Development of maintainability index for mechanical systems

A procedure based on a digraph and matrix method is developed for evaluation of maintainability index of mechanical systems. Features which characterize or ease in maintenance of a system are identified and are called the maintainability attributes. Consideration of these attributes and their interrelations are rudiment in evaluating the index. This is modeled in terms of a Maintainability Attributes Digraph for the system. Nodes in the digraph represent these attributes and their interrelations are represented by the edges. The digraph is represented by one-to-one matrix for development of a maintainability expression, which is characteristic of the system. A Variable Maintainability Attributes Facilitation Permanent Matrix is defined to develop maintainability expression (VPF-m) which is also useful in comparing two systems. Maintainability Index of the system is obtained from the permanent of the matrix or from the maintainability expression by substituting numerical values of the attributes and their interrelations. A higher value of the index implies good maintainability of the system. The ideal value of maintainability index (Imi) is also obtained from the matrix expression, which is useful in assessing relative maintainability, Ir, of the system alternative. The procedure is useful in design and development of maintainable systems. A step by step procedure for evaluation of maintainability index is also suggested and is illustrated by means of an example.