Sharif Digital Repository

In this research two stage deep drawing has been analyzed by the upper bound method. During this study, the deep drawings of cylindrical parts have been analyzed. In this method, for the first stage the whole deformation region is divided into five zones including punch bottom, punch radius, between punch and die, die radius and flange. Then, the geometric equations of each zones is generated by sweeping the section curves defined on the boundary of each zone. The velocity fields are expressed in a similar manner by sweeping the boundary velocity functions. At each stage, with the change of height between punch and die, the point location is changed and movement and tension in the sheet are... 

The inverse finite element method was derived from ideal forming to predict the development blank of sheet forming process and the strain distribution according to the geometry of final product. In this project we present an inverse finite element method to obtain strain and stress distribution in final shape and design initial blank of deep drawing process. The procedure is as follows: First, strain distribution in deep drawn part is estimated by kinematics. Then by using Hill’s anisotropic plasticity and according to the associated plastic flow rule, stress distribution is obtained in deep drawn orthotropic part.Finally, initial blank is designed by considering external forces between... 

This work presents a quick method in estimation of spring back effect in sheet metal forming. In this method, the so called Inverse Finite Element Method (IFEM) has been adopted for compution of strains and also blank shape. Although the of element used is membrane, the effect of bending/ unbendiing is considered by addition of some extra forces as the bending forces to the nodal forces. The results of strain distribution obtained by IFEM are applied to another algorithm developed for computation of the spring back . this algorithm has been developed for the sections with plane starin assumption. Therefore, spring back of longitudinal parts, can be estimated by this method in a short time.... 

It is the goal of this thesis to develop an analytical model for the hydro-mechanical deep drawing (HDD) process of an axisymmetric sheet metal with the fixed gap method to evaluate the effects of some assumptions such as: proportional loading, plane stress, and constant thickness conditions. The effect of parameters on the HDD process is also studied. The main model is developed with considering the normal stress and part thickness change, non-proportional loading, bending and unbending effects at the top of the cup wall. The interrelationships between geometrical and mechanical variables are obtained in the finite difference form based on the incremental strain theory, thereby being solved... 

Recently, isogeometric methodology has been successfully implemented in one-step inverse analysis of sheet metal stamping processes. However, these models are not capable of analyzing forming processes which require severe deformation and/or several forming stages. This paper presents a multi-step inverse isogeometric methodology to enhance the precision of one-step models in predictions of the initial blank, strain distributions, and drawability of the formed parts. This methodology deals with the minimization of potential energy, deformation theory of plasticity, and considering membrane elements. The presented methodology utilizes the NURBS basis functions to create the final, middle, and... 

This research presents inverse isogeometric models based on the deformation theory of plasticity to predict the blank and strain distribution in sheet metal forming processes. In this study, the NURBS functions are utilized for both modeling of a final part and analysis of the forming process. Therefore, the developed models require only one modeling and analysis representation, in contrast to finite element models which deal with two separate modeling and analysis representations. In this research, a membrane one-step inverse isogeometric model is initially presented to analyze sheet metal forming processes. This method has various advantages such as solving the governing equations in...