Abstract

"jats:p" The paper contains results of experimental research carried out helicopter bench. In order to create an attenuation chart for AE signal amplitude in helicopter fuselage, a number of experiments were performed on the frame and stringers, inside the fuselage. Later helicopter test bench was used to develop defect localization methodology of helicopter structure fatigue damage technical diagnostics. Analysing helicopter structural defects for different helicopters types it is concluded that the joint elements of helicopter tail boom are still exposed to fatigue crack formation. AE method shows highly effective results predicting fracture of helicopter joint elements. Document type: Article

Abstract

Warehouses are big architectonical structures mostly made of spruce wood and utilized as storage buildings principally by food traders in Northern Countries. Trondheim’s warehouses currently observable along the river Nidelva, date back between the 17th and half of the 19th century were mostly used to stock and process fish. Therefore, where the food goods were stored, residuals are expected to be still present and/or to be responsible for the formation of alteration products on the wooden surfaces as well as inside the wooden structure. Here we propose a characterization of residual and neo-formed compounds inside and on the surface of wooden logs by means of vacuum microbalance that allowed both to individuate the type of salts, as well as, to estimate the maximum water film thickness adsorbed on the wooden samples at 93% of RH. These data have been related to variations in the acoustic emission (AE) intensity detected at the log surface and to the wood moisture content measured with capacitive and resistance operating moisture meters. The application of three independent techniques have allowed obtaining interestingly information indicating their potentiality as decay assessment techniques in the field of historical materials and specifically in the study of salts weathering on wood. The methodology allowed identifying a clear relationship between the amount of water in logs as a function of their distance from the ground and variations in the amplitude of the acoustic emission signals.

Abstract

This work is being carried out under the framework of a thesis at the center of materials Mines -Paristech. The goal of this thesis is to realize a first digital twinning for a composite structure which is the Composite Pressure Vessel (CPV). By using the technique of data assimilation, we have a numerical model which was developed in the laboratory of Mines and which consists of a simplified stochastic FE2 model. It turns out that this model is limited, because it is too expensive in terms of computing time and moreover it is only used for fixed finite elements. We therefore used the homogenization technique to have a deterministic constitutive model, which reduces the calculation time and which liberate us from the existing mesh. With this model, we aim to use machine learning techniques to be able to learn parameters that models the generation of acoustic emission data and to be able to assimilate it in order to determine the damage of the composite pressure vessel during its service.