An Investigation of ductile fracture criteria for sheet metal forming /

Abbasnejad Dizaji, Shahram
Deep drawing is a sheet metal forming process in which a sheet metal stock, commonly referred to as a blank, is drawn into a die by a punch. Forming limit diagram (FLD), a representation of the critical combination of the principal surface strains, is an important concept utilized for the evaluation of the formability of sheet metals. Most of the theoretical methods for determining FLDs are strain-path dependent and cannot exactly clarify the location of necking or fracture. Using stress-based forming limits (FLSD) can resolve this problem, but numerical implementations of the FLSDs are difficult and sometimes not reliable. Another way to determine the limits of formability is to apply a ductile fracture criterion (DFC). The main goal of ductile fracture criteria is to predict the location of the fracture in the sheet metals and overcome the deficiency of strain path dependency of FLDs. The objective of the present thesis work is to develop a robust DFC for sheets. The algorithm of proposed criterion is implemented into a commercial explicit finite element code by using user-defined material subroutines. Recently developed constitutive models are used with appropriate hardening rules in the explicit code. The results of numerical implementations are compared with the results of the other known criteria and the experimental tests to validate the newly developed criterion. It is observed that the newly developed ductile fracture criterion can be used efficiently for different materials and predicts the fracture initiation better than the existing DFCs.


Investigating the effect of deformation and annealing texture on magnetic anisotropy in low-C steel sheets by magnetic Barkhausen noise method
Akçaoğlu, Fehmi Ümit; Gür, Cemil Hakan; Department of Metallurgical and Materials Engineering (2013)
Deformation and annealing texture in the cold rolled low carbon steels is important for sheet metal forming operations and service performance. The aim of this study is to non-destructively investigate the effect of texture on magnetic anisotropy. Various samples having different textures and residual stress states, due to different % reduction in thickness, annealing and stress relieving treatment, were prepared. Texture maps were obtained by Magnetic Barkhausen noise measurements performed with 100 steps ...
Determining surface residual stress in steel sheets after deep drawing and bulging processes
Adıgüzel, Sinem; Gür, Cemil Hakan; Karadoğan, Celalettin; Department of Metallurgical and Materials Engineering (2011)
The aim of this thesis is to investigate the effects of bulging and deep drawing processes on St4 cold rolled steel by simulation and experimental characterization. In the simulations, commercial software programs MSC Marc and Simufact.forming were used. The experimental studies cover metallographic investigations, hardness measurements, and residual stress measurements. Residual stress measurements were carried out by different non- destructive characterization methods; X-ray diffraction and Magnetic Barkh...
Experimental and numerical analysis of compression on a forging press
Biçer, Gökhan; Gökler, Mustafa İlhan; Department of Mechanical Engineering (2010)
Forging is a metal forming process which involves non-linear deformations. Finite element and finite volume software programs are commonly used to simulate the process. In these simulations, material properties are required. However, stress-strain relations of the materials at some elevated temperatures are not available in the material libraries of the related software programs. In this study, the stress-strain curves have been obtained by applying the Cook and Larke Simple Compression Test to AISI 1045 st...
The effect of strain rate and temperature on forming limit diagram for DKP-6112 and AZ31 materials
Goksen, Seckin; Darendeliler, Haluk (2020-01-01)
Forming limit diagrams (FLDs) are used in sheet metal operations widely for predicting blank fracture and forming characteristics of materials. There are three approaches for building forming limit diagrams which are the experimental, theoretical and numerical methods. Experimental method, which includes Nakazima formability test, is generally preferred for determining forming limit diagrams, although it requires complex experimental setup and effort. This study, firstly, compares the experimentally determi...
Effect of constitutive modeling in sheet metal forming
Uçan, Meriç; Darendeliler, Haluk; Department of Mechanical Engineering (2011)
This study focuses on the effects of different constitutive models in sheet metal forming operations by considering the cylindrical and square cup drawing and V-bending simulations. Simulations are performed using eight different constitutive models; elastic plastic constitutive model with isotropic hardening, elastic plastic constitutive model with kinematic hardening, elastic plastic constitutive model with combined hardening, power law isotropic plasticity, piecewise linear isotropic plasticity, Barlatth...
Citation Formats
S. Abbasnejad Dizaji, “An Investigation of ductile fracture criteria for sheet metal forming /,” Ph.D. - Doctoral Program, Middle East Technical University, 2014.