Operational Failures Research Articles

Size effect characteristics and influences on fatigue behavior of laser powder bed fusion of thin wall GRCop-42 copper alloy

Size effects, influencing a material's strength, elongation, fatigue limit, and longevity, depend on the operative and dominant deformation and failure mechanisms. This study explores the size effects in additive manufactured (AM) GRCop-42 (Cu-4at%Cr-2at%Nb) thin wall structures fabricated via laser-powder bed fusion (L-PBF) and their impact on fatigue life. The influence of internal defects and surface topography on the fatigue life of specimens in both as-built and hot isostatic pressed (HIP) conditions across different thicknesses is investigated. Where micro-computed tomography (μCT) was used to quantify the internal porosity of as-built, pristine HIP'd, and fatigued HIP'd specimens, and laser microscopy was employed to quantify the surface topography of specimens prior to fatigue. Additionally, quasi-static tests were used to establish baseline mechanical properties (i.e. yield strength (YS), ultimate tensile strength (UTS), and elongation) to frame fatigue testing conditions. Results indicate a significant enhancement in fatigue life for HIP'd specimens for both thicknesses, with internal defects depicting a greater impact than surface topography. Furthermore, fractographic analysis suggests that thicker specimens exhibit higher resistance to crack propagation during fatigue testing in the absence of substantial porosity. Thus, the size effects observed on the fatigue life of L-PBF GRCop-42 appears to be dominated by internal defects.

Mechanisms of Waterflood Inefficiency: Analysis of Geological, Petrophysical and Reservoir History, a Field Case Study of FWU (East Section)

The petroleum reservoir represents a complex heterogeneous system that requires thorough characterization prior to the implementation of any incremental recovery technique. One of the most commonly utilized and successful secondary recovery techniques is waterflooding. However, a lack of sufficient investigation into the inherent behavior and characteristics of the reservoir formation in situ can result in failure or suboptimal performance of waterflood operations. Therefore, a comprehensive understanding of the geological history, static and dynamic reservoir characteristics, and petrophysical data is essential for analyzing the mechanisms and causes of waterflood inefficiency and failure. In this study, waterflood inefficiency was observed in the Morrow B reservoir located in the Farnsworth Unit, situated in the northwestern shelf of the Anadarko Basin, Texas. To assess the potential mechanisms behind the inefficiency of waterflooding in the east half, geological, petrophysical, and reservoir engineering data, along with historical information, were integrated, reviewed, and analyzed. The integration and analysis of these datasets revealed that several factors contributed to the waterflood inefficiency. Firstly, the presence of abundant dispersed authigenic clays within the reservoir, worsened by low reservoir quality and high heterogeneity, led to unfavorable conditions for waterflood operations. The use of freshwater for flooding exacerbated the adverse effects of sensitive and migratory clays, further hampering the effectiveness of the waterflood. In addition to these factors, several reservoir engineering issues played a significant role in the inefficiency of waterflooding. These issues included inadequate perforation strategies due to the absence of detailed hydraulic flow units (HFUs) and rock typing, random placement of injectors, and uncontrolled injected fresh water. These external controlling parameters further contributed to the overall inefficiencies observed during waterflood operations in the east half of the reservoir. A detailed understanding of the mechanistic factors of inefficient waterflood operation will provide adequate insights into the development of the improved recovery technique for the field.

Automated Wall Thickness Evaluation for Turbine Blades Using Robot-Guided Ultrasonic Array Imaging

Abstract Nondestructive testing has become an essential part of the maintenance of modern gas turbine blades and vanes since it provides an increase in both safety against critical failure and efficiency of operation. Targeted repairs of the blade's airfoil require localized wall thickness information. This information, however, is hard to obtain by nondestructive testing due to the complex shapes of surfaces, cavities, and material characteristics. To address this problem, we introduce an automated nondestructive testing system that scans the part using an immersed ultrasonic array probe guided by a robot arm. For imaging, we adopt a two-step, surface-adaptive Total Focusing Method (TFM) approach. For each test position, the TFM allows us to identify the outer surface, followed by calculating an adaptive image of the interior of the part, where the inner surface's position and shape are obtained. To handle the large volumes of data, the surface features are automatically extracted from the TFM images using specialized image processing algorithms. Subsequently, the collection of 2D extracted surface data is merged and smoothed in 3D space to form the outer and inner surfaces, facilitating wall thickness evaluation. With this approach, representative zones on two gas turbine vanes were tested, and the reconstructed wall thickness values were evaluated via comparison with reference data from an optical scan. For the test zones on two turbine vanes, average errors ranging from 0.05 mm to 0.1 mm were identified, with a standard deviation of 0.06–0.16 mm.

Необходимость и область применения нержавеющих анкеров

Corrosion wear of the rock bolt elements with loss of their bearing capacity is sometimes observed in operation of the rock bolt support. Studies carried out in the mine workings secured with resin grouted rebar bolts allowed us to determine the patterns of corrosion wear of the rock bolt elements and measures to prevent it. Development of the rock bolt element corrosion is observed when they are moistened. The probability of free water content in the roof rocks increases with the growth of rock fracturing. The rate of the corrosion process increases with a decrease in the hydrogen index of water. Analysis of possible ways to prevent rock bolt support failures caused by the corrosion wear revealed that the most economical of them is the application of anti-corrosion coatings on the rock bolt support elements. Technical requirements were developed for the means of anti-corrosion protection of the metal rock bolt supports, they were selected among the anti-corrosion means available in the market of the Russian Federation, and their mine tests were carried out as the anti-corrosion coatings of the rock bolts in the most aggressive mine environment. According to the results of the mine tests, one anti-corrosion medium was identified that successfully passed the tests. The anti-corrosion coating created with this medium did not fail, corrosion failure of the rock bolt support elements was not observed. According to the test results, it was concluded that the anti-corrosion coating can prevent the failure of the rock bolt support operation. The field of application for stainless rock bolts is mine workings with long service life of the rock bolt support when the roof rocks are saturated water which pH < 7. The economic effect of using the rock bolts with anti-corrosion coating would amount to 6.6 million rubles/km. On average, only 4.2% of the rock bolts supplied to mines should have an anti-corrosion coating. It is possible to predict the need for the use of stainless rock bolts before driving the mine working, which will allow determining the necessary volume of their purchase in advance.

Technology for reducing gas emissions from livestock farms

The study provides an overview of methods for neutralizing pollutants from emissions from livestock facilities. The principal possibility of gas purification with the use of sorbents based on natural materials is presented. Pilot tests were conducted on the territory of an operating livestock farm in the Republic of Kalmykia. During the experiment, the type of sorption loading of the biofilter varied, which made it possible to assess the basic requirements, engineering fundamentals, principles of operation, applicability, economic efficiency and potential failures of the proposed method.

A Lightweight Chaotic Map-Based Key Agreement Scheme for the Advanced Metering Infrastructure

In the advanced metering infrastructure (AMI), impersonation, eavesdropping, man-in-the-middle and other attacks occur in the process of communication between entities through public channels, which will lead to the leakage of user privacy or the incorrect issuance of control instructions, resulting in economic losses and even power system operation failures. In view of this situation, we design a lightweight key agreement scheme based on a chaotic map for the AMI. We use the chaotic map to replace the time-consuming bilinear pairing and elliptic curve method and establish a secure communication channel between legal entities. In addition, we also design a multicast key generation mechanism for message transmission in AMI. The security analysis proves the security of the proposed scheme in the random oracle model, which can meet the security characteristics of anonymity and forward secrecy, and can effectively resist common attacks such as impersonation, replay and man-in-the-middle. The performance analysis results show that the proposed scheme requires lower computational and communication costs than related schemes, so it is more suitable for AMI scenarios with limited resources.

Assessment of the organizational factors in incident management practices in healthcare: A tree augmented Naive Bayes model.

Despite the exponential transformation occurring in the healthcare industry, operational failures pose significant challenges in the delivery of safe and efficient care. Incident management plays a crucial role in mitigating these challenges; however, it encounters limitations due to organizational factors within complex and dynamic healthcare systems. Further, there are limited studies examining the interdependencies and relative importance of these factors in the context of incident management practices. To address this gap, this study utilized aggregate-level hospital data to explore the influence of organizational factors on incident management practices. Employing a Bayesian Belief Network (BBN) structural learning algorithm, Tree Augmented Naive (TAN), this study assessed the probabilistic relationships, represented graphically, between organizational factors and incident management. Significantly, the model highlighted the critical roles of morale and staff engagement in influencing incident management practices within organizations. This study enhances our understanding of the importance of organizational factors in incident management, providing valuable insights for healthcare managers to effectively prioritize and allocate resources for continuous quality improvement efforts.

Hamas-Izrael War, Short Analysis of First Two Phases of War

At the end of 2023, Middle East faced new challenges. Among these new challenges, one of most important is the Hamas-Israel war. To understand the factors of Hamas operational success, and the strategic surprise attack on Israel from Gaza, on October 7, 2023, needs a thorough analysis to understand all its political, intelligence and operational failures aspects. In this article three issues related to new Gaza war will be addressed. Firstly, this article highlights the political background of the bloodiest attack in modern Israel's history happened on October 7, 2023. Secondly, this article seeks to answer the question, how was Hamas able to attack a country with operates one of the best intelligence organizations in the world by an extreme surprise? Finally, based upon the available data, this article analyzes the first and second phases of war.

Experimental Study on the Characterization of Aging Resistance Properties of Optical Cables in the Hydrogen-Containing Downhole Environment.

The utilization of downhole optical cables has significantly enhanced the efficiency and reliability of oilfield production operations; however, the challenging high-temperature and high-pressure conditions prevalent in oil-gas fields markedly reduce the service lifespan of these optical cables. This limitation severely impedes their application and further development in subterranean environments. In this study, a qualitative analysis was conducted on the structural materials utilized in two types of optical cables to identify these materials and assess the high-temperature tolerance and aging resistance properties of the optical fibers incorporated within. It was discovered that hydrogen infiltration into the subterranean optical cables predominantly accounts for their operational failure. To address this issue, an optical loss testing platform was established, facilitating the execution of a high-temperature and high-pressure hydrogen permeation aging experiment on the optical fibers, allowing for the evaluation of the hydrogen resistance capabilities of the two types of optical fibers. The findings from this study provide a theoretical foundation and methodological guidance for the optimization of optical fibers, aiming to enhance their durability and functional performance in adverse environmental conditions encountered in oil-gas field applications.

Identifying failure types in cyber-physical water distribution networks using machine learning models

Abstract Water cyber-physical systems (CPSs) have experienced anomalies from cyber-physical attacks as well as conventional physical and operational failures (e.g., pipe leaks/bursts). In this regard, rapidly distinguishing and identifying a facing failure event from other possible failure events is necessary to take rapid emergency and recovery actions and, in turn, strengthen system's resilience. This paper investigated the performance of machine learning classification models – support vector machine (SVM), random forest (RF), and artificial neural networks (ANNs) – to differentiate and identify failure events that can occur in a water distribution network (WDN). Datasets for model features related to tank water levels, nodal pressure, and water flow of pumps and valves were produced using hydraulic model simulation (WNTR and epanetCPA tools) for C-Town WDN under pipe leaks/bursts, cyber-attacks, and physical attacks. The evaluation of accuracy, precision, recall, and F1-score for the three models in failure type identification showed the variation of their performances depending on the specific failure types and data noise levels. Based on the findings, this study discussed insights into building a framework consisting of multiple classification models, rather than relying on a single best-performing model, for the reliable classification and identification of failure types in WDNs.

The Spatiotemporal Evolution Mechanism of Urban Rail Transit Fault Propagation in Networked Operation Modes

The cascading propagation and evolution of metro operation failures can significantly impact the safety of metro operation. To overcome this challenge, this study pre-processes a massive amount of metro operation log data through noise reduction. Moreover, a professional terminology dictionary is constructed along with a custom stop-word dictionary to segment the preprocessed data. Subsequently, the AFP-tree algorithm is employed to mine the segmented log data and identify key hazards. A weighted urban rail transit network is established, considering the effective path time cost, and the shortest travel OD path. To simulate the dynamic evolution of the failure chain propagation, a model based on disaster propagation theory is constructed. Taking the Shanghai Metro line as a case, multiple simulation scenarios are established with 25 key hazards as triggering points, and the number of cascade failure stations affected under different scenarios is outputted. The results indicate that the fault stations caused by the large passenger flow are the largest. Meanwhile, the number of stations affected by the door clamp is the smallest. The scale of fault stations reaches a maximum value in 16–20 min. Through case analysis, a positive correlation is found when the self-recovery factor is between 14 and 18, and the number of fault stations shows a significant increasing trend. The research results can provide decision-making support and theoretical guidance for rail transit operation safety management enterprises.

Do corporate environmental protection efforts reduce firm‐level operating risk? Evidence from a developing country

AbstractThis study investigates the impact of corporate environmental protection efforts on firm‐level operating risk. The importance of environmental protection has gained attention in recent years, as proliferation in ESG rating agencies has significantly increased. As suggested by stakeholder theory, the corporations for their survival are required to take care of the environment in which they operate. We used a sample of 245 non‐financial publicly listed firms of developing economy, Pakistan, from 2007 to 2019, to examine whether firms that engage in environmental protection activities have lower operating risk than firms that do not. We identified four important dimensions based on previous literature, to develop a unique index for measuring the firms' environmental performance. These dimensions included voluntary standardization, product environmental compliance, process environmental compliance, and environmental social drives. Focused on downside operating risk in terms of firm operating income, we used binary codes to distinguish firms that are negatively deviating from their industrial average. Using logistic regression on our hand‐collected environmental performance index data, this study finds that firms maintaining effective environmental protection activities are less likely to experience operational failure compared to peers who do not. This relationship holds true even after controlling for various firm‐specific factors such as firm size, leverage, growth opportunity, and profitability. Our findings have implications for policymakers and corporate managers who seek to improve their firms' environmental and financial performance simultaneously. By highlighting the potential benefits of corporate environmental protection efforts, our study provides valuable insights for firms operating in emerging economies.

Operation failure of risk analysis on floating storage and offloading

The need for petroleum in daily life is increasing. The oil comes from the seabed, so it is necessary to have adequate facilities during the exploration and exploitation of crude oil. The process of distributing crude oil to FSO is assisted by the Product Transfer System pipeline. In this process there is a possibility of failure that occurs form several factors, namely tools, weather and sea conditions, and human. In this study, the analysis of the risk of operational failure during loading-unloading of crude oil is discussed. The analysis was carried out using the HAZOP Analysis and Bow-Tie Analysis methods. HAZOP Analysis for hazard identification, and Bow-Tie Analysis for finding the appropriate mitigation. From this method, an overview of the risks than can occur can be obtained so that the risk control required by FSO can be implemented. From the results of this study, it was found that there are 41 potential hazards on the process of loading-unloading crude oil FSO, with the highest risk is inadequate quality of the transfer equipment components with the likelihood rank is 4 and severity rank is 4. The results of Bow-Tie visualization of dominant risk found five causes, namely corrosion, inadequate material quality, eroded material, service life, and material degradation, and five consequences, namely property damage, delayed operational activities, oil spills, environmental damage due to oil spill, and corrosion occurs on the product transfer equipment.

Maintenance and Reliability Improvement of Roller Bearings Operating at High Temperature: Thermal Stress Analysis Approach

In this paper the authors present the outcome of an experimental maintenance and reliability investigation conducted to prevent operation failure of pinion bearings caused by excessive temperature with a case study of a 1360kW ball mill driveline system in mineral processing application. Aiming to improve the overall plant performance, the lubrication regime of pinion bearings as key component within the ball mill driveline system was studied to determine possible causes of temperature increase at 80 to over 100°C with a 25 - 30°C gap over the maximum operating temperature. An analytical review of maintenance data is conducted to mitigate future operational risks by implementing a new lubrication regime and shutdown frequency for overall statutory inspection. Accelerated life test based inverse power law has been applied to identify the root causes of excessive bearings temperature to establish immediate short-term solution paths towards a guaranteed less required maintenance asset improvement practice, less operational cost, and plant availability enhancement. Furthermore, long-term solutions have been proposed based on modelling by thermal network approach of pinion bearings for thermomechanical stress prevention. A single parameter based accelerated test on pinion bearings was applied to establish operational fault tolerant factors to be considered for asset capability improvement, which remains an open question for future studies. These actions have shown significant improvement with temperature decrease between 15 and 25°C below the maximum required temperature.

Intact stability analysis of crane barge due to loading orientation effect during heavy lifting operation

Changes in the position of the lifting load on the crane barge during heavy lifting operation significantly affect the stability of the vessel. The changes in stability during this heavy lifting operation must be analysed to prevent operational failures. This study conducted an intact stability analysis of the crane barge during lifting of topside structures in the installation phase. The analysis was performed with variations in the position of the lifted load from starboard to bow for every 15° change in the crane angle. The stability results of the Crane Barge for all variations, using both analytical and numerical methods, have met the IMO requirements. The extreme condition occurred in load case 8, with a maximum GZ value of 2.904 m at a 22° angle and an area of 103,894 m.deg. The comparison of the stability results of the crane barge during the structural lifting operation using analytical calculation and numerical methods indicates that the overall validation error values have met the ±5% requirement according to the ABS Rules. However, when considering the corrections for changes in the lifting load moment in the analytical calculation, stability error values increase significantly as the heeling angle of the vessel increases.

Characterization of magnetostrictive bi-stable rotational vibration energy harvester with integrated centrifugal effect

Rotational machinery is a common presence in dust still production, and the occurrence of operational failures in components like engines and turbine blades necessitates effective measures. To solve this challenge, remote structural health monitoring using energy harvesting and wireless sensors has been widely employed to realize self-powered sensing. This study proposes a magnet-induced bi-stable rotational energy harvester (REH), which utilizes the centrifugal effect to broaden the effective frequency bandwidth, enabling efficient energy harvesting in complex environments. A comprehensive mathematical model has been established to facilitate the dynamic characteristics of the bi-stable system, taking into account the centrifugal effect. The theoretical results demonstrate that the gap distance of magnetic configuration has great effects on the bi-stable system. Additionally, the centrifugal effect decided by the centrifugal radius and rotational speeds also affects the stable high-energy orbit oscillations. Furthermore, experimental results indicate that the proposed REH can effectively operate within the frequency range of 230–290 rpm, with a maximum RMS voltage of 780 mV and corresponding power of 4.35 mW. These findings validate the performance of the bi-stable magnetostrictive REH with the centrifugal effect and indicate its potential to effectively address the power supply challenges for wireless sensors. Overall, this study presents a promising solution for enhancing the energy harvesting performance of REH and also provides insights into the design of high-efficiency REH by magnet-induced nonlinearity and the centrifugal effect.

Metoda Sederhana untuk Memperbaiki Kinerja Motor Listrik 3 Fasa berdasarkan Insulation Resistance Test

In the electrical energy conversion laboratory, the stable operation of the induction motor is one of the most important factors. Failure of induction motor operation can be fatal in research activities in energy conversion laboratories. Prevention is needed so that the performance of induction motors remains optimal. this paper was created as an alternative for laboratory users of electrical energy conversion in maintaining the performance of induction motors. Based on a survey conducted by the Institute of Electrical and Electronics Engineers (IEEE), the main cause of electric motor operation failure is generally caused by insulation failure, so electric motor testing is generally dominated by insulation testing. Many insulation testing methods such as Insulation Resistance (IR) testing, Polarization Index (PI), Delta tangent, and other tests. In this paper, IR-based testing is proposed, because it is relatively cheap and easy to implement. The IR testing process is carried out using direct voltage from the Insulation Tester to the sample to be tested using the IEEE 43TM-2013 Standard. The test results show the IR value of the sample motor is good. This condition is categorized as safe to operate, so research activities that use induction motors can run well and safely.

PNEUMATIC RETINOPEXY: Analysis of Risk Factors and Complications in 850 Cases.

To study out types and incidence of the complications and reveal the risk factors that affect anatomical and visual success of pneumatic retinopexy with a high number of rhegmatogenous retinal detachment cases. Eight hundred and fifty eyes of the 837 patients who admitted at a tertiary center, between January 2015 and January 2022 for the diagnosis of rhegmatogenous retinal detachment, then underwent pneumatic retinopexy and had at least sixth month follow-up, were included in the study. The multivariate logistic regression model was created to investigate the factors affecting anatomical and visual success. The anatomical success rate was 53.4% with the first pneumatic retinopexy and 99.8% after subsequent procedures. Visual acuity of >0.4 logMAR (<20/50 Snellen), proliferative vitreoretinopathy, and macular involvement was determined as significant preoperative risk factors for single operation and visual success in all univariate and multivariate analyses. In addition, pseudophakic/aphakic lens status was associated with single operation failure in all analyses. Besides, in all analyzes for single operation and visual success, new or missed tears, proliferative vitreoretinopathy, delayed subretinal fluid, macular hole, and subretinal gas were identified as significant postoperative risk factors. Among these, new or missed tears was determined as the most common complication with a rate of 24%. There are many risk factors influencing the success of pneumatic retinopexy. These factors and complications should always be considered, before applying this rapid, effective, inexpensive, and minimally invasive method.

Capacity-based daily maintenance optimization of urban bus with multi-objective failure priority ranking

There is a specific correlation between bus operational failures and work intensity. The hysteresis effect identified the correlation between the number of repairs and the bus capacity of urban bus fleets. Therefore, administrators can determine whether to perform maintenance on a specific bus based on the severity of detected potential failures. At this stage, administrators should make a maintenance decision after considering maintenance costs, operational losses, and bus capacity. As a result, we propose a model for optimizing maintenance decisions with multi-objective failure priority ranking in this article. We employ the TOPSIS to prioritize the maintenance of failed buses based on indicators such as transport capacity loss, downtime, and maintenance cost. Finally, the study verifies the model's validity by utilizing real data from urban bus operation and maintenance data in China. The outcomes of the case study indicate that implementing the model can reduce operating expenses by 18.8143% when considering a corrective maintenance cost of 300. The model adoption provides a significant reduction in operating costs.

Functional Anatomy of Urogenital Hiatus Closure: the Perineal Complex Triad Hypothesis.

Urogenital hiatus enlargement is a critical factor associated with prolapse and operative failure. This study of the perineal complex was performed to understand how interactions among its three structures: the levator ani, perineal membrane, and perineal body-united by the vaginal fascia-work to maintain urogenital hiatus closure. Magnetic resonance images from 30 healthy nulliparous women with 3D reconstruction of selected subjects were used to establish overall geometry. Connection points and lines of action were based on perineal dissection in 10 female cadavers (aged 22-86years), cross sections of 4 female cadavers (aged 14-35years), and histological sections (cadavers aged 16 and 21years). The perineal membrane originates laterally from the ventral two thirds of the ischiopubic rami and attaches medially to the perineal body and vaginal wall. The levator ani attaches to the perineal membrane's cranial surface, vaginal fascia, and the perineal body. The levator line of action in 3D reconstruction is oriented so that the levator pulls the medial perineal membrane cranio-ventrally. In cadavers, simulated levator contraction and relaxation along this vector changes the length of the membrane and the antero-posterior diameter of the urogenital hiatus. Loss of the connection of the left and right perineal membranes through the perineal body results in diastasis of the levator and a widened hiatus, as well as a downward rotation of the perineal membrane. Interconnections involving the levator ani muscles, perineal membrane, perineal body, and vaginal fascia form the perineal complex surrounding the urogenital hiatus in an arrangement that maintains hiatal closure.