Soft Failure Research Articles

Remaining useful life (RUL) estimation of electronic solder joints in rugged environment under random vibration

The remaining useful life (RUL) of electronic modules under the influence of rugged random-vibration and operational conditions is investigated in this paper. The effects of storage conditions and soft failures, caused by the vibrations to solder joints of a printed circuit board (PCB) are analyzed. The RUL is estimated with the help of vibration testing and finite element analysis techniques. Keeping in view the standard and working environmental conditions, the PCB of a power distribution module is subjected to random and sine vibrations. Besides the significance of fatigue damage and RUL estimation of solder joints, caused by storage or operation for a period of five years has not been addressed in existing literature so far. The current study performs the modal analysis to find the natural frequencies, mode shapes, and participation factor ratios of a PCB and its components. These natural frequencies are subsequently verified via comparison with experimental sine sweep results. A random vibration test over the frequency range from 10 Hz to 2000 Hz is also applied for recording the time-to-failure ratio of the PCB. Moreover, the spectrum analysis is performed using the commercial ANSYS software, to assess the acceleration response and the stress power spectral density (PSD) of the critical solder joints. The stress PSD is then used to estimate the random vibration fatigue damage of the solder joint. The calculated fatigue life, based on the modified Miner's rule and the Basquin power-law conform to the actual random vibration testing results.

System Availability Modelling and Optimization considering Multigeneral Quality Characteristics

This paper analyzes the necessity that multigeneral quality characteristic parameters should be considered in availability modelling and optimization and then constructs an availability model including the indicators of reliability, maintainability, supportability, testability, and environmental factor. In the research process, it is assumed that the system has soft and hard failure mode, adopting mixed maintenance strategies, system delay time, and repair time, and test time are independent. On the basis of this, the single parameter, binary parameters, and multiparameters optimization were carried out with the maximum availability as the optimization function. Especially, the multiparameters availability optimization model in time dimension was designed based on particle swarm optimization. The design method was proved feasible through a numerical example, which can provide method support for the design and evaluation of general quality characteristic thresholds in the life cycle of a repairable system.

Study on Improved Nonlinear Viscoelastic-Plastic Creep Model Based on the Nishihara Model

The description of rock creep by existing rheological models mainly focuses on the first two stages of creep. However, the description of the accelerated creep stage is rare, which is contrary to the common study of soft rock failure in engineering applications. Therefore, the study of the accelerated creep stage is an important research direction at present. In this paper, a new model that can describe accelerated creep is proposed on the basis of the Nishihara model, and creep constitutive relation of the model is deduced via relevant laws. The parameters of the model are obtained by the whole rheological curves of the sandy mudstone of the diversion tunnel of a hydropower station and the strongly weathered sandstone in the bottom of the Xiangjiaba dam foundation. A fitting analysis of the theoretical results and experimental data indicates that the fitting results are highly consistent; the correlation coefficients are all above 0.98, which shows the rationality and correctness of the model. The nonlinear viscoelastic-plastic model proposed in this paper can accurately describe the accelerated creep stage of rock, and its applicability is obviously broader than that of the traditional Nishihara model. This nonlinear viscoelastic-plastic model can be used to not only predict the critical sliding of a rock mass in slope, tunnel and hydraulic engineering but also enrich the theory of rock rheology.

A Cost-Effective Structure for Secondary Discharge Control to Improve System-Level ESD Immunity of a Mobile Product

A structure embedded in a printed circuit board is proposed to control secondary discharge currents and improve the system-level electrostatic discharge (ESD) immunity for a mobile product with a metal frame. Noise voltages and discharge currents were measured and analyzed according to several secondary discharge paths, such as an air arc, a voltage suppressor device, and with the interlaced suppression device. ESD events that caused soft failures of a real commercial mobile product were tested while a high-definition video was playing. System-level ESD-induced noise and soft failures were cost effectively reduced by the interlaced suppression device.

Optimal condition-based maintenance with general repair and two dependent failure modes

This paper proposes a condition-based maintenance (CBM) policy for a system subject to dependent soft and hard failures. When the deterioration exceeds a predetermined level, the system experiences a soft failure that can be rectified by corrective general repair or corrective replacement. Three possible actions, namely no maintenance, preventive general repair, and preventive replacement, are considered at each inspection epoch. The hard failure rate depending on both age and deterioration is described by a proportional hazards model with the covariate characterized by a gamma process. The hard failure can be corrected by minimal repair, general repair, or by replacement. Different from previous CBM policies, no thresholds are used to define maintenance actions. The objective is to determine the optimal maintenance policy that minimizes the long-run expected average cost per unit time. The optimization problem is formulated in the semi-Markov decision process (SMDP) framework and solved by the policy iteration algorithm. Two practical numerical examples are provided to illustrate the proposed policy. The comparison with other CBM policies shows an outstanding performance of the proposed policy, as well as the significance of minimal repair and general repair in CBM decision making.

Constant‐Resistance, Rigid, and Flexible Coupling Support Technology for Soft Rock Entrances in Deep Coal Mines:A Case Study in China

The stability control of a soft rock roadway is a crucial problem for sustainable utilization of limited coal resources in deep mining practices. To solve it, the soft rock types and failure mechanism of −890 entrance surrounding rock have been analyzed, taking Daqiang Coal Mine of China as an engineering example. The analysis shows that the damage to the surrounding rock was characterized by asymmetry, large deformation, severe damage, and extended durations. The surrounding rock can be divided into high‐stress‐jointed‐strong expansion soft rock based on S‐M scanning and mineral analysis. Numerical simulation is used to reproduce the failure process of the original supporting system and analyze the deformation of the surrounding rock, range of plastic zone, and distribution of the stress field. The failure mechanism is thus defined for a deep soft rock roadway. Combined with the above studies, the deformation mechanics of the surrounding rock is summarized as type IABIIABIIIABC. The stability transformation mechanism of the surrounding rock is proposed, based on which the control principle of deformation stability of a surrounding rock is formed. According to the control principle, “high strength support controls the surrounding rock deformation. The large deformation of the flexible support system releases the accumulated energy to the surrounding rock, and long‐term deformation of the surrounding rock is controlled by high strength truss support.” Meanwhile, the constant‐resistance, rigid, and flexible coupling (CRRFC) support system is proposed. The numerical analysis demonstrated that the CRRFC support system can effectively reinforce the shallow surrounding rock and improve the bearing capacity. Simultaneously, the development of the surrounding rock malignant plastic zone is effectively controlled. The application results show that the large deformation of the roadway can be effectively controlled by the CRRFC support system, which provides applications for similar engineering.

Investigation of soft ESD failure on capacitive transimpedance amplifier for hybrid integrated infrared sensor

Investigation of soft ESD failure on capacitive transimpedance amplifier for hybrid integrated infrared sensor

Evaluation method of voltage fluctuation performance considering cyber soft failure

Voltage regulation based upon cyber system has been extensively used with the development of cyber-physical system. Still, cyber failure may result in controlling failure, which inevitably has an effect on the overall voltage performance of distribution network. In order to access the influence of cyber fault on voltage regulation, a cyber system validity model considering cyber soft failure is proposed. The analytical approach of voltage fluctuation and measurement indices of voltage fluctuation are also developed. Based on simulation of IEEE 33-bus system, proposed model is proved to simulate voltage regulation process taking cyber soft failure into consideration. Each influence of different fault factors is analyzed, which provides practical technical support for the planning and operation of the distribution system. This paper provides strategies for the research into cyber fault of distribution network, which has essential significance along with follow-up value.

Combination of stiffness, strength, and toughness in 3D printed interlocking nacre-like composites

Constituted by mineral tablets and organic interlayers, nacre is known for its attractive combination of stiffness, strength, and toughness. The impressive mechanical property of nacre can be attributed to the ‘brick-and-mortar’ structure which is usually defined with two geometric parameters: tablet aspect ratio and volume fraction of the stiff phase. Inspired by the interlocking tablets found in red Abalone and Hyriopsis cumingii, we study the effect of interlock by introducing a third parameter: tablet waviness angle. Tension tests and single edge notched bend fracture tests are performed on the specimens of interlocking and non-interlocking nacre-like composites that are fabricated using a high-resolution multi-material 3D printer. Stress distribution, deformation pattern and parameter analysis reveal the mechanical behavior of interlocking and non-interlocking nacre-like composites and how these three parameters affect the performance. Two failure patterns (soft phase failure and tablet break) and three toughening mechanisms (uncracked-ligament bridging, constrained microcracking, and crack deflection/twist) are found in three-point bending fracture tests, which uncovers the key to high toughness. Interlocking nacre-like composites clearly show enhanced tensile and fracture performance with an unusual combination of stiffness, strength, and toughness.

BLUEs and Reliability Analysis for General Censored Data Subject to Inverse Gaussian Distribution

Working on product lifetime data is of significant importance for evaluating safety and reliability, predicting remaining useful life and formulating maintenance strategy or replacement policy. In practical applications, observed datasets often consist of failure data and randomly censored data, which are referred as general censored data. Meanwhile, inverse Gaussian (IG) distribution has been widely adopted to depict lifetime data because it not only can possess flexible expression formats but also can explain the mechanism of first hitting time from a soft failure viewpoint. Motivated by these two regards, this paper develops a novel method on best linear unbiased estimations (BLUEs) for general censored data. A three-parameter IG distribution type is adopted. A novel method is established to optimize the skewness parameter. Then, BLUEs of mean and standard deviation can be obtained. The proposed method can construct closed-form parameter estimations in linear functions of order statistics. The computation process has been further simplified for flexible applications. The frequently utilized maximum likelihood estimation method is also introduced as a reference for a better understanding. Comparative results of both comprehensive simulation study and empirical application illustrate that the proposed method can significantly enhance the estimation accuracy and keep a stable performance, because more life information can be extracted and adopted from the censored datasets.

Stability analysis of vertical caisson breakwater on soft intercalated ground under cyclic loading

A vertical caisson breakwater on soft intercalated ground (sand replacement in the upper layer) is highly susceptible to catastrophic failure when subjected to excessive cyclic loadings. In this paper, the cyclic stability of a caisson-rubble-ground system under different sand replacement conditions is investigated via finite element methods. Structure-soil interfaces and undrained strength degradation of the soft intercalated layer are two key considerations. The latter is implemented by modifying the Yasuhara model to quantify the strength degradation in terms of the number of cycles and stress level. Cyclic responses with different replacement ratios r (i.e., the ratio of backfilled sand layer thickness to initial total soft layer thickness) are presented in terms of pore pressure and strength degradation. Failure modes and safety factors are also investigated. Numerical results show that the pore pressure and strength degradation of the soft layer mainly occurred underneath the rubble mound, and were evident at small replacement ratios. The failure modes could be caisson sliding (r ≤ 0.35), soft ground bearing capacity failure (r > 0.50), or a combination thereof (0.35<r ≤ 0.50). The safety factor first increased and then approached a constant value with increasing replacement ratios. The findings herein provide a practical implication for safety evaluation and structural design.

Total femur prosthesis in oncological and not oncological series. Survival and failures

Total femur prosthesis (TFP) can be used in both oncological and prosthetic revision surgery. A retrospective analysis of 32 patients receiving a TFP at a single Center between 2002 and 2018 was performed. The average follow-up was 60 months. Revision implant free survival (RIFS) of the implants was 87% at 5 and 10 years and 72% at 15 years. Overall implant survival (OIS) of the prosthesis was 90% at 5, 10 and 15 years. Complications observed: two soft tissue failures, two infection failure and one tumor progression failure.

Predictive maintenance of systems subject to hard failure based on proportional hazards model

The remaining useful lifetime (RUL) estimated from the in-situ degradation data has shown to be useful for online predictive maintenance. In the literature, the RUL is often estimated by assuming a soft-failure threshold for the degradation data. In practice, however, systems may not be subject to the degradation-induced soft failures. Instead, the systems are deemed to be fail when they cannot perform the intended function, and such failures are known as hard failures. Because there are no fixed thresholds for hard failures, the corresponding RUL estimation is not an easy task, which causes difficulties in finding the optimal maintenance schedule. In this study, a Weibull proportional hazards model is proposed to jointly model the degradation data and the failure time data. The degradation data are treated as the time-varying covariates so that the degradation does not directly lead to system failures, but increases the hazard rate of hard failures. A random-effects Wiener process is proposed to model the degradation data by considering the system heterogeneities. Based on the developed proportional hazards model, closed-form distribution of the RUL is derived upon each inspection and the optimal maintenance schedule is then obtained by minimizing the system maintenance cost. The proposed maintenance strategy is successfully applied to predictive maintenance of lead-acid batteries.

Equivalent Mechanical Model for Cylindrical Lithium-ion Battery Under Mechanical Abuse and Soft Short-circuit Failure Warning

Based on the analysis of the experimental data for cylindrical lithium-ion battery under mechanical abuse, an equivalent mechanical model of spring-damping parallel unit connects a damping unit in series is proposed in this paper. By combining the equivalent mechanical model with the Crushable-Foam material model, the experiments and simulations on the flat plate tests, rigid rod tests and hemispherical punch tests are performed, the prediction error of the simulation model to the failure displacement is less than 11%. After that, the equivalent mechanical model is analyzed, a soft short-circuit failure prediction model is proposed. A failure warning system is designed according to the prediction model, and the warning system can prompt the soft short-circuit failure of the battery in time and has a certain safety margin.

PerfSONAR: An Importance of Multi-Domain Network Monitoring

Research community interacts by means of multi-domain networks. Operating policies, set of hardware components, customers, bandwidth configuration varies from network to network. Hard failures like fiber cut, power failures are easy to detect while soft failures which result in packet loss and degrade the throughput are difficult to detect. Present network monitoring tools are subject to single administrative domain. Hence, network cannot be monitored over multiple domains. Performance focused Service Oriented Network monitoring ARchitecture (perfSONAR) is designed and developed by open source community which supports advanced level of network monitoring across multi domain network. In this paper, I have focused on the importance of multi-domain network monitoring and reviewed the work of perfSONAR proposed by various researchers.

Dual-Stage Soft Failure Detection and Identification for Low-Margin Elastic Optical Network by Exploiting Digital Spectrum Information

Supported by advanced digital signal processing algorithms and application specific integrated circuits, coherent receivers in elastic optical networks will be capable of measuring link impairments in real time. Specifically, coherent receivers can work as soft optical performance monitors. Optical spectra usually contain rich information about optical links and have been exploited to assist soft failure detection and identification. However, acquiring optical spectra needs the deployment of numerous optical spectrum analyzers. Instead, the digital spectra of received signals in coherent receivers are easy to obtain without the penalty of additional hardware. In this paper, we explore the feasibility of the digital spectra in assisting soft-failure detection (SFD) and soft failure identification (SFI). A digital spectrum based SFD and SFI framework is proposed. A dual-stage SFD structure is employed to reduce the monitoring and processing overhead in optical nodes. At the first-stage SFD, only bit error rate and received optical power are collected. When an anomalous sample is detected, extra digital spectrum features are extracted and collected for the second-stage SFD. Extensive numerical results are presented to analyze the digital spectrum characteristics and feature distributions of four common soft failures. Finally, we experimentally evaluate the detection and identification performance of the proposed method. With reasonable complexity, a false positive rate of 0.42% and a false negative rate of 1.47% can be achieved for SFD, and an identification accuracy of 99.55% can be obtained for SFI.

A Perspective on Test Methodologies for Supervised Machine Learning Accelerators

Neural Network (NN) accelerators are essential in many emerging applications e.g., autonomous systems in making mission-critical decisions, health-care solutions to assist with diagnoses, etc. Any soft or hard failure during operation can potentially have catastrophic consequences in many of these applications. For instance, inaccurate classification during object recognition and tracking in autonomous vehicles can lead to crashes and subsequent injuries to the passengers. Therefore, testing Neural Network accelerators to ensure reliability and integrity of the underlying hardware is a crucial task to ensure the functionality, especially the ones that are used in mission-critical applications. Conventional functional, stuck-at and delay tests are not sufficient to characterize the ML systems since they face new test and validation challenges. This paper is aimed to provide a perspective on new test requirements and design for test techniques to cover ML features and detect various type of faults in NN accelerator. We discuss First-In-First-Out (FIFO) and Scratchpad based neural network hardware accelerators and propose test methods to detect the faults as well as fault location in different modules of the accelerator including MAC unit, Activation function module, and Processing Element (PE) registers.

Dependent Competing Failure Modeling for the GIL Subject to Partial Discharge and Air Leakage With Random Degradation Initiation Time

Confronted with the ever-growing demand for electricity delivery over long distances, the gas insulated transmission line (GIL), as an advanced underground technology, has been under rapid development recently. Physics-of-failure analysis for the GIL indicates that it experiences two competing failure modes: 1) Once the amount of air leakage is greater than a predetermined threshold level, a deterioration-based soft failure happens. 2) The arrival of a partial discharge with overlarge voltage will result in a shock-based hard failure. Furthermore, statistical analysis of some engineering projects shows that the beginning of the GIL degradation, i.e., the inner air begins to leak, occurs after an initiation time. In addition, the flashover voltage decreases considerably as the SF6 in the GIL leaks outside and the moisture penetrates inside, which reflects that the hard failure threshold level is related to the degradation process. Confronted with these problems, a new dependent competing failure model is presented for the GIL, with the consideration of degradation initiation time. The GIL reliability assessment is obtained through theoretical derivation, and the numerical calculation method with controllable approximation accuracy. Finally, a case study is carried out to show the implementation of the proposed model.

Measurement Techniques to Identify Soft Failure Sensitivity to ESD

Electrostatic discharge (ESD)-induced soft failures are a critical issue for electronic systems as the failures are mostly found after the hardware design is completed. Any changes applied to the hardware may delay the project. Diagnostic tools capable of identifying soft failure-induced malfunctions in an early stage of product design help to reduce the risk of late stage ESD-induced project delays. In many cases, soft failures can be directly observed by the user interface, system crash, or other obvious indicators. However, in an early product design stage the operation system may be marginal and applications may not be available. To improve the ability to detect soft failure critical design choices, this paper presents several methods to identify ESD-induced changes which may not be observable via direct observation. These methods include the observation of ac or dc currents, monitoring dc voltages, capturing near fields and processing them via short-term fast fourier transform (FFT), wavelet transformation, down mixing to audible range, and monitoring for latch-up via thermal imaging. The paper introduces the basis of each method, shows examples, and compares them for their detection ability.

Modeling criteria of older non-ductile concrete frame–wall buildings

The purpose of seismic provisions included in modern building codes is to obtain a satisfactory structural performance of buildings during earthquakes. However, in the United States and elsewhere, there are large inventories of buildings designed and constructed several decades ago, under outdated building codes. Some of these buildings are classified as non-ductile buildings. Currently, under the ATC-78 project, a methodology is being developed to identify seismically hazardous frame–wall buildings through a simple procedure that does not require full nonlinear analyses by the responsible engineer. This methodology requires the determination of the controlling plastic collapse mechanism, the base shear strength, and the ratio between the story drift ratio and the roof drift ratio, called parameter \(\alpha\), at collapse level. The procedure is calibrated with fully inelastic nonlinear analyses of archetype buildings. In this paper we first introduce an efficient scheme for modeling frame–wall buildings using the software OpenSees. Later, the plastic collapse mechanism, the base shear strength, and values of \(\alpha\) are estimated from nonlinear static and dynamic analyses considering a large suite of ground-motion records that represent increasing hazard levels. The analytical experiment included several frame–wall combinations in 4 and 8-story buildings, intended to represent a broad range of conditions that can be found in actual buildings, where the simplified methodology to evaluate the risk of collapse can be applicable. Analysis results indicate that even walls of modest length may positively modify the collapse mechanism of nonductile bare frames preventing soft story failures.