Jakub Wieczorek

Evaluation of jute fiber preforms absorbability using optical profilographometer

The article presents an analysis of absorbability of polyester resin by jute fabric – untreated and treated in KOH water solutions (various exposure times), toluene diisocyanate, methanol, vinyl acetate and vinylsilane. A change with time in height of a resin droplet put on the fabric specimen was measured using optical profilographometer. The height of droplet was taken as a criterion of absorbability. Additional profilometric scanning observations, scanning electron microscopic observations and a saturation time in vacuum resin infusion tests were conducted in order to confirm and explain the results of the droplet height measurements. Although scanning electron microscopic analysis showed improvement in wetting between the treated fibers and the resin, the droplet height measurements showed that chemical treatment impairs translaminar absorbability of jute fabric. Deterioration of absorbability is caused by swelling of jute strands. However, technological tests showed that in most cases the treatment shortens the saturation time, which testifies an improvement in in-plane absorbability. Especially treatment with vinylsilane and KOH solution visibly shortened the preform impregnation time.

Physical and Mechanical Properties of Composites with Aluminum Alloy Matrix Designed for Metal Forming

The change of matrix and usage of the aluminum alloys designed for the metal forming in making the composite suspension allows to extend the processing possibility of this type of materials. The possibility of the metal forming of the composites obtained by mechanical mixing will extend the range of composite materials usage. Applying of the metal forming e.g. matrix forging, embossing, pressing or rolling, will allow to remove the incoherence of the structure created while casting and removing casting failures. In order to avoid the appearance of the casting failures the homogenization conditions need to be changed. Inserting the particles into the matrix influences on the shortening of the composite solidification. The type of the applied particles influenced the sedimentation process and reinforcement agglomeration in the structure of the composite. Opposite to the composites reinforced with one-phase particles applying the fasess mixture (glassy carbon and silicon carbide) triggered significant limitation in the segregation process while casting solidification. Inserting the particles into the AW-AlCu2SiMn matrix lowers the mechanical properties tension and impact value strength. The most beneficial mechanical properties were gained in case of heterofasess composites reinforced with the particle mixture of SiC and glass carbon. The chemical composition of the matrix material (AW-AlCu2SiMn) allows to increase additionally mechanical characteristics by the precipitation hardening reached through heat casting forming.

Influence of wet chemistry treatment on the mechanical performance of natural fibres

Influence of wet chemistry treatment on the mechanical performance of natural fibres The paper presents determination of the effect of various chemical treatment on the strength of 288 tex jute yarn arisen from the plain weave fabric produced by LENTEX, Poland. The yarn was put to alternative treatments in: NaOH and KOH water solutions with various concentration (from 1 to 15%) and treatment duration (from 0.5 to 6 hours), vinyl acetate, methanol and toluene diisocyanate. After the treatment it was put to tensile tests. Yarn diameter and elementary fibre twist angle were also measured using MICRO PROF FRT optical profilographometer. The SEM micro-photographs have also been performed in order to evaluate the structural changes of the yarn after the treatment. Optimal conditions of alcali-treatment are: 5% concentration and 2h duration for NaOH, 3% concentration and 4h duration for KOH. Such treatments give a growth in yarn rupture force up to 10% and they are well applicable in composite materials manufacturing. Also interaction with vinyl acetate and toluene diisocyanate has practically not negative influence on the mechanical performance of the yarn. Two effects were observed which can explain the influence of chemical treatment on mechanical performance of jute yarn: swelling and change in the orientation of elementary fibres.

Resistance to Electrochemical Corrosion of Extruded Magnesium Alloy AZ61

The purpose of the study was the evaluation of the electrochemical corrosion resistance of extruded magnesium alloy AZ61 in solutions with concentration of 0.012 M NaCl. Resistance to electrochemical corrosion was evaluated on the ground of registered anodic polarisation curves by means of potentiodynamic method. Immersion tests were performed in NaCl solution and time periods of 1-6 days. Scanning microscopy was used to obtain images of the alloy microstructure after immersion tests. Electrochemical impedance spectroscopy was used to evaluate phenomena that take place on the surface of the tested alloy. The results of all performed tests prove explicitly deterioration of corrosion properties of magnesium alloy AZ31 with the increase of molar concentration of NaCl solution. It was found that irrespective of molar concentration of NaCl solution, pitting corrosion can be detected on the surface of the tested alloy. Test results prove that it is necessary to apply protective layers on elements made of the tested alloy.

Machinability of Aluminium Matrix Composites

The todays interest in MMCp results from a number of their creative properties, which can be designed through a proper selection of reinforcing components and technological parameters. The composite machine elements such us engine, compressor parts obtained by casting methods require the specially final machining. The introduction of hard ceramic particles increase wear resistance of composite material compared to unreinforcement alloy. Simultaneously increase wear and reducing the durability of tools cutting. The presence of ceramic particles (SiC, Cs) in aluminium matrix influence on surface geometry formed in track of processing. In this paper the results of investigations of geometry surface of composite after machining will be presented. Applied machining conditions for composite material were the same as for unreinforcement alloy, it made possible to compare the conditions of machining processing. It the piston skirt was conducted light profilometry investigation were the parameters 2D and 3D surface topography evaluated. Results shows dependency of surface parameters (Ra, Rz) after machining on kind, size and volume fraction of reinforcement particles applied in composite material.

The effect of pressureless densification on mechanical and tribological properties of fine-grained silicon nitride ceramics

The paper presents a new economic method of silicon nitride ceramic preparation for high wear resistant applications as sealing valves or the brake pad lining. The excellent mechanical properties and wear resistance of the resultant ceramic were improved by reduction of silicon nitride grain size to the one-two micrometer level as a result of mechanochemical processing and special procedure of compact densification. All experiments were conducted on specimens prepared from α-Si3N4-AlN-Y2O3 powders with application of mechanochemical processing (MCP). The chosen specimens were tested for hardness, elastic modulus, bending strength and wear resistance. The results showed mechanical properties in the range of hot-pressed ceramics and superior wear resistance due to micrometer-sized β-Si3N4 grains.

Evaluation of corrosion resistance of casting magnesium alloy AZ31 in NaCl solutions

The results of tests of corrosion resistance of casting magnesium alloy AZ31 in NaCl solutions of 0,01÷2 M concentration have been presented. Electrochemical measurements were carried out with application of VoltaLab®PGP201 system by Radiometer. On the ground of registered polarisation curves, typical features characterising alloy resistance to electrochemical corrosion, i.e. corrosion potential, polarisation resistance, corrosion current density and corrosion rate, were determined. Electrochemical impedance spectroscopy was applied for evaluation of phenomena that occurred on the surface of the tested alloy. Resistance to corrosion was tested by means of immersion method for 1÷5 days. By means of scanning electron microscope with field emission FE SEM S-4200 Hitachi in cooperation with spectrometer EDS Voyager 3500 Noran Instruments, quantitative and qualitative analysis of chemical composition in micro-zones was made. The study also presents the results of measurements of geometrical features of AZ31 alloy surface after corrosion tests. The results of the tests show undoubtedly deterioration of corrosion properties of magnesium alloy AZ31 together with the increase in molar concentration of NaCl solution.

The Properties of ZnAlMg Alloys for Batch Hot Dip Metallization

In the paper the melting point of Zn-Al alloys with the addition of Mg has been determined, based on solidification curves. The alloys used for the tests were alloys containing 7, 15, 23 and 31 wt.% Al with the addition of 3 or 6 wt.% Mg. It has been determined that the solidification temperature of the ZnAlMg alloy is a synergistic effect of the Al and Mg contents. In alloys with lower contents of Al (7, 15 wt.% Al) an increase in the content of Mg leads to an increase of the melting point. In baths with higher contents of Al (23, 31 wt.% Al) the addition of Mg causes a decrease of the melting point. It has been determined that the melting point of the Zn-31Al6Mg alloy drops to 438°C, due to which the alloy can be used for metallization in temperature conditions close to the temperature of traditional hot dip galvanizing.

The Effect of Metal Forming Direction on the Tribological Properties of MMCp Composites

This article presents the results of the research on tribological composites with AlCu2SiMn matrix that underwent the process of extrusion. The research was conducted on the composites that underwent extrusion, which was carried out with a pneumatic press with a heated matrix of 14mm and 20mm diameter. The research was carried out under technical dry friction conditions in reciprocating motion. The results allowed to describe the influence of the plastic work direction on the tribological properties of the composites reinforced with silicone carbide and glassy carbon. The process of wearing was conducted in two directions: the perpendicular and parallel to the axis of the extruded composite rod. In the examined composites the tribological wear in the direction perpendicular to the direction of the extrusion was greater than wear in the parallel direction. The difference between the values for the parallel and perpendicular directions to the rod decreases with the increase of the degree of plastic work.

Profilometric Assessment of Surface Condition of Zinc Coatings Formed by the Continuous Galvanizing Method

The paper presents the results of research on surface condition of zinc coatings. Profilometric studies were performed for zinc coatings formed in industrial continuous hot-dip galvanization process and for the same coatings after two years of use. The results include the geometrical shape of 2D and 3D surfaces, distribution of vertices on the surface and roughness and waviness profiles. The parameters Ra, Rz, Sa and Sz were used to define the surface roughness. The study was conducted using FRT Microprof optical profilometer with data acquisition and analysis by MARK III software package.