长孔螺栓板式摩擦耗能器滞回性能试验研究

设计一种长孔螺栓板式摩擦耗能器,通过低周往复荷载试验重点研究了螺栓预紧力、滑动位移幅值和摩擦片等因素对摩擦耗能器滞回性能的影响.试验结果表明:长孔螺栓板式摩擦耗能器滞回曲线接近理想矩形,耗能器在多次循环荷载作用下耗能能力强,工作性能稳定;随预紧力吨位的增加,耗能器滑动界面抵抗机理由摩擦型向摩擦-咬合型转变,咬合作用提高了耗能器的滑动荷载;长孔螺栓板式耗能器最大稳定滑动摩擦力达178.66 kN,能较好的满足新建工程和加固工程的需要.在试验研究基础上,建立了长孔螺栓板式摩擦耗能器的恢复力模型,模型与试验结果吻合良好,具有较强的适用性.

抗震锚索及其应用

介绍了一种新型预应力锚固结构——抗震锚索，它通过可调节控制锚固力大小的内锚具，有效地耗散地震能量，与此同时为边坡岩土体提供足够的支护抗力确保边坡安全。工程应用表明，该锚索结构安全可靠，可用于高烈度地震区、爆破与振动环境下岩土锚固。

钢板橡胶复合耗能器试验研究

对一种新型钢板橡胶复合耗能器进行了试验研究,结果表明,钢板橡胶复合耗能器的耗能效果与螺栓扭矩大小线性相关。该耗能器滞回曲线呈菱形,且在疲劳荷载作用下耗能效果良好,工作性能稳定。增大预紧螺栓扭矩值,耗能器的启滑位移显著降低,刚度和滑动摩擦力随之增大。在设定扭矩下,该型耗能器最大稳定耗能摩擦力达178. 79kN,且试验结果与拟合计算吻合良好,为钢板橡胶复合耗能器的结构优化设计及工程运用提供了依据。

Friction and wear properties of in-situ synthesized Al_2O_3 reinforced aluminum composites

Al-5%Si-AI2O3 composites were prepared by powder metallurgy and in-situ reactive synthesis technology. Friction and wear properties of Al-5%Si-Al2O3 composites were studied using an M-2000 wear tester. The effects of load, sliding speed and long time continuous friction on friction and wear properties of Al-5%Si-Al2O3 composites were investigated, respectively. Wear surface and wear mechanism of Al-5%Si-Al2O3 composites were studied by Quanta 200 FE-SEM. Results showed that with load increasing, wear loss and coefficient of friction increased. With sliding speed going up, the surface temperature of sample made the rate of the producing of oxidation layer increase, while wear loss and coefficient of friction decreased. With the sliding distance increasing, coefficient of friction increased because the adhesive wear mechanism occurred in the initial stage, then formation and destruction of the oxide layer on the surface of the sample tended to a dynamic equilibrium, the surface state of the sample was relatively stable and so did the coefficient of friction. The experiment shows that the main wear mechanism of Al-5%Si-Al2O3 composites includes abrasive wear, adhesive wear and oxidation wear.

Optimization of friction and wear behaviour of Al-Si_3N_4 nano composite and Al-Gr-Si_3N_4 hybrid composite under dry sliding conditions

The tribological behaviour of gravity die stir cast LM6alloy with graphite(Gr)and silicon nitride nanoparticles was investigated.Al?Gr?Si3N4hybrid composite,Al?Si3N4nanocomposite and Al?Gr nanocomposites were separately fabricated to investigate their frictional and wear characteristics under dry sliding conditions.EDS was used to ensure the uniform presence of nano Si3N4and graphite in the cast.L9orthogonal array method was chosen to conduct the experiments to study the effect of different applied loads(20,30and40N)and sliding distances(1,2and3km).The results showed that the respective wear rate and coefficient of friction(COF)decreased by25%and15%for hybrid composite when compared with those of Al?Si3N4nanocomposite whereas the wear rate and COF of Al?Gr was found to be very minimal.The micro Vickers hardness of the hybrid composite was14%more than that of the simple nanocomposite and there was not much notable variation for Al?Gr and Al?Si3N4nanocomposite materials.Scanning electron microscope was used to analyze the worn surface and subsurface,from which it was noted that the predominant wear mechanisms observed were abrasive for nanocomposite and both abrasive and adhesive mechanism for hybrid composite.Analysis of variance(ANOVA)and F-test were used to check the validity model and to determine the significant parameters affecting the wear rates.

Numerical study on the flow field characteristics of the new high-speed maglev train in open air

With the increasing demand of higher travelling speed,a new streamlined high-speed maglev train has been designed to reach a speed of 600 km/h.To better capture the flow field structures around the maglev train,an improved delayed detached eddy simulation(IDDES)is adopted to model the turbulence.Results show that the new maglev train has good aerodynamic load performance such as small drag coefficient contributing to energy conservation.The main frequencies of aerodynamic forces for each car have a scattered distribution.There are two pairs of counter-rotating large vortices in the non-streamlined part of the train that make the boundary layer thicker.Many high-intensity vortices are distributed in the narrow space between skirt plates or train floor and track.In the gap between the train floor and track(except near the tail car nose),the main frequency of vortex shedding remains constant and its strength increases exponentially in the streamwise direction.In the wake,the counter-rotating vortices gradually expand and reproduce some small vortices that move downward.The vortex has quite random and complex frequencydomain distribution characteristics in the wake.The maximum time-averaged velocity of the slipstream occurs near the nose of the head car,based on which,the track-side safety domain is divided.