HYDROGEN INDUCED CRACKING

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Crystallographic Texture Helps Reduce Hydrogen Induced Cracking in Pipeline Steels

Crystallographic Texture Helps Reduce Hydrogen Induced Cracking in Pipeline Steels

It has been shown that it is feasible to improve the HIC resistance of pipeline steels using crystallography texture control and grain-boundary engineering. At a macroscopic scale, this can be achieved through controlled warm (ferritic) rolling schedules. These thermomechanical processes lead to a crystallographic texture dominated by the {111}ND-fiber texture and to a mesotexture with a high proportion of low-angle, low-energy grain boundaries. These two characteristics are critical to reduce, beyond traditional practices, the susceptibility of these steels to hydrogen-induced cracking.
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Influence of S Contents on the Hydrogen Blistering and Hydrogen Induced Cracking of A350LF2 Steel

Influence of S Contents on the Hydrogen Blistering and Hydrogen Induced Cracking of A350LF2 Steel

and Hydrogen blistering (HB). HIC and HB can result in premature failure of equipment. Some researchers believe HIC and HB are caused by inclusion distribu- tion, especially by the elongated MnS inclusion distri- bution [5,6]. But the relationship between chemical compositions, especially the S content and cracking sensitivity has not been studied systematically in A350LF2 steels and the influence of S content on the corrosion rate is not very clear. In this paper, the ef- fects of chemical compositions of four types of A350LF2 steels with different sulfur content on crack- ing and corrosion rate are investigated.
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Mechanisms of hydrogen-induced cracking in ultrahigh-strength steels

Mechanisms of hydrogen-induced cracking in ultrahigh-strength steels

It is known that ultrahigh-strength steel has an advantage over low strength steel due to the potential reduction in welding and other construction costs from the reduction in the quantity of materials required. Although the corrosion protection of steels in the oil and gas industries by CP impressed current method may be effective, the absorption of hydrogen from seawater that is promoted when CP is applied to steel is of great concern. High strength steels are known to be more prone to HIC (Hilditch et al. 2003; Depover et al. 2014), but austenitic steels are less prone to HIC compared to ferritic steel, due to the low hydrogen diffusivity in austenite (Kim et al. 2008). Recent reports have indicated some uncertainty over the susceptibility of high strength austenitic steel to HIC (So et al. 2009; Chin et al. 2011; Koyama et al. 2012; Kim et al. 2008), given that the nanostructured bainitic steel and TWIP steel have varying contents of austenitic phase, and are also high strength due to their refined microstructural features such grain size and dislocation density. The distribution of these features within the microstructure of the steel can influence the mobility of hydrogen generated during CP and influence their HIC behaviour. Hence, it is critical to understand the HIC susceptibility of the steels to finally determine their suitability for use in the oil and gas sector.
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MINIMISING HIC/HAC IN STEEL USING LOW HYDROGEN ELECTRODE FOR SMAW

MINIMISING HIC/HAC IN STEEL USING LOW HYDROGEN ELECTRODE FOR SMAW

Hydrogen Assisted Cracking (HAC)" or "Hydrogen Induced Cracking (HIC)" can thus occur either in the solidified Weld-Metal or the HAZ or both based on its diffusion mechanism together with the locked up stresses due to contraction, welding restraints etc; over a long period of time. This is the reason for which, such defects are also known as 'Delayed/Cold Cracking or Defect'. It is, therefore, wise and reasonable, as the general practice is, to inspect such weldments and the adjoining HAZ; at least 48 Hrs. Later than complete solidification of the molten weld- puddle. Such defects are influenced by three principal parameters/components, which are :- a) Presence of a certain level of adversely effective Internal-Stress
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Pitting-induced hydrogen embrittlement of magnesium–aluminium alloy

Pitting-induced hydrogen embrittlement of magnesium–aluminium alloy

Fig. 7 shows representative fractographs of the SSRT samples tested in air, distilled water and in 0.5wt.% NaCl solution. As expected, the alloy tested in air showed typical ductile fracture features (Fig. 7a). In contrast, the alloy tested in distilled water showed a brittle failure (Fig. 7b). A higher magnification of the fracture surface revealed predominantly transgranular cracking with some secondary cracks (Fig. 7c). The alloy tested in 0.5 wt.% NaCl solution showed a different mode of failure. Noticeably, the edge of the fracture surface exhibited significant pitting corrosion (Fig. 7d). The circumference of the failed tensile sample revealed localized corrosion attack (Fig. 7e) similar to that of the flat samples immersed in 0.5wt.% NaCl solution for 24 hours (Fig. 2b). The fracture surface revealed a mixed-mode of failure, i.e. brittle features and a few fine dimples (Fig. 7f).
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Hydrogen inhalation ameliorates ventilator induced lung injury

Hydrogen inhalation ameliorates ventilator induced lung injury

Recently, the biological functions of therapeutic gases have received considerable attention and hydrogen was identified as a physiologically relevant gaseous signaling molecule like other endogenously generated gases, including nitric oxide (NO), carbon monoxide, and hydrogen sulfide [22-24]. Thus, hydrogen has been described as ‘the fourth signaling gaseous molecule’ [25]. Hydrogen has great potential as a safe and potent therapeutic medical gas as well as several potential advantages as a therapeutic option for VILI. Inhalation therapy is a straightforward approach to lung disease and can be administered by simply providing gas for the patient to inhale. Hydrogen may be relatively easily incorporated into our current interventional or surgical procedures without increasing their complexity. Inhaled hydrogen gas has been safely used for treatment of decompression syndrome in divers [26], suggesting that hydrogen can be safely administered to patients. Hydro- gen is a stable molecule and does not react with other therapeutic medical gases at room temperature and thus may be administered as a combined gas with other ther- apeutic gases or inhaled anesthesia agents [18]. Hydro- gen does not alter NO levels [11]. Endogenous NO signaling pathways are critical for modulating pulmon- ary vascular tone and leukocyte/endothelial interactions; therefore, it may be beneficial to spare endogenous NO [27]. Hydrogen treatment does not eliminate superoxide anion (O 2 - ) or hydrogen peroxide (H 2 O 2 ) [11]. O 2 - and
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DEVELOPMENT OF A MODIFIED PALM-NUT CRACKER

DEVELOPMENT OF A MODIFIED PALM-NUT CRACKER

This section (Figure 5) mainly composes of rotating screen and shaft. A pre-screening section was incorporated to screen out dirt and immature kernels while the other section is designed to classify kernel-shell mixture. This was to enhance better product purity. The physical properties of kernel and shell such as differences in sizes and shapes were considered in the development of this compartment, which mainly consists of rotating cylindrical screen and shaft. In most cases, shells are flat or dish shaped, while kernels vary from nearly spherical to ellipsoidal in shape. Also, it has been established that the least mean diameter of palm kernels is greater than 10 mm (Akubuo and Eje, 2002; Koya et al., 2004; Koya and Faborode, 2005). It was expected that mixture of kernel and shell particles smaller than these kernels will be classified after mechanical cracking process. Consequently, sieve cleaner with regular apertures of 10 mm was used as aclassifier. It was a cylindrical framework 900 mm long with a diameter of 350 mm (Figure 5). A section of the frame, 300 mm long, near the feed-end, overlaid with net of uniform 5 mm apertures, was used as pre-cleaner, to sieve out small shell particles and immature kernels, while the remaining length was the classifier. The unit is mounted on the supporting frame through the driving shaft and directly attached to the outlet discharge of the cracking chamber, and it was made up of galvanized steel and expanded metal.
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Development of an improved crack propagation model for corrosion induced cover cracking in RC structures

Development of an improved crack propagation model for corrosion induced cover cracking in RC structures

Several attempts have been made to study corrosion-induced cracking by using accelerated corrosion tests [3, 4]. However, results from these studies were not very encouraging due to limitations which have been highlighted in the study by Mullard and Stewart [3]. These limitations include the unrealistic geometry of specimens as well as limited investigation of variables such as concrete cover, bar diameter and concrete strength. The occurrence of the confinement effect on crack propagation was observed when cracks over the reinforcing bars located at the edge of specimens have a higher propagation rate than the cracks located at the internal positions and this is particularly significant for columns and other structural elements which have many edges. The Mullard and Stewart [3] study was based on experimental data for one-way RC slab specimens and did not include any transverse reinforcement in the RC slab specimens. The limitations present in these previous works provide an opportunity for pursuing research in this area by developing more realistic models for corrosion- induced damage. The first series of accelerated corrosion test, ACT (1) studied by Sabtu and Stewart [5] was successfully demonstrated that the presence of transverse reinforcement and spacing of reinforcing bars have a significant effect on the rate of crack propagation. Therefore, the second series of the accelerated corrosion test, ACT (2) was conducted to further investigate the cracking behaviour of chloride-induced cracking included crack patterns, crack width, time to first cracking, T 1st (the time
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Reliability analysis and life cycle costing of rehabilitation strategies for RC structures exposed to marine environment

Reliability analysis and life cycle costing of rehabilitation strategies for RC structures exposed to marine environment

This paper presented results obtained from acceler- ated corrosion tests of two RC slab specimens. The results demonstrated that reinforcement confine- ments and spacing of reinforcing bars have a signifi- cant effect on the rate of crack propagation. Rein- forcing bars located at the edge of specimens were observed to reach certain crack width earlier than the reinforcing bars located at the internal location. Clearly, the reinforcement confinement reduces cor- rosion-induced cover cracking by a significant ex- tent. Finally, two-way slab (ie. transverse reinforce- ment) appears to have significantly reduced rates of
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Effect of tropical marine microclimates on depassivation and corrosion-induced cracking of reinforced concrete

Effect of tropical marine microclimates on depassivation and corrosion-induced cracking of reinforced concrete

Such relationships between structural distress and corrosion from accelerated corrosion tests performed in laboratory have been presented [10-16], while natural corrosion investigations are scant due to its complexity on data analysis, which may include various parameters involved in this corrosion phenomenon [16]. In the case of structures exposed in a marine environment, chloride ions are deposited on the surface of the concrete and penetrate until they reach the surface of the reinforcing steel, causing the breakdown of the passive layer [17-19]. Once reinforcing bar corrosion starts, corrosion products starts to build up around the reinforcing bar, causing volumetric expansions that will result in concrete cover cracking (Figure 1) [20].
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Smart Management of Heavy Traffic Urban Roads

Smart Management of Heavy Traffic Urban Roads

The attempts are being made all over the world to develop standards for maintenance quality level for which roads are to be maintained to achieve the requisite level of expediency, ease and safety to the road users. The maintenance of roads should be kept up to such a level that the vehicle operating costs and accident costs are minimized. Environmental concerns are also being given due consideration to reduce the level of exhausts from road traffic. The measure of maintenance quality levels which have been accepted in most of the developed countries consists of measuring the service conditions of roads in terms of surface defects such as roughness, potholes, cracking and rutting etc. to determine a ‘Serviceability Index’ which varies from country to country. The recommended serviceability and the permissible levels are shown in Table 5 (MoRT&H 2013).
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STABILITY INDICATING HPLC METHOD FOR THE DETERMINATION OF CANDESARTAN IN PHARMACEUTICAL DOSAGES FORM

STABILITY INDICATING HPLC METHOD FOR THE DETERMINATION OF CANDESARTAN IN PHARMACEUTICAL DOSAGES FORM

1. Acid induced degradation: The 50 mg of Candesartan was dissolved in 20 mL of methanol; 5 mL of 1N Hydrochloric acid (HCl) was added. The solution was refluxed for 6.0 h at 96-98°C on boiling water bath. After cooling at room temperature acid was neutralized with 1 N NaOH then volume was completed up to 50 mL with methanol to obtain concentration 1.0 mg/mL.

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The antioxidant properties of carnitine in vitro

The antioxidant properties of carnitine in vitro

The beneficial effects of carnitine appear to be mediated, at least in part, by its antioxidant properties, which include the upregulation of the level of glutathione [8, 9] and the elevation of the activities of antioxidant enzymes [8]. The in vivo effects may be mediated by the direct antioxidant action of carnitine or by its effects on the biosynthesis of antioxidant enzymes and other proteins. In this context, it is of interest to characterize the antioxidant properties of carnitine in well-defined systems in vitro, as this may contribute to the elucidation of the mechanisms of the antioxidant action of this compound. Previous studies have demonstrated that carnitine reacts with superoxide and hydrogen peroxide, has reducing properties, chelates iron, and prevents lipid peroxidation and DNA cleavage [11, 12]. The aim of this study was to further characterize the antioxidant properties of carnitine in vitro, particularly with regard to pathophysiologically relevant oxidants such as peroxynitrite and hypochlorite. These oxidants are not neutralized enzymatically in vivo, so low-molecular weight antioxidants that would protect against their action would be even more important than ones protecting against superoxide or hydrogen peroxide, which are removed enzymatically.
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Strain Energy Release Rate Analyse of Matrix Micro Cracking in Composite Cross Ply Laminates

Strain Energy Release Rate Analyse of Matrix Micro Cracking in Composite Cross Ply Laminates

tinuous. In the present study, only results pertaining to thin 8-ply cross-ply laminates are presented. The energy model used here gives good results for small stiffness laminates. However, although the proposed approach is successful for thin laminates, for thicker and more rigid laminates, the method gives approximate good results. Based on linear elastic fracture mechanics, the estimated values of the strain energy release rates are computed in a pre-damaged laminate, a method used in several dam- age models. Thus, there are already existing transverse and longitudinal cracks. Then, the progression of trans- verse cracking damage is described in the following way. We consider a laminate with a periodic array of trans- verse cracks in the inner 90˚ layer. Damage initiation occurs when the spacing between two consecutive cracks is very large (say, infinite). The relevance of this “infi- nite” value was numerically assessed with several models [24,30]. Using as a damage parameter the ratio of the distance between two consecutive cracks to the damaged thickness layer ( a  a t 90 ), the strain energy evolution
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3D characterisation of indentation induced sub-surface cracking in silicon nitride using FIB tomography

3D characterisation of indentation induced sub-surface cracking in silicon nitride using FIB tomography

To investigate the influence of directional FIB serial sectioning on the observed 3D crack patterns, additional 1 kg indentations on the SN- 1 composition were sectioned ‘ top down ’ by serial polishing and imaged optically. Fig. 2(a) shows dark and bright field images of one of the 1 kg indentation on the SN-1 sample prior to polishing. Radial cracks can be seen extending out from the indentation corners to a length of up to 10 μm. No lateral cracking was observed in images of the 1 kg in- dentations prior to polishing (Fig. 2(a)). After ten polishing increments, the central residual indentation impression and radial cracks of the 1 kg indentations were no longer visible in bright field mode (as shown in Fig. 2(b)). However, under dark field the radial cracks are visible as well as a border zone (arrowed) surrounding where the residual indent impression previously was. The visible border zone scatters light in the same manner as the radial cracks, which suggests that it may consist of localized micro-cracking or a region of high dislocation density plasti- cally deformed zone [23].
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An influence of thermally-induced micro-cracking under cooling treatments: mechanical characteristics of Australian granite

An influence of thermally-induced micro-cracking under cooling treatments: mechanical characteristics of Australian granite

Crystalline rock formations with multiple sub-minerals undergo thermal expansion with temperature increase, and this behaviour is heterogeneous among individual mineral types [15]. Therefore, the mismatch in thermal expansion coefficients in these minerals leads to micro-cracking in crystalline rocks. Studies of this thermo-elastic behaviour of crystalline rock formations and the subsequent micro-cracking under the effect of temperature increase have revealed that the decay of poly-mineral crystalline rocks is dependent upon preliminary parameters such as mineral composition, grain size distribution and the thermal properties of individual minerals [15]. Furthermore, the accompanying α to β transition of quartz at 573 ◦ C and β to cristobalite transition at 870 ◦ C have a significant influence on the crystalline deformation of rocks [16]. Here, α - β transition defines the irreversible change in trigonal crystal structure of quartz ( α -quartz) at room temperature to hexagonal crystal structure (β-quartz) at 573 ◦ C and β-cristobalite transition defines the conversation of β-quartz crystal structure into tridymite hexagonal crystal structure (cristobalite quartz) at 870 ◦ C [17]. Overall, past studies have revealed that the induced thermal stresses are confined within grains through existing crack closure with temperature increase up to a threshold temperature, and the development of micro-cracks starts with subsequent heating beyond this temperature [18]. The deep underground geothermal reservoirs and nuclear waste disposal sites with hot rock formations generally undergo rapid cooling close to the injection point upon exposure of injection fluid, especially during the injection of cold fluids. This rapid cooling process alters the reservoir porosity and permeability by inducing micro-cracks due to the release of compressive stresses restrained in grains under high temperatures [19]. Therefore, it is important to investigate the induced micro-cracking during heating followed by cooling processes which finally alters the long-term performance of geothermal reservoirs and nuclear waste disposal sites in terms of reservoir permeability and porosity.
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Understanding and mitigating hydrogen embrittlement of steels : a review of experimental, modelling and design progress from atomistic to continuum

Understanding and mitigating hydrogen embrittlement of steels : a review of experimental, modelling and design progress from atomistic to continuum

b. Despite the application of a coating, hydrogen may still enter the microstructure and provide a route for embrittling processes. In this case, an intrinsic resistance may be considered when designing a material’s microstructure. It is nec- essary to provide sufficient trapping capabilities in order to absorb any hydrogen that may enter during the component’s in-service lifetime. Alter- natively, degassing treatments used to release hydrogen during a part’s life cycle need to be considered [164, 166, 234]. If the traps saturate, then they may ultimately not mitigate hydrogen ingress. Hence, it is required that the material has a sufficient number density of traps to provide an appropriate uptake. As an example, bearings for off-shore wind turbines can accumulate up to 3 wppm hydrogen over their lifetime [177]. It is feasible to trap this amount of hydrogen through engineered microstructural traps [138] improving the hydrogen embrittlement resistance. Traps can take on a variety of forms, and this has been the subject of extensive research in the literature. A significant quantity of hydrogen can be trapped at dislocations; however, these traps are shallow and easily release hydrogen back into the matrix. Experimental work carried out by Takasawa et al. [209] and Hejazi et al. [71] suggested that a reduction in dislocation density and grain refine- ment is effective in reducing HE susceptibility. From these experiments, it is clear that ‘‘trapping’’ alone may be an insufficient predictor of HE experiments, as this is based upon a somewhat arbitrarily chosen binding energy cut-off [113]. However, it is important from a theoretical perspective to consider more complex local equi- librium scenarios [21], with both binding energy E B and trap density N T B , which may better
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Cracking the Discovery Code

Cracking the Discovery Code

Services Work Best When We Collaborate – Actions You Can Take A Library Perspective: Graham Stone, Information Resources Manager, University of Huddersfield A Discovery Service Perspecti[r]

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Cracking Down on Bribery

Cracking Down on Bribery

The figure contains the difference in punishment expenditure between US and Pakistani subjects, and shows that while punishment of firms is not significantly different between the two co[r]

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STRAIN-INDUCED INTERACTION ENERGIES BETWEEN HYDROGEN-ATOMS IN PALLADIUM

STRAIN-INDUCED INTERACTION ENERGIES BETWEEN HYDROGEN-ATOMS IN PALLADIUM

The elastic interaction energies presented for pairs and clusters refer to what is essentially the infinitely dilute solution. In the calculation of the partition function [r]

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