Determination of Tensile and Compressive Stress Strain Curves from Bend Tests

2004 ◽  
Vol 1-2 ◽  
pp. 133-138 ◽  
Author(s):  
G. Urriolagoitia-Sosa ◽  
J.F. Durodola ◽  
N.A. Fellows
Keyword(s):  
Compressive Stress ◽  
Inverse Method ◽  
Bauschinger Effect ◽  
Stress Strain ◽  
Bending Tests ◽  
Strain Behaviour ◽  
Strain Data ◽  
Tension And Compression ◽  
Bend Tests

A new inverse method has been developed for the simultaneous derivation of tensile and compressive stress strain behaviour from bending tests only. This new procedure can be applied to materials having asymmetric tensile and compressive stress strain behaviour and also materials that have been previously strain hardened (Bauschinger Effect). This paper presents results obtained using the new method and compares them with experimentally obtained tensile and compressive stress strain curves. The agreement of the derived stress strain data in tension and compression is encouraging.

A method for the simultaneous derivation of tensile and compressive behaviour of materials under Bauschinger effect using bend tests

2006 ◽  
Vol 220 (10) ◽  
pp. 1509-1518 ◽  
Author(s):  
G Urriolagoitia-Sosa ◽  
J F Durodola ◽  
A Lopez-Castro ◽  
N A Fellows
Keyword(s):  
Compressive Stress ◽  
Bauschinger Effect ◽  
Experimental Testing ◽  
Kinematic Hardening ◽  
Theoretical Data ◽  
Test Results ◽  
Stress Strain ◽  
Element Analysis ◽  
Strain Behaviour ◽  
Hardening Rules

Some materials exhibit Bauschinger effect as a consequence of strain hardening. The effect leads to asymmetric tensile and compressive stress-strain behaviour. If the hardening behaviour in either tension or compression is known, combined isotropic/kinematic hardening rules can be used to estimate the hardening behaviour in the other. These rules are, however, only approximate empirical relationships that are derived from the analysis of separate tensile and compressive test results. This article presents a method for the simultaneous derivation of tensile and compressive stress-strain behaviour from bending tests only. The information required is strains at the top and bottom surfaces of beams and moment as load is incrementally applied. The derivation of the method is based on the application of tensile and moment equilibrium conditions. The proposed method is tested on theoretical data obtained from finite-element analysis and as well as on data from actual experimental testing. The agreement between the results obtained is very good.

A General Autofrettage Model of a Thick-Walled Cylinder Based on Tensile-Compressive Stress-Strain Curve of a Material

2005 ◽  
Vol 40 (6) ◽  
pp. 599-607 ◽  
Author(s):  
X. P Huang
Keyword(s):  
Strain Hardening ◽  
Compressive Stress ◽  
Bauschinger Effect ◽  
Strain Curve ◽  
Accurate Prediction ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Perfectly Plastic ◽  
Hardening Models ◽  
Elastic Perfectly Plastic

The basic autofrettage theory assumes elastic-perfectly plastic behaviour. Because of the Bauschinger effect and strain-hardening, most materials do not display elastic-perfectly plastic properties and consequently various autofrettage models are based on different simplified material strain-hardening models, which assume linear strain-hardening or power strain-hardening or a combination of these strain-hardening models. This approach gives a more accurate prediction than the elastic-perfectly plastic model and is suitable for different strain-hardening materials. In this paper, a general autofrettage model that incorporates the material strain-hardening relationship and the Bauschinger effect, based upon the actual tensile-compressive stress-strain curve of a material is proposed. The model incorporates the von Mises yield criterion, an incompressible material, and the plane strain condition. Analytic expressions for the residual stress distribution have been derived. Experimental results show that the present model has a stronger curve-fitting ability and gives a more accurate prediction. Several other models are shown to be special cases of the general model presented in this paper. The parameters needed in the model are determined by fitting the actual tensile-compressive curve of the material, and the maximum strain of this curve should closely represent the maximum equivalent strain at the inner surface of the cylinder under maximum autofrettage pressure.

Tension—compression behaviour of annealed oxygen-free high-conductivity copper after strain cycling in the plastic range

1975 ◽  
Vol 10 (1) ◽  
pp. 10-18 ◽  
Author(s):  
P W J Oldroyd
Keyword(s):  
Bauschinger Effect ◽  
Strain Range ◽  
Compression Stress ◽  
Plastic Range ◽  
Stress Strain ◽  
Compression Properties ◽  
Compression Behaviour ◽  
Tension And Compression ◽  
Strain Cycling ◽  
Structural Strain

When copper is cycled between fixed limits of strain it ends towards a settled cyclic state. The two curves which form the tension-compression stress-strain loop will have the same shape but, no matter what point is chosen on the loop for the return to zero stress, the material will not be left with symmetrical tension-compression properties. This is because of the Bauschinger effect. It is demonstrated that the Bauschinger effect can be eliminated by cycling down to zero stress and zero strain using progressively decreasing strain amplitudes. Relatively few cycles suffice and, when the strain range is small, the structural strain-hardening effect is not noticeably reduced. Even with the largest range investigated (± 1 per cent plastic strain) the structural resoftening is slight. The significance of the subsequent tension and compression stress-strain curves is discussed.

Inverse Calculation of Uniaxial Stress-Strain Curves From Bending Test Data

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
G. S. Schajer ◽  
Y. An
Keyword(s):  
A Priori ◽  
Strain Curve ◽  
Uniaxial Stress ◽  
Inverse Solution ◽  
Surface Strain ◽  
Bending Test ◽  
Stress Strain ◽  
Strain Data ◽  
Tension And Compression ◽  
Priori Information

Uniaxial tension and compression stress-strain curves are simultaneously evaluated from load and surface strain data measured during a bending test. The required calculations for the uniaxial results are expressed as integral equations and solved in that form using inverse methods. This approach is taken to reduce the extreme numerical sensitivity of calculations based on equations expressed in differential form. The inverse solution method presented addresses the numerical sensitivity issue by using Tikhonov regularization. The use of a priori information is explored as a means of further stabilizing the stress-strain curve evaluation. The characteristics of the inverse solution are investigated using experimental data from bending and uniaxial tests.

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