جستجوی مقالات مرتبط با کلیدواژه « Design of Experiment » در نشریات گروه « مکانیک »

In this article, the mechanical properties of biocomposites reinforced with kenaf fibers/nanographene in the field of polypropylene with the addition of PP-G-MA compatibilizer have been investigated. Response surface method (RSM) with Box-Behnken Design (BBD) has been used to investigate and present a mathematical model for the behavior of biocomposite according to the parameters of weight percentage of Kenaf fibers, nanographene, and PP-G-MA. The behavior of the samples was analyzed under tensile, bending, and impact tests, and the results were confirmed using FE-SEM images. The failure surface of the samples showed that the main mechanism in improving the behavior of the introduced biocomposite is the failure of the fibers and their separation along with the stretching of the fibers from the base material. The multi-objective optimization process was performed using two methods metaheuristic and utility function. Optimization was carried out to increase flexural strength, impact resistance, and tensile strength while simultaneously reducing the weight of the specimens. The weight percentages of fibers, nanoparticles, and compatibilizer were defined as the variables of the problem. The results showed that the values of the biocomposite sample in the optimal state for three mechanical properties including tensile, impact, and bending strength are 28.5 MPa, 92.29 J/m, and 50 MPa respectively. At the end of the optimal mode, it showed that the weight of the biocomposite can be reduced by 32%.

One of the main methods for strengthening and increasing the hardness of the materials is the use of the severe plastic deformation (SPD) processes. Equal channel angular pressing (ECAP) method is one of the SPD methods. Two challenging issues including (1) the very high required punching force, and (2) the deflection of the punch restrict the application of the method in industry. In this paper, a new design of ECAP process is proposed, which in addition to reducing the punching force, eliminates the deflection problem. The main purpose of this paper is to investigate the effect of the process parameters including process temperature (100- 200-300) ° C, lubrication (dry and graphite) and the number of ECAP passes (1-2-3) on the hardness of 7075 aluminum material and determining their optimal levels. The Taguchi design is used for design of experiment and the S/N ratio is used to find the optimal levels of the parameters and to maximize the hardness of the material. Based on the analysis of the variance, the process temperature and the number of ECAP passes have the greatest effect on the hardness of the post ECAP samples. However, the lubrication condition has not a significant effect on the hardness of the post ECAP samples in all temperatures.

Population growth and freshwater scarcity have led people to think about renewable energy sources. In this research, a stepped solar still has been used to produce drinking water. In order to improve the device's performance, absorbent fabrics were utilised to increase the heat transfer area between the saline water and the environment, resulting in increased evaporation and fresh water production. Water inlet flow rate, fabric material, fabric thickness or number of layers, fabric colour, and fabric placement angle are all variables that have been used at the same time. Three different fabrics in three different layers were used in the experiments, with flow rates of 50, 100, and 150 ml/min and angles of 30, 60, and 90 degrees. There were also three colours for fabrics: white, brown, and black. The response level approach was used for the design of the experiments in this study, and 27 experiments were examined. The findings revealed that the black color, material # 1 with the highest water absorption, more layers, larger angles of fabrics, and lowering the flow rate all had an effect on increasing the amount of fresh water produced.

Today, additive manufacturing methods have found wide applications in various industries due to their many advantages, including not needing tools and molds, as well as short production time. Among these methods, the FDM process is widely used due to its cheapness and ease of production. As a result, it is very important to discover the relationship between the mechanical properties of the product produced in this way and the parameters used in the process. In this research, the effects of layer lamination angle, infill extrusion width and layer thickness on the normal force and tensile strength of PLA printed samples are examined. In order to investigate the effects of the parameters, the design of experiment, using surface response and Box-Benken method was used with the help of Minitab software. The results of the tests show that the maximum tensile strength and normal tensile force of the printed samples were equal to 38.36 MPa and 1.50 kN, respectively, which is at zero-degree lamination angle, infill extrusion width of 150% and the thickness of the layer 0.3 mm.

Due to the importance of the joints in the pressurized instruments and the abilities of the laser welding in this study, the welding of AISI316L tubes have been studied and analyzed. In this regard a fixture has been drawn in order to positioning of the tubes and fixed on the welding desk. The welding input parameters includes the laser welding adjusting variables, includes (welding current, welding pulse width, and welding frequency). Moreover, the effect of the two other variables (rotating speed and the force applied to the welding seam) has also been studied. The welding output characteristics comprises the welding width, depth of penetration and welding strength. The experimental data has been collected using L27 Taguchi design. The relation between the process input variables and output characteristics has been established using different regression models. Based on the analysis of variance (ANOVA) results, pulse width and welding current with 70% contribution have an influential effect on all the three response characteristics. Moreover, the seam force has only the influential effect on the depth of penetration and strength. Next, in optimization step based on the importance of the process characteristics (strength, depth of penetration, welding width), the optimized levels have been determined. At the end, the optimized condition has been conducted using laser welding, in comparison of which the samples in the design matrix, the welding depth has a close relation with the thickness of the wall, the welding boundaries smother and the strength has a close value to the base metal.

The calibration of modern internal combustion engines is complex and requires a lot of time and cost on the test bench. A large number of calibration parameters and a tradeoff between fuel consumption and emissions make calibration a complex multi-objective optimization problem. The purpose of this article is the development of calibration and model-based optimization techniques for internal combustion engines to reduce calibration time and cost and improve optimization accuracy. This paper focuses on empirical modeling of engines and optimization concerning emissions standards and fuel consumption. To identify the combustion models, a modeling toolbox is developed with an intelligent identification method. To optimize the data collection, the design of experiment methods is reviewed and appropriate methods are selected to collect information with the minimum data from all over the design space. Finally, a study is performed on the EF7 engine in the test room of IPCO and it is shown that the number of experimental data is reduced from 5500 data to 1500 data with the help of the design of experiment by Sobol method and modeling by a deep neural network. so, the virtual engine can replace the real engine in the calibration process.

Bio-fouling as a worldwide marine industries concern is the accumulation of micro and macro-organisms on the submersed surfaces in the sea water. It has destructive effects on the sunk parts of the ships, fish cages and all other marine submersed structures. To reduce bio-fouling on the nylon fibers a dual mix of 2-Hydroxy ethyl methacrylate(HEMA) and methyl acrylate(MA) was grafted on the fiber surface using a pre-irradiation technique in different conditions. Subsequently, degree of grafting and homo and or co-polymer % of the aforementioned monomers at different operative parameters including reaction temperatures (60-90℃), and times (1-4h), pre-irradiation time (10-40min) and also initiator concentration (3-9wt%) were measured and the results were compared and discussed with those calculated values by a traditional design of experiment software (Design expert®). The optimum grafting conditions and the interaction between above mentioned parameters were evaluated by the software using four variables and two surface responses with central point design method. It found that increasing pre-irradiation time and also initiator concentration improved the grafting % of the monomers on the fiber surface. The reason referred to increasing the active sites on the fiber surface after pre-irradiation. With the aid of variance analysis and considering p-values variable with 0.05 confidence interval, it revealed that the important parameters lied down in the order of reaction temperature, reaction time, pre-irradiation time and initiator concentration. Also, the results were confirmed statistically by the characteristic coefficient, adjustment coefficient and fit precision of 96%,93% and 30.302, respectively. The real values for degree of grafting and also homo and co-polymer percent were 47.9% and 41.15% respectively. They were in conformity with predicted values by mathematical model with the values of 38.59 and 43.42%. Also, two equations were proposed by the software for calculation of the aforementioned parameters with studied operative parameters.

Laser welding is a significant method for welding all kinds of alloys. High speed welding, low distortion and easy automation are the advantages of this method. In this study, pulsed Nd:YAG laser butt joint welding was performed on 304 and 316 Austenitic stainless Steels workpieces. All the parameters were designed by Full Factorial Method which the center point was repeated for 10 times. Henceforth, the effect of power, pulse duration, laser velocity and chemical composition on width and depth of welding area, ultimate tensile strength, elongation and Ferrite Number were studied. The welding process was performed in 1.2 and 1.8 KW as power, 3 and 4.4 ms as pulse duration and 0.2 and 0.8 mm/s as velocity of welding. Thus, the upper level of input parameters were selected as the optimal case. This was done by surveying all the samples to achieve maximum UTS, size of the weld and Ferrite Number. In these conditions, output error for width of weld, depth of weld, U.T.S, elongation and Ferrite Number was 2, 5, 1.6, 25 and 2%.