Failure Analysis in Conceptual Phase toward a Robust Design: Case Study in Monopropellant Propulsion System (original) (raw)

As a system becomes more complex, the uncertainty in the operating conditions increases. In such a system, implementing a precise failure analysis in early design stage is vital. However, there is a lack of applicable methodology that shows how to implement failure analysis in the early design phase to achieve a robust design. The main purpose of this paper is to present a framework to design a complex engineered system resistant against various factors that may cause failures, when design process is in the conceptual phase and information about detailed system and component is unavailable. Within this framework, we generate a population of feasible designs from a seed functional model, and simulate and classified failure scenarios. We also develop a design selection function to compare robust score for candidate designs, and produce a preference ranking. We implement the proposed method on the design of an aerospace monopropellant propulsion system.

System Reliability Design Analysis of Propulsion Structures

Volume 3B: General, 1993

The reliability of a gas turbine engine structure is affected by the uncertainties in the operating environment (speed, temperature etc.) as well as in the structural properties (material properties, geometries, boundary conditions etc.). A computational method for accurate reliability estimation under such uncertainties is described in this paper. Reliability computation for individual failure modes (burst, LCF etc.) as well as overall system failure is addressed. System failure probability is computed through the union of individual mode failures. The method also provides precise sensitivity information about the effect of each uncertain parameter on the individual failure probabilities as well as on the system failure probability. Such quantitative information helps rational design decisions as well as risk assessment and certification.

Methodologies to improve reliability engineering in early design

2011

approved: ___________________________________________________ Robert B. Stone ___________________________________________________ Irem Y. Tumer This thesis is the summation of two publications with the motivation to move reliability analysis earlier in the design process. Current analyses aim to improve reliability after components have been selected. Moving specific analyses earlier in the design process reduces the cost to the designer. These early design analyses provide information to the designer so that critical design changes can be made to avoid failures. The first presents failure rates for function-flow pairs. These function-flow failure rates are used in the Early Design Reliability Method (EDRM) to calculate system level reliability during functional design. This methodology is compared to the traditional reliability block diagram for three examples to show its usefulness during early conceptual design. Next, an extension to the Function Failure Design Method (FFDM) is p...

Design Exploration, Robust Design and Reliable Design: Three Successive and Complementary Approaches

Once a design concept chosen and parameterized, the embodiment design stage consists in choosing materials and dimensions to ensure a « good matching » with the expected performances. In this context, several approaches exist which correspond to slightly different complexities and issues, which are more or less easy to implement and must, consequently, be used at different stages. We consider in this paper three families of approaches: exploring design dimensioning under uncertainty (through constraint programming techniques, representations of feasible design points or Pareto frontiers), robust design and multi-disciplinary optimization, and lastly design for reliability. One states that these approaches must be used in that order. Indeed, applying an approach allows to quickly figure out inadequacies with performance specifications or initial allowable bounds of design parameters and then to backtrack or to refine the design issue before passing to the next stage or approach. We i...

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