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low-temperature fracture toughness
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Series: ASM Failure Analysis Case Histories
Volume: 3
Publisher: ASM International
Published: 01 December 2019
DOI: 10.31399/asm.fach.v03.c9001835
EISBN: 978-1-62708-241-9
... fracture stress concentration metallographic analysis silicate and oxide inclusions stress analysis low-temperature fracture toughness Fe-0.34C-0.7Mn-0.34Cr (chromium alloy steel) Introduction Wind power generation has rapidly spread in recent years as one of the clean energy resources...
Abstract
Wind turbine blades are secured by a number of high-strength bolts. The failure of one such bolt, which caused a turbine blade to detach, was investigated to determine why it fractured. Based on the results of a detailed analysis, consisting of stress calculations, chemical composition testing, metallurgical examination, mechanical property testing, and fractographic analysis, it was determined that the bolt failed by fatigue accelerated by stress concentration at low temperatures. The investigation also provided suggestions for avoiding similar failures.
Series: ASM Failure Analysis Case Histories
Volume: 1
Publisher: ASM International
Published: 01 December 1992
DOI: 10.31399/asm.fach.v01.c9001114
EISBN: 978-1-62708-214-3
... was found. The cleavage features on the fracture surface of the clamp material were indicative of brittle fracture. This mechanism is favored in materials with low toughness, rapid rate of loading, and/or low temperatures. In this particular failure, the service temperature and the rate of loading were...
Abstract
An API type 2 steel clamp located on the riser of a semisubmersible drilling rig between the lower ball joint and riser blowout preventer (BOP) conductor failed after 7 years of service. Failure analysis revealed the cause of failure to be the low toughness of the clamp material. Contributing factors included the presence of a hard, brittle, heat-affected zone and weld defects at the handling pad eye. It was recommended that the replacement clamp be made from a material with good toughness and that any installation of attachments by welding be done according to qualified procedures.
Series: ASM Handbook
Volume: 11A
Publisher: ASM International
Published: 30 August 2021
DOI: 10.31399/asm.hb.v11A.a0006809
EISBN: 978-1-62708-329-4
... mitigation storage tanks METAL TEMPERATURE highly influences the fracture toughness of carbon and low-alloy steel materials. At low temperatures, the material tends to behave in a brittle manner, making it much more susceptible to sudden fracture without warning. At high temperatures, the material...
Abstract
A detailed fracture mechanics evaluation is the most accurate and reliable prediction of process equipment susceptibility to brittle fracture. This article provides an overview and discussion on brittle fracture. The discussion covers the reasons to evaluate brittle fracture, provides a brief summary of historical failures that were found to be a result of brittle fracture, and describes key components that drive susceptibility to a brittle fracture failure, namely stress, material toughness, and cracklike defect. It also presents industry codes and standards that assess susceptibility to brittle fracture. Additionally, a series of case study examples are presented that demonstrate assessment procedures used to mitigate the risk of brittle fracture in process equipment.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.rail.c0089716
EISBN: 978-1-62708-231-0
... was initiated by weld imperfections and propagated in a brittle manner as a result of service stresses acting on plate having low toughness at the low service temperatures encountered. Recommendations On the basis of fracture toughness studies, it was suggested that the specifications for the steel...
Abstract
A railway tank car developed a fracture in the region of the sill and shell attachment during operation at -34 deg C (-30 deg F). On either side of the sill-support member, cracking initiated at the weld between a 6.4 mm thick frontal cover plate and a 1.6 mm thick side support plate. The crack then propagated in a brittle manner upward through the side plate, through the welds attaching the side plate to a 25 mm (1 in.) thick shell plate (ASTM A212, grade B steel), and continued for several millimeters in the shell plate before terminating. Other plates involved were not positively identified but were generally classified as semi-killed carbon steels. Investigation (visual inspection, hardness testing, chemical analysis, Charpy V-notch testing, and drop-weight testing) supported the conclusions that the fracture was initiated by weld imperfections and propagated in a brittle manner as a result of service stresses acting on the plate having low toughness at the low service temperatures encountered. Recommendations included that the specifications for the steel plates be modified to include a toughness requirement and that improved welding and inspection practices be performed to reduce the incidence of weld imperfections.
Series: ASM Failure Analysis Case Histories
Volume: 1
Publisher: ASM International
Published: 01 December 1992
DOI: 10.31399/asm.fach.v01.c9001111
EISBN: 978-1-62708-214-3
..., the microstructure contained islands of ferrite in combination with pools of martensite of higher-than-average carbon content. As a result, plate A developed very low fracture toughness (compare Figs. 4 and 7 ) and widely different fracture characteristics between surface and midthickness of the plate ( Fig. 6...
Abstract
A catastrophic brittle fracture occurred in a welded steel (ASTM A517 grade H) trapezoidal cross-section box girder while the concrete deck of a large bridge was being poured. The failure occurred across the full width of a 57 mm (2 1 4 in.) thick, 760 mm (30 in.) wide flange and arrested 100 mm (4 in.) down the slant web. Failure analysis revealed a major deficiency in fracture toughness. The failure occurred as a brittle fracture after the formation of a welding hot crack and approximately 40 mm (1 1 2 in.) of slow crack growth. It was recommended that bridges fabricated from this grade of steel undergo frequent inspection and that stringent test requirements be imposed as a condition of use in non-redundant main load-carrying components.
Series: ASM Failure Analysis Case Histories
Volume: 1
Publisher: ASM International
Published: 01 December 1992
DOI: 10.31399/asm.fach.v01.c9001079
EISBN: 978-1-62708-214-3
... the fracture toughness level. Surface Examination Scanning Electron Microscopy/Fractography Figure 2 shows the ring sample with the flaw. This sample was cut in half. One half was examined as a cross section, and the other half was broken open at a low temperature and examined in a scanning...
Abstract
Numerous flaws were detected in a steam turbine rotor during a scheduled inspection and maintenance outage. A fracture-mechanics-based analysis of the flaws showed that the rotor could not be safely returned to service. Material, samples from the bore were analyzed to evaluate the actual mechanical properties and to determine the metallurgical cause of the observed indications. Samples were examined in a scanning electron microscope and subjected to chemical analysis and several mechanical property tests, including tensile, Charpy V-notch impact, and fracture toughness. The material was found to be a typical Cr-Mo-V steel, and it met the property requirements. No evidence of temper embrittlement was found. The analyses showed that the observed flaws were present in the original forging and attributed them to lack of ingot consolidation. A series of actions, including overboring of the rotor to remove indications close to the surface and revision of starting procedures, were implemented to extend the remaining life of the rotor and ensure its fitness for continued service.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.matlhand.c9001196
EISBN: 978-1-62708-224-2
...-section at room temperature, indicated an energy absorption of only 1.75 kpm/cm 2 confirming the expected low shock resistance. Fig. 2 Coarse bainitic structure of steel in condition as received, etched with Nital. 200 × An attempt was made to improve the toughness of the steel...
Abstract
A forged alloy steel arm of a lifting fork with an approximate cross section of 150 x 240 mm (5.92 x 9.45 in.) fractured after only a short service life on a lift truck. The fracture surface had the appearance of a fracture originating from a surface crack. Analysis (visual inspection, 200x micrographs, chemical analysis, and metallographic examination) supported the conclusion that the primary cause of the failure was the brittleness (lack of impact toughness) of the steel. The coarse bainitic microstructure was inadequate for the service application. The microstructure resulted from either improper heat treatment or no heat treatment after the forging operation. The surface cracks in the lifting-fork arm acted as starter notches (stress raisers), assisting in the initiation of fracture. No recommendations were made.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.bldgs.c9001135
EISBN: 978-1-62708-219-8
... , 5 . Figure 4 shows the amount of energy needed to fracture versus the testing temperature. Figure 5 is a plot of dynamic fracture toughness versus temperature for both sets of samples. The non-banded samples show an increase in toughness over the banded cores. Fig. 4 Charpy impact energy...
Abstract
In 1979, during a routine bridge inspection, a fatigue crack was discovered in the top flange plate of one tie girder in a tied arch bridge crossing the Mississippi River. Metallographic analysis indicated a banding or segregation problem in the middle of the plate, where the carbon content was twice what it should have been. Based on this and results of ultrasonic testing, which revealed that the banding occurred in 24-ft lengths, it was decided to close the bridge and replace the defective steel. The steel used in the construction of this bridge was specified as ASTM A441, commonly used in structural applications. Testing showed an increase in hardness and weight percent carbon and manganese in the banded region. Further testing revealed that the area containing the segregation and coarse grain structure had a lower than expected toughness and a transition temperature 90 deg F higher than specified by the ASTM standards. The fatigue crack growth rate through this area was much faster than expected. All of these property changes resulted from increased carbon levels, higher yield strength, and larger than normal grain size.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.power.c9001136
EISBN: 978-1-62708-229-7
... of a large industrial fan. The failure occurred from high cycle bending fatigue and appeared to have originated from a weld defect. The fracture toughness of the plate was relatively low, equivalent to K Q = 65 ± 9 MPa m over the operating temperature range of 0 to 400°C. By means...
Abstract
A fracture mechanics based failure analysis and life prediction of a large centrifugal fan made from low-carbon, medium-strength steel was undertaken following shortcomings in attempts to explain its fatigue life from start stop cycles alone. Measurements of the fracture toughness and flaw size at failure, coupled with quantitative SEM fractography using striation spacing methods, revealed that the cyclic stress amplitudes just prior to failure were much larger than expected, in this particular case. Subsequent improvements in fan design and fabrication have effectively alleviated the problem of slow, high cycle fatigue crack growth, at normal operating stresses in similar fans.
Series: ASM Failure Analysis Case Histories
Volume: 1
Publisher: ASM International
Published: 01 December 1992
DOI: 10.31399/asm.fach.v01.c9001053
EISBN: 978-1-62708-214-3
... that this imperfection, although small, initiated fracture because of the local geometry and stress conditions and the low toughness of the steel. It was recommended that (1) the probability of flaws be reduced by welding over or grinding out arc strikes, (2) the local stresses be lowered by post weld stress relief...
Abstract
A carbon steel (ASTM A515 grade 70) pressure vessel failed by brittle fracture while being hydro tested in the fabricating shop. The fracture origin was a small crack at a welding arc strike associated with the toe of a nozzle weld. A fracture mechanics calculation indicated that this imperfection, although small, initiated fracture because of the local geometry and stress conditions and the low toughness of the steel. It was recommended that (1) the probability of flaws be reduced by welding over or grinding out arc strikes, (2) the local stresses be lowered by post weld stress relief and improved weld toe geometry, and (3) toughness be improved by specifying fine-grain steel and/ or by normalizing.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.petrol.c9001137
EISBN: 978-1-62708-228-0
... philosophy was consequently regarded as acceptable. Fracture mechanics Low temperature Pressure vessels 1ZEET Fatigue fracture An extended ‘fitness for purpose’ evaluation of cold service pressure vessels (CSPV) used in the oil from coal industry was undertaken in 1982 ( 1 ). This study made...
Abstract
Following a fracture mechanics “fitness-for-purpose” analysis of petroleum industry cold service pressure vessels, using the British Standard PD 6493, it was realized that an analogous approach could be used for the failure analysis of a similar pressure vessel dome which had failed in service some years previously. The failed pressure vessel, with a diam of 2.5 m and several meters tall, had been made of 12 mm thick IZETT steel plate of the same type and heat treatment as used in the earlier fitness-for-purpose already measured. Examination of the fracture surfaces suggested, from fatigue striations manifested by SEM, that the vessel was subject to significant fatigue cracking, which was probably corrosion assisted. From COD measurements at the operating temperature of -130 deg C (-202 deg F), and a finite stress analysis, a fracture mechanics evaluation using BS PD6493 yielded realistic critical flaw sizes (in the range 51 to 150 mm). These sizes were consistent with the limited fracture surface observations and such flaws could well have been present in the vessel dome prior to catastrophic failure. For similar pressure vessels, an inspection program based on a leak-before-break philosophy was consequently regarded as acceptable.
Series: ASM Handbook Archive
Volume: 11
Publisher: ASM International
Published: 01 January 2002
DOI: 10.31399/asm.hb.v11.a0003543
EISBN: 978-1-62708-180-1
... was secondary• Short-term, high-temperature, high-stress rupture has ductile appearance (see creep) • Load exceeded the dynamic strength of the part• Check for proper alloy and processing as well as proper toughness, grain size• Loading direction may show failure was secondary or impact induced• Low...
Abstract
Overload failures refer to the ductile or brittle fracture of a material when stresses exceed the load-bearing capacity of a material. This article reviews some mechanistic aspects of ductile and brittle crack propagation, including a discussion on mixed-mode cracking, which may also occur when an overload failure is caused by a combination of ductile and brittle cracking mechanisms. It describes the general aspects of fracture modes and mechanisms. The article discusses some of the material, mechanical, and environmental factors that may be involved in determining the root cause of an overload failure. It also presents examples of thermally and environmentally induced embrittlement effects that can alter the overload fracture behavior of metals.
Series: ASM Handbook
Volume: 11B
Publisher: ASM International
Published: 15 May 2022
DOI: 10.31399/asm.hb.v11B.a0006944
EISBN: 978-1-62708-395-9
... temperature (DBTT) behavior in thermoplastics for high strain-rates resembles the fracture behavior of BCC metals, such as low-carbon and low-alloy steels. Figure 8 shows the variation of the apparent fracture toughness, K Q , as a function of temperature for a rubber-toughened thermoplastic. The K Q...
Abstract
The discussion on the fracture of solid materials, both metals and polymers, customarily begins with a presentation of the stress-strain behavior and of how various conditions such as temperature and strain-rate affect the mechanisms of deformation and fracture. This article describes crazing and fracture in polymeric materials, with a review of the behavior of the elastic modulus as a function of temperature or time parameters, emphasizing the importance of the viscoelastic nature of their deformation and fracture. The discussion covers the behavior of polymers under stress, provides information on ductile and brittle behaviors, and describes craze initiation in polymers and crack formation and fracture by crazing. Macroscopic permanent deformation of polymeric materials caused by shear-yielding and crazing, which eventually can result in fracture and failure, is also covered.
Series: ASM Handbook
Volume: 11
Publisher: ASM International
Published: 15 January 2021
DOI: 10.31399/asm.hb.v11.a0006774
EISBN: 978-1-62708-295-2
... energy absorption at fracture, and adequate toughness or ductility may be evaluated and defined by impact data, where criteria to determine whether the fracture is ductile or brittle involve some minimum level of absorbed energy at the service temperature of interest. The macroscale definition...
Abstract
Engineering component and structure failures manifest through many mechanisms but are most often associated with fracture in one or more forms. This article introduces the subject of fractography and aspects of how it is used in failure analysis. The basic types of fracture processes (ductile, brittle, fatigue, and creep) are described briefly, principally in terms of fracture appearances. A description of the surface, structure, and behavior of each fracture process is also included. The article provides a framework from which a prospective analyst can begin to study the fracture of a component of interest in a failure investigation. Details on the mechanisms of deformation, brittle transgranular fracture, intergranular fracture, fatigue fracture, and environmentally affected fracture are also provided.
Series: ASM Handbook
Volume: 11
Publisher: ASM International
Published: 15 January 2021
DOI: 10.31399/asm.hb.v11.a0006778
EISBN: 978-1-62708-295-2
... toughness, grain size • Loading direction may show failure was secondary or impact induced • Low temperatures • Cyclic stress exceeded the endurance limit of the material • Check for proper strength, surface finish, assembly, and operation • Prior damage by mechanical or corrosion modes may have initiated...
Abstract
This article aims to identify and illustrate the types of overload failures, which are categorized as failures due to insufficient material strength and underdesign, failures due to stress concentration and material defects, and failures due to material alteration. It describes the general aspects of fracture modes and mechanisms. The article briefly reviews some mechanistic aspects of ductile and brittle crack propagation, including discussion on mixed-mode cracking. Factors associated with overload failures are discussed, and, where appropriate, preventive steps for reducing the likelihood of overload fractures are included. The article focuses primarily on the contribution of embrittlement to overload failure. The embrittling phenomena are described and differentiated by their causes, effects, and remedial methods, so that failure characteristics can be directly compared during practical failure investigation. The article describes the effects of mechanical loading on a part in service and provides information on laboratory fracture examination.
Series: ASM Failure Analysis Case Histories
Volume: 2
Publisher: ASM International
Published: 01 December 1993
DOI: 10.31399/asm.fach.v02.c9001272
EISBN: 978-1-62708-215-0
... level of the ratio of fracture toughness to applied nominal stress. However, brittle fracture in a hot-rolled steel of 0.2% C, in a thin section (4.06 mm, or 0. 160 in., in this instance) at a service temperature of −1 to 4 °C (30 to 40 °F) is somewhat surprising. It should also be noted...
Abstract
A 22 m (72 ft) diameter filled grain storage bin made from a 0.2% carbon steel collapsed at a temperature of −1 to 4 deg C (30 to 40 deg F). Failure analysis indicated that fracture occurred in a two-step process: first downward, by ductile failure of small ligament from a bolt hole near the bottom of the tank to create a crack 25 mm (1 in.) long, and then upward, by brittle fracture through successive 1.2 m (4ft) wide sheets of ASTM A446 material. Site investigation showed that the concrete base pad was not level. Chemical analysis indicated that the material had a high nitrogen content (0.020%). The allowable stress based on yield was estimated using four different design criteria. Correlation among those results was poor. The different criteria indicated that the material was loaded from the maximum allowable to approximately 30% less than allowable. Nevertheless, at this stress level, fracture mechanics indicated that the 25 mm (1 in.) starter crack exceeded or was very near the critical crack length for the material. Additional factors not taken into account in the design equations included cold work from a hole punching operation, thread imprinting in bolt holes, and an additional hoop stress created by forcing an incorrectly formed panel to fit the pad base radius. These factors increased the nominal design stress to a sufficiently large value to cause the critical crack length to be exceeded.
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
... with smooth grain boundaries Likely either improper thermal processing or environmental assisted fracture (high temperature, corrosive environment) Less common is low Δ K fatigue Intergranular with dimpled grain boundaries “Decohesive rupture—fracture at high fraction of melting point...
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 Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.power.c9001004
EISBN: 978-1-62708-229-7
...) fracture, viz., in low temperature RTE fracture, initiation and propagation of microcracks are rate controlling while at high temperatures the nucleation and growth of creep cavitation, dislocation mobility and grain boundary sliding are important. Wilkinson et al ( 6 ) observed that the ductility of P...
Abstract
The results of a failure analysis of a series of Cr-Mo-V steel turbine studs which had experienced a service lifetime of some 50,000 h are described. It was observed that certain studs suffered complete fracture while others showed significant defects located at the first stress bearing thread. Crack extension was the result of marked creep embrittlement and reverse temper embrittlement (RTE). Selected approaches were examined to assess the effects of RTE on the material toughness of selected studs. It was observed that Auger electron microscopy results which indicated the extent of grain boundary phosphorus segregation exhibited a good relationship with ambient temperature Charpy data. The electrochemical polarization kinetic reactivation, EPR, approach, however, proved disappointing in that the overlapping scatter in the minimum current density, Ir, for an embrittled and a non-embrittled material was such that no clear decision of the toughness properties was possible by this approach. The initial results obtained from small punch testing showed good agreement with other reported data and could be related to the FATT. Indeed, this small punch test, combined with a miniature sample sampling method, represents an attractive approach to the toughness assessment of critical power plant components.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.petrol.c9001167
EISBN: 978-1-62708-228-0
... transition temperature in excess of 1000C. The sequence of events leading to failure was detailed. The main recommendation was to quench and temper existing couplings and to use a lower carbon quenched and tempered steel for new couplings. Couplings Drilling rigs 4142 UNS G41420 Brittle fracture...
Abstract
Visual examination, optical and scanning electron microscopy were used to determine the cause of failure in the connector groove of a marine riser coupling. The specified steel was AISI 4142 (0.40 to 0.45% C; 0.75 to 1.00% Mn; 0.20 to 0.35% Si; 0.80 to 1.10% Cr; 0.15 to 0.25% Mo) normalized from 9000C. Microscopic examination revealed the crack's initiation point and subsequent propagation. SEM examination of chemically stripped corrosion showed that corrosion fatigue and stress corrosion might have contributed to the initial slow crack growth. Impact tests revealed a fracture transition temperature in excess of 1000C. The sequence of events leading to failure was detailed. The main recommendation was to quench and temper existing couplings and to use a lower carbon quenched and tempered steel for new couplings.
Series: ASM Failure Analysis Case Histories
Volume: 3
Publisher: ASM International
Published: 01 December 2019
DOI: 10.31399/asm.fach.v03.c9001780
EISBN: 978-1-62708-241-9
... propagation rates, fracture toughness, notch toughness, and transverse tensile properties, and do so in an anisotropic manner with respect to rolling direction. Significant property anisotropy has been documented in the failures investigated, providing evidence that designers failed to account for it. Typical...
Abstract
A number of failures involving carbon and alloy steels were analyzed to assess the effects of inclusions and their influence on mechanical properties. Inclusions, including brittle oxides and more ductile manganese sulfides (MnS), affect fatigue endurance limit, fatigue crack propagation rates, fracture toughness, notch toughness, and transverse tensile properties, and do so in an anisotropic manner with respect to rolling direction. Significant property anisotropy has been documented in the failures investigated, providing evidence that designers failed to account for it. Typical fracture morphologies observed in such cases and metallographic appearances of MnS-containing materials are illustrated.
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