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[EN] While the founding members of CHERNE gradually retire, the memory of the early steps of the network should not be lost. CHERNE (`Cooperation for Higher Education on Radiological and Nuclear Engineering¿) is the product of a specific Erasmus activity possible in the early 2000s: the intensive programmes (IP). The first step was a collaboration of three partners (Czech Technical University CTU, Institut Supérieur Industriel de Bruxelles ISIB, Universitat Politècnica de València UPV) organising in 2002 the 3-year IP `PAN: Practical Approach to Nuclear techniques¿, soon integrating two other partners (Aachen University of Applied Science AcUAS, XIOS Hogeschool Limburg). A second IP `SPERANSA: Stimulating Practical Expertise in RAdiation and Nuclear SAfety¿ was first organised without Erasmus support in 2005. A workshop was held in 2005 at UPV, including colleagues from other universities. Its main goal was to put in contact professors and researchers from European Institutions in order to share experiences in education and research in Radiation Protection and Nuclear Engineering. The creation of an informal group of universities to develop activities for the benefit of students was discussed. With the addition of Università degli Studi di Bologna (UniBo) to the initial group, the CHERNE network was created. It attracted rapidly more members (6 adhesions in 2006). CHERNE was conceived as a non-formal wide-scope open network, easily integrating new members, offering affordable activities to the students and mostly relying on Erasmus subsidies. The main goal was still the organisation of Erasmus IP¿s based on practical activities, benefitting of the access to big experimental facilities offered by several partners, like reactors, accelerators, or a radiochemical laboratory. SPERANSA was organised from 2006 to 2008, `JUNCSS: JÜlich Nuclear Chemistry Summer School¿ from 2007 to 2011 and `RAPIX-NOCOS: Radiation protection in non-conventional sectors¿ in 2007 and 2008 without Erasmus support. The annual workshops triggered exchanges between partners and attracted more institutions. The first workshops saw intense discussions about the network organisation and the types of activities that could be organised. A kind of maturity was reached from 2008.

An overview of calculation methods of load carrying capacity of gears is given in the paper. The standard procedure for determining tooth-root and contact stresses in spur gears is defined in ISO 6336 standard. Tooth-root stress is approximated by bending stress caused by tangential force component, while compressive stress, caused by radial force component, and shear stress are neglected. The whole force acting on one tooth is used in calculations. This simplification of calculation is taking into account by using numerous influence factors in formulae. Finite element method is the most commonly used numerical method for determining tooth-root stresses in gears' teeth. Linear analysis or nonlinear contact analysis can be used. In linear analysis the whole force acting on one tooth is used for the calculation. The procedure for determination of load distribution on teeth in simultaneous contacts is given to improve the accuracy of this numerical method, especially when high contact ratio gears are analysed. The application of nonlinear contact analysis of gears in mesh gives very accurate results, without necessity of previously known load distribution. Instead of the force applied on one point on the tooth flank, the load is applied by putting the pinions' and wheels' teeth in contact and applying the torsion moment on the pinion. The formulations for these analyses are presented in the paper.