بررسي پارامترهاي موثر در چروكيدگي در فرآيند كشش عميق هيدرومكانيكي به كمك شبيه سازي اجزاء محدود

چكيده انگليسي :

Study of Effective Parameters in Wrinkling by Hydromechanical Deep Drawing Process Using FE Simulation Hamed Ziaeipoor h ziaeipoor@me iut ac ir Date of Submission 2010 12 12 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Hasan Khademizadeh hkhademyza@cc iut ac ir Hasan Moosavi moosavi@cc iut ac ir Abstract Hydroforming is an efficient technique to enable economical production of complicated parts Among the different methods derived from the basic hydroforming configuration hydromechanical deep drawing HDD process has particular advantages in manufacturing cup type components Compared with the conventional deep drawing CDD process in HDD method because of counter pressure profile enables the manufacture with more complex forms and the drawing of the sheet to a greater extent HDD process is the most well known and greatly used method for production of a broad spectrum of parts in simple home products up to aircraft complicated parts Higher economic efficiency and flexibility can be achieved by using this process the part quality and thickness distribution obtain by using HDD process is better than CDD process this is due to the blank compressed to the punch surface which is caused by counter pressure profile Wrinkling is one of the major defects that occurs in sheet metals formed by CDD process Wrinkling is a kind of buckling phenomenon that prevents from forming of the sheet During the deep drawing of axisymmetric cups the value of the blank holder force BHF is an important factor to eliminate wrinkling and also not to cause fracture If the BHF is low wrinkling may occur And also if BHF is too high fracture will occur If a constant BHF is used then the BHF should be kept within a certain operating range to obtain the desired depth Considering the fact that different modes of failure becomes important at different punch displacement during the deformation the BHF does not have to be kept constant throughout the deformation Wrinkling at the beginning of the deformation due to large compressive stresses in the flange of the cup will occur Furthermore as the deformation progresses radial stresses buildup in the wall of the cup and fracture may occur due to an excessive amount of stretching Therefore the BHF should be varied during the forming process instead of being kept constant In this project at first a theoretical analysis has been done then and the effect of hydrostatic pressure on wrinkling and rupturing in HDD process of hemispherical cups was investigated numerically Beginning of the stage of wrinkling and growth of wrinkles in the flange area is considered and Hill s yield function for simulation of HDD process was used Furthermore forming limit diagram FLD damage criterion has been used for determining rupture instability The results of CDD process and HDD process compared and height of wrinkles in the flange area and major and minor strain distribution for HDD and CDD processes determined In the next section the effect of tool design variables such as punch die clearance and friction factor and etc on HDD process of cylindrical cups was discussed And in the final section an numerical investigation on control of the BHF in HDD process is carried out Also a profile for the BHF with using an new method based on punch force is proposed Finite element analysis FEA codes could be used to understand the deformation behavior of a material during the forming process and therefore Abaqus Explicit was used for simulations of processes Key Words Hydromechanical Deep Drawing Wrinkling Finite Element Method Blank Holder Force

ضيايي پور، حامد

بررسي پارامترهاي موثر در چروكيدگي در فرآيند كشش عميق هيدرومكانيكي به كمك شبيه سازي اجزاء محدود

نيروي ورق گير