Actual Failure Research Articles

Research progress on the corrosion behavior of titanium alloys

Abstract Titanium and its alloys show outstanding application prospects in many industrial fields due to their high specific strength, good corrosion resistance, high temperature resistance, etc. However, at present the corrosion failure of Ti alloys is attracted great attention with gradual increasing applications. The different localized corrosion forms are introduced in this review, including galvanic corrosion, crevice corrosion, pitting corrosion, hydrogen-induced cracking, stress corrosion crack, microbiological corrosion, corrosion fatigue, and corrosion wear. Among them, the corrosion failure caused by stress corrosion crack and hydrogen-induced cracking is the most serious, accounting for about 40–60% of the actual failure accidents. The effects of temperature, pressure, corrosive media and microstructure on the failure of titanium alloys are discussed. Particularly noteworthy, F− is extremely aggressive to the passive film of titanium alloys. The corrosion behavior of titanium alloys applied in aerospace, marine, petrochemical industries and biomedical environments are introduced. In the above environments, the passive film is most easily damaged and difficult to passive in high temperature and oxygen-deficient environments. The current controversies in the corrosion mechanism have also been proposed, especially the stress corrosion that has the most serious impact on titanium alloys, and its mechanism will be the focus of future research.

Integrated waterproofing evaluation method for longitudinal joints of shield tunnel subjected to extreme surcharge: Numerical analysis and experimental validation

Sufficient waterproofing performance is critical to ensure a normal operation and safety of tunnels, and certain safety margin is essential to cope with uncertain external loads. This study proposes a novel methodology for evaluating the waterproofing performance of shield tunnels subjected to extreme surcharges, by integrating an analytic derivation, numerical analysis, and experimental validation. First, the analytical derivations of stresses at longitudinal joints and a finite element (FE) model for calculating the internal forces of tunnel linings under external loads are established; these are subsequently combined to compute the gasket deformation. Then, the stress–deformation curve of the gasket is fitted by a material-scale FE model to evaluate the contact stress against the underground water pressure. Finally, the methodology is validated via measurements from a full-scale experiment. The results help establish that the presumptions derived from the proposed method are consistent with the experimental results. It is also anticipated that the waterproofing performance would reach the actual failure point at the approximate 4–7 m depth of the equivalent dumped soil, which is remarkably consistent with the on-site observations in the Shanghai Metro tunnel. This study provides an efficient and economical method in terms of engineering applications, with emphasis on the importance of structural analysis in the waterproofing evaluation.

Multiple Instance Learning With Random Forest for Event Logs Analysis and Predictive Maintenance in Ship Electric Propulsion System

In this article, a novel weakly supervised machine learning approach is proposed for intelligent predictive maintenance (IPdM). It employs balanced random forest and multiple instance learning based on event logs from ships’ electric propulsion systems. The objectives are predicting failure likelihood, time to failure, and explainable predictions to ensure timely crew intervention. The IPdM approach uncovers, then learns, and classifies <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sequences of</i> events that represent early causes or symptoms to forecast imminent failures. In particular, this article contributes effective solutions to irregular, imbalanced, and unlabeled data issues where conventional methods become obsolete. First, the events occur at irregular intervals; they include alarms, warnings, and operational information collected across multiple units and control systems. Second, the datasets exhibit extreme imbalance due to few failures and multiple failure modes; this entails biased predictions. Third, the training datasets are weakly labeled; only the failure timestamp is known without any expert input on prior causes or early symptoms. Temporal random indexing is proposed to transform textual log messages into a numerical lower dimensional space where timeseries analyses are applicable. Balanced random-forest models are developed for unbiased classification and regression. The overall approach learns recursively the ungiven data labels while training the base learners. The IPdM approach is validated through millions of events of multithousand types collected from two years of seagoing vessels. It successfully forecasts actual propulsion failures and performs better when compared with contemporary methods.

Failure criteria evaluation of steel pipe elbows in nuclear power plant piping systems using cumulative damage models

A steel pipe elbow is an important component in the piping system of a nuclear power plant. Accordingly, its structural performance requires a piping system with high-structural integrity, especially when it is subjected to seismic loads. This component fails when subjected to cyclic loads, such as earthquakes, because of low-cycle fatigue in conjunction with ratcheting. Therefore, steel pipe elbows in piping systems should exhibit sufficient strength, ductility, and energy dissipation capacity characteristics to withstand seismic loads. In this study, various cumulative damage models were used to express quantitatively the failure criteria of the actual failure mode of an SCH40 steel pipe elbow. Experiments were performed until the point of leakage via fatigue cracking, which is the actual failure mode of steel pipe elbows, and in-plane cyclic bending was performed by using displacement control. Based on the experimental results, damage indices were calculated by using various cumulative damage models that considered ductility, energy dissipation, and their combination. Consequently, it was confirmed that the Banon index can express quantitatively the failure criteria for the leakage caused by fatigue cracking.

Numerical modeling and design approach on restrained Q690 steel beams in fire

This paper presents a comprehensive numerical analysis of high-strength Q690 steel beams in fire. A FE model is developed and validated against the full-scale experiments on restrained high-strength Q690 steel beams in fire presented in a previous study by the authors. The FE model adequately replicates the deflection, axial force, and actual failure modes identified experimentally. An extensive parametric investigation was performed to determine the variables affecting the behavior of restrained Q690 steel beams in fire. The analysis indicates that several factors, including load ratio, cross-section temperature distribution, rotational restraint stiffness, and span-to-depth ratio are critical for the fire resistance of restrained high-strength Q690 steel beams. Furthermore, additional numerical analysis for the ultimate bearing capacity of high-strength Q690 steel beams under bending was carried out to estimate the flexural-torsional buckling behavior of Q690 steel beams at elevated temperatures. Additionally, based on the results of the FE models, design curves for determining the flexural-torsional buckling strength of high-strength Q690 steel beams at high temperatures were proposed. The findings were compared to the design curves specified by several design standards.

Strength of transverse plate-to-rectangular HSS connection under single-concentrated compression

According to the American Institute of Steel Construction (AISC) Specification for Structural Steel Buildings (AISC 360), the transverse plate-to-HSS bearing strength of rectangular hollow structural sections (HSS) under single-concentrated compression shall be determined based on the applicable limit states in Section J10. From all the limit states, both the web local yielding (WLY) and web local crippling (WLC) are applicable for transverse plate-to-HSS concentrated compression. However, all the limit state equations in J10 were originally developed for wide-flange sections. Unlike the in-plane compression on the web of a wide-flange section, the concentrated compression on an HSS member acts like an eccentric load on the HSS web and a distributed load along the HSS flange. The eccentric load on the web and flange local bending due to the distributed load can considerably reduce the failure load as compared to the wide-flange sections. Experimental and nonlinear finite element analyses (NLFEA) carried out in this study indicate that WLY, WLC, and flange bending always simultaneously occur at failure of an HSS; hence, they are not independent limit states. While AISC WLY equation predicts a strength closer to the experimental and NLFEA results, the bearing strength of HSS members can range from 16% to 66% of that predicted by AISC WLC equations. Based on actual failure modes, 251 FE models were analyzed, and a single transverse plate-to-HSS bearing strength equation under compression for HSS members was formulated.

Effect of Residual Stresses on Wheel Fatigue Life and Experimental Validation

Steel wheels, consisting of rims and spokes, are important load-bearing parts of vehicles, and the fatigue fractures’ life estimation accuracy directly determines the stability and safety when applied in the transportation industry. The most common form of failure is fatigue fracture. The strong elastic–plastic deformation during the rim roll-forming process generates a residual stress field in its surface layer, which changes the actual stress distribution in the rim when it is loaded and thus affects the fatigue life of the steel wheel. In this paper, ABAQUS software was used to establish a rim-rolling simulation model to obtain the residual stress field distribution after forming and compare it with the actual residual stress on the formed surface of the rim to verify the reliability of the model. On the basis of this model establishment, the service hazard areas and maximum stresses of steel wheels with or without superimposed residual stress fields were calculated separately, and their fatigue lives were predicted separately using the local stress-strain method. The simulation results show that the maximum stress of the rim before and after the superimposed residual stress occurs in the area of the bottom of the groove, which is consistent with the actual failure location. However, the maximum stress after superposition increased from 120.7 MPa to 332.9 MPa, and the corresponding calculated life decreased from 158,340,000 to 459,500 cycles, which is closer to the actual test results. The results of the study can provide a theoretical basis for the lightweight design and process improvement of automotive steel wheels.

Myths and Realities of the Salt Lake Temple Foundation

Myths and Realities of the Salt Lake Temple Foundation

Wind-induced failure analysis of a transmission tower-line system with long-term measured data and orientation effect

This paper proposes a comprehensive wind-induced performance evaluation framework for transmission tower-line systems (TTLSs) from both structural safety and normal operation dimensions, incorporating the joint effect of wind speed and direction, as well as the line orientation. Based on the field wind data recorded in Weifang, China during 1971–2020, the actual failure probability of a local TTLS is calculated considering the joint probability distribution (JPD) of wind speed and direction, and the optimal layout of the transmission line is provided. The results show that the developed QS copula model can not only account for the continuity and cyclicity of wind direction but also have a fine goodness-of-fit. The wind direction with a relatively lower occurrence probability does not necessarily yield smaller failure probability of the TTLS, thereby the JPD of wind speed and direction should be incorporated to achieve reliable performance assessment. For the failure analysis with respect to structural damage, the most favorable layout of the exemplar TTLS is the orientation of 265°; while the most advantageous layout is the orientation of 38° in terms of flashover risk. The presented framework is conducive to performance assessment and optimization design of TTLSs subjected to wind hazards.

Computational model for bending fatigue life and failure location prediction of surface-hardened running gears

In this paper, a numerical model is proposed to predict the location and the number of cycles for bending fatigue failure of surface-hardened gears. The predictions are validated against experimental results. Linear-elastic stresses and strains obtained by a finite element simulation are imported into the fatigue model. Bending fatigue lives at the observed tooth root region are estimated based on the multilayer method, hardness method, and strain-life approach. The critical plane approach is employed due to non-proportional loading. Good agreement between actual and predicted bending fatigue lives was observed, as well as between the estimated and actual subsurface failure location.

Reliability evaluation of thermal barrier coatings for engine combustion chambers based on Monte-Carlo simulation

Due to their outstanding high temperature resistance, thermal barrier coatings are commonly applied in hot section such as aero-engine combustion chambers to protect components from high-temperature airflow. However, its material properties are insecure, the service environment is harsh, and the service life is uncertain. This paper uses a Monte-Carlo simulation-based dependability evaluation method to resolve this uncertainty. To begin with, the failure criteria for thermal barrier coatings were defined, as was the limit state equation. Second, using the Monte-Carlo simulation approach, the failure probability was calculated. Finally, the TBCs' dependability in a thermal gas flow environment was assessed and compared to actual measurement results. The thermal barrier coating in the area where the surface temperature of the combustion chamber is above 1100 °C begins to fail after 4000 h of service under the action of the hot air flow, with a failure rate of more than 60 %. The service life of the thermal barrier coating at surface temperatures of 1000, 1100, and 1197 °C was 6327, 3125, and 1642 h, respectively, based on the time it took to attain 60 % failure probability under the impact of hot air flow. The numerical relative error of the actual failure probability PT of the thermal barrier coating of the combustion chamber obtained by hole detection technology is less than 10 % (except for 3000 h), demonstrating the dependability and applicability of the reliability assessment technique. The reliability of thermal barrier coatings is influenced by temperature and TGO development.

Nano-vascularized polymers: how nanochannels impact the mechanical behaviour at the macroscale

In recent decades, nature has inspired the engineering of many structural and smart materials. Nano-vascularization has been stimulating research on advanced materials for novel biomedical, orthopaedic, industrial, and aeronautical applications. The continuous development of nano-vascularized materials requires a more accurate understanding of their mechanical behaviour. This work provides a multiscale methodology to predict the macroscale properties of nano-vascularized materials. The methodology is experimentally validated for the case of a nano-vascularized epoxy resin manufactured using sacrificial electrospun nanofibers. It is based on the development of representative volume elements (RVEs) that encompass information about both the nanochannels distribution and on the mechanical properties of the material at different dimensional scales. The RVEs simulations allowed obtaining a homogenized model describing the nano-vascularized material properties and studying the most intimate failure mechanisms. A virtual stress tomographic investigation on the RVEs was adopted as a digital twin to reveal the damage evolution and the actual failure mechanisms of the nano-vascularized material: damage occurred mainly at the nanochannels intersections, particularly where the intersections become dense. Interestingly, the simulations revealed a correlation between the stress state and the formation of feather markings as well as local failures on the nanochannels linking directions, as evidenced by SEM analysis.

Fault-Tolerant Algorithm for Software Preduction Using Machine Learning Techniques

Many software reliability algorithms have been used to predict and approximate the reliability of software. One general expectation of these traditional algorithms is to predict the fault and automatically delete the observed faults. This presumption will not be reasonable in practice and may not always exist. In this paper, the various algorithms have been used such as probabilistic neural network (PNN), generalized neural network (GRNN), linear regression, support vector machine (SVM), bagging, decision trees (DTs), and k-nearest neighbor (KNN) to measure the accuracy of various data and comparison has been done. The proposed algorithm has been used for predicting the reliability of software and the algorithms have been implemented to check the accuracy while using different machine learning (ML) techniques. Experimental studies based on actual failure evidence indicate that the proposed algorithm can more effectively explain the change in failure data and predict the software development behavior than conventional techniques.

Application of Combination Forecasting Model in Aircraft Failure Rate Forecasting.

Effective prediction of aircraft failure rate has important guiding significance for formulating reasonable maintenance plans, carrying out reliable maintenance activities, improving health management levels, and ensuring the safety of aircraft flight, etc. Firstly, combining the advantages of time series model in eliminating random accidental factors interference, grey model in dealing with poor information, and the characteristics of artificial neural network in dealing with nonlinear data, the failure rate of aircraft equipment is predicted by ARIMA model, grey Verhulst model, and BP neural network model, and secondly, based on the idea of variable weight, the method of sum of squares of errors is used to reciprocate. Shapley value method and IOWA operator method determine the weighting coefficient and establish three combined forecasting models for aircraft failure rate prediction, so as to improve the accuracy of the algorithm. Finally, taking the data of actual aircraft failure rate as the research object, the performance indexes of design prediction model are judged by Mean Absolute Percentage Error (MAPE), Root Mean Square Error (RMSE), Mean Absolute Error (MAE), Index of Agreement (IA), Theil Inequality Coefficient (TIC), Equal Coefficient (EC), Nash-Sutcliffe Efficiency coefficient (NSE), Pearson test, and violin diagram of forecast error distribution. The experimental results show that: The forecasting precision of the combination model is better than that of the single model, and the evaluation index of combination forecasting model based on IOWA operator is better than that of other combination forecasting models, thus improving the forecasting accuracy and reliability. Compared with other typical prediction models simultaneously, it is verified that the proposed combined prediction model has strong applicability, high accuracy, and good stability, which provides a practical and effective technical method for aircraft fault prediction and has good application value.

ANALISA DAN REDESAIN SPROCKET ASSEMBLY CONVEYOR RAKE C2 DI STASIUN KETEL PG NGADIREJO

Abstract. In the Ngadirejo sugar plant, sprocket shaft on the east C2 rake conveyor at the boiler station always failure every year. This conveyor is used for the process of fuel dregs supply at the boiler station. In this research, the analysis of failure and fatigue with the finite element method in Ansys will be carried out. The material analyzed is HQ705 with static loading. The analysis carried out includes static structural analysis and fatigue analysis on the sprocket shaft. Based on this analysis, found that the maximum displacement is 0.001163 m, the maximum equivalent stress is 71.8 MPa, the minimum life is 17.237 cycles, the maximum shear stress is 38.44 MPa, the minimum safety factor is 0.557744. The failure in the FEM analysis results in accordance with the actual failure location. The redesign process was carried out with HQ709 material, with this material the minimum life value is 50539 cycles.

SRGM Decision Model Considering Cost-Reliability

Aiming at the current software cost model and optimal release research, which does not fully consider the actual faults in the testing phase, a cost-reliability SRGM evaluation and selection algorithm SESABCRC is proposed. From the perspective of incomplete debugging, introducing new faults, and considering testing effort, the imperfect debugging SRGM is established. The proposed SRGM can be used to describe the testing process of the software through the actual failure data set verification, and is superior to other models. Based on the proposed SRGM, the corresponding cost function is given, which explicitly considers the impact of imperfect debugging on the cost. Furthermore, an optimal release strategy is proposed when given restricted reliability target requirements and when considering the uncertainty that the actual cost may exceed the expected cost. Finally, an experimental example is given to illustrate and verify the optimal publishing problem, and parameter sensitivity analysis is carried out.

Limit equilibrium method-based 3D slope stability analysis for wide area considering influence of rainfall

We propose a method for evaluating the risks of slope failure induced by heavy rain over a wide area by combining infiltration analysis, surface flow analysis, and slope stability analysis based on three-dimensional limit equilibrium method. The influence of the resolution of terrain data is also examined. To determine rainfall-induced water transportation, we employ an infiltration analysis, using the Green-Ampt model, and a surface flow analysis, using the diffusion wave model. For the slope stability analysis, a three-dimensional arc-slip calculation applying the Hovland method is used. The infiltration depth is obtained from the results of the infiltration analysis, whereas the simulated data are used as input data for the slope stability analysis. A region in Kamaishi City, Iwate Prefecture, Japan, where slope failures were observed during typhoon Hagibis on October 12 and 13, 2019, is selected in this study as the target area and a series of analyses are performed. The topographical survey data by an Unmanned Aerial Vehicle (UAV) observed before and after the typhoon are used to identify the actual collapse locations and compare them with the results of the slope stability analysis. In addition, high-resolution topographic data of the target area using UAV data is created and differences in the factor of safety distribution with and without the UAV data for terrain data are compared and discussed. The obtained results revealed that the proposed method can roughly represent the actual slope failure, which is useful for evaluating rainfall-induced slope failure hazards. The results derived from utilizing detailed terrain data by UAV show the importance of using a high-resolution terrain model for evaluating the stability of microtopography, such as forest roads.

Mechanical Performance Test and Numerical Simulation Analysis of Building Steel Plate and Concrete Composite Structure.

The study aims to continuously improve the level of the construction industry, such as the improvement of construction capacity and efficiency and reduction of the project cost and construction period, and find a specific way to improve the development of the construction industry. First, the study analyzes the research status of mechanical properties of horizontal joints, vertical joints, and the overall structure of worldwide prefabricated buildings. Next, the built-in steel fabricated concrete shear wall model is established. Moreover, the quasi-static experimental analysis is conducted on the joints of the fabricated shear wall with built-in section steel. The finite element software is used to analyze the numerical simulation test of the new built-in shear wall. According to the relevant test parameters, the finite element model is constructed, and the parameters are set. Finally, the shear wall model is established and tested by a simulation experiment, and the simulation results are compared with the numerical simulation results. The final results show that the proposed connection mode of the reinforced skeleton and new fabricated joints improves the stability of prefabricated buildings. The use of the quasi-static test to test the relevant performance parameters has a short calculation time, high efficiency, and high parameter optimization accuracy. It can better simulate the actual working conditions and the actual stress-strain and damage failure conditions. Moreover, the conclusion is drawn that the shear wall structure with steel plate concrete has good ductility and deformation capacity. The study has a certain reference significance for the construction optimization of steel plate concrete prefabricated buildings and related research in the future.

Predicting Time-to-Failure of Red Sandstone by Temporal Precursor of Acoustic Emission Signals

The evolution pattern of rock damage is a progressive failure process of rock materials. It is the basis for predicting failure time of rock materials. By theoretical and experimental analysis, the acoustic emission (AE) precursor characteristics of rock fracture and the gradual evolution pattern of rock damage were analyzed detailedly. Then, the time-to-failure of red sandstone was predicted and compared by several different methods. The results demonstrated that the failure process of red sandstone can be divided into the stable deformation stage and the critical acceleration failure stage. In the critical acceleration failure stage, the AE precursor of rock failure was easy to be observed, and the AE event rate occurred as jump-like increase phenomenon. Moreover, the gradual evolution pattern of rock damage obeyed an exponential function, and the damage acceleration phenomenon existed in the critical failure stage. Furthermore, the higher values of the average of rock damage was, the more obvious linear evolution pattern will be, which was beneficial to improve the prediction accuracy of time-to-failure of rocks. Clearly, the linear prediction results of rock failure time, after taking average values of five rock damage variables, had more higher accuracy when damage variable exceeded D = 0.5 . The predicting result of specimen R1 was 0.2 s ahead of its actual failure time, and the predicting result of specimen R6 was 8.1 s ahead of its actual failure time. Therefore, this method is meaningful and it can be used for the early warning of rockburst.

Seismic Fragility Evaluation of Main Steam Piping of Isolated APR1400 NPP Considering the Actual Failure Mode

An isolation system installed in a nuclear power plant (NPP) could increase seismic safety during seismic events. On the other hand, a more significant relative displacement may occur due to the isolation system. The seismic risk could be increased in the case of an interface piping system that connects isolated and nonisolated structures. Therefore, it is necessary to consider the piping systems when evaluating the safety of isolated-NPPs. This study performed seismic fragility analysis with isolated APR1400 nuclear power plants with the main steam piping. The main steam piping is the interface pipe connecting the isolated auxiliary building and the turbine building. The failure mode for seismic fragility analysis was defined as cracks caused by leakage. The experimental and numerical analysis results quantified the leak-through crack point as a damage index. The seismic fragility curves are suggested based on peak ground acceleration and the relative displacement between the isolated and nonisolated buildings.