Dynamic Fault Models Research Articles

Dynamic modeling and analysis of rolling bearing faults under time-varying excitations considering defect deformation

Fault mechanism analysis is one of the methods in fault diagnosis, and the dynamic modeling of rolling bearing faults plays a crucial role in studying fault mechanisms. Existing dynamic fault models only consider the impact of fault size and bearing speed on the impact force, providing an incomplete description of the impact force. In order to more accurately describe the dynamic fault model of impact forces, this paper focuses on the deep groove ball bearing with outer race faults. Factors such as defect deformation, speed, and fault size are considered, and an instantaneous impact force excitation function is proposed. Based on this proposed excitation function, a dynamic model for the outer race fault of deep groove ball bearings is established. Finally, through simulation and experimental comparison, the results indicate that the fault characteristic frequencies and their harmonics of the model in this paper are closer to the actual fault characteristic frequencies, reducing the error by 1 to 2 Hz. Therefore, the model proposed in this paper is more effective and accurate, providing a more precise rolling bearing fault model for the study of fault mechanisms.

Towards computational models of animal communications, an introduction for computer scientists

Animals communicate with each other via varieties of signal modalities such as visual, acoustic, semiochemicals, gestural, or communication behavior. Although animal communication has been studied as a signaler-receiver dyadic system until recently, it is actually a complex network due to the ubiquitous existence of third-party receivers in their signaling space, such as eavesdroppers, bystanders, and audiences. A question of fundamental importance in both science and humanity is whether or not animal signals are honest or deceitful (i.e., communication reliability) since it may shed light on the study of trust and altruism in human beings. The objective of this paper is twofold. First, the state-of-the-art research in animal communication (dyadic paradigm) and animal communication networks (network paradigm) and their potential inspiration for secure, resilient and pervasive computing are reviewed. Secondly, by arguing that competition, cooperation and communication are the three fundamental elements that natural selection acts upon in the evolution of organisms, and by comparing the study of cooperation (such as formulated as the Prisoner’s Dilemma (PD) game), with the study of animal communication (such as formulated with Sir Philip Sydney (SPS) game), it is suggested that the latter field may spawn important cross-disciplinary research with the potential influence similar to or beyond that generated by the PD game research. The paper also summarizes the recent extension to evolutionary game theory (EGT) with survival analysis and dynamic hybrid fault models by the author. Finally, seven open questions, with regard to animal communication inspired computing and communication, primarily from the interdisciplinary perspective are posed. As a side note, this is the second article of a two-part series in which I review the state-of-the-art research in behavior biology inspired computing and communication. Given the extensive scope of behavior biology, I only focus on two fields most relevant to computing and communication animal cognition (part one, Ma, 2014) and communication (this article). The previous part one reviewed animal-cognition inspired computing; part one also presented an overview of the behavior biology inspired computing. This part two is focused on animal communication; the relationship between cognition and communication is mainly discussed in this part also.

An efficient routing methodology to tolerate static and dynamic faults in 2-D mesh networks-on-chip

The move towards nanoscale Integrated Circuits (ICs) increases performance and capacity, but poses process variation and reliability challenges which may cause several faults on routers in Networks-on-Chips (NoCs). While utilizing healthy routers in an NoC is desirable, faulty regions with different shapes are formed gathering faulty routers. Fault regions can be used to lead the fault-tolerant routing algorithms to perform data transmission between healthy routers. In this paper a distributed fault-tolerant routing methodology for mesh networks is proposed which supports static and dynamic fault model. The static fault model supports minimal routing path which tolerates both convex and concave fault regions, while keeping the area and power overhead at a minimum level. Moreover, unlike most previous methods that support dynamic fault models, the presented method is able to tolerate any number of faults with any shapes of fault regions without disabling healthy nodes. The performance of the method is extensively evaluated, and the results show that our proposed method is valid for mesh topology, which has graceful performance degradation and allows the network to remain fully operational facing with the failures.

Frailty modelling for risk analysis in network security and survivability

The common usage of the term frailty, which literally means the condition (quality) of being frail or a fault, may be too ambiguous to be very useful for characterising network security. Nevertheless, the mathematical concept of frailty, which originated in the study of aging and demography, may offer a powerful approach for analysing the risks in network security and survivability. This is because network security analysis is essentially a risk analysis problem, and identifying risks, especially those that are uncertain, latent, unobserved or unobservable (UUUR) (Ma, 2008), and further analysing the potential dependence between those risks are two critical challenges for risk analysis in any field. Frailty modelling excels in addressing these two challenges. When it is integrated with dynamic hybrid fault models (DHF) and extended evolutionary game theory (EEGT) (Ma and Krings, 2011), frailty modelling should provide powerful approaches for analysing risks in network security and survivability.

Surface Rupturing and Buried Dynamic-Rupture Models Calibrated with Statistical Observations of Past Earthquakes

In the context of the slip-weakening friction model and simplified asper- ity models for stress state, we calibrate dynamic rupture models for buried and surface-rupturing earthquakes constrained with statistical observations of past earth- quakes. These observations are the kinematic source models derived from source in- versions of ground-motion and empirical source models of seismic moment and rupture area. The calibrated parameters are the stress-drop distribution on the fault and average stress drop. We develop a set of dynamic rupture models that consist of asperities and surrounding background areas. The distribution of dynamic stress drop outside the asperity is characterized by a fraction of the stress drop on the as- perity. From this set of models, we identify dynamic fault models with defined stress- drop characteristics that satisfy the observations. The selected dynamic fault models show that surface-rupturing earthquakes are characterized by a large area of negative stress-drop surrounding the asperities, while buried earthquakes present positive or zero stress drop. In addition, the calibrated fault models that match the observations show that the average stress drop is independent of earthquake size for buried earth- quakes, but scale dependent for surface-rupturing earthquakes. This suggests that, in the context of our parameterization, buried earthquakes follow self-similarity scaling, and surface-rupturing earthquakes break this self-similarity. We apply the calibrated dynamic models to simulate near-source ground motion consistent with observations that suggest that buried earthquakes generate stronger ground motion than surface- rupturing earthquakes at high frequency. We propose possible mechanisms that satisfy this observation, as follows: buried rupture has a hypocenter location below the as- perity; this can produce strong directivity of the slip velocity function toward the free surface. That effect, in addition to a reduced fault area and low fracture energy during rupture, may be significant in enhancing high-frequency ground motion. On the other hand, surface-rupturing earthquakes have a shallow hypocenter, large fracture energy on the asperities, and enhanced energy absorption due to large areas of negative stress drop in the background area. These characteristics of large earthquakes inhibit severe directivity effects on the slip velocity function directly toward the free surface, redu- cing the high-frequency ground motion.

Analysis of Dynamic Faults in Embedded-SRAMs: Implications for Memory Test

This paper presents the results of resistive-open defect insertion in different locations of Infineon 0.13 ?m embedded-SRAM with the main purpose of verifying the presence of dynamic faults. This study is based on the injection of resistive defects as their presence in VDSM technologies is more and more frequent. Electrical simulations have been performed to evaluate the effects of those defects in terms of detected functional faults. Read destructive, deceptive read destructive and dynamic read destructive faults have been reproduced and accurately characterized. The dependence of the fault detection has been put in relation with memory operating conditions, resistance value and clock cycle, and the importance of at speed testing for dynamic fault models has been pointed out. Finally resistive Address Decoder Open Faults (ADOF) have been simulated and the conditions that maximize the fault detection have been discussed as well as the resulting implications for memory test.

Testing with decision diagrams

Decision diagrams (DDs) are the state-of-the-art data structure in VLSI CAD. They are widely used and in the mean time have also been integrated in commercial tools. In the following special interest is devoted to the use of DDs in the area of testing. We give a brief review of test algorithms successfully using the capabilities of DDs as a data structure for tasks like fault detection, synchronization and built-in-self-test. In the main part of the paper we concentrate on synthesis for testability approaches where circuits are derived from DD representations. Depending on the type of the DD and its structural properties differing classes of DD-circuits result. Their testability properties with respect to static and dynamic fault models are analysed. In summary, the computation of complete test sets and of all occurring redundancies can be done easily and efficiently based on DD manipulation algorithms. Circuits with high testability can be obtained. Finally, generalizations of the concepts are discussed, in particular we consider the synthesis of circuits with reduced depth resulting from a combination of the DD approach with a composition method based on Boolean matrix multiplication.

Learning dynamic fault models based on a fuzzy set covering method

The synthesis of a real-time diagnostic expert system to monitor plant performance and identify faults in the event of process failure as well as signal potential failures is described. The crucial features which have been included are system reliability, use of dynamic trends in data and parameters to identify problem as well as the ability to handle complex knowledge. The emphasis here is on how a dynamic simulator is used to incorporate a learning algorithm based on a fuzzy set covering method for formulating a knowledge model of the operational characteristics, which enables debugging and testing of the system to be carried out continuously. The procedure is illustrated by reference to the operation of refinery crude oil distillation columns.

Integral equation method for plane crack with arbitrary shape in 3D elastic medium : E. Fukuyama & R. Madariaga, Bulletin — Seismological Society of America, 85(2), 1995, pp 614–628

Abstract We have derived stress integral equations for an arbitrary shaped plane crack in a three-dimensional (3D) infinite homogeneous isotropic elastic medium. First we obtained the integral equation for static crack, which is consistent with previous works. Then we derived a new boundary integral equation for the study of dynamic tensile and shear cracks. We removed the hypersingularity that appears in the usual formulation of the stress-boundary integral equation method by a regularization technique. The dynamic stress integral equation consists of three terms which can be physically explained. The first term is a modification of the static solution, the second one represents the diffraction of waves at slip discontinuities, and the last term is related to the effect of an instantaneous change in slip velocity. The first term controls the overall shape of the stress drop inside the crack. This term is important when we consider the final stress drop on the fault. However, the second and the third terms are dominant at a moving crack tip, and are responsible for the radiation of P and S waves. They are also very important for the application of a fracture criterion at the rupture front. Using this boundary integral equation we have calculated several numerical examples for both the static and dynamic fault models.

Integral equation method for plane crack with arbitrary shape in 3D elastic medium

AbstractWe have derived stress integral equations for an arbitrary shaped plane crack in a three-dimensional (3D) infinite homogeneous isotropic elastic medium. First we obtained the integral equation for static crack, which is consistent with previous works. Then we derived a new boundary integral equation for the study of dynamic tensile and shear cracks. We removed the hypersingularity that appears in the usual formulation of the stress-boundary integral equation method by a regularization technique. The dynamic stress integral equation consists of three terms which can be physically explained. The first term is a modification of the static solution, the second one represents the diffraction of waves at slip discontinuities, and the last term is related to the effect of an instantaneous change in slip velocity. The first term controls the overall shape of the stress drop inside the crack. This term is important when we consider the final stress drop on the fault. However, the second and the third terms are dominant at a moving crack tip, and are responsible for the radiation of P and S waves. They are also very important for the application of a fracture criterion at the rupture front. Using this boundary integral equation we have calculated several numerical examples for both the static and dynamic fault models.

Analysis and Design of Regular Structures for Robust Dynamic Fault Testability

Recent methods of synthesizing logic that is fully and robustly testable for dynamic faults, namely path delay, transistor stuck-open and gate delay faults, rely almost exclusively on flattening given logic expressions into sum-of-products form, minimizing the cover to obtain a fully dynamic-fault testable two-level representation of the functions, and performing structural transformations to resynthesize the circuit into a multilevel network, while also maintaining full dynamic-fault testability. While this technique will work well for random or control logic, it is not practical for many regular structures.To deal with the synthesis of regular structures for dynamic-fault testability, we present a method that involves the development of a library of cells for these regular structures such that the cells are all fully path-delay-fault, transistor stuck-open fault or gate-delay-fault testable. These cells can then be utilized whenever one of these standard functions is encountered.We analyze various regular structures such as adders, arithmetic logic units, comparators, multipliers, and parity generators to determine if they are testable for dynamic faults, or how they can be modified to be testable for dynamic faults while still maintaining good area and performance characteristics. In addition to minimizing the area and delay, another key consideration is to get designs which can be scaled to an arbitrary number of bits while still maintaining complete testability. In each case, the emphasis is on obtaining circuits which are fully path-delay-fault testable. In the process of design modification to produce fully robustly testable structures, we have derived a number of new composition rules that allow cascading individual modules while maintaining robust testability under dynamic fault models.