Dynamic Failure Mechanism Research Articles

Model test study on the dynamic response of surrounding rock in deep buried tunnel under explosive plane wave

In order to clarify the dynamic failure mechanism in deep buried tunnels, a modeling test of the dynamic response of the surrounding rock in deep buried tunnels under the action of explosion plane wave was carried out by using the geotechnical multi-functional test device. Based on Froude’s similarity theory, a model with dimensions of 1600 × 1300 × 400 mm was constructed using low-strength cement mortar. Using the detonating fuse as the explosive source, the explosion tests were conducted with an equivalent TNT amount of 52.8 g and 105.6 g, respectively. According to the measured data, the stress and deformation characteristics of the surrounding rock, the motion and deformation characteristics of the tunnel and the dynamic instability process of the tunnel were analyzed. The results show that explosive stress waves exhibit exponential attenuation above the arch crown of the tunnel, with the rate of attenuation depending on the amount of explosive used. The deformation process of the surrounding rock of the crown in the tunnel arch under the action of the explosion stress wave was compression followed by tension, which fully proves the existence of the reflected tensile wave. Movement and deformation parameters within the tunnel escalate as the explosive charge increases, especially at the crown of the arch. According to the monitoring results of the motion camera, the dynamic instability process of the tunnel was divided into several stages, such as initial calm, tunnel vibration, particle ejection, atomization, local block ejection, and return to calm. The results of the study have important reference value for the safe excavation and effective support of deep underground engineering.

Dynamic mechanical behaviors of load-bearing battery structure upon low-velocity impact loading in electric vehicles

As the electrification trend of vehicles continues, new energy vehicles such as electric vehicles (EVs) and plug-in hybrid electric vehicles (PHEVs) are being equipped with new functional energy storage devices demanding a trade-off between electrical and mechanical property. Accordingly, composite-battery integrated structures which simultaneously carry mechanical resistance and energy-storage capacity, are being explored to offer great potential for the next generation of EVs or PHEVs. Herein, the dynamic responses and failure mechanisms of the integrated structure under the commonly occurring low-velocity impact events are studied both experimentally and numerically. A macro-scale finite element (FE) model was developed by implementing constitutive models of component materials, including lithium‐ion polymer (LiPo) battery cells, polymer foams, and carbon fiber-reinforced polymers (CFRP). The numerical method demonstrates good feasibility and accurately predicts impact behaviors, with the maximum error of the peak impact load not exceeding 8 %. The integrated structures are proven to reduce mechanical damage while maintaining mechanical and electrochemical performance within a range of impacts. The electrical and mechanical behaviors and their correlations were revealed. Sensitivity of the mechanical behaviors and electrical failure to battery arrangement were discussed as well as the structure design on energy absorption capacity. These results hold significant potential for the safety and lightweight design of energy storage composite structures incorporating lithium-ion batteries.

Experimental and theoretical investigation of failure mechanism in Al2O3/SiC composite under plane shock waves

The investigation of fracture and fragmentation is essential for evaluating the protection performance and structural design of ceramic armour. This paper focused on the dynamic failure and fracture mechanisms of the fine-grained Al2O3/SiC composite subjected to plane shock waves. The macroscopic shock response characteristic was determined through a series of plane impact tests, which included the Hugoniot curves of the composite. The results indicated that the fracture mechanism is significantly influenced by specific stress characteristics. The transgranular fracture in large grains and intergranular fracture in small grains exhibit obvious local plastic deformation characteristics. Moreover, the presence of second-phase SiC particles markedly influences both crack propagation and the microfracture mode of the composite. Lastly, a statistical analysis of the ceramic fragments was conducted after the soft recovery of specimens in impact experiments, and analytical models were developed and modified to predict the distribution of fragments under plane shock loading.

Dynamic responses and interactive failure mechanisms of carbon fiber composite face sheets/double-layer corrugated core sandwich structures under low-velocity impacts loading

A single-layer and double-layer corrugated core sandwich structure consisting of carbon fibre–reinforced polymer (CFRP) panels and aluminium alloy core layers was designed. Numerical simulations were carried out in HyperMesh/LsDyna, and the simulation results of single-layer and double-layer corrugated sandwich structure were compared with the experimental results to verify the reliability of the proposed numerical model. Compared with the results of single-layer and double-layer corrugated sandwich structure, the superiority of a double-layer corrugated sandwich structure in anti-collision performance is verified. Considering the effects of impact energy and impact position on impact force, energy absorption capacity, and failure mode, a series of low-velocity impact finite element simulations was carried out. It was found that the main failure mode of composite laminates included fibre damage, matrix damage and delamination, and core buckling. At the same impact position, the higher the impact energy, the greater the initial slopes of the contact force-time and absorbed energy-time curves, the higher the peak force, and the larger the energy absorption capacity. Under the same impact energy, when the impactor hit the wave crest of the sandwich structure, the damage to the structure was small; however, the maximum impact force on the structure was large (∼8 kN).

Seismic dynamic response characteristics and failure mechanisms of an accumulation body slope

Seismic dynamic response characteristics and failure mechanisms of an accumulation body slope

Dynamic increase factors for progressive collapse analysis of steel structures considering column buckling

Progressive or disproportionate collapse of structures may have severe socio-economic consequences. Aiming at buildings that can withstand such events, one solution is to prevent or minimize the propagation of damage that may lead to progressive collapse by means of robust design strategies. As a typical approach to model progressive collapse and assess robustness, the Alternate Path Method (APM) allows for static analyses, in which the dynamic effects induced by a sudden column loss are taken into account by amplifying loads through a Dynamic Increase Factor. Current recommendations for Dynamic Increase Factors to be used within non-linear static analyses have mainly considered beam-type collapse, overlooking other failure mechanisms, e.g., column buckling. The present paper investigates the dynamic effects of steel structures subjected to progressive collapse when buckling of columns is relevant. Five low- to high-rise case study building structures are considered together with three different column loss scenarios. A numerical procedure is introduced to evaluate the Dynamic Increase Factors considering two different Engineering Demand Parameters (EDPs), suited for describing beam- and column-type mechanisms, respectively. As Dynamic Increase Factors are typically assessed by increasing the loads on all the spans (DIF), a procedure was proposed for deriving factors that apply only on the spans above the removal (DIF*), consistently with UFC guidelines. The obtained DIF and DIF* are compared with the current literature and with values recommended in the UFC guidelines, highlighting the limits of current recommendations. Relevant considerations on the derived Dynamic Increase Factors and failure mechanisms involved are provided.

On the strain-rate dependent compressive failure behavior of 2.5D woven composites

Understanding the mechanical failure behavior of 2.5D woven composites (2.5DWC) is challenging due to their complex fabric configurations and multi-scale structural properties. This challenge is particularly prominent in the realm of dynamic mechanical properties and damage failure mechanisms under high strain rates. Therefore, a comprehensive approach combining a series of quasi-static and dynamic mechanical tests with mesoscale finite element simulation methods is adopted to perform an in-depth analysis of the mechanical response and progressive damage behaviors of a Twilled 2.5D Woven Composite (T-2.5DWC) under different strain rate loads. The results indicate that the compressive strengths as well as the failure behaviors of the T-2.5DWC exhibit an obvious strain rate strengthening effect in both the weft and warp directions. In addition, the rate-dependent finite element model developed in this study accurately simulates the compressive modulus and strength of T-2.5DWC along both the warp and weft directions under various strain rates.

A review on Machine Learning Enhanced Predictive Maintenance for Electric Vehicle Power Electronics: A Pathway to Improved Reliability and Longevity

The emergence of electric vehicles (EVs) as a mainstream mode of transportation presents new challenges in the realm of power electronics, particularly concerning reliability and longevity. Power electronics are the cornerstone of EV performance, dictating efficiency, durability, and overall vehicle health. Traditional maintenance strategies fall short in addressing the dynamic operational demands and complex failure mechanisms inherent in EV power systems. This paper introduces a machine learning (ML)-enhanced predictive maintenance framework designed to revolutionize the upkeep of EV power electronics. By harnessing advanced ML algorithms, the framework predicts potential system failures and degradation patterns, enabling preemptive maintenance actions. A robust data-driven approach is employed, utilizing operational data and failure modes to train the predictive models. The efficacy of the proposed method is demonstrated through extensive simulation and real-world EV power system analyses, showcasing significant improvements in fault identification accuracy and maintenance scheduling optimization. The result is a substantial extension of component lifespan and a reduction in unplanned downtimes, propelling EV power electronics towards higher reliability standards. This work not only contributes a novel predictive maintenance methodology but also paves the way for adaptive maintenance regimes, tailored to the unique demands of EV power electronics systems in the pursuit of sustainable and resilient transportation solutions.

Investigating the failure mechanism of loess-mudstone landslides with a high water content interface subjected to earthquakes through the shaking table test

Loess mudstone landslides are widespread on the Loess Plateau of China and are primarily triggered by earthquakes or heavy rainfall. Field investigations have revealed the presence of a high-water-content layer at the interface, which often serves as a sliding surface for these landslides. However, the dynamic responses and failure mechanisms of these landslides during earthquakes remain unclear. We conducted a comparative shaking table test on Model 2 (the loess-mudstone slope with a high-water-content interface layer) and Model 1 (the loess-mudstone slope without a high-water-content interface layer) to investigate the failure mechanism of the slope under the influence of earthquakes. The test results revealed that water accumulated at the interface, creating a layer with a high water content that resembled a mudflow after shaking. This layer plays a critical role in the dynamic response and failure mechanisms of landslides. Under seismic loading, the pore water pressure within this layer increases to a positive value, reducing the effective stress of the loess. The acceleration amplification factor in the loess layer was approximately 16 % higher in Model 2 than in Model 1, indicating that Model 2 experienced larger inertial forces. Significant seismic subsidence and X-displacement were recorded in Model 2. Additionally, an increase in the electrical resistivity was observed under 0.8 g, suggesting the development and propagation of cracks within the slope. These findings indicate that the high water-content layer loses its strength and starts to slide initially, which then drags the overlying loess layer, resulting in the generation of penetrated tensile cracks, large X-displacement, and subsidence. The slope experiences slippage and tensile cracking failures. This study provides valuable experimental evidence that enhances our understanding of the failure mechanism of this type of landslide.

Dynamic Compressive Properties and Failure Mechanism of the Laser Powder Bed Fusion of Submicro-LaB6 Reinforced Ti-Based Composites.

In this study, lanthanum hexaboride (LaB6) particle-reinforced titanium matrix composites (PRTMCs, TC4/LaB6) were successfully manufactured using the laser powder bed fusion (LPBF) process. Thereafter, the effect of the mass fraction of LaB6 on the microstructure and the dynamic compressive properties was investigated. The results show that the addition of LaB6 leads to significant grain refinement. Moreover, the general trend of grain size reveals a concave bend as the fraction increases from 0.2% to 1.0%. Furthermore, the texture intensity of prior β grains and α grains was found to be weakened in the composites. It was also observed that the TC4/LaB6 have higher quasi-static and dynamic compressive strengths but lower fracture strain when compared with the as-built TC4. The sample with 0.5 wt.% LaB6 was found to have the best strength-toughness synergy among the three groups of composites due to having the smallest grain size. Furthermore, the fracture mode of TC4/LaB6 was found to change from the fracture under the combined action of brittle and ductility to the cleavage fracture. This study was able to provide a theoretical basis for an in-depth understanding of the compressive properties of additive manufacturing of PRTMCs under high-speed loading conditions.

Dynamic response and blast resistance mechanism of polyurea coating on RC slab during contact explosions

Polyurea (PU) coated reinforced concrete (RC) has been widely studied in structural strengthening under contact explosion, however, experimental investigations on dynamic response and failure mechanism of the coating during explosion remain scarce. In this paper, four contact explosion experiments are conducted on uncoated and rear side coated RC slabs. Dynamic strains and dynamic deformation of the coating are obtained by large-range strain gauges and a proposed measurement method based on a high-speed camera. Dynamic response characteristics of the coating are discussed and the blast resistance mechanism is further analyzed. Additionally, the effect of coating rebounding on the RC substrate and the effect of explosive placement on the coating are discussed. The results show that PU coating dissipates the blast energy through elastic deformation, plastic deformation, rupture and debonding. Glass transition at high strain rate may cause the rupture of the coating, and coating thickening significantly reduces the tensile strain rate under the same contact explosion conditions. With the development of breach and spalling of the RC substrate, PU coating on the rear side can be divided into four zones, and the blast resistance mechanism of the coating varies in different zones. Additionally, the elastic potential energy release of the coating may produce a secondary impact on the RC substrate. Coatings are more severely damaged when contact explosives are placed in locations that avoid rebars and should be considered as the most unfavorable load for the retrofitting of RC structures.

Orientation-dependent dynamic shearing properties and underlying failure mechanisms of laser powder bed fusion of CoCrFeNi high-entropy alloy

In order to study the influence of building orientation on the dynamic shearing properties and failure mechanism of laser powder bed fusion (LPBF) of CoCrFeNi high-entropy alloy (HEA) under impacting load, a series of high speed impact tests were systematically conducted on a split Hopkinson pressure bar (SHPB) device at different strain rates. For this purpose, flat hat-shaped samples with a preset shear region were designed. The samples HS0 and HS90 respectively possessed a shear direction parallel and perpendicular to the building orientation. The respective columnar grain orientations of HS0 and HS90 influence the synergistic interaction between dislocation slip and deformation twinning, which is reflected in the differences in mechanical properties. It was observed that HS0 had higher shear yield strength whereas HS90 exhibited better plasticity. Moreover, the two samples show different adiabatic shear sensitivities as adiabatic shear bands (ASBs) were observed when the shear strain reached ∼9.5 and 11.2, respectively. Typical dynamic responses such as adiabatic temperature rise and grain refinement took place in the shear regions. Further, the formation of ultrafine equiaxed grains may be explained using the classical rotational dynamic recrystallization (RDRX) mechanism, which can furnish a sound theoretical basis to understand the deformation behaviors and mechanisms of LPBF CoCrFeNi HEA under impact loads.

Dynamic responses and failure mechanisms of the existing tunnel under transient excavation unloading of an adjacent tunnel

Dynamic responses and failure mechanisms of the existing tunnel under transient excavation unloading of an adjacent tunnel

Insights into dynamic cracking and failure mechanisms of weakly cemented siltstone under impact loading

Soft strata composed of weakly cemented rock normally suffer from the dynamic load in underground energy mining engineering, yet there is a notable lack of research into the dynamic mechanical characteristics of such materials. In this study, the split Hopkinson pressure bar system was adopted to conduct compression tests under four different impact pressures to reveal the dynamic mechanical performances of the weakly cemented siltstone (WCS). Results showed that under different strain rates, dynamic stress-strain curves of the specimen displayed similar trends. The dynamic compressive strength, critical strain and dynamic toughness of WCS all increased as the strain rate increased, while the dynamic elastic modulus had almost no strain rate effect. Besides, combined with the high-speed camera, the dynamic failure process of WCS was analyzed, and the crack area ratio was defined to quantitatively analyze the damage evolution law of WCS under impact loading. Moreover, the dynamic failure mechanism of WCS was clarified from the microstructure level. Finally, the scaling law model for calculating the dynamic compressive strength was proposed for WCS, and the modeling results exhibited a close agreement with the test results. The research results can provide mechanical parameters and a theoretical basis for the safety assessment of weakly cemented rock strata during energy mining.

Dynamic crushing behaviors and failure of cylindrical lithium-ion batteries subjected to impact loading

The mechanical property and failure prediction play a significant role in engineering applications of lithium-ion batteries (LIBs), but with great difficulties due to their complicated internal structures. This paper mainly focused on dynamic crushing behaviors and internal failure mechanisms of cylindrical LIBs subjected to different impact loadings for the safety assessment and protection design. A series of dynamic experiments were conducted on typical 18650 LIBs using the drop weight impact test system. The force-electric-thermal responses and impact failure modes of the cells with state of charge (SOC) dependence were experimentally explored under different impactor types. The finite element (FE) model was also established to reveal the failure mechanisms of the battery under high-velocity impact, and its accuracy was validated by the comparison between the experimental and corresponding FE results. Furthermore, the dynamic failure mechanisms of cylindrical cells using the stress wave theory were also explored in this work. It was shown that except from impact velocities, there were significant effects of the SOCs and impactor types on dynamic responses and internal failure modes of LIBs. The failure displacement of the cell will decrease with the increase of impact velocity, but it was insensitive under low-velocity crushing. Based on the FE results, the relationships between failure displacement and impact velocity and impactor diameter were established under flat-end cylinder head impacting. This work can provide some references for multi-functional dynamic integrity design and safety assessment of LIBs.

Dynamic mechanical properties and failure mechanism investigation of multiscale toughened basic magnesium sulfate concrete

The dynamic impact compressive properties of a novel whisker composite material (i.e., ultra-high toughness basic magnesium sulfate cement concrete, UHTBMSC) is investigated in this study. First, X-CT and scanning electron microscopy are used to characterize the three-dimensional distribution characteristics of two types of fibers in the UHTBMSC, as well as the microstructure. Second, the Hopkinson compression bar technique is used to investigate the dynamic impact compression behavior of UHTBMSC under different strain rates. Finally, a novel 3D random packing model of steel fibers (straight and hooked) is established, and the 3D mesoscopic numerical simulation of the dynamic impact compression behavior of UHTBMSC is performed. The results show that the steel fibers are crossed and evenly distributed in the UHTBMSC matrix, whereas needle-rod-like 5–1–7 whiskers appear in large quantities in the UHTBMSC. Dynamic impact compression results show that UHTBMSC is a rate-dependent material, and a mathematical relationship between strain rate and dynamic increase factor is established for UHTBMSC materials. The numerical simulation results agree well with the test results, indicating that the newly established 3D meso-model can be used to effectively analyze the dynamic compression mechanical behavior of UHTBMSC. In addition, the results confirm that UHTBMSC exhibits excellent resistance to dynamic impact compression, which is primarily attributed to the crack inhibition effects of 5-1-7 whiskers and steel fibers, thereby effectively improving the dynamic mechanical properties of UHTBMSC.

Experimental studies and numerical analysis of the dynamic mechanical properties of concrete at low temperatures

Concrete building structures in cold regions are frequently exposed to low-temperature environments and inevitably subjected to impact loads during service. This study aimed to investigate the water–ice phase transformation process of concrete at low temperature and its response to impact loads ranging from 20 °C to −30 °C, using nuclear magnetic resonance and a split Hopkinson pressure bar. Concrete mesoscopic model, with mortar, aggregates, interfacial transition zones (ITZs), and ice particles, was developed to carry out numerical simulation. Under impact loads, the dynamic compressive strength of concrete exhibited an exponential strain rate strengthening effect, with an average increase of 18% at −30 °C compared with 20 °C. Based on the T2 spectrum, bound water in the concrete took up above 80% of the pore water, while 50% of the pore water remained unfrozen at −30 °C. The concrete was primarily damaged by compression, with a tensile damage rate of less than 10%. The damage of each phase material is sensitive to the strain rate, but not to the low-temperature. Numerical simulations of concrete mesoscopic models can be used to analyze the damage evolution and crack propagation mechanisms of concrete at low temperatures, providing a reference for understanding the dynamic failure mechanisms of composite materials.

Improved Ballistic Impact Resistance of Nanofibrillar Cellulose Films with Discontinuous Fibrous Bouligand Architecture.

Natural protective materials offer unparalleled solutions for impact-resistant material designs that are simultaneously lightweight, strong, and tough. Particularly, the Bouligand structure found in the dactyl club of mantis shrimp and the staggered structure in nacre achieve excellent mechanical strength, toughness, and impact resistance. Previous studies have shown that hybrid designs by combining different bioinspired microstructures can lead to enhanced mechanical strength and energy dissipation. Nevertheless, it remains unknown whether combining Bouligand and staggered structures in nanofibrillar cellulose (NFC) films, forming a discontinuous fibrous Bouligand (DFB) architecture, can achieve enhanced impact resistance against projectile penetration. Additionally, the failure mechanisms under such dynamic loading conditions have been minimally understood. In our study, we systematically investigate the dynamic failure mechanisms and quantify the impact resistance of NFC thin films with DFB architecture by leveraging previously developed coarse-grained models and ballistic impact molecular dynamics simulations. We find that when nanofibrils achieve a critical length and form DFB architecture, the impact resistance of NFC films outperforms the counterpart films with continuous fibrils by comparing their specific ballistic limit velocities and penetration energies. We also find that the underlying mechanisms contributing to this improvement include enhanced fibril sliding, intralayer and interlayer crack bridging, and crack twisting in the thickness direction enabled by the DFB architecture. Our results show that by combining Bouligand and staggered structures in NFC films, their potential for protective applications can be further improved. Our findings can provide practical guidelines for the design of protective films made of nanofibrils.

Dynamic mechanical properties and failure mechanism of magnesium aluminum spinel based on experiments and peridynamic simulations

Experiments and peridynamic simulations of the split-Hopkinson pressure bar (SHPB) have been conducted to investigate the dynamic mechanical behaviors of magnesium aluminate (Mg-Al) spinel. The high-speed camera and scanning electron microscopy were used to observe the failure process and the fracture surface. In our modified model, the crystal orientation and grain boundary strength were explicitly quantified, accompanied by the dual-horizon peridynamic technique, resulting in high calculation accuracy and efficiency. Then effects of the stress state and strain rate on the failure mechanism of spinel have been investigated with the damage evolution process. Micro-pores tend to be generated at the intersection of grain boundaries, while cracks will propagate along these micro-pores, leading to trans-granular and inter-granular failures. Finally, the microstructure effects on the mechanical properties of spinel have been systemically investigated. The strength and distribution of grain boundaries were found to significantly affect the strength and crack propagation of Mg-Al spinel.

Effect of fluid–structure interaction on the underwater blast response and failure of composite panels

With the increasing application of typical composite structures in ocean engineering, underwater blasts have begun to be a focus for the complexity of the fluid–structure interaction (FSI) effects. In this research, the dynamic responses and failure of composite laminated and sandwich panels subjected to an underwater blast were analyzed. The influence of the FSI on the response process and failure characteristics was studied numerically to gain insight into the dynamic failure mechanism. Different failure evolution forms were found, and each failure characteristic was closely correlated with FSI effects due to the respective mechanism. Additionally, based on Hamilton’s principle, a one-dimensional theoretical model considering the equivalent stiffness of plate as elastic foundation was established to predict the response process. Through comparison with the results obtained from similar set-up numerical model, the validity of the energy balance model is discussed. The work of this research laid a foundation for the application of composite panels in underwater protection.