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Repurposing existing natural gas pipelines for hydrogen transport requires an accurate assessment of the distribution of hydrogen (H) atoms at defects, such as dents, under frequent pressure fluctuations experienced by gas pipelines. In this work, a 3-dimensional finite element-based model was developed to determine the stress/strain and H atom concentrations at an unconstrained dent on an X52 steel pipe which experienced denting, spring-back and cyclic loading processes. As expected, stress and strain concentrations generate at the dent center. However, the cyclic loading reduces the stress level and shifts the stress concentration zone from the dent center along the circumferential direction. As the dent depth increases, the maximum H atom concentration is further shifted from the dent center to the side. There are no certain relationships among the maximum H atom concentration, von Mises stress, hydrostatic stress, and plastic strain in terms of their distributions and quantities. Pressure fluctuations decrease both the stress and H atom concentrations at the dent, providing a beneficial effect on reduced risk of the dented pipelines to hydrogen embrittlement in high-pressure hydrogen gas environments. The indenter size has little influence on the H atom distribution in the dent area. [ABSTRACT FROM AUTHOR]

During pipeline construction and operation, the occurrence of surface dents presents a critical concern, primarily arising from factors such as pipeline installation and geological forces exerted upon the pipeline, particularly in the form of rock protrusion. These dents pose a significant threat to the pipeline's safe functionality and have the potential to diminish its load-bearing capacity. Presently, China's oil and gas pipelines predominantly employ X80 high-grade steel. It is noteworthy that prior research into the ultimate load capacity of dented pipelines has largely centered on medium and low-grade steels. The implications of these findings for the suitability of the X80 pipeline remain inconclusive. Consequently, it is imperative to undertake a comprehensive investigation into the load-bearing capacity of high-grade steel pipelines with dent defects. In addition to internal pressure, variations in the pipeline's transported medium, ambient temperature fluctuations, soil displacement, and other factors introduce additional loading effects, including bending moments and axial loads. These supplementary loads introduce latent hazards to the pipeline's operational safety. Hence, this research endeavors to investigate the ultimate load-bearing capacity of X80-grade dented pipelines under the influence of typical loading conditions and to identify pertinent factors that affect this capacity. Finite element analysis (FEA) is deployed to study the behavior of the dented pipelines under typical loads. Failure criterion for ascertaining the ultimate load is proposed and verified by the comparison to test results. Furthermore, the impact of varying dent sizes on the ultimate load capacity of X80-grade dented pipelines is examined. These findings serve as a robust foundation for the safety assessment of dented pipelines, ensuring the sustained safe operation of these vital infrastructures. [ABSTRACT FROM AUTHOR]

BACKGROUND: Mycotoxin monitoring in cereal grains has great importance in the food and feed industries. This study evaluated mycotoxin contamination in corns with different endosperm textures in 2 years of cultivation. Samples of dent, semi‐dent, flint and semi‐flint corns from field experiments were analyzed by high‐performance liquid chromatography coupled with tandem mass spectrometry (HPLC‐MS/MS). RESULTS: Occurrences of fumonisins B1 (FB1) and B2 (FB2) in 2020 were 45.72% (mean 270 μg kg−1) and 35.89% (94.97 μg kg−1), respectively, and 68.98% (446 μg kg−1) and 45.83% (152 μg kg−1) in 2021. Occurrence of aflatoxin B1 was 11.96% (0.16 μg kg−1) in 2020 and 11.11% (0.13 μg kg−1) in 2021. In 2020, deoxynivalenol (DON) and zearalenona (ZEA) presented occurrences of 1.28% and 1.70%, with means of 4.08 and 2.45 μg kg−1, respectively. In 2021, results were 8.33% (31.00 μg kg−1) for DON and 8.79% (4.38 μg kg−1) for ZEA. Citrinin, diacetoxyscirpenol and fusarenon‐X did not occur in 2020 but presented 1.66%, 0.83%, and 2.50% positive rates in 2021, respectively. In 2020, flint corn presented the lowest concentration of FB1 whereas dent corn presented the highest concentration of FB1 and FB2 (P < 0.05). In 2021, dent corn presented the highest means of FB1, FB2 and diacetoxyscirpenol (P < 0.05). Dent and semi‐dent presented the highest concentration of nivalenol (P < 0.05). CONCLUSION: The endosperm texture influenced mycotoxin contamination in corn grains, especially FB1 and FB2, which had the highest concentration in dent corn in the 2 years of this study. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Copyright of Cahiers d'Études Africaines is the property of Editions EHESS and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

High strength and highly reflective metal sheets are widely applied in industry; industrial requirements for defect detection are extremely demanding, particularly in the aviation and automotive industries. Classifying and recognizing surface defects on steel plate surfaces is highly challenging. Currently, defect detection is still inspected visually by personnel. However, given the high temperatures at inspection sites and the high risks in the operating environments, machine vision inspection systems are expected to replace manual inspection processes eventually. Therefore, this study developed an automated defect detection system that reduces the high reflectivity of examined objects. The light sources emitted light rays to the rays diffused and reflected multiple times inside the hemispherical cover to produce uniform illumination. Subsequently, image processing was conducted to highlight defect features on the stainless-steel plates. Relatively favorable light source positions were identified, which reduced the difficulty of class identification, the omission rate in defect detection to be decreased, and frequently encountered reflection problems in the automated optical inspection of metallic products to be overcome. [ABSTRACT FROM AUTHOR]

The mutual influence of stress concentrators in the form of a dent (made by a hemispherical indenter 25 mm in diameter to a depth of the sheet thickness) and a hole 4 mm in diameter in a thin 1.5- or 3.0-mm-thick skin on the static strength and fatigue life of structurally similar samples made of a 1163AT aluminum alloy is studied. The presence of a dent does not decrease the static strength, while the strength decreases by ~8% regardless of the location of a hole with respect to a dent for combined dent + hole stress concentrators. The position of a hole relative to the center of a dent weakly affects the slope of a fatigue curve, whereas the displacement of a hole from the center to the edge of the dent leads to a decrease in the fatigue life. [ABSTRACT FROM AUTHOR]

Denting, a common geometric defect in oil and gas pipelines, can threaten the structural integrity and safety of pipelines. A pipeline dent is usually caused by the collision or extrusion of hard objects during the pipeline construction and service stages. Some rebound occurs in the dented zone when the external load is removed. In actual engineering, unconstrained dents tend to reround with increasing internal pressure of the pipeline. This study experimentally and numerically investigated the processes of springback and rerounding of a dented pipeline. First, full-scale testing was carried out to simulate the springback and rerounding processes, and the strain variations at the dent were measured. Then, a 3-dimensional numerical model was developed and then validated against the experimental results. According to the experimental and numerical results, the stress and strain responses of the pipeline during the springback and rerounding processes were studied in detail. Furthermore, the factors influencing the springback and rerounding coefficients were discussed. Finally, equations for predicting the springback and rerounding coefficients of dented pipelines were proposed on the basis of a nonlinear regression analysis. The results show that mainly elastic recovery occurs during springback. After a dent is unloaded, the elastic strain and von Mises stress of the pipeline decrease greatly, while the plastic strain remains unchanged. The elastic strain increases with increasing internal pressure. The springback and rerounding coefficients increase with increasing indenter diameter and diameter-to-wall thickness, while the loading depth has a negative effect on these coefficients. The proposed formulas can be used as a reference for estimating the ratios of dent springback and rerounding of dented pipelines. • Springback and re-rounding processes of a dented pipeline were experimentally and numerically investigated. • The variations in stress and strain in the processes of springback and re-rounding were analysed in detail. • Effects of dent and pipeline geometry on the springback and re-rounding behavior were examined. • New predictive formulas of springback and re-rounding coefficients for dented pipelines were derived. [ABSTRACT FROM AUTHOR]

• Model-based method to assess pipe dent due to external interference by excavators. • Numerical scheme for calculating excavator maximum force and kinetic energy. • Excavator-pipe interaction model suitable for static and dynamic contacts. • Dent charts for selecting the excavator to be employed to avoid damaging the pipe. • Preventive action that involve limiting the excavator workspace for risk mitigation. Despite the presence of numerous safety precautions, the primary cause of damage to underground pipes is often attributed to external interference from excavators during their operations. To address this issue, this paper introduces a model-based approach that incorporates both static and dynamic contact in assessing the damage caused by excavators on pipes. The objective of this method is to offer a practical tool that can assist in determining the appropriate excavator size for buried gas pipes. By identifying the maximum safe excavator size, the aim is to minimize the potential risks of mechanical damage to the pipe, to prevent hazards for operators and to protect the integrity of the pipeline. For this purpose, a comprehensive excavator model is constructed. Following this, a suitable damage model for the pipe is selected and the interaction between the bucket tooth and the pipe is modelled. To enhance accuracy, the excavator and pipe are interconnected through the solution of damped contact equations, which take into account the stiffnesses of both the pipe and excavator, as well as the damping effect resulting from pipe deformation. Results provide valuable insight into the potential damage caused to the pipe, which can be attributed to either static or dynamic contacts, depending on which excavator is being used. Failure is addressed by plastic dent, that can be avoided by selecting the most suitable excavator size. Moreover, the analysis of dent depth caused by various excavators on different pipes for gas transmission, opens to the possibility of mitigating the risk of failures by limiting the excavator workspace. [ABSTRACT FROM AUTHOR]

Dents are one of the most common defects on pipelines and compromise the structural integrity. To date, relevant studies on failure assessment of dented pipelines have been limited, and the existing standard, mainly American Society of Mechanical Engineering (ASME) B31.8, contains major problems, making assessment results not sufficiently accurate and reliable. In this work, a new method based on ductile damage failure indictor (DFDI) criterion combined with improved strain determination by a finite element (FE) model was developed for pipeline dent assessment. Dents with different depths were created by applying a spherical indenter of 100 mm in diameter on a pipe segment of 720 mm in outer diameter and 8.1 mm in pipe wall thickness. The DFDI formula considers the influence of spring-back upon removal of indenter, and the difference between the equivalent strain at dent apex and the maximum equivalent strain at the whole dent area. When the indenter displacement is smaller than 8% of pipe outer diameter, the maximum DFDI can be determined from the equivalent strain at the dent apex. When the initial displacement exceeds 8% of the pipe outer diameter, the maximum equivalent strain at the dent area, which deviates from the dent apex, should be determined by the FE model. Moreover, the limitations of ASME B31.8 in dent assessment were explained.

The rolling element bearing is a fundamental component of any rotating machinery. During operation, wear debris and lubricant impurities create dents and bumps on the bearing raceway surfaces. Such localized defects produce transient vibration impulses at one of the bearing characteristic frequencies. Having a combination of multiple types of point defects on the raceway results in superimposed vibration patterns, which reduce the ability to recognize these defects' effects. In this paper, a 6-DOF dynamic model is developed to accurately investigate the vibration characteristic of a ball bearing with a multipoint defect comprising a dent and bump on its raceway surface. The model considers the effects of time-varying contact force produced due to defects, lubricant film damping, bearing preload, and the inertia effect of rolling elements. The simulation results reveal the vibration behavior of multipoint defect bearings. In addition, bearing vibration response is affected by the number of defects, the angle between them, and the type and size of each defect. Furthermore, it is challenging to predict bearing defects parameters such as the numbers, types, sizes, and angles between adjacent defects from acceleration signal analysis without jerk signal analysis. The validation of the model is proved using signals from the Case Western University test setup. [ABSTRACT FROM AUTHOR]

In the study, experimental and theoretical studies were carried out to assess the influence of the shapes of dents in the tank wall on the stress-strain state of the defect zone. By testing fragments of a cylindrical tank, it was found that the most appropriate expression is (5), which could take into account the leaching of the tank wall, resulting in a decrease in the stress concentration index. At the same time, during theoretical studies in this paper, it was found that polynomials determined the stress concentration coefficient, where the obtained analytical expression data were compared with the data determined numerically in the ANSYS program, and it was found that the spread was from 2% to 10%. According to the results of a numerical study of the stress-strain state of the dent zone in the tank wall, graphical dependences of the stress concentration coefficient on the dimensionless depth of the dent for various values of the dimensionless radius of the dents and do not exceed 2% of the indicators that are obtained. At the conclusion of the experimental and numerical studies, a conclusion was made about the degree of influence of the geometric dimensions of the dents on the stress concentration index. [ABSTRACT FROM AUTHOR]

Existence of defects on pipe surface deteriorates the product quality. This article presents the results of integrated studies of surface defects such as: dent, skin, and lap. Regarding the TPA-140 rolling mill, the locations, reasons of occurrence, and remedial methods are specified. [ABSTRACT FROM AUTHOR]

The present study carries out fatigue reliability analyses of oil and gas pipelines containing unconstrained plain-smooth dents under the variable amplitude loading caused by cyclic internal pressure. The API 1156 S-N curve and Miner’s rule are employed to establish the limit state function for fatigue, and the stress concentration at the dent is accounted for based on findings reported in the literature. The reliability analysis is carried out on two pipeline examples containing dents with depths ranging from 2% to 5% of the pipe diameter. The examples are subjected to cyclic internal pressures at the discharge and suction ends of a compressor station on an actual in-service oil transmission pipeline. In the context of the cyclic pressure records considered in the present study, the analysis results suggest that fatigue failure of dents under suction-end pressure cycles is highly unlikely, whereas the probability of fatigue failure of dents under discharge-end pressure cycles can be significant if the diameter-over-wall thickness ratio of the pipeline is large. This study provides a methodological framework to carry out reliability-based fitness-for-service assessments of dented pipelines with respect to fatigue.

High strength and highly reflective metal sheets are widely applied in industry; industrial requirements for defect detection are extremely demanding, particularly in the aviation and automotive industries. Classifying and recognizing surface defects on steel plate surfaces is highly challenging. Currently, defect detection is still inspected visually by personnel. However, given the high temperatures at inspection sites and the high risks in the operating environments, machine vision inspection systems are expected to replace manual inspection processes eventually. Therefore, this study developed an automated defect detection system that reduces the high reflectivity of examined objects. The light sources emitted light rays to the rays diffused and reflected multiple times inside the hemispherical cover to produce uniform illumination. Subsequently, image processing was conducted to highlight defect features on the stainless-steel plates. Relatively favorable light source positions were identified, which reduced the difficulty of class identification, the omission rate in defect detection to be decreased, and frequently encountered reflection problems in the automated optical inspection of metallic products to be overcome.

In the development of oil and gas fields, subsea pipes are used in various applications, like pipelines and risers. During operation, risers can be subjected to accidents, such as collisions with other risers, anchors, rocks, or any heavy equipment or objects, which may lead to mechanical damages. These mechanical damages are commonly characterized as dents. The objective of this work is to study the effect of the introduction of plain dents on the fatigue life of rigid risers under fully reversed bending with the conduction of resonant bending tests. A three-dimensional finite element model was developed to estimate the stress concentration on dented risers under bending. Numerical simulations and experimental tests were carried out to evaluate the resulting stress concentration factors (SCFs). These SCFs can be used in the prediction of the remaining fatigue life of dented rigid risers. [ABSTRACT FROM AUTHOR]

Copyright of Journal of China University of Petroleum is the property of China University of Petroleum and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A fluid drive in-pipe inspection robot is an essential device for the inner inspection of long-distance oil and gas pipelines. Obstacles such as dents and welds can significantly affect the operation stability of the robot as well as the accuracy of inspection. In this paper, a dynamic model is created to investigate the vibrational response of an in-pipe inspection robot moving through a dented pipe. A mechanical model of the polyurethane sealing disc is established based on the Kelvin spring damping model to simulate its bending deformation. Using the simplified model of the in-pipe inspection robot, the axial vibration equation of the robot is analyzed in detail. Furthermore, a dynamic simulation of the virtual prototype of the in-pipe inspection robot is conducted using the MSC/ADAMS software, considering the interaction between the fluid and the structure. Then, the effects of the robot's speed, sealing disc interval, and dent height on the vibration response during the pigging are examined. The results indicate that the faster the in-pipe inspection robot passes over the pipe dents, the higher the axial vibration generated by the robot, while the time needed for returning to the stable state is shorter. The pitch vibration caused by the dent substantially intensifies with an increase in the sealing disc interval. The axial and pitch vibration caused by the dent intensify significantly with increasing the dent height. The results obtained herein should prove useful to the optimization of the structural design and precise positioning of the in-pipe inspection robot. [ABSTRACT FROM AUTHOR]

In the process of the stretching of the shaft forgings, if the process parameters are not properly selected, the end-face dent will take place. The end-face dent affects the performance of large forgings and leads to much material wasting. Finite element method was employed to perform numerical simulation of the stretching of a main shaft with an upper flat anvil and a lower V-shaped anvil. The orthogonal test table was designed by selecting the anvil width, the Reduction ratio and the feed as influencing factors. Accordingly, simulations were carried out to solve the end-face dent values under different parameter combinations. The analysis showed that the optimal parameter combination gave an anvil width ratio of 0.75, a Reduction ratio of 0.2, and an initial feed of 300 mm. Through extremum difference analysis, it was found that among the three factors are the feed, the reduction ratio, and the anvil width ratio in the decreasing order of the influence on the end- face dent. Comprehensive analysis showed that when the anvil is relatively narrow, increasing the relative feed can reduce the end-surface dent remarkably. It is advisable that during the stretching of shaft forgings with a flat upper anvil and a V-shaped lower anvil, the combination of the anvil width ratio of 0.75, the reduction ratio of 0.2, and increasing the feed can reduce the end-face dent, thereby reducing the end cutting and saving material costs.

The rolling element bearing is a fundamental component of any rotating machinery. During operation, wear debris and lubricant impurities create dents and bumps on the bearing raceway surfaces. Such localized defects produce transient vibration impulses at one of the bearing characteristic frequencies. Having a combination of multiple types of point defects on the raceway results in superimposed vibration patterns, which reduce the ability to recognize these defects’ effects. In this paper, a 6-DOF dynamic model is developed to accurately investigate the vibration characteristic of a ball bearing with a multipoint defect comprising a dent and bump on its raceway surface. The model considers the effects of time-varying contact force produced due to defects, lubricant film damping, bearing preload, and the inertia effect of rolling elements. The simulation results reveal the vibration behavior of multipoint defect bearings. In addition, bearing vibration response is affected by the number of defects, the angle between them, and the type and size of each defect. Furthermore, it is challenging to predict bearing defects parameters such as the numbers, types, sizes, and angles between adjacent defects from acceleration signal analysis without jerk signal analysis. The validation of the model is proved using signals from the Case Western University test setup.

Comme pour tout traitement, la prescription d'inhibiteurs de la résorption osseuse (IRO) implique de mettre en balance les bénéfices et les risques attendus du traitement. Peu fréquente mais invalidante, l'ostéonécrose des mâchoires d'origine médicamenteuse (ONM) n'en reste pas moins l'effet indésirable le plus redouté des patients(e)s comme de certains professionnels de santé, possiblement en rapport avec une méconnaissance des éléments constituant cette balance bénéfices/risques. Une approche multidisciplinaire concertée, la prévention primaire via la réalisation systématique d'un bilan bucco-dentaire préthérapeutique dès lors que la situation clinique le permet, mais aussi l'instauration d'un suivi oral régulier permettent de considérablement limiter le risque d'ONM associé aux IRO, de faciliter l'adhérence au traitement et d'améliorer la qualité des soins. Prescription of bone resorption inhibitors implies a thorough evaluation of associated risks weighed against expected benefits. Although quite infrequent but highly debilitating, medication-related osteonecrosis of the jaw (MRONJ) is the most highly feared complication of such treatments, both by patients and some healthcare professionals. A concerted multiprofessional approach, primary prevention via systematic oral health examination as whenever possible, but also regular follow-up with an oral health professional, could all help limit the risk of MRONJ, increase patient adherence to treatment and improve the overall quality of care. [ABSTRACT FROM AUTHOR]

Les cellulites cervico-faciales d´origine dentaire sont des infections des tissus cellulo-adipeux, de la face et du cou, ayant des potentialités extensives pouvant parfois être graves et engager le pronostic vital. La dissémination cervico-thoracique est favorisée par la parfaite continuité anatomique qui existe entre ces régions. Les premiers signes cliniques sont parfois frustres et peuvent conduire à un retard diagnostique. L´examen clé est la tomodensitométrie cervicale et thoracique. Le traitement consiste en un double drainage cervicale et thoracique associées une antibiothérapie dirigée contre les germes aréo et anaérobies. Nous rapportons le cas d´un jeune patient de 30 ans, tabagique, présentant une cellulite cervicale d´origine dentaire compliquée de pyothoax.

Проблематика. Зовнішнє безконтактне вирівнювання деформованих ділянок поверхні автомобільних кузовів, яке не потребує, на відміну від відомих аналогів, розбирання на елементи з метою безпосереднього доступу з внутрішньої сторони вм’ятини, що видаляється, є нагально затребуваною операцією на багатьох станціях технічного обслуговування. Для цієї операції в її класичному розумінні (механічним способом) характерні такі недоліки: низька швидкість виконання операції вирівнювання, її висока собівартість та, як правило, неможливість збереження лакофарбового покриття. Запропонована методика дає змогу позбутися перерахованих вище недоліків при виконанні операції рихтування. Мета дослідження. Практична апробація інструмента магнітно-імпульсної обробки металів – циліндричної індукторної системи з екраном, що притягає, на прикладі зовнішнього безконтактного вирівнювання деформованих ділянок поверхонь кузовів автомобілів. Методика реалізації. Використання технологій магнітно-імпульсної обробки металів (МІОМ) в операціях зовнішнього видалення вм’ятин на поверхні автомобільних кузовів, а саме на дверях автомобіля, за допомогою індукторної системи з екраном, що притягає, – інструмента МІОМ. Результати дослідження. Успішно апробовано спосіб зовнішнього безконтактного вирівнювання деформованих ділянок поверхні автомобільних кузовів. Практично реалізовано керований (дозований) силовий магнітно-імпульсний вплив, що дає змогу здійснювати контрольоване деформування листового металу в зоні обробки при видаленні вм’ятин циліндричною індукторною системою з екраном, що притягає. Висновки. Експериментально продемонстровано практичні можливості видалення вм’ятин на поверхні двері автомобіля індукторною системою з екраном, що притягає, – ефективним інструментом магнітно-ім­пульс­ної обробки листових металів. Продемонстровано на практиці переваги зовнішнього безконтактного рихтування з використанням технологій МІОМ, яке не потребує, на відміну від відомих аналогів, розбирання на елементи з метою обов’язкового доступу з внутрішньої сторони вм’ятини, що вирівнюється, і це значно скорочує витрати часу на операцію і дає можливість зберегти лакофарбове покриття.

The depth of the pipeline depression has different influence on the safety of X60 pipeline steel,combining Oyane ductile fracture criterion with numerical simulation method to study damage degree of the pipeline. Establishing three dimensional spherical concave defect pipeline model by finite element software and solving the model,discussing internal pressure influence of the pipeline and the indenter size on the relationship between the depth of sag and the damage degree of oil and gas pipelines.The results show that: when the depth of the pipeline depression is in a certain range the internal pressure is beneficial to resist ductile rupture. Once the depth of the pit exceeds 100 mm,the internal pressure will increase the extent of damage of the pipeline.In the case of the ratio of wall thickness to pipe diameter and the constant pressure in the pipe,the smaller the size of the indenter,the more serious the damage degree increases with the depth of the depression. Under certain conditions,when the pipe sag depth exceeds the standard 7% pipe diameter,the degree of pipe damage still meet the integral value I > 1. The Oyane ductile fracture criterion can be applied to the evaluation of sags in engineering projects because of the limitation of sag depth evaluation criteria.

Considering that the use of thin-walled shells is expanding every day, it is important to examine the problem of instability in this form of structure. Many steel structures such as high-water tanks, water and oil reservoirs, marine structures, and pressure vessels, including shell elements, are under stress tension. In addition, shell elements are subject to instability owing to the loads applied. Ten thin-walled cylindrical shell specimens in two groups with different dent depths of tc and 2tc, and the different dent number subject to uniform external pressure were tested in the present research (tc is the thickness of cylindrical shell). The samples were modified to include either one or two dent line with amplitudes of h/3 in height (h the height of cylinder shell). Moreover, CFRP Strips on the dent depth was used in one of the groups. The results of testing under different theories and codes are compared. [ABSTRACT FROM AUTHOR]

Although the first identification of an Asian spinosaurid theropod, Siamosaurus suteethorni from the Sao Khua Formation of Thailand, was published in 1986, what was in all likelihood a spinosaurid tooth was collected from the type section of the Sao Khua Formatio in the course of a stratigraphic survey of the Khorat Plateau (north-eastern Thailand) as early as 1962. The specimen, the present whereabouts of which are unknown, was described in 1963 as an ichthyosaur tooth, but apparently was the first dinosaur specimen to be reported from Thailand. On the basis of the description and figures, it is referred to the spinosaurid genus Siamosaurus. A purported plesiosaur tooth from the Phu Kradung Formation, described in the same paper, apparently belonged to a crocodile. The reasons for the initial misidentification of the spinosaurid tooth are reminiscent of those of other misinterpretations of similar teeth found in other parts of the world. [ABSTRACT FROM AUTHOR]

Interaction of defects tends to intensify their crack driving force response compared to the situation where these defects act independently. The interaction between multiple defects is addressed in engineering critical assessment standards like BS7910 and ASME B&PV Section XI. Nonetheless, the accuracy of these rules is open to debate since all of them are based on re-characterization procedures which in essence introduce conservativeness. The authors have developed a fully parametric finite element (FE) model able to generate multiple notches in different topologies, in order to investigate their interaction effect. An experimental validation study is conducted to verify the FE model in terms of CTOD response and surface strain distribution. To that end, symmetrically and asymmetrically double edge notched tension specimens are tensile tested and their deformation monitored by means of 3D digital image correlation. In this study the CTOD is opted as a local criterion to evaluate the interaction between notches. These results are compared with an evaluation of strain patterns on a specimen’s surface, as a global interaction evaluation. Through this comparison a deeper understanding is gained to allow us to develop a novel approach to address flaw interaction. Moreover, the validation of the FE model allows future studies of interaction between other defect types (e.g., semi-elliptical, surface breaking) in plate-like geometries.

Crashworthiness of square tube with reduced thickness at impacted end and dent under axial impact is analyzed by dynamic explicit FEM. Peak impact force can be reduced by reducing thickness of impacted end,but at same time irregular folding comes out. By stamping dent on tube,progressive buckling folding can be achieved. So crashworthiness of tube is improved by reducing thickness at impacted end and stamping dent.

Much research has been conducted on circular hollow steel tubes subjected to indentation loads, but the response of a circular hollow steel tube when subjected to a combination of an indentation load (the load applied by an indenter) acting together with other loading conditions has received markedly less appraisal. An experimental study was conducted on two groups of circular hollow steel tubes that were either free-spanning or were base-supported. These tubes were first subjected to a uniform axial pre-compression, which is the most common service load across many tube applications, followed by the application of indentation loads while the magnitude of axial pre-compression was maintained. Strength, top surface and mid-height cross-sectional deformation, longitudinal and circumferential strains, and the failure mechanism of the tubes were compared, with a significant difference found between the response of the two groups of tests, and with this difference increasing as the magnitude of axial pre-compression and indenter displacement were increased. Additionally, it was identified that for the same level of absorbed energy, a deeper dent was produced for base-supported tubes than for free-spanning specimens. Moreover, analytical equations available in the literature were compared to the experimental results and good correlation was found between the experiments and the predictions. Bases-supported and free-spanning tubes are compared as below: • Both tube groups had similar indentation strength within the elastic range • Base-supported tubes had greater indentation strength within the inelastic range • A deeper dent formed in base-supported tubes for the same energy absorbed • Larger strains formed in the base-supported tubes • Modifications were made to analytical models to predict tubes indentation strength [ABSTRACT FROM AUTHOR]

Six cold-rolled steel sheet samples having surface defects like slivers and dents have been metallurgically analyzed to identify the reasons for generation of such defects. In all the cases, large inclusions/entrapments were located at the defect site. Energy-dispersive spectroscopy (EDS) of the entrapments in samples 1 and 2 having dents revealed incidences of O, Mg and Ca, confirming that these entrapments are essentially complex oxides of probable slag genesis. The dents in samples 1 and 2 must have occurred due to heavy cold rolling load on the preexisting cracks in the coil. Apart from dents, sliver defects were also observed in some of the samples. Slivers are, however, of various types and appearances, and there could be many reasons for occurrences of these slivers in the cold-rolled sheets. In the present study, the SEM–EDS analyses of the subsurface entrapment/deposit observed in sample 3 revealed complex oxides of CaO-MgO of possible slag genesis and could be the reason for incidences of slivers in this sample. On the other hand, the wavelength-dispersive spectroscopy of samples 4 and 5 having sliver defects carried out in an electron probe microanalyzer (EPMA) revealed subsurface chains of dark and angular brittle inclusions of either alumina or silicate of possible deoxidation product genesis. EPMA analysis of sample 6 having pencil line sliver defects, however, revealed entrapments of possible casting powder origin. [ABSTRACT FROM AUTHOR]

Copyright of Natural Gas Industry is the property of Natural Gas Industry Journal Agency and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Colorless polyimide (CPI) film is one of promising candidates for a foldable display because of its excellent mechanical and optical properties. To achieve a good and high reliable foldability, engineers must take into account thickness for foldability and mechanical hardness for pen touch function. To compromise this trade‐off relationship, LG Display chose CPI as a base film of the cover window and double‐sided thin hard coating for a pen touch solution. This paper shows why LG Display choose the proposed configuration with detail data. [ABSTRACT FROM AUTHOR]

In this work, a three-dimensional finite element-based mechanics-diffusion coupling model is developed to determine the stress/strain distribution and hydrogen (H) atom concentration at an unconstrained dent on an X52 steel pipe which is to be used for transport of high-pressure hydrogen gas. Both von Mises stress and equivalent plastic strain concentrations and a high hydrostatic stress gradient exist at the dent. The distribution of H atom concentration coincides with that of the hydrostatic stress. The maximum H atom concentration in the steel lattice locates at the dent bottom, while the distribution of the H atom concentration at metallurgical traps is consistent with that of the equivalent plastic strain. A competitive effect exists between the hydrostatic stress and the plastic strain on the H atom distribution. At low initial H atom concentrations (e.g., 0.001 mol/m3), the equivalent plastic strain dominates the distribution of H atoms. At high initial H atom concentrations (e.g., 0.1 and 1 mol/m3), the hydrostatic stress is more important to determine the distribution of H atom concentration. As the dent depth increases, both the von Mises stress and plastic strain at the dent increases, while the total H atom concentration decreases due to decreased hydrostatic stress. When the internal pressure increases from 5 MPa to 15 MPa, there are slightly increases in von Mises stress, equivalent plastic strain and the total H atom concentration. • A novel numerical model to determine the hydrogen atom distribution at a dent on pipelines. • The effect of internal pressure and dent depth on hydrogen atom accumulation at the dent. • The quantitative evaluation and location of hydrogen atom distribution at the dent. [ABSTRACT FROM AUTHOR]

• Failure indications were identified at the kinked dent location. • Micro-cracks related to the corrosion process was confirmed in the dent region. • FEM models date the crack indications to the pipe manufacturing process. • The crack indications were identified as laps. Pipeline failure causes can be divided in two groups: corrosion damage and mechanical damage. Mechanical damage usually includes dents, wrinkles, gouges, and combinations thereof. Dents can be considered the most common mechanical damage. In our study, a dent was located at the lower pipe region (5–7o'clock) as a consequence of indentation of the rocks on which the pipe was placed. The damaged pipe section was analyzed using visual, non-destructive testing (NDT), optical microscopy, scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), hardness testing and transmission electron microscopy (TEM) analyses were performed to determine the origin, form, and mechanism of the crack indications at the dent location. Finite element method (FEM) was used for the creation and propagation cracks. The presence of micro-cracks in the dent region was confirmed, the formation of which on both pipe surfaces was related to the corrosion process. A deformation hardening was identified in the refined structure region in the kinked dent location. TEM analysis confirmed a higher concentration of dislocations in the deformed area compared to recrystallized area (undeformed area). The hardness and TEM analyses of the crack indications date them from to manufacturing process of the gas pipe. The FEM models of the pipe dent process supported this contention and confirm random presence of the crack indications in the dent location. The indications detected by NDT and the associated change in microstructure and mechanical properties occurred during the production process of the pipe. The dent, which included the mentioned indications, occurred during the operation of the pipeline. [ABSTRACT FROM AUTHOR]

The mechanically lined pipe, which consists of a carbon steel carrier and a thin-walled corrosion-resistant alloy liner, has proved to be a practical way to prevent the pipeline from internal corrosion. However, the local dent caused by third-party falling objects severely threatens the integrity of the lined pipe, especially the more fragile liner. This work investigates the influence of a local dent on the plastic responses and stability of a lined pipe system during bending. After validation of the numerical framework with the experimental results of a 12-inch lined pipe, the indentation and bending responses of two typical scenarios, namely, TDI and LDI, are examined. It is found that the liner could maintain a certain moment level after reaching the maximum instead of collapsing promptly. Furthermore, classic diamond buckling mode is observed in the TDI case, while the LDI case exhibits a twin triangular-shaped buckling mode. In addition, extensive parametric studies regarding important variables of the full-scale problem are performed. Amongst other findings, the buckling and collapse of the dented lined pipe are found to be affected by the orientation of the dent, which should be taken into account for practical dent evaluation. • Validation of the FE model with four-point bending experimental results of a 12-inch lined pipe. • Buckling and collapse analysis of dented mechanically lined pipes under bending, including two types of dents, namely TDI and LDI. • An extensive parametric study is investigated, including dent length, angle, depth, and key factors of the full-scale problem. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate the interaction effect of maize grain texture (dent vs semi-flint) and two different stages of maturity (1/2 vs 3/4 milk line) on ruminal starch degradability and total tract digestibility using in situ and combined in situ-in vitro methods, respectively. The content of whole plant dry matter was 324.6 vs 399.5 g/kg (1/2 vs 3/4 milk line, respectively) for dent maize and 330.2 vs 401.3 g/kg for semi-flint maize. Organic nutrients (neutral detergent fibre, crude protein, ether extract, starch), 1000-grain weight, vitreousness, and mean particle size were determined. The evaluation was performed using two non-lactating Holstein cows fitted with ruminal cannulae. Effective degradability of dry matter and starch was calculated at ruminal outflow rates of 4, 6, and 8%/h. Vitreousness was lower for dent than for semi-flint grain, averaging 65.6% and 74.3% (P < 0.001). Ground dent maize grain showed lower mean particle size than did that of semi-flint maize (1.76 vs 1.88 mm, respectively, P < 0.001). Effective starch degradability calculated for the medium outflow rate (6%/h) was 69.1% vs 65.3% (P < 0.01) for dent and semi-flint maize and 69.0% vs 65.4% (P < 0.01) for lower (1/2 milk line) and higher (3/4 milk line) maturity, respectively. Higher (P < 0.001) mean starch total tract digestibility was found for dent maize (88.5%) than for semi-flint maize (82.5%) and for kernels harvested at 1/2 milk line (87.4%) than for those harvested at 3/4 milk line (83.6%, P < 0.001). Small differences in grain texture and silage maturity stage significantly influenced ruminal in situ degradability and total tract in situ-in vitro dry matter and starch digestibility.

Mechanical damage is recognized as a problem that reduces the performance of oil and gas pipelines and has been the subject of continuous research. The artificial neural network in the spotlight recently is expected to be another solution to solve the problems relating to the pipelines. The deep neural network, which is on the basis of artificial neural network algorithm and is a method amongst various machine learning methods, is applied in this study. The applicability of machine learning techniques such as deep neural network for the prediction of burst pressure has been investigated for dented API 5L X-grade pipelines. To this end, supervised learning is employed, and the deep neural network model has four layers with three hidden layers, and the neural network uses the fully connected layer. The burst pressure computed by deep neural network model has been compared with the results of finite element analysis based parametric study, and the burst pressure calculated by the experimental results. According to the comparison results, it showed good agreement. Therefore, it is concluded that deep neural networks can be another solution for predicting the burst pressure of API 5L X-grade dented pipelines.

In the current study a numerical simulation approach has been chosen to simulate the force-deflection response of tubular member under lateral impact in the absence of internal pressure or axial force and the results have then been compared with analytical relations. Two series small scale experiments were carried out by the authors on X70 steel tubes and D/t of 22 and the numerical model has then been verified against experimental results. The results show that the analytical relations estimate greater lateral resistance than experimental results for the spherical indentor and in the unpressurized tubular members. The numerical model has then been used to study the effect of D/t and d/D and yield stress on lateral resistance of steel tubes. It has been noticed that, the lateral resistance was governed by: 1) D/t ratio 2) Yield stress 3) d/D ratio. The comparison between analytical and numerical results show that analytical relations are more accurate results for large D/t and d/D ratios.

The purpose of this study is to model the ductile fracture phenomenon using experimental and numerical methods. The stainless steel AISI 304L thin sheets are studied including two thicknesses (0.8 and 1.5 mm). A mechanical characterization is firstly done in order to obtain the main mechanical properties useful for the numerical modeling. In order to determine the essential work of fracture (EWF), DENT specimens are used involving the two thicknesses. The results obtained in terms of EWF for the two thicknesses are close; we find that the essential work of fracture can be considered as an intrinsic criterion for thin sheets. A cohesive zone modeling (CZM) is used in the present study; the model is represented by a traction-separation law (TS). The cohesive elements are implemented in the finite element model, and the material parameters of the model are determined by the mechanical and fracture characterizations. A satisfactory reproduction of the experimental tests is obtained. A good correlation is also obtained between the essential work of fracture determined experimentally and the work of separation used as cohesive zone model parameter. [ABSTRACT FROM AUTHOR]

Because carbon fiber reinforced polymer (CFRP) laminated composites have electric conductivity, damage monitoring was performed using electrical resistance changes. The authors previously proposed an anisotropic electric-potential function method to calculate the electric-potential field of laminated CFRP composites. The method, however, did not deal with the effects of dents. The present study deals with the effects of dents on the anisotropic electric-potential function method. The dent causes an electric conductivity increase in the through-thickness direction. The increase was modeled and applied to a beam-type specimen. The results were compared with the finite-element method results, and the method using equivalent conductivity in the through-thickness direction was confirmed to be effective. [ABSTRACT FROM AUTHOR]

Numerical investigation is conducted in this paper on both intact and dented seamless metallic pipelines (diameter-to-thickness ratio D / t around 21), deploying nonlinear finite element method (FEM). A full numerical model is developed, capable of predicting the residual ultimate strength of pipes in terms of bending capacity ( M c r ) and critical curvature ( κ c r ). The simulation results are validated through test results by using the measured material properties and specimen geometry. An extensive parametric investigation is conducted on the influences of material anisotropy, initial imperfection, friction of the test set-up and dent parameters. It is found that the structural response is quite sensitive to the frictions that have been introduced by the test configuration. For a pipe with a considerable dent size, the effect of manufacturing induced initial imperfection is insignificant and can be neglected in the FEM simulation. The material yield stress in the pipe longitudinal direction dominates the bending capacity of structures. In the end, formulas are proposed to predict the residual ultimate strength of dented metallic pipes under pure bending moment, which can be used for practical purposes. A satisfying fit is obtained through the comparison between the formulas and FEM methods. [ABSTRACT FROM AUTHOR]

In this study, indentation responses of high strength steel pipe with local wall thinning (gouge) under internal pressure have been studied through experimental procedure and numerical analysis. The experimental study was carried out on laboratory scale specimens from API 5 L X80 steel. Dent produced by a hemi-spherical indenter with diameter of 20 mm and axial gouge introduced to the pipe’s outer surface. In experimental work, the influence of some parameters such as depth of dent, axial gouges of different sizes and presence of the internal pressure have been investigated. A numerical modeling approach has also been employed. The current numerical simulation has first been validated by experimental results previously conducted by the authors. The numerical results show well agreement with the experimental results. Effects of internal pressure level, boundary condition and D/t ratio on the response of pipelines subjected to lateral impacts numerically studied and the results have then been compared with analytical equations provided in some design codes. The results show that the analytical relations estimate greater lateral resistance than numerical results. Validated model were then used to derive a semi-empirical equation for predicting structural behavior of locally damaged tubes as a function of internal pressure. Furthermore, the elastic-plastic finite element analyses were performed to estimate the variations of failure depth with several internal pressures and gouge sizes. [ABSTRACT FROM AUTHOR]

Copyright of Naukovi visti NTUU - KPI is the property of National Technical University of Ukraine KPI and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A 3D scanning method is proposed for the measurement of surface damage on aircraft structural panels. Dent depth measurements were shown to be within 0.04 ± 0.06 mm (95%) of those taken using a Starrett 643J dial depth gauge based on 54 flat panel dents, and 0.04 ± 0.05 mm (95%) based on 74 curved panel dents. Dent depths were quantified by the difference between a point cloud rendering of the damaged surface and a surface fit approximating the original, undamaged surface. Convergence studies were used to evaluate the accuracy of the surface fit, enabling this technique to be used as a stand-alone inspection method. Image processing was used to measure dent length and area, and the results showed that this method is more efficient and reliable compared to manual methods. This novel non-destructive evaluation technique thus demonstrates potential to enable the timely extraction of surface dent measurements during on-site aircraft inspections. [ABSTRACT FROM AUTHOR]

A dent is one of the main structural damages that may affect ultimate strength. In this paper, the residual ultimate strength of dented metallic pipes subjected to a bending moment is quantitatively investigated. The numerical model is developed accounting for the variation of the dent length (ld), dent depth (dd), dent width (wd), dent rotation angle (θd) and dent location based on ABAQUS Python. The numerical model is validated by test results from a four-point bending test. Subsequently, a parametric investigation is performed on the effects of wave-type initial imperfection, D/t and dent geometrical parameters. It is found that both ld and dd have a significant effect on the residual ultimate strength of dented metallic pipes, while the effect of wd is slight. Finally, an empirical formula with respect to ld and dd has been proposed for the prediction of bending moment, which can be deployed for practical purposes. [ABSTRACT FROM AUTHOR]

Copyright of Orthodontie Française is the property of John Libbey Eurotext Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)