Sharif Digital Repository

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... 

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... 

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.... 

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 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... 

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... 

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, the high temperature deformation behavior of Al-Cu aluminum alloy and the results of single-stage and multi-stage creep tests have been investigated. To investigate the behavior of alloy fluidity in temperature range 150 ° C to 500 ° C and strain rate 0.0005 s-1 – 0.05 s-1 were subjected to tensile test. The results show that in the temperature range of 200 ° C to 225 ° C, the sensitivity coefficient to the strain rate is negative, which indicates the occurrence of dynamic precipitation during deformation. In the meantime, the reverse processes in the mentioned temperature range were investigated and it was found that 250 ° C was the starting temperature of the dynamic... 

In this study, creep behavior and cavitation as well as high temperature deformation of Al-Zn-Mg aluminum alloy were investigated by means of uni-axial creep and tensile tests. The as-received material i.e. AA7075 plate, was first stabilized utilizing over-aging heat treatment and then stress-controlled creep tests were performed in the temperatures ranging between 120℃ to 210℃ under the applied stresses varying 130MPa to 250MPa. Accordingly, the stress exponent and creep activation energy were determined as 5.7 and 149kJ/mol.K to 189kJ/mol.K, respectively. Considering these parameters, it was found that the governing creep mechanism, in the mentioned temperature range, would be dislocation... 

In this research, hot deformation and creep behavior of aluminum alloy i.e.AA2017 were taken into account while the impact of the initial microstructure of the examined alloy was also studied. In order to investigate the behavior of the alloy, tensile tests were conducted at temperatures ranging from 120°C to 400°C under the nominal strain rates of 0.0005 s-1, 0.005 s-1, 0.05 s-1. In these experiments, two different initial microstructures were employed including solution treated samples as well as artificially aged specimens. The results show that in the temperature range of 180°C to 250°C, the strain rate sensitivity parameter is negative in the solution treated samples which indicates... 

In austenitic stainless steel types 304 and 316, due to the instability of the austenite phase, the martensite phase is formed by plastic deformation below the Md temperature. In this research, the cold rolling of 304L austenitic stainless steel and the transformation of austenite to strain-induced martensite and its effect on mechanical properties, especially wear, were studied. In this way, the samples were rolled in two modes and four passes in each mode. In the first case, the samples were cooled between each pass in water as a cooling liquid, and in the second case, the samples were cooled in each pass without using water and by air. Next, tests such as hardness measurement, uniaxial... 

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 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 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... 

Industrial programs are known as engine of development plans in Iran. These types of programs also known as mega projects that have multi dimension nature of the project. In fulfillment of doing mega project, consideration on many dimensions as several engineering process, complex project management issues, social responsibilities, cultural issues, and many other affecting dimensions should be done.As a point of view in successful project, the management (HAROLD KERZNER, 2006) requires finishing projects at cost, time, and quality and so on, but success of the industrial programs and mega projects also have effects on countries economy and improvements.For a country development, it is needed... 

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 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... 

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...