scholarly journals Nonlocal vibration of carbon/boron-nitride nano-hetero-structure in thermal and magnetic fields by means of nonlinear finite element method

2020 ◽  
Vol 7 (5) ◽  
pp. 591-602 ◽  
Author(s):  
Hamid M Sedighi ◽  
Mohammad Malikan ◽  
Ali Valipour ◽  
Krzysztof Kamil Żur
Keyword(s):  
Finite Element ◽  
Boron Nitride ◽  
Dynamic Behavior ◽  
Thermal Environment ◽  
Boron Nitride Nanotubes ◽  
Nonlinear Finite Element ◽  
The Other ◽  
Beam Model ◽  
Nonlinear Frequency ◽  
Other Hand

Abstract Hybrid nanotubes composed of carbon and boron-nitride nanotubes have manifested as innovative building blocks to exploit the exceptional features of both structures simultaneously. On the other hand, by mixing with other types of materials, the fabrication of relatively large nanotubes would be feasible in the case of macroscale applications. In the current article, a nonlinear finite element formulation is employed to deal with the nonlocal vibrational behavior of carbon/boron-nitride nano-hetero-tubes in the presence of magneto-thermal environment. Euler–Bernoulli beam model in conjunction with the Eringen’s nonlocal theory of elasticity is adopted to derive the governing equation of motion. In order to conduct a nonlinear frequency analysis, the von-Kármán nonlinearity associated with moderate rotations is also considered. It is well known that temperature gradients can significantly change the dynamic behavior of nanotubes. On the other hand, the coefficients of thermal expansions of carbon and boron-nitride nanotubes are quite different that may affect the structural stability of hybrid nanotubes. Hence, to explore the vibration characteristic of such composite structures, the influence of magneto-thermal environment is also taken into account. Finally, the eigenvalue analysis is performed to exhibit the nonlinear mode shapes and natural frequencies of the system due to initial displacement. It is expected that the recognition of dynamic behavior of such hybrid nanotubes may open the doors to the creative design of next-generation nano-devices.

Effect of Friction Coefficients Regarding Bolt Self-Loosening

2020 ◽  
Author(s):  
Yasumasa Shoji
Keyword(s):  
Finite Element ◽  
Torque Control ◽  
Tension Control ◽  
Friction Reduction ◽  
The Other ◽  
Finite Element Analyses ◽  
Bearing Surface ◽  
Friction Coefficients ◽  
Male And Female ◽  
Other Hand

Abstract As there have been many researches for bolt self-loosening and a lot of knowledge have been accumulated, the phenomena has been understood more and more clearly. On the other hand, it is quite difficult to achieve both non-self-loosening and easy bolting tasks. In practical situations, easy and stable bolting is more focused and torque control is employed for tension control in the fields. For the stable bolting, friction of the threads is reduced by lubrication. However, the effect of this friction reduction is not yet investigated in the aspect of self-loosening. In this paper, the effect of frictions between male and female threads and between nut and bearing surface is investigated by FEA simulations. This provides information how self-loosening can be controlled. In this paper, the motion of the fastened plate transverse to the bolt axis is considered. This motion is known as the easiest motion to make self-loosening in experience and also as shown so in the author’s previous researches. The friction seems to increase self-loosening and also decrease self-loosening at the same time. It seems that the friction on the bearing surface drives self-loosening and friction on the thread surfaces prevents it. In this paper, both the frictions are examined in the relative manner with the Finite Element Analyses.

Finite element investigation of the vibrational behavior of concentric multi-walled boron nitride and carbon nanotubes

2017 ◽  
Vol 31 (04) ◽  
pp. 1750018 ◽  
Author(s):  
R. Ansari ◽  
S. Rouhi ◽  
A. Nikkar
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Boron Nitride ◽  
Natural Frequencies ◽  
Vacancy Defect ◽  
Boron Nitride Nanotubes ◽  
The Finite Element Method ◽  
Zigzag Nanotubes ◽  
Vibrational Behavior ◽  
Vibrational Characteristics

This paper concerns the vibrational behavior of concentric double-walled and triple-walled carbon and boron nitride nanotubes using the finite element method. Armchair and zigzag nanotubes with different lengths and diameters are considered. Moreover, different boundary conditions are applied on the nanotubes. It is observed that in double-walled nanotubes, when the inner and outer layers are respectively from boron nitride and carbon, the frequencies are larger than those in the reverse arrangement. Investigating the effect of diameter on the first 10 natural frequencies of double-walled and triple-walled nanotubes showed that nanotubes with larger diameters possess smaller frequencies. The effect of diameter is more significant for higher modes. Finally, comparisons are made between the vibrational behavior of concentric carbon and boron nitride double-walled and triple-walled nanotubes. Considering the effect of vacancy defect on the vibrational characteristics of the nanotubes revealed that when all of the walls of the nanotubes are defective, the largest diminish occurs for the fundamental natural frequencies.

Doubly-Clamped Single Walled Boron Nitride Nanotube Based Nanomechanical Resonators: A Computational Investigation of Their Behavior

2012 ◽  
Vol 3 (4) ◽  
Author(s):  
Mitesh B. Panchal ◽  
S. H. Upadhyay
Keyword(s):  
Finite Element ◽  
Boron Nitride ◽  
Resonant Frequency ◽  
Frequency Shift ◽  
Dynamic Behavior ◽  
Added Mass ◽  
Boron Nitride Nanotube ◽  
Landing Position ◽  
Nanomechanical Resonators ◽  
Resonant Frequency Shift

This paper illustrates the dynamic behavior of a doubly-clamped single walled boron nitride nanotube (SWBNNT) as a mass sensor. To this end, a 3-dimensional atomistic model based on molecular structural mechanics is developed such that the proximity of the model to the actual atomic structure of the nanotube is significantly retained. Different types of zigzag and armchair layouts of SWBNNTs are considered with doubly-clamped end constraints. Implementing the finite element simulation approach, the resonant frequency shift based analysis is performed for doubly-clamped end-constraints, for an additional nanoscale mass at the middle of the length, and at the intermediate landing position along the length of the nanotube. The effect of the intermediate landing position of added mass on the resonant frequency shift is analyzed by considering excitations of the fundamental modes of vibration. The finite element method (FEM) based simulation results are validated using the continuum mechanics based analytical results, considering the effective wall thickness of the SWBNNT. The present approach is found to be effectual in terms of dealing with different chiralities, boundary conditions, and the consideration of the added mass to analyze the dynamic behavior of the doubly-clamped SWBNNT based nanomechanical resonators.

Luggage Impact and Structure Optimization for Rear Seat Frame of Automobile

2016 ◽  
Vol 693 ◽  
pp. 155-162
Author(s):  
Zhi Ping Wang ◽  
Jin Ting Ni ◽  
Xin Zhang
Keyword(s):  
Finite Element ◽  
Structure Optimization ◽  
Rear Seat ◽  
Nonlinear Finite Element ◽  
The Other ◽  
Cad Model ◽  
Back Seat ◽  
Simulation Results ◽  
Seat Frame ◽  
Finite Element Methodology

It is essential that the back seat of a vehicle has to be designed safely and reliably and at the same time meet the ECE R17, as to reduce the back seat casualties in accidents caused by luggage impact. This paper studies a sample of back seat frame and establishes its precise CAD model. It adopts nonlinear finite element methodology to simulate the object under the ECE R17. The results reflect two problems. One is the force absorption and anti-deformation of the split seat frame is too weak; the other is the fixed connections linking the frame to the holder is not tight enough causing easy fall-off if being shocked. The test and simulation results suggest the following alterations, respectively to substitute the previous split seat frame for a one-piece seat frame as to improve the overall stiffness and anti-deformation, to adopt one-piece structure on the center support bracket and increases its thickness by 0.5mm, keep the remaining mounting bracket structure unchanged. The analyses of the improved program demonstrate its superior anti-deformation under the regulations.

scholarly journals Aeroelasticity in Turbomachines: Some Aspects of the Effect of Coupling Modeling and Blade Material Changes

2000 ◽  
Vol 6 (4) ◽  
pp. 265-273 ◽  
Author(s):  
François Moyroud ◽  
Georges Jacquet-Richardet ◽  
Torsten H. Fransson
Keyword(s):  
Dynamic Behavior ◽  
Energy Method ◽  
The Other ◽  
Feedback Effect ◽  
Test Cases ◽  
Eigenvalue Approach ◽  
Structural Dynamic ◽  
Other Hand ◽  
Aeroelastic Analysis

Two methods are generally used for the aeroelastic analysis of bladed-disc assemblies. The first, often referred to as the energy method, assumes that the fluid does not modify invacuum structural dynamic behavior. On the other hand, the second, based on an eigenvalue approach, considers the feedback effect of the fluid on the structure. In this paper, these methods are compared using different test cases, in order to highlight the limitations of the energy method. Within this comparison, the effect of material modifications on the coupled behavior of the assembly is examined.

scholarly journals A review on recent research studies on vibration analysis of fluid-conveying nanotubes

2020 ◽  
Vol 7 (2) ◽  
pp. 42-54
Author(s):  
E. Fatahian ◽  
Ebrahim Hosseini ◽  
H. Fatahian
Keyword(s):  
Carbon Nanotubes ◽  
Boron Nitride ◽  
Thermal Environment ◽  
Thermal Fluctuations ◽  
Modern Technology ◽  
Boron Nitride Nanotubes ◽  
Thermal Vibration ◽  
Strain Gradient Theory ◽  
Gradient Theory ◽  
Cylindrical Shape

Nanotube (such as carbon and boron nitride nanotubes) is a key component of modern technology applications of nanostructures due to their unique mechanical, electrical, and physical characteristics such as high elasticity modulus, suitable heat transfer, and electrical conductivity. Carbon and boron nitride nanotubes are among the promising choices in nano-fluidic, gas storage, and drug delivery systems due to their hollow cylindrical shape and appropriate chemical, mechanical, and physical properties. Thermal vibration assessment should be conducted on fluid-conveying carbon nanotubes since the effect of thermal fluctuations on the mechanical characteristics of nanostructure are significant. Previous studies have revealed that when thermal vibration is taken into account, quantum effects can become extremely important in nanoscale electronics and structures. Hence, the present review focuses mostly on previous work on fluid-conveying nanotubes and the dynamical characteristics of size-dependent vibration and non-local strain gradient theory of fluid-conveying nanotubes. Furthermore, a special effort is made to address recent and rare investigations on the vibration of fluid-conveying nanotubes in thermal environment, as well as thermal vibration concerns of carbon nanotubes.

On the vibrational characteristics of single-walled boron nitride nanotubes/polymer nanocomposites: A finite element simulation

2017 ◽  
Vol 31 (22) ◽  
pp. 1750208 ◽  
Author(s):  
S. Rouhi ◽  
R. Ansari ◽  
A. Nikkar
Keyword(s):  
Finite Element ◽  
Boron Nitride ◽  
Polymer Nanocomposites ◽  
Volume Fraction ◽  
Boron Nitride Nanotubes ◽  
Frame Structure ◽  
Boron Nitride Nanotube ◽  
Volume Percentage ◽  
Vibrational Behavior ◽  
Vibrational Characteristics

The finite element method is used here to investigate the vibrational behavior of single-walled boron nitride nanotube/polymer nanocomposites. The polymer matrix is modeled as a continuous media. Besides, nanotubes are modeled as a space-frame structure. It is shown that increasing the length of nanotubes at a constant volume fraction leads to decreasing of the nanocomposite frequency. By investigating the effect of volume percentage on the frequencies of the boron nitride nanotube-reinforced polymer nanocomposites, it is observed that for short nanotubes, the nanocomposites with larger nanotube volume fractions have larger frequencies. Also, through studying the first 10 frequencies of nanocomposites reinforced by armchair and zigzag nanotubes, it is shown that the effect of chirality on the vibrational behavior of nanocomposite is insignificant.

Study of Nonlinear Dynamic Behavior of a Typical Jacket Type Platform Under Environmental Loading (Wave and Current) and Blast Overpressure

2004 ◽  
Author(s):  
M. Dousti ◽  
A. R. M. Gharabaghi ◽  
M. R. Chenaghlou
Keyword(s):  
Finite Element ◽  
Dynamic Behavior ◽  
Persian Gulf ◽  
Nonlinear Dynamic ◽  
The Other ◽  
Plastic Strains ◽  
Environmental Loading ◽  
Finite Element Software ◽  
Blast Overpressure ◽  
The One

In this paper the behavior of a jacket platform, which is installed in Persian Gulf under blast overpressure, is evaluated and interaction between blast and operating environmental wave and current loads is studied. Using finite element software the whole parts of platform, which include topside and jacket sections are modeled. The real pressure of blast load is applied for conducting the analyses. The study involves elastic and elasto-plastic analyses, which in the last one (elasto-plastic) the geometry and material nonlinearity have been considered. In the studied platform the results show that the interaction between blast and operating environmental wave and current loads is negligible but the comparison between two models, the one in which the whole parts of platform are modeled and the other one which only topside is modeled indicates that there are appreciable differences between the axial plastic strains.

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