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 order to improve the accuracy of abrasive water jet (AW) machining the precise value of the jet diameter has to be known. Because of an aggressive environment caused by high velocity abrasive grains, the diameter is not easily measured. That is why a measuring device consisting of a load cell and a wear resistant probe was developed. The device measures the force of the jet while it passes over the edge of the probe. If the feed rate of the jet is constant and the time needed for jet to pass is known, the diameter can be determined. Because of probe wear issue several preliminary tests were made with water jet only in order to determine the measuring uncertainty and accuracy of the device. In the end the measurement of the AWJ was performed for two different focusing nozzles of different diameters.
COBISS.SI-ID: 10980635
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
Before starting, the production forming processes require real experiments in order to accurately define forming limits. For this reason and because incremental sheet metal forming technology requires a relatively long production time, an autonomous on-line system for fracture identification has been developed. The system is a versatile tool for the identification of the location and time of the occurrence of the fracture, without human influences or oversight. The system is based on an investigation of the forming forces, responsive to very small variations, appearing during the forming process, andworks effectively with different material types, material thicknesses and product shapes.
COBISS.SI-ID: 10919195
This paper investigates the reliability of workpiece material removal per discharge (MRD) estimation for application in electrode wear compensation based on workpiece material removal. An experimental investigation involving discharge counting and automatic on the machine measurement of removed material volume was carried out in a range of process parameters settings from fine finishing to roughing. MRD showed a decreasing trend with the progress of the machining operation, reaching stabilization after a number of machined layers. Using the information on MRD and discharge counting, a material removal simulation tool was developed and validated.
COBISS.SI-ID: 13237531