scholarly journals FE Prediction of Hysteretic Component of Rubber Friction

2012 ◽  
Vol 2012 ◽  
pp. 1-12 ◽  
Author(s):  
L. Pálfi ◽  
T. Goda ◽  
K. Váradi ◽  
E. Garbayo ◽  
J. M. Bielsa ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Storage Modulus ◽  
Viscoelastic Material ◽  
Loss Factor ◽  
Master Curve ◽  
Reaction Force ◽  
Maxwell Model ◽  
Material Models ◽  
Rubber Friction ◽  
Maxwell Models

The hysteretic part of the friction coefficient for rubber sliding on an ideal rigid, rough surface has been investigated by FE technique. The FE models were created by using two different FE softwares, ABAQUS and MSC.MARC. The surface roughness has been considered by using two different sine waves having a wavelength of 100 μm and 11.11 μm, as well as their superposition. Parameters of the viscoelastic material models of the rubber were gained, firstly from a fit to the measured storage modulus, secondly from a fit to the measured loss factor master curve of the rubber. The effect of viscoelastic material models, comparing 10-term and 40-term generalized Maxwell models was also considered together with the temperature effect between −50 and150°C. According to the results, both postprocessing methods, namely, the reaction force and the energy-based approach, show very similar coefficients of friction. The 40-term Maxwell model fitted to both the storage modulus and loss factor curve provided the most realistic results. The tendency of the FE results has been explained by semianalytical theory.

scholarly journals Mechanical Consequences of Dynamically Loaded NiTi Wires under Typical Actuator Conditions in Rehabilitation and Neuroscience

2021 ◽  
Vol 12 (1) ◽  
pp. 4
Author(s):  
Umut D. Çakmak ◽  
Zoltán Major ◽  
Michael Fischlschweiger
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Storage Modulus ◽  
Loss Factor ◽  
Empirical Relation ◽  
Material Behavior ◽  
Chemical Compositions ◽  
Loading Frequency ◽  
Frequency Dependency ◽  
Controlled Conditions

In the field of rehabilitation and neuroscience, shape memory alloys play a crucial role as lightweight actuators. Devices are exploiting the shape memory effect by transforming heat into mechanical work. In rehabilitation applications, dynamic loading of the respective device occurs, which in turn influences the mechanical consequences of the phase transforming alloy. Hence in this work, dynamic thermomechanical material behavior of temperature-triggered phase transforming NiTi shape memory alloy (SMA) wires with different chemical compositions and geometries was experimentally investigated. Storage modulus and mechanical loss factor of NiTi alloys at different temperatures and loading frequencies were analyzed under force-controlled conditions. Counterintuitive storage modulus- and loss factor-dependent trends regarding the loading frequency dependency of the mechanical properties on the materials’ composition and geometry were, hence, obtained. It was revealed that loss factors showed a pronounced loading frequency dependency, whereas the storage modulus was not affected. It was shown that force-controlled conditions led to a lower storage modulus than expected. Furthermore, it turned out that a simple empirical relation could capture the characteristic temperature dependency of the storage modulus, which is an important input relation for modeling the rehabilitation device behavior under different dynamic and temperature loading conditions, taking directly into account the material behavior of the shape memory alloy.

scholarly journals Simultaneous Characterization of Relaxation, Creep, Dissipation, and Hysteresis by Fractional-Order Constitutive Models

2021 ◽  
Vol 5 (2) ◽  
pp. 36
Author(s):  
Jun-Sheng Duan ◽  
Di-Chen Hu ◽  
Yang-Quan Chen
Keyword(s):  
Constitutive Model ◽  
Storage Modulus ◽  
Loss Factor ◽  
Creep Compliance ◽  
Loss Modulus ◽  
Constitutive Models ◽  
Stationary Points ◽  
Logarithmic Scale ◽  
Zener Model ◽  
Fractional Zener Model

We considered relaxation, creep, dissipation, and hysteresis resulting from a six-parameter fractional constitutive model and its particular cases. The storage modulus, loss modulus, and loss factor, as well as their characteristics based on the thermodynamic requirements, were investigated. It was proved that for the fractional Maxwell model, the storage modulus increases monotonically, while the loss modulus has symmetrical peaks for its curve against the logarithmic scale log(ω), and for the fractional Zener model, the storage modulus monotonically increases while the loss modulus and the loss factor have symmetrical peaks for their curves against the logarithmic scale log(ω). The peak values and corresponding stationary points were analytically given. The relaxation modulus and the creep compliance for the six-parameter fractional constitutive model were given in terms of the Mittag–Leffler functions. Finally, the stress–strain hysteresis loops were simulated by making use of the derived creep compliance for the fractional Zener model. These results show that the fractional constitutive models could characterize the relaxation, creep, dissipation, and hysteresis phenomena of viscoelastic bodies, and fractional orders α and β could be used to model real-world physical properties well.

Identification of Viscoelastic Properties of Finite Element Structures With Joints

1997 ◽  
Author(s):  
Torsten Herrmann ◽  
Valdas Chaika
Keyword(s):  
Finite Element ◽  
Viscoelastic Properties ◽  
Sparse Matrix ◽  
Maxwell Model ◽  
Least Square ◽  
Identification Algorithm ◽  
Domain Identification ◽  
Generalized Maxwell Model ◽  
Maxwell Models ◽  
Complex Modal Analysis

Abstract Identification of the damping and stiffness parameters of the composite joints in finite element structures is analyzed. For the modeling of the viscoelastic properties of the joints the classical Voigt-Kelvin and generalized Maxwell model (three parameter solid) are used. A time domain identification algorithm for classically and non-classically damped dynamic systems is developed. It is based on the application of an extended Kalman filter and least square technique. The algorithm uses complex modal analysis and sparse matrix technology. Both force and base excited systems are considered. Experimental verification of the identification results is carried out on a test structure. The accuracy of the modeling of damping in the joint using the Voigt-Kelvin and generalized Maxwell models is investigated.

Experimental and molecular dynamics study of boron nitride nanotube-reinforced polymethyl methacrylate composites

2019 ◽  
Vol 54 (1) ◽  
pp. 3-11 ◽  
Author(s):  
Sumit Sharma ◽  
Prince Setia ◽  
Rakesh Chandra ◽  
Nitin Thakur
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Boron Nitride ◽  
Molecular Dynamics Simulations ◽  
Storage Modulus ◽  
Polymethyl Methacrylate ◽  
Loss Factor ◽  
Boron Nitride Nanotubes ◽  
Weight Percentage ◽  
Dynamics Simulations

Heat dissipation is very essential for the efficient working of electronic devices. There is a widespread demand for high thermal conductivity materials. Boron nitride nanotubes have high thermal conductivity but due to their poor interfacial adhesion with polymers, their use as heat dissipating material is restricted. In this study, a silane-coupling agent has been used to modify the boron nitride nanotubes. These tubes were then inserted in polymethyl methacrylate matrix. Various properties such as thermal conductivity, storage modulus, and loss factor have been predicted. Molecular dynamics simulations have also been used for accurate prediction of the properties of boron nitride nanotubes/polymethyl methacrylate composites. The boron nitride nanotubes weight percentage was varied from 0% to 70% for studying the effect on thermal conductivity, storage modulus, and loss factor. The experimentally obtained thermal conductivity increased rapidly from 0.6 W/mK at 40 wt.% of boron nitride nanotubes to about 3.8 W/mK at 80 wt.% of boron nitride nanotubes in polymethyl methacrylate matrix (an increase of nearly 533%). A similar trend was obtained using molecular dynamics simulations. The storage modulus increased from 2 GPa (for pure polymethyl methacrylate) to about 5 GPa (for 70 wt.% boron nitride nanotubes). The glass transition temperature of boron nitride nanotubes/polymethyl methacrylate composites shifted to higher temperatures with an increase in boron nitride nanotubes weight percentage.

CHARACTERISATION OF THE COMPLEX SHEAR MODULUS PROPERTIES OF ELECTRO-RHEOLOGICAL FLUIDS BY THE DIRECT STIFFNESS AND MASTER CURVE TECHNIQUES

1996 ◽  
Vol 10 (23n24) ◽  
pp. 3227-3236 ◽  
Author(s):  
S O Oyadiji
Keyword(s):  
Field Strength ◽  
Shear Modulus ◽  
Electric Field ◽  
Electric Field Strength ◽  
Loss Factor ◽  
Master Curve ◽  
Measured Temperature ◽  
Direct Stiffness ◽  
Er Fluid ◽  
Field Strengths

The direct stiffness technique was employed to characterise the complex modulus properties of a silicone oil-based electrorheological fluid over a frequency range from 30Hz to 300Hz and a temperature range from 0°C to 60ºC. The ER fluid device utilised was a set of concentric cylinders possessing a radial gap of 3mm between adjacent cylinders. Electric field strengths of between 0kV/mm and 2kV/mm were applied across the ER fluid. The results show that the shear modulus of the ER fluid decreased monotonically as the temperature was increased from 0ºC to 60ºC. Overall, the shear modulus decreased by a factor of up to 20. On the other hand, the shear loss factor increased from a low value of about 0.05 at 0ºC to a high value of about 1.0 at 60ºC. Conversely, as the electric field strength was increased from 0kV/mm to 2kV/mm, the shear modulus increased whereas the loss factor decreased. At all temperatures and electric field strengths of these investigations, both the shear modulus and loss factor increased in value as the excitation frequency was increased. The sets of measured temperature- and frequency-dependent data were converted, using the master curve technique, to master curves of shear modulus and loss factor which vary with frequency over several decades at a constant reference temperature and for varying levels of the electric field strength.

scholarly journals Effect of Ultraviolet-A (UV-A) and Ultraviolet-C (UV-C) Light on Mechanical Properties of Oyster Mushrooms during Growth

2014 ◽  
Vol 2014 ◽  
pp. 1-6 ◽  
Author(s):  
Tindibale L. Edward ◽  
M. S. K. Kirui ◽  
Josiah O. Omolo ◽  
Richard G. Ngumbu ◽  
Peter M. Odhiambo
Keyword(s):  
Mechanical Properties ◽  
Storage Modulus ◽  
Loss Factor ◽  
Loss Modulus ◽  
Control Sample ◽  
Ultraviolet A ◽  
Significant Difference ◽  
Ultraviolet C ◽  
Oyster Mushrooms ◽  
Uv C

This study investigated the effects of ultraviolet-A (UV-A) and ultraviolet-C (UV-C) light on the mechanical properties in oyster mushrooms during the growth. Experiments were carried out with irradiation of the mushrooms with UV-A (365 nm) and UV-C (254 nm) light during growth. The exposure time ranged from 10 minutes to 60 minutes at intervals of 10 minutes and irradiation was done for three days. The samples for experimental studies were cut into cylindrical shapes of diameter 12.50 mm and thickness 3.00 mm. The storage modulus, loss modulus, and loss factor of the irradiated samples and control samples were determined for both UV bands and there was a significant difference between the storage modulus, loss modulus, and loss factor of the irradiated samples by both UV bands with reference to the control sample, P<0.05. UV-C light irradiated samples had higher loss modulus and loss factor but low storage modulus as temperature increased from 35 to 100°C with respect to the control sample while UV-A light irradiated samples had lower loss modulus, low loss factor, and higher storage modulus than UV-C irradiated samples.

scholarly journals Combining adhesive contact mechanics with a viscoelastic material model to probe local material properties by AFM

Soft Matter ◽  
2018 ◽  
Vol 14 (1) ◽  
pp. 140-150 ◽  
Author(s):  
Christian Ganser ◽  
Caterina Czibula ◽  
Daniel Tscharnuter ◽  
Thomas Schöberl ◽  
Christian Teichert ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Atomic Force Microscopy ◽  
Viscoelastic Material ◽  
Material Properties ◽  
Material Model ◽  
Adhesive Contact ◽  
Force Microscopy ◽  
Atomic Force ◽  
Local Material ◽  
Local Material Properties

We present an atomic force microscopy based method to study viscoelastic material properties at low indentation depths with non-negligible adhesion and surface roughness.

Applicability of time temperature superposition principle to an immiscible blend of polyphenyleneoxide and polyamide

2011 ◽  
Vol 31 (2-3) ◽  
Author(s):  
Narendra A. Hardikar ◽  
Somasekhar Bobba ◽  
Roshan Jha
Keyword(s):  
Storage Modulus ◽  
Master Curve ◽  
Loss Modulus ◽  
Superposition Principle ◽  
Strict Sense ◽  
Cole Plot ◽  
Temperature Superposition ◽  
Immiscible Blend ◽  
Thermorheological Behavior ◽  
Time Temperature Superposition

Abstract The immiscible blend of polyphenyleneoxide (PPO) and polyamide (PA) is used in several applications exposed to high temperature. The complexity of numerical modeling of such materials is dependent on their thermorheological behavior with significant simplification possibilities, if the material is found to follow the time temperature superposition (TTS) principle and show thermorheological simplicity (TRS). Hence as a precursor to selecting accurate constitutive modeling approach, the paper investigates the applicability of the TTS principle and the nature of thermorheological behavior to the blend. Dynamic mechanical analysis (DMA)frequency scans were performed in the range of 0.1–100 rad/s from 0°C to 210°C at 10°C intervals. Temperature dependency was observed on the Cole-Cole plot pointing to the thermorheological complexity and the need for vertical shift factors. 2-D minimization algorithm was used to shift the isotherms horizontally and vertically to obtain master curves. Except, in the vicinity of glass transition temperature T g , the isotherms overlap to form a master curve, but further analysis considering various conditions indicate that in a strict sense TTS is not applicable to the blend when both storage G′ and loss modulus G″ are considered. However, a continuous master curve of storage modulus spanning 31 decades of time is obtained using horizontal shifting alone when loss modulus is neglected. Further testing is required to ascertain if relaxation modulus can be approximated with storage modulus alone before taking recourse to characterization methods developed for thermorheologically complex (TRC) materials.

Estimation of model errors in the calibration of viscoelastic material models

2008 ◽  
Vol 76 (10) ◽  
pp. 1568-1582 ◽  
Author(s):  
Håkan Johansson ◽  
Fredrik Larsson ◽  
Kenneth Runesson
Keyword(s):  
Viscoelastic Material ◽  
Model Errors ◽  
Material Models

Development of Free Surface Roughness in Expanding/Contracting Cylinders

2008 ◽  
Author(s):  
Sergei Alexandrov ◽  
Ken-Ichi Manabe ◽  
Tsuyoshi Furushima
Keyword(s):  
Surface Roughness ◽  
Finite Element ◽  
Free Surface ◽  
Classical Problem ◽  
Modern Technology ◽  
Simple Problem ◽  
Material Models ◽  
Theoretical Predictions ◽  
Element Technique ◽  
Metallic Parts

Microforming is a modern technology for fabricating very small metallic parts, such as micro-tubes, required in many sectors of industry. Free surface roughness of such components is a very important parameter since the roughness can be considered as the variation of component dimensions in this case. It is therefore of importance to understand an effect of process parameters and parameters of material models used to describe the evolution of roughness on the final result of theoretical predictions. To this end, it is possible to study the solution behavior of a simple problem even if it is not feasible for experimental verification. In the present paper, the solution to a classical problem of plasticity, expansion/contraction of a hollow cylinder, is combined with a finite element technique to predict the evolution of roughness at the free surface.

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