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Prolonged simulation of near-free surface underwater explosion based on Eulerian finite element method

Ming He, A-Man Zhang, Yun-Long Liu

Accepted Manuscript , doi: 10.1016/j.taml.2020.01.003

[Abstract] (23) [FullText HTML] (9) [PDF 3055KB] (1)

Abstract:
In the area of naval architecture and ocean engineering, the research about the underwater explosion problem is of great significance. To achieve prolonged simulation of near-free surface underwater explosion, the underwater explosion transient numerical model is established in this paper based on compressible Eulerian finite element method (EFEM). Compared with Geers-Hunter formula, the Eulerian finite element method is availably validated by simulating the free-field underwater explosion case. Then, the bubble pulsation and flow field dynamic characteristics of the cases with different underwater explosive depth are compared in this work. Lastly, the height of the water hump and the pressure of flow flied are analyzed quantitatively through the simulation results.

On the plastic buckling of curved carbon nanotubes

Mohammad Malikan

Accepted Manuscript , doi: 10.1016/j.taml.2020.01.004

[Abstract] (12) [FullText HTML] (9) [PDF 3066KB] (0)

Abstract:
This research, for the first time, predicts theoretically static stability response of a curved carbon nanotube (CCNT) under an elastoplastic behavior with several boundary conditions. The CCNT is exposed to axial compressive loads. The equilibrium equations are extracted regarding the Euler-Bernoulli displacement field by means of the principle of minimizing total potential energy. The elastoplastic stress-strain is concerned with Ramberg-Osgood law on the basis of deformation and flow theories of plasticity. To seize the nano-mechanical behavior of the CCNT, the nonlocal strain gradient elasticity theory is taken into account. The obtained differential equations are solved using the Rayleigh-Ritz method based on a new admissible shape function which is able to analyze stability problems. To authorize the solution, some comparisons are illustrated which show a very good agreement with the published works. Conclusively, the best findings confirm that a plastic analysis is crucial in predicting the mechanical strength of CCNTs.

An analytical model to predict diffusion induced intermetallic compounds growth in Cu-Sn-Cu sandwich structures

Yuexing Wang, Yao Yao, Leon Keer

Accepted Manuscript

[Abstract] (0) [FullText HTML] (0) [PDF 2821KB] (0)

Abstract:
A mass diffusion model is developed to describe the growth kinetics of Cu₆Sn₅ intermetallic compounds (IMC) in the Cu-Sn-Cu sandwich structure. The proposed model is based on the local interfacial mass conversation law where interfacial Cu/Sn reactions and atomic diffusion are considered. Theoretical analysis shows that the IMC thickness growth is proportional to the square root of the product of the diffusion coefficient and time. The proposed model can explain the polarity effect of electromigration on kinetics of IMC growth where all the parameters have clear physical meaning. The theoretical predictions are compared with experimental results and show reasonable accuracy.

Spatial artificial neural network model for subgrid-scale stress and heat flux of compressible turbulenc

Chenyue Xi, Jianchun Wang, Hui Li, Minping Wan, Shiyi Chen

Accepted Manuscript

[Abstract] (12) [FullText HTML] (6) [PDF 3004KB] (0)

Abstract:
The subgrid-scale (SGS) stress and SGS heat flux are modeled by using an artificial neural network (ANN) for large eddy simulation (LES) of compressible turbulence. The input features of ANN model are based on the first-order and second-order derivatives of filtered velocity and temperature at different spatial locations. The proposed spatial artificial neural network (SANN) model gives much larger correlation coefficients and much smaller relative errors than the gradient model in an a priori analysis. In an a posteriori analysis, the SANN model performs better than the dynamic mixed model (DMM) in the prediction of spectra and statistical properties of velocity and temperature, and the instantaneous flow structures.

Universal scaling law of an origami paper spring

Bo-Hua Sun

Accepted Manuscript , doi: 10.1016/j.taml.2020.01.002

[Abstract] (86) [FullText HTML] (59) [PDF 2469KB] (4)

Abstract:
This letter solves an open question of origami paper spring risen by Yoneda et al.(Phys. Rev. E 2019). By using both dimensional analysis and data fitting, an universal scaling law of a paper spring is formulated. The scaling law shows that origami spring force obeys power square law of spring extension, however strong nonlinear to the total twist angle. The study has also successfully generalized the scaling law from the Poisson ratio 0.3 to an arbitrary Poisson's ratio with the help of dimensional analysis.

Neurodynamics analysis of cochlear hair cell activity

Weifeng Rong, Rubin Wang, Jianhai Zhang, Wanzeng Kong

Accepted Manuscript , doi: 10.1016/j.taml.2019.06.007

[Abstract] (86) [FullText HTML] (54) [PDF 3000KB] (3)

Abstract:
There have been many studies on the effect of cochlea basal membrane movement on the resolution of different frequencies and intensities. However, these studies did not take into account the influence of power and energy consumption of the hair cells in the process of the electromotility movement, as well as the neurodynamic mechanism that produced this effect. This makes previous studies unable to fully clarify the function of outer hair cells (OHCs) and the mechanism of sound amplification. To this end, we introduce the gate conductance characteristics of the hair cells in the mechanical process of increasing frequency selectivity. The research finds that the low attenuation of OHCs membrane potential and the high gain in OHC power and energy consumption caused that OHC amplification is driven by electromotility. The research results show that the amplification of the OHCs is driven by low attenuation of membrane potential and high gain of power and energy consumption. This conclusion profoundly reveals the physiological mechanism of the electromotility movement.

Molecular investigation on the compatibility of epoxy resin with liquid oxygen

Mingfa Ren, Lei Wang, Tong Li, Bingqing Wei

Accepted Manuscript , doi: 10.1016/j.taml.2019.06.010

[Abstract] (156) [FullText HTML] (56) [PDF 3270KB] (4)

Abstract:
Conventional fiber reinforced plastics (FRPs) have compatibility issues with solid oxygen while used as a fuel tank, which might cause combustion and explosion. To study the compatibility of different epoxy resins with liquid oxygen, molecular dynamics was used to simulate the phase changes of cross-linked epoxy resins under the impact of solid oxygen. Three curing resin systems, which are bisphenol A epoxy resin (DGEBA), bisphenol F epoxy resin (DGEBF), and tetrahydrophthalate diglycidyl ester (epoxy resin 711), are modeled to investigate the rational material system for the application of fuel tanks in launching vehicles. The simulation results show that the order of solid oxygen compatibility of these epoxy resins is DGEBA > DGEBF > epoxy resin 711 at the same density of crosslinking. The selection of curing agent also has an impact on the compatibility, with the same epoxy, diaminodiphenyl methane (DDM) has more advanced performance comparing to diaminodiphenyl sulfone (DDS).

Minimizing electrostatic interactions from piezoresponse force microscopy via capacitive excitation

Qingfeng Zhu, Ehsan Nasr Esfahani, Shuhong Xie, Jiangyu Li

Accepted Manuscript , doi: 10.1016/j.taml.2020.01.001

[Abstract] (21) [FullText HTML] (10) [PDF 2811KB] (0)

Abstract:
Piezoresponse force microscopy (PFM) has emerged as one of the most powerful techniques to probe ferroelectric materials at the nanoscale, yet it has been increasingly recognized that piezoresponse measured by PFM is often influenced by electrostatic interactions. In this letter, we report a capacitive excitation PFM (ce-PFM) to minimize the electrostatic interactions. The effectiveness of ce-PFM in minimizing electrostatic interactions is demonstrated by comparing the piezoresponse and the effective piezoelectric coefficient measured by ce-PFM and conventional PFM. The effectiveness is further confirmed through the ferroelectric domain pattern imaged via ce-PFM and conventional PFM in vertical modes, with the corresponding domain contrast obtained by ce-PFM is sharper than conventional PFM. These results demonstrate ce-PFM as an effective tool to minimize the interference from electrostatic interactions and to image ferroelectric domain pattern, and it can be easily implemented in conventional atomic force microscope (AFM) setup to probe true piezoelectricity at the nanoscale.

Neurodynamics analysis of cochlear hair cell activity

Weifeng Rong, Rubin Wang, Jianhai Zhang, Wanzeng Kong

Accepted Manuscript

[Abstract] (82) [PDF 3000KB] (1)

Abstract:
There have been many studies on the effect of cochlea basal membrane movement on the resolution of different frequencies and intensities. However, these studies did not take into account the influence of power and energy consumption of the hair cells in the process of the electromotility movement, as well as the neurodynamic mechanism that produced this effect. This makes previous studies unable to fully clarify the function of outer hair cells and the mechanism of sound amplification. To this end, we introduce the gate conductance characteristics of the hair cells in the mechanical process of increasing frequency selectivity. The research finds that the low attenuation of outer hair cell (OHCs) membrane potential and the high gain in OHC power and energy consumption caused that OHC amplification is driven by electromotility. The research results show that the amplification of the outer hair cells is driven by low attenuation of membrane potential and high gain of power and energy consumption. This conclusion profoundly reveals the physiological mechanism of the electromotility movement.

Universal scaling law of an origami paper spring

Bo-Hua Sun

Accepted Manuscript

[Abstract] (90) [PDF 2469KB] (1)

Abstract:
This letter solves an open question of origami paper spring risen by Yoneda et al.(2019). By using both dimensional analysis and data fitting, an universal scaling law of a paper spring is formulated. The scaling law shows that origami spring force obeys power square law of spring extension, however strong nonlinear to the total twist angle. The study has also successfully generalized the scaling law from the Poisson ratio 0.3 to an arbitrary Poisson's ratio with the help of dimensional analysis.

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Article

Crack propagation simulation in brittle elastic materials by a phase field method

Xingxue Lu, Cheng Li, Ying Tie, Yuliang Hou, Chuanzeng Zhang

2019, 9(6): 339 -352. doi: 10.1016/j.taml.2019.06.001

[Abstract] (185) [FullText HTML] (144) [PDF 3845KB] (55)

Abstract:
To overcome the difficulties of re-meshing and tracking the crack-tip in other computational methods for crack propagation simulations, the phase field method based on the minimum energy principle is introduced by defining a continuous phase field variable

\begin{document}$\phi $\end{document}

(x)∈[0,1] to characterize discontinuous cracks in brittle materials. This method can well describe the crack initiation and propagation without assuming the shape, size and orientation of the initial crack in advance. In this paper, a phase field method based on Miehe's approach [Miehe et al., Comp. Meth. App. Mech. Eng. (2010)] is applied to simulate different crack propagation problems in two-dimensional (2D), isotropic and linear elastic materials. The numerical implementation of the phase field method is realized within the framework of the finite element method (FEM). The validity, accuracy and efficiency of the present method are verified by comparing the numerical results with other reference results in literature. Several numerical examples are presented to show the effects of the loading type (tension and shear), boundary conditions, and initial crack location and orientation on the crack propagation path and force-displacement curve. Furthermore, for a single edge-cracked bi-material specimen, the influences of the loading type and the crack location on the crack propagation trajectory and force-displacement curve are also investigated and discussed. It is demonstrated that the phase field method is an efficient tool for the numerical simulation of the crack propagation problems in brittle elastic materials, and the corresponding results may have an important relevance for predicting and preventing possible crack propagations in engineering applications.

Sensitivity analysis of the vane length and passage width for a radial type swirler employed in a triple swirler configuration

Foad Vashahi, Shahnaz Rezaei, Reza Alidoost Dafsari, Jeekeun Lee

2019, 9(6): 363 -375. doi: 10.1016/j.taml.2019.05.004

[Abstract] (140) [FullText HTML] (88) [PDF 3869KB] (6)

Abstract:
The design of axial or radial swirlers typically governs a number of geometrical parameters that are determined by the desired flow field. In the meantime, the number of unknown parameters increases with the number of concentrically mounted swirlers. The available literature is nonetheless limited, and designers are obligated to increase the number of initial assumptions. In this article, three kinds of triple swirlers are employed and simulations are performed to determine the effect of each parameter on the swirler performance. Based on the correlation provided, over-lengthening the radial vane length could result in significant changes in the flow field from the jet-like pattern to a wide swirl-jet angle due to the Coanda effect. Passage width should also have the potential to alter the swirl-jet angle and velocity field at the exit of the swirler.

Letter

Generalized canonical transformation for second-order Birkhoffian systems on time scales

Y. Zhang, X.H. Zhai

2019, 9(6): 353 -357. doi: 10.1016/j.taml.2019.06.004

[Abstract] (126) [FullText HTML] (86) [PDF 2395KB] (4)

Abstract:
The theory of time scales, which unifies continuous and discrete analysis, provides a powerful mathematical tool for the study of complex dynamic systems. It enables us to understand more clearly the essential problems of continuous systems and discrete systems as well as other complex systems. In this paper, the theory of generalized canonical transformation for second-order Birkhoffian systems on time scales is proposed and studied, which extends the canonical transformation theory of Hamilton canonical equations. First, the condition of generalized canonical transformation for the second-order Birkhoffian system on time scales is established. Second, based on this condition, six basic forms of generalized canonical transformation for the second-order Birkhoffian system on time scales are given. Also, the relationships between new variables and old variables for each of these cases are derived. In the end, an example is given to show the application of the results.

Modified slow-fast analysis method for slow-fast dynamical systems with two scales in frequency domain

Zhengdi Zhang, Zhangyao Chen, Qinsheng Bi

2019, 9(6): 358 -362. doi: 10.1016/j.taml.2019.05.010

[Abstract] (120) [FullText HTML] (64) [PDF 4861KB] (6)

Abstract:
A modified slow-fast analysis method is presented for the periodically excited non-autonomous dynamical system with an order gap between the exciting frequency and the natural frequency. By regarding the exciting term as a slow-varying parameter, a generalized autonomous fast subsystem can be defined, the equilibrium branches as well as the bifurcations of which can be employed to account for the mechanism of the bursting oscillations by combining the transformed phase portrait introduced. As an example, a typical periodically excited Hartley model is used to demonstrate the validness of the method, in which the exciting frequency is far less than the natural frequency. The equilibrium branches and their bifurcations of the fast subsystem with the variation of the slow-varying parameter are presented. Bursting oscillations for two typical cases are considered, which reveals that, fold bifurcation may cause the the trajectory to jump between different equilibrium branches, while Hopf bifurcation may cause the trajectory to oscillate around the stable limit cycle.

On time independent Schrödinger equations in quantum mechanics by the homotopy analysis method

Jyotirmoy Rana, Shijun Liao

2019, 9(6): 376 -381. doi: 10.1016/j.taml.2019.05.006

[Abstract] (139) [FullText HTML] (86) [PDF 2539KB] (3)

Abstract:
A general analytic approach, namely the homotopy analysis method (HAM), is applied to solve the time independent Schrödinger equations. Unlike perturbation method, the HAM-based approach does not depend on any small physical parameters, corresponding to small disturbances. Especially, it provides a convenient way to gain the convergent series solution of quantum mechanics. This study illustrates the advantages of this HAM-based approach over the traditional perturbative approach, and its general validity for the Schrödinger equations. Note that perturbation methods are widely used in quantum mechanics, but perturbation results are hardly convergent. This study suggests that the HAM might provide us a new, powerful alternative to gain convergent series solution for some complicated problems in quantum mechanics, including many-body problems, which can be directly compared with the experiment data to improve the accuracy of the experimental findings and/or physical theories.

Creep relaxation in FGM rotating disc with nonlinear axisymmetric distribution of heterogeneity

Hodais Zharfi

2019, 9(6): 382 -390. doi: 10.1016/j.taml.2019.05.005

[Abstract] (149) [FullText HTML] (89) [PDF 3403KB] (13)

Abstract:
Rotating discs are the vital part of many types of machineries. Usually there is a tendency to make use of them in higher rotational speeds, but ahead of their complete break down the incidence of vibration, plastic failure or creep relaxation can create serious damages which finally prevent the increase of the rotational speed. The invention of new materials has provided new opportunities to increase the loading capacity and speed of the discs. Functionally graded materials (FGMs) are a kind of new materials utilized in the construction of rotating discs. Consequently an important aspect in the analyses of heterogeneous FGM discs is the study of their creep relaxation. One of the well known constitutive equations for the modeling of creep phenomenon is known as the Sherby's law. Based on the steady state creep, the behavior of a variety of FGM rotating discs are studied. The analysis considers the conditions in which the distribution of volume fraction follows a power-law pattern. The required mathematical model and its solution for the analysis of stress and creep strain rate is represented. Some case studies are considered in which the effects of nonlinearly distributed volume fractions are studied. In the case studies, the analysis of rotating FGM discs made of Aluminum-Silicon Carbide compounds is considered. Besides, the analyses of discs with outside tractions are considered and the effects of typical material compositions upon the creep deformations are studied. For instance, the investigation discloses the significance of the use of FGM hubs in the turbine constructions.

Dynamic response of clamped sandwich beams: analytical modeling

Lang Li, Bin Han, Qian-Cheng Zhang, Zhen-Yu Zhao, Tian Jian Lu

2019, 9(6): 391 -396. doi: 10.1016/j.taml.2019.06.002

[Abstract] (155) [FullText HTML] (97) [PDF 2779KB] (5)

Abstract:
An improved analytical model is developed to predict the dynamic response of clamped lightweight sandwich beams with cellular cores subjected to shock loading over the entire span. The clamped face sheets are simplified as a single-degree-of-freedom (SDOF) system, and the core is idealized using the rigid-perfectly-plastic-locking (RPPL) model. Reflection of incident shock wave is considered by incorporating the bending/stretching resistance of the front face sheet and compaction of the core. The model is validated with existing analytical predictions and FE simulation results, with good agreement achieved. Compared with existing analytical models, the proposed model exhibits superiority in two aspects: the deformation resistance of front face sheet during shock wave reflection is taken into account; the effect of pulse shape is considered. The practical application range of the proposed model is therefore wider.

Modeling shale with consideration of bedding planes by cohesive finite element method

Chunfang Li, Zhennan Zhang

2019, 9(6): 397 -402. doi: 10.1016/j.taml.2019.06.003

[Abstract] (47) [FullText HTML] (24) [PDF 3463KB] (2)

Abstract:
Shale contains distributed directional bedding planes, which make the shale transverse isotropic. To model shale with consideration of the bedding planes, a cohesive finite element method (CFEM) is developed based on the randomized triangular mesh. The interface orientation generated from such mesh tends to be uniformly distributed with the element number increasing. To represent the bedding plane, the interfaces aligned with the bedding plane are assigned the cohesive law that characterizes the bedding plane while the other interfaces are assigned the cohesive law that characterizes the matrix. By this means, the anisotropy characteristics of the stiffness and the strength of shale are well represented. The simulation examples demonstrate that the bedding plane has a significant influence on the fracture trajectory, which is consistent with the observation in the experiment. It is suggested that this modeling method of shale is feasible. It provides an alternative approach to fracture simulation in shale.

The spatial evolution of velocity and density profiles in an arrested salt wedge

Adam J.K. Yang, E.W. Tedford, G.A. Lawrence

2019, 9(6): 403 -408. doi: 10.1016/j.taml.2019.06.005

[Abstract] (248) [FullText HTML] (78) [PDF 2891KB] (34)

Abstract:
The spatial variation in the properties of an arrested salt wedge have been investigated, both analytically and in the laboratory. In the laboratory particle image velocimetry and laser induced fluorescence were used to obtain flow velocities and the height of the density interface. An analytical solution for the profile of interface height, in the absence of interfacial instabilities, has been developed from two-layer internal hydraulic theory. The evolution of the velocity profile is predicted using a momentum diffusion equation following a Lagrangian frame of reference along the interface of the salt wedge. The centre of the shear layer is predicted to lie above the density interface, with this offset decreasing in the downstream direction. Our theoretical predictions are in good agreement with our laboratory measurements.