Morteza Ahmadi; Behrouz Samandari
Ahmad Jafari; Mohammad Farough Hosseini; Aref Alipour
Vahid Azizi; Hossein Memarian; Arash Khosravi
Abstract
Numerous parameters influence bit selection process, which considering all them is not normally feasible. Existing methods use limited number of these parameters to choose a suitable bit for a specific drilling condition. One of the widely used methods is cost per foot. Specific energy and drilling strength ...
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Numerous parameters influence bit selection process, which considering all them is not normally feasible. Existing methods use limited number of these parameters to choose a suitable bit for a specific drilling condition. One of the widely used methods is cost per foot. Specific energy and drilling strength are another methods currently used for bit selection. Different methods of bit selection and bit lifetime estimation were tested on a gas field, in southern Iran. Although cost per foot method is most widely used, present study showed that similar bits may have different cost per foot in different wells, rock formations or drilling conditions. Therefore, where geological and geothechnical conditions widely vary in a single formation, this method cannot be used alone for bit selection. The specific energy method was also found to have some deficiencies as it is highly dependent on drilling parameters. The outcome of using existing formula for predicting unconfined compressive strength from petrophysical data of oil and gas wells is in fact drilling resistance, which is a very rough estimate of unconfined compressive strength. On the other hand, the drilling strength method, using Young's Modulus and clay content, showed to have rewarding results on the studied field. This method, if used together with cost per foot method, will give better results. The present study also showed that the results derived from the drilling strength method should be modified according to drilling parameters.
Soheila Aslani; Abbas Bahroudi; Jalal Karami; Amir Khodras Haghighi
Abstract
Sarbisheh mineral occurrence is located in the vicinity of the Tourshab village about 50 km south of Birjand, the center of Southern Khorassan province, east Iran. The predominant geologic characteristics of the region are highly-tectonic deformation, and intrusive, granodiroritic-dioritic, to volcanic, ...
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Sarbisheh mineral occurrence is located in the vicinity of the Tourshab village about 50 km south of Birjand, the center of Southern Khorassan province, east Iran. The predominant geologic characteristics of the region are highly-tectonic deformation, and intrusive, granodiroritic-dioritic, to volcanic, dacitic-andsitic rocks associated with broad alteration. To the northern part of the studied area, extensive variety of alteration, kaolanitic, sillicified to choloritic, can be observed clearly in the filed and remotely sensed data. Concerning to previous geologic works, these alteration zones have been formed apparently NW-trending extensional trends. This is more obvious feature to the southeast part of the area where the main tectonic features with NW-SE trend delimited the southern border of Kaolinitic alteration in adjacent of the Torshab spring. Based on previous geologic surveying and preliminary mineral prospecting, the area apparently has a convincing mineral potential, especially for copper, gold etc., to encourage some governmental organization or any private company to launch more detailed exploration study. The main goal of the present study was to introduce an integrated method for mineral exploration for the copper-gold prospects using the remote sensing and field observations and to produce different alteration maps. To distinguish between different types of alteration developed within the studied area, ASTER satellite data were collected and analyzed using various methods. In this manner, argillaceous alteration haloes and iron-oxide zones representing possible high-mineral potential extents were extracted successfully by applying the Korsta method. Meantime, other remote sensing techniques, such as color composite maps, principle component analysis, supervised classification, least-squares fit, band rationing and MF methods. By applying the above methods, this study produced different accurate alteration maps of the area.
Ebrahim Azimi; Samad Banisi; Gholamreza Langarizadeh; Malek Dehghani
Abstract
Discharge grates are one of the most important parts of SAG mills. These grates prevent balls and unbroken ores from discharging the mill and they have a significant effect on the mill filling and size distribution of the discharge flow. To consider the effect of openings of the grates on the overall ...
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Discharge grates are one of the most important parts of SAG mills. These grates prevent balls and unbroken ores from discharging the mill and they have a significant effect on the mill filling and size distribution of the discharge flow. To consider the effect of openings of the grates on the overall efficiency of the comminution operation, the variation of the grates shape and size were closely monitored for a period of 5600 hours at the Sarcheshmeh copper concentration plant. Using measured values the changes in the amount of open area, the thickness of grates plates, the width of grates openings with respect to their radial position and grate plugging were determined. The results indicated that 1% increase in open area causes 0.4% increase in the circulating load of the circuit. The useful operational time of the grates was found to be 5000 hours beyond which the efficiency decreases.
Mohammad Farough Hosseini; Hossein Mahmoudi Dovvom Niasar; Morteza Ahmadi; Vahid Sa'ati
Abstract
Gotvand dam is a rock fill dam located in Khoozestan province in Iran on Karun River. It will be constructed on weak mudstone and layers of sandstone. These layers are intermittent of medium strength with uniaxial compressive strength of 15 and 25MPa respectively. Some regional factors as continuous ...
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Gotvand dam is a rock fill dam located in Khoozestan province in Iran on Karun River. It will be constructed on weak mudstone and layers of sandstone. These layers are intermittent of medium strength with uniaxial compressive strength of 15 and 25MPa respectively. Some regional factors as continuous unloading, caused by river flood washed off and horizontal tectonic loading have created a local anticline in the base of the dam. It is estimated that such deformation will last over the time. Therefore, in order to determine creep parameters assessing the time dependent behavior of the foundation rock during the life of the dam through numerical and analytical methods is inevitable. In this research, by conducting creep tests under constant loads the strain- time graphs were produced for the two rock types. Applying the Burger rheological model for both rocks, their creep parameters were determined. In order to validate the produced data numerical modeling was conducted. A comparison between the results of numerical modeling and laboratory tests showed that the difference between the two methods is less than 6%. Also the time required for both rocks to enter the tertiary creep was determined to be 40 days for sandstone under 17.72MPa and 35 days for mudstone under 7.8MPa of load.
Seyyed Bijan Mahbaz; Hossein Memarian
Abbas Majdi; Siavash Litkouhi; Mehdi Hajian Hosseinabadai
Abstract
In deep mixing method lime or cement and or a combination of the two are mixed with in-situ soils by means of an auger to improve the strength properties of the soils. Strength of the improved soils may be evaluated in different ways, so that, the uniaxial compressive strength assessment is one of the ...
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In deep mixing method lime or cement and or a combination of the two are mixed with in-situ soils by means of an auger to improve the strength properties of the soils. Strength of the improved soils may be evaluated in different ways, so that, the uniaxial compressive strength assessment is one of the most commonly used methods. The project site is located at Zaytoon 2 in Bandar Abbas City. In order to make the excavation of the sandy soils feasible and to mitigate the liquefaction potential hazard, deep mixing method was employed. In an attempt to establish a relation between strength properties of cement grout (cement + water) and the soil-cement mixed (cement grout + soils) two types of grouts; "A" and "B" with different admixtures were used. Type "A" with a water/cement ratio (w/c) = 0.8, where no bentonite was added, whilst in grout Type "B" the ratio w/c = 1.0, with 3% (by cement weight) and bentonite was added. In order to evaluate the strength properties of the grout and soil-cement, some representative samples were obtained. The 7 and 14 days cured samples were tested under uniaxial compressive loading condition. Several in-situ samples were also taken for reliability and quality control purposes. Comparative study of the results revealed that the rate of strength increase in grout type "B", due to using bentonite, is low as compared with the grout type "A". The relationship of uniaxial compressive strength and modulus of elasticity with both density and with the final strain of soil-cement mixed were investigated. Finally, based on the results of uniaxial compressive strength of cement grout, an empirical equation to predict the uniaxial compressive strength of soil-cement mixed has been suggested. The predicted strength was compared with the strength of in-situ samples. It has proven that the prediction method can be used as a reliable approach for determination of the uniaxial compressive strength of soil-cement mixed.
Mohammad Kazem Besharati Givi; Amir Sarvari
Abstract
In all engineering applications where solid surfaces slide on each other, friction plays an important role. It becomes even more important, particularly in metal forming processes where the two sliding materials are metallic. Among forming processes, forging is an important process, because of improving ...
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In all engineering applications where solid surfaces slide on each other, friction plays an important role. It becomes even more important, particularly in metal forming processes where the two sliding materials are metallic. Among forming processes, forging is an important process, because of improving material structure, mechanical properties and reducing production time. An inverse analysis technique has been developed to determine the flow stress and friction at the tool/work piece interface simultaneously. The inverse problem is aimed at minimizing the error between experimental data and predictions made by rigid-plastic simulations. The ring compression test was selected for evaluating the method for bulk forming of Aluminum7075. The determined friction data were compared with corresponding data obtained independently using standard calibration curves for cold forging in the ring compression test. Results show that the method discussed in the study is efficient and accurate.
Majid Parvizi; Hamid Reza Ghasemi Monfared Rad; Mohammad Habibi Parsa
Abstract
Wire-brushing is used for different purposes such as removing metal surfaces oxides, increasing surface brightness, improving fatigue properties and surface activation before coating. The wire-brushing severely scratches and stirs the metals in the surface layers, so that complicated metal flow gives ...
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Wire-brushing is used for different purposes such as removing metal surfaces oxides, increasing surface brightness, improving fatigue properties and surface activation before coating. The wire-brushing severely scratches and stirs the metals in the surface layers, so that complicated metal flow gives rise to very large amount of plastic strain and increases dislocation density of the surface layer. After recovery, subdivided grains and a nanocrystalline structure are formed on the surface. Formation of nanocrystalline structure on the surface of Al 6061 alloy by wire brushing at various brushing speeds was investigated by using atomic force microscopy and X-ray diffraction. The results showed that the severe plastic deformation decreased the surface grain size to 30-70 nm.
Maryam Haj Fath'alian; Mahmoud Nili Ahmadabadi; Mohammad Habibi Parsa; Tahereh Shah Hosseini; Hannaneh Ghadirian; Tahereh Hosseinzadeh Nik
Abstract
Equi-atomic Nickel-Titanium (NiTi or Nitinol) has the ability to return to a former shape when subjected to an appropriate thermo-mechanical regime. Pseudoelastic and shape memory effects are some of the behaviors presented by these alloys. The unique properties concerning these alloys have encouraged ...
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Equi-atomic Nickel-Titanium (NiTi or Nitinol) has the ability to return to a former shape when subjected to an appropriate thermo-mechanical regime. Pseudoelastic and shape memory effects are some of the behaviors presented by these alloys. The unique properties concerning these alloys have encouraged many investigators to look for applications of NiTi for biomedical applications. One of the most successful applications of Nitinol is orthodontic archwire. The best features of these wires are super-elasticity, the phenomena that causes easy engagement (loading conditions). Superelastic nitinol wires deliver clinically desired light continuous force during deactivation (unloading conditions), enabling effective tooth movement with minimal damage for periodontal tissues. Superelasticity is characterized by a load-deflection plot with a horizontal region [plateau] during unloading, implying that a constant force may be exerted over that particular range of tooth movement. It is known that the NiTi alloy wire undergoes a phase transformation from an austenitic to a martensitic phase as the load increases during the loading process. Metallurgical studies have attributed these characteristics to a reversible phase transformation from the body centered cubic structure to the monoclinic structure of nickel-titanium when the stress reaches a certain level during deformation.The increasing amount of energy stored inside the NiTi wire during this process is consumed during the unloading process as the transformation is reversed, and the martensite structure reverts to austenite . Superelasticity is only exhibited by wires showing high endothermic energy in the reverse transformation from the martensitic phase to the parent phase and with low Load/deflection ratios. These wires show nearly constant forces in the unloading process, a desirable physiological property for orthodontic tooth movement. NiTi archwires have gained acceptable by orthodontists as initial alignment wires. Most of the information about the behavior of orthodontic wires is based on mechanical laboratory three point bending tests to study load-deflection characteristics. A three-point bending test allowed load-deflection curves offer reproducibility. Variations in model design have been shown to affect load- deflection plots. The load deflection performance of NiTi wires depends on the design of the test model. Modified three point bending test which simulates wire force on the teeth in the oral conditions has more correct results than ordinary three point bending test. The purpose of this study is to investigate the load-deflection characteristics of superelastic nickel titanium wires with a new model design trough modified bending tests. In this research a new three point bending fixture was invented and designed to determine the superelastic property in clinical conditions, and the wire samples were held in the fixture similar to oral cavity. By means of this instrument the three point bending test simulates wire force on the teeth in the oral configuration. The lower section of fixture is a rail fabricated from steel, a special movable base with a curved canal assembled over the rail. The upper section designed to simulate the teeth arrangement and curvature: A stainless steel disk (316L, ?80 mm, h10 mm) selected; and twelve rods (316L, ?5 mm, h10 mm) welded to the points representing center of teeth on the disk. The center points of teeth were located on the medium upper standard arc. Distance between the center points of teeth (interbracket distance) was similar to Wilkinson model.To achieve deflections 1, 2 and 4 mm, teeth 5,3 (right) and 2 (left) were selected respectively and rods in these points were movable. A fillet face machined on the rod surface parallel to the standard arc. Brackets fixed on the flat face of rod by superglue and orthodontic wire attached to fixed appliance. The superelastic behavior has been investigated through load-deflection test
Ali Dabbagh; Shahram Rayegan; Hossein Abdizadeh; Ramez Vaghar
Ali Ammari Allahyari; Hassan Farhangi; Seyyed Mohammad Mehdi Hadavi
Abstract
The effects of isothermal aging at temperatures between 550-850 ?C for durations of 1-100 h on microstructure, tensile properties, and impact fracture behavior of 316L austenitic stainless steel weld metal have been investigated. For this purpose, various techniques including metallographic observations, ...
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The effects of isothermal aging at temperatures between 550-850 ?C for durations of 1-100 h on microstructure, tensile properties, and impact fracture behavior of 316L austenitic stainless steel weld metal have been investigated. For this purpose, various techniques including metallographic observations, measurement of ferrite content using ferritscope, and fractographic investigations have been utilized. It was found that increasing aging temperature and time lead to dissolution of delta ferrite and formation of a continuous network of sigma phase, followed by partial spherodization of sigma phase. These microstructural changes are found to induce a transition from ductile to brittle fracture mode which is accompanied by a sharp decrease in fracture strain and charpy impact energy, of up to 90%, and is characterized by specific types of fragmented and brittle microvoid fracture surface morphologies. The consequences of such behavior in regards to the selection of proper stress relief heat treatment temperature are discussed based on dividing the aging processing window into three distinct regions.
