Jiří Klich

Sandstone Turning by Abrasive Waterjet

The machining of materials with specific mechanical properties causes problems in terms of the required quality, economic efficiency, and overall effectiveness of the process. A number of works have been published which indicate that the subjects of interest are still important (Krolczyk et al. 2013). The machining of the aforementioned materials based on conventional methods does not always meet the requirements of eco-friendly technology nor the efficiency potential of the technological device and tool (Vasilko and Strojný 1967; Krolczyk et al. 2014). The abrasive waterjet (AWJ) represents a suitable technological method that has specific benefits resulting from the nature of the tool. Many scientific reports have been written about using the water jet and the AWJ for cutting (Summers 1972; Ciccu and Grosso 2014), drilling (Teale 1965), turning (Sitek 2009; Sitek 2005, 2011), and for the purposes of underground mining (Summers 1992; Sharma et al. 2011). The AWJ can be used for the creation of rotating symmetric parts from rocks by turning. The production of parts using standard methods is very complicated and even impossible for some rock materials due to their properties (Summers 1972; Agus et al. 1993; Aydin et al. 2013). The use of the AWJ is an option for how to eliminate problems related to the standard method of turning (Sitek et al. 2005). The first results were published by Dr. Hashish (1987) 28 years ago. Ansari and his colleagues (1992) undertook relatively extensive research into turning visualizations using a high-speed camera. Hlavac and Palicka (2006) applied this method for the turning of many materials used in industry. Axinte et al. (2009) applied this method for the turning of grinding wheels. Interesting results were obtained in glass turning (Zhong and Han 2002), alumina ceramic turning (Liu et al. 2014), and the turning of hard-strength materials (Sitek 2009). The application of this turning method enables the machine rotating of semifinished products of varying structures and shapes (Henning 1999).

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.

The Use of Areal Parameters for the Analysis of the Surface Machined Using the Abrasive Waterjet Technology

The paper deals with areal evaluation of the surface texture of AISI 304 material created by the abrasive waterjet. The sample examined was measured using an optical profilometer and an optical microscope. The surface topography is most frequently evaluated according to the surface profile parameters defined in ISO 4287. However, for a more complex analysis of a studied surface, it is more advantageous to use an areal (three-dimensional) method which applies the knowledge acquired from the profile (two-dimensional) method extended by new research findings. The areal parameters of the surface texture are described in the standard ISO 25178-2.

Comparison of Non-destructive Sensing Methods on Surface Created by Waterjet Technology

The article is a response to the lack of information, especially in the area of non-destructive techniques suitable for wide practical application. The article deals with evaluation of the disintegrated material volume removed from the samples by a water jet. The study presents a quantified disintegrated material volume by means of an optical profilometer MicroProf FRT, a digital microscope VHX-5100 and X-ray computed micro-tomograph XT H 225 ST. Based on a comparison of measured data, it is possible to state that the methods of optical profilometer and a digital microscope give us very close volume values. While the values of the volume of removed material analysed by X-Ray μ-CT reach higher its values. After detailed analysis of the individual tomographic cross-sections in area of kerf surface it can be concluded that complex morphology of this surface can explain differences in the results. There are visible some re-entrant features like an overhangs and undercuts at the surface created by high pressure water jet.

Effect of Frequency Change During Pulsed Waterjet Interaction with Stainless Steel

In the present work a detailed effect of pulsating water jet treatment with the variation of standoff distance on the flat austenitic stainless steel surface has been studied. During the experimentation, at a traverse speed of 30 mm/s accidently the change in frequency was encountered in the repeated test (under same treatment condition) which has been reported in this work. The frequency was changed from f = 20.11 kHz to f = 20.27 kHz during the treatment process at the pressure of p = 70 MPa with variation in standoff distance was increased from z = 5 mm up to z = 101 mm (with step distance of 2 mm between successive standoff distance). The change in microstructural topography of the treated surface under the above-mentioned conditions was observed using scanning electron microscopy (SEM). The strengthening mechanism on the surface and sub-surface region due to the plastic deformation phenomenon caused by the impact of the pulsating jet was evaluated by Vickers microhardness test. The micro hardness test was conducted along the depth of the treated region to analyze the effects in the sub-surface layers. Also, the erosion stages at different standoff distance was evaluated by scanning the surface by optical MicroProf FRT profilometer in order to analyze the nature of erosion phenomenon with the variation of standoff distance and frequency during the treatment process. The results obtained indicates that the change in frequency of the pulsations and the variation in standoff distance has a significant impact on the surface integrity of the treated material. As compare to the untreated surface the hardness of the treated surface was increased up to a certain depth and the higher frequency of pulsations has shown better improvement in the hardness values. The above observations elaborated the effect of an important parameter frequency and standoff distance for better and effective utilization of the technology for the surface treatment application.

Evaluation of Possibility of AISI 304 Stainless Steel Mechanical Surface Treatment with Ultrasonically Enhanced Pulsating Water Jet

Experimental study described in this article is focused on evaluation of dynamic effect of PWJ on disintegration efficiency on AISI 304 stainless steel surface. AISI304 stainless steel was disintegrated with circular nozzle diameter 1.19 mm, pressure 70 MPa, frequency 20.25 kHz and traverse speed 100 mm.s−1 (202 impacts per millimeter). Disintegration efficiency was evaluated based on surface and subsurface characteristics. Surface characteristics were evaluated based on surface topography and roughness parameters Ra [μm], Rz [μm], Rp [μm] and Rv [μm] comparison of disintegrated and non-affected area. Subsurface changes in material structure were described based on metallographic analysis and hardness measurement HV0.2 under the eroded area. The results of the disintegration efficiency evaluation of AISI 304 stainless steel surface show that was no massive erosion of material. Surface quality was slightly changed. Small microscopic craters were predominantly created on surface. Craters were characterized with predominant pitting mechanism and prevails fracture mechanism of material removal.