Papers by Keyword: Extreme Conditions

Abstract: The UHPC (Ultra High Performance Concrete) is a promising material suitable for application in special structures. However, the knowledge on performance of this relatively new material is rather limited. The exceptional mechanical properties of UHPC allow for a modification of the design rules, which are applicable in ordinary or high strength concrete. The research executed already in the Czech Republic showed that the anchorage length of ordinary and prestressing steel may be significantly shorter than that which is usually required in code specifications. This paper deals in more detail with impact of thermal stress on bond of prestressing strands and UHPC. Samples were subjected to the cycling heat/frost device and effect of a number of cycles on final bond behaviour of both UHPC and ordinary concrete were investigated. The article describes differences between ordinary concrete and UHPC.

Abstract: The main statements of nanomaterials concept are shortly considered. Current developments in the metallic nanomaterials stability under thermal, irradiation, deformation and corrosion actions are generalized and discussed in detail. Special attention is paid to possible prediction of thermal grain growth characteristics using the regular solution approximation. The key role of nanotwinned interfaces in the stability increase at extremes is described and pointed out. The attention is paid to unresolved and insufficiently studied problems.

Abstract: The article is dealing with the principle of measuring bending rigidity by the method of Cantilever test which is suitable for measuring different types of textile and also non-textile materials. The authors are presenting a modification of the device and a simple method for calculation bending rigidity. It is a method by means of which bending rigidity, in extreme conditions - high temperature and humidity of the air-can be measured. In the discussion, the authors are pointing out the advantages and difficulties of this method of measuring.

Abstract: A two-disk test rig researching surface damage and ultimate performance of rolling-sliding tribo-parts in extreme conditions is designed. Variable speed (rolling speed up to 83.6m/s, sliding speed up to 16.4m/s) of the rolling/sliding contact are input by motor spindle and regulated with gear. Variable load (Hertzian contact up to 4GPa) is applied with hydraulic cylinder. High temperature (~+300°C) and cryogenic environment(liquid nitrogen) is implemented by changing the lubricant condition. Thermal-stress analysis with ANSYS shows that the temperature and stress of the tester body is reasonable. As the signals judging failure, such parameters as temperature and vibration of the supporting bearing, power consumption of the main spindle, temperature of the tribo-parts surface are monitored in real time. Kingview, PLC, VB and MATLAB software are employed in the online monitoring system to collect data automatically. Types of tribo-parts were tested in the test rig, getting their ultimate performance and the effect of each parameter on surface damage.

Abstract: Hydraulic dynamic and static bearing has the advantages of hydraulic pressure bearing and liquid hydrostatic bearing, with the peculiarities of higher load capacity, smallest oil film thickness, higher stiffness, and lower power and so on. It was suitable for not only high-speed precision spindle bearing but also low-speed heavy bearing. Because of the loading traits, ball mill will have a greater impact on the role of bearing, leading to the increasing temperature of bearing. The designers take many measures to reduce the temperature, but there are hardly any reports about mechanism of the increasing temperature. According to the study about the present situation and the research strategies of increasing temperature of dynamic and static bearing in the extreme conditions, this article explores the questions of the increasing temperature of dynamic and static bearing in the extreme conditions and the scarcity of this question at present, and proposes the mechanism and the research strategies of the questions of the increasing temperature of dynamic and static bearing of ball mill in the extreme conditions.