Page 70 - 《摩擦学学报》2021年第4期

第 4 期 王俊翔, 等: 泡沫镍/聚氨酯双连续复合材料的液滴冲蚀行为研究 513

Under 6.9 MPa pipeline pressure, the droplet velocity was about 70 m/s, the flow rate was 5.870 L/min, and the
average droplet diameter was 480 μm; under 8.3 MPa pipeline pressure, the droplet velocity was about 90 m/s, the flow
rate was 6.264 L/min, and the average droplet diameter was 512 μm; under 10.3 MPa pipeline pressure, the droplet
velocity was about 115 m/s, the flow rate was 6.814 L/min, and the average droplet diameter was 543 μm. The higher
the pipeline pressure was, the higher the flow rate was, the higher the droplet velocity was, and the higher percentage of
large droplets in the total number of droplets was. When the pipeline pressure increased, the speed of the droplets
increased, the size of the droplets increased, the total number of droplets per unit time increased, and the impact
frequency of the droplets also increased. Therefore, as the pipeline pressure increased, the impact energy of the droplets
increased significantly.
Under the condition of 6.9 MPa-30 min, the mass loss of a few composites was less than that of pure PU; under the
condition of 8.3 MPa-30 min, the mass loss of most composites was less than that of pure PU; under the condition of
10.3 MPa-30 min, the mass loss of all composites was less than pure PU. The composites exhibited better droplet
erosion resistance under higher impact energy. Under the condition of 10.3 MPa-30 min, the erosion craters of the
composite 100PPI 0.8/PU were small and shallow, a small piece of resin was peeled off from the surface, and the metal
arris were damaged slightly. The erosion craters of the 50PPI composite were large and deep, the resin phase was peeled
off from the metal skeleton, and the metal arris had a small amount of plastic deformation and fracture. The erosion
craters of the 25PPI composite were very deep with large pieces of resin peeling off from the metal arris, but the metal
arris were damaged slightly. In general, the metal arris damage of all composites was relatively small, and resin peeling
from the metal arris was the main source of damage for all composites. The erosion craters of pure PU were larger and
deeper than that of all the composites.
When the droplets impacted, pure PU cracked under the action of water hammer pressure and stress wave. The crack
widened and deepened under the action of lateral jet and hydraulic penetration. As impact energy of the droplets
increased, the composites' resistance to high-speed droplet erosion was significantly better than pure PU. The Ni foam
metal skeleton could block the impact of droplets, played a good protective role for the resin under the metal arris, which
showed the shadow protection effect. The droplets of the forward and lateral jets rebounded when hitting the metal arris,
and the rebounded droplets blocked the droplets that arrive later, which showed the carpet protective effect. The smaller
the pore size of the Ni foam, the better the erosion resistance of the composite. The metal skeleton in the composite had
strong resistance to the effects of water hammer pressure, stress wave, lateral jet and hydraulic penetration, and had
shadow protection and carpet protection effects on the resin phase, while the resin phase can provide support effects on
Ni foam absorbing the impact energy of droplets. The synergistic effect of the two phases improved the droplet erosion
resistance of the composite. The composite 100PPI 0.8/PU exhibited the best droplet erosion resistance due to its dense
metal skeleton. Application of Ni foam with small pore size and small volume density was beneficial to droplet erosion
resistance of the Ni foam/PU co-continuous composites.
Key words: droplet erosion; co-continuous composite; PIV; polyurethane; nickel foam

液滴冲蚀是指大量的高速液滴反复撞击固体表 好 [6-7] . 其中，高硬度通过延缓液滴冲蚀中发生的材料
[1]
面，对材料造成的损伤，它是一种特殊的冲蚀形式 . 表面变形，可发挥比其他性质更重要的作用. 而延展
在火电站燃气轮机的压缩机叶片上，核电站蒸汽管道 性使材料能够适应局部的应力集中，在液滴冲蚀中也
[8]
中的弯管、阀门上，和雨中高速运动的飞机、导弹上， 发挥着重要的作用 . 尽管已经有了一些相关研究，但
液滴冲蚀现象十分常见 [2-4] . 液滴冲蚀能对材料造成极 是到目前为止，还不能通过定义、量化1个绝对的参数
[9]
大的损伤，降低服役零部件的使用寿命，带来极大的 来评价材料的抗液滴冲蚀性能 .
安全隐患. 由于涉及许多参数，液滴冲蚀的机理十分 聚氨酯弹性体是一种高分子材料，它具备良好的
复杂，常见的参数包括：冲击速度、攻角、液滴粒径尺 弹性变形能力、阻尼减振性能和抗腐蚀性能. 液滴冲
寸、液滴密度、撞击频率、液膜形成厚度和靶材料的机 蚀发生时，聚氨酯能通过发生弹性变形，很好地吸收
械性能等. 表1中总结了过去对液滴冲蚀起始速度的 和转移能量. 在喷砂、空蚀试验中，改性聚氨酯和含聚
一些研究，因为试验方法、材料和液滴直径等试验条 氨酯成分的复合材料，均表现出了良好的抗冲蚀性
[5]
件不同，研究结果高度分散 . 材料的硬度、延展性、断 能 [10-14] ，但聚氨酯弹性体强度低，明显制约了其应用 [15-16] .
裂韧性和疲劳极限高，其抗液滴冲蚀性能往往比较 作者采用真空灌注工艺，在聚氨酯里加入泡沫镍金属