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ASM Failure Analysis Case Histories: Air and Spacecraft最新文献

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Airplane Fuel Line Support Bracket Failure 飞机燃油管路支撑支架失效
ASM Failure Analysis Case Histories: Air and Spacecraft Pub Date : 2019-06-01 DOI: 10.31399/asm.fach.aero.c9001506
J. Hutchinson
{"title":"Airplane Fuel Line Support Bracket Failure","authors":"J. Hutchinson","doi":"10.31399/asm.fach.aero.c9001506","DOIUrl":"https://doi.org/10.31399/asm.fach.aero.c9001506","url":null,"abstract":"\u0000 A single-engine aircraft was climbing to 8000 ft when the engine suddenly lost power. The landing gear was torn off during the emergency landing. During the field investigation, the fuel line was found to be separated from the fuel pump outlet due to a failure of the elbow fitting. A bracket which supports the in-line fuel flow transducer also was found broken. Examination of the elbow fracture revealed characteristics of low-cycle fatigue failure. Examination of the support bracket fractures revealed a high-cycle mode of fatigue failure, with the primary fatigue extending along the full length of the 90 deg bend in the bracket. It was concluded that the failure was caused by an incorrectly-installed support bracket. It was recommended that the installation procedure be clarified.","PeriodicalId":326464,"journal":{"name":"ASM Failure Analysis Case Histories: Air and Spacecraft","volume":"45 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127172609","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Stress-Corrosion Cracking of Pitostatic System Connectors 静压系统连接器的应力腐蚀开裂
ASM Failure Analysis Case Histories: Air and Spacecraft Pub Date : 2019-06-01 DOI: 10.31399/asm.fach.aero.c0006409
{"title":"Stress-Corrosion Cracking of Pitostatic System Connectors","authors":"","doi":"10.31399/asm.fach.aero.c0006409","DOIUrl":"https://doi.org/10.31399/asm.fach.aero.c0006409","url":null,"abstract":"\u0000 Pitostatic system connectors were being found cracked on several aircraft. Two of the cracked connectors made of 2024-T351 aluminum alloy were submitted for failure analysis. The connectors had cut pipelike threads that were sealed with Teflon-type tape when installed. Longitudinal cracks were located near the opening of the female ends of each connector. A cross section showed intergranular cracking with multiple branching in one connector. Scanning electron microscopy (SEM) showed intergranular cracking and separation of elongated grains. A cross section of connector threads showed an incomplete thread form resulting from improper tapping. It was concluded that the pitostatic system connectors failed by SCC. The stress was caused by forcing the improperly threaded female nut over its fully threaded male counterpart to effect a seal. The one connector tested for chemical composition was not made of 2024 aluminum alloy as reported but of 2017 aluminum. It was recommended that the pitostatic system connector manufacturing process be revised to produce full-depth threads rather than pseudo pipe threads. Wall thickness should be increased to increase the hoop stress bearing area if pipe threads were to be used. A determination of proper torque values for tightening the connectors was suggested also.","PeriodicalId":326464,"journal":{"name":"ASM Failure Analysis Case Histories: Air and Spacecraft","volume":"38 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123312216","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Premature Failure of a Turbine Blade by Thermal Fatigue Fracture 涡轮叶片热疲劳断裂的过早失效
ASM Failure Analysis Case Histories: Air and Spacecraft Pub Date : 2019-06-01 DOI: 10.31399/asm.fach.aero.c0046972
{"title":"Premature Failure of a Turbine Blade by Thermal Fatigue Fracture","authors":"","doi":"10.31399/asm.fach.aero.c0046972","DOIUrl":"https://doi.org/10.31399/asm.fach.aero.c0046972","url":null,"abstract":"\u0000 During disassembly of an engine that was to be modified, a fractured turbine blade was found. When the fracture was examined at low magnification, it was observed that a fatigue fracture had originated on the concave side of the leading edge and had progressed slightly more than halfway from the leading edge to the trailing edge on the concave surface before ultimate failure occurred in dynamic tension. Analysis (including visual inspection, SEM, and 250x/500x micrographic examination) supported the conclusions that the blades failed due to thermal fatigue. Recommendations included application of a protective coating to the blades, provided the coating was sufficiently ductile to avoid cracking during operation to prevent surface oxidation. Such a coating would also alleviate thermal differentials, provided the thermal conductivity of the coating exceeded that of the base metal. It was also determined that directionally solidified blades could minimize thermal fatigue cracking by eliminating intersection of grain boundaries with the surface. However, this improvement would be more costly than applying a protective coating.","PeriodicalId":326464,"journal":{"name":"ASM Failure Analysis Case Histories: Air and Spacecraft","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114150385","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Failures in Landing Gear Spring Legs 起落架弹簧腿故障
ASM Failure Analysis Case Histories: Air and Spacecraft Pub Date : 2019-06-01 DOI: 10.31399/asm.fach.aero.c9001902
Jivan B. Shah
{"title":"Failures in Landing Gear Spring Legs","authors":"Jivan B. Shah","doi":"10.31399/asm.fach.aero.c9001902","DOIUrl":"https://doi.org/10.31399/asm.fach.aero.c9001902","url":null,"abstract":"\u0000 In a spring leg of a main landing gear, large brittle fracture zones indicated a predominately cleavage pattern with some ductile dimples, and a tiny fatigue segment disclosed fine striations. Factors influencing failure were surface decarburization, notch sensitivity of the modified SAE 6150 spring steel, Canada's cold weather which may have had an embrittling effect on the steel, and cumulative fatigue damage from severe landing loads during service life. Replacement with heavier-duty spring legs will probably not eliminate this type of failure, but their use has reduced the number of failures substantially. Precautionary measures recommended to preclude accidents include removal of decarburization, proper operation of main landing gears, and adequate magnetic particle inspection of the legs at the beginning and end of the ski season to detect any fatigue cracks that might develop in attachment holes.","PeriodicalId":326464,"journal":{"name":"ASM Failure Analysis Case Histories: Air and Spacecraft","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125183980","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Failure of a Stainless Steel Bomb Fin Retaining Band 不锈钢弹翼固定带失效
ASM Failure Analysis Case Histories: Air and Spacecraft Pub Date : 2019-06-01 DOI: 10.31399/asm.fach.aero.c9001905
M. Pepi
{"title":"Failure of a Stainless Steel Bomb Fin Retaining Band","authors":"M. Pepi","doi":"10.31399/asm.fach.aero.c9001905","DOIUrl":"https://doi.org/10.31399/asm.fach.aero.c9001905","url":null,"abstract":"\u0000 A bomb retaining ring fabricated from type 302 stainless steel unwrapped during a practice flight, causing the bomb fins to deploy. The retaining ring was able to unwrap itself because it was thinner and softer than required. Hardness testing, metallography, and tensile testing confirmed that the component was in the annealed condition and not in the required work-hardened 1/4-hard condition.","PeriodicalId":326464,"journal":{"name":"ASM Failure Analysis Case Histories: Air and Spacecraft","volume":"51 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133198092","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Corrosion Cracking of Aircraft Components 飞机部件的腐蚀开裂
ASM Failure Analysis Case Histories: Air and Spacecraft Pub Date : 2019-06-01 DOI: 10.31399/asm.fach.aero.c9001745
Jivan B. Shah
{"title":"Corrosion Cracking of Aircraft Components","authors":"Jivan B. Shah","doi":"10.31399/asm.fach.aero.c9001745","DOIUrl":"https://doi.org/10.31399/asm.fach.aero.c9001745","url":null,"abstract":"\u0000 A 2000-T6 aluminum alloy bracket failed in a coastal environment because corrosive chlorides got between the bracket and attachment bolt. The material used for the part was susceptible to stress corrosion under the service conditions. Cracking may have been aggravated by galvanic action between aluminum alloy bracket and steel bolt. To preclude or minimize recurrences, fittings in service should be inspected periodically by dye penetrant for signs of cracking on the end face and within the fitting hole and protected with a suitable coating to exclude damaging chlorides. Also, a 2000-T6 aluminum alloy swivel fitting experienced intergranular corrosion fracture as the result of stress-accelerated corrosion. Corrosion began because of a loose fit between the aluminum swivel fitting and steel tube assembly, which caused fretting. Inadequate maintenance and/or abnormal service operation may have loosened the fitting.","PeriodicalId":326464,"journal":{"name":"ASM Failure Analysis Case Histories: Air and Spacecraft","volume":"54 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114660626","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Failure of an External Tank Pressure/Vent Valve 外部油箱压力/排气阀失效
ASM Failure Analysis Case Histories: Air and Spacecraft Pub Date : 2019-06-01 DOI: 10.31399/asm.fach.aero.c0006424
{"title":"Failure of an External Tank Pressure/Vent Valve","authors":"","doi":"10.31399/asm.fach.aero.c0006424","DOIUrl":"https://doi.org/10.31399/asm.fach.aero.c0006424","url":null,"abstract":"\u0000 An external tank pressure/vent valve regulates the external tank fuel feed system, which transfers fuel under pressure to the internal tanks of the aircraft. A dual-position valve was found to be sticking at the intermediate positions. Also, service air check valves located on the incoming lines contained poppets that were being stuck in a closed or partially closed position because of suspected corrosion product. Residue taken from the check valve poppet and from the dual-position valve was chemically analyzed. Chloride was present in both samples. It was suspected that moisture entering the service air lines left a chloride-containing compound upon evaporation within the air check valves and pressure/vent assembly. This compound subsequently reacted with the anodized, dichromate sealed check valve housing to lock the check valve poppets in a closed or partially closed position, decreasing the actual pressure being supplied to the pressure/vent valve. It was recommended that an inspection be conducted to ensure that the service air check valves are operating properly prior to removal and servicing of the pressure/vent valve assembly. It was also recommended that dry-film lubricant be checked to ensure that it meets specifications for the pressure/vent valve assembly.","PeriodicalId":326464,"journal":{"name":"ASM Failure Analysis Case Histories: Air and Spacecraft","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114207306","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Investigation of Jet Engine Oil Scavenge Pump Failure 喷气发动机扫油泵故障的研究
ASM Failure Analysis Case Histories: Air and Spacecraft Pub Date : 2019-06-01 DOI: 10.31399/asm.fach.aero.c9001575
L.D. Cologna
{"title":"Investigation of Jet Engine Oil Scavenge Pump Failure","authors":"L.D. Cologna","doi":"10.31399/asm.fach.aero.c9001575","DOIUrl":"https://doi.org/10.31399/asm.fach.aero.c9001575","url":null,"abstract":"\u0000 An oil scavenge pump was found to have failed when a protective shear neck fractured during the start of a jet engine. Visual inspection revealed that the driven gear in one of the bearing compartments was frozen as was the corresponding drive gear. Spacer wear and thermal discoloration (particularly on the driven gear) were also observed. The gears were made from 32Cr-Mo-V13 steel, hardened and nitrided to 750 to 950 HV. Micrographic inspection of the gear teeth revealed microstructural changes that, in context, appear to be the result of friction heating. The spacers consist of Cu alloy (AMS4845) bushings force fit into AA2024-T3 Al alloy spacing elements. It was found that uncontrolled fit interference between the two components had led to Cu alloy overstress. Thermal cycling under operating conditions yielded the material. The dilation was directed inward to the shaft, however, because the bushing had only a few microns of clearance. The effect caused the oil to squeeze out, resulting in metal-to-metal contact, and ultimately failure.","PeriodicalId":326464,"journal":{"name":"ASM Failure Analysis Case Histories: Air and Spacecraft","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117074051","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Fretting and Corrosion in Aircraft Components 飞机部件的微动和腐蚀
ASM Failure Analysis Case Histories: Air and Spacecraft Pub Date : 2019-06-01 DOI: 10.31399/asm.fach.aero.c9001903
Jivan B. Shah
{"title":"Fretting and Corrosion in Aircraft Components","authors":"Jivan B. Shah","doi":"10.31399/asm.fach.aero.c9001903","DOIUrl":"https://doi.org/10.31399/asm.fach.aero.c9001903","url":null,"abstract":"\u0000 Fretting and/or fretting corrosion fatigue have been observed on such parts as main rotor counterweight tie rods, fixed-pitch propeller blades, propeller blade clamps, pressure regulator lines, and landing gear support brackets. Microcracks started from severe corrosion pits in a failed control rotor spar tube assembly made of cadmium-plated AISI 4130 Cr-Mo alloy steel. Inadequate design was responsible for the failure. A lower tine of the main rotor blade cuff failed in fatigue. The rotor blade cuff was forged of 2014-T6 aluminum alloy. Initial stages of crack growth displayed features typical of low stress intensity fatigue of aluminum alloys. The fatigue resulted from abnormal fretting owing to inadequate torquing of the main retention bolts. Aircraft maintenance engineers and owners were advised to adhere to specifications when torquing this joint.","PeriodicalId":326464,"journal":{"name":"ASM Failure Analysis Case Histories: Air and Spacecraft","volume":"54 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116451775","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Microbially Influenced Corrosion of Aluminum Alloy Aircraft Fuel Tanks 微生物对铝合金飞机油箱腐蚀的影响
ASM Failure Analysis Case Histories: Air and Spacecraft Pub Date : 2019-06-01 DOI: 10.31399/asm.fach.aero.c0091809
{"title":"Microbially Influenced Corrosion of Aluminum Alloy Aircraft Fuel Tanks","authors":"","doi":"10.31399/asm.fach.aero.c0091809","DOIUrl":"https://doi.org/10.31399/asm.fach.aero.c0091809","url":null,"abstract":"\u0000 Aluminum 7075 aircraft wing tanks failed in the 1950s. Investigation (visual inspection, biological analysis, and chemical analysis) supported the conclusion that MIC was the cause of the failures. Water condensed into the fuel tanks during flight led to microbial growth on the jet fuel. Pitting attack occurred under microbial deposits on the metal surface in the water phase or at the water-fuel interface. Previously, exposure of aluminum 7075 to cultures of various isolates showed that 27 bacterial isolates and 3 fungi could seriously corrode the aluminum alloy over several weeks. No recommendations were made.","PeriodicalId":326464,"journal":{"name":"ASM Failure Analysis Case Histories: Air and Spacecraft","volume":"42 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127918378","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
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