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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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Portable Testing Device for In-situ Testing of Building Material
Vavřík, Daniel ; Jandejsek, Ivan
Examination of brittle buildings materials using mechanical tests requires sampling of studied elements and materials (stones, bricks or concrete). In case of existing integral structures the best suitable sampling method is core drilling. It is preferred to test samples in situ in all cases where it is possible to avoid changes of the material properties during transportation and storing. Moreover it is possible to prepare other samples operationally wen some uncertainty occurred if in situ testing is possible. For such a purpose, a portable testing device has been designed and manufactured. This device is primary devoted for so called split test technique which is based on well know testing of Brazilian disk. Analytical equation used for evaluation of the split test is based on several assumptions which have to be verified. For such verification Digital Image Correlation technique was used in our work.
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Experimentální měření J integrálu
Vavřík, Daniel ; Jandejsek, Ivan
Experimental measurement of the J integral on the thin planar specimen is presented. It is possible measure J integral directly as curve integral as it is defined. This approach is not as comfortable as standard measurement on CT specimen but is more appropriate for thin planar specimens.
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Určování aktuální polohy trhliny pomocí metody digitální obrazové korelace
Jandejsek, Ivan ; Vavřík, Daniel
This paper presents utilization of Digital Image Correlation and other image processing methods in determination of the actual position of the crack during the crack propagation in ductile material. This task is very important in fracture mechanics studies, especially in evaluation of full-field stress and strain in the vicinity of the crack. It encompasses detection of the crack faces, tracing of the crack tip and measuring the crack length.
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Porovnání deformační a přírustkové teorie plasticity používané pro problémy experimetnální mechaniky
Vavřík, Daniel
Deformation Theory of Plasticity is often used for evaluation of the experimental data. Main reason of this theory using is its simple implementation into experimental-numeric software. It is supposed that difference between power low and appropriate incremental theory applied is negligible if monotonic loading is presented and isotropic material is used. It is shown in this paper that this presupposition can be no longer valid if high ductile material is used although external loading is strictly monotonic and proportional.
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Zjišťování mikrostrukturálních vlastností acetabula lidské pánve pomocí mikro-CT
Kytýř, Daniel ; Jiroušek, Ondřej ; Vavřík, Daniel
The paper deals with microstructure investigation of trabecular bone in acetabular region. Trabecular bone microstructure is the main factor of the bone quality and mechanical propertites at macroscopic level. Data from high resolution micro Computed Tomography can be used to reconstruct the complex geometry of the trabecular bone inner structure and interface between bone and implant. The data are usable as for micro-FE modeling as well as for experimental loading tests evaluation.
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Mikro radiografické měření rozvoje materiálového poškození
Vavřík, Daniel ; Jakůbek, J.
Studies concerning the functionality and integrity of the loaded materials require information about crack tip evolution. The X-ray Dynamic Defectoscopy (XRDD) has spatial resolution of the micrometric scale thanks to usage of microspot X-ray source, high resolution detector system and advanced processing of radiographic data.
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