Hysteresis Identification of Carbon Nanotube Composite Beams

2018 ◽  
Author(s):  
Michela Taló ◽  
Walter Lacarbonara ◽  
Giovanni Formica ◽  
Giulia Lanzara
Keyword(s):  
Phenomenological Model ◽  
Differential Evolution Algorithm ◽  
Hysteresis Loops ◽  
Hysteretic Behavior ◽  
Damping Capacity ◽  
Stick Slip ◽  
Slip Mechanism ◽  
Material Optimization ◽  
Constitutive Parameters ◽  
Mean Square Errors

Nanocomposites made of a hosting polymer matrix integrated with carbon nanotubes as nanofillers exhibit an inherent hysteretic behavior arising from the CNT/matrix frictional sliding. Such stick-slip mechanism is responsible for the high damping capacity of CNT nanocomposites. A full 3D nonlinear constitutive model, framed in the context of the Eshelby-Mori-Tanaka theory, reduced to a 1D phenomenological model is shown to describe accurately the CNT/polymer stick-slip hysteresis. The nonlinear hysteretic response of CNT nanocomposite beams is experimentally characterized via displacement-driven tests in bending mode. The force-displacement cycles are identified via the phenomenological model featuring five independent constitutive parameters. A preliminary parametric study highlights the importance of some key parameters in determining the shape of the hysteresis loops. The parameter identification is performed via one of the variants of a genetic-type differential evolution algorithm. The nanocomposites hysteresis loops are identified with reasonably low mean square errors. Such outcome confirms that the 1D phenomenological model may serve as an effective tool to describe and predict the nanocomposite nonlinear hysteretic behavior towards unprecedented material optimization and design.

scholarly journals Phenomenological model of the generation of the seismic mode «drumbeats» earthquakes accompanying the eruption of Kizimen volcano in 2011-2012

2020 ◽  
pp. 86-101
Author(s):  
А.А. Шакирова ◽  
П.П. Фирстов ◽  
Р.И. Паровик
Keyword(s):  
Lava Flow ◽  
Phenomenological Model ◽  
Nonlinear Oscillator ◽  
Time Intervals ◽  
Stick Slip ◽  
Slip Mechanism ◽  
Long Time ◽  
The Mathematical Model ◽  
First Time ◽  
Mode Generation

Извержение вулкана Кизимен в 2011-2012 гг. характеризовалось устойчивым, почти равномерным выжиманием вязкого лавового потока объемом 0.3 км³. Формирование лавового потока сопровождалось возникновением квазипериодических землетрясений режима «drumbeats» с энергетическими классами Ks<7, регистрируемых на длительных временных участках. Показано, что землетрясения генерировались движением фронта вязкого лавового потока, что в практике вулканологических исследований наблюдалось впервые. Предложена феноменологическая модель генерации сейсмического режима «drumbeats». Движение фронта лавового потока по склону вулкана происходило в результате прерывистого скольжения с включением механизма «stick-slip» и возбуждением автоколебательного процесса с генерацией сейсмического режима «drumbeats». Правдоподобность феноменологической модели режима ««drumbeats» на качественном уровне подтверждена математической моделью дробного нелинейного осциллятора. The eruption of the Kizimen volcano in 2011-2012 characterized by stable, almost uniform squeezing of a viscous lava flow with a volume of 0.3 km³. The formation of the lava flow was accompanied by the occurrence of quasiperiodic earthquakes of the “drumbeats” mode with energy classes Ks < 7, recorded at long time intervals. Shown that earthquakes were generated by the movement of the front of a viscous lava flow, which was observed for the first time in the practice of volcanological research. A phenomenological model of “drumbeats” seismic mode generation is proposed. The movement of the front of the lava flow along the slope of the volcano occurred because of intermittent sliding with the inclusion of the «stick-slip» mechanism and the initiation of a self-oscillating process with the generation of a seismic mode «drumbeats». The mathematical model of a fractional nonlinear oscillator qualitatively confirms the plausibility of the phenomenological model of the “drumbeats” mode.

Parametric Identification of Carbon Nanotube Nanocomposites Constitutive Response

2019 ◽  
Vol 86 (4) ◽  
Author(s):  
Giovanni Formica ◽  
Michela Taló ◽  
Giulia Lanzara ◽  
Walter Lacarbonara
Keyword(s):  
Carbon Nanotube ◽  
Mesoscale Model ◽  
Differential Evolution Algorithm ◽  
Material Design ◽  
Fine Tuning ◽  
Model Parameters ◽  
Restoring Force ◽  
Stick Slip ◽  
Proposed Model ◽  
Constitutive Parameters

Hysteresis due to stick-slip energy dissipation in carbon nanotube (CNT) nanocomposites is experimentally observed, measured, and identified through a one-dimensional (1D) phenomenological model obtained via reduction of a three-dimensional (3D) mesoscale model. The proposed model is shown to describe the nanocomposite hysteretic response, which features the transition from the purely elastic to the post-stick-slip behavior characterized by the interfacial frictional sliding motion between the polymer chains and the CNTs. Parametric analyses shed light onto the physical meaning of each model parameter and the influence on the material response. The model parameters are determined by fitting the experimentally acquired force–displacement curves of CNT/polymer nanocomposites using a differential evolution algorithm. Nanocomposite beam-like samples made of a high performance engineering polymer and high-aspect-ratio CNTs are fabricated and tested in a bending mode at increasing deflection amplitudes. The entire time histories of the restoring force are fitted by the model through a unique set of parameters. The parameter identification is carried out for nanocomposites with various CNT weight fractions, so as to highlight the model capability to identify a wide variety of nanocomposite hysteretic behaviors through a fine tuning of its constitutive parameters. By exploiting the proposed model, a nanostructured material design and its optimization are made possible toward the exploitation of these promising materials for engineering applications.

Dynamic Behaviour of Plain Slideways

1966 ◽  
Vol 181 (1) ◽  
pp. 169-184 ◽  
Author(s):  
R. Bell ◽  
M. Burdekin
Keyword(s):  
Machine Tool ◽  
Dynamic Behaviour ◽  
Damping Capacity ◽  
Friction Characteristic ◽  
Stick Slip ◽  
Friction Characteristics ◽  
Physical Systems ◽  
Major Emphasis

The friction characteristics resulting from the motion of one surface over another form a very important facet of the behaviour of many physical systems. This statement is particularly valid when considering the behaviour of machine tool slideways. Most slideway elements consist of two plain surfaces whose friction characteristic is modified by the addition of a lubricant. In many cases the complete slideway consists of many mating surfaces and the choice of slideway material, slideway machining and lubricant is often influenced by the long term problem of wear. The aim of this paper is to present results of experiments on a test rig designed to be representative of machine tool slideway conditions; the experiments were wholly concerned with the behaviour of the bearing under dynamic conditions. The major emphasis is on results obtained with a polar additive lubricant which appears to exclude the possibility of ‘stick-slip’ oscillations. A parallel series of tests are reported where a normal hydraulic oil was used as lubricant. The use of this second lubricant allowed some study of the ‘stick-slip’ process. The dynamic friction characteristics, cyclic friction characteristics and damping capacity of several slideway surface combinations have been obtained and are discussed in the context of earlier work in the field and the role of slideways in machine tool behaviour.

Interface Engineering of CNT/Polymer Nanocomposites With Tunable Damping Properties

2018 ◽  
Author(s):  
Michela Talò ◽  
Giulia Lanzara ◽  
Maryam Karimzadeh ◽  
Walter Lacarbonara
Keyword(s):  
Load Transfer ◽  
Mechanical Response ◽  
Material Design ◽  
Tensile Tests ◽  
Nanocomposite Films ◽  
Damping Capacity ◽  
Interfacial Region ◽  
Material Damping ◽  
Stick Slip ◽  
Multi Walled Carbon Nanotubes

In this work, the arising of stick-slip dissipation as well as the global mechanical response of carbon nanotube (CNT) nanocomposite films are tailored by exploiting a three-phase nanocomposite. The three phases are represented by the CNTs, a polymer coating localized on the CNTs surface and a hosting matrix. In particular, a polystyrene (PS) layer coats multi-walled carbon nanotubes (MWNTs) that are randomly dispersed in a polyimide (PI) matrix. The coating phase is strongly bonded to the CNTs outer sidewalls ensuring the effectiveness of the load transfer mechanism and reducing the material damping capacity. The coating phase can be thermally-activated to modify, and in particular, decrease the CNT-matrix interfacial shear strength (ISS) thus facilitating the stick-slip onset in the nanocomposite. The ISS decrease finds its roots in a partial degradation of the coating phase and, in particular, in the formation of voids. By weakening the CNT/polymer interfacial region, a significant enhancement in the material damping capacity is observed. An extensive experimental campaign consisting of monotonic and cyclic tensile tests proved the effectiveness of this novel multi-phase material design.

Stick-slip mechanism in a granular medium

2010 ◽  
Vol 46 (6) ◽  
pp. 600-605 ◽  
Author(s):  
A. P. Bobryakov
Keyword(s):  
Granular Medium ◽  
Stick Slip ◽  
Slip Mechanism

scholarly journals Hysteretic Behavior of Steel Reinforced Concrete Columns Based on Damage Analysis

2019 ◽  
Vol 9 (4) ◽  
pp. 687 ◽  
Author(s):  
Bin Wang ◽  
Guang Huo ◽  
Yongfeng Sun ◽  
Shansuo Zheng
Keyword(s):  
Reinforced Concrete ◽  
Damage Index ◽  
Hysteresis Loops ◽  
Time History ◽  
Hysteretic Behavior ◽  
Loading Path ◽  
Test Results ◽  
Hysteresis Model ◽  
Skeleton Curve ◽  
Steel Reinforced Concrete

With the aim to model the seismic behavior of steel reinforced concrete (SRC) frame columns, in this research, hysteresis and skeleton curves were obtained based on the damage test results of SRC frame columns under low cyclic repeat loading and the hysteretic behavior of the frame columns was further analyzed. Then, the skeleton curve and hysteresis loops were further simplified. The simplified skeleton curve model was obtained through the corresponding feature points obtained by mechanical and regression analysis. The nonlinear combination seismic damage index, which was developed by the test results and can well reflect the effect of the loading path and the number of loading cycle of SRC frame columns, was used to establish the cyclic degradation index. The strength and stiffness degradation rule of the SRC frame columns was analyzed further by considering the effect of the accumulated damage caused by an earthquake. Finally, the hysteresis model of the SRC frame columns was established, and the specific hysteresis rules were given. The validity of the developed hysteresis model was verified by e comparison between the calculated results and the test results. The results showed that the model could describe the hysteresis characteristics of the SRC frame columns under cyclic loading and provide guidance for the elastoplastic time-history analysis of these structures.

scholarly journals Effect of Nitrogen Implantation on Metal Transfer during Sliding Wear under Ambient Conditions

2013 ◽  
Vol 2013 ◽  
pp. 1-16 ◽  
Author(s):  
Luke Autry ◽  
Harris Marcus
Keyword(s):  
Wear Mechanism ◽  
Heat Treating ◽  
Metal Transfer ◽  
Interstitial Free ◽  
Volumetric Wear ◽  
Ambient Conditions ◽  
Nitrogen Implantation ◽  
Stick Slip ◽  
Near Surface ◽  
Slip Mechanism

Nitrogen implantation in Interstitial-Free steel was evaluated for its impact on metal transfer and 1100 Al rider wear. It was determined that nitrogen implantation reduced metal transfer in a trend that increased with dose; the Archard wear coefficient reductions of two orders of magnitude were achieved using a dose of 2e17 ions/cm2, 100 kV. Cold-rolling the steel and making volumetric wear measurements of the Al-rider determined that the hardness of the harder material had little impact on volumetric wear or friction. Nitrogen implantation had chemically affected the tribological process studied in two ways: directly reducing the rider wear and reducing the fraction of rider wear that ended up sticking to the ISF steel surface. The structure of the nitrogen in the ISF steel did not affect the tribological behavior because no differences in friction/wear measurements were detected after postimplantation heat treating to decompose the as-implantedε-Fe3N toγ-Fe4N. The fraction of rider-wear sticking to the steel depended primarily on the near-surface nitrogen content. Covariance analysis of the debris oxygen and nitrogen contents indicated that nitrogen implantation enhanced the tribo-oxidation process with reference to the unimplanted material. As a result, the reduction in metal transfer was likely related to the observed tribo-oxidation in addition to the introduction of nitride wear elements into the debris. The primary Al rider wear mechanism was stick-slip, and implantation reduced the friction and friction noise associated with that wear mechanism. Calculations based on the Tabor junction growth formula indicate that the mitigation of the stick-slip mechanism resulted from a reduced adhesive strength at the interface during the sticking phase.

Cyclic extrusion of a lava dome based on a stick-slip mechanism

2012 ◽  
Vol 337-338 ◽  
pp. 39-46 ◽  
Author(s):  
A. Costa ◽  
G. Wadge ◽  
O. Melnik
Keyword(s):  
Lava Dome ◽  
Stick Slip ◽  
Slip Mechanism

Experimental characterization and control of a magnetic shape memory alloy actuator using the modified generalized rate-dependent Prandtl–Ishlinskii hysteresis model

2018 ◽  
Vol 232 (5) ◽  
pp. 506-518 ◽  
Author(s):  
Saeid Shakiba ◽  
Mohammad Reza Zakerzadeh ◽  
Moosa Ayati
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Excitation Frequency ◽  
Hysteresis Loops ◽  
Experimental Results ◽  
Hysteretic Behavior ◽  
Magnetic Shape Memory ◽  
Shape Memory Alloy Actuator ◽  
Rate Dependent ◽  
Magnetic Shape Memory Alloy

In this article, two models are used, namely rate-independent and rate-dependent generalized Prandtl–Ishlinskii, to characterize a magnetic shape memory alloy actuator. The results show that the rate-independent model cannot consider the effect of input excitation frequency, while the rate-dependent model omits this drawback by defining a time-dependent operator. For the first time, the effects of excitation frequency on the hysteretic behavior of magnetic shape memory alloy actuator are investigated. In this study, five excitation voltages with different frequencies in the range of 0.05–0.4 Hz are utilized as inputs to the magnetic shape memory alloy actuator and the displacement outputs are measured. Experimental results indicate that, with increasing the excitation frequency, the size of the hysteresis loops changes. Since the generalized rate-dependent Prandtl–Ishlinskii model cannot consider the asymmetric hysteresis loops, in the developed model, a tangent hyperbolic function is applied as an envelope function in order to improve the capability of the model in characterizing the asymmetric behavior of magnetic shape memory alloy actuator. The parameters of both rate-dependent and rate-independent models are identified by genetic algorithm optimization. The results reveal that the rate-independent form is not capable of accurately describing the hysteretic behavior of magnetic shape memory alloy actuator for different input frequencies. Simulation and experimental results also demonstrate the proficiency of the developed model for precise characterization of the saturated rate-dependent hysteresis loops of magnetic shape memory alloy actuator. In addition, the proposed model is utilized for determining a proper range for controller coefficients during controller design.

Sign in / Sign up

Export Citation Format

Share Document