Refine
Document Type
- Conference Proceeding (31)
- Article (13)
- Other Publications (7)
- Book (2)
- Part of a Book (1)
Language
- English (29)
- German (24)
- Multiple languages (1)
Has Fulltext
- no (54) (remove)
Keywords
- Abrasive grain material (1)
- Actuators (1)
- Aktuatorik (1)
- Anhaftung (1)
- Aquaculture (1)
- Aufsatzsammlung (1)
- Austenitic stainless steels (1)
- Behälterbau (1)
- Biokompatibilität (1)
- Chemische Beständigkeit (1)
- Corrosion Resistance (1)
- Corrosion resistance (1)
- Duplex stainless steel (1)
- Dynamic testing plant (1)
- Dynamic tests (1)
- Edelstahl Rostfrei (1)
- Espanded austenite, Magnetic force microscopy, Low temperature carburisation, Ferrofluid (1)
- Expanded austenite (1)
- Expanded austenite layer (1)
- Fish farming (1)
- Formgedächtnislegierung (1)
- Geological protection (1)
- High strength (2)
- Low-temperature carburization (1)
- Low-temperature surface-hardening (1)
- Magnetizability (1)
- Martensitic Stainless Steels (1)
- Metastable austenitic stainless steel (1)
- Net system (1)
- Ni-Ti wires (1)
- Nichtrostende Stähle (1)
- Nichtrostender Stahl (1)
- Oberfläche (1)
- Oberflächenhärtung (1)
- Pitting susceptibility (1)
- Predator net (1)
- Redesign (1)
- Schleifen (1)
- Shape memory alloy (1)
- Shape memory alloys (1)
- Stacking fault energy (1)
- Stainless steel (3)
- Surface treatment (1)
- Sustainability (1)
- Verschleißbeständigkeit (1)
- Weight reduction (1)
- Wire (1)
The evolution of strain induced martensite in austenitic stainless steel AISI 304 was investigated in a rolling contact on a two-discs-tribometer. The effects of surface roughness, slip and normal force as well as the number of load cycles were examined. In comparison to the investigations of martensitic phase transformation during cold rolling, the applied stresses are considerably lower. The formation of strain induced martensite was detected in-situ by means of a FERITSCOPE MP30 and ex-situ by optical microscopy after etching with Kane etchant. Both number of load cycles and magnitude of normal force appeared to be the main influencing factors regarding strain induced martensitic evolution in low stress rolling contacts.
Low temperature carburizing of a series of austenitic stainless with various combinations of chromium and nickel equivalents was performed. The investigation of the response towards low temperature carburized for three stainless steels with various Cr- and Ni-equivalents showed that the carbon uptake depends significantly on the chemical composition of the base material. The higher carbon content in the expanded austenite layer of specimen 6 (1.4565) and specimen 4 (1.4539/AISI 904L) compared to specimen 2 (1.4404/AISI 316L) is assumed to be mainly related to the difference in the specimens’ chromium content. More chromium leads to more lattice expansion. Along with the higher carbon content, higher hardness values and higher compressive residual stresses in the expanded austenite zone are introduced than for low temperature carburized AISI 316L. The residual stresses obtained from X-ray diffraction lattice strain investigation depend strongly on the chosen X-ray elastic constants. Presently, no values are known for carbon (or nitrogen) stabilized expanded austenite. Nevertheless, first principle elastic constants for γ′&minus Fe4C appear to provide realistic residual stress values. Magnetic force microscopy and measurement with an eddy current probe indicate that austenitic stainless steels can become ferromagnetic upon carburizing, similar for low temperature nitriding. The apparent transition from para- to ferromagnetism cannot be attributed entirely to the interstitially dissolved carbon content in the formed expanded austenite layer but appears to depend also on the metallic composition of the alloy, in particular the Ni content.
In the automotive industry a strong effort has been undertaken to reduce the weight of modern vehicles. In order to reduce the energy consumption and to improve the environmental sustainability, the importance of weight reduction activities is even growing faster. As lightweight designing is becoming more and more expensive and show less potential savings, new approaches are needed. One promising technology could be the use of shape memory elements. In the last years a lot of potential application possibilities were presented, demonstrating the benefit of these functional elements in automotive design solutions: they often reduce complexity, weight and design space of an actuation device and enable new functions. In addition they work silently and are therefore ideally suitable for comfort applications in the passenger cabin. Because of the current trend to electric vehicle the hitherto existing drawback of a high electrical energy consumption of shape memory actuators in some design proposals is not given any more.
Characterization of NiTi Shape Memory Damping Elements designed for Automotive Safety Systems
(2014)
Actuator elements made of NiTi shape memory material are more and more known in industry because of their unique properties. Due to the martensitic phase change, they can revert to their original shape by heating when subjected to an appropriate treatment. This thermal shape memory effect (SME) can show a significant shape change combined with a considerable force. Therefore such elements can be used to solve many technical tasks in the field of actuating elements and mechatronics and will play an increasing role in the next years, especially within the automotive technology, energy management, power, and mechanical engineering as well as medical technology. Beside this thermal SME, these materials also show a mechanical SME, characterized by a superelastic plateau with reversible elongations in the range of 8%. This behavior is based on the building of stress-induced martensite of loaded austenite material at constant temperature and facilitates a lot of applications especially in the medical field. Both SMEs are attended by energy dissipation during the martensitic phase change. This paper describes the first results obtained on different actuator and superelastic NiTi wires concerning their use as damping elements in automotive safety systems. In a first step, the damping behavior of small NiTi wires up to 0.5 mm diameter was examined at testing speeds varying between 0.1 and 50 mm/s upon an adapted tensile testing machine. In order to realize higher testing speeds, a drop impact testing machine was designed, which allows testing speeds up to 4000 mm/s. After introducing this new type of testing machine, the first results of vertical-shock tests of superelastic and electrically activated actuator wires are presented. The characterization of these high dynamic phase change parameters represents the basis for new applications for shape memory damping elements, especially in automotive safety systems.