Sharif Digital Repository

So far many investigations was performed in the field of energy absorption of mono and bi-layer sheets. As respects, severe plastic deformation process causes grain refinement and strength increase, there is not any study in feild of energy absorption of the severely plastic deformed sheets. The aim of this project was to investigate energy absorption of constrain groove pressed sheets by using different methods such as tensile test and wedge tear test. In this project, low carbon steel was processed by constrain groove press and mechanical properties of sheets was investigated, by using tensile test. It has been observed that ductility reduced and strength increased with increasing 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... 

Joining between aluminum alloys and steels by resistance spot welding accompanies critical technological and metallurgical difficulties. The main problem is formation of brittle intermetallic compounds (IMC) at the welding interface which results in poor mechanical properties. There are some researches based on the microstructure and mechanical properties of resistace spot welding of aluminum to steel and each of them has tried to enhance the joint properties. Using Zn interlayer is an approach to improve Al to steel resistance spot welding properties. Up to now there is few information on the influence of Zn as an interlayer between steel and aluminum on the Al/Steel dissimilar welding... 

In the present study, multistage strain aging phenomenon using rolling pre-strain and solution treatment at 680℃ for 40 min was used to study the effect of temperature and inter-pass time (IPT) on the static strain aging behavior of a low carbon steel sheet. The increase in hardness and strength caused by work hardening and the aging at each pass were separately calculated.The samples were rolled and subjected to aging process both in a single pass of 20% rolling reduction in thickness and in four stages consisted of 5% reduction at each stage. The mechanical properties of the samples aged at different time and temperature, were compared. In order to evaluate the effects of pre-strain type,... 

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.... 

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... 

Low carbon steel is widely used in the automotive industry by improving ductility and minimizing hardness to achieve greater strain. Applying severe plastic deformation to metals and alloys increases strength and decreases ductility. In the process of severe plastic deformation, the pressure is limited in the grooved form. Low carbon steel, after two passes of severe plastic deformation, experiences a rapid drop in strength in addition to ductility, which may indicate the presence of microcracks. Therefore, in this research, annealing between passes during the pressure process in the form of limited grooves has been used so that without a serious decrease in strength, some ductility... 

In recent years, various research has been done on the severe deformation of low carbon steel sheets. One of the methods used is the pressing in the grooved die, only two passes of the pressing process in the grooved mold have been successful when applied to these sheets, but on the other hand, these two passes also lessen the sheet's ductility while increasing its strength. Due to the fact that the sheet surface produced by the pressing in the grooved die is not entirely smooth, the attempt in this project was to improve the ductility to some extent using warm rolling in addition to the smoothness of the surface using higher temperature while improving the strength or maintain it. To... 

According to the conducted research, severe deformation of low-carbon steel sheets using the constrained groove pressing method causes a decrease in grain size and increases the strength and hardness of the sample after one pass. However, continuing this process in subsequent passes does not significantly increase strength and hardness, and sometimes it remains constant. Therefore, in this project, cold rolling has been used to improve the strength of the steel sheet and improve the surface smoothness of the final piece. After severe deformation and rolling due to the high applied strain, the strength of the sample increased and the percentage of its elongation decreased. Therefore,...