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| Author | : Ekkarut Viyanit |
| Publisher | : |
| Total Pages | : 196 |
| Release | : 2005 |
| Genre | : |
| ISBN | : 9783865092700 |
| Author | : Thomas Böllinghaus |
| Publisher | : Springer |
| Total Pages | : 502 |
| Release | : 2016-02-10 |
| Genre | : Technology & Engineering |
| ISBN | : 3319284347 |
This is the fourth volume in the well-established series of compendiums devoted to the subject of weld hot cracking. It contains the papers presented at the 4th International Cracking Workshop held in Berlin in April 2014. In the context of this workshop, the term “cracking” refers to hot cracking in the classical and previous sense, but also to cold cracking, stress-corrosion cracking and elevated temp. solid-state cracking. A variety of different cracking subjects are discussed, including test standards, crack prediction, weldability determination, crack mitigation, stress states, numerical modelling, and cracking mechanisms. Likewise, many different alloys were investigated such as aluminum alloys, copper-aluminum dissimilar metal, austenitic stainless steel, nickel base alloys, duplex stainless steel, creep resistant steel, and high strength steel.
| Author | : Werasak Udomkichdecha |
| Publisher | : Springer |
| Total Pages | : 125 |
| Release | : 2015-08-11 |
| Genre | : Technology & Engineering |
| ISBN | : 981287724X |
This book presents contributions to the topics of materials for energy infrastructure with a focus on data and informatics for materials. This spectrum of topics has been chosen because challenges in terms of materials are identified to lie in transport and storage of energy, adequate supply of food and water, well-working infrastructure, materials for medical application and health, efficient use of scarce resources or elements and alternate materials solutions as well as recycling. The contributions were invited at the 4th WMRIF Young Materials Scientist Workshop held at the National Institute for Standards and Technology (NIST) in Boulder, Colorado, USA during September 8-10, 2014.
| Author | : Zengbao Jiao |
| Publisher | : Springer Nature |
| Total Pages | : 302 |
| Release | : 2022-09-19 |
| Genre | : Technology & Engineering |
| ISBN | : 9811947430 |
This book integrates aspects of computational materials science, physical metallurgy, alloy design, structure-properties relationships, and applications of advanced multicomponent alloys. It can serve as a textbook for courses on advanced structural and functional materials for undergraduate and graduate students. Notably, the book compiles cutting-edge research on the progress of materials science of multicomponent alloys from fundamentals to engineering applications. It can be of considerable interest for researchers and scientists in the field of materials science and engineering, mechanical engineering, and metallurgy engineering. In addition, this book not only summarizes the compositions, properties, and applications of various types of multicomponent alloys but also presents a complete idea on the efficient design of materials and processes to satisfy targeted performance in materials and structures. Thus, it can also be used as a reference book for engineers and researchers in industries.
| Author | : Nilesh Raykar |
| Publisher | : |
| Total Pages | : 336 |
| Release | : 2013 |
| Genre | : |
| ISBN | : |
Modelling of hydrogen assisted stress corrosion cracking (HASCC) within the framework of mechanics is very important for its control and avoidance. The main focus of this study is to develop suitable approach for modelling and analysis of stable crack growth through high strength steels under HASCC. A new strategy based on combined analytical/numerical solution and finite element based cohesive zone model (CZM) has been developed. This has helped to couple analysis of hydrogen diffusion and crack growth during HASCC. The strategy has been applied to study crack growth in compact tension (CT) specimens. The solution to diffusion process is obtained through either an analytical or a numerical solution to the governing differential equation. The crack growth is analysed by CZM. For the analytical solution, both one- and two-dimensional approximations of the domain have been considered. The new CZM strategy, termed as hydrogen concentration dependent cohesive zone model (HCD-CZM), has been used for both CT and circumferentially notched tensile (CNT) round specimens. The CNT specimen has been employed for the first time to obtain the fracture toughness data of high strength steel under internal and external supply of hydrogen. The experimental scheme involving CNT specimen under slow strain rate loading is demonstrated as a valid experimental procedure for study of HASCC for high strength steels. Both types of HASCC, internal hydrogen assisted cracking (IHAC) and hydrogen environment assisted cracking (HEAC), are found to induce a proportionate drop in fracture toughness under higher hydrogen concentration near the crack tip. The experimentally obtained lowest fracture toughness data compare favourably with lower range of published threshold values for the similar material. The experimental average crack growth rates too agree with the reported data for the material. For CT specimens, both schemes of analysis of diffusion, excluding or including the effect of hydrostatic stress and plastic strain, predict variation of crack opening displacement with crack growth with good accuracy. Diffusion solution based on one- and two-dimensional analyses do not significantly alter the prediction of crack growth. The effect of hydrostatic stress on the distribution of hydrogen concentration is observed to be significant as long as plastic strain is less than 5%. The study has given rise to an important correlation between hydrogen concentration dependent strength reduction and plastic strain rate. A new modelling technique is presented for the CNT specimen with eccentrically placed ligament using two-dimensional finite element approximations; this has considerably simplified analysis of the problem which otherwise would require a three-dimensional solution. For CNT specimens, the HCD-CZM approach employing both analytical and finite difference based diffusion solutions predicted the critical fracture toughness in agreement with experimental results. In this case too, the inclusion of hydrostatic stress in the diffusion analysis has been found to have not so significant influence on the prediction of experimental observations. The K-resistance curve obtained for the case is included. The proposed HCD-CZM has been found to satisfactorily handle variation in specimen geometry, material and source of hydrogen supply. The thesis is divided into six chapters dealing sequentially with introduction, literature review, experiments with CNT specimen, analysis of CT specimens, modelling of CNT specimens and conclusions.
| Author | : James R. Rule |
| Publisher | : |
| Total Pages | : 217 |
| Release | : 2019 |
| Genre | : Dissimilar welding |
| ISBN | : |
This work builds upon the previous research regarding hydrogen assisted cracking (HAC) of low alloy steel to nickel-base filler dissimilar metal welds (DMWs). In particular, this work is focused on DMWs commonly experienced in offshore oil and gas production systems in subsea use. The HAC tendency of these welds has been attributed to formation of susceptible microstructures at the fusion boundary during welding. As such, a post-weld heat treatment (PWHT) is utilized to temper these microstructures as well as relieve residual stresses. However, these microstructures can persist even after PWHT due to the steep compositional gradient driving migration of carbon from the base metal toward the fusion boundary and into the partially mixed zone (PMxZ) of the weld. The degree to which this migration occurs is a function of materials selection (base metal and filler metal) as well as weld and PWHT procedure. Due to this phenomenon, there is a balance that must be found to provide tempering of the susceptible microstructures that form during welding and limiting the formation of new susceptible microstructures during PWHT. Previous research has established a test method in the form of the delayed hydrogen cracking test (DHCT) which can delineate the effects of materials combination, weld procedure, and PWHT on HAC of DMWs. This test's qualitative ranking of susceptibility agreed well with industry experience. The current study worked towards refining the test methodology investigating the effects of test parameter influence on realized results. Of the investigated variables, it was found that how the test samples are coated is of primary importance where a consistently exposed fusion boundary scheme providing the most repeatable result in test. Additionally, a comparison was made between the test hydrogen charging condition which uses a dilute acid and constant current density of 10mA/cm2 and the service environment which is seawater with a constant potential (-850 to -1100mVAgIAgCl). Through this comparison it was understood that the dilute acid is indeed an accelerated charging environment where the level of acceleration scales with nascent hydrogen concentration differences as indicated by pH and charging current density differences with the dilute acid providing roughly a 1000x acceleration factor. Further work focused on establishing a pass/fail criterion which would transform the DHCT method from qualitative to quantitative. This was done by measuring the diffusible hydrogen content of each DMW at various charging times to find the saturation time. This diffusible hydrogen saturation time was then compared with DHCT results from previous and current work to show that samples which sustain load beyond saturation do not fail due to HAC. This methodology proved successful for sound welds without prior defects and correlated well with service experience. The final focus of the work related to modeling and prediction of DMW microstructures towards predicting HAC susceptibility. The modeling involved thermodynamic and kinetic simulations to model the diffusion of alloying elements both during weld and PWHT thermal cycles. The model was validated using quantitative measurements of the composition through electron probe microanalysis as well as through hardness and microstructural evaluation. The results were correlated with HAC experience to provide a microstructural/character map to facilitate identifying trends which led to susceptibility. The findings confirmed previous research showing fresh martensite to be the main driver for behavior followed by precipitation of M7C3 carbides. This model was applied to a previously untested DMW to predict the microstructure and gauge the relative HAC susceptibility. The predictions proved to be accurate and aligned with both microstructure and HAC susceptibility. The framework of the model can be used as an engineering tool early in the design stage for materials selection and weld procedure development. The final focus of the work related to modeling and prediction of DMW microstructures towards predicting HAC susceptibility. The modeling involved thermodynamic and kinetic simulations to model the diffusion of alloying elements both during weld and PWHT thermal cycles. The model was validated using quantitative measurements of the composition through electron probe microanalysis as well as through hardness and microstructural evaluation. The results were correlated with HAC experience to provide a microstructural/character map to facilitate identifying trends which led to susceptibility. The findings confirmed previous research showing fresh martensite to be the main driver for behavior followed by precipitation of M7C3 carbides. This model was applied to a previously untested DMW to predict the microstructure and gauge the relative HAC susceptibility. The predictions proved to be accurate and aligned with both microstructure and HAC susceptibility. The framework of the model can be used as an engineering tool early in the design stage for materials selection and weld procedure development.
| Author | : Karl-Heinrich Grote |
| Publisher | : Springer Science & Business Media |
| Total Pages | : 1588 |
| Release | : 2009-01-13 |
| Genre | : Science |
| ISBN | : 3540491317 |
This resource covers all areas of interest for the practicing engineer as well as for the student at various levels and educational institutions. It features the work of authors from all over the world who have contributed their expertise and support the globally working engineer in finding a solution for today‘s mechanical engineering problems. Each subject is discussed in detail and supported by numerous figures and tables.
| Author | : Ekkarut Viyanit |
| Publisher | : |
| Total Pages | : |
| Release | : 2005 |
| Genre | : |
| ISBN | : |
| Author | : Ian Milne |
| Publisher | : Elsevier |
| Total Pages | : 4647 |
| Release | : 2003-07-25 |
| Genre | : Business & Economics |
| ISBN | : 0080490735 |
The aim of this major reference work is to provide a first point of entry to the literature for the researchers in any field relating to structural integrity in the form of a definitive research/reference tool which links the various sub-disciplines that comprise the whole of structural integrity. Special emphasis will be given to the interaction between mechanics and materials and structural integrity applications. Because of the interdisciplinary and applied nature of the work, it will be of interest to mechanical engineers and materials scientists from both academic and industrial backgrounds including bioengineering, interface engineering and nanotechnology. The scope of this work encompasses, but is not restricted to: fracture mechanics, fatigue, creep, materials, dynamics, environmental degradation, numerical methods, failure mechanisms and damage mechanics, interfacial fracture and nano-technology, structural analysis, surface behaviour and heart valves. The structures under consideration include: pressure vessels and piping, off-shore structures, gas installations and pipelines, chemical plants, aircraft, railways, bridges, plates and shells, electronic circuits, interfaces, nanotechnology, artificial organs, biomaterial prostheses, cast structures, mining... and more. Case studies will form an integral part of the work.
| Author | : Mei He |
| Publisher | : |
| Total Pages | : 107 |
| Release | : 2016 |
| Genre | : |
| ISBN | : |
Approximately ten years ago, carbon steel was replaced by duplex stainless steel (DSS) to fabricate the reactor effluent air cooler (REAC) of hydrocracker units in order to improve the performance and service lifetime of these units. Unfortunately, several catastrophic failures from around the world have been reported in REAC units constructed of DSS, most within five years of service. Based on failure analysis reports, the failures were generally associated with welded joints and were caused by crevice/pitting corrosion and stress corrosion cracking. Given the condition of hydrogen-rich environment, high-pressure process fluid, and service temperature, this type of cracking is most likely a form of hydrogen assisted cracking (HAC). It is highly influenced by phase balance (ferrite/austenite) after welding and welding procedures, with high levels of ferrite in the weld metal or HAZ increasing the susceptibility to HAC. In this study, different weld metal phase balances were prepared by autogenous gas tungsten arc welding (GTAW) for using different welding parameters and shielding gases. The delayed hydrogen cracking test (DHCT) was used to evaluate the effects of the weld phase balance on the susceptibility to HAC in DSS 2205 welds. Using this approach, weld metal ferrite levels on the order of 90 vol% ferrite led to very rapid failure, while reducing the ferrite level to approximately 50-60 vol% greatly increased resistance to HAC. Fractography was performed using a scanning electron microscope (SEM) and showed that brittle fracture morphologies occurred in the higher ferrite pass of overlapping two pass welds for each DHCT sample. A mixture of quasi-cleavage and intergranular fracture modes occurred during the crack nucleation and propagation process, and final sample failure was caused by overload exhibiting a microvoid coalescence fracture mode. The failure mechanism closely reproduced the actual service failures in REAC welds. For different phase balances in HAZ, the HAZ samples were simulated over a range of cooling rates by Gleeble® 3800 system. It was found that the microstructure had significantly higher ferrite content with faster cooling rate controlled by different free span distances. The same approaches of DHCT and fractography to evaluate the susceptibility to HAC will be used for the simulated HAZ samples. The additional testing will be needed to examine the reproducibility of DHCT and to establish guidelines for the maximum ferrite content in 2205 weld metal and HAZ that will prevent service failures. In summary, the DHCT exhibited high sensitivity and good reproducibility in determining the effect of weld metal ferrite content on HAC susceptibility in autogenous GTA welds of DSS 2205, and it can be an effective method to evaluate the effect of ferrite/austenite balance on the susceptibility to HAC in both the weld metal and HAZ.
