Sharif Digital Repository

One of the oldest and most used methods in shaping metals is the formation of metal sheets. In designing the process of printing, it's important to know how much the strain on the sheet prior to slipping is. In order to predict the permissible strains in the two-axis stretch of the sheet, they introduced an empirical diagram called the shape-forming diagram. There are various methods for analyzing the formation of metallic sheets, which can be referred to by M-K method, GTN method, continuous damage mechanics method (CDM). In this research, we have tried to obtain the shape of a metal sheet in various strain paths by studying the method of CDM and modeling the mechanical behavior of the... 

A special steel beam-to-column connection, named Khor-jini, is commonly used for steel framing system in Iran. In this system, two continuous beams are passed next to the columns and are connected to the column side using seated brackets.This type of connection has been common in Iran from the late past. Unfortunately, the seismic behavior of Khorjini frames had not been sufficiently studied prior to Manjil Earthquake of 1990. Due to very large damages which occurred in steel structures especially in connections during the said earthquake, the seismic behavior of this type of connection was studied and some of its weak points were recognized.In this study non-linear... 

Concrete has long been considered by engineers as one of the most used constructional materials. Therefore, recognition of mechanical behavior of concrete materials is of particular importance. So, extensive studies have been undertaken to understand and analyze its behavior under different loading conditions. Based on these studies, many models for describing the behavior of concrete are presented. Of these, many models are based on the combination of plastic theory and damage mechanics, and by using them, significant success has been achieved in the correct modeling of concrete materials. On the other hand, one of the important loading conditions encountered by concrete structures is in... 

In the present study, by considering the damage effects, the governing equations for elastoplastic behavior of a rotating disk are derived. Then several numerical solutions are presented for specific examples. First, by means of elastic strain energy functions along with the damage appearing in the literature and irreversible Thermodynamics laws, an analytical solution is generated for a rotating disk undergoing elastic deformations. For this purpose, the components of strain tensor are obtained in terms of the damage variable and the stress tensor components. Then, by employing the damage evolution relations mixed with the damage surface relation, damage variable is derived as a function of... 

Metal and inter-metallic matrix composites offer high performance materials suitable for many low weight applications which are of growing interest in high tech industries. However, to submit their entire potential applications, their complex mechanical behavior has to be understood. Nevertheless, one of the major setbacks of designing with these materials has been the delamination phenomenon. So far, this phenomenon has been considered from macro-mechanical point of view regarding laminates to be semi-isotropic or orthotropic; which indicates the importance of micro-mechanical research to be done. Furthermore, the fact that macroscopic response and failure mechanisms of these composites are... 

Prestressed and reinforced concrete slabs are common structural elements that could be exposed to impact loading. Although, use of reinforced concrete slabs and utilization of Fiber Reinforced Polymer (FRP) as alternative to traditional steel reinforcement slabs are growing, but the influence of various parameters on their response under impact loads is not properly evaluated. In addition, studies on steel reinforced concrete slabs have been found in literature, but investigation of prestressed slabs and GFRP reinforced concrete slabs under impact load is limited. This study investigated the effect of rebar’s material, amount and arrangement of reinforcements, concrete strength and slab... 

A finite element model for seismic analysis of concrete arch dams is proposed. Material inelasticity as well as joints nonlinearity is considered. In order to provide a precise description of concrete response, a novel plastic-damage constitutive model for plain concrete is developed. For this purpose, the microplane theory is proposed for overcoming the deficiency of available anisotropic continuum plastic-damage models in reproducing the true anisotropic nature of damage in multidimensional loadings.Based on the microplane theory, the degeneration process in concrete is considered along with plastic deformations. Using the principle of strain energy equivalence, a transformation between... 

Crack nucleation and growth is unfavorable in many industrial and every day-life cases. designers’ effort is to prevent or delay it by taking into account safety and maintenance considerations; but in some industrial operations, the main target is to form a crack in a part to achieve a particular shape; and designers’ duty is to control the way it happens. so numerical modeling of this phenomena has many useful applications in preventing the structures’ failure and designing the production processes for industrial goods; and because of this, a great attention has been paid to it in the last two decades. a situation usually encountered in every day-life is the earthquake excitation which... 

In this dissertation, using experimental and numerical methods, the effects of grain morphology on the formability of sheet metals are investigated. In this regard, in the first stage, by conducting heat treatment on two different sheet metals with bcc and fcc crystal structures, different grain sizes are produced. Using metallographic observations, these grain structures are examined and the grain sizes are measured. Tensile test and Nakazima formability test have been implemented on these specimen. The grains are also shaped in the rolling process and different grain morphologies are created. In the second stage, a software has been developed to generate various grain structures and...