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Forming limit diagram of tubular hydroformed parts considering the through-thickness compressive normal stress
, Article Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications ; Volume 230, Issue 1 , 2016 , Pages 332-343 ; 14644207 (ISSN) ; Abri Nia, K ; Assem Pour, A ; Khakpour Nejadkhaki, H ; Shahbazi Mastan Abad, A ; Sharif University of Technology
SAGE Publications Ltd
Abstract
In this study, the effect of a compressive normal stress has been considered in the determination of forming limit diagrams and forming limit stress diagrams to predict neck initiation failure in tube hydroforming of T-shaped parts. Computation of the forming limit diagrams and FLSDs is based on the generalized Marciniak and Kuczynski method to consider the existence of through-thickness compressive normal stress. The proposed forming limit diagrams and FLSDs were used in conjunction with ABAQUS/EXPLICIT finite element simulations to predict the onset of necking in tube hydroforming of T-shaped part. The amount of calibration pressure and axial feeding required to produce an acceptable part...
An upper bound approach for analysis of hydroforming of sheet metals
, Article International Journal of Engineering, Transactions B: Applications ; Volume 17, Issue 4 , 2004 , Pages 389-398 ; 1728-144X (ISSN) ; Bagherzadeh, M ; Emami, M. R ; Sharif University of Technology
Materials and Energy Research Center
2004
Abstract
Considering a kinematical velocity admissible field, the upper bound method has been used for predicting the amount of pressure in hydroforming of sheet metals. The effects of work hardening, friction and blank size have been considered in pressure prediction. Also the effect of sheet thickness variation has been considered in the present work formulations. The relation between pressure and punch stroke has been obtained and optimized by changing the selective parameters in the velocity components. The results for cylindrical and hemispheric parts have been obtained and compared with the published experimental results. The effects of work hardening, friction and blank size on hydroforming...
Application of Inverse Finite Element in Tube Hydroforming
, M.Sc. Thesis Sharif University of Technology ; Assempour, Ahmad (Supervisor)
Abstract
The inverse Finite Element method (IFEM) has been used for estimation of the initial length of tube, axial feeding and fluid pressure in tube hydroforming. The already developed IFEM algorithm, which has been used in this work, is based on the total deformation theory of plasticity. Although the nature of tube hydroforming is three-dimensional deformation, a technique has been used to perform the computations in two-dimensional space. Therefore, compared with conventional forward finite element methods, the present computations are quite fast with no try and error process. The solution provides all the components of strain. Using the forming limit diagram (FLD), the components of strain can...
Development of a model for Hydro-Mechanical Deep Drawing Process to Analyze the Effects of Assumptions and Parameters
, M.Sc. Thesis Sharif University of Technology ; Assempour, Ahmad (Supervisor)
Abstract
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...
The strain gradient approach to predict necking in tube hydroforming
, Article Journal of Manufacturing Processes ; Volume 15, Issue 1 , 2013 , Pages 8-13 ; 15266125 (ISSN) ; Abrinia, K ; Assempour, A ; Sharif University of Technology
2013
Abstract
A stress-based forming limit diagram for necking prediction which is based on the strain gradient theory of plasticity in conjunction with the M-K model has been represented and used in tube hydroforming. In this study, the finite element model for bulge forming of straight tube has been constructed and verified with published experimental data. The adaptive simulation technique is based on the ability to detect the onset and growth of defects (e.g., wrinkling, and bursting) and to promptly readjust the loading paths. Thus, a suitable load path has been obtained by applying Adaptive Simulation Method in ANSYS Parametric Design Language (APDL)
The effect of normal stress on hydro-mechanical deep drawing process
, Article International Journal of Mechanical Sciences ; Volume 53, Issue 6 , 2011 , Pages 407-416 ; 00207403 (ISSN) ; Taghipour, E ; Sharif University of Technology
2011
Abstract
Normal stress has some role in the deformation analysis of hydroforming processes. In this study, analytical modeling is pursued to evaluate the effect of normal stress on the hydro-mechanical deep drawing (HDD) process. Analyses are carried out for axisymmetric elements of the formed cup-shaped part for increments of the punch travel. The formulations are obtained using mechanical and geometrical relations and the finite difference method, thereby being solved by proper numerical algorithms. Furthermore, in the present work, part thickness is variable, the loading and straining are non-proportional, and bending/unbending effects over the part curvature are considered. The results show that...
An analytical approach in prediction of necking and suitable load path in tube hydroforming by using the strain gradient
, Article SAE Technical Papers, 20 April 2009 through 20 April 2009, Detroit, MI ; 2009 ; Masoumi, E ; Safikhani, A. R ; Hashemi, R ; Abrinia, K ; Sharif University of Technology
Abstract
A theoretical forming limit stress diagram (FLSD) for necking prediction which is based on the strain gradient theory of plasticity in conjunction with the M-K approach was represented and used in tube hydroforming. This approach introduces an internal length scale into conventional constitutive equations and takes into account the effects of deformation inhomogeneity and material softening. The nonlinear second order ordinary differential equation of the thickness of tube has been solved by collocation method. It has been shown that this method overcomes the imperfection sensitivity encountered in the conventional M-K method. The predicted FLSD has been compared with published experimental...