جستجوی مقالات مرتبط با کلیدواژه « response surface methodology » در نشریات گروه « مکانیک »

In this research, the parameters of brazing temperature, time, and joint seam have been optimized in brazing joints of 420 stainless steel with BNi-2 filler metal on the shear strength of lap joint samples using response surface methodology. The parameters of brazing temperature, time, and joint seam were determined by the design of the experiment using the Benken box method. The thickness of BNi-2 filler metal was considered to be 0.04, 0.07, and 0.1 mm in this research. After preparing the samples, they were placed in a vacuum furnace at temperatures of 1000°C, 1070°C, and 1140°C for 10, 30, and 50 minutes. The mechanical tensile test was performed to determine the shear strength. It was observed that increasing the joint seam from 0.04 to 0.1 mm caused a 14% decrease in shear strength. Also, increasing the brazing temperature from 1000°C to 1140°C has increased the shear strength by 21%, and increasing the brazing time from 10 to 50 minutes has increased the shear strength by 27%. In the end, it was optimized that the maximum shear strength is 164.429 MPa in the joint seam of 0.04 mm, the temperature is 1109.84 °C and the time is 46.58 minutes.

Preparing composites before welding and using nanocomposites is one of the new methods of joining. In this research, the mechanical strength of thermosetting composites surface prepared by chemical etching using polyvinyl chloride (PVC) polymer in the presence of aluminum oxide nanoparticles has been investigated. Thermal analysis of PVC containing different weight percentages of aluminum oxide nanoparticles shows a 45% increase in thermal conductivity. A regression model based on the response surface methodology using the effective parameters of welding time, weight percentage of nanoparticles and thermal conductivity obtained from variance analysis was developed to predict the maximum force and displacement of joint failure. The results show the maximum breaking strength and strain of 59 MPa and 0.04 of the welded sample, respectively, in the presence of 1% by weight of aluminum oxide nanoparticles. The increase of 1.3 and 1.2 times of the maximum tensile strength and breaking strain of the joint, respectively, in comparison with pure PVC samples, indicates the improvement of mechanical properties. Examining the microstructure with SEM shows that a uniform connection has been established along the weld line.

Metal matrix composites have attracted a lot of attention for application in the aerospace, defense, and automotive industries. Machining these materials with traditional machining methods is very difficult due to the presence of abrasive particles. Electrical Discharge Machining (EDM) is one of the most widely used advanced machining methods and seems to be a good method for machining metal matrix composites. Tool wear occurs during the process and cannot be reduced to zero, but it can be reduced as much as possible. In this research, the effect of discharge peak current, pulse on time, and pulse off time on the workpiece made of AZ91 magnesium alloy, reinforced with 5% of powdered silicon carbide particles has been investigated. The effect of these parameters on the wear rate of copper electrode is studied. The tests of this process have been modeled using the response surface methodology. 17 experiments have been done to reach the results. Discharge peak current, pulse on time, the interaction effect of discharge peak current and pulse on time, and the interaction effect of pulse off time and discharge peak current are effective factors on electrode wear rate. The lowest electrode wear rate is on the 300 microseconds pulse on time, 11.69 amp discharge peak current, and pulse off time of 20 microseconds.

The combustion flow field in domestic gas stove burners plays a fundamental role in the structure and shape of the flame, the distribution of the temperature gradient, and, consequently, the thermal efficiency and emission of pollutants. Obtaining a valid numerical model makes it easier to understand this complex flow and its influencing factors. To provide a valid numerical simulation, the thermal efficiency of the burner was experimentally tested in the pressure range of 12 to 24 mbar. The validity of the numerical results was then examined by comparing them with the experimental results. Additionally, the response surface methodology was utilized to investigate the simultaneous and mutual effects of various factors such as gas source pressure, initial temperature of the mixture, and load height on thermal efficiency, burner thermal power, the ratio of radiant heat flux to total flux, and the amount of CO emission. The algorithm proposed 20 cases that were numerically investigated, and the obtained contours were extracted based on the fitted regression models for the output parameters. The results show that although increasing the pressure increases the thermal power of the burner, it decreases its thermal efficiency. As the pressure of natural gas decreases, the flame temperature increases and the temperature peaks approach each other. In fact, the concentration of the flame increases with the decrease in pressure, and as a result, the thermal efficiency increases. Additionally, the results show that CO gas emission decreases with increasing pressure.
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In this study, finite element method is applied to simulate thermal spraying of Stellite-6 microparticles on steel substrate. The effects of particle size, substrate pre-heating temperature and spraying angle are investigated on the process output parameters including stress, equivalent plastic strain, penetration depth, and temperature distribution. The simulations are designed and performed based on the Design of Experiments (DOE). Response surface methodology (RSM) is used to explore the relationships between the input factors and responses. The simulation results revealed that penetration depth as the main factor, affecting the bonding strength of coating, is highly dependent on the particle size. Spraying angle is also found to be a significant and effective parameter on the penetration depth. On the other hand, the pre-heating temperature of the substrate is observed to have no substantial effect on the penetration depth.The depth of penetration increases with increasing the particle size and spraying angle, and reaches its maximum value in spraying angle of 90˚.

In this article, the friction stir process (FSP) was used to add various weight percentages of silicon carbide (SiC) nanoparticles to the base phase of PA6/NBR. Also, the effect of three variables of the rotation speed tool (ω), traverse speed (V) and the weight percentage of silicon carbide nanoparticle (S) on the mechanical properties (young’s modulus and impact strength) were investigated by response surface methodology (RSM) based on the Box-Behnken design. Scanning electron microscope (SEM) was used to determine the dispersion of nanoparticles in the base phase and the effect of their addition on the microstructure of PA6/NBR thermoplastic elastomer. Moreover, the thermal properties of PA6/NBR/SiC samples with different weight percentages of silicon carbide nanoparticles were investigated by differential scanning calorimetry (DSC) and thermo gravimetric analysis (TGA). The values obtained from the regression equations showed that, under optimal conditions of the rotational speed of 1200 rpm, traverse speed of 20 mm/min and the weight percentage of nanoparticles of 3.8 wt. %, the maximum young's modulus and impact strength 665.18 MPa and 62.26 J/m, respectively could be obtained. Also the crystallization and melting temperature increased to 198 and 222.8 °C, respectively.

Electrochemical polishing is a nontraditional finishing process by which the surface roughness of the metallic workpiece is reduced due to anodic dissolution. In this process, an electrochemical cell is formed using the workpiece as the anode, a tool as the cathode, and a power supply.  Different parameters like inter electrode gap, the chemical composition of the electrolyte, and its temperature along with the electric potential affect the finishing performance. The important performance parameters are surface roughness, material removal rate, and the dimensional tolerance of the workpiece. In this article, the effect of inter electrode gap, cathode geometry, tool feed rate, and electric potential on the process outputs are evaluated experimentally. Due to the high number of input and output variables and possible interactions between the input variables, Box-Behnken design in response surface methodology is selected for designing the experiments. The experimental models are evaluated by analysis of variance. Using the response surface methodology, the effect of input parameters on process outputs and the possible interactions between the input variables are extracted. Also, multi-objective optimization is performed for determining the input variables which are adequate for maximizing the material removal rate along with achieving a predetermined amount for surface smoothness and geometric tolerance.

The friction stir welding method was first developed in 1991 at the British Welding Institute as a solid-state bonding method and employed for welding aluminum alloys. This method has high energy efficiency and good compatibility with the environment. In general, the frictional stir welding process is suitable for metals with a low melting point, whose melting welding is not of good quality. In this research, multi-objective optimization of the mechanical properties in the friction welding of AH12 1050 aluminum alloy has been performed experimentally using a combination of response surface methods and multi-objective particle swarm optimization. The Taguchi method has also been utilized to design experiments with two types of threaded cylindrical and simple tapered pins. Pin diameter, shoulder diameter, tool rotational speed, tool feed, and tool deviation angle are selected as the process variables. Specimen strength, toughness, and hardness are considered as objective functions. The optimization results and a prediction accuracy of more than 93%, show a good agreement between the surface prediction model and the experiments despite the complexity of the process.

In this study, a method for uncertainty analysis of laminated rectangular plate made of glass/epoxy with interlaminar crack (delamination) in loading mode I, II and I/II is performed using energy criterion. Limit state functions have been obtained to analyze the reliability of delamination growth in each loading mode according to the concepts of fracture mechanics and energy release rate. By using random variables and limit state functions according to energy criterion, uncertainty assessment will be performed using Response Surface Methodology (RSM). The main idea of the response surface methodology is to approximate the implicit response surface function using an explicit mathematical equation with random variables involved in the limit state function. Since the approximation of the limit state function is explicit, the first/second order reliability method can be used to estimate the probability of failure. It was indicated that in all modes the probability of delamination growth calculated by the surface response method has the highest value. Finally, the effects of initial delamination, laminate layer and loading in different modes on the delamination growth are obtained from the perspective of the reliability of composites laminates.

In present study, the optimization of hydrogen production by water splitting over TiO2/treated clinoptilolite photocatalyst was investigated using Box–Behnken design (BBD) combined with response surface methodology (RSM). In the photocatalyst preparation, the combined ion exchange-alkaline treatment was used to achieve a chemical homogenous, reproducible and effective natural support. Moreover, 10 wt.% of TiO2 nanoparticles was loaded over zeolitic supports using facile and cost effective solid state dispersion (SSD) method in the presence of ultrasound irradiation. The characterization results indicated suitable optical and physico-chemical properties of the as-synthesized photocatalyst which making it effective in the water splitting reaction. The operational variables considered in Box-Behnken method included pH solution, photocatalyst dosage and sacrificial agent concentration. Based on the ANOVA results, all three process variables affect the hydrogen production. Among them, the most significant effect is attributed to pH solution. The application of the RSM resulted in the formulation of several models out which the quadratic model with the highest value of the determined R2 coefficients (R2=0.9967 and R2adj=0.9942) was adjudged to adequately fit the experimental data. By examining how the process variables and their interactions affect the response, it can be found that the maximum efficiency of hydrogen production was obtained at optimum conditions of alkaline solution pH of 10, catalyst dosage of 1.1 g/L and sacrificial agent concentration of 12.5 vol.%.

In this paper, experimental and regression analysis of the effective parameters in the free and die forming of circular metallic plates using gas mixture detonation were investigated. In the experimental section, steel, aluminum, and brass plates in different thicknesses were used. To better evaluate the experimental results, the condition of the same areal density was used to compare the results of steel, aluminum, and brass plates under the same loading conditions. In the regression analysis section, the Design-Expert software package and response surface methodology were used. The effect of parameters measured in experimental tests including the pressure of Oxygen, the pressure of Acetylene, plate thickness and die apex angle on the deflection of circular plates were investigated simultaneously. To find a significant model, the confidence level of 95% was considered in the analysis. Experimental results showed that using a die with an apex angle of 60° leads to the decrease of the maximum permanent deflection. On the other hand, using aluminum and brass plates in the die forming resulted in a more reduction of permanent deflection in comparison with free forming. The results of the regression analysis show that the predicted values of the model are in good agreement with the experimental data and the presented model is suitable. Optimal conditions for the minimum deflection of the circular plates under explosive loading were also presented. The pressure of Oxygen and the die apex angle has the highest effect and the least effect on the forming of circular metallic plates.

The thermal cycles involved in friction stir welding process cause softening in the joint of heat-treatable aluminum alloys. To overcome this limitation, submerged friction stir welding process has been developed. In this study, firstly, the butt joints were produced from Al7075-T6 alloy using friction stir welding process. To this end, the response surface methodology was selected as the experiment design technique. So, the factors such as tool rotational speed, tool feed rate, tool shoulder diameter, and tool tilt angle were identified as the input variables. Then, a statistical analysis of variables affecting the tensile strength of joints was performed. Afterward, the butt joints were produced using submerged friction stir welding process based on the optimal values of tool feed rate and tool tilt angle. The obtained results from analysis of variance and regression analysis of experimental data confirmed the accuracy of regression equations. Furthermore, it is shown that the linear, interactional and quadratic terms of the tool rotational speed and tool shoulder diameter are effective on the ultimate tensile strength of the underwater welded joints. Also, the optimal condition of input variables was determined using the desirability method. In addition, the optimal condition has been confirmed by implementing the verification test.

In this paper, the experimental study and regression analysis of the dynamic response of metal plates under impulsive loading are investigated. For this purpose, in the experimental section, 86 experiments were performed on metal plates under different conditions. The plates were made of steel, copper and aluminum in a circular shape. The effect of the measured parameters in the experimental tests such as plate thickness, loading impulse, charge mass, and standoff distance on the circular plates deflection were evaluated simultaneously using the Design-Expert software package and response surface methodology. In this study, the material of the plates is considered as an independent qualitative parameter. In order to find a significant model, the confidence level of 95% was considered in the analysis. In this study, the value of R2 and R_adj^2 was 0.9746 and 0.9673, respectively. The results show that the predicted values of the models are in good agreement with the experimental tests and the presented models are suitable. Optimal conditions for the minimum deflection of the circular plates under impulsive loading were also presented. The impulse loading has the highest effect and the mass of the charge has the least effect on the plate deflection.

In this study, E-glass/epoxy laminated composites with [0]12 stacking sequence manufactured by hand lay-up method. Afterwards, by considering the most important input parameters of the micro-drilling process including tool rotational speed, feed rate and tool diameter, the statistical mathematical modeling is performed to accurately investigate the thrust force response behavior versus the mentioned variables. For this purpose, using full factorial experimental design and response surface methodology and performing 54 experimental tests and considering repeatability of experiments in order to improve modeling accuracy, a second-order linear regression equation has been obtained. Also, by using the Sobel sensitivity analysis method, the quantitative effect of force behavior sensitivity versus input parameters is investigated. Moreover, the Derringer optimization algorithm is used to achieve the minimum amount of thrust force in micro-drilling process of laminated composites. The results of the statistical analysis show that the lowest feed rate, maximum tool rotational speed and smaller diameter lead to produce lowest thrust force of laminated composites. The Sobol sensitivity analysis shows that the diameter of the tool (57.8%), the feed rate (24.4%), and the rotational speed (17.8%) will have the greatest effect on thrust force in micro-drilling process, respectively. Finally, the optimization analysis show that, the lowest thrust force was obtained at a rotational speed of 2515 rpm, a feed rate of 10 mm / min and a tool diameter of 0.5 mm.

The thermal cycles involved in friction stir welding (FSW) cause softening in the joint. This phenomenon generally occurs in heat-treatable aluminum alloys leading to decrease in mechanical properties. Submerged friction stir welding (SFSW) has been developed to overcome this limitation. In this study, firstly, the butt joints were produced from Al7075-T6 alloy using FSW process. To this end, the RSM was selected as the experiment design technique. So, the factors such as: tool rotational speed, tool feed rate, tool shoulder diameter, and tool tilt angle were identified as the input variables. Then, statistical analysis and optimization of variables affecting the hardness of cross-sections was performed. In attention to the high value of desirability function (0.976), it could be found that the procedure of optimization has well fulfilled the pre-determined target. In addition, the optimal condition has been confirmed by implementing the verification test. Afterward, the butt joints were produced using SFSW based on the optimal values of tool feed rate and tool tilt angle. The obtained results from analysis of experimental data, confirmed the accuracy of regression equation. Furthermore, it is shown that the final model can predict the MHD parameter with an error less than 5%. Also, the linear terms of the tool shoulder diameter and tool rotational speed are effective on the hardness of cross-sections of the underwater welded joints.

In this paper, the effect of differed loading conditions, as well as structure geometries on the behavior of sandwich panel structures under uniform blast loading, has been investigated. For this, a full 3D numerical model by using ABAQUS/Explicit commercial software was employed in order to simulate the dynamic response and plastic deformation of sandwich panel structures with a honeycomb core. The available experimental results were used to validate the numerical model. Afterward, in a rigorous parametric study, the influences of several effective parameters on the resistance of structure such as the front and back metallic layer thicknesses, the number of webs, and thickness of honeycomb core cell wall under three different mass weights of 0.5, 1 and 1.5 kg were studied. In the following, by using Response Surface Methodology, an appropriate equation was developed to predict the central permanent deflection of back and front layers. The obtained results showed that there is a well-agreement between experimental and numerical results predicted by the regression model. The high correlation coefficient between the studied parameters and the structure behavior (R2 = 0.99) indicates that the proposed model has great accuracy.

In the present study, the experimental study and regression analysis of the dynamic response of circular plates under uniform and localized blast loading were investigated. To this end, several experiments were performed on steel plates under different conditions in the experimental section. In order to complete the database and perform a comprehensive analysis, fourteen series of experiments and 562 data in the open literature were added to the experimental results of the present study. Subsequently, the effect of the radius and thickness of the plate, the impulse of applied load, the mechanical properties of the plate, the loading radius, and the standoff distance on the maximum deflections of circular plates were simultaneously investigated using the Design-Expert software package and response surface methodology. In order to find a significant model, the confidence level of 95% was considered in the analysis. Two separate analyses were done based on the types of loading. The values of R2 for uniform and localized blast loading are equal to 0.9712 and 0.9548, respectively. The results show that the predicted values of the models are in good agreement with the experimental data and the presented models are suitable. Optimal conditions for the minimum deflection of the circular plates under dynamic loading with uniform and local distribution were also presented.