直升机桨叶安装螺栓强度与疲劳寿命计算分析

目的 分析桨叶安装螺栓在不同位移载荷真实试车载荷以及螺牙缺齿情况下的剩余强度以及疲劳寿命。方法 基于有限元方法分析不同载荷下桨叶安装螺栓的对数应变，依据失效应变判定其强度，提取有限元模型的单元应力，通过临界平面法计算最大组合应力平面，运用曲线走势、损伤准则预估桨叶安装螺栓的疲劳寿命。结果 0.36 mm位移载荷下螺栓应变未达到破坏值，真实试车载荷超过4倍情况下，螺栓失效的可能性较高，螺栓断牙超过2个，失效风险较高。依据试车载荷谱，初始长度螺栓寿命为20 794 h，初始长度螺栓断1螺牙寿命为10 912 h，拉伸至29.36 mm螺栓疲劳寿命为7 725 h。结论 在额定载荷状态下，材料结构破坏的可能性小。实际载荷超过4倍、螺栓断牙超过2个情况下，应力应变状态显著恶化，桨叶安装螺栓失效的风险较高，需要预防超载荷过大的情况，还需在修理过程中关注螺栓螺纹的损伤情况，即螺纹的正常磨损可不作为故障进行更换，但出现掉牙、断牙情况则需要更换。

Finite Element Strength and Fatigue Life Analysis of Blade Mounting Bolts

The work aims to analyze the residual strength and fatigue life of propeller bolts under different displacement loads and missing threads. First, the logarithmic strain of the screw bolt under different loads was analyzed based on the finite element method. The strength of the screw bolt was determined according to the failure strain. The element stress of the finite element model was extracted. The maximum combined stress plane was calculated by critical plane method, and the fatigue life of propeller bolts was estimated by curve trend and damage criterion. According to the analysis, the failure probability of the bolt was higher when the strain of the bolt under the displacement load of 0.36 mm does not reach the failure value, and the failure risk of the bolt was higher when the actual test load was more than 4 times. According to the test load spectrum, the life of the bolt with initial length was 20 794 hours, the life of the bolt with broken screw with initial length was 10 912 hours, and the fatigue life of the bolt with tensile length of 29.36 mm was 7 725 hours. Under the condition of rated load, the failure probability of the material structure is small. When the actual load is more than 4 times, and the bolt tooth broken is more than 2, the stress-strain state is obviously deteriorated, and the risk of failure of the propeller bolts is higher, overloading needs to be prevented, and bolt breakage needs to be considered during repair. Namely, bolts with normal thread wear may not be replaced as a fault, but those of thread missing and breaking should be replaced.