Josef Foldyna

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.

Surface integrity of Mg-based nanocomposite produced by Abrasive Water Jet Machining (AWJM)

ABSTRACT This paper investigates the influence of jet traverse speed on the surface integrity of 0.66 wt% Al2O3 nanoparticle reinforced metal matrix composite (MMC) generated by Abrasive Water Jet Machining (AWJM). Surface morphology, surface topography, and surface roughness (SR) of the AWJ surface were analyzed. The machined surfaces of the nanocomposites were examined by laser confocal microscope and field emission scanning electron microscope (FESEM). Microhardness and elasticity modulus measurement by nanoindentation testing were also performed across thickness of the samples to see depth of the zone, affected by AWJ cutting. The result reveals that extent of grooving by abrasive particle and irregularity in AWJ machined surface increases as the traverse speed increased. Similarly, the rise in value of surface roughness parameters with traverse speed was also seen. In addition, nanoindentation testing represents the lower hardness and elastic modulus due to softening occurs in AWJ surface.

Surface Treatment of AISI 304 Using Pulsating Water Jet Peening

Water jet peening has gained attention as a potential surface treatment process for improving the fatigue life of a component. The tensile residual stress in the component initiates the stress corrosion cracking and reduces its fatigue life. The mitigation of this tensile residual stress can be effectively achieved by water jet peening process due to its resistance to corrosion, flexibility in treating complex areas and capability to maintain the eco-friendly environment. In the present work, the AISI 304 plates were treated with pulsating water jet (actuator frequency f = 20.19 Hz) at the pressure of p = 20 MPa with traverse speed of v = 0.5 mm/s and v = 2.5 mm/s using two different types of nozzles; flat nozzle of diameter d = 1 mm (HAMMELMANN) and circular nozzle of diameter d = 1.9 mm (STONEAGE). The microstructural analysis of the treated and untreated region was conducted to analyse the effect of traverse speed and the type of nozzle on the erosion process. The study revealed that more erosion occurs at lower traverse speed; however, fewer surface depressions were observed in the case of flat nozzles. The X-ray diffraction technique was also used to analyse the effect of traverse speed and the type of nozzle on the residual stress of the samples. In addition to this, the acoustic emission during the ongoing process was monitored using LabView 2012 SP1 f5 ver. 12.0.1. The results indicate that acoustically monitored pulsating water jet peening process can be used as tool for the controlled local treatment process arising from the impact of the pulsed water jet on the surface of sample.

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 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.