An Innovative ECA Approach For Reeled CRA Welds And Its Validation Programme

This paper presents an innovative defect growth ECA methodology for pipeline girth welds and its validation programme, applied specifically to reeling ECA of pipelines with under-matched strength welds. The ECA method is a tear-fatigue approach that accounts for the blunting limit in JR curves during pipe spooling and reel-lay. Fatigue crack growth may occur by low cycle high stress fatigue and by tearing, but the latter only if the crack tip opening displacement exceeds the blunting limit. Conventional ECA with BS7910 is limited because the weld's strength needs to be over-matched. Alternative industry methods for the application of FEA to under-matched strength welds are computationally more intensive than the presented innovative approach. Fatigue crack growth for low cycle high stress fatigue is calculated using Paris’ Law in the approach but, if the crack tip opening due to the tearing mechanism is less than the blunting limit then tearing growth is zero. With the innovative method, if the crack tip opening displacement exceeds the blunting limit then the tearing defect growth is included. Hence, the method is a combined tear-fatigue approach. Welded pipe strings were fabricated from pups composed of clad material; i.e. carbon backing steel pipe with a 3 mm layer of corrosion resistant alloy (CRA) on the inner circumference. Each test string was approximately 10.5m long and fabrication was from a mix of six 0.5m length pups in the central zone of each string and two longer end pups. Three girth welds included EDM notches for test purposes which simulated planar flaws. The notches were on the extreme tension fibre, as the test string gets pulled to the reel former in a reeling test rig. Full scale reeling simulations involved pulling the test strings up to 6 times to the reel former in a reeling test rig. Measurement of defect growth associated with the EDM notches was by scanning electron microscope (SEM), from specimen segments extracted from the test strings. Predictions of defect growth were by finite element models in combination with pipe-specific data that was the outcome of an associated small-scale test programme. Validation of the ECA-by-FEA approach is by a predictive best estimate study, for which there is excellent agreement between the measured values and the calculated defect growths. The ECA-by-FEA approach is conservative for project work, as shown by a high estimate study and an offset blunting limit study. Early development of the ECA approach was for small diameter CRA pipelines during the execution of the Guara-Lula project (Sriskandarajah et al, 2015). The presented full-scale tests, innovative defect growth measurement by scanning electron microscope and the FEA and defect growth calculations were full validation of the approach, with pipe strings that had outer diameter of 323.9mm.

Scratch Detection on Hard Disk Drive Media to Reduce Head Disk Interaction and Prevent Data Loss

Accurately detecting irregularities in the media — thermal asperities and delamination — and mapping them out from further usage is critical to prevent data loss and minimize head disk interaction (HDI). Defect growth is a common concern in hard disk drives (HDD) and the immediate vicinity of media defects are also mapped out to provide sufficient protection against defect growth. A class of media defects that prove more complex to protect against defect growth is scratches on the media. Margining a media scratch involves filling in the gaps between the components of a scratch and margining the vicinity of the scratch in the defect growth direction. While Hough transform based techniques and deeplearning models have been developed to identify media patterns, they cannot be implemented in the hard disk drive firmware due to memory and computational limitations. Here, we present a computationally simple and efficient alternative to identify scratches on the media by combining clustering and an iterative parameter estimation to fit a line to the scratch in noisy conditions. The result is a method that is capable of modeling linear, spiral and parabolic scratches on a media and fill gaps in the scratch and extend the margining at either end of the scratch.

Characterizing Corrosion Defects With Apparent High Growth Rates on Transmission Pipelines

Consecutive in-line inspections of transmission pipelines enable a comparison between the inspection results to characterize corrosion growth. Despite the high levels of in-line inspection tool accuracy and detection capabilities, corrosion defects with low calculated burst capacities may be detected on a subsequent inspection that were not reported in a previous inspection. These newly reported defects can pose a substantial challenge as the apparent growth rates between inspections of these defects can potentially drive unnecessary repair digs. This paper characterizes the contributing factors that can explain these phenomena, including: • Typical corrosion growth rates and their associated statistical frequency • The diminishing detection capability of inspection tools for smaller defects • The inspection tool minimum reporting threshold • The measurement accuracy of inspection tools. A statistical analysis was developed to quantify this interacting set of factors using Monte Carlo simulations that work retrospectively, covering a range of observed measured defect depths and then simulating the processes that could lead to newly reported defects being un-matched in a previous inspection. This analysis can be used to quantify the likelihood that a defect of a specific measured size would have been unreported in an earlier inspection due only to the performance characteristics of the inspection tool, and not as a result of defect growth that initiated since the time of the previous inspection. A set of case studies covering a range of pipeline inspection intervals ranging from 2 to 10 years are presented to demonstrate how this approach can be used to quantify appropriate growth rates that may be applied to these un-matched defects when assessing the remaining life or predicted probability of failure.

15q26 Deletion in a Patient with Congenital Heart Defect, Growth Restriction and Intellectual Disability: Case Report and Literature Review

Background 15q26 deletion is a relatively rare chromosomal disorder described in only few cases. Patients with this aberration display numerous symptoms particularly pre- and postnatal growth restriction, microcephaly, intellectual disability, dysmorphic gestalt, and various congenital malformations. Case presentation We report on a girl, four years old, of consanguineous parents, with a de novo 15q26 deletion. Clinical manifestations included failure to thrive, microcephaly, dysmorphic facies with broad forehead, hypertelorism, narrowed eyelid slits, protruding columella. The patient also showed skeletal abnormalities, especially clinodactyly of the 5th finger, right foot varus equine, and left club foot. Additionally, she had teething delay and divergent strabismus. Further clinical investigations showed right-to-left atrial shunting, and enlarged right heart. Routine cytogenetic analysis revealed a derivative 15 chromosome with an abnormally short long (q) arm. Subsequent array analysis disclosed a terminal 9.15 Mb deletion detected in band 15q26.1q26.3. Five candidate genes causing the phenotype were within the deleted region, i.e. IGF1R, NR2F2, MEF2A, MCTP2, and CHD2. Conclusion 15q26 monosomy should be considered when growth retardation is associated with ear anomaly, clinodactyly and/or abnormal toe, heart defect mainly atrioventricular septal defects (AVSDs) and/or aortic arch anomaly (AAA).

Defect Growth Characterization in Modern Rail Steels

The Federal Railroad Administration (FRA) has been sponsoring research on rail integrity for several decades. This research has been chiefly managed and conducted by the Volpe National Transportation Systems Center (Volpe). Particular focus has been given in this research to rail head defects, known as detail fractures, since they are the most commonly encountered defect in continuous welded rail track [1]. Testing and analyses have been performed on railroad rails manufactured without head hardening. Modern rail, however, are now heat treated during the manufacturing process to harden the rail surface to increase its resistance to wear. As such, the heat treatment and nonuniform cooling induce complex residual stress patterns in the rail that can affect microstructure and fatigue crack growth rate behavior. This paper will describe research to examine defect growth behavior of modern rail steels. This research is a collaboration among several organizations: Thornton-Tomasetti, Arcelor-Mittal, Lehigh University, Harvard University, National Institute of Standards and Technology (NIST), Fraunhofer Institute, and Volpe. Arcelor Mittal donated rails with different grades of steel: advanced head hardened, head hardened, and standard strength (i.e. non-head-hardened). Lehigh conducted laboratory tests on specimens cut from these rails to perform various tests, which include: hardness measurements, mechanical testing to measure tensile properties, fracture toughness measurements, and fatigue crack growth rate tests. All of these tests were performed in accordance with applicable ASTM International standards. NIST and Fraunhofer performed preliminary neutron diffraction measurements of residual stresses on the different rails. Moreover, this paper will present results from the laboratory testing program. Implications of these results on detail fracture growth behavior will also be discussed.