Failure Mechanism Analysis Research Articles

Analysis of the Support Failure Mechanism Caused by Bolt Pre-Tightening Force Loss

The pre-tightening force loss (PTFL) of bolts is an important but underestimated cause of roadway instability. In mine anchorage systems, the actual pre-tightening force of bolts is only 50% to 80% of the design value. Through a case study at Xiahuo Coal Mine, it was found that the essential causes of PTFL are the increasing friction coefficient between supporting units controlled by factors such as pre-tightening torque levels, pre-tightening cycles, and surrounding rock roughness. This study investigates the behavioral characteristics of PTFL and its influence on surrounding rock failure in roadways. This research reveals a linear correlation between pre-tightening force and torque, with an average torque conversion coefficient of approximately 0.19. However, the PTFL increases with higher levels of pre-tightening torque, increasing pre-tightening cycles, and rougher surrounding rock conditions. For every 30 N·m increase in pre-tightening torque, the PTFL increases by approximately 1.67 kN. Reducing the PTFL can expedite the stress redistribution process and shorten the self-stabilizing period of the roadway by approximately 10 days, thereby enhancing the active supporting potential of bolts.

Unified Models for Bond Strength and Bond-Slip Response of Deformed Rebars in Cracked Concrete

Cracks in reinforced concrete structures pose a potential risk to their long-term stability and safety, necessitating an accurate analysis of the bond failure mechanism between the reinforcement and the cracked concrete. However, currently, there is a lack of comprehensive bond prediction models for the entire cracking stage, and limited understanding of the bond slip response. To address the aforementioned issues, an improved model incorporating internal pressure, crack width, and failure modes, aiming to provide a more precise estimation of the bond strength between deformed bars embedded in concrete under various cracked cases. The proposed model demonstrates superior performance in predicting cracked cases and failure modes. The performance of the proposed model in predicting cracked cases and failure modes is superior to existing models, as demonstrated by a comparative analysis. Additionally, a comprehensive model is proposed to analyze the bond-slip behavior in cracked concrete. This model introduces a bond reduction factor for cracks, aiming to determine the critical bond length required for bond strength.

Mechanical properties and failure analysis of PLA/copper composites fabricated by fused deposition modelling

The Fused Deposition Modelling process is an additive manufacturing process that is influenced by numerous parameters that affect the strength of the components. This paper article is dedicated to the study of the effects of Fused Deposition Modelling parameters on the strength of PLA/Copper infill composites. The influence on tensile, impact and flexural strength was investigated by varying the process parameters. The printer properties, i.e. the Nozzle Temperature and Printing speed, and the processing parameters, i.e. the Layer Thickness and the density of the infill are the most important parameters considered in this study. Mathematical models were developed to predict the strength of the composites as the process parameters were varied. The strength of the composites decreased with increasing layer thickness and printing speed. On the other hand, in the strength of the composites increased when the nozzle temperature and the density of the infill were increased. The composite samples were subjected to failure analysis to determine the fracture mechanisms. Both brittle and ductile failure mechanisms were observed in the samples, which are influenced by the process parameters affecting the layered composite and porosity.

Analysis of Failure Mechanism of Reverse Leakage Current in GaN-based Micro-LEDs

Analysis of Failure Mechanism of Reverse Leakage Current in GaN-based Micro-LEDs

Investigation on the failure mechanism of a tunnel entrance high-steep slope with ultra-large wedge blocks based on discrete element method

An unstable wedge block with a volume of approximately 1,200,000 m3, intersected by an anti-dipped large fault and two outward-dipped faults, has been identified on the high-steep slope at the entrance of the tunnel spillway of the Shuangjiangkou hydropower station in China, a region characterized by high tectonic stresses. In this study, kinematic analysis was first conducted to preliminarily assess the possibility of block sliding, and then a three-dimensional discrete element code (3DEC) was utilized to analyze the mechanism of block instability during sequential excavation and reinforcement. The results showed that block sliding is caused by continuous excavation and deterioration of the mechanical properties of the bottom sliding surface. The failure behavior of the slope is primarily governed by the wedge block, which slides along the intersection line of two outward-dipped faults. After the excavation of Layers 1–4, the shear displacements of the faults exhibited accelerated and abrupt characteristics. Finally, the pretension cable proved effective in restraining block sliding, increasing the factor of safety for the slope from 1.16 to 1.28 after complete excavation and reinforcement. This study offers significant insights into the analysis of failure mechanisms in similar engineering challenges.

A novel method for competitive failure behavior and mechanical degradation online monitoring of laser additive work roll under multidimensional damage

A novel test apparatus was designed and constructed to investigate the competitive failure and mechanical degradation online monitoring of laser additive remanufacturing work roll under multidimensional damage. Furthermore, a formula was established to calculate the equivalent test parameters for simulating real hot rolling load. The present study investigated the characteristic damage morphologies such as oxidation, wear and thermal fatigue that occurred in the remanufacturing work roll under varying temperatures. In addition, a thorough analysis of the competitive failure mechanism was also conducted. Based on the magnetic softening phenomenon due to decomposition of carbide and the precipitation of carbon during the degradation of high speed steel (HSS) cladding layer, a non-contact method for assessing the performance degradation of remanufacturing work rolls was developed using pulsed eddy current (PEC). The low frequency increment in the Hilbert marginal spectrum of PEC exhibited a negative linear correlation with the decrease in microhardness of the HSS cladding layer, which allowed for a quantitative evaluation of mechanical performance changes in remanufacturing work rolls.

Failure Mechanism Analysis of the Stochastic Galerkin Method in EMC Simulation Considering Geometric Randomness

By virtue of its high calculational accuracy and efficiency, the stochastic Galerkin method (SGM) has been successfully applied many times in electromagnetic compatibility (EMC) simulation in recent years. This paper proposes a calculating example taking geometric uncertainty factors into consideration. As is proved in the paper, there is a relatively large error when using the SGM to solve the example mentioned above. According to failure mechanism, the fundamental reason of the failure of the simulation lies in the additional error caused by using numerical integration to solve the inner product formula. Meanwhile, it is proved that no additional errors are introduced when using the stochastic collocation method (SCM), so the SCM is better than the SGM in stability. In the end, the paper revised the general selective strategy for uncertainty analysis methods, thus providing theoretical basis for their universal application in EMC field.

Performance of round-ended CFST columns under combined actions of eccentric compression and impact loads

Round-ended concrete-filled steel tubular (RECFST) columns are gaining increasing usage in bridge structures. During their service life, RECFST columns under eccentric compression may suffer from impact loading. This study conducted test and numerical investigations to assess the performance of RECFST columns under the coupled actions of compression, bending and lateral impact loads. Fourteen columns were fabricated and tested, considering the influences of axial-load ratio, bending moment and impact energy. The damage mode and the time histories of impact force and displacement were accessed and analyzed. The experimental findings revealed that the initial bending moment negatively affected the impact resistance of RECFSTs. In addition, finite element model was established in ABAQUS and calibrated against the test results. The calibrated model was then employed to conduct the failure mechanism analysis and parametric study. Finally, a single-degree-of-freedom (SDOF) analysis was conducted to predict the mid-height deflection of RECFST columns under combined action of compression, bending and lateral impact loads, by incorporating the influences of pre-axial load and initial bending moment.

Strength Formation and Failure Mechanism Analysis of Cement-Stabilized Laterite Granules Based on Numerical Simulation

The poor grading and significant differences in the mechanical properties of laterite granules in West Africa limit the application of this typical material in road structures. In this paper, the poorly graded laterite granule was blended with fine sand and stabilized with cement to improve the strength of laterite granules. An innovative combination of laboratory tests and numerical simulation analysis using the numerical simulation software PFC2D 5.0 was used to investigate the cement-stabilized laterite granule’s strength formation and failure mechanisms. Laboratory test results show that when the sand content is 40%, the grading curve is close to the maximum theoretical density lines (MTDLs), and the unconfined compressive strength of cement-stabilized laterite granules increased by 35.2% as the cement dosage increased from 2.5% to 5.0%. Numerical simulation tests show that the strength failure of cement-stabilized laterite granules is shear. The failure surface is tilted and through with the axial direction, and the compressive and tensile stresses between the particles cause the failure of the specimen. The simulation test results are close to the laboratory test results, and the deviation rate is less than 10%. It can guide the optimal grading design and strength prediction of cement-stabilized laterite granular materials and provides a basis for reducing laboratory tests and accurate design for such research in the future.

Multi-scale analysis of corrosion-induced fracture failure mechanisms of high-strength steel wire

Currently, research on the mechanical properties of corroded steel wire is primarily conducted through corrosion testing, with a lack of in-depth theoretical investigations into the underlying mechanisms. Addressing this research gap, this study employs molecular dynamics (MD) and finite element theory to explore the corrosion process, micro- and macro-mechanical properties of corroded steel wire, and the fracture mechanisms after corrosion. The study achieves a coupling of micro- and macro-scale analyses. Firstly, a molecular dynamics model is established based on the chemical composition of high-strength steel wire, and a novel mixed potential function derived from quantum mechanics is employed to analyze the fracture mechanisms of corroded steel wire. Secondly, a simplified model of randomly corroded pits in steel wire is developed using Python in Abaqus, based on experimental measurements. Finally, the macroscopic fracture process and fracture strength of corroded steel wire are analyzed based on the results from molecular dynamics simulations. These results are then compared to experimental data to validate the accuracy of the theoretical analysis.

Step-like displacement prediction and failure mechanism analysis of slow-moving reservoir landslide

Landslides triggered by extreme rainfall due to global climate change are becoming more frequent. The Earth surface processes activity and landform evolution caused by landslide movement seriously affect human survival and the environment. In recent years, the reservoir slope located in the Three Gorges reservoir (TGR) area has been subject to the combined effects of extreme rainfall and reservoir regulation, which have been highly susceptible to inducing landslides. Reservoir landslides usually show step-like slow movement characteristics. The causes of slow-moving landslides are complex, the mechanisms behind them are difficult to grasp, and it may evolve into violent landslide disasters. Therefore, accurately predicting step-like displacement in slow-moving landslides is an effective solution for risk reduction. To achieve the accurate prediction of the step-like displacement of slow-moving landslides and the analysis of the failure mechanism, this study establishes a prediction model applicable to step-like displacement prediction of slow-moving reservoir landslides is developed based on 16 years of continuously monitored cumulative displacement of the Jiuxianping landslide, combined with the Empirical Mode Decomposition (EMD) method and the Improved Particle Swarm Optimization (IPSO) optimized the Long short-term memory (LSTM) neural network. This approach can effectively improve step-like displacement prediction accuracy. In particular, this approach can better represent the association between the step displacement of slow-moving landslides with environmental characteristics (e.g., rainfall, reservoir level). The study reveals that there are differences in the mechanisms and influencing conditions that cause the deformation of different areas of the landslide. Additionally, the reservoir water level fluctuation and seasonal rainfall are identified as the primary reasons contributing to the stepped displacement of the Jiuxianping landslide. The method provides a basis for the step-like displacement prediction, instability mechanism and landform evolution study of slow-moving reservoir landslides and provides valuable guidance for the prevention and control of similar reservoir geomorphic hazards worldwide.

Analysis of Blocking Capability Failure Mechanism in IGBT Module Under High Salt Spray Environment

High salt spray environment is a threat to the long-term stability and the robustness of an insulated gate bipolar transistor (IGBT) module. Failure mechanisms of IGBTs have been discussed in normal and high humidity environment, which in high salt spray environment is unclear and seldom reported. In this paper, experiments in high salt spray environment are conducted on wire-bonding IGBT modules to reveal failure mechanism. Different degradations of the blocking capability are observed for the same packaged IGBTs in the salt spray environment. Based on experiment results, degradation substances in the internal package are analyzed by means of scanning electron microscope (SEM) and X-ray diffraction (XRD) to reveal the key composition affecting the blocking capability of IGBT switches. Finally, a failure model is used to reveal the mechanism that the insulation strength of the terminal area in the chip edge is reduced by substances, resulting in the blocking failure of IGBT switches. The analysis of IGBT module failure mechanism is of great significance to reliability evaluation and optimal design for package structures of power modules applied in harsh environments.

Pilot study on high-resolution radiological methods for the analysis of cerebrospinal fluid (CSF) shunt valves

ObjectivesDespite their life-saving capabilities, cerebrospinal fluid (CSF) shunts exhibit high failure rates, with a large fraction of failures attributed to the regulating valve. Due to a lack of methods for the detailed analysis of valve malfunctions, failure mechanisms are not well understood, and valves often have to be surgically explanted on the mere suspicion of malfunction.The presented pilot study aims to demonstrate radiological methods for comprehensive analysis of CSF shunt valves, considering both the potential for failure analysis in design optimization, and for future clinical in-vivo application to reduce the number of required shunt revision surgeries. The proposed method could also be utilized to develop and support in situ repair methods (e.g. by lysis or ultrasound) of malfunctioning CSF shunt valves. Materials and methodsThe primary methods described are contrast-enhanced radiographic time series of CSF shunt valves, taken in a favorable projection geometry at low radiation dose, and the machine-learning-based diagnosis of CSF shunt valve obstructions. Complimentarily, we investigate CT-based methods capable of providing accurate ground truth for the training of such diagnostic tools. Using simulated test and training data, the performance of the machine-learning diagnostics in identifying and localizing obstructions within a shunt valve is evaluated regarding per-pixel sensitivity and specificity, the Dice similarity coefficient, and the false positive rate in the case of obstruction free test samples. ResultsContrast enhanced subtraction radiography allows high-resolution, time-resolved, low-dose analysis of fluid transport in CSF shunt valves. Complementarily, photon-counting micro-CT allows to investigate valve obstruction mechanisms in detail, and to generate valid ground truth for machine learning-based diagnostics.Machine-learning-based detection of valve obstructions in simulated radiographies shows promising results, with a per-pixel sensitivity >70%, per-pixel specificity >90%, a median Dice coefficient >0.8 and <10% false positives at a detection threshold of 0.5. ConclusionsThis ex-vivo study demonstrates obstruction detection in cerebro-spinal fluid shunt valves, combining radiological methods with machine learning under conditions compatible to future in-vivo application.Results indicate that high-resolution contrast-enhanced subtraction radiography, possibly including time-series data, combined with machine-learning image analysis, has the potential to strongly improve the diagnostics of CSF shunt valve failures. The presented method is in principle suitable for in-vivo application, considering both measurement geometry and radiological dose. Further research is needed to validate these results on real-world data and to refine the employed methods.In combination, the presented methods enable comprehensive analysis of valve failure mechanisms, paving the way for improved product development and clinical diagnostics of CSF shunt valves.

Failure Mechanism and Precursor Analysis of Foam Concrete Subgrade with Different Densities Based on Acoustic Emission Data

Failure Mechanism and Precursor Analysis of Foam Concrete Subgrade with Different Densities Based on Acoustic Emission Data

Failure mechanism analysis and mass movement assessment of a post‑earthquake high slope

Failure mechanism analysis and mass movement assessment of a post‑earthquake high slope

Failure Mechanism Analysis of Titanium Anode for Electrolytic Copper Foils

Failure Mechanism Analysis of Titanium Anode for Electrolytic Copper Foils

Failure process and mechanism analysis of rock slope induced by underground mining: a case study in Yanqianshan open-pit mine, China

Failure process and mechanism analysis of rock slope induced by underground mining: a case study in Yanqianshan open-pit mine, China

Experimental study and failure mechanism analysis at the meso-scale of the fatigue performance of a CFRP tendon novel composite anchorage

This paper investigates the fatigue performance of CFRP tendon novel composite anchorages. The fatigue mode of the novel composite anchorage was analysed. Furthermore, based on the meso-morphology of the contact surface between tendons and epoxy resin, the fatigue mechanism of composite anchorage was explored. Finally, the effects of fatigue cyclic load on the slippage of tendons at both free end and loaded ends and clamps, the barrel strain and the stiffness of CFRP tendons were investigated. Results revealed that the novel composite anchorage can subject 2 million fatigue cycles load under 0.45 fu fatigue maximum stress and 200 MPa stress range. The failure modes of FS-2, FS-3 and FTD-1 specimens with fatigue failure were the damage of the contact surface between the tendons and the epoxy resin, which leads to the tendons slip out from the epoxy resin. Furthermore, the fatigue performance of the three-tendon specimens with dispersed anchoring was worse than that of the anchorage with parallel anchoring. Steel barrels and clamps can work effectively in all specimens, but the tendons stiffness increases slightly initially and then decreases rapidly. In summary, the novel composite anchorage has good fatigue performance and the potential for practical application.

Probabilistic-based burst failure mechanism analysis and risk assessment of pipelines with random non-uniform corrosion defects, considering the interacting effects

Corrosion defects were primary causes for pipeline burst failures. Traditional methodologies simplified the realistic irregular-shaped defects as uniform ones, ignoring the effects of random morphologies on failure behaviours, which caused deviations in remaining strength pb estimation and reliability analysis. Addressing this issue, through coupling random field, non-linear finite element analysis and Monte-Carlo Simulation, an integrated methodology was developed to describe failure behaviours of pipelines with random defects. The failure mechanism and reliability analysis were performed. The pbs for random defects exhibited significant variabilities, of which the probability distribution patterns altered with different corrosion depths attributed to multiple failure modes. The main value of pb for random defects was lower than that of uniform defects, especially for deeper corrosion and interacting defects. At maximum, this reduction attained over 28%; The spatial variation gradient of remaining wall thickness dominated failure developments, based on which three failure modes were revealed; The wall thickness, corrosion degree and interacting effects were influential on failure probabilities Pfs. An average failure risk of Pf over 0.6 would be suffered for employing traditional methodologies. Polynomial chaos expansion models were fitted to estimate pb from corrosion morphologies, showing reasonable accuracies. Besides, the performance variations with different cases were discussed.

Mechanical Performance and Failure Analysis of a 3D-Printed "Continuous Layer-Lattice Layer-Continuous Layer" Sandwich Structure.

Sandwich structures are engineered with continuous layers surrounding the inner lattices, which combines the advantages of the high strength of the continuous layer and the light weight of the lattice layer. They are widely employed in weight-critical energy-absorbing engineering fields such as aerospace, automobile, and robotics. However, the application of sandwich structures made of polymer matrix composites is still limited due to lack of essential performance investigation and adequate reference data. The following innovative works are accomplished in this paper: (i) Continuous long glass fiber (CGF) is employed within the continuous layer of the sandwich structure, with composite short carbon fiber/polyamide (SCF/N) applied within the lattice layer. (ii) Sandwich structures with different cell types and orientations of the lattice infills are designed and prepared by additive manufacturing. (iii) The basic mechanical properties of the sandwich structures, i.e., the bi-directional tension/compression compound performance, failure modes and mechanisms in characteristic directions, are analyzed systematically. (iv) The effects of geometric features on the three-point bending properties of L-shaped sandwich structures are investigated and compared with those of pure SCF/N structures. The results show that the bending resistance per unit weight was up to 54.3% larger than that of pure SCF/N, while the weight could be decreased by 49%, and the bending flexibility before fracture could be increased by 44%. These studies contribute fundamental research data to the application of sandwich structures prepared by fiber reinforced polymer matrix composites.