The time and effort required for maintenance of an automobile system are highly dependent on its disassemblability, which is one of the most important attributes of its maintainability. To evaluate the disassemblability index, i.e. to measure the ease of disassembly, the disassemblability factors (both the design factors and the contextual factors) of an automobile system are identified. These and their interrelations are modelled by considering their structure using the graph theory. The directed graph (digraph) of the disassemblability of the automobile system is defined; the nodes of this represent its disassemblability factors, while the edges represent their degrees of influence. An equivalent matrix of the digraph establishes the system’s disassemblability function which characterizes the disassemblability of the system, leading to development of the disassemblability index. A high value of the disassemblability index indicates that it is very easy to remove or replace parts. The disassemblability index ratio is used to compare the actual conditions of disassembly with the ideal conditions of disassembly. A case study of an automobile gearbox is illustrated using the step-by-step procedure of the proposed methodology of disassemblability. The proposed methodology is helpful to evaluate and compare various alternative designs of the automobile system and, therefore, can aid the design and development of automobile systems from the disassembly viewpoint.

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Purpose The purpose of this paper is to develop an ontological model of failure knowledge of automobile systems that will enhance the knowledge management of automobile system failures, which will help for design and maintenance of automobiles. Failure knowledge of automobile systems and components gained through maintenance and repair can mitigate future failures, if integrated in the design. This is an outcome of this paper. Design/methodology/approach A failure coding scheme is developed for assimilating various entities of automobile failure knowledge and an ontological model is developed for its systematic structuring and representation. The developed failure code is a combination of alphanumeric and numeric code that incorporates ingredients of the failure knowledge, which will help database management, with reduced data entry time and storage space. Findings The maintenance of automobiles not only brings back the systems into operating conditions but also convey a lot of information regarding the failures. This is a useful input to the designers in development of reliable and maintainable automobile systems. A knowledge base can be created for automobile systems/components failures from their maintenance and service experience. Research limitations/implications Developed ontological model of automobile failure knowledge gained through maintenance experience can be shared across automobile manufacturers and service providers. This would help in design improvements, with ease and efficient undertaking of maintenance activities. This paper proposes the conceptual ontology structure, which is populated with three cases of automobile maintenance. Originality/value This research work is a first attempt to develop an ontological model for automobile failures from their maintenance and service experience. The novelty of the work is in its explicit consideration of all knowledge related to failures and maintenance of automobile systems, with their coding and structuring.