Dynamic Failure Mechanism Research Articles

On the dynamic failure mechanism of Vit-1 bulk metallic glass: Coupling effects of pre-made damage and strain rate

To clarify the two distinct effects and the underlying physical mechanisms of pre-made damage on the failure strength of bulk metallic glass (BMG), i.e. strengthening or weakening, the influence of axial pre-compression on the dynamic failure of Vit-1 BMG are investigated experimentally. Quasi-static and dynamic compression tests were conducted on pre-compressed BMG specimens for a wide range of nominal strain rates between 0.001 s−1 to 6000 s−1. The focus is on the coupled effects of pre-compression and strain rate on the dynamic failure stress. Two contrasting mechanisms were identified that influence how the pre-made shear bands affect the propagation of cracks under different strain rates. It will be shown that the dynamic failure stress exhibits a transition from strengthening to knockdown with increasing strain rate; and, that the extent of these strengthening and knockdown effects depends on the pre-compression strain level. Finally, a failure model that captures the effects of both strain rate and pre-made damage is proposed.

Factual observations of dynamic bone crushing

Dynamic bone-crushing, exemplified by the pig bone rib, is characterized thermo-mechanically in relation to the bone’s microstructural characteristics. The cortical bone’s dominant role consists of shielding the trabecular component by resisting deformation, sustaining high load levels, and ultimately cracking. Here we present a qualitative factual study to show that this behavior is the absolute opposite of its quasi-static counterpart in which the trabecular bone was found to play the dominant role. Using infrared thermography, we observed for the first time a significant localized temperature rise of up to 11 degrees Celsius in both cortical and trabecular damaging regions. Such observations call for additional clinically oriented research. Such a high contrast between static and dynamic failure mechanisms was not reported previously, and it paves the way for forensic-oriented studies in which the nature of the sustained load must be determined.

Influence of relative distance between fault and tunnel on dynamic response of tunnel: An experimental and numerical investigation

The effect of earthquakes on deep tunnels near faults has always been a significant issue in underground engineering research. The presence of fault fracture zones tends to intensify the seismic response of tunnels. On the basis of the Xianglushan tunnel project, the influence of relative distance between fault and tunnel on the dynamic response of tunnel was investigated utilizing laboratory test, shaking table test, and numerical simulation. The results indicated that as the relative distance between the fault and the tunnel increased, the peak acceleration and peak strain of the tunnel first increased and then decreased. The results of numerical simulations and experimental tests demonstrated that changes in relative distance had a significant influence on the dynamic response of the tunnel. Since the Xianglushan tunnel is located near the fault, the superposition of seismic load and the residual tensile and compressive stress led to the appearance of through-type cracks, which eventually resulted in large deformation or even failure. The left arch springing and left spandrel of the tunnel closer to the fault were prone to failure first. This study provides a reference for the seismic dynamic response and failure mechanism of near-fault tunnels.

Dynamic behaviour and failure mechanism of bamboo scrimber panels under single and repeated impacts: Experimental tests

Bamboo scrimber, as a renewable and sustainable material engineered from bamboo, is inevitably subjected to impact loadings in engineering applications. To study the dynamic behaviour and failure mechanism of bamboo scrimber panels under low-velocity impact, a series of drop hammer impact tests were conducted on 36 panels. The peak force, deformation and energy absorption of bamboo scrimber panels were obtained and analysed. The influence of impact energy, impactor shape and impact angle on the dynamic behaviour of panels was quantitatively characterised. Besides, based on test observations and microscopic views, the failure mechanism of bamboo scrimber panels under different impact types was revealed, including the energy absorption mechanism through fibre fracture, fibre debonding, fibre pull-out and matrix failure. Test results showed that with increasing impact energy, the peak force of panels impacted by the spherical and flat impactors increased, while that of panels impacted by the wedge impactor did not vary significantly. The deformation and energy absorption of panels also increased with increasing impact energy. Notably, the impactor shape obviously influenced the dynamic behaviour of panels, causing a higher peak force of panels impacted by the flat impactor and a larger deformation of panels impacted by the wedge impactor. The failure mechanism of panels depended highly on the impact energy and the impactor shape. Finally, a comparative study of single versus repeated impacts revealed that the deformation of bamboo scrimber panels under repeated impacts was less than that of panels under a single impact when the same amount of energy was imposed to the panel. This study provided a basis for the use of bamboo scrimber to resist impact loadings.

Mechanical behavior of water ingress process for the locally damaged submerged floating tunnel and its interpretation: A full-length experimental study

The submerged floating tunnel (SFT) is an innovative transportation solution for traversing deep-water regions. However, local damage and subsequent water ingress pose significant threats to the structural integrity and safety of SFTs. This critical issue has been unexplored in the field. This study addresses this gap by presenting a comprehensive experimental investigation using a full-length physical model of the SFT. The dynamic response and failure mechanisms caused by water ingress within the SFT tube, influenced by various factors such as immersion depth, damaged opening angle, damaged opening area, and external connectivity, are systematically investigated. The results indicate that the failure of the anchor cable and tube structure of the SFT progresses through three stages after water ingress occurs in the damaged SFT. It is observed that damage closer to the bottom of the tube reduces the risk of failure in the mooring system. Notably, air pressure is a critical factor influencing the water ingress into the tube body. The attenuation of cable tension and tube deformation is significantly slower when the internal air is isolated from the external environment. The proposed novel structural sealing segmental disaster prevention design scheme substantially mitigates the risk of structural damage under compromised conditions and water ingress. This study provides valuable insights into enhancing disaster prevention strategies for SFTs and advances the understanding of their mechanical behavior in response to damage and water ingress.

Damage calculation method for prestressed thin-walled aqueducts subjected to water pressure blasting

In recent years, the blast resistance of hydraulic structures under explosion loads has attracted more and more attention. The damage calculation method of prestressed aqueducts subjected to blasting load is still a complicated problem. For this purpose, the theory of computation of the water pressure blasting is introduced and the formula for calculating the charge weight of the water pressure blasting is presented. The accuracy of the Coupled Eulerian-Lagrangian (CEL) algorithm of the underwater explosion model is verified by the previous experiment. Then, a fully coupled three-dimensional numerical model of a prestressed aqueduct is established to acquire the dynamic performances and failure mechanisms of the prestressed aqueduct subjected to water pressure blasting. The influence of the prestress and pull rod on nonlinear dynamic performances and failure modes of a prestressed aqueduct subjected to water pressure blasting are discussed. Finally, based on the wave and material mechanics, a method of calculation for the prestressed aqueduct subjected to water pressure blasting is presented. The accuracy of the suggested method is validated by the damage mode of the prestressed aqueduct subjected to water pressure blasting under various TNT weights. The analysis results show that the proposed method can satisfy the relationship between the damage characteristics of the prestressed aqueduct to water pressure blasting and various TNT weights. 1.5 kg TNT is insufficient to completely shatter the prestressed aqueduct, while 3.5 kg TNT can cause a perfect crushing effect. 7.5 kg TNT will result in excessive fragmentation of the prestressed aqueduct and inefficient utilization of the explosive energy. The proposed damage calculation method can provide significant support for explosion analysis of the prestressed thin-walled aqueduct structure.

Investigation on flooding dynamic response and mitigation measure of river bridge

Flood-induced failure of river bridges is intense due to frequently extreme and undesigned precipitation for global climate change. To reveal the dynamic characteristics and failure mechanism of bridges, flooding dynamic analysis is fully investigated via fluid–structure interaction simulation and Arbitrary Lagrangian-Eulerian method. Parametric analysis of different fluids and bridge configurations and pre-ballast mitigation measure are further conducted based on a simply-supported box-girder bridge. This study reveals several significant findings: the narrow channel can accelerate downstream flood velocity of the bridge piers to over double that of the upstream flow; moreover, unsubmerged piers experience vertical downward wave force surpassing buoyancy; the box girders exhibit three flood-response states, i.e., intact, slip and collapse, dependent on the hydraulic loading and bridge resistance capacity. Maximum horizontal wave force and displacement increase exponentially with the depth of water storage. Post-slip damage, bearing stress on the wave-facing side tends towards zero, while the wave-backing side presents a twofold increase. Maximum horizontal displacement (Xmax) distinguishes the failure states, such as 0 m ≤ Xmax ≤ 0.03 m (intact), 0.03 m < Xmax ≤ 1.39 m (slip), Xmax > 1.39 m (collapse), whose relation to the maximum horizontal wave force has been proposed for design reference and the inversion analysis of the bridge force. Applying a pre-ballast equivalent to 75 % of girder weight reduces Xmax by up to 91.5 %, shifting failure from collapse to slip. These insights offer crucial guidance for enhancing bridge safety amidst escalating flood risks.

Dynamic Progressive Failure Analysis of 3D Five-directional Braided Composites under Transverse Compression Based on Macro-scale Heterogeneous Model

At present, there are few systematic researches on macro-scale heterogeneous modeling and numerical simulation of dynamic mechanical properties of 3-D braided composites. In this paper, the parametric virtual simulation model of 3D five-directional braided composites is realized in the way of “point-line-solid” based on the integrated design idea of process-structure-performance. And the impact compression numerical simulation of the material is carried out by using multi-scale analysis method. The effects of strain rate and braiding angle on transverse impact compression properties and fracture characteristics of composites is studies and verified by comparing the test results with the numerical simulation results systematically. The dynamic failure mechanism of the matrix and fiber bundles during the impact compression process is revealed. The results show that the macro-scale heterogeneous simulation model of 3D five-directional braided composites established is effective, and the numerical simulation results agree well with the test results. The matrix fracture and shear failure of fiber bundles are presented simultaneously under transverse impact compression. The failure of fiber bundles and matrix mainly concentrates on two main fracture shear planes. And the included angle between the fracture shear planes and the vertical direction is consistent with the corresponding internal braiding angle of specimens.

Dynamic splitting tensile mechanical behavior of magnesia-carbon refractories under impact loading

To enhance understanding of the dynamic tensile failure mechanism of MgO-C refractories, the Split Hopkinson Pressure Bar test combined with digital image correlation techniques were utilized. The dynamic failure behavior of specimens with different heat treatments and graphite content was investigated under various impact velocities. The MgO-C specimens exhibit severer damage and a more tortuous crack path with higher impact velocity. The SiC and forsterite phases generate during heat treatment are advantageous in inhibiting crack propagation, while the formation of oxide layer makes the material more susceptible to brittle fracture. Due to the presence of microcracks, high graphite samples lead to a reduction in tensile strength, but result in a wider fracture zone, which dissipates impact energy. Compared with the significant increase of strength under compressive impact loading, the critical tensile strain rate of MgO-C is easier to achieve after which the tensile strength decreases.

Numerical Investigation on Dynamic Response of Carbon Fiber Honeycomb Sandwich Panels Subject to Underwater Impact Load

This study investigates the dynamic response and failure mechanisms of carbon fiber honeycomb sandwich structures under underwater impact loads using finite element numerical simulation. The geometric modeling was performed using HyperMesh, and the dynamic response simulations were carried out in ABAQUS, focusing on honeycomb core configurations with varying edge lengths, heights, and gradient forms. The Hashin damage model was employed to describe the damage evolution of the composite materials. The simulation results revealed that the dynamic response was significantly influenced by the initial shock wave pressure and the geometrical parameters of the honeycomb cells. Larger cell-edge lengths and heights generally resulted in improved energy absorption and reduced rear panel displacement. Among the different configurations, interlayer gradient honeycomb structures demonstrated superior impact resistance compared to homogeneous and in-plane gradient structures, particularly under higher initial shock wave pressures. These findings contribute to optimizing the design of carbon fiber honeycomb sandwich structures for enhanced impact resistance in relevant applications.

Dynamic modeling and failure mechanism study of herringbone gear planetary transmission system for wind turbine under gear cracks

The herringbone gear planetary transmission system (HGPTS) is a common component in the gearbox of wind turbines. Studying the dynamic performance of gear systems is the key to improving their stability. To reveal the influence of cracks on the dynamic characteristics of the HGPTS, using slicing method, we explore the influence of different crack factors on the time-varying meshing stiffness (TVMS) of the system. A 55-degrees of freedom bending torsion axis pendulum dynamic model was constructed using the centralized mass parameter method; in the model, factors such as TVMS of cracks as well as receding groove and errors are considered. The Runge–Kutta method was used to solve the dynamics, and the evolution diagram of the vibration and load distribution characteristics of the system under crack changes was obtained. Vibration tests were conducted on the system studied in this work. The results show that under the influence of cracks, the TVMS of the external and internal meshing pairs of the system will decrease, and as the cracks intensify, the fluctuation of the TVMS will decrease. Cracks can lead to regular impact behavior in the system. A modulation sideband centered on the meshing frequency appears in the vibration response, and the vibration trajectory of the gears will also become disordered, at the same time, under the influence of cracks, there are significant excitation factors in the load-sharing characteristics of the system. As the cracks continue to intensify, the vibration of the system becomes increasingly evident, and the load-sharing characteristics show a trend of first decreasing and then increasing. The vibration test results are in good agreement with the theoretical predictions. The correctness of the established model is verified. The research results can provide reference for the reliability research of wind turbine HGPTS.

Dynamic tensile failure mechanism of hollow rocks: a numerical study based on AE moment tensors

Dynamic tensile failure mechanism of hollow rocks: a numerical study based on AE moment tensors

Investigation on the dynamic failure characteristics of concrete slab based on mesoscopic simulation and energy conversion analysis

In this study, Continuous Discontinuous Element Method (CDEM) was employed to analyze the failure of concrete slab under drop-hammer impact at the mesoscopic level. Initially, simulation models of the impact system were established, and concrete slab models, including three-dimensional random aggregates, were generated. Mesoscopic simulations of concrete failure were then conducted by considering different variables, such as impact energy, slab size and the number of hammerheads. Corresponding drop hammer tests were used to validate the simulation results. Furthermore, an energy conversion formula for the dynamic failure of concrete slabs was derived, and the energy conversion process within the impact system was analyzed. The study also revealed the dynamic failure mechanisms of concrete slabs under various impact conditions. The research demonstrates that the simulation results are generally consistent with the impact tests. CDEM effectively investigates the impact characteristic and the energy conversion process of concrete slab failure. Under varying impact energies, slab sizes and hammerhead numbers, distinct differences in the failure characteristics of concrete-slab structure were observed. Increased impact energy accelerates the failure of concrete slabs, whereas larger concrete slab sizes inhibit crack propagation. The number of impact heads determines the initial crack position and its propagation path within the concrete slab. Moreover, the energy conversion process of the impact system significantly influences the failure behavior of the concrete slab. The effect of slab size on the energy utilization rate is greater than those of hammerhead number and impact speed.

Mechanical response and failure mechanism of circular inclusion embedded in brittle materials under dynamic impact

Inclusions are prevalent in both natural and synthetic materials. Gaining a comprehensive understanding of their dynamic response and interaction with the surrounding matrix is essential in fundamental mechanics and engineering applications. This study aims to achieve such understanding through theoretical analysis, experimental investigations, and numerical simulations, focusing on the dynamic destruction of inclusions and the underlying mechanisms. Firstly, the circumferential, radial, and shear stresses around elastic heterogeneous inclusions were derived by the wave function expansion and Duhamel integration methods. Subsequently, a set of experiments on sandstone specimens containing three types of inclusions (plaster, epoxy resin, cement) were conducted utilizing the Split Hopkinson Pressure Bar (SHPB) system in conjunction with high-speed photography and Digital Image Correlation (DIC) techniques to obtain the surface deformation of inclusion specimens. Eventually, a series of Finite Element Method (FEM) numerical simulations adopted suitable materials were also carried out to investigate the fracture process of inclusion and matrix under dynamic impact. The results demonstrate that the stress distributions and fracture mode of matrix and inclusion are highly dependent on the physical and mechanical properties of the inclusions and the surrounding matrix, specifically, density ρ, elastic modulus E, Poisson's ratio v, and strength. With an increase in the E and v, there is a reduction in the concentration of circumferential stress, while the radial and shear stresses experience an increase. The experimental and numerical results corroborated the theoretical findings and indicated that the localized dynamic stress concentrations induced by wave scattering around the inclusions directly dominated both local and overall specimen failure. Due to the dissimilarities in elastic parameters and strength between the inclusion and the matrix, the stress state of the inclusion and the interface is not homogeneous. Under dynamic loading, the weaker inclusion experiences tensile cracking at both ends of the loading, and as the mechanical properties (ρ, E, v, and strength) of the inclusion rise, a transition from tensile- hybrid-shear failure occurs within the inclusion. The findings of this study help us understand the dynamic failure mechanisms of dissimilar inclusions in brittle material.

Influence of fissure distribution characteristics on the dynamic response of fissured Rock: Quantity and spacing

The impact test of red sandstone with different fissure distribution was carried out by Split Hopkinson Pressure Bar (SHPB). The failure process of the specimen in the time dimension was captured by high-speed camera and digital image correlation (DIC). The crushing characteristics of the specimen were discussed from the fractal dimension. Furthermore, the influence of fissure distribution characteristics (quantity and spacing of fissures) on the mechanical properties and fracture behavior of fissured red sandstone was analyzed. The experimental results show that the fissure spacing is negatively correlated with the dynamic compressive strength and peak strain of specimen, while the fissure quantity is negatively correlated with the dynamic compressive strength and positively correlated with the peak strain. Cracks are categorized into five types based on the manner of their initiation and expansion. The crack initiation and propagation are jointly affected by tensile stress and shear stress, but the tensile stress is dominant. With the increase of the fissure quantity, the failure mode changes from tensile failure to tensile-shear mixed failure. The increase of fissure spacing does not change its failure mode, but the formation mode of the main crack changes. The fractal dimension increases with the increase of the fissure quantity, and decreases with the increase of the fissure spacing, i.e., the larger the fissure quantity is, the higher the degree of fragmentation is, and the larger the fissure spacing is, the lower the degree of fragmentation is. The research results can provide a theoretical reference for the study of dynamic failure mechanism of rock mass with non-persistent discontinuities.

Towards accurate prediction of the dynamic behavior and failure mechanisms of three-dimensional braided composites: A multiscale analysis scheme

In this paper, a dynamic multiscale model is proposed for three-dimensional four-directional (3D4D) braided composites, considering the effects of strain rate and shear enhanced failure mechanism. The strain rate-dependent constitutive models are established for both resin and yarns. The accuracy of the yarn model is validated by comparing the simulated stress-strain curves with the experimental results obtained from the Split Hopkinson Pressure Bar (SHPB) tests with various strain rates. The shear enhancement coefficient of the yarn is determined from the failure envelopes with a discussion of crack propagation angles. The results show that, based on the calculated microscale properties, the mesoscale model accurately predicts both the longitudinal and transverse compressive strain-stress behavior of 3D4D braided composites at different strain rates. A comparative analysis reveals that the shear-enhanced failure model achieves a better prediction compared with other counterparts, such as Hashin-Rotem and Tsai-Wu Models. The proposed dynamic multiscale scheme for 3D braided composites is an efficient and accurate tool to characterize their multiscale features and strain rate-dependent behavior.

Dynamic responses of rubberised concrete: A study using short-length F-shape barriers subjected to pendulum impact

This study evaluates rubberised concrete barriers' dynamic responses and failure mechanisms subjected to pendulum impacts. We constructed short-length F-shaped barriers from concrete mixed with varying proportions of steel fibres (0 %, 1 % and 2 %) and recycled crumb rubber (0 %, 30 % and 60 %). These barriers were then tested under controlled pendulum impacts, where we measured their peak impact forces, displacements, and energy absorption capacities at different impact velocities. Our findings reveal that barriers with rubber displayed significantly higher energy absorption and lower peak impact forces at low velocities than standard concrete barriers. Conversely, incorporating steel fibres into rubberised concrete increased the peak impact forces and reduced displacements, indicating enhanced stiffness. The experimental data facilitated the development of a predictive equation for peak impact forces, accounting for impact velocity and material composition. This research demonstrates rubberised concrete's less hazardous failure modes and enhanced impact resistance and energy absorption capabilities when used in roadside barriers. Our findings offer valuable insights for developing safer, more resilient infrastructure and contributing to environmental sustainability by repurposing waste materials.

Experimental Study on Small-Scale Shake Table Testing of Cable-Stiffened Single-Layer Spherical Latticed Shell

The cable-stiffened single-layer latticed shell is an innovative structural design that achieves a perfect balance between lightweight and stability by combining cables and a latticed shell. However, the study on dynamic response and failure mechanism of cable-stiffened single-layer latticed shell under seismic action is still lacking. Therefore, small-scale shaking table tests of two kinds of single-layer spherical latticed shells are carried out; the dynamic response and failure mode of the two shells under sine wave earthquake are investigated by using time history analysis. The conclusions show that the introduction of the prestressed cable plays an important role in improving the seismic performance of the single-layer latticed shell, and the cable-stiffened single-layer latticed shell has better load capacity and seismic performance under earthquake action than the ordinary single-layer latticed shell structure.

Centrifuge modelling on seismic failure of MSW landfills with high water level

Landfill failure threatens the safety of surrounding cities and causes soil and water pollution. High water levels can usually spur landfill failure. With the presence of earthquake, landfill instability is triggered in a greater possibility. However, the dynamic response and failure mechanism of landfills with high water level subjected to earthquakes are not yet clearly understood, and relevant experimental studies are quite scarce. This study includes a series of seismic centrifuge tests to investigate the seismic response of the landfill at different water levels. An improved method is proposed to prepare synthetic municipal solid wastes (MSWs) with similar static-dynamic properties to the actual MSWs. The failure and evolution mechanism of landfills with high water levels induced by the earthquake is revealed. Significant transitions are observed in the dynamic response of deformation, acceleration, and pore-water pressure as the water level changes. With the rise of water level, the settlement at the top of the landfill decreases first and then increases, while the horizontal displacement at the toe increases slowly, followed by a sudden drop; the acceleration amplification coefficient in the middle of the landfill increases first and then decreases; the dynamic pore-water pressure gradually decreases from positive to negative, but oscillates at the moderate water level. Three failure criteria and a hydro-earthquake coupled failure limit are proposed to demonstrate the combined effect of water level and earthquake on landfill stability. The test results provide a basis to establish seismic failure standards for landfills with different water levels and guide the seismic instability design of landfills with high water level.

Dynamic mechanical properties and failure mechanisms of rock-like materials containing main and auxiliary holes with various arrangement inclinations and spacing ratios

As a typical rock defect, circular holes significantly influence rock masses, diversifying their failure modes and ultimately weakening their bearing capacities. To study the effects of hole arrangement inclination and spacing ratio on the mechanical properties and failure mechanisms of rock-like specimens, dynamic uniaxial compressive tests were conducted by employing a modified split Hopkinson bar apparatus and digital image correlation. The results reveal a V-shaped trend in the peak stress, Young’s modulus, and absorbed energy proportion as the hole arrangement inclination increases from 0° to 90°. However, the peak strain is insensitive to changes in the hole arrangement inclination and spacing ratio. The hole spacing ratio has no significant effect on the Young’s modulus, but it causes a gradual reduction in the proportion of energy absorbed in the specimens. Moreover, shear and tensile cracks emanating from the main hole dominate the failure mode of specimens with main and auxiliary holes, as demonstrated by the resultant displacement and vertical strain contours. Rock bridges experience shear failure as the hole arrangement inclination increases from 15° to 75°, whereas the rock bridges of specimens with various hole spacing ratios tend to fail owing to tensile cracks. The interaction between main and auxiliary holes with an arrangement inclination of 0° is the weakest, suggesting that tunnel groups should be arranged perpendicularly to the direction of dynamic loading.