Effects of Al–5Ti–1B master alloy on the microstructural evaluation of a highly alloyed aluminum alloy produced by SIMA process

M. Alipour,M. Emamy,M. Azarbarmas,M. karamouz 한국소성가공학회 2010 기타자료 Vol.2010 No.6

This study was undertaken to investigate the influence of Al?5Ti?1B master alloy on the structural characteristics of Al?12Zn?3 Mg?2.5Cu aluminum alloy. The optimum amount of Ti containing master alloy for proper grain refining was selected as 6 wt.%. A modified strain-induced, melt-activated (SIMA) process for semi-solid processing of alloys was proposed. In order to examine the effectiveness of the modified SIMA process, the recrystallized microstructures of the Al alloy (Al?12Zn?3 Mg?2.5Cu) prepared by the modified SIMA processes were macroscopically. The modified SIMA process employed casting, warm multi-forging, recrystallization and partial melting instead of the conventional process. Reheating condition to obtain a fine globular microstructure was optimized. The microstructure evolution of reheated Al?12Zn?3 Mg?2.5Cu aluminum alloy was characterized by SEM (Scanning electron microscopy) and optical microscopy. In this study the relation between the induced strain with size and shape of grain size has been studied. Results indicated that with the increase of strain sphericity of particles, their size decreases and sphericity takes place in less reahiting time.

Effects of Boron on Microstructure and Tensile Properties of Al–Mg₂Si Metal Matrix Composite

M. Azarbarmas,M. Emamy,M. Alipour,M. karamouz 한국소성가공학회 2010 기타자료 Vol.2010 No.6

The effects of Boron (B) modification on the microstructure and tensile properties of an in situ prepared Al?15%Mg2Si composite were studied. The results show that the addition of B reduces the average size of primary Mg2Si particles from 25 to 15 μm and increases the amount of alpha phase. Meanwhile, with the addition of 3.0 wt.% B, The ultimate tensile strength (UTS) and elongation to rupture (Er) of the composite reach as high as 160 MPa and 4.7%, respectively. SEM images of the specimens showed that with the addition of B the pseudo-eutectic Al-Mg2Si refined ,that improved the ductility of specimens.

Numerical Analysis of the Nonlinear Performance of Concentrically Braced Frames Under Cyclic Loading

M. Alipour,A. A. Aghakouchak 한국강구조학회 2013 International Journal of Steel Structures Vol.13 No.3

Concentrically braced frames (CBFs) are widely used as lateral-load resisting system in steel structures. This study examines the effects of different parameters especially those associated with connections, on the behavior of CBFs. A single bay, singlestory frame is used to evaluate the interaction between structural members. Nonlinear analyses using a detailed inelastic finiteelement model (FEM) are carried out to study the behavior of frames subjected to cyclic loading. Models are designed based on seismic codes and analyzed to evaluate the performance of both SCBFs and OCBFs. The equivalent plastic strain concept is used to determine the ductility capacity and to predict fracture and failure in these models. Results show that the seismic performance of CBFs, which are designed according to current provisions can be improved by configuring the details of gusset plate connections in a way that inelastic demands are balanced in middle of brace and gusset plate corners.

Nonlinear fluctuation, frequency and stability analyses in free vibration of circular sector oscillation systems

M. Shaban,D.D. Ganji,M.M. Alipour 한국물리학회 2010 Current Applied Physics Vol.10 No.5

In the present paper, the modified homotopy perturbation method (MHPM) is employed to investigate about both nonlinear swinging oscillation and the stability of circular sector oscillation systems. The sensitivity study performed for frequency analysis of the mentioned oscillatory circular sector body shows that frequency of nonlinear oscillation depends on some specific parameters and can be optimized. Furthermore onset of the instability is dependent to angle α and initial amplitude. Comparisons made among the results of the present closed-form analytical solution and the traditional numerical iterative time integration solution confirms the accuracy and efficiency of the presented analytical solution. In contrast to the available numerical methods, the present analytical method is free from the numerical damping and the time integration accumulated errors. Moreover, in comparison with the traditional multistep numerical iterative time integration methods, a much less computational time is required for the present analytical method. Responses of the dynamical systems to some extent are affected by the natural frequencies. Results reveal that for nonlinear systems, the natural frequency is remarkably affected by the initial conditions.

Design and simulation of a magnetohydrodynamic micro-pump to provide time varying tensile force for vibration suppression in viscoelastic micro-beams

A. Alipour,M. H. Korayem,D. Younesian 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.5

In this paper, a new strategy for providing tensile force to suppress the transverse vibration of a micro-beam is introduced. This axial tensile force is supplied by a specific fluid flow called "magnetohydrodynamics" (MHD), which flows in a micro-pump, and then the fluid enters the micro-beam. The micro-beam is vibrated by an oscillating external force acting at its base. Therefore, a fluid structure interaction problem arises. The pressure of the fluid is increased due to the Lorentz force appears in the micro pump, and is directed by the channel towards the micro-beam and suppress the vibration of the micro-beam. It was observed that when the magnetic field rises from 0.25 Tesla to 0.5 Tesla, the amplitude of the micro-beam fluctuations will decrease from 13 6 10 m - ´ to 13 3 10 m - ´ . Assuming a laminar and incompressible flow, the finite volume method (FVM) is used to solve the governing equations. In the design of the micropump, the parameters studied are the value of the magnetic field, the amount of voltage applied to the micro-pump, the external force oscillation amplitude and the Reynolds number, and the effect of each parameter on the fluid and micro-beam behavior. The results show that with increasing fluid pressure in the micro-pump, the micro-beam vibration is suppressed. In addition, the pressure of the fluid along the micro-beam remains constant at 0.1 percent.

Vibration suppression of atomic-force microscopy cantilevers covered by a piezoelectric layer with tensile force

M. H. Korayem,A. Alipour,D. Younesian 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.9

In this paper, vibration suppression of a micro-beam covered by a piezoelectric layer is studied. The micro-beam is modeled with the specific attention to its application in AFM. The AFM micro-beam is a cantilever one which is stimulated close to its natural frequency by applying a harmonic voltage to the piezoelectric layer. The beam is an Euler-Bernoulli beam which abbeys Kelvin-Voigt model. Using such model supplies the comparison between elastic and viscoelastic beams; and one of the most important properties of viscoelastic materials, damping effect can readily be investigated. The pump provides an axial load with the result that it suppresses the vibrations. First, the vibration equations are extracted using Lagrangian and extended Hamiltonian method in vertical, longitudinal, as well as torsional directions and are discretized by exploiting the Galerkin mode summation approach. The discretized time-domain equations are solved by the aid of the Runge-Kutta method. The viscoelastic beam is compared with the elastic one, and the effects of damping ratio on vibration responses are presented. Additionally, the effects of micro-pump load, excitation voltage, and initial twist angle are investigated on the amplitude of vibration and natural frequency of system. It is observed that viscoelasticity of beam and axial load of the pump reduce vibrations and provide uniform time-domain responses without beatings.

Fabrication, Characterization and Investigating Properties of PVA Based Nanocomposite Films Reinforced with Mechano-chemically Synthesized CuO Nanoparticles

Gh. Dehghan Khalili,S. Alipour,M. R. Akbarpour,S. Moniri Javadhesari 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.8

In this study, copper oxide (CuO) nanoparticles were incorporate within polyvinyl alcohol (PVA) matrix and CuO–PVAnanocomposite film was fabricated by solution casting technique. In order to synthesize nanoparticles, a cost-competitive andfacile approach namely mechanochemical method was implemented. As nanoparticles precursors, pre-determined amountof CuSO4,NaCl, and NaOH were mixed. The mixture was ball-milled in zirconia medium for 10 h at ambient temperatureand rotational speed of 300 rpm. The XRD characterization analysis indicated CuO nanoparticles formation by ball milling. The CuO size was estimated to be in the ≈ 37 nm range. SEM images demonstrated the spherical morphology andlittle agglomeration for the nanoparticles. Furthermore, the bandgap energy of CuO was determined to be 1.84 eV. TheCuO content in the nanocomposite was set to be 2, 4, 8, and 10 wt%. Strong interaction between the PVA matrix and CuOnanofiller was confirmed by XRD and FT-IR investigations. Moreover, integration of CuO to the polymer matrix resultedin a decreased PVA crystallinity. The antibacterial behavior of PVA was increased by the addition of nanoparticles, and theCuO–PVA nanocomposite containing up to 4 wt% CuO had desirable antibacterial properties demonstrated against Escherichiacoli activity. CuO nanoparticles incorporating to PVA network led to reinforced mechanical and dielectric propertiesfor the nanocomposites. Besides, nanoparticles loading had direct impact on the intensified properties. Tensile strength wasenhanced from 85.8 (pure PVA) to 154.9 MPa (PVA-10 wt% CuO). The tensile modulus for neat PVA was 0.9 GPa andraised dramatically to 4.5 GPa for PVA-10 wt% CuO. Dielectric constant also improved more than three times at 1 kHzcomparing PVA and PVA-10 wt% CuO.