叶片属于典型的薄壁曲面构件，其服役环境恶劣，在交变应力作用下经过一定循环周次后发生疲劳断裂，严重影响发动机的可靠性和耐持久性。为了研究叶片振动状态下的疲劳性能，采用不同工艺参数加工叶片，测试其表面粗糙度、残余应力、显微硬度，并进行叶片的振动疲劳试验和疲劳断口分析。结果表明：TC17钛合金叶片的危险位置在叶背，距叶尖48.1mm，距进气边26.9mm处；叶片的表面粗糙度为0.373μm，表面应力集中系数为1.014，表面残余应力为-319.38MPa，表面显微硬度为412.53HV时，获得最高疲劳寿命8.91×105周次；残余应力对叶片振动疲劳寿命的影响最显著，其次是表面应力集中系数，最后是显微硬度；铣削加工叶片的疲劳失效模式为表面单源起始，疲劳源区有明显的放射线特征，裂纹扩展区有疲劳条带和二次裂纹，瞬断区有韧窝特征，属于韧性断裂。
Abstract
Blades are typical thin-walled curved components that operate in harsh environments. Under the action of alternating stress, fatigue fracture occurs after a certain number of cycles, which seriously affects the reliability and durability of the engine. In order to study the fatigue performance of blades under vibration, blades were processed with different process parameters, and their surface roughness, residual stress, and microhardness were tested. Vibration fatigue tests and fatigue fracture analysis of the blades were also performed. The results show that the dangerous position of the TC17 titanium alloy blade is on the back of the blade, 48.1mm from the blade tip and 26.9mm from the air inlet edge; the surface roughness of the blade is 0.373μm, the surface stress concentration coefficient is 1.014, the surface residual stress is -319.38MPa, and the surface microhardness is 412.53HV. The highest fatigue life of 8.91×105 cycles was obtained when the surface residual stress was considered. The residual stress has the most significant effect on the fatigue life of the blade, followed by the surface stress concentration coefficient, and finally the microhardness. The fatigue failure mode of the milled blade is a surface single-source start, and the fatigue source area has obvious radiation characteristics, the crack extension area has fatigue stripes and secondary cracks, and the instantaneous fracture area has toughness characteristics, which belongs to toughness fracture.
关键词
叶片 /
TC17钛合金 /
表面应力集中系数 /
残余应力 /
振动疲劳寿命
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Key words
Blades /
TC17 titanium alloy /
surface stress /
concentration coefficient /
residual stress /
vibration fatigue life.
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