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Book Chapter
Premature Torquing Failures of Cast A356 Aluminum Actuators
Available to PurchaseSeries: ASM Failure Analysis Case Histories
Volume: 1
Publisher: ASM International
Published: 01 December 1992
DOI: 10.31399/asm.fach.v01.c9001029
EISBN: 978-1-62708-214-3
... Abstract Two investment-cast A356 aluminum alloy actuators used for handles on passenger doors of commercial aircraft fractured during torquing at less than the design load. Visual examination showed that cracking had occurred through a machined side hole. Fractography revealed that the cracks...
Abstract
Two investment-cast A356 aluminum alloy actuators used for handles on passenger doors of commercial aircraft fractured during torquing at less than the design load. Visual examination showed that cracking had occurred through a machined side hole. Fractography revealed that the cracks originated in hot tear locations in the castings. Microprobe analysis of fracture surfaces in the hot tear region indicated a much higher silicon-to-aluminum ratio compared with the overload fracture area. No microstructural anomalies related to the failure were found during metallographic examination. It was concluded that the strength of the castings had been compromised by the presence of the casting defects. Modification of the gating system for casting was recommended to eliminate the hot tear zone. It was also suggested that the balance of the castings from the same manufacturing lot be radiographically inspected.
Book Chapter
Corrosion in Pyrotechnic Actuators
Available to PurchaseSeries: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.process.c0049796
EISBN: 978-1-62708-235-8
... Abstract Problems with materials compatibility were encountered in pyrotechnically driven devices used in a number of ordnance applications requiring rapid mechanical actuation. A fine bridgewire is located in contact with the chemical pyrotechnic, and the charge is ignited by electrical...
Abstract
Problems with materials compatibility were encountered in pyrotechnically driven devices used in a number of ordnance applications requiring rapid mechanical actuation. A fine bridgewire is located in contact with the chemical pyrotechnic, and the charge is ignited by electrical heating of the bridgewire. Evidence of severe corrosion was revealed on examination of the nickel-chromium-iron alloy bridgewire and the nickel-iron alloy pins. Metallic elements in the pin or bridgewire and substantial amounts of chlorine were detected from the x-ray spectra. Morphological changes indicative of decomposition and dissolution were revealed to have occurred in regions of the pyrotechnic that had been in contact with the bridgewire and pin surfaces by examination of the titanium-potassium perchlorate (Ti-K-Cl-O4) pyrotechnic. Substantial amounts of water were revealed to be associated with the surfaces of the titanium particles in the pyrotechnic by nuclear magnetic resonance. It was proposed that the chlorine-containing residue combined with the water from the pyrotechnic to form a thin aqueous film corroding the bridgewire and pins. A new cleaning procedure was implemented for the glass headers to eliminate the chloride contamination and a vacuum drying procedure was instituted for the pyrotechnic.
Book Chapter
Fatigue Fracture of a Precipitation-Hardened Stainless Steel Actuator Rod End
Available to PurchaseSeries: ASM Failure Analysis Case Histories
Volume: 2
Publisher: ASM International
Published: 01 December 1993
DOI: 10.31399/asm.fach.v02.c9001361
EISBN: 978-1-62708-215-0
... Abstract A 17-4 PH steering actuator rod end body broke during normal take-off. Results of failure analysis revealed that the wall thickness of the race was much below the design limits, thus causing the race to rest on the body's swaged edges rather than on the load carrying centerline...
Abstract
A 17-4 PH steering actuator rod end body broke during normal take-off. Results of failure analysis revealed that the wall thickness of the race was much below the design limits, thus causing the race to rest on the body's swaged edges rather than on the load carrying centerline of the body. This assembly condition generated abnormal high loads on the swaged edges, ultimately resulting in fatigue failure. To prevent a recurrence of similar failure in the future, the dimensions of the race in the spherical bearing were changed, no further failure occurred.
Image
Forged aluminum alloy 2014-T6 actuator barrel lug that failed by SCC. (a) V...
Available to PurchasePublished: 01 January 2002
Fig. 38 Forged aluminum alloy 2014-T6 actuator barrel lug that failed by SCC. (a) View of the lug. 2×. Fracture at top was the initial fracture; arrow indicates location of a tiny region of pitting corrosion (on back side of lug) at which failure originated. Final fracture is at left. (b
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Components for the mounting surface of a hydraulic actuator that failed in ...
Available to Purchase
in Failure of Aluminum Alloy Spacers by Galvanic Attack
> ASM Failure Analysis Case Histories: Failure Modes and Mechanisms
Published: 01 June 2019
Fig. 1 Components for the mounting surface of a hydraulic actuator that failed in service because of galvanic attack on the aluminum alloy spacer. The galvanic attack occurred on the aluminum alloy spacer (a) when a vellum gasket (b) that separated the spacer from a nickel-plated steel housing
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in Solving an Aluminum Bracket Failure
> ASM Failure Analysis Case Histories: Failure Modes and Mechanisms
Published: 01 June 2019
Fig. 1 As-received actuator—note removal of paint and location of fracture.
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Both sides of an as-received actuator casting. Arrow (b) indicates the hot ...
Available to Purchase
in Premature Torquing Failures of Cast A356 Aluminum Actuators
> Handbook of Case Histories in Failure Analysis
Published: 01 December 1992
Fig. 1 Both sides of an as-received actuator casting. Arrow (b) indicates the hot tear cracks.
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Image
Broken steering actuator rod end. No environmental damage was apparent on t...
Available to Purchase
in Fatigue Fracture of a Precipitation-Hardened Stainless Steel Actuator Rod End
> Handbook of Case Histories in Failure Analysis
Published: 01 December 1993
Fig. 2 Broken steering actuator rod end. No environmental damage was apparent on the rod-end assembly 0.9×
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in Failure Analysis of Door Lock Assemblies Illustrating the Statistical Aspects of Failure Analysis
> ASM Failure Analysis Case Histories: Automobiles and Trucks
Published: 01 June 2019
Fig. 5 Actuating link failure.
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Image
in Corrosion in Pyrotechnic Actuators
> ASM Failure Analysis Case Histories: Processing Errors and Defects
Published: 01 June 2019
Fig. 1 Cross section of a pyrotechnic actuator.
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Image
Forged aluminum alloy 2014-T6 actuator barrel lug that failed by SCC. (a) V...
Available to Purchase
in Stress-Corrosion Cracking of a Forged Aircraft Lug
> ASM Failure Analysis Case Histories: Air and Spacecraft
Published: 01 June 2019
Fig. 1 Forged aluminum alloy 2014-T6 actuator barrel lug that failed by SCC. (a) View of the lug. 2×. Fracture at top was the initial fracture; arrow indicates location of a tiny region of pitting corrosion (on back side of lug) at which failure originated. Final fracture is at left. (b
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Image
(a) Photograph of forged aluminum alloy 2014-T6 actuator barrel lug that fr...
Available to PurchasePublished: 15 January 2021
Fig. 49 (a) Photograph of forged aluminum alloy 2014-T6 actuator barrel lug that fractured due to stress-corrosion cracking. Arrow indicates location of a region of pitting corrosion on back side of lug at which the fracture originated. Final fracture occurred at bottom left. (b) Micrograph
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Book Chapter
Failure of Aluminum Alloy Spacers by Galvanic Attack
Available to PurchaseSeries: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.modes.c0046512
EISBN: 978-1-62708-234-1
... Abstract Immediately after installation, leakage was observed at the mounting surface of several rebuilt hydraulic actuators that had been in storage for up to three years. At each joint, there was an aluminum alloy spacer and a vellum gasket. The mounting flanges of the steel actuators had...
Abstract
Immediately after installation, leakage was observed at the mounting surface of several rebuilt hydraulic actuators that had been in storage for up to three years. At each joint, there was an aluminum alloy spacer and a vellum gasket. The mounting flanges of the steel actuators had been nickel plated. During assembly of the actuators a lubricant containing molybdenum disulfide had been applied to the gaskets as a sealant. The vellum gasket was found to be electrically conductive, and analysis (visual inspection, 500x unetched micrographs, galvanic action testing, and x-ray diffraction) supported the conclusions that leakage was the result of galvanic corrosion of the aluminum alloy spacers while in storage. The molybdenum disulfide was apparently suspended in a volatile water-containing vehicle that acted as an electrolyte between the aluminum alloy spacer and the nickel-plated steel actuator housing. Initially, the vellum gasket acted as an insulator, but the water-containing lubricant gradually impregnated the vellum gasket, establishing a galvanic couple. Recommendations included discontinuing use of molybdenum disulfide lubricant as a gasket sealer, and assembling the actuators using dry vellum gaskets.
Book Chapter
Failure of Nylon Hinges
Available to PurchaseSeries: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.auto.c0090466
EISBN: 978-1-62708-218-1
... Abstract A production lot of mechanical hinges used in an automotive application had failed during incoming quality-control routine actuation testing. A change in part supplier had taken place between the approval of the prototype parts that performed acceptably and the receipt of the first lot...
Abstract
A production lot of mechanical hinges used in an automotive application had failed during incoming quality-control routine actuation testing. A change in part supplier had taken place between the approval of the prototype parts that performed acceptably and the receipt of the first lot of production parts. The mechanical hinges were specified to be injection molded from an impact-modified, 13% glass-fiber-reinforced nylon 6/6 resin. Investigation of samples representing the failed components and the original prototype parts included visual inspection, 118x SEM images, micro-FTIR, DSC analysis, and TGA. It supported the conclusion that the hinge assemblies failed through brittle fracture associated with stress overload during the actuation of the parts. The failed part material was found to be degraded, most likely occurring during the compounding of the resin or during the actual molding of the parts. While resins for both failed and non-failed parts produced results characteristic of a 13% glass-fiber-reinforced, impact-modified nylon 6/6, the failed part material, contained a significantly lower level of rubber, which rendered the parts less impact resistant and subsequently lowered the ductility of the molded hinge assemblies. No recommendations were made.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.modes.c9001734
EISBN: 978-1-62708-234-1
..., indicated that little stress had been applied to the part. Comparisons of the service failure and laboratory-induced failures in conjunction with macroscopic and metallographic observations showed that the bracket assembly failed because an intense, localized flame had melted the material. Actuator...
Abstract
An aircraft engine in which an in-flight fire had occurred was dismantled and examined. A bracket assembly fabricated from 2024 aluminum, one of several failed components, was of prime interest because of apparent heat damage. Scanning electron microscopy was used to compare laboratory-induced fractures made at room and elevated temperatures with the bracket failure. The service failure exhibited grain separation and loss of delineation of the grain boundaries due to melting. SEM revealed deep voids between grains and tendrils that connected grains, which resulted from surface tension during melting. Microscopic examination of polished, etched section through the fractured surface verified intergranular separation and breakdown of grain facets. The absence of any reduction of thickness on the bracket assembly at the point of fracture, along with evidence of intense heat at this point, indicated that little stress had been applied to the part. Comparisons of the service failure and laboratory-induced failures in conjunction with macroscopic and metallographic observations showed that the bracket assembly failed because an intense, localized flame had melted the material.
Image
Slider-on-flat-surface testing rig. (a) Overview. (b) Tool holder with load...
Available to PurchasePublished: 15 January 2021
Fig. 16 Slider-on-flat-surface testing rig. (a) Overview. (b) Tool holder with load cells and actuator (A, normal load; B, friction force; C, load actuator). (c) Testing progression. Adapted from Ref 52
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Book Chapter
Thrust Bearing Failure Leading to the Destruction of a Propeller Rotor
Available to PurchaseSeries: ASM Failure Analysis Case Histories
Volume: 2
Publisher: ASM International
Published: 01 December 1993
DOI: 10.31399/asm.fach.v02.c9001363
EISBN: 978-1-62708-215-0
... the pitch control thrust bearing set, head bolts, hub fork, and actuator rod end, were examined in more detail The thrust bearing set (52100 steel) was identified as the probable source of the uncommanded pitch angle change. A complete failure analysis of the bearing indicated that failure was precipitated...
Abstract
An accidental overspeed condition during wind tunnel testing resulted in the destruction of a propeller rotor The occurrence was initially attributed to malfunction in the collective pitch control system. All fractured parts in the system were inspected. Highly suspect parts, including the pitch control thrust bearing set, head bolts, hub fork, and actuator rod end, were examined in more detail The thrust bearing set (52100 steel) was identified as the probable source of the uncommanded pitch angle change. A complete failure analysis of the bearing indicated that failure was precipitated by excessive heating, causing cage disintegration, plastic flow of the races and balls, and eventual separation of inner and outer races. It was recommended that the bearing set be resized to accommodate the large thrust as and that a thermocouple be added to monitor the condition of the bearing during testing.
Book Chapter
Stress-Corrosion Cracking of a Forged Aircraft Lug
Available to PurchaseSeries: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.aero.c0091678
EISBN: 978-1-62708-217-4
... Abstract During a routine shear-pin check, the end lug on the barrel of the forward canopy actuator on a naval aircraft was found to have fractured. The lug was forged from aluminum alloy 2014-T6. Investigation (visual inspection, 2x views, and 140X micrographs etched with Keller's reagent...
Abstract
During a routine shear-pin check, the end lug on the barrel of the forward canopy actuator on a naval aircraft was found to have fractured. The lug was forged from aluminum alloy 2014-T6. Investigation (visual inspection, 2x views, and 140X micrographs etched with Keller's reagent) supported the conclusion that the cause of failure was SCC resulting from exposure to a marine environment. The fracture occurred in normal operation at a point where damage from pitting and intergranular corrosion acted as a stress raiser, not because of overload. The pitting and intergranular attack on the lug were evidence that the surface protection of the part had been inadequate as manufactured or had been damaged in service and not properly repaired in routine maintenance. Recommendations included anodizing the lug and barrel in sulfuric acid and giving them a dichromate sealing treatment, followed by application of a coat of paint primer. During routine maintenance checks, a careful examination was suggested to look for damage to the protective coating, and any necessary repairs should be made by cleaning, priming, and painting. Severely corroded parts should be removed from service.
Image
SEM micrograph showing a typical brittle overload fracture observed in a fa...
Available to Purchase
in Premature Torquing Failures of Cast A356 Aluminum Actuators
> Handbook of Case Histories in Failure Analysis
Published: 01 December 1992
Fig. 6 SEM micrograph showing a typical brittle overload fracture observed in a failed actuator casting. 315×.
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Image
Schematic of the collective pitch control system, showing the thrust bearin...
Available to Purchase
in Thrust Bearing Failure Leading to the Destruction of a Propeller Rotor
> Handbook of Case Histories in Failure Analysis
Published: 01 December 1993
Fig. 2 Schematic of the collective pitch control system, showing the thrust bearing set, control tube, and actuator
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