Search Results

You are looking at 1 - 3 of 3 items for

  • Author: A. Wierzba x
Clear All Modify Search
Open access

A. Wierzba, S. Mróz, P. Szota, A. Stefanik and R. Mola

The paper presents the results of the experimental study of the three-layer Al-Mg-Al sheets rolling process by the ARB method. The tests carried out were limited to single-pass symmetric and asymmetric rolling processes. An Al-Mg-Al package with an initial thickness of 4 mm (1-2-1 mm) was subjected to the process of rolling with a relative reduction of 50%. To activate the shear band in the strip being deformed, an asymmetry factor of av=2 was applied. From the test results, an increase in the tensile strength of the multi-layer Al-Mg-Al sheets obtained from the asymmetric process was observed. Microhardness tests did not show any significant differences in aluminium layer between respective layers of sheets obtained from the symmetric and the asymmetric process. By contrast, for the magnesium layer, an increase in microhardness from 72 HV to 79 HV could be observed for the asymmetric rolling. The analysis of the produced Al-Mg-Al sheets shows that the good bond between individual layers and grain refinement in the magnesium layer contributed to the obtaining of higher mechanical properties in the multi-layer sheets produced in the asymmetric process compared to the sheets obtained from the symmetric process.

Open access

M. Gnyba, J. Smulko, A. Kwiatkowski and P. Wierzba

Portable Raman spectrometer - design rules and applications

Raman spectroscopy has become more popular due to its new prospective field applications in forensic sciences, war against terrorism, environment protection and other field chemical analysis. Raman spectrometers can be miniaturised to portable devices and their price is decreasing due to development of optoelectronics components. Unfortunately, this technology has still numerous limitations that influence their design and limit the scope of possible applications. The conception and design of the portable Raman spectrometer is described, including discussion of performance and limitations of representative components of such device available on the market. An enhanced portable Raman spectrometer using two lasers, one emitting at 355 nm and the other at 785 nm, and employing advanced signal acquisition and data processing methods is presenented. Advantages of such system are outlined and example measurement results acquired using equivalent hardware are presented. Data processing flow for identification of chemicals is also described.

Open access

Andrzej Krasiński, Patrycja Wierzba, Agata Grudzień, Halina Hajmowicz, Krzysztof Zawada and Ludwik Synoradzki


In this work the esterification of diethyl tartrate was studied. The research was focused on the enhancement of reversible reaction yield, which is accomplished by dewatering of the reaction mixture. The removal of water shifts the equilibrium towards the main product. Pervaporation was applied for this purpose, and results were compared to distillation. The advantages and limitations of both processes are discussed. The experimental part consists of dewatering of mixture after the reaction had reached the equilibrium, and was subsequently fed to the test rig equipped with a single zeolite membrane purchased from Pervatech B.V. Results show a significant conversion increase as a result of water removal by pervaporation. Compared to distillation no addition of organics is necessary to efficiently remove water above the azeotrope. Nevertheless, some limitations and issues which call for optimisation are pointed out. A simple numerical model is proposed to support design and sizing of the pervaporation system. Various modes of integrated system operation are also briefly discussed.