Libuše Sýkorová

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.

On Flexural Stiffness of Polymer Sandwich Walls

This paper deals with the flexural stiffness of sandwich structures based on fiberglass and polymeric foams. The influence of geometrical and material parameters on the resulting effective flexural stiffness of the sandwich structure is being studied experimentally, analytically and using FEM models. The effective elasticity module of the sandwich-structured element is being studied and it’s theoretical and model dependencies on the stiffness of the foam core are being investigated. These dependencies are then compared with experimentally observed values. This study shows it is necessary to pay special attention to the issue of flexural stiffness of walls when designing sandwich shell products in order to prevent possible failures in the practical applications of these types of structures.

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.

Application of Theory of Hypothesis Testing in Process of Laser Micromachining

The article focuses on the field of PMMA laser micromachining at change of the technological parameters. The aim was to evaluate machined surface roughness at different setting of DPI definition (number of dots – paths on square inch). The aim is application of the Theory of Hypothesis testing for evaluation changing of final surface during imputing variable technological parameters.

Evaluation of DPI Change Impact on Laser Machined Surface Quality

The article focuses on the field of PMMA laser micromachining at change of the technological parameters. The aim was to evaluate machined surface roughness at different setting of DPI definition (number of dots paths on square inch). Commercial CO2 laser Mercury L-30 by firm LaserPro, USA was used for experimental machining. Ray of laser could be focused on mark diameter d=185 mm.

Application of Fractal Geometry for Laser Engraving of Artificial Leather Surface

The article deals with application of fractal geometry on a surface of polymeric material (artificial leather) obtained by laser micromachining. There was done an experimental manufacturing of the chosen entities at the change of a technological parameters and laser beam mode. The aim was to consider possible changes of the given surfaces resulting from different laser beam mode (pulse vs. continuous).

Scanning and Evaluation of Biological Surfaces Using the Technique of Rapid Prototyping

One of the most important characteristics of a cosmetic product is maintain or improving the condition and characteristics of the skin surface. In dermatological, respectively cosmetic practice, there is very often a problem of an objective assessment of the obtained data, which corresponds to visual changes in skin relief. With technical advancements has it been proposed many approaches of solution: mechanical needle devices, optical interference devices, and microscopic, holographic, laser and photometers ones. Each of them has its advantages and negative qualities. The newest devices allow not only two-dimensional assessment (2D), but also spatial one (3D). Scientific literature such as Measuring the Skin recommends for these cases scanning the surface in 3D, using the contact scanners for made imprints. Here, however, errors that may be caused by mechanical method of scanning skin relief are not taken into consideration and there is also not clearly described the material suitable for the production of custom impression. The following article focuses precisely on this issue, specifically on the implementation of the biological surface relief imprint using a silicone impression material, its 3D scanning without contact and forming an enlarged replica by rapid prototyping technology.