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    • List of Articles Hamid Zarepour

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        1 - Empirical and Numerical Study of Gas Turbine Disks under Mechanical Stress and Temperature Gradient
        Rasoul Yari Yari Hamid Zarepour Aazam Ghassemi
        Gas turbine disks usually operate at very high temperatures and rotate at very high angular velocities under normal working conditions. High temperature in turbine disks causes changes in their properties. High angular velocity creates a large centrifugal force in the d More
        Gas turbine disks usually operate at very high temperatures and rotate at very high angular velocities under normal working conditions. High temperature in turbine disks causes changes in their properties. High angular velocity creates a large centrifugal force in the disk and high temperature reduces the strength of the material and causes deformation. Complexity of these parameters has turned the determination of stress distribution in gas turbine disks to one of the bottlenecks in the analysis, design and manufacturing of turbine engines. Therefore, using an applicable method for stress analysis is essential in order to better determine stress distribution in turbine disks. In this study, the finite element method (FEA) is used for predicting the behavior of rotating disks under mechanical and thermal stresses. In order to increase the certainty of simulation, gas turbine disk is first simulated and analyzed based on dimensions and loading conditions extracted from previous studies. Then, the results are compared with previous studies in order to determine the accuracy of analysis method applied in ANAQUS software. Afterwards, gas turbine disks are evaluated under both rotational movement and temperature gradient. The results show that the presence of angular velocity and centrifugal force cause expansion to the disk radius. The results show an acceptable correlation between the results of empirical and numerical studies. According to the results, the approach proposed in this study is a suitable method for analysis of the stress, temperature and displacement in turbine disks and other components with similar functions. Manuscript profile
      • Open Access Article

        2 - An Experimental Investigation on Surface Roughness and Edge Chipping in Micro Ultrasonic Machining
        Hamid Zarepour
        Surface quality including surface roughness and edge chipping is a key process measure in microultrasonic machining (Micro-USM) as an efficient process for micromachining of hard and brittlematerials. Process parameters such as ultrasonic vibration amplitude, static loa More
        Surface quality including surface roughness and edge chipping is a key process measure in microultrasonic machining (Micro-USM) as an efficient process for micromachining of hard and brittlematerials. Process parameters such as ultrasonic vibration amplitude, static load, type of toolmaterial, type and size of abrasive particles and slurry concentration can influence the surfacequality. However, there is limited study on the parametric effects on the surface quality in micro-USM. The objective of this study is to investigate the effects of the workpiece material as well asprocess parameters including abrasive type, particle size and vibration amplitude on surfaceroughness and edge chipping in micro-USM. Silicon, alumina ceramics and soda-lime glass wereselected as workpiece materials and polycrystalline diamond and alumina as abrasives. Particle sizeranging from 0.3 to 3 μm and vibration amplitude ranging from 0.8 to 3 μm were selected in thisstudy. Results indicate that workpiece material and vibration amplitude have significant effects onsurface roughness. Workpiece material was found to be the most significant parameter with apercentage contribution of about 45 % in the variation of mean Ra, followed by vibration amplitudeand particle size of about 28 % and 5% contributions, respectively. Results also show that aluminaceramic is a material capable of achieving better surface quality in micro-USM as compared tosilicon and soda-lime glass. Manuscript profile
      • Open Access Article

        3 - The Effect of Al2O3-MWCNT Hybrid Nanofluid on Surface Quality in Grinding of Inconel 600
        Behnam Taghizadeh Hamid Zarepour
        Grinding is finishing process aimed at achieving surface quality and dimensional accuracy in workpieces with tight tolerances especially from materials with a high degree of hardness and strength. The grinding process of superalloys is faced with problems and challenges More
        Grinding is finishing process aimed at achieving surface quality and dimensional accuracy in workpieces with tight tolerances especially from materials with a high degree of hardness and strength. The grinding process of superalloys is faced with problems and challenges caused by the generation of excessiveheatas well as the adhesion of workpiecematerialon the grinding tool. Therefore, in-depth research is still under way to introduce and develop new techniques for optimization of output parameters in the grinding of superalloys. One of such techniques is to apply minimum quantity lubrication (MQL) using nanofluids.In this research, we study the effect of using a type of mixed nanofluid comprising multiwall carbon nanotubes (MWCNT) and nano-aluminum oxide (Al2O3) on the surface quality in the grinding process of Inconel 600.For this purpose, the input parameters of the process are first determined. Following that, the design of experiments were performed based on full factorial method and the, grinding experiments were conducted accordingly to study the effect of various parameters including the nanoparticles size , volume concentration, and mixing ratio on surface quality of the workpiece. Based on the results obtained from this study, while using the vegetable oil for MQL with nanofluids, the highest surface quality with Ra=0.15µm is achieved by applying a nanofluid with a mixing ratio of 75% -25% for Al2O3 -MWCNT nanoparticles, volume concentration of 0.6%, and with size of 20 nm and 15 nm for Al2O3and MWCNT nanoparticles, respectively. Manuscript profile