Mock Exam: Optimum Useful Life and Optimum Replacement Time

Author(s):  
Kay Poggensee
Keyword(s):  
Author(s):  
B. J. Rogus ◽  
E. P. Weinert

Investigators have compared results of gas turbine hot section material rig tests to field experiences with identical materials. They proposed that such correlation would be useful for turbine design engineers. But gas turbine users, particularly in the marine field, need a guide to correlate the few reported hot section experiences and realistically project when parts should be replaced. It is suggested that most hot section materials in properly protected marine gas turbines have much lower deterioration rates than those predicted. After coatings on turbine nozzles and blades have been operationally removed, increasingly better predictions of replacement time are possible. Sample at-sea experiences and environmental full-scale test results are offered to illustrate some unity among isolated experiences within a generalized framework of gas turbine hot section deterioration. A method for predicting further useful life of hot parts is proposed. A procedure and tool for in-place nondestructive evaluating of hot section deterioration are offered with a guide for scheduling future maintenance sections.


Author(s):  
John R. Devaney

Occasionally in history, an event may occur which has a profound influence on a technology. Such an event occurred when the scanning electron microscope became commercially available to industry in the mid 60's. Semiconductors were being increasingly used in high-reliability space and military applications both because of their small volume but, also, because of their inherent reliability. However, they did fail, both early in life and sometimes in middle or old age. Why they failed and how to prevent failure or prolong “useful life” was a worry which resulted in a blossoming of sophisticated failure analysis laboratories across the country. By 1966, the ability to build small structure integrated circuits was forging well ahead of techniques available to dissect and analyze these same failures. The arrival of the scanning electron microscope gave these analysts a new insight into failure mechanisms.


2005 ◽  
Vol 48 (2) ◽  
pp. 208-217 ◽  
Author(s):  
Matthew Watson ◽  
Carl Byington ◽  
Douglas Edwards ◽  
Sanket Amin

Soil Horizons ◽  
1967 ◽  
Vol 8 (4) ◽  
pp. 15
Author(s):  
A H. Martinson
Keyword(s):  
Soil Map ◽  

2020 ◽  
Vol 14 ◽  
Author(s):  
Dangbo Du ◽  
Jianxun Zhang ◽  
Xiaosheng Si ◽  
Changhua Hu

Background: Remaining useful life (RUL) estimation is the central mission to the complex systems’ prognostics and health management. During last decades, numbers of developments and applications of the RUL estimation have proliferated. Objective: As one of the most popular approaches, stochastic process-based approach has been widely used for characterizing the degradation trajectories and estimating RULs. This paper aimed at reviewing the latest methods and patents on this topic. Methods: The review is concentrated on four common stochastic processes for degradation modelling and RUL estimation, i.e., Gamma process, Wiener process, inverse Gaussian process and Markov chain. Results: After a briefly review of these four models, we pointed out the pros and cons of them, as well as the improvement direction of each method. Conclusion: For better implementation, the applications of these four approaches on maintenance and decision-making are systematically introduced. Finally, the possible future trends are concluded tentatively.


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