Michal Zeleňák

Experimental in-vitro bone cements disintegration with ultrasonic pulsating water jet for revision arthroplasty

The paper deals with the study of using the selective property of ultrasonic pulsating water jet for the disintegration of the interface created by bone cement between cemented femoral stem and trabecular bone tissue as a potential technique for revision arthroplasty. Six types of commercial bone cements based on Polymethyl Methacrylate were used for investigation. The cements were mixed using the DePuy - SmartMix® CTS / vacuum mixing bowl. Mechanical properties of hardened bone cements were determined by nanoindentation. The bone cement samples were disintegrated using the pulsating water jet technology. The water pressure varied between 8÷20 MPa. A circular nozzle with an orifice diameter of 0, 7 mm was used for water jetting. The stand-off distance from the target material was 2 mm and the traverse speed 1 mm/s. The volume of material removal and depth of created traces were measured by MicroProf FRT optical profilometer. The results positively support an assumption that pulsating water jet has a potential to be a suitable technique for the quick and safe disintegration of bone cement during revision arthroplasty.

Influence of Abrasive Water Jet Turning Parameters on Variation of Diameter of Hybrid Metal Matrix Composite

Abrasive water jet turning is one of the recently developed manufacturing technologies. It has gained its importance due to its capability to machine difficult-to-cut material with advantages such as absence of thermal effects, high machining flexibility and little cutting force. In this study, the influence of water jet turning parameters such as abrasive type and abrasive mass flow rate has been analysed on the variation of diameter with the target diameter of metal matrix composite. Composite material A359/Al2O3/B4C fabricated by electromagnetic stir casting process was used in the experiment. To select the level of parameter, one-variable-at-a-time analysis was used. The results revealed that the abrasive type had a greater influence on the deviation of diameter from the target diameter as compared to mass flow rate.

Surface Quality Control of Materials Being Cut by Laser with Respect to Corrosion Resistance

In the field of laser cutting, the research area is oriented mainly to understanding of the mechanism of removal, as well as to the combination of factors entering the process. This process of disintegration of materials presents a problem of analytical approximation, elaboration, and description [1 - . Compared with previous approach to a solution, we have chosen our own way and we focus on mechanical respectively stress-strain parameters of the material being cut and the mechanical balance system: material properties tool properties deformation properties. We shall present here the basic forms of prediction equations for calculating the roughness of cutting walls, as well as other equations which were derived by modifying the basic equations for different application purposes, especially to calculate the optimum traverse speed vpopt, optimal laser performance Wlasopt and technologically important ratio INDvpwopt = vpopt/Wlasopt. These contain easily available input variables for substitution. The basic forms, including the modified forms are aimed at predicting the quality of cut with its depth limits. The paper presents the method of optimization of the ratio between the traverse speed vpand laser power Wlas which minimizes the final surface roughness after cutting with a direct impact on corrosion resistance of materials.

Effect of Water Pressure During Abrasive Waterjet Machining of Mg-Based Nanocomposite

The pressure of the waterjet influences the overall performance of the abrasive waterjet cutting system through operational and phenomenological effects. In this study, the effect of water pressure in surface quality of Mg-based nanocomposite was investigated. The as-machined surfaces were examined by field emission scanning electron microscope to determine the surface morphology. The surface topography of selected nanocomposite was examined and compared. The results show that the surface quality is better at higher pressure. However, at lower water pressure, there is too much interaction among the low-energy abrasive particles and this may cause insufficient material removal. Abrasive waterjet cutting seems to be promising tool for machining metal matrix composites in terms of no thermal damages, no micro-structural changes and negligible sub-surface damages on the machined surface.

The measurement of abrasive particles velocities in the process of abrasive water jet generation

An optimization of the design of the abrasive cutting head using the numerical simulation requires gathering as much information about processes occurring in the cutting head as possible. Detailed knowledge of velocities of abrasive particles in the process of abrasive water jet generation is vital for the verification of the numerical model. A method of measurement of abrasive particles at the exit of focusing tube using the FPIV technique was proposed and preliminary tests are described in the paper. Results of analysis of measured velocity fields are presented in the paper.