Singh, S.B.Pawan Kumar2017-03-302017-03-302016-01http://krishikosh.egranth.ac.in/handle/1/5810006406The present work consists of five chapters. A brief summary of these chapters is given below. Chapter one of the thesis is purely introductory in nature and contains history related to reliability theory with several definitions of different reliability tools which are often used in the study of reliability theory. Some different probabilistic distributions are also introduced in this chapter. This chapter also discusses the fundamental concepts of fuzzy set theory and gives some application of fuzzy set theory (FST) to reliability engineering. The chapter two contains review of literature pertaining to classical reliability analysis techniques of different researchers and recent research papers related to reliability theory, fuzzy theory and fuzzy reliability theory. Chapter three describes the different methodology of reliability evaluation of different complex systems using interval-valued intuitionistic fuzzy set, generalized trapezoidal intuitionistic fuzzy number, different types of level ( ߩ, ߣ ) interval-valued fuzzy number, and different types of conflicting bifuzzy failure rates. Concept of intuitionistic fuzzy Weibull lifetime distribution and intuitionistic fuzzy random lifetimes are also discussed in this chapter. The reliability and mean time to failure (MTTF) of the different systems are also evaluated. In chapter four some numerical examples are presented to illustrate how to calculate the fuzzy reliability using different methods under different fuzzy environments. The results obtained from the examples illustrated in this research also support the traditional facts of the system reliability. We can conclude from the present study that the proposed methods have no restrictions and it is applicable in situations where there are subjectivity, imprecision, uncertainty, ambiguity and hesitancy. In the final chapter, conclusions and future works are summarized.ennullThesis