Daniel Besnea

Influence of technological parameters on the dynamic behavior of a MEMS accelerometer

The paper deals with studying the mechanical structure of a bulk-micromachined silicon piezoresistive accelerometer by using FEM (Finite Element Method). The vibration modes (resonant frequencies) and sensitivity were predicted. The results of numerical simulation, validated experimentally have pointed out the influence of manufacturing process parameters on the accelerometer performance.

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.

Hardware Structures for High Precision Pneutronic Systems

Pneutronic systems come with a series of advantages that are natural to working with compressed air, such as the large power/weight ratio of pneumatic actuators, easy and affordable installation and maintenance as well as being clean working systems. However, due to working with compressed air, there are a series of issues, such as static and transient nonlinear behavior, mostly due to the high compressibility of air. Thus, the behavior of such systems is hard to control, especially in terms of precision positioning. The paper deals with proposing three hardware configurations of pneutronic positioning systems in order to assure the imposed positioning accuracy in the presence of disturbances and the preservation in time of the obtained position.

Theoretical and Experimental Researches Regarding the Performances of a New Type of Rotating Machine with Profiled Rotors

The paper establishes an original computation formula for the flow rate of the fluid transported by a new type of rotating machine with profiled rotors; the theoretical characteristic diagram of the machine - flow rate versus machine speed - is built. The scheme of the test stand used for performing measurements needed in order to build the experimental diagram is presented. The variation of the volumetric efficiency of the working machine in function of the machine speed is finally described.

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.

Mechanism for the displacement of an oxygen meter probe in stationary waters

The paper presents a mechanism that displaces an oxygen meter probe on a circular trajectory inside a water basin, with a speed of 0.39m/s. Compressed air is introduced in the basin through a fine bubble generator. The increase of the dissolved oxygen in function of the time is monitored.

Additive Technologies and Materials for Realization of Elastic Elements

The paper presents a method of realization of representative types of elastic elements by means of additive technologies with the presentation of the main functional characteristics based on solid material deposition, FDM (Fused Deposition Modelling) technology, as well as the presentation of the main characteristics of the material used (PLA), highlighting domains and specific applications. Experimental results were obtained on a Hans Schmidt demonstration stand by comparing the deflections of various types of helical springs with circular, square and rectangular cross section.

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.