Milena Kubišová

The Influence of the Static Electrical Field on the Phase Transformation II-I of the Isotactic Polybutene-1

The spontaneous phase transformation of the unstable phase II to the stable phase I of isotactic polybutene-1 can be affected by several factors (temperature, pressure, mechanical deformation, environments, nucleation agents or presence of –CH2- groups in polymer chains or in blends). Here we study the effect of the external static electrical field on the iPB-1 structure and phase II →I transformation rate. The phase transition II to I is accelerated by the effect of the static electrical field up to 36%. This effect increases with increasing macromolecular chain length and increasing voltage. The electrical field did not substantially influence the total amount of crystalline phase. The phase transformation of neutral type changed into minus type. This change decreases the transformation rate by blocking the transformation nuclei.

Structural Changes in Metals during Laser Cutting

The presented paper deals with the problems associated with laser machining of metal materials. Specifically, it solves the question of structural changes that occur as a result of the transfer of heat to the material. Experimental machining of selected technical materials was carried out, and on the basis of the hardness measurement near the cutting point, the heat-affected zone was evaluated after passing the laser beam. To confirm the detection of the affected zone width the models of transient temperature field were arranged, to represent the distribution of temperature in the vicinity of the cutting edge.

The Influence of Laser Beam Technological Parameters on the Polymethyl Methacrylate Surface Quality

The paper is focused on the determination of the course and change of the surface quality parameters obtained by the laser engraving of the material known under commercial name polymethyl methacrylate. The paper aims to find mathematical relations based on regression analysis for amplitudes parameters Ra and Rz. For this purpose, a sample of variable technology parameters will be machined followed by the surface measuring and evaluation using the Talysurf CLI 500 3D Surface Scanner. Thus the data obtained will be subjected to the detailed statistical analysis to check homoscedasticity, the presence of outliers, and multidimensional normality testing.

The “Laser Machinability” of Polymeric Materials

This article deals with the area of non-conventional technologies, in particular results of CO2 laser micro-machining are the subject of this experimental study. Laser beam and its impact on different types of polymeric materials were studied in details. The aim was to find an optimal combination of laser cutting parameters (power and feed) for ABS, POM, PS, PMMA, PA 6, PA 66, PC, POM, PP, PTFE and PVC. The laser machinability was evaluated with different technological parameters. Next, the Theory of hypothesis testing for evaluation of the laser machinability was applied.

Resolving Problems of Finding Surface Boundaries during Laser Machining

During of aluminum alloy materials, it is possible to find three surface types which can be distinguish as primary, secondary and tertiary sections. In practice this is a big problem in case of finding the basic parameters of roughness and waviness as described by ISO 4288. According to our research, it is possible to use optical microscopy in the first step and subsequently to scan the surface in 3D in order to distinguish the type of. Another problem is how to determine the boundaries between the individual structures. The article describes methods to distinguish the boundaries in a more precise way by the cumulative functions, leading to more accurate determination of the surface quality parameters.

Simulation of the Transient Temperature Field when Laser Machining Polymeric Materials

The paper deals with possibilities of using the laser in technologies. The parametric temperature field analysis was realized by the finite element method. The analysis was run in COSMOS/M software solver. A thermal module HSTAR makes it possible to realize cases of the temperature dependences on the material properties. Material data can be entered as a function of a temperature. The thermal and physical characteristics of the polymeric materials change significantly. The output of the analysis was described by spectrograms with temperature field distribution of various materials.