Editorial: Videos in der (Hochschul-)Lehre

24.04.2014 | Thomas Antretter, Johannes Dorfinger, Martin Ebner, Michael Kopp, Walther Nagler, Jutta Pauschenwein, Michael Raunig, Manfred Rechberger, Herwig Rehatschek, Patrick Schweighofer, Reinhard Staber & Martin Teufel (Graz

A core outcome set for pre‐eclampsia research: an international consensus development study

Objective To develop a core outcome set for pre‐eclampsia. Design Consensus development study. Setting International. Population Two hundred and eight‐one healthcare professionals, 41 researchers and 110 patients, representing 56 countries, participated. Methods Modified Delphi method and Modified Nominal Group Technique. Results A long‐list of 116 potential core outcomes was developed by combining the outcomes reported in 79 pre‐eclampsia trials with those derived from thematic analysis of 30 in‐depth interviews of women with lived experience of pre‐eclampsia. Forty‐seven consensus outcomes were identified from the Delphi process following which 14 maternal and eight offspring core outcomes were agreed at the consensus development meeting. Maternal core outcomes: death, eclampsia, stroke, cortical blindness, retinal detachment, pulmonary oedema, acute kidney injury, liver haematoma or rupture, abruption, postpartum haemorrhage, raised liver enzymes, low platelets, admission to intensive care required, and intubation and ventilation. Offspring core outcomes: stillbirth, gestational age at delivery, birthweight, small‐for‐gestational‐age, neonatal mortality, seizures, admission to neonatal unit required and respiratory support. Conclusions The core outcome set for pre‐eclampsia should underpin future randomised trials and systematic reviews. Such implementation should ensure that future research holds the necessary reach and relevance to inform clinical practice, enhance women's care and improve the outcomes of pregnant women and their babies

A numerical model for Transformation Induced Plasticity (TRIP)

The peculiar behavior of steels exhibiting a TRIP (Transformation Induced Plasticity) effect, especially for the case of non-proportional loading paths, has given rise to a wide variety of different material descriptions ranging from purely phenomenological models to more rigorous approaches based on thermodynamic principles as proposed by this group of authors [1]. While this latter model gives reasonable results for the multigrain compound, its validity has limitations at the integration poit level since it selects only one variant within each time increment. Alternatively, this paper suggests an implicit formulation capable of reflecting the simultaneous evolution of multiple variants during transformation and suitable for an implementation into a finite element program. Particular attention has to be paid to the mechanisms inhibiting transformation, collectively characterized as hardening terms. To this end the well known yield surface concept of classical plasticity is extended by the notion of an additional phase transformation surface in stress space. The algorithm allows to identify the active variants and to monitor their contribution to the transformation kinetics. The overall strain component in loading direction is worked out and discussed in context with the orientation effect as the dominating mechanism for the accommodation of the new phase

The thermo-mechanical response to a general loading path of a martensitically transforming steel

International audienceAn extensive experimental program on a 9% Ni, 12% Cr, 2% Mo steel is introduced. This material transforms from the austenitic ({gamma}) phase into the martensitic ({alpha}') phase at a low temperature level around 150°C upon cooling on air only, thus making it especially suitable for testing purposes since it exhibits practically no creep effects during and after transformation (Fischer et al., 1996). Dilatometric tests are carried out for two types of specimens (longitudinal specimens (LSs) with a rolling texture and radial specimens (RSs)). Interestingly, the dilatation loops do not close after cooling down to room temperature. For an increasing annealing temperature the gap becomes smaller and closes for RSs. It turns out that the dilatometric loops close for preloaded specimens, pointing to an initial backstress in the material in the same order of magnitude as the load stress so it must not be neglected. Monitoring the martensite start (Ms) and finish temperature (Mf) for different loading conditions and stress levels reveals a strong influence of the type of loading (tension, shear, compression) on Ms. The overall yield stress as a function of temperature is noticeably disturbed immediately after transformation starts. As the temperature approaches Mf the composite effect in the {alpha}'-{gamma} region prevails. Experiments including mixed, nonproportional loading paths for cooling as well as at constant temperature have been performed. The orientations of the martensitic variants account for the different deformation behavior for different loading types but equal global equivalent stresses (see also Fischer et al., 2000a). A comprehensive micromechanical modeling concept is presented based on the numerical implementation of a transformation condition (Fischer and Reisner, 1998) governing the variant selection into a finite element algorithm (see Reisner et al., 1998). Finally, the issue of an improved constitutive law for the TRIP strain rate has been tackled. A novel approach for an evolution law including the backstress has first been presented by Videau et al. (1996) and has later been refined by Fischer et al. (2000b)

A micromechanical and experimental reconsideration of the transformation induced plasticity (TRIP) strain rate term.

International audienc