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microfractography
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Series: ASM Handbook
Volume: 11
Publisher: ASM International
Published: 15 January 2021
DOI: 10.31399/asm.hb.v11.a0006760
EISBN: 978-1-62708-295-2
... fracture surfaces. It discusses damage characterization of metals, covering various factors that influence the damage, namely stress, aggressive environment, temperature, and discontinuities. damage characterization failure analysis fracture surfaces metals microfractography optical...
Abstract
Visual examination, using the unaided eye or a low-power optical magnifier, is typically one of the first steps in a failure investigation. This article presents the guidelines for selecting samples for scanning electron microscope examination and optical metallography and for cleaning fracture surfaces. It discusses damage characterization of metals, covering various factors that influence the damage, namely stress, aggressive environment, temperature, and discontinuities.
Image
in Failure in Steam Turbine Blades
> ASM Failure Analysis Case Histories: Power Generating Equipment
Published: 01 June 2019
Fig. 5 Microfractography of the fracture surface. Two stage Rodoid-carbon replica. 6000×
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Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.power.c9001193
EISBN: 978-1-62708-229-7
... as fatigue cracks produced by vibration in the operation of the turbine as a result of steplike growing of microcracks could not be deduced from the fracture surfaces. Microfractography showed that the cracks developed in stages. Brazing Residual stress Steam turbines X20Cr 13 Joining-related...
Abstract
When a steam turbine was put out of service, cracks were noticed on many of the blades in the low pressure section round the stabilization bolts and perpendicular to the blade axis. The blades were made from chrome alloy steel X20-Cr13 (Material No. 1.402). When the bolts were brazed into the blades inadmissible localized overheating of the steel must have occurred, which resulted in transformation stresses and hence reduced deformability. The cracks arose as a consequence of careless brazing. Whether the cracks should be considered as stress cracks over their entire extent or partially as fatigue cracks produced by vibration in the operation of the turbine as a result of steplike growing of microcracks could not be deduced from the fracture surfaces. Microfractography showed that the cracks developed in stages.
Series: ASM Handbook Archive
Volume: 11
Publisher: ASM International
Published: 01 January 2002
DOI: 10.31399/asm.hb.v11.a0003520
EISBN: 978-1-62708-180-1
... Abstract This article outlines the basic steps to be followed and the range of techniques available for failure analysis, namely, background data assembling, visual examination, microfractography, chemical analysis, metallographic examination, electron microscopy, electron microprobe analysis...
Abstract
This article outlines the basic steps to be followed and the range of techniques available for failure analysis, namely, background data assembling, visual examination, microfractography, chemical analysis, metallographic examination, electron microscopy, electron microprobe analysis, X-ray techniques, and simulations. It also describes the steps for analyzing the data, preparing the report, preservation of evidence, and follow-up on recommendations.
Series: ASM Failure Analysis Case Histories
Volume: 3
Publisher: ASM International
Published: 01 December 2019
DOI: 10.31399/asm.fach.v03.c9001845
EISBN: 978-1-62708-241-9
... platelets ( Fig. 4b ). No evidence of ductile fracture was noticed on the failed fracture surfaces. However, microfractography of the artificial fracture ( Fig. 4f ) confirmed the tough nature characterized by dimple morphology. Also, no dark flakes were detected in the regions. EDX was performed to analyze...
Abstract
Two clamps that support overhead power lines in an electrified rail system fractured within six months of being installed. The clamps are made of CuNiSi alloy, a type of precipitation-strengthening nickel-silicon bronze. To identify the root cause of failure, the rail operator led an investigation that included fractographic and microstructural analysis, hardness testing, inductively coupled plasma spectroscopy, and finite-element analysis. The fracture was shown to be brittle in nature and covered with oxide flakes, but no other flaws relevant to the failure were observed. The investigation results suggest that the root cause of failure was a forging lap that occurred during manufacturing. Precracks induced by the forging defect and the influence of preload stress (due to bolt torque) caused the premature failure.
Series: ASM Failure Analysis Case Histories
Volume: 1
Publisher: ASM International
Published: 01 December 1992
DOI: 10.31399/asm.fach.v01.c9001058
EISBN: 978-1-62708-214-3
....” Testing Procedure and Results Surface Examination Microfractography Fracture surfaces on both parts of the submitted 32 mm ( 1 1 4 in.) plug showed no evidence of fatigue or of any preexisting crack or cavity ( Fig. 3 and 4 ). The portion of the plug that was freed from the system...
Abstract
A white cast iron water-line plug in a fire sprinkler systems split during leak repair. Examination revealed no material flaws, fatigue, or excessive corrosion. The plug head exhibited signs of excessive loads used in attempts to force the plug farther into the pipe. The evidence obtained indicated that the failure resulted from human error.
Series: ASM Failure Analysis Case Histories
Volume: 3
Publisher: ASM International
Published: 01 December 2019
DOI: 10.31399/asm.fach.v03.c9001838
EISBN: 978-1-62708-241-9
.... pipe hot cracking grain boundary segregation stainless steel tear ridges melt bridging microfractography induction heating frequency X6CrNiMoTi17-12-2 (titanium-stabilized austenitic stainless steel) UNS S31635 Introduction Large austenitic stainless steel piping used for manifolds...
Abstract
Stainless steel pipe (273-mm OD x 8-mm wall thickness) used in the fabrication of large manifolds developed crack-like decohesions during a routine inductive bending procedure. The imperfections, which were found near the outside diameter, were around 3 mm in length oriented in the circumferential direction and penetrated nearly 2 mm into the pipe wall. The pipes were made of titanium-stabilized austenitic stainless steel X6CrNiMoTi17-12-2. Six hypotheses were considered during the investigation, which ultimately concluded that the failure was caused by liquation cracking due to overheating.
Series: ASM Failure Analysis Case Histories
Volume: 1
Publisher: ASM International
Published: 01 December 1992
DOI: 10.31399/asm.fach.v01.c9001057
EISBN: 978-1-62708-214-3
... Microfractography In order to expose the crack surface for examination, a cut was made parallel to and 13 mm ( 1 2 in.) from the crack, and a 13 mm ( 1 2 in.) wide strip containing one of the fracture surfaces was removed from the nipple. Fig. 2 shows the exposed mating fracture surfaces...
Abstract
A brass (CDA alloy 230) pipe nipple that was part of a domestic cold water bath system failed two weeks after installation. Macrofractography, SEM examination, metallography, and chemical analyses were performed on specimens cut through the main fracture surface. The physical and background evidence obtained indicated failure due to cracking initiated by stamped markings on the pipe wall and extended by high circumferential residual stresses. It was recommended that annealed pipe be used.
Series: ASM Failure Analysis Case Histories
Volume: 1
Publisher: ASM International
Published: 01 December 1992
DOI: 10.31399/asm.fach.v01.c9001026
EISBN: 978-1-62708-214-3
.... The overload fracture resulting from breaking open this crack was identical to the apparent overload areas of the original fracture, consisting of nearly microscopic cleavage facets. Fig. 3 SEM macrograph of area of flakes 2 (upper) and 3 (lower), showing cleavage step patterns. Microfractography...
Abstract
Cracks were discovered in the cast 17-4 PH stainless steel outboard leading edge flap support of an aircraft wing during overhaul inspection. Failure analysis focused on an apparently intergranular area of fracture surface. It was determined that the original mode of crack growth was cleavage, probably caused by cast-in hydrogen. The intergranular appearance resulted from heat treatment of the already cracked part, which caused the formation of grain-boundary “growth figures” on the exposed crack surfaces. It was recommended that the castings be more closely inspected for defects before further processing and that foundry practices be reviewed to correct deficiencies leading to excessive hydrogen absorption during melting and casting.
Series: ASM Failure Analysis Case Histories
Volume: 1
Publisher: ASM International
Published: 01 December 1992
DOI: 10.31399/asm.fach.v01.c9001077
EISBN: 978-1-62708-214-3
... was minimal. There was little evidence to suggest that any abnormal loading of the gear had taken place. Both macrofractography and microfractography revealed that cracking initiated internally in a region of defective material in a heavily loaded area of the two gear teeth. Although it was difficult...
Abstract
The failure of a spiral bevel gear from the transmission of a helicopter was discovered when the transmission was removed after an in-flight incident. Two adjacent teeth from the carburized AISI 9310 steel gear were found to have undergone fatigue failure. Internal initiation occurred in a region depleted of chromium and nickel. This condition coincides with a microstructural inhomogeneity consisting of large, soft ferrite grains. Its origin was probably contamination of the solidifying ingot during the consumable vacuum arc remelting operation.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.bldgs.c9001544
EISBN: 978-1-62708-219-8
... radius; but after the part cracked in the shop, the radius shown here was milled on all four junction pieces used on the bridge. The repair weld material was not determined, but it is apparently a tougher material than the base metal. Metallography and electron microfractography completed...
Abstract
A large crack developed at a girder-truss joint area of the Fremont bridge in Portland, OR, on 28 Oct 1971. It occurred during a positioning procedure involving a junction piece welded to a girder, starting as a brittle fracture and terminating in plastic hinges in the girder web welds. The arch rib top plate, as it met the main girder, formed a composite beam of A588/A36 composition. Investigation showed the original design of the failed component called for an angle of high geometric stress concentration (90 deg with no radius) in a region of substantial transverse weld joints. While the material met chemical and mechanical property requirements, tests showed it had low fracture toughness and critical-sized flaws oriented normal to the principal stress in the failed junction piece. Fabrication procedures resulted in high residual stresses and a metallurgical notch at the radius in the junction piece. Stresses induced during jacking (the procedure used to raise bridge components into position) applied the stresses in the critical radius that triggered the cracking.
Book Chapter
Series: ASM Handbook
Volume: 11
Publisher: ASM International
Published: 15 January 2021
DOI: 10.31399/asm.hb.v11.a0006757
EISBN: 978-1-62708-295-2
.... ceramic materials corrosion damage macroscopic examination metallic components metallographic specimens microchemical analysis microfractography microstructure polymers visual examination wear EXAMINATION of a damaged component involves a chain of activities that, first and foremost...
Abstract
Examination of a damaged component involves a chain of activities that, first and foremost, requires good observation and documentation. Following receipt and documentation, the features of damage can be recorded and their cause(s) investigated, as this article briefly describes, for typical types of damage experienced for metallic components. This article discusses the processes involved in visual or macroscopic examination of damaged material; the interpretation of fracture features, corrosion, and wear damage features; and the analysis of base material composition. It covers the processes involved in the selection of metallurgical samples, the preparation and examination of metallographic specimens in failure analysis, and the analysis and interpretation of microstructures. Examination and evaluation of polymers and ceramic materials in failure analysis are also briefly discussed.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.aero.c9001144
EISBN: 978-1-62708-217-4
.... , “ Use of Microfractography in the Study of Fatigue Crack Propagation under Spectrum Loading ,” Fractography in Failure Analysis , ASTM STP 645, 213-3Z ( 1978 ). 10.1520/STP38093S 4. McSwain R. H. , “ Digital Fractographic Imaging Analysis ,” Ph.D. Dissertation, University of Florida...
Abstract
A helicopter was hovering approximately 10 ft above a ship when one spar section failed explosively. Visual inspection revealed a crack had progressed through one member of a dual spar plate assembly at a fold pin lug hole. The remaining spar plate carried the blade load until the aircraft was landed. The helicopter main rotor blade spar fracture was analyzed by conventional and advanced computerized fractographic techniques. Digital fractographic Imaging Analysis of theoretical and actual fracture surfaces was applied for automatic detection of fatigue striation spacing. The approach offered a means of quantification of fracture features, providing for objective fractography.
Series: ASM Failure Analysis Case Histories
Volume: 3
Publisher: ASM International
Published: 01 December 2019
DOI: 10.31399/asm.fach.v03.c9001849
EISBN: 978-1-62708-241-9
... mill for failure analysis. Visual inspection, macro-and microfractography along with optical microscopy and microhardness testing were used to determine the cause of the observed spalling. Experimental Procedure Cleaning dust, metal fines, and oil residues from the samples was performed...
Abstract
Spalled fragments from the work rolls of a steel bar straightening machine were received for failure analysis. Visual inspection coupled with optical and scanning electron microscopy were used as the principal analytical techniques for the investigation. Fractographic analysis revealed the presence of a characteristic fatigue crack propagation pattern (beach marks) and radial chevron marks indicating the occurrence of final overload through a brittle intergranular fracture. The collected evidence suggests that surface-initiated cracks propagated by fatigue led to spalling, resulting in severe work roll damage as well as machine downtime and increased maintenance costs.
Series: ASM Handbook Archive
Volume: 11
Publisher: ASM International
Published: 01 January 2002
DOI: 10.31399/asm.hb.v11.a0003518
EISBN: 978-1-62708-180-1
... and other methods. Cracks, porosity, and unsoundness of various types may be able to be detected without cutting the part. Microfractrography and other techniques with SEM, including localized chemical analysis Microfractography may simply be used to add weight to a macro scale determination of ductile...
Abstract
Failure analysis is a process that is performed to determine the causes or factors that have led to an undesired loss of functionality. This article describes some of the factors and conditions that might be considered when approaching a failure analysis problem. It focuses on the key principles, objectives, practices, and procedures of failure analysis. The article provides guidelines on the preparation of a protocol for a failure analysis. It also demonstrates the proper approaches to failure analysis.
Series: ASM Handbook
Volume: 11
Publisher: ASM International
Published: 15 January 2021
DOI: 10.31399/asm.hb.v11.a0006754
EISBN: 978-1-62708-295-2
... Microfractography may simply be used to add weight to a macroscale determination of ductile or brittle behavior. Evidence for distinguishing intergranular from cleavage fracture is most easily obtained by this method. Fine characteristics of ductile dimples can reveal additional information not available...
Abstract
Failure analysis is a process that is performed in order to determine the causes or factors that have led to an undesired loss of functionality. This article is intended to demonstrate proper approaches to failure analysis work. The goal of the proper approach is to allow the most useful and relevant information to be obtained. The discussion covers the principles and approaches in failure analysis work, objectives and scopes of failure analysis, the planning stages for failure analysis, the preparation of a protocol for a failure analysis, practices used by failure analysts, and procedures of failure analysis.
Series: ASM Failure Analysis Case Histories
Volume: 1
Publisher: ASM International
Published: 01 December 1992
DOI: 10.31399/asm.fach.v01.c9001071
EISBN: 978-1-62708-214-3
... of the valve and bolt hole 7. The fracture surface of the flange between bolt hole 7 and its outer rim (point C in Fig. 4 ) exhibited no sulfates. Fig. 8 Closeup view of fractured specimen from point A in Fig. 7 . Microfractography Examination of the fracture surfaces at low magnification...
Abstract
A gray cast iron (ASTM 247 type A) gate valve in an oleum and sulfuric acid piping loop at a chemical process plant fractured catastrophically after approximately 10 years of service. The valve was a 150 mm (6 in.) bolted flange type rated to conform to ANSI B16.1 for service at 1034 kPa (150 psi) and 120 deg C (250 deg F) maximum in 93 to 99% sulfuric acid. The fracture originated at stress-corrosion cracks that occurred in a high-stress transition region at the valve body-to-flange juncture. The mechanical properties of the failed valve were below those of the manufacturer's cited specification, and the wall thickness through which the fracture occurred exceeded the minimum 9.5 mm (38 in.) thickness cited by the manufacturer The valve flange had been unbolted and rebolted to a maintenanced piping coil immediately prior to failure. It was recommended that the flange-to-valve body juncture be redesigned to reduce stress levels. A method of maintenance and inspection in concert with a criterion for life prediction for this and other valves and components in the system was also recommended.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.petrol.c9001148
EISBN: 978-1-62708-228-0
... by microfractography has previously been noted to be 0.175″ deep by 0.165″ wide (0.44cm × 0.419cm). The critical stress intensity of the steel at the fracture origin site may then be calculated using the standard relationship (Eq 2) K 1 = σ 1 C π a where σ 1 is the principal normal stress...
Abstract
A natural gas pipeline explosion and subsequent fire significantly altered the pipeline steel microstructure, obscuring in part the primary cause of failure, namely, coating breakdown at a local hard spot in the steel. Chemical analysis was made on pieces cut from the portion of the pipe that did not fracture during the explosion and from piece 5-1 which contained the fracture origin site. Both pieces were found to have 0.30% carbon and 1.2% Mn with sulfur and phosphorus impurities acceptably low. Fracture mechanics analysis used in conjunction with fractographic results confirmed the existence of a very hard spot in the steel prior to the explosion, which was softened significantly in the ensuing fire. This finding allowed the micromechanism leading to fracture to be identified as hydrogen embrittlement resulting from cathodic charging.
Series: ASM Handbook Archive
Volume: 11
Publisher: ASM International
Published: 01 January 2002
DOI: 10.31399/asm.hb.v11.a0003537
EISBN: 978-1-62708-180-1
... also be striking. Because of the early use of the TEM in microfractography, a substantial amount of fractographic images via TEM replicas have been published. In 1966, for example, Cedric Beachem published the results of an extensive study of fractographic features and interpretation at the Naval...
Abstract
This article provides an overview of fractography and explains how it is used in failure analysis. It reviews the basic types of fracture processes, namely, ductile, brittle, fatigue, and creep, principally in terms of fracture appearances, such as microstructure. The article also describes the general features of fatigue fractures in terms of crack initiation and fatigue crack propagation.
Series: ASM Handbook
Volume: 11A
Publisher: ASM International
Published: 30 August 2021
DOI: 10.31399/asm.hb.v11A.a0006814
EISBN: 978-1-62708-329-4
... to photographs of the fracture surface; macrofractography involves low magnification (<25×), while microfractography is at high magnification (>25×) ( Ref 1 ). Fractography is a valuable tool when performing failure analyses on welded connections, and macrofractrography is particularly useful. Perhaps...
Abstract
Welded connections are a common location for failures for many reasons, as explained in this article. This article looks at such failures from a holistic perspective. It discusses the interaction of manufacturing-related cracking and service failures and primarily deals with failures that occur in service due to stresses caused by externally applied loads. The purpose of this article is to enable a failure analyst to identify the causative factors that lead to welded connection failure and to identify the corrective actions needed to overcome such failures in the future. Additionally, the reader will learn from the mistakes of others and use principles that will avoid the occurrence of similar failures in the future. The topics covered include failure analysis fundamentals, welded connections failure analysis, welded connections and discontinuities, and fatigue. In addition, several case studies that demonstrate how a holistic approach to failure analysis is necessary are presented.
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