陶瓷基复合材料涡轮动叶榫头元件静强度实验及缺陷影响

Static strength tests and effects of defects on dovetail elements of ceramic matrix composites turbine rotor blades

陶瓷基复合材料(ceramic matrix composites,CMC)涡轮动叶榫头是动叶装配与承受离心载荷的关键。为了研究熔渗工艺制备CMC榫头在叶片旋转径向拉伸载荷下的力学行为,验证榫头内部质量对其静拉伸强度与破坏模式的影响,设计并制备燕尾形CMC高压涡轮动叶榫头元件试件,对其进行单轴静态拉伸实验,采用X射线CT无损检测对实验前试件内部质量进行扫描,采用DIC与声发射方法对实验过程进行监测。结果表明:燕尾形CMC榫头在单轴静态拉伸下保持完好接触,其静态拉伸强度与破坏模式对其内部质量(尤其是分层缺陷)非常敏感。试件不含分层缺陷时,损伤起始于榫头颈部,并迅速扩展,损伤起始载荷与最大破坏载荷接近,断口呈横向锯齿状;试件内部含分层缺陷时,损伤起始于缺陷,分层逐渐扩展并导致试件断裂,损伤起始载荷下降99.05%,最大破坏载荷下降14.29%,断口位置与分层缺陷一致。

The dovetail of ceramic matrix composites(CMC)turbine blade is the key to the assembly and ability to withstand centrifugal loads of the blade.In order to study the mechanical behaviour of the blade dovetail prepared by the melt infiltration(MI)method under the tensile load in the radial direction of rotating,and verify the influence of the internal quality of the dovetail on its static tensile strength and failure mode,the CMC high pressure turbine dovetail element specimens were designed and fabricated,and a uniaxial static tensile test was conducted,the internal quality of the test specimens was scanned using non-destructive X-ray CT.The test process was monitored using DIC and acoustic emission method.The results show that the CMC dovetail is able to maintain in complete contact under uniaxial static tensile loads,and its static strength and failure are very sensitive to its internal quality,especially to the delamination defects.When there are no delamination defects in the dovetail,the damage generally starts from the neck and quickly spreads,the damage starting load is near the maximum fracture load,and the fracture surface is zigzag.When there are delamination defects in the dovetail,the fracture starts from the defects,and the delamination gradually spread and cause the fracture surface of the dovetail,the damage starting load is decreased by 99.05%,and the maximum failure load is decreased by 14.29%compared to the case of no delamination defects,and the fracture surface is consistent with the delamination defects.