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Efficient model for the elastic load of film-substrate system involving imperfect interface effects

Wenwang Wu, Huabin Yu, Rui Xue, Tian Zhao, Ran Tao, Haitao Liao

Accepted Manuscript , doi: 10.1016/j.taml.2020.01.048

[Abstract] (0) [FullText HTML] (0) [PDF 3800KB] (0)

Abstract:
In this paper, an efficient calculation method based on discrete Fourier transformation is developed for evaluating elastic load induced elastic deformation fields of film-substrate system. Making use of 2D discrete Fourier transformation, the elastic fields induced by Hertz load is harvested in frequency domain, and the displacement and stress fields across the interface are enforced to satisfy the elasticity conditions for each Fourier modes. Given arbitrary distributed stress field at free surface plane of the three types of film-substrate systems, unique resultant elastic field within the can be harvested. Hertz load of half space, elastic film on elastic substrate, elastic film on rigid substrate system and elastic film-substrate system with three types of imperfect interface models are investigated: (a) the spring-like imperfect interface model which can be described as:

\begin{document}${\left. {u_k^f} \right|_{{z^f} = - h}} - {\left. {u_k^s} \right|_{{z^s} = 0}} = \left[ {{K_T}} \right]{\sigma _{kz}}$\end{document}

and

\begin{document}${\left. {u_z^f} \right|_{{z^f} = - h}} - {\left. {u_z^s} \right|_{{z^s} = 0}} = \left[ {{K_N}} \right]{\sigma _{zz}}$\end{document}

; (b) the dislocation-like interface model, where interface displacement and stress components relation can be described as:

\begin{document}${\left. {u_i^f} \right|_{{z^f} = 0}} = \left[ {k_{ij}^u} \right]{\left. {u_i^s} \right|_{{z^s} = 0}}$\end{document}

and

\begin{document}${\left. {\sigma _{iz}^f} \right|_{{z^f} = 0}} = {\left. {\sigma _{iz}^s} \right|_{{z^s} = 0}}$\end{document}

; (c) the force-like interface model, where interface displacement and stress components relation can be described as:

\begin{document}${\left. {u_i^f} \right|_{{z^f} = 0}} = {\left. {u_i^s} \right|_{{z^s} = 0}}$\end{document}

and

\begin{document}${\left. {\sigma _{iz}^f} \right|_{{z^f} = 0}} = \left[ {k_{ij}^t} \right]{\left. {\sigma _{iz}^s} \right|_{{z^s} = 0}}$\end{document}

respectively. Finally, several simulation examples are performed for verification of the reliability and efficiency of the proposed semi-analytical methods.

A modified Lin equation for the energy balance in isotropic turbulence

W. D. McComb

Accepted Manuscript , doi: 10.1016/j.taml.2020.01.055

[Abstract] (8) [FullText HTML] (6) [PDF 2538KB] (0)

Abstract:
At sufficiently large Reynolds numbers, turbulence is expected to exhibit scaleinvariance in an intermediate (‘inertial’) range of wavenumbers, as shown by powerlaw behaviour of the energy spectrum and also by a constant rate of energy transfer through wavenumber. However, there is an apparent contradiction between the definition of the energy flux (i.e. the integral of the transfer spectrum) and the observed behaviour of the transfer spectrum itself. This is because the transfer spectrum T(k) is invariably found to have a zero-crossing at a single point (at k = k_*, say), implying that the corresponding energy flux cannot have an extended plateau but must instead have a maximum value at k = k_*. This behaviour was formulated as a paradox and resolved by the introduction of filtered/partitioned transfer spectra, which exploited the symmetries of the triadic interactions (J. Phys. A: Math. Theor., 41:75501, 2008). In this paper we consider the more general implications of that procedure for the spectral energy balance equation, also known as the Lin equation. It is argued that the resulting modified Lin equations (and their corresponding Navier-Stokes equations) offer a new starting point for both numerical and theoretical methods, which may lead to a better understanding of the underlying energy transfer processes in turbulence. In particular the filteredpartitioned transfer spectra could provide a basis for a hybrid approach to the statistical closure problem, with the different spectra being tackled using different methods.

A novel method for investigation of acoustic and elastic wave phenomena using numerical experiments

Alena Favorskaya, Igor Petrov

Accepted Manuscript , doi: 10.1016/j.taml.2020.01.040

[Abstract] (162) [FullText HTML] (150) [PDF 3177KB] (1)

Abstract:
The emergence of new types of composite materials, the depletion of existing hydrocarbon deposits, and the increase in the speed of trains require the development of new research methods based on wave scattering. Therefore, it is necessary to determine the laws of wave scattering in inhomogeneous media. We propose a method that combines the advantages of a numerical simulation with an analytical study of the boundary value problem of elastic and acoustic wave equations. In this letter we present the results of the study using the proposed method: the formation of a response from a shear wave in an acoustic medium and the formation of shear waves when a vertically incident longitudinal wave is scattered by a vertical gas-filled fracture. We have obtained a number of analytical expressions characterising the scattering of these wave types.

Constructal design method dealing with stiffened plates and symmetry boundaries

Rodrigo R. Amaral, Grégori S. Troina, Cristiano Fragassa, Ana Pavlovic, Marcelo L. Cunha, Luiz A.O. Rocha, Elizaldo D. dos Santos, Liércio A. Isoldi

Accepted Manuscript , doi: 10.1016/j.taml.2020.01.042

[Abstract] (203) [FullText HTML] (171) [PDF 3171KB] (12)

Abstract:
A new computational procedure for modelling the structural behavior of stiffened plates with symmetry boundary conditions is here presented. It uses two-dimensional finite elements as a way to decrease computational time without losing precision thanks to a relatively small number of elements applied for analyzing out-of-plane displacements (deflections) and stresses. Adding, the constructal design method was included in the procedure, together with the Exhaustive Search technique, with the scope to optimize the stress/strain status of stiffened plates by design changes. For the purpose, a reference plate without stiffeners was initially design and used as starting point. Part of the volume was reshaped into stiffeners: thickness was reduced maintaining unchanged weight, length and width. The main goal was to minimize strains and stresses by geometric changes. Results demonstrated that, thanks to this design procedure, it is always possible to find an adequate geometry transformation from reference plate into stiffeners, allowing significant improvements in mechanical behavior.

A note on a family of proximal gradient methods for quasi-static incremental problems in elastoplastic analysis

Yoshihiro Kanno

Accepted Manuscript , doi: 10.1016/j.taml.2020.01.044

[Abstract] (117) [FullText HTML] (127) [PDF 2599KB] (1)

Abstract:
Accelerated proximal gradient methods have recently been developed for solving quasi-static incremental problems of elastoplastic analysis with some different yield criteria. It has been demonstrated through numerical experiments that these methods can outperform conventional optimization-based approaches in computational plasticity. However, in literature these algorithms are described individually for specific yield criteria, and hence there exists no guide for application of the algorithms to other yield criteria. This short paper presents a general form of algorithm design, independent of specific forms of yield criteria, that unifies the existing proximal gradient methods. Clear interpretation is also given to each step of the presented general algorithm so that each update rule is linked to the underlying physical laws in terms of mechanical quantities.

A unidirectional SH wave transducer based on phase-controlled antiparallel thickness-shear (d₁₅) piezoelectric strips

Mingtong Chen, Qiang Huan, Faxin Li

Accepted Manuscript , doi: 10.1016/j.taml.2020.01.050

[Abstract] (133) [FullText HTML] (83) [PDF 3125KB] (3)

Abstract:
In recent years, shear horizontal (SH) waves are being paid more and more attention to in structural health monitoring as it has only one displacement component. In this paper, a unidirectional SH wave transducer based on phase-controlled antiparallel thickness-shear (d₁₅) piezoelectric strips (APS) is proposed. Here two pairs of identical APS were used each of which is a bidirectional SH wave transducer. By setting the interval between the two pairs of APS as 1/4 wavelength and the excitation delay between them as 1/4 period of the central operating frequency, unidirectional SH waves can be excited. Both finite element simulations and experiments were performed to validate the proposed design. Results show that SH₀ waves were successfully excited only along one direction and those along the unwanted directions were suppressed very well. The proposed unidirectional SH wave transducer is very helpful to study the fundamentals and applications of SH waves.

Dynamic mode decomposition and reconstruction of transient cavitating flows around a Clark-Y hydrofoil

Rundi Qiu, Renfang Huang, Yiwei Wang, Chenguang Huang

Accepted Manuscript , doi: 10.1016/j.taml.2020.01.051

[Abstract] (105) [FullText HTML] (64) [PDF 2850KB] (15)

Abstract:
The transient cavitating flow around the Clark-Y hydrofoil is numerically investigated by the dynamic mode decomposition with criterion. Based on the ranking dominant modes, frequencies of the first four modes are in good accordance with those obtained by fast Fourier transform. Furthermore, the cavitating flow field is reconstructed by the first four modes, and the dominant flow features are well captured with the reconstructed error below 12% when compared to the simulated flow field. This paper offers a reference for observing and reconstructing the flow fields, and gives a novel insight into the transient cavitating flow features.

Modeling rock fragmentation by coupling Voronoi diagram and discretized virtual internal bond

Sai Liu, Zhennan Zhang

Accepted Manuscript , doi: 10.1016/j.taml.2020.01.045

[Abstract] (185) [FullText HTML] (88) [PDF 3120KB] (3)

Abstract:
The rock fragmentation involves the inter-block and the intra-block fracture. A simulation method for rock fragmentation is developed by coupling Voronoi diagram (VD) and discretized virtual internal bond (DVIB). The DVIB is a lattice model that consists of bonds. The VD is used to generate the potential block structure in the DVIB mesh. Each potential block may contain any number of bond cells. To characterize the inter-block fracture, a hyperelastic bond potential is employed for the bond cells that are cut by the VD edges. While to characterize the intra-block fracture, an elastobrittle bond potential is adopted for the bonds in a block. By this method, both the inter-block and intra-block fracture can be well simulated. The simulation results suggest that this method is a simple and efficient approach to rock fragmentation simulation with block smash.

Achieving an optimal shock-wave mitigation inside open channels with cavities for weak shock waves: A computational study

N. Brahmi, A. Hadjadj

Accepted Manuscript , doi: 10.1016/j.taml.2020.01.046

[Abstract] (122) [FullText HTML] (127) [PDF 3826KB] (2)

Abstract:
This paper deals with a numerical study of weak shock-waves propagation and their attenuation in channel flow having different heights and exhibiting a hollow circular cavities with different depths and diffraction angles inside. The effect of initial diffraction angle and cavity depth on the shock mitigation is investigated. A better shock attenuation is achieved with diffraction angle

\begin{document}$ \theta_{w} = 90^\circ $\end{document}

by a factor of approximately 17% in terms of shock-Mach number and 38% in terms of total energy. The obtained results show also, in addition to the initial diffraction angle and cavity depth, the importance of reducing the channel heights as well as the position of the reduced section in achieving an optimal shock-wave attenuation. The presence of a cavity inside the channel helps to attenuate faster the shock wave. The underlying physics relies on the shock diffraction phenomenon that generates large amount of vortical structures capable of dissipating part of the shock energy by inducing a pressure loss behind it. A subtle arrangement of channel position/height and a cavity location leads to an efficient pressure attenuation by approximately a factor of 57% for

\begin{document}$ M_s = 1.6 $\end{document}

and 16% for

\begin{document}$ M_s = 1.1 $\end{document}

Numerical investigations to design a novel model based on the fifth order system of Emden–Fowler equations

Zulqurnain Sabir, Mehmet Giyas Sakar, Manshuk Yeskindirova, Onur Saldir

Accepted Manuscript , doi: 10.1016/j.taml.2020.01.049

[Abstract] (114) [FullText HTML] (24) [PDF 2769KB] (10)

Abstract:
The aim of the present study is to design a new fifth order system of Emden–Fowler equations and related four types of the model. The standard second order form of the Emden–Fowler has been used to obtain the new model. The shape factor that appear more than one time discussed in detail for every case of the designed model. The singularity at η = 0 at one point or multiple points is also discussed at each type of the model. For validation and correctness of the new designed model, one example of each type based on system of fifth order Emden–Fowler equations are provided and numerical solutions of the designed equations of each type have been obtained by using variational iteration scheme. The comparison of the exact results and present numerical outcomes for solving one problem of each type is presented to check the accuracy of the designed model.

Ultrasound calibration with ladder phantom at multiple depths for breast biopsy navigation system

Jackrit Suthakorn, Narucha Tanaiutchawoot, Cholatip Wiratkapan

Accepted Manuscript , doi: 10.1016/j.taml.2020.01.037

[Abstract] (288) [FullText HTML] (154) [PDF 2953KB] (3)

Abstract:
Ultrasound guided breast biopsy navigation system with a graphical user interface and a passive robotic needle holder is developed to increase the performance and reliability of the radiologist. Ultrasound calibration and tool tip calibration are required before using the system. A ladder phantom is developed to be used for ultrasound calibration in real time system with only one ultrasound image required. The passive robotic needle holder structure results in an identity matrix for the makes the rotation matrix; therefore, only translation and scaling are required in the system. This method can be applied to multiple ultrasound depths, which has a relationship at each depth and a relationship to the ultrasound image on the display. The results show high accuracy (<1 mm.) and rapid calibration (5–10 minutes) which is suitable for a real time system like a breast biopsy navigation system based on tests with a breast phantom.

Interactions of human islet amyloid polypeptide with lipid structure of different curvatures

Le Mei, Wenhui Shen, Xuwei Wu, Jie Liu, Dechang Li, Baohua Ji

Accepted Manuscript , doi: 10.1016/j.taml.2020.01.053

[Abstract] (167) [FullText HTML] (63) [PDF 4542KB] (8)

Abstract:
Curvature is one of the most important features of lipid membranes in living cells, which significantly influences the structure of lipid membranes and their interaction with proteins. Taken the human islet amyloid polypeptide (hIAPP), an important protein related to the pathogenesis of type II diabetes, as an example, we performed MD simulations to study the interaction between the protein and the lipid structures with varied curvatures. We found that the lipids in the high curvature membrane pack loosely with high mobility. The hIAPP initially forms H-bonds with the membrane surface that anchored the protein, and then inserts into the membrane through the hydrophobic interactions between the residues and the hydrophobic tails of the lipids. hIAPP can insert into the membrane more deeply with a larger curvature and with a stronger binding strength. Our result provided important insights into the mechanism of the membrane curvature-dependent property of proteins with molecular details.

Evolution of vortices in the wake of an ARJ21 airplane: Application of the lift-drag model

Jun-Duo Zhang, Qing-Hai Zuo, Meng-Da Lin, Wei-Xi Huang, Wei-Jun Pan, Gui-Xiang Cui

Accepted Manuscript , doi: 10.1016/j.taml.2020.01.054

[Abstract] (13) [FullText HTML] (11) [PDF 3576KB] (0)

Abstract:
Wake separation is crucial to aircraft landing safety and is an important factor in airport operational efficiency. The near-ground evolution characteristics of wake vortices form the foundation of the wake separation system design. In this study, we analysed the near-ground evolution of vortices in the wake of a domestic aircraft ARJ21 initialised by the lift-drag model using large eddy simulations based on an adaptive mesh. Evolution of wake vortices formed by the main wing, flap and horizontal tail was discussed in detail. The horizontal tail vortices are the weakest and dissipate rapidly, whereas the flap vortices are the strongest and induce the tip vortex to merge with them. The horizontal tail and flap of an ARJ21 do not significantly influence the circulation evolution, height change and movement trajectory of the wake vortices. The far-field evolution of wake vortices can therefore be analysed using the conventional wake vortex model.

Investigation of Agave cantala-based composite fibers as prosthetic socket materials accounting for a variety of alkali and microcrystalline cellulose treatments

Sakuri Sakuri, Eko Surojo, Dody Ariawan, Aditya Rio Prabowo

Accepted Manuscript , doi: 10.1016/j.taml.2020.01.052

[Abstract] (41) [FullText HTML] (11) [PDF 3396KB] (3)

Abstract:
This study was aimed to determine the mechanical strength of composites made from Agave cantala with an unsaturated polyester matrix and microcrystalline cellulose. Cantala fiber (CF) was treated with 6% NaOH with immersion times of 0 h (UF), 3 h (AK3), 6 h (AK6), 9 h (AK9), and 12 h (AK12). Thermogravimetric analysis (TGA) analysis shows that treated CF has higher thermal stability than CF without treatment. Cantala fiber was tested by X-ray diffraction. After alkali treatment with a 6-h soaking, it had a crystallinity index of 73.65%. Scanning electron microscopy (SEM) showed that the fibers were cleaner after alkali treatment because hemicellulose, wax, and other impurities were removed. Examination of the contact angle and surface energy showed that treated CF has smaller contact angles and greater surface energy.

Universal scaling law of an origami paper spring

Bo-Hua Sun

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

[Abstract] (496) [FullText HTML] (288) [PDF 2469KB] (7)

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.

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Letter

An improved semi-empirical friction model for gas-liquid two-phase flow in horizontal and near horizontal pipes

M. Gharehasanlou, M. Emamzadeh, M. Ameri

2020, 10(4): 213 -223. doi: 10.1016/j.taml.2020.01.013

[Abstract] (310) [FullText HTML] (239) [PDF 3402KB] (11)

Abstract:
Pressure drop and liquid hold-up are two very important fluid flow parameters in design and control of multiphase flow pipelines. Friction factors play an important role in the accurate calculation of pressure drop. Various empirical and semi-empirical closure relations exist in the literature to calculate the liquid-wall, gas-wall and interfacial friction in two-phase pipe flow. However most of them are empirical correlations found under special experimental conditions. In this paper by modification of a friction model available in the literature, an improved semi-empirical model is proposed. The proposed model is incorporated in the two-fluid correlations under equilibrium conditions and solved. Pressure gradient and velocity profiles are validated against experimental data. Using the improved model, the pressure gradient deviation from experiments diminishes by about 3%; the no-slip condition at the interface is satisfied and the velocity profile is predicted in better agreement with the experimental data.

Simulation of shear layers interaction and unsteady evolution under different double backward-facing steps

Fang Deng, Guilai Han, Zonglin Jiang

2020, 10(4): 224 -229. doi: 10.1016/j.taml.2020.01.020

[Abstract] (366) [FullText HTML] (284) [PDF 2688KB] (12)

Abstract:
High-order accurate schemes are employed to numerically simulate the interaction of a supersonic jet and a co-directional supersonic inflow. A double backward-facing step model is proposed to investigate the interaction between the jet shear layer and the supersonic inflow shear layer. It is found that due to the interaction of the shear layer, a secondary jet is injected into the recirculation zone at the intersection of the two shear layers. The secondary jet produced by the interaction of the two shear layers has a periodicity because of shear layers interaction. The distinction in the shape of double backward-facing steps will induce changes in the period of the secondary jet. The analysis and discussion of the periodicity of the secondary jet are mainly focused in this letter.

On the mechanism by which nose bluntness suppresses second-mode instability

Armani Batista, Arham Amin Khan, Joseph Kuehl

2020, 10(4): 230 -240. doi: 10.1016/j.taml.2020.01.024

[Abstract] (373) [FullText HTML] (435) [PDF 3223KB] (13)

Abstract:
A physical mechanism by which nose bluntness suppresses second-mode instability is proposed. Considered are 7 degree half-angle straight cones with nose bluntness radii of 0.15 mm, 3.556 mm, 5 mm, 9.525 mm, 12.7 mm and 25.4 mm at tunnel conditions relevant to the AFOSR-Notre Dame Large Mach 6 Quiet Tunnel. It is shown that second-mode suppression is achieved via entropy layer modulation of the basic state density gradient. A weakening of the density gradient disrupts the acoustic resonance necessary to sustain second-mode growth. These results are consistent with the thermoacoustic interpretation which posits that second-mode instability can be modeled as thermoacoustic resonance of acoustic energy trapped within an acoustic impedance well. Furthermore, the generalized inflection point criterion of Lees and Lin is applied to develop a criterion for the existence of second-mode instability based on the strength of the basic state density gradient.

Particles-induced turbulence: A critical review of physical concepts, numerical modelings and experimental investigations

Guodong Gai, Abdellah Hadjadj, Sergey Kudriakov, Olivier Thomine

2020, 10(4): 241 -248. doi: 10.1016/j.taml.2020.01.026

[Abstract] (319) [FullText HTML] (241) [PDF 3005KB] (8)

Abstract:
The presence of solid particles or water droplets in continuous fluid flow can either induce turbulence attenuation or amplification. The modification of the state of the turbulence depends on the characteristics of the particles, such as volume fraction, mean diameter, mass density, or carrier phase flow properties. In this brief review, the main physical concepts related to the most important physical aspects of turbulence modulation are summarized. Different criteria used to distinguish the enhancement or the attenuation effects of the particles on the carrier phase flows are recalled. For the interest of large-scale industrial applications, several theoretical, experimental and empirical approaches are discussed, which provides an interesting framework for the study of the effect of particles on turbulence behavior modification.

Deformation and failure in nanomaterials via a data driven modelling approach

M. Amir Siddiq

2020, 10(4): 249 -252. doi: 10.1016/j.taml.2020.01.029

[Abstract] (290) [FullText HTML] (187) [PDF 3264KB] (15)

Abstract:
A data driven computational model that accounts for more than two material states has been presented in this work. Presented model can account for multiple state variables, such as stresses, strains, strain rates and failure stress, as compared to previously reported models with two states. Model is used to perform deformation and failure simulations of carbon nanotubes and carbon nanotube/epoxy nanocomposites. The model capability of capturing the strain rate dependent deformation and failure has been demonstrated through predictions against uniaxial test data taken from literature. The predicted results show a good agreement between data set taken from literature and simulations.

Nonlinear energy harvesting from vibratory disc-shaped piezoelectric laminates

Abdolreza Pasharavesh, Reza Moheimani, Hamid Dalir

2020, 10(4): 253 -261. doi: 10.1016/j.taml.2020.01.032

[Abstract] (364) [FullText HTML] (195) [PDF 3050KB] (18)

Abstract:
Implementing resonators with geometrical nonlinearities in vibrational energy harvesting systems leads to considerable enhancement of their operational bandwidths. This advantage of nonlinear devices in comparison to their linear counterparts is much more obvious especially at small-scale where transition to nonlinear regime of vibration occurs at moderately small amplitudes of the base excitation. In this paper the nonlinear behavior of a disc-shaped piezoelectric laminated harvester considering midplane-stretching effect is investigated. Extended Hamilton's principle is exploited to extract electromechanically coupled governing partial differential equations of the system. The equations are firstly order-reduced and then analytically solved implementing perturbation method of multiple scales. A nonlinear finite element method (FEM) simulation of the system is performed additionally for the purpose of verification which shows agreement with the analytical solution to a large extent. The frequency response of the output power at primary resonance of the harvester is calculated to investigate the effect of nonlinearity on the system performance. Effect of various parameters including mechanical quality factor, external load impedance and base excitation amplitude on the behavior of the system are studied. Findings indicate that in the nonlinear regime both output power and operational bandwidth of the harvester will be enhanced by increasing the mechanical quality factor which can be considered as a significant advantage in comparison to linear harvesters in which these two factors vary in opposite ways as quality factor is changed.

Investigation on Savonius turbine technology as harvesting instrument of non-fossil energy: Technical development and potential implementation

Aditya Rio Prabowo, Dandun Mahesa Prabowoputra

2020, 10(4): 262 -269. doi: 10.1016/j.taml.2020.01.034

[Abstract] (342) [FullText HTML] (231) [PDF 3192KB] (14)

Abstract:
Environmental risk due to excessive residual emission is rising. Greenhouse effect, ice melting in the Arctic, reduction of air quality are several concerns which need immediate development and change. Energy harvesting equipment is one of the key solutions. Environment potential, e.g. water resource can be collaborated with mechanical equipment to harvest clean energy. Savonius turbine has been proposed and studied for this purpose and can be placed on several energy resources, i.e. water and wind. Still, real-world implementation of this technology is lacking, especially in tropical archipelago countries which have abundant water resources. In this work, assessment of Savonius turbine technology as instrument to harvest clean energy is conducted. A series of development on the turbine performance and technical modification is considered as reference to implement the technology in water and open air environments. It is noted that rotor design, operation depth and nozzle attachment are several key influencing factors.

On plane Λ-fractional linear elasticity theory

K.A. Lazopoulos, A.K. Lazopoulos

2020, 10(4): 270 -275. doi: 10.1016/j.taml.2020.01.035

[Abstract] (293) [FullText HTML] (238) [PDF 2637KB] (3)

Abstract:
Non-local plane elasticity problems are discussed in the context of Λ-fractional linear elasticity theory. Adapting the Λ-fractional derivative along with the Λ-fractional space, where geometry and mechanics are valid in the conventional way, non-local plane elasticity problems are solved with the help of biharmonic functions. Then, the results are transferred into the initial plane. Applications are presented to homogeneous and the fractional beam bending problem.

The nonlinear response of Cattaneo-type thermal loading of a laser pulse on a medium using the generalized thermoelastic model

Farshad Shakeriaski, Maryam Ghodrat

2020, 10(4): 286 -297. doi: 10.1016/j.taml.2020.01.030

[Abstract] (289) [FullText HTML] (222) [PDF 3194KB] (9)

Abstract:
The nonlinear thermoelastic responses of an elastic medium exposed to laser generated short-pulse heating are investigated in this article. The thermal wave propagation of generalized thermoelastic medium under the impact of thermal loading with energy dissipation is the focus of this research. To model the thermal boundary condition (in the form of thermal conduction), generalized Cattaneo model (GCM) is employed. In the reference configuration, a nonlinear coupled Lord-Shulman-type generalized thermoelasticity formulation using finite strain theory (FST) is developed and the temperature dependency of the thermal conductivity is considered to derive the equations. In order to solve the time-dependent and nonlinear equations, Newmark's numerical time integration technique and an updated finite element algorithm is applied and to ensure achieving accurate continuity of the results, the Hermitian elements are used instead of Lagrangian's. The numerical responses for different factors such as input heat flux and nonlinear terms are expressed graphically and their impacts on the system's reaction are discussed in detail. The results of the study are presented for Green–Lindsay model and the findings are compared with Lord-Shulman model especially with regards to heat wave propagation. It is shown that the nature of the laser's thermal shock and its geometry are particularly determinative in the final stage of deformation. The research also concluded that employing FST leads to achieving more accuracy in terms of elastic deformations; however, the thermally nonlinear analysis does not change the results markedly. For this reason, the nonlinear theory of deformation is required in laser related reviews, while it is reasonable to ignore the temperature changes compared to the reference temperature in deriving governing equations.

Review

Review on charging model of sand particles due to collisions

Li Xie, Junjie Li, Yakui Liu

2020, 10(4): 276 -285. doi: 10.1016/j.taml.2020.01.047

[Abstract] (245) [FullText HTML] (139) [PDF 2814KB] (6)

Abstract:
In this paper, the models describing the charge transfer between two sand particles due to collisions are reviewed. By comparing the experimental results and the calculated results by the models carried on an individual particle due to a single collision, it indicates the Mosaic model is more reasonable to describe the collision charging mechanism. The Mosaic model cannot only describe the dependence of the collision charges on the relative collision speed and the particle size, but also reveal the relationship between the collision charges with the environmental temperature, the relative humidity and the material parameters, e.g., the absorption energy. Based on the Mosaic model, the model to describe the charges transfer due to multiple collisions is also developed, which can be used to calculate the charges carried by sand particles due to multiple collisions in the wind blown sand flux.