Failure Mechanism Analysis Research Articles

Experimental study and theoretic analysis of shear failure mechanism for short precast bridge columns with grouted splice sleeve (GSS) connectors under direct shear load

Precast bridge structures have been increasingly applied in recent civil engineering applications, which shortens construction time, lowers cost, improves structure quality, decreases traffic interruption, and reduces environment pollution. However, studies regarding to the shear behavior of short precast columns are limited. In this study, five short precast bridge columns, with span-to-depth ratio of 0.43, are tested under direct shear load. This is to understand shear failure mechanism of precast bridge columns with different design details. Two types of shear failure are found due to different embedment location of grouted splice sleeve (GSS) connectors. Different design details (e.g. steel grade of rebar, bonding material of joint interface, and existence of shear keys) also have certain impact on the shear strength of precast columns. Based on the test results, a new theoretic method is proposed to estimate shear strength of tested precast column specimens. The proposed method incorporates possible influencing factors of shear strength along with different failure stages and types. The parameters and formulas are calibrated and adjusted accordingly. It is found that, for short precast columns with GSS connectors, the theoretic solutions are within 5% in difference compared with test results, which shows better accuracy than other methods. This indicates that the proposed method is effective for the estimation of shear strength in this case.

Numerical analysis of deformation and failure mechanism of metal truss structure of spacecraft under re-entry aerothermodynamic environment

A coupled aerodynamic-thermoelastic analysis framework is presented to simulate the deformation and failure mechanism of metal truss structure for spacecraft under re-entry aerothermodynamic environment. The three-dimensional dynamic thermo-mechanical coupling finite element algorithm is developed by computable modeling of thermoelasticity and heat conduction equations to solve the thermo-mechanical coupling response of spacecraft structure. The aerodynamic boundary conditions such as temperature, heat flux and pressure distribution are computed and provided by the gas-kinetic unified algorithm (GKUA) based on the Boltzmann model equation. The linear interpolation method is designed and employed to couple the boundary conditions between the external aerodynamic flow field and the solid structure interface. The present thermo-mechanical coupling algorithm is verified on one-dimensional and two-dimensional transient heat flow problems with analytical solutions, and good consistency is achieved. The reliability of the GKUA for solving the boundary conditions of the external flow field and the dynamic thermo-mechanical coupling algorithm for the thermal response behavior of the internal structure material is verified by the consistency calculation of the internal and external temperature distribution. Then, the aerodynamic-thermoelastic analysis framework is further applied to study the deformation behavior of structural thermo-mechanical responses and failure mechanism of a hollow sphere under re-entry aerothermodynamic environment with emphasis placed on the influence of flight speeds, rarefied effects, algorithm schemes and damping effects. The numerical results obtained by the presented algorithm including the internal temperature, thermal stress and deformation distribution law are compared and analyzed. Finally, the deformation and failure mechanism of spacecraft structure during re-entry process are solved and analyzed by the present algorithm framework. The displacement, temperature and stress distribution contours of the structure are presented to make a preliminary understanding and evaluation on the process of spacecraft deformation and failure disintegration. It is indicated that the present coupled aerodynamic-thermoelastic analysis framework can provide a reliable, applicable and efficient platform for the thermo-mechanical coupling responses and failure mechanism of re-entry spacecraft in the end of life.

An experimental study on the mechanical performance of BFRP-Al adhesive joints subjected to salt solutions at elevated temperature

In order to study the mechanical properties of basalt fiber reinforced resin polymers–aluminum alloy (BFRP-Al) single lap joints (SLJ) under different humid and hot conditions. 80 °C/deionized water (DI-water), 80 °C/3.5%NaCl solution and 80 °C/5%NaCl solution were used as the aging conditions of BFRP-Al joints. Through the hygroscopic experiment, the maximum water absorption rate of dumbbell-shaped adhesive in the three environments was 7.15%, 4.12% and 4.96%, respectively. The maximum water absorption of basalt fiber reinforced resin polymers (BFRP) in the three environments was 2.24%, 1.2% and 1.55%, respectively. It is concluded that salt solution inhibits the absorption of water by adhesive and BFRP. The quasi-static tensile test of the joint was carried out. And the result shows that the failure strength of the joint in the three environments increases at first and then decreases with the prolongation of aging time. And the failure strength of the joint in the high-temperature salt solution is better than that in high-temperature DI-water. DSC experiments show that changes in glass transition temperature (T g) reflect changes in failure strength. SEM image analysis of the joint failure mechanism can show that the resin matrix damage in BFRP increases with aging time. The mechanical properties of the joint at the later stage of aging depend on the performance of BFRP.

Study on the slope dynamic stability considering the progressive failure of the slip surface under earthquake

The strength of a rock-soil mass shows complex and obvious weakening characteristics under seismic dynamic load. The previous stability analysis methods of a seismic slope do not fully depict the attenuation law of geotechnical materials and cannot truly reflect the stable state of a slope under earthquake action. Based on the theoretical analysis of the progressive failure mechanism and the evolution law of a seismic slope, the adverse effect of progressive failure on slope stability is clarified. According to the progressive failure process of a slope under dynamic load, the strain-softening model and vibration deterioration model are introduced to represent the attenuation law of rock strength parameters, and a calculation method of seismic slope stability coupled with vibration disturbance and progressive failure is proposed. The method considers the strength parameter characteristics of a rock-soil mass in different stages and is combined with the vector sum method to obtain the time-history curve of the slope safety factor under earthquake action, which makes the evaluation result of slope stability more accurate and reliable. The numerical examples show that this method can effectively reflect the dynamic stability of seismic slopes, and solve the problem that the traditional calculation methods are difficult to characterize the strength attenuation characteristics of rock and soil mass. If these characteristics are not considered, the calculation results will be unsafe.

Analysis of flexural failure mechanism of ultraviolet cured-in-place-pipe materials for buried pipelines rehabilitation based on curing temperature monitoring

Flexural properties is one of the important parameters for the evaluation of buried pipeline ultraviolet cured-in-place pipe (UV-CIPP) rehabilitation effectiveness. The flexure failure mechanism of UV-CIPP materials under the influence of different construction parameters (curing time, UV lamp irradiation intensity, curing distance, and material thickness) is unclear. In this paper, a method was proposed to approximate evaluation of the curing quality by monitoring the surface temperature of UV-CIPP material during the curing process. The flexure failure process and the causes of flexure failure of UV-CIPP materials were analyzed by considering the effects of construction parameters, combined with the monitored material surface peak temperature, and using a three-point bending test incorporating HD video and SEM observations, and sensitivity analysis of construction parameters was carried out by using random forest, and the flexural properties of UV-CIPP materials were predicted by support vector machine. The results showed that matrix cracking, debonding delamination and fiber pull-out fracture are the main reasons for the flexural failure of UV-CIPP materials. Under the influence of a single variable, the exothermic temperature of curing reaction on the surface of UV-CIPP material increases with the increase of curing time, UV lamp power and material thickness within a certain range, and decreases with the increase of curing distance. With the increase of curing time, UV lamp irradiation intensity and curing distance within a certain range, the flexural strength and flexural modulus show a trend of first increase and then decrease, but gradually decrease with the increase of material thickness. The monitoring and analysis results of the curing reaction exothermic temperature show that curing time and UV lamp irradiation intensity are still important factors affecting the curing performance of the material, and the flexural properties of the pipeline UV-CIPP material and the surface curing reaction exothermic temperature satisfy a nonlinear decreasing function relationship, and excessive curing reaction temperatures can reduce the flexural properties of UV-CIPP materials and accelerate its flexural failure.

Mechanical failure analysis during direct shear of double-joint rock mass

Mechanical failure analysis during direct shear of double-joint rock mass

Mechanical Behaviour and Failure Analysis of Glass Fibre-Reinforced Plastic Panels for a Directional Tunnel: An Underground Water Storage Device

Mechanical Behaviour and Failure Analysis of Glass Fibre-Reinforced Plastic Panels for a Directional Tunnel: An Underground Water Storage Device

Strain-rate-dependent compressive and compression-shear response of an alumina ceramic

This paper assessed the microstructure and properties of CeramTec ALOTEC 98 SB alumina ceramic through microscopic characterization and mechanical experiments. The rate-dependent strength and failure response of an alumina ceramic were studied under both uniaxial compression and compression-shear loading. Under quasi-static uniaxial compression at rates of 10−5 to 103 s−1, the strength had an average of 3393 ± 306 MPa, and at dynamic strain rates of 102 to 103 s−1, the strength ranged from 3763 to 4645 MPa. The CeramTec ALOTEC 98 SB alumina ceramic was found to have greater mechanical properties than other commercial alumina ceramics from the literature (i.e., AD-995). To monitor the strain field and the failure process of the alumina ceramic during testing, an ultra-high-speed camera coupled with digital image correlation (DIC) was used to visualize crack initiation and propagation processes, and obtain quantitative stress-strain information. A new data processing method was then proposed in this study to calculate the shear components for the compression-shear tests. Validation of the proposed method was confirmed by the shear strain obtained from the DIC analysis with the ultra-high-speed camera. Using the results obtained by the proposed model and the DIC analysis, new observations and understandings of failure mechanisms are obtained. (1) In compression-shear tests, the shear failure happens before complete failure, and shear behavior plays an important role during the failure process. (2) The equivalent peak stress (strength) of compression-shear test is smaller than the uniaxial compression one. (3) The directional cracks have weak influence on the compressive stiffness, but have a strong influence on the shear response.

Linear/Nonlinear Dynamic Analysis and Prediction of Failure Mechanism of Irgandi Bridge

The goal of this study is to investigate the behavior and failure mechanism of historical Irgandi Bridge located in Bursa City under earthquake loads by using linear and nonlinear dynamic analysis. Dynamic characteristics of the bridge is investigated by using in-situ Operational Modal Analysis (OMA) tests. The finite element model is updated according to the OMA tests. Three different artificial earthquake records from weak to very strong are applied to the model for understanding the damage zones and the failure mechanism of the historical bridge. The results show that the bridge does not reach the failure mechanism under weak earthquakes for nonlinear dynamic analysis. However, under strong earthquake even if damage zones are occurred and the stiffness of the bridge is decreased, there is no failure mechanism observed according to the nonlinear dynamic analyses. Under very strong earthquake loads the bridge reaches the failure mechanism according to the nonlinear dynamic analysis. As the earthquake level increases, the difference between linear and nonlinear dynamic analysis results increases due to structural damages. In addition, considering the soil-structure interactions, it is concluded that the dynamic characteristics could be reflected more accurately.

A Comparative Investigation of Various Binders for Silicon Anodes: Interactions with Other Components, Rheological Property, and Behavior in Operando Dilatometry

AbstractBenefitting from its outstanding advantages, silicon (Si) has been considered as one of the best candidates of anode materials for next‐generation lithium ion batteries (LIBs). Among various influencing factors on the electrochemical performance of Si anodes, binder attracts more and more attention though occupying only a small portion. Well‐designed binders play a critical role in improving cycling performance of Si anodes. Herein, sodium carboxymethyl cellulose (CMC), poly (acrylic acid) (PAA), sodium alginate (SA), polyvinylidene difluoride (PVDF), and polyacrylonitrile (PAN) are selected as binders, and their effects on the electrochemical performance are investigated. PAA, CMC, and SA form both dynamic hydrogen bonds and covalent bonds with Si while PAN and PVDF form monotonous hydrogen bonds with Si. Defects of PAA and CMC in slurry mixing and subsequent drying process originated from high modulus and poor liquidity are exposed. The binder influence on expansion/contraction behavior of silicon anodes is innovatively investigated in real time. Electrodes with PAA binder exhibit the greatest expansion but the highest reversibility, which contributes to superior electrochemical performance. This article aims to provide useful information for failure mechanism analysis of binders as well as design of advanced binders for high energy LIBs.

Failure Mechanism Analysis of Reinforced Foundation from Experimental and Numerical Simulations

Geogrid has been extensively used in engineering practice as a horizontal reinforcing material to improve the performance of foundations, embankments, and road base systems. This paper presented the results of laboratory static load tests on transparent soil foundations reinforced with biaxial polylactic acid geogrid and studied the reinforcement mechanism and foundation failure mode of the reinforced foundation. The different load settlement behaviour between reinforced foundations with different reinforcement layer numbers was studied by varying the number of geogrid layers. The deformation of reinforcements and foundation soil was recorded with an industrial camera. The strain of the reinforcements was monitored by Fiber Bragg Grating (FBG) sensors. In addition, a two-dimensional discrete element model was established based on the model tests to analyse the load transfer behaviour and deformation law of the reinforced foundation. The results indicated that geogrid can effectively improve the bearing capacity of the foundation. As the number of reinforcement layers increases, the improving effect is more significant. The reinforced soil can provide a stronger upward resistance than unreinforced soil by activating the tensile force of the geogrid. The simulation results present the load transfer behaviour and reinforcement mechanism of geogrid. With the increase of reinforcement layers, the position of the sliding surface moves downward, and the area of the sliding surface increases. Geogrid can limit soil displacement and delay the development of the sliding surface.

Terahertz probe assisted failure mechanism analysis of silver nanowire film heaters under high working power

The silver nanowire film heaters have the breakdown problem under high working power. It is related with the Rayleigh instability of the silver nanowires and with the electromigration of silver atoms under high electric field localized within nanowire diameter due to the percolation conduction of the silver nanowire films. During the instability of the two structures, the carrier is confined to the nanostructure and suffers different backscattering, which is studied by non-contact Terahertz (THz) spectroscopy. In this paper, structural collapse of heaters presented by THz spectroscopy is to be studied in depth, and the Rayleigh instability and electromigration on device failure are paid attention to by extracting the characteristic parameters of THz time domain spectroscopy and by evaluating the changing trend of the characteristic parameters during device failure. Failure mechanism of heaters under high working power is to be revealed and countermeasures are to be developed. The implementation of this project could drive forward further research on intelligent heaters, which is valuable for scientific research and industrial applications.

Mechanical Degradation and Failure Analysis of Different Glass/Basalt Hybrid Composite Configuration in Simulated Marine Condition.

This work aims to evaluate the failure mechanisms of plain glass and basalt fiber reinforced composites and a selected glass/basalt hybrid composite sequence subjected to artificial seawater conditions. Sets of plain and five hybrid composite configurations were fabricated by vacuum assisted resin injection technique (VARI), and subjected to seawater aged for 258 days at 30 °C and 70 °C followed by tensile, flexural and charpy impact testing, respectively. Failure analysis for dry and seawater-aged composites were undertaken using scanning electron microscopy (SEM). Results showed that some hybrid laminates with sandwich-like and alternating sequencing exhibited superior mechanical properties and ageing resistance than plain laminates. GB3 ([B2G2]S) type hybrid composite with basalt fiber outer plies retained 100% tensile strength and 86.6% flexural strength after ageing, which was the highest among all the laminates. However, GB4 ([BGBG]S) type specimen with alternating sequencing retained the highest residual impact strength after ageing. SEM analysis on the failed specimens showed fiber breaking, matrix cracking and debonding caused by fiber–matrix interface degradation due to seawater exposure. However different hybrid configurations to a considerable extent prevented crack propagation across specimens, hence altering the overall damage morphology among different specimens.

Failure mechanism and life estimate of metallized film capacitor under high temperature and humidity

Studying the failure mechanism of thin film capacitors is of great significance to improve the service safety and life of capacitors. In this paper, firstly, the accelerated aging test and failure mechanism analysis under conditions of high temperature and high humidity were carried out. Secondly, the life prediction models were established based on the experimental data. The results showed that at 120 °C or higher, the polypropylene (PP) film of the capacitor shrank and degraded, and the electrode was damaged. The contact with oxygen caused the electrode oxidation and the capacitor failed. Under the high humidity (>69 % relative humidity, RH) service environment, water molecules and oxygen kept intruding into the interior of the capacitor, causing electrochemical corrosion and damaging the Al Zn layer on the capacitor film. Based on the life data of test samples, the life estimate models were established and the parameter values were calculated. In the temperature failure mode, the failure activation energy Ea = 1.48 eV, and under the humidity failure mode, the humidity coefficient n = 4.

Vibration signal collection and analysis of mechanical equipment failure based on computer simulation detection

Abstract This article addresses the challenge of large error rate and low accuracy of the vibration signal collection of mechanical equipment failure, and proposes a mechanical equipment failure vibration signal collection and analysis based on computer simulation detection. Then, it uses the Kalman filter algorithm for data filtering, according to the mathematical model established by the system, thus choosing a suitable noise covariance calculation method. In the integration process after filtering, using a piecewise integration method between acceleration peaks, the integration calculation is optimized to obtain the vibration displacement. The simulation results of this article show the vibration data collected by the main controller, after Kalman filtering and piecewise trapezoidal integration method optimization. The error of the proposed method is 0.5% when the frequency is 80 Hz, relative to the displacement measurement method of the three-axis acceleration sensor at 8.3%, and the error of data calculation results is greatly reduced. The greater the amplitude of vibration, the smaller the error. This method significantly improves the accuracy of vibration signal collection of mechanical equipment.

Wear failure mechanism analysis of self-lubricating fabric composites at high temperature

The friction and wear properties of self-lubricating fabric composites were closely related to fiber properties. In this paper, polyimide (PI), polyetheretherketone (PEEK), polyisophthalamide (PMIA) and cyclic aramid (Aramid III) fibers were selected as reinforcing fibers to compare and investigate the friction and wear properties of self-lubricating fabric composites at high temperature. The tribological behavior of self-lubricating fabric composites was evaluated by ball-on-disk friction test. The wear mechanism was investigated by scanning electron microscope and mechanical test. As a result, the composite with PI as warp and weft reinforcing fiber has outstanding wear resistance because of the higher modulus of PI fiber. Its wear rate is 1.29 × 10−8 mm3/(N·mm). It shows that the stronger the rigidity of the reinforcing fiber at high temperature, the better the wear resistance of the composite. However, the friction coefficient of composites with PI as weft reinforcing fibers is about 0.8, which is much higher than that of composites with PMIA, PEEK and Aramid III as weft reinforcing fibers. Their friction coefficients are about 0.1. In addition, the self-lubricating fabric composites with different warp and weft reinforcing fibers were prepared as self-lubricating joint bearing liners to evaluate bearing applications.

Progressive Damage Behaviour Analysis and Comparison with 2D/3D Hashin Failure Models on Carbon Fibre-Reinforced Aluminium Laminates.

It is known that carbon fibre–reinforced aluminium laminate is the third generation of fibre metal materials. This study investigates the response of carbon fibre–reinforced aluminium laminates (CARALL) under tensile loading and three-point bending tests, which evaluate the damage initiation and propagation mechanism. The 2D Hashin and 3D Hashin VUMAT models are used to analyse and compare each composite layer for finite element modelling. A bilinear cohesive contact model is modelled for the interface failure, and the Johnson cook model describes the aluminium layer. The mechanical response and failure analysis of CARALL were evaluated using load versus deflection curves, and the scanning electron microscope was adopted. The results revealed that the failure modes of CARALL were mainly observed in the aluminium layer fracture, fibre pull-out, fracture, and matrix tensile fracture under tensile and flexural loading conditions. The 2D Hashin and 3D Hashin models were similar in predicting tensile properties, flexural properties, mechanical response before peak load points, and final failure modes. It is highlighted that the 3D Hashin model can accurately reveal the failure mechanism and failure propagation mechanism of CARALL.

Analysis of embankment failure mechanism in reservoirs due to rainfall infiltration during heavy rainfall

Many heavy rain disasters have occurred in recent years in Japan. The maintenance of water storage facilities such as dams has become a global issue. The aim is to simulate the failure mechanism of reservoirs in which slip failure occurred on the downstream slope of the embankment due to the heavy rainfall in August 2019 in Japan. This study proposes a simulation method for evaluating embankment stability with respect to the fluctuations in the water level and the rainfall infiltration from the embankment surface using the two-dimensional saturated–unsaturated seepage flow simulation based on the finite element method. Moreover, the safety factors of the slip surface during heavy rain were calculated based on the simulated seepage line. By considering rainfall infiltration, the safety factor of the slip surface decreased significantly, and the occurrence of slip failure in the in-situ position could be reproduced. In conclusion, rainfall infiltration must be considered when evaluating the stability of a reservoir body during heavy rainfall.

Determination of Landslide Displacement Warning Thresholds by Applying DBA-LSTM and Numerical Simulation Algorithms

Numerical simulation has emerged as a powerful technique for landslide failure mechanism analysis and accurate stability assessment. However, due to the bias of simplified numerical models and the uncertainty of geomechanical parameters, simulation results often differ greatly from the actual situation. Therefore, in order to ensure the accuracy and rationality of numerical simulation results, and to improve landslide hazard warning capability, techniques and methods such as displacement back-analysis, machine learning, and numerical simulation are combined to create a novel landslide warning method based on DBA-LSTM (displacement back-analysis based on long short-term memory networks), and a numerical simulation algorithm is proposed, i.e., the DBA-LSTM algorithm is used to invert the equivalent physical and mechanical parameters of the numerical model, and the modified numerical model is used for stability analysis and failure simulation. Taking the Shangtan landslide as an example, the deformation mechanism of the landslide was analyzed based on the field monitoring data, and subsequently, the superiority of the DBA-LSTM algorithm was verified by comparing it with DBA-BPNN (displacement back-analysis based on back-propagation neural network); finally, the stability of the landslide was analyzed and evaluated a posteriori using the warning threshold calculated by the proposed method. The analytical results show that the displacement back-analysis based on the machine learning (DBA-ML) algorithm can achieve more than 95% accuracy, and the deep learning algorithm exemplified by LSTM had higher accuracy compared to the classical BPNN algorithm, meaning that it can be used to further improve the existing intelligent inversion theory and method. The proposed method calculates the landslide’s factor of safety (FOS) before the accelerated deformation to be 1.38 and predicts that the landslide is in a metastable state after accelerated deformation rather than in failure. Compared to traditional empirical warning models, our method can avoid false warnings and can provide a new reference for research on landslide hazard warnings.

Research on Dynamic Compressive Performance and Failure Mechanism Analysis of Concrete after High Temperature and Rapid Cooling.

To investigate the dynamic compressive properties of concrete after high temperature and rapid cooling, an experimental study was carried out by considering five temperatures and four strain rates. The coupling effect of high temperature and strain rate on concrete damage morphology and mechanical parameters was comparatively analyzed. The main conclusions are as follows: the compressive damage morphology of concrete is affected by strain rate development trends of significant variability under different temperature conditions. As the strain rate increases, the compressive stress and elastic modulus of concrete are gradually increased. As the temperature increases, the increase in compressive stress is gradually reduced by the strain rate. For the temperatures of 20 °C and 800 °C, the increase in compressive stress by the strain rate is 38.69% and 7.78%, respectively. Meanwhile, SEM and CT scanning technology were applied to examine the mechanism of the effect of high temperature and strain rate on the mechanical properties of concrete from the microscopic perspective, and the corresponding constitutive model was proposed.