Academic literature on the topic 'Reverse Detail Fracture'
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Journal articles on the topic "Reverse Detail Fracture"
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Pan, Yue, Xiao He, Jixin Yang, and Xiuming Wang. "Q-compensated viscoelastic reverse time migration in crosswell seismic imaging." Journal of Geophysics and Engineering 19, no. 3 (May 24, 2022): 295–315. http://dx.doi.org/10.1093/jge/gxac017.
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Abstract Viscoelastic reverse time migration (RTM) is a practical approach to compensats for attenuation effects in migration, commonly studied in surface seismic research. Compared with conventional surface seismic imaging, the sources and receivers of crosswell seismic imaging are distributed in different wells with higher main frequencies and lower surface noises. The finer structures can be imaged. In this paper, we apply attenuation compensated RTM in crosswell migration to improve the resolution of images in attenuation regions. We solve the viscoelastic equations using the constant Q model because of its advantage of decoupling the amplitude and phase. The fractional-order amplitude and phase Laplacian operators are used. By spectral ration techniques, we observe the relationship between attenuation and frequency in crosswell seismic imaging. We describe the alignment and muting of direct P- and S-waves from full waves in detail. Synthetic examples demonstrate that Q-RTM images the geological structure more clearly than the traditional RTM. We reveal that compensated images describe the three-layer model, tilted fractures and randomly distributed caves more accurately. As the tilted angles increase, only two end points of the tilted fracture can be identified by conventional RTM, the boundary is blurred. We find that caves far from the source well can barely be imaged. By comparison, the compensated RTM approach obtains precise migration results of tilted fractures with arbitrary dip angles and caves. Finally, to approximate the real measurement data, noise is added to the viscoelastic data of the five-layer model. The effective noise immunity in crosswell seismic applications is verified.
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Sharma, Bishruti, Nabin Paudyal, Binod Rajbhandari, Amit Pradhanang, Nikita Dwa, Ajay Pradhan, and Mohan Raj Sharma. "Major Spinal Surgery Between Two Documented COVID-19 Infections in an Elderly Female: A Case Report." Journal of Nepal Medical Association 59, no. 242 (October 23, 2021): 908–11. http://dx.doi.org/10.31729/jnma.6507.
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Documented re-infection of COVID-19 is uncommon and doing a major spinal surgery in an elderly patient right after the recovery from the first event is itself a major undertaking. Re-infection after successful surgery points to the possibility of COVID-19 infection being a post-surgical complication. Here, we report a case of a 72-years-old elderly female who had presented to us with features of COVID-19 infection confirmed by reverse transcription polymerase chain reaction assay and unstable spinal fracture who underwent a pedicle screw fixation for the fracture of the third and fourth thoracic vertebrae after two consecutive negative serology assays. A month after discharge from the hospital, she presented with severe symptoms of COVID-19 again confirmed by two consecutive polymerase chain reaction assays. She was managed conservatively and was discharged without significant respiratory and neurological complications. We described this case in detail in addition to reviewing the pertinent literature.
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Mahfuz, Hassan, Anwar Haque, Daixu Yu, and Shaik Jeelani. "Response of Resin Transfer Molded (RTM) Composites Under Reversed Cyclic Loading." Journal of Engineering Materials and Technology 118, no. 1 (January 1, 1996): 49–57. http://dx.doi.org/10.1115/1.2805933.
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Compressive behavior and the tension-compression fatigue response of resin transfer molded IM7 PW/PR 500 composite laminate with a circular notch have been studied. Fatigue damage characteristics have been investigated through the changes in the laminate strength and stiffness by gradually incrementing the fatigue cycles at a preselected load level. Progressive damage in the surface of the laminate during fatigue has been investigated using cellulose replicas. Failure mechanisms during static and cyclic tests have been identified and presented in detail. Extensive debonding of filaments and complete fiber bundle fracture accompanied by delamination were found to be responsible for fatigue failures, while fiber buckling, partial fiber fracture and delamination were characterized as the failure modes during static tests. Weibull analysis of the static, cyclic and residual tests have been performed and described in detail. Fractured as well as untested specimens were C-scanned, and the progressive damage growth during fatigue is presented. Optical Microscopy (OM) and Scanning Electron Microscopy (SEM) for the fractured specimen were also performed and the analysis of the failure behavior is presented.
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Petrosyan, A. S. "Reverse Total Shoulder Arthroplasty in Proximal Humeral Fractures." Vestnik travmatologii i ortopedii imeni N.N. Priorova, no. 4 (December 30, 2017): 46–51. http://dx.doi.org/10.32414/0869-8678-2017-4-46-51.
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Primary reverse total shoulder arthroplasty was performed in 13 patients, aged 65 – 83 years, with three- and four-part (by Neer classification) proximal humeral fractures. Rotator cuff injuries and shoulder contractures of various degrees were present in all patients. Surgical technique and postoperative rehabilitation program were described in details. Treatment results were assessed roentgenologically by Constant-Murley score in 6 months, 1, 2 and 3 years after intervention. Reverse total shoulder arthroplasty enabled to achieve good functional outcomes and considerable pain relief even in elderly patients with compound fractures and rotator cuff injuries.
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Petrosyan, Armenak S. "Reverse total shoulder arthroplasty in proximal humeral fractures." N.N. Priorov Journal of Traumatology and Orthopedics 24, no. 4 (December 15, 2017): 46–51. http://dx.doi.org/10.17816/vto201724446-51.
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Primary reverse total shoulder arthroplasty was performed in 13 patients, aged 65 - 83 years, with three- and four-part (by Neer classification) proximal humeral fractures. Rotator cuff injuries and shoulder contractures of various degrees were present in all patients. Surgical technique and postoperative rehabilitation program were described in details. Treatment results were assessed roentgenologically by Constant-Murley score in 6 months, 1, 2 and 3 years after intervention. Reverse total shoulder arthroplasty enabled to achieve good functional outcomes and considerable pain relief even in elderly patients with compound fractures and rotator cuff injuries.
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Pankratov, A. S., Yu V. Lartsev, J. G. Alayo, S. V. Ardatov, D. A. Ogurtsov, and A. A. Rubtsov. "A preoperative planning method for long tubular bone osteosynthesis." Science and Innovations in Medicine 5, no. 4 (December 7, 2020): 267–71. http://dx.doi.org/10.35693/2500-1388-2020-5-4-267-271.
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Objectives the development of a preoperative planning method for long tubular bone osteosynthesis using the contralateral healthy bone.
Material and methods.To justify the usage of the opposite limbs intact segment model in order to reconstruct the damaged one, their matching in shape and size was analyzed. We built three-dimensional models of the right and left segments of the upper limbs of 20 people and compared them using the Hausdorff distance calculation algorithm. For treatment of a 24-year-old patient with a closed humerus fracture, an individual stereolithographic surgical template with fracture lines was created with the help of computed tomography data of the healthy humerus bone processed by AUTOPLAN EXPERT software. This template was used for pre-bending the plate for osteosynthesis. The plate positioning on the template defined the surgical approach, taking into account the anatomical structures located in the projection of the fracture line and the plate. The technique of "reverse bone reposition" on the prepared plate was applied.
Results.With the help of the created 3D models we revealed the size differences of the symmetrical segments of upper limbs. The greatest difference in the limits was registered in the area of the epiphyses (heads of the humeri) up to 6.8 mm, and the smallest throughout the entire diaphysis, less than 1.5 mm. Due to preoperative planning there were no intraoperative and postoperative complications, the installation of the plate and osteosynthesis was convenient. The fracture consolidation took place in 3 months.
Conclusion.The proposed method has a number of advantages. It is possible to make a stereolithographic template even for a seriously damaged bone with a copied fracture line. This allows the surgeon to plan the details of osteosynthesis, to model the plate according to the template, to determine the required length and shape of the surgical approach, thus reducing the surgical risks and injury for the patient.
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Rongqian, Yang, and Zhou Xuejun. "Experimental study on the seismic behavior of concentrically braced steel frames with extended end-plate bolted connections." Science Progress 103, no. 3 (July 2020): 003685042095228. http://dx.doi.org/10.1177/0036850420952289.
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The prefabricated semi-rigid concentrically braced steel frame has always been the main form of residential steel structures, much work so far has focused on the earthquake-resistance performance of such structures. However, little attention has been devoted to systematic model testing, further effort is still required to explore the structural performance with experimental studies. Two semi-rigid concentrically braced steel frames were designed and tested to failure under reversed low-cyclic loading. The hysteretic curves, bearing capacity, energy dissipation capacity, ductility and stiffness degradation performance were studied in detail. Then the performance was compared to analyze the advantages and disadvantages of the two frames. The tests showed that the plastic deformation and damage were primarily concentrated at the braces, and the columns and semi-rigid connections exhibited hardly any plastic deformation. The specimens went through the elastic stage, elastic-plastic stage and failure stage during the tests. The results indicated the specimen with chevron braces has better seismic performance. The structure presents the characteristic of ductile failure on the whole. The steel frame and braces of the specimens cooperatively perform together so that the structure has two seismic fortification lines. The structure with chevron braces possesses an excellent bearing capacity, a high lateral stiffness, a reliable lateral-resistance performance and a strong energy dissipation capacity. In contrast, because of the premature fracture of the cross joints, the structure with X-shaped braces has a lower material utilization efficiency, which leads to a dramatic decrease in the bearing capacity and stiffness, as well as low ductility and a poor energy dissipation capacity.
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Bellezza, Cinzia, Flavio Poletto, Biancamaria Farina, Giorgia Pinna, Laurent Wouters, Noël Vandenberghe, and Elio Poggiagliolmi. "Processing of seismic diffractions from carbonate nodules in clay formations." GEOPHYSICS 87, no. 2 (February 15, 2022): D67—D81. http://dx.doi.org/10.1190/geo2020-0794.1.
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The problem of localizing small (relative to wavelength) scatterers by diffractions to enhance their use in identifying small-scale details in a seismic image is extremely important in shallow exploration to identify interesting features such as fractures, caves, and faults. The conventional approach based on seismic reflection is limited in resolution by the Rayleigh criterion. In certain acquisition geometries, such as crosswell surveys aimed at obtaining high-resolution signals, the availability of suitable data sets for effective migration depends on the spatial extent of the available source and receiver data intervals. With the aim of overcoming the resolution limits of seismic reflection, we study the detectability, response, and location of meter- and possibly submeter-dimension carbonate concretions (septaria) in the Boom Clay Formation (potential host rocks for radioactive waste disposal) by diffraction analysis of high-frequency signals. We investigate diffraction wavefields by signal separation, focusing, and high-resolution coherency analysis using the multiple signal classification method and semblance. The investigation is performed for two different surveys in Belgium, a shallow and high-resolution reverse vertical seismic profile (RVSP) and a near-offset crosswell application at Kruibeke and ON-MOL-2 sites, respectively. The data analysis is supported by synthetic wavefield modeling. The multioffset RVSP provides the appropriate geometry to observe and investigate the septaria diffractions from depth and the surface. The crosswell approach, calibrated using synthetic data in the analysis of wavefield patterns in 2D, indicates promising imaging results with field data of a selected diffraction zone in the interwell area.
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Carpenter, Chris. "Gas-Diffusion Coefficient in Organic Matter Affects Estimation of Shale-Gas Reservoirs." Journal of Petroleum Technology 74, no. 08 (August 1, 2022): 80–82. http://dx.doi.org/10.2118/0822-0080-jpt.
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This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 201653, “On the Inference of Gas Diffusion Coefficient in Organic Matter of Shale Gas Reservoirs,” by Esmail Eltahan, SPE, Mehran Mehrabi, and Kamy Sepehrnoori, SPE, The University of Texas at Austin, et al. The paper has not been peer reviewed. US shale reservoirs are tight and inherently heterogeneous, with an abundant presence of kerogenic material. Modeling fluid flow in shale reservoirs is complex because of flow physics such as pressure flow and diffusion. Many field-performance forecasts underestimate production from these reservoirs constantly because most current models ignore important governing physics. This study provides new insights on diffusion in organic matter to correct a main source of underestimation of gas production in shale-gas models. In the complete paper, the authors implement a multiscale diffusion model to estimate gas-diffusion coefficient in organic matter. Background Pores in shale-gas resources, which are on the order of a few to tens of nanometers in diameter, are much smaller than pores in conventional resources. At such small pore size, the ratio of surface area to pore volume becomes large, giving importance to transport mechanisms that depend on the surface area. According to other researchers, in addition to the free gas, considerable amounts of gas molecules will exist on the surface of organic material (adsorbed gas) and inside the solid matrix of kerogen (dissolved gas). Although typically neglected in conventional gas resources, the adsorbed and dissolved gas should receive attention in the case of shale-gas resources because of an abundance of organic material and substantial pore surface area. Gas production from shale is largely facilitated by maximizing the contact a well creates with the formation. In practice, the contact is established by numerous hydraulic fractures along a wellbore that extends for a lengthy horizontal distance in the formation. The induced-fracture networks grant direct access to the free gas in organic and inorganic pores as well as the adsorbed and dissolved gas through organic pores. Gas is depleted in the same manner as it is stored (in laboratory experiments, but in reverse order). Free gas is expanded first, creating local pressure sinks that force adsorbed gas to detach from the pore surface. As the desorption process continues, the number of unoccupied spots on the pore walls increases. Local concentration disruptions occur at those spots, which cause the dissolved gas to diffuse back into the pores. The contribution of dissolved gas in field cases has been reported in several studies, which provides motivation to study the physics of dissolved-gas diffusion on the pore scale and to develop consistent predictive models on the mesoscale. In a previous work by the authors, they presented a mathematical model for the evolution of dissolved gas that considers detailed pore geometry. However, the authors write that they have shown that pore geometry has minor influence, in contrast to the involved diffusion-length scales. Thus, the key components of previously obtained insights are used to build a simple model. The proposed model is considerably simpler in implementation, yet descriptive of the key components that govern dissolved-gas evolution. The mathematical model and its associated equations are detailed in the complete paper.
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Leung, Ting Fan, Chi Kong Li, Christopher W. K. Lam, Yvonne Chu, Matthew M. K. Shing, Chung Yi Li, Iris H. S. Chan, Ki Wai Chik, Vincent Lee, and Patrick M. P. Yuen. "Bone Density in Thalassemia Major Improves in Longterm Transplant Survivors." Blood 104, no. 11 (November 16, 2004): 3622. http://dx.doi.org/10.1182/blood.v104.11.3622.3622.
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Abstract Background: Bone-related complication is a major longterm morbidity for thalassemia major (TM), and osteoporosis significantly increases the risk of fractures. Up to 60% of adult TM patients suffer from osteoporosis. It remains unclear whether diminished bone mineral density (BMD) in TM can be reversed after bone marrow transplantation (BMT). Objective: This study investigates the effects of BMT on BMD measurement in TM patients by comparing BMD in those receiving regular blood transfusion (BT) with patients following BMT. Patients and Methods: This study recruited all Chinese TM patients managed in the pediatric department of a university teaching hospital in Hong Kong. Medical history and details on BT or BMT and drug treatments were obtained from chart review. All BMT patients were ≥ 2 years post-transplant. They did not receive any medication or suffer from any transplant-related complication for ≥ one year. Pubertal development was assessed clinically by Tanner staging, and supplemented with hormonal studies if indicated. BMD at lumbar spine (L1-L4) and left hip were measured by dual-energy x-ray absorptiometry (DEXA). Osteoporosis was defined quantitatively as T-score for BMD < -2.5. Paired blood and urine samples were collected in the mornings of DEXA scan for biochemical markers, including serum osteocalcin and bone-specific alkaline phosphatase (ALP) levels for bone formation and serum beta-crossLap and urine cross-linking deoxypyridinoline (DPD) levels for bone resorption. Student t test was used to analyze numerical values and chi-square was used to compare proportions. Results: 53 TM patients on regular BT and 33 post-BMT patients were recruited. Their mean (SD) ages were 14.4 (5.9) years and 15.6 (5.8) years (p=0.346). Patients in the latter group were 5.7 (1.9) years after BMT. Thirteen (25%) BT patients and 13 (39%) post-BMT patients suffered from endocrinopathy (p=0.144). Similar proportions of BT and BMT patients showed signs of puberty (62% versus 67%; p=0.679). The mean (SD) serum ferritin concentrations in these two groups were 7401 (3770) pmol/L and 1348 (1144) pmol/L, respectively (p<0.0001). BMD T-scores were < -2.5 at spine and hip in 62% and 35% of BT-dependent TM patients, and in 36% (p=0.063) and 6% (p=0.036) of post-BMT patients. Absolute BMD at spine in these two groups were 0.636 (0.115) g/cm2 and 0.684 (0.155) g/cm2 (p=0.102), whereas the respective values at hip were 0.651 (0.121) g/cm2 and 0.706 (0.149) g/cm2 (p=0.092). Sub-group analysis revealed that pubertal post-BMT patients had significantly higher hip BMD as compared to those on regular BT (p=0.044). Serum osteocalcin concentrations were significantly higher in BMT than BT patients (mean [SD]: 96.4 [72.7] μg/L versus 68.9 [40.3] μg/L; p=0.037). The other biochemical markers of bone turnover did not differ between the two groups of TM patients. Lastly, BMD values were not associated with the presence of endocrinopathy, extent of iron overload or dosage of desferrioxamine in BT-dependent TM patients. Conclusions: Osteoporosis is common among Chinese teenagers and young adults with TM. Our results support that BMD measurement should form an integral part of longterm follow-up in TM patients. Transplant survivors of TM had significantly better BMD at left hips as compared to those on regular BT, and this may result from increased bone formation in the post-transplant patients.
Book chapters on the topic "Reverse Detail Fracture"
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Wyatt, Jonathan P., Robert G. Taylor, Kerstin de Wit, Emily J. Hotton, Robin J. Illingworth, and Colin E. Robertson. "Wounds, fractures, and orthopaedics." In Oxford Handbook of Emergency Medicine, 408–518. Oxford University Press, 2020. http://dx.doi.org/10.1093/med/9780198784197.003.0009.
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This chapter in the Oxford Handbook of Emergency Medicine investigates wounds, fractures, and orthopaedics in the emergency department (ED). It reviews classification and assessment of skin wounds, puncture wounds, and foreign bodies, and discusses wound cleaning, closure, aftercare, infected wounds, bites and stings, tetanus, and needlestick injury. It explores fractures, including open (compound) fracture and dislocation (and subluxation), casts and their problems, and osteoporosis, as well as soft tissue injury, physiotherapy in the ED, and fracture clinic and alternatives. It describes different areas of fracture and injury in detail, including hand, thumb, scaphoid, and carpal injury, Colles’ fracture, Smith’s fracture, Barton’s and reverse Barton’s fracture, wrist injury, forearm fracture, elbow injury, humeral fracture, shoulder dislocation, clavicle injury, neck injury, facial wounds, pelvic fracture, hip dislocation, sacral and coccygeal fracture, femur fracture, knee injury, tibial and fibular shaft fracture, pretibial laceration, calf and Achilles tendon injury, ankle injury, foot fracture and dislocation, toe injury, low back pain, arthritis, and eponymous fractures.
Conference papers on the topic "Reverse Detail Fracture"
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Craig, Steven, and Patcharapun Soodsakorn. "Overcoming Extreme Technical and Logistical Challenges to Successfully Cleanout 76,000-LBM Proppant." In SPE/ICoTA Well Intervention Conference and Exhibition. SPE, 2021. http://dx.doi.org/10.2118/204437-ms.
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Abstract A fracture treatment in offshore Tunisia screened out leaving over 76,000-lbm proppant in the wellbore. The well was significantly under-hydrostatic. The platform was small and had limited deck space and low capacity cranes. The completion incorporated chrome tubulars with a history of causing abrasion failure to coiled tubing strings. The challenge was to efficiently and safely clean out the proppant with coiled tubing (CT). A prior cleanout campaign had been conducted with concentric CT and jet pumps. An initial design focused on repeating this method. The engineering analysis had to account for fluid and nitrogen pumping being conducted from a supply vessel, limited nitrogen volume, low the solids return rate due to surface handling limitations, and no fluid discharge permitted to sea. A combined engineering, logistical study, laboratory testing and risk assessment was undertaken over the course of three months. Engineering utilized advanced cleanout modelling software to review concentric CT cleaning, forward cleaning (with and without optimizing cleaning Bottom Hole Assembly (BHA) and with various sizes of CT), and reverse circulating. Logistics analyzed the overall operation time, fluid and nitrogen requirements and the number of boat trips to replenish/change well returns and nitrogen. Three additional challenges were present. First, proppant could have packed off creating difficulties for some of the processes under review. Laboratory testing was conducted and confirmed this would not be a concern. Second, the well was sour and considerations for protecting the CT string and handling hydrogen sulfide (H2S) in the return stream were required. Third, CT string optimization was required to reduce potential abrasion failures. Avoiding CT failure was paramount as the string would be boat spooled onto the platform and any failure would severely impact operating time and project finances. The chosen method was primarily fluid only reverse circulating when cleaning above the formation, changing to forward circulated two phase operation when close to the formation. The downhole pressure gauge in the completion provided early warning of lost returns or of gas kicks. The operation was successfully, efficiently and safely completed in August 2019. The well was handed back to production 8 days ahead of schedule. The paper will cover the complete concept and detail design, execution and post-job analysis.
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Jeong, David Y., and Pawel Woelke. "Probabilistic Fatigue Crack Growth of Detail Fractures in Different Rail Steels." In 2020 Joint Rail Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/jrc2020-8077.
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Abstract The most common rail defect encountered in continuously welded rail is known as the detail fracture. The U.S. Department of Transportation, Federal Railroad Administration has sponsored and managed research over the past several decades to understand the structural integrity of rail in general, and the fatigue crack growth behavior of detail fractures in particular. Control of rail integrity and defect growth is conducted via periodic rail tests (i.e. inspections) to ensure that rail defects do not become large enough to cause rail failure. Moreover, federal regulations have been codified to establish a maximum interval between rail inspections based on the results of government-sponsored research. Over the past several decades, however, rail manufacturing has evolved and improved, particularly the head-hardening process to improve wear resistance. Propagation life of railroad rail was examined in previous research using fatigue crack growth data for non-head-hardened rail. Recently Thornton-Tomasetti conducted research, sponsored by FRA, to examine the fatigue crack growth behavior of modern rail steels (i.e. railroad rails with head-hardening). The initial results of the more recent research effort were reported in the 2019 Joint Rail Conference. In this paper, fatigue crack growth rate data generated for head-hardened rail are used to examine the fatigue crack growth life of detail fractures under nominal revenue service conditions. Moreover, this paper applies a probabilistic approach to estimate rail life to account for the inherent variability or scatter typically observed in fatigue crack growth rate data. Regression methods are employed to derive the parameters for the Walker crack growth rate equation, which are subsequently treated as correlated, multivariate, and normally distributed random variables. Data from four different rail steels are used in the regression analyses, which are referred to as: Advanced Head Hardened (AHH), Head Hardened (HH), Standard Strength (SS), and Colorado Fuel and Iron (CF&I). Monte Carlo simulations of fatigue growth of detail fractures are carried out to estimate fatigue life distributions for each of the different rails. The results from these four rail steels are compared to those based on the previous research for non-head-hardened rails. Implications of these comparisons on determining rail testing intervals are discussed.
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Leis, Brian N., Xian-Kui Zhu, and Andrew Cosham. "Modeling Stress-Activated Creep at Axial Cracks in Pipelines." In 2020 13th International Pipeline Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/ipc2020-9392.
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Abstract The failure of a pipeline that had just passed a proof-pressure test as it was being re-pressurized for its return to service (a so-called pressure reversal) reflects the stable growth due to stress-activated creep of a near-critical anomaly that had remained stable as the proof test ended. In the same way that stable growth of a near-critical anomaly can lead to a pressure reversal, stable tearing (cracking) can occur and remain stable at the pressure first imposed upon the pipeline’s return to service, and so pose concern for in-service failure. Ductile failures that are absent evidence of time-dependent degradation mechanisms, like corrosion, and show the traits of stable tearing have been termed time-delayed failures. As time passed, the reasons for time-delayed failures became clear, and criteria to prevent such failures through a pressure reduction were established. The advent of much tougher steels opened to the potential for crack initiation and stable tearing at service pressures under circumstances that differed from that for the early line pipe steels. The 2004 incident at Ghislenghien involving a modern high-toughness X70 pipeline raised the need to better understand how to manage time-delayed failures in such steels. This paper develops a model to quantify stable tearing and possible instability at axial part-through-wall defects as a function of the steel, the length and depth of the defect, and the operating pressure. The theoretical basis for this nonlinear fracture mechanics (NLFM) model is outlined first. Case-specific finite-element analysis were used to benchmark NLFM Handbook results, which extended the use of predictive technology developed previously for lower toughness steels. As before, this solution is recast for time-marching analysis that is coupled with isochronous stress-strain response and NLFM resistance curves. Finally, the model is used to make blind predictions of cracking and instability in step-load and hold testing, and found to be viable in that context. Companion papers at this conference present the details of related work.
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Ibekwe, Achinike, Kjeld Sorensen, Jonathan Fernández, Alberto Arredondo, and Alex Mena. "Remnant Life Assessment of Bonga FPSO and SPM Mooring Chains." In ASME 2018 37th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/omae2018-77941.
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Delivering full service life performance for mooring systems of Floating Production Storage & Offloading assets (FPSO) has been a frustrating challenge to operators across the industry. Remaining strength and fatigue assessment on degraded top mooring chains of the Bonga FPSO and Single Point Mooring (SPM) loading Buoy has been investigated as part of an in-house Bonga Asset Preservation Program. Both facilities are located approximately 120 km off the coast of Nigeria in the Gulf of Guinea operating in tropical waters just North of the Equator, where top chain links have been subjected to accelerated deterioration from Sun Corals and other forms of Microbiologically Induced Corrosion (MIC). These phenomena have led to overall corrosion rates being slightly above general design requirements, but more importantly to formations of large pitting on several sections of the top chain links. Remotely Operated Vehicles (ROV) assisted inspections, chain link cleaning and underwater 3D photogrammetry have allowed capturing the surface geometry of representative degraded chain links of the mooring lines to provide detailed input data for further analyses. Reverse engineering has been performed via Finite Element Analysis and fracture mechanics methodologies using the scanned geometry of selected highly exposed critical links to estimate the residual strength and fatigue life performance of the degraded links relative to their original design criteria. To evaluate the potential impact of cracks on the capacity of degraded chains relative to a reference link, crack tip Stress Intensity Factors have been computed at worst case stress-raising pits and parametric analyses using varying initial crack sizes have been performed to calculate the number of years for the cracks to propagate to critical sizes. A baseline for benchmarking the strength, fatigue and crack growth behaviour of the degraded links investigated has been provided by analysing non-degraded and uniformly corroded links after 12 years of service with projection to end of service life capacity. The paper provides a comprehensive application of numerical methods for assessing the fitness-for-service of the chains and recommendations on in-situ performance integrity management by circumventing the need to retrieve chain samples for testing.
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Smyth, Andrew, Kevin Carmody, and Derek Maier. "Fitness-for-Service Assessment of Passenger Railcars and Trucks." In 2018 Joint Rail Conference. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/jrc2018-6147.
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An important consideration when operating a fleet of passenger rail consists is the remaining service life of both the car structure and the trucks. Agencies may choose to undertake studies like this when considering a fleet wide capital improvement program, ranging from minor aesthetic upgrades to major system replacements and interior reconfigurations. With this in mind, the owner needs to determine the remaining fatigue life of the individual cars and trucks within the fleet. This paper describes the fitness-for-service (FFS) assessment performed on railcars and trucks and an example of the method applied in practice. To establish the current condition of the fleet, an initial structural and service history review was undertaken. In addition, nondestructive examinations (NDE) of a sample of cars and trucks were performed to investigate any regions that have experienced damage due to the years of service. After the baseline condition of the cars and trucks was determined, finite element analyses (FEA) were performed on both the cars and the trucks to assist in locating the potential fatigue critical regions. Strain gages and accelerometers were then installed on both the cars and trucks for field testing. Multiple runs of in-service testing were performed and a typical revenue service fatigue life of both the cars and trucks was calculated based on an S-N approach. Based on the calculated fatigue life and the current accumulated consist mileage, the remaining car and truck service lives were determined. For regions with known flaws more detailed fracture mechanics based crack growth analyses were developed to determine critical flaw sizes and their propagation times to critical from the known initial flaw sizes. Results of the FFS assessment provide information on the susceptible areas within the car structure and trucks. Depending on those results, decisions can be made on the required inspections, repairs, or decommissioning necessary to operate the fleet in the short term, while also providing valuable insight into long term fleet planning.