Current Issue : April - June Volume : 2012 Issue Number : 2 Articles : 7 Articles
Steering module is a part of automotive suspension system which provides a means for an accurate vehicle placement and stability\ncontrol. Components such as steering knuckle are subjected to fatigue failures due to cyclic loads arising from various driving\nconditions. This paper intends to give a description of a method used in the fatigue life reliability evaluation of the knuckle used\nin a passenger car steering system. An accurate representation of Belgian pave service loads in terms of response-time history\nsignal was obtained from accredited test track using road load data acquisition. The acquired service load data was replicated\non durability test rig and the SN method was used to estimate the fatigue life. A Pearson system was developed to evaluate the\npredicted fatigue life reliability by considering the variations in material properties. Considering random loads experiences by the\nsteering knuckle, it is found that shortest life appears to be in the vertical load direction with the lowest fatigue life reliability\nbetween 14000ââ?¬â??16000 cycles. Taking into account the inconsistency of the material properties, the proposed method is capable of\nproviding the probability of failure of mass-produced parts....
We propose an asymptotic nonparametric confidence interval for quantile-based process capability indices (PCIs) based on the\r\nsuperstructure CNp(u, v) modified from Cp(u, v) which contains the four basic PCIs, Cp, Cpk, Cpm, and Cpmk, as special cases.\r\nSince the asymptotic variance of the estimator for quantile-based PCIs involves the density function of the underlying process,\r\nthe existing asymptotic results cannot be used directly to construct confidence limits for PCIs. To obtain a consistent estimator\r\nfor the asymptotic variance of the estimated quantile-based PCIs, in this paper, we propose to use the kernel density estimator for\r\nthe underlying process. Consequently, the confidence limits for PCIs are established based on the consistent estimates. A real-life\r\nexample from manufacturing engineering is used to illustrate the implementation of the proposed methods. Simulation studies\r\nare also presented in this paper to compare the two quantile estimators that are used in the definition of PCIs....
Microelectromechanical systems (MEMS) are a fast-growing field in microelectronics. MEMS are commonly used as actuators\nand sensors with a wide variety of applications in health care, automotives, and the military. The MEMS production cycle can\nbe classified as three basic steps: (1) design process, (2) manufacturing process, and (3) operating cycle. Several studies have\nbeen conducted for steps (1) and (2); however, information regarding operational failure modes in MEMS is lacking. This paper\ndiscusses reliability in the context of MEMS functionality. It also presents a brief review of the most relevant failure mechanisms\nfor MEMS....
Multivariate analysis is increasingly used to include all dimensions of quality concept, in light of rapid development of customer\r\nrequirements. With the recent advances in information technology and in recording, large amounts of multivariate data are now\r\nneeded to be analyzed. Many charting procedures are based on Mahalanobis distance, but their applicability relies heavily on the\r\nrequirement of normality and their performance is related to the choice of a type I error rate. An alternative charting scheme based\r\non data depth is pursued and its performance is assessed through a real example. This performance and that of a T2 chart for\r\nindividual observations are discussed. Using the centre-outward ranking, this new method named DD-diagram is used to detect\r\nany multivariate quality datum that one of its components exceeds its limiting variation interval. For a given error-free sample, the\r\nDD-diagram can be used to signal out any point of another observed sample taken from a multivariate quality process. This new\r\nscheme based on data depth uses a properly chosen limiting variation line or Lvalue in order to evaluate the outlyingness of every\r\npoint in the observed sample in all directions of the considered P-variates of quality process....
This paper considers the estimation problem for the Frechet distribution under progressive Type II censoring with random\r\nremovals, where the number of units removed at each failure time has a binomial distribution. We use the maximum likelihood\r\nmethod to obtain the estimators of parameters and derive the sampling distributions of the estimators, and we also construct the\r\nconfidence intervals for the parameters and percentile of the failure time distribution....
We study the loss of power of the stratified log-rank test (SLRT) compared to the unstratified log-rank test (ULRT) in the case of\na large number of strata with relatively a small number of stratum sizes in terms of the asymptotic distributions of test statistics\nunder local alternatives. The SLRT tends to lose information due to overstratification. It is better to test the homogeneity among\nstrata before using the stratified log-rank test....
It is incontrovertible that financial markets are dominated by risk averse. This does not prevent investors from expecting high returns. The age-long challenge facing them had always been the intricacies of determining appropriate measure of risk and the equilibrating relationship between the measure of risk and the associated expected return of an investor. The tail conditional variance, TCV for short, provides a measure of the variability of the risk along the tail distribution. In this paper, we derive explicit formulas for computing TCV for a Weibull Distribution. We further examine the distortion risk measure to the degree of variability of a loss random variable in the tail of the Weibull Distribution....
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