Libor Sitek

TURNING OF MATERIALS WITH HIGH-SPEED ABRASIVE WATER JET

In addition to already standard cutting of materials by a high-speed abrasive water jet (2D machining), the technology of turning by the high-speed abrasive water jet can be applied for the production of spatial rotation-symmetrical bodies. Turning by the water jet is similar to the conventional singlepoint turning by a mechanical tool on a lathe, since a workpiece rotates and a cutting tool is continually moved parallel to the workpiece axis and incrementally fed toward the axis of the workpiece. Contrary to the classical turning, the water jet can be moved in all directions with much larger lateral increments. Jet forces on the workpiece are negligible. The material removed from the workpiece is converted to very fine debris, as opposed to the chips formed by conventional turning [Hashish 1995]. All advantages of standard cutting by the abrasive water jet can also be applied to the turning with the jet: possibility to machine even difficult-to-machine materials, almost zero thermal effects on the cutting surface of the workpiece, possibility to carry out various operations with the same tool during one clamping of the workpiece, one technological manufacturing method used for various shapes of the workpiece and various materials, etc. (see Fig. 1).

Laboratory Experiments on Effects of Water Jet on Heat-Affected Concretes

The paper is dealing with the effects of flat high-speed water jet on concretes affected by high temperature. Research should help to correct use of water jet technology in repair works on concrete structures especially after wildfires in tunnels, underground garages, etc., which are exposed to enormous thermal stress.

Comparison of the actual costs during removal of concrete layer by high-speed water jets

This paper describes the process of possible evaluation of costs of using high speed water jet technology for concrete removal methods. High speed water jet technology is a progressive technology of removing damaged concrete used in civil engineering since the 80s of 20-super-th century. It has been changing and developing since that time. But there is little information in literature devoted to the economic evaluation of this technology. Detailed economic analysis is still missing. This paper aims to compare comprehensively in economic terms the costs of removing concrete using the technology of both continuous oscillating and pulsating oscillating water jets. The research was realized in cooperation with research institutions and industrial companies and was supported by state budget of the Czech Republic and from the European Union. The scheme of cooperation of the University, research institutions, industrial companies and government follows the Triple helix model.

Erosion Test with High-speed Water Jet Applied on Surface of Concrete Treated with Solution of Modified Lithium Silicates

The paper focuses on the erosion resistance test based on surface treatment by a high-speed water jet applied on concrete. A reference concrete sample and concrete samples with three types of solution of modified lithium silicates applied on the concrete surface were tested under various erosion conditions. Two different jet impact angles (45° and 90°) were investigated. A significant difference in the erosion rate in the surface layers was observed comparing the untreated concrete and the concrete treated by various solutions of modified lithium silicates, but only in the initial phase of erosion.