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Environmental stress cracking (ESC) is one of the most prominent failure mechanisms for polymer components. The high sensitivity of plastics in regard to environmental influences has always meant that plastics as materials have been viewed very critically in outdoor applications. Recently, the massive occurrence of microplastics in the environment means that questions about the long-term stability of plastic parts and the studies of plastic fragmentation are of great scientific interest. ESC behavior also plays an important role in connection with the formation of microplastics. In this work, the influence of two different sample wetting methods on ESC behavior was investigated. In case A, the sample was in situ wetted with the medium during the measurement by using a sponge. In case B, the sample was wetted by storage in the medium prior to measurement. Different stress cracking agents (SCA) were examined for polymethylmethacrylate (PMMA). Fracture-mechanical fatigue crack propagation (FCP) tests were carried out to quantitatively determine the sensitivity to ESC. Correlations between the absorption behavior and the ESC behavior of the SCA and the resulting morphological phenomena were established. Depending on the wetting method, significant differences in FCP were observed. The in situ wetting of the samples (case A) during the FCP measurement with ethylene glycol (EG) and with deionized water (DI) led to a significant shift in the crack propagation curves to higher ∆K—compared to the PMMA reference. In the case of n-heptane (NH), a more brittle crack propagation behavior was observed due to the chemical interaction with PMMA. The previously immersed samples (case B) give different results. Storage in NH and EG showed no influence on the crack propagation behavior. Samples immersed in DI showed a completely different course of crack growth. At a certain load, a sudden deceleration of the crack propagation and thus a horizontal curve could be seen. Above a certain ∆K value, crack growth began again. Depending on the immersion time (14, 30, or 60 days), this so-called stepped behavior shifted to lower da/dN values.

The effect of crack propagation management by using a fused deposition modeling (FDM) technique on the environmental stress cracking (ESC) behavior of neat polycarbonate (PC) and PC with 1 vol% SiO2 nanocomposites were investigated. The results demonstrate that the crack growth behavior of materials and their ESC resistance are strongly dependent on the printing direction. The ESC resistance and failure time of an FDM print-on injection-molded specimen exhibit the greatest values when the printing direction parallels to the load direction. Comparative analyses of the fracture surfaces reveal that the excellent stress cracking resistance can contribute to favorable stress and load distribution at the crack front area, where the printed continuous strands in alignment with the load can efficiently carry and transfer it. However, the degree of ESC improvement by managing the direction of craze/crack propagation via printing direction is more pronounced in neat PC than those of PC-SiO2 nanocomposites.

High-strength carbon steels typically used as oil country tubular goods (OCTG) made from high-strength carbon steels can be susceptible to sulfide stress cracking (SSC) when in service in environments that contain H2S. In the last 25 y, linear-elastic fracture mechanics has been used to understand both the mechanistic aspects of this form of cracking and to quantify the susceptibility to SSC of different OCTG steel grades. This paper presents a review on the evolution of the double cantilever beam method as a standard practice to assess the threshold stress intensity factor KISSC. The paper evaluates the capabilities and limitations of this testing method to describe the conditions associated with crack propagation. The review study indicates that new fracture parameters based on the energy required for crack propagation such as J-integral might be required to overcome the limitations of the static conditions implied in the stress intensity factor evaluation approach.

The crack propagation rate of environmental stress cracking was studied on high-density polyethylene compact tension specimens under static loading. Selected environmental liquids are distilled water, 2 wt% aqueous Arkopal N100 solution, and two model liquid mixtures, one based on solvents and one on detergents, representing stress cracking test liquids for commercial crop protection products. The different surface tensions and solubilities, which affect the energetic facilitation of void nucleation and craze development, are studied. Crack growth in surface-active media is strongly accelerated as the solvents induce plasticization, followed by strong blunting significantly retarding both crack initiation and crack propagation. The crack propagation rate for static load as a function of the stress intensity factor within all environments is found to follow the Paris–Erdogan law. Scanning electron micrographs of the fracture surface highlight more pronounced structures with both extensive degrees of plasticization and reduced crack propagation rate, addressing the distinct creep behavior of fibrils. Additionally, the limitations of linear elastic fracture mechanisms for visco-elastic polymers exposed to environmental liquids are discussed.

The review presented herein is regarding the stress corrosion cracking (SCC) phenomena of carbon steel pipelines affected by the corrosive electrolytes that comes from external (E) and internal (I) environments, as well as the susceptibility and tensile stress on the SCC. Some useful tools are presented including essential aspects for determining and describing the E-SCC and I-SCC in oil and gas pipelines. Therefore, this study aims to present a comprehensive and critical review of a brief experimental summary, and a comparison of physicochemical, mechanical, and electrochemical data affecting external and internal SCC in carbon steel pipelines exposed to corrosive media have been conducted. The SCC, hydrogen-induced cracking (HIC), hydrogen embrittlement, and sulfide stress cracking (SSC) are attributed to the pH, and to hydrogen becoming more corrosive by combining external and internal sources promoting cracking, such as sulfide compounds, acidic soils, acidic atmospheric compounds, hydrochloric acid, sulfuric acid, sodium hydroxide, organic acids (acetic acid, mainly), bacteria induced corrosion, cathodic polarization, among others. SCC growth is a reaction between the microstructural, chemical, and mechanical effects and it depends on the external and internal environmental sources promoting unpredictable cracks and fractures. In some cases, E-SCC could be initiated by hydrogen that comes from the over-voltage during the cathodic protection processes. I-SCC could be activated by over-operating pressure and temperature at flowing media during the production, gathering, storage and transportation of wet hydrocarbons through pipelines. The mechanical properties related to I-SCC were higher in comparison with those reviewed by E-SCC, suggesting that pipelines suffer more susceptibility to I-SCC. When a pipeline is designed, the internal fluid being transported (changes of environments) and the external environment concerning SCC should be considered. This review offers a good starting point for newcomers into the field, it is written as a tutorial, and covers a large number of basic standards in the area.

Sulfide stress cracking (SSC) failure is a main concern for the pressure vessel steel Q345 used in harsh sour oil and gas environments containing hydrogen sulfide (H2S). Methods used to improve the strength of steel usually decrease their SSC resistance. In this work, a quenching and tempering (Q&T) processing method is proposed to provide higher strength combined with better SSC resistance for hot-rolled Q345 pressure vessel steel. Compared to the initial hot-rolled plates having a yield strength (YS) of ~372 MPa, the Q&T counterparts had a YS of ~463 MPa, achieving a remarkable improvement in the strength level. Meanwhile, there was a resulting SSC failure in the initial hot-rolled plates, which was not present in the Q&T counterparts. The SSC failure was not only determined by the strength. The carbon-rich zone, residual stress, and sensitive hardness in the banded structure largely determined the susceptibility to SSC failure. The mechanism of the property amelioration might be ascribed to microstructural modification by the Q&T processing. This work provides an approach to develop improved strength grades of SSC-resistant pressure vessel steels.

Background The environmental stress cracking resistance (ESCR) of polymers is characterized most conveniently by the bent strip method standardized as ASTM D1693. The method has, however, suffered from poor reproducibility of the ESCR results. Objective In this study we propose modifications on the standardized method to reduce the variability of the ESCR results. Methods The notch is introduced to the specimens with the aid of automate testing machine instead of manual notching. The proposed method is then applied for a systematic investigation on the influence notch offset distance, notch inclination angle, notch depth on the environmental stress cracking behavior of polyethylene material. Results The results reveal interesting phenomenon that crack initiation occurs at the interior point between the endpoint and the middle of the notch, instead of at the middle point of the notch, where the maximum stress or strain is located. Finite element simulation has been conducted to elucidate root cause of this phenomenon. It has been found that the crack initiates at a point that is very close to the position of the maximum stress triaxiality, although the crack initiation position shifts slightly toward the position of the maximum stress or strain. Conclusions As a result, the crack initiation is controlled by the stress, strain and stress triaxiality, but stress triaxiality plays a dominant role in the initiation of environmental stress cracking.

This work aimed to investigate the direct cause of a pipeline rupture that occurred in 2013 in Western Nebraska. Visual inspection, non-destructive laser scanning, scanning electron microscopy with energy-dispersive X-ray, mechanical testing, and chemical analysis were conducted during metallurgical examination. The results indicate that the rupture was caused by progressive cracking due to hydrogen stress cracking that occurred at a “hard spot” in the subject 1954 AO Smith pipe.

Alloy 625 overlay on 2.25Cr-1Mo (F22) Steel or AISI 8630 is used in oil and gas industry for corrosion protection. In some cases, F22/625 or 8630/625 interface is possibly exposed to the H2S-containing production fluid and there is a risk of sulfide stress cracking (SSC). The postweld heat treatment (PWHT) is used to reduce the cracking susceptibility of the F22/625 or 8630/625 dissimilar metal weld (DMW). The effect of PWHT on SSC resistance was investigated using four-point bend tests in a pH buffered brine solution with 8.2 wt% H2S. PWHT was found to improve the SSC resistance. The F22/625 DMW was more resistant to SSC than the 8630/625 DMW. The SSC of DMW between Alloy 625 and steel can be understood as a combination of stress corrosion cracking and hydrogen assisted cracking. It proved that the hardness requirement 250 Vickers hardness number (VHN) mandated in NACE Standard MR0175/ISO 15156 is overly conservative and the hardness can be increased at least to 275 VHN to 280 VHN.

Keywords: Friction Stir Welding (FSW), Super Duplex Stainless Steel (SDSS), UNS1 S32760, Stir Zone (SZ), Hydrogen Induced Stress Cracking (HISC) INTRODUCTION The excellent corrosion resistance of super duplex stainless steels (SDSS), notable for localized forms of corrosion, is due to high concentrations of Cr and Mo [1]. The elements Ni and N, on the other hand, stabilize the microstructure at the optimized volume fraction of austenite and ferrite phases, thus providing the best combination of mechanical properties and corrosion resistance [2-5]. Different SDSS have been welded by FSW and practically no changes in the ferrite-austenite ratio were observed, although some increase in strength has been noticed as a consequence of the refinement of the microstructure in the stir zone [6-8,10].The aim of this investigation is to evaluate the fracture behavior of friction stir welded UNS1 S32760 super duplex stainless steel under cathodic protection. Electron backscatter diffraction (EBSD) specimens were electrochemically polished with a 57 mL glycerol, 7 mL distilled water and 50 mL phosphoric acid solution at 90°C for 10 min applying a voltage of 30 V. This analytical tool was used to determine the proportion of ferrite and austenite and also to produce both the orientation image maps and the effective grain size (high-angle grain boundaries with differences in crystallographic orientation higher than 15°).