Milena Kušnerová

A Proposal for Simplifying the Method of Evaluation of Uncertainties in Measurement Results

Abstract The paper deals with the innovative ways of nonstandard, simplifying applications of the valid method for evaluating uncertainties in measurement results and with the definition of conditions of their usability. The evaluation of a substitute criterion for measurement accuracy by means of a relative difference between the measurand and its reference value is proposed. This nonstandard relative uncertainty is comparable with the overall relative standard uncertainty in the measurement result, and thus the evaluation of it enables other simplifications in the calculations of measurement result uncertainties. The use of the simplified evaluation of measurement results is illustrated in two experiments in measurement of the coefficient of thermal conductivity of an insulating material newly developed for the needs of building practice, namely measurement using commercial instruments, and measurement using a newly developed original measuring instrument.

Non-contact method for surface roughness measurement after machining

Abstract The paper deals with the measurement and identification of surfaces after machining in a non-contact manner. It presents a new modified measurement method and its implementation, the results of intensity distribution in the defocusing plane, their analysis and interpretation. The scanned intensity distribution at the defocusing plane gives information necessary to assess the second derivatives, and thus, surface functions which can be used to determine groove curvatures of the real surface morphology. The proposed method of measurement has proved to be very sensitive in evaluating the differences between surface finishing methods by which the measured surface standards (etalons) were machined. Two methods of machining were chosen: face grinding and planning. By comparing the roughness standard values Ra, there were obtained relationships between these values and the parameter of the characteristic frequency of vertical inequality being measured according to the presented method. A good correlation between the measured and surface standard values with the correlation coefficient taking a range of values from 0.8 to 1 was achieved.

A new method for the prediction of laser cut surface topography

Abstract The submitted contribution focuses on the clarification of a laser beam cutting technology especially from the point of view of created surface topography. It provides a new view on a deformation process caused by laser beam action and on possibilities of using the surface topography. The measurement and characterisation of surface topography was performed in depth traces using a contact profilometer Surftest SJ 401 and by and an optical-contact profilometer Talysurf CLI 2000 (measured from the top edge of the sample). Thanks to this procedure, it was possible to observe and to measure a development of the numerical values of the surface (profile) roughness parameter Ra. Based on the measurement of the surface topography, there were analyzed and interpreted data with a purpose to theoretically describe surface topography and to develop an analytical solution for the profile topographical function. By using the profile topographical function, it is possible to solve the practical problems the most engineers and users face in laser beam cutting technology (LBC) process, as well as to maximize LBC manufacturing system performance and to determine the values of the process parameters that will reach the desired product quality.

Mechanism of Creating the Topography of an Abrasive Water Jet Cut Surface

The development and application of new materials brings, in connection with their technological machining, a number of new questions. Classical methods of machining are supplemented by new technologies. An abrasive water jet represents a universal flexible tool enabling the machining of all natural and artificial materials that are not damaged by direct contact with water. Great attention is paid to the study of the cut surface topography after abrasive water jet machining. The study of surface topography is important from the point of view of modelling and prediction of the topographic function of the abrasive water jet. On the basis of knowledge of the topographic function, we are able to optimise the technological parameters of the abrasive water jet machining process, which has an impact on the output, quality and price of the final product. The mechanism to remove material is an area which has not received much attention. In material disintegration, the mechanisms of cutting, plastic deformation, fatigue and fracture participate physically. By studying the surface topography we can better understand the process of abrasive water jet machining, specify the theory and correctly quantify the mechanism of material removal, which is the subject of this paper.

Drainage Concrete Based on Cement Composite and Industrial Waste

The ongoing development of urbanization of our landscape has resulted in continuous demand for building materials, which are even nowadays produced mainly from primary natural resources. The continuous reconstructions and modernizations of already built-up areas are the cause of the production of construction waste which, for example, in Europe represents ¼ of the volume of all waste materials. Such a trend is inconsistent with sustainable development and considerate impact on the environment. The contemporary society is aware of these adverse impacts and it actively participates in the integration of construction waste back into production. Thanks to the systems of recycling, construction waste can return to the building industry as a fully valuable building material. The production of shaped pieces from grey cellular concrete after the autoclave process results in the creation of residual material in the form of waste blocks (rubble). This waste material is stored in dumps. The presence of these dumps has an adverse effect on the surrounding environment. This article presents the first results of a basic research dealing with the treatment process of waste cellular concrete rubble by means of a crushing process and its subsequent use as filler in the production of new porous concretes. The article presents 3 basic recipes of porous concrete, where 100 % of the filler was replaced with crushed porous concrete rubble with the fraction of 0/6 mm. The proposed recipes have been tested in regards to: density of fresh concrete mixture, concrete mixture consistency, strength, and thermal conductivity coefficient.

Quantifying the Mechanical Properties of Materials and the Process of Elastic-Plastic Deformation under External Stress on Material

The paper solves the problem of the nonexistence of a new method for calculation of dynamics of stress-deformation states of deformation tool-material systems including the construction of stress-strain diagrams. The presented solution focuses on explaining the mechanical behavior of materials after cutting by abrasive waterjet technology (AWJ), especially from the point of view of generated surface topography. AWJ is a flexible tool accurately responding to the mechanical resistance of the material according to the accurately determined shape and roughness of machined surfaces. From the surface topography, it is possible to resolve the transition from ideally elastic to quasi-elastic and plastic stress-strain states. For detecting the surface structure, an optical profilometer was used. Based on the analysis of experimental measurements and the results of analytical studies, a mathematical-physical model was created and an exact method of acquiring the equivalents of mechanical parameters from the topography of surfaces generated by abrasive waterjet cutting and external stress in general was determined. The results of the new approach to the construction of stress-strain diagrams are presented. The calculated values agreed very well with those obtained by a certified laboratory VÚHŽ.

Measurement of physical properties of polyurethane plaster

Fizikalna svojstva građevnih materijala mogu se definirati pomocu koeficijenata materijala kao sto su srednja gustoca, specificni toplinski kapacitet, toplinska provodljivost i toplinska difuzivnost. U radu je prikazano ispitivanje fizikalnih svojstava novorazvijenog materijala (poliuretanske žbuke) nerazornim postupkom. Također je provedeno određivanja svojstava komparativnih uzoraka izrađenih od porobetona pri cemu je primijenjena ista metoda kao i isti uvjeti ispitivanja. Za određivanje toplinske provodljivosti i specificnog toplinskog kapaciteta razvijena je i verificirana nova komparativna metoda za cije je provođenje razvijen novi kalorimetrijski uređaj.

The Use of Industrial Waste as a Secondary Raw Material in Restoration Plaster with Thermal Insulating Effect

The article describes the results of an experimental research dealing with the use of industrial waste in the form of secondary raw material - polyurethane foam after the end of its life cycle, as a 100% substitute of filler in restoration plaster with thermal insulating effect. The article presents the formulas of restoration plaster and its properties. They are: mortar consistency, volume weight, strength characteristics, thermal conductivity coefficient, coefficient of capillary water absorption, porosity and resistance against salts.

Surface and topographical parameters investigation at abrasive waterjet machining by means of optical measurement

The paper deals with an application of a shadow method which enables monitoring and checking a state of surface geometry. The data obtained from the measurement of the surface topography are analysed and simultaneously interpreted with the view of a quality increase. Data analysis from the surface enables us to formulate our ideas on the mechanism of the surface establishment created by a hydroabrasive division. It offers as well the analysis possibilities of wider connections dealing with next technology development of materials hydroabrasive dividing. Further, it emphasised the creation of parameters database of surface geometry irregularities. The utilisation of the database leads to an objective projection and a technology control of materials hydroabrasive dividing so that this technology produces more efficient and simultaneously more quality final production. New knowledge about dividing mechanism should support abstractedly an option of cutting parameters which are optimal for a given material and for required parameters concerning the quality, power and general dividing economy.

Modeling the Temperature Dependence of Dynamic Mechanical Properties and Visco-Elastic Behavior of Thermoplastic Polyurethane Using Artificial Neural Network

This paper presents one of the soft computing methods, specifically the artificial neural network technique, that has been used to model the temperature dependence of dynamic mechanical properties and visco-elastic behavior of widely exploited thermoplastic polyurethane over the wide range of temperatures. It is very complex and commonly a highly non-linear problem with no easy analytical methods to predict them directly and accurately in practice. Variations of the storage modulus, loss modulus, and the damping factor with temperature were obtained from the dynamic mechanical analysis tests across transition temperatures at constant single frequency of dynamic mechanical loading. Based on dynamic mechanical analysis experiments, temperature dependent values of both dynamic moduli and damping factor were calculated by three models of well-trained multi-layer feed-forward back-propagation artificial neural network. The excellent agreement between the modeled and experimental data has been found over the entire investigated temperature interval, including all of the observed relaxation transitions. The multi-layer feed-forward back-propagation artificial neural network has been confirmed to be a very effective artificial intelligence tool for the modeling of dynamic mechanical properties and for the prediction of visco-elastic behavior of tested thermoplastic polyurethane in the whole temperature range of its service life.