جستجوی مقالات مرتبط با کلیدواژه « آنالیز حساسیت » در نشریات گروه « مکانیک »

Nanomanipulation and displacement of nanoparticles has found wide applications in various sciences today.One of the basic tools for performing the Nanomanipulation process is the atomic force microscope.Today the atomic force microscope has found various applications, including surface imaging, manipulation and movement of particles, extracting the properties of materials and textures.The manipulation of nanoparticles usually involves two phases.The first phase includes the extraction of the critical force and the critical time before the start of the particle movement.The second phase also includes the investigation of particles during movement during Nano manipulation and displacement.Due to the fact that in micro/Nano dimensions,surface forces are more effective than volume forces,so it is very important to choose the appropriate contact model in modeling and simulating the Nano manipulation process.Various parameters affect contact models on the micro/Nano scale.In this research, the effect of different parameters on Hertz, JKR and DMT contact models has been investigated.For this purpose, in order to investigate the effect of different input parameters, the statistical method of sensitivity analysis called E-fast, which is one of the fast methods,has been used.The input parameters examined in this research include tip radius,volume of the particle,elastic modulus of the tip,elastic modulus of the particle,Poisson's coefficient of the tip and Poisson's coefficient of the particle, as well as penetration depth and force, which are explained as output parameters.The obtained results show that the volume of the target particles and the tip radius have a great influence on the force and depth of penetration in the contact models

The development of the use of reinforced composites, as well as the increasing progress of technology in various industries, such as aerospace, biomedicine, and structures, has increased the investigation of production processes. Reinforcement of polypropylene composites with natural jute fibers is a suggested solution to protect the environment and also improve the quality of the composite. On this basis, it is necessary to study the effect of the influencing parameters on the manufacturing process of composites reinforced with jute fibers. In this research, by using existing linear regression equations, the sensitivity analysis of various parameters affecting tensile strength, flexural strength, and impact strength has been investigated. The effect of molding temperature parameters, compression pressure and compression time has been investigated using the E-fast sensitivity analysis method. Molding temperature is determined as the most influential variable in the compression molding process with the greatest impact compared to other variables. Compression pressure parameter and compression time are known as the second and third influential parameters after the mentioned parameter. The importance and influence of defined variables in the compression molding process will be considered in creating the desired quality and mechanical properties.

In orthopedics, the drilling process is one of the most important steps in the preparation of medical tools and implants. Improving the performance of medical tools and implants is of great importance, because these tools and implants are used in the repair of bone and joint injuries. One of the ways to improve the efficiency of these tools and implants is to use titanium nitride nano coatings on drilling tools. This article is presented with the aim of experimental analysis and optimization of axial force in the orthopedic drilling process using a tool coated with titanium nitride nano coating by physical deposition method. The purpose of this research is to improve the performance and efficiency of this process by optimizing various parameters such as tool rotation speed, cutting depth and titanium nitride coating. For this purpose, experimental tests were conducted using the response surface method. the sensitivity analysis was also performed. The results have shown that the rotational speed, as the most effective parameter, has a lesser effect (45% effect) on the axial force in the case without nanocoating, while it shows a greater effect (73% effect) in the case with nanocoating.

Endmilling is a type of machining tool for chipping the surfaces of parts, which has received attention due to its wide application in industries such as molding. Therefore, today, the need of the industry to find the optimal parameters of the process is felt so that the quality of the desired surface can be achieved. In general, the selection of effective parameters in any milling process significantly affects the surface quality of a finished part. In this research, using E-fast statistical sensitivity analysis method, the simultaneous influence of input parameters including spindle speed, depth of cut, and feed rate on the output parameter of surface roughness for the samples has been investigated quantitatively. Machining experiments have been carried out under different cutting parameters as defined in steady state conditions for the milling tool. surface roughness and vibration rate of machining with non-linear quadratic forms; It has been modeled based on the cutoff parameters and its interactions through several regression analysis methods. The results of this research showed that the spindle speed time parameter is known as the most influential parameter on the surface roughness with 67% influence. It was also observed that the feed rate parameter with 30% effect of cutting depth with 3% are known as the second and third influencing parameters on surface roughness.

The properties of metal-based composites, such as their high strength-to-weight ratio and good resistance to wear and fatigue, have caused a significant growth in their use in the aerospace, automotive, and aircraft industries. Magnesium-based composites have particularly attracted the attention of researchers in various fields, especially aerospace scientists, due to their lower density than other metal-based composite alloys such as titanium and aluminum. However, due to the presence of very abrasive reinforcing material in these materials, machining them is difficult and presents numerous challenges. Therefore, it to study the machining process of these is necessary composites and to examine the effect of the main turning parameters such as cutting speed, feed rate, and depth of cut on machining forces and surface roughness. Sobol's sensitivity analysis method was used for this purpose. Using this method, it was determined that the feed rate, cutting depth, and cutting speed have the greatest effect on the machining forces, respectively. Additionally, the feed rate has a greater effect on the surface roughness than the cutting depth and cutting speed. As the feed rate increases, the surface roughness and cutting forces increase.

Providing electrical, thermal and cooling energy in greenhouses is a very important issue. Due to the low efficiency of most of the conventional systems in greenhouses, the use of simultaneous production of electricity, heat and cooling (CCHP) systems has been highly considered in recent years. The main purpose of this article is the technical and economic feasibility of CCHP technology for use in a greenhouse in Tehran. In this research, a cucumber greenhouse with an area of 1 hectare, which consists of two structures of 0.5 hectare, has been analyzed and investigated. In order to analyze the technical-economic system used, calculations for four scenarios including the basic and conventional system, CCHP with absorption chiller and selling electricity to the grid, CCHP with absorption chiller and self-supply and CCHP with compression chiller and self-supply accepted. According to the results obtained for each scenario as well as the comparison of the selected scenarios, the greenhouse considered for the implementation of the CCHP system is not economical. The results of the research show that in case of using the CCHP system with absorption chiller and selling electricity to the grid, in order to make the system economical, the minimum rate of buying electricity from these units should be 3223 Rials per kilowatt hour. In the CCHP system with absorption chiller and self-supply, if the location of the greenhouse is such that 176 kilometers of transmission line is needed, this scenario becomes economical.

Advances in many engineering fields depend on materials with appropriate properties. The use of metal-matrix composites is rapidly growing as a suitable alternative to conventional materials due to their strength-to-weight ratio, resistance to wear and creep, etc. Machining of metal-based composites is a difficult task due to the presence of very abrasive reinforcing particles in its based metal. Therefore, it is necessary to investigate the factors affecting these materials. In this research, a methodical study has been conducted to investigate the effect of the parameters of spindle  speed, feed rate, depth of cut and the percentage of reinforcing particles on the behavior of cutting force and tool wear using experimental design methods, modeling and statistical sensitivity analysis methods. . Detailed analysis of behaviors has been done by providing statistical regression equations and optimization by Deringer's method and E-Fast-Sensitivity Analysis. According to the obtained results, the cutting depth had the greatest effect on the machining force. Also, cutting speed with 77%, advance rate with 9% percent and cutting depth and weight percent of reinforcing particles with 7% percent are other parameters affecting tool wear in the milling process of this composite.

The most important goal of the craftsmen is to maximize the material removal rate while controlling the surface quality. In this article, according to the regression equation obtained from the design of the experiment using the response surface method, to investigate the extent and manner of influence of seven process parameters including, pulse on time, pulse off time, arc off time, gap voltage, wire feeding rate, wire tension and water pressure has been studied on two characteristics of material removal rate and surface roughness using Sobol sensitivity analysis method. The purpose of this research is to select the most optimal parameter in the machining process in order to increase the material removal rate and reduce the surface roughness. According to the results obtained from the sensitivity analysis, it can be seen that the factor of pulse on time and pulse off time each have an effect of 59% and 28%, respectively, the most effective parameters on the material removal rate, and the parameters of pulse on time and water pressure, respectively, with 81% and 18% influence are the most effective parameters on surface roughness.

Today, various military, aerospace, automotive, etc. industries need materials with a high strength-to-weight ratio. The use of metal-based composite materials, especially aluminum-based composites, has increased greatly. Machining is needed to achieve high dimensional accuracy in products made with aluminum-based composites. Due to the presence of reinforcing material such as silicon carbide, machining of this type of material is difficult. Therefore, it is important to study the parameters affecting the machining of aluminum-based composites. In this study, the effect of spindle speed, feed rate, depth of cut and percentage of reinforcing particles were discussed using experimental and statistical test methods. The responses of surface roughness and material removal rate were investigated. The behavior of the input parameters on the responses of the process has been carefully investigated quantitatively and qualitatively. Answers have also been optimized. According to the obtained results, the spindle speed has the greatest effect on the surface roughness. Also, feed rate 33%, spindle speed 28%, depth of cut 26% and the percentage of reinforcing particles 13% have an effect on the chipping rate.

Drilling is one of the most common methods during surgery on human bones with the aim of keeping broken bones together. Due to the complexity of the material under the machining process and the sensitivity of the process, it is one of the most important and widely used mechanical methods in the field of medical engineering. Cracking, breaking and serious damage to bone tissue is a problem that may arise with increased machining forces during orthopedic operations. In this article, a second-order linear regression equation was presented in order to predict the behavior of drilling forces in terms of feed speed, tool rotational speed, drill diameter and their effective interactions. Also, to check the influence of each parameter, E-fast sensitivity analysis method was used. According to the obtained results, the rotational speed of the drill is the most effective input parameter on bone drilling forces with 57% influence. After that, the feed rate with 23% and the cutting depth with 20% are the parameters affecting the force in the bone drilling process.

Cyclones are devices used to separate two or more phases from each other. Cyclones are centrifugal particle collection systems that use the effect of a tornado to separate solid particles from the gas stream. The purpose of this article is to investigate the effect of 5 inlet parameters including inlet height, inlet width, outlet diameter, total cyclone height and body cyclone height on both pressure outlet and cut-off diameter. These parameters have not yet been investigated by Sobel analysis. In this article, the effect of 5 cyclone inlet parameters including inlet height, inlet width, outlet diameter, total cyclone height and cyclone body height on two outlet parameters including pressure drop and shear diameter was investigated through their regression equation and Sobel statistical sensitivity analysis. So far, the effect of these 5 parameters on these outputs has not been investigated through Sobel statistical sensitivity analysis. The results show that inlet width with 40%, inlet height with 36% and outlet diameter with 24% had the greatest effect on pressure drop, respectively, and the height of the cyclone and the square height of the body had no effect on pressure. On the other hand, the inlet height with 40%, the inlet height with 38%, the height of the cyclone with 12% and the body height of the cyclone with 10% have the greatest effect on the shear diameter, respectively, and the cyclone outlet diameter has no effect on the cut-off diameter.

Optimum oil displacement is the most important goal of pre-flush stage during matrix acidizing. In this study, the visco-capillary behavior of the two-phase flow in the pore-scale is analyzed using computational fluid dynamics. A two-dimensional model, based on Cahn–Hilliard phase-field and Navier–Stokes equations, was established and solved using the finite element method. To recognize the effective forces of two-phase flow displacement, a stability phase diagram based on the Logarithm of capillary number (Nc) versus the Logarithm of viscosity ratio (M) was constructed and then compared with the reported experimental data. After identifying both viscous fingering and capillary fingering regions, the most stable displacement region was found to be located at Log M ≈ 0.5 and Log Nc ≈ -2. Furthermore, the impact of four independent variables that critically affect the efficiency of the pre-flush stage, including pore volume of injection (1<PV<5), capillary number (-60.95) occurred at Log M > 0, -4.5 1, and θ> π/6 conditions. It is worth mentioning that for Log M< 0, the optimum condition occurred at Log M ≈ 0, Log Nc ≈ -3.5, PV ≈ 4 and θ ≈ π/6.

Using Hydrogen instead of fossil fuels has grown significantly due to its high energy density and zero carbon emission during consumption. The most economical method of storing hydrogen is liquefaction. In this study, after pre-cooling by the cold energy of the PRICO and liquefied natural gas (LNG) regasification systems, hydrogen gas enters the next stage and it liquefies by a mixed refrigeration cycle. The novelty of this cycle is based on the new design of a high-efficiency hydrogen liquefaction cycle which is using the cold energy of a LNG regasification process, in turn, results in less power consumption in the compression part and also less cost of power consuming for one kilogram of liquid hydrogen compared to that for a similar cycle. Energy, exergy, and economy analyses are implemented to investigate the proposed cycle. In the proposed hydrogen liquefaction cycle with the capacity of 14 tons per hour, the specific energy consumption (SEC) 15 % and payback period 20% decreased in comparison to the similar cycle.

One of the most attractive modern machining methods is electrical discharge machining, which was introduced in the late 1960s. Electric discharge machining with wires has a number of uses, including high accuracy machining of all conductive materials such as metals, metal alloys, graphite, and ceramics, as well as aerospace, automotive, and other industries. In order to increase the rate and reduce surface roughness and gap width, optimal cutting parameters play a crucial role in selecting output parameters. In this study, input parameters (discharge, pulse duration, pulse frequency, wire speed, wire tension, and dielectric current velocity) were compared to output variables (cutting rate, surface filter, and width). The sensitivity analysis shows that pulse duration parameters, wire speed, and discharge flow are most effective parameters for cutting rate, and pulse duration parameters, dielectric rate, and discharge flow are most effective parameters for surface roughness, as well as pulse duration, wire speed, and discharge current for gap width. Pulse duration with 72%, wire speed with 14%, and discharge current with 10% has the greatest impact on the chip removal rate.

The performance of the impeller of a radial flow compressor is highly affected by its geometric uncertainties. The geometrical characteristics of the impeller may change slightly during the manufacturing process or as a result of long-term operation, resulting in deviations from design performance curves. In this research, the performance sensitivity to each geometric parameter is determined using global sensitivity analysis, and the performance deviation interval is extracted using uncertainty quantification by the Kriging surface response method. For this purpose, initially, three categories of databases with a different number of impellers are created using geometric characteristics deviating from the original sample. For different geometries, the flow simulation in the impeller is performed using computational fluid dynamics in a viscous three-dimensional turbulent solver. A surrogate model which uses the Kriging method for each database to quantify the uncertainty more quickly is utilized. The results show that in 95.5% of cases, the pressure ratio and total to total efficiency and total to static efficiency fluctuate by 1.88%, 1.03%, and 1.56% around the predicted value, respectively. Moreover, the impeller's outlet radius is the most sensitive geometric parameter.

By reviewing the research conducted on the eddy current braking system's analysis and optimization, it is observed that eddy current braking's physical characteristics are not studied in the automotive application, and its braking torque is not sufficient. In this paper, the governing equations of the braking torque of the eddy current brake with the addition of skin effect and heat are applied, and the results of the two basic and modified models are compared. Then the sensitivity analysis was performed by the finite element method. The analysis results show that by applying the skin effect and heat, the skin effect and heat, the braking torque increases and decreases, respectively. The sensitivity analysis results show the effect of the system's geometric, dynamic, and electromagnetic parameters and structural modifications on the initial value, peak value, and durability of the braking torque produced by the eddy current brake.Keywords: Eddy currentbraking, braking torque, skin effect, heat effect, sensitivity analysis

The perturbation friction process is a solid state method used to modify the surface, improve mechanical properties, and produce composites. In this research, the effect of effective parameters on the surface compositing of AZ31B / CNT alloy with carbon nanotubes has been investigated by the frictional perturbation process method and Sobel sensitivity analysis. Input parameters in this study were advance speed, rotation speed, weight percentage of carbon nanotubes and number of welding passes, as well as considered outputs including hardness and weight loss. In order to analyze the results, Sobel sensitivity analysis has been used to investigate the qualitative and quantitative impact of inputs on outputs. The results of this study showed that the weight percentage of carbon nanotubes, rotation speed, number of welding passes and advancement speed affect hardness, respectively. The weight percentage of carbon nanotubes, the rotation speed, the number of welding passes and the advancing speed also affect the weight loss.

A new approach to the design and development of launchers is the use of advanced technologies to reduce design and development costs as much as possible. In this paper, an approach to reduce costs and increase reliability is proposed, which is based on the use of a non-turbo pump propulsion system (pressure-fed propulsion system) instead of a turbo pump propulsion system. For this purpose, the multidisciplinary conceptual design optimization of a two-stage launch vehicle with a pressure-fed propulsion system with the aim of sending max payload with a least gross mass to the orbit (500 km) in terms of structure, aerodynamics, propulsion, pressure vessels, simulation, and pitch program disciplines. Then, the sensitivity analysis was performed on the optimum launcher to determine the efficiency of the launcher at different orbital heights and the ability to carry a suitable payload.

In this paper, the hydrodynamic behavior and heat transfer of a nanofluid turbulent flow in an exchanger equipped with perforated conical rings are simulated numerically. Water-based fluid and Al2O3 nanoparticles with a weight percentage of zero to 5% are considered as nanoparticles that increase heat transfer. The governing equations are solved using the computational fluid dynamics method with the help of ANSYS-Fluent software in the range of Reynolds 12000-2000. After validation of the numerical solution method with the available experimental results, the effect of geometric parameters and flow characteristics such as Reynolds number, number of rings used, number of holes used and volume fraction of nanoparticles on the heat transfer characteristics of the heat exchanger have been studied. The results show that the use of perforated conical rings has a significant effect on improving heat transfer in heat exchangers and this method can be used in practical applications. The results show that with increasing the number of conical rings, decreasing the number of holes, and increasing the weight fraction of nanoparticles, the Nusselt number and the coefficient of friction increase. Based on the results, it can be seen that the proposed loop can increase the Nusselt number by 5.3 times compared to the tube without the loop. In addition, Al2O3 nanoparticles have a favorable effect on increasing heat transfer and with increasing the volume fraction of Al2O3 nanoparticles from zero to 5%, Nusselt number per m = 1 and n = 3 about 92% increase in Nusselt number has been observed.

Today, the drilling process is one of the most fundamental machining processes among industrial processes. The drilling process is expanding to high-speed, high-precision machining due to productivity improvements. The drill bits used in this process play an important role and can increase the surface quality and improve the surface roughness. It should be noted that the costs of breaking the drill bit are high. In the micro-drilling process, increasing the rotational speed decreases the machining time, but also causes a faster tool wear rate. Also, reducing the feed rate improves the surface quality, but on the other hand, reduces the material removal rate. Therefore, an accurate selection of various parameters in micro-drilling is necessary to achieve the desired surface roughness. In this paper, firstly, by performing experimental tests, a second-order linear regression mathematical model is presented to predict the surface roughness during micro-drilling operations of brass by input parameters of rotational speed, feed rate, and tool diameter and their effective interactions. Then, using the E-Fast statistical sensitivity analysis method, the effect of the studied parameters on the surface roughness is obtained. The results obtained from the e-Fast statistical sensitivity analysis method show that among the three input parameters, the feed rate with 62% effect on surface roughness as the most important parameter, the rotational speed with 34% effect as the second parameter affecting roughness. The final surface, as well as the tool diameter with only 4% impact, is known as the least effective parameter on the surface roughness in the micro-drilling process of brass micro-drilling.Today, the drilling process is one of the most fundamental machining processes among industrial processes. The drilling process is expanding to high-speed, high-precision machining due to productivity improvements. The drill bits used in this process play an important role and can increase the surface quality and improve the surface roughness. It should be noted that the costs of breaking the drill bit are high. In the micro-drilling process, increasing the rotational speed decreases the machining time, but also causes a faster tool wear rate. Also, reducing the feed rate improves the surface quality, but on the other hand, reduces the material removal rate. Therefore, an accurate selection of various parameters in micro-drilling is necessary to achieve the desired surface roughness. In this paper, firstly, by performing experimental tests, a second-order linear regression mathematical model is presented to predict the surface roughness during micro-drilling operations of brass by input parameters of rotational speed, feed rate, and tool diameter and their effective interactions. Then, using the E-Fast statistical sensitivity analysis method, the effect of the studied parameters on the surface roughness is obtained. The results obtained from the e-Fast statistical sensitivity analysis method show that among the three input parameters, the feed rate with 62% effect on surface roughness as the most important parameter, the rotational speed with 34% effect as the second parameter affecting roughness. The final surface, as well as the tool diameter with only 4% impact, is known as the least effective parameter on the surface roughness in the micro-drilling process of brass micro-drilling.