Influence of Modal Coupling on the Nonlinear Dynamics of Augusti’s Model

The non-linear behavior and stability under static and dynamic loads of an inverted spatial pendulum with rotational springs in two perpendicular planes, called Augusti’s model, is analyzed in this paper. This 2DOF lumped-parameter system is an archetypal model of modal interaction in stability theory representing a large class of structural problems. When the system displays coincident buckling loads, several post-buckling paths emerge from the bifurcation point (critical load) along the fundamental path. This leads to a complex potential energy surface. Herein, we aim to investigate the influence of nonlinear modal interactions on the dynamic behavior of Augusti’s model. Coupled/uncoupled dynamic responses, bifurcations, escape from the pre-buckling potential well, stability and space–time-varying displacements, attractor-manifold-basin phase portraits are numerically evaluated with the aim of enlightening the system complex response. The investigation of basins evolution due to variation of system parameters leads to the determination of erosion profiles and integrity measures which enlighten the loss of safety of the structure due to penetration of eroding fractal tongues into the safe basin.

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Influence of Modal Coupling on the Nonlinear Dynamics of Augusti’s Model

Journal of Computational and Nonlinear Dynamics ◽

10.1115/1.4003880 ◽

2011 ◽

Vol 6 (4) ◽

Cited By ~ 14

Author(s):

Diego Orlando ◽

Paulo B. Gonçalves ◽

Giuseppe Rega ◽

Stefano Lenci

Keyword(s):

Nonlinear Behavior ◽

Dynamic Responses ◽

Phase Portraits ◽

Modal Interactions ◽

Structural Problems ◽

Lumped Parameter ◽

Modal Coupling ◽

Post Buckling ◽

Static And Dynamic Loads

The nonlinear behavior and stability under static and dynamic loads of an inverted spatial pendulum with rotational springs in two perpendicular planes, called Augusti’s model, is analyzed in this paper. This 2DOF lumped-parameter system is an archetypal model of modal interaction in stability theory representing a large class of structural problems. When the system displays coincident buckling loads, several post-buckling paths emerge from the bifurcation point (critical load) along the fundamental path. This leads to a complex potential energy surface. Herein, we aim to investigate the influence of nonlinear modal interactions on the dynamic behavior of Augusti’s model. Coupled/uncoupled dynamic responses, bifurcations, escape from the pre-buckling potential well, stability, and space-time-varying displacements; attractor-manifold-basin phase portraits are numerically evaluated with the aim of enlightening the system complex response. The investigation of basins evolution due to variation of system parameters leads to the determination of erosion profiles and integrity measures which enlighten the loss of safety of the structure due to penetration of eroding fractal tongues into the safe basin.

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Investigation of a Stochastic Inverse Method to Estimate an External Force: Applications to a Wave-Structure Interaction

Mathematical Problems in Engineering ◽

10.1155/2012/175036 ◽

2012 ◽

Vol 2012 ◽

pp. 1-25 ◽

Cited By ~ 3

Author(s):

S. L. Han ◽

Takeshi Kinoshita

Keyword(s):

External Force ◽

Inverse Method ◽

Inverse Function ◽

Wave Structure ◽

Dynamic Responses ◽

Structure Interaction ◽

External Forces ◽

Interaction Problem ◽

Wave Structure Interaction

The determination of an external force is a very important task for the purpose of control, monitoring, and analysis of damages on structural system. This paper studies a stochastic inverse method that can be used for determining external forces acting on a nonlinear vibrating system. For the purpose of estimation, a stochastic inverse function is formulated to link an unknown external force to an observable quantity. The external force is then estimated from measurements of dynamic responses through the formulated stochastic inverse model. The applicability of the proposed method was verified with numerical examples and laboratory tests concerning the wave-structure interaction problem. The results showed that the proposed method is reliable to estimate the external force acting on a nonlinear system.

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Dynamics of the Gear Train Set in Wind Turbine

Materials Science Forum ◽

10.4028/www.scientific.net/msf.697-698.701 ◽

2011 ◽

Vol 697-698 ◽

pp. 701-705

Author(s):

D.D. Ji ◽

Y.M. Song ◽

J. Zhang

Keyword(s):

Wind Turbine ◽

Dynamic Model ◽

Harmonic Balance Method ◽

Planetary Gear ◽

Gear Train ◽

Dynamic Responses ◽

Multi Stage ◽

Lumped Parameter ◽

Cartesian Coordinate ◽

The Impact

A lumped-parameter dynamic model for gear train set in wind turbine is proposed to investigate the dynamics of the speed-increasing gear box. The proposed model is developed in a universal Cartesian coordinate, which includes transversal and torsional deflections of each component, time-varying mesh stiffness, gear profile errors and external excitations. By solving the dynamic model, a modal analysis is performed. The results indicate that the modal properties of the multi-stage gear train in wind turbine are similar to those of a single-stage planetary gear set. A harmonic balance method (HBM) is used to obtain the dynamic responses of the gearing system. The responses give insight into the impact of excitations on the vibrations.

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Heat Input Influence on the Fatigue Life of Welds from Steel S460MC

Metals ◽

10.3390/met10101288 ◽

2020 ◽

Vol 10 (10) ◽

pp. 1288 ◽

Cited By ~ 1

Author(s):

Jaromir Moravec ◽

Jiri Sobotka ◽

Pavel Solfronk ◽

Robin Thakral

Keyword(s):

Fatigue Life ◽

Heat Input ◽

Strengthening Mechanism ◽

Dynamic Loads ◽

Microalloyed Steels ◽

Fine Grained ◽

Weld Fatigue ◽

Static And Dynamic Loads ◽

Fine Grained Steels

Fine-grained steels belong to the progressive materials, which are increasingly used in the production of welded structures subjected to both static and dynamic loads. These are unalloyed or microalloyed steels hardened mainly by the grain-boundary strengthening mechanism. Such steels require specific welding procedures, especially in terms of the heat input value. At present, there are studies of the welding influence on the change of thermomechanically processed steels’ mechanical properties, however mainly under static loading. The paper is therefore focused on the assessment of the welding effect under dynamic loading of welded joints. In the experimental part was determined the influence of five different heat input values on the change of weld fatigue life. As a result, there is both determination of five S-N curves for the double-sided fillet welds from the thermomechanically processed fine-grained steel S460MC and the quantification of the main influences reducing the fatigue life of the joint.

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Simultaneous HPLC Determination of Three Bioactive Alkaloids in the Asian Medicinal Plant Stephania rotunda

Natural Product Communications ◽

10.1177/1934578x1000500611 ◽

2010 ◽

Vol 5 (6) ◽

pp. 1934578X1000500 ◽

Cited By ~ 2

Author(s):

Sothavireak Bory ◽

Sok-Siya Bun ◽

Béatrice Baghdikian ◽

Fathi Mabrouki ◽

Sun Kaing Cheng ◽

...

Keyword(s):

High Performance ◽

Potassium Phosphate ◽

Solvent System ◽

Hplc Method ◽

Photodiode Array Detection ◽

Linear Behavior ◽

Photodiode Array ◽

Array Detection ◽

The Mean

A reliable high-performance liquid chromatography (HPLC) method coupled with photodiode array detection has been developed and validated for the determination of three major alkaloids: cepharanthine, tetrahydropalmatine and xylopinine in Stephania rotunda Lour. (Menispermaceae) collected in Cambodia. The chromatographic separation was carried out on a Symmetry C8 column (250 mm x 4.6 mm, 5 μm, Waters), with an isocratic solvent system of 25 mM potassium phosphate buffer (pH 3.5) – acetonitrile. UV detection was performed at 282 nm. Good linear behavior over the investigated concentration ranges was observed with values of r2>0.9964 for all the analytes. The method was reproducible with intra- and inter-day variations of less than 3.91%. The mean recoveries of the analytes ranged from 95.7 to 104.6%. The proposed method was linear, accurate, precise and specific. The validated method was successfully applied to quantify the three alkaloids in various parts of Stephania rotunda and in tubers collected from different Cambodian regions. The results indicated that the developed HPLC method could be used for the quality control of S. rotunda.

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Simultaneous Determination of Bioactive Xanthone Glycosides and Norlignans from Ethanolic Extract of Anemarrhena asphodeloides by Liquid Chromatography

Journal of AOAC International ◽

10.1093/jaoac/91.6.1271 ◽

2008 ◽

Vol 91 (6) ◽

pp. 1271-1277 ◽

Cited By ~ 3

Author(s):

M Nurul Islam ◽

Hye Hyun Yoo ◽

Jun Lee ◽

Joo Won Nam ◽

Eun Kyoung Seo ◽

...

Keyword(s):

Ethanolic Extract ◽

Reversed Phase ◽

Linear Behavior ◽

Liquid Chromatographic Method ◽

Relative Standard ◽

Aggregation Inhibition ◽

Phase Liquid ◽

Liquid Chromatographic ◽

Anemarrhena Asphodeloides

Abstract The rhizomes of Anemarrhena asphodeloides Bunge (Liliaceae) are prescribed as crude drugs in herbal medication for the treatment of various diseases such as diabetes, inflammation, and platelet aggregation inhibition. A simple, sensitive, and precise reversed-phase liquid chromatographic method was developed to study the quantitative determination of 5 bioactive compounds from these rhizomes, namely, neomangiferin, mangiferin, isomangiferin, nyasol, and methylnyasol. Chromatographic analysis was performed on Capcell Pak C18 column (150 4.6 mm, 3 m) with a mobile phase consisting of acetonitrile, methanol, and 0.1 formic acid at a flow rate of 1.00 mL/min. Quantitation was performed using a UV-visible detector at 260 nm. The method for the determination of reported medicinal agents was accurate and reproducible. Excellent linear behavior was observed over the investigated concentration range of 2.5100.0 g/mL for neomangiferin; 1.560.0 g/mL for mangiferin; 0.520.0 g/mL for nyasol; and 0.220.0 g/mL for methylnyasol; correlation coefficient >0.99. The intraday and interday precision over the concentration range of compounds was <6.6 (relative standard deviation) and accuracy was between 94.9 and 109.3. This method can be successfully applied for the analysis of medicinal compounds from the ethanolic extract of A. asphodeloides Bunge.

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Issues about the Determination of a Mechanical Model for Masonry Analysis

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.876.121 ◽

2018 ◽

Vol 876 ◽

pp. 121-127

Author(s):

Concetta Cusano ◽

Claudia Cennamo

Keyword(s):

Great Difficulty ◽

Tailored Intervention ◽

Structural Configuration ◽

Structural Intervention ◽

Structural Problems ◽

Unique Model ◽

Masonry Material ◽

Computational Processes ◽

Invasive Intervention

The work aims to describe the issue of the approach related to structural problems, both for valuable and minor manufacts existing in the Italian historical town centers. The heterogeneity shown by these constructive typologies should coincide with some heterogeneity of the structural approach, but this is not always feasible, so computational processes and a strict application of the norms are often used in automatically. A representative case, as an example of the above-mentioned kinds of buildings (which are valuable, but not so much as to require a tailored intervention that takes into account the whole constructive history and the changes over the time), is shown. Ricciardelli palace (or Palazzo Ricciardelli) presents a great difficulty as to the structural intervention, but the approach used was a "classical engineer approach", formulated on the basis of the new computing tools and the new constructive norms. The restoration and the consolidation of this artifact have been well conducted by technicians, but the result is an invasive intervention that doesn't respect the original structural configuration of the construction. So the paper explains and discusses some investigation methodologies, alternative to an elastic analysis, which could be used in these cases, with the awareness that they are not completely exhaustive and far far away from the determination of a general formulation for a “unique model”, which can be representative of the masonry material, as well as from a definition that catalogues all its several features.

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