Precise laser triangulation measurements of Er:YAG laser ablated volumes in hard dental tissues were made in order to verify the possible existence of a “hydrokinetic” effect which has been proposed as an alternative mechanism for hard-tissue laser ablation. No evidence of the hydrokinetic effect could be observed under a broad range of tested laser parameters and water cooling conditions. On the contrary, the application of water spray during laser exposure of hard dental material was observed to diminish the laser ablation rate in comparison with laser exposure under the absence of water spray. Our findings are in agreement with the generally accepted principle of action for Erbium laser ablation, which is based on fast subsurface expansion of laser-heated water trapped within the interstitial structure of hard dental tissues.
F.02 Acquisition of new scientific knowledge
COBISS.SI-ID: 12641307This paper reports on the treatment of different Al-Si alloys after laser surface remelting through analysis of the changes in microstructure and hardness of a modified surface layer. On as cast samples, laser remelting of the thin surface layer was carried out with different energy inputs into the sample surface. The remelting conditions were varied by application of different lase beam power, different degrees of defocusing and different laser beam travel speeds across the sample surface. With the selected remelting conditions for the thin surface layer a sufficiently high energy input into the surface of individual samples was ensured. It varied between 165 and 477 J/mm2. After solidification of the surface remelted layer a fine-grained microstructure was formed. Such a microstructure was found to increase the hardness of the Al-Si alloys by 20 to 50%. The variation and sizeof the residual stresses greatly depend on the coolings rates determined by the laser travel speeds.
F.02 Acquisition of new scientific knowledge
COBISS.SI-ID: 11872539In collaboration with the R & D group Danfoss Trata d.o.o. Ljubljana, we have developed a new system and technology for the manufacture of thermostats that are embedded in the integrated thermostatic controller without auxiliary energy. The new technology is based on laser joining of the components and computerized process control. With the new technology we achieve better quality of thermostats, significantly lower ejection and shorten and simplify work operations. On this basis, a new industrial system has been developed, which has replaced the existing.
F.02 Acquisition of new scientific knowledge
COBISS.SI-ID: 12529691The paper presents savings in time and costs achieved by a transition from sequential to simultaneous product realisation. Such a transition is not possible without prior well-organised teamwork or virtual teamwork. The article demonstrates the team structure in simultaneous product realisation. A two-level team structure is suitable for small companies, with a core team on the first level and several project teams in simultaneous product realisation loops on the second level. In order to ensure successful work of the core team and several project teams, appropriate communication tools are suggested and a communication matrix has been developed, defining information exchange during the execution of activities in simultaneous product realisation. The communication matrix is used for identifying information system connections. The results of organising teamwork and virtual teamwork are shown on a case study of simultaneous realisation of a pedal assembly.
F.02 Acquisition of new scientific knowledge
COBISS.SI-ID: 12323099The investigation of aluminium alloy die casting die failures was done with the emphasis on thermal cracks. The aim of the study was to prolog the in-service die life by cladding with maraging steels, which would be economically beneficial. A vast analysis of thermal fatigue cracks in aluminium alloy die casting is done. Immersion test apparatus was developed, which enables simulation of conditions during aluminium alloy die casting and enables controlled thermal fatigue testing of materials. Special specimens made of the AISI H13 tool steel were differently heat treated. On the edges of some specimens, the maraging steel is cladded using gas tungsten arc (GTA) welding. These samples are tested in as-welded and in optimally aged condition. After completion of a particular number of cycles, the specimen edge surfaces were examined visually. The specimens were then sectioned and examined with light and scanning electron microscopy (SEM). The energz-dispersive X-ray spectroscopy (EDS) mapping of areas around the cracks was done. The number and length of thermal fatigue cracks were statistically evaluated and a Vickers hardness profiles were measured. The results confirmeda good thermal fatigue resistance of the properly hardened H13 hot work tool steel. The surface cracks growth is accelerated by surface oxidati on.
F.02 Acquisition of new scientific knowledge
COBISS.SI-ID: 12133403