Energy evolution and structural health monitoring of coal under different failure modes:An experimental study

Structural instability in underground engineering,especially in coal-rock structures,poses significant safety risks.Thus,the development of an accurate monitoring method for the health of coal-rock bodies is crucial.The focus of this work is on understanding energy evolution patterns in coal-rock bodies under complex conditions by using shear,splitting,and uniaxial compression tests.We examine the changes in energy parameters during various loading stages and the effects of various failure modes,resulting in an innovative energy dissipation-based health evaluation technique for coal.Key results show that coal bodies go through transitions between strain hardening and softening mechanisms during loading,indicated by fluctuations in elastic energy and dissipation energy density.For tensile failure,the energy profile of coal shows a pattern of “high dissipation and low accumulation” before peak stress.On the other hand,shear failure is described by “high accumulation and low dissipation” in energy trends.Different failure modes correlate with an accelerated increase in the dissipation energy before destabilization,and a significant positive correlation is present between the energy dissipation rate and the stress state of the coal samples.A novel mathematical and statistical approach is developed,establishing a dissipation energy anomaly index,W,which categorizes the structural health of coal into different danger levels.This method provides a quantitative standard for early warning systems and is adaptable for monitoring structural health in complex underground engineering environments,contributing to the development of structural health monitoring technology.

Dynamic response and failure process of horizontal-layered fractured structure rock slope under strong earthquake

Rock slope with horizontal-layered fractured structure(HLFS)has high stability in its natural state.However,a strong earthquake can induce rock fissure expansion,ultimately leading to slope failure.In this study,the dynamic response,failure mode,and spectral characteristics of rock slope with HLFS under strong earthquake conditions were investigated based on the large-scale shaking table model test.On this basis,multiple sets of numerical calculation models were further established by UDEC discrete element program.Five influencing factors were considered in the parametric study of numerical simulations,including slope height,slope angle,bedding-plane spacing and secondary joint spacing as well as bedrock dip angle.The results showed that the failure process of rock slope with HLFS under earthquake action is mainly divided into four phases,i.e.,the tensile crack of the slope shoulder joints and shear dislocation at the top bedding plane,the extension of vertical joint cracks and increase of shear displacement,the formation of step-through sliding surfaces and the instability,and finally collapse of fractured rock mass.The acceleration response of slopes exhibits elevation amplification effect and surface effect.Numerical simulations indicate that the seismic stability of slopes with HLFS exhibits a negative correlation with slope height and angle,but a positive correlation with bedding-plane spacing,joint spacing,and bedrock dip angle.The results of this study can provide a reference for seismic stability evaluation of weathered rock slopes.

Failure mechanisms and destruction characteristics of cemented coal gangue backfill under compression effect of non-uniform load

Backfill mining is one of the most important technical means for controlling strata movement and reducing surface subsidence and environmental damage during exploitation of underground coal resources. Ensuring the stability of the backfill bodies is the primary prerequisite for maintaining the safety of the backfilling working face, and the loading characteristics of backfill are closely related to the deformation and subsidence of the roof. Elastic thin plate model was used to explore the non-uniform subsidence law of the roof, and then the non-uniform distribution characteristics of backfill bodies’ load were revealed. Through a self-developed non-uniform loading device combined with acoustic emission (AE) and digital image correlation (DIC) monitoring technology, the synergistic dynamic evolution law of the bearing capacity, apparent crack, and internal fracture of cemented coal gangue backfills (CCGBs) under loads with different degrees of non-uniformity was deeply explored. The results showed that: 1) The uniaxial compressive strength (UCS) of CCGB increased and then decreased with an increase in the degree of non-uniformity of load (DNL). About 40% of DNL was the inflection point of DNL-UCS curve and when DNL exceeded 40%, the strength decreased in a cliff-like manner;2) A positive correlation was observed between the AE ringing count and UCS during the loading process of the specimen, which was manifested by a higher AE ringing count of the high-strength specimen. 3) Shear cracks gradually increased and failure mode of specimens gradually changed from “X” type dominated by tension cracks to inverted “Y” type dominated by shear cracks with an increase in DNL, and the crack opening displacement at the peak stress decreased and then increased. The crack opening displacement at 40% of the DNL was the smallest. This was consistent with the judgment of crack size based on the AE b-value, i. e., it showed the typical characteristics of “small b-value-large crack and large b-value-small crack”. The research results are of significance for preventing the instability and failure of backfill.

Prediction of column failure modes based on artificial neural network

To implement the performance-based seismic design of engineered structures,the failure modes of members must be classified.The classification method of column failure modes is analyzed using data from the Pacific Earthquake Engineering Research Center(PEER).The main factors affecting failure modes of columns include the hoop ratios,longitudinal reinforcement ratios,ratios of transverse reinforcement spacing to section depth,aspect ratios,axial compression ratios,and flexure-shear ratios.This study proposes a data-driven prediction model based on an artificial neural network(ANN)to identify the column failure modes.In this study,111 groups of data are used,out of which 89 are used as training data and 22 are used as test data,and the ANN prediction model of failure modes is developed.The results show that the proposed method based on ANN is superior to traditional methods in identifying the column failure modes.

Reliability modeling of mutual DCFP considering failure physical dependency

Degradation and overstress failures occur in many electronic systems in which the operation load and environmental conditions are complex.The dependency of them called dependent competing failure process(DCFP),has been widely studied.Electronic system may experience mutual effects of degradation and shocks,they are considered to be interdependent.Both the degradation and the shock processes will decrease the limit of system and cause cumulative effect.Finally,the competition of hard and soft failure will cause the system failure.Based on the failure mechanism accumulation theory,this paper constructs the shock-degradation acceleration and the threshold descent model,and a system reliability model established by using these two models.The mutually DCFP effect of electronic system interaction has been decomposed into physical correlation of failure,including acceleration,accumulation and competition.As a case,a reliability of electronic system in aeronautical system has been analyzed with the proposed method.The method proposed is based on failure physical evaluation,and could provide important reference for quantitative evaluation and design improvement of the newly designed system in case of data deficiency.

Development characteristics and failure modes of reactivated ancient landslides in the Sichuan–Tibet transportation corridor,China

The risk of reactivated ancient landslides in the Sichuan–Tibet transportation corridor in China is significantly increasing,primarily driven by the intensification of engineering activities and the increased frequency of extreme weather events.This escalation has resulted in a considerable number of fatalities and extensive damage to critical engineering infrastructure.However,the factors contributing to the reactivation and modes of destruction of ancient landslides remain unknown.Therefore,it is imperative to systematically analyze the developmental characteristics and failure modes of reactivated ancient landslides to effectively mitigate disaster risks.Based on a combination of data collection,remote sensing interpretation,and field investigations,we delineated the developmental attributes of typical ancient landslides within the study area.These attributes encompass morphological and topographic aspects,material composition,and spatial structure of ancient landslides.Subsequently,we identified the key triggers for the reactivation of ancient landslides,including water infiltration,reservoir hydrodynamics,slope erosion,and excavation,by analyzing representative cases in the study area.Reactivation of ancient landslides is sometimes the result of the cumulative effects of multiple predisposing factors.Furthermore,our investigations revealed that the reactivation of these ancient landslides primarily led to local failures.However,over extended periods of dynamic action,the entire zone may experience gradual creep.We categorized the reactivation modes of ancient landslides into three distinct types based on the reactivation sequences:progressive retreat,backward thrusting,and forward pulling–backward thrusting.This study is of great significance for us to identify ancient landslides,deepen our understanding of the failure modes and risks of reactivated ancient landslides on the eastern margin of the Tibetan Plateau,and formulate effective disaster prevention and mitigation measures.

Failure Mode and Effects Analysis （FMEA） by Fuzzy Data Envelop Analysis （Fuzzy-DEA）

Failure mode and effects analysis （FMEA） offers a quick and easy way for identifying ranking-order for all failure modes in a system or a product. In FMEA the ranking methods is so called risk priority number （RPN）, which is a mathematical product of severity （S）, occurrence （0）, and detection （D）. One of major disadvantages of this ranking-order is that the failure mode with different combination of SODs may generate same RPN resulting in difficult decision-making. Another shortfall of FMEA is lacking of discerning contribution factors, which lead to insufficient information about scaling of improving effort. Through data envelopment analysis （DEA） technique and its extension, the proposed approach evolves the current rankings for failure modes by exclusively investigating SOD in lieu of RPN and to furnish with improving sca.les for SOD. The purpose of present study is to propose a state-of-the-art new approach to enhance assessment capabilities of failure mode and effects analysis （FMEA）. The paper proposes a state-of-the-art new approach, robust, structured and useful in practice, for failure analysis.

Drop failure modes of Sn-3.0Ag-0.5Cu solder joints in wafer level chip scale package

To reveal the drop failure modes of the wafer level chip scale packages （WLCSPs） with Sn-3.0Ag-0.5Cu solder joints, board level drop tests were performed according to the JEDEC standard. Six failure modes were identified, i.e., short FR-4 cracks and complete FR-4 cracks at the printing circuit board （PCB） side, split between redistribution layer （RDL） and Cu under bump metallization （UBM）, RDL fracture, bulk cracks and partial bulk and intermetallic compound （IMC） cracks at the chip side. For the outmost solder joints, complete FR-4 cracks tended to occur, due to large deformation of PCB and low strength of FR-4 dielectric layer. The formation of complete FR-4 cracks largely absorbed the impact energy, resulting in the absence of other failure modes. For the inner solder joints, the absorption of impact energy by the short FR-4 cracks was limited, resulting in other failure modes at the chip side.

Mechanical model for failure modes of rock and soil under compression

The failure modes of rock and soil under compression are complex phenomena that have not been explained in a mechanical perspective. However, large amounts of studies indicate that the failure modes of rock and soil samples can be categorized into eight types. In this work, the inner tensile stress and the dissipation and conversion of energy of rock and soil under compression are analyzed, then the effective conversion coefficient of energy is deduced, thus the tensile failure criterion of rock and soil under compression is established. Combined with the shear strength criterion of Mohr–Coulomb, a tensile joint shear strength criterion for rock and soil under compression is built. Therefore, a mechanical criterion model concerning the failure modes of rock and soil under compression is established and verified by tests. This model easily explains the test results in the existing literature and many natural phenomena, such as collapse.

基于FMEA法的住院药房智能药柜用药安全研究

目的提高住院药房智能药柜(ADC)的用药安全管理。方法采用失效模型和效应分析(FMEA)法,经医院护士、药师等讨论后,从信息系统、人员操作、药品信息、硬件设备、管理方法5个方面建立20个失效模型(包括32个风险点),汇总为调查问卷,并通过专家咨询和药师讨论后建立问卷评分标准。于干预前发放问卷进行调查,根据发现的风险对其中30个可操作的风险点设定干预措施,持续干预5个月后(干预后)再次进行问卷调查,比较干预前后的风险优先级数(RPN)。结果干预后,30个风险点的RPN值均不同程度降低,其中22个显著降低(P<0.05)。管理方法方面的全部风险点RPN值均显著降低(P<0.05);硬件设备方面的全部风险点RPN值均无显著改变(P>0.05)。结论FMEA法用于住院药房ADC的用药安全研究,可减少其用药风险,促进药护共同管理安全使用ADC规则的形成,尤其适用于麻醉药品等特殊药品的用药管理。

基于改进FMEA的污水厂设备故障风险评估模型

为保障污水处理厂正常运行,预防厂内设备发生故障,提出一种改进的故障模式与影响分析(FMEA)的风险评估模型。首先采用FMEA法识别污水厂设备故障模式,并结合毕达哥拉斯模糊集(PFS)刻画不确定评估信息;其次利用逐步权重评估比率分析法(SWARA)和最大偏差法计算主客观权重,通过博弈论组合权重计算3个风险因子的综合权重;然后采用多目标优化比率分析法(MOORA)对设备故障模式进行风险排序。最后以长春市Z污水厂设备故障风险评估为例,并将所提模型与传统FMEA、毕达哥拉斯模糊(PF)-优劣解距离法(TOPSIS)和PF-妥协折衷排序法(PF-VIKOR)等方法对比,验证该模型的有效性。结果表明:污水厂设备故障模式前3位是除砂机抽取的砂浆所含有机物过多、膜片脱落或破裂和大块异物进入水泵。

基于FMEA的药剂科岗位廉政风险防控

目的:降低药剂科岗位廉政风险。方法:运用失效模式与效应分析方法评估药剂科各岗位流程中潜在的失效模式,将各班组岗位相似的失效模式进行整合,进而分析整改措施并实施;将实施前后失效模式优先风险值(RPN)进行配对t检验。结果:实施整改措施后,药剂科各岗位RPN值显著下降(P<0.05)。结论:失效模式与效应分析法的运用和改进措施的实施可以有效降低药剂科岗位廉政风险,促进药剂科开展科学、有效的廉政建设工作。

基于多学科协作的HFMEA对医院感染的控制效果

目的:探讨基于多学科协作的医疗失效模式与效应分析(HFMEA)在降低医院感染率方面的应用效果。方法:对2022年1月至12月中山大学附属第三医院院感数据进行回顾性分析,运用HFMEA模式进行风险评估,针对高风险环节制定预防措施和整改方案,并在2023年1月至12月实施改进措施。2023年12月再进行风险评估,分析应用多学科协作的HFMEA后,医院感染的控制效果。结果:与2022年相比,2023年应用多学科协作的HFMEA后,医院感染发生率、多重耐药菌(MDRO)感染发生率和呼吸机相关性肺炎(VAP)发生率均无显著差异(P值分别为0.650、0.653和0.219),抗菌药物病原学送检率、导尿管相关性尿路感染(CAUTI)发生率、中心静脉导管相关性血流感染(CLABSI)发生率、手卫生依从率和手卫生正确率均有明显改善(P<0.05)。结论:基于多学科协作的HFMEA应用在医院感染管理中,可显著提高抗菌药物病原学送检率,显著降低CAUTI和CLABSI发生率,大幅提升手卫生依从率和正确率。

FMEA在消毒供应中心口腔科器械管理中的应用效果

目的探讨失效模式与效应分析(FMEA)在消毒供应中心口腔科器械管理中的应用效果。方法自2019年12月起,医院消毒供应中心开始通过FMEA对口腔科器械实施管理。于FMEA实施前后所使用的口腔器械中随机选取1638件,对其展开FMEA分析,对比实施前后的失效模式危急值(Risk Priority Number,RPN)、器械管理效果及服务满意度。结果FMEA实施后的口腔器械交接数目不符合、器械损坏、器械包装名称错误、器械清洗、消毒与灭菌不合格的RPN值明显比实施前低(P<0.05);FMEA实施后的口腔科器械清洗、包装合格率比实施前高,器械耗损率、湿包发生率比实施前低,及时发放率比实施前高(P<0.05);实施后的服务满意度总分实施前高(P<0.05)。结论消毒供应中心对口腔科器械展开管理时,应用FMEA并针对分析结果制定相应措施可有效降低口腔科器械管理中的风险,提升器械管理效果,并且有助于提升服务满意度。

基于VWM-GRA的新型Fuzzy-FMEA复杂装备风险评估方法

失效模式和影响分析(Failure Mode and Effect Analysis,FMEA)是一种识别和预防复杂装备潜在故障模式的风险评估方法,然而,现有FMEA方法采用等权重和精确数表征不确定情形下的风险因素评估信息,导致风险优先数(Risk Priority Number,RPN)难以准确评估复杂装备故障模式的风险优先级。针对这一难题,文中提出了一种基于变权方法-灰色关联分析(Variable Weight Method-Grey Relation Analysis,VWM-GRA)的新型Fuzzy-FMEA复杂装备风险评估方法。在风险因素权重分配方面,在模糊熵值法的基础上,考虑风险评估信息对风险因素权重的影响,构建风险因素变权综合模型以动态调整风险因素权重值,据此确定风险因素的客观变权重;在风险优先数排序方面,在模糊语言变量表征风险因素评估信息的基础上,考虑风险因素评估信息不确定性量化对故障模式排序精度的影响,构建故障模式模糊灰色关联分析模型,以获取评估信息数据序列间的相对关联度,据此评估故障模式的风险优先级。最后,通过航空发动机主轴轴承的故障模式风险实例,分析验证文中方法的有效性。案例分析表明:该方法能够有效解决不确定情形下准确评估复杂装备故障模式风险优先级的难题。

运用FMEA降低住院患者自杀风险的研究

目的识别住院患者自杀风险,针对性制定防范策略。方法利用失效模式与效应分析(FMEA)从住院患者入院前、入院时、住院中3个环节厘清风险点并进行评价,计算风险系数,确定改进措施优先级。结果针对14个需要干预的风险点制订改进策略,执行后风险系数值明显下降。结论应用FMEA可以降低住院患者自杀事件发生风险。还需进一步提高自杀风险识别能力,强化人文关怀,提升服务质量,以确保住院患者安全。

Experimental and numerical investigation on failure characteristics and mechanism of coal with different water contents

Water injection, as a widely used technique to prevent coal burst, can restrain the fractured coal seam and released the energy storage. In this study, laboratory tests were frstly carried out on standard coal specimens with fve diferent water contents (i.e., 0%, 0.6%, 1.08%, 1.5%, 2.0%, and 2.3%). The failure mode, fragment size, and energy distribution characteristics of coal specimens were investigated. Experimental results show that strength, elastic strain energy, dissipated energy, brittleness index, as well as impact energy index decrease with increasing water content. Besides, the failure mode transitions gradually from splitting ejection to tensile-shear mixed failure mode as water content increases, and average fragment size shows positively related to water content. Moreover, scanning electron microscope tests results indicate that water in coal sample mainly causes the mineral softening and defects increase. Furthermore, a numerical model containing roadway excavation was established considering the water on coal burst prevention. Modelling results revealed that water injection can reduce degree of coal burst and ejection velocity of coal blocks, while it will raise up the depth of crack zone and surface displacement of roadway. Combined with laboratory tests and numerical results, the micro mechanism, energy mechanism, and engineering signifcance of water injection on coal burst prevention were fnally analyzed.

DFMEA在500 kW楼宇机组换热器设计中的应用

按照国家碳中和发展战略规划要求,供热行业应加速向智能化方向发展。楼宇机组因其成本低、技术先进、节约资源等优势已成为未来发展的必然趋势。文章首先研究了DFMEA(设计失效模式及后果分析)相关理论的国内外现状,然后基于DFMEA可靠性设计技术分析了楼宇机组换热器的结构和功能,再通过DFMEA对楼宇机组换热器进行失效分析、失效后果分析以及风险优先技术计算,最后针对输出结果提出改进方案,改进方案可有效避免失效模式风险的发生,进而提高并保障了产品质量、工作效率和安全性。

Effect of gravel on rock failure in glutenite reservoirs under different confining pressures

Due to the existence of gravel,glutenite is heterogeneous and different from fine-grained rocks such as sandstone and shale in structure.To fully understand the effect of gravel on failure mode in glutenite,we performed triaxial compression tests on different glutenites.The results indicate that failure modes of glutenite are complex due to the existence of gravel.Under different confining pressures,three failure modes were observed.The first failure mode,a tensile failure under uniaxial compression,produces multiple tortuous longitudinal cracks.In this failure mode,the interaction between gravels provides the lateral tensile stress for rock splitting.The second failure mode occurs under low and medium confining pressure and produces a crack band composed of micro-cracks around gravels.This failure mode conforms to the Mohr-Coulomb criterion and is generated by shear failure.In this failure mode,shear dilatancy and shear compaction may occur under different confining pressures to produce different crack band types.In the second failure mode,gravel-induced stress concentration produces masses of initial micro-cracks for shear cracking,and gravels deflect the fracture surfaces.As a result,the fracture is characterized by crack bands that are far broader than in fine-grained rocks.The third failure mode requires high confining pressure and produces disconnected cracks around gravels without apparent crack bands.In this failure mode,the gravel rarely breaks,indicating that the formation of these fractures is related to the deformation of the matrix.The third failure mode requires lower confining pressure in glutenite with weak cement and matrix support.Generally,unlike fine-grained rocks,the failure mode of glutenite is not only controlled by confining pressure but also by the gravel.The failure of glutenite is characterized by producing cracks around gravels.These cracks are produced by different mechanisms and distributed in different manners under different confining pressures to form different fracture patterns.Therefore,understanding the rock microstructure and formation stress state is essential in guiding glutenite reservoir development.

Method for Evaluating Bolt Competitive Failure Life Under Composite Excitation

In this study,the competitive failure mechanism of bolt loosening and fatigue is elucidated via competitive failure tests on bolts under composite excitation.Based on the competitive failure mechanism,the mode prediction model and“load ratio-life prediction curve”(ξ-N curve)of the bolt competitive failure are established.Given the poor correlation of theξ-N curve,an evaluation model of the bolt competitive failure life is proposed based on Miner’s linear damage accumulation theory.Based on the force analysis of the thread surface and simulation of the bolt connection under composite excitation,a theoretical equation of the bolt competitive failure life is established to validate the model for evaluating the bolt competitive failure life.The results reveal that the proposed model can accurately predict the competitive failure life of bolts under composite excitation,and thereby,it can provide guidance to engineering applications.