Addressing challenges when performing a multidisciplinary design approach - a case study for evaluating robustness in early design studies

Abstract: This thesis work aims to get an insight into how the organisation at GKN Aerospace Sweden takes on multidisciplinary design and, in particular, how they work with manufacturing aspects in early phases. In addition, the work investigates an approach and explores how this approach can be improved. Firstly, an interview study was conducted to gain more understanding on how the product design processes in the organisation look like today and what challenges the engineers experience. Then a case study was performed to test a method for multidisciplinary robustness evaluation.  In the interview study, 11 engineers from various disciplines at GKN were asked about their opinions, ideas and problems with different components of multidisciplinary work, such as automation, robust design and manufacturability evaluation.  The case study focused on analysing the robustness of a Turbine Rear Structure (TRS) design. A TRS is linked to many different engineering disciplines and must withstand high thermal and structural loads as well as fulfil requirements regarding aerodynamic performance and weight. If these requirements change during the product development process it can in some cases lead to a costly redesign loop in order to meet the updated requirements. In this use case the variation of thermal loads and the impact on stresses and life cycle fatigue is investigated. Based on experience from previous product development programs, the temperatures are often subject to changes during the later phases of the design process. Traditionally, thermal loads are applied on different zones of the structure as certain values, and if the design is optimised only for the nominal values, there is a risk that the component will not meet the life cycle fatigue requirements when the temperature loads change. This is why a robustness evaluation is needed.  The interview study results show that there are challenges related to each of the themes explored when it comes to the multidisciplinary design approach at GKN. From the challenges identified, the ones deemed most important were problems with evaluating and defining robustness, the lack of quantitative tools for considering manufacturability in the early design stage, and the lack of communication and knowledge sharing between disciplines. Overall, a conclusion drawn from the findings is that there is a need for more systematic MD approaches. The case study in turn resulted in an outline of a method for early robustness evaluation using the software platform OptiSLang.