Abstract: In view of the complexity of the conceptual design of mechanical products, an iteration-based function–behavior- mechanisms-structure (FBMS) model is proposed. According to the characteristics of the design of mechanical products, the close relationships among the function, behavior, mechanisms and structure of the mechanical systems are studied, which imply that the behavior and mechanisms are a bridge across function and structure. Therefore, a new model, which supports the iterative process in the conceptual design and func-tion-behavior-mechanisms-structure mapping approaches, is established, further, the formal description method of the model is proposed by taking key points of the model into account. Based on the analysis of the operational characteristics of be-haviors and mechanisms in iterative design process, the detailed steps of iterative design and the corresponding iterative algo-rithm are presented. Finally, the design of a real-life mechanical product is taken as an example to validate the effectiveness of the FBMS model, and then the integral characteristics of the model are analyzed by comparing with those of existed models. The results show that the model is helpful for the innovative synthesis of mechanisms and optimal function-structure match- ing in the conceptual design.

Key words: Conceptual design, Design model, Iteration, Qualitative reasoning