Materials Science Forum Vols. 539-543

Abstract: As we enter the 21st century, we confront three global challenges that can be resolved only with forefront science and technology: growing demands for energy, the adverse effects of climate change, and emerging threats to national and global security. Materials science is critical to the fields of research, development, and application that are essential to meeting these challenges. The increasing globalization of scientific research and technology development presents its own challenges at the national level, but also opens the way to new opportunities for fruitful collaboration in materials science.

Abstract: Industrial thermomechanical processing of hot rolled steel strip products with rolling operations in the austenite + ferrite (γ + α) range offers, on one hand, unique possibilities for more precise control of microstructure and mechanical properties of as hot rolled products after accelerated cooling. On the other hand, there are significant technical problems related to the rolling stability induced by steel grade dependent non-monotonous variations in deformation resistance and its sensitivities to temperature and strain rate within the γ + α range. Based on laboratory results, the deformation behavior of low carbon (up to 0.2 %) steels alloyed with Mn, Si, Al and their combinations, as well as microalloyed with Nb at the intercritical temperatures is discussed.

Abstract: Materials engineering plays vital role in Solid Oxide Fuel Cell (SOFC) technology. For example, engineered porous materials are needed to support delicate electrolyte membranes, where mechanical integrity and effective diffusivity to fuel gases is critical; and to construct fuel cell electrodes, where an optimum combination of ionic conductivity, electronic conductivity, porosity and catalyst distribution is critical. Material engineering also underpins selection of cell designs and material systems to minimise failure, particularly during transient operations such as thermal cycling. The paper will address these issues, making reference to high temperature (>900C) SOFCs for integration with gas turbines, and metal supported SOFCs designed to operate at temperatures of 500-600C.

Abstract: There are two obstacles to be overcome in the CSP production of HSLA heavy gauge strip and skelp, especially for API Pipe applications. First, the microalloying should be conserved by eliminating the high temperature precipitation of complex particles. Second, the heterogeneous microstructure that normally results from the 800 micron initial austenite in the 50mm slab as it is rolled to 12.5mm skelp must be eliminated to optimize the final microstructure and improve the final mechanical properties. Alteration in the hot rolling sequence can strongly homogenize the final austenite and resulting final ferritic microstructure. When coupled with a low coiling temperature near 550°C, the new rolling practice can result in Nb HSLA steels that can easily meet requirements for strength, toughness and ultrasonic testing in 12.5mm skelp gauges for X70 API pipe applications. The underlying physical metallurgy of these two breakthroughs will be presented and discussed in detail.

Abstract: Flying robots with flapping wings are preferred over conventionally fixed or rotational wings in terms of hovering capability for a simple mechanical configuration. Until recently, available actuators for such a robot are limited to (1) a conventional motor with four-bar linkage mechanism or (2) a piezo electric actuator, but none of them could provide enough lift because of low flapping frequency, small stroke angles, and/or frequent mechanical failure. A new actuator capable of generating large stroke angles with high frequency is developed. It consists of an out-runner brushless motor with a modified motor driver attached to a torsion spring. The wing is attached directly on the cap of the motor. A prototype is built and preliminary thrust force measurements are performed. Properties of wing materials suitable for powerful and robust actuators will be discussed. The actuator employed in the present study utilizes resonance oscillation, which leads to high energy efficiency. Further study of wing shape and directional stiffness is needed for generating higher lift capability.

Abstract: In this work we have outlined the use of micromechanical models which can rationalize the behaviour of a number of structural steels by including both static and dynamic length scales and considering the interaction of the phases. The approach treats the steels as composites but includes the influence of both volume fractions and physically based length scales and processes. In essence it can be extended to utilise the methodology outlined by Ashby&al. to include length scales in the development diagrams of composite materials.

Abstract: Besides reducing fuel consumption, the chief motivating factor behind the development of new vehicle structures is the desire to decrease climate-affecting emissions. One approach to addressing this involves reducing the vehicle mass and, as such, the various strategies relating to lightweight construction. Various methods of lightweight construction are used as a basis for deriving the technically relevant criteria for designs and material concepts. The work conducted in this field today centres around the synthesis of construction method and material development with the objective of devising a multi-material-design [1, 2]. Modularisation is an economic approach aimed at shaping the diversification of the vehicle concepts and implementing this effectively [3]. As a result of hybrid and later fuel cell drives, the requirements on the vehicle concepts will continue to grow in future. Modularisation also sometimes opposes the striving for a high level of integration. The modular lightweight concept of the DLR aims at designing powertrain evolutions in a scalable and cost-efficient manner and in a way that retains the concept flexibility or, in some cases, even increases this. These approaches lead to the strategy known as “hybrid3”. This strategy not only involves matching different materials and various construction methods with each other, but also taking account of the integration of functional effects. This entails, for example, optimising the design of thin-walled structural components in terms of their vibratory or acoustic properties with structure- integrated, active materials. Further examples of the approach with “hybrid3” effects could be selectable surfaces or integrated energy conversion. The various development directions are depicted in the form of a roadmap and discussed on the basis of forward-looking examples from the field of vehicle construction.