International Journal of Pressure Vessels and Piping最新文献

Detecting damage in coated pipelines is a challenging and costly task. This study proposes a method for pipeline defect identification based on VMD-DWT noise reduction and GA-SENet-ResNet18. Combining wavelet transform to convert denoised defect signals into time-frequency representations enhances the model's ability to capture both time-domain and frequency-domain features of defect signals, thereby improving its recognition capability for different types of defects. The study analyzed the feature extraction capabilities of ALexNet, GooleNet, VGG16, ResNet18, SENet-ResNet18, and GA-SENet-ResNet18 models in pipeline defect recognition. Experimental results show that SENet-ResNet18 achieved an accuracy of 0.9591 on the training set in 9m38s, significantly outperforming the first four models. GA-SENet-ResNet18 achieved 96.83 % accuracy, 96.67 % precision, 96.73 % recall, and 96.68 % F1 score in pipeline defect signal recognition. Compared to ResNet18, it improved accuracy by 2.06 %, precision by 1.94 %, recall by 2.09 %, F1 score by 2.37 %, with a reduction in time by 1m1s. The study demonstrates that the combined improvement of GA and SENet enhances ResNet18 not only in feature selection and response enhancement but also significantly improves its performance compared to traditional ResNet18 networks, making it more effective in pipeline defect recognition tasks. This research is crucial for ensuring pipeline system integrity and preventing pipeline accidents.

This research investigates the severe weld failures in L360QS pipelines, which are integral to the infrastructure of high-pressure natural gas transportation systems. Even with strict compliance to engineering standards, two pivotal welds experienced sulfide stress corrosion cracking (SSCC) due to continuous exposure to hydrogen sulfide and stresses from construction activities. A comprehensive material analysis and stress simulation has been utilized, revealing a maximum stress concentration of 544.9 MPa that surpasses the yield strength of the pipeline material. This discovery prompts a reevaluation of current safety margins and underscores the urgent need for enhanced pipeline integrity management. Our findings, corroborated by stress distribution simulations, not only illuminate the complex interplay of material properties and environmental factors in SSCC but also provide a new perspective for the safe service of pipeline.

A medium-entropy alloy of CoCrNi exhibits excellent cryogenic mechanical properties. It is possible to enhance the ductility of weld metal for cryogenic storage tank materials at cryogenic temperatures by employing CoCrNi alloys as filler metal. In this study, a CoCrNi multi-principal filler wire and a 308L stainless steel wire were used for welding 9 % Ni steel. The effects of the CoCrNi filler wire on the microstructure, hardness, mechanical properties, and deformation mechanisms of the weld metals were evaluated and discussed. A remarkable finding was that as the tensile temperature decreased from 298 K to 77 K, the fracture elongation of the CoCrNi joint increased by approximately 34.7 %, rather than decreasing. In contrast, a significant reduction in fracture elongation was observed in the 308L joint. The CoCrNi filler wire could promote the activation of twinning deformation in the weld metal at 77 K, thereby enhancing the ductility of the welded joints at cryogenic temperatures.

Martensitic heat-resistant steel (MHRS) serves as an important structural material for manufacturing ultra-supercritical unit due to its excellent fatigue resistance and corrosion resistance. Post weld heat treatment (PWHT) is a common method for regulating the microstructure and properties of MHRS welded parts. In this work, we investigated the influence of different PWHT methods on the microstructure, mechanical properties, and room temperature creep properties of Co3W2 welded joints. The results showed that post-weld direct tempering (PWDT) or post-weld re-automatizing and tempering (PWNT) treatment significantly reduces the differences in microstructure and local mechanical properties of as-welded joints. Compared to the as-welded specimens, the PWDT and PWNT welds show lower strength and hardness, but better impact resistance. The PWNT treated welds show more homogeneous microstructure and local mechanical performance, and better tensile property and impact resistance than PWDT welds. Furthermore, the fine grain heat affected zone in PWNT welds shows the smallest strain rate sensitivity value, which implies the PWNT method may alleviate type IV brittle fracture in martensitic heat-resistant steel weldments.

The fatigue assessment of safety relevant components is of importance for ageing management with regard to safety and reliability of nuclear power plants. Austenitic stainless steels are often used for reactor internals due to their excellent mechanical and technological properties as well as their corrosion resistance. During operation reactor internals are subject to mechanical and thermo-mechanical loading which induce low cycle (LCF), high cycle (HCF) and even very high cycle (VHCF) fatigue. While the LCF behavior of austenitic steels is already well investigated the fatigue behavior in the VHCF regime has not been characterized in detail so far. Accordingly, the fatigue curves in the applicable international design codes have been extended from originally 10⁶ to the range of highest load cycles up to 10¹¹ load cycles by extrapolation. Nevertheless, the existing data base for load cycles above 10⁷ is still highly insufficient. The aim of the cooperative project of the Institute of Materials Science and Engineering (WKK) at RPTU Kaiserslautern-Landau, Materials Testing Institute (MPA) Stuttgart and Framatome GmbH, Germany is to create a comprehensive database up to the highest load cycles N = 2·10⁹ for austenitic stainless steels and their welds at ambient and elevated temperature.

Promoting tensile failure by providing a proper orientation angle between the pipe axis and the fault line is the main seismic design philosophy for buried steel pipelines. However, most of the severe damage and failures experienced by pipelines are mainly due to negative crossing angle and thus compressive loads acting along the pipeline. This paper investigates different earthquake damage mitigation methods such as Carbon Fiber Reinforced Polymer (CFRP) wrapped pipes, Steel Pipes for Fault Crossing (SPF), and corrugated pipes for buried steel pipelines which are mainly subjected to compressive loads. Therefore, the Thames water transmission pipeline, which is a well-known case study, that suffered major and minor damage due to compressive forces in the 1999 Kocaeli earthquake, is considered to simulate and compare the earthquake damage mitigation capabilities of these countermeasures. The numerical studies are performed by using a three-dimensional nonlinear finite element model. The results show that the use of CFRP composites in buried pipelines, regardless of their thickness, wrapping length, or layer orientation, does not have the expected damage reduction effect, but does increase the effective length between major wrinkles or change the type of pipe failure. On the other hand, SPFs and corrugated pipes are more effective in earthquake damage reduction due to their high axial and rotational capabilities.

As global greenhouse gas emissions become increasingly severe, carbon capture, utilization, and storage (CCUS) technology, as a major approach for achieving carbon peak and carbon neutrality, is attracting growing attention. Pipeline networks play a crucial role in implementing CCUS technology, connecting carbon sources from capture points to storage facilities. However, pipelines are inevitably susceptible to leaks or ruptures due to various factors, which can lead to catastrophic accidents. Research on the pressure and temperature inside pipelines after the rupture of defective pipelines, as well as the mechanisms of crack propagation and diffusion behavior, forms an important foundation for risk assessment of CO₂ pipelines. This research will provide effective technical support for the implementation of large-scale CCUS projects and contribute to pipeline safety. In this study, an API X52 full-scale CO₂ pipeline rupture experiment was conducted, and data from various sensors and instruments were collected to track the pressure evolution, temperature changes in both axial and vertical directions, microscopic morphology of cracks at different locations, and the evolution of gas clouds from leakage to rupture. The developed pressure relief wave prediction model showed high consistency with experimental results, and the safe design of the experimental pipeline was conducted based on the modified Battelle two-curve method (BTCM).

To satisfy the requirements of hardness and corrosion resistance for laser additive manufacturing of hydraulic supports, this study applied the synergistic addition of C, B, Cr, Ni, Nb and Mo elements in Fe-based alloys. The multi-phases, martensite + austenite + ferrite were designed. The microstructure, hardness and corrosion resistance of the coatings were analyzed. Increasing the C and B contents could significantly increase the hardness of the coatings, while the corrosion resistance was decreased. The corrosion resistance of the coatings was determined by the Cr contents. However, increasing the Cr contents to 20.0 wt % resulted in the ferrite structure with lower hardness (21 HRC). The coatings with 0.25 wt % C, 1.2 wt % B and 19.0 wt % Cr showed the optimal matching of hardness (56 HRC) and corrosion resistance (survived in neutral salt spray test≥300h). The resulted coatings were mainly consisted of dendritic structure. Fine lath martensite phase was dominant in the dendrite regions. The interdendritic regions were consisted of nano-sized intermetallics with a mixture of σ+Nb + FeNb + Cr₂Nb+(Fe,Cr)₂B + NbC compounds. These interdendritic regions (14.2 GPa) showed higher hardness than that of the dendritic regions (7.1 GPa). The high Cr contents with finer dendritic structures were the major mechanisms for the excellent combination of hardness and corrosion resistance. The precipitation and growth mechanisms of the interdendritic phases were elaborated. This work provides a valuable reference for laser hot-wire cladding to prepare Fe-based alloys with high hardness and excellent corrosion resistance.

Austenitic stainless steel welds (ASSWs) suffer from severe pre-strain during assembly process, which threatens the long-term operation safety of pipelines in nuclear power plant. In this work, the 316L weld metals (WMs) with 0 % and 8 % pre-strain were thermally aged at 400 °C for up to 39000 h to investigate the pre-strain effect on thermal aging of ASSWs. The results showed that the pre-strain caused work hardening and further promoted the hardening of thermally aged ferrite. After thermal aging for 39000 h, the nano-hardness increment of ferrite with 8 % pre-strain was about 1.6 GPa more than that without pre-strain. By microstructure characterization, it is found that the high dislocation density induced by pre-strain promoted spinodal decomposition and G-phase precipitation. The spinodal decomposition morphology and corresponding element concentration fluctuations were more obvious in the WM with 8 % pre-strain. Moreover, the size and density of G-phase along dislocations were larger in the ferrite with 8 % pre-strain than those without pre-strain.