Materials Science Forum Vol. 919

Abstract: Effects of the changing of cutting on the two-and three-dimensional roughness parameters of surfaces machined by face milling are investigated in the paper. The focus is on how the changing of the ratio of the feed and depth of cut affects the generated surface topography and its parameters in the case of constant undeformed uncut chip cross-section. Additionally, it is demonstrated how setting errors of individual inserts affect the roughness parameters of machined surfaces.

Abstract: The paper deals with the comparison of surface hardness and porosity of stainless steel 316L (1.4404) produced by additive technology (SLM) and cold rolled steel. The subject of the paper is a comparison of two sets of samples where the first set of samples was made on a Renishaw AM400 with a laser output of 200 W and 400 W. In each set of samples, were the samples without heat-treated and heat-treated by annealing. Measurement of porosity and surface hardness were performed on all samples. The surface hardness of the material was evaluated by a static test according to Brinell CSN EN 10003-1. The porosity measurement was performed by the optical method. The measured values were compared with the reference material, which was cold-rolled steel, in which both the porosity and the hardness of the surface were measured.

Abstract: In order to increase the cutting and breaking capacity of abrasive water jet machining (AWJM), abrasive particles are usually added to water. The AWJM technology is generally used for harder and heavier machinable materials like thick sheets, composite materials with metal and ceramic properties and others within these categories to just cite a few. The contribution is mainly focused on the analysis of the surface properties of the steel S235 after the cutting process, and this depending on the cutting speed of the water jet. Three different cutting speeds were used for the analysis because this cutting parameter significantly affects the resulting quality of the machined surface. A contact profile method was used to analyze surface roughness. The observed surface roughness parameters were the Ra, Rt and Rz respectively. The above-mentioned surface roughness parameters were measured in three positions, i.e.: at the inlet, middle and exit positions of the water jet with respect to the machined material.

Abstract: Cross-linking is a process in which polymer chains are associated through chemical bonds. Radiation, which penetrated through specimens and reacted with the cross-linking agent, gradually formed cross-linking (3D net), first in the surface layer and then in the total volume, which resulted in considerable changes in specimen behavior. This paper describes the effect of electron beam irradiation on the nanoindentation creep of unfilled and glass fiber filled polypropylene (25%). nanoindentation creep were measured by the DSI (Depth Sensing Indentation) method on samples which were non-irradiated and irradiated by different doses of the β – radiation (0, 30, 45 and 60 kGy). The purpose of the article is to consider to what extent the irradiation process influences the resulting nanoindentation creep measured by the DSI method. The unfilled and filled polypropylene tested showed significant changes of indentation creep. The measured results indicate, that electron beam irradiation is very effective tool for improvement of creep properties of unfilled and filled polypropylene. The nanoindentation creep after irradiated unfilled Polypropylene was decreased up to 16 % (filled polypropylene was decreased up to 9%) compared to non-irradiated surface. These changes were examined and confirmed by Gel content.

Abstract: Cross-linking is a process in which polymer chains are associated through chemical bonds. Radiation, which penetrated through specimens and reacted with the cross-linking agent, gradually formed cross-linking (3D net), first in the surface layer and then in the total volume, which resulted in considerable changes in specimen behavior. This paper studies the effect of different doses of ionizing beta radiation on the micro-mechanical properties of commercially available polyamide. The measured results indicate, that electron beam irradiation is very effective tool for improvement of surface properties of PA6. In terms of micro-mechanical properties, the values of micro-hardness of surface layer increased by 24% at radiation dose of 132 kGy, stiffness of surface micro layer by 26% (132 kGy) as a result of different loads (0.5N and 2N). Improvement of micro-mechanical properties of radiated polyamide has a great significance also for industry. The modified polyamide shifts to the group of materials that have considerably better properties. Its micro-mechanical properties make polyamide ideal for a wide application in areas where higher resistance to wear, creep are required. Commonly manufactured PA6 can hardly fulfil these criteria.

Abstract: Nowaday´s trend is the effort to replace metal materials with the polymers, which already have the irreplaceable place in the field of the construction of various applications. Development offices effort is to achieve the best polymer quality for which various ways of modification are used. Besides common fillers and e.g. modification using beta radiation, there is a possibility to modify these properties (creep resistance, hardness, tensile strength) with the nanofillers, which have also the irreplaceable place in the field of development. This article deals with the possibilities of use of the nanofillers in HDPE material and primarily with the influence on creep properties of thus modified matrix. The influence of nanofillers shows a considerable influence in various materials, which should contribute to better resistance during these long-term tests.

Abstract: Paper is focused on analysis of a local shrinkage and injection pressure of the biodegradable materials PLLA and PLA. Analysed products were prepared with thickness of 4 mm in the patent injection mould. The technological parameters of the injection moulding were established by the Taguchi method. In this article, the influence of these main technological parameters on the local shrinkage and injection pressure is evaluated.

Abstract: The aim of this paper is to investigate the behavior of the recycled polymer containing the filler. The recycled polymer under investigation is polypropylene with a glass fiber filler. During grinding of plastic waste particles are formed which have a different size, shape and surface, from larger pieces to dust particles. Several recycled mixtures were made, all from original material. Samples with different particle size of recycled material were subsequently tested by mechanical testing. Included tests were Charpy impact test and Shore hardness test. Testing was conducted at different temperatures; ambient 23 °C and increased temperatures 60 ° and 100 °C. The results show a very large effect on Charpy properties and a lesser influence on the hardness of these mixtures. Mixture of smallest dust particles indicates larges change of measured properties.

Abstract: Reinforcing thermoplastic polymers with nanotubes or nanoplatelets to form nanocomposites is a way to increase the usage of polymeric materials in engineering applications by improving their mechanical properties. The contribution presents the results of research from basic processing and mechanical properties of nanocomposites. Low-Density Polyethylene (LDPE) was used as a matrix for experiments. The material LDPE was modified by Halloysite nanotubes (HNT) with a mass share of 2, 4, 6 wt% of the matrix. Nanocomposites were filled with 5 wt% Polyethylene grafted with maleic anhydride (PE-graft-MA) as a compatibilizer. The specimens were prepared by injection molding and their selected mechanical properties were tested by static tensile test, Charpy impact test and Shore hardness test.

Abstract: This article deals with assessment of mechanical properties and possible technical usability of flax prepreg composite materials. Mechanical properties of materials are the decisive factor for selection of their suitable industrial application. The main step was to describe the process of acquiring basic mechanical properties of one layer. Then, these properties were used for creation of a numerical model of a primary laminate and subsequently for modeling a multilayered composite. The performed FEM model has been verified based on the experimentally tested samples in tensile and flexural loading.