Marcel Sabin Popa

Ultrasonic Assisted Machining for Hard-to-Cut Materials

This study presents new machining types of advanced materials. Super alloys, ceramics and fiber reinforced plastics started being used on a large scale in the last period, this making necessary the development of new machines and machining processes. This paper describes different methods of ultrasonic machining and makes a comparison between them. By ultrasonic machining can be understood a process that involves axial vibrations with a high frequency and low amplitude, for improving the machining conditions like chip flute removal, tool wear and temperature reducing. In this paper, are presented three different ultrasonic machining methods. In the first one, the cutting process is made by abrasive slurry inserted between the tool and the workpiece, in the second one is made by a rotating diamond-brazed tool and in the last one is made by a special drill. This paper aims to study the current status in this field in order to make a research program through collaboration between the Technical University of Cluj-Napoca and the tool company Gühring KG by which to develop ultrasonic drilling.

Analytical Approach to the Development of End Milling Cutter Tools

The complex variable nature of the milling process complicates the scientific effort to understand it. Most scientific papers in this domain have focused on giving a particular solution for a specific subject of study, like: tool life, cutting forces, obtained surfaces after machining and so on. However a systematical analytical method for developing end milling cutter tools has not been found in the current literature. The main goal of this paper is to introduce and to give a general overview in the field of developing end milling cutters. The step-by-step approach focuses on the main element of a cutting tool: material, coating and geometry. Through an analytical study of the development of end milling cutters all elements in the design, manufacturing and testing have been taken into consideration. Such a method can be implemented when trying to analyze and summarize the research in the field of end milling cutters. The current paper is a preliminary evaluation in the development of end milling cutters. Further research will be accomplished in partnership between the Technical University of Cluj-Napoca and tool company Gühring KG.

Evaluation of the Problems that Arise during CFRP Drilling

In this paper are presented and analyzed a series of problems that are appearing during the CFRP machining. Due to their properties, the composite materials began to replace traditional materials (ferrous and non-ferrous) in a lot of industries leading out the development of new methods of machining or adaptation of the classic. Unlike traditional material, drilling in CFRP is more difficult due to inhomogeneity of the material, its high hardness but also due to lack of knowledge relating to how these materials behave. This paper investigates different types of tool wears as corner wear, welding, crater wear that are appearing in drilling operation due to the highly abrasive nature of the carbon fibers. Also, here is presented an evaluation that refers to the machined hole quality and describe defects as delamination, pull outs, fibers projections, pyrolysis and shape errors. The main goal of this paper is to verify the current status of technique in CFRP drilling in order to develop and produce a new drill geometry in a cooperation between the Technical University of Cluj-Napoca and the cutting tool company Gühring KG.

Industrial application of micro geometrical cutting edge optimization for solid carbide boring tools

This paper aims to establish the mechanism of quality optimization and geometrical improvements for the micro-geometry of solid carbide drills. The purpose of micro-geometrical optimization of the cutting edge tools of drills is to improve tool live, cutting speeds and minimizing cutting forces. The most important geometrical feature when drilling with solid carbide drills is the radius or chamfer of the cutting edge, which can be achieved through brushing under a certain angle. Improving this procedure by adding another step, soft granulated polishing, can positively influence on the cutting parameters and decrease the wear effects.

Field Investigation of Volatile Organic Compounds' Levels and Origin in an Unpolluted Residential Area

It has been found that various volatile organic compounds (VOC) are present in the indoor environments. Studies on the volatile organic compounds have become one of current interests, since the VOCs’ impact on comfort and health of occupants has been recognized. This paper describes the results of investigation on concentrations and sources of volatile organic compounds in renovated and non-renovated residences. The concentration of volatile organic compounds in newly renovated residences is higher than those found in non renovated house. Gas heating and cosmetics’ use were found to be important sources of VOCs in the undecorated residence. The concentrations of total volatile organic compounds (TVOC) in the renovated houses and the not renovated house with gas heating were much higher than those found outdoors.

Anthropometric Measurements for Assessment of Body Fat in Young People

Excessive body fat is associated with various diseases, particularly cardiovascular diseases, diabetes mellitus type 2, obstructive sleep apnea, certain types of cancer, and osteoarthritis. As a result, obesity has been found to reduce life expectancy. The aim of our study was to assess body fat mass by anthropometric measurements and to compare the results with those obtained by bioelectrical impedance analysis in a collectivity of 124 teens, ranging from 18 to 21 years old. Our results proved that skinfold thickness and Body Mass Index are very useful tools in population screening for nutritional risk, due to the strong correlation with the results of bioelectrical impedance method.

Technological approaches by laser beam welding of aluminium alloys and influence of errors in manufacturing process

The explosive development of modern manufacturing technologies, particularly the laser beam manufacturing, has raised new challenges in the field of research. The laser beam welding process may be influenced by errors appearing from different causes. In this paper the authors present the influence of errors during the experiments regarding the laser beam welding of aluminium alloy. In the physical experiment, two major geometric welding characteristics (the welding surface and the welding width) of an aluminium alloy AlMgSi 1 were measured at different welding speeds, using a solid state laser Nd:YAG, HL 4006D. With the aim of obtaining the best results, a CCD-Camera was assembled on the device allowing to capture the most accurate photos from the experiments. The appearance of errors is more likely to be found in the domain of high rate welding speeds than in those of low welding speeds. The data analysis based on the dispersion criterion is useful to characterize the influence of thermal parameters of aluminium alloy upon the laser beam welding surface and width, which may be extended to other new materials with the same characteristics. The present researches started together with the University of Stuttgart will be continued at the Technical University of Cluj-Napoca with a new laser equipment.

Use of volatile organic compounds as an indicator in indoor air quality investigations

It is generally accepted that buildings shelter us from the most unpleasant and unhealthy outdoor conditions and pollutants. However, reductions in ventilation rates to conserve energy and extensive use of new building materials, many of which emit organic compounds have made us aware that the indoor environment poses its own threats of discomfort and injury to health. Hundreds of volatile organic components (VOC) have been detected in the indoor air. Some of them are known to be toxic, mutagenic, or carcinogenic. Volatile organic compounds are now a major source of air pollution in Europe. However, none has attracted as much attention as formaldehyde. There is a growing awareness that VOC concentrations existing in indoor and outdoor air is very high, whereas the number of sources that emit VOCs is just enormous. Research is urgently needed for development of reasonable standards for indoor air quality, in the design of healthful built environments from this point of view.