonlinear ODE is solved to attain the vibrational amplitude of the system as well as its forward and backward natural frequencies. Lastly, an all-out parametric study is conducted to appraise the impact of some important factors like the nonlocal theory parameter, the strain gradient length scale parameter, the rotational speed, the amount of mass eccentricity and the internal damping coeffcient on the motion amplitude and natural frequencies. The numerical outcomes illuminate well that depending on the relative value of two non-classical parameters of NSGT, this theory have the potential to reflect the hardening or softening attribute of small-scaled mechanical elements.
2
Content available Forced oscillation and asymptotic behavior of solutions of linear differential equations of second order
Shoukaku Yutaka
Opuscula Mathematica
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2022
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Vol. 42, no. 6
867--885
EN
The paper deals with the second order nonhomogeneous linear differential equation (p(t)y′(t))′ + q(t)y(t) = f(t), which is oscillatory under the assumption that p(t) and q(t) are positive, continuously differentiable and monotone functions on [0,∞). Throughout this paper we shall use pairs of quadratic forms, which obtained by different methods than Kusano and Yoshida. This form will lead to a property of qualitative behavior, including amplitudes and slopes, of oscillatory solutions of the above equation. In addition, we will discuss the existence of three types (moderately bounded, small, large) of oscillatory solutions, which are based on results due to Kusano and Yoshida.
3
Content available remote Forced oscillation measurements of seismic attenuation in fluid saturated sandstone
Subramaniyan S., Quintal B., Saenger E.
Acta Geophysica
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2017
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Vol. 65, no. 1
165--172
EN
Adopting the method of forced oscillation, attenuation was studied in Fontainebleau sandstone (porosity 10%, permeability 10 mD) at seismic frequencies (1–100 Hz). Confining pressures of 5, 10, and 15 MPa were chosen to simulate reservoir conditions. First, the strain effect on attenuation was investigated in the dry sample for 11 different strains across the range 1 × 10-6–8 × 10−6, at the confining pressure of 5 MPa. The comparison showed that a strain of at least 5 × 10-6 is necessary to obtain a good signal to noise ratio. These results also indicate that nonlinear effects are absent for strains up to 8 × 10-6. For all the confining pressures, attenuation in the dry rock was low, while partial (90%) and full (100%) saturation with water yielded a higher magnitude and frequency dependence of attenuation. The observed high and frequency dependent attenuation was interpreted as being caused by squirt flow.
4
Content available remote Exploitation of the universe with regard to controlled thermonucIear fusion reaction of the sun
Ghosh S. K.
International Journal of Applied Mechanics and Engineering
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2007
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Vol. 12, no 2
571-573
EN
A physical interpretation of relevance to a mathematical argument is the determination of the reality of the universe by applying a radio frequency accelerator with the Sun. The exploitation of the universe deals with the controlled thermonuclear fusion reaction of the Sun at the re sonant level to produce X-ray ernission subject to an irregular fluctuation of a magnetic field in vacuum.
5
Content available remote Report on plasma behavior over the interstellar medium
Ghosh S. K.
International Journal of Applied Mechanics and Engineering
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2006
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Vol. 11, no 4
981-983
EN
The authors in compliance with investigations (Ghosh, 1997; 2001; Ghosh and Pop, 2002) prove that resonance exhibits a thermonuclear fusion reaction over the Sun in the presence of an applied inclined magnetic field when a forced oscillation is taken into account. The interstellar space is a great deal of controversy when a forced oscillation is applied to the Sun.
6
Content available remote An analytical approach to MHD plasma behavior of a rotating environment in the presence of an inclined magnetic field as compared to excitation frequency
Ghosh S. K., Pop I.
International Journal of Applied Mechanics and Engineering
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2006
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Vol. 11, no 4
845-856
EN
We have examined the MHD plasma behavior of a rotating environment in the presence of an inclined magnetic field with the positive direction of the axis of rotation. The interplay of a hydromagnetic force and Coriolis force exerts its influence of a dynamo mechanism with reference to the solar and terrestrial context when the Hall current is taken into account. It is stated that the electrical discharge of the solar corona in the presence of a traveling magnetic field experiences an irregular fluctuation at the resonant level to produce thermonuclear fusion reaction of the Sun with regard to excitation frequency. On the other hand, the thermonuclear fusion reaction of the Sun stops when the excitation frequency is switched off and the MHD plasma flow tends to an equilibrium position with regard to a neutral plasma stability parameter.
7
Content available remote Oscillation properties for certain hyperbolic equations with distributed arguments
Peiguang W., Weigao G.
Demonstratio Mathematica
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2000
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Vol. 33, nr 1
83-89
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