India's road transport system relies heavily on its extensive network of bridges, many of which are reinforced cement concrete RCC structures. Fatigue is a critical issue for these road bridges, significantly influencing their life span. This study focuses on the fatigue analysis of an RCC bridge on NH275, connecting Mysore to Hunsur in Karnataka State, India to ensure the long term safety and reliability of aged RCC road bridges by assessing their structural integrity in the face of fatigue induced damage. The methodology involved a systematic approach by collecting load data to calculate annualized traffic and cross-sectional data was gathered from documentation to accurately model the bridge. A moving load analysis was conducted to evaluate the stress distribution under vehicular loads. The study then applied Linear Elastic Fracture Mechanics (LEFM) to analyze fatigue cracks caused by cyclic loads using crack initiation and propagation theories. But, due to the high randomness of LEFM parameters and associated uncertainties, structural reliability principles were incorporated and the Reliability Index (β), was calculated using a limit-state approach. MATLAB 7.12.0 (R2011a) was used for computational analysis which enabled precise calculations. This study provides a detailed understanding of the relationship between load cycles, crack size, and the Reliability Index (β) for Reinforced Concrete Bridge. It emphasizes the importance of equivalent stress range and detected crack size in fatigue analysis and offers a methodology for predicting bridge reliability over time. The results indicated that the Reliability Index (β) consistently decreased as the number of load cycles increased. At 2x10^⁶ cycles, the highest β value was observed in the scenario with a single moving vehicle, reflecting lower stress levels. The analysis also showed that bridges with detected cracks and varying traffic growth exhibited different β values depending on the crack size and vehicle speed. This developed method enabled the assessment of bridge dependability and helped determine an acceptable risk level and optimal inspection intervals, ensuring a safe and reliable bridge. The findings contribute to the development of more accurate inspection strategies and maintenance plans, ensuring the safety and longevity of bridge structures.

During pipeline operation, internal cracks may occur. The severity around the crack tip can be quantified by the stress intensity factor (KI), which is a linear–elastic fracture mechanics parameter. For pressurized pipes featuring infinitely long internal surface cracks, KI can be interpolated from a function considering pressure, geometry, and crack size, as presented in API 579-1/ASME FFS-1. To enhance KI prediction accuracy, an artificial neural network (ANN) model was developed for such pressurized pipes. Predictions from the ANN model and API 579-1/ASME FFS-1 were compared with precise finite element analysis (FEA). The ANN model with an eight-neuron sub-layer outperformed others, displaying the lowest mean squared error (MSE) and minimal validation discrepancies. Nonlinear validation data improved both MSE and testing performance compared to uniform validation. The ANN model accurately predicted normalized KI, with differences of 2.2% or lower when compared to FEA results. Conversely, API 579-1/ASME FFS-1′s bilinear interpolation predicted inaccurately, exhibiting disparities of up to 4.3% within the linear zone and 24% within the nonlinearity zone. Additionally, the ANN model effectively forecasted the critical crack size (aC), differing by 0.59% from FEA, while API 579-1/ASME FFS-1′s bilinear interpolation underestimated aC by 4.13%. In summary, the developed ANN model offers accurate forecasts of normalized KI and critical crack size for pressurized pipes, providing valuable insights for structural assessments in critical engineering applications.

The study presents the crack mouth opening and propagation of cracks in a composite material printed by material extrusion subjected to monotonic loading. The composite material is made out of a nylon matrix (with embedded short carbon fiber—called Onyx®) and reinforced with continuous Kevlar fibers. Three-point bending tests were performed on notched specimens built according to ASTM-E399. Tests were digitally recorded to extract crack opening displacement (COD) and crack length data through image treatment techniques (using ImageJ), and results were analyzed using linear elastic fracture mechanics parameters through the use of COD. Therefore, the crack mouth opening was established, and fracture toughness was found to be 46 MPa√m. Additionally, microscopy analysis identified fracture zones, crack initiation, transition, and final rupture. The observed failure mechanisms were matrix cracking, fiber pull-out, fiber breakage, and defects such as non-proper fiber-matrix bonding.

Abstract A study has been conducted to evaluate the mechanical and fatigue crack propagation properties of wire + arc additively manufactured ER70S‐6 components. A parallel‐built deposition strategy was employed to fabricate the additively manufactured wall. The hardness values were slightly higher at the bottom and top of the wall due to the presence of Widmanstätten ferrite and carbides. The characterization of mechanical properties in both orientations; parallel and perpendicular to the deposition direction showed a marginal difference in yield strength and ultimate tensile strength. The crack growth rates were correlated with linear elastic fracture mechanics parameter ΔK and compared with an oscillation‐built deposition strategy from the literature. The crack growth rates of both deposition strategies were found to be very similar to each other. Furthermore, it has been demonstrated that the variability in the crack growth histories can be reasonably well captured by using the NASGRO crack growth equation.

Molecular dynamics method and finite element analysis are applied for the analysis of the stress field in the neighborhood of the crack tip in a copper plate with a single edge notch. The molecular dynamics simulations implemented in a classical molecular dynamics code LAMMPS (Large-scale Atomic/Molecular Massively Parallel Simulator) are aimed at evaluating classical continuum linear elastic fracture mechanics parameters such as stress intensity factors, T-stresses and higher order coefficients of the Williams power series expansion of the near crack stress field for Mode I, Mode II and Mixed Mode (Mode I + Mode II) loadings of the cracked specimen in isotropic linear elastic materials. The key objective of the study is the comparison of continuum and atomistic approaches for the estimation of the near crack tip fields using the example of one of the most common cracked configurations. Stress intensity factors, T-stresses and higher order coefficients of the Williams series expansion for a copper plate with the single edge notch under Mode I and Mixed Mode loadings are evaluated by atomistic modeling and by finite element method. The wide class of the computations in LAMMPS is performed. The atomistic values of stress intensity factors and higher order terms of the Williams series expansion are compared with the values obtained from the numerical solutions given by finite element method. It is shown that the continuum fracture theory successfully describes fracture and the near crack tip fields even at extremely confined singular stress field of only several nanometers. The angular distributions of the stress components from atomistic modeling are retrieved and compared with the angular distributions of the stresses from continuum linear elastic fracture mechanics. The comparison shows good agreement between two approaches.

Coefficients of the williams power expansion of the near crack tip stress field in continuum linear elastic fracture mechanics at the nanoscale

Stress corrosion cracking (SCC) has been detected in the welded components of nuclear power plants. The components of nuclear power plants consist of highly ductile materials such as austenitic stainless steels, and their failure mode is expected to be plastic collapse due to ductile fracture. The limit load analysis, which is applied to fracture assessment for ductile materials, is employed in the fitness-for-service (FFS) codes such as JSME Code “Rules on Fitness-for-Service for Nuclear Power Plants”. The FFS codes provide flaw characterization rules for multiple flaws, and the technical basis seems to be based on interaction of stress intensity factors which are linear elastic fracture mechanics parameters based on small scale yielding. Thus, the applicability of current flaw characterization rules for multiple flaws to limit load analysis is unclear. The limit load analysis for non-aligned multiple flaws was developed based on the net-section approach and the test results of flat plates with two flaws in the past studies. The test results can be represented by using the defined net-section of non-aligned multiple flaws. Finite element analyses were conducted to interpolate the test conditions. The effect of flaw positions on collapse load was estimated by the test and analysis results.

Computational and experimental identification of coefficients of the Williams series expansion by considering higher order terms in the cracked specimens through digital image analysis

Experimental study on the interaction between two cracks by digital photoelasticity method: construction of the Williams series expansion

In the Al alloy A2024-T3 extruded material, a rod-like structure is generated parallel to the extrusion direction. In this study, the effects of rod-like structures on fatigue crack initiation and growth behavior were comprehensively investigated. Two types of specimens were used in a fatigue experiment, in which the direction of the load stress amplitude was parallel (specimen P) and perpendicular (specimen V) to the rod-like structure. Based on the experimental and analytical results, the following findings were obtained regarding the fatigue life, location of crack initiation, and fatigue crack growth behavior. Because the fatigue life of specimen P was longer than that of specimen V, it is inferred that the rod-like structure significantly affects the fatigue life. In specimen P, fatigue cracks were generated from the grain boundaries of the Al matrix. By contrast, in specimen V, cracks were generated from the Cu–Mg-based intermetallic compound in the Al matrix. In specimen P, fatigue cracks were more likely to propagate across the rod-like structure, which decreased the fatigue crack growth rate. In specimen V, fatigue cracks did not propagate across the rod-like structure; instead, they propagated through the Al matrix. Therefore, the fatigue crack growth resistance of specimen V was lower than that of specimen P. The relationship between the fatigue crack growth rate and the modified linear elastic fracture mechanics parameter could be used to predict the S–N curve (stress amplitude vs. fatigue life) and fatigue crack growth behavior. The predicted results agreed well with the experimental results.

The new emerging Wire and Arc Additive Manufacturing (WAAM) technology has significant potential to improve material design and efficiency for structural components as well as reducing manufacturing costs. Due to repeated and periodic melting, solidification and reheating of the layers, the WAAM deposition technique results in some elastic, plastic and viscous deformations that can affect material degradation and crack propagation behaviour in additively manufactured components. Therefore, it is crucial to characterise the cracking behaviour in WAAM built components for structural design and integrity assessment purposes. In this work, fatigue crack growth tests have been conducted on compact tension specimens extracted from ER70S-6 steel WAAM built components. The crack propagation behaviour of the specimens extracted with different orientations (i.e. horizontal and vertical with respect to the deposition direction) has been characterised under two different cyclic load levels. The obtained fatigue crack growth rate data have been correlated with the linear elastic fracture mechanics parameter varDelta K and the results are compared with the literature data available for corresponding wrought structural steels and the recommended fatigue crack growth trends in the BS7910 standard. The obtained results have been found to fall below the recommended trends in the BS7910 standard and above the data points obtained from S355 wrought material. The obtained fatigue growth trends and Paris law constants from this study contribute to the overall understanding of the design requirements for the new optimised functionally graded structures fabricated using the WAAM technique.

Notch effect on the linear elastic fracture mechanics values of a polysulfone thermoplastic polymer

Risk assessment based on analytical evaluation of structural integrity and life of drilling rig pipe

Comparison of experimental, numerical and analytical risk assessment of oil drilling rig welded pipe based on fracture mechanics parameters

Risk assessment of oil drilling rig welded pipe based on structural integrity and life estimation

In this study, fatigue tests under different R ratios were conducted on the AZ61 Mg alloy to investigate its fatigue lifetimes and fatigue crack growth (FCG) behavior. The fracture surface of the failed specimens was investigated using a scanning electron microscope to study the size of the intermetallic compounds from which the pioneer fatigue crack initiated and led to the final failure of the specimen. To determine the maximum size of the intermetallic compounds existing within the cross section of the specimen at higher risk, Gumbel’s extreme-value statistics were utilized. In the present study, the intermetallic compounds contained within the specimen were assumed to be the initial cracks existing in the material before the fatigue tests. A modified linear elastic fracture-mechanics parameter, M, proposed by McEvily et al., was used to analyze the short FCG behavior under different stress ratios, R. The relation between the rate of FCG and M parameter was found to be useful and appropriate for predicting the fatigue lifetimes under different R ratios. Moreover, the probabilistic stress-fatigue life (P-S-N) curve of the material under different R ratios could be predicted with this method, which utilizes both the FCG law and a statistical distribution of sizes of the most dangerous intermetallic compounds. The evaluated results were in good agreement with the experimental ones. This correspondence indicates that the estimation method proposed in the present study is effective for evaluation of the probabilistic stress-fatigue life (P-S-N) curve of the material under different R ratios.

Analysis of fatigue crack propagation in laser sintering metal

The present study focuses on applying the fracture mechanics approach to the fracture assessment of a cracked member/component strengthened with fiber-reinforced polymer composite stiffeners. The parameters of linear elastic fracture mechanics (LEFM) — the stress intensity factor and the crack opening displacement — are estimated using a finite-element analysis. A metallic plate with an edge crack repaired with fiber-reinforced polymer composite stiffeners is considered in the study. The effects of crack length, debonding length, and adhesive stiffness on the LEFM parameters are examined. Two different loading conditions are considered — axial tension and bending. The results obtained show that fiber-reinforced polymer composite stiffeners are very useful in repairing cracked metallic components.

The stress intensity factor (SIF) is the linear elastic fracture mechanics parameter that relates remote load, crack size and structural geometry. It predicts very accurately the stress state. In this work, cylinders with multiple cracks are considered. The following parameters are varied during the analysis of the cylinders: the number of cracks, (the variation in number of cracks ultimately led to a variation in the inter-crack spacing), the crack length to cylinder thickness ratio (a/t), the diameter ratio of the cylinders. Very good agreement between the finite element stresses and the theoretical stresses is seen.

Identification of interlaminar fracture properties of a composite laminate using local full-field kinematic measurements and finite element simulations