A Preventive Maintenance Model Subject to Sequential Inspection for a Three-Stage Failure Process

For a system subject to gradual degradation, it can be in one of three different states: normal, minor defective, or severe defective stages, which can overall be referred to as a three-stage failure process.For this system, periodic inspection may not be the most ideal policy.Fewer inspections will lead to lower costs if the system is in the normal stage, but if the system is in the defective stage, frequent inspections are recommended to prevent failure.Therefore, it may be more economical to take the sequential time ( 0,1, 2, )