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Ohmic heating has an advantage over conventional indirect heating methods because heater (electrode) surfaces temperatures are comparatively lower as heat is generated within bulk fluid. Conventional ohmic heating under typical low frequency alternating current (50 or 60 Hz) could cause hydrogen and oxygen evolution due to electrolysis of water. This process could develop the electrodes decay or corrosion. Any decay or corrosion of electrodes shorten the life time and contaminate the food. The main objective of this study was to investigate the rate of the electrodes corrosion in the ohmic heating process. For this purpose the concentrations of Fe, Cr, Ni, Mn, and Mo from the stainless steel electrode migrated into ohmic and conventionally treated soup were measured. In this study migration of the major key metal ions from stainless steel measured by Atomic Absorption. The results showed that overall ohmic treatment yielded the same migration residues of all metal ions, compared to the conventional retorting with similar electrodes. Concentrations of all metal ions migrated into food samples after ohmic treatment were far lower than dietary exposure levels so that this technique can ensure the safety and quality of food supplies.  

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In this paper, ratcheting behavior of stainless steel 304L cylindrical shells under cyclic combined and axial loadings are studied, experimentally. Tests were performed by a servo-hydraulic INSTRON 8802 machine and the shells were fixed normal and oblique under 20 degree and subjected to cyclic loads. In this paper, the effect of length of cylindrical shell and the effect of angle of cylindrical shell on ratcheting behavior were investigated. Based on the experimental results, it was found that bending moment plays a crucial role in waste of energy and increase in plastic deformations. Seen that due to the existence of bending moment in different cross section of oblique cylindrical shell, there are more plastic deformation and accumulation in comparison to normal cylindrical shell. Also, analyzing the loading history of cylindrical shell under combined loading, it has been seen that by keeping the mean force at constant value while increasing the force amplitude, the ratcheting displacement became higher and by the prior load with higher force amplitude retards the ratcheting behavior and plastic deformation with samller force amplitude.

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Drilling is the most widely used process for producing holes through the manufacturing parts. Drilling, as well as other machining processes, produce undesired raised material on both entrance and exit edges. The raised material caused by plastic flow is defined as burr, which is necessary to be removed for critical and precise part. In this work, magnetic abrasive deburring (MAD) was used to investigate the deburring performance of stainless steel. Firstly preliminary simulations were carried out by Maxwell software to determine appropriate MAD tool. Then, influence of MAD variables such as height of gap, mesh number and rotational speed were studied on burr height variation. Results indicated that mesh number of abrasive particles has the dominate effect in burr removal of stainless steel plate by this process.

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Using in low temperatures causes embrittlement of many structures, consequently, selection of welding parameters for maintaining the toughness of welded structures, is so important. In this paper, effects of arc heat input and welding speed on the cryogenic impact strength of type 304L austenitic stainless steel weld metal, are investigated. For this purpose, 304L austenitic stainless steel sheet with 5 mm thickness, was welded with gas tungsten arc welding process and by changing the parameters of arc heat input and welding speed, the effect of these parameters on the microstructure, the weld metal ferrite content and low temperature charpy impact energy of samples, was determined. The arc heat input range applied was between 1.04 and 3.23 kW, and the welding speed varied between 30 and 240 mm/min. It was found that, increasing of arc heat input can reduce weld metal ferrite content, which improves low temperature impact strength, but on the other hand, slow cooling due to increasing heat input results in coarser dendritic structures in the weld metal, and can adversely affect on impact strength. Changes of Welding speed can also affect on the amount of ferrite and microstructure and thus have influence on the impact strength. Finally having carried out the numerous tests, optimum impact properties at low temperature, were obtained at 1.67 kW arc heat input and 120 mm/min welding speed.

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Friction drilling is a nontraditional hole-making process used to create and form the holes in thin sheets. The process involves penetration of a rotating conical tool into a sheet metal work piece and creation of a bushed hole in a single step. The tools are conical without having cutting edges, and the heat caused by friction between the tool and workpiece is used to soften the material, penetrate into the workpiece and make the bush. In this process, the temperature is high, and so that the deformation. The simulation by finite element analysis is a useful tool for understanding the material flow, stress, strain and length of bush. In this research, Abacus software was used to simulate the behavior of friction drilling. To verify the simulation results, the length of bushes created by tools with different diameters at different rotational speeds and federate were measured, and results were compared with experimental data. The aim of this study was to determine the process parameters to provide the bush with a uniform thickness, and study their effect on the shape of bush. Therefore, DOE was performed using a full factorial method and results were interpreted using ANOVA. Results showed that the tool diameter has the greatest effect (95%) on the length of bush during friction drilling, then feed rate (3%) and finally rotational speed (2%) has the smallest effect.

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Residual stress measurement of in-service parts of a system is practically impossible by means of destructive methods. Therefore, the use of ultrasonic method as a non-destructive method has an important role. One of the problems in non-destructive measurement of residual stresses by means of ultrasonic waves is determination of acoustoelastic constants. In fact, for conversion of ultrasonic method data to stress state, it is needed to determine these coefficients very precisely. But for reasons like HAZ inclination and small width of this zone, determination of coefficient of this zone does not perform accurately. In this study, the practical simulation is performed for determination of acoustoelastic coefficient of HAZ. For this simulation, the heat affected zone divided to four separate zones and then the microstructure of those four zones has been simulated on standard tensile test specimen by different heat treatment cycles. This coefficient has been used in evaluation of welding residual stresses of austenitic stainless steel by LCR Ultrasonic waves and the results has been compared with the hole-drilling strain-gage method. By comparison of stress values achieved by HAZ simulation method, the conventional method and hole-drilling strain-gage method, it is seen that the HAZ simulation method cause an improvement in welding residual stress measurement accuracy.

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Bulging with elastomer tool has been used in the production of integrated hollow parts as one of flexible forming methods. Nowadays, most industries such as Aerospace and military are using flexible die forming methods due to their flexibility, high quality and lower cost. In this research, finite element simulation has been implemented by ABAQUS software to investigate the behavior of stainless steel 304 tube bulging process using elastomer tool. By comparing the geometry of deformed tubes in experimental tests and simulation results, the FEM model was verified. The aim of this study is to determine the process factors and their effects on the average thickness and depth of bulged tube. In this regard, design of experiment (DOE) was performed using a full factorial method and the results were interpreted using analysis of variance (ANOVA). Also a regression model was presented to predict these responses. Results showed that among the studied factors, friction (between tube and rubber), rubber height, punch displacement and tube axial feeding have significant effects on the process. Finally, the optimal values for significant factors were presented.

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In this paper, laser brazing of austenitic stainless steel (type 321) and martensitic stainless steel (type 410) was performed using 400W pulsed Nd:YAG laser with nickel-based filler metal (BNi-2). Laser brazing process was carried out at different gap distances. Microstructure and composition analysis of the filler metal and the brazed joints were examined by optical Microscopy (OM) and Scanning Electron Microscopy (SEM). Mechanical properties of the brazed joints were measured in the form of Micro hardness and tensile test. Results show that filler metal shows good wetting and spreading on 321 and 410 stainless steel in laser brazing process. Filler metal consists of nickel solid solution, nickel-rich boride and chromium-rich boride. The laser brazed joints are mainly comprised of the nickel solid solution, nickel-rich boride in the center of the joints and chromium-rich boride in near interface with substrates. The average micro hardness for filler metal was 550 HV compared to 500 HV for laser brazed joints. The tensile strength of laser brazed joints is varied from 200 to 500 MPa because of different gap distances.

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This paper aims at investigating the effect of heat input in resistance spot welding on microstructure and mechanical behavior of 2304 duplex stainless steel, as a promising candidate for automotive application. The results showed that due to rapid cooling rate inherent to resistance spot welding, the ferrite-austenite phase balance is destroyed and nitride-type precipitates are formed within the ferrite grains. The amount of austenite in the weld nugget was a function of welding current, as the most important factor affecting welding heat input. Increasing welding current increased the austenite volume fraction from 4 to 18%. Moreover, the nitride precipitation was reduced upon using higher welding currents. Investigation of weld mechanical performance during the tensile-shear loading showed that increasing welding current enhances both load bearing capacity and energy absorption capability. The maximum achievable peak load and energy absorption of 2304 duplex stainless steel resistance spot welds were 25 kN and 40 J indicating a superior weldability.

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In the present study, microstructure and wear resistance of in-situ composite coatings TiC-Al2O3 and TiB2-TiC-Al2O3 product by gas tungsten arc welding process on AISI 304 austenite stainless steel were investigated. For this, a paste of the mixed powders of 3TiO2-4Al-3C and 3TiO2-4Al-B4C was provided and applied on the surface of AISI 304 austenite stainless steel substrate, then fused using gas tungsten arc welding process. The microstructural features and phase characterization of the cladded samples were investigated using optical and electron microscopy and X-ray diffraction analysis. The mechanical properties of clad layers were studied by Vickers microhardness and pin-on-disk wear tests. The microstructural investigations of cladded layers indicated that high heat input during welding led to high temperature synthesis and formation of significant reinforcing particles on the surface of steel. Also, the cubic TiC particles formed separately or inhomogeneously nucleated on Al2O3 particles in the austenitic matrix of 304 stainless steel. Likewise, the formation of TiB2 particles was approved with X-ray diffraction analysis. The rei

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In this paper the capability of laser surface hardening of martensitic stainless steel AISI 410 is conducted by using a Nd:YAG pulsed laser with a maximum power of 700 W. Focal point position (22mm to 34mm) and laser pulse energy (14.7J to 16.8J) were considered as process variable parameters. microhardness was measured in depth and surface of hardened layer. Metallography of samples was conducted in order to study the microstructure of hardened zone. Also geometrical dimensions of hardened zone (width and depth), microhandness distributions in depth and width of hardened layer, microstructure of hardened layer were investigated. Results show that by increasing laser pulse energy and decreasing the laser focal point position, the hardness and depth of hardened layer increases. Observations indicated that solid state transformation and carbide solution in steel during laser surface hardening process, improved the surface hardness. Lower delta ferrite in martensitic structure in laser hardened layer lead to higher microhardness. Maximum hardened layer of 350 µm in depth and 2208 µm in width and maximum surface hardness of 747 HV0.3 is obtained in maximum pulse energy of 16.8J.

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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

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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.

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Laser surface hardening is one of the modern technology used to improve the surface of materials in order to modification of tribological properties. This paper investigate the ability of laser surface hardening of AISI 410 martensitic stainless steel using a continuous high power diode laser with a maximum power of 1600w. Laser power, scanning speed and focal plane position are variable parameters in this research. The effect of the process parameters on the hardness, depth and width of the hardened layer has been investigated. The results show that with increasing laser power and reducing the scanning speed, higher hardness and hardening depth are obtained. Results also reveal that width of hardened layer increases by increasing in focal plane position and reduction the laser power. Modeling of controllable variables (laser power, scanning speed and focal plane position) by Response Surface Methodology method to study the effect of process input parameters on how to change responses, and analysis of ANOVA tables, providing regression equation for output parameters, analysis The Surface Plots, Interaction Plots of the input parameters, were investigated. The results show that in RSM modeling method, the effect of laser power parameter on the results of maximum hardness, depth and width of hardness is more than the parameters of the focal plane position and scanning speed. Due to percentage of coverage of the parameters by the regression equations the RSM method is a suitable model for investigating the effects of the surface hardening process by diode laser.

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With regard to the industry demand for welding dissimilar metals, which are not possible to be welded by conventional welding, friction welding process can be a proper approach. In this study, friction welding of two stainless steels, martensitic 410 to austenitic 304, with variable parameters of friction time (40, 50, and 40 s), friction force (90, 100, and 120 kN), and forging force (130, 150, and 180 kN), under the constant rotating speed (850 RPM) and forge time (60 s), was investigated. Microscopic characterization using optical and scanning electron microscopes, and elemental analysis using energy dispersive X-ray spectroscopy were carried out on the welds. Soundness of the weld joints was evaluated using tensile and microhardness tests. Fracture surfaces of the tensile specimens were examined as well. The structure of the welded samples composed of acicular and rough martensite and elongated grains adjacent to 410 and 304 stainless steels, respectively. Tempering heat treatment locally caused converting rough martensite to lath martensite. The results showed that the tensile strength of the samples was in the range of 400-520 MPa, and the fractography revealed the occurrence of a brittle fracture. Microhardness measurement revealed that the highest hardness value was obtained in 410 stainless steel, at the heat-affected zone close to the interface. An appropriate friction weld joint with a tensile strength of 751 MPa was obtained after heat treatment of the weld location, and with the aid of selecting optimal parameters of 50 s friction time, 120 kN friction force, 180 kN forging force.

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In this paper, finite element analysis with combined (nonlinear isotropic/AF kinematic hardening model) and chaboche hardening models are employed to investigate ratcheting behavior in stainless steel branch pipes under dynamic moments and internal pressure. Obtained results show that the maximum value of ratcheting strain takes place in the junction of branch pipes in the hoop stress direction. In this case, the rate of progressive strains increases with the increase of the bending moment levels in constant internal pressure. Furthermore, this study reveals that the geometry and dimensions of branch pipes have a significant impact on the rate of progressive strains. The bending moment levels to initiate strain accumulation phenomena will be increased with the increase of the dimensions of branch pipes. In the BSS1 sample, comparison between results obtained using progressive strains with combined and chaboche hardening models are much better than those of Armstrong-Fredrick hardening model and are near to the experimental data. Of course, in BSS2 sample, the behavior of ratcheting with combined hardening model is near the experimental results. For the BSS3 sample, the prediction of ratcheting with the chaboche hardening model is better than using the other strain hardening models and are near to the experimental data. Like the carbon steel samples studied in the recent paper, compared to the Armstrong-Frederick hardening model, the chaboche and combined hardening models exhibit an appropriate prediction and similar to experimental results in stainless steel samples.
 

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