Effect of cyclic loading on the internal damping of magnesium alloy AZ31

The article focuses on the analysis of the internal damping changes depending on the amplitude of the magnesium alloy AZ31. Internal damping reflects the ability of the material irreversibly dissipating mechanical energy oscillations. It means that the material of high internal damping ability is able to significantly reduce the vibration amplitude. Internal damping is, generally, dependent on many factors (temperature, material purity, grain size, mechanical and thermal processing, etc.) and its value is determined by interactions between various mechanisms dissipation of mechanical energy. Ultrasonic resonance method was used in experimental measurements, which is based on continuous excitation of oscillations of the specimen, and the entire apparatus vibrates at a frequency which is near to the resonance. Starting resonance frequency for all measurements was about f = 20470 Hz

Change of internal friction on aluminium alloy EN AC 51200 depending on temperature

The article is focused on the analysis of changes in the dependence on temperature on the aluminium alloy EN AC 51200 (10,1% Mg, 1,32% Si and 0,43% Mn) by internal friction. Internal friction is a property of the material measured on the ultrasonic resonant apparatus at a frequency of about f = 20470 Hz. The measured temperature range was from 50 °C up to 420 °C. The precise measurement of the internal friction can be monitored on an ongoing process by structural changes and various mechanisms that prevent these changes

Change of internal friction on aluminium alloy EN AC 51200 depending on temperature

The article is focused on the analysis of changes in the dependence on temperature on the aluminium alloy EN AC 51200 (10,1% Mg, 1,32% Si and 0,43% Mn) by internal friction. Internal friction is a property of the material measured on the ultrasonic resonant apparatus at a frequency of about f = 20470 Hz. The measured temperature range was from 50 °C up to 420 °C. The precise measurement of the internal friction can be monitored on an ongoing process by structural changes and various mechanisms that prevent these changes

The Fatigue lifetime of AlZn10Si8Mg cast alloy with different percentage of iron

To increase the proportion of Al-cast alloys in a variety of industrial applications, it appears useful to control their fatigue behavior. In general, that behavior is affected by many factors, such as chemical composition, heat treatment, inclusions etc. The problem with utilization of the Al-scrap as a material for casting the Al-Si alloys lies in the fact that the scrap, unfortunately as a rule, is contaminated with iron. The Fe-rich intermetallics, formed during the solidification process, appear in a great variety of shapes and sizes. The most important are platelets or needles Al 5 FeSi, because they greatly decrease mechanical and corrosion properties of Al-cast alloys. The effect of the brittle Fe-rich phases on the fatigue properties in the secondary self-hardening AlZn10Si8Mg cast alloys with different percentage of iron (0.150 and 0.559 wt. %) was studied. Microstructure of alloys and the 3D-morphology of phases were analyzed by the optical and SEM microscopy. Rotating bending fatigue tests were realized for a defined number of cycles 3 x 10 6 . The results show that with increasing the content of Fe, the area proportion and the average length of Al 5 FeSi phases increased a significant influenced on the fatigue life and pores formation

The effect of iron content on fatigue lifetime of AlZn10Si8Mg cast alloy

The problem with utilization of the Al-scrap as a material for casting the Al-Si alloys lies in the fact that the scrap, unfortunately as a rule, is contaminated with iron. The current study presents an investigation of the effect of different iron contents (0.150 and 0.559 wt%) on microstructure, porosity and bending fatigue properties in the secondary (recycled) self-hardening AlZn10Si8Mg cast alloy. Rotating bending fatigue tests were realized for a defined number of cycles 3 x 10(6) with a stress asymmetry ratio R = -1 at room temperature. Observation by the optical and SEM microscopy using deep etching and image analysis highlight the role of the plate/needle-like Fe-rich intermetallic (Al5FeSi phase), formed during the solidification process. The quantitative metallography and CT scan was used to quantify the amount of pores.The results show that Al5FeSi phases play an important role in the low cycle region. The higher amounts of needle/plate like Fe-rich particles (Al5FeSi) with increased porosity degraded fatigue lifetime in the short and medium life-time regime ( < 10(6) cycles) and there was no effect or slight increases the fatigue lifetime for long life-time regime (>> 10(6) cycles). In the high cycle's region are the pores more detrimental than Fe-rich phases to the fatigue strength. Fracture surface of the fatigue specimens were analysed by SEM to characterize the micromechanism and the initiation fracture local

Vliv svařování na dynamickou lomovou houževnatost oceli Strenx 700MC

Thermomechanically processed high-strength steels feature specific fracture behavior. One of the decisive criteria for their application is their stability against internal defects during impact loads, especially in connection with the welding. The work is focused on experimental analyses of the influence of welding on static and dynamic fracture toughness of Strenx 700MC steel. The fracture toughness was determined using the circumferentially notched round bar specimens during static loads and two dynamic load levels. To achieve a homogeneous zone for the requirements of fracture toughness tests, simulation of the welding influence was performed. Fractographic and metallographic analyses described a specific fracture behavior controlled by the internal structural heterogeneity. A limiting degradation process due to welding was identified by the microstructural analysis.Termomechanicky zpracované vysokopevné ocele vykazují specifické chování lomové houževnatosti. Jedno z rozhodujících kritérií pro jejich použití je jejich stabilita vůči vnitřním poruchám při rázovém namáhání, zejména ve spojitosti se svařováním. Tato práce se zaměřuje na experimentální analýzy vlivu svařování na statickou a dynamickou lomovou houževnatost oceli Strenx 700MC. Lomová houževnatost byla vyhodnocována pomocí válcových vzorků s obvodovým vrubem, zatěžované staticky a dynamicky ve dvou úrovních. Pro získání homogenní zóny nutné pro zkoušky lomové houževnatosti byly provedeny simulace vlivu svařování. Fraktografické a metalografické analýzy popsaly specifické lomové chování řízené vnitřní strukturní heterogenitou. Mikrostrukturní analýza byla zaměřena na degradační proces vlivem svařování