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Improved precision of stereometric measurement of relief's surface by means of structured light enhanced photometric stereo method
Valach, Jaroslav ; Bryscejn, Jan
Photometry is an interesting method for 3D measurement of surfaces with relief. It utilizes a relationship between depth of shadow determined intensity of light and surface normal orientation towards source of light. Advantage of methods incorporating this principle is their independence on distance between measured object and the measuring apparatus and scalable sensitivity suitable for relatively flat surfaces. On the other hand, there is a drawback as the photometric methods yield results up to an unknown multiplicative factor. One way how to overcome this limitation is to simultaneously describe the measured surface by means of another optical method. Among the -candidates-, the structured light projection is the most promising one for a simple implementation. The presentation of the possibility to integrate these two methods in unified system is main topic of this contribution.
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Operation Test of a New Experimental Technology for Research of Lateral Pressure
Koudelka, Petr ; Valach, Jaroslav ; Bryscejn, Jan
Hardware and software accessories of a original advanced experimental equipment was finished and debugged at the beginning of the last year. The equipment was constructed for a basic research of lateral pressure multi-phase granular materials and to verify a theoretically derived -General Lateral Pressure Theory- (GLPT). A number of technical tests of measuring components and computer controlling system were performed before the finish of the equipment development. Several quasi-experiments without a sample ended the equipment preparation at last. The first real experiment E5/0,2 with pressure at rest and passive pressure was used for an operation test of the new equipment. The paper deals the experimental technology (apparatuses, hardware, software, etc.) and experiences of them during an extremely slow movement of front wall. Also, it is mentioned a visual monitoring, 3D scan technology including.
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Investigation of C/PPS Composites Degradation Process Using Acoustic Measurement
Fíla, Tomáš ; Valach, Jaroslav ; Kytýř, Daniel ; Šperl, Martin
The article deals with assessment of fatigue degradation of C/PPS composites using simple acoustic measurement technique. Changes in natural frequency and attenuation decrement were chosen as indicators of fatigue damage accumulation in the studied composite material. New testing device was developed for acoustic measurement. The experimental setup was designed to chime the specimen by repeatable force of stiff striker exciting a specific natural mode of vibration and to record the acoustic response of the specimen to the impact simultaneously. From the power spectral density of the signal the natural frequency was obtained. Using the same signal, the attenuation decrement was estimated from regression of the its envelope.
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Pore Size Distribution of Human Trabecular Bone - Comparison of Intrusion Measurements with Image Analysis
Doktor, Tomáš ; Valach, Jaroslav ; Kytýř, Daniel ; Jiroušek, Ondřej
This paper deals with pore size distribution assessment of trabecular structure of human proximal femur. Two distinct methods for estimation of the pore size distribution histograms are tested, mercury intrusion porosimetry and image analysis. For the image analysis two-dimensional images of crosssections of the specimens were used and the pore size distribution was estimated using a stereological calculation method based on the geometrical properties of an idealized pore. Comparison of the results of both methods is presented. Suitability of both methods for biological materials is discussed regarding to mechanical properties of these materials, characteristics of pores and range of pore sizes present in the structure.
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Assessment of C/PPS composites degradation indicators using acoustic measurement
Kytýř, Daniel ; Valach, Jaroslav ; Doktor, Tomáš ; Jiroušek, Ondřej
Changes of mechanical properties, namely of modulus of elasticity, often play a role of damage accumulation indicators in the framework of fatigue behaviour of composite materials. In order to improve the reliability of these indicators for identification of material degradation process it is necessary to eliminate the influence of external loading and volume forces associated with thermal expansion of heterogeneous material at various temperatures. Therefore the paper deals with description of experimental assessment of relation between external load and material stiffness and also studies the dependency of material stiffness on temperature. For the monitoring of degradation process ultrasonic measurement was used. Obtained results are discussed with respect to fatigue testing of material and also interpreted from the micromechanical point of view.
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Srovnání pole přetvoření CT vzorku určeného MKP a termoplastickým měřením
Žďárský, M. ; Valach, Jaroslav
Pomocí termokamery byl studován průběh tahové zkoušky CT vzorku a zaznamenáváno proměnlivé teplotní pole spojené s přeměnou mechanické práce na teplo při plastické deformaci. Současně byl týž proces modelován pomocí MKP s cílem srovnáním zjistit použitelnost tohoto přístupu pro vyšetřování rozvoje plastických deformací v složitějších konstrukcích, případně pro parametrizaci konstitutivních elastoplastických vztahů materiálu.
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