scholarly journals Dynamic response of a simplified nonlinear fluid model for viscoelastic materials under random parameters

2011 ◽  
Vol 54 (11-12) ◽  
pp. 2587-2596
Author(s):  
T.-P. Chang
Keyword(s):  
Dynamic Response ◽  
Fluid Model ◽  
Random Parameters ◽  
Viscoelastic Materials ◽  
Nonlinear Fluid

Stochastic Dynamic Response of a Simplified Nonlinear Fluid Model for Viscoelastic Materials

2012 ◽  
Vol 28 (2) ◽  
pp. 365-372 ◽  
Author(s):  
T.-P. Chang
Keyword(s):  
Dynamic Response ◽  
Closed Form ◽  
Fluid Model ◽  
Closed Form Solution ◽  
Mean Value ◽  
Form Solution ◽  
Stochastic Dynamic ◽  
Viscoelastic Materials ◽  
Viscoelastic Modeling ◽  
Nonlinear Fluid

AbstractIn the present study, we propose a simplified nonlinear fluid model to characterize the complex nonlinear response of some viscoelastic materials. Recently, the viscoelastic modeling has been utilized by many researchers to simulate some parts of human body in bioengineering and to represent many material properties in mechanical engineering, electronic engineering and construction engineering. Occasionally it is almost impossible to evaluate the constant parameters in the model in the deterministic sense, therefore, the damping coefficient of the dashpot and the spring constants of the linear and nonlinear springs are considered as stochastic to model the stochastic properties of the viscoelastic materials. After some transformations, the closed-form solution can be obtained for the mean value of the displacement of the simplified nonlinear fluid model, subjected to constant rate of displacement. Based on the closed-form solution, the proposed method generates the stochastic dynamic response of the simplified nonlinear model, which plays an important role in performing the reliability analysis of the nonlinear system.

Statistical Response of a Simplified Nonlinear Fluid Model Under Random Parameters

2007 ◽  
Author(s):  
T-P. Chang
Keyword(s):  
Fluid Model ◽  
Closed Form Solution ◽  
Mean Value ◽  
Form Solution ◽  
Viscoelastic Materials ◽  
Nonlinear Springs ◽  
Constant Rate ◽  
Viscoelastic Modeling ◽  
Spring Constants ◽  
Nonlinear Fluid

In this paper, a simplified spring-dashpot model is proposed to represent the complicated nonlinear response of some viscoelastic materials. Recently, the viscoelastic modeling has been adopted by many researchers to characterize some parts of human body in bioengineering. Among others, the following researchers have already contributed to the development of this field (Weiss et al., [1]; Guedes et al., [2]). Sometimes it is impossible to estimate the constant parameters in the model deterministically, therefore, the damping coefficient of the dashpot and the spring constants of the linear and nonlinear springs are considered as stochastic to characterize the random properties of the viscoelastic materials. The mean value of the displacement of the nonlinear model, subjected to constant rate displacement, can be solved analytically. Based on the closed-form solution, the proposed method produces the statistical responses of the simplified nonlinear fluid model, which is fairly useful in estimating the reliability of the nonlinear system.

Improved nonlinear fluid model in rotating flow

2012 ◽  
Vol 33 (11) ◽  
pp. 1419-1430 ◽  
Author(s):  
N. Ashrafi ◽  
H. Karimi-Haghighi
Keyword(s):  
Fluid Model ◽  
Rotating Flow ◽  
Nonlinear Fluid

Multiple Dynamic Response Patterns of Flexible Multibody Systems With Random Uncertain Parameters

2019 ◽  
Vol 14 (2) ◽  
Author(s):  
Zhe Wang ◽  
Qiang Tian ◽  
Haiyan Hu
Keyword(s):  
Dynamic Response ◽  
Multibody System ◽  
Uncertain Parameters ◽  
Response Patterns ◽  
Algebraic Equations ◽  
Flexible Multibody System ◽  
Random Parameters ◽  
Collocation Points ◽  
Nonlinear Algebraic Equations ◽  
Flexible Multibody

The mechanisms with uncertain parameters may exhibit multiple dynamic response patterns. As a single surrogate model can hardly describe all the dynamic response patterns of mechanism dynamics, a new computation methodology is proposed to study multiple dynamic response patterns of a flexible multibody system with uncertain random parameters. The flexible multibody system of concern is modeled by using a unified mesh of the absolute nodal coordinate formulation (ANCF). The polynomial chaos (PC) expansion with collocation methods is used to generate the surrogate model for the flexible multibody system with random parameters. Several subsurrogate models are used to describe multiple dynamic response patterns of the system dynamics. By the motivation of the data mining, the Dirichlet process mixture model (DPMM) is used to determine the dynamic response patterns and project the collocation points into different patterns. The uncertain differential algebraic equations (DAEs) for the flexible multibody system are directly transformed into the uncertain nonlinear algebraic equations by using the generalized-alpha algorithm. Then, the PC expansion is further used to transform the uncertain nonlinear algebraic equations into several sets of nonlinear algebraic equations with deterministic collocation points. Finally, two numerical examples are presented to validate the proposed methodology. The first confirms the effectiveness of the proposed methodology, and the second one shows the effectiveness of the proposed computation methodology in multiple dynamic response patterns study of a complicated spatial flexible multibody system with uncertain random parameters.

Minimal Order Nonlinear Observer for Leak Detection

2004 ◽  
Vol 126 (3) ◽  
pp. 467-472 ◽  
Author(s):  
C. Verde
Keyword(s):  
Fluid Model ◽  
Practical Method ◽  
Nonlinear Observer ◽  
Minimal Order ◽  
Nonlinear Observers ◽  
Proposed Model ◽  
Robust Filters ◽  
Output Component ◽  
Nonlinear Fluid ◽  
Nonlinear Robust

A method for leaks location in a pipeline, using sensors only at the extremes of the line is presented. The detection problem is solved, assuming a nonlinear fluid model of finite dimension with uncertainty in the leak position, and generating the residual with two minimal order nonlinear observers. Flow and pressure data at the beginning and at end of the line are considered as output and input of the system respectively. Since the proposed model satisfies (1) the condition to generate a residual, assuming at the most two leaks, and (2) the strong detectability fault property for each output component, two nonlinear robust filters with respect to a leak are designed to generate the residual. To simplify the residual evaluation and estimate the leak position, a static relationship between each component of the residual and the position error is derived. The main contribution of this paper is to take advantage of the residual equation with uncertainty to isolate a fault. The effectiveness of this approach is shown by a comparison with the practical method reported in [1] using results obtained from simulated and experimental data of a water pilot pipeline of 132 m long, with a diameter of 0.1 m and with a flow rate of 12 l/s.

A Nonlinear Generalized Maxwell Fluid Model for Viscoelastic Materials

2001 ◽  
Vol 68 (5) ◽  
pp. 787-790 ◽  
Author(s):  
D. T. Corr ◽  
M. J. Starr ◽  
R. Vanderby, ◽  
T. M. Best
Keyword(s):  
Fluid Model ◽  
Maxwell Fluid ◽  
Viscoelastic Materials ◽  
Force Equation ◽  
Constant Rate ◽  
Parallel Arrangement ◽  
Noteworthy Feature ◽  
In Series ◽  
Linear Spring ◽  
Generalized Maxwell Fluid

A nonlinear Maxwell fluid model consisting of a linear dashpot in series with a parallel arrangement of a linear spring and a second-order nonlinear spring, was developed. This configuration provides the flexibility necessary to describe both the stiffening and the softening responses of some viscoelastic materials. A noteworthy feature of the model is that under constant rate displacement, the force equation can be solved in closed form, thereby providing a continuous, exact general solution.

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