Failure Propagation Research Articles

Strength and cracking resistance of concrete containing different percentages and sizes of recycled tire rubber granules

In order to use recycled materials in the composition of greener and cleaner concrete products, it is vital to ensure that the produced concrete have the appropriate level of strength. This paper investigates the effect of gradation (size) and percentage of recycled rubber granules on the physical parameters (slump and density), strength parameters (tensile and compressive strength values), and in particular the crack initiation and propagation characteristics (under the opening, shearing, and tearing modes). The tensile strength, compressive strength, fracture toughness (KIc, KIIc, and KIIIc), and fracture energy values at the initial crack initiation and ultimate failure propagation stages were determined by testing specimens containing 0, 1, 2, 4, and 12% of fine and coarse recycled rubber granules. Rubber particles were graded in two distinct ways so that they could serve as both filler and granules. In contrast to fine rubber granules, the addition of coarse granules had a positive effect on mode-II and mode-III fracture toughness. But, the addition of fine and coarse rubber granules reduces mode I fracture toughness. The analysis of fracture values indicates that coarse rubber granules have a positive effect on the post-peak failure energy absorption (i.e., the crack propagation stage) of all fracture modes. However, this increase in fracture energy for the fine rubber combination was only observed for mode-II fracture stress. The fracture toughness and fracture energy values of the similar concrete were empirically determined based on their corresponding tensile strength. The link between fracture toughness and fracture energy values was also discovered. According to the experimental results, the concrete containing 4% coarse rubber granules provides good mechanical and cracking resistance properties.

Robustness of networks with dependency groups considering fluctuating loads and recovery behaviors

Dependency groups describe different characteristics of interactions among nodes, which provide an emerging way to explore the dynamical behaviors of complex networks. To study the effects of dependency groups on the robustness of flow networks, this paper proposes a cascading failure model of networks which combines fluctuating loads and dependency groups. Different from the previous hypothesis that the dependency group is completely invalid once one node in the same dependency group fails, in this paper, the failure and recovery mechanism of dependency groups under certain rules to prevent catastrophic collapses of networks is proposed. To describe the resistance of network to damage caused by cascading failures, we introduce the overload coefficient to characterize the overload state when the node handles excess loads. Considering the network cost should be controlled within a reasonable range while improving network robustness, the cost index based on the relationship between the load and capacity of the node is established. By theoretically analyzing the network cost, the relationship between the network robustness and network cost is discussed when the network cascading process happens. The proposed model is employed to study the dynamics of cascading failures evolution in BA network, ER network and two actual networks. Simulation results reveal the effects of traffic flows and dependency groups on the dynamic loads propagation of cascading failures.

Non-conventional failures caused by the edge effect in cross-ply laminates made of ultra-thin plies

In a fatigue testing programme of carbon/epoxy cross-ply laminates made of ultra-thin plies, non-conventional failures are observed. These non-conventional failures consist in longitudinal cracks in the 90° layer parallel to the loading direction instead of the conventional transverse cracks in the 90° layer perpendicular to the load direction. A potential reason for this failure is the presence of a normal stress in the thickness direction. Classical Lamination Theory predicts zero values for this stress component under longitudinal loading, but the presence of a free-edge alters the stress state. The so-called “edge-effect” has been widely studied in the past, but the presence of ultra-thin plies introduces new lower limits of the thickness of the 90° layer. Additionally, the presence of a stress singularity, in the bimaterial corner generated by the 0° and 90° plies, is also investigated to check its influence on the stress state due to the low thickness values of the 90° layer. A slight geometrical modification is conceived to remove the stress singularity, isolating its effect from the pure edge effect. Numerical simulations of the stress alteration in the free edge of the samples, due to mechanical and thermal loading, are carried out, and stress distributions are numerically computed, depending on the 90° layer thickness. Detailed failure inspection by 3D tomography is also done to assess the through-the-width propagation of the non-conventional failures from the free edge. Numerical predictions and experimental 3D X-ray inspections seem to corroborate that the edge effect is responsible for these non-conventional failures.

Fracture toughness of bio-fiber reinforced polymer composites- a review

The growing green and ecological awareness has motivated researchers to develop new innovative composite materials using bio-fiber. Bio-fiber composites are well known for their higher specific and impact strength at a lower weight as compared to conventional materials. Currently, researchers are interested in finding the crack growth rate, life-limiting factor, and delamination failures for various bio-fiber reinforced polymer composites. However, it helps to reduce the crack propagation and catastrophic failure of the material. The review also focuses on the fracture toughness properties of different bio-fiber reinforced Polymer composites This paper also highlights the effects of different bio-fibers and matrix on fracture toughness and possible techniques to improve fracture toughness. A brief overview of the fracture toughness of bio-fiber polymer reinforced composites is provided, which may provide insights into interlaminar strength and fracture behaviour of bio-fiber reinforced composites. Finally, the review concluded that the future direction of bio-composites in various dynamic applications has been discussed in this article. This review can help researchers and engineers design and develop bio-composite materials for dynamic applications.

Double side friction stir welding effect on mechanical properties and corrosion rate of aluminum alloy AA6061

Friction Stir Welding (FSW) is a solid-state welding method that has diffusion and different metal structures can blend well. Friction stir welding (FSW) has a weakness, one of which is the lack of flexibility the welding process is only carried out on one side of the plate being welded, so it is not applied on thick materials. Double side friction stir welding is a double working process in which the plate to be welded is subjected to friction from two tools on opposite sides. In the DS-FSW welding process, the dimensions and geometry of the tool and pin greatly affect the quality of the joint. This study to determine the mechanical properties and corrosion rate of Double side friction stir welding aluminum 6061 with variation rotation speed and axis of top and bottom tools. The results of this radiographic test can be seen that specimen 4 welded with variations in speed and tool position has defects in the form of incomplete fusion (IF). The results of microstructural observations showed that the heat caused by the welding process resulted in recrystallization in the form of fine grains in the stirring area and there was no phase change. The highest hardness value in the welding area is specimen B. The largest bending value at the 1G welding positions is specimen D, which is 41.86 MPa with a strain value of 13.23%, while the smallest value at the 4G welding position is specimen A, which is 38.18 MPa with a strain value of 5.03%. The fracture and crack surfaces showed that crack initiation, propagation and material stirring failure occurred in all test specimens, even though the impact test specimen was cut in a small area of Incomplete Fusion, but the test results showed that there was still a surface of the parent metal that had not been stirred. The corrosion test method uses three electrode cells with corrosion media as a substitute for seawater with a salinity of 3.5% NaCl, result of corrosion test is specimen B at the 1G welding position has the highest corrosion rate value of 0.63856 mm/year and specimen An at the 1G welding position has the lowest corrosion rate of 0.058567 mm/year.

Interface constitutive modeling and failure propagation mechanisms of integrated polymer-metal hybrid (PMH) structures

Interface constitutive modeling and failure propagation mechanisms of integrated polymer-metal hybrid (PMH) structures

A Method for Variance-Based Sensitivity Analysis of Cascading Failures

Cascading failures of relay operations in power systems are inherently linked with the propagation of wide-area power system blackouts. In this paper, we consider a power system cascading failure as an indicator matrix encoding: what power system relays operated within a cascading failure inherently capturing the component and the sequence of tripping events. We propose that this matrix may then be used with extended forms of variance-based sensitivity estimators to quantitatively rank how sensitive observed power system cascading failures are to power system variables, considering overall system cascading failures as well as cascading failures grouped by network area and relay types. We demonstrate our proposed method by investigating the sensitivity of cascading failures to relay parameters, system conditions, and fault location using a version of the IEEE 39 bus model modified to include protection relays, wind farms, and tap-changing transformers. Input power system variables included: system operational scenario, disturbance location, relay parameters or thresholds. The Case Studies' results confirm the method's utility by successfully generating relative rankings of input variables' importance with respect to cascading failure propagation. The results also show cascading failures' sensitivity to input variables to be high due to non-linear relationships between input variables and cascading failures.

Slope Reliability Analysis in Locating and Observing the Direction of Failure Propagation

Slope stability analysis is traditionally carried out with the ultimate equilibrium methods. In these approaches, the global assessment of slope stability is obtained through the evaluation of the factor of safety. The strength parameters that allow the evaluation of resistant forces along the hypothetical slip surface are considered unique and constant. The shape of the stress-strain curve of the soil may substantially affect the stability of the soil mass over, particularly in the case of the potential of a progressive failure. As a part of this work, the influence of uncertainties on the peak and post-peak strength parameters and the impact of a progressive failure on the failure probability of a hypothetical slip surface are discussed. The conventional method of Morgenstern-Price of slope stability analysis consisted of locating the critical slip surface by evaluating the minimum factor of safety. The probability of failure was estimated using three different techniques, i.e. FORM, FOSM, and Monte Carlo simulation. This study improved the assessment of the impact of progressive failure on the risk of slope failure. The reliability analysis of slices allowed for locating the failure area and observing the direction of failure propagation.

Modeling failure propagation to analyze the vulnerability of the complex electromechanical systems under network attacks

Since the complex electromechanical system (CMES) is a complex integration of multiple minimum maintenance units (MMUs), a single faulty MMU can trigger multi-step failures and eventually damage a substantial portion of the CMES. To investigate the failure propagation process and analyze the impact of the CMES under MMU attacks, we first abstract the system as a directed network composed of MMUs, machine-electricity-information connections, and functional properties. Subsequently, a fault propagation model is constructed based on the fault occurrence probability and matrix transformation, which considers the topological and functional attributes of the system. Then, we build the attack graphs to evaluate the faulty edges on the system’s vulnerability and propose some vulnerable indices based on the node attack strategies to quantify the attack impact of the malfunctioning nodes on the CMES network. Finally, a bogie system of the high-speed train is selected as a case study to verify the validity of the proposed method. Based on the findings, we can clarify the failure propagation behavior and quantify the impact of the faulty nodes and edges on the CMES network. Furthermore, the critical connections and nodes that significantly impact system vulnerability can be identified. Hence, our work can provide guiding significance for developing maintenance strategies to reduce losses and optimize the management scheme.

Room- and High-Temperature Fatigue Strength of the T5 and Rapid T6 Heat-Treated AlSi10Mg Alloy Produced by Laser-Based Powder Bed Fusion

The AlSi10Mg alloy produced by laser-based powder bed fusion (L-PBF) is widely used to produce high-value-added structural parts subjected to cyclic mechanical loads at high temperatures. The paper aims to widen the knowledge of the room- and high-temperature (200 °C) fatigue behavior of the L-PBF AlSi10Mg alloy by analyzing the fully reversed rotating bending test results on mechanically polished specimens. Two heat-treated conditions are analyzed: T5 (direct artificial aging: 4 h at 160 °C) and novel T6R (rapid solution: 10 min at 510 °C, artificial aging: 6 h at 160 °C). The study highlights that (i) the T6R alloy is characterized by higher fatigue strength at room (108 MPa) and high temperatures (92 MPa) than the T5 alloy (92 and 78 MPa, respectively); (ii) thermal exposure at 200 °C up to 17 h does not introduce macroscopical microstructural variation; (iii) fracture surfaces of the room- and high-temperature-tested specimens show comparable crack initiation, mostly from sub-superficial gas and keyhole pores, and failure propagation mechanisms. In conclusion, the L-PBF AlSi10Mg alloy offers good cyclic mechanical performances under various operating conditions, especially for the T6R alloy, and could be considered for structural components operating at temperatures up to 200 °C.

Effects of Retained Austenite and Softened Martensite on High‐Cycle Fatigue Behavior of Spring Steel under Two Loading Modes

A novel quenching‐partitioning‐tempering (Q‐P‐T) process is applied to 60Si2Mn spring steel, resulting in multiphase microstructures consisting mainly of retained austenite (RA) and softened martensite (SFM). The influence of multiphase microstructures on the high‐cycle fatigue behavior of Q‐P‐T and traditional quenching and tempering (Q&T) spring steels are investigated under rotating–bending and tension–tension loading. The results indicate that the fatigue strength of Q‐P‐T spring steel with RA, SFM, and lower quenching stress increases by 23.9 and 14.4% under cyclic rotating–bending and tension–tension loadings, respectively, compared with that of Q&T spring steel. Under both loading modes, the fatigue crack of the Q‐P‐T spring steel is mainly initiated from the interface between the martensitic matrix and inclusions or carbides. In contrast, the fatigue crack of the Q&T spring steel is mainly initiated from the plastic area around the martensitic matrix rather than inclusions. The RA, SFM, and lower quenching stress of the Q‐P‐T spring steel are conducive to the formation of dimples and tear ridges in the crack propagation and ultimate failure areas, whereas the inadequate SFM and higher quenching stress of the Q&T spring steel are prone to the formation of quasi‐cleavage facets and secondary cracks.

Experimental and modeling characterization of nickel–manganese–cobalt (532) lithium ion battery arrays with thermal separators

Lithium-ion (Li-ion) cells are increasingly used in large format batteries for high energy and power applications, such as grid-scale energy load leveling and uninterruptible power supplies (UPS). While Li-ion energy storage systems (ESS) are nominally safe, abnormal conditions can occur which may result in a catastrophic failure known as thermal runaway (TR). TR is characterized by internal, exothermic chemical reactions outpacing external cooling, and results in cell temperatures of ∼1000 °C and flammable, toxic reaction product gas venting. This can lead to cell-to-cell failure propagation and ultimately a total ESS failure. Destructive testing experiments were conducted with arrays of lithium–nickel–manganese–cobalt-oxide (NMC) 532 Li-ion, pouch-format cells with varying thermal separators between cells. Using this experimental data, a low-order computational model for predicting TR propagation with thermal separators between cells was created, calibrated, and validated. The effect of thermal separators is discussed from experimental and computational results, along with discussion on the non-trivial calibration process required for the model. Once calibrated, decision makers can use the computational model to predict TR propagation, evaluate numerous thermal separator designs’ performance, and ultimately reduce the amount of experimental data necessary in the design process.

Investigation of the microstructure, corrosion resistance and hardness of bone particle reinforced cast iron for engine blocks application in automotive and marine industries

This paper aims to examine the microstructure, corrosion resistance and hardness of bone particles reinforced cast iron for advanced applications in marine and automotive industries, especially for the fabrication of engine blocks. In most marine and automobile industries, cast irons remain the major material used for the manufacture of engine components such as flywheels, piston rings, cylinder heads and engine blocks. Nevertheless, several categories of cast iron possess poor impact strength, low corrosion resistance, easy crack propagation and brittle failure over time. As a result of these challenges, cast iron scraps melted and reinforced with particles from goat bone. Samples of reinforced and unreinforced cast iron were produced. The microstructure of the samples was studied using SEM/EDS (scanning electron microscope equipped with energy dispersive spectroscope) and XRD (X-ray diffractometer), while the corrosion rate of the samples was studied using potentiodynamic polarization technique following ASTM G102 standard and using 3.65% NaCl solution as the corrosive medium. The SEM micrographs indicated that the goat bone particle (GBP) reinforced cast iron possessed more refined microstructure, smoother morphology and microstructural homogeneity. For the unreinforced cast iron sample (control), the corrosion rate (Cr) and Brinell hardness of 1.427 ​mm year−1 and 275.3 HBN, respectively. On the other hand, the goat bone particle (GBP) reinforced cast iron samples possessed a Cr and hardness ranging from 0.510 to 1.006 ​mm year−1 and 288.9–297.4 HBN, respectively. These results indicated that the goat particle reinforced cast iron sample (control) possessed higher passivation and superior indentation resistance relative to the unreinforced cast iron sample.

Crack propagation law of rock with single fissure based on PFC2D

In the study of pre-fabricated single-fissured rock, the failure mode, mechanical properties and propagation law of rock are affected by the length and inclination angle of fissure. In this study, artificially prepared marble-like rocks with different fissure characteristics were used as rock representatives, using PFC2D software to establish a uniaxial compression model tests for rocks with fissures. The effects of different fissure lengths and inclination angles on the failure mode and crack initiation and propagation of rock-like structures were systematically studied, revealing the mechanism of macroscopic mechanical behavior of rocks containing single fissures in the process of crack initiation, propagation, and failure at the micro-level. The results show that: 1) Failure mode of the rock sample is mainly controlled by fissure inclination angle and fragmentation degree is mainly controlled by fissure length. 2) The initiation stress, damage stress, and peak stress of rock samples during loading deformation increase with the increase of fissure inclination angle, and decrease with the increase of fissure length. The crack initiation angle decreases with the increase of the fissure inclination angle. 3) Crack initiation characteristics: at a low fissure inclination angle (α< 45°), the crack initiation position has a certain offset to the center of the prefabricated fissure, or starts from the tip of the prefabricated fissure. At high fissure inclination angles (α≥45°), the crack initiates from the tip of the prefabricated fissure and forms a “dispersed” distribution. 4) The crack propagation law is mainly shear cracks, at a low fissure inclination angle (α< 45°), the crack propagation has obvious aggregation band formation. At high fissure inclination angles (α≥45°), the crack aggregation zone gradually weakened and expanded in the direction of dispersion.

Multifactor-Influenced Reliability-Constrained Reserve Expansion of Integrated Electricity-Gas Systems Considering Failure Propagation

Multifactor-Influenced Reliability-Constrained Reserve Expansion of Integrated Electricity-Gas Systems Considering Failure Propagation

ANALYTICAL MODEL FOR COMPOSITE TRANSVERSE STRENGTH BASED ON COMPUTATIONAL MICROMECHANICS

The transverse strength of fiber-reinforced composites is a matrix-dominated property whose accurate prediction is crucial to designing and optimizing efficient, lightweight structures. State-of-the-art analytical models for composite strength predictions do not account for fiber distribution, orientation, and curing-induced residual stress that greatly influence damage initiation and failure propagation at the microscale. This work presents a novel methodology to develop an analytical solution for transverse composite strength based on computational micromechanics that enables the modeling of stress concentration due to representative volume elements (RVE) morphology and residual stress. Finite element simulations are used to model statistical samples of composite microstructures, generate stress-strain curves, and correlate statistical descriptors of the microscale to stress concentration factors to predict transverse strength as a function of fiber volume fraction. Tensile tests of thin plies validated this approach for carbon- and glass-reinforced composites showing promise to obtain a generalized analytical model for transverse composite strength prediction.

Numerical modelling technique for rock mass in underground coal mine by using grain-based model

The stability of rock mass around longwall or excavation in underground coal mine is a prerequisite for the safe and continuous coal production. In practice, instability incidents commonly occur at longwall face or longwall roof that causes serious occupational injury or even death. Current research on the instability has not sufficiently interpreted the formation and propagation of rock mass failure, mostly due to the discontinuous, anisotropic, inhomogeneous and non-elastic nature of rock mass. To assist interpretation of the above stability behaviour, this paper presents a study to improve the numerical modelling technique of rock mass around longwall by using Grain-Based Model. The modelling technique uses Discrete Element Methods and the grain structure Voronoi. A procedure for calibrating rock properties in modelling technique is proposed and validated through application for field rock mass at Ha Lam coal mine, Quang Ninh province, Vietnam. The paper also presents a technique for selecting grain size and monitoring the modelling efficiently. The proposed procedure along with the modelling code are useful for investigation of rock mass around underground excavations from which technical solutions for safe and continuous production can be established.

Use of automated tools for analyzing the propagation of failures in aircraft system

One of the problems of modern aviation is the saturation of software equipment and electronics. Safety Architect is an automated tool for reliability analysis using functional flow architectural models. This article introduces Safety Architect technology for building fault propagation models and a fault tree. After the analysis, conclusions were drawn about the flaws of this tool: the failure propagation model is built only on the basis of the architectural model of functional flows without taking into account the various operating modes of the system and the transitions between them. The basic principles for developing a new failure propagation model were derived.

The study of diffuse interface propagation of dynamic failure in advanced ceramics using the phase-field approach

Dynamic failure in advanced ceramic materials is a complex mechanical phenomenon, which is challenging to study in experimental and computational works. This work models and investigates the crack initiation, growth, propagation, and branching in two-dimensional single crystalline boron carbide at the nanometer length-scale and picosecond time-scale. A phase-field approach is used by carefully selecting the interfacial energy allowing a monolithic numerical solution method capturing strong coupling between mechanics and damage. Specifically, the transient Ginzburg–Landau equation is coupled with the balance of momentum including geometric nonlinearities and solved by using the open-source computing platform FEniCS. The monolithic computation ensures necessary accuracy for dynamic fracture under pure mode I loading, and also demonstrates the capability of crack branching depending on the loading rate. The effect of crack regularization length and kinetic coefficient on the crack interface profile and crack tip velocity is also studied. Altogether, the results are important for modeling anisotropic fracture in advanced ceramics and designing materials with desired dynamic failure characteristics.

Depinning transition of travelling waves for particle chains

In this paper we apply Aubry–Mather theory for equilibria of 1D Hamiltonian lattice systems and the theory of invariant ordered circles to investigate the depinning transition of travelling waves for particle chains. Assume A < B are two critical values such that the particle chain has three homogeneous equilibria if the driving force . It is already known that there exist transition thresholds of the driving force such that the particle chain has stationary fronts but no travelling fronts for and travelling fronts but no stationary fronts if or . The novelty of our approach is that we prove the transition threshold () coincides with the upper (lower) limit of the upper (lower) depinning force as the rotation number tends to zero from the right. Based on this conclusion, we demonstrate that when the driving force , besides stationary fronts there are various kinds of equilibria with rotation numbers close to zero such that the spatial shift map has positive topological entropy on the set of equilibria. Furthermore, we give a necessary and sufficient condition for the absence of propagation failure, i.e. , in terms of a minimal foliation. Finally we show that are continuous with respect to potential functions in C 1 topology.