International Journal of Pressure Vessels and Piping最新文献

Fracture behavior of dissimilar metal weld joint consisting of mod. 9Cr–1Mo steel, AISI 316LN stainless steel, Inconel 82 butter layer and Inconel 182 weld has been investigated through experiments and FE simulations. The metallographic studies on weld joint and its interfaces have been carried out to determine the influence of microstructure on tensile and fracture properties. Tensile properties of different weld regions viz., weld metal, butter layer and HAZ have been evaluated using sub-size specimens. Fracture resistance behavior of weld joint has been studied through testing of compact type specimens with initial cracks machined at different locations. The plastic η factors for estimation of J-R curve have been obtained using FE analysis for crack in different regions viz., weld metal, butter layer and HAZ. Crack in weld metal exhibits lower fracture resistance as compared to butter layer and HAZ. Further, the constraint acting on crack and its susceptibility for deviation have been discussed in terms of stress triaxiality ahead of crack tip.

Buried pipelines are crucial for the transportation of oil and natural gas resources. However, pipeline failure accidents have frequently occurred due to corrosion. Therefore, an accurate corrosion depth prediction model is necessary for the reliable supply of energy. In this paper, a theory-guided machine learning (ML) model is developed for maximum pitting corrosion depth prediction, the engineering theory and domain knowledge are integrated into feature space to improve the model interpretability. Firstly, several new feature variables are constructed based on the interactions between independent variables. Then, feature importance of all feature variables is obtained using random forest (RF). A hybrid multi-objective grey wolf optimization (HMOGWO) is proposed to optimize the hyper-parameters of RF model, considering feature number, prediction accuracy, and stability simultaneously. Finally, a comprehensive pitting corrosion dataset is utilized for performance evaluation. The results indicate that the proposed theory-guided model can achieve high prediction accuracy and stability, the optimal feature subset can be determined using multi-objective optimization method simultaneously, which solves the problems of model interpretability and feature selection for traditional ML models with the single-objective optimizer. This study is of great significance to the transportation safety of buried pipelines.

This paper presents a comprehensive analysis of conical components in pressure vessels emphasizing their significance when utilized to transition between different diameters or slopes. A thorough design and analysis are underscored as essential for ensuring the safety and reliability of these components under diverse loading circumstances. The paper aims to propose enhancements to the European Pressure Vessel Standards concerning conical components under internal pressure, with a focus on improving safety, reliability, and compliance with industry standards. Existing European standards are reviewed, identifying potential gaps and proposing practical solutions. The paper also presents research findings on the influence of cone apex angles, shell geometries and design pressure on cone plate thickness calculations. A new methodology for the design and analysis of conical components in pressure vessels is proposed, offering a potential pathway to safer and more efficient pressure vessels. A range of cylinder diameter between 1000 and 2500 mm and cone angles between 30° and 60° are used as input to quantify the difference in cone thickness for a design pressure ranging between 10 and 200 bar_g. The proposed method yields results much closer to AD2000 compared to EN13445, leading to slightly thicker cones (up to 2.2 mm for the selected range of cone diameters and angles) compared to the former, resulting in safer pressure vessel design, and thinner cones (up to 22 mm) compared to the latter resulting in significant material savings. A comparative analysis was performed through Finite Element Analysis validating the EN13445 unsuitability for cone thickness calculations. A modification is proposed for equation (7.6)-(8) in EN13445 resulting in thinner plates reducing the cone plate thickness difference to 0.9 % on average compared to the current deviation of -9.6 % on average for the selected range of cylinder diameters and cone angles.

In practical engineering components, due to the existence of non-uniform stress and strain field near the notch, it brings severe challenges to fatigue life prediction when evaluating the integrity of notched components. In this study, a probabilistic fatigue life prediction model for notched specimens was established by coupling the stress field intensity (SFI) method and Weibull distribution. Firstly, the position of the dangerous point is determined by finite element calculation, and the maximum strain energy density plane through the dangerous point is defined as the critical plane. Secondly, from the perspective of 2D features, the traditional SFI method is modified based on the stress distribution on the critical plane, and a new concept of effective stress is proposed to predict the fatigue life of notched specimens by the experimental data of smooth specimens. Finally, a new non-proportional additional hardening factor is established to characterize the influence of material properties and loading path on fatigue life. The experimental data of Q345 low alloy steel and GH4169 nickel base alloy are used to compare and analyze the proposed model. The results show that the predicted life of the proposed model is in good agreement with the experimental life.

Bellows is a flexible component whose volume can be changed by compression or expansion under pressure. Rounded rectangular type bellows is most applied where the internal space of application is strict. The Expansion Joint Manufacturers Association (EJMA) code is world-recognized code for design by formulas method. However, the calculation formulas of stress and deformation in EJMA code does not consider the shape of corner. Therefore, this study proposed a structural assumption of curved beam model to calculate the stress and deformation for rounded rectangular bellows under pressure load by formula calculation method. A parametric study by means of finite element analysis (FEA) was performed to assess the impact of different structural parameters and the applicable scope was investigated. The experimental and numerical results showed that the proposed method can obtain a suitable precision and safe result when ratio of wave height to corner radius is lower than 35 % and the ratio of length of short side length to corner radius is in range 5–20. This study will enrich existing bellows design code and help industry designers to accelerate the optimization iteration in preliminary design stage instead of FEA.

Explosion is one of the primary factors influencing the safety of gas pipelines. To investigate the bucking deformation and failure mechanism of gas pipeline in an explosion shock wave environment, a study was conducted on the stress, deformation, center deflection and energy variation of the pipeline. The analysis was grounded in elastic-plastic theory and utilized the finite element method. Additionally, the study delved into the impact of explosion distance, diameter-to thickness ratio, and charge quantity on the dynamic behavior of pipeline. The research results revealed that high-stress and plastic strain regions emerge on the pipeline during initial loading, causing compression on the outer wall and stretching on the inner wall. As the loading process progresses, the zero circumferential stress surface shifts towards the outer wall, ultimately leading to cracks and pipeline failure. Furthermore, the study observed that pipeline deformation exhibits a direct correlation with charge quantity and an inverse correlation with the diameter-to-thickness ratio. As the explosion distance increases, the center deflection of the pipeline abruptly decreases and then stabilizes. Concurrently, the influence of the diameter-to-thickness ratio and charge quantity on pipeline deformation diminishes. The difference of diameter-thickness ratio gives rise to various failure mechanisms and modes. Finally, the engineering prediction model of the maximum deformation of pipeline is obtained. The study offers valuable insights and references for pipeline design, safety assessments practices.

Plate and Shell Heat Exchangers (PSHE) are vital in industries due to their adaptability and efficiency. This study applied the finite element method to analyze PSHE plate behavior, which is challenging to assess experimentally. The equivalent von Mises stress field was determined for four-plate setups under different conditions: internal channel pressure, external channel pressure, and pressure in both branches. Peak stresses were found at corrugation tops during contact, varying stress levels based on operating conditions. Stresses decreased when both branches were pressurized but increased with single-branch pressurization. Internal and external pressure-only scenarios had distinct stress patterns. The chevron angle and corrugation contact points influenced plate stiffness and stress distribution. A fatigue analysis assessed plate lifespan under cyclic loads, with fatigue strength reduction factors applied according to Soderberg, Goodman, and Gerber failure criteria. This comprehensive analysis provides critical insights into PSHE plate performance, aiding in their reliable application in the industry. All numerical data obtained in this work were validated based on experimental studies previously published in the literature for stress and fatigue analysis.

The present study proposes a finite element method (FEM)-based framework to assess the synergistic effect of hydrogen-induced damage (HID), internal pressure, and corrosion effects on the failure behavior of elbows. The mechanical properties degradation of pipeline steel subjected to HID is incorporated into the FE modeling to model corroded pipe elbows serviced in a hydrogen-rich environment. Two dimensionless metrics (${\sigma }_{\max }/{\sigma }_y$ and ${\sigma }_{\max }/{\sigma }_u$) are proposed to quantify the parameter effects and sensitivity. The results demonstrate that 1) the combination of corrosion effects, internal pressure, and HID significantly reduces the load-bearing capacity at the pipe elbow; 2) ${\sigma }_{\max }/{\sigma }_u$ exceed 1 in all cases under a hydrogen-rich environment for more than 12 h, indicating that prolonged exposure to an environment abundant in hydrogen may promote elbow failure; 3) the critical defect length ($\varphi /\pi =9\%$) and neutral-line bend radius ($R/D=4.5$) are determined, exceeding which the elbow failure behavior is significantly affected; 4) ${\sigma }_{\max }/{\sigma }_y$ and ${\sigma }_{\max }/{\sigma }_u$ are lower than 1 when the defect occurs at the extrados, implying that the synergistic effects of HID and corrosion are unlikely to cause the elbow failure if corrosion occurs at the extrados, but it is not applicable to defects occurring at other locations, especially at the intrados; 5) The maximum von Mises stress exhibits the highest sensitivity to internal pressure, followed by defect location, defect depth, neutral-line bend radius, defect length, and hydrogen damage.

Steel pipelines are increasingly essential for many applications, including the transport of oil, natural gas, and soon hydrogen gas. Steel pipelines are subject to harsh operating conditions. Corrosion is considered to be the most common type of failure in steel pipelines. This report focuses on corrosion and assessment in gas and oil pipelines. The most common method of repairing corroded pipelines by composite repair is included in the review. Based on conservative codes and deterministic and reliable FEM approaches, different tool designs and models of corroded pipelines without and with repair are summarized and compared. The evaluation of defects in determining the failure pressure of pipelines and the study of the contribution of composite wrap repair to corroded pipelines are discussed.

Strain-based engineering critical assessment methods allows certain amount of plastic strain during installation and in service, for pipelines crossing seismically-active areas. Most strain-based engineering critical assessment methods are established for materials with smooth stress-strain relationship, leaving the so-called Lüders plateau influence on ductile fracture response seldomly explored. This work studied the effect of the Lüders plateau on mode I ductile crack growth with the modified boundary layer (MBL) model under plane strain conditions. The “up-down-up” constitutive model was implemented and the Gurson damage model was selected to simulate crack propagation. Factors including the plateau length and softening modulus in the “up-down-up” constitutive model, strain hardening of the matrix material and the initial void volume fraction parameter were analyzed. Numerical results show that the Lüders plateau modifies the crack tip constraint and the damage evolution, and the plateau length plays the dominant role on ductile crack growth behaviour in the presence of Lüders plateau.