Octavian Dontu

Study on laser welding of stainless steel/copper dissimilar materials

In this paper stainless steel/copper laser welding was investigated by controlling the processing parameters like welding speed and laser power. Welding the dissimilar materials of stainless steel and copper presents a series of problems. Differences in the physical properties of the two metals, including the melting point, thermal conductivity and thermal dilatation are the main reasons for obtaining an inappropriate laser welding bead. Particularly, the laser welding process of copper is complex because of the very high reflectivity of cooper and in almost situations it requires a specific surface pre-treatment. The main objective of the study conducted in this work was to laser weld a structure used in pressure measuring and control equipments. In order to satisfy the conditions imposed by the sensor manufacturer, the difficulty of obtaining flawless joints was represented by the very small dimensions of the parts to be welded especially of the elastic spiral thickness made of steel.

Inertial system used to analyze normal and pathological human gait

Human motion analysis is one of the research directions which shows an increased interest worldwide due to the complete information we can get on human walking, normal or pathological, in order to confirm or exclude a diagnosis or to monitor patients who are receiving motor recovery program. In accordance with these new requirements a number of facilities were developed that provide information about variables, parameters and determinants of human gait allowing a complete analysis of it, but most are dependent on laboratory use, so we designed a device that can be used both laboratory and ambulatory, with a high degree of portability due to its small size and autonomy of the battery for several hours.

Effects of the laser welding parameters on the weld geometry and evaporation

The paper presents some investigations about the influence of the Nd: YAG laser welding parameters on the penetration and metal evaporation of single and dual pass weld in the case of thin sections of stainless steel sample. The metal loss during welding process was measured in order to establish the optimal values of welding parameters. The geometric size of the welded zone was measured using an SEM microscope in order to establish the correlation between the penetration and width at different values of welding parameters. The microhardness values, measured for 3, 6, 8 and 9 focal point position, in the weld and base material, allow estimating the softening effect caused by the metal vaporization during welding. At the same time, the cooling conditions of the welded zones differ with the local heating and melting volume of the weld.

Researches Regarding the Use of Additive Technologies in the Construction of Water Aeration Elements

The paper presents the technology of execution of a fine bubble generator; the air inlets in the water are O 0.1 mm and made in silicon plates. The scheme of the experimental installation where this fine bubble generator is fitted is presented. The end of the paper shows the methodology of the researches and the obtained results.

Applications of Additive Technologies in Realization of Customized Dental Prostheses

The paper presents 3D DLP (Digital Light Processing) digital printing technology, which belongs to the additive technology category using liquid raw material allowing the obtaining of dental prostheses with complex and detailed geometry, fine and precise printed surfaces, fairly resistant dental crowns, with a variety of resins, including biomedical materials (certified for medical use), characterized by high print speed and productivity for complex geometries and high productivity with numerous applications in the medical field. In the paper, a prototype of a dental bridge was made using 3D DLP printing technology, which can serve as a model for future dental restorations.

Applications of Additive Technologies in the Food Industry

The article presents a new concept that can be used in the food industry by manufacturing customized food products with 3D printers. This technique allows the production of personalized food products both as shape, colour, aroma and even as a nutritional value. Applications in the food industry can offer an engineering solution for new products and a tool for design specialists by creating food products with complex shapes that cannot be obtained by classical processes. Also, this technology can be a solution for researchers exploring cosmic space and long-distance space missions.

CAD Analysis Applied to Self-Centering Compliant Grippers

The self centering grasping mechanisms aim to improve the positioning accuracy of the object movement. The paper presents the FEM method applied to such mechanism using compliant joints with elastic properties. We have studied the tensions and displacements for the three dimensional model and the experimental results achieved the goal of our work.

Modular system used for treating fuel fluids in a magnetic field

Given the rising prices of energy, the prospect of exhausting the hydrocarbon reserves and the harsh restrictions imposed in order to protect the environment, the problem of saving energy resources thus constitutes a major concern for mankind. According to these issues our team has designed and developed a system who generate a magnetic field used for treatment of some fuel fluids, aiming to raise the combustion efficiency and decreasing the amount of pollutants removed after combustion in large power plants.

Automate generation of incremental linear networks masks by using photocomposition method with with multiple microphotographical reductions using laser microsystems

The paper treats high precision micro technologies for automate generation of linear incremental networks masks by using the photocomposition method with multiple micro photographical reductions using laser high sensitivity microsystems, for the manufacture of micro-sensors and micro-transducers for micro displacements with endowment in industrial and metrological laboratories. These laser micro technologies allow automate generation of incremental networks masks with incremental step of 0,1 µm ensuring necessary accuracy according to European and international standards as well as realization of linear incremental photoelectric rules divisor and vernier as marks ultra precise components of micro-sensors and microtransducers for micro displacements.

Micro - welding of stainless steel by pulsed Nd: YAG laser

The paper presents the results of the experimental research regarding the microwelding of stainless steel by pulsed Nd :YAG laser (STARWELD PERFORMANCE SWP 6002 - ROFIN). The analytical and experimental investigation on laser weldability of a stainless steel allowed to draw the following conclusions. The micro-welds produced by the optimized Nd: YAG laser parameters featured a narrow and regular weld metal zone devoid of any solidification and shrinkage defects. The as weld metal structure was made up of elongated ferrite graints with limited amount of austenite, mainly located at grain boundaries.