Accounting for future redesign to balance performance and development costs

Most components undergo tests after they are designed and are redesigned if necessary. Tests help designers find unsafe and overly conservative designs, and redesign can restore safety or increase performance. In general, the expected changes to the performance and reliability of the design after the test and redesign are not considered. In this paper, we explore how modeling a future test and redesign provides a company an opportunity to balance development costs versus performance by simultaneously designing the design and the post-test redesign rules during the initial design stage. Due to regulations and tradition, safety margin and safety factor based design is a common practice in industry as opposed to probabilistic design. In this paper, we show that it is possible to continue to use safety margin based design, and employ probability solely to select safety margins and redesign criteria. In this study, we find the optimum safety margins and redesign criterion for an integrated thermal protection system. These are optimized in order to find a minimum mass design with minimal redesign costs. We observed that the optimum safety margin and redesign criterion call for an initially conservative design and use the redesign process to trim excess weight rather than restore safety. This would fit well with regulatory constraints, since regulations usually impose minimum safety margins. & 2013 Elsevier Ltd. All rights reserved.