Boris Aberšek

Expert system for designing and manufacturing of a gear box

Abstract This paper presents the expert system STATEXS for dimensioning optimization and manufacture of gears and gearing. To determine the optimum dimensions of gearing, we used genetic algorithms which are well suited for such problems, particularly because of their robustness and ability to detect global extremes. After completion of calculations and optimization of gears or gear pairs, one of the most difficult operations follows, i.e. the manufacture of the product with theoretically determined and optimized properties. To this end, at our Faculty we have also started to develop an expert system for the field of manufacture of various products of demanding shapes.

Review of mathematical and experimental models for determination of service life of gears

Abstract For designing machines and devices the dimensioning with respect to service life is increasingly taken into account. This applies also for gearing which are still today one of very important components of almost all machines. We have developed a stochastic model for determination of service life of gears. In our model we propose a new parameter by which we describe the fracture mechanics conditions in the tooth root where the defects, causing destruction, occur statistically most frequently as shown. We named that factor the tooth stress intensity factor Z. The value of the factor Z is related to dislocation, propagation of the plastic zone, deformation and orientation of grain in case of short cracks and stress intensity factor K in case of long cracks. For determination of the service life for the area of short cracks we used Bilby, Cottrell and Swinden model which is based on the theory of continuously distributed dislocations and we complemented it with random generation of structure of material before cracks. For the long crack we have developed a stochastic model for determination of service life of gears. For confirm mathematical models we developed different non-standard test pieces and on this pieces we used combination of mixed experimental methods. The aim of these combinations was to obtain as complete information about the individual influences as possible and to determine the interaction between different fracture mechanic magnitudes. In this way we confirmed the mathematical models as a whole and also determined some physical interpretations in models. With this we were able to ensure that the presented model is not purely a mathematical model.

Evaluation of the service life of gears in regard to surface pitting

A computational model for determining the service life of gear teeth flanks in regard to surface pitting is presented. The model considers the material fatigue process leading to pitting, i.e. the conditions required for the short fatigue crack propagation originating from the initial crack in a single material grain. In view of small crack lengths observed in surface pitting, the simulation takes into account the short crack growth theory. The stress field in the contact area and the required functional relationship between the stress intensity factor and the crack length are determined by the finite element method. An equivalent model of two contacting cylinders is used for numerical simulations of crack propagation in the contact area. On the basis of numerical results, and with consideration of some particular material parameters, the probable service life period of contacting surfaces is estimated for surface curvatures and loadings that are most commonly encountered in engineering practice.

TECH8 intelligent and adaptive e-learning system

E-materials and various e-learning systems have become regular features in lower secondary schools in Slovenia and around the world. Many different systems and materials have been created for students, but only a few offer the same amount of individualisation that is present in traditional one to one teaching (one teacher to one student). The purpose of this research is to demonstrate the design and evaluation of an adaptive, intelligent and, most important, an individualised intelligent tutoring system (ITS) based on the cognitive characteristics of the individual learner. The TECH8 model presented is designed modularly, based on a system for collecting a range of metadata and variables that are vital for the teaching process. Prepared in such a way, the proposed system supports individualization and differentiation; because of this, it can be adapted to each individuals level of knowledge and understanding of the subject matter.This TECH8 system was evaluated in a real learning environment. The evaluation sample of the study consists of 117 students from five schools (suburban and urban). Qualitative and quantitative data was gathered with a system for collecting metadata and variables. The assembled data was analysed and statistically processed using descriptive analysis. This data was also compared to data from national assessments of knowledge, which encompassed the entire student population (approx. 5000) in the years 2008, 2010 and 2013. The study and the comparisons indicated that appropriately created TECH8 e-learning material, yields results that are better than those from traditional teaching but not better than one to one teaching. With the help of the collected metadata, optimisation, evaluation and an upgrade of the TECH8 itself will be carried out. In addition, such individualized e-learning systems can reinforce knowledge gained through traditional classroom education. Research question: Is it possible to replace a human teacher with a virtual one?The presented modified version of ITS includes hybrid model TECH8.TECH8 can adapt the learning process to the needs of an individual student.TECH8 does not only symbolise the learning process, but also the social environment.Cybernetic pedagogy and presented model TECH8 can lead to the progress of ITS.

Model of an integrated intelligent design and manufacturing system

The expert system STATEXS is presented for dimensioning, optimization and manufacture of gears and gearings. The optimum dimensions of the gearing were determined using genetic algorithms, well suited to such problems especially because of their robustness and their ability to detect global extremes. After completion of the calculations and optimization of the gears or gear pairs, there follows one of the most difficult operations, the manufacture of the product with theoretically determined and optimized properties. To this end we have also started to use the genetic algorithm approach for the manufacture of various products with demanding shapes.

Target Group Questionnaire in the “ISG for Competence” Project

This paper introduces the “Intelligent Serious Games for Social and Cognitive Competence” project. The aim of these games are to teach youth with disabilities on creativity. The development of interactive mobile games and 3D simulations helps the social integration and personal development of children and youth with disabilities. The project targets to improve the quality of education and trainings to gain more efficiency. To enhance creativity and innovation the project uses serious games and 3D simulations this way teaching and learning becomes interesting, playful, attractive and efficient.

Fatigue Assessment of High Loaded Bolted Bar Connection Using Strain-Life Approach

The paper deals with the problem of service life evaluation of counterweight bar bolted connection by means of computational analysis and experimental testing. Computational analysis has been performed using the local strain-life approach (ε-N), where appropriate material properties for treated high strength steel S1100Q has been determined previously. Experimental fatigue tests of bars were carried out in a specially constructed hydraulic pulsation machine. Comparison of computational and experimental results shows a reasonable agreement.

Quasi - Numerical Model for the Determination of Residual Stresses

If we don’t have the adequate measuring equipment we can also use t he implified but enough accurate substitute, the quasi-numerical models. The model for the computation of the residual stresses and/or their inclusion in the determining stress field b y FEM will be presented. The model are suitable for the determination of the residual stresse s on the tooth gears and the gear wheels. They can be also used with minimum modifications for other ex amples where the expected course of the residual stresses is known.

Evaluation of the Service Life of Gear in Regard to Bending Fatigue in a Gear Tooth Root

A computational model for evaluation of service life of gears in r ega d to bending fatigue in a gear tooth root is presented. The fatigue process leading to toot h breakage is divided into crack initiation and crack propagation period. The Coffin-Manson relationship is us ed to determine the number of stress cycles Ni required for the fatigue crack initiation, where it is assumed t hat the initial crack is located at the point of the largest stresses in a gear tooth root. The simple Paris equation is then used for the further determination of the required number of loading cycles Np for crack propagation from the initial to the critical length, where r quired material parameters have been determined previously with appropriate test specimens. The total number of stress cycles N for the final failure to occur is then a sum N = Ni +Np. Introduction Several classical standardised procedures (DIN, AGMA, ISO, etc.) can be used for the approximate determination of load capacity of gear tooth root. They are commonly ba sed on the comparison of the maximum tooth-root stress with the permissible bending stress and consider only the final stage of the fatigue process in a gear tooth root, i.e. the occurrence of final failure. However, the complete process of fatigue failure of mechanical elements may be divided into the following stages [1, 2]: (1) crack nucleation; (2) short crack growth; (3) long crack growth; and (4) occurrence of final failure. In engineering applications the first two stages are us ually termed as “crack initiation period”, while long crack growth is termed as “crack propagation peri od”. However, the crack initiation period generally accounts for most of the service life, especially in high-cycle fatigue (HCF), see Fig. 1. The total number of stress cycles N can than be determined from the number of stress cycles Ni required for the fatigue crack initiation and the number of stress cycles Np required for a crack to propagate from the initial to the critical crack length:

Designing Trainer’s Manual for the ISG for Competence Project

The 3-year project “Intelligent Serious Games for Social and Cognitive Competence” targets children and youth with disabilities, teaching them on creativity and social competencies, using serious desktop and mobile games. The intellectual output (IO) 4 “Trainers manual” is based on the results and conclusions from desktop and survey findings from IO1 Scoping Report, the curriculum and learning scenarios of IO2 Suite of serious game on accessible learning objects (learning content creation) and IO3 Interactive games for mobile learning which can be reviewed/downloaded from the official project website www.isg4competence.com.