Study On Large Plastic Constitutive Relation Of Metallic Damping Material With High Ductility

Low-yield-strength steel damper is a new generation of structural element extensively used in energy dissipation system. Damping function is realized by using the plastic deformation of low-yield-strength steel. It has a stable and reliable performance and good energy-dissipating capacity. The low yield point of the low-yield-strength steel enables the damper to plastic deform rapidly before external load from earthquake, which impacts on main structure like buildings,to guarantee the main structure's safety. The large plastic deformation capacity of the low-yield-strength steel ensures adequate energy dissipation capacity of the damper in earthquake to absorb the energy generated by earthquake to protect main structures.This article has analyzed the dissipative characteristics of several kinds of metal materials, which commonly used for damper. The comparison of quantitative analysis of the yield strength, cyclic effect, and large plastic deformation of different metals have been made. Under the shear load, the deformation capacity of metals is larger than that on stretching condition; besides, the low-yield-strength steel has great advantages in deformation capacity and energy dissipation, comparing with other material. Therefore, this article takes the low-yield-strength steel as the research object, and performed deep study on its large deformation under multiple load conditions.The large plastic deformation of mild steel with uni-axial elongation under necking effect have been studied based on linear optimization principle, to build the precision constitutive model of mild steel with uni-axial elongation as well as constitutive model with equivalent shear. The large plastic deformation of low-yield-strength steel with monotonic shear as well as the cyclic hardening effect of material under cyclic shearing have been studied to build the constitutive model equation of mild steel under monotonic shear and recycle shear. Based on the consideration of the two yield surface model evolved from the preliminary yield strength and the consideration of the multi-axis effect of the structure under cyclic loading, the constitutive model has been optimized and corrected, and the precision constitutive model exactly depicting the large plastic deformation of mild steel damper has been built. Meanwhile, based on the established accurate material constitutive,the simplified bilinear constitutive model has been proposed and its accuracy has been verified.The accurate numerical analysis model of damper structure and accurate constitutive model of material built in this article have realized the accurate simulation of the mechanical property and deformation behavior of the damper structure from small deformation to large plastic deformation.This has significant meaning for evaluating the damper's dissipation capacity and analyzing its structure steadiness exactly. At the same time, the accurate constitutive modeling process proposed in detail by this article has an important referential meaning to the accurate constitutive modeling of large plasticity material afterwards.