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Characteristics of Damage to the Structural Element by Creating its "Degradation Profile"
Frankl, Jiří
This paper presents results of experimental establishment of the extent of damage and changes in strength of a wooden structural element (a rafter base) through the creation of its -degradation profile. The tested part of the structural element was divided into segments by the means of a regular network from which standard test specimens were made with dimensions of 20x20x30 mm on which strength tests under compression along the fibres of wood were carried out. Readings were divided, according to the decrease in the property observed against the values of healthy (undamaged) wood, into 4 quality groups and then transferred back to the network of segments. A graphic model description of the shape and course of degradation of wood caused by wood-destroying fungi was created, marked as the - degradation profile of an element.
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Changes in physical properties of wood damaged by activities of wood damaging fungi
Frankl, Jiří
Abstract: This paper presents results of experimental, laboratory establishment of the extent of changes in physical properties (swelling, water absorbability) of timber (spruce) damaged by the activity of wood-damaging fungi. The experiment was carried out using standard test samples (20 x 20 x 30 mm) prepared from new timber and subsequently exposed to the activities of wood-damaging fungi (Serpula lacrymans, Trametes versicolor) under optimal growth conditions for the period of 15 to 60 days. Changes in physical properties were observed in the damaged samples as per the CSN 490126 and CSN 490104 Czech National Standards. The experiment proved significant changes in the observed properties depending on the fungi type and duration of the activity thereof.
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X-ray Observation of the Loaded Silicate Composite
Vavřík, Daniel ; Fíla, Tomáš ; Jandejsek, Ivan ; Veselý, V.
An intensive internal material damage evolution precedes a failure in quasi-brittle materials. Not only the existence of damage but also its quantification and the geometry of the Fracture Process Zone have to be identified in order to validate approaches on both numerical modelling of quasi-brittle behaviour and experimental determination of fracture properties. Radiographic techniques and Digital Image Correlation method are very appropriate for analysing of the Fracture Process Zone evolution during specimen loading.
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Experimental measurement of full-field strains in the vicinity of U-notch in ductile material
Jandejsek, Ivan ; Jiroušek, Ondřej ; Vavřík, Daniel
The paper deals with the measurement of full-field displacements and strains evolution in the vicinity of the U-notch in the flat high-ductile aluminum specimen during its loading. The full-field displacements are measured using Digital Image Correlation method in a set of vertices of a triangular mesh reflecting the presence of the stress concentrator. From the known displacements strain distribution is computed. The resulting strain field is compared with simultaneous strain gauge measurement. These strain gauges are located just in a few well-defined positions and serve for correction of a systematical error caused by rigid-body motion of the specimen during loading. The experimental results are used as referential for Finite Element simulation using the same triangular mesh.
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MONDIS: Knowledge-Based System of Failure of Historical Constructions
Valach, Jaroslav ; Cacciotti, Riccardo ; Čerňanský, Martin ; Kuneš, Petr
The main aim of introducing and developing a knowledge-based system of failure of historical constructions called MONDIS is to overcome a lack of data on defects of monuments. MONDIS proposes a methodology capable of reproducing the logical relationship between the manifestation of damage, its diagnosis and the possible interventions. Based on novel information sciences tools, like semantic technologies, the system will be able to assist users in finding similar failures cases, in analyzing the causes of damage and also suggesting suitable restoration techniques accordingly to conservation principles of intervention.
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Indirect determination of material model parameters for single trabecula based on nanoindentation and three-point bending test
Zlámal, P. ; Jiroušek, Ondřej ; Kytýř, Daniel ; Doktor, Tomáš
The aim of the paper is to develop a procedure for determination of elasto-visco-plastic constitutive model with damage for human single trabecula. The procedure is suited for indirect establishing of material model based on nanoindentation and three-point bending test. Constants of the material model are identified by Finite Element (FE) simulations and curve fitting using an algorithm based on least squares fitting of the experimental curves. In the case of nanoindentation, the penetration depth of tip during the FE analyses (FEA) is fitted to experimental nanoindentation curves. In the case of three-point bending, displacements of nodes are compared with displacements of markers observed during the experiment using digital image correlation.
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Large-scale micro-finite element simulation of compressive behavior of trabecular bone microstructure
Jiroušek, Ondřej ; Zlámal, Petr
Microstructural finite element analysis has become a standard technique for evaluation of mechanical properties of trabecular bone. Due to the high complexity of the trabecular bone microstructure, the FE models have a very large number of elements (about 1 million elements per cubic cm in 50 μm3 resolution). To perform FE analysis of the microstructural FE models based on micro-CT scanning of whole bone samples (e.g. vertebral bodies) it is needed to solve 107 -- 108 equations. This article deals with comparison of approaches using voxel-based microstructural FE models to calculate the overall mechanical properties of trabecular bone.
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Mass lumping methods for the semi-loof shell element
Sháněl, Vít ; Kolman, Radek ; Plešek, Jiří
Mass matrix diagonalization in terms of a finite element method (FEM) is essential for an effective deployment of the explicit method as one of the direct integration methods of the motion equations of elastodynamics. A particular attention is focused on the mass matrix diagonalization of the semi-loof shell element. Its diagonalization requires a specially designed universal diagonalization scheme that is derived from the scaling HRZ method. Another analyzed aspect is the problem of preserving the moment of inertia for various types of finite elements. The proposed scheme is implemented in the finite element program and consequently tested on several problems
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