ABSTRACT
Many researchers (including Dhillon 1992, Murari and Goyal 1984, Singh 1989, Srinivasan and Gopalan 1973) have studied the different types of systems under the assumption that the system becomes as good as new after repair. In real life situations, however, it is not always possible to do so, since the working capacity of a repaired unit depends, more or less, on the repair mechanism exercised as well as the age of the system. We can observe sometimes that if a failed unit is not being repaired by an expert server then the unit does not work as new and becomes degraded with increased chances of failure. Mokaddis et al. (1997) have analyzed a two-unit warm standby system subject to degradation. Malik et al. (2008) have discussed a system with inspection subject to degradation. Chander and Singh (2009), Kumar et al. (2010), and Promila et al. (2010) have studied the different systems subject to degradation after repair. In their study, they have assumed that the degraded unit after failure is not repaired completely. However, in practical life, there may be situations when the degraded failed unit does not work as good as new after repair or the repair of the degraded failed unit is neither possible nor economical due to excessive use as well as high cost of maintenance. In such a situation, inspection plays an important role in deciding whether the unit that failed after degradation (degraded failed) can be operable as new after repair, or not. If the degraded failed unit does not work with full working capacity after repair, then it is advisable to replace it with new one in order to avoid unnecessary expenses on repair. Researchers (Nailwal and Singh 2011, 2012a, b, 2017, Ram, Singh and Singh 2013, Ram and Kumar 2014a, b, Manglik and Ram 2015, Kumar and Singh 2016, etc.) have discussed and studied different systems under different assumptions, and estimated their respective reliability parameters.
