Precursor Of Failure Research Articles

Failure precursor detection in complex electrical systems using symbolic dynamics

Failures in a plant's electrical components are a major source of performance degradation and plant unavailability. In order to detect and monitor failure precursors and anomalies early in electrical systems, we have developed a signal processing method that can detect and map patterns to an anomaly measure. Application of this technique for failure precursor detection in electronic circuits resulted in robust detection. This technique was observed to be superior to conventional pattern recognition techniques such as neural networks and principal component analysis for anomaly detection. Moreover, this technique based on symbolic dynamics offers superior robustness due to averaging associated with experimental probability calculations. It also provided a monotonically increasing smooth anomaly plot which was experimentally repeatable to a remarkable accuracy.

Elasto-viscoplastic finite element study of the effect of degradation on bearing capacity of footing on clay ground

The bearing capacity of footing has been studied by both conventional and numerical methods by many researchers. However, degradation of the microstructure of material, that is, a change in the microstructure of the soil, has not been adequately taken into account. Degradation of microstructure causes strain softening of materials and it leads to strain localization such as shear bands and slip bands. From an engineering point of view the strain localization is crucial because it is a precursor of failure. In the present study, finite element analyses of the bearing capacity of a shallow foundation on homogeneous and inhomogeneous saturated clay strata have been conducted using an elasto-viscoplastic soil constitutive model of microstructure change. A series of analyses of footing on clay deposit with different microstructure parameters have been carried out. Numerical results show that strain localization can be predicted during the loading of rigid footing on highly structured soil and strain localization affects the footing–soil interaction. The effects of footing roughness on the failure mechanism are also discussed in the study.

Experimental study of energy accumulation and dissipation in iron in an elastic-plastic transition

Modern experimental studies of the temperature evolution at the surface of plastically deformed metals show that processes of energy accumulation and dissipation in the material are nonlinear even in the quasi-static case and obviously depend on the loading conditions as well as past history of deformation. Considerable intensification of investigations in this field, which has been observed during the last decade, is due to the fact that this class of problems has wide application apart from its fundamental importance. High-sensitivity IR detectors used in such experiments make it possible to develop new effective methods of nondestructive control, which are based on analysis of thermal precursors of deformation localization and failure. In this study, the features of propagation of thermal waves on the surface of pure iron under an elastic-plastic transition are investigated and time dependences of energy accumulation rate are obtained during quasi-static deformation.

Trace anomalies as precursors of field failures: an empirical study

Reproducing and learning from failures in deployed software is costly and difficult. Those activities can be facilitated, however, if the circumstances leading to a failure can be recognized and properly captured. To anticipate failures we propose to monitor system field behavior for simple trace instances that deviate from a baseline behavior experienced in-house. In this work, we empirically investigate the effectiveness of various simple anomaly detection schemes to identify the conditions that precede failures in deployed software. The results of our experiment provide a preliminary assessment of these schemes, and expose the tradeoffs between different anomaly detection algorithms applied to several types of observable attributes under varying levels of in-house testing.

How to diagnose diastolic heart failure: a consensus statement on the diagnosis of heart failure with normal left ventricular ejection fraction by the Heart Failure and Echocardiography Associations of the European Society of Cardiology

Diastolic heart failure (DHF) currently accounts for more than 50% of all heart failure patients. DHF is also referred to as heart failure with normal left ventricular (LV) ejection fraction (HFNEF) to indicate that HFNEF could be a precursor of heart failure with reduced LVEF. Because of improved cardiac imaging and because of widespread clinical use of plasma levels of natriuretic peptides, diagnostic criteria for HFNEF needed to be updated. The diagnosis of HFNEF requires the following conditions to be satisfied: (i) signs or symptoms of heart failure; (ii) normal or mildly abnormal systolic LV function; (iii) evidence of diastolic LV dysfunction. Normal or mildly abnormal systolic LV function implies both an LVEF > 50% and an LV end-diastolic volume index (LVEDVI) <97 mL/m(2). Diagnostic evidence of diastolic LV dysfunction can be obtained invasively (LV end-diastolic pressure >16 mmHg or mean pulmonary capillary wedge pressure >12 mmHg) or non-invasively by tissue Doppler (TD) (E/E' > 15). If TD yields an E/E' ratio suggestive of diastolic LV dysfunction (15 > E/E' > 8), additional non-invasive investigations are required for diagnostic evidence of diastolic LV dysfunction. These can consist of blood flow Doppler of mitral valve or pulmonary veins, echo measures of LV mass index or left atrial volume index, electrocardiographic evidence of atrial fibrillation, or plasma levels of natriuretic peptides. If plasma levels of natriuretic peptides are elevated, diagnostic evidence of diastolic LV dysfunction also requires additional non-invasive investigations such as TD, blood flow Doppler of mitral valve or pulmonary veins, echo measures of LV mass index or left atrial volume index, or electrocardiographic evidence of atrial fibrillation. A similar strategy with focus on a high negative predictive value of successive investigations is proposed for the exclusion of HFNEF in patients with breathlessness and no signs of congestion. The updated strategies for the diagnosis and exclusion of HFNEF are useful not only for individual patient management but also for patient recruitment in future clinical trials exploring therapies for HFNEF.

Understanding mudslides through micro-seismic monitoring: the Super-Sauze (South-East French Alps) case study

Abstract The macroscopic deformation of rocks, at scales ranging from laboratory samples (cm) to rock hillslopes and earth crust (hm to km), is associated with local irreversible processes (cracks/faults propagation and shearing). These movements involve propagation of acoustic waves, which can be observed by remote sensing. Seismic monitoring during strain progression can help our understanding of rock behaviour and lead to the recognition of failure precursors. Although of significant potential, this observational tool has had only limited application in the study of gravitational instabilities such as landslides. This paper presents seismic monitoring data acquired on a mudslide located in the South French Alps. Results show that recordable seismicity exists in the frequency range of 0.01 Hz to 10 Hz associated with landslide deformation. Acceleration of landslide movement is controlled by rainfall and appears to be well correlated with seismic activity. The origin of the seismicity is attributed to shearing of the moving mass at the interface with the in-situ stable bedrock. Spectral analysis of the seismic wave reveals that the range 0.1–1 Hz is the most sensitive to the variations in landslide velocity. The results emphasize the strong potential of seismic monitoring for improving our understanding of mechanisms controlling rock mass deformation and gravitational instability. The determination of operational failure precursors based on seismic monitoring has yet to be achieved but remains a major target of future research.

Systolic Dysfunction in Heart Failure with a Normal Ejection Fraction: Echo-Doppler Measurements

Heart failure with a normal ejection fraction, also called heart failure with preserved ejection fraction or diastolic heart failure, is thought to be characterized by normal systolic function and disturbed diastolic function only. However, studies using newer Doppler-echocardiographic techniques have shown that ventricular function is not normal particularly in the long axis. Ejection is relatively preserved because of increased radial function. Similar findings are seen with normal ageing and the typical precursors of heart failure with a normal ejection fraction such as hypertension, diabetes, and ischemia. There appears to be a spectrum of abnormalities of systolic function from the truly normal to systolic heart failure with heart failure with a normal ejection fraction occupying an intermediate position. The use of ejection fraction, which has a normal distribution, to dichotomize patients with heart failure is not supported on theoretical or experimental grounds, and any cutoff is arbitrary. Patients with heart failure have a mixture of systolic and diastolic abnormalities and variable degrees of remodeling. It is more important to correctly identify these in the individual patient.

Modelling and simulation of dynamic anisotropic degradation of structures under adiabatic shear banding

The present work deals with the three-dimensional modelling of the behaviour of structural metallic materials allowing for adiabatic shear banding (ASB) as a mode of dynamic failure precursor. The anisotropic deterioration induced in the material by the presence of the bands is described via the concept of a super dislocation (see [6-8]) in the context of large viscoplastic deformation. The model accounts for strain hardening, thermal softening, rate sensitivity and includes ASB-induced anisotropy and softening in the post-critical stage. The onset of dynamic plastic localization in the form of ASB is controlled by a energy release rate threshold obtained from a linear perturbation method based analysis. 3D numerical simulations of the dynamic shearing of a hat shape structure (HSS) have been performed employing the code LS-DYNA and compared with experimental observations. The confrontation between numerical and experimental results constitutes the primary objective of this paper.

Three-dimensional strain localization of water-saturated clay and numerical simulation using an elasto-viscoplastic model

Since strain localization is a precursor of failure, it is an important subject to address in the field of geomechanics. Strain localization has been analysed for geomaterials by several researchers. Many of the studies, however, treated the problems brought about by strain localization as two-dimensional problems, although the phenomena are generally three-dimensional. In the present study, undrained triaxial compression tests using rectangular specimens and their numerical simulation are conducted in order to investigate the strain localization behaviour of geomaterials under three-dimensional conditions. In the experiments, both normally consolidated and over-consolidated clay samples are tested with different strain rates. Using the distribution of shear strain obtained by an image analysis of digital photographs taken during deformation, the effects of the strain rates, the dilation, and the over-consolidation on strain localization are studied in detail. The analysis method used in the numerical simulation is a coupled fluid-structure finite element method. The method is based on the finite deformation theory, in which an elasto-viscoplastic model for water-saturated clay, which can consider structural changes, is adopted. The results of the simulation include not only the distribution of shear strain on the surfaces of the specimens, but also the distributions of strain, stress, and pore water pressure inside the specimens. Through a comparison of the experimental results and the simulation results, the mechanisms of strain localization are studied under three-dimensional conditions.

Numerical investigation of coal and gas outbursts in underground collieries

Coal and gas outbursts are a complex catastrophic unstable phenomenon that involve the ejection of large volumes of coal, and are often accompanied by gas, such as methane, carbon dioxide or a mixture of the two. Coal and gas outbursts are prevalent in deep and gassy mines where face advance rates are rapid, and where gas drainage is either poor or absent. The occurrence of progressively larger coal and gas outbursts, and the potential for the catastrophic collapse of coal pillars, is of increasing importance as mining is extended deeper in seams rich in methane and other hydrocarbons. A unique coupled gas flow and solid deformation numerical model, viz., RFPA 2D-GasFlow, has been developed and is applied to simulate the evolutionary process of such catastrophic coal failures in underground collieries. The finite element model, which incorporates the physics of gas flow in the coal seam, the physics of coal deformation and instantaneous failure, and the cross-couplings between them, is proposed. The model also incorporates small-scale variability in deformation modulus and strength of the coal and surrounding rock. The variability in modulus and strength is distributed via a fine-scale resolution model according to the Weibull distribution, where the distribution parameter determines the level of heterogeneity. This numerical model is applied to simulate the whole process of coal and gas outbursts, including stress concentration, coal fracturing, gas pressure-driven expansion, and outburst. The instantaneous outburst process and associated stress fields, gas pressure gradients and displacement vectors are presented step by step. The numerical simulations indicate that the instantaneous outburst is a complex phenomenon involving interactions between gas pressure, stress and the physico-mechanical properties of the coal, and it can occur under a variety of conditions. Successful numerical simulation of the whole coal and gas outburst process provides the basis for identifying the outburst mechanisms, parameterizing the causative processes, and to defining potential precursors of failure.

Prognostics and health management of electronics

There has been a growing interest in monitoring the ongoing "health" of products and systems in order to predict failures and provide warning to avoid catastrophic failure. Here, health is defined as the extent of degradation or deviation from an expected normal condition. While the application of health monitoring, also referred to as prognostics, is well established for assessment of mechanical systems, this is not the case for electronic systems. However, electronic systems are integral to the functionality of most systems today, and their reliability is often critical for system reliability. This paper presents the state-of-practice and the current state-of-research in the area of electronics prognostics and health management. Four current approaches include built-in-test (BIT), use of fuses and canary devices, monitoring and reasoning of failure precursors, and modeling accumulated damage based on measured life-cycle loads. Examples are provided for these different approaches, and the implementation challenges are discussed.

B-Type Natriuretic Peptide Testing for Structural Heart Disease Screening: A General Population-Based Study

Background Several types of structural heart disease are important precursors for congestive heart failure or cardioembolic stroke. We have previously demonstrated that plasma B-type natriuretic peptide (BNP) measurement is useful for detection of structural heart disease in a multiphasic health screening setting. To extend our hypothesis to the general population, the utility of BNP testing for identifying structural heart disease was assessed in a general population and in subgroups divided by sex, age, and presence/absence of risk factors. Methods and Results This cross-sectional cohort study measured plasma BNP concentrations in 993 randomly selected community-dwelling adults (mean age 58 years). All subjects underwent plasma BNP measurement and transthoracic echocardiography. Using prejudged criteria, 41 subjects were diagnosed to have some form of structural heart disease (mild left ventricular systolic dysfunction in 11, valvular heart disease in 9, hypertensive heart disease in 3, hypertrophic cardiomyopathy in 2, ischemic heart disease in 2, lone atrial fibrillation in 14). The utility of BNP testing was evaluated by receiver operating characteristic (ROC) analysis and by cost analysis for detection of 1 case within each subgroup of the cohort. Overall, the sensitivity and specificity of BNP testing for identification of structural heart disease were 61% and 92%, respectively. The area under the ROC curve was 0.77 (95% CI; 0.74–0.79). When sex-specific ROC analyses were performed, sensitivity and specificity were 61% and 91% in men, and 50% and 95% in women, respectively. Although the performance of BNP testing on the basis of these figures might be suboptimal, efficacy was improved in subgroups with a high prevalence of heart disease (>8%) such as the cohort aged ≥65 years (men, area under ROC curve = 0.88; cost <US$1400: women, area under ROC curve = 0.83; cost <US$3000) as well as the cohort having cardiovascular risk factors such as hypertension or diabetes (men, area under ROC curve = 0.85; cost <US$1700: women, area under ROC curve = 0.83; cost <US$3100). Conclusion The present results suggest that BNP testing for structural heart disease screening in community-based populations is useful for cohorts with a high prevalence of heart disease. However, its efficacy is reduced in cohorts with a low prevalence rate.

Precursors for rock fracturing and failure—Part II: IRR T-Curve abnormalities

There are many precursors including the abnormality of infrared radiation (IRR) for rock fracturing. The temporal evolution of surface IRR from loaded rock is the combined effect of rock thermoelasticity, pore gas desorbing–escaping, fracture propagation and extension, rock friction, heat transfer and environmental radiation. Being the integral indicator of the surface IRR energy, the mean IRR temperature (AIR T) is selected as the quantitative index to study the temporal evolution of IRR from loaded rock and to identify the precursors for rock fracturing and failure. This paper introduces some typical AIR T curves of uniaxially loaded, compressively sheared and biaxially loaded rock samples. The temporal evolution features of the AIR T curves and three precursor messages, which are short dropping, fast rising and dropping-to-rising, for rock fracturing are analyzed. For theoretical interpretation, the mechanism of AIR T abnormality is studied by taking the actuator, the rock sample and the environment as an independent system in an energy balance state. The heat transfer, as well as the thermoelastic effect based on the sum of principal stresses, has a positive or negative effect on AIR T; the desorbing and escaping of pore gas, as well as the production of new fractures and the expansion of initial fissures, joints and new produced fractures, have a negative effect on AIR T, while the friction action between fractures and between grains has a positive effect on AIR T. It is concluded that the occurrence of precursors is at 77–94% rock strength, i.e., stress peak, and the compressively loaded rock and biaxially loaded rock have clear AIR T precursors for rock fracturing and failure.

Precursors for rock fracturing and failure—Part I: IRR image abnormalities

There are many precursors, including the abnormality of infrared radiation (IRR), for rock fracturing and failure. As the comprehensive effect of rock thermoelasticity and rock friction, the study of the IRR abnormality of loaded rock, as one of the important issues of remote sensing rock mechanics (RSRM), is facilitated by the fast development of IR remote sensing imaging technology. In view of energy input and consumption by the loading system, comprised of loader, rock and air, the mechanism of surface IRR from loaded rock is studied. The concepts that surface IRR is the comprehensive effect of a series of physical–mechanical processes inside loaded rock and that the thermoelastic effect and the frictional–thermal effect are two of the main mechanisms are presented here. Based on retrospective investigation of the fundamental experiments on RSRM during the past decade, it is concluded that there are two kinds of IRR abnormality as precursors of rock fracturing and failure: IRR image abnormality and IRR temperature curve abnormality. The spatial–temporal evolution of abnormal surface IRR images of loaded rock in a condition of uniaxial stress, compressive shear, biaxial stress, frictional slide and impact is systematically analyzed. The fact that large IRR can occur in the fracturing center of compressively loaded and shearing fractured strong and brittle rock is also revealed. Finally, the relation between rock stress and IRR temperature are studied based on thermomechanical coupling theory for solid materials. It is concluded that IRR image abnormalities are important precursors for rock fracturing and meaningful for the forecast of rockbursts and tectonic earthquakes.

Lone atrial fibrillation and atrial fibrillation with hypertension are precursors of overt heart failure

Introduction: Atrial fibrillation (AF) and heart failure (HF) are each risk factors for the other. Alterations in the natriuretic peptide axis are well recognized in overt HF, and we recently identified elevations of nt-proBNP in lone AF (LAF). We sought to determine whether known markers of HF were altered in subjects with AF and hypertension (AF/HTN) without evidence of structural heart disease.

Radiofrequency catheter ablation of premature ventricular complexes from right ventricular outflow tract improves left ventricular dilation and clinical status in patients without structural heart disease

The present study evaluated clinical benefits of radiofrequency catheter ablation (RFA) for premature ventricular complexes from right ventricular outflow tract (RVOT-PVC) in patients without structural heart disease. It is unknown whether PVC causes left ventricular (LV) dilation, which is a well-recognized precursor of LV dysfunction and heart failure, and whether eliminating PVC by RFA produces clinical benefits in patients with RVOT-PVC. Frequency of PVC per total heart beats by 24-h Holter monitoring, left ventricular ejection fraction (LVEF), left ventricular end-diastolic internal dimension (LVDd), mitral regurgitation (MR) by echocardiogram, cardiothoracic ratio (CTR) by chest radiogram, and New York Heart Association (NYHA) functional class of 40 patients with RVOT-PVC without structural heart disease were evaluated before and 6 to 12 months after RFA. Before RFA, a subgroup of patients with frequent (>20%) PVC demonstrated significantly enlarged LVDd and CTR, reduced LVEF, increased MR, and deteriorated NYHA functional class as compared to the subgroup with rare (<20%) PVC (54 +/- 1 mm vs. 45 +/- 1 mm, 52 +/- 2% vs. 46 +/- 1%, 66 +/- 2% vs. 73 +/- 2%, 1.2 +/- 0.2 degree vs. 0.4 +/- 0.1 degree, and 1.8 +/- 0.2 vs. 1.3 +/- 0.1, respectively; p < 0.05). Furthermore, ablating RVOT-PVC readily produced the improvement of all these abnormalities (47 +/- 1 mm, 41 +/- 1%, 72 +/- 2%, 0.3 +/- 0.1 degree, and 1.0 +/- 0.0, respectively; p < 0.05 compared with before RFA). These findings suggest that frequent (>20%) RVOT-PVC may be a possible cause of LV dysfunction and/or heart failure, and RFA produces clinical benefits in these patients.

A sudden drop of fractal dimension: a likely precursor of catastrophic failure in disordered media

The variation of fractal dimension and entropy during a damage evolution process, especially approaching critical failure, is investigated. The results show that, as damage evolves, the fractal dimension and entropy of the spatial distribution of microcracks/voids decrease. A sudden drop of fractal dimension can be viewed as a quantitative indicator of damage localization or a likely precursor of an impending catastrophic failure. Using mining-induced rock bursts as an example, the complexity and difficulties of prediction are discussed.

Cochlear reimplantation in children: soft signs, symptoms and results

Objectives Cochlear implant device failures and reimplantation have mainly been reported on in adults. The purpose of this study was to isolate precursors of device failures and assess the effects of reimplantation in children. Methods From 1997 to 2003, 27 children underwent cochlear reimplantation at our institution. The pre-failure complaints were categorized and correlated with actual failure modes and postimplantation results. Speech-recognition tests were used to evaluate preand post-reimplantation performance. Results Pre-failure length of usage ranged from 0 to 12 years. Symptoms including pain, intermittence, reduced performance, noise and the need for frequent device adjustments were associated with device failures, although not with a particular mode of failure. Post reimplantation performance was equal to but not immediately better than pre-failure results in children who received upgraded devices. Conclusions Specific complaints, frequent need for device adjustments and reduced speech recognition can be precursors to device failures, underscoring the need for routine follow-up evaluations. Reimplantation with newer technology does not guarantee improved speech understanding and often requires an adjustment period to reach prereimplantation levels.

Cochlear reimplantation in children: soft signs, symptoms and results

Objectives Cochlear implant device failures and reimplantation have mainly been reported on in adults. The purpose of this study was to isolate precursors of device failures and assess the effects of reimplantation in children.Methods From 1997 to 2003, 27 children underwent cochlear reimplantation at our institution. The pre-failure complaints were categorized and correlated with actual failure modes and postimplantation results. Speech-recognition tests were used to evaluate preand post-reimplantation performance.Results Pre-failure length of usage ranged from 0 to 12 years. Symptoms including pain, intermittence, reduced performance, noise and the need for frequent device adjustments were associated with device failures, although not with a particular mode of failure. Post reimplantation performance was equal to but not immediately better than pre-failure results in children who received upgraded devices.Conclusions Specific complaints, frequent need for device adjustments and reduced speech recognition can be precursors to device failures, underscoring the need for routine follow-up evaluations. Reimplantation with newer technology does not guarantee improved speech understanding and often requires an adjustment period to reach prereimplantation levels.

Diagnostics and prognostics based on adaptive time-frequency feature discrimination

This paper presents a novel diagnostic technique for monitoring the system conditions and detecting failure modes and precursors based on wavelet-packet analysis of external noise/ vibration measurements. The capability is based on extracting relevant features of noise/ vibration data that best discriminate systems with different noise/vibration signatures by analyzing external measurements of noise/vibration in the time-frequency domain. By virtue of their localized nature both in time and frequency, the identified features help to reveal faults at the level of components in a mechanical system in addition to the existence of certain faults. A prima-facie case is made via application of the proposed approach to fault detection in scroll and rotary compressors, although the methods and algorithms are very general in nature. The proposed technique has successfully identified the existence of specific faults in the scroll and rotary compressors. In addition, its capability of tracking the severity of specific faults in the rotary compressors indicates that the technique has a potential to be used as a prognostic tool.