Design engineering approach to ensuring specified dependability. Case study of unique, highly critical systems with short operation life

Abstract

Aim. To examine the design engineering approach to ensuring specified dependability on the basis of engineering disciplines and design engineering methods of quality and dependability assurance using the case of unique, highly critical products with short operation life. Such approach, unlike the statistical procedures of modern dependability, allows associating the dependability indicator calculations with the calculated operability parameters and established design criteria that are to be met in order to confirm the specified dependability indicators for products with an indefinite number of critical elements, each of which operates according to a functional principle that is different in its nature. Methods. The paper examined the prerequisites for the implementation of the design engineering approach to dependability, such as the distinctive features of ensuring the dependability of unique, highly critical products with short operation life, the applicability of design engineering approach to dependability, the effect of the genesis on the assurance of design engineering dependability, behavioural models of technical products in terms of dependability and specifics of highly critical product calculation. It was identified that, for items with high specified probability of no failure exceeding three-sigma random value variation interval, dependability is to be calculated not by identifying the dependability function, but rather by proving that undependability function is below the acceptable value, which ultimately ensures the specified dependability. Such approach enables the development of methods of early failure prevention using procedures of design engineering analysis of dependability for the purpose of achieving the required parameters of functionality, operability and dependability of products on the basis of a generalised parametric functional model. Results. The design engineering analysis of dependability allows substantiating the criteria for error-free design (selection of sound principles of operability and validation of engineering solutions for achieving the required dependability indicators). The effect of the error-free engineering criteria combined with the criteria for defect-free engineering (observance of the generally accepted principles, rules, requirements, norms and standards of drawing generation) and defect-free manufacture (strict adherence to the requirements of drawings with no deviation permits) enables a designer to achieve the specified dependability values without using the statistical methods of the modern dependability theory. Conclusion. Dependability as a comprehensive property is characterised by a probability that, on the one hand, determines the rate of possible failures, and, on the other hand, indicates the number of errors that were made by engineers during the design, manufacture and operation of products and can lead to failures. Additionally, the failure rate is determined by the engineers’ efforts to eliminate or mitigate the consequences of possible failures at each life cycle stage. The greater and earlier are such efforts adopted, the higher the product’s dependability will be. Ultimately, dependability is determined by consistent and rigorous implementation of error-free design, defect-free design and defect-free manufacture procedures whose efficiency is in no way associated with the number of manufactured products. Their efficiency and effectiveness are determined by specific decisions and actions by the engineers who make sure that the product performs the required functions with the specified dependability in the established modes and conditions of operation. Ensuring that only takes using engineering disciplines, as well as design engineering methods for quality and dependability assurance.