Study On Cyclic Constitutive Model Of Stainless-clad Bimetallic Steel And Welded Connection

Stainless-clad(SC)bimetallic steel is a new type of high performance steel,which uses carbon steel or low alloy structural steel as the base metal and stainless steel as the cladding metal with metallurgical bonding being achieved through hot rolling or other bonding processes.The SC bimetallic steel has both the strength of base metal and the corrosion resistance of cladding mental,and has good comprehensive performance.It has significant advantages and application prospects in structural engineering.At present,the research on stainless-clad(SC)bimetallic steel is still in its infancy,but it has attracted the attention of scholars world widely.In this paper,the cyclic constitutive model of stainless-clad bimetallic steel and welded connection is studied,which provides an essential basis for seismic analysis of structures fabricated from the SC bimetallic steel.The main research work of this thesis are as follows.(1)Tests of specimens made of 316L+Q235B SC bimetallic steel with thickness of 3+5mm and 3+3mm are conducted under monotonic tension and compression loading as well as cyclic loading with 15 different loading systems.The monotonic and cyclic behavior,macro-and micro-failure are analyzed.The cyclic envelop curves are fitted by using R-O three-parameter model and compared with monotonic tensile curves.A modified constitutive model based on Chaboche model is proposed,the specific parameters are determined,and its accuracy and applicability are verified.Comparative analyses such steel with two cladding ratios on cyclic envelop curves,hysteresis curves and cyclic constitutive model are carried out.The research results provide an important basis for developing a uniform cyclic constitutive model of such advances bimetallic steel.(2)Tests of welded connection of 316L+Q235B SC bimetallic steel with a thickness of 3+5mm under monotonic and cyclic loading are conducted.The monotonic and cyclic behavior,macro-and micro-failure are analyzed.The cyclic envelop curves under partial loading spectrums are fitted by using R-O model and compared with monotonic test curves.A modified constitutive model based on Chaboche model is proposed,the specific parameters are determined,and its accuracy and applicability are verified.The welded connection and base metal of the SC bimetallic steel are compared in cyclic envelop curves and cyclic constitutive relation.The research results provide an important support for the feasibility of using weld connecting for the SC bimetallic steel structures.(3)Through mechanical processing of 316L+Q235B SC bimetallic steel with a thickness of 3+5mm,the specimens with material Q235B and 316L are obtained.Tests of specimens under cyclic system are conducted.Based on the experimental data,the cyclic constitutive model parameters of the base metal and the cladding metal are calibrated.The refined multi-layers modeling method is used to simulate the cyclic loading tests of 316L+Q235B SC bimetallic steel with thickness of 3+5mm and 3+3mm by finite element software ABAQUS.The applicability of the refined multi-layers modeling method is verified.The research results provide an important reference for the establishment of finite element model of the bimetallic steel structures.(4)The finite element models with various cladding ratios are established by refined multi-layers modeling method,and the parameters of cyclic constitutive model are calibrated.Based on parameter analysis,a cyclic constitutive unified model of bimetallic steel is proposed.By comparing the finite element calculation curves of the models with the refined multi-layers modeling method and the cyclic constitutive unified model under various cyclic loading systems,the correctness of the proposed cyclic constitutive unified model is verified.The research results provide a significant basis for simplifying the calculation of the bimetallic steel structures under earthquake.