Purpose This research elucidates two assumptions regarding the initiation mechanism and practical detectability of micro-cracks in welded joints made of S235JR steel, as well as their often-neglected influence on structural integrity. Design/methodology/approach Research investigates the initiation, detection and influence on structural integrity of small defects, specifically (in most cases neglected) micro-cracks in the weld root, made under controlled laboratory conditions. Consequently, this research investigates two assumptions (through two welding procedures) that can lead to initiation of micro-cracks in welded joint root, while the influence of discovered micro-cracks discovered by microstructural analysis were examined via failure assessment diagram (FAD). Findings Detected micro-cracks are sharp with potential towards further propagation. Examined micro-crack with depth of 0.3 mm lies deep within the safe region of the FAD; its presence and its growth could compromise structural integrity. Research limitations/implications Future research will be focused on more comprehensive investigation on micro-cracks initiation in welded joint with the practical impact on structural integrity assessment of welded structures by using analytical and numerical methods. In addition, the study emphasizes the practical limitations of conventional non-destructive testing (NDT) methods in detecting micro-cracks and emphasizes the need for development and use of more advanced methods. Practical implications This study's findings suggest that the focus regarding structural integrity analysis should shift to more detail characterizing and understanding the mechanisms of micro-crack initiation, detection and propagation, in addition to detecting larger defects. Given that conventional NDT methodologies failed to identify these sub-millimeter defects, the presented approach indicates their importance, especially if located in critical zones in welded joint such as the weld root. Social implications Indirectly, the findings of this study emphasize the necessity of early micro-crack detection, which can directly contribute to the prevention of catastrophic failures along with associated economic consequences. Originality/value The originality of this research lies in the dual experimental and analytical characterization (via FAD) of micro-cracks in structural steel welded joints. These defects can significantly impair overall structural integrity through inevitable crack growth under tensile loading.
Purpose This study investigates the failure mechanism of a cracked piping elbow in a crude-oil transport system after approximately 20 years of service, with the aim of identifying the dominant degradation mechanisms and assessing structural integrity using numerical and risk-based approaches. Design/methodology/approach The study combines field inspection, non-destructive testing, wall-thickness measurements, fracture-mechanics concepts, finite element method (FEM)/extended finite element method (XFEM) numerical simulations and American Petroleum Institute: API 581-based risk-based inspection (RBI) analysis. Findings The results showed that the failure was caused by the combined action of erosion–corrosion, naphthenic acid corrosion, localized corrosion and pressure transients. Numerical simulations identified the elbow–pipe transition as the critical stress region, consistent with the observed crack location. Research limitations/implications The analysis was based on a real industrial case study and limited by the absence of experimentally determined fracture toughness data. Nevertheless, the integrated methodology provides useful insight into localized degradation and failure development in aging pipeline systems. Practical implications The study demonstrates the importance of combining inspection data, numerical analysis and RBI methodologies in the integrity assessment of geometrically sensitive pipeline components. The results support complete elbow replacement as the most reliable remediation strategy. Social implications The study contributes to improved operational safety and reliability of aging oil-transport infrastructure by supporting earlier identification of locally critical damage mechanisms that may lead to leakage and environmental incidents. Originality/value The study presents an integrated analysis of a real pipeline elbow failure combining field observations, FEM/XFEM simulations, fracture-mechanics concepts and RBI methodology. The study highlights how multiple moderate degradation mechanisms can interact to produce locally critical conditions that may be underestimated by global risk assessments.
Purpose This work provides a structural integrity assessment of a spent fuel casks using BS7910. The containment barrier of the casks is designed following ASME Section III. Accordingly, it is necessary to demonstrate the integrity of the materials all along the range of operation temperatures, based on the determination of the corresponding reference temperature for nil-ductile temperature. This approach may be very conservative for the case being analyzed, with a low Lowest Service Temperature, −40°C, established to obtain the Certificate of Compliance for a Type B(U) package. The present work provides an alternative analysis to evaluate and guarantee the structural integrity. Design/methodology/approach The analysis is based on the use of the BS7910 and a number of engineering conservative assumptions for the treatment of material properties, defect types and loading conditions. Findings The results show that the cask operation is safe in both Normal Operating Conditions (NOC) and Accidental Conditions (AC), also complying with minimum safety factors established by the nuclear industry for this kind of components and applications. Originality/value The work provides a sound original methodology for assessing the structural integrity of casks in cases where the direct application of ASME Code Section III is not capable of demonstrating the absence of non-ductile fracture.
Purpose This paper aims to systematically investigate the coalescence modes and coalescence criteria of circular defects. Design/methodology/approach In this work, a homogeneous plate containing circular double defects was used, and based on the Gurson–Tvergaard–Needleman (GTN) damage model, a series of finite element simulations were conducted. These circular double defects have different sizes, horizontal distances s, and vertical distances h. Then, the coalescence behaviors of these double defects were obtained, and the coalescence results was plotted with the horizontal defect spacing ratio s/(2R + s) as the abscissa and the vertical defect spacing ratio h/(2R + h) as the ordinate. Findings First, the results showed that there are three types of coalescence modes for circular double defects: defect tip is coalesced with defect tip (DT-DT), the middle of defect is coalesced with the middle of defect (DM-DM), and defect tip is coalesced with the middle of defect (DM-DT). Moreover, in the coordinate system constructed with the defect spacing ratio, there is a clear boundary between the defect coalescent area and the independent area. Then, based on the defect spacing ratio, a new coalescence criterion for circular double defects was established. Originality/value A new coalescence criterion for circular double defects is established based on the defect spacing ratios, providing a theoretical basis for evaluating defect interaction and structural integrity.
Purpose This paper aims to address the limitations of single-sensor feature capture and the interference of environmental noise during the dynamic stress acquisition of built-in axle box bogies for rail vehicles under wheel flat conditions, while avoiding the unintended elimination of periodic impact features by conventional denoising methods.Design/methodology/approach A targeted denoising method is proposed: Multi-Sensor Dynamic Weighted Fusion (MSDWF) fuses multi-sensor data using correlation coefficient-based dynamic weights, wavelet packet-optimized Further ICEEMDAN (F-ICEEMDAN) overcomes the fixed noise intensity constraint of the Improved Complete Ensemble Empirical Mode Decomposition with Adaptive Noise (ICEEMDAN), Multi-Dimensional Feature Screening (MDFS) screens Intrinsic Mode Functions (IMFs) through entropy-weighted Median Absolute Deviation (MAD) and energy curvature detection, Impact Enhancement (IE) strengthens weak impacts through Hilbert envelope analysis. The effectiveness of the method is validated by simulations (SNR = 5/10/15 dB) and field tests (50-300 km/h), compared with wavelet denoising, Variational Mode Decomposition (VMD), and Singular Spectrum Analysis (SSA).Findings The method outperforms traditional approaches in signal unbiasedness, morphological fidelity, and fatigue damage calculation accuracy (minimal Miner damage deviation (Delta D)), enhancing dynamic stress signal reliability for precise bogie structural fatigue life evaluation.Originality/value Targeting dynamic stress signals of built-in axle box bogies under wheel flat conditions, this study innovatively integrates four modules (MSDWF, F-ICEEMDAN, MDFS, IE). It breaks the contradiction between denoising and impact feature retention in traditional methods via adaptive noise injection, multi-dimensional IMF screening and weak impact enhancement, ensuring efficient retention of key impact features for reliable fatigue evaluation.
