Number of found documents: 539
Published from to

Proposal for loading tests of bridges - simulation and laboratory experiments
Bayer, Jan; Urushadze, Shota; Černý, Miloš
2018 - English
A new dynamic load testing of bridges is proposed and theoretically investigated. A transient analysis of passing vehicle over a bridge in ANSYS and an analytical program in MATLAB for the transient solution of piecewise linear mechanical structures were developed to assess the effects of the proposed dynamic load on a bridge model. According to the first laboratory experiments, it seems that the proposed travelling impulse load could surpass some of the shortcomings and limitations of the currently applied methods of bridge testing. The investigation is a part of a project aimed at drive-by identification of dynamic properties of bridges and further experimental and analytical research will follow. Keywords: dynamic loading tests; transient analysis; vibrations; vehicle-bridge interaction Available at various institutes of the ASCR
Proposal for loading tests of bridges - simulation and laboratory experiments

A new dynamic load testing of bridges is proposed and theoretically investigated. A transient analysis of passing vehicle over a bridge in ANSYS and an analytical program in MATLAB for the transient ...

Bayer, Jan; Urushadze, Shota; Černý, Miloš
Ústav teoretické a aplikované mechaniky, 2018

Asymmetry of the response probability density of a system with parametric random noises
Náprstek, Jiří; Fischer, Cyril
2018 - English
Recording of time variable processes is accompanied by various internal disturbing effects as a rule. They influence parameters of the measuring facility, transducer-device transmission, etc. These parasitic processes are usually of the random character and, consequently, they exercise as parametric noises. Moreover, the input signal mostly consists of a useful signal which can be taken as composed from deterministic and random additive part. Various combinations of these noises are the origin of random and also systematic measuring errors which can have under certain circumstances a cumulative character, deteriorate the output signal quality and can lead finally to the stochastic stability loss. These effects can be theoretically described using differential systems with stochastic coefficients and stochastic right hand side considering all input and output processes to be of the Markov type. Keywords: random vibration; signal reconstruction; parametric noise; response asymmetry Available at various institutes of the ASCR
Asymmetry of the response probability density of a system with parametric random noises

Recording of time variable processes is accompanied by various internal disturbing effects as a rule. They influence parameters of the measuring facility, transducer-device transmission, etc. These ...

Náprstek, Jiří; Fischer, Cyril
Ústav teoretické a aplikované mechaniky, 2018

Basic biomechanical characterization of polyurethane based artificial cancellous structures
Šleichrt, Jan; Kytýř, Daniel; Pithartová, Kateřina; Senck, S.; Fürst, D.; Schrempf, A.
2018 - English
The main goal of this study is to validate elementary mechanical parameters of a newly designed open-cell foam. The purpouse for investigating artificial material is to approach the properties of the human bone in the case of its adequate replacement. Investigated material can be also used as an artificial bone to train surgical procedures and to improve the skills of the surgeons. Four sets of the foam with different chemical composition were subjected to an uniaxial quasi-static loading to describe basic mechanical behaviour of these samples. Based on these experiments, the stress-strain diagrams were created as a comparative tool including calculation of the effective Young’s modulus. The acquired knowledges will be used as input parameters of a follow-up study aimed at describing the morphology of presented structures and their response to mechanical experiments. A distortion effect of porosity on the results is not considered in this study. Keywords: polyurethane foam; artificial bone; uniaxial loading; digital image correlation Available at various institutes of the ASCR
Basic biomechanical characterization of polyurethane based artificial cancellous structures

The main goal of this study is to validate elementary mechanical parameters of a newly designed open-cell foam. The purpouse for investigating artificial material is to approach the properties of the ...

Šleichrt, Jan; Kytýř, Daniel; Pithartová, Kateřina; Senck, S.; Fürst, D.; Schrempf, A.
Ústav teoretické a aplikované mechaniky, 2018

Instrumentation of four-point bending test during 4D computed tomography
Kytýř, Daniel; Fíla, Tomáš; Koudelka_ml., Petr; Kumpová, Ivana; Vopálenský, Michal; Vavro, Leona; Vavro, Martin
2018 - English
High-resolution time-lapse micro-focus X-ray computed tomography is an effective method for investigation of deformation processes on volumetric basis including fracture propagation characteristics of non-homogeneous materials subjected to mechanical loading. This experimental method requires implementation of specifically designed loading devices to X-ray imaging setups. In case of bending tests, our background research showed that no commercial solution allowing for reliable investigation of so called fracture process zone in quasi-brittle materials is currently available. Thus, this paper is focused on description of recently developed in-situ four-point bending loading device and its instrumentation for testing of quasi-brittle materials. Proof of concept together with the pilot experiments were successfully performed in a CT scanner TORATOM. Based on results of the pilot experiments, we demonstrate that crack development and propagation in a quasi-brittle material can be successfully observed in 3D using high resolution 4D micro-CT under loading. Keywords: in-situ loading device; four-point bending; 4D micro-CT; crack propagation Available at various institutes of the ASCR
Instrumentation of four-point bending test during 4D computed tomography

High-resolution time-lapse micro-focus X-ray computed tomography is an effective method for investigation of deformation processes on volumetric basis including fracture propagation characteristics of ...

Kytýř, Daniel; Fíla, Tomáš; Koudelka_ml., Petr; Kumpová, Ivana; Vopálenský, Michal; Vavro, Leona; Vavro, Martin
Ústav teoretické a aplikované mechaniky, 2018

Forced movement of a ball in spherical cavity under kinematic excitation
Náprstek, Jiří; Fischer, Cyril
2018 - English
In the paper the response of a heavy ball rolling inside a semi-spherical cavity under horizontal kinematic excitation is investigated. The system with six degrees of freedom with three non-holonomic constraints is considered. The contact between the ball and the cavity surface is supposed to be perfect without any sliding. The mathematical model using the Appel-Gibbs function of acceleration energy is developed and discussed. The most important post-critical regimes are outlined and qualitatively evaluated on the frequency axis. Numerical experiments have been performed when excitation frequency is slowly swept up and down. Results obtained by means of semi-analytical investigation and numerical simulation are evaluated and physically interpreted. Some applications in civil engineering as a tuned mass damper used on slender structures is outlined. Strengths and weaknesses of solution method are evaluated. Keywords: nonlinear dynamics; non-holonomic systems; Appell-Gibbs formulation; singular states; tuned mass damper Available at various institutes of the ASCR
Forced movement of a ball in spherical cavity under kinematic excitation

In the paper the response of a heavy ball rolling inside a semi-spherical cavity under horizontal kinematic excitation is investigated. The system with six degrees of freedom with three non-holonomic ...

Náprstek, Jiří; Fischer, Cyril
Ústav teoretické a aplikované mechaniky, 2018

Accuracy and numerical efficiency of approximate method for complex eigensolution of structure with specialized damping device
Hračov, Stanislav
2018 - English
The paper provides a detailed parametric analysis of the recently proposed approximate method for complex eigensolution of non-classically damped structures. This method is based on a combination of perturbation and incremental approaches and is applicable to the classically damped structures equipped with a specialized passive damping device. The numerical efficiency in terms of the required calculation times and the accuracy is demonstrated on a model of an existing structure for various combination of computational parameters. Wide numerical simulations revealed the selection of real eigenmodes of undamped system used in the approximate eigensolution as the most important parameter affecting the final accuracy. Keywords: non-classical damping; complex eigensolution; perturbation method; passive damper Available at various institutes of the ASCR
Accuracy and numerical efficiency of approximate method for complex eigensolution of structure with specialized damping device

The paper provides a detailed parametric analysis of the recently proposed approximate method for complex eigensolution of non-classically damped structures. This method is based on a combination of ...

Hračov, Stanislav
Ústav teoretické a aplikované mechaniky, 2018

Engineering mechanics 2018. Book of full texts
Fischer, Cyril; Náprstek, Jiří
2018 - English
The proceedings contains papers presented at the 24th International Conference on Engineering Mechanics, which has been held in Svratka resort in Czech Republic under auspices of the Czech Society of Mechanics and being a part of IFTOMM (The International Federation for the Promotion of Mechanism and Machine Science) activities. As it corresponds with character of the conference, this proceedings consists of several topic oriented parts: Biomechanics, Fluid mechanics, Dynamics, Fracture mechanics, Kinematics, Mechatronics, Reliability of structures, Mechanics of solids, Techological processes, Thermodynamics. The volume represents a well-balanced overview of theoretical, numerical and experimental work on fundamental and applied studies. Keywords: mechanics; dynamics; reliability Available at various institutes of the ASCR
Engineering mechanics 2018. Book of full texts

The proceedings contains papers presented at the 24th International Conference on Engineering Mechanics, which has been held in Svratka resort in Czech Republic under auspices of the Czech Society of ...

Fischer, Cyril; Náprstek, Jiří
Ústav teoretické a aplikované mechaniky, 2018

Influence of printing and loading direction on mechanical response in 3D printed models of human trabecular bone
Doktor, Tomáš; Kumpová, Ivana; Wroński, S.; Śniechowski, M.; Tarasiuk, J.; Forte, G.; Kytýř, Daniel
2018 - English
The paper deals with investigation on directional variations of mechanical response in 3D printed models of human trabecular bone. Sample of trabecular bone tissue was resected from human donor and 3D model was obtained by X-ray computed tomography. Then a series of cubical samples was prepared by additive manufacturing technique and tested by uniaxial compression loading mode. Mechanical response was compared in nine different combinations of direction of 3D printing and loading direction. The results show neglectible influence on the deformation response in elastic region (stiffness) and significant changes of the behaviour in plastic region (stress and strain at yield point, strain at full collapse). Keywords: additive manufacturing; tomography; deformation response Available at various institutes of the ASCR
Influence of printing and loading direction on mechanical response in 3D printed models of human trabecular bone

The paper deals with investigation on directional variations of mechanical response in 3D printed models of human trabecular bone. Sample of trabecular bone tissue was resected from human donor and 3D ...

Doktor, Tomáš; Kumpová, Ivana; Wroński, S.; Śniechowski, M.; Tarasiuk, J.; Forte, G.; Kytýř, Daniel
Ústav teoretické a aplikované mechaniky, 2018

Crystallization force of sodium chloride
Koudelková, Veronika; Wolf, Benjamin
2018 - English
Soluble salts are one of the most deteriorating factor causing damage of historical building materials due to generation of crystallization pressure inside pore space. Direct measurement of crystallization force is quite challenging, hence we developed at our institute a novel device able to detect the force of growing crystal. The device is based on the monitoring of force developed with upper microscopic glass on the growing crystal to maintain constant position. The crystal could generate force because of the existence of thin liquid layer of solution between both surfaces come into contact. The driving force for the subsequent growth of crystal against obstacle is supersaturation, which is mainly induced by evaporation of the salt solution. In this experiment, the crystal of sodium chloride generated force 16.8 mN and the corresponding crystallization pressure was equal to the value 0.48 MPa. Keywords: crystallization force; sodium chloride; salt deterioration Available at various institutes of the ASCR
Crystallization force of sodium chloride

Soluble salts are one of the most deteriorating factor causing damage of historical building materials due to generation of crystallization pressure inside pore space. Direct measurement of ...

Koudelková, Veronika; Wolf, Benjamin
Ústav teoretické a aplikované mechaniky, 2018

Utilization of image and signal processing techniques for assessment of built heritage condition
Koudelka_ml., Petr; Koudelková, Veronika; Doktor, Tomáš; Kumpová, Ivana; Kytýř, Daniel; Valach, Jaroslav
2018 - English
Historical buildings represent invaluable heritage from the past and therefore their protection is a very important task. Assessment of their condition must not cause damage accumulation thus the least possible volume removed from the structure is essential. As many historical buildings in the Czech Republic are built using sandstone that can be considered as a typical heterogeneous system, statistical signal processing is a promising approach for determination of the representative volume element (RVE) dimensions. Such calculations can be carried out on the domain of logical arrays representing binary images of the materials microstructure. This paper deals with processing of image data obtained using SEM-BSE and high resolution flatbed scanner for determination of RVE dimensions. Advanced image processing techniques are employed and results from calculation using grayscale data are presented and compared with results calculated on the basis of color input images. Keywords: heterogeneous systems; natural stones; image processing; K-means clustering; representative volume element Available at various institutes of the ASCR
Utilization of image and signal processing techniques for assessment of built heritage condition

Historical buildings represent invaluable heritage from the past and therefore their protection is a very important task. Assessment of their condition must not cause damage accumulation thus the ...

Koudelka_ml., Petr; Koudelková, Veronika; Doktor, Tomáš; Kumpová, Ivana; Kytýř, Daniel; Valach, Jaroslav
Ústav teoretické a aplikované mechaniky, 2018

About project

NRGL provides central access to information on grey literature produced in the Czech Republic in the fields of science, research and education. You can find more information about grey literature and NRGL at service web

Send your suggestions and comments to nusl@techlib.cz

Provider

http://www.techlib.cz

Facebook

Other bases