Experimental and Numerical Investigation of Kinematic Hardening Behavior in Sheet Metals

2007 ◽  
Author(s):  
Hang Shawn Cheng ◽  
Wonoh Lee ◽  
Jian Cao ◽  
Mark Seniw ◽  
Hui-ping Wang ◽  
...  
Keyword(s):  
Numerical Investigation ◽  
Kinematic Hardening ◽  
Sheet Metals ◽  
Hardening Behavior

Experimental and numerical investigation of combined isotropic-kinematic hardening behavior of sheet metals

2009 ◽  
Vol 25 (5) ◽  
pp. 942-972 ◽  
Author(s):  
Jian Cao ◽  
Wonoh Lee ◽  
Hang Shawn Cheng ◽  
Mark Seniw ◽  
Hui-Ping Wang ◽  
...  
Keyword(s):  
Numerical Investigation ◽  
Kinematic Hardening ◽  
Sheet Metals ◽  
Hardening Behavior

Generation of Cyclic Stress-Strain Curves for Sheet Metals

2000 ◽  
Author(s):  
K. M. Zhao ◽  
J. K. Lee
Keyword(s):  
Constitutive Model ◽  
Kinematic Hardening ◽  
Optimization Procedure ◽  
High Strength ◽  
Cyclic Stress ◽  
Bending Moments ◽  
Sheet Metals ◽  
Stress Strain ◽  
Normal Anisotropy ◽  
Material Parameters

Abstract The main objective of this paper is to generate cyclic stress-strain curves for sheet metals so that the springback can be simulated accurately. Material parameters are identified by an inverse method within a selected constitutive model that represents the hardening behavior of materials subjected to a cyclic loading. Three-point bending tests are conducted on sheet steels (mild steel and high strength steel). Punch stroke, punch load, bending strain and bending angle are measured directly during the tests. Bending moments are then computed from these measured data. Bending moments are also calculated based on a constitutive model. Normal anisotropy and nonlinear isotropic/kinematic hardening are considered. Material parameters are identified by minimizing the normalized error between two bending moments. Micro genetic algorithm is used in the optimization procedure. Stress-strain curves are generated with the material parameters found in this way, which can be used with other plastic models.

Non-Linear Kinematic Hardening Identification for Anisotropic Sheet-Metals With Bending-Unbending Tests

2000 ◽  
Author(s):  
M. Brunet ◽  
F. Morestin ◽  
S. Godereaux
Keyword(s):  
Kinematic Hardening ◽  
Bending Moment ◽  
Complex Loading ◽  
Sheet Metals ◽  
Element Analysis ◽  
Initial Anisotropy ◽  
Non Linear ◽  
Identification Technique ◽  
Stress Behaviour ◽  
Constitutive Parameters

Abstract An inverse identification technique is proposed based on bending-unbending experiments on anisotropic sheet-metal strips. The initial anisotropy theory of plasticity is extended to include the concept of combined isotropic and non-linear kinematic hardening. This theory is adopted to characterise the anisotropic hardening due to loading-unloading which occurs in sheet-metals forming processes. To this end, a specific bending-unbending apparatus has been built to provide experimental moment-curvature curves. The constant bending moment applied over the length of the specimen allows to determined numerically the strain-stress behaviour but without Finite Element Analysis Four constitutive parameters have to be identified by an inverse approach. Our identification results show that bending-unbending tests are suitable to model quite accurately the constitutive behaviour of sheet metals under complex loading paths.

The Effect of the Initial Stress and Strain State in Sheet Metals on the Roller Levelling Process

2015 ◽  
Vol 651-653 ◽  
pp. 1023-1028 ◽  
Author(s):  
Markus Grüber ◽  
Marius Oligschläger ◽  
Gerhard Hirt
Keyword(s):  
Process Control ◽  
Initial Stress ◽  
Sheet Metal ◽  
Process Parameters ◽  
Kinematic Hardening ◽  
Sheet Material ◽  
Stress And Strain ◽  
Fe Model ◽  
Sheet Metals ◽  
Initial State

Due to increasing requirements regarding the flatness of sheet metals, the process of roller levelling is of particular importance. The process itself is influenced by a high number of parameters such as machine design, sheet dimension, and material properties. Therefore, it is desirable to provide an online process control to react on changes of those process parameters. One possible approach for the layout of a process control and the identification of reference values is the use of the Finite Element Method (FEM). Considering the alternate bending a sheet metal undergoes when passing through a roller leveller, kinematic hardening of the sheet material must be taken into account. Additionally, the initial stress and strain distribution of the sheet metal – e.g. induced by coiling – has an influence on the material behaviour and consequently on the process parameters. With respect to these effects, a coupled FE model, which accounts for the initial state of the sheet metal, is introduced. An inverse calculation of material parameters describing the behaviour under cyclic load conditions has been done for an aluminium alloy AA5005 and a mild steel DC01. Based on this numerical setup, the influence of the initial stress state in the pre-levelled sheet metal on the roller levelling process has been deduced. Accompanying experiments on a down-sized roller leveller were carried out for a validation of the numerical setup.

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