The damage operator approach is extended to time dependent viscoplasticity and creep. The oxidation is taken into account indirectly. Time efficient viscoplastic approximation based on the nonlinear Maxwell model and the corresponding lifetime prediction is presented. Both thermo-mechanical fatigue tests on the specimens and the thermal shock tests on turbine housings of a turbocharger subject to a complex change of temperature and strain are conducted for identification and verification purposes. The material is casting material Ni-resist D-5S. The research points out that the mean stress correction and the multiaxial criterion affect the predictive lifetimes significantly. For the turbine housing of a turbocharger the Smith-Watson-Topper mean stress correction, tensile-compressive creep and the critical plane mode I approach is the most suitable parameter combination. The lifetime predictions are convenient. The time consuming elastoviscoplastic finite element analyses can thus often be replaced by the elastoplastic FEA with kinematic hardening even at extreme conditions.
COBISS.SI-ID: 11663387
From an engineering point of view, church bells are structures that, during ringing, are exposed to severe loading conditions. They are damaged due to material wear, fatigue loading, material deficiencies, different clapper-to-bell layouts, ringing conditions, etc. To get an insight into the wear-related damage of bells, experimental investigations and numerical simulations of the local contact between the clapper and the bell were carriedout as part of the activities of an EU-funded project called Maintenance and Protection of Bells. In order to make a full-scale comparison between the measured and simulated results a simplified model was set up. In this model the clapper was replaced by a cylinder with a rounded tip that was dropped against a block representing the bell wall. The aim of the simplified model was to study the impact phenomenon in a controlled way and to adapt the numerical model for simulating the local contact. In the article the synthesis of a finite-element model for simulating the cylinder-drop test is presented. The results of the finite-element simulations of repetitive cylinder drops are compared to the data that were measured in the laboratory. The effects of the cylinder material, the cylinder radius and the drop height of the cylinder on the local elastic-plastic behaviour of the cylinder and the block are also presented and discussed.
COBISS.SI-ID: 11605275
The article extends the REBMIX to multivariate data. Random variables may follow normal, lognormal, or Weibul parametric families and should be independent within components. The initial weights and component parameters are not required. Preprocessing of observations folows the histogram, Parzen window, or k-nearest neighbour approach. The number of components, weights, and component parameters are gained interatively by using information measures of the distance, such as the total of positive relative deviations and the information criterion. The number of classes or the number of the nearest neighbours can be optimized, as well. The REBMIX software is availableon http://www.fs.uni-lj.si/lavek
COBISS.SI-ID: 11780635