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List of Articles
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Open Access Article
1 - Design and Fabrication of a Composite Energy Absorber
Hamid Reza Shalian Mohammad Hossein Alaee Jafar Eskandari Jam Mohsen Heydari Beni Majid Eskandari Shahraki Naser AsiabanIn this paper, the quasi-static test and the damage of the thin-walled composite cylinder were numerically simulated using ABAQUS. Then, a comparison was made between the results of this simulation and those obtained from experimental studies followed by their validatio MoreIn this paper, the quasi-static test and the damage of the thin-walled composite cylinder were numerically simulated using ABAQUS. Then, a comparison was made between the results of this simulation and those obtained from experimental studies followed by their validation. In the next step, several parameters affecting the energy absorption rate including outer diameter-to-cylinder height ratio, thickness-to-outer diameter ratio, and angle of damage initiation mechanism were selected. They were optimized by modelling different states in ABAQUS. The number of tests is reduced by the design of experiments using response surface methodology and the optimal specimen is extracted by this software. Finally, optimum adsorbent is fabricated and tested. Considering enhanced energy absorption, increased mean reaction force, and reduced initial maximum force, the optimal design parameters include the inner diameter-to-cylinder height ratio of 0.2, thickness-to-inner diameter ratio of 0.1, and angle of damage initiation mechanism of 45°. Manuscript profile -
Open Access Article
2 - Multi-objective Optimization of Volute Springs using an Improved NSGA II
navid moshtaghi yazdaniDue to the variable stiffness through their length, their resistance against buckling, damping characteristics due to the friction between their chains, and their small solid length, volute springs are widely used in applications where other mechanisms cannot be employe MoreDue to the variable stiffness through their length, their resistance against buckling, damping characteristics due to the friction between their chains, and their small solid length, volute springs are widely used in applications where other mechanisms cannot be employed to provide variable spring stiffness. Meanwhile, the complexities of equations, governing their dramatic non-linear behavior caused the designers to use experimental equations, as well as some simplifications. Therefore, no research has been reported yet that aims to simultaneously optimize the evaluation criteria of these springs (i.e. their weight and energy conservation capacity) considering their strength, stiffness and natural frequency. In this article providing the governing equations for mechanical behaviors of volute springs, the problem of optimized design for this type of springs are addressed as an optimization problem with its constraints, taking into account the aforementioned goals and considerations. To find a set of Pareto front, an improved version of a multi-objective genetic algorithm is employed, performance of which has been improved, adding a migration operator to a classical NSGA II algorithm. To indicate the proposed method efficiency, a volute spring used in a suspension system of a military motorcar was modeled, and its design was optimized. The results show that the functional performance of the designed volute spring, such as minimizing the spring mass and maximizing the stored energy while maintaining design limitations such as dimensions, strength and critical frequency, has been significantly improved. Manuscript profile -
Open Access Article
3 - Study on the Wettability and Optical Properties of Polydimethylsiloxane-SiO2 Nano-composite Surfaces
Reza Abedinzadeh Hamid Shirian Janan ParhizkarIn this paper, the effects of different weight percentages of silica nano-particles on the wettability and optical properties of polymer based surfaces were investigated. The Polydimethylsiloxane (PDMS)-SiO2 nano-composites containing 0.5, 1, 2, 3 and 4 wt% silica were MoreIn this paper, the effects of different weight percentages of silica nano-particles on the wettability and optical properties of polymer based surfaces were investigated. The Polydimethylsiloxane (PDMS)-SiO2 nano-composites containing 0.5, 1, 2, 3 and 4 wt% silica were prepared and coated on the fabric surfaces by immersion technique at the ambient conditions. Then, the characterization of nano-composite coated samples was carried out by water contact angle technique, scanning electron and atomic force microscopes and diffuse reflectance spectroscopy. It was found that increasing the silica content caused to increase the water contact angle of sample to 158° which results in an improvement in the water repellency property. This can be due to the aggregation of silica nano-particles which led to higher surface roughness of sample. The AFM and SEM images validated the results of surface roughness. However, Silica-PDMS composite coated sample exhibited a lower transmittance value (57%) in comparison to the uncoated sample (90%). This can be ascribed to the light scattering by silica nano-particles. Manuscript profile -
Open Access Article
4 - Analysis of Material Flow and Phase Transformation in Friction Hydro-Pillar Processing of 1045 Steel
Moosa Sajed S. M. Hossein SeyedkashiIn the present study, a 3D finite element model was developed using DEFORM commercial software to analyse the material flow and phase transformation, as two key phenomena affecting the joint properties in friction hydro-pillar processing of 1045 steel alloy. The microst MoreIn the present study, a 3D finite element model was developed using DEFORM commercial software to analyse the material flow and phase transformation, as two key phenomena affecting the joint properties in friction hydro-pillar processing of 1045 steel alloy. The microstructure changes significantly due to the high temperature and strain rate. The final microstructure was intergranular pearlite and grain boundary allotriomorphic ferrite. Pearlite was the dominant phase at the final microstructure; thus, its volume fraction was used to validate the model where a good agreement was obtained with the experiment. According to the model, the pearlite volume fraction varies from 100% to 70% moving from the bottom of the stud to the top. The model suggests an inverse relation between the strain rate and pearlite volume fraction. The highest temperature which was experienced in the welding step was 1490 ºC while it dropped to 890 ºC in the forging step. Downward and then radial material flow was detected in the welding step while upward extrusion of material was the dominant material flow pattern during the forging step. Flash was formed mainly in the forging step from stud side material. Manuscript profile -
Open Access Article
5 - Numerical simulation of multilayer cellular scaffolds with 3D and 1D elements
Hamid Reza khanaki Sadegh Rahmati Mohammad Nikkhoo Mohammad Haghpanahi Javad AkbariIn this paper, an attempt has been made to provide a numerical method for investigating the mechanical properties of multilayer scaffolding. These scaffolds can be used as implants in bone fractures. For this purpose two numerical simulation methods are introduced to pr MoreIn this paper, an attempt has been made to provide a numerical method for investigating the mechanical properties of multilayer scaffolding. These scaffolds can be used as implants in bone fractures. For this purpose two numerical simulation methods are introduced to predict the elastic properties of multilayer cell scaffolds. These simulations are based on two models: a 3D model with a volumetric element, and a 1D model with a linear element. To compare the results of these models, three types of two- and three-layer titanium alloy scaffolds have been simulated by the two methods. Also, Young's modulus of the scaffolds has been compared with the experimental conclusions of earlier studies. The results confirm that simulations with 1D models are more cost-effective compared to 3D ones. Additionally, because of the more reliable agreement of Young's modulus results of numerical modeling with the linear element (1.8 to 5 times) compared to the volumetric element (11 to 23 times) compared to the experimental findings, the numerical method with the linear elements can be a reliable tool for studying multilayer scaffoldings. Manuscript profile -
Open Access Article
6 - Preparation of Nitrogen-Doped Graphene Aerogel/Epoxy Nanocomposites and Experimental Study of Mechanical Properties
ali kordi saeed adibnazari Ali Imam mohammad najafi maryam ghasabzadeh saryazdiNitrogen-Doped Graphene Aerogel (N-GA) nanomaterials can significantly improve the functional efficiency of polymer composites due to its three-dimensional structure and suitable physical properties. The preparation process affects the performance improvement. In this s MoreNitrogen-Doped Graphene Aerogel (N-GA) nanomaterials can significantly improve the functional efficiency of polymer composites due to its three-dimensional structure and suitable physical properties. The preparation process affects the performance improvement. In this study, the effect of preparation method and the mechanisms affecting the strength behavior of Nitrogen-doped Graphene Aerogel/Epoxy (N-GA/E) nanocomposites was investigated. For this purpose, nanoparticles of Graphene Oxide (GO) were produced using Hummers’ method; then, the N-GA was synthesized using the hydrothermal method and the freeze-drying process. The characterization experiments were used in order to confirm the structure and quality of the synthesized nanomaterials. Then, specimens of nanocomposite were prepared by adding weight percentages of 0.05, 0.1, 0.2, 0.5, 1, and 2 from the synthesized N-GA to the epoxy resin. In other preparation processes, N-GA/E nanocomposite specimens were produced using auxiliary solvents. After tensile tests, the best strength performance was observed in the specimens with the preparation process in which acetone solvent was used. The tensile strength and modulus of these nanocomposite specimens have increased by 23% and 20% compared to neat epoxy specimens, respectively. Also, the optimal weight percentage of N-GA nanomaterials for distribution in epoxy is 0.1 wt.%. Microscopic images of the fracture surfaces of the specimens used in the tensile test showed that the placement of N-GA porous plates in epoxy with the creation of the mechanism for micro crack formation led to more energy absorption during the stretching process of the N-GA/E nanocomposites. Manuscript profile -
Open Access Article
7 - Vibration Sensitivity Analysis of Nano-mechanical Piezo-Laminated Beams with Consideration of Size Effects
mostafa nazemizadeh Firooz Bakhtiari-Nejad Behrooz ShahriariThe presented article investigates vibration sensitivity analysis of Nano-mechanical piezo-laminated beams with consideration of size effects. To do this, the vibration governing equation of the stepped Nano-mechanical piezo-laminated beam is firstly derived by implemen MoreThe presented article investigates vibration sensitivity analysis of Nano-mechanical piezo-laminated beams with consideration of size effects. To do this, the vibration governing equation of the stepped Nano-mechanical piezo-laminated beam is firstly derived by implementation of the nonlocal elasticity theory. The nonlocal formulation is considered for both of the beam and the piezoelectric layer and the obtained equation is solved analytically. Moreover, there is a need to recognize the importance and relative effects of the beam parameters on the natural frequencies and resonant amplitudes of the nonlocal beam. Therefore, the Sobol sensitivity analysis is utilized to investigate the relative effects of geometrical and the nonlocal parameters on the natural frequencies and the resonant amplitude of the nanobeam. The obtained results show that the length and the thickness of the piezoelectric layer have prominent effects on the vibration characteristics of the beam. Moreover, it is indicated that nonlocal parameter effect on the resonant amplitudes is more than resonant frequency. Also, the effect of the nonlocal term is more important at higher modes of vibration. Therefore, the nonlocal size effects cannot be ignored in vibration analysis of the nanobeam especially at higher modes. Manuscript profile -
Open Access Article
8 - Joint Optimization of Spare Parts Strategy and Maintenance Policies for Manufacturing Systems
mohammadali farsi Enrico ZioCost is the most important factor in engineering systems, thus cost reduction and producing components with a reasonable cost are mandatory for manufacturing engineers. Effective maintenance influences the total cost of manufacturing systems, and its efficiency depends MoreCost is the most important factor in engineering systems, thus cost reduction and producing components with a reasonable cost are mandatory for manufacturing engineers. Effective maintenance influences the total cost of manufacturing systems, and its efficiency depends on spare parts management. Therefore, maintenance and spare parts should be jointly managed and significant characters such as ordering, repair and replacement times, shortage, cost, quality, and storage condition of spare parts have to be considered. In this paper, intelligent manufacturing systems with the multi-component structure are considered, that three types of maintenance policies (condition-based maintenance, corrective maintenance, and preventive maintenance) simultaneously support these systems. A joint optimization method based on GA-PS and Monte Carlo simulation is proposed to achieve minimum cost and maximum availability. Also, the influence of spare parts degradation in storage to evaluate system performance is considered. A framework is proposed for this; it can successfully consider the manufacturing machines, maintenance policies and spare parts inventory to obtain the optimal system with the maximum availability and the minimum cost. Also, the results demonstrate that different factors impress the system, and these parameters must be jointly considered. The ordering and replacement times, storing conditions and suppliers' situation are the main factors considered to obtain an optimal system. Manuscript profile -
Open Access Article
9 - Geometric Optimization of APCs anti Explosion Blades using LS-DYNA Finite Element Software
Jalil Jamali alireza rezaieIn this research, several different types of geometries have been compared to prevent the influence of an explosion wave on the glasses of the APCs. This was done using validation and then using LS-DYNA software. Pre and post-processing was done in LS-PrePost software. MoreIn this research, several different types of geometries have been compared to prevent the influence of an explosion wave on the glasses of the APCs. This was done using validation and then using LS-DYNA software. Pre and post-processing was done in LS-PrePost software. So, a mathematical function in this software was used to generate the pressure of the wave on the structure. In order to compare, the displacement parameter was used and the minimum total displacement of the structure as a criterion for optimal performance was considered. Also, two types of cosine curves, two types of polynomial curves (third and fourth order) and a flat blade are investigated. The results showed that for the use of a 150*100 mm2 square flat blade (which is half simulated according to the model's symmetry), the explosion of a wave coming from a distance of 75 mm on the adjacent sheet requires a sheet with a thickness of 11 mm. Using a curved blade, this thickness is reduced to 3 mm. According to the recent issue, the use of curved blades will lead to a sharp decrease in the weight of armored equipment. Manuscript profile -
Open Access Article
10 - Quick and Effective Modal and Flutter Analyses for Low Aspect Ratio Wings
Masoud Basiri Hamid Farrokhfal Masoud Mosayebi Reza KoohiIn the present work, an analytical study is proposed to investigate the flutter behavior of low-aspect-ratio wings in subsonic flow. An equivalent plate model is used for structural modelling of a semi-monocoque main wing, consisting of ribs, skins, and spars. Legendre MoreIn the present work, an analytical study is proposed to investigate the flutter behavior of low-aspect-ratio wings in subsonic flow. An equivalent plate model is used for structural modelling of a semi-monocoque main wing, consisting of ribs, skins, and spars. Legendre polynomials are used in the Rayleigh-Ritz method as trial functions, and the first-order shear deformation theory is utilized to formulate the structural deformation. Boundary conditions are enforced by applying proper artificial springs. A doublet point method is used to calculate the unsteady aerodynamic loads. Chordwise pressure coefficient distribution at the tip and root of a rectangular wing oscillating in pitching motion is calculated. Flutter analysis is performed using the k method. Instead of using the computationally expensive finite element method, the proposed approach is intended to achieve purposes of quick modelling and effective analysis in free vibration and flutter analyses of low-aspect-ratio wings for preliminary design applications. The effects of aspect ratio on the flutter behavior of wings in subsonic flow are investigated. The obtained results are validated with the results available in the literature. Manuscript profile -
Open Access Article
11 - Investigation of the AFM Indenter’s Geometry Effect On Micro/Nano Biological Cells’ Indentation
Yousef Habibi Sooha Moharam Habibnejad Zahra RastegarThe elasticity modules of the micro/Nanoparticles, especially biological particles are measured using different tools such as atomic force microscopy. The tip of the atomic force microscopy as an indenter has different shapes such as spherical, conical and pyramidal. In MoreThe elasticity modules of the micro/Nanoparticles, especially biological particles are measured using different tools such as atomic force microscopy. The tip of the atomic force microscopy as an indenter has different shapes such as spherical, conical and pyramidal. In the contact of these tips and biological cells, avoiding the cell damage is a necessity. The goal of this paper is investigation and comparison of different tips’ geometries. Different tip’s geometries and their related theories were collected and proposed. To generalize theories’ application for any kind of particle (even non-biological particles) some of simplifying assumptions used in these theories, such as tip rigidity, were removed. Simulation of the force- indentation depth was done for gold nanoparticle and observed that if simplifying assumptions were not removed there would be big errors in calculating the elasticity module of some particles. Then, simulations were done for two yeast and mouse embryo cells. For both cells, in general, the geometry of the curve group, the geometry of the pyramidal group and finally the geometry of the conical group were positioned from the highest to the lowest places. For hyperbolic, conical and pyramidal tips, the important parameter was semi vertical angel. To observe its effect, different magnitudes of this parameter were simulated. According to observed results in three investigated geometries and for both cells, bigger semi vertical angel created higher curves and this means in bigger angels the possibility of cell damage is higher. Manuscript profile -
Open Access Article
12 - Influence of Tool Offset Distance on Microstructure and Mechanical Properties of the Dissimilar AA2024–AA7075 Plates Joined by Friction Stir Welding
Hossain Soleimany kamran amini Farhad GharaviIn the present study, the effect of tool offset on microstructure and mechanical properties of dissimilar friction stir welding of Al2024 and Al7075 alloys were investigated. In this regard, base metals were welded by FSW under different tool offsetting conditions, 1.5 MoreIn the present study, the effect of tool offset on microstructure and mechanical properties of dissimilar friction stir welding of Al2024 and Al7075 alloys were investigated. In this regard, base metals were welded by FSW under different tool offsetting conditions, 1.5 and 2 mm shifted into Al2024 and Al7075 alloys, respectively, in addition to constant rotation rates and traverse speeds named as 710 rpm and 28 mm/min respectively. The microstructure of different welding zones and fracture surface were investigated by an Optical Microscope (OM) and Scanning Electron Microscopy (SEM), respectively. The results showed that by tool offsetting from the weld center through Al2024, an onion-shaped area has been created and mixture happens completely. However, by tool off-setting towards Al7075, onion-shaped microstructure fails to be formed in the stirred area. From the results of the tensile test, it is presented that maximum tensile strength is obtained in samples with a tool offsetting into the Al7075. With 1.5 mm tool offsetting into Al2024, first, joint tensile strength increases by 22.2 % in comparison to non-offset condition, and then, with more tool offset as much as 2 mm, tensile strength decreases by 22.2 %. In addition, by tool offsetting towards Al7075 by 1.5 and 2 mm, joint tensile strength decreases by 4.5 and 28.5 %, respectively. It is also concluded that in the offset samples towards the 7075 alloy, the microhardness in the HAZ area decreased compared to the microhardness of the offsets samples towards the 2024 alloy. Finally, the best mechanical behavior and microstructural properties were obtained in the sample with the tool offset of about 1.5 mm towards the welded Al2024 base metal (70215 samples) alloy. Manuscript profile
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