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The tension test was used for studying the effect of stress variance on stress corrosion cracking susceptibility of low carbon steel immersed in 0.1 M of the sulphuric acid solution. Three unequal values of stress applied on three similar specimens after preparing and grinding them in three metal frames that were manufactured for this purpose were used for 30 days of exposure. The stress increased and the acidic solution effect caused more corrosion and cracking so, the weight loss was more. The relation between stress and weight loss variance was approximately linearly dependent. The corrosion rate was calculated using the weight loss method, and its value was also increased because of the increase of weight loss. The sulphuric acid solution was a good corrosive medium for low carbon steel because of the high percentage of Iron (Fe) which is approximately 98, and a low percentage of Cr and Mo minerals. [ABSTRACT FROM AUTHOR]

A detailed description of the preparation and management of reliable and safe corrosion laboratory experiments requiring the presence of hydrogen sulphide (H2S) is reported in this work. The adopted method is based on a modified Kipp's apparatus allowing to produce on demand just the amount of H2S required for electrolyte saturation. Two benchmark corrosion cases were studied: electrochemical corrosion, monitored by means of potentiodynamic measurements, and sulphide stress corrosion cracking tests, both in H2S-saturated acidic aqueous chloride solutions. The sensitivity to H2S corrosion of a few classical materials of interest in the oil and gas sector, corrosion-resistant alloys, was then examined, proving as the presence of H2S leads to a denobling effect, increases the passive current density and influences significantly the time of cracking in the sulphide stress corrosion cracking tests. [ABSTRACT FROM AUTHOR]

The ethylene production plant is one of the most important units in petrochemical industry, and the ethylene cracking furnace is the heart of the plant. The ethylene cracking furnace is a multivariable, strong coupling, and nonlinear process, and therefore, it is difficult to be manipulated by traditional proportional–integral–derivative controls. This paper reports a real application of advanced process control in five 470-kton/year SC-I tubular reactors. The advanced process control deployed includes cracking outlet temperature control and feed volume control. This control system has been operating since 2012. The variation of cracking outlet temperature has been reduced from ±5 to ±1 °C with a setting time less than a few minutes even under a large-scale disturbance. The variation of feed volume has been controlled within ±1%. As a result, the advanced process control system has achieved a total production increase by 0.3%. [ABSTRACT FROM PUBLISHER]

Reaction products formed at the welding interface of aluminium/steel can deteriorate mechanical properties. It would therefore be quite beneficial to analyse the mechanism of crack propagation to obtain strong joints. In this study, we directly observed the fracture process of the aluminium/ steel sample by in situ scanning electron microscopy. In situ observation revealed that the crack propagated in the reaction layer and aluminium, and that crack propagation was arrested by the interface between the reaction layer and steel. [ABSTRACT FROM AUTHOR]

The objective of this paper is to investigate geometric and material parameters that affect the interaction of multiple pre-existing (initiated) cracks due to rolling contact fatigue (RCF) loading conditions. In particular, the behaviour of short cracks (head checks) in railway rail is studied. Parameters of interest are initial crack angle and spacing, distribution of initial crack lengths, width of the load/contact zone, and the material properties (in particular, the friction coefficient). Furthermore, the sensitivity of the finite element (FE)-mesh density is investigated. An open question of particular interest is the effect of crack interaction, e.g. shielding, on the prevailing crack spacing. In view of all uncertainties of the material model as well as the three-dimensional geometric complexity of the RCF problem, it is important to obtain a good understanding of the sensitivity of parameter changes. This is achieved in the presented investigation, although it is carried out using simplifying assumptions such as plane strain, linear elasticity, and Hertzian pressure distribution. [ABSTRACT FROM AUTHOR]

Stress corrosion cracking (SCC) tests were conducted on American Petroleum Institute (API) grade X-70 line pipe steel using smooth specimens in a standard near neutral pH solution, NS4. Both constant loading and cyclic loading conditions were employed. There were some SCC cracks on the surfaces of specimens under constant loading conditions when the applied load and test duration were appropriate. These cracks were related to stress concentration at corrosion pits. Generally, the local strain rate around corrosion pits in constant load tests was not high enough for the transition from pits to cracks to take place, and so long test times were needed for crack initiation. In contrast, cyclic loading tests facilitated near neutral pH SCC by making the local strain rate at the crack tip change under the applied load spectrum and by enhancing the crack tip local strain rate, which appreciably shortened the crack initiation incubation. [ABSTRACT FROM AUTHOR]

The present study investigates the impact deformation behaviour of Fe–2Ni sintered alloy as a function of the strain rate and sintered density using an MTS 810 servohydraulic machine and a compressive split Hopkinson bar. Impact deformation is conducted at room temperature at strain rates ranging from 10-3 to 8·1 × 103 s-1 for specimens with sintered densities of 85, 90 and 95% respectively. The impact flow response is found to be sensitive to both the strain rate and the sintered density. Changes of the strain rate and sintered density induce corresponding changes in the flow strength, work hardening rate, strain rate sensitivity and activation volume. A constitutive law based on Gurson's plastic potential and the flow rule of Khan, Huang and Liang (KHL) provides a reasonable description of the flow behaviour of Fe–2Ni sintered alloy. Specimen fracture occurs when the strain rate exceeds 4 × 103 s-1 and is dominated by a localised shearing mode. The degree of cracking increases with increasing strain rate or decreasing sintered density. The microstructural characteristics of the undeformed specimens vary with the sintered density. Following impact, the structural phase is unchanged from the undeformed condition, but the grain size is found to decrease with increasing strain rate for each sintered density. The reduction in grain size induces an increase in the flow stress. At a constant strain rate, the lower flow stress and smaller grain size observed in the specimens with a lower sintered density are attributed primarily to a higher overall porosity. [ABSTRACT FROM AUTHOR]

This article describes the wear and mechanical behaviour of TiC base cermets studied by durability tests, including testing of blanking performance and fatigue endurance. Comparative laboratory trials in the abrasive erosion, sliding, and adhesive wear conditions were conducted and complemented by SEM studies. It was found that the blanking performance (durability during blanking of sheet metals) of a carbide composite (hardmetal, cermet) is controlled by its resistance to adhesive wear, and origin and propagation of fatigue cracks (fatigue damage). [ABSTRACT FROM AUTHOR]

The crack state in the regenerator of the heavy oil catalytic cracking unit of Daqing Petrochemical Complex is summarized. The reasons for a large number of welding seam cracks in the regenerator-third-stage cyclone system of the heavy oil catalytic cracking unit are analysed. Correlated countermeasures to prevent cracks and several repair plans for the present cracks are proposed. The key technology and measures of repairs are described and could be used as guides for crack repair of similar equipment. [ABSTRACT FROM AUTHOR]