Aquesta és una còpia de la versió author's final draft d'un article publicat a la revista Materials and Design. ABSTRACTThere is a wide variety of stainless steel alloys, but all are characterized by a rounded stressstrain response with no sharply defined yield point. This behaviour can be represented analytically by different material models, the most popular of which are based on the RambergOsgood formulations or extensions thereof. The degree of roundedness, the level of strain hardening, the strain at ultimate stress and the ductility at fracture of the material all vary between grades, and need to be suitably captured for an accurate representation of the material to be achieved. The aim of the present study is to provide values and predictive expressions for the key parameters in existing stainless steel material models based on the analysis of a comprehensive experimental database. The database comprises experimental stress-strain curves collected from the literature, supplemented by some tensile tests on austenitic, ferritic and duplex stainless steel coupons conducted herein. It covers a range of stainless steel alloys, annealed and cold-worked material, and data from the rolling and transverse directions. In total, more than 600 measured stress-strain curves have been collected from 15 international research groups. Each curve from the database has been analysed in order to obtain the key material parameters through a curve fitting process based on least squares adjustment techniques. These parameter values have been compared to those calculated from existing predictive models, the 2 accuracy of which could therefore be evaluated. Revised expressions providing more accurate parameter predictions have been proposed where necessary. Finally, a second set of results, containing material parameters reported directly by others, with information of more than 400 specimens, has also been collected from the literature. Although these experimental results were not accessible as measured raw data, they enabled further confirmation of the suitability of the proposed equations. KEYWORDSConstitutive law, material modelling, nonlinear stress-strain behaviour, stress-strain curves, stainless steel, tensile tests HIGHLIGHTS Tensile tests on austenitic, ferritic and duplex stainless steel coupons are presented. A database of over 600 stainless steel stress-strain curves has been collected.
Stainless steel tubular members are employed in a range of load-bearing applications due to their strength, durability and aesthetic appeal. From the limited existing test data on stainless steel circular hollow sections (CHS) columns it has been observed that the current Eurocode 3 provisions can be unconservative in their capacity predictions. A comprehensive experimental programme has therefore been undertaken to provide benchmark data to validate numerical models and underpin the development of revised buckling curves; in total 17 austenitic, 9 duplex and 11 ferritic stainless steel CHS column buckling tests and 10 stub column tests have been carried out. Five di↵erent cross-section sizes (covering class 1 to class 4 sections) and a wide range of member slendernesses have been examined. The experiments were initially replicated using finite element (FE) simulations; the validated FE models were then used to generate 450 additional column buckling data points. On the basis of the experimental and numerical results, new design recommendations have been made for cold-formed stainless steel CHS columns and statistically validated according to EN 1990 (2005).
An investigation into the material response and local buckling behaviour of ferritic stainless steel structural cross-sections is presented in this paper. Particular attention is given to the strain hardening characteristics and ductility since these differ most markedly from the more common austenitic and duplex stainless steel grades. Based on collated stress-strain data on ferritic stainless steel, key aspects of the material model given in Annex C of EN 1993-1-4 [1] were evaluated and found to require adjustment. Proposed modifications are presented herein.The local buckling behaviour of ferritic stainless steel sections in compression and bending was examined numerically, using the finite element (FE) package ABAQUS. The studied section types were cold-formed square hollow sections (SHS), rectangular hollow sections (RHS) and channels, as well as welded I-sections. The models were first validated against experimental data collected from the literature, after which parametric studies were performed to generate data over a wide range of section geometries and slendernesses. The obtained numerical results, together with existing experimental data from the literature were used to assess the applicability of the slenderness limits and effective width formulae set out in EN 1993-1-4 [1] to ferritic stainless steel sections.The comparisons of the generated FE results for ferritic stainless steel with the design provisions of EN 1993-1-4 [1], highlighted, in line with other stainless steel grades, the inherent conservatism associated with the use of the 0.2% proof stress as the limiting design stress. To overcome this, the continuous strength method (CSM) was developed as an alternative design approach to exploit the deformation capacity and strain hardening potential of stocky cross-sections. An extension of the method to ferritic stainless steels, including the specification of a revised strain hardening slope for the CSM material model, is proposed herein. Comparisons with test and FE data showed that the CSM predictions are more accurate and consistent than existing provisions thus leading to significant material savings and hence more efficient structural design.
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