| Mental iteration in conceptual design involves repetition of cognitive activities when designers perceive the discrepancy of desired state and the current state of design. Although it is believed that mental iteration has significant impact on design process and design performance, little proof has been developed and our current understanding of mental iteration is still limited. This lack of understanding limits our ability to provide effective methods and tools for improving current design practice.; This dissertation develops a framework that provides insight into mental iteration in conceptual design. A cognitive activity model is developed to identify and capture various iteration loops of cognitive activities in conceptual design. A series of experiments using protocol analysis was conducted to validate the model, study the effects of design problems and constraints on mental iteration, and investigate the impact of mental iteration on designers' performance. The results revealed that designer's iteration behavior varies in response to design problem types and constraint conditions, and the variation follows certain patterns. Moreover, it was found that mental iteration has not only positive but also negative impact on design performance and different iteration loops yield different impacts.; This research made following contributions to the field of engineering design research. First, it advances the knowledge on mental iteration behavior in conceptual design and deepens the understanding of the impact of mental iteration on design performance. Second, the developed findings can be applied to improve current design practice and the development of supporting tools. Third, it introduces a new research method and a model for studying mental iteration in design. |
