► Influence of hydrogen and low temperature on fatigue crack growth of steel. ► Temperature and frequency influence is related to the hydrogen diffusion rate. ► da/dN increases when the temperature ...increases or the frequency decreases. ► Charged specimens show different kinds of brittle fracture propagation modes. ► Brittle fracture may appear as brittle facets, “cells” or intergranular fracture.
In the presence of gaseous hydrogen or of H2S, metallic materials, such as carbon and low alloy steels, may suffer hydrogen damage and hydrogen embrittlement. In this paper the influence of hydrogen and low temperature on fatigue crack growth properties of two pipeline materials, X65 micro-alloyed and F22 low alloy steels, is studied. An electrochemical charging method has been adopted and fatigue propagation tests were carried out on hydrogen charged and uncharged specimens, by varying the test temperature and the frequency of the load application cycle. The experimental results show an evident effect of the hydrogen presence on the fatigue crack growth. The diffusion rate of hydrogen in the steels seems to be the most important parameter in order to explain the influence of temperature and frequency on the fatigue crack propagation rate. Fracture surface examination has been correlated with the results of mechanical testing.
In the presence of H2S, metallic materials, such as carbon and low alloy steels, may suffer hydrogen damage and hydrogen embrittlement. Sour service materials must be used in compliance with ...international standards when fluids are classified as sour.
Gas transporting pipes in low temperature environment, during the shutdown and the subsequent re-starting operations, are exposed to very low temperatures (T=−40°C). In presence of high H2S content in the gas the risk of brittle failure can be increased due to the effect of hydrogen on steel toughness.
In this paper the influence of hydrogen and low temperature on mechanical properties of two pipeline materials, X65 micro-alloyed and F22 low alloy steels, is studied.
An electrochemical hydrogen charging method has been setup, avoiding any critical condition from the point of view of preparation, safety and disposal. Diffusible hydrogen content of steels is in the range 0.6 to 2ppm.
Charpy and J–R curve tests were carried out in the range from room temperature to T=−120°C. Hydrogen affects mechanical properties of the tested materials, mainly reducing fracture toughness in J integral tests, while little influence has been observed in Charpy tests. Fracture surface examination confirms the results of mechanical testing.
The elastic stress field around a crack tip is fully defined through multiparameter equations such as the general relations of Westergaard proposed by Sanford or the most recent of Atluri and ...Kobayashi. Using the relations of Atluri and Kobayashi, a code was implemented to evaluate the characteristic parameters of the stress field around a crack tip by photoelastic analysis. The possibility to change the number of parameters makes it possible to adapt the study to different cases, increasing the extension of the analyzed area in order to have a correct modeling of the photoelastic fringes. The performed experimental tests allow emphasizing the importance of using multiparameter equations in the study of the stress field around the crack tip.
In the presence of H2S, metallic materials, such as carbon and low alloy steels, may suffer hydrogen damage and hydrogen embrittlement. Gas transporting pipes in low temperature environment, during ...the shutdown and the subsequent re-starting operations, are exposed to very low temperatures (T=-40°C). In the presence of high H2S content in the gas, the risk of brittle failure can be increased due to the effect of hydrogen on steel toughness. In this paper the influence of hydrogen and low temperature on mechanical properties of two pipeline materials, F22 low alloy and X65 micro-alloyed steels, is studied. Steels have been hydrogen charged by means of an electrochemical method: diffusible hydrogen content of steels is in the range 0.6 to 2ppm. Charpy and J-R curves tests were carried out in the range from room temperature to T=-120°C. Hydrogen affects mechanical properties of the tested materials, mainly reducing fracture toughness in J integral tests, while little influence has been observed in CV tests. Fracture surface examination confirms the results of mechanical testing.
In the presence of H2S, metallic materials, such as carbon and low alloy steels, may suffer hydrogen damage and hydrogen embrittlement. In this paper the influence of hydrogen and low temperature on ...mechanical properties of two pipeline materials, X65 micro-alloyed and F22 low alloy steels, is studied. An electrochemical hydrogen charging method has been setup. Diffusible hydrogen content of steels is in the range 0.6 to 2 ppm. Fatigue propagation tests were carried out on charged and uncharged specimens, by varying the test temperature and the frequency of the load application cycle. The experimental results show an evident effect of the hydrogen presence on the fatigue crack growth. The diffusion rate of hydrogen in the steels seems to be the most important parameter in order to explain the influence of temperature and frequency on the fatigue crack propagation rate. Fracture surface examination confirms the results of mechanical testing.
A testbeam telescope, based on ATLAS IBL silicon pixel modules, has been built. It comprises six planes of planar silicon sensors with 250 x 50 um^2 pitch, read out by ATLAS FE-I4 chips. In the CERN ...SPS H8 beamline (180 GeV pi+) a resolution of better than 8 x 12 um^2 at the position of the device under test was achieved. The telescope reached a trigger rate of 6kHz with two measured devices. It is mainly designed for studies using FE-I4 based prototypes, but has also been successfully run with independent DAQ systems. Specialised trigger schemes ensure data synchronisation between these external devices and the telescope. A region-of-interest trigger can be formed by setting masks on the first and the last pixel sensor planes. The setup infrastructure provides centrally controlled and monitored high and low voltage power supplies, silicon oil cooling, temperature and humidity sensors and movable stages.
The inclusion of familial myeloid malignancies as a separate disease entity in the revised WHO classification has renewed efforts to improve the recognition and management of this group of at risk ...individuals. Here we report a cohort of 86 acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) families with 49 harboring germline variants in 16 previously defined loci (57%). Whole exome sequencing in a further 37 uncharacterized families (43%) allowed us to rationalize 65 new candidate loci, including genes mutated in rare hematological syndromes (ADA, GP6, IL17RA, PRF1 and SEC23B), reported in prior MDS/AML or inherited bone marrow failure series (DNAH9, NAPRT1 and SH2B3) or variants at novel loci (DHX34) that appear specific to inherited forms of myeloid malignancies. Altogether, our series of MDS/AML families offer novel insights into the etiology of myeloid malignancies and provide a framework to prioritize variants for inclusion into routine diagnostics and patient management.
The relevance of molecular mechanisms governing mitochondrial proteostasis to the differentiation and function of hematopoietic and immune cells is largely elusive. Through dissection of the network ...of proteins related to HCLS1-associated protein X-1, we defined a potentially novel functional CLPB/HAX1/(PRKD2)/HSP27 axis with critical importance for the differentiation of neutrophil granulocytes and, thus, elucidated molecular and metabolic mechanisms underlying congenital neutropenia in patients with HAX1 deficiency as well as bi- and monoallelic mutations in CLPB. As shown by stable isotope labeling by amino acids in cell culture (SILAC) proteomics, CLPB and HAX1 control the balance of mitochondrial protein synthesis and persistence crucial for proper mitochondrial function. Impaired mitochondrial protein dynamics are associated with decreased abundance of the serine-threonine kinase PRKD2 and HSP27 phosphorylated on serines 78 and 82. Cellular defects in HAX1-/- cells can be functionally reconstituted by HSP27. Thus, mitochondrial proteostasis emerges as a critical molecular and metabolic mechanism governing the differentiation and function of neutrophil granulocytes.
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