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Influence of different load models on gear crack path shapes and fatigue lives
Srđan Podrug, Damir Jelaska, Srečko Glodež, 2008, izvirni znanstveni članek

Opis: A computational model for determination of the service life of gears with regard to bending fatigue at gear tooth root is presented. In conventional fatigue models of the gear tooth root, it is usual to approximate actual gear load with a pulsating force acting at the highest point of the single tooth contact. However, in actual gear operation, the magnitude as well as the position of the force changes as the gear rotates. A study to determine the effect of moving gear tooth load on the gear service life is performed. The fatigue process leading to tooth breakage is divided into crack-initiation and crack-propagation period. The critical plane damage model has been used to determine the number of stress cycles required for the fatigue crack initiation. The finite-element method and linear elastic fracture mechanics theories are then used for the further simulation of the fatigue crack growth.
Ključne besede: crack closure, crack initiation, crack propagation, gear tooth root, moving load
Objavljeno: 31.05.2012; Ogledov: 729; Prenosov: 55
URL Povezava na celotno besedilo

Investigation of crack propagation scatter in a gear tooth's root
Stanislav Pehan, Janez Kramberger, Jože Flašker, Boštjan Zafošnik, 2008, izvirni znanstveni članek

Opis: This paper describes the problem of determining crack initiation location and its influence on crack propagation in a gear tooth's root. Three different load positions on the gear tooth's flank were considered for this investigation of crack initiation and propagation. A special test device was used for the single tooth test. It can be concluded from the measurements thata crack can be initiated at very different locations in a tooth's root and then propagate along its own paths. A numerical investigation into a crack initiation's position and its influences on its propagation were carried out within the framework of linear fracture mechanics. The influence of a tooth's load position, the geometry of the tooth's root, and the influence of nonparallel load distribution on the tooth's flank were considered when investigating the crack initiation's position. Results show that linear fracture mechanics can be used for determining crack propagation, if better initial conditions for crack initiation are considered.
Ključne besede: fracture mechanics, crack initiation, experimental crack propagation, numerical crack propagation, crack location, gearbox, tooth root, load distribution, linear elastic fracture mechanics
Objavljeno: 01.06.2012; Ogledov: 875; Prenosov: 62
URL Povezava na celotno besedilo

Determination of stresses and forces on the orthodontic system by using numerical simulation of the finite elements method
Janko Ferčec, Branislav Glišić, I. Šćepan, Evgenija Marković, Dragoslav Stamenković, Ivan Anžel, Jože Flašker, Rebeka Rudolf, 2012, izvirni znanstveni članek

Opis: This study was addressed to use knowledge about the orthodontic system with numerical simulation of the nite elements method. For the rst time we simulated the stresses on the orthodontic system and, in this manner, calculated the orthodontic force on the tooth. A 3D orthodontic model or orthodontic system was designed resembling moderate crowding in the dental arch with all supporting structures. CATIA V5 computer software was used to set up a model for the orthodontic system and ABAQUS was used for simulation of the stresses on the orthodontic system. Our attention was focused on the stresses on the tooth lateral incisor and its periodontal ligament. The results of the numerical simulation showed complex stresses on the tooth lateral incisor and its periodontal ligament. In this paper is presented a calculation of the orthodontic force acting on the tooth lateral incisor due to the orthodontic wire. This orthodontic force was calculated from the stresses on the bracket. The calculated orthodontic force was in the area which is considered as the optimal orthodontic force for movement of the tooth.
Ključne besede: okluzija, ortodontski sistem, metoda končnih elementov, ortodonske sile, zobje, malocclusion, orthodontic system, finite elements method, orthodontic force, tooth
Objavljeno: 10.07.2015; Ogledov: 364; Prenosov: 62
URL Povezava na celotno besedilo

Automated landmark points detection by using a mixture of approaches
Božidar Potočnik, 2015, izvirni znanstveni članek

Opis: This paper deals with the automated detection of a closed curvećs dominant points. We treat a curve as a 1-D function of the arc length. The problem of detecting dominant points is translated into seeking the extrema of the corresponding 1-D function. Three approaches for automated dominant points detection are presented: (1) an approach based on fitting polynomial, (2) an approach using 1-D computer registration and (3) an innovative approach based on a multi-resolution scheme, zero-crossing and hierarchical clustering. Afterwards, two methods are introduced based on the linearly and non-linearly mixing the results from the three approaches. We then mix the results in a mean-square error sense by using the linear and non-linear fittings, respectively. We experimentally demonstrate the problem of detecting 21 landmarks on 38 vole-teeth that by mixing, the detection accuracy is improved by up to 41.47 % with respect to the results for individual approaches, as applied within the mixture.
Ključne besede: closed curve, dominant point, landmark, automated detection, mixing model fitting, vole-tooth
Objavljeno: 10.07.2015; Ogledov: 552; Prenosov: 7
URL Povezava na celotno besedilo

Artificial tooth and polymer-base bond in removable dentures: the influence of pre-treatment on technological parameters to the bond`s strength
Martin Pavlin, Rebeka Rudolf, Vjekoslav Jerolimov, 2008, izvirni znanstveni članek

Opis: The aim of this study was to evaluate the artificial tooth and polymerbase bond, and to measure any formatted gaps between tooth and base. Acrylic models were classified into four groups depending on the type of surface pre-treatment. A pre-treatment surface combining mechanical and chemical led to the highest bond strength between acrylic tooth and denture-base. The fore-mentioned pre-treatment had an influenced on gap formation with an average value of 68.250 micro m, which is 70 % of the gap for the untreated samples. Furthermore, the measured compressive strength was above 6000 N/mm2, yet only 3200 N/mm2 on the untreated samples.
Ključne besede: artificial tooth, acrylic tooth, polymer base bond, dentistry
Objavljeno: 21.12.2015; Ogledov: 324; Prenosov: 14
URL Povezava na celotno besedilo

The influence of surface coatings on the tooth tip deflection of polymer gears
Boštjan Trobentar, Srečko Glodež, Jože Flašker, Boštjan Zafošnik, 2016, izvirni znanstveni članek

Opis: When designing gear drives made of polymer, the tooth tip deflection is a crucial parameter in respect to the proper gear drive operation. Excessive tooth tip deflection can lead to serious disturbances of gear meshing and consequently to increased noise and wear of the teeth flanks. In such cases the tooth tip deflection can be reduced through the use of stiff surface coatings on the tooth flanks. In this paper the influence of different coating materials and thicknesses on the tooth tip deflection of polymer gears is analysed using comprehensive finite element computational analysis. The numerical results obtained are then used to define an approximate equation for the calculation of gear tooth tip deflection for the coating material used and the thickness of the surface coating layer. The results show that the tooth tip deflection decreases with large values of the coating material Young’s modulus and with the coating layer thickness.
Ključne besede: polymer gears, surface coatings, tooth deflection, numerical analysis
Objavljeno: 27.03.2017; Ogledov: 367; Prenosov: 184
.pdf Celotno besedilo (578,86 KB)
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Methods for detecting fatigue cracks in gears
Aleš Belšak, Jože Flašker, 2009, objavljeni znanstveni prispevek na konferenci

Opis: A crack in the tooth root is the least desirable damage caused to gear units and it often causes failure of gear unit operation. For fault analyses presented in this article, gear units with real damages or faults produced on the basis of numerical simulations of real operating conditions are used; tests were carried out in a laboratory test plant. Damages in gear units can be identified by monitoring vibrations. The influences of a crack in a single-stage gear unit on produced vibrations are presented. Significant changes in tooth stiffness are caused by a fatigue crack in the tooth root whereas, in relation to other faults, changes of other dynamic parameters are more expressed. Non-stationary signals are analysed, using the family of Time Frequency Analysis tools, which include Wavelets and Joint Time Frequency Analyses.
Ključne besede: gear unit, vibrations, tooth root, time frequency analysis tool
Objavljeno: 30.06.2017; Ogledov: 260; Prenosov: 183
.pdf Celotno besedilo (705,13 KB)
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Hypodontia prevalence and pattern in women with epithelial ovarian cancer
Anita Fekonja, Andrej Čretnik, Iztok Takač, 2014, izvirni znanstveni članek

Opis: Objective: To analyze the possible association between hypodontia and epithelial ovarian cancer (EOC), with the special interest in hypodontia pattern. Materials and Methods: One hundred twenty women with EOC treated at the Department of Gynecologic and Breast Oncology at the University Clinical Centre and 120 gynecologically healthy women of the same average age were reviewed for the presence and pattern of hypodontia. Collected data were analyzed for frequency, tooth type, location per jaw and side, number of missing teeth per person, and family history of hypodontia. Results: The results of the study showed prevalence of hypodontia in 19.2% of women with EOC and in 6.7% of women in the control group (P = .004). The most frequently missing teeth for women with EOC and women in the control group were maxillary second premolars and maxillary lateral incisors, respectively. Unilateral occurrence of hypodontia was more common than bilateral occurrence in women with EOC (P = .034). Of women with EOC and hypodontia, 21.7% reported a positive family history of hypodontia compared with no report in the control group of women with hypodontia (P = .150). Conclusions: The results statistically support possible association between EOC and hypodontia. Because hypdontia can be recognized early in life, this finding could possibly help in earlier detection of EOC, resulting in better prognosis and treatment in earlier stages of the disease. Earlier EOC diagnosis and treatment could save many lives.
Ključne besede: hypodontia, tooth agenesis, ovarian cancer, neoplasms
Objavljeno: 07.08.2017; Ogledov: 358; Prenosov: 176
.pdf Celotno besedilo (64,81 KB)
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