1. A computational model for analysing the dry rolling/sliding wear behaviour of polymer gears made of POMAljaž Ignatijev, Matej Borovinšek, Srečko Glodež, 2024, izvirni znanstveni članek Opis: This study presents a computational model to determine the wear behaviour of polymer gears. Using PrePoMax finite element numerical calculation software, a proposed computational model was built to predict dry rolling/sliding wear behaviour based on Archard’s wear model. This allows the calculation of the wear depth in each loading cycle with constant mesh updating using the finite element method. The developed computational model has been evaluated on a spur gear pair, where the pinion made of POM was meshed with a support gear made of steel. The computational results obtained were compared with the analytical results according to the VDI 2736 guidelines. Based on this comparison, it was concluded that the proposed computational model could be used to simulate the wear behaviour of contacting mechanical elements like gears, bearings, etc. The main advantage of the model, if compared to the standardised procedure according to the VDI 2736 guidelines, is the geometry updating after a chosen number of loading cycles, which enables a more accurate prediction of wear behaviour under rolling/sliding loading conditions.
Ključne besede: polymer gears, rolling/sliding contact, wear, computational modelling
Objavljeno v DKUM: 12.04.2024; Ogledov: 189; Prenosov: 12
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3. Computational model for analysing the tooth deflection of polymer gearsAljaž Ignatijev, Srečko Glodež, Janez Kramberger, 2024, izvirni znanstveni članek Opis: A computational model for analysing the tooth deflection of polymer gears is presented in this paper. Because polymer gears have less stiffness compared to metal gears, the proposed approach considers a comprehensive analysis to determine the most suitable numerical model, i.e., the number of teeth that should be modelled for a given gear’s geometry and material. The developed computational model has been evaluated using a spur gear pair, where the pinion made of POM was meshed with a support gear made of steel. Material properties were assigned with linear elastic characteristics for the gear, while the pinion was characterised by hyperelastic properties using POM material. Furthermore, a nonlubricated frictional contact between the gear and pinion was considered in the numerical computations. The computational results that were obtained were compared to the empirical results according to VDI 2736 guidelines. Here, the computational approach showed more accurate results due to the hyperelastic material characteristics of POM and the simulation of multiple teeth meshing. However, VDI 2736 calculation showed comparability with the computational results, with a slightly larger deviation at higher loads. In this respect, the proposed computational approach is more suitable for analysing the tooth deflection of polymer gears under higher loads.
Ključne besede: polymer gears, tooth deflection, computational modelling
Objavljeno v DKUM: 19.03.2024; Ogledov: 266; Prenosov: 16
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4. Wear Behaviour of Multilayer Al-PVD-Coated Polymer GearsTonica Bončina, Brigita Polanec, Franc Zupanič, Srečko Glodež, 2022, izvirni znanstveni članek Opis: A comprehensive experimental investigation of the wear behaviour of coated spur polymer gears made of POM is performed in this study. Three different thicknesses of aluminium (Al) coatings were investigated and deposited by the Physical Vapour Deposition (PVD) process. The Al coating was deposited in three steps: By plasma activation, metallisation of the aluminium by the magnetron sputtering process, and plasma polymerisation. The wear of the gears was tested on an in-house developed testing rig for different torques (16, 20, and 24 Nm) and a rotational speed of 1000 rpm. The duration of the experiments was set to 13 h, when the tooth thickness and, consequently, the wear of the tooth flank were recorded. The experimental results showed that the influence of metallisation with aluminium surface coatings on the wear behaviour of the analysed polymer gear is not significantly important. The results also showed that the gears with a thicker aluminium coating showed greater wear than gears with a thinner coating or even without a coating. This is probably due to the fact that the aluminium particles that started to deviate during gear operation represented the abrasive material, which led to the faster wear of the contacting surfaces of the meshing gear flanks.
Ključne besede: polymer gears, aluminium PVD coating, Physical Vapour Deposition process, multilayer coating, wear
Objavljeno v DKUM: 15.11.2022; Ogledov: 580; Prenosov: 58
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5. The influence of surface coatings on the tooth tip deflection of polymer gearsBoštjan 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 v DKUM: 27.03.2017; Ogledov: 1816; Prenosov: 401
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6. Numerical modelling of crack growth in a gear tooth rootSrđan Podrug, Srečko Glodež, Damir Jelaska, 2011, izvirni znanstveni članek Opis: A computational model for determination of crack growth in a gear tooth root is presented. Two loading conditions are taken into account: (i) normal pulsating force acting at the highest point of the single tooth contact and (ii) the moving load along the tooth flank. In numerical analysis it is assumed that the crack is initiated at the point of the largest stresses in a gear tooth root. The simple Paris equation is then used for a further simulation of the fatigue crack growth. The functional relationship between the stress intensity factor and crack length K=f(a), which is needed for determining the required number of loading cycles N for a crack propagation from the initial to the critical length, is obtained using a displacement correlation method in the framework of the FEM-method considering the effect of crack closure. The model is used for determining fatigue crack growth in a real gear made from case carburised and ground steel 14CiNiMo13-4, where the required material parameters were determined previously by appropriate test specimens. The results of the numerical analysis show that the prediction of crack propagation live and crack path in a gear tooth root are significantly different for both loading conditions considered.
Ključne besede: zobniki, utrujanje, širjenje razpoke, numerično modeliranje, gears, fatigue, crack growth, numerical modelling
Objavljeno v DKUM: 10.07.2015; Ogledov: 1347; Prenosov: 84
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8. Review of experimental models for confirmation of mathematical models of gearsBoris Aberšek, Jože Flašker, 2008, izvirni znanstveni članek Opis: In order to calculate the service life as precisely and reliably as possible we need good mathematical models for describing loading, geometry, properties of materials and fracture mechanics parameters. It can be established whether a mathematical model is precise and reliable only by comparison of results of the method such as analytical methods in case of simple problems and experiment when real complex structure are deal with. Since gears and gearing belong to the second group, by correctly selected and developed test pieces and carefully planned experiments we obtained results with which we confirmed and justified the mathematical model for calculating mentioned parameters. To this end we will show in this paper series of experimental methods and test pieces used on the gears.
Ključne besede: machine elements, gears, mathematical models, testing, experimental methods, numerical analyses
Objavljeno v DKUM: 07.06.2012; Ogledov: 1654; Prenosov: 67
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9. A computational model for determination of service life of gearsSrečko Glodež, Matjaž Šraml, Janez Kramberger, 2002, izvirni znanstveni članek Opis: A computational model for determination of service life of gears in regard to bending fatigue in a gear tooth root is presented. The fatique process leading to tooth breakage is divided into crack initiation and crack propagation period. The strain-life method in the framework of the FEM-methods has been used to determine the number of stress cycles Ni required for the fatique crack initiation, where it is assumed that the crack is initiated at the point of the largest stresses in a gear tooth root. The simple Paris equations is then used for the further simulation of the fatigue crack growth. The functional relationship between the stress intensity factor and crack length K=f(a), which is needed for determination ofthe required number of loading cycles Np for a crack propagation from the initial to the critical length, is obtained using displacement correlation method in the framework of the FEM-method. The total number of stress cycles N for the final failure to occur is then a sum of Ni and Np. The model is used for determination of service life of real spur gear made from through-hardened steel 42CrMo4, where required material parameters have been determined previously by the appropriate test specimens.
Ključne besede: machine elements, fatigue, fatigue crack growth, numerical modelling, gears, service life
Objavljeno v DKUM: 01.06.2012; Ogledov: 2418; Prenosov: 124
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10. Numerical procedure for predicting the rolling contact fatigue crack initiationMatjaž Šraml, Jože Flašker, Iztok Potrč, 2003, izvirni znanstveni članek Opis: A computational numerical model for contact fatigue damage analysis of mechanical elements is presented in this paper. The computational approach is based on continuum mechanics, where a homogenous and elastic material model isassumed in the framework of the finite element method analysis. Cyclic contact loading conditions are simulated with moving Hertzian contact pressure. The time-depending loading cycles are defined for each observed material point on and under the contact area. Furthermore, the influence of friction upon rolling-sliding contact loading cycles is analysed in detail, using Coulombćs friction law. The model for prediction of the number of loading cycles, required for initial fatigue damages to appear, is based on Coffin-Manson relations between deformations and loading cycles, and includes characteristic material fatigue parameters. As a general example, the model isused to analyse a fundamental contact problem of a cylinder and flat surface, which is usually a substitutional model for analysing real mechanicalproblems. However, the results concerning the identification of critical material points and the number of loading cycles, required for initial fatigue damages to appear at those points, are the main purpose of thepresented study.
Ključne besede: machine elements, gears, contact problems, contact fatigue, crack initiation, numerical modelling
Objavljeno v DKUM: 01.06.2012; Ogledov: 1935; Prenosov: 81
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