Bending of an Aircraft-Wing Slat Track

ASM Failure Analysis Case Histories: Air and Spacecraft Pub Date : 2019-06-01 DOI:10.31399/asm.fach.aero.c0092142

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Abstract

During a routine inspection on an aircraft assembly line, an airframe attachment bolt was found to be broken. The bolt was one of 12 that attach the lower outboard longeron to the wing carry-through structure. Failure occurred on the right-hand forward bolt in this longeron splice attachment. The bolt was fabricated from PH13-8Mo stainless steel heat treated to have an ultimate tensile strength of 1517 to 1655 MPa (220 to 240 ksi). A water-soluble coolant was used in drilling the bolt hole where this fastener was inserted. Investigation (visual inspection, 265 SEM images, hardness testing, auger emission spectroscopy and secondary imaging spectroscopy, tensile testing, and chemical analysis) supported the conclusion that failure of the attachment bolt was caused by stress corrosion. The source of the corrosive media was the water-soluble coolant used in boring the bolt holes. Recommendations included inspecting for corrosion all the bolts that were installed using the water-soluble coolant at the spliced joint areas, rinsing all machined bolt holes with a noncorrosive agent, and installing new PH13-8Mo stainless steel bolts with a polysulfide wet sealant.

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机翼板条轨道的弯曲

在一次对飞机装配线的例行检查中，发现一个机身连接螺栓坏了。这个螺栓是12个连接较低的舷外长翼和机翼穿过结构的螺栓之一。故障发生在右手前螺栓在这个较长的接头附件。螺栓由经过热处理的PH13-8Mo不锈钢制成，其极限抗拉强度为1517至1655 MPa(220至240 ksi)。在插入该紧固件的螺栓孔上钻孔时使用了一种水溶性冷却剂。调查(目视检查、265张SEM图像、硬度测试、螺旋发射光谱和二次成像光谱、拉伸测试和化学分析)支持了附件螺栓失效是由应力腐蚀引起的结论。腐蚀介质的来源是螺栓孔钻孔时使用的水溶性冷却剂。建议包括在拼接区域使用水溶性冷却剂检查所有安装的螺栓的腐蚀情况，用非腐蚀性剂冲洗所有加工螺栓孔，并使用聚硫湿密封胶安装新的PH13-8Mo不锈钢螺栓。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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ASM Failure Analysis Case Histories: Air and Spacecraft

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