FGH96粉末涡轮盘结构模拟件疲劳小裂纹扩展试验

为了分析涡轮盘轮缘榫槽等几何不连续部位对疲劳裂纹萌生及小裂纹扩展行为的影响，基于FGH96粉末盘实际构型设计结构特征模拟件，并对其在高温条件下开展自然萌生疲劳小裂纹扩展试验，通过疲劳中断试验和表面复型技术对榫槽和螺栓孔结构模拟件在500℃下的裂纹萌生和小裂纹扩展行为进行了观测和分析。结果表明：2种结构模拟件缺口表面存在多裂纹萌生现象，随着应力水平的降低，裂纹萌生位置由表面晶界转变为近表面特定方向的晶面以及非金属夹杂物处；2种结构模拟件裂纹萌生寿命占比约为36%～73%，且随着应力水平的降低而提高，裂纹扩展至工程可检裂纹尺寸时的寿命占比约为82%～96%，应力水平对其影响相对较小；特征模拟件缺口附近高水平的塑性变形能够导致小裂纹扩展速率分段特征现象消失，并延缓裂纹扩展过程中的合并行为，延长裂纹扩展寿命。

Fatigue Small Crack Propagation Test of FGH96 Turbine Disc Structure Simulation Specimen

In order to analyze the influence of geometric discontinuities (mortise and groove, etc.) of turbine disk rim on fatigue crackinitiation and small crack propagation behavior, a structure characteristics simulation specimens were designed based on the actualconfiguration of an FGH96 powder disc, naturally-initiated small crack propagation tests of the specimens were carried out under high-temperature conditions. The fatigue crack initiation and small crack propagation behaviors of the mortise and groove and bolt-holestructure simulation specimens at 500℃ were observed and analyzed by fatigue interruption tests and surface replication techniques. Theresults show that there are multi-site crack initiation phenomena on the notch surface of the two structural simulation specimens. With thestress level decreases, the location of crack initiation changes from surface grain boundaries to near-surface specific crystallographic facetsand non-metallic inclusions. The crack initiation life accounts for about 36% to 73% of the total predicted fatigue life for the two kinds ofstructure simulation specimens, and increases with the decrease of stress level. The crack initiation life is about 82% to 96% of the totalpredicted fatigue life when the crack propagates to the detectable size, and the influence of stress level is relatively small. High-levelplastic deformation near the notch leads to the disappearance of the segmented characteristics in the small crack propagation rate, anddelays coalescence behavior during crack propagation, extending the crack propagation life.