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Constitutive modelling of stainless steel
J. Construct. Steel Res. Vol. 46, Nos. 1-3, pp. 457. paper number 242, 1998 01998 Elsevier Science Ltd. All rights reserved Printed in Great Britain 0143-974W98 $19.00 + 0.00 PII: SOl&974x(98)00140-5 ELSEVIER
Constitutive Modelling of Stainless Steel A. Olsson Division of Steel Structures, Lulei University of Technology,
SE-971 87 Lulel, Sweden
Paper Number 242 Full paper on enclosed CD-ROM
In this paper experimental results from an extensive prograrnme of biaxial testing of three different grades of stainless steel, two austenitic and one austenitic-ferritic grade, are presented. The tests comprise one preloading and then one reloading and have been performed in the full principal stress plane (T~-cJ~,i.e. also in compression. Flat cruciform specimens have been used as this enables testing of the material as it is most commonly delivered, as flat sheet. The experimental results show a significant reduction of the yield strength in a direction opposite to preloading, i.e. the Bauschinger effect is very evident. In directions transverse to the preloading an increased yield strength has been observed. Another important observation is the gradual and direction-dependent transition from elastic to plastic state at reloading. From the experimental results it has been concluded that, in order to predict the mechanical responise at reloading of stainless steel subjected to one preloading, a constitutive model has to include these experimentally observed phenomena. A proposal of a relatively simple constitutive model, originally proposed for structural steel modified to suit stainless steel, utilizing the concept of distortional hardening is also presented. The proposed model has only three parameters more than a single surface model utilizing isotropic hardening. Compared to the simpler models normally used, i.e. models utilizing isotropic or kinematic‘hardening, large improvements of the ability to predict the mechanical response of material subjected to loadings including stress reversals has been shown. 0 1998 Elsevier Science Ltd. All rights reserved
KEYWORDS
Stainless steel, biaxial testing, constitutive modelling, plasticity, strain rate.
457
Constitutive Modelling of Stainless Steel A. Olsson Division of Steel Structures, Lulei University of Technology,
SE-971 87 Lulel, Sweden
Paper Number 242 Full paper on enclosed CD-ROM
In this paper experimental results from an extensive prograrnme of biaxial testing of three different grades of stainless steel, two austenitic and one austenitic-ferritic grade, are presented. The tests comprise one preloading and then one reloading and have been performed in the full principal stress plane (T~-cJ~,i.e. also in compression. Flat cruciform specimens have been used as this enables testing of the material as it is most commonly delivered, as flat sheet. The experimental results show a significant reduction of the yield strength in a direction opposite to preloading, i.e. the Bauschinger effect is very evident. In directions transverse to the preloading an increased yield strength has been observed. Another important observation is the gradual and direction-dependent transition from elastic to plastic state at reloading. From the experimental results it has been concluded that, in order to predict the mechanical responise at reloading of stainless steel subjected to one preloading, a constitutive model has to include these experimentally observed phenomena. A proposal of a relatively simple constitutive model, originally proposed for structural steel modified to suit stainless steel, utilizing the concept of distortional hardening is also presented. The proposed model has only three parameters more than a single surface model utilizing isotropic hardening. Compared to the simpler models normally used, i.e. models utilizing isotropic or kinematic‘hardening, large improvements of the ability to predict the mechanical response of material subjected to loadings including stress reversals has been shown. 0 1998 Elsevier Science Ltd. All rights reserved
KEYWORDS
Stainless steel, biaxial testing, constitutive modelling, plasticity, strain rate.
457