Doctoral dissertation

Doctoral dissertation: Graph representation helps make early decisions in complex projects

Hossein Mokhtarian - Photograph Sanna-Mari Ratilainen
A new conjoint design and modeling methodology introduces a new category of tools for early simulation and decision support in engineering projects. The method is generic and supports multiple aspects and complexity levels in the development and manufacturing process. The approach integrates and encodes different forms of knowledge into visual, colour-coded graphs.

Design changes in products or processes late in the development process often cost companies dearly. Being able to understand how the product and manufacturing process go together and affect each other early in the design process helps reduce operational costs and produce sustainable products. Current early design approaches involve abstract product or process model development and, therefore, do not provide the required level of detail that designers need to make informed decisions about potential improvements or redesigns. Different models may also be difficult to combine and evaluate together as a whole.

In his dissertation, Hossein Mokhtarian aimed to provide designers the capability to create a visual graph representation of their product or process models with varying levels of detail as needed for evaluation purposes. The approach combines different types of models, knowledge from experts as well as experimental data.

In a joint project between Tampere University and Université Grenoble Alpes in France, Mokhtarian developed an approach to operationalise and automate certain engineering design concepts, such as that of contradiction. Genrich Altshuller said, “Inventing is the resolution of technical contradictions.” Hence, inventing new products or manufacturing processes or improving existing products or processes requires detecting and resolving technical weaknesses and contradictions in the design of parts and manufacturing methods. The continuous improvement of product and process design is a means to improve product quality, material efficiency and the value of products to support sustainable development goals.

“This method has a vast domain of potential applications, also beyond traditional engineering. The approach could benefit the realms of system design, modeling and simulation, smart manufacturing and artificial intelligence, for example,” Mokhtarian says.

In the study, a design framework called Dimensional Analysis Conceptual Modeling, or DACM, is developed to improve products and processes through the development of oriented graphs and a systematic search for weaknesses and contradictions in them. The method integrates and encodes different forms of knowledge in a hypergraph representation, or a graph with color-coding. The method enables designers to anticipate any limitations in their solutions and make informed decisions towards the redesign of either the product or the manufacturing process.

“The DACM framework realises the idea of combining different forms of knowledge, different models of a product and the process in a unified way by means of graphs. Industry 4.0, or the fourth industrial revolution, is already underway in Europe. The advancement of new complex technologies, such as additive manufacturing (AM), also known as 3D printing, can benefit from this tool,” Mokhtarian notes.

Developing integrated modeling approaches has been the goal of major research institutions and national labs in Europe and USA. This research direction is seen as a potential means to move AM technology forward in industrial settings. DACM is a tool that serves that purpose and provides the necessary attributes to integrate several engineering domains and concepts under a single approach.

Hossein Mokhtarian comes from Iran and currently works at Tampere University.

The doctoral dissertation of Hossein Mokhtarian in the field of mechanical and industrial engineering entitled Product-process integrated meta-modeling using a graph-based approach: application to additive manufacturing will be publicly examined at the Faculty of Engineering and Natural Sciences at Tampere University at noon on Wednesday, 27 March 2019 in auditorium FA032 of the Festia building in Tampere University, Hervanta Campus, Korkeakoulunkatu 8. The opponents will be Professor Lionel Roucoules (Universités Arts et Métiers ParisTech, France) and Professor Kai Cheng (Brunel University, London). Professor Eric Coatanéa from the Faculty of Engineering and Natural Sciences at Tampere University will act as Chairman.

The dissertation is available online at

Photo: Sanna-Mari Ratilainen