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With the production activities continue progressing into deeper underground spaces, the rising ground stress poses new challenges in the fracturing of hard rock. Previous research mostly focused on the outer actions of blasting on conventional rock mass, while research on the inner actions of blasting via discrete element method (DEM) is relatively scarce, especially for deep-buried hard rocks under high ground stress. Relying on the pre-cracking project of hard rock protective layer in the thousand-meter deep well of Pingdingshan coal mine, this paper aims to numerically investigate the fracture mechanism of deep-buried hard rock under blasting loads via DEM. To this end, the algorithm of simulating explosion load is improved. The improved algorithm ensures a more reliable correspondence between numerical results and engineering practice, significantly enhancing the accuracy and credibility of calculations. After the calibration of mesoscopic parameters on the basis of laboratory tests, a series of parametric study, including confining pressure, peak blast stress and lateral stress coefficient, have been performed to understand the effects of in-situ stress on the behaviors of rock blasting. The obtained numerical results exhibit that confining pressure inhibits the fracture growth: under low confining pressure, confining pressure mainly inhibits the development of fractures in sparsely fractured zone while the crack growth in densely fractured zone and crushed zone is also inhibited under high confining pressure. According to the stress state, hoop peak stress is more sensitive to confining pressure than radial peak stress. Rock breakage in the vicinity of blasthole is essentially controlled by the radial peak stress, while crack propagation in the far-field is mainly induced by the hoop peak stress. With different lateral stress coefficients, the failure characteristics of rock mass are principally related to the hoop stresses in the vertical direction. The obtained numerical results and mesoscopic analysis are capable of providing new insights into the fracturing mechanism of deep-buried hard rock.

An experimental investigation was conducted to study the fretting wear behavior of low alloyed construction steel in the tempered fully martensitic state. The resulting damage mechanism and the resistance to fretting wear of martensitic steels subjected to different tempering temperature was evaluated and compared with the virgin (un-tempered) martensitic steel under the different loading conditions. The results show that the friction coefficient increases with the increase of the tempering temperature for all the applied loads. The fretting wear resistance mainly depends on the tempering temperature. Compared to the virgin (un-tempered) full martensite, most of the tempered martensites have better fretting wear resistance, in which the tempered martensitic (TM) steel of $200^{\circ }$ due to a good balance of strength and ductility has a super fretting wear resistance for all loading conditions. In addition, the correlation of fretting wear resistance with the initial hardness was discussed.

Conventionally, reliability prediction of electronic components is carried out using standard handbooks such as MIL STD 217 plus, Telcordia, etc. But these methods fail to provide a realistic estimate of reliability for upcoming technologies. Currently, electronic reliability prediction is moving towards applying the Physics of Failure approach which considers information on process, technology, fabrication techniques, materials used, etc. Industries employ different technologies like CMOS, BJT and BICMOS for various applications. The possibility of chance of failure at interdependencies of materials, processes, and characteristics under operating conditions is the major concern which affects the performance of the devices. They are characterized by several failure mechanisms at various stages such as wafer level, interconnection, etc. For this, the dominant failure mechanisms and stress parameters needs to be identified.

Optocouplers are used in input protection of several instrumentation systems providing safety under over-stress conditions. Hence, there is a need to study the reliability and safety aspects of optocouplers. Design of experiments is an efficient and prominent methodology for finding the reliability of the item, as the experiment provides a proof for the hypothesis under consideration. One of the important techniques involved is Taguchi method which is employed for finding the prominent failure mechanisms in semiconductor devices. By physics of failure approach, the factors that are affecting the performance on both environmental and electrical parameters with stress levels for optocouplers are identified. By constructing a 2-stage Taguchi array with these parameters where output parameters decides the effect of top two dominant failure mechanisms and their extent of chance of failure can be predicted. This analysis helps us in making the appropriate modifications considering both the failure mechanisms for the reliability growth of these devices. This paper highlights the application of design of experiments for finding the dominant failure mechanisms towards using physics of failure approach in electronic reliability prediction of optocouplers for application of instrumentation.

This paper presents a series of pseudo-dynamic tests (PDTs) and quasi-static tests (QSTs) on a dual wing-walled frame system, represented here by a 1/7-scaled composite moment frame with steel reinforced concrete (SRC) columns and reinforced concrete (RC) wing walls. Special characteristics of this scaled system are irregular story layout, strong-beam weak-column mechanism and large axial load. A series of scaled El-Centro (NS) waves were used as the input ground motion for the PDTs, the results of which showed that the seismic behavior was significantly improved by the RC wing walls. With the strong-beam weak-column connections, severe damages sustained by the longitudinal wing walls (LWW) prevented the potential collapse of column, and the transverse wing wall (TWW) efficiently avoided the fragile shear failure of short columns and panel zone of beam-column joints. The failure mechanisms were identified indicating that wing walls improved the ductility for the bare frame. This study provides a solid experimental support on the evaluation of seismic behavior of irregular SRC frames with RC wing walls, which could be applied in the main factory buildings of thermal power plants (TPP).

The dynamic failure behavior of double-layer-domes subjected to impact is studied numerically through the nonlinear finite element software LS-DYNA. The parameters considered in this work include the mass, velocity, and size of impactor, impact direction, roof weigh, geometric imperfection, rise-to-span ratio, and depth of dome. The dynamic time-history response and energy conversion of the structure are utilized to distinguish between the failure mechanism types. For the cases studied, it is found that failure of the structures falls into one of the three categories: (1) local shear failure, (2) partial progressive failure, and (3) full progressive failure. Non-failure case dominates the dome response when the kinetic energy of the impactor is small enough, and the structure can convert most of the kinetic energy into the strain energy, thereby absorbing the impact. Local shear failure occurs in a double-layer-dome when an impactor with very high kinetic energy strikes the dome. For an impactor striking with a mass of 5 to 300ton and a velocity of 50 to 120m/s, the double-layer-dome studied will suffer from partial progressive failure. Varying mass and velocity of the impactor in the range of 1 to 300ton and 200 to 400m/s, respectively, results in a tendency of the dome to exhibit local shear failure. Although impact direction does not cause a change in the failure mechanism type, there is a reduction in the severity of failure of the system as the impact angle increases. Roof weight has no dominant effect on the failure mechanism of the double-layer-dome. A small initial member imperfection with amplitude 0.001$L$ does not change the progressive failure type. A large member imperfection of 0.01$L$ triggers member buckling and leads to local shear failure of the dome. Except for some loading cases, the change in the rise to span ratio and depth of the dome does not seriously affect the failure mode.

A series of bridge overturning accidents in recent years indicates that single-column pier bridges are susceptible to overturning failure. However, the traditional calculation method was incapable of ensuring an accurate prediction of the ultimate overturning capacity, which may lead to serious consequences in engineering practice. In this work, an analytical method was proposed based on the identified failure mechanisms. The forensic survey was first carried out on two typical overturning cases, and the findings of the surveys were summarized into three typical overturning failure modes and their corresponding criterion for failure evaluation. Further, the analytical method was proposed on the assumption that overturning of the girder consists of rigid and deformable body rotation and characters including radial bending and torsional deformation were considered. The method was later validated by the field data of the overturning cases. Besides, factors influencing the results were also compared and analyzed. The results demonstrate that, in comparison with the conventional calculation method, the proposed approach more effectively accounts for spatial parameter variations and nonlinear factors during girder rotation, thereby aligning better with the actual overturning process.

This paper presents an investigation of the possibility of improving the fatigue properties of an epoxy resin through dispersion of modified layered silicates within the polymer matrix. Montmorillonite-epoxy nancocomposites were successfully synthesized with a commercially available 1-Methylimidazole curing agent. The morphology of these materials was investigated by XRD and TEM. The findings demonstrated a pattern of clay morphology typically found in nanocomposite systems. Four point loading measurements showed an increase in modulus for 2.5 wt% and 10 wt% clay contents when compared to the unfilled epoxy, whereas the moduli showed a decrease for 5 wt% and 7.5 wt% clay contents. This behavior is typical for most particulate-filled systems. Fracture surfaces were examined using an E-SEM. The failure mechanism of the nanocomposites varied from that of the unfilled epoxy. Below a critical strain amplitude, the fatigue life of the filled epoxy improved significantly compared to that of the unfilled epoxy. In conclusions, the addition of silicates changes the fatigue failure mechanism and improves significantly the fatigue life.

We propose a novel computational model for the high fidelity prediction of failure mechanisms in brittle polycrystalline materials. A three-dimensional finite element model of the polycrystalline structure is reconstructed to explicitly account for the micro-features such as grain sizes, grain orientations, and grain boundary misorientations. Grain boundaries are explicitly represented by a thin layer of elements with non-zero misorientation angles. In addition, the Eigen-fracture algorithm is employed to predict the crack nucleation and propagation in the grain structure. In the framework of variational fracture mechanics, an equivalent energy release rate is defined at each finite element to evaluate the local failure state by comparing to the critical energy release rate, which varies at the grain boundaries and the interior of grains. Moreover, constitutive models are considered as functions of the local microstructure features. As a result, a direct mesoscale simulation model is developed to resolve the anisotropic response, intergranular and transgranular fractures during the microstructure evolution of brittle materials under general loading conditions. A micromechanics-based interpretation for the rate dependent strength of brittle materials is derived and verified in examples of dynamic compression tests. In specific, the compressive dynamic response of hexagonal SiC with equiaxed grain structures is studied under different strain rates.

The compaction of a package of monosized spherical solid grains by rate-independent plasticity deformation is examined in this paper through the use of both yield design homogenization method and finite element simulation. Both modes of compaction, isostatic and closed die, are considered. In this study, the arrangement of powder consists of hexagonal array of identical spherical grains touching each other in its initial state. During the compaction process the response of the powder compacts is monitored in terms of behaviors of appropriate representative unit cells subject to axisymmetrical loading conditions. The kinematic approach of the yield design homogenization method has been used to determine external estimates of macroscopic strength criteria of powders at various stages of compaction. The obtained upper bound estimates are based on consideration of discontinuous incompressible velocity fields satisfying conditions of homogeneous strain rate. The shapes and sizes of the macroscopic yield surfaces are determined at various stages of compaction and it has been found that they depend upon the loading history as well as the relative density of the compact. Finite element simulations similar to those of Ogbonna N. and Fleck N. A. [1995] "Compaction of an array of spherical particles," Acta Metall. Mater.43(2), 603–620. have also been performed in order to (i) obtain the deformation modes as well as the evolution of the deformation mechanism of the powder compact during the whole process of compaction; (ii) derive the evolution of contact sizes between adjacent grains; (iii) examine the dependence of the macroscopic yield surface upon the degree of compaction, using the "yield probing technique" Gurson, A. L. and Yuan, D. W. [1995] A Material Model for a Ceramic Powder Based on Ultrasound, TRS Bend Bar, and Axisymmetric Triaxial Compression Test Results (ASME, New York), pp. 57–68, and (iv) validate, to some extent, the results provided by the kinematic approach.

Being widely used in engineering, the optimization of sandwich beams to achieve greater stiffness-to-weight ratio is of great research interest. In this paper, the optimization process was carried to obtain minimum weight designs in three-point bending based on prescribed stiffness index. Results indicate that honeycomb-cored sandwich beams possess smaller minimum weight index in comparison with metal foam-cored beams. In addition, failure mechanisms of the optimized designs were also investigated to reveal that the sandwich-cored beams were more prone to face wrinkling than metal foam-cored beams. In the optimization process, five different core topologies and four different parent materials were investigated under a given load index. It was found for low prescribed load values where bending is dominant, unidirectional lattice composite sandwich beams bear loads more efficiently than steel cored beams. However, the primary mode of failure for high prescribed load index is core shear, thus implying no significant advantage in lattice composite sandwich beams over other materials. Comparing the different materials, that laminate lattice composite sandwich beams possess the best bending performance for varying levels of prescribed load index, making it suitable for applications in the aerospace field.

By taking building structures as systems, the difference between the safety margins of a structure and that of its element is clarified and the robustness of the structure to resist unexpected disasters is discussed. The system concept is further used to introduce the concepts of importance levels and functionality levels in structural systems, the designability of structural systems is then pointed out. The local and global failure mechanisms of building structures under earthquake are summarized, and the failure mechanism control method is discussed based on the concepts of system and designability. For global failure mechanism, the desirable seismic performance is put forward, and at last some practical methods to control the seismic failure mechanism and the failure procedures are proposed based on the hierarchy concept of the structural system.

The large-scale construction of underground structures prompts researchers and engineers to reconsider seismic safety of existing and new underground structures against future strong earthquakes. This paper attempts to assess the current state-of-the-art in experimental and analytical researches on large-scale urban underground buildings. Three key issues, which need to be urgently resolved in numerical computation, are also discussed. Finally, necessity and applicability of damage control techniques are explored. The techniques, which are proved to be effective in surface buildings, are expected to update seismic performances of underground structures.

There are three major fault zones in Turkey scattered around the country known as East Anatolian Fault (EAF), North Anatolian Fault (NAF) and Anatolian-Aegean Subduction Zone (AASZ). Last two decades, EAF has been rather quiescent compared with NAF. However, this quiescence was broken in the beginning of the millennium. The strong shaking was started in 2003 with Bingöl earthquake (Mw = 6.3) and the last earthquake on the EAF is the Sivrice-Elazığ (Mw = 6.8) on January 24, 2020. Strong seismicity of these faults damaged the structures severely and caused death of the habitants. This study aims to present, seismotectonic of the region, general characteristics of the earthquakes and more specifically to report structural damage of infill walls of the structure’s damages caused by these earthquakes. Damage evaluation and identification of the observed infill wall damages due to 2003 Bingöl, 2011 Van earthquakes and January 24, 2020 Sivrice-Elazığ earthquake occurred Turkey’s Eastern region, were presented, and possible solutions were suggested. Moreover, the effects of the infill walls on the behavior of structures under static and dynamic load cases are discussed that experienced in these earthquakes. Damages are classified according to formations such as in-plane or out-of-plane, evaluations and the results obtained from the discussions are presented for each category.

All-solid-state Li-ion batteries (ASSLiBs) are considered as promising next-generation energy storage devices, and the one that is based on oxide ceramic solid-state electrolyte (SSE) has attracted much attention for its high safety and stability in ambient conduction compared with that of used sulfur and polymer SSEs. However, the undeformable nature of the ceramic SSEs brings new issues such as poor interface bonding, limited contact area and limited cathode utilization for the ASSLiBs. In addition, the interface reaction and resistance are also obstacles for ASSLiBs application. In this review, we focus on the synthesis and electrochemical properties, interface modification and failure mechanism of ASSLiBs. Finally, perspectives of future researches on the ceramic SSEs-based ASSLiBs are discussed.

Most widely used dielectrics for MLCC are based on BaTiO₃ composition which inevitably shows performance degradation during the application due to the migration of oxygen vacancies ($V_{\mathrm{o}}^{\cdot \cdot }$). Here, the BaTiO₃, (${\text{Ba}}_{0.97}$${\text{Ca}}_{0.03}$)TiO₃, Ba(${\text{Ti}}_{0.98}$${\text{Mg}}_{0.02}$)O₃, (${\text{Ba}}_{0.97}$${\text{Ca}}_{0.03}$)(${\text{Ti}}_{0.98}$${\text{Mg}}_{0.02}$)O₃, (${\text{Ba}}_{0.96}$${\text{Ca}}_{0.03}$${\text{Dy}}_{0.01}$)(${\text{Ti}}_{0.98}$${\text{Mg}}_{0.02}$)O₃ ceramics (denoted as BT, BCT, BTM, BCTM and BCDTM, respectively) were prepared by a solid-state reaction method. The core-shell structured grains ($\sim$200 nm) featured with 10-20 nm wide shell were observed and contributed to the relatively flat dielectric constant-temperature spectra of BTM, BCTM and BCDTM ceramics. The TSDC study found that the single/ mix doping of Ca${}^{2+}$, especially the Mg${}^{2+}$, Mg${}^{2+}$/Ca${}^{2+}$ and Mg${}^{2+}$/Ca${}^{2+}$/Dy${}^{3+}$ could limit the emergence of $V_{\mathrm{o}}^{\cdot \cdot }$ during the sintering and suppress its long-range migration under the electric-field. Because of this, the highly accelerated lifetimes of the ceramics were increased and the value of BCDTM is 377 times higher than that of BT ceramics. The $p-n$ junction model was built to explain the correlation mechanism between the long-range migration of $V_{\mathrm{o}}^{\cdot \cdot }$ and the significantly increased leakage current of BT-based dielectrics in the late stage of HALT.

As motors used for automobiles use battery-stored electricity, most motors are of the small-sized DC variety, of which typical failures are primarily classified into brush wear, coil burn-out, and bearing damage. From such failures, it is required to understand the failure mechanism due to the brush wear as it relates to the life of DC motors, as a result of the wearing defects. As the lifespan of DC motors is strongly associated with brush wear and as the effect factors of brush wear relate to several mixed actions, it is necessary to conduct research on the analysis of the effects of such wear processes. This study aims to analyze the main effect factors emerging from a brush wear test of the blower motor, a representative DC motor used in automobiles. The main effect factors of brush wear are associated with both mechanical wear and electrical wear. For examples, there are voltage, current, rotation speed, spring load, and temperature effects on the operational and environmental conditions. This study was intended to examine the effects of these major factors on brush wear through a brush-wearing test for each factor. With an adequate analysis of these effects, the extracted acceleration factors for DC motors may be applied to the development of an accelerated life test method for DC motors.

Ground fissures have a huge impact on the safety of engineering structures. Based on weakly active and relative stable ground fissure, a building striding over ground fissure in Xi’an was researched. From the cause and distribution of ground fissure, failure mechanism, destroy mode and preventive countermeasures were studied. Finite element software SAP2000 was used to research the structure by linear static and nonlinear static analysis. Initial displacement which imitated the value of ground fissure activity was applied to the structure, and quantitative analysis was conducted in adverse effect of ground fissure activity on the structure. Critical location of the structure, the time, position and amount of plastic hinges were studied. Based on the analysis results, preventive countermeasures were proposed.