Failure Mechanisms Research Articles

Investigation on mechanical property and failure mechanism of the carbon/glass hybrid laminate bolted joints using acoustic emission

In this study, tensile tests and acoustic emission (AE) monitoring were performed on single lap specimens of carbon/glass hybrid laminates with different carbon fiber layer angles. The results indicated that the carbon fiber layer angle not only affects the bearing strength and bearing stiffness of hybrid laminates, but also influences the macroscopic extension direction of damage. The study also found that carbon fiber and glass fiber damage exhibit different centroid frequencies. Building on these findings, the analysis identified the primary fiber type involved in fiber damage to different hybrid fiber laminates. Additionally, it was noted that the friction generated between the bolt and the laminate under load triggers AE signals with a high centroid frequency.

Atomistic study of selenium doping effects on the mechanical properties of zinc-blende and wurtzite CdTe nanowires

CdSexTe1–x semiconductor materials, having potential to be used to design dependable and reproducible nanowire devices, require an extensive study of their mechanical behaviors. The uniaxial tensile deformation mechanism of CdSexTe1–x nanowires (NWs) with different Se dopant concentration are yet to be explored. By integrating theoretical analysis with computational simulation, this research demonstrated that Se doping in CdTe NWs influences the mechanical response and failure modes. Ultimate tensile strength (UTS) and elastic modulus (EM) were studied for both zinc-blende (ZB) and wurtzite (WZ) structures with different crystal orientations. The findings revealed that these mechanical properties increase linearly with increasing Se concentration in all cases. In addition, the WZ structures exhibited similar mechanical properties under both zigzag and armchair loadings, unlike the ZB structures, which exhibited a strong dependence on the crystal orientation. The [111]-oriented ZB structures showed the highest EM and UTS whereas [100]-oriented ZB structures showed lowest EM and UTS. The failure mechanism was explored for CdSe50Te50 to underscore the influence of the dopant on the NWs failure for tensile loading. In both the cases of WZ structure, the failure planes were perpendicular to the loading direction. Furthermore, the failure plane varied with the Se content in ZB CdSexTe1–x. Atomic coordination and bond length affected by doping defined the alterations of mechanical properties and the preferred modes of failure. The significance of the interaction between doping elements and nanowire structures offers insights that unite material science and mechanics, contributing to the scientific understanding of solid materials’ behavior.

Microstructure evolution and enhanced mechanical properties of CF/Mg composites with optimized fiber/matrix interfacial adhesion

In this study, the optimal carbon fiber/matrix (CF/matrix) interfacial adhesion was explored by tailoring sintering pressures, aiming to enhance the ultimate tensile strength (UTS) of CF/Mg composites. With increasing the pressure, the interfacial shear strength (IFSS) gradually increased from 28.8 MPa to 43.6 MPa. Remarkably enhanced UTS (152 MPa) of the composite was achieved, which was 120.3 % higher than that of the matrix, through optimizing the IFSS to 39.7 MPa. Correspondingly, the main failure mechanism was fiber pulling-out and direct fiber-cutting. Whereas, excessive IFSS (43.6 MPa) deceased the UTS of the composite, with the dominant failure mechanism of direct fiber-cutting.

Articular cartilage fatigue causes frequency-dependent softening and crack extension

Soft biological polymers, such as articular cartilage, possess exceptional fracture and fatigue resistance, offering inspiration for the development of novel materials. However, we lack a detailed understanding of changes in cartilage material behavior and of crack propagation following cyclic compressive loading. We investigated the structure and mechanical behavior of cartilage as a function of loading frequency and number of cycles. Microcracks were initiated in cartilage samples using microindentation, then cracks were extended under cyclic compression. Thickness, apparent stiffness, energy dissipation, phase angle, and crack length were measured to determine the effects of cyclic loading at two frequencies (1 Hz and 5 Hz). To capture the fatigue-induced material response (thickness, stiffness, energy dissipation, and phase angle), material properties were compared between pre-and-post diagnostic tests. The findings indicate that irreversible structural damage (reduced thickness), cartilage softening (reduced apparent stiffness), and reduced energy dissipation (including phase angle) increased with an increase in the number of cycles. Higher frequency loading resulted in less reduction in energy dissipation, phase angle, and thickness change. Crack lengths, quantified through brightfield imaging, increased with number of cycles and frequency. This study sheds light on the complex response of cartilage under cyclic loading resulting in softening, structural damage, and altered dynamic behavior. The findings provide better understanding of failure mechanisms in cartilage and thus may help in diagnosis and treatment of osteoarthritis.

The failure mechanism of crystallization blockage in tunnel drainage system and preventive measure of scale inhibitor

In recent years, the incidence of crystallization blockages in tunnel drainage systems has become increasingly frequent. This not only poses a serious threat to tunnel operational safety but also significantly escalates maintenance costs. Using a specific tunnel as a case study, this paper offers a preliminary insight into the failure mechanism of the drainage system by examining the characteristics of crystallization blockage issues. Furthermore, from a preventive standpoint, this paper introduces the scale inhibitor and validates its viability through laboratory testing. The findings indicate that the main component of the crystal blockage is CaCO3, which is closely related to the geological and hydrological environment, as well as the design and construction characteristics. Scale inhibitor has a certain anti-crystallization effect, which is mainly achieved by inhibiting the growth process of calcium carbonate crystals, leading to unstable formation. Additionally, within a certain range, the suppression effect of the scale inhibitor will gradually increase with the increase of its concentration.

Martensite size and morphology influence on strain distribution and micro-damage evolution in dual-phase steels; comparing segregation-neutralised and banded grades

A change in strain partitioning and microscale failure mechanisms in dual-phase (DP) steel was found when both the morphology and distribution of martensite were altered compared to a banded DP steel grade benchmarked against a specific commercial DP grade. To achieve a DP microstructure with equiaxed and well-dispersed martensite, the concept of segregation neutralisation was utilised, where the ratio of Mn to Si elements was decreased (from 7.4 to 0.3) to neutralise the effect of Mn segregation on generating the banded martensite. A combination of micromechanical modelling simulations and in-situ notch tensile testing (within an SEM) was employed to compare the micro strain field and void formation rate between the segregation-neutralised and the benchmark grades. The benchmark grade showed extensive void coalescence along the direction of shear bands in the tensile sample after the average tensile strain of 30%. In contrast, no void coalescence was observed in the segregation-neutralised DP steel even at the average tensile strain of 80% just before failure. As a result, post-uniform elongation in the segregation-neutralised grade increased to 63.3%, compared to 30.1% in the benchmark grade.

In-situ water retention monitoring system of an operational dike

The severe droughts in recent decades and the lack of regular flooding have caused considerable fissures to develop on clay embankments. Previous surveys in Hungary have identified the examined dike section as prone to desiccation cracks. It is essential to determine the possible extent of these desiccation cracks, as they degrade the dikes’ resistance against several failure mechanisms. A representative dike cross-section was equipped with a unique water retention monitoring system comprising 17 sensors, including 14 soil moisture and 3 water potential sensors. These devices were validated with laboratory measurements to obtain accurate results. The gravimetric water content (w) ranged from 8.3 % to 31.3 %, and the matric potential was recorded between 0.1 kPa and 2350.7 kPa over one and a half years. The study examined the differences in soil behaviour under pavement and turf cover, identifying common moisture content distribution patterns and areas of the cross-section prone to desiccation cracking. The uniqueness of the monitoring system lies in the fact that it was established in an operational embankment, which regulates the flow of a river. Furthermore, it was instrumented along the Tisza River, which is among Europe’s most significant watercourses. The results may help better understand the moisture content change in clay embankments and the role of the crest pavement in the moisture content distribution.

Accurate prediction of discontinuous crack paths in random porous media via a generative deep learning model

Accurate prediction of discontinuous crack paths in random porous media via a generative deep learning model

Visualization of stepwise electrode decomposition in a nail penetrated commercial lithium-ion cell using low-temperature synchrotron X-ray computed tomography

The transition towards zero carbon emissions in power generation hinges on the integration of efficient electrical energy storage systems, with lithium-ion batteries (LIBs) positioned as a pivotal technology. While generally safe, deviations in their operational guidelines due to manufacturing defects or misuse can lead to critical safety concerns, notably thermal runaway (TR) events. Internal short circuits (ISCs) are primary initiators of TR within LIBs. For abuse testing, ISCs are often triggered by nail penetration. This study explores the morphological changes and mechanisms underlying ISC-induced TR in LIBs using operando synchrotron X-ray computed tomography (SXCT) at subzero temperatures. A novel cryogenic setup was developed to control a stepwise temperature increase in the damaged sample while monitoring electrochemical characteristics and simultaneously enabling acquisition of high-resolution SXCT images. The findings reveal that conducting nail penetration at minus 80 °C prevents immediate TR, enabling detailed analysis of subsequent structural and electrochemical behavior during controlled thawing. Thus, the initiation of TR processes at localized ISC sites has been observed, evidenced by voltage fluctuations and morphological changes, such as cathode material cracking and decomposition. These results underscore the importance of temperature control in mitigating TR risks and provide critical insights into the internal dynamics of LIBs under abusive conditions. The developed cryogenic SXCT methodology offers a powerful tool for non-destructive, high-resolution investigation of battery failure mechanisms, contributing to the enhancement of LIB safety.

The Influence of Pipeline-Backfill-Trench Interaction on Pipeline Response to Ice Gouging: A Numerical Investigation

Ice gouging is a destructive incident to subsea pipelines in Arctic regions. Trenching and backfilling is a cost-effective solution to physically protect the pipeline against ice gouging. Ice gouging imposes a complex combination of stresses and strains through the soil medium, the pipeline, and the interface. Remolded backfill materials with considerably less stiffness than native soil result in more complexity in soil failure mechanisms and pipe trajectories. However, this critical aspect is less explored in the literature on ice gouges. This paper investigated the influences of pipeline-backfill-trench interaction on the soil failure mechanisms and the pipeline responses by coupled Eulerian-Lagrangian (CEL) method. Two model configurations (shallowly buried and deeply buried pipeline) were set up to investigate the influence of trenching/backfilling, as well as pipe burial depth. Incorporation of the strain-rate dependency and strain-softening effects in the soil constitutive model involved the development of a user-defined subroutine and incremental update of the undrained shear strength within the Abaqus software. The research findings indicate that the conventional approach of assuming uniform seabed soil for trenched and backfilled pipelines may not accurately capture the pipeline behavior and soil failure mechanisms.

Tensile strength and failure mechanism of rock–cement sample: Roles of curing temperature, nano-silica and rock type

Understanding the tensile strength and failure mechanism of rock–cement interfacial transition zone (ITZ) is of vital significance to the sealing integrity of cement sheath under downhole condition. Taking advantage of multiple techniques, i.e., digital image correlation (DIC), nano-indentation, XRD-Rietveld analysis, 29Si MAS solid NMR, and SEM-EDX, this study is devoted to investigating the impacts of curing temperature, rock type, and the addition of nano-silica (NS), on the tensile strength and failure mechanism of rock–cement sample. The experimental results show that both the curing temperature and the addition of NS leads to the formation of more C-S-H, which densifies the ITZ microstructure and responsible for high tensile strength of rock–cement samples; the tensile strengths of shale-cement samples are consistently higher than those of sandstone-cement sample; the crack velocities for rock–cement samples under three-point bending tests are approximately 1 mm/s, the crack velocities for rock–cement samples are slowed down when the NS is incorporated in cement paste, but they are independent on the rock type and curing temperature.

Experimental Study on Acoustic Emission Features and Energy Dissipation Properties during Rock Shear-Slip Process

The features of rock shear-slip fracturing are closely related to the stability of rock mass engineering. Granite, white sandstone, red sandstone, and yellow sandstone specimens were selected in this study. The loading phase of “shear failure > slow slip > fast slip” was set up to explore the correlation between fracture type, acoustic emission (AE) features, and energy dissipation during the rock fracturing process. The results show that there is a strong correlation between fracture type, energy dissipation, and AE features. The energy dissipation ratio of tension-shear (T-S) composite, shear, and tensile types is 10:100:1. The fracture types in the shear failure phase are mainly tensile and TS composite types. The differential mechanism of energy dissipation of different rocks during the shear-slip process is revealed from the physical property perspectives of mineral composition, particle size, and diagenetic mode. These results provide a necessary research basis for energy dissipation research in rock failure and offer an important scientific foundation for analyzing the fracture propagation problem in the shear-slip process. They also provide a research basis for further understanding the acoustic emission characteristics and crack type evolution during rock shear and slip processes, which helps to better understand the shear failure mechanism of natural joints and provides a reference for the identification of precursors of shear disasters in geotechnical engineering.

Physics-Informed Neural ODE with Heterogeneous Control Inputs (PINOHI) for Quality Prediction of Composite Adhesive Joints

Composite materials have long been used in various industries due to their superior properties such as high strength, lightweight and corrosive resistance. Bonded composite joints are finding increasing applications as they provide extensive structural benefits and design flexibility. On the other hand, the failure mechanism of composite adhesive joints is not fully understood. A model that bridges manufacturing parameters and final quality measures is highly desired for the design and optimization of the composite adhesive joints manufacturing process. In this study, a novel framework of physics-informed Neural Ordinary Differential Equation (ODE) with heterogeneous control input (PINOHI) is proposed, which links the heterogeneous manufacturing parameters to the final bonding quality of composite joints. The proposed model structure is heavily motivated by engineering knowledge, by incorporating a calibrated mathematical physics model into the Neural ODE framework, which can significantly reduce the number of data samples required from costly experiments while maintaining high prediction accuracy. The proposed PINOHI model is implemented in the quality prediction of composite adhesive joints bonding problem. A set of experiments and associated data analytics are conducted to demonstrate the superior property of the PINOHI model by using both the leave-one-batch-out cross-validation and sensitivity analysis.

Influence Mechanism of Water Level Variation on Deformation of Steep and Toppling Bedding Rock Slope

The construction of major hydropower projects globally is challenged by slope deformation in reservoir areas. The deformation and failure mechanisms of large rock slopes are complex and poorly understood, making prevention and management extremely challenging. In order to explore the influence mechanism of the water level variation on the deformation of steep toppling bedding rock slopes, this paper takes the right bank slope near the dam area of the Longtou Hydropower Station as an example, and field investigations, deformation monitoring, physical simulation tests and numerical analyses are carried out. It is found that the slope deformation response is obvious under the influence of the reservoir water level variation, which is mainly reflected in the change in the slope groundwater level, rock mechanical parameters and seepage field in the slope body. The toe of the slope produces plastic deformation and maximum displacement. With the increase in the reservoir water level, the plastic zone expands and the displacement increases, which leads to the intensification of the slope deformation. This paper puts forward that the deformation and failure modes of the steep and toppling bedding rock slope caused by water level variation are due to shear dislocation, bending deformation and toppling fracture. This study reveals the influence mechanism of the water level variation on the deformation of steep and toppling bedding rock slopes, which can provide theoretical support for the construction of major hydropower projects.

Electrical contact reliability investigation of high-speed electrical connectors under fretting wear behavior

Fretting is one of the common phenomena during the use of electrical connectors, which is usually affected by the working environment and has a significant impact on the electrical contact life. In this work, the influence of different fretting wear conditions on electrical contact failure is studied by combining theoretical analysis, finite element simulation and experimental verification. The mechanical and electrical properties are related through experiments in different environments. It can be concluded that the main causes of electrical contact failure are contact structure deterioration and surface coating loss. Increased fretting cycles aggravate the surface fretting wear of high-speed electrical connectors. The failure of electrical connectors can be delayed by a decrease in frequency and amplitude in addition to an increase in coating thickness. The insertion and withdrawal force gradually decreases due to continuous wear. The failure mechanism of electrical contact during wear is also explained. It provides theoretical guidance for predicting the life of electrical connectors.

Application of scalable sensor-assisted multi-scale computational methods in the simulation of micro mechanical behavior of composite materials

Micro mechanics involves the examination of the mechanical behavior of heterogeneous materials, taking into account inhomogeneities such as voids, fractures, and inclusions, and building on mathematical models developed. Composites bring engineering design barriers despite their strengths. Composite manufacturing and processing need specialized equipment, strategies, and labor, ensuring they are challenging and expensive. Mechanical behavior deals with how a composite material performs if faced with mechanical effects and action. Scalable sensor-assisted multi-scale computational Methods (SS-MSCM) are used to investigate topics ranging from the molecular basis of soot production in combustion to how molecule-level flaws influence macroscopic mechanical qualities. Carbon fiber reinforced polymers (CFRP) are generated by mixing graphene fiber with a resin, like vinyl ester and epoxy, to render a composite material with superior performance to the component ingredients. Hence, SS-MSCM-CFRP has Improved mechanical qualities achieved by incorporating nano-reinforcements, including carbon nanofibers and graphene nanoplates, into the CFRP matrix: enhanced flexural and compressive strengths, energy absorption upon impact, toughness to fracture, and interlaminar bonding. Composite materials feature excellent mechanical qualities like high strength and stiffness, fatigue resistance, and durability. It is possible to insert scalable sensors throughout the manufacturing process, which enables real-time monitoring of structural health, strain, and other factors. Scalable sensor-assisted multi-scale computational methods offer enhanced accuracy, real-time monitoring, and cost-effectiveness by integrating sensor data with computational models, improving predictions and failure mechanism insights. However, they face limitations like sensor dependency, computational complexity, data integration challenges, and high implementation costs, leading to potential discrepancies between simulation and experimental results. Important qualities include corrosion resistance, thermal conductivity, and electrical conductivity. As the composite materials develop to satisfy the established mechanical stress and temperature conditions, they offer high durability and strength.

Finite element analysis of thermal barrier properties under relevance vector machine in coated pistons and blades

Internal Combustion (IC) engines require Thermal Barrier Coatings (TBCs) to preserve their effectiveness and performance. By coating engine parts with TBCs, thermal fatigue and environmental heat loss may be minimised. To reduce heat loss in IC engines during the combustion stage, piston thermal barrier coating is extremely beneficial. Additionally, it is well known that power plants with higher energy efficiency tend to operate their gas turbines at higher operating temperatures. To produce TBCs for the thermal design of gas turbines and diesel engines with higher performance, an in-depth study on the thermophysical properties of TBCs is required. This article presents an experimental investigation into the combined effect of gas turbine blades and diesel engine pistons coated with a heat barrier, utilising two distinct Thermal Barrier Coatings. Initially, numerical calculations are used to assess the wall heat transfer model’s ability to control temperature and density. The piston and blade top surfaces received plasma-sprayed, Yttria-Stabilised Zirconia (YSZ) with different material combinations on the piston and blades are evaluated. The Finite Element Method is developed for the coating of the ideal thickness to analyse the failure mechanism of the TBC sample. To evaluate the fatigue residual lifespan of TBC pistons, as well as blades in high-power engines, the authors also created a relevant vector Machine-based lifetime prediction model. The CO, HC and NOx emissions, as well as the fuel depletion and braking thermal efficiency, are used to calculate the performance analysis of the coated piston and blades. The results demonstrated improved thermal process endurance and decreased thermal conductivity by 28% when compared to YSZ using the RVM method respectively.

A study on radial oil seal leakage failure due to viscoelasticity under dynamic eccentricity

Purpose This study aims to investigate the causes of leakage in radial oil seals under dynamic eccentricity, elucidate the influence of operating parameters on leakage failure and develop methods for predicting and preventing such leakage. Design/methodology/approach Based on the principle of cam motion and considering viscoelasticity, develops a motion model of the compression and release of the shaft seal and proposes a method to determine its failure. In addition, this study quantifies the leakage gap and formulates a quantitative calculation model to accurately determine the location and shape parameters of the leakage gap. Findings Leakage gaps predominantly occur during the release phase of the shaft seal. Their presence can be identified by comparing the descending times of the seal and the shaft during this phase. An increase in rotation speed and eccentricity heightens the likelihood of gap formation, with both the dimensions and leakage rate of the gap increasing as these factors escalate. Eccentricity, in particular, has a more pronounced effect on gap formation. Originality/value This study clarifies the failure mechanisms of radial oil seals under dynamic eccentricity and introduces a criterion for identifying leakage gaps, providing valuable theoretical guidance for the design and optimization of radial oil seals. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-05-2024-0192/.

Experimental Study of the Influence of Supplementary Reinforcement on Tensile Breakout Capacity of Headed Anchors in Nuclear Power Plant Equipment Foundations

Anchor bolts are often used in nuclear power plants to connect equipment and equipment foundations. Under a severe earthquake, tensile breakout failure is prone to occur in the anchor bolts. As the total amount of installed machines rises, the inertial forces transferred to the anchor bolts under seismic loads also increase significantly. Therefore, the capacity is no longer satisfied by concrete alone, and specialized supplementary reinforcement needs to be installed around the bolts. The study analyzed the tensile behavior of anchor bolts in foundations with supplementary reinforcement experimentally. A total of 16 single-headed anchors in RC foundations with various diameters, yield strengths, and forms of supplementary reinforcement were tested under monotonic tensile loading. The results show that supplemental tie bars and supplemental U-shaped bars, respectively, rely on the bond with the concrete and their own tensile strength to increase the tensile breakout capacity. Furthermore, based on the failure mechanism, a new model considering the terms of concrete resistance and reinforcement resistance for the tensile breakout capacity of headed anchors around with supplementary reinforcement was proposed. Compared with the strut–tie model by EN 1992-4:2018, the predicted results of the model proposed by this study are relatively consistent with the experimental results, while the results by EN 1992-4:2018 are overly conservative.

Experimental study on constitutive relation of coal gangue coarse aggregate concrete under uniaxial compression

As an efficient method for utilizing coal gangue (CG), concrete incorporating coal gangue as coarse aggregate has significantly reduced the reliance on natural aggregates, offering substantial environmental and economic benefits. In this study, coal gangue concrete was prepared with coal gangue replacement rates of 0, 20, 40, 60, 80, and 100%, and mechanical tests under unconfined compression were conducted to evaluate the stress-strain behavior and failure mechanism of coal gangue coarse aggregate concrete (CGC). Utilizing scanning electron microscope (SEM) microscopic characterization, the microscopic failure mechanism of CGC was further elucidated. With increased coal gangue replacement, the CGC's uniaxial compression failure mode shifts from shear to longitudinal splitting failure. The slope, peak stress and elastic modulus of the stress–strain curve's rising section are negatively correlated with the coal gangue content, while the falling section's slope, peak strain and ultimate strain are positively correlated. Next, building upon the classical constitutive model, we adjust the constitutive parameters utilizing the uniaxial compressive strength and coal gangue content. Finally, we introduce a predictive model for the CGC's constitutive compressive behavior across various content levels. There is a notably high agreement between the model and experimental data.