Material disintegration

The project is aimed at strengthening the international cooperation and personal development of scientists from the Institute of Geonics of the CAS. The project implementation will enhance cooperation with major research organizations and their scientists. The realization of individual mobility stays will significantly contribute to the professional development of project participants and improvement of their workplaces. In addition, higher publishing activity and engagement of the IGN in international projects is expected at the same time.

The aim of the project is to support the professional development of young researcher as well as experienced researchers who will gain new skills and contacts at prestigious international workplaces. The final goal is the strengthening of the science and research in the Czech Republic. The fellowship will also contribute to the subsequent transfer of the acquired experiences to other IGN researchers during the return phase of the project.

The expected outputs are the participation and paper presentation at international conferences and the development of cooperation with foreign scientific institutions. An internal condition of the international mobility project is the preparation of a publication at a particular foreign workplace which will be published in a foreign journal of high impact.

The following 6 activities will be carried out: 3 working stays abroad for junior researchers and 3 working stays abroad for senior researchers - with the subsequent return phase.

The project is focused on experimental analysis of the influence of gas accumulated in the pore space of rocks on the energy balance during their comminution. The planned studies will help estimate the energy required to destroy the rock as a result of tensile stress. That energy will be correlated with the fracture surface of the samples to show the relationship between the grain size distribution formed as a result of comminution and the energy used. In addition, the pore structure will be analysed, which will help determine the influence of the porosity (described by a series of parameters) on the energetics of the process.

The project is oriented on performance enhancement of high-speed water jets for submerged cutting. Experimental work consists of high-speed camera visualization and observation of high-speed jets in submerged conditions, studying the flow structure of the jet and the effect of cavitation. The theoretical part consists of modeling of water jets using special in-house software to clarify the structure of high-speed cavitating jets and their effects on materials. The 6-months stay at Nihon University in Koriyama, Japan will be realized. The project will help to strengthen cooperation with Japan scientists, sharing knowledge, establishing new contacts with the vision of future cooperation on joint research.

The main objectives of the project are: A: Verification of the technology for the production of new abrasives with specific properties focused on the machining of hard-to-machine materials, AWJ technology increasing machining (cutting) productivity by up to 20% B: Development and production of a prototype of Smart Recycling Unit for efficient and optimized recycling of used abrasives with up to 70% efficiency. C: Creating an Internet Knowledge Portal of abrasives for AWJ technology and for implementation of automated control of abrasive recycling line based on Industry 4.0 principles.

Within the project, a pulsating water jet is applied to the surface of materials and then changes on material surface and in the surface layer of materials are specified in detail using X-ray diffraction, microhardness measurement, profilometry and electron microscopy (SEM, TEM). In parallel, fatigue tests are carried out to set ideal parameters of pulsating water jet in order to extend the lifetime of materials, because the pulsating jet is likely to have a similar effect on materials as shot peening.

The basic goal of the project is the research and development of advanced production technology by high-speed water jet machining of materials. The partial goals of the project are: - Research and development of conditions and dependencies to apply the advanced technology in the machining process of materials by the high-pressure waterjet turning, creation of a database of materials to determine the effect of waterjet cutting parameters on the surface features creation of a database of waterjet cutting parameters plus its disclosure to the wider professional public, - Research and development of a new cutting head equipped with an emphasis on increasing its service life, while retaining cutting capabilities comparable to traditional products and the associated cost savings in machining - Research and development of a new abrasive delivery unit focusing on the possibility of serving a fine abrasive currently considered waste - Development and validation of new knowledge function to Internet knowledge portal (IPZ) enabling optimization of the design of a new cutting head, increasing its service life and performance. Development and validation of new knowledge function to control recycling and abrasive recovery and optimization of cutting conditions in the IZP.

Project deals with the effect of the flow of the process fluids to produce mechanical wear and corrosion surface of the cement composites and their durability. Waterjet with a different content of solid particles is used as the flowing medium for simulation of real conditions. The influence of cavitation with respect to the durability characteristics of the composite surface is studied. Important evaluation parameter is the efect the microhardness and roughness of the surface. The texture and the wear surface of the composite is assessed. Physico-mechanical properties are monitored from the viewpoint of the degradation. Parameters such as the rigidity, the surface treatment composition or the cement composition and the parameters of a flowing fluid (flow, velocity, temperature, amount of abrasive particles, chemicals, pH) are monitored to determine the degree of prediction of violations of the composite effect of the flowing fluid. Computational model of wear rates is compiled based on the results for flowing fluid with durability of 30 to 50 years.

The project was oriented on clarifying the relation of machining property of abrasive suspension jet, especially surface treatment, with the jet flow structure, working conditions and cutting parameters. Experiments with submerged abrasive suspension jet, abrasive suspension jet and comparative experiments with abrasive water jet were performed. Samples were analysed using a digital microscope Keyence VHX-6000. Analytical information on the relationship of geometrical parameters of surface topography, technological working conditions and cutting parameters was obtained. The Swiss standard SN 214001 (2010) Contact-free cutting – Water jet cutting – Geometrical product specification and quality was used for the analysis. Study of abrasive and nylon particles dyed with rhodamine used for the LIF-PIV method were integral part of project task.

The basic goal of the project was the research and development of advanced production technology by high-speed water jet machining of metallic, non-metallic, ceramic, and special materials. The partial goals of the project were: (i) Research and development of conditions and dependencies to apply the advanced technology in the machining process of non-traditional materials by the high-speed waterjet, creation a database of materials to determine the effect of waterjet cutting parameters on the surface features and the database of waterjet cutting parameters plus its disclosure to the wider professional public, (ii) Research and development of a new cutting head equipped by multiple water nozzles, with the task to increase the cutting speeds and the associated energy savings during the machining/cutting process, (iii) Development of a new control software and its integration into the new generation of machines, (iv) Development and validation of Internet knowledge portal (IPZ) to secure the multiple industrial applications of advanced production technology of waterjet machining - milling by various types of non-traditional materials, using a database of cutting parameters provided by the IPZ.

The basic objective of the project is the development and operation of infrastructure and research-scientific teams created in the framework of the project Institute of clean technologies for mining and utilization of raw materials for energy use on the premises of the applicant VSB – Technical University of Ostrava and the participant Institute of Geonics of the CAS. The project preserves the built-up system of research teams interconnected with the laboratory infrastructure and is divided into two research programs that are interconnected and supplement each other.

The scope of Research Program 1 Multiphase Rock Environment is to obtain the knowledge of physical, chemical, isotopic, structural and mechanical properties of environmental components using modern instrument equipment, which basically increases the level of knowledge and possibilities of its generalization for the given geological conditions by means of mathematical modelling. This information is the basic precondition for the design of environmentally friendly technologies for the exploitation of mineral resources and also for the further utilization of rock environment.

Research Program 2 Environmentally Friendly Technologies is based on the findings from Research Program 1 and deals with oriented research and application solutions in the area of mining of energy raw materials, use of byproducts for the introduction of wasteless technologies to the mining of mineral resources, creation of conditions for minimization of safety risks based on the knowledge of causal processes, and with methods of valuation and influencing of the rock environment in connection with large projects under preparation that are concerned with the use of geothermal energy, permanent deposition of nuclear waste and underground storage facilities for energy raw materials.

Main research objectives which are solved in the Institute of Geonics are as follows:

• Properties and behaviour of geomaterials depending on their inner structure, type of loading and physical conditions. The comprehensive knowledge of petrological, chemical-physical and mechanical properties of rock environment is the basic precondition for the effective, safe and environmentally friendly design of technologies for the mining, processing and use of mineral resources or the driving of mine workings and the building of demanding underground and geotechnical constructions. The objective is to acquire knowledge of the influence of composition and character of inner structure of rocks and rock mass on their strength-deformation and transport behaviour and to acquire reliable and relevant data that can be used directly as input into numerical models and data for their experimental verification and inverse analysis.
• Intensification of effects of high-velocity water jets in the course of disintegration. The objective of solving this activity is to intensify the effects of high-velocity water jets using the physical phenomenon originating at the impingement of a droplet on a solid surface, because during the collision of a liquid moving at a high velocity with a solid, a short-term transient phenomenon appears, which is accompanied by a marked increase in pressure at the point of liquid impingement on the surface and can cause serious damage both to the surface and to the inner structure of materials subjected to the action of the falling liquid. For this reason, the solving will focus on the study of possibilities of influencing the flow before the nozzle to generate a jet utilizing the above-mentioned physical phenomenon for material disintegration.
• Development of changes in induced stress and deformation fields in underground utilization of a rock mass. In underground exploitation of mineral deposits and building of underground construction works, as a result of these activities, changes in the stress states in the rock mass take place. In the case of exceeding of relevant limit parameters of structural units of the rock mass, changes in stress can induce brittle fracture damage, which induces seismic events in affected areas. In complicated natural and mining conditions, this process may be accompanied by a sudden release of energy accumulated in the rock mass and the origin of anomalous geomechanical phenomena with manifestations in underground cavities. Significant stress and strain changes in the rock mass may also show themselves on the surface, play a significant role in the process of design of mine workings driven in the rock mass and affect the transport properties of the rock mass. The research objective will be to acquire findings in this area and to apply them to mining activity and underground construction.

Within the project, the Institute of Geonics has acquired several unique devices for the investigation of rock environment and development of geo-technologies. They are analytic devices, software, but mainly a servo-hydraulic testing system with a triaxial cell for testing THM (thermo-hydro-mechanical) properties of rocks, equipment for water jet application, and X-ray CT (computer tomograph) for non-destructive research of plane and space inhomogeneity in materials and for crack detection.

Owing to the new unique laboratory equipment, centre enables to start new research directions like in the laboratory of tomography, or substantially enlarge existing research directions - the laboratory of THM processes in rock mass or the innovation of the laboratory of pulsating high pressure water jet applications.

The project was focused mainly to: 1. Study of dispersion of nanoparticles (especially carbon nanotubes - CNTs) oriented at the determination of the influence of the method and parameters of the dispersion and identification of the quality of the dispersion and determination of the efficient dispersion method in aqueous environment. 2. Preparation of cement composites with nanoparticles (especially CNTs) and studying of the influence of the concentration and type of nanoparticles on structure, physical-mechanical properties, and resistance of the cement composites to aggressive environments 3. Study of the resistance of cement composites with nanoparticles (especially CNTs) to the action of continuous and pulsating water jets.