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Momeni-Khabisi, Hamed,Tahani, Masoud Techno-Press 2022 Advances in nano research Vol.12 No.4
In the present study, the nonlocal strain gradient theory is used to predict the size-dependent buckling and post-buckling behavior of geometrically imperfect nano-scale piezo-flexomagnetic plate strips in two modes of direct and converse flexomagnetic effects. The first-order shear deformation plate theory is used to analyze analytically nano-strips with simply supported boundary conditions. The nonlinear governing equations of equilibrium and associated boundary conditions are derived using the principle of minimum total potential energy with consideration of the von Kármán-type of geometric nonlinearity. A closed-form solution of governing differential equation is obtained, which is easily usable for engineers and designers. To validate the presented formulations, whenever possible, a comparison with the results found in the open literature is reported for buckling loads. A parametric study is presented to examine the effect of scaling parameters, plate slenderness ratio, temperature, the mid-plane initial rise, flexomagnetic coefficient, different temperature distributions, and magnetic potential, in case of the converse flexomagnetic effect, on buckling and post-buckling loads in detail.
A. Momeni,K. Dehghani 대한금속·재료학회 2010 METALS AND MATERIALS International Vol.16 No.5
Hot deformation behavior of AISI 410 martensitic stainless steel was investigated by conducting hot compression tests at a temperature range of 900 °C to 1150 °C and a strain rate of 0.001-1s−1. The relation between flow stress and Zener-Hollomon (Z) parameter was successfully modeled via the hyperbolic sine function under a wide range of deformation conditions, and the values were determined for the apparent activation energy, Q, and the empirical material constants A and n. Power-law equations show that the values of the peak and steady-state stress are related to the dimensionless parameter Z/A. The results also show that the flow stress deviates from linear dependence on the Z/A parameter at ασ < 0.8 and ασ > 1.2. The deviations reflect the power and exponential equations, respectively, for low and high stress levels. The way the peak and steady-state strains vary with the Z parameter was studied and best models were developed. A model based on the Avrami equation was developed to estimate the kinetics of the dynamic recrystallization (DRX)for different deformation conditions. The results of the model show that the Avrami exponent decreases as Z rises. In addition, the Avrami constant of k bears no distinct relation with Z. The optical microscopy observations of prior austenite grains confirm that the DRX grain size has an adverse relation with the Z parameter. The best relation between the DRX grain size and the Z/A ratio is proposed on the basis of the grain size measurements.
Mohammad Ehsan Momeni Heravi 한국섬유공학회 2020 Fibers and polymers Vol.21 No.6
In this paper, silver nanoparticles (Ag-NPs) colloidal suspensions with different particle sizes of 5 to 40 nm wereprepared. Dynamic light scattering (DLS) technique showed that the average hydrodynamic diameters of Ag-NPs were muchlarger than the particle diameters obtained using transmission electron microscopy and UV-Vis spectroscopy. The as-preparedAg-NPs with different average hydrodynamic diameters were incorporated in cotton fabrics by the pad-dry-cure method. Thesilver content before and after washing cycles were determined by inductively coupled plasma spectrometry (ICP). Theantibacterial properties of the fabrics after 0, 5 and 10 laundering cycles against both the Gram-negative bacterium ofEscherichia coli (E. coli) and the Gram-positive bacterium of Staphylococcus aureus (S. aureus) were examined and a clearvolcano trend was observed between the bacterial reduction rate (BR) and the hydrodynamic diameter of Ag-NPs loaded onthe fibers. The cotton fabric treated by the Ag-NPs with the hydrodynamic diameter of 52 nm, exhibited the highestantibacterial activity (about 98 %) after 10 laundering cycles, while the other samples on either side of the volcano were lessactive. The cytotoxicity of the cotton fabrics treated with Ag-NPs was assayed on mouse embryonic fibroblast cells andevaluated by an MTT assay. The results showed that Ag-NPs were not toxic. Field emission scanning electron microscopy(FESEM) obtained from the cotton fabric before and after washing cycles demonstrated that the Ag-NPs had tight bonds withthe surface of cotton fabric.
Fuzzy Surface-Based Control for Uncertain Unified Chaotic Systems
Sara Dadras,Hamid Reza Momeni,Vahid Johari Majd 제어로봇시스템학회 2008 제어로봇시스템학회 국제학술대회 논문집 Vol.2008 No.10
This paper proposes a fuzzy sliding mode control strategy for an uncertain unified chaotic system with input nonlinearity. Using the sliding mode control technique, a sliding surface is determined and the control law is established. A fuzzy system is used instead of sign function in the sliding mode control to reduce the chattering phenomenon on the sliding surface. Based on Lyapunov stability theory, stability of the fuzzy sliding control law is determined. Chattering in the system with nonlinearity input is also damped due to this control law. The illustrative simulation results are given to demonstrate the effectiveness of the proposed fuzzy sliding mode control design.
Abolghassem Zabihollah,Saman Momeni,Ali Selk Ghafari 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.1
The dynamic behavior of nonuniform-thickness laminated composite beams, such as helicopter blades, wind turbine blades, and robotarms, is of high importance in the design and fabrication of such elements. Changing the thickness of laminated structures is a significantchallenge during fabrication because different tapering configurations may significantly alter the stiffness of the structures and thus thedynamic response of the structures. In this study, the effect of adding nanoparticles to resin on the stiffness and dynamic behavior ofnonuniform-thickness laminated composite beam elements was investigated. A set of experiments were conducted to examine the naturalfrequencies and damping coefficients of nonuniform-thickness laminated composite beams with different tapering configurations. Addingnanoparticles up to 3% increased the natural frequencies for all tapering configurations. Beyond 3% and up to 7% of nanoparticles,the natural frequency of the beam decreased. The addition of 10% of nanoparticles to resin sharply reduced the natural frequency of thebeam but significantly improved the damping coefficient for all the investigated taper models.
Control of Uncertain Butterfly-Shaped Chaotic System: Sliding-mode Approach
Sara Dadras,Hamid Reza Momeni,Vahid Johari Majd 제어로봇시스템학회 2008 제어로봇시스템학회 국제학술대회 논문집 Vol.2008 No.10
A sliding mode control scheme for an uncertain Butterfly-shaped chaotic dynamical system is proposes in this paper. A sliding surface is determined according to the sliding mode control technique and the control law is established. Stability of the sliding control law is determined using Lyapunov stability theory. The chattering phenomenon, which deteriorates the system performance and may cause unforeseen instabilities, is attenuated due to this control law. The effectiveness of the presented sliding mode control design is confirmed through numerical simulations.
A Sliding Mode Observer Approach To Chaos Synchronization
Abdolkarim Daryabor,Hamid Reza Momeni 제어로봇시스템학회 2008 제어로봇시스템학회 국제학술대회 논문집 Vol.2008 No.10
In this paper, synchronization of the chaotic systems based on sliding mode observer is presented. This observer has a simple structure that contains a sliding mode term which turns out to be robust against output noises as well as sustained disturbance. Only one of the states of the master that satisfies the observability matching condition is sent to the slave system via a public channel, which is a sliding mode observer designed to reconstruct all of the states of the master system. For verification and demonstration, this approach is applied to the unified chaotic systems. Simulation results are proposed to demonstrate the effectiveness of this method.
Constitutive Analysis and Processing Map for Hot Working of a Ni-Cu Alloy
Gholam Reza Ebrahimi,Amir Momeni,Seyed Mehdi Abbasi,Hossein Monajatizadeh 대한금속·재료학회 2013 METALS AND MATERIALS International Vol.19 No.1
The hot deformation behavior of a Ni-Cu alloy was studied using hot compression testing in the temperature range of 950 °C-1150 °C and at strain rates of 0.001 s.1-1 s.1. Flow curves at low strain rates, up to 0.01 s.1, were typical of DRX characterized by a single peak, while at higher strain rates, the typical form of a DRX flow curve was not observed. The power-law constitutive equation was used to correlate flow stress to strain rate and temperature, and the apparent activation energy of hot deformation was determined to be about 462.4 kJ/mol. The peak strain and stress were related to the Zener-Hollomon parameter and the modeling formula was proposed. The dependence of flow stress to the Z changed at ln Z=38.5,which was considered to be a critical condition for the change in the mechanism of dynamic recrystallization. The efficiency of power dissipation was determined to be between 10-35 percent at different deformation conditions. According to the dynamic material model, stable flow was predicted for the studied temperature and strain rate ranges. Highly serrated grain boundaries at low strain rates were considered to be a reason for the occurrence of continuous dynamic recrystallization. On the contrary, at high strain rates, equiaxed grain structure was attributed to the typical discontinuous dynamic recrystallization.