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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: 664; Prenosov: 30
URL Povezava na celotno besedilo

Evaluation of Green`s function for vertical point-load excitation applied to the surface of a semi-infinite elastic medium
Andrej Štrukelj, Tomaž Pliberšek, Andrej Umek, 2006, izvirni znanstveni članek

Opis: The topic of this paper is to show that the integrals of infinite extent representing the surface displacements of a layered half-space loaded by a harmonic, vertical point load can be reduced to integrals with finite integration range. The displacements are first expressed through wave potentials and the Hankel integral transform in the radial coordinate is applied to the governing equations and boundary conditions, leading to the solutions in the transformed domain. After the application of the inverse Hankel transform it is shown that the inversion integrands are symmetric/antimetric in the transformation parameter and that this characteristic is preserved for any number of layers. Based on this fact the infinite inversion integrals are reduced to integrals with finite range by choosing the suitable representation of the Bessel function and use of the fundamental rules of contour integration, permitting simpler analytical or numerical evaluation. A numerical example is presented and the results are compared to those obtained by the CLASSI program.
Ključne besede: civil engineering, soil mechanics, Green`s function, layered half-space, vertical point load
Objavljeno: 31.05.2012; Ogledov: 1366; Prenosov: 7
URL Povezava na celotno besedilo

Analysis of composite T beam composed of timber, concrete and carbon strip
Matjaž Tajnik, Peter Dobrila, Miroslav Premrov, 2007, izvirni znanstveni članek

Opis: This paper provides a mathematical model and numerical example of composite T-section composed of a concrete plate and a timber beam strengthened at the bottom tension side with a carbon fibre-reinforced polymer (CFRP) strip. Analysis is provided in accordance with the European standards for timber, steel and concrete structures. The tensile strength of the carbon strip as well as the compressive strength of the concrete plate are higher than the bending strength of the timber beam, therefore it is convenient to use such composition of material to gain a higher load bearing capacity. It has been shown that the inclusion of CFRP strip reinforcement on the increase of load carrying and bending stiffness capacity was not as high as expected. On the other hand, we realized the importance of variety of material grade and geometrical properties combinations between sub-components which can significantly improve load bearing capacity and stiffness of composed beam. Furthermore, the CFRP strip contribution to the bending resistance and stiffness of the element is presented as a function of the fastener spacing intervals between concrete plate and timber beam.
Ključne besede: composite structures, timber structures, carbon strip, load bearing capacity, modeling
Objavljeno: 31.05.2012; Ogledov: 1095; Prenosov: 48
URL Povezava na celotno besedilo

On critical buckling load estimation for slender transversely cracked beam-columns by the application of a simple computational model
Matjaž Skrinar, 2008, izvirni znanstveni članek

Opis: This paper brings new insights into the implementation of a simplified computational model in the prediction of buckling load Pcr for slender beam-type structures with a transverse crack. From among several approaches discussed, two of them produced applicable results exhibiting considerably good agreement with those values from more precise and complex computational models. In the first approach, the critical load value is obtained from numerical solutions of analytically expressed characteristic equations (obtained from governing differential equations). Although producing excellent results, this approach limits the application since an analytical solution of the governing differential equation can only be obtained for moderate structures. The second approach implements a new cracked beam-columnfinite element, derived at on the basis of a fairly accurate approximation of the governing differential equation's solution. It allows for flexible utilization and also yields the smallest compact computational model, thus exhibiting itself as very suitable for inverse identification problems. Numerical examples covering several structures with different boundary conditions are briefly presented in order to support the discussed approaches. The results obtained using the presented approaches are further compared with those values from either references or more complex models, thus clearly proving the quality of the presented compact FE model.
Ključne besede: beam columns, transverse cracks, stability problems, buckling load, computational model, finite element method
Objavljeno: 31.05.2012; Ogledov: 1492; Prenosov: 36
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: 804; Prenosov: 37
URL Povezava na celotno besedilo

On the application of a simple computational model for slender transversely cracked beams in buckling problems
Matjaž Skrinar, 2007, izvirni znanstveni članek

Opis: This paper discusses the implementation of a simplified computational model that is widely used for the computation of transverse displacements in transversely cracked slender beams into the Euler's elastic flexural buckling theory. Two alternatives are studied instead of solving the corresponding differential equations to obtain exact analytical expressions for the buckling load ▫$P_{cr}$▫ due to the complexity of this approach. The first approach implements wisely selected polynomials to describe the behavior of the structure, which allows the derivation of approximate expressions for the critical buckling load. Although the relevance of the results strongly depends on the proper prime selection of the polynomial, it is shown that the later upgrading of the polynomials can lead to even more reliable results. The second approach is a purely numerical approach and presents the geometrical stiffness matrix for a beam finite element with a transverse crack. To support the discussed approaches, numerical examples covering several structures with different boundary conditions are briefly presented. The results obtained with the presented approaches are further compared with the values from enormous 2D finite elements models, where a detailed description of the crack was achieved with the discrete approach. It is evident that the drastic difference in the computational effort is not reflected in the significant differences in the results between the models.
Ključne besede: columns, transverse cracks, stability problems, buckling load, computational model, polynomial solutions, finite element method, geometrical stiffness matrix
Objavljeno: 01.06.2012; Ogledov: 1228; Prenosov: 28
URL Povezava na celotno besedilo

Application of the european SINTAP procedure to the failure analysis of a broken forklift
Nenad Gubeljak, Uwe Zerbst, Jožef Predan, Maks Oblak, 2004, izvirni znanstveni članek

Opis: The recently developed European flaw assessment procedure SINTAP was applied to the failure analysis of a broken fork of a forklift. Based on the service load at failure, critical crack sizes were determined at different analysis levels of the procedure. It was shown in the present case study that the failure was caused by defective design.
Ključne besede: structural integrity, mechanics of structures, forklift, fracture mechanics, critical crack size, failure analysis, SINTAP procedure, load bearing capacity
Objavljeno: 01.06.2012; Ogledov: 1018; Prenosov: 25
URL Povezava na celotno besedilo

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