Imre Bojtár's research while affiliated with Budapest University of Technology and Economics and other places

Publications (30)

Article
We aim to introduce a novel, inverse method for in vivo material parameter identification of human abdominal aortic aneurysms (AAA), which could overcome one of the greatest sources of uncertainty in patient-specific simulations, and could also serve as a rapid, patient-calibrated, novel measure of aneurysm rupture risk. As an initial step, the det...
Article
To evaluate and compare the mechanical properties of anterior capsule opening performed with femtosecond laser capsulotomy at different energy settings in ex vivo porcine anterior lens capsule specimens. Twenty-five fresh porcine eyes per group were included in the study. Femtosecond laser capsulotomy was performed with three different pulse energy...
Article
Full-text available
Local biomechanical effects play an important role in aneurysm formation and rupture. It is hypothesised that the main governing factors of the pathogenetic process are the temporal variation and spatial distribution of the flow induced wall shear stress (WSS). The present paper investigates the geometry of the carotid bifurcation, a typical locati...
Chapter
Clinical treatment of abdominal aortic aneurysms is decided mainly on the maximal dilatation diameter. Biomechanics based criteria calculated by numerical fluid structure interaction simulations on patient specific geometries are superior to that approach, but are extremely time and resource consuming and require high expertise, furthermore they fa...
Article
Full-text available
The present paper introduces a numerical simulation aided, experimental method for the measurement of Young’s modulus of the trabecular substance in the human mandible. Compression tests were performed on fresh cadaveric samples containing trabecular bone covered with cortical layer, thus avoiding the destruction caused by the sterilization, preser...
Article
Purpose: To evaluate and compare the mechanical properties of anterior capsule openings performed with the continuous curvilinear capsulorhexis (CCC) technique and femtosecond laser capsulotomy (FLC) in ex vivo porcine lens capsule specimens. Methods: Fresh porcine eyes were included in the study (CCC group, n = 50; FLC group, n = 30). The capsu...
Article
The mechanical behaviour of zonular fibres greatly affects the accommodation process in mammalian eyes. This paper introduces a detailed measurement procedure for the purpose of obtaining the force-displacement diagram necessary to evaluate the mechanical properties of porcine zonular fibres in situ. It is a complex technique, keeping the integrity...
Article
This paper deals with the biomechanical analyse of the human eye with a complex numerical model. We present our three dimensional finite element model including the built-up parts, applied material and geometric properties. Hereupon we describe the subjects which we want to investigate with this 3D model, such as accommodation, presbyopia and so on...
Article
Full-text available
Resume Present study deals with the mesostructure analysis of the structural glass. The subject is about to prepare a comprehensive mechanical analysis, aimed on the understanding of the multiscale mechanical behaviour of soda-lime-silica glass used as an architectural element. After a brief description of the micro and mesostructure of glass we wi...
Article
Most human bones are divided into an external cortical and an internal trabecular substance. Both kinds of bone tissue are capable of adapting their strength to the loads acting upon them; they are in a state of continuous remodelling. The present study introduces a new method for modelling the functional adaptation of the trabecular bone by means...
Article
The aim of this article is to investigate the hyperelastic mechanical response of brain human arterial tissue. Biaxial biomechanical characterization of living tissues - like the artery walls - provides important information about their in vivo behaviour. We investigate the biomechanical properties of samples from human cerebral aneurysms and from...
Article
Dental implantation is currently the most commonly used and physiologically the most favourable procedure for tooth replacement in dental surgery Implants can have either advantageous or destructive effect on the surrounding bone, depending on several physiological, material and mechanical factors. The most general method for estimating the biomech...
Article
This paper presents the experimental and numerical investigations for both rectangular and half-cylindrical specimens, and suggests analytical formula for calculation of stress intensity factor based on the new geometry
Article
The paper deals with the theoretical and numerical analysis of granular assemblies. Introduction of the re-interpretation of classical continuum-mechanical state variables is followed by a summary of continua with higher degrees of freedom. Results of numerical experiments are shown to point out that classical continua cannot contain enough informa...
Article
We provide, in this work, estimation of critical value of stress intensity factor of the human skull (KIC). Our research assists examinations concerning dynamic effects exerted on human skull (cracks, etc.).
Article
A quasi-static numerical algorithm is introduced for the analysis of quasi-static state-changing processes of granular materials. The paper presents the application possibilities of the model. Both sand-like and cemented materials can be analysed; rearrangements, instabilities, local slips, crack opening, etc., can easily be followed.
Article
A discrete model made for the analysis of state-changing processes of granular assemblies is introduced here. Our numerical experiments can help in the analysis of some theoretically suggested variables that could be used later in the macro-level description of the behaviour of granular materials.
Article
A numerical method has been developed for the analysis of the internal behaviour of granular materials. State-changing processes of microstructure can be followed; the final aim is to find state variables that can reliably describe these processes.
Article
Full-text available
Our paper focuses on the uniaxial compression failure strength of granular rocks. The results of laboratory tests usually show a rather high scatter that has mostly been explained by the small random errors when doing the experiments. Our aim was to supervise this problem from microstructural point of view and to point out that the geometrical rand...

Citations

... Particularly, the calculation of a continuum strain field of a discrete granular system from its discrete kinematics field is termed a kinematics homogenization process. The most commonly used methods for kinematics homogenization are spatial discretization approaches [8][9][10][11][12]. In these approaches, a nodal network connecting particle centroids is generated, and interpolation is then performed between adjacent nodes to calculate the displacement gradient. ...
... The infant cranial suture was modeled as a linear elastic material with an elastic modulus of 8.1 MPa [21]. The skull fracture toughness was assumed to be transversely isotropic with fracture toughness along the fiber direction assumed to be 5 MPa ffiffiffiffiffiffiffiffi mm p , which is 21% of fracture toughness of adult skull [24] and almost the same as that of young human adult femurs [25]. Fracture toughness across the fibers was assumed to be ten times larger than fracture toughness along the fiber direction, which was based on the parallel to perpendicular relationships of infant cranial bone elastic modulus reported by Metcalf [22]. ...
... In a previous study (Molnár et al., 2012) we examined the mesoscopic material structure of glass. We divided a glass plate into regions as the external surface, the edge and the glass volume itself. ...
... Unfortunately this is not the case. Though there are some interesting suggestions (a very good summary of which was given by Satake (1989) ), they are rather questionable both from a theoretical and from a practical point of view (Bagi, 1991). Section 3 of the present paper tries to give a definition of the strain tensor in terms of relative displacements of neighbouring grains. ...
... Mapping the different properties of the vessel wall is also essential for the development of tools and a deeper understanding of the problem area. Because most of these problematic vascular sections or in vivo studies of the implant are difficult, researchers are able to draw conclusions based on input data from in vitro measurements using various material and mechanical models and simulations [3][4][5][6]. ...
... It is recognized that the implant and bone tissue must be subjected to a limited range of stress in order to maintain physiological homeostasis. Overloading can cause bone resorption or a fatiguing fracture at the implant neck, while underloading can cause atrophy and bone loss [9]. ...
... where M=π/8 is a parameter for Dugdale model, E is the Young modulus, σ Ic =f t are the stresses that initiates the crack growth. G Ic is the critical strain energy release rate for mode I: (2) K Ic =14.56 N/m 3/2 is the stress intensity factor in mode I for sandstone which was adopted from Rechtorisz et al. [7]. The force P was calculated from equilibrium of vertical forces. ...
... The 'time of the diastolic (systolic) pressure' is the time corresponding to the minimal (maximal) aortic pressuretdp (tsp) in Figure 21. tdp and tsp were computed to be 0.0589 and 0.2946 s after the start of the cycle (Nagy et al., 2015). ...
... Although the probability of achieving a complete capsulotomy increases when 150% of energy is used, as indicated by results of the previous study, 21 an increase in laser energy can adversely affect capsulorhexis, such as capsular adhesion and an increased risk of anterior-capsular tags. 22 Therefore, it is important to increase laser energy appropriately through accurate calculations. Moreover, considering the results of this study, power attenuation due to absorption must be included in the calculation. ...
... The models developed are represented in Table 2, where models Band3 and Band7 have a band width correspondence with literature values [24,33], and the remaining models evaluate the intermediary values between the forementioned band widths. The gravitational force impact in the lens complex was assessed, where the density values of cortex, nucleus, and capsule were equivalent (δC = δN = δCB = 1099 kg/m 3 ) [34], and the density of the zonules was determined as δZ = 1000 kg/m 3 [35]. ...