Comparison of engineering failures and seismic responses of 500 kV transformer-bushing systems in the 2022 Luding earthquake

Cemented and mechanically clamped types of end fittings(fitting-C and fitting-M)are commonly used in transformer bushings.During the Luding Ms 6.8 earthquake that occurred in China on September 5,2022,all transformer bushings with the two types of end fittings in a 500 kV substation were damaged.Post-earthquake field investigations were conducted,and the failures of the two types of bushings were compared.Two elementary simulation models of the transformer-bushing systems were developed to simulate the engineering failures,and further compute their seismic responses for comparison.The results indicate that the hitch lugs of the connection flange are structurally harmful to seismic resistance.Fitting-M can decrease the bending stiffness of the bushing due to the flexible sealing rubber gasket.Since it provides a more flexible connection that dissipates energy,the peak accelerations and relative displacements at the top of the bushing are significantly lower than those of the bushing with fitting-C.Compared with fitting-C,fitting-M transfers the high-stress areas from the connection flange to the root of the porcelain,so the latter becomes the most vulnerable component.Fitting-M increases the failure risk of the low-strength porcelain,indicating the unsuitability of applying it in high-intensity fortification regions.

Post-Failure Rheological Properties of Rockmass ——An Important Object of Study for Engineering Rockmass Mechanics

Post failure rheology, as an important deformable behavior of average to very poor rockmass,is discussed in this paper. Three kinds of deformations, transition deformation, post failure rheological deformation and swelling deformation, are also introduced for they are totally different from that of traditional concepts. Transition and post failure deformations are sensitive to the environmental factors, and need to be studied in the future.

Failure Assessment of Aero-engine Support Structure due to Blade-off

Aero-engine blade-off event could cause serious malfunction and endanger flight safety,which is an important issue widely concerned for a long period.This paper presents a comprehensive review on the regulation requirements,the major research methods and status at home and abroad.Firstly,the relevant certification regulations and standards about aero-engine structure safety due to blade-off event were overviewed and the research gaps between the abroad and the domestic were compared.Then,the simulation and experimental methodologies on aero-engine supporting structures undertake abnormal load due to blade-off event were discussed as major issue.Finally,the safety certification verification technology system for aero-engine support structures during blade-off event was proposed.

Corrosion engineering on AlCoCrFeNi high-entropy alloys toward highly efficient electrocatalysts for the oxygen evolution of alkaline seawater

Seawater splitting is a prospective approach to yield renewable and sustainable hydrogen energy.Complex preparation processes and poor repeatability are currently considered to be an insuperable impediment to the promotion of the large-scale production and application of electrocatalysts.Avoiding the use of intricate instruments,corrosion engineering is an intriguing strategy to reduce the cost and presents considerable potential for electrodes with catalytic performance.An anode comprising quinary AlCoCrFeNi layered double hydroxides uniformly decorated on an AlCoCrFeNi high-entropy alloy is proposed in this paper via a one-step corrosion engineering method,which directly serves as a remarkably active catalyst for boosting the oxygen evolution reaction(OER)in alkaline seawater.Notably,the best-performing catalyst exhibited oxygen evolution reaction activity with overpotential values of 272.3 and 332 mV to achieve the current densities of 10 and100 mA·cm^(-2),respectively.The failure mechanism of the obtained catalyst was identified for advancing the development of multicomponent catalysts.

An Evaluation of Human Error Probabilities for Critical Failures in Auxiliary Systems of Marine Diesel Engines

Human error,an important factor,may lead to serious results in various operational fields.The human factor plays a critical role in the risks and hazards of the maritime industry.A ship can achieve safe navigation when all operations in the engine room are conducted vigilantly.This paper presents a systematic evaluation of 20 failures in auxiliary systems of marine diesel engines that may be caused by human error.The Cognitive Reliability Error Analysis Method(CREAM)is used to determine the potentiality of human errors in the failures implied thanks to the answers of experts.Using this method,the probabilities of human error on failures were evaluated and the critical ones were emphasized.The measures to be taken for these results will make significant contributions not only to the seafarers but also to the ship owners.

Building Failure Causes in Nigeria and Mitigating Roles by Engineering Regulation and Monitoring

This paper assessed some of the reported cases of building failures and their possible causes in Nigeria between 1977 and 2011. The reported major failure causes are structural failure (SF), Carelessness (CLSS), poor workmanship (PW), poor supervision (PS), poor materials (PM), and quackery (Q).These causes of failure were subjected to Chi-Square statistical test at 5% significant level and 4 degree of freedom to know the most common cause of failure in Nigeria. The analysis showed quackery as the principal culprit in the reported building failures in Nigeria with prevalence of 8 over poor supervision being the minimum in occurrence. Structural failure occurred 5 times, while poor materials, carelessness and poor workmanship occurred 4, 2 and 2 respectively. The Council for the Regulation of Engineering in Nigeria (COREN) with Engineering Regulation and Monitoring (ERM) as her arm as a technical professional group discouraging quackery and failures generally in Engineering Practice. The holistic approach needs effective training of Engineers starting with strong mathematical and scientific background at the secondary and tertiary education levels in conjunction with rigorous field and Industrial training exercises. There after effective scrutiny, professional registration process of competent engineers is followed.

关于16PC2-6V400型柴油机连杆断裂故障原因分析及改进措施

针对某船的16PC2-6V400型柴油机在使用过程中出现的连杆断裂飞出,缸套破损,活塞顶卡滞、连杆大段掉落的故障现象,结合故障出现的环境和使用工况进行分析,通过建立故障树,对各故障原因进行排除,定位故障部位,通过对故障件进行微观形貌分析,明确故障为连杆螺纹根部刀痕应力集中处促使裂纹源萌生并以疲劳的方式发展最终断裂。针对该故障暴露的问题,提出具有可行性的解决方法,避免再次因该类型问题导致较大故障及损失的发生。

基于DEMATEL-ISM的飞行学员飞行中发动机失效时的处境意识影响因素研究

研究了飞行中发动机失效后影响飞行学员处境意识和处理能力的因素。通过20位飞行教员的经验评估与问卷打分,在发动机失效时,选取了11个影响飞行学员的处境意识的核心因素。使用决策实验室分析法构建解释结构模型,确定每种影响因素对处境意识的影响程度,得出飞行员的飞行经历经验与天气的恶劣程度对飞行中发动机失效的处置影响最大的根源因素,并提出指导性的解决方案。

A Deep Learning-Based Computational Algorithm for Identifying Damage Load Condition: An Artificial Intelligence Inverse Problem Solution for Failure Analysis

In this work,we have developed a novel machine(deep)learning computational framework to determine and identify damage loading parameters(conditions)for structures and materials based on the permanent or residual plastic deformation distribution or damage state of the structure.We have shown that the developed machine learning algorithm can accurately and(practically)uniquely identify both prior static as well as impact loading conditions in an inverse manner,based on the residual plastic strain and plastic deformation as forensic signatures.The paper presents the detailed machine learning algorithm,data acquisition and learning processes,and validation/verification examples.This development may have significant impacts on forensic material analysis and structure failure analysis,and it provides a powerful tool for material and structure forensic diagnosis,determination,and identification of damage loading conditions in accidental failure events,such as car crashes and infrastructure or building structure collapses.

Design of Fine Life Cycle Prediction System for Failure of Medical Equipment

The inquiry process of traditional medical equipment maintenance management is complex,which has a negative impact on the efficiency and accuracy of medical equipment maintenance management and results in a significant amount of wasted time and resources.To properly predict the failure of medical equipment,a method for failure life cycle prediction of medical equipment was developed.The system is divided into four modules:the whole life cycle management module constructs the life cycle data set of medical devices from the three parts of the management in the early stage,the middle stage,and the later stage;the status detection module monitors the main operation data of the medical device components through the normal value of the relevant sensitive data in the whole life cycle management module;and the main function of the fault diagnosis module is based on the normal value of the relevant sensitive data in the whole life cycle management module.The inference machine diagnoses the operation data of the equipment;the fault prediction module constructs a fine prediction system based on the least square support vector machine algorithm and uses the AFS-ABC algorithm to optimize the model to obtain the optimal model with the regularized parameters and width parameters;the optimal model is then used to predict the failure of medical equipment.Comparative experiments are designed to determine whether or not the design system is effective.The results demonstrate that the suggested system accurately predicts the breakdown of ECG diagnostic equipment and incubators and has a high level of support and dependability.The design system has the minimum prediction error and the quickest program execution time compared to the comparison system.Hence,the design system is able to accurately predict the numerous causes and types of medical device failure.

Initial support distance of a non-circular tunnel based on convergence constraint method and integral failure criteria of rock

For deep tunnel projects,selecting an appropriate initial support distance is critical to improving the self-supporting capacity of surrounding rock.In this work,an intuitive method for determining the tunnel’s initial support distance was proposed.First,based on the convergence-confinement method,a three-dimensional analytical model was constructed by combining an analytical solution of a non-circular tunnel with the Tecplot software.Then,according to the integral failure criteria of rock,the failure tendency coefficients of hard surrounding rock were computed and the spatial distribution plots of that were constructed.On this basis,the tunnel’s key failure positions were identified,and the relationship between the failure tendency coefficient at key failure positions and their distances from the working face was established.Finally,the distance from the working face that corresponds to the critical failure tendency coefficient was taken as the optimal support distance.A practical project was used as an example,and a reasonable initial support distance was successfully determined by applying the developed method.Moreover,it is found that the stability of hard surrounding rock decreases rapidly within the range of 1.0D(D is the tunnel diameter)from the working face,and tends to be stable outside the range of 1.0D.

Rock engineering design of post-tensioned anchors for dams - A review

High-capacity, post-tensioned anchors have found wide-spread use, originally in initial dam design and construction, and more recently in the strengthening and rehabilitation of concrete dams to meet modern design and safety standards. Despite the advances that have been made in rock mechanics and rock engineering during the last 80 years in which post-tensioned anchors have been used in dam en- gineering, some aspects of the rock engineering design of high-capacity rock anchors for dams have changed relatively little over the last 30 or 40 years. This applies, in particular, to the calculations usually carried out to establish the grouted embedment lengths required for deep, post-tensioned anchors. These calculations usually make simplified assumptions about the distribution and values of rock-grout interface shear strengths, the shape of the volume of rock likely to be involved in uplift failure under the influence of a system of post-tensioned anchors, and the mechanism of that failure. The resulting designs are generally conservative. It is concluded that these aspects of the rock engineering design of large, post- tensioned rock anchors for dams can be significantly improved by making greater use of modern, comprehensive, numerical analyses in conjunction with three-dimensional （3D） models of the rock mass structure, realistic rock and rock mass properties, and the results of prototype anchor tests in the rock mass concerned.

Model test of the overburden deformation and failure law in close distance multi-seam mining

Based on characteristic of the associated mining of multi-coal seam and the engineering geological characteristics of overburden,the mining impact pattern of multi- seam mining and the dynamic fracture mechanism of overburden were characterized by applying the engineering geological mechanical model test.The related strata movement parameters and influence area of multi-seam mining were obtained,the strike boundary angle is 61°,the full extraction coefficient is 0.93,the greatest subsidence angle is 81°,the horizontal movement factor is 0.38,the deviation of inflection point/mining deep is 0.11. The development height of caving zone and water flowing fractured zone of multi-seam mining were calculated,is 32 m and 81.5 m separatly.The assess of influence degree of coal layer safety mining is that,there exists the possibility of water and sand inflow when mining,some messures for mine water prevention and control should be used,and the mining thickness should be local strictly limit.

Numerical analysis of the failure process of soil-rock mixtures through computed tomography and PFC3D models

Soil-rock mixture （SRM） is a unique type of geomaterial characterized by a heterogeneous composition and a complicated structure. It is intractable for the continuum-based soil and rock mechanics theories to accurately characterize and predict the SRM＇s mechanical properties. This study reports a novel numerical method incorporating microfocus computed tomography and PFC3D codes to probe the deformation and failure processes of SRM. The three-dimensional （3D） PFC models that represent the SRM＇s complex structures were built. By simulating the entire failure process in PFC3D, the SRM＇s strength, elastic modulus and crack growth were obtained. The influence of rock ratios on the SRM＇s strength, deformation and failure processes, as well as its internal mesoscale mechanism, were analyzed. By comparing simulation results with experimental data, it was verified that the 3D PFC models were in good agreement with SRM＇s real structure and the SRM＇s compression process, deformation and failure patterns; its intrinsic mesomechanism can be effectively analyzed based on such 3D PFC models.

I-123 metaiodobenzylguanidine imaging for predicting ventricular arrhythmia in heart failure patients

Compared to antiarrhythmic drugs, implantable cardioverter defibrillator （ICD） leads to a more significant im- provement in preventing ventricular arrhythmia in heart failure patients. However, an important question has been raised that how to select appropriate patients for ICD therapy. 1-123 metaiodobenzylguanidine （MIBG） planar and SPECT imaging have shown great potentials to predict ventricular arrhythmia in heart failure patients by as- sessing the abnormalities of the sympathetic nervous system. Clinical trials demonstrated that several parameters measured from 1-123 MIBG planar and SPECT imaging, such as heart-to-mediastinum ratio, washout rate, defect score, and innervation/perfusion mismatch, predicted ventricular arrhythmias in heart failure patients. This paper introduces the current practice of ICD therapy and reviews the technical background of 1-123 MIBG planar and SPECT imaging and their clinical data in predicting ventricular arrhythmia.

Contents and Abstracts of Journal of Mechanical Engineering ISSN 0577-6686,CN 11-2187/TH

Cooperative Reconfiguration for a Reconfigurable Mobile Robot LIU Tonglin, WU Chengdong, LI Bin, LIU Jinguo （1. State Key Laboratory of Robotics, Shenyang Institute of Automation, Chinese Academy of Sciences, Shenyang 110016, China; 2. Graduate School, Chinese Academy of Sciences, Beijing 100049, China; 3. School of Information Science ＆ Engineering, Northeast University, Shenyang 110004, China）Abstract： A main characteristic of the reconfigurable mobile robot AMOEBA-1 is that it has diverse configurations, but some reconfigurations are difficult to realize under the influence of ground conditions. A cooperative reconfiguration method is proposed to reduce reconfiguration resistance and enhance the adaptability of the robot to the environment. The mathematical model is established correspondingly. The kinematics and mechanical properties of each section of the robot are analyzed. A part of resistance is transformed into active force of reconfiguration, and transforms are actualized among five specific configurations. Further, the linearization of model based on a perturbation analysis method is used to reduce the computational complexity. Finally, an evaluation criterion is proposed for AMOEBA-I＇s cooperative reconfiguration performance. The validity of the cooperative reconfiguration method is proved by simulations and experiments.

埋入式应变感测光缆-冻土界面渐进破坏机制研究

冻胀融沉作用引起的地基土体变形是冻土地区工程建设的典型地质灾害,光纤传感技术为冻土变形的精细化、分布式实时监测提供了重要的技术手段。为探究分布式光纤应变传感在监测冻土变形方面的可行性,利用自主研制的光缆-冻土界面力学特性试验仪,探究了不同干密度和初始含水率的冻土试样中缆-土界面的破坏机制。试验结果表明,光纤应变监测结果准确地反映出缆-土界面呈现渐进性破坏特征,应变软化模型能够较好地描述界面的力学特性。在冻结过程中,土体内液态水相变成冰,引起了冻结锋面移动和水分迁移,使得界面的力学特性存在显著的差异性。不同深度处缆-土界面剪应力的演化过程反映了在光缆拉拔过程中与冻土的变形协调状态,表明光缆测量范围、界面耦合性与土体干密度、初始含水率密切相关。该研究为光纤传感技术在寒区冻土地基变形监测中的应用提供了参考。

Contents and Abstracts of Journal of Mechanical Engineering ISSN 0577-6686, CN 11-2187/TH

Research on Categorizing Innovation of Speed Reducers,Optimization Algorithm for Robotic Belt Surface Grinding Process,Design and Viscoelasticity Dynamics Modeling of Flexible Driven Unit for Robot＇s Joint