Post-failure Analysis Research Articles

Experimental investigation on the bond-slip behavior of rebars coated with epoxy and polyurethane systems: A comparative study

This study presents a comprehensive experimental investigation into the effectiveness of various rebar coating systems in mitigating corrosion and maintaining bond strength with concrete. Three coating systems were evaluated: a conventional two-component epoxy system (KC-R), a zinc-rich epoxy system (FR-R), and a moisture-cure polyurethane coating with Micaceous Iron Oxide-Enriched System (MC-R). Accelerated corrosion tests showed that uncoated rebars had a mass loss of about 3.793 ± 0.266 %, while all coated rebars exhibited negligible mass loss. However, coated rebars experienced a reduction in bond strength: KC-R and FR-R coatings resulted in 16.3 % and 48 % reductions, respectively, whereas MC-R showed the least reduction at 9.4 %. Notably, all specimens, whether coated or not, displayed a slight increase in bond strength after corrosion. Additionally, the MC-R coating reduced rebar slip at ultimate bond strength. However, the other coatings increased rebar slip compared to uncoated specimens. Overall, this study underscores the importance of proper rebar coating selection and highlights the effectiveness of the polyurethane coating system in mitigating corrosion while maintaining bond strength with concrete. Additionally, it emphasizes the significance of post-failure analysis in understanding the behavior of coated rebar specimens under different conditions.

Multivariate copula-based framework for stochastic analysis of landslide runout distance

The increasing frequency of landslide disasters worldwide highlights the importance of accurate prediction of post-failure runout distances for effective risk management. However, the prediction of runout distances of gravitational mass flow remains challenging due to the inherent complex heterogeneities of geomaterials and their inter-correlated spatially varying mechanical properties. To address this challenge, this study proposes a novel multivariate stochastic method based on the combination of the Generalised Interpolation Material Point (GIMP) analysis and the multivariate copula-based approach. The method considers geotechnical uncertainties by simulating copula-based cross-correlated random fields from sparse field data and incorporating them into the GIMP analysis through Monte Carlo simulations (MCS). Two slope cases with similar geometries but different sources of probability information are presented to illustrate the effectiveness of the proposed method. The results show that considering the influence of multivariate random fields can significantly affect the post-failure analysis of landslides. Both slope cases show that over 40 % of all MCS samples exceed the deterministic case, which indicates that the current deterministic analysis notably underestimates the risk associated with large runout distances of landslides. This study highlights the necessity of considering the interdependency of spatial heterogeneity in post-failure modelling of landslides.

Ex Vivo Biomechanical Bone Testing of Pig Femur as an Experimental Model.

This study investigates the mechanical behavior of femur bones under loading conditions, focusing on the transition from elastic to plastic deformation and eventual fracture. The force-displacement curves reveal distinct phases of deformation, with an initial linear relationship indicating elastic behavior, followed by deviation from linearity marking the onset of plastic deformation. Fracture occurs beyond a critical load, leading to a sharp drop in the force-displacement curve. The maximum fracture force varies among specimens and is influenced by bone geometry, size, cross-sectional area, and cortical thickness. Post-failure analysis highlights additional insights into fracture mechanics and bone material toughness. Reinforcing bones with screws enhances their strength, which is evident in the higher fracture forces observed in force-displacement diagrams. Fixation procedures following fractures further increase bone strength. Comparing specimens with and without strengthening underscores the effectiveness of reinforcement methods in improving bone mechanical properties. After analyzing the results, it is evident that femur bones with reinforcement can withstand greater loads, and they can also absorb higher impact energies while remaining in the elastic deformation range and without suffering permanent plastic damage. This study provides valuable insights into bone biomechanics and the efficacy of reinforcement techniques in enhancing bone strength and fracture resistance.

Electromigration and electrical sintering in printed silver from high current at room temperature

Improved understanding of the reliability and failure physics of metal nanoparticle conductive inks would facilitate their large-scale deployment across a range of flexible electronics applications. We conduct room-temperature electromigration experiments on printed silver nanoparticle conductive ink test devices. We observe significant variation in failure time, location, and structure during these tests and during post-failure analysis with optical and electron microscopy. We use in situ Atomic Force Microscopy measurements to track volume changes in the sample as a function of time. These measurements provide additional data and understanding of the failure process within printed silver nanoparticle conductive inks.

Strain energy density and entire fracture surface parameters relationship for LCF life prediction of additively manufactured 18Ni300 steel

In this study, the connection between total strain energy density and fracture surface topography is investigated in additively manufactured maraging steel exposed to low-cycle fatigue loading. The specimens were fabricated using laser beam powder bed fusion (LB-PBF) and examined under fully-reversed strain-controlled setup at strain amplitudes scale from 0.3% to 1.0%. The post-mortem fracture surfaces were explored using a non-contact 3D surface topography measuring system and the entire fracture surface method. The focus is on the relationship between fatigue characteristics, expressed by the total strain energy density, and the fracture surface topography features, represented by areal, volume, and fractal dimension factors. A fatigue life prediction model based on total strain energy density and fracture surface topography parameters is proposed. The presented model shows good accordance with fatigue test results and outperforms other existing models based on the strain energy density. This model can be useful for post-failure analysis of engineering elements under low-cycle fatigue, especially for materials produced by additive manufacturing (AM).

Post-failure analysis of model resin-composite restorations subjected to different chemomechanical challenges

ObjectiveThe current study aimed to evaluate the effects of different combinations of chemical and mechanical challenges on the failure load, failure mode and composition of the resulting fracture surfaces of resin-composite restorations. MethodsThree resin composites were used to fill dentin disks (2 mm inner diameter, 5 mm outer diameter, and 2 mm thick) made from bovine incisor roots. The model restorations, half of which were preconditioned with a low-pH buffer (48 h under pH 4.5), were subjected to diametral compression with either a monotonically increasing load (fast fracture) or a cyclic load with a continuously increasing amplitude (accelerated fatigue). The load or number of cycles to failure was noted. SEM was performed on the fracture surfaces to determine the proportions of dentin, adhesive, and resin composite. ResultsBoth cyclic fatigue and acid preconditioning significantly reduced the failure load and increased the proportion of interfacial failure in almost all the cases, with cyclic fatigue having a more pronounced effect. Cyclic fatigue also increased the amount of adhesive/hybrid layer present on the fracture surfaces, but the effect of acid preconditioning on the composition of the fracture surfaces varied among the resin composites. SignificanceThe adhesive or hybrid layer was found to be the least resistant against the chemomechanical challenges among the components forming the model restoration. Increasing such resistance of the tooth-restoration interface, or its ability to combat the bacterial actions that lead to secondary caries following interfacial debonding, can enhance the longevity of resin-composite restorations.

Post-failure analysis of slope under seismic motion by random material point method

Post-failure analysis of slope under seismic motion by random material point method

Random field failure and post-failure analyses of vertical slopes in soft clays

This research investigates the spatial heterogeneity of cohesion within soft clay and its implications for slope stability and post-failure analysis. In-situ cone penetration tests were conducted in alluvial soft clays to calibrate probabilistic strength properties. Slope stability analyses employed deterministic, semi-deterministic, and comprehensive probabilistic approaches, while post-failure analysis utilised the nodal integration-based particle finite element method. The undrained shear strength (cu) demonstrated a log-normal distribution (mean: 19 kPa, standard deviation: 3 kPa), with correlation lengths modeled through Bayesian inference. Treating correlation lengths as distributions resulted in a negligible 2% difference compared to using a single value for the probability of failure. Semi-deterministic analyses exhibited results similar to probabilistic analyses, offering computational advantages. Nevertheless, probabilistic analysis, considering spatial variability, provided more comprehensive insights for post-failure analysis. For a vertical slope of critical height in the studied soft clay, probabilistic analyses predicted a range of runout distances from 0 m to over 125 m. Specifically, 89% of these distances were less than 80 m, and 82% were less than 40 m. The findings contribute to an enhanced understanding of spatial variations in soil strength within soft clay slopes, providing valuable insights for future geotechnical assessments and design considerations.

In situ damage characterization of CFRP under compression using high-speed optical, infrared and synchrotron X-ray phase-contrast imaging

The strain rate dependency and failure modes of carbon fiber reinforced plastic (CFRP) laminate were investigated under out-of-plane compressive loading. Simultaneous high-speed optical and infrared imaging were used to measure full-field deformation and temperature in the dynamically loaded specimens. The damage initiation and propagation inside the CFRP laminates at high strain rates were characterized using in-situ ultra-fast synchrotron X-ray phase contrast imaging (XPCI). The visually observed damage onset occurs at the strain value of 4.2 ± 0.6% as a transverse shear fracture at the free edge of specimens. The local temperature increases significantly to 185 °C due to damage initiation at high strain rates, while at low strain rates the temperature rise occurs after the final shear band forms. The XPCI and post-failure analysis provide an integrated perspective on the formation of a diagonal shear crack and disintegration of the specimen into two pieces with the fracture of plies in the in-plane transverse direction. Scanning electron microscopic (SEM) study was integrated with XPCI results to append the time scale for the post-mortem failure pattern as well as the length scale for microcracks and filament-level failure.

Wear behavior and tribo-surface characteristics of nano magnesium composites

A nano magnesium composite was synthesized with the addition of 5.6 wt.% of titanium, 3 wt.% of aluminum and 2.5 wt.% of nano boron carbide particles through the disintegrated metal deposition process. To validate the metallurgical features of the synthesized magnesium composite, the samples were exposed to X-ray diffraction study and scanning electron microscopic analysis with dispersive spectroscopy analysis. Wear behavior of the nano magnesium composite was studied through pin-on-disc dry sliding wear experiments by changing the load and sliding velocity over a sliding distance of 3000 m. Further, wear rate of the produced material was analyzed for varied wear parameters. Wear behavior of the magnesium composite revealed an adverse effect with an increased load and a positive effect with increased sliding velocity. The microscopic analysis of the worn surface and the collected debris revealed the characteristics of the wear surface of the nano magnesium composite. Adhesion, abrasion, delamination, oxidation and thermal softening were the mechanisms observed in the post-failure analysis.

Parametric analysis for the large deformation characteristics of unstable slopes with linearly increasing soil strength by the random material point method

Soils often exhibit spatial variability with nonstationarity, which has not yet been studied in the context of postfailure analysis of slopes. In this study, the random material point method is adopted to investigate the influence of nonstationarity on the large deformation characteristics of a slope with spatially variable undrained shear strength (Su). The nonstationarity has significant influences on the mean and standard deviation of the large deformation characteristics, where ignoring the nonstationarity can lead to higher mean and standard deviation values. In addition, when the nonstationarity is insignificant with a small increase in the rate of the soil strength, the model boundary can significantly affect the standard deviation of influence and run-out distances, but the influence is slight on those of the volume of the sliding mass. In addition, the mean and standard deviation of the large deformation characteristics increase with a higher coefficient of variation of Su. This study reveals that the nonstationarity of soil spatial variability can influence the failure mechanism in the failure initiation stage and thus the volume of the sliding mass, which controls the kinetic energy of the sliding mass in the postfailure stage and affects the influence and run-out distances.

Post-failure behavior of lazy-wave risers

This paper addresses the modeling and post-failure analysis of flexible lazy-wave risers to understand their behavior after the rupture since the impact of falling risers can damage neighboring equipment and structures. Effects of important parameters, such as integration algorithm, time step, longitudinal drag coefficient, riser slenderness, moment–curvature relationship, soil stiffness, failure point, and current direction, are assessed. A methodology for the definition of a safe zone to avoid impact with the falling riser is presented. It is shown that longitudinal drag coefficient and riser slenderness significantly influence the physical response of lazy-wave risers after failure. Furthermore, use of nonlinear moment–curvature relationship is necessary to obtain more realistic results, and consideration of currents in different directions is important to properly determine the safe zone. Methods and results presented in this paper may assist in reducing the occurrence of damage in elements of offshore systems due to impact with falling risers.

Preventing Corrosion-Related Failures in Electronic Assembly: A Multicase Study Analysis

Corrosion is a prevalent failure mode in electronic products. The initiation of failure often stems from pre-existing corrosion contamination on soldering terminations prior to assembly. This corrosion is further accelerated by environmental factors such as humidity, temperature, and acidity, ultimately leading to degradation of the board and failure during both post-assembly testing and the product’s lifespan. This study presents a method for the real-time, early detection of corrosion contamination on electronic components during the mounting process using pick-and-place technology. The method utilizes the correlation between light reflectance from soldering terminations during placement photography and the degree of corrosion present. Corroded terminations possess a rougher surface and pitting spots which result in different light reflectance compared to pristine terminations. This difference can be detected through AI forensic analysis of component images. The study presents an AI model that correlates termination finish with corrosion content and progression, and evaluates its performance on large-scale data. This study also presents a real-world case where corroded components were identified during the pick-and-place process, but later failed during in-circuit testing (ICT). The post-failure analysis, using scanning electron microscopy/energy-dispersive spectroscopy (SEM/EDS) and cross-section analysis, confirms the accuracy of the AI failure predictions on multiple components with corrosion, during large-scale production. The proposed method has been implemented in multiple production lines, where it inspects all components without compromising throughput, and identifies contaminated components that are unsafe. The method has been tested on over 3.5 billion components, and has achieved an accuracy rate of over 99.5% in its predictions.

Post-failure analysis of landslide blocking river using the two-phase double-point material point method: a case of western Hubei, China

Post-failure analysis of landslide blocking river using the two-phase double-point material point method: a case of western Hubei, China

Application of tailored fiber placement to fabricate automotive composite components with complex geometries

Fabrication of continuous carbon fiber composite components with complex geometries has traditionally been a challenge, yet automotive components are rarely simple in design or loading. Unidirectional and woven fabrics dominate the industry but are limited to generally homogenous microstructure across a layer. Tailored fiber placement (TFP) is a relatively new composite preforming technology that provides a means to address this limitation. In TFP, tows of fibers are positioned by a robotic gantry and stitched in place. This process affords unmatched control over the local fiber orientation. In this study, we design, fabricate, and test a simplified carbon fiber composite connecting rod for an internal combustion engine. Design is aided by performance simulation using the finite element BSAM program. The connecting rods are tested in monotonic compression, monotonic tension, and fatigue. Results show that the TFP process is able to successfully fabricate a high strength carbon fiber composite component featuring a complex structure. Discussion focuses on evaluating achieved performance relative to design targets, correlation between simulated predictions and test results, and evaluation of failure modes from post-failure analysis. The TFP process could be useful to many automotive applications, including seat frames, chassis components, and electric propulsion system components.

Impacts of Climate Change on the Environment, Increase in Reservoir Levels, and Safety Threats to Earthen Dams: Post Failure Case Study of Two Cascading Dams in Michigan

Abstract Climate change has received significant attention lately as it has adverse environmental impacts. Among them, rising water levels in the reservoirs are of key concern for infrastructures such as dams. Dam officials are compelled to reconsider dam safety with the increment in catastrophic floods and accelerated dam failure issues. Relatedly, there are numerous earthen dams in the US that may not be up to the current design standards as these dams are aging. They possess a higher risk of failure due to various factors such as defects in design geometry, geologic materials, and hydrologic deficiency due to extreme storms associated with changing climate. Hence, this study focuses on evaluating the impacts of climate change on earthen dams and spillways by conducting a post-failure analysis of the two cascading dams, Edenville Dam and Sanford Dam, located in Michigan, USA, that failed in series in May 2020. The study aims to accomplish three main objectives: 1) to identify the role of climate change on recent dam failures of Edenville and Sanford, 2) to perform a Windows Dam Analysis Modules (WinDAM) C simulation for the failure analysis of the two dams, and 3) to perform Hydrologic Engineering Center - River Analysis System (HEC-RAS) simulation for the failure analysis of both dams by observing downstream propagation of flood with the detailed evaluation of depth and velocity. The overall results show that extreme storms and flooding are associated with the increase in temperature and precipitation rates, impacting overall dam safety. Careful precautions should be undertaken before any of these catastrophic dam events occur. The analysis is useful for the dam agencies as they reconsider their guidelines and policies for future updates.

Comparison of Material Point Method and Finite Element Method for Post-Failure Large Deformation Geotechnical Analysis

Finite Element Method (FEM) has been the state-of-the-art method in geotechnical analysis since it first formulated in the 40s. It capable to handle Multiphysics simulation, soil-structure and soil-water interaction, and time history analysis. Though powerful, the standard Lagrangian FEM suffers mesh distortion when handling large strain deformation problem. This mesh entanglement problem makes post-failure analysis is considerably challenging to model if not impossible to do using FEM. The Material Point Method (MPM) then later introduced to solve these large strain deformation problems. Adapted from the Particle in Cell (PIC) method, MPM is a hybrid method that combines Eularian and Lagrangian approach by utilizing moving material points which are moving over spatially fixed computational mesh. This approach enables MPM to calculate not only fluid mechanics such in PIC but also solid mechanics and its intermediatory states. To demonstrate the capability of MPM and its consistency with FEM in geotechnical analysis, this article presents a comparison of FEM and MPM analysis on a hypothetical slope using Mohr-Coulomb constitutive model. The simulation shows that both FEM and MPM analyses are consistent to each other especially in small strain scheme. However, in large strain deformation, MPM is still able to get convergent result while FEM is not. The MPM simulation is also able to animate post failure behavior clearly, calculate post-failure strains and stresses distribution, and present final geometry of the model.

Slope stability and post-failure analysis of soil-rock-mixture using the modified 2D DDA-SPH method

Soil-rock-mixture (SRM), consisting of high-strength rock blocks and low-strength soil, is widely distributed in nature. In traditional methods such as limit equilibrium methods , this geomaterial was simplified as a uniform medium without considering the influence of rocks due to its heterogeneity and complex physical and mechanical properties. A coupling method that bridges discontinuous deformation analysis (DDA) for rock simulation and smoothed particle hydrodynamics (SPH) for soil simulation is a promising tool for SRM problems. In this study, the 2D coupled DDA-SPH method is extended to the applications of stability and post-failure analysis of SRM slopes. First, the determination of the contact spring stiffness in the contact algorithm is presented and the reasonable value is discussed. Then, to eliminate the oscillations in some simulations with polygonal rock blocks inside the soil, the contact algorithm is modified by implementing a special treatment for the contact between the SPH particles and the convex vertices of DDA blocks. In addition, the criterion based on the distribution of plastic zone is used to define the critical stable state of the slope when applying the strength reduction technique for stability analysis, and its effectiveness is demonstrated. Finally, a series of numerical analyses are carried out, and through these numerical simulations, some conclusions and suggestions can be reached. • A determination of the contact spring stiffness in the DDA-SPH coupled method was proposed and discussed. • The oscillations in the simulations with polygonal rock blocks inside soil has been eliminated by modifying the contact algorithm. • The effectiveness of the modified method has been demonstrated through several numerical simulations. • The modified method has showed advantages in modeling soil-rock-mixture materials.

Post-failure analysis of landslides in spatially varying soil deposits using stochastic material point method

Post-failure analysis of landslides in spatially varying soil deposits using stochastic material point method

Pre- and Post-Failure Experimental Bending Analysis of Glass Elements Coated by Aged Anti-Shatter Safety Films

The main goal of Anti-Shatter Films (ASFs) applications for structural glass is to create a barrier able to keep together fragments and minimize risk after any impulsive or static load that could lead glass to cracking. The influence of ASF properties on the flexural strength of coated glass elements is thus a relevant topic for safe design purposes, but still little investigated. To this aim, an experimental material investigation is presented in this paper, in order to achieve a good knowledge of common ASFs from a chemical point of view. Moreover, the deterioration of mechanical and adhesion characteristics for ASF samples subjected to different environmental conditions and accelerated ageing is also investigated, so as to simulate the effects of long-term exposure to high humidity (HU) or high temperature (HT). An experimental campaign carried out on 20 small scale ASF-coated glass specimens is finally presented, based on a three-point bending (3PB) test setup. The out-of-plane bending response of unaged or aged samples is performed by taking into account two different displacement-rate levels, to assess their performance and bending capacity under steady-static or impulsive loads. In both cases, the attention is given to the characterization of elastic and post-failure performances. Finally, support for the interpretation of experimental outcomes is derived from a simplified theoretical model of composite beam with partial connection, in order to estimate the shear stiffness of ASF adhesive components in the elastic stage.