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Tolmin, Slovenia

Zidari B.,Hidria AET | Miljavec D.,University of Ljubljana
Journal of Magnetism and Magnetic Materials

A new ferromagnetic hysteresis model for soft magnetic composite materials based on their specific properties is presented. The model relies on definition of new anhysteretic magnetization based on the CauchyLorentz distribution describing the maximum energy state of magnetic moments in material. Specific properties of soft magnetic composite materials (SMC) such as the presence of the bonding material, different sizes and shapes of the Fe particles, level of homogeneity of the Fe particles at the end of the SMC product treatment, and achieved overall material density during compression, are incorporated in both the anhysteretic differential magnetization susceptibility and the irreversible differential magnetization susceptibility. Together they form the total differential magnetization susceptibility that defines the new ferromagnetic hysteresis model. Genetic algorithms are used to determine the optimal values of the proposed model parameters. The simulated results show good agreement with the measured results. © 2010 Elsevier B.V. All rights reserved. Source

Cesnik D.,Hidria Rotomatika | Bratus V.,Hidria AET
HTM - Journal of Heat Treatment and Materials

The distortion of steel flat ring type products after fine-blanking and subsequent carbonitriding was investigated. All the analyzed products were produced from the same coil and under the same conditions of fine-blanking. The fine blanked products were afterwards heat treated by using three different procedures - carbonitriting, stress relief annealing and heat treatment in a neutral atmosphere under the same temperature regime as for carbonitriding. The contribution of fine-blanking, relief of residual stresses, uneven heating and cooling and the formation of carbonitrided cases on the overall distortion were determined. The results were complemented with hardness measurements, residual stresses measurements and observations of microstructure. The presented research work is the first step towards the understanding of the mechanisms and factors that influence the quality of the final products during the production cycle. © 2013 Carl Hanser Verlag, München. Source

Slavic J.,University of Ljubljana | Bolka S.,University of Ljubljana | Bratus V.,Hidria AET | Boltezar M.,University of Ljubljana
Journal of Materials Processing Technology

High-quality blanking depends on several blanking parameters that are difficult to investigate with industrial blanking presses. In this research, a novel laboratory blanking apparatus that allows quasi-static and dynamic blanking at different blanking speeds is presented. With a clear focus on the dynamics of the blanking process, the inertial correction of the punch force, the surface velocity and the surface temperature of sheet-metal are researched. In addition, measurements of the punch-die misalignment and the punch-die inclination-angle are discussed. The apparatus is also able to perform a partial penetration of the punch to a selected depth with an accuracy of better than 10 μm. The apparatus was shown to offer us a new insight into the blanking process that can increase our understanding and therefore result in better numerical models and better products. © 2013 Elsevier B.V. Source

Kontarcek A.,Hidria AET | Bajec P.,Hidria Rotomatika | Nemec M.,University of Ljubljana | Ambrozic V.,University of Ljubljana | Nedeljkovic D.,University of Ljubljana
IEEE Transactions on Industrial Electronics

This paper presents a low-cost fault-tolerant system for open-phase fault (OPF) in a power-converter-fed permanent-magnet synchronous machine. The proposed fault-tolerant system is based on field orientation control with additional fault tolerance functionality. A current predictive method for OPF detection is presented, together with an estimation of the threshold level for detection. The proposed method is based on the prediction of stator current for the next sampling interval. Furthermore, a new method for postfault operation of the machine is proposed. For optimal performance of the complete drive, a prefiring angle is introduced in order to avoid the temporary generation of negative torque. This improvement increases the average generated postfault electromagnetic torque, and consequently, it reduces the mechanical stress on various machine parts. The proposed fault detection and postfault operation solutions were simulated in MATLAB, and they were also tested on an experimental setup. The results show several advantages of the proposed fault-tolerant solution, like its short fault-detection time, substantial robustness against variation of machine parameters or load fluctuations, and negligible implementation costs, since no hardware modifications are needed. The fault detection algorithm does not require high computing power, and it operates well even during transients. © 1982-2012 IEEE. Source

Gorjan L.,Hidria AET | Gorjan L.,Jozef Stefan Institute | Kosmac T.,Jozef Stefan Institute | Dakskobler A.,Jozef Stefan Institute
Ceramics International

We have investigated the possibility of merging the wick-debinding and sintering of injection-molded ceramic parts into a single-step operation. The basic idea is to use an embedment that serves as a wicking agent in the first stage of the procedure, but then burns out completely when the temperature exceeds approximately 500 C, leaving the samples free of any organic binder or contamination so that they are ready for sintering. Carbon black was used as the wicking agent for two reasons. First, it has great wicking-agent properties, due to its high porosity with a small pore size, while exhibiting good wetting with the molten paraffin binder. Second, it burns in air at high temperature, at which point the wick-debinding has already been completed. The whole process from molded parts to fully sintered parts can be completed in a single furnace. Besides making the process shorter, the tedious and delicate operations of cleaning and transporting the fragile debinded parts after wick-debinding are avoided. © 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved. Source

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