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Author | : Nilesh Raykar |
Publisher | : |
Total Pages | : 336 |
Release | : 2013 |
Genre | : |
ISBN | : |
Download Modelling of Hydrogen Assisted Stress Corrosion Cracking Book in PDF, ePub and Kindle
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 | : Alexander Robert Troiano |
Publisher | : ASM International |
Total Pages | : 356 |
Release | : 1984-01-01 |
Genre | : Technology & Engineering |
ISBN | : 9781615031788 |
Download Hydrogen Embrittlement and Stress Corrosion Cracking Book in PDF, ePub and Kindle
Author | : Ellis E. Fletcher |
Publisher | : |
Total Pages | : 28 |
Release | : 1966 |
Genre | : Metals |
ISBN | : |
Download Stress-corrosion Cracking and Hydrogen-stress Cracking of High-strength Steel Book in PDF, ePub and Kindle
High-strength steels are susceptible to delayed cracking under suitable conditions. Frequently such a brittle failure occurs at a stress that is only a fraction of the nominal yield strength. Considerable controversy exists over whether such failures result from two separate and distinct phenomena or whether there is but one mechanism called by two different names. Stress-corrosion cracking is the process in which a crack propagates, at least partially, by the stress induced corrosion of a susceptible metal at the advancing tip of the stress-corrosion crack. There is considerable evidence that this cracking results from the electrtrochemical corrosion of a metal subjected to tensile stresses, either residual or externally applied. Hydrogen-stress cracking is cracking which occurs as the result of hydrogen in the metal lattice in combination with tensile stresses. Hydrogen-stress cracking cannot occur if hydrogen is prevented from entering the steel, or if hydrogen that has entered during processing or service is removed before permanent damage has occurred. It is generally agreed that corrosion plays no part in the actual fracture mechanism. This report was prepared to point out wherein the two fracture mechanisms under consideration are similar and wherein they differ. From the evidence available today, the present authors have concluded that there are two distinct mechansims of delayed failure. (Author).
Author | : Ekkarut Viyanit |
Publisher | : |
Total Pages | : |
Release | : 2005 |
Genre | : |
ISBN | : |
Download Numerical Simulation of Hydrogen Assisted Cracking in Supermartensitic Stainless Steel Welds Book in PDF, ePub and Kindle
Author | : R. Gibala |
Publisher | : |
Total Pages | : 324 |
Release | : 1986 |
Genre | : |
ISBN | : |
Download Hydrogen Embrittlement and Stress Corrosion Cracking Book in PDF, ePub and Kindle
Author | : Ivan S. Cole |
Publisher | : |
Total Pages | : |
Release | : 1994 |
Genre | : Hydrogen |
ISBN | : |
Download An Assessment of a Micro-mechanic Model of Hydrogen-induced Stress Corrosion Cracking, Based on a Study of an X65 Line Pipe Steel Book in PDF, ePub and Kindle
The susceptibility of an X65 line pipe steel to hydrogen-induced stress corrosion cracking (SCC) is investigated. SCC tests on the steel are carried out in three environments of different aggressivity based on a NACE TM-01-77 solution with dissolved gaseous H2S. The threshold stress intensity factor is calculated for each environment using the multiple specimen technique. The steel is tested in the as-received condition and after homogenisation. Permeation tests are carried out on specimens of the same steel in the same environment. The relationship between threshold stress intensity factor and hydrogen concentration is obtained. The results from these studies are used to generate the parameters in the micro-mechanic model of Akhurst and Baker. The validity and physical significance of the model is assessed.
Author | : Blaise Bourdin |
Publisher | : Springer Science & Business Media |
Total Pages | : 173 |
Release | : 2008-04-19 |
Genre | : Technology & Engineering |
ISBN | : 1402063954 |
Download The Variational Approach to Fracture Book in PDF, ePub and Kindle
Presenting original results from both theoretical and numerical viewpoints, this text offers a detailed discussion of the variational approach to brittle fracture. This approach views crack growth as the result of a competition between bulk and surface energy, treating crack evolution from its initiation all the way to the failure of a sample. The authors model crack initiation, crack path, and crack extension for arbitrary geometries and loads.
Author | : Ekkarut Viyanit |
Publisher | : |
Total Pages | : 196 |
Release | : 2005 |
Genre | : |
ISBN | : 9783865092700 |
Download Numerical Simulation of Hydrogen Assisted Cracking in Supermartensitic Stainless Steel Welds Book in PDF, ePub and Kindle
Author | : William Donald Needham |
Publisher | : |
Total Pages | : 554 |
Release | : 1986 |
Genre | : Naval architecture |
ISBN | : |
Download Hydrogen Embrittlement of Thick Section High Strength Low Alloy Steel, Stress Corrosion Cracking and Book in PDF, ePub and Kindle
An experimental study was conducted to evaluate the corrosion performance of weldments of a high strength low alloy(HSLA) steel in a simulated seawater environment. This steel, designated HSLA80, was developed by the United States Navy for use in ship structural applications. Stress corrosion CRACKING(SCC) and hydrogen embrittlement(HEM) were investigated by conducting 42 Wedge-Opening load(WOL) tests as a function of stress intensity and corrosion potential and 33 Slow Strain Rate(SSR) tests as a function of strain rate and corrosion potential. The corrosion potentials were chosen to simulate the environmental conditions of free corrosion, cathodic protection and hydrogen generation. The results from this investigation indicated that HSLA 80 base metal and weldments were susceptible to hydrogen assisted cracking(HAC) in a seawater environment under conditions of continuous plastic deformation and triaxial stress in the presence of hydrogen. The heat-affected zone of the weldment was found to be the most susceptible portion of the weld joint. A lower bound was established for the critical stress intensity for stress corrosion cracking for HSLA 80 base metal and weldments.(Theses).
Author | : |
Publisher | : |
Total Pages | : 47 |
Release | : 2000 |
Genre | : |
ISBN | : |
Download Computer Simulation of Intergranular Stress Corrosion Cracking Via Hydrogen Embrittlement Book in PDF, ePub and Kindle
Computer simulation has been applied to the investigation of intergranular stress corrosion cracking in Ni-based alloys based on a hydrogen embrittlement mechanism. The simulation employs computational modules that address (a) transport and reactions of aqueous species giving rise to hydrogen generation at the liquid-metal interface, (b) solid state transport of hydrogen via intergranular and transgranular diffusion pathways, and (c) fracture due to the embrittlement of metallic bonds by hydrogen. A key focus of the computational model development has been the role of materials microstructure (precipitate particles and grain boundaries) on hydrogen transport and embrittlement. Simulation results reveal that intergranular fracture is enhanced as grain boundaries are weakened and that microstructures with grains elongated perpendicular to the stress axis are more susceptible to cracking. The presence of intergranular precipitates may be expected to either enhance or impede cracking depending on the relative distribution of hydrogen between the grain boundaries and the precipitate-matrix interfaces. Calculations of hydrogen outgassing and in gassing demonstrate a strong effect of charging method on the fracture behavior.