Analysis on the Seismic Performance of Steel Fiber-Reinforced High-Strength Concrete Beam–Column Joints

The present research study aims to investigate numerically the behavior of steel fiber-reinforced high-strength concrete (SFRHC) beam–column joints (BCJs) under seismic action. Based on the plastic damage constitutive model of concrete and elastic–plastic mixed-strengthen constitutive model of steel material, the finite element software ABAQUS was utilized to establish the 3D finite element (FE) model of BCJs. Additionally, the feasibility and accuracy of the numerical simulation were verified by comparing the computed results and experimental observations in terms of the hysteresis curves, skeleton curves, and failure mode. Furthermore, based on the validated FE modeling approach, load vs. displacement hysteresis curves of SFRHC–BCJs during the loading process were analyzed in detail; the failure process was also investigated. Furthermore, the effect of various parameters on the seismic behavior of BCJs was analyzed comprehensively, including the concrete strength, the volume ratio of steel fiber, and the stirrup ratio in the core area. Finally, parametric studies illustrated that increasing the concrete strength helps in enhancing the ultimate load, while the ductility decreased noticeably. Both adding the steel fiber and increasing the stirrup ratio can significantly improve the seismic performance of BCJs.

Magnetic Reversal in Wiegand Wires Evaluated by First-Order Reversal Curves

The magnetic structure of Wiegand wires cannot be evaluated using conventional magnetization hysteresis curves. We analyzed the magnetization reversal of a Wiegand wire by measuring the first-order reversal curves (FORCs). A FeCoV Wiegand wire with a magnetically soft outer layer and a hard magnetic core was used in this study. The magnetization reversal of the soft and hard regions in the wire was identified in the FORC diagrams. The magnetization reversal of the dominantly irreversible process of the soft layer and the magnetic intermediate region between the soft and hard regions was clarified.

A novel two-input asymmetric dynamic cross-coupled hysteresis modeling and identification for piezoelectric stack actuators

Piezoelectric Stack Actuators (PEAs) have been widely used in high-precision positioning system because of its fast response. However, under different excitation voltages and external loads with dynamic frequencies, the width and inclination of PEAs hysteresis curves verified correspondingly, and exhibit asymmetry phenomenon. The main contribution of this paper is to present a two-input asymmetric dynamic cross-coupled hysteresis (TADCH) model to describe the complex nonlinear hysteresis of PEAs in dynamic excitation and loading engineering applications. Moreover, we also develop the corresponding identification method of TADCH model. Finally, several experiments are carried out to verify the accuracy of the proposed model.

Second magnetization peak, rhombic-to-square Bragg vortex glass transition, and intersecting magnetic hysteresis curves in overdoped BaFe2(As1−xPx)2 single crystals

The second magnetization peak (SMP) in the fourfold symmetric superconducting single crystals (such as iron pnictides and tetragonal cuprates) has been attributed to the rhombic-to-square transition (RST) of the quasi-ordered vortex solid (the Bragg vortex glass, BVG). This represents an alternative to the pinning-induced BVG disordering as the actual SMP mechanism. The analysis of the magnetic response of BaFe2(As1−xPx)2 specimens presented here shows that the SMP is not generated by the RST. However, the latter can affect the pinning-dependent SMP onset field if this is close to the (intrinsic) RST line, through the occurrence of a “shoulder” on the magnetic hysteresis curves m(H), and a maximum in the temperature variation of the DC critical current density. These features disappear in AC conditions, where the vortex system is dynamically ordered in the RST domain, emphasizing the essential role of vortex dislocations for an efficient accommodation of the vortex system to the pinning landscape and the SMP development. The m(H) shoulder is associated with a precipitous pinning-induced proliferation of dislocations at the RST, where the BVG elastic “squash” modulus softens. The DC magnetization relaxation indicates that the pinning-induced vortex system disordering continues above the RST domain, as the basic SMP mechanism.

A new hysteresis model for magneto–rheological dampers based on Magic Formula

This paper investigates a novel model based on the Magic Formula and the Pan’s model to effectively predict the inherent nonlinear hysteresis behavior of magneto–rheological (MR) dampers. In the proposed model, the hysteresis element is employed from the Magic Formula and Pan’s model, and two new independent horizontal shift parameters, which are separated from one original parameter of the Pan’s model, are added. Each of them characterizes an offset with respect to the origin for each branch of hysteresis curves, providing more flexibility and effectiveness for simulating curves with high asymmetry. In addition, a parameter to further control the sharpness of hysteresis curves in the backward region of damping force–velocity is proposed, which is useful to simulate the behavior of MR dampers in rather extreme operating cases. A case study is performed on a prototype MR damper for washing machines, in which the model incorporates applied current and excitation frequency as variables to make it more adaptable to a wide range of working conditions. For comparison, performance of three hysteresis models, including the Spencer’s model, the Pan’s model and the proposed model, are analyzed and evaluated. The research results show that, as compared with the others, the proposed model can not only predict the nonlinear hysteresis behavior of MR dampers more precisely, but is also more compatible with different operating excitations, and the clearer meanings of the model parameters make them easier to study and identify.