Showing 44 results for gorji
Volume 15, Issue 7 (9-2015)
Abstract
In recent years the use of metallic bipolar plates for fuel cells is considered. Several studies have been conducted on the various methods of forming these plates. Most of this research has been done on the serpentine flow fields. While in some cases that the pressure drop is important factor, the pin-type flow fields shows good performance. In this research, hydroforming of metallic bipolar plates with circular pin-type pattern from stainless steel 304 with 0.11mm thickness is investigated experimentally and numerically. For this purpose, the effect of geometrical parameters such as the die wall angle, the die chamfer dimension, the depth-to-width ratio of the die, and forming pressure on the profiles, filling percent, thickness distribution and thinning percent of the formed parts are investigated. In this regard, two dies with wall angle of 0 and 15 degree were prepared. Then experimental tests were done at different pressures. After performing the required tests, the results show that the die wall angle leads to a more uniform thickness distribution and higher precision of the parts profile. Also the suitable range of die geometrical parameters was determined.
Volume 15, Issue 10 (1-2016)
Abstract
In present study, impact of single bubble on an inclined wall and its movement are investigated by applying volume of fluid method (VOF) in OpenFOAM open source cfd package using a solver called interFoam. Both phases are incompressible and surface tension between two phases is estimated by CSF method. The effect of some parameters such as contact angle, wall slope and Bond and Morton dimensionless numbers on bubble shapes and velocity are studied. The numerical results show bubble velocity along wall increases with the increase of wall slope angle. The maximum bubble velocity happens at 50 degree. Three bubble regimes are recognized and introduced in this study named as: sliding, bouncing, and zigzagging based on wall slope. The bubble regime changes from sliding to bouncing when wall slope changes from 30 to 40 degrees. In constant Morton number, increment of Bond number increases both velocity and amplitude of fluctuations. In addition, an increment of Morton number in constant Bond number, decreases velocity and amplitude of fluctuations. Moreover, by increment of Morton number, the bubble motion will change from an accelerating motion to a constant velocity condition.
Volume 15, Issue 11 (1-2016)
Abstract
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.
Volume 17, Issue 5 (7-2017)
Abstract
Prediction and prevention of wrinkling are very important in tool design and determining the effective parameters in sheet metal forming processes. In forming metallic cups, wrinkling generally occurs in the two regions of flange and wall. The control of wrinkling in flange area is not so difficult by controlling the blankholder pressure, but it is difficult in the wall region because the sheet is not supported in this area. In this paper, using a geometric method based on numerical simulation, the wrinkling in the wall of the symmetric conical parts in the developed hydrodynamic deep drawing with radial pressure and inward flowing liquid is investigated. In the process, two independent pressure supplies have been used for forming the sheets. Due to the nature of the process, the effects of radial and cavity pressures on wrinkling have been investigated. In addition, the effects of material, initial blank thickness and punch velocity on wrinkling in wall area were investigated. To verify the results of the simulation, several experimental tests have been done on the St13 and copper sheets. Good agreement between the simulation and experimental results shows the reliability of this method in the wrinkling study. It was also demonstrated that increasing the maximum radial pressure or decreasing cavity pressure leads to increasing wrinkling. Additionally, wrinkling was decreased with increasing blank thickness. Moreover, it was shown that wrinkling simulation is much depended on input parameters such as punch velocity and appropriate element size
Volume 17, Issue 6 (8-2017)
Abstract
Tube hydroforming is a process which is considered to produce integrated and seamless parts in recent years. The numerical prediction of tearing to design the right equipment in this process is important. In this study, the formability of 304 stainless steel tube by free bulge test was experimentally and numerically evaluated to determine the forming limit diagram. The Gurson- Tvergaard- Needleman (GTN) is a micromechanical model to predict ductile fracture of metals. In order to determine the defining parameters of the GTN damage model, the experimental tensile test of the standard sample and the finite element simulation using ABAQUS software was performed. Using this criterion in the ABAQUS software and comparing the force-displacement diagram obtained from the experimental tensile test and the finite element simulation, the parameters of the GTN model was obtained by the inverse method. Then, the geometrical parameters of the die in the free bulge hydroforming process were investigated by the GTN ductile fracture criterion and the forming limit diagram of the 304 stainless steel tube was numerically obtained. The experimental tests were also carried out to verify the results of the finite element simulation. It’s shown an acceptable agreement
Volume 17, Issue 7 (Supplementary Issue - 2015)
Abstract
Solar radiation data play an important role in solar energy relevant researches. These data are not available for some locations due to the absence of the meteorological stations. Therefore, solar radiation data have to be predicted by using solar radiation estimation models. This study presents an integrated Artificial Neural Network (ANN) approach for estimating solar radiation potential over Iran based on geographical and meteorological data. For this aim, the measured data of 31 stations spread over Iran were used to train Multi-Layer Perceptron (MLP) neural networks with different input variables, and solar radiation was the output. The accuracy of the models was evaluated using the statistical indicators of Mean Absolute Percentage Error (MAPE), Root Mean Square Error (RMSE), and Correlation Coefficient (R); hence, the best model in each category was identified. The Stepwise Multi NonLinear Regression (MNLR) method was used to determine the most suitable input variables. The results obtained from the ANN models were compared with the measured data. The MAPE and RMSE were found to be 2.98% and 0.0224, respectively. The obtained R value was about 99.85% for the testing data set. The results testify to the generalization capability of the ANN model and its excellent ability to predict solar radiation in Iran.
Volume 17, Issue 11 (1-2018)
Abstract
Hydroforming is a convenient method for applying fluid to produce parts with high strength to weight ratio. Hydrodynamic deep drawing assisted by radial pressure with inward flowing liquid process is considered as a type of hydroforming. In this method, radial and cavity pressures are two most important parameters, the values of which at any moment play an important role on the quality of final part. In this study, based on a hybrid method, the cavity and radial pressure paths in hydrodynamic deep drawing assisted by radial pressure with inward flowing liquid process are optimized. In this method, an adaptive simulation that is integrated with the fuzzy control system with the ABC algorithm is used to determine the optimized radial and cavity pressure paths. The achievement of a cup with least thinning and without wrinkling has been defined as the optimization goal. The validity of radial and cavity pressure paths obtained from optimization algorithm is verified through an experiment. Results showed that utilization of the optimized loading path yields the part with lower maximum thinning and without wrinkling.
Volume 18, Issue 1 (3-2018)
Abstract
Surface engineering in many manufacturing industries plays an important role in improving product performance and increasing the operating time of parts. Pure aluminum has a very high electrical conductivity, good corrosion resistance and strength to weight ratio. However, due to very low hardness and wear resistance, its application is limited. Therefore, this paper is studied may improve the surface properties of pure aluminum using copper and nickel as alloying elements using electric discharge process. The pulse on time and pulse current as input parameters and surface hardness, alloyed layer texture and surface roughness as output parameters have been considered. According to the microhardness testing results, in this alloying method, the average hardness of the aluminum parts is about more than 8 times and in some parts of the 38.5 Vickers reached up to 450 Vickers, Based on the results of XRD analysis, the formation of intermetallic compounds Al3Ni2, ALCu, and Al4C3 increased surface hardness. The results show that by increasing the pulse on time surface hardness increased and surface roughness becomes greater. Also, Increasing pulse current the surface roughness increasing trend.
Volume 18, Issue 113 (july 2021)
Abstract
In this study, the effect of basil and cress seed gum concentrations (0.00, 0.25, 0.50, and 1.00 % w/w) were individually investigated on the rheological, color, and textural properties of the fresh paste gel samples. The mixture of fresh fish paste and various concentrations of gum were heated at 75 °C for 30 minutes to obtain heat-induced gels. The strain test results showed that the elastic properties (storage modulus) of the gel samples at low frequency were higher than their plasticity properties (loss modulus), while they crossed over each other in the middle of the strain range. The Gchr('39')LVE, G "LVE, Υ c, and Ƭf parameters of the gel samples reduced with increasing gum concentration compared with the control sample. The obtained data by the frequency sweep test is nicely fitted by the Power Law Model. Also, the results of the frequency test at low frequencies showed solid-like behavior for all gel samples, while at higher frequencies the loss modulus and the storage modulus increased. This behavior can be related to the weak structure of gels. The temperature sweep test showed that the values of Gchr('39') (storage modulus) and G" (Loss modulus) for the mixture of samples decreased gradually with increasing temperature, and increased with decreasing temperature. The texture profile analysis showed that the type and concentration of gum significantly (p <0.05) affected the hardness, elasticity, and cohesiveness of the samples. Results of the puncture test showed that the gel strength of the samples changed significantly with the concentration and type of gum. As the concentration of gum increased, the strength of the gel decreased and the intensity of the decrease was greater in the type of cress gum. The type and concentration of gum affected significantly the yellow and red index of the sample of fish pastes
Volume 18, Issue 116 (October 2021)
Abstract
In this study, the effect of the free extract, nanoliposome, and nanoniosome containing myrtle extract and sodium benzoate as a preservative on microbial, sensory, and chemical properties of mayonnaise during 90 days at 4 °C was investigated at 15 days intervals. The results of chemical tests showed that mayonnaise samples containing nanoliposome and nanoniosome significantly (p < 0.05) reduced peroxide, thiobarbituric acid compared to the control samples. There was a significant difference between the pH of the sauce samples prepared on the first day so that the highest pH (4.2) was related to the sauce sample containing sodium benzoate. The acidity values of all samples were in the standard range (0.62 to 1.4). Microbial results showed that the counts of Escherichia coli and heterofermentative lactobacilli were negative for all treatments and following the standard. During the storage time, the microbial growth of the sauce containing the natural preservative, nanoliposome, and nanoniosome, was effective in controlling mold and yeast and acid-resistant bacteria compared to the control sample (p <0.05). The results of sensory evaluation in this study showed that mayonnaise samples were significantly different in sensory properties during storage time so that the sauce containing free extract had a lower color score. Also, the lowest brightness index (L* = 74.31 ± 1.03) was related to the sauce containing the free extract. Sauce samples containing nanoniosome and nanoliposome had the highest acceptable spreadable property. The results of this study showed that using nanoniosome and nanoliposome containing the myrtle extract can reduce the use of the chemical additive sodium benzoate and this is a step in improving the health of the consumer community.
Volume 19, Issue 1 (Spring 2015)
Abstract
House of the Representatives in the U.S., as the National Assembly of this state and one of the two pillars of the Congress, is headed by Speaker and, Chairman of the Majlis is the head of the Islamic Consultative Assembly of Iran. Although the constitutional texts and fundamental laws do not provide a special place for these two authorities, however, they have an undeniable role in the structure of government and in the courtyard of their houses. A comparative study of the two shows that parliamentary traditions and historical practices have made a range of qualifications and powers for the Speaker of the House of the Representatives that are hard to see in the Iranian Majlis. The chairman of Majlis has been limited by the internal regulations statute, and it has explicitly resolved these issues. It is should is to be noted that the President of the Majlis, compared to their counterparts in the United States, has a greater administrative powers.
* Corresponding author’s E-mail: gorji110@yahoo.fr
Volume 19, Issue 10 (October 2019)
Abstract
Incremental forming is considered as one of the rapid prototyping methods and has a high degree of flexibility and cost-effectiveness at low production volume. Meanwhile, the lack of technical knowledge has challenged the use of this method in the industry. One of the things that can help the actual usage of this process is the suitable process window; a window used to determine maximum tearing depth of the sheet with respect to the material, thickness and wall angle. In this study, firstly, the formability of low-carbon steel sheet, St12, with the thicknesses of 1.25 and 1.50 mm in single point incremental forming of a truncated pyramid with different constant wall angles has been investigated experimentally. Then, it is compared with the formability of the truncated pyramid with variable wall angles under two different wall geometries. Based on the experimental results, the process windows are presented in terms of the maximum depth and wall angle and compared to each other under different circumstances. The results showed that the critical wall angle for St12 sheet in incremental forming of a truncated pyramid with a fixed wall angle differs from the pyramid with variable wall angle, but doesn't depend on the size of the pyramid base. The critical wall angle for the fixed and variable wall angle pyramids was obtained 67⁰ and 75⁰, respectively. For a pyramid with a fixed wall angle, the thickness distribution of the wall is almost constant, while for a pyramid with a variable wall, it varies along the path.
Volume 20, Issue 10 (October 2020)
Abstract
Research results performed by researchers have illustrated that applying electric current to a deforming metal can lead to a reduction in the required deformation force and an improvement in the formability. This technique is known as electrically assisted forming and is used in various forming processes. In this paper, the forming of square cups through electrically assisted deep drawing process was investigated experimentally and the effects of process parameters, including current magnitude, pulse frequency, and waveform (sinusoidal and square) on the forming force, thickness distribution, and drawing depth are examined. In this regard, after designing and preparing the test setup and forming square cups, the experimental results obtained were compared to those of the conventional deep drawing tests. The results showed that increasing the current magnitude leads to reducing the maximum thinning and the forming force in the deep drawing process of the formed parts. Furthermore, it was found that at a higher frequency, the deformation force decreases significantly and thickness distribution becomes more uniform. The comparison of the two waveforms of pulses demonstrated that the sinusoidal waveform has a relatively more significant effect on the reduction of the force and thickness distribution and a considerable effect on the drawing depth.
Volume 21, Issue 1 (1-2019)
Abstract
The scarcity of water, along with the concern of safe production of food, emphasizes the need for new agricultural techniques. Increasing dissolved oxygen concentration in water promotes the growth of plants in many ways. The aim of the present research was to investigate how cucumbers (Cucumis sativus L.) morphologically and physiologically respond to water enriched with air Micro-NanoBubbles (MNBs) as an oxygen saturating measure. The plants from early stage of seed planting (two groups, 32 plants in each) were cultured either with air-nanobubbles water or with tap water for 12 weeks, and the steric stability of MNBs in water was confirmed through zeta potential measurements (-20.47 mV). The number of blossoms in the plants irrigated by air MNBs water was almost 3.8 times more than the number of blossoms in those that were irrigated by tap water. MNBs water increased leaf area up to an average of 77%. Physiological indices such as chlorophylls a, b, and carotenoids were, respectively, 1.34, 1.44, and 1.35 times greater in the plants watered with MNBs than those with tap water. Overall, this study demonstrated that water with air micro-nanobubble had a positive effect on cucumber plants and is potentially an effective tool for the environmental friendly, economical, and profitable production of the plant.
Volume 21, Issue 3 (March 2021)
Abstract
Due to the increasing expansion of products made of plastic materials, high percentage of plastic waste enters the waste and waste annually, and the recycling of these plastic wastes is usually accompanied by decrease in their mechanical properties. One of the simplest and the most affordable ways to overcome the decline in mechanical properties during use recycled polymer, is achieving optimal combination virgin polymer and recycled polymer via mixing together. In order to produce products with both high quality and optimal mechanical properties will be desirable. Accordingly is beneficial for both environment and economic point of view, reducing use of virgin polymer. In this study, in order to investigate the effect of weight percentage of recycled polyamide 6.6 with virgin polyamide 6.6 on the mechanical properties by injection molding proses, mix recycled polyamide 6.6 and virgin polyamide 6.6 with different weight percentages is prepared and then is injected. The results of mechanical tests on injected samples showed that adding more than 50% by weight of recycled polyamide 6.6 to virgin polymeric materials increased melt flow index, glass transition temperature and crystal temperature. While, the mechanical properties of samples decreased with increasing weight percentage of recycled polyamide in the composition. These changes were less for some properties such as tensile and flexural strength and more for impact resistance. Tensile and flexural strength and impact resistance in samples with 50% by weight of recycled polyamide in the composition, respectively, decreased by about 6%, 9% and 34% compared to the new polyamide sample.
Volume 21, Issue 4 (April 2021)
Abstract
Forming Limit Diagrams (FLDs) are very useful measures for safe forming of sheet metals without failure due to necking or fracture under different loading conditions. This paper uses ductile fracture criteria to predict the formability of low carbon steel sheets to evaluate their accuracy in predicting the FLDs. In addition, the fracture forming limit curves (FFLD) and necking forming limit curves (NFLD) for St12 low-carbon steel have been extracted experimentally and numerically. In the experimental procedure, the Nakazima stretching test was used. In the numerical procedure, by defining six phenomenological ductile fracture criteria in ABAQUS / Explicit finite element software, the failure is predicted and compared with the experimental results. These criteria were calibrated using 6 tests namely as In-plane shear, uniaxial tensile test, circle hole test, notched tension test, plane stress test, and Nakazima stretching test. The results showed that the criteria, which include both the stress triaxiality (η) and Lode parameter (L), provide a more accurate prediction of failure. Also to predict necking during numerical simulation of Nakazima test and also to extract the NFLD, three criteria of the second derivative of major strain, the second derivative of thickness strain and the second derivative of equivalent plastic strain have been used.
Volume 21, Issue 5 (May 2021)
Abstract
In forming conical parts by traditional deep drawing techniques, due to the stress concentration at the contact area between the punch and the workpiece, thinning and rupture occurs on the sheet. There is also a high possibility of wrinkling in the free area of the sheet; where there is no contact between the punch and the sheet. Therefore, new methods have been examined in forming this group of parts. Electromagnetic forming is one of the relatively old methods of high-speed forming that has attracted more attention in recent years. In the present study, the process of pre-forming of aluminum conical parts using electromagnetic force has been discussed numerically and experimentally. First, experiments were carried out by a simple spiral coil and after confirming the validity of the numerical simulations, the effect of electromagnetic force density in radial and axial directions was investigated in different areas of the sheet. Using the obtained results, a new coil was designed and built that has the ability to provide suitable distribution of the force in the radial and axial directions. Reduction in power consumption by up to a quarter, an increase in the amount of radial inward force and the height of the preform formed cone up to 2 times, minimizing the friction force, reduction of the workpiece center thinning by 3% (while increasing the height by 2 times) and elimination of wrinkles in the flange area of the sheet are the advantages of using the new coil compared to the primary coil.
Volume 21, Issue 156 (February 2025)
Abstract
Milk chocolate is one of the most popular and enjoyable foods, and it has many fans of all ages. The purpose of this research is to replace the gelatin extracted from chicken feet with commercial (bovine) gelatin in different concentrations (0, 3, 5 and 7 percent) with cocoa butter to reach a high melting point with the aim of preventing chocolate from melting at high temperatures in tropical regions. The physicochemical and sensory properties of milk chocolate were investigated, and the obtained results showed that the density of the samples increased with an increase in the concentration of gelatin. The hardness of chocolate samples decreased by increasing the concentration of chicken Feet gelatin and increasing the concentration of commercial gelatin, so that the highest level of hardness among the sample’s containing gelatin was related to the sample containing 3% commercial gelatin (5936.3) and the lowest one was related to the sample containing 7% chicken Feet gelatin (5342.5). Also, by examining the surface roughness of the treatments, the highest roughness is related to the control sample. The apparent viscosity of treatments increased by increasing the concentration of chicken feet gelatin and commercial gelatin. The melting point of the samples increased independently with the addition of chicken feet gelatin and commercial gelatin. By increasing the level of chicken feet gelatin and commercial gelatin, the aqueous activity of the treatments decreased independently. In terms of color parameters (L, a, b), the treatments were investigated, and the sample containing 7% chicken feet gelatin had the highest amount of brightness. From the sensory point of view, the parameters of color, taste, smell, texture and finally the overall acceptance of chocolates were investigated. In terms of parameters, a significant difference between the samples was observed, and all the samples had the required acceptance.
Volume 23, Issue 2 (3-2021)
Abstract
Box tree moth, Cydalima perspectalis (Walker, 1859), is one of the major destructive pests that feed on the leaves and shoots of various Buxus species. In the course of this survey, the life cycle of C. perspectalis was studied in laboratory and natural (Hyrcanian Forests) conditions. The laboratory experiments were carried out at temperature of 25±1ºC, 70±10% relative humidity and a photo phase of 16 light: 8 dark hours. The average duration of an egg, larva, pre-pupa, pupa, as well as female and male longevity were 5.09±0.04, 23.15±0.17, 1.04±0.02, 7.80±0.05, 15.31±0.73 and 12.92±0.71 days, respectively. As an important pest newly introduced in northern Iran, the Box tree moth completes two and partial third generations per year. The results of this study would be useful for improving pest management strategies.
Volume 24, Issue 2 (February 2024)
Abstract
Today, the industry's need to join dissimilar metals has increased, especially in the automotive and aircraft industries. In this regard, in order to join metals, new methods, called solid state joining, have been used, among which electromagnetic joining is performed with a lower cost and at a higher speed. In this research, firstly, the feasibility of joining copper tubes to composite tubes by electromagnetic method and the quality of the joinit have been studied. Then, the effect of the welding voltage process parameter on the mechanical properties of the strength has been investigated by the ring test. Finally, in order to examine the surface hardness of the welded samples, the Vickers hardness test was performed. The results show that the joining of the copper samples to the composite tubes has been done well. It has been observed that with the increase in voltage, due to the increase in the collision energy of the two tubes, the connection force has increased by about 2 times. In the 8 kV voltage, due to the increase in the impact speed, a more severe plastic deformation has occurred than in other samples which has caused more local deformation of the weld interface and, as a result, an increase in the hardness. The hardness of the interface in this condition was about 8% higher than that of the 5 kV voltage.
