High strength steel grade 51CrV4 in thermo-mechanical treated condition is used as bending parabolic spring of heavy vehicles. Several investigations show that fatigue threshold for very high cycle fatigue depends on inclusion's size and material hardness. In order to determine allowed size of inclusions in spring's steel the Murakami's and Chapetti's model have been used. The stress loading limit regarding to inclusion size and applied stress has been determine for loading ratio R=-1 in form of S-N curves. Experimental results and prediction of S-N curve by model for given size of inclusion and R ratio show very good agreement. Pre-stressing and shot-peening causes higher compress stress magnitude and consequently change of loading ratio to more negative value and additionally extended life time of spring.
B.03 Paper at an international scientific conference
COBISS.SI-ID: 15078678Belleville washer steel springs are characterized by long fatigue life, better space utilization, low creep tendency and high load capacity with a small spring deflection. In the case of a thicker spring, a higher loading and higher stiffness are obtained, but the deflection of the spring is reduced. In this case fatigue life is reduced and there is a very high probability that a Belleville washer spring can fail in a brittle manner, causing additional damages to the machinery. In order to prevent the fracture of a Belleville washer the elastomer filling was used on both free surfaces of the spring. Experimental testing and numerical analyses show that progressive loading characteristics were obtained when the elastomer filling was increasingly involved in the loading process. When the elastomer filling is compressed, the stresses in Belleville washer steel are reduced, because the majority of the deflection stress is taken by the elastomer instead of the steel.
B.05 Guest lecturer at an institute/university
COBISS.SI-ID: 15272726Lecture provide common issue of Fracture mechanics approach and Woheler curve design in order to determine fatigue limit of demage non-tolerant high strength steel. High strength steel (with yiled stress over 1500 MPa) does not provide any warning or possibility for crack size detection. Such steel are used for high loaded componets as spings but it can be used for rope’s steel on the bridges. Therefore, the determination of fatigue limit is crusal for fatigue life time of dynamicaly loaded steel’s structure, even in case when we have no-possibility to evaluate fatigue crack length. For first time, we applied fracture mechanics parameters as fracture toughness and fatigue crack growth constants in order to design S-N (Wöhler’s) curve in order to determine number cycles to failure regarding to dynamic loading.
B.05 Guest lecturer at an institute/university
COBISS.SI-ID: 16118550The invention relates to a device for balance and body orientation support, solving the technical problem of how to provide control of balance and body orientation during hands free standing and walking to individuals with compromised physical abilities caused by injury or disease of the central nervous system or other reasons, e. g., age related disability, by a device that is modular and adaptive in size to the individual and her/his needs.
F.32 International patent
COBISS.SI-ID: 15916566