Investigation of the effect of initial magnetization state on the force-magnetic coupling effect of rebars

Abstract

To investigate the effect of the initial magnetization state on the force-magnetic coupling effect of rebars, magnetic field magnetization experiments and axial tensile experiments of rebars were conducted. The tangential/normal components of spontaneous magnetic leakage field (SMLF) intensity BT/N were collected. The “SMLF intensity distribution parameters” DT/N were introduced to quantify the degree of stress-induced changes in the distribution of the BN/T curves on the rebar surface. The results show that both the stress state and the initial magnetization state affect the variation pattern of SMLF intensity of rebars, and BT/N have different characteristics of the force-magnetic coupling effect. With the increase of tensile stress, BT curves shift downward and BN curves rotate counterclockwise. With the increase of magnetization, the convexity degree of BT curves and the variation range of BN curves enlarge. And both BT/N values change abruptly at the yield strength point. The initial magnetization state drives the force-magnetic coupling effects in the elastic and plastic stages to exhibit differences. The σ-DT/N curves in the elastic stage are linearly monotonically decreasing, where the σ-DT fitted straight line has a large downward slope. DT is more sensitive to stress changes. The DT/N variations in the plastic stage can effectively characterize the stable development region of plastic deformation. The modified J-A magnetomechanical model reveals the contribution of the initial magnetization state to the characterization of the force-magnetic coupling effect. The morphological analysis of the rebar microstructure clarifies the physical reasons for the SMLF variation under different stress states. This research provides a new idea for the non-destructive detection of the rebar stress state.