Sharif Digital Repository

In this study, hot extrusion of AA6061-%5 SiCp composite has been predicted and flow behavior of material during deformation process has been investigated. At the first step, hot compression tests have been carried out to obtain the flow behavior of the material at different temperatures and strain rates. In the next step, an FE-based temperature-displacement coupled model by employing ABAQUS software has been proposed in order to solve the energy and heat transfer equations and to determine the required energy and force for the extrusion process. Experimental investigations have also been performed to verify the proposed model. Comparison between the results from the model and the... 

In this study, transformation of austenite to ferrite under continuous cooling condition of a low carbon steel was investigated. In the first step, a heat transfer model was employedconsidering governing heat transfer boundary conditions and a microstructure model based on Cellular Automaton method was used simultaneouslyto predict austenite to ferrite transformation progress. The influence of pre-heating temperature and primary austenite grain size on the final ferrite grain size and distribution were perdected. To verify the simulation results, experimental processes were utilized. The microstructure distribution was determined by means of Clemex Pro software then, these results were... 

A mathematical model has been proposed to estimate the deformation pattern and the required power in cold plate rolling using the stream function method and upper bound theorem. In the first place admissible velocity distributions as well as the geometry of deformation zone were derived from the proposed stream functions. Then, the optimum velocity field was obtained by minimization of the power function computed based on the upper bound theorem. Then a steady state heat transfer equation has been solved in whole model using finite element method. In order to verify the predictions, rolling experiments on aluminum plates were conducted and also, a finite element analysis performed employing... 

In this research, the extrusion of composite AA6061-SiC has been investigated and the temperature distribution field and energy required for the process has been predicted. In this regard, to predict the flow behavior of material, hot extrusion tests conformed at various ranges of temperatures and strain rates. Afterward, the finite element method coupled with the upper bound technique to calculate the temperature distribution and energy required during hot extrusion. This model has also used for wire drawing and cold extrusion processes. The present model is capable of considering various process parameters such as speed of extrusion, reduction and the initial billet/die temperature on the... 

In this research, the hot and warm rolling of stainless steel 304 was studied. First the rolling process was simulated using Finite Element Method software ABAQUS and the distribution of temperature and strain in the process under discontinuous conditions were predicted. Next, hot and warm rolling of stainless steel 304 under different conditions was carried out. Specimens were cut and subject to mechanical testing, metallography and electron microscopic studies. Data obtained from these experiments and the predicted trends from ABAQUS were compared, therefore studying the effect of different parameters on the microstructure and mechanical properties of the rolled specimen. Results indicate... 

A mathematical model was developed to assess thermomechanical behavior of work rolls during warm rolling processes of AA2017. A combined finite element analysis-slab method was first developed to determine thermal and mechanical responses of the strip being rolled under steady-state conditions; Then, the calculated roll pressure and temperature field were utilized as the governing boundary conditions for the thermomechanical problem of the work roll. Finally, the thermomechanical stresses within the work rolls were predicted by a thermoelastic finite element approach. The results indicate that, in warm strip rolling, thermal and mechanical stresses developed in the work rolls are comparable.... 

In this research, temperature distribution and roll force during steady state warm and hot rolling of 6061 Al alloy strip have been simulated, using finite element method and upper bound solution. At first, the velocity field and deformation zone shape have been determined, by means of upper bound solution, then using 2D finite element method, the temperature distribution within rolling and considering rate of heat of deformation, has been calculated. This model generalized for two pass steady state warm and hot rolling. Also, in order to evaluate the predictions, the experimental recorded of temperature variation, during hot rolling and temperature variation predicted by model has been... 

Control of the product manufacturing and evaluating its behavior during deformation is one of the most important issues in hot deformation, especially hot rolling. One of the factors affecting on quality of hot rolled steel strips is the flatness after run-out table cooling.Distortion in a steel strip results from non-uniform temperature profile as the strip cools to room temperature. Increase in the rolling velocity and subsequently the cooling rate affect thermal stresses. In this study a mathematical model for prediction of austenite- ferrite phase transition kinetics and thermo-mechanical stresses on the run-out table after hot rolling was developed for low carbon ferrite steels.... 

In this research, distribution of stress, strain and temperature fields in the strip and workroll were determined during steady state cold rolling process. To do this, first an initial guess based on the approach proposed by Hill for the velocity field was taken and accordingly, the real velocity distribution and then the strain rate and stress fields in the strip were calculated. Then, using the obtained stress and strain rate fields, the deformation power was determined and used as a boundary condition for solving the thermal behavior of the strip. By considering the Streamline Upwind Petrov-Galerkin method and solving the finite element relations, the temperature distribution within the... 

Austenite in the 300 stainless steels is not a table phase in deformation processing during which martensite phase forms. This causes significant changes in the microstructures as well as the mechanical properties of deformed steel. In this work, the effects of rolling speed, reduction, temperature and strain pass on the strain-induced martensite during strip rolling operation of stainless steel 304L are studied. Cold rolling experiments under different speeds, reduction and temperature are conducted and then, the microstructural events and mechanical properties of the rolled steel are evaluated. For doing so, different testing techniques including tensile test, hardness measurement, optical... 

In this work a three-dimensional thermo-mechanical finite element analysis has been utilized to predict the large deformation of workpiece during the friction stir welding process using Arbitrary Lagrangian-Eulerian formulation in commercially finite element code, ABAQUS. The model can consider various process parameters including rotational and longitude speeds of the tool, backing plate and delay time. Ultimately, with optimizing the process parameters by presented model, experimental works carry out to improvement appropriate mechanical parameters of the weld. Comparison between the predicted and the experimental data displays a good consistency between distributions of the equivalent... 

In this work a mathematical model has been developed to predict large deformation of work piece in friction stir welding process. Commercially finite element package; ABAQUS is used to solve the governing equations while an elasto-viscoplastic materials behavior is utilized in the model. The model is capable of considering the effects of process parameters such as welding speed and tool geometry on various aspects of the process including temperature and stress distribution within the work piece as well as tool, and velocity and strain fields with in the work piece. Experimental works have been carried out to assess the accuracy of the model and also to determine the effects of various... 

Mechanical behavior of aluminum-magnesium alloy, AA5083, was studied at high temperatures using hot tensile testing together with uniaxial creep experiments. In the first place, the as-received AA5083 sheet was subjected to annealing heat treatment to remove the effect previous plastic straining. Then, creep experiments were conducted at temperatures in the range of 190°C to 300 ° C under constant the stress varied between 30 MPa to 100 MPa. The hot tensile testing was also carried out from room temperatures up to 400 °C under nominal constant strain rates of 0.0005, 0.005, 0.01 and, 0.05 (1/s). In addition to the mechanical testing, optical metallography and scanning electron microcopy were... 

In this study, behavior of softening after hot tensile and hot rolling processes in isothermal and non-isothermal conditions in AA5083 Aluminium alloy has been simulated using cellular automata. Also effect of temperature and strain rate in hot tensile test and effect of temperature and strain in hot rolling has been investigated. First distribution of temperature in material using the finite element method computed and used as initial temperature in CA and computing the static recovery in hot tensile. Also for hot rolling, computing static recovery and CA are used for initial temperature in ABAQUS. For investigating effect of dynamic recovery and recrystallization, the neural network has... 

In this study, static softening kinetics and microstructural evolution during isothermal and non-isothermal annealing of aluminum-magnesium alloy and low carbon steel after cold plastic deformation was investigated. It is known that in industrial cold forming processes, the material properties and microstructure changes during the annealing depends on the inhomogeneous initial microstructure and the deformation history of the cold worked material. To predict the microstructural changes during the annealing of cold worked alloys, a multiscale model based on probabilistic cellular automata (at mesoscale), and the finite element method (at macroscale), was used. To do so, a two-dimensional... 

Static recrystllization in low carbon steel after two type of deformation –sidepress as an inhomogeneous deformation and rolling as a common industrial process - has been simulated using Cellular Automata (CA). The finite element method was utilized to compute the strain and stored energy distribution due to deformation. The initial microstructures were created by simulation of recrystallization with homogeneous site-saturated nucleation and topologic deformation was also considered in model. Subsequently using the result of FEM, stored energy of deformation was calculated and transferred into a two dimensional CA lattice. Nucleation rate and grain boundary velocity were considered... 

Softening behavior containing static recovery and static recrystallization in isothermal and non-isothermal conditions in aluminum 1050 after cold rolling has been simulated using Cellular Automata(CA). The effect of strain pass on recrystallization process has been investigated. The finite element method was employed to simulate 1,2 and 3 pass rolling processes and compute the stored energy distribution and transferred to the CA model. For the initial microstructure the topologic deformation and site-saturated nucleation has been considered. For non-isothermal conditions the thermal model has been utilized to compute temperature distribution and decreasing in stored energy due to... 

In this study, static recrystallization (Rex) of a low carbon steel after cold rolling has bees simulated under non-isothermal condition by employing cellular automata (CA) method. Symmetric cold rolling and asymmetric cold rolling (ASR) which was arisen by inequality of friction coefficient have been applied as primary cold deformation. Residual stress and strain field after deformation, and temperature rate and distribution of specimens during annealing has been evaluated by employing two different models based on finite element method. Initial microstructure has been developed by haphazardly distribution of grains and topological adjustments were imposed on it. Results of FEM models were... 

In this work, annealing procedure of cold-deformed AA5052-SiC composite has been simulated by using cellular automata approach and the effect of SiC second phase on softening kinetics has been studied. To do so, site saturated nucleation has been employed to establish initial microstructure. In addition, topological changing due to deformation has been implemented on the microstructure. During annealing, recovery and recrystallization phenomena occur simultaneously, and it has strong effect on the annealed microstructure. Therefore, during annealing, recrystallization and recovery has been considered simultaneously and decreasing in the stored energy, which has developed during deformation... 

In this research, non-isothermal annealing process at temperatures ranging between 400°C to 830 °C was investigated in warm and cold-rolled austenitic stainless steel 304L. First, the wide variety of austenitic to martensitic structure was produced by the multi-pass rolling process at room temperature -8 °C, 200 °C, and 280°C. The n exponent in Olson-Cohen equation was governed 2.83 after non-linear curve fitting to assess the fraction of deformation-induced martensite as a function of strain. Afterward, Abaqus/Explicit method was utilized to achieve the stored energy and plastic strains distribution through the thickness. Then, Cellular automata and Galerkin-finite element models were...