Identification of local phenomena of plasticity in concrete under compression test

A Risitano, A. D'Aveni, G. Fargione, C. Clienti
2016 Procedia Structural Integrity  
During their operation, modern aircraft engine components are subjected to increasingly demanding operating conditions, especially the high pressure turbine (HPT) blades. Such conditions cause these parts to undergo different types of time-dependent degradation, one of which is creep. A model using the finite element method (FEM) was developed, in order to be able to predict the creep behaviour of HPT blades. Flight data records (FDR) for a specific aircraft, provided by a commercial aviation
more » ... mpany, were used to obtain thermal and mechanical data for three different flight cycles. In order to create the 3D model needed for the FEM analysis, a HPT blade scrap was scanned, and its chemical composition and material properties were obtained. The data that was gathered was fed into the FEM model and different simulations were run, first with a simplified 3D rectangular block shape, in order to better establish the model, and then with the real 3D mesh obtained from the blade scrap. The overall expected behaviour in terms of displacement was observed, in particular at the trailing edge of the blade. Therefore such a model can be useful in the goal of predicting turbine blade life, given a set of FDR data. Abstract Department of Civil Engineering and Architecture In this paper are specifically derived parameters useful to estimate the fatigue behaviour of concrete subject to uniaxial compression. For this, methodologies and experience already adopted in the study of fatigue steel and composite materials are used. These parameters are obtained by detecting the surface temperature of the specimen in the traditional static compression tests. In this way, the beginning of the crisis of the concrete for fatigue stress is linked to the loss of linearity of the temperaturetest time curve (ΔT-t) and correlated to stress-test time curve (σ-t) of the tested cubic concrete specimens. In fact, the thermal analysis performed on the cubic specimen surface extended to the whole test time, shows interesting data on the crack beginning and on the subsequent evolution that after a certain number of loading cycles could determine the complete material failure. The slope variation in the interpolating curve temperature-test time allows to identify the critical points of the start fracture. This suggests a methodology to apply to civil infrastructures to evaluate in-situ, during the approval phase or during the working, critical situations. In this paper we propose a method to estimate the value of the "stress limit" (fatigue limit) of concrete material by means of an easy static uniaxial compression test according to an energetic method already proposed by Risitano.
doi:10.1016/j.prostr.2016.06.266 fatcat:ntc6fkvdavcdvnepgbcam4bsuq