Libor M. Hlaváč

Abrasive Water Jet Cutting of the Steels Samples Cooled by Liquid Nitrogen

The paper is aimed at abrasive water jetting of non-corroding steels treated by cryogenic temperatures in liquid nitrogen. The investigation of cut walls shows that cryogenic temperatures influence material structure and respective properties. This research is focused on improvement of material reliability in various states of production systems and operation conditions.

Testing of the High-Velocity Water Jetting on Concrete Samples Inside the Overpressure Vessel

The concrete samples with various erosion states were disintegrated inside the overpressure vessel using high-velocity water jet. Their erosion states were prepared by application of several laboratory techniques simulating the concrete aging under the natural conditions due to the real applications in practice. The influence of the erosion state on the disintegration rate was tested and the surface topography was studied both prior the application of water jet and post it. The water jet was applied in the overpressure vessel used for simulation of pressures equivalent to the submersion to several depths under the water level. Usual experimental scale responsive to the national practical application range was from the depth of submersion close to the water level up to the depth about 100 meters with the 20 meters step. Nevertheless, the data were obtained for overpressures equivalent to the submersion levels up to 140 meters enlarging so the range of results useful for regression analysis of the physical trend. Several samples were tested even in overpressures simulating depth of submersion equal to 160 meters and more. Few samples of special decorative concretes were also studied and special techniques of their working up were prepared and tested. All results are discussed regarding their application in practice and further development of special routings.Copyright

Operation of Water Jet System in a Sandstone Quarry and its Impact on Production

The experiments with pure water jets were performed both in laboratory and in a quarry. The basic information about water jet system operation in quarry conditions has been acquired and some relations between data from a quarry and the laboratory ones have been determined. The efficiency of the cutting system in quarry conditions is considered and discussed.

Investigation of Samples From the High-Velocity Water Jet Driven Micro/Nano Particle Collider

The power of the high-velocity waterjets has been utilized for intentional disintegration of material particles, namely minerals. Firstly, the garnet particles were tested and studied being used usually as the most common abrasive additives for waterjets improving their cutting abilities. Later on, other mineral particles have been investigated because there are some practical applications of them. Primarily, the product generated inside the mixing chamber and the focusing tube has been studied. Subsequently, the special colliding chamber has been designed and produced enabling the collision of the two opposite moving waterjets containing material particles. This device was named “Water Jet Driven Particle Collider”, shortly WJDPC. The product created in the collision of the opposite moving particle containing waterjets has particle sizes covering partially both the nano-scale and the micro-scale. The investigation of parameters influencing the amount of particles with sizes in respective dimension scales is the topic of the contribution. Some samples of special materials were studied and tested. The discussion of the results of the computational modeling of the suction process and its influence on the final product is included. All results are discussed regarding their application in practice and further development of special routings for material particle preparation.Copyright

Vicinage of the laser beam impact zone in rocks

The paper is aimed at some recent results of both the theoretical end experimental research of interaction of the laser beam with rock materials. The topic of the theoretical research is to determine the amount of energy transferred into rock like material more preciously. The experimental task is to identify the temperature fields in the vicinage of the impact zone to be able to reconstruct the heat flow and losses. Some problems of these tasks are discussed in the paper.

Relief produced by abrasive water jet and its visualization by contactless optical method

The optical method appropriate for studying of the specific surfaces created by abrasive water jets has been assembled and tested. It is based on shadow visualization of random rough surfaces and it makes possible to obtain the shadowing function from distribution of light and shadows. Evaluation of shadowing functions and spectral analyses of signals obtained from surface were performed. Values of a stochastic distribution of light intensity in shadows were quantified using calibration of the experimentally obtained shadowing functions thus defining height distributions of measured profiles of roughness and/or waviness.