Austenitic stainless steel for separating safeguards: development of an FEA-model for the simulation of impact tests in reference to material specific parameters

Austenitic stainless steels have a high potential for the use in separating safeguards of machine tools based on the TRIP (Transformation Induced Plasticity) effect. The problem with these materials is the high variance of the alloy composition. Therefore, the specific penetration resistance W _D,spec varies significantly. The presented research analyses the impact of material specific parameters on the specific penetration resistance W _D,spec and the FEA simulation of impact tests. The result of the project is the knowledge of the penetration resistance and hence the security (factor of safety) against penetration.     

Recrystallization kinetics of ultrafine-grained Ni studied by dilatometry

The release of excess volume upon recrystallization of ultrafine-grained Ni deformed by high-pressure torsion was measured with a high-precision difference-dilatometer employing constant heating rates in the range from 0.3 to 10 K min^?1. The kinetics of the recrystallization process was analyzed according to the Johnson–Mehl–Avrami–Kolmogorov theory adapted to the case of constant heating rates. An effective Avrami exponent of 2 and a value of 1.20 eV for the activation energy of recrystallization was determined. Analysis by the Kissinger method yielded the same result for the activation energy.     

Modular Functionalization of Electrodes by Cross‐Coupling Reactions at Their Surfaces

Due to the increasing importance of modified electrodes for many applications in nanotechnology, including molecular electronics, bioelectronics, and sensors, there is a need to find ways to chemically attach suitable molecular films onto the electrodes. Combining the electroreduction of aryl diazonium salts with the Sonogashira cross‐coupling reaction, a new modular technique to modify electrodes is presented. The new technique allows a wide range of functional groups to be introduced onto electrode surfaces with high surface coverage by the functional subunit. Various organic subunits, including redox chromophores, are successfully attached to platinum electrodes. The corresponding films are characterized using cyclic voltammetry, X‐ray photoelectron spectroscopy, atomic force microscopy, and contact‐angle measurements. The electroreduction of diazonium salts is successfully achieved on a broad variety of conducting and semiconducting surfaces, which shows that the technique is applicable to a broad variety of substrates.     

Modeling the fatigue crack growth behavior of Ti-6Al-4V by considering grain size and stress ratio

Ti-6Al-4V is a commonly used titanium base alloy in aerospace applications. The increasing demand for damage-tolerant designs of such components necessitates a detailed knowledge of its crack growth behavior. The aim of this research was the characterization and phenomenological modeling of long crack growth behavior with respect to microstructure and stress ratio. Therefore, the long crack propagation was characterized for eight different heat treatment conditions and four stress ratios. For comparison, physically short crack growth tests were also performed. The long crack growth threshold was found to be dominated by roughness-induced crack closure, and the fracture surface roughness is controlled by the primary α-grain size. The reason for this correlation is a near-threshold crack propagation mode, which is dominated by the transcrystalline fracture of α-grains. This correlation was used to model the crack growth threshold with respect to microstructure. A linear relation was determined between the stress ratio and the threshold value, which was also found in this approach. Further presented models cover the crack growth behavior in the near-threshold (Stage I) and mid-growth rate regions (Stage II).     

Metal Forming of Vibration‐Damping Composite Sheets

Composite materials with vibrations damping qualities can be made of two steel sheets enclosing a viscoelastic plasticcorelayer. These sandwich sheets often need to be formed. Material parameters are determined to describe the forming process. Based on these parameters, pilot studies are carried out in order to develop recommendations for forming this class of material.     

Analysis of the Stakeholder Engagement in the Deployment of Renewables and Smart Grid Technologies

The implementation of higher shares of renewables in a global energy mix has to be accompanied by simultaneous deployment of enabling smart grid technologies (SGTs). This combination will inevitably lead to a revolutionary change in a conventional energy system, particularly, the shifting role of consumers to prosumers. But resistance may arise from such a dramatic shift, since it is associated with high uncertainty in conjunction with increasing responsibilities of all stakeholders, the urgent need of effective control, and the development of a process. To ensure the positive influence, coherent actions of all players, and appropriate treatment of the spots of resistance, the analysis of the interplay between key stakeholders has been done. The paper introduces the framework for stakeholders' analysis, applies it on the European Union (EU) example, and provides recommendations to reduce the resistance of SGTs deployment.