Micromixers are essential components of microreactor technology. In this paper, a simple two-step design protocol for patterned groove micromixers based on numerical simulations is presented. In the first step, one groove of the staggered herringbone micromixer (SHM) is designed based on the average magnitude of transversal velocity vAVGyz at the end of the groove. In the second step, different configurations of six grooves are investigated. A slightly better mixing is achieved compared to the established SHM and significantly fewer grooves are needed. Due to fewer grooves and rounded groove corners, the new design is easier to be produced by microengineering technologies (MET). Additionally, good mixing was also achieved with a modified slanted groove micromixer (SGM) configuration with the largest rounding radius at the edges. A SGM prototype was machined by micro EDM milling. The simulation results were experimentally verified with flow visualization and a good agreement was observed. The presented protocol vastly reduces the number of optimal patterned groove geometry configuration candidates to be evaluated; it is simple and effective for practical applications.
COBISS.SI-ID: 12668443
In this paper the influence of vibrations on the process of cheese cutting in order to reduce friction and cutting force was researched. Forces needed to cut through the cheese samples were measured against variation of temperature, cutting speed and vibration frequency. The hypothesis which induced the research work was that assisting vibrations reduce cutting forces and make cutting easier for the user. For the experiments Gouda cheese with 10°C and 22°C was used. In experiments conventional kitchen knife with four different cutting speeds from 12.5 mm/s to 75 mm/s and six vibration frequencies from 0 Hz to 150 Hz was used. Results confirmed the hypothesis that up to 3.4 times lower forces are needed to cut through cheese sample of 22°C and 1.55 times lower when cutting cheese samples with 10°C. Results also showed already known facts that cutting forces are increased with increasing cutting velocity on average from 2 - 4 times if cutting with 75 mm/s instead of 12.5 mm/s. Also 2.5 times lower cutting forces were measured when cutting cheese sample with 22°C instead of 10°C.
COBISS.SI-ID: 11817243
The mechanical response of wood- and cellulose-filled polymers and its comparison to analytical models is studied in this article. To model the elasto-plastic response of the wood-plastic composite (WPC), two explicit semi-analytical micromechanical methods were used: Mori-Tanaka Method (MTM) and Generalised Method of Cells (GMC). For experimental purpose, several test specimens composed of matrix polypropylene (PP) or polystyrene (PS) and filled with wood or cellulose short fibres of different length to width aspect ratio and various volume fractions were injection moulded. Tensile testing was then used to gain experimental data, which were then compared to the calculated prediction of proposed micromechanical models to test their applicability. The comparison of results show that both methods can accurately predict the response of the composite in the elastic area; however Mori-Tanaka Method can achieve better results when forecasting plastic deformations of wood-plastic composites.
COBISS.SI-ID: 35979781
Optimal tool making is of great importance for reducing costs and increasing the performance of toolsets. The dies and punches, which are basic components of any metal forming toolset, are usually produced by machining, but this technology requires relatively long manufacturing times, characterized by significant material and energy waste. By replacing machining operations or combining them with forming ones, such as cold hobbing (indenting), significant cost and time savings, as well as improvement of tool performance could be achieved. Cold hobbing could be applied to making die cavities as well as shaping punch profiles. Investigations showed that a large number of variables influence the successful application of this technique. However, there is a scarcity of literature regarding the choice of relevant process parameters for the hobbing process. With this in mind, the aim of this paper is to yield further insight into the hobbing process. Special focus will be placed on the influence of the hob geometry on the deformation process and relevant process parameters. This paper presents theoretical, numerical, and experimental investigations of a cold hobbing process in which a cone-like punch is obtained. The upper-bound method was used for metal flow analysis andoptimization of hob geometry. Stress-strain distribution, workpiece geometry prediction, and load estimation were obtained with the finite elementmethod (FEM) using Simufact. Forming 8.1 software. The results were analyzed, compared, and discussed.
COBISS.SI-ID: 11922715
In certain domains of production engineering we are faced with very small batch production as it is the case in the production of heavy hydro energy equipment. In this domain manual welding is one of the most time consuming operations. Monitoring of the welding process is essential from the point of work organization as well as from the point of process control. In this paper a novel concept of data acquisition and recording of welding parameters to the welding diary is presented. Several considerations on signal acquisition, sampling rate, processing, data aggregation, wireless information transfer, and presentation are discussed. Implementation of the concept is discussed on laboratory and industrial examples.
COBISS.SI-ID: 12360731