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Showing 8 results for Khalkhali

A. Khalkhali, S. Samareh Mousavi,
Volume 2, Issue 3 (7-2012)

In order to reduce both the weight of vehicles and the damage of occupants in a crash event simultaneously, it is necessary to perform a multi-objective optimization of the automotive energy absorbing components. In this paper, axial impact crushing behavior of the aluminum foam-filled thin-walled tubes are studied by the finite element method using commercial software ABAQUS. Comparison of the present simulation results with the results of the experiments reported in the previous works indicated the validity of the numerical analyses. A meta-model based on the feed-forward artificial neural networks are then obtained for modeling of both the absorbed energy (E) and the peak crushing force (Fmax) with respect to design variables using those data obtained from the finite element modeling. Using such obtained neural network models, a modified multi-objective GA is used for the Pareto-based optimization of the aluminum foam-filled thinwalled tubes considering three conflicting objectives such as energy absorption, weight of structure, and peak crushing force.

A. Khalkhali, V. Agha Hosseinali Shirazi, M. Mohseni Kabir,
Volume 3, Issue 2 (6-2013)

One of the most important structural components of engine compartment assembly in a car body is the Srail. S-rails has significant role in absorbing energy during crash events and therefore it is designed for efficient behavior in such conditions. Driving the peak crushing force of the S-rails is one of the important objectives in the design process of such structures. Peak crushing force is exactly the force applied to the downstream components and then will be transferred to the cabin of vehicle. In this paper, closed form solution is performed to drive the peak crushing force of the S-rails. Results of such analytical model finally are compared with the results of finite element simulation. Good agreement between such results shows the accuracy of the proposed analytical model.

A. Khalkhali, M. Afroosheh, M.r. Seyedi,
Volume 4, Issue 1 (3-2014)

In this paper, numerical simulation of FRP composite cylinder tubes progressive crushing processes is conducted using LS-Dyna. Details on the numerical modeling strategy are given and discussed. It is found that triggers introduced in the numerical simulation can effectively model the bevel trigger at the end of the tubular specimens. It is also found that two-layer finite element model based on the TsaiWu failure criteria is effective in representing the crushing failure mode of the tubular composite specimens and energy absorption characteristics. Employing GEvoM software, two meta-models are then obtained for modeling of both the absorbed energy (E) and the peak crushing force (Fmax) with respect to geometrical design variables using input output data obtained from the finite element modeling. Comparison between obtained meta-models and numerical results in both of training and testing sets show good approximation by using obtained polynomial models.

A. Khalkhali, M. J. Saranjam,
Volume 5, Issue 1 (3-2015)

7000 series Aluminum alloys are widely used in the automotive industries for structural lightweight components due to their exceptional high strength to weight ratio. However, this class of aluminum alloy is difficult to join by conventional fusion welding techniques so Friction stir welding (FSW) widely is used for welding this alloys. The process has been demonstrated to be effective and is currently industrially utilized for materials difficult to be welded or “un weldable”, especially aluminum and magnesium alloys. In this paper in order to predict the average grain size occurring in FSW of AA7050 plates due to the dynamic recrystallization (DRX) phenomena due to the welding process, a microstructure evolution model have been implemented in 3D fully coupled thermo-mechanical FEM in which the tool – work piece interaction in FSW of butt joint was investigated.

A. Khalkhali, M. Sarmadi, A. Bodaghi,
Volume 6, Issue 1 (3-2016)

This study aims to numerically investigate on the crashworthiness of thin-walled square tubes by consideration of 3-D oblique loading. In this type of loading, direction of loading is defined by using two spatial angles relative to the position of the tube. To this aim, finite element (FE) analysis is employed to simulate the loading for 8 different numerical models with different loading orientation. Subsequently, load-displacement diagrams as well as deformation shapes during the loading are derived for each model. Moreover, a study is done on the tube collapse mode for each case. Effect of loading orientation and tube thickness on the maximum crushing load and energy absorption are also studied via a parametric study on the FE simulations. Results indicated a different trend for all cases of 3D oblique loading compared to axial loading. This study highlights the significance of consideration of a 3D orientation in analysis of crushing behavior of thin-walled tubes.

M. Mohseni Kabir, M. Izanloo, Ab. Khalkhali,
Volume 7, Issue 2 (6-2017)

Automotive design engineers face the challenging problem of developing products in highly competitive markets. In this regard, using conceptual models in the first step of automotive development seems so necessary. In this paper, to make a body in white conceptual model, an engineering approach is developed for the replacement of beam-like structures, joints, and panels in a vehicle model. The proposed replacement methodology is based on the reduced beam, joint, and panel modeling approach, which involves a geometric analysis of beam member cross-sections and a static analysis of joints. In order to validate the proposed approach, an industrial case-study is presented. Two static load cases are defined to compare the original and the concept model by evaluating the stiffness of the full vehicle under torsion and bending in accordance with the standards used by automotive original equipment manufacturer (OEM) companies. The results show high accuracy of the concept models in comparison with the original model in bending and torsional stiffness prediction.
Prof Mohammad Hasan Shojaeefard, Mrs Azadeh Sajedin, Dr. Abolfazl Khalkhali,
Volume 8, Issue 4 (12-2018)

Dual turbocharger turbine is fed by an unequal out-of-phase mass flow charge almost all the time which have significant effects on its performance parameters and flow phenomena which are not well known. Besides fully understanding the flow behavior in the radial turbine suffers from lack of detailed information about the secondary flows. This article studies the secondary flow structure within a dual entry turbine in different admission conditions. Results showed that with increasing the inequality of pressure ratio in the entries, performance of the turbine significantly decrease. From the results a profoundly disturbed flow in the interspace region was recognized. The pressure distribution of each limb shows some dependency between entries. To fully understand the flow physics, the 3D computational fluid dynamics (CFD) was implemented and compared with the experimental results of Copeland et al. (2010). The results are used to study the physical origin and the effect of nonuniform mass flow on secondary vortices. The generation and the development of the inflow, horseshoe and the corner vortex was investigated by evaluating contour plot of velocity distribution. Results demonstrated that the inflow vortex is due to the asymmetrical flow into the passage from the volute.
Mahsa Rahimbeigi, Dr. Abolfazl Khalkhali, Amirali Parivar,
Volume 11, Issue 4 (12-2021)

Elastomeric engine mounts are being used in heavy vehicles as well as passenger cars to absorb the vibrations of the engine, carry its weight and reduce its movement while driving. The aim of this research is some studies that have been done to find the components of the elastomeric compound. Moreover, the feasibility study of constructing three different specimens with different percentages of soot and oil has been carried out in order to achieve the desired characteristics in the heavy vehicle engine mount. A rheometric test was then performed to determine the temperature and time of sintering. The tensile strength test has been used to determine the elasticity of the rubber specimens and to achieve high damping coefficients. Also the tensile strength test was performed with the aim of obtaining a specimen with a suitable stress-strain relationship and comparing the results with the reference engine mount. Consequently, the elastomeric compound is used to make the elastomeric engine mount of heavy duty vehicle in the form of rubber and reverse engineering.

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