Industry 4.0 is moving forward under technology upgrades, utilizing information technology to improve the intelligence of the industry, whereas Industry 5.0 is value-driven, aiming to focus on essential societal needs, values, and responsibility. The manufacturing industry is currently moving towards the integration of productivity enhancements and sustainable human employment. Such a transformation has deeply changed the human–machine interaction (HMI), among which digital twin (DT) and extended reality (XR) are two cutting-edge technologies. A manufacturing DT offers an opportunity to simulate, monitor, and optimize the machine. In the meantime, XR empowers HMI in the industrial field. This paper presents an XR application framework for DT-based services within a manufacturing context. This work aims to develop a technological framework to improve the efficiency of the XR application development and the usability of the XR-based HMI systems. We first introduce four layers of the framework, including the perception layer with the physical machine and its ROS-based simulation model, the machine communication layer, the network layer containing three kinds of communication middleware, and the Unity-based service layer creating XR-based digital applications. Subsequently, we conduct the responsiveness test for the framework and describe several XR industrial applications for a DT-based smart crane. Finally, we highlight the research challenges and potential issues that should be further addressed by analyzing the performance of the whole framework.

The Friction Stir Channelling (FSC) is a novel advanced solution for producing internal closed channels along any desired path with a constant or continuously modified shape along the path in a single manufacturing step. The channels are formed by continuous extraction of part of the stirred processed material into external flash. In this work, the performance of channels with the same shape and dimensions but produced by FSC and milling respectively, are compared using an experimental calorimeter setup with a focus on the influence of the geometrical features of the channels on the thermal efficiency. The investigation is implemented in a plate of AA5083-H111, with a thickness of 10 mm. The material properties of the channels produced by FSC are investigated with a microhardness field and optical microscopic analysis, assessing the thermomechanically processed and heat affected zones. The mechanical resistance of the channels produced by FSC is evaluated with an application of internal pressure up to 380 bar. The results show that the FSC enhanced the heat transfer by about 45 % compared with smoother milled channels. The optical microscopy shows evidence of a good consolidation of the solid state joining mechanisms activated during the FSC, with a small reduction of the hardness around the channel in the stirred zone and heat affected zone, being assisted by a harder top region at the ceiling of the channel.

Digital twin documents are expected to form a global network of digital twins, a “Digital Twin Web”, that allows the discovery and linking of digital twins with an approach similar to the World Wide Web. Digital twin documents can be used to describe various aspects of machines and their twins, such as physical properties, nameplate information, and communication interfaces. Digital twin is also one of the core concepts of the fourth industrial revolution, aiming to make factories more efficient through optimized control methods and seamless information flow, rendering them “smart factories”. In this paper, we investigate how to utilize digital twin documents in smart factory communication. We implemented a proof-of-concept simulation model of a smart factory that allowed simulating three different control methods: centralized client-server, decentralized client-server, and decentralized peer-to-peer. Digital twin documents were used to store the necessary information for these control methods. We used Twinbase, an open-source server software, to host the digital twin documents. Our analysis showed that decentralized peer-to-peer control was most suitable for a smart factory because it allowed implementing the most advanced cooperation between machines while still being scalable. The utilization of Twinbase allowed straightforward removal, addition, and modification of entities in the factory.

Digital twins (DTs) and eXtended Reality (XR) are two core technological enablers for engineering in the Metaverse that can accelerate the human-centric Industry 5.0 transformation. The digital twin technology provides a digital representation of a physical asset with data linkages for inspection, monitoring, and prediction of complex processes or systems, while eXtended reality offers real-and-virtual combined environments for human users to interact with machines. However, the synergies between digital twins and eXtended reality remain understudied. This work addresses this research gap by introducing a novel method “TwinXR” that leverages ontology-based descriptions of Digital twins, i.e., digital twin documents, in industrial eXtended reality applications. To ease the use of the TwinXR method, we publish a Unity package that allows data flow and conversion between eXtended reality applications and digital twin documents on the server. Finally, the work applies the TwinXR method in two industrial eXtended reality applications involving overhead cranes and a robot arm to demonstrate the use and indicate the validity of the method. We conclude that the TwinXR method is a promising way to advance the synergies between digital twins and eXtended reality: For eXtended reality, TwinXR enables efficient and scalable eXtended reality development; For digital twins, TwinXR unlocks and demonstrates the potential of digital twins for data interchange and system interoperation. Future work includes introducing more detailed principles of Semantic Web and Knowledge Graph, as well as developing factory-level TwinXR-compatible applications.

Solid Oxide Fuel Cell (SOFC) systems achieve high electrical efficiency and can utilize many types of fuels such as methanol or biogas. These systems operate at high temperatures up to 600–1000 °C. Due to high temperatures, mechanical engineering must be combined with thermal engineering through the design work. System design for SOFC systems should take into account several functions such as mechanical support of components, thermal insulation, instrumentation, compensation for thermal expansion and heat recovery as well as conduction of gases through channels, piping or open cavities. One should note that many of these functions have strong interactions and cannot be designed without an effect on the system as a whole. When a system is designed to fulfill all the expectations, it will have a compact size, good thermal properties, small pressure losses and good overall performance together with a competitive price, long system lifetime and easy maintenance. This article aims to improve the mechanical structure of SOFC systems. In addition, our aim is to give sophisticated recommendations for a system design. To achieve this, we have used systematic concept development tools and methodologies to investigate the interactions and relative importance of system requirements and functions. Our key result from this study is that engineers must use a holistic approach when designing a high temperature system with strong interactions between system functions and components. Contrary to our former expectations, these systems could not be designed well by methods that are based on reductionism. In practice, this means that thermal engineering must be utilized from the very beginning. Thermal insulation concept should be selected during the first design steps since this has a great effect on system layout. Mechanical engineering is needed in system layout design in order to solve problems related to the thermal expansion and support of components. Combined thermal and structural analysis utilizing finite element methods can be used to develop or optimize mechanical key components and system layout. The best results can be achieved by using a holistic approach during the design process. In addition, it is beneficial to keep the system as simple and compact as possible. To achieve this, the integration of functions and components must be increased. Thus, SOFC system performance is greatly dependent on system design, not only of its components alone. Findings obtained from this study can be used by researchers designing experimental apparatuses or by companies manufacturing full scale SOFC systems.