On Phenomenological Mechanism of Transformation Plasticity and Inelastic Behavior of a Steel Subjected to Varying Temperature and Stress –Application of Unified Transformation-Thermoplasticity Theory

Abstract

Based on the well known fact for the transformation plasticity that the plastic deformation takes placee in mother phase due to the progressing new phase when applying small stress during transformation, an simple phenomenological mechanism on pearlite and martensite transformation from austenite is discussed by considering the difference in thermal expansion coefficients : Numerical analysis of both phases connected each other shows that stress in mother phase increases to the yield level under small applied stress even lower than the yield stress, which gives the background of theory of unified transformation-thermoplastic constitutive law proposed by the present author. As an application of the theory, thermoplastic behavior for a fire resistant steel is simulated for complicated variation of stress and temperature, which shows fairly good agreement with experimental data. This may motivate to provide key knowledge for the decrease in strength of steel structure due to fire sometimes occurring after earthquake.