In the present work, a novel explicit analytical solution is proposed for obtaining twisting deformation and optimal shape control of smart laminated cantilever composite plates/beams using inclined ...piezoelectric actuators. The linear piezoelectricity and plate theories are adapted for the analysis. A novel double integral multivariable Fourier transformation method and discretised higher order partial differential unit step function equations are employed. For the first time, an exact solution is developed to analyse electro-mechanical twisting moments in smart composite structures. Since there are no published benchmark results for verification, a series of simple, accurate and robust finite element (FE) analysis models and realistic electro-mechanical coupled FE procedures are developed for the effective prediction of the structural behaviour of the smart laminated piezo-composite structures under arbitrary loads. In addition to the novelty of the explicit solution, more comprehensive FE simulations of smart structures and step-by-step guidelines are discussed. The effect of various parameters including electro-mechanical twisting coupling, layup thickness, actuators size, placement, and inclination angle, electrical voltage, stacking sequence, and geometrical dimension are taken into account. The comparison of results shows an excellent agreement. Unlike the earlier studies, the proposed method does not require the characteristic and trial deflection function to be predetermined.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
In this paper, a new explicit exact analytical solution is proposed for obtaining static deformation and optimal shape control of smart laminated cantilever piezo composite hybrid plates and beams ...under thermo-electro-mechanical loads using piezoelectric actuators. The linear piezoelectricity and plates theories were adapted for the analysis. A novel double integral multivariable Fourier transformation method combined with discretised higher order partial differential unit step function equations were employed. The effect of various parameters including arbitrary loads such as non-uniform thermal stresses, electrical and mechanical loads, layup thickness, piezoelectric actuators size and placement, stacking sequence, and geometrical dimension were considered. The results were then compared with some published benchmark results and good agreement was observed. Unlike the earlier studies, the proposed method does not require the characteristic and trial deflection function to be predetermined. Both, the embedded and bounded actuators are considered. Until now, the shape control task of reducing mid-plane deformation at free end in smart laminated cantilever plates and beams was unsolvable and approximations were typically employed in numerical analysis Yu et al. (2009). This problem becomes more complicated for wider and longer plates but the method proposed herein successfully resolves this issue.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•Aluminium alloy 1050 was treated by zirconium-based (Zr) conversion coating.•The surface morphology and surface free energy of the samples were obtained.•The adhesion properties of the epoxy coating ...was studied on the treated samples.•The corrosion resistance of the epoxy coating was enhanced on treated samples.
The objective of this work is to investigate the effects of zirconium-based (Zr) conversion coating on the adhesion properties and corrosion resistance of an epoxy/polyamide coating applied on the aluminium alloy 1050 (AA1050). Field emission scanning electron microscope (FE-SEM), energy dispersive X-ray spectrum (EDS), atomic force microscope (AFM) and contact angle measuring device were employed in order to characterize the surface characteristics of the Zr treated AA1050 samples. The epoxy/polyamide coating was applied on the untreated and Zr treated samples. The epoxy coating adhesion to the aluminium substrate was evaluated by pull-off test before and after 30 days immersion in 3.5% w/w NaCl solution. In addition, the electrochemical impedance spectroscopy (EIS) and salt spray tests were employed to characterize the corrosion protection properties of the epoxy coating applied on the AA1050 samples. Results revealed that the surface treatment of AA1050 by zirconium conversion coating resulted in the increase of surface free energy and surface roughness. The dry and recovery (adhesion strength after 30 days immersion in the 3.5wt% NaCl solution) adhesion strengths of the coatings applied on the Zr treated aluminium samples were greater than untreated sample. In addition, the adhesion loss of the coating applied on the Zr treated aluminium substrate was lower than other samples. Also, the results obtained from EIS and salt spray test clearly revealed that the Zr conversion coating could enhance the corrosion protective performance of the epoxy coating significantly.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
•Epoxy/polyamide nanocomposites were prepared using nano-alumina particles.•Corrosion and hydrolytic degradation resistance of the coatings were studied.•Nanoparticles dispersed well in the coating ...matrix.•Addition of 3.5% nanoparticles caused significant improvements of coating properties.
The aim of this work was studying the effects of addition of Al2O3 nanoparticles on the anticorrosion performance of an epoxy/polyamide coating applied on the AA-1050 metal substrate. For this purpose, the epoxy nanocomposites were prepared using 1, 2.5 and 3.5 (w/w) pre-dispersed surface modified Al2O3 nanoparticles. Field-emission electron microscope (FE-SEM) and ultraviolet–visible (UV–Vis) techniques were utilized in order to evaluate the nanoparticles dispersion in the epoxy coating matrix. The anticorrosion performance of the nanocomposites was studied by electrochemical impedance spectroscopy (EIS) (in 3.5wt% NaCl solution for 135 days immersion) and salt spray test for 1000h. The coating resistance against hydrolytic degradation was also studied by optical microscope and Fourier-transform infrared spectroscopy (FTIR). Results obtained from FE-SEM micrographs and UV–visible spectra showed that the nanoparticles dispersed in the coating matrix uniformly with particle size less than 100nm even at high loadings. Results revealed that nano-Al2O3 particles could significantly improve the corrosion resistance of the epoxy coating. Nanoparticles reduced water permeability of the coating and improved its resistance against hydrolytic degradation.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The effect of hydrogen on the mechanical properties of X70 pipeline steel was investigated by a combination of macro- and microscale approaches. Various tensile tests under vacuum, in-situ H-plasma ...charging (IHPC), and ex-situ electrochemical H-charging (EEHC) conditions were conducted to elucidate the hydrogen effect in the macroscale approach. All tensile tests were performed inside an environmental scanning electron microscopy (ESEM) chamber. The IHPC, as a novel hydrogen charging technique, was compared with conventional EEHC while uncharged tensile specimens were used as a reference. The results demonstrated that the variations in the IHPC condition were negligible compared to the vacuum condition, whereas the differences in the ex-situ condition were more prominent. Furthermore, susceptibility to hydrogen in the vacuum-ex situ regime was manifested in the reduction of yield strength and ultimate tensile strength. These findings were confirmed by the fractographic analysis, where some of the effects of hydrogen (e.g. the formation of secondary cracks by detrimental inclusions (MnS and Al2O3) and the transition of fracture features from ductile dimples to cleavage patterns) were well illustrated. On the other hand, micro-cantilever bending tests were performed in the air to avoid hydrogen effects and applied inside a miniaturized electrochemical cell to promote hydrogen uptake. The bending results and post-mortem analysis of the tested cantilevers indicated that the hydrogen-reduced flow stress and hydrogen-induced cracking occurred for the H-charged bent cantilever, while only increased plastic behavior occurred for the cantilever bent in the air.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In the present study, carbon nanotubes/AZ31 magnesium composite filler rods of gas tungsten arc (GTA) welding were fabricated for the first time by powder metallurgy. After welding, the effect of ...carbon nanotubes (CNTs) on the microstructure and mechanical properties of nanocomposite welds was evaluated. By applying ball milling, CNTs were uniformly distributed in the filler rods. Consequently, the nanocomposite welds produced by these filler rods had a uniform distribution of CNTs in their compositions. Tensile tests revealed that the tensile strength of 1wt% CNTs-reinforced weld was increased by 65% compared with unreinforced weld. Therefore, it can be concluded that CNTs can be good reinforcement candidates in GTA welding of magnesium and its alloys.
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•CNTs/AZ31 magnesium composite filler rods were fabricated for the first time by PM.•CNTs were uniformly distributed in the weld matrix.•CNTs improved the mechanical properties of weld.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
In this article, bitubal circular energy absorbers consist of two AL-6063-O tubes with unequal diameters placed coaxially and compressed under quasi-static axial load are studied experimentally. The ...effects of diameter and wall-thickness of each tube and the interaction between two tubes on the crashworthiness parameters are investigated in detail. In order to reduce the high value of peak load induced in the bitubal absorbers, two worthwhile solutions are proposed. The first one is to use two tubes with different lengths and the other one is to cut groove at the end portion of one of the tubes.
•Experimental study of axial quasi-static crushing of bitubal circular absorbers.•Investigating the influence of different variables on crashworthiness parameters.•Bitubal specimens are more efficient than the equivalent monotubal specimens.•Introducing two solutions to reduce the maximum crushing load of bitubal absorbers.•Cutting groove on the upper portion of tube decreases peak loads significantly.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
•Sensori/motor network disentangled with novel closed-loop fMRI setup.•The inferior olive seems to play a modulating role in essential tremor.•Sensorimotor network function related to voluntary ...movement in ET was normal.•PD patients showed less motor-related activity in the cerebellum and basal ganglia.
Tremor is thought to be an effect of oscillatory activity within the sensorimotor network. To date, the underlying pathological brain networks are not fully understood. Disentangling tremor activity from voluntary motor output and sensorimotor feedback systems is challenging. To better understand the intrinsic sensorimotor fingerprint underlying tremor, we aimed to disentangle the sensorimotor system into driving (motor) and feedback/compensatory (sensory) neuronal involvement, and aimed to pinpoint tremor activity in essential tremor (ET) and tremor-dominant Parkinson's disease (PD) with a novel closed-loop approach.
Eighteen ET patients, 14 tremor-dominant PD patients, and 18 healthy controls were included. An MR-compatible wrist manipulator was employed during functional MRI (fMRI) while muscle activity during (in)voluntary movements was concurrently recorded using electromyography (EMG). Tremor was quantified based on EMG and correlated to brain activity. Participants performed three tasks: an active wrist motor task, a passive wrist movement task, and rest (no wrist movement).
The results in healthy controls proved that our experimental paradigm activated the expected motor and sensory networks separately using the active (motor) and passive (sensory) task. ET patients showed similar patterns of activation within the motor and sensory networks. PD patients had less activity during the active motor task in the cerebellum and basal ganglia compared to ET and healthy controls. EMG showed that in ET, tremor fluctuations correlated positively with activity in the inferior olive region, and that in PD tremor fluctuations correlated positively with cerebellar activity.
Our novel approach with an MR-compatible wrist manipulator, allowed to investigate the involvement of the motor and sensory networks separately, and as such to better understand tremor pathophysiology. In ET sensorimotor network function did not differ from healthy controls. PD showed less motor-related activity. Focusing on tremor, our results indicate involvement of the inferior olive in ET tremor modulation, and cerebellar involvement in PD tremor modulation.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
A new analytical approach for the determination of natural frequencies of a long cylindrical shell containing a variably oriented semi–elliptical surface crack is presented in this paper. Equations ...of motion for the cracked shell are obtained based on classical shell theories and are simplified using the Donell–Mushtari–Vlasov (DMV) theory. It has been assumed that the crack length is far smaller than the radius of curvature of the shell and line-spring model (LSM) is used in order to calculate crack compliance coefficients which are subsequently to be added into the equations of motion to include crack effects in the problem. An analytical solution has been developed using Hamilton's principle and the results are obtained for the shells considering clamped-clamped (C–C) and simply supported (S–S) boundary conditions at both ends. Results obtained from the proposed model are verified using a finite element model created with ABAQUS and there is an acceptable agreement between analytical and FEM results. Effects of the shell properties such as length, radius and thickness as well as the effects of the crack characteristics such as its length and orientation on the natural frequencies of the cracked shell are analyzed in this study.
•A formulation for governing equations of motion of a variably oriented cracked shell.•Utilizing Line-Spring model to impose crack effects in the formulation.•An analytical solution for the free vibration of the variably oriented cracked shell.•Evaluating the effects of crack length and orientation on the natural frequency.•Evaluating the effects of shell length, radius and thickness on the natural frequency.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
This study is conducted to investigate the effect of nano-droplets concentration and size on linear and nonlinear optical properties of Rhodamine 6G by UV–Vis, spectrofluorometer and Z-Scan ...techniques. Nano-droplets were prepared by mixture of AOT, n-Decane and Water at three different water to surfactant molar ratios (W = 3, 6.7 and 40) and two dye to water mass ratios (R). At high enough dye concentration, the fluorescence intensity and its red shift depend on the concentration of dye in water nano-droplets (R). Moreover, the fluorescence spectra of R6G can be enhanced by confined water nano-droplets (microemulsion) at higher dye to water mass ratios. The Raman Spectra reveal no dependence of R6G local polarity in the AOT reversed micelles to nano-droplet size. From the Bakhshiev equation, the excited to ground state dipole moment ratio (
μ
e
/
μ
g
) was calculated through solvatochromic shift method for different nano-droplet concentrations. The results show that
μ
e
/
μ
g
of R6G in water nano-droplets is smaller than that of bulk water. At high enough dye concentration,
μ
e
/
μ
g
depends on the nano-droplets’ dye content. The dye aggregation can affect the dipole moment R6G in microemulsion. Two photon absorption coefficient (
β
), nonlinear refractive index (
n
2
), the real third order susceptibility (
χ
R
) and the second order hyperpolarizability (
γ
R
) were measured using the Z-Scan technique at different nano-droplet concentration and two sizes of nano-droplet. The results show a good compatibility with the attained consequence by Quantum Perturbation theory. In this content, the interaction of nano-droplet was studied by dynamic light scattering, whose results indicate an ascending trend in mobility of nano-droplets by the increase of nano-droplets dye content. Hence increase of dye in nano-droplets influences the dye aggregation, fluorescence red shift and dipole moment ratio (
μ
e
/
μ
g
) by the nano-droplet collision.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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