Aging of High Speed Train Wheelsets and its Quantitative Characteristics Based on Fracture Mechanics for Optimization of In-Service Inspection

The fracture mechanics characteristics in the critical locations of the wheelset for high-speed train have not been studied enough yet despite of severe conditions due to increase in operating speeds. Moreover, the fracture mechanics characteristics with respect to the aging effects of wheelset materials have not been clearly studied. In the present study, the following fracture mechanics characterization tests were carried out in accordance with various locations on the wheelset for high-speed train: fracture toughness depending on load rate, fatigue crack growth rate and fatigue thresholds. The results show that the fatigue crack growth rates in accordance to the locations on wheelset were not remarkably different, and the fatigue threshold in the region of the bolt-hole is lower than that in other regions. The fracture toughness depending on load rate data shows that once the downward curve from quasi-static values was reached, subsequent values showed a slow increase with respect to the impact velocity. This means that dynamic fracture toughness should be considered in the design code of the wheelset material.

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Repercussion of Autofrettage on the Fatigue Crack Growth in the Vicinity of Catalyst Entry Opening for Polyethylene Autoclave Reactor

Volume 5: High-Pressure Technology; Rudy Scavuzzo Student Paper Competition and 23rd Annual Student Paper Competition; ASME NDE Division ◽

10.1115/pvp2015-45402 ◽

2015 ◽

Author(s):

Navid Haeri ◽

Brian A. Cornah

Keyword(s):

Fatigue Crack ◽

Fatigue Crack Growth ◽

Fracture Mechanics ◽

Residual Stresses ◽

Crack Growth ◽

Corner Crack ◽

Linear Elastic ◽

Study Results ◽

The Impact ◽

Autoclave Reactor

Background. The authors conducted a study to analyse the impact of autofrettage practice on the fatigue crack growth in the vicinity of the catalyst entry nozzle in a MK.15 ICI LDPE autoclave reactor. Methods. The authors created 3-D finite element models of the quadrant of the opening. Elastic-plastic analysis was carried out to evaluate the residual stresses from the autofrettage which were then used as an input to the fracture mechanics analysis. Linear Elastic Fracture Mechanics (LEFM) methodology was then deployed associating a Radial Direction, Quarter-Circular Corner Crack pattern as per API 579/ASME VIII Div.3 for the purpose of calculating the crack tip stress intensity. A number of hypothetical pressure cycles were considered in order to calculate the crack growth rate as per ASME Div.3 (Paris’ Law) both with and without residual stresses from autofrettage analysis. Results. The study results showed the change in the crack behaviour as a result of adding the autofrettage residual stresses onto the model and discussed the implications of such a practice on the design life for autoclave reactors.

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Pipeline Steel Fracture Toughness and the Need for a Toughness Database of API 5L Line Pipe

Volume 1: Pipeline and Facilities Integrity ◽

10.1115/ipc2020-9389 ◽

2020 ◽

Author(s):

Lyndon Lamborn ◽

Shenwei Zhang ◽

Sergio Limón ◽

Roger Lai

Keyword(s):

Fracture Toughness ◽

Fatigue Crack ◽

Fatigue Crack Growth ◽

Fracture Mechanics ◽

Crack Growth ◽

Pipeline Steel ◽

Data Sets ◽

Similar Data ◽

Line Pipe ◽

Toughness Test

Abstract In order for the pipeline industry to usher in the next-level fracture mechanics engineering analysis, reasonable and prudent fracture toughness characterizations are needed to improve burst pressure predictions and fatigue crack growth analysis of pipelines with planar cracks. Converting Charpy V-Notch (CVN) value to fracture toughness via different empirical correlation models derived throughout the years, while laudable, have inherent shortcomings. The main issues being that the Charpy toughness test is not a fracture mechanics-based measurement and the transferability of sub-scale fracture toughness testing is often not completely understood nor is correctly applied. This paper expands on these shortcomings and presents solutions which are supported by fracture toughness data obtained from the pipe boy and seam weld of API 5L line pipe steels. In this manner, best available toughness derivations for mean toughness in base metal and long seam welds are presented. Suggestions for standard fracture mechanics sub-scale coupon testing, such as ASTM E1820, on pipeline steel samples are delineated with rationale for each test type. The transferability of fracture toughness from sub-scale coupon testing results to that exhibits in full-scale pipe failure are demonstrated in the paper. This fracture toughness test database and other similar data sets can be combined and serve as the basis for establishing an industry wide Pipeline Material Database which would mirror established material databases in the aerospace industry such as NASGRO and AFMAT. It is envisioned that a centralized and validated Pipeline Material Database will be expanded to include fatigue crack growth rate data and other pipeline material characterization data sets. These data will support minimizing material assumptions and increase the accuracy of structural integrity predictions to improve the overall pipeline performance. This combined database would be accessible to engineers, analysts, and researchers and updated at regular intervals as more data becomes available.

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Fracture and Fatigue Testing of Micro-Sized Materials for MEMS Applications

Advances in Electronic Packaging, Parts A, B, and C ◽

10.1115/ipack2005-73038 ◽

2005 ◽

Author(s):

Kazuki Takashima ◽

Timothy P. Halford ◽

Yakichi Higo

Keyword(s):

Fracture Toughness ◽

Fatigue Crack ◽

Fatigue Life ◽

Fatigue Crack Growth ◽

Fracture Mechanics ◽

Amorphous Alloy ◽

Crack Initiation ◽

Crack Growth ◽

Testing Machine ◽

Fatigue And Fracture

We have developed a new type of mechanical testing machine for micro-sized specimens, which can apply a small static or cyclic load, and have investigated fracture and fatigue crack growth behavior of micro-sized specimens. Cantilever beam type specimens (10 μm × 10 μm × 50 μm), with notches were prepared from thin films of a Ni-P amorphous alloy by focused ion beam machining. Fatigue and fracture toughness tests were carried out in air at room temperature using the mechanical testing machine. Fatigue and fracture testing was completed successfully for micro-sized cantilever specimens. Once fatigue crack growth occurs, rapid sample failure was observed in these micro-sized specimens. This indicates that the fatigue life of micro-sized specimens is mainly dominated by crack initiation. This also suggests that even a micro-sized surface flaw can be a fatigue crack initiation site which will shorten the fatigue life of micro-sized specimens. As a result of fracture toughness tests, plane strain criteria for small scale yielding were not achieved for this amorphous alloy. Plane stress and plane strain dominated regions were clearly observed on the fracture surfaces and their sizes were consistent with those estimated by fracture mechanics calculations. This suggests that fracture mechanics is still valid for such micro-sized specimens.

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Effective Modeling of Fatigue Crack Growth in Pipelines

Volume 6: Materials and Fabrication, Parts A and B ◽

10.1115/pvp2012-78575 ◽

2012 ◽

Author(s):

Steven J. Polasik ◽

Carl E. Jaske

Keyword(s):

Fatigue Crack ◽

Stress Intensity ◽

Fatigue Crack Growth ◽

Fracture Mechanics ◽

Crack Growth ◽

Growth Models ◽

Critical Parameters ◽

Operating Pressure ◽

Mechanics Model ◽

Key Variables

Pipeline operators must rely on fatigue crack growth models to evaluate the effects of operating pressure acting on flaws within the longitudinal seam to set re-assessment intervals. In most cases, many of the critical parameters in these models are unknown and must be assumed. As such, estimated remaining lives can be overly conservative, potentially leading to unrealistic and short reassessment intervals. This paper describes the fatigue crack growth methodology utilized by Det Norske Veritas (USA), Inc. (DNV), which is based on established fracture mechanics principles. DNV uses the fracture mechanics model in CorLAS™ to calculate stress intensity factors using the elastic portion of the J-integral for either an elliptically or rectangularly shaped surface crack profile. Various correction factors are used to account for key variables, such as strain hardening rate and bulging. The validity of the stress intensity factor calculations utilized and the effect of modifying some key parameters are discussed and demonstrated against available data from the published literature.

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Fatigue Crack Growth Rate and Fracture Toughness of API5L X65 in Sweet Environments

Volume 3: Materials Technology; Ocean Space Utilization ◽

10.1115/omae2013-10216 ◽

2013 ◽

Cited By ~ 1

Author(s):

Michael A. Tognarelli ◽

Ramgopal Thodla ◽

Steven Shademan

Keyword(s):

Fracture Toughness ◽

Growth Rate ◽

Fatigue Crack ◽

Crack Growth Rate ◽

Fatigue Crack Growth ◽

Crack Growth ◽

Fatigue Crack Growth Rate ◽

Environmental Conditions ◽

Initiation Toughness ◽

Diffusible Hydrogen

Corrosion fatigue and fracture toughness in sour environments of APIX65 5L have typically been studied in relatively severe environments like NACE A and NACE B solutions. There are very limited data in sweet and mildly sour environments that are of interest in various applications. This paper presents fatigue crack growth frequency scans in a range of sweet and mildly sour environments as well as on different microstructures: Parent Pipe, Heat Affected Zone (HAZ) and Weld Center Line (WCL). The fatigue crack growth rate (FCGR) increased with decreasing frequency and reached a plateau value at low frequencies. FCGR in the sweet environments that were investigated did exhibit a frequency dependence (increasing with decreasing frequency) and had plateau FCGR in the range of 10–20× the in-air values. In the mildly sour environments that were investigated, FCGR was found to be about 25 to 30× higher than the in-air values. By comparison, in NACE A environments the FCGR is typically about 50× higher than the in-air values. The FCGRs of parent pipe and HAZ were found to be similar over a range of environments, whereas the WCL FCGR data were consistently lower by about a factor of 2×. The lower FCGR of the WCL is likely due to the lower concentration of diffusible hydrogen in the weld. FCGRs as a function of ΔK (stress integrity factor range) were measured on parent pipe at the plateau frequency. The measured Paris law curves were consistent with the frequency scan data. Rising displacement fracture toughness tests were performed in a range of sweet and sour environments to determine the R-curve behavior. Tests were performed in-situ at a slow K-rate of 0.05Nmm−3/2/s over a range of environmental conditions on parent pipe. The initiation toughness and the slope of the R-curve decreased sharply in the sour environments. The initiation toughness and slopes were largely independent of the notch location as well as environmental conditions. Typical values of initiation toughness were in the range of 90–110N/mm.

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