FERROFRAC · Fracture in Ferroelastic Ceramics
6РП — Действия „Мария Кюри“
- Период
- 2006-06-01 → 2008-05-31
- Финансиране от ЕС
- 227 059 €
- Участници
- 1
- Схема
- IIF
Линиите свързват координатора с партньорите.
Накратко на български
Механичното поведение и пукането на фероеластични керамики, като перовскитите на основата на лантан и кобалт, се анализират при натиск. Това помага за разбирането на деформациите в тези материали и създаването на модел за предвиждане на тяхната устойчивост.
Кратко обяснение, генерирано от езиков модел по текста на CORDIS. Оригиналът е по-долу.
Резултати накратко
Final Activity Report Summary - FERROFRAC (Fracture in Ferroelastic Ceramics)
The mechanical and fracture behaviour of notched LaCoO3 based perovskites under compressive loading at room temperature was analysed. The fracture mechanism of these materials could be explained by considering strain incompatibility and high shear stresses in the lateral directions of the samples. The residual tensile stresses which were produced by strain irreversibility at the notch tip were not large enough to generate direct crack growth as compared to elastic ceramics. While the majority of the mixed ionic electronic conducting (MIEC) ferroelastic perovskites exhibited a single softening followed by hardening during loading, we reported an unusual dual softening in (La0.9Sr0.1)0.95Cr0.85Ni0.05Mg0.1O3 perovskite because of a pressure-induced first order phase transition from orthorhombic Pnma to rhombohedral phase during loading. The effects of temperature and cyclic incremental loading on the deformation behaviour of LSCNM were studied. The experimental investigation of room temperature creep at different stresses in polycrystalline LaCoO3 based oxides under compression was carried out. A new phenomenological approach for ferroelastic creep was proposed to identify the most important parameters that affected creep strain over different time periods. An analytical expression was obtained instead of the previously used power law, allowing for the equilibrium strain at constant stress to be estimated. An expression was also proposed to calculate the characteristic time of creep and recovery processes. The equilibrium creep diagrams for LaCoO3 and La0.8Ca0.2CoO3 perovskites were determined. Finally, a general scheme for describing the mechanical behaviour of ferroelastic materials was developed. It was possible to predict the equilibrium stress-strain curve of ferroelastic materials using this scheme. Relevant results were anticipated to guide the design and modelling of components using ferroelastic materials, such as solid oxide fuel cells and ferroelectric ceramic actuators.
Текст от CORDIS, на английски · Данни: CORDIS, © Европейски съюз
Цел на проекта
Many important ceramics are ferroelastic, eg, lanthanum strontium manganate (LSM), which is used as a cathode in solid oxide fuel cells. The objective of the proposed research is to investigate the problem of fracture at notches in ferroelastic ceramics subjected to compressive loading. Ceramics are often preloaded in compression to avoid brittle failure. Preliminary work at QMUL on ferroelectric/ferroelastic ceramics has demonstrated that compression-compression loading of notches can produce fracture at a surprisingly small far-field stresses.The results of this work have significant implications for the design and performance of ferroelastic materials containing fabricated or machined notched structures, such as solid oxide fuel cell components and interdigitated multi-layer ferroelectric ceramic actuators. The origin of the effect may be the relatively large strain irreversibility produced in ferroelastic ceramics and the tensile stresses that this can generate on unloading. We propose to investigate the factors (eg, notch geometry, peak load, load ratio, loading rate / frequency, and material properties) that influence fracture and to model the problem using finite element analysis. An important outcome of the work will be an improved knowledge of good design practice for ferroelastic ceramic components.
Оригинален текст от CORDIS (на английски).
Участници
- QUEEN MARY AND WESTFIELD COLLEGE · LONDONКоординаторОбединеното кралство
Връзки
Данни: CORDIS, © Европейски съюз