In the failure analysis a motor-car coil spring of a rear shock absorber has been investigated and analyzed. Since the protective layer on the surface of the spring was damaged the corrosion occurred. The combination of corrosion and fatigue led to the fracture of a motor-car coil spring. A motor car coil spring of a rear shock absorber has been ruptured during car operation. The surface of a spring was protected against corrosion with a thick layer of paint on polymer basis. Around the fracture surface, a protective layer was damaged and removed over a length of several centimeters. In this area, spring has long been exposed to corrosion attack and thus surface heavily corroded and winkled.
F.10 Improvements to an existing technological process or technology
COBISS.SI-ID: 1422687In this study we investigated the microstructural changes after a variety of heat treatments of the quasicrystalline Al–Mn–Be–Cu alloy. In addition, we report on Vickers microhardness measurements and tensile-test results for the same materials. The samples were produced in a conventional manner, i. e., melting in an electrical resistance furnace in air and a gravitational casting process using a round copper die, which was in the form of a tensile-test specimen with a diameter of 5 mm. After the casting, some of the samples were just solution treated (annealed) and then quenched in water, while others were additionally aged (artificially – T6, or naturally – T4) or directly aged after the casting. In comparison to the as-cast state, the Vickers microhardness values of the aluminum-based matrix and the tensile properties of the samples decreased when just the solution treatment, T4 or T6 treatment was performed. The tensile properties also decreased after the heat treatments. A microstructural inspection revealed that the microstructural changes occurred already during the solution treatment, i. e., the formation of the phases Be4Al(Mn, Cu) and τ1-Al29Mn6Cu4 on the approximant H-Al4Mn and quasicrystalline i-phase particles' edges and the occurrence of precipitates in the αAl matrix. The precipitates that would additionally contribute to the hardening of the alloy did not form. The directly aged samples showed little or no increase in microhardness values in comparison to the as-cast samples, but possibilities of θ″ precipitates being formed from the already saturated matrix after the casting could not be excluded. After all the heat treatments the quasicrystalline i-phase, as a primary and eutectic phase, was preserved.
F.09 Development of a new technological process or technology
COBISS.SI-ID: 1518687Lining of tundish is in Štore three stand continuous casting machine is predominantly made from a magnesia based material. The material for the cover powder is alumina and silica based with some aluminum and carbon. During casting, the composition of cover slag is constantly changing. The composition of tundish cover slag at the end of the casting sequence is in the area of gehlenite (2CaO•Al2O3•SiO2). The result of the reaction between melted steel, refractory material and tundish cover slag are enstatite (MgO•SiO2) and monticellite (CaO•MgO•SiO2). Merwinite (3CaO•MgO•SiO2) is formed in the end of the casting sequence because of high basicity of the gehlenite based tundish cover slag.
F.10 Improvements to an existing technological process or technology
COBISS.SI-ID: 1518175The context of the work is the processing of MANNLICHER - CARCANO mod. 91 and MANNLICHER M 1895 rifles, carried out at the conservation - restoration workshop of the Museum of Contemporary History of Slovenia. Analysis of steel barrel and lock, and analysis of damage and errors were made in the laboratories of the Department of Materials and Metallurgy, Faculty of Natural Sciences and Engineering, University of Ljubljana and laboratories of authorized institutions.
F.13 Development of new production methods and tools or processes
COBISS.SI-ID: 1539167In this work we studied the response of newly developed armored steel plates PROTAC 500 to the ballistic test with armored piercing bullets with a core of tungsten carbide, charge 7.62 mm. Interactions between the bullets and the steel plate was investigated by the metallographic methods. We were interested in the geometric features of interaction, the phenomenon of adiabatic shear bands, cracks and local failure, local melting and interaction of the components and plate with metal balls fragments in the melt, rate of deformation and the plate hardening.
F.06 Development of a new product
COBISS.SI-ID: 1537887