悬索桥主缆平行钢丝动态接触与滑移机理研究

Research on Dynamic Contact and Slip Mechanisms of Parallel Steel Wires in the Main Cable of Suspension Bridge

为揭示悬索桥主缆钢丝动态接触与滑移机理,运用自制钢丝动态接触与滑移试验台开展单摩擦周期中平行钢丝间动态接触与滑移试验,通过高速度数码显微系统原位观测、扫描电子显微镜、能谱仪和有限元仿真揭示了平行钢丝间动态接触和滑移特性(横向滑移、纵向变形、接触状态、摩擦力、摩擦因数、应力分布)及磨损机理(磨痕形貌和元素分布)及其受到横向和纵向接触位置、循环周次、滑移幅值和接触载荷的影响规律。结果表明:在单摩擦周期中,钢丝间动态接触状态均为黏着-完全滑移-黏着-完全滑移,钢丝横向滑移和摩擦力均呈增加-稳定-减小-稳定-增加的变化趋势,上、下钢丝纵向变形总体呈相反变化趋势。固定的下钢丝沿上钢丝运行方向的横向位置及与接触面距离增大方向的纵向位置的横向滑移和纵向变形均降低。循环周次增加导致下钢丝的横向滑移和纵向变形均增加,摩擦因数呈增加-减小-增加-稳定变化趋势,磨损机理包括黏着磨损、磨粒磨损、挤压磨损、疲劳磨损。滑移幅值和接触载荷的增加均导致冲程第2阶段下钢丝横向变形均值增大,分别导致上、下钢丝纵向变形波动幅值增大、纵向变形差异性变化,摩擦因数分别增大和降低,磨损机理包括黏着磨损、挤压磨损、疲劳磨损和磨粒磨损。

In order to reveal dynamic contact and slip mechanisms of steel wires in the main cable of suspension bridge, a self-made dynamic contact and slip test rig of steel wires is employed to carry out dynamic contact and slip tests between parallel steel wires in a single friction cycle. The in-situ observation by high-speed digital microscope system, scanning electron microscope, energy spectrometer and finite element simulation were employed to reveal effects of transverse and longitudinal contact locations, number of cycles, slip amplitude and contact load on dynamic contact and slip characteristics between parallel steel wires(transverse slip, longitudinal deformation, contact state, friction force, coefficient of friction, and stress distribution) and wear mechanisms(wear scar morphology and element distribution). The results show that in a single cycle, dynamic contact states between steel wires are adhesion, gross slip, adhesion and gross slip, respectively. The transverse slip and and friction force of steel wire both exhibit change trends of an increase, the stabilization, a decrease and the the stabilization. Longitudinal deformations of upper and lower steel wires present the overall reverse change trends. Increases of fatigue cycles cause both increases in the transverse slip and longitudinal deformation of lower steel wire. The coefficient of friction shows the change trends of an increase at first, then a decrease, afterwards an increase and the final stabilization with increasing fatigue cycles. Increases of displacement amplitude and contact load cause increases in the average value of transverse deformation at stage 2 of the stroke, and the fluctuation amplitudes of longitudinal deformations of upper and lower steel wires. The coefficient of friction presents an increase and a decrease with increasing displacement amplitude and contact load, respectively. Wear mechanisms consist of adhesive wear, abrasive wear, extrusion wear and fatigue wear in all cases.