Fatigue performance of the Deeply Embedded Ring Anchor

Yield gap and resource utilization efficiency of three major food crops in the world – A review

This paper carried out fatigue reliability analysis on braced monopod structure located in Madura North Java Sea to find the most suitable fatigue performance function so better service life prediction of each structure’s components can be done by testing the influence of some load random variable. Fatigue reliability analysis is a local analysis therefore analysis will be conducted only on four critical joints. Reliability analysis is done on several performance function using First Order Reliability Method (FORM). The load random variables which will be tested are yearly fatigue damage, local and global stress analysis, and S-N curve parameter. Randomness of fatigue damage is obtained by running fatigue analysis using only one-year wave data for 59-year SEAFINE wave data. Fatigue damage from analysis will be divided by safety factor and service life to obtain yearly fatigue damage. Reliability index from several performance functions show S-N curve parameter hardly influence the result of reliability analysis. Therefore, fatigue reliability analysis will only include yearly fatigue damage and local and global stress analysis as load random variable. Reliability index with 2 as the value of safety factor and 20 years of service life for four critical joint which are 301L, 303L, 203L, and 201L respectively are 1.24, 1.30, 1.30, and 1.30.

Background: Nearly three-quarters of anterior cruciate ligament (ACL) injuries occur as “noncontact” failures from routine athletic maneuvers. Recent in vitro studies revealed that repetitive strenuous submaximal knee loading known to especially strain the ACL can lead to its fatigue failure, often at the ACL femoral enthesis. Hypothesis: ACL failure can be caused by accumulated tissue fatigue damage: specifically, chemical and structural evidence of this fatigue process will be found at the femoral enthesis of ACLs from tested cadaveric knees, as well as in ACL explants removed from patients undergoing ACL reconstruction. Study Design: Controlled laboratory study. Methods: One knee from each of 7 pairs of adult cadaveric knees were repetitively loaded under 4 times–body weight simulated pivot landings known to strain the ACL submaximally while the contralateral, unloaded knee was used as a comparison. The chemical and structural changes associated with this repetitive loading were characterized at the ACL femoral enthesis at multiple hierarchical collagen levels by employing atomic force microscopy (AFM), AFM–infrared spectroscopy, molecular targeting with a fluorescently labeled collagen hybridizing peptide, and second harmonic imaging microscopy. Explants from ACL femoral entheses from the injured knee of 5 patients with noncontact ACL failure were also characterized via similar methods. Results: AFM–infrared spectroscopy and collagen hybridizing peptide binding indicate that the characteristic molecular damage was an unraveling of the collagen molecular triple helix. AFM detected disruption of collagen fibrils in the forms of reduced topographical surface thickness and the induction of ~30- to 100-nm voids in the collagen fibril matrix for mechanically tested samples. Second harmonic imaging microscopy detected the induction of ~10- to 100-µm regions where the noncentrosymmetric structure of collagen had been disrupted. These mechanically induced changes, ranging from molecular to microscale disruption of normal collagen structure, represent a previously unreported aspect of tissue fatigue damage in noncontact ACL failure. Confirmatory evidence came from the explants of 5 patients undergoing ACL reconstruction, which exhibited the same pattern of molecular, nanoscale, and microscale structural damage detected in the mechanically tested cadaveric samples. Conclusion: The authors found evidence of accumulated damage to collagen fibrils and fibers at the ACL femoral enthesis at the time of surgery for noncontact ACL failure. This tissue damage was similar to that found in donor knees subjected in vitro to repetitive 4 times–body weight impulsive 3-dimensional loading known to cause a fatigue failure of the ACL. Clinical Relevance: These findings suggest that some ACL injuries may be due to an exacerbation of preexisting hierarchical tissue damage from activities known to place larger-than-normal loads on the ACL. Too rapid an increase in these activities could cause ACL tissue damage to accumulate across length scales, thereby affecting ACL structural integrity before it has time to repair. Prevention necessitates an understanding of how ACL loading magnitude and frequency are anabolic, neutral, or catabolic to the ligament.

We tested the hypothesis that introduced populations may have higher resource capture ability and utilization efficiency than native ones of invasive plants. We compared ecophysiological traits including maximum photosynthetic rate (Pmax), apparent quantum yield (Q), specific leaf area (SLA), photosynthetic energy use efficiency (PEUE), photosynthetic nitrogen use efficiency (PNUE), water use efficiency (WUE), mass-based and area-based leaf construction cost (CCmass and CCarea), and mass-based and area-based leaf nitrogen concentration (Nmass and Narea) between native (Argentina) and introduced (USA) populations of two varieties (North Apa and South Apo) of Alternanthera philoxeroides under common garden conditions in China. For Apo and Apa, Pmax, Q, Nmass and WUE were not significantly different between native and introduced populations; introduced populations had significantly lower SLA and lower CCmass but significantly higher Narea and CCarea than native ones. For Apa, the introduced populations showed significantly lower PEUE and lower PNUE while for Apo, PEUE and PNUE were not significantly different between native and introduced populations. The results indicated that introduced populations of A. philoxeroides do not show higher resource capture ability and resource utilization efficiency than their native ones in the common garden experiment, suggesting that these traits may not necessarily contribute to successful invasion of invasive plants.

The time-dependent effects in steel-concrete composite beam bridges can intensify track irregularities, subsequently leading to amplified train-bridge coupling vibrations. This phenomenon may increase the stress amplitudes in the bridge steel, thereby impacting the fatigue performance of the composite structures. This paper employs multiple rigid body dynamics to construct a high-speed train model and utilizes the finite element method to develop a steel-concrete composite beam element model that accounts for time-dependent effects, interfacial slip, and shear hysteresis. This approach enables the computational analysis of the train-bridge coupling system, facilitating an investigation into the influence of concrete’s time-dependent effects on the fatigue performance of railway steel-concrete composite bridges. Focusing on a 40-m simply supported composite bridge, the train-bridge coupling dynamic responses were computed for each operational year within a decade of the completion of construction. Applying the P-M linear fatigue damage accumulation theory, statistical analysis of stress history data across various operational periods was conducted to quantify the fatigue damage induced by a single eight-car high-speed train on the lower flange of the mid-span steel beam and the beam-end studs. The findings reveal that the beam-end studs sustain greater damage than the mid-span steel beam. Moreover, the detrimental impact of time-dependent effects diminishes with the increase of operational years. Notably, compared to the initial year, the fatigue damage to the lower flange of the mid-span steel beam by an eight-car train in the tenth year has surged by 39.3%. Conversely, the damage to the beam-end studs has decreased by 47.5%.

An approach to identify fatigue sensitive joints to be considered in an inspection programme is presented. Joint selection is based on inspection records, fatigue and reliability analysis. Fatigue analysis is used to identify fatigue sensitive tubular joints, thus reliability analysis and inspection records are used to assess the joint selection. The objective is to reduce the number of inspected joints whilst maintaining the platform risk level within acceptable limits. A relation between the reliability index β, a weighted average stress range value and tubular joint geometrical expressions is presented for the selection of joints for inspection. Experience obtained from inspection records is considered for an assessment of the joints selected for inspection. Cost reduction is determined from a comparison of this approach with inspection programmes applied in the past.

Influence of shear yield strength of rail material on the shakedown limit in shakedown map

This paper describes the fatigue analysis of Kizomba 'A' FPSO based on the FPSO Fatigue Methodology Specification (FMS) [1] which is developed on the direct stochastic calculation. The FMS provides designers with technical guidance for fatigue control of newly built FPSO and can be characterized as integrated fatigue analysis to ensure the structural safety of all critical FPSO details by means of full stochastic analysis as well as component based one. At the cost of modeling complexity and computer resources, the full stochastic method gives the accurate fatigue damage for FPSO-specific details such as topside, piperack, flare etc., which are governed by hull-wave interactions. On the other hand, the component based one provides the cost-effective tools to screen the most fatigue prone area in topside supports for full stochastic analysis. Besides, the spectrum combination method that is suggested in order to consider both wave-line and wave-hull interactions, is adopted in fatigue damage calculation of the supports for FTL, OOL, riser and mooring. Apart from technical aspect, the interface management between other groups in charge of FPSO-hull, topside, riser and mooring system turns out very important due to tight project schedule. This paper proves the practical possibility and appropriateness of full stochastic fatigue analysis for FPSO and envisions its usefulness for other floating structures such as TLP, semisubmersibles and etc. The considered Kizomba 'A' FPSO to be installed on Angola Block 15 is 285 meters long, 63 meters wide, and 32 meters high, and can store 2.2 million barrels of crude oil in its lower hull facilities [2]. Introduction As the offshore oilfields shift into the deeper waters with little infrastructures, FPSOs have become the more popular solution. Currently one of the most active areas in FPSO installation is the West Africa where the weather is benign and the swell from the south is dominant. Whereas strength of the FPSO in such a calm site is mostly controlled on towing route, the fatigue control is directly dependent on the site-specific environment. It should be ensured that FPSOs could stay for decades without drydocking for maintenance. ExxonMobil has developed FPSO Fatigue Methodology Specification (FMS) with DNV for providing designers with technical guidance for fatigue control of newly built shipshaped FPSOs [3]. The aim of the fatigue control is to ensure that all critical structural details meet the fatigue design requirements. Also, the calculated fatigue lives form the basis of FPSO design and are used as inputs to the inspection plans during fabrication and in-service. The focus of the FMS is a full stochastic fatigue analysis method that gives the accurate fatigue damage for the FPSOspecific details like topside support, piperack, flare tower foundation etc. The structural behaviors of these supports are governed by wave-hull interactions and describable using linear analysis. The wave loads based on the metocean data of installation site are directly calculated and transferred to the structural model. Generally, full-ship structural model is utilized in the analysis. Figure 1 shows the general procedure of full stochastic fatigue analysis.

The fatigue of structural details of ships is of great importance in the maritime industry as they can lead to cracks which can jeopardize structural integrity. The hopper knuckle is among the most vulnerable areas in a ship with respect to fatigue damage. Analysis of the hopper knuckle has become mandatory for tankers in the Class Ship Rules and in the International Association of Classification Societies Common Structural Rules. Along with the fatigue damage record of the vessels, the fatigue analysis of the hopper knuckles is essential to ensure that the vessels have sufficient fatigue strength. In the current work, fatigue calculations are performed of the upper and lower hopper knuckle connections within midship of the oil tanker using simplified fatigue calculations based on Det Norske Veritas (DNVGL) Classification Note No. 30.7. The fatigue analysis is based on 25 years of operation in worldwide wave environment. A cargo hold model (½ + 1 + ½) amidships and a local finite element model of the hopper knuckle are generated. The local model provides relevant hotspot stress for fatigue life calculations. The results from the hopper knuckle fatigue analysis show that the vessels may expect fatigue cracks at lower hopper knuckle before the vessel reaches its design life of 25 years. Based on the findings, it is recommended to fit soft brackets and close scallops at the lower hopper knuckle on selected common frames in all cargo holds.

Technip Energies has recently completed a fit-for-service and life extension project for nearly 200 submarine pipelines with a total length of over 2,000 km in the Gulf of Thailand. One of the main challenges in this project was to accurately determine the remaining life and necessary intervention works for free spans, which are a typical concern for pipeline integrity with respect to local buckling and fatigue capacity. Initial assessments revealed that the conventional free span evaluation method of comparing observed free span lengths with analytically determined allowable lengths would lead to extensive intervention works. Additionally, ROV (Remotely Operated Vehicle) surveys showed a continuous increase in free span lengths due to scouring, and pipeline Inline Inspections (ILI) identified multiple active corrosion defects at span locations. These findings underscored the importance of developing an automated approach to enhance free span assessment accuracy with higher workflow efficiency. The automated approach developed integrates industry-standard design tools with tailored in-house programs to streamline the free span assessment process. The workflow begins with a detailed analysis of pipeline design data, ROV survey and inline inspection data. ROV survey data from multiple inspection campaigns are analyzed to determine free span lengths, gaps, and growth rates, while inline inspection data are used to identify major corrosion defects and their growth. An in-house program is then used to develop a global finite element (FE) model for the entire pipeline – either on a flat seabed with predefined free spans or on a more realistic undulated seabed profile to account for rotated boundary conditions. This FE model accurately captures the on-bottom condition of the free spans, including the effective axial force. Free span growth is either incorporated directly in the global model (through multiple analysis iterations) or its effect is considered separately through a mapping function. For spans affected by corrosion, a separate specialized program develops a localized 3D shell element finite element model featuring local pipe wall thickness reduction from corrosion to determine equivalent pipe stiffness for fatigue analysis and corroded bending moment capacity for local buckling assessment. Outputs extracted from the global FE models serve as inputs to pipeline local buckling assessment and Vortex-Induced-Vibration (VIV) fatigue analysis software for a comprehensive fatigue analysis. This paper presents the developed automated free span assessment methodology together with a case study of a typical free spanning pipeline with internal corrosion. The paper compares various modelling techniques and their effects on fatigue damage and local buckling assessment results. The findings provide valuable insights for the assessment of free spans in corroded pipelines in dynamic seabed environments, enhancing the service life of operating subsea pipelines while substantially reducing unnecessary intervention costs.

3R24. Fatigue Damage.Mechanical Vibration and Shock Series, Vol IV.- C Lalanne (French Atomic Energy Authority, France). Hermes Sci Publ, Paris. Distributed in USA by Taylor & Francis Publ, New York NY. 2002. 352 pp. ISBN 1-56032-989-0. $150.00.Reviewed by SF Stiemer (Civil Eng Dept, Univ of British Columbia, 2324 Main Mall, Vancouver BC, V6T 124, Canada).This reference book provides a very complete discussion of the behavior of material suffering fatigue and basics dealing with fatigue accumulation. The format of the book and its presentation is of high quality and in a classic style. The text is well written and reads easily, while the formula and graphs are presented in a very orderly and appealing way. This book is unique in that it tightly integrates random vibration procedures with fatigue analysis. Many authors have attempted to effectively combine the topics of random vibration and fatigue analysis. Christian Lalanne is one of the few who succeeded in covering as well as relating both topics. This book can be highly recommended to students, researchers, and development engineers involved in random vibration related fatigue analysis and design. The author emphasizes the complete and systematic presentation of often-used formulations and theories related to random vibrations and fatigue designs. The coverage on related topics in random analysis and fatigue is comprehensive, which is rarely found in engineering books of the same category. The formulations are clearly laid out and properly referenced. A minor weak point of the book is its lack of dealing with practical design issues. While focusing more on theories and formulations, the author fails to expand on comprehensive design examples. These are needed to illustrate as well as verify complex calculation formulations in today’s design scenario. A few simple and precisely described calculation examples are provided in the book; however, if the book is to be used by practicing engineers and designers, more concrete numerical examples of higher complexity are desirable. This reviewer can highly recommend this outstanding book, Fatigue Damage: Mechanical Vibration and Shock Series, Volume IV for use mainly in the academic and theoretical fields. The author needs to be commended for concentrating on the basic theories and smooth integration of the issues in vibration and fatigue. This might reduce the appeal of the book to the practicing engineer; however, it could make the book one of the standard reference tools for academics.

<p>Actuators are essential components for motion in machines, and warranty service lives are basic specifications of actuators. However, fatigue damage or wear of actuators are very complex and related to many design factors, such as materials properties, surface conditions, loads, and operating temperature. Actuator manufacturers still rely heavily on physical experiments to determine the fatigue lives of actuators. This paper investigates the state-of-the-art of using numerical simulations for fatigue analysis of mechanical actuators. Failure criteria of machine elements are discussed extensively; existing works on using finite element methods for machine element designs are examined to (1) explore the feasibility of using a numerical simulation for fatigue analysis and (2) discuss the technical challenges in practice. Moreover, a systematic procedure is suggested to predict fatigue lives of mechanical actuators with Teflon impregnated hard coatings. A virtual fatigue analysis allows for optimizing a mechanical structure, reducing design verification costs, and shortening the development time of actuators.</p>

Flexible pipelines are widely used in the offshore oil and gas projects. Comparing to steel pipes, flexible risers consist of multiple components layers, with each layer serving designated functions. For example, the helical tensile layers are used to work against axial tension from static pipe weight and amplification from the dynamic motions. As the risers are constantly experiencing stress variations due to different loadings, the fatigue performance of the tensile layers is essential to the design and operation of the flexible pipe system. Global and local fatigue analyses are usually performed in the design stage to estimate the fatigue life of tensile layers. Various parameters like vessel characteristic, pressure and temperature, environmental loadings affect the riser long-term performance. Also, multiple locations like top end fitting, bend stiffener region, touch-down zone are all potential fatigue hot-spots. To evaluate the fatigue damage at these locations, the industry standard practice is to run fatigue analysis in time domain with irregular wave. This approach is however time and resource consuming, especially when the designers have to consider thousands of load cases with long duration for numerous combinations of sea-states and operating conditions. Baker Hughes developed a frequency domain technique for fatigue assessment on tensile layers of flexible risers. The approach builds transfer functions based on chosen time domain simulation and predict the total stress spectrum for other cases. Dirlik’s approximation method is used to estimate the fatigue damage based on the stress spectrum. Comparing to time domain approach, this approach is considerably more efficient in implementation. Since frequency domain technique simplifies the riser response as a linear system, the discrepancy must be addressed by calibration factors. To improve accuracy, more transfer functions are required to be built prior to the damage calculation. In this paper, Baker Hughes introduces artificial neural network (ANN) technique to the developed frequency domain fatigue damage methodology. The ANN model is built between the wave spectrum and stress spectrum. Unlike the general AI technique, the type of neuron at each layer is carefully selected to represent the dynamic behavior of the riser system to improve the model efficiency. The ANN model is trained based on selected sea states. The trained model is used to predict riser damage and compared to that calculated from the time domain approach.

PurposeRecent studies have proposed the application of local fatigue approaches based on fracture mechanics or on strain-life material relations for the fatigue analysis of metallic structures. However, only few studies in the literature apply local approaches in the riveted bridges analysis; although these approaches can be applied to any type of connections, requiring a detailed stress analysis of joints and, consequently, considerable computational resources costs. The approach based on S-N curves, formulated in nominal or net stresses, is more usual in the fatigue analysis of riveted bridges. Due to economic factors, riveted bridges have had their operating life extended, while changes in the transport system over the years have subjected such structures to overloads different from those originally planned. These bridges, most of them centenary, were not originally designed accounting for fatigue damage; they represent an important group of structures that are very likely subjected to significant fatigue damage indexes. These factors make necessary detailed residual fatigue life studies to substantiate the decisions of extend (or not) the operational period of these bridges. The paper aims to discuss these issues.Design/methodology/approachThe present paper presents a methodology aiming at applying the local approaches in the fatigue analysis of riveted joints of metallic bridges, through the use of sub-modeling techniques and procedures automation. The use of such techniques made such an application viable by keeping the computational costs involved at a moderate level. The proposed procedures were demonstrated using the Trezói Railway Bridge, located on the Beira Alta line, Portugal, built shortly after the Second World War. The proposed set of procedures allowed, through finite elements analysis, to obtain the relevant stresses to perform local fatigue damage analysis. A global structural model was constructed, using beam elements, and local models of a critical node were built with solid finite elements. The structure is analyzed under the passage of regulatory trains. The details of the modeling performed and the computation of the principal stresses in the vicinity of a node and the tangential/circumferential stresses at the holes of two critical riveted connections of that node are analyzed and a fatigue damage analysis is carried out.FindingsIn the proposed submodelling approach, disassembling the complex riveted nodes into riveted subassemblies allowed the evaluation of the local stresses at riveted holes at an affordable computational cost.Originality/valueA methodology is proposed to allow the application of local fatigue analysis in real complex riveted joints, mitigating the computational costs that would result from a full model of the node with all rivets.

Fatigue assessment of FPSO hull side shell longitudinals using component stochastic and full spectral method