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Vasiliy V Krivtsov

Vasiliy V Krivtsov
The Ford Motor Company · Global Data Insights & Analytics

PhD
Director of Reliability Analytics

About

47
Publications
23,831
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Introduction
Director of Reliability Analytics at the Ford Motor Company. Adjunct Professor of the University of Maryland. A Ph.D. degree in EE from Kharkov Polytechnic Institute (Ukraine) and a Ph.D. in Reliability Engineering from the University of Maryland (USA). Author of over 50 professional publications, including 2 books 9 patented inventions and 6 trade secret inventions on statistical algorithms of Ford. Further info is avaiable at www.krivtsov.net

Publications

Publications (47)
Article
Forecasting warranty claims for complex products is a reliability challenge for most manufacturers. Several factors increase the complexity of warranty claims forecasting, including, the limited number of claims reported at the early stage of launch, reporting delays, dynamic change in the fleet size, and design/manufacturing adjustments for the pr...
Article
In the era of internet of things and Industry 4.0, smart products and manufacturing systems emit signals tracking their operating condition in real-time. Survival analysis shows its strength in modeling such signals to determine the condition of in-service equipment and products to yield critical operational decisions, i.e., maintenance and repair....
Article
There is a variety of models available for repairable systems with general repairs. Most popular are the Kijima models (reflecting the generalized renewal process of recurrent failures) and the Lam model (reflecting the geometric process). The Kijima models relating system's real and virtual ages can be thought of as the time shift transformation,...
Article
Rapid developments in information technologies enabled recording big data environments in near real-time. Such big data environments provide an unprecedented opportunity for efficient event detection and therefore effective reliability models, but they also pose interesting challenges. One challenge is modeling the number of recurrent events for he...
Chapter
Full-text available
We consider a reliability maximization problem for a high–voltage commutation device, wherein the total voltage across the device is shared by the components in series configuration. Here, the increase of the number of load–sharing components increases component–level reliability (as the voltage load per component reduces) but may decrease system–l...
Article
Full-text available
In reliability engineering, load sharing is typically associated with a system in parallel configuration. Examples include bridge support structures, electric power supply systems, and multiprocessor computing systems. We consider a reliability maximization problem for a high-voltage commutation device, wherein the total voltage across the device i...
Article
Full-text available
This paper is a sequel to [1], wherein we proposed a simple procedure to construct the joint prior and posterior distributions of Weibull parameters based on the underlying reliability function estimates in two time cross–sections. In this paper, we extend the procedure in three aspects: a) the prior data can now be taken in terms of a simple proba...
Conference Paper
Full-text available
The problem of recurrent failure prediction arises in forecasting warranty repairs/cost, maintenance optimization and evaluation of repair quality. The most comprehensive prediction model is the g–renewal process proposed by Kijima, which allows for modelling of both perfect and imperfect repairs through the use of the so–called restoration factor....
Article
Consider a set of the so-called sibling components in a multi-socket repairable system. In the case of an automobile, for example, these siblings would be spark plugs, light bulbs, tires, that is, identical components that are coded with the same part number. When field data are analyzed, a dilemma arises as to how to interpret a recurrent replacem...
Conference Paper
Full-text available
This paper considers a point process model with a monotonically decreasing or increasing ROCOF and the underlying distributions from the location-scale family, known as the geometric process. In terms of repairable system reliability analysis, the process is capable of modeling various restoration types including “better-than-new”, i.e., the one no...
Conference Paper
Full-text available
The purpose of this paper is to share some practical applications of advanced probabilistic models in reliability data analysis. In particular, we will focus on reliability models with fixed and time−dependent covariates. While these models are popular in biological and medical studies, their application in engineering reliability data analysis is...
Article
Engineering systems often contain some identical components (parts), the so-called "siblings". In the case of an automobile, these would be engine spark plugs, light bulbs, wheels, etc. These sibling components are typically coded with the same part number. When field (warranty) data are analyzed, a dilemma arises as to how to interpret a recurrent...
Article
Full-text available
Statistical estimation of G-renewal process parameters is an important estimation problem, which has been considered by many authors. We view this problem from the standpoint of a mathematically ill-posed, inverse problem (the solution is not unique and/or is sensitive to statistical error) and propose a regularization approach specifically suited...
Article
Full-text available
Various replacement policies under Kijima's general repair model with the underlying Weibull distribution function are studied via two efficient methods. The first one is based on our previously derived approximate formula for the g-renewal function; the second is an improved Monte Carlo method. These methods enable an in-depth, comparative analysi...
Article
Full-text available
An important characteristic of the g–renewal process, of great practical interest, is the g–renewal equation, which represents the expected cumulative number of recurrent events as a function of time. Just like in an ordinary renewal process, the problem is that the g–renewal equation does not have a closed form solution, unless the underlying even...
Chapter
Full-text available
This paper introduces a simple index that helps to assess the degree of aging or rejuvenation of repairable systems and non-repairable systems (components). The index ranges from − 1 to 1. It is negative for the class of decreasing failure rate distributions and point processes with decreasing ROCOF and is positive for the increasing failure rate d...
Article
Full-text available
This paper considers a point process model with a monotonically decreasing or increasing ROCOF and the underlying distributions from the location-scale family, known as the geometric process (Lam, 1988). In terms of repairable system reliability analysis, the process is capable of modeling various restoration types including "better-than-new", i.e....
Article
Full-text available
Probability distributions traditionally used in reliability analysis (e.g. exponential, Weibull, lognormal, normal, gamma and inverse Gaussian) do not always provide enough flexibility to model real-world lifetime data. Considered in this paper is a quadratic spline with a single free knot as a model of the cumulative hazard function for increasing...
Article
Full-text available
This paper introduces a simple index that helps to assess the degree of aging or rejuvenation of a (non)repairable system. The index ranges from -1 to 1 and is negative for the class of decreasing failure rate distributions (or deteriorating point processes) and is positive for the increasing failure rate distributions (or improving point processes...
Article
Corrections to (6) in "A simple procedure for Bayesian estimation of the Weibull distribution" (vol. 54, pp. 612-616, Dec 05) are presented here.
Article
An overwhelming majority of publications on Nonhomogeneous Poisson Process (NHPP) considers just two monotonic forms of the NHPP's rate of occurrence of failures (ROCOF): the log-linear model the power law model. In this paper, we propose to capitalize on the fact that NHPP's ROCOF formally coincides with the hazard function of the underlying lifet...
Conference Paper
Full-text available
This paper is a sequel to the work published in 2004 RAMS Transactions on the nonparametric estimation of the marginal in time and mileage failure distributions. Depending on the failure mode, accumulated time in service (hereafter just time) and mileage could be either a survival variable (i.e. the one "driving" failures and representing failure d...
Article
Full-text available
Practical use of Bayesian estimation procedures is often associated with difficulties related to elicitation of prior information, and its formalization into the respective prior distribution. The two-parameter Weibull distribution is a particularly difficult case, because it requires a two-dimensional joint prior distribution of the Weibull parame...
Article
Fatigue life regression models with constant and non-constant variance are evaluated and compared with a Random Fatigue Limit Model and a Probit model to estimate the fatigue strength and S-N relationship from fatigue test data. The Maximum Likelihood method is used to estimate parameters of the above models. Emphasis also is given to assessing the...
Conference Paper
Full-text available
It is not uncommon that a component's reliability characteristics depend on two usage variables. As an example, for automotive components such variables are time in service and accumulated mileage. For certain airplane chassis components, these variables are accumulated flight hours and the number of landings. The problem of failure time distributi...
Article
Full-text available
The paper considers an empirical approach to the root-cause analysis of a certain kind of automobile tire failure. Tire life data are obtained from a laboratory test, which is developed to duplicate field failures. A number of parameters related to tire geometry and physical properties are selected as explanatory variables that potentially affect a...
Article
Full-text available
This undergraduate and graduate textbook provides a practical and comprehensive overview of reliability and risk analysis techniques. Written for engineering students and practicing engineers, the book is multi-disciplinary in scope. The new edition has new topics in classical confidence interval estimation; Bayesian uncertainty analysis; models fo...
Conference Paper
A brief overview of the statistical aspects of warranty prediction is given as an introduction. The main discussion then focuses on warranty claim prediction for repairable products. Introduced by Kijima and Sumita (1986), a g-renewal process (GRP) can be considered as a model for major repair assumptions encountered in repairable product reliabili...
Article
Variants of technical solutions of high-voltage devices with current-free commutation, hercone-thyristor and hercone-transistor communitation devices are considered. These devices enable to commutate currents from milliampere units up to tens of ampere under 5-15 kV voltages with fastresponse from 1 to 0.01 millisecond. The considered devices cover...

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