用于应力腐蚀试验的飞机铝合金装配模拟件内部应力无损测定

目的 减少或避免服役飞机机体的应力腐蚀和腐蚀疲劳开裂.方法 采用短波长特征X射线衍射技术和仪器无损检测飞机铝合金装配模拟件的内部残余应力和装配应力的分布.结果 0.5 mm矩形间隙使下缘条根部上表层产生高达110 MPa及以上的拉应力;0.3 mm矩形间隙使下缘条根部上表层产生约80 MPa的拉应力;0.5 mm楔形间隙使下缘条根部上表层产生的拉应力平均值约55 MPa.结论 利用短波长特征X射线衍射技术能够无损测定和表征铝合金装配件内部应力及其分布,装配间隙使下缘条根部上表层产生较大拉应力,这与服役飞机机身螺接件出现较多非典型裂纹的部位吻合.矩形间隙装配件下缘条根部上表层的拉应力大于相同间隙值的楔形间隙装配件下缘条根部上表层的拉应力,并且,装配间隙越小,产生的拉应力越小.减小螺母靠根部处的装配间隙与螺母靠根部处到壁板距离的比值,将减小装配件的拉应力,减少或避免SCC&CFC的发生,以及非典型裂纹的产生.

Non-destructive Measurement of Internal Stress of Aircraft Aluminum Alloy Assembly Simulation Part for Stress Corrosion Test

To reduce or avoid stress corrosion and corrosion fatigue cracking of the aircraft body in service, short-wavelength characteristic X-ray diffraction technology and equipment were used to non-destructively detect the distribution of internal residual stress and assembly stress of aircraft aluminum alloy assembly simulation parts. The 0.5 mm rectangular gap caused a tensile stress of 110 MPa and above on the upper surface of the root of lower edge of the strip parts; the 0.3 mm rectangular gap caused a tensile stress of about 80 MPa on the upper surface of the root of lower edge of the strip parts; the 0.5 mm wedge-shaped gap caused an average tensile stress of about 55 MPa on the upper surface of the root of lower edge of the strip parts. By short-wavelength characteristic X-ray diffraction technology, the internal stress of aluminum alloy components and the distribution of it are non-destructively measured and characterized. The assembly gap caused large tensile stress on the upper surface layer of the lower edge of the strip parts, which is consistent with the position where there are more atypical cracks in the screwed parts of the aircraft fuselage in service; the tensile stress of the upper surface layer of the lower edge of the strip parts of the rectangular gap assembly is greater than that of wedge-shaped assembly parts with the same gap value, and the smaller the assembly gap, the smaller the tensile stress. Reducing the ratio of the assembly gap at the root of the nut to the distance from the root of the nut to the wall plate will decrease the tensile stress of the assembly parts, reduce or avoid the occurrence of SCC&CFC and the occurrence of atypical cracks.