EVALUATION OF THE RELIABILITY OF BUILDING STRUCTURES IN SIMULIA ABAQUS: MODELING OF STOCHASTIC MATERIAL PROPERTIES

This article describes a software module component integrated with the SIMULIA Abaqus engineering analysis software package and designed to simulate random values of material parameters in a finiteelement model based on specifiedstatistical characteristics, with the possibility of taking into account the physical nonlinearity of material behavior under various combinations of loads and influences.The target group of materials under study is materials of load-bearing elements of building structures, such as concrete, stone, steel. This software module can be recommended for use by specialists, engineers and scientists engaged in probabilistic analysis of the reliability of structures of buildings and structures, apparatus, machines, devices, with the combined use of complexes of computer modeling and engineering analysis. Has a certificateof state registration of the computer program "AS for modeling stochastic properties of materials" No. 2019667439 dated 12.24.2019.

Freeze cast porous barium titanate for enhanced piezoelectric energy harvesting

Energy harvesting is an important developing technology for a new generation of self-powered sensornetworks. This paper demonstrates the significant improvement in the piezoelectric energy harvestingperformance of barium titanate by forming highly aligned porosity using freeze casting. Firstly, a finiteelement model demonstrating the effect of pore morphology and angle with respect to poling fieldon the poling behaviour of porous ferroelectrics was developed. A second model was then developedto understand the influence of microstructure-property relationships on the poling behaviour of porous freeze cast ferroelectric materials and their resultant piezoelectric and energy harvestingproperties. To compare with model predictions, porous barium titanate was fabricated using freeze casting to form highly aligned microstructures with excellent longitudinal piezoelectric straincoefficients, d33. The freeze cast barium titanate with 45 vol.% porosity had a d33 = 134.5 pC/N, which compared favourably to d33= 144.5 pC/N for dense barium titanate. The d33 coefficients of the freezecast materials were also higher than materials with uniformly distributed spherical porosity due toimproved poling of the aligned microstructures, as predicted by the models. Both model andexperimental data indicated that introducing porosity provides a large reduction in the permittivity of barium titanate, which leads to a substantial increase in energy harvesting figure of merit, with a maximum of 3.79 pm2/N for barium titanate with 45 vol.% porosity, compared to only 1.40 pm2/N for dense barium titanate. Dense and porous barium titanate materials were then used to harvest energy from a mechanical excitation by rectification and storage of the piezoelectric charge on a capacitor. The porous barium titanate charged the capacitor to a voltage of 234 mV compared to 96 mV for the dense material, indicating a 2.4-fold increase that was similar to that predicted by the energy harvesting figures of merit.