Biserka Runje

Assessment of uncertainty in modelled ultrasonic thickness measurements

Abstract Recently, through several documents ranging from guidelines to standards, it has been suggested to strengthen the quantitative character of non-destructive testing results and its implementation has been proposed. For the study behind this article, the formulated scheme on the ultrasonic thickness measurement has been applied, which is a typical procedure within ultrasonic testing. The regular situation is described, formalized through formulating the accompanied model, and its measurement uncertainty is estimated by using a Monte-Carlo based simulation. The obtained results provide a significant contribution to the approach to evaluate the testing system capability, to its step-by-step improvement as well as to direct tracing of consequences of any change in its characteristics.

Analysis of influential factors for ultrasonic disc size evaluation

Abstract The accuracy and reliability of any ultrasonic testing depends on the calibration procedure and sensitivity settings. In the present experimental research, it has been investigated how the changes of ultrasound beam shape influence the disc size evaluation. It was investigated how three selected factors and their interactions affect the disc size evaluation when probe frequencies are changing what is in correlation with changing the ultrasound beam shape. The experiment revealed that different factors and their interactions are significant for disc size evaluation.

Uncertainty Estimation of Coating Thickness Measurement Results

Abstract This contribution presents an estimation of the measurement uncertainty of coating thickness measurement results. The measurements were performed on a steel sheet sample with an outside shell plating. The sample is protected against corrosion with two layers of 100 ¼m thick dry film. In the present case, the criteria of “80-20” have been applied. The measurement uncertainty evaluation has been carried out using Monte Carlo simulations (MCS method) in accordance with the document OIML G 1-101 Edition 2008 (E) Evaluation of Measurement Data – Supplement 1 to the Guide to the Expression of Uncertainty in Measurement – Propagation of Distributions Using a Monte Carlo Method. The criteria “80-20” was evaluated based on the mean coating thickness measurement results, as well as, on the basis of the complete measuring information. Aside from the expected value, complete measuring information comprises the value of measurement uncertainty. In the case where measurement result is described only as the mean of the measurement values a wrong conclusion regarding the fulfillment “80-20” is reached.

Wear Resistance of Chromium-Nitride and Diamond-like Carbon Thin Hard Coatings

Abstract This contribution reports research concerning the wear behaviour of two thin hard coatings, diamond-like carbon (DLC) and chromium-nitride (CrN), deposited on substrate of different level of hardness. Prior to wear testing, all coatings were characterised with respect to their thickness, Youngs modulus, hardness, and cohesion/adhesion. Afterwards, all samples were tested on particle erosion and abrasion. The particle erosion test shows a very low resistance of DLC coatings on that type of wear for all substrate hardnesses. CrN coating shows significantly better particle erosive wear resistence for very hard substrate than for soft. Abrasion tests have been performed by the use of two different methods: microscale abrasion, and dry sand/rubber wheel test under various normal loads. It was found that for the normal loads in range 0,1 N—1 N substrate hardness has no influence on the CrN lifetime, but for the higher normal loads 5 N—45 N hardness of the substrate strongly affects the CrN wear lifetime. DLC coating shows significant dependence on substrate hardness for all applied loads.

Development of Models for Prediction of Corrosion and Pitting Potential on AISI 304 Stainless Steel in Different Environmental Conditions

Stainless steels are found in various aerated aqueous electrolytes in a passive state which protects them from corrosion. In many aggressive solutions, stainless steels are easily depassivated, which can lead to different types of corrosion. This paper tested the impact of chloride ions at different concentration, temperatures and pH values on the corrosion and pitting potential of AISI 304 stainless steel. In order to predict the behaviour of AISI 304 stainless steel design of experiment and artificial neural network methods were applied. Results of the developed models showed good agreement with the experimental results and no significant differences between models.

Simulacija mjerenja kvalitete usluge primjenom modeliranja pomoću agenata

Quality level, achieved by a service-providing company, has complex dynamics. It is demanding to optimise the company’s performances in a realistic, non-characterised environment. This article contributes to stated optimisation by formulating the agent-based model for performance of a service-providing company. A set of elements and relations representing a structure of such a company is described and explained. In addition, some elements occurring in realistic situations are not included in the model and their absence is explained. Parameters of the model are divided into two groups. First group consists of parameters describing interactions between the company and its environment and second group of the parameters describing internal interactions among the company’s elements. Interactions are represented using time-dependent information entropy. Quality of the company’s performances is related to values of accompanying information entropies. Relatively simple agent-based model makes possible reliable representations of a variety of observed functions of service companies.

Nano-calibration standard with multiple pitch and step height values

In 2011 Croatian National Laboratory for Length (HMI/FSB-LPMD) developed calibration standards which have been physically implemented in cooperation with the company MikroMasch Trading OU and the Ruđer Boskovic Institute. Specific design of standards makes them suitable for calibration of optical instruments, stylus instruments, scanning electron microscopes, atomic force microscopes and scanning tunnelling microscopes. Therefore, the developed calibration standards greatly contribute to the reproducibility of measurement results for groove depth well as the 2D and 3D roughness parameters obtained by various measuring methods. After a number of measurements conducted on developed standards, based on which new knowledge was acquired, HMI/FSB-LPMD designed a new standard for the field of dimensional nanometrology. This paper presents the design of a new standard that is still suitable for calibration of different types of measuring instruments, i.e. methods, but has a larger measurement capability in terms of measuring ranges in vertical and lateral direction.

Coating Distribution Depending on Surface Microgeometry

Abstract This paper investigates the effects of surface microgeometry on coating thickness, both theoretically and experimentally. In the theoretical part of the paper, surface roughness parameters are analyzed and basic definitions and general requirements on coating quality defined. The experimental part of the paper gives a calculation for the coating quantity required in order to fill “dead volume” depending on surface roughness. Coating distribution is analyzed using scanning electronic microscopy (SEM). The paper also evaluates quality of a measuring system using magnetic method for measuring coating thickness.

Waste Water Treatment after Removal of Thermic Oxides from Stainless Steel Welding Joints

This work describes chemical methods of removal of thermic oxides from stainless steel welding joints, as well as waste water treatment. Thermal oxides were removed from the stainless steel surface using chemical and electrochemical procedures. A pickling paste that contains HNO3 and HF in different ratios was used for chemical cleansing of thermal oxides (A, B, and C). Electrochemical removal was done using an apparatus Magic Cleaner, and as electrolyte a solution H2SO4

Surface structural changes of feldspathic ceramics before and after immersion in corrosive medium using Atomic Force Microscopy

Abstract Ceramics are attractive dental materials as a result of their supe- rior aesthetics and biocompatibility. However, they are brittle and prone to premature failure, especially at repeated contact strain and in moist environments. The chemical stability of dental ceramics is important, because it directly affects mechanical properties and aesthetic value of restorations. The aim of this study was to investigate the effects of a corrosive agent, i.e. 4% acetic acid, on the surface of glazed and unglazed feldspathic ceramics. Metal-ceramic plates (9.0 × 9.0 × 1.2 mm) composed of a Ni-Cr alloy (Wiron 99, Bego Germany) and glazed or unglazed feldspathic ceramics (IPS Classic, Ivoclar-Vivadent, Schaan, Liechtenstein) were prepared according to the manufacturer‧s instructions. The samples were immersed in the solution at 80 °C and kept there for 16 h (ISO 6872). The surfaces of the samples before and after immersion in the corrosive medium were examined by atomic force microscopy (AFM). The pre- and post- corrosion AFM images of the surfaces of the feldspathic ceramics samples clearly show that the glazed surfaces are much less prone to deterioration by corrosion than the unglazed ones.