新型耐火耐候钢材高温力学性能与本构模型研究

MECHANICAL PROPERTIES AND CONSTITUTIVE MODEL OF AN INNOVATIVE FIRE-RESISTANT WEATHERING STEEL AT ELEVATED TEMPERATURES

采用标准试验方法,对首钢集团生产的楼承板用SQ410FRW耐火耐候钢冷轧钢带进行稳态拉伸试验,以测定其典型高温力学性能指标,包括钢材高温弹性模量、规定塑性延伸强度、抗拉强度、断后伸长率和断面收缩率。通过非线性回归方法得出相应的高温折减系数表达式,包括弹性模量折减系数、规定塑性延伸强度折减系数和抗拉强度折减系数。根据试验应力-应变关系曲线,回归得出基于Ramberg-Osgood模型(R-O模型)的应力-应变本构模型,以用于后续有限元参数化建模过程中对结构构件的温度场分析和顺序热力耦合分析。试验结果表明:绝大多数拉伸试样均在平行段内或标距段内发生断裂,且断后伸长率随温度升高呈现总体增大趋势;高温弹性模量、高温规定塑性延伸强度和抗拉强度在600℃及以下时降低较少,均保持在常温名义值的60%以上,基本满足耐火钢的力学性能指标要求;基于R-O模型的应力-应变本构关系表达式的拟合优度均在90%以上,与试验应力-应变曲线吻合良好,故提出的本构模型可用于相关钢结构或组合结构构件的有限元抗火分析。

Based on the standard test method,the steady-state tensile coupon testing on SQ410FRW fire-resistant weathering cold rolled steel strips for floor decking system manufactured by Shougang Group,was carried out in order to investigate their characteristic mechanical properties at elevated temperatures.These properties mainly include high-temperature modulus of elasticity,proof strength at specified plastic strain,tensile strength,percentage elongation after fracture and percentage reduction of cross section.The corresponding expressions for the reduction factors were obtained by nonlinear regression method,so as to represent the high-temperature mechanical performance indicators.The stress-strain constitutive model was further established by adopting Ramberg-Osgood model for the experimental stress-strain relation curve.The model will be applied in the subsequent finite element parametric modelling,aiming at the thermal analysis and sequentially coupled thermal stress analysis of structural members.The following conclusions are drawn from the test results:Most tensile specimens show fracture within the gauge length,and the percentage elongation after fracture increases with temperature rising.The high-temperature modulus of elasticity,proof strength at specified plastic strain and tensile strength drop slowly under 600℃,and still maintain over 60%of nominal values at room temperature,basically meeting the requirements of the properties of fire-resistant steel.The fitting goodness of stress-strain constitutive model all exceeds 90%,showing good agreement with the experimental stress-strain curves.Therefore,the proposed constitutive model can be applied in the finite element analysis of the fire resistance of relevant structural members.