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Defects
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Series: ASM Failure Analysis Case Histories
Volume: 2
Publisher: ASM International
Published: 01 December 1993
DOI: 10.31399/asm.fach.v02.c9001005
EISBN: 978-1-62708-215-0
... the level of power assistance to the wheels to encourage the driver to put the vehicle in motion prior to turning. Chromium-molybdenum steel - 4135 Chromium-molybdenum steels, mechanical properties Crack initiation Fatigue failure Forging defects Steering arms Stress concentration 4135 UNS...
Abstract
Several heavy truck Cr-Mo steel steering arms in service less than three years fractured during stationary or low-speed turning maneuvers that required power-assisted steering. Metallographic examination of the cracked AISI 4135 arms, heat treated to a hardness of 285 to 341 HB, revealed that fatigue crack initiation occurred from the tip of oxide scale inclusions forged into the U-shaped arm at the inside radius. Corrective action involved redesigning the steering arm to increase the minimum forging radius and reduce the stress level at the inner-bend radius, and reducing the level of power assistance to the wheels to encourage the driver to put the vehicle in motion prior to turning.
Book Chapter
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.power.c9001422
EISBN: 978-1-62708-229-7
.... Specimens were prepared for microscopical examination to include the defective zone and a section through a circumferential crack. The defective zone was found to contain numerous inclusions of slag and oxides of globular form. Regions surrounding the inclusions were decarburized, the indications being...
Abstract
During a hydraulic test on one of the boilers in a range, leakage occurred from the lower surface of a horizontal S bend in the main steam pipe between the drum connector box and the junction valve. The pipe in question was 15 in. bore and had been in service for about 50 years. Specimens were prepared for microscopical examination to include the defective zone and a section through a circumferential crack. The defective zone was found to contain numerous inclusions of slag and oxides of globular form. Regions surrounding the inclusions were decarburized, the indications being that this region of the plate had been heated to an excessively high temperature. A corrosion-fatigue fissure was at one location, this having originated at the internal surface of the pipe and run into an inclusion in the defective zone. The failure resulted from the development of corrosion-fatigue fissures which originated at a zone containing defects introduced at the time of manufacture. These may have had their origin in the ingot from which the plate was rolled or, alternatively, be indicative of a zone which suffered overheating and local burning at the time the forge weld was made.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.process.c9001909
EISBN: 978-1-62708-235-8
... parameters resulted in acceptable welds. Bombs (weapons) Bomb fins Welded joints Weld defects Low-carbon steel Joining-related failures Introduction Component: MK#83 and MK#84 general purpose bomb fins Manufacturing defects: Nonpenetrating plug welds Background A First Article...
Abstract
Welded low-carbon steel bomb fins were rejected because of poor weld practice. Visual and metallographic examination revealed that the resistance plug welds that attach the outer skin to the inner spar displayed inadequate weld penetration. Recommended changes to the resistance welding parameters resulted in acceptable welds.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.process.c9001589
EISBN: 978-1-62708-235-8
... Abstract The paper discusses the analysis of a coating defect on a high phosphorus electroless nickel (Ni-11 wt. % P) deposit plated on an aluminum alloy substrate. Preliminary investigations had indicated that the elongated defects were possibly caused by the entrapment of long fibers...
Abstract
The paper discusses the analysis of a coating defect on a high phosphorus electroless nickel (Ni-11 wt. % P) deposit plated on an aluminum alloy substrate. Preliminary investigations had indicated that the elongated defects were possibly caused by the entrapment of long fibers or particles during the plating. The possible sources of fibers were identified. The SEM/EDS analysis of fibers collected from the air duct filters correlated very well with the defect shape and the EDS profile collected from under the defect site. It appears that the fibers from air duct filters directly above the plating line were blown into the plating tank and getting co-deposited. The paper describes the step-by-step analysis of the defect that led to successful identification of the root cause of the defect.
Book Chapter
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.process.c0089651
EISBN: 978-1-62708-235-8
... etched 300x magnification) supported the conclusion that the rocker levers failed in fatigue, with casting defects, or spiking, acting as stress raisers to initiate failures in highly loaded engine tests. Recommendations included shot peening of the levers as an interim measure to reduce the possibility...
Abstract
Several diesel-engine rocker levers (malleable iron similar to ASTM A 602, grade M7002) failed at low hours in overspeed, over-fuel, highly loaded developmental engine tests. Identical rocker levers had performed acceptably in normal engine tests. The rocker levers were failing through the radius of an adjusting screw arm. The typical fracture face exhibited two distinct modes of crack propagation: the upper portion indicated overload at final fracture, whereas the majority of the fracture suggested a fatigue fracture. Investigation (visual inspection, 1.5x/30x/60x magnification, and nital etched 300x magnification) supported the conclusion that the rocker levers failed in fatigue, with casting defects, or spiking, acting as stress raisers to initiate failures in highly loaded engine tests. Recommendations included shot peening of the levers as an interim measure to reduce the possibility of failure and redesign to increase the cross-sectional area of the levers.
Book Chapter
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.process.c9001443
EISBN: 978-1-62708-235-8
... Abstract Following the fusing of one of the copper leads in the choke circuit of an electric welder, a piece of the affected lead was obtained for examination. The sample had large internal cavities and surface bulges. It is remarkable that a wire containing defects of the magnitude present...
Abstract
Following the fusing of one of the copper leads in the choke circuit of an electric welder, a piece of the affected lead was obtained for examination. The sample had large internal cavities and surface bulges. It is remarkable that a wire containing defects of the magnitude present in this case could have been drawn without failure. Failure in service was due to overheating resulting from the inability of the conductor to carry the current where its cross section was reduced by the presence of a cavity. Another failure of a conductor occurred in one of the field coils of a direct-current motor. The mode of failure and the changes in the microstructure showed that fracture was due to a defective resistance butt-weld which had been made when the wire was in process of drawing. A further example of a conductor failure occurred in a 12 SWG copper connection between the rotor contactor and the resistance in a starter. A transverse section through the zone of failure showed an oxide layer extended almost completely across the plane of a weld, and also the grain growth that had occurred in this region.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.process.c9001601
EISBN: 978-1-62708-235-8
... Abstract Flow forming technology has emerged as a promising, economical metal forming technology due to its ability to provide high strength, high precision, thin walled tubes with excellent surface finish. This paper presents experimental observations of defects developed during flow forming...
Abstract
Flow forming technology has emerged as a promising, economical metal forming technology due to its ability to provide high strength, high precision, thin walled tubes with excellent surface finish. This paper presents experimental observations of defects developed during flow forming of high strength SAE 4130 steel tubes. The major defects observed are fish scaling, premature burst, diametral growth, microcracks, and macrocracks. This paper analyzes the defects and arrives at the causative factors contributing to the various failure modes.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.med.c0089543
EISBN: 978-1-62708-226-6
... Abstract Threads of a bone screw (Co-Cr-Mo alloy, type ASTM F75) had broken off, and other threads had cracked. 15x sectioning showed porosity, and 155x magnification showed gas holes, segregation, and dissolved oxides. This supports the conclusion that manufacturing defects caused the failure...
Abstract
Threads of a bone screw (Co-Cr-Mo alloy, type ASTM F75) had broken off, and other threads had cracked. 15x sectioning showed porosity, and 155x magnification showed gas holes, segregation, and dissolved oxides. This supports the conclusion that manufacturing defects caused the failure.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.marine.c9001445
EISBN: 978-1-62708-227-3
... longitudinally through the upper wall over a length of approximately 68 in. The sample received for examination was ultrasonically tested, which indicated a band of internal defects extending 1 in. in from the edge. Subsequently, the portion of the pipe embodying the other side of the rupture was obtained...
Abstract
An explosion occurred in a portion of a horizontal, U-shaped expansion loop in a steam main approximately 10-in. diam which had been operating at 400 psi for six years. Steam conditions varied from 538 deg C (450 deg F) saturated to 343 deg C (650 deg F) superheated. Fracture occurred longitudinally through the upper wall over a length of approximately 68 in. The sample received for examination was ultrasonically tested, which indicated a band of internal defects extending 1 in. in from the edge. Subsequently, the portion of the pipe embodying the other side of the rupture was obtained for examination. Transverse sections through this and the mating portion already received, followed by magnetic crack detection, revealed the presence of defective zones. Subsequent ultrasonic examination of other sections of the steam main indicated suspect areas in a number of lengths of pipe. These defects were basically laminations of a similar form to those which resulted in the failure of the portion of pipe.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.modes.c9001446
EISBN: 978-1-62708-234-1
..., about 2 in. long, developed at the approximate mid-length of the vessel, and allowed slow de-pressurization. Subsequent examination by radiography and ultrasonic means indicated the crack was associated with an irregularly shaped, laminar type of defect located within the wall of the vessel...
Abstract
A 2 ft. diam 20 ft. long cylinder with a wall thickness of 1 in. used for the transportation of a compressed gas failed by cracking. The cylinder was forged in a low ally steel. The working pressure was 3000 psi and it had been in service for about seven years. A longitudinal crack, about 2 in. long, developed at the approximate mid-length of the vessel, and allowed slow de-pressurization. Subsequent examination by radiography and ultrasonic means indicated the crack was associated with an irregularly shaped, laminar type of defect located within the wall of the vessel. It was concluded that failure of this vessel resulted from the development of a radial crack orientated in the axial direction. This appeared to have originated on the bore surface in a region where the laminar defect closely approached this surface. The defect was introduced during the manufacture of the vessel, probably originating as a secondary pipe in the ingot which was subsequently displaced and forced into the wall of the vessel during the piercing operation.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.aero.c0047165
EISBN: 978-1-62708-217-4
... inspection, and micrographs with deep etching in aqueous 20% sodium hydroxide) supported the conclusion that failure on both wheel halves was by fatigue caused by a forging defect resulting from abnormal transverse grain flow. The crack in the first wheel half occurred during service, and the surfaces became...
Abstract
Two outboard main-wheel halves (aluminum alloy 2014-T6 forged) from a commercial aircraft were removed from service because of failure. One wheel half was in service for 54 days and had made 130 landings (about 1046 roll km, or 650 roll mi) when crack indications were discovered during eddy-current testing. The flange on the second wheel half failed after only 31 landings, when about 46 cm (18 in.) of the flange broke off as the aircraft was taxiing. Stains on the fracture surfaces were used to determine when cracking was initiated. The analysis (visual inspection, liquid penetrant inspection, and micrographs with deep etching in aqueous 20% sodium hydroxide) supported the conclusion that failure on both wheel halves was by fatigue caused by a forging defect resulting from abnormal transverse grain flow. The crack in the first wheel half occurred during service, and the surfaces became oxidized. Because the fracture surface of the second wheel half had chromic acid stains, it was obvious that the forging defect was open to the surface during anodizing. No recommendations were made except to notify the manufacturer.
Series: ASM Failure Analysis Case Histories
Volume: 3
Publisher: ASM International
Published: 01 December 2019
DOI: 10.31399/asm.fach.v03.c9001785
EISBN: 978-1-62708-241-9
... produced by a single manufacturer which were removed from tool boxes and store stock. The nonfailed wrench population was visually inspected for any obvious defects and none were found. To determine the cause of the failure, 15 wrenches along with the failed wrench were submitted for failure analysis...
Abstract
A maintenance worker was injured when his 3/4 in. (19 mm) open-ended wrench failed, fracturing in overload fashion along the jaw. The failed wrench was unavailable for testing, but an identical one that failed in the same manner was acquired and subjected to hardness, chemistry, SEM, and metallurgical analyses. SEM imaging revealed microvoid coalescence within the fracture zone. The microvoids were flat and smooth edged indicating insufficient bonding. In addition, a cross sectional sample, mounted and etched using alkaline chromate, revealed an oxygen-rich zone in the jaw. It was concluded that the failures stemmed from forging laps in the jaw that broaching failed to remove.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.process.9781627082358
EISBN: 978-1-62708-235-8
Image
Published: 01 January 2002
Fig. 29 Examples of strength-limiting defects in ceramics. (a) Silicon inclusion in reaction-bonded silicon nitride. (b) Powder agglomerate in sintered silicon carbide. (c) Machining damage in hot pressed silicon nitride. SEM; picture widths (a) ∼150 μm. (b) ∼300 μm, (c) ∼150 μm. Source: Ref
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Published: 01 January 2002
Fig. 1 Typical crack defects found on ceramic ball surfaces under ultraviolet light. (a) Star defect. (b) Pressing defect. (c) Single ring crack. (d) Double ring cracks
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Published: 01 January 2002
Fig. 2 Example of fault tree chart for forgings with dye-penetrant defects
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Published: 01 January 2002
Fig. 5 Example of corrective action tree for forgings with dye-penetrant defects. LIMCA, liquid metal cleanness analyzer device
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Published: 01 January 2002
Fig. 16 Close-up views of surface casting defects on a paper-drier head. (a) At the 12 o'clock position. (b) At the 9 o'clock position, with arrow indicating a surface defect. (c) At the 6 o'clock position. All approximately 0.2×
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Published: 01 January 2002
Fig. 2 Schematic of defects and discontinuities in welded joints
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in Premature Failure of 200T Crane Hook From a Weld Deposit
> ASM Failure Analysis Case Histories: Material Handling Equipment
Published: 01 June 2019
Fig. 4 Showing shear fracture of weld metal and root defects.
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