Stainless steel plasticity material modelling and structural applications

University dissertation from Luleå : Luleå tekniska universitet

Abstract: The thesis addresses stainless steel in construction with focus on plasticity and shear resistance of welded girders respectively. In the area of plasticity it comprises an account of an experimental study with emphasis on phenomenological observations followed by theorethical modelling. the area of shear resistance comprises an experimental study and a numerical interpolative study that together were used to arrive at a proposed design procedure. The plastic behaviour was studied utilizing a concept for biaxial testing of cross-shaped specimen that allow for tests in the full principal stress plane, i.e. also in compression. Results showed pronounced Bauschinger as well as cross effects. From the results it was concluded that the response to loadings subsequent to an initial loading is depending on the level of plastic strains in the first as well as the direction of the subsequent loading. Based on the test results a constitutive model was formulated within the area of the mathematical theory of plasticity. A distortion concept that enable good predictions of subsequent yield criteria was utilized. The gradual transition from elastic to plastic state at subsequent loadings is described with the concept of a transition surface which is used to modify the plastic modulus at subsequent loadings. The constitutive model presented is a large improvement compared to commonly used models. Test results with respect to shear resistance of welded girders showed that available design procedures under estimate the resistance with respect to shear. Based on the test results and results from a numerical study a new design procedure based on rotated tension fields was developed. The proposed design procedure is an improvement compared to available design procedures.

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