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Heisam Heidarzadeh,Mohammad Oliaei 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.4
Numerical analyses precision performed by software, depends mostly on the accuracy of constitutive model. Therefore, the issueof accuracy has led to significant achievements in the development of constitutive models simulating the mechanical behavior ofsoils. However, these constitutive models often needs to a lot of parameters to be calibrated for each type of soil, and it’s consideredas a disadvantage. especially, when the model parameters should be obtained through trial and error, the number of the parametersbecomes a considerable issue. This paper presents an advanced constitutive model. Despite requiring much lower number of modelparameters, it provides the same level of accuracy in compression of other advanced constitutive models for sand in literature. Toshow that the presented model achieved to this purpose, it is evaluated by various experimental data and some predictions made bytwo successful advanced models in literature. Consequently, it shows the presented model can accurately predict the sand behaviorunder different conditions despite using smaller number of parameters. Also, the accuracy of the presented model is on a par withadvanced constitutive models available in the geotechnical engineering literature.
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Rahim Jafari,Müge Kahya,Samad Nadimi Bavil Oliaei,Hakkı Özgür Ünver,Tuba Okutucu Özyurt 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.11
Microchannel heat exchangers are used to remove the high heat fluxes generated in compact electronic devices. The roughness of the microchannels has a significant effect on the heat transfer characteristics, especially the nucleate boiling and pumping power. Therefore, development of predictive models of surface texture is of significant importance in controlling heat transfer characteristics of these devices. In this study, micro-Wire electrical discharge machining (µ-WEDM) was employed to fabricate metal-based microchannel heat sinks with different surface textures. First, experiments were conducted to achieve the desired surface roughness values. Oxygen-free copper is a common material in the cooling systems of electronic devices because of its high thermal conductivity and low cost. Design of experiment approach based on the Taguchi technique was used to find the optimum set of process parameters. An analysis of variance is also performed to determine the significance of process parameters on the surface texture. An artificial neural network model is utilized to assess the variation of the surface roughness with process parameters. The predictions are in very good agreement with results yielding a coefficient of determination of 99.5 %. The results enable to determine µ-WEDM parameters which can result in the desired surface roughness, to have a well-controlled flow and heat transfer characteristics for the microchannels.
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Mohammadreza Shabgard,Samad Nadimi Bavil Oliaei,Mirsadegh Seyedzavvar,Ahmad Najadebrahimi 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.12
An axisymmetric three-dimensional model for temperature distribution in the electrical discharge machining process has been developed using the finite element method to estimate the surface integrity characteristics of AISI H13 tool steel as workpiece. White layer thickness, depth of heat affected zone, and arithmetical mean roughness consisting of the studied surface integrity features on which the effect of process parameters, including pulse on-time and pulse current were investigated. Additionally, the experiments were carried out under the designed full factorial procedure to validate the numerical results. Both numerical and experimental results show that increasing the pulse on-time leads to a higher white layer thickness, depth of heat affected zone, and the surface roughness. On the other hand,an increase in the pulse current results in a slight decrease of the white layer thickness and depth of heat affected zone, but a coarser surface roughness. Generally, there is a good agreement between the experimental and the numerical results.
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