---

The effect of the antioxidant extracts on the quality indices of rainbow trout fillet stored at refrigerator (4±1ºC) for 15 days was investigated. The fillets in 3 treatments, including salted in 10% brine, salted in 10% brine plus 1% nettle leaf extract, and salted in 10% brine plus synthetic antioxidant BHT were evaluated at every 3 days interval, using the quality indices including the free fatty acids (FFA), thiobarbituric acid (TBA), peroxide (PV), moisture content, pH levels and sensory characteristics. The results showed that TBA and FFA values increased significantly (p<0/05), but PV significantly decreased in all treatments during the course of storage (p<0/05). Samples containing antioxidants had significantly lower TBA, PV and FFA values in comparison with the control sample throughout the storage. Also, the methanol extract from nettle leaves (at 1% balance) controlled the TBA, PV and FFA indices and entirely replaced the synthetic BHT antioxidants (at 1% balance). Since the sensory evaluation (smell, texture, taste and after taste elements) showed no significant differences between the two antioxidants, both are recommended to preserve the quality of rainbow trout fillet. The nettle leaf extract was found to be more efficient on shelf life extension the fillet.

---

In this study, pulsating hydroforming of tube in a box die is simulated using the three dimensional finite element method to investigate the mechanism of improvement of the corner filling. In addition, the results obtained from the simulation are compared with experimental observations, and the validity of the simulation results is verified. Based on a better understanding of the mechanism of improvement of the corner filling, a new pulsating pressure path is proposed to increase the corner filling. It has been shown that the proposed pulsating pressure path is more effective in increasing the corner filling of the box shape tube hydroforming process.

---

Bipolar plates are the most important and expensive components used in fuel cells. Metallic bipolar plates are the best choice to replace graphite or machined thick metal plates due to their lightweight and low cost. Selection of suitable forming process is one of the main subjects in fuel cell technology. Nowadays, hydroforming process is commonly used for the production of metallic bipolar plates because of its capability in forming light weight and complex parts. Among the various patterns of bipolar plates, serpentine flow field pattern inevitably brings two main defects of rupture of material during forming process and uneven flow distribution in practical operations. In this research, forming of a slotted interdigitated serpentine pattern on SS304 stainless steel sheet by hydroforming process has been examined using finite element simulation and experimental approach. The effects of process parameters and die geometry on the thickness distribution and filling percent are also studied. It is concluded that by increasing the forming pressure, filling percent of the die increases and the thickness of critical region is more reduced due to the increasing of drawing ratio. Also, it was found that hydroforming process has high repeatability.

---

Bipolar plates are the most important of fuel cells components. These plates are made with different methods such as machining, molding and forming and they are made of variety materials such as graphite, composite and metal plates. In this research, forming of metallic bipolar plates with pin-type pattern from stainless steel 304 with 0.11mm thickness is investigated numerically and experimentally using hydroforming process in convex die. In this regard, several parameters such as applied pressure, pin geometry, and depth to width ratio of the profiles has been changed and the experimental and simulation results of formed profiles, filling percent, thickness distribution and thinning percent of the formed parts have been compared. The results have been shown that no safe sample has been reached in depth to width ratio 1, while safe samples have been formed in depth to width ratio 0.67 in circle (a/b=1) and ellipse (a/b=0.7) samples and all samples in depth to width ratio 0.33 at 300 MPa pressure level in viewpoint of filling and thinning percentage. In general, increasing the small diameter to big diameter ratio (a/b) and decreasing the depth to width ratio (h/w) makes the thinning percent and filling percent more desirable.

---

Aluminum alloys are using widely duo to high strength-to-density ratio in the industries of automotive, shipbuilding and aerospace as a substitution of steel sheets. .To increases the formability of aluminum alloys in deep drawing process and due to formability problems of these alloys in room temperature using of warm deep drawing process is necessary. According to recent researches, warm deep drawing in gradient condition has better results as isothermal case. In this paper the process parameters in production of cylindrical parts from aluminum alloys 5083 sheet with 2mm thickness is investigated. For this purpose, gradient warm deep drawing in temperatures of ambient (25˚C), 80˚C, 150˚C, 180˚C, 250˚C, 350˚C , 450˚C and 550˚C have been used. The blank in flange region is heated by die heating and the blank center to increases the strength of the region which contact with punch corner radius is cooled by water circulating punch. The results show that increasing the temperature of the blank in flange region and also cooling of blank center lead to improve the limit drawing ratio. In forming temperature of 550˚C and ram speed of 378 mm/min and lubrication by graphite powder can reach to the limit drawing ratio equal to 2.83.

---

In this paper, the effect of ductile damage on the behavior of a dented pipe subjected to internal pressure is investigated by experimental and numerical methods. In the numerical investigation, the plastic behavior of pipes under indentation is studied using continuum damage mechanics theory and the elastic-plastic finite element analysis. Finite element calculations are carried out using the damage plasticity model proposed by Xue and Wierzbicki (X-W). The proposed damage plasticity model incorporates effects of four parameters that play important role in predicting the fracture initiation, namely the damage rule, the softening effect, the hydrostatic pressure and the Lode angle. The target dent depth is considered as an indication of the load bearing capacity of the pipe under indentation process by a rigid spherical indenter. To validate numerical calculations, a series of experimental tests are conducted on the API XB steel pipe with atmospheric pressure. After verification, numerical calculations for different ranges of internal pressures, wall thicknesses and indenter diameters with and without damage effect are carried out for aluminum 2024-T351 pipe and results are compared. It is shown that damage plays an important role on the load bearing capacity of an indented pipe. Results of the present study confirm the credibility of the proposed model in predicting the ductile fracture under multi-axial state of stress loadings.

---

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.

---

Metal bipolar plates are key components in fuel cells that are considered as the best alternative to replace graphite plates. Material selection in bipolar plates depends on its weight and corrosion resistance. Metallic bipolar plate can be considered as the best alternative instead of graphite and composite plates. One of the new processes in order to produce this plat is gas blow forming process. In this study, forming of AA8111 bipolar plates with 200 µm thickness in concave groove dies is investigated by gas blow forming process at various pressures (20, 30 and40 bar) and temperatures (300 and 400 ° C). The filling percent of die at various wall angles and depth to width ratios are examined. According to the dimension of channels, maximum and minimum thinning percentage at high temperature and pressure are investigated. Results show that at wall angle of ∝=0, and the depth to width ratio of h/w=0.5, rupture occurs at pressure of 20bar and at temperature of 300° C and at pressures of 20 and 40 bar at temperature of 400° C. The best channel filling with lowest thinning obtained at ∝=15 and h/w=0.5.

---

A Forming Limit Diagram (FLD) is a graph which depicts the major strains versus values of the minor strains at the onset of localized necking. Experimental determination of a FLD is usually very time consuming and requires special equipment. Many analytical and numerical models have been developed to overcome these difficulties. The Gurson- Tvergaard- Needlemann (GTN) damage model is a micromechanical model for ductile fracture. This model describes the damage evolution in the microstructure with physical equations, so that crack initiation due to mechanical loading can be predicted. In this work by using the GTN damage model, a failure criterion based on void evolution was examined. The aim is to derive constitutive equations from Gurson's plastic potential function in order to predict the plastic deformation and failure of sheet metals. These equations have been solved by analytical approach. The Forming Limit Diagrams of some alloys which studied in the literatures have been predicted using MATLAB software. The results of analytical approach have been compared with experimental and numerical results of some other researchers and showed good agreement. The effects of GTN model parameters including 〖 f〗_0 〖,f〗_C 〖,f〗_N,f_f , as well as anisotropy coefficient and strain hardening exponent on the FLD and the growth procedure of void volume fraction have been investigated analytically.

---

Due to the low formability of aluminum alloys at ambient temperature, forming of these alloys is performed at high temperature. Research has shown that the results of simple tensile test to predict the materials behavior at high temperatures are not sufficiently accurate to predict the formability of aluminum tubes at high temperature. The mechanical properties of the tube are very important at high temperatures. In this study the formability of 6063 aluminum alloy tubes are investigated by free bulging test at temperature range 430°C to 600°C. Then the mechanical properties including flow stress, strain rate sensitivity coefficient and strength constant are obtained using tube multi-bulge test at temperature range 530°C to 580°C. For this purpose, hot metal tube gas forming process is used and the effect of process parameters such as the effect of temperature, pressure and time on the expansion ratio and height of the bulge are studied. The results show that the maximum expansion ratio is 58% at 580°C. Bursting pressure decreases from 1.9MPa to 0.6MPa with temperature increasing from 430°C to 600°C. The bulge height increases with increasing forming time at constant pressure. Also with increasing temperature in the temperature range 530°C to 580°C the flow stress and strength constant decrease and strain rate sensitivity coefficient increases.

---

Gravitational search algorithm (for the first time) has been used for two-objective optimization of airfoil shape, in this article. 2D compressible Navier-Stokes equations with Spalart-Allmaras model has been used to simulate viscous and turbulent flow. First, efficiency and accuracy of the optimizer sets have been evaluated using inverse optimization. Objective functions were differences between drag and lift with their corresponding values of the NACA0012 objective airfoil, as a set of airfoils randomly were chosen as starter airfoils, in this case and the aim was to obtain the airfoils that satisfy the considered objective functions. In direct optimization, gravitational search algorithm that has been used in the present work, has achieved proper parameters (related to the Parsec method) and consequently has found optimized airfoils with maximum lift and minimum drag objective functions. This algorithm starts to slove using a set of airfoils and it is directed towards the airfoils that provide the mentioned objective functions. Comparison of the results (Pareto fronts) shows better and more proper performance of the gravitational search algorithm rather than particle swarm optimization algorithm and former researches (done using other meta-heuristic algorithms) for aerodynamic optimizations.

---

In the present study, the mechanical and microstructural properties of dissimilar joint of 304 austenite stainless steel and C70600-copper-nickel alloy made by Gas Tungsten Arc Welding process has been investigated. The aim of this joint is using the twin metallurgical properties such as; heat dissipation and corrosion resistance of copper-nickel alloy and mechanical properties of 304 austenite stainless steel alloy. Welding of two dissimilar metal steel to copper-nickel alloy due to differences in melting point, the difference in thermal conductivity, rapid solidification of copper nickel are facing many problems. In this research due to solubility and weldability of nickel with two both alloys, three filler metals Inconel 625, Inconel 82 and 61 were used. According to microstructural investigations welds made by Inconel 625 and Inconel 82 show a finer equiaxed dendrite structure as compare as in Inconel 61 filler metal. The tensile strength of samples welded by Inconel 625, 82 and 61 filler metals was 324, 323 and 293 MPa, while the elongation percent of three samples show small difference. According to mechanical properties of joints, the Inconel 625 and 82 filler metal are appropriate for dissimilar welding 304 austenite stainless steel and C70600-copper-nickel alloy.

---

The sheet metals formability can be restricted by localized necking and internal cavitation. On the one hand, nucleation and growth of cavities during plastic deformation can increase the inhomogeneity of sheet metal and accelerate the localized necking. On the other hand, localized necking at the intervals between the cavities can lead to accelerate the joining and coalescence of the internal cavities. In this paper an analytical model based on Marciniak-Kuczynski (M-K) model and Gurson plastic potential function in order to exert the internal voids effect on localization necking has been developed. Stowell’s model was used to illustrate void growth behavior during plastic deformation. In order to examine the effect of the voids on localized necking, the void volume fraction was considered in the imperfection factor and the plastic volume constancy principle. The nonlinear system of equations was solved with the modified Newton-Raphson method using MATLAB software. This new analytical method (M-K-Gurson) was used to predict the forming limit diagram (FLD) of IF steel alloy sheets and the results were compared with those of other researchers. The results showed that the M-K-Gurson method predicted the FLD with better agreement comparing with experimental results. Thereafter, the effects of strain hardening exponent, anisotropy coefficients, geometrical imperfection factor, the void volume fraction and the void growth rate parameter on the FLD were investigated.

---

Aluminum alloys have become widespread in the various industries due to the characteristic of high strength-to-density ratio. These alloys do not have a suitable formability at ambient temperature so they formed at high temperatures. The main hot forming methods used for aluminum alloys include deep drawing and gas forming. Both of these methods have their own advantages and disadvantages. In this study, a combined process involving deep drawing and gas forming has been used. In this process, the first step is to create a pre-formed deep drawing and in the second stage, the final piece is produced by gas forming process. The purpose of this study is to optimize the levels of the main process parameters for the shaping of cubic parts of aluminum sheet 5083 sheet. These parameters include the temperature and blank-holder force of deep drawing stage and the temperature and gas pressure at the gas forming stage. The best levels of process parameters were selected using the Taguchi experimental design method. The results show that the temperature at 350 ° C and the blank-holder force of 1000 N for deep drawing, as well as the temperature of 485 ° C and the gas pressure of 0.6 MPa for the gas forming stage, can be achieved with the least degree of thinning in the specimen. The maximum thinning achieved is 22%.

---

---

The aim of this paper is to analyze the strain components in the direct extrusion process to predict the curvature of the exit product. For this purpose, Riemann mapping theory is used to model the deformation zone and create a one-to-one correspondence between the input and output cross sections of the die. With the help of the Bezier curves, flow lines are created between these points and then an upper bound solution is obtained for the velocity field. The process pressure and the distribution of the strain components are determined for the square, hexagonal, and rectangular sections using the obtained velocity field. A theoretical method based on the elastic-plastic bending of beams is presented for calculating the curvature of the exit product for the eccentric dies. In this theoretical method, the distribution of stress components and the bending moments is calculated using the specified strain components. In fact, the amount of bending moments indicates the curvature of the exit product. Finally, the presented theoretical model is validated through comparison with the results of the finite element simulation and the previous studies. The results show that Riemann conformal mapping theory and upper bound method can be used to determine the distribution of strain components and predict the curvature of the output product, in addition to estimate the process pressure.

---

Fire blight, caused by Erwinia amylovora bacteria, is one of the well-known plant diseases in the world including major diseases of the fruit trees, especially apples and pears. In recent years, due to chemical nature of the pesticides damaging human health and environment, the importance of biological control is considered as alternative measure to manage plant diseases. To investigate the possibility of biological control of the pathogens, healthy foliar samples of apple, pear, and quince trees were collected from different regions of Kerman Province, Iran, and then, biocontrol activity of antagonist agents was evaluated under laboratory conditions. On the basis of the results, some of the antagonists could decrease the symptoms of the disease by 14.28-79.59%. Laboratory evaluation included investigating the disease severity in immature pears, biocontrol activity of antagonist agents in the plate assay, inhibitory siderophore production, biofilm formation capacity, drought stress tolerance, and silver nanoparticle synthesis capability, which showed that these antagonist agents could potentially control the disease. Among the 9 well-performed antagonistic isolates from apples and pears, Vr87 isolate was selected. The studies were confirmed by amplifying part of 16S rDNA region of the isolate, using specific primers. By comparing the results on the NCBI website, the selected isolate was identified as Enterobacter sp. genus. Among all selected isolates as successful factors in controlling fire blight pathogen, including isolated isolates and isolates in the collection of Vali-e-Asr University, Bacillus subtilis strain BsVRU1 in the Vali-e-Asr University collection, with 73.5% inhibition, had higher inhibitory power than the other antagonist isolates against the pathogen of fire blight disease.