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RISS 인기검색어
- 검색키워드
- 저자 : Mohammad Azadi (검색결과 9 건)
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Mohammad Azadi,Mahboobeh Azadi 대한기계학회 2009 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.23 No.10
Nonlinear transient heat transfer and thermoelastic stress analyses of a thick-walled FGM cylinder with temperaturedependent materials are performed by using the Hermitian transfinite element method. Temperature-dependency of the material properties has not been taken into account in transient thermoelastic analysis, so far. Due to the mentioned dependency, the resulting governing FEM equations of transient heat transfer are highly nonlinear. Furthermore, in all finite element analysis performed so far in the field, Lagrangian elements have been used. To avoid an artificial local heat source at the mutual boundaries of the elements, Hermitian elements are used instead in the present research. Another novelty of the present paper is simultaneous use of the transfinite element method and updating technique. Time variations of the temperature, displacements, and stresses are obtained through a numerical Laplace inversion. Finally, results obtained considering the temperature-dependency of the material properties are compared with those derived based on temperature independency assumption. Furthermore, the temperature distribution and the radial and circumferential stresses are investigated versus time, geometrical parameters and index of power law. Results reveal that the temperature-dependency effect is significant.
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Mohammad Azadi 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.1
This paper presents a finite element method (FEM) free and forced lateral vibration analysis of beams made of functionally graded materials (FGMs). The temperature dependency of material properties along with damping had not previously been taken into account in vibration analysis. In the present study, the material properties were assumed to be temperature-dependent, and were graded in the thickness direction according to a simple power law distribution of the volume fractions of the constituents. The natural frequencies were obtained for functionally graded (FG) beams with various boundary conditions. First, an FG beam was assumed to be isotropic (metal rich) and the results were compared with the analytical solution and the results for ANSYS and NASTRAN software. Finally, dynamic responses were obtained for damped and un-damped systems. Numerical results were obtained to show the influences of the temperature dependency of the materials properties, the boundary conditions, the volume fraction distribution (the index of power law, N) and the geometrical parameters.
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NVH analysis and improvement of a vehicle body structure using DOE method
Shahram Azadi,Mohammad Azadi,Farshad Zahedi 대한기계학회 2009 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.23 No.11
The improvement of a vehicle body structure under the constraint of noise, vibration and harshness (NVH) behavior is investigated by using design of experiments (DOE) method. First, car body geometry is modeled in CATIA and meshed in HYPERMESH software. Then, a modal analysis between 0-50 Hz is done by MSC NASTRAN. A frequency map of the body is extracted and compared with a reference map to identify shortcomings. By using factorial and response surface Methods (RSM), optimization of the NVH performance is accomplished. An algorithm is proposed to improve the car NVH behavior. At last, in order to verify the present algorithm, forced vibration is analyzed under real road inputs for the model before and after improvement.
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Saeid Rezanezhad,Mohammad Azadi,Mahboobeh Azadi 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.5
In the present article, the influence of the heat treatment on high-cycle fatigue and fracture behaviors of piston aluminum–silicon alloys was studied. For this objective, standard samples were tested under fully-reversed cyclic bending by a rotaryfatigue machine and then, fracture behaviors were investigated by the field emission scanning electron microscopy. Beforeexperiments, two heat treatments were performed on as-cast aluminum specimens, including a cooling process on samplesafter casting and the T6 treatment (solutioning for 5 h at 500 °C, quenching and ageing for 9 h at 180 °C). Obtained resultsshowed that the heat treatment changed the distribution and the size and of silicon phases in the aluminum matrix andincreased the hardness, significantly. In addition, the high-cycle fatigue lifetime increased by the heat treatment, surprisinglyas 2146% and 411%, at the highest stress level and the lowest stress level, respectively. This enhancement was more thanthe improvement by cooling samples after casting. Observing cleavage and quasi-cleavage marks on the specimen fracturesurfaces was the reason for the brittle fracture behavior. Besides, cleavage planes were smaller in heat treated samples, withshorter micro-cracks or lower crack densities, which affected the fatigue lifetime of the material.
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Temperature and thickness effects on thermal and mechanical stresses of rotating FG-disks
Mehrnoosh Damircheli,Mohammad Azadi 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.3
In the present paper, radial and hoop thermal and mechanical stress analysis of a rotating disk made of functionally graded material (FGM) with variable thickness is carried out by using finite element method (FEM). To model the disk by FEM, one-dimensional twodegree elements with three nodes are used. It is assumed that the material properties, such as elastic modulus, Poisson’s ratio and thermal expansion coefficient, are considered to vary using a power law function in the radial direction. The geometrical and boundary conditions are in the shape of two models including thermal stress (model-A) and mechanical stress (model-B). In model-A there exists no pressure in both external and internal layers, and there is a temperature distribution considered as a second order function in the radial direction of the rotating disk. In this case, the temperature dependency of the material properties is considered and a hyperbolic type is assumed for the geometry of the disk. In model-B, there is a constant pressure only on the internal layer and a pressure on the internal layer of the disk without temperature distribution but with different types of surface profiles. Furthermore, the displacements and stresses for various power law indices (N) and angular velocities are calculated and compared to other results in the literature. The effect of varying thicknesses and dependency of material properties on temperature distribution is investigated.
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Multidisciplinary optimization of a stiffened shell by genetic algorithm
Mahdi Maghsoudi Mehrabani,Ali Asghar Jafari,Mohammad Azadi 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.2
Vibration analysis of simply supported rotating cross-ply laminated stiffened cylindrical shell is performed using an energy approach which includes variational and averaging method. The stiffeners include rings and stringers. The equations are obtained by Rayleigh-Ritz method and Sander’s relations. To validate the present method, the results are compared to the results available in other literatures. A good adoption is observed in different type of results including isotropic shells, rotating laminated shells, stiffened isotropic shells and stiffened laminated shells. Then, the optimization of parameters due to shell and stiffeners is conducted by genetic algorithm (GA) method under weight and frequency constraints. Stiffener shape, material properties and dimensions are also optimized.
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Abolfazl Amini,Mahdi Rojhani,Asghar Azadi,Mohammad Amin Raoof 대한토목학회 2024 KSCE Journal of Civil Engineering Vol.28 No.2
Uncertainty about the geometry of jet grouting columns is a serious challenge to the efficiency of jet grouting technology. If this challenge can be met, jet grouting can become an efficient method of soil improvement. One proposed approach is measurement based on changes in the electrical resistivity between the column and surrounding soil. This approach is non-destructive, easy to use, fast and accurate. This paper reviews jet-grouting methods using the experimental research approach and reports on the design and construction of a probe equipped with ring electrodes that is suitable for measurement of the column diameter. The approach is based on the geoelectric method and Wenner theory. The probe was field tested on jet-grouting columns in a project in Bandar-e Gaz. The probe results were validated by visually observing the dimensions of the excavated column. The results showed that the probe performed well. The device measured a 90-cm column as being from 81 to 88 cm with an error of about 10%. The method of measuring the difference in electrical resistance was shown to be an accurate approach to solving the problem of uncertainty in the geometry of jet-grouting columns.
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Abu Ahmed,Atiar Rahman,Sarowar Jahan Khan,Nipun Mojumder,Farjana Sharmin,Muhammad Abu Bakar,Kamirul Hasan Chowdhury,Mohammad Ali Azadi 경희대학교 융합한의과학연구소 2016 Oriental Pharmacy and Experimental Medicine Vol.31 No.4
Water hyacinth (Eichhornia crassipes) has been used in phytoextraction to uptake heavy metals and trace elements in various experiments. This research investigated the protective effects of Water hyacinth extracts on Lead (Pb)-induced toxicity in the albino rat. Forty-eight six-weeks-old Wistar albino male rats (average weight, 180 ± 6.45 g) were divided into six groups: normal control (NC), Pb control (PbC), Chloroform extract (ChEx), Ethyl acetate extract (EAEx), Methanol extract (MeEx) and Ascorbic acid treated groups (AA, positive control). All animals except NC group have been administered with Lead acetate (Pb(CH3COOH)2) before the therapeutic dose. Thrombolytic and cytotoxic effects were evaluated by modified clot lysis and Brine shrimp lethality tests respectively. Biochemical analyses reports revealed that ChEx significantly (P ≤ 0.05) reduced the elevated alkaline phosphatase (ALP) and aspartate amino transferase (AST) whereas MeEx did the alanine amino transferase (ALT) in comparison to positive control. ChEx significantly inhibited the Pb deposition in kidney and liver than two other extracts. ChEx significantly increased the liver protein compared to PbC group. In the thrombolytic assay, EAEx showed the pronounced clot lysis (49.24 %) while ChEx and MeEx showed 45.18 % and 29.13 % of clot lysis respectively. In Brine shrimp lethality bioassay, the LC50 value of the ChEx, EAEx and MeEx were 4.16, 4.47 and 9.27 μg/mg respectively and values were statistically significant (p < 0.05) compared to that of reference cytotoxic agent, Vincristine sulfate (LC50’ 0.55). Histopathological screening of kidney, liver and spleen showed that ethyl acetate extract recovered the highest of the cellular damage caused by Lead acetate. Biochemical and histopathological screening, therefore, demonstrate that Water hyacinth could be one of the promising sources of normalizing the Pb-poisoning and enhancing the thrombolysis in an animal model. Therapeutic prospects of Water hyacinth could be further studied through highlighting a dose-response study.
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