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Residual stress measurement is one of the most interesting research areas in experimental mechanics. Residual stress is introduced to material due to plastic deformation of parts and can be one of the most effective parameters on design and operation of parts. ASTM E837-01 standard studies residual stress determination in parts by hole drilling method and represent calibration coefficients for flat sheets with constant stress profile. However, there is no certain standard on the residual stress measurement by Incremental Hole Drilling Method (IHDM) which is the subject of this study. IHDM can obtain stress profile by using two modified stress calibration coefficients. In this article, the stress calibration coefficients have been extracted for incremental hole drilling by using finite element analysis (FEA). FEA contains both biaxial tension test and pure shear test which a hole has been drilled step by step in the parts by removing elements and the strains changes were determined at three strain gauge positions on the surface. At last, the calibration coefficients are determined for each step and the accuracy of coefficients have been verified by a set of experimental test and a FE analysis. The experimental test contains four-point bending of an AA5056 flat aluminum sheet. The numerical analysis contains four-point bending of a flat sheet. In both cases, the stress profile can be determined easily by using analytical equations. Average analytical stress in each increment has been calculated and compared with the result of numerical incremental hole drilling method. The comparisons show that numerical and experimental results have no significant differences in first six steps but in the last four steps show an increasing errors due to the change in stress profile and hole geometry. Results presents that the calibration coefficients have suitable accuracy in stress profile determination.

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The aim of this paper is to analyze the sensor errors in measurement while drilling (MWD) instrument used in directional drilling operations. The MWD consist of three orthogonal accelerometers, three orthogonal magnetometers and one temperature sensor. The system formulation is achieved through the system analysis and functional consideration. The obtained formulation is validated and verified by comparing the results obtained from measurements and simulations. The accelerometers calibration, to estimate bias factors, scale factors and non-orthogonal factors of sensors, is done using optimal non-linear Newton Raphson algorithm by considering the high temperature calibration coefficients. The accuracy of the experimental results, obtained from several measurement while drilling systems in Iranian national oil drilling company shows the effectiveness of the approach.
 
 

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Accurate estimation of the pressure losses for non-Newtonian drilling fluids inside annulus is quite important to determine pump rates and select mud pump systems during wellbore drilling operation. The aim of this study is to simulate non-Newtonian (power law and Herschel-Bulkly) foam flow in underbalanced drilling condition through wellbore annulus using finite volume method. The effect of various operational parameters on pressure loss such as fluid rheology, foam fluid velocity, foam quality, drillpipe rotation and wellbore eccentricity, have been considered. Simulation results were compared with the previously published experimental data. The agreement was close with a relative error less than 5%. The results of numerical method are closer to experimental data for Herschel Bulkly model for foam fluid. Also, the results of numerical method, showed that pressure drop increases with increasing the foam fluid velocity and quality and it decreases with increasing eccentricity, but drillpipe rotation don’t have noticeable effect on pressure drop.

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Internal immobilization of fractured parts of bone depends on the drilling of fracture site and screw fixation of implanted devices to the bone. During drilling, the temperature may rise allowable temperature of 47°C and causes irreversible thermal necrosis. This study is concerned with methods of drilling to determine the best processing condition to minimize the osteonecrosis. Drilling tests were performed with two drilling techniques: conventional, and high speed drilling on the bovine femur and increase of temperature in drilling site, duration of temperature raise and thrust force were measured. The result for conventional drilling shows that in all processing conditions, the generated heat is over the allowable limit, which makes thermal necrosis inevitable. On other hand, it was found that increase of cutting speed of drill bit to 7000 rpm, leads to considerable decrease of thrust force and increase of heat dissipation with chips, simultaneously and leads to decrease of local temperature raise in drilling site. But with more increase of rotational speed of drill bit, because of not sensible change in drilling force and considerable increase of friction between chips, drill bit body and drilled hole, amount of temperature elevation is increased.

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Drilling of composite materials is one of the major processes in the manufacturing and assembly of sub-component. However, drilling of composite laminates can cause several damages such as degradation in residual tensile strength. In this study, effects of cutting speed, feed rate and drill angle on residual tensile strength of drilled laminates has been investigated. For this purpose, the Taguchi method was employed for three factors at three levels. Acoustic emission signals and wavelet analysis are used to monitor residual tensile strength. The experimental results indicated that the feed rate has the most significant effect. Based on time-frequency analysis of AE signals, it was found that AE signals with frequency ranges of (62.5-125), (250-312.5) and (312.5-375) KHz were generated from matrix cracking, fiber slipping and fiber breakage respectively.

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Drilling is the most widely used process for producing holes through the manufacturing parts. Drilling, as well as other machining processes, produce undesired raised material on both entrance and exit edges. The raised material caused by plastic flow is defined as burr, which is necessary to be removed for critical and precise part. In this work, magnetic abrasive deburring (MAD) was used to investigate the deburring performance of stainless steel. Firstly preliminary simulations were carried out by Maxwell software to determine appropriate MAD tool. Then, influence of MAD variables such as height of gap, mesh number and rotational speed were studied on burr height variation. Results indicated that mesh number of abrasive particles has the dominate effect in burr removal of stainless steel plate by this process.

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AISI 4340 steel is a low alloy steel with high tensile strength that has numerous applications in industry. Machinability of this alloy steel has difficulties due to its low heat conduction and high heat concentration in cutting zone. Therefore, use of cutting fluids in machining of this steel is inevitable. On the other hand, environmental problems of using mineral lubricants lead industries into use of biodegradable oils such as Vegetable based cutting fluids. The aim of this study is to investigate the drilling of AISI4340 alloy steel in presence of semi-dry lubricant and using soybean vegetable-based oil. For this purpose, drilling parameters including feed rate and cutting speed at three levels and workpiece hardness at two levels were chosen. Totally 18 experiments were carried out using coated carbide drill. Results revealed that vegetable-based oil can effectively be used in drilling using a semi-dry lubrication method. In addition, feed rate was the most effective parameter on cutting force and surface roughness and by increasing it, the cutting force increased, and the surface quality deteriorated. Also, workpiece hardness showed significant effect on surface roughness.

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Residual stresses reduce life time of welded joints and change the welded structure formation. Residual stress is stresses that remain in the body some specific operation like welding and is available when body is not under external loads. Different methods are available for residual stress relieved in any welded samples. In this research, samples A, B and C have been prepared and welded. Stress of Samples A and B have been relieved using heat treatment method and ultrasonic method, respectively. Also, no operation has been taken on the sample c. for different amount of residual stress of each sample, hole drilling method used and amount of residual stress in welding heat affected area of each sample determined. Results show that residual stress in ultrasonic method is for less than heat treatment method. To validate the results the x-ray diffraction method was also used and results of this method show that sample with ultrasonic stress, stress reliving had no peek in 2Ө angles, but for sample with heat treatment stress reliving had a peek in 137° that shows some residual stress.

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The productivity of a part is assessed based on factors such as dimensional and geometrical tolerances. In fact, tolerance features are the most important factors in shop drawing of an industrial part. The aim of present study is to empirically investigate the precision of holes created by helical milling method on AISI 4340 alloyed steel. This method refers to create the hole using milling tool, which moves along a helical path. By using helical milling, a high quality hole has been produced and there is no need for boring. Taguchi design of experiment was used to study the effects of process parameters including; cutting speed, feed rate, axial depth of cut and workpiece hardness on dimensional and geometrical tolerances of created hole. In addition, effect of minimum quantity lubrication method with two different oils and dry milling methods was studied. Results showed that the helical milling can be a suitable replacement for conventional drilling. In addition, cutting speed as the main parameter had significant effect on quality improvement of the created hole. On the other hand, in the helical milling, minimum quantity lubrication method using vegetable-based oil showed the best performance compared to mineral oil or dry cutting.

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Offshore platforms are exposed to random cyclic loads imposed on the structure by natural phenomena including waves, sea currents, wind and etc, so fatigue analysis of these structures is one of the most important design steps. Hot spot method is one of the most common techniques for evaluating of the fatigue life of offshore platforms. In this approach, the stress adjacent to the weld is estimated by extrapolation from the stress distribution approaching the weld, as obtained by finite element method or perhaps from strain measurements on the surface. In order to calculate the fatigue life of Amir Kabir semi-submersible drilling platform, first a model of platform is created. Then according to the environmental conditions of the Caspian sea, hydrodynamic forces exerted on the platform are calculated. The simulated hydrodynamic forces are then applied to the platform structure for calculating the stress and strain fields in the whole structure. It is found that the intersection of column and pontoon is the critical section of the platform and hence the fatigue life of the structure is predicted in terms of conditions of this location.

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Helical milling has been known as an innovative method for making high quality holes. In this method, milling tool generates efficiently a high quality hole by moving along a helical path. The hole diameter can be adjusted through the diameter of this helical path. Regarding accuracy of hole in industrial parts, it is necessary to compare this method with conventional hole drilling. Therefore, in this study helical milling and conventional drilling, have been compared with each other. Eight experiments were conducted considering two levels of cutting speed and feed rate on the samples made of AISI 4340 steel at 45 HRC. Minimum quantity lubricant system with two nozzles was used. 100 ml/h of Behran-11 mineral oil at air pressure of 4 bar was employed in this system. Machining forces, surface roughness, nominal diameter, roundness, and cylindricity were output parameters. According to the obtained results, cutting speed was the only one with positive effect on all qualitative parameters of the machined holes. On the other hand, independency of cutting parameters, helical milling lessened machining forces, surface roughness, and geometrical tolerances in compare with conventional drilling.

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In this paper, the incremental hole-drilling method is used to measure experimentally with accuracy non-uniform residual stresses in each ply of fiber metal laminate (FML) composites. Integral method was used for the approximation of residual stress. This method, considered a constant and uniform residual stress analysis at each hole-drilling depth increment. At the first, finite element method is used to calculation of the calibration coefficients matrix of the incremental hole drilling process. The calibration coefficients matrix determined by a finite element analysis can be used directly in the experiment. Calibration coefficients matrix used to relate the measured strain relaxation field with the existing residual stresses prior to the hole-drilling process. Also, for the experimental determination, released strains induced by high speed drilling process on FML composites with a stacking sequence of [AL/02/902]S have been quantified. At the end, the experimental measurements are compared with the theoretical predictions of the classical laminate theory. The good agreements between the experimental and theoretical results show that, incremental hole-drilling technique can be improved to be successfully applied for measuring non-uniform residual stresses in FML composites.

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In multi-pass groove welding, residual stress distribution, value and associated distortion are dependent on several factors, including the welding process-dependent parameters, mechanical properties of materials and fixtures. In present study, temperature distribution of three welding processes with different geometric designs are registered by the K type thermocouple. Each of the samples contains the same thickness of stainless steel plate A316 that was welded based on welding procedure specification with gas tungsten arc welding method with groove corner joints single bevel without gap and bevel face, single and double bevel with gap and bevel face. Created residual stress on a sample was initially measured by nondestructive ultrasonic transverse waves method. After cutting the vertical part (plate without Groove), for hole drilling device installation purposes, aforementioned stress was measured by the semi-destructive hole drilling method. While for two other geometrical designs only ultrasonic method has been used to prevent parts destruction. All three aformentioned designs were modeled in Simufact.welding finite element code (FE) and results were compared with experimental temperature and residual stress measurements. The comparison shows that experimental measurements and numerical values match well with each other highlighting a reasonable validation of finite element models resutls. Current research results show that changing the geometry of the weld configuration have a significant effect on changes in the distribution and maximum value of transvers residual stress, but trivial influence on maximum longitudinal residual stress.

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Friction drilling is a nontraditional hole-making process used to create and form the holes in thin sheets. The process involves penetration of a rotating conical tool into a sheet metal work piece and creation of a bushed hole in a single step. The tools are conical without having cutting edges, and the heat caused by friction between the tool and workpiece is used to soften the material, penetrate into the workpiece and make the bush. In this process, the temperature is high, and so that the deformation. The simulation by finite element analysis is a useful tool for understanding the material flow, stress, strain and length of bush. In this research, Abacus software was used to simulate the behavior of friction drilling. To verify the simulation results, the length of bushes created by tools with different diameters at different rotational speeds and federate were measured, and results were compared with experimental data. The aim of this study was to determine the process parameters to provide the bush with a uniform thickness, and study their effect on the shape of bush. Therefore, DOE was performed using a full factorial method and results were interpreted using ANOVA. Results showed that the tool diameter has the greatest effect (95%) on the length of bush during friction drilling, then feed rate (3%) and finally rotational speed (2%) has the smallest effect.

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Residual stress measurement of in-service parts of a system is practically impossible by means of destructive methods. Therefore, the use of ultrasonic method as a non-destructive method has an important role. One of the problems in non-destructive measurement of residual stresses by means of ultrasonic waves is determination of acoustoelastic constants. In fact, for conversion of ultrasonic method data to stress state, it is needed to determine these coefficients very precisely. But for reasons like HAZ inclination and small width of this zone, determination of coefficient of this zone does not perform accurately. In this study, the practical simulation is performed for determination of acoustoelastic coefficient of HAZ. For this simulation, the heat affected zone divided to four separate zones and then the microstructure of those four zones has been simulated on standard tensile test specimen by different heat treatment cycles. This coefficient has been used in evaluation of welding residual stresses of austenitic stainless steel by LCR Ultrasonic waves and the results has been compared with the hole-drilling strain-gage method. By comparison of stress values achieved by HAZ simulation method, the conventional method and hole-drilling strain-gage method, it is seen that the HAZ simulation method cause an improvement in welding residual stress measurement accuracy.

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In this paper, gas-liquid two-phase flow in the annulus of a real well during under-balanced drilling operations is simulated numerically. Oil and gas flow from the reservoir in to the annulus is considered due to under-balanced drilling condition. A numerical code based on one-dimensional form of steady-state single pressure two-fluid model in the Eulerian frame of reference is developed and its results are validated using experimental data from two real wells. The results of numerical simulation show better accuracy in comparison with other researches. Given the importance of prediction and control of the bottom-hole pressure and the amount of oil and gas production during the drilling operations, the effects of controlling parameters such as liquid and gas injection flow rate and choke pressure are discussed. Also, the effects of different controlling parameters on the characteristics of two-phase flow pattern, including liquid and gas void fractions, liquid and gas velocities and pressure distribution along with the annulus are discussed. According to the results, the effects of choke pressure and injected liquid flow rate on the production of the oil from the reservoir are independent of the values of each other and are dependent on the injected gas flow rate.

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Composites are widely being used due to their good properties such as high strength to weigh ratio, stiffness, resistance to buckling and fatigue, and etc. in different industries. Parabeam three-dimensional composites have found a remarkable situation due to their high bending strength and extremely low weight compared to other sandwich composites. Drilling is necessary to connect them to other structures. In this research, the effects of rotational speed, feed rate and tool diameter have been studied on the amount of damage in drilling of 3D composites. A full-factorial design of experiments was used to assess the significance of drilling parameters, and digital photography technique with auto focus was used to evaluate the damages from drilling. . The drilling operation was assessed based on two introduced factors including the matrix fracture factor (MFF) and uncut fiber factor (UCFF). The analysis of experimental results showed that among the main Parameters, Feed rate and rotational speed, have highest and lowest impact on MFF by 23.83% and 0.34%, respectively. But the experimental results for UCFF showed tool diameter with 17.17% is the most effective parameter. Both factors have similar behavior against the rotational speed which has the least impact on the output parameter. Rotational speed of 1750 rpm, feed rate of 0.1 mm/rev, and tool diameter of 10 mm were found to be optimal levels to obtain the minimum MFF and UCFF.

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In this research, microhardness variations of subsurface in hole making on a AISI4340 steel workpiece was studied experimentally. For this purpose, four hole making methods were used including; helical milling, profile milling, drilling with and without predrilling. The design of experiments utilized full factorial method in which two main cutting parameters including cutting speed (Vc) and feed rate (fz) were changed in three levels. Nine experiments were performed for each process and Hardness variations of substrate layer along the hole radial and axial distances were investigated (216 hardness measurements points). Results showed that the measured hardness in all of the experiments were higher than bulk material hardness, regardless of cutting conditions and the maximum hardness value was found in the upper levels of cutting parameters of traditional drilling method (729 Vickers). In addition, due to workpiece temperature and work hardening increasing with prolongation of the process time, the maximum hardness value was obtained on the exit surface of hole in all processes. Also, least microhardness variations was found when using traditional drilling with predrill which represents superiority of non-continues, multistage hole making processes and conventional drilling using predrill in creation of holes with more uniform properties.

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Bone fracture occurs as a result of accident, old age and disease. Generally bone fracture treatment consists of stabilizing the fractured bone in the right position. In complex fractures, stabilizing internal and external tools and equipment is used to stabilize the fractured bone in position. Bone drilling is required in order to connect fixating devices. The forces required for chip formation, increase the temperature during bone drilling. The phenomenon of thermal necrosis of the bone occurs if the temperature exceeds 47 degrees Celsius. Thermal necrosis inhibit bone fixation and causes the wrong bone healing. The current study has been trying to examine the effect of the cooling gas on the reduction of temperature rise on drilling site as well as statistical analysis of the process. Tests have been carried out using direct injection of nitrogen gas using internal coolant drill bits. Using cooling gas reduced the increase in drilling temperature to 15 degrees Celsius and prevented the thermal necrosis. The maximum increase in temperature in conventional drilling was 56 degrees Celsius, while using cooling gas the increase in temperature of 43 degrees Celsius was achieved. This reduces the risk of thermal necrosis. Statistical analysis also indicates that in the drilling with direct cooling with nitrogen gas the temperature changes are almost independent of the rotational speed.

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One of the most important machining processes in the field of orthopedic surgeries and biomedical engineering is the drilling process. Applying excessive forces on the bone tissue, it can be caused cracking and damage bone tissue during the drilling process. In this paper, it is produced an improved analytical model based on early work done by Bono and Ni, Chandrasekharan, and Lee to predict the thrust force in the bone drilling process. In this model, the cutting action at the drill point is divided into three regions: the primary cutting lips, outer portion of the chisel edge (the secondary cutting edges), and inner portion of the chisel edge (the indentation zone). All three regions have been investigated for the cutting process by the analytical model. In order validating the model, some experiments performed on the fresh bovine bone. Feed rate and rotational speed are adapted as the effective parameter in the drilling process, The statistical model to obtain the mathematical model and provide interaction diagrams of input variables experiments, to response surface methodology and experimental investigation of bone drilling have been offered. Comparing the analytical model and experimental results show good agreement. From both analytical model and experiments, it is can conclude that with decreasing feed rate and increasing rotational speed, thrust force on the bone tissue decreases.