Nejistoty přesných délkových měření z pohledu terminologie a jejich definic

V dnešní době samotný výsledek bez udání nejistoty je již zcela bezcenný. Měřením reprezentativního vzorku téže veličiny, třebaže za podmínek opakovatelnosti, získáme totiž pokaždé různé hodnoty. Tuto „různorodost“ mají na svědomí tzv. zdroje nejistoty, které proces měření ovlivňují. Cílem tohoto příspěvku je uvést čtenáře do problematiky nejistot měření z pohledu terminologie a jejich definic

Contact–less System for Gauge Blocks Length Measurement

Předkládaná habilitační práce poskytuje nové informace o možnostech využití principů nízkokoherenční interferometrie pro měření délky koncových měrek. Hlavním cílem předkládané práce bylo připravit bezkontaktní systém pro zavedení do běžného provozu Českého metrologického institutu k měření délky koncových měrek. K dosažení cíle bylo nutné zoptimalizovat bezkontaktní systém pro přímé potřeby laboratorního měření, vytvořit kompletní dokumentaci k validaci dané metody měření tj. stanovit nejistotu měření a následně metodiku (kalibrační postup) pro měření na daném přístroji a porovnat nový systém se stávajícími systémy a jejich metodami měření běžně využívaných v Českém metrologickém institutu, Oblastním inspektorátu Liberec. Nezbytné základní pojmy týkající se řešené problematiky, vztahy a definice jsou uvedeny v teoretické části práce. Do této části práce jsou zahrnuty přehledně informace o interferenci, koncových měrkách a nejistotě měření. Dále jsou zde stručně uvedeny popisy metod a zařízení pro měření délky koncových měrek na pracovišti Českého metrologického institutu, Oblastního inspektorátu Liberec. Jedná se popis metody interferenční prováděné na přístroji TESA NPL A.G.I. 300 a komparační prováděné na přístroji TESA–UPC. Nedílnou součástí teoretické části jsou také informace vztahující se k základnímu popisu měření délky koncových měrek na bezkontaktním systému. Dosažení cíle je věnována kompletně celá experimentální část práce, která obsahuje informace o optimalizaci systému z hlediska konstrukčního řešení, stanovení nejistoty měření pro daný přístroj a metodu měření, kompletně zpracovanou metodiku pro měření délky koncových měrek na daném přístroji (kalibrační postup). Pro ucelený pohled týkající se zavedení systému je v poslední části řešení práce provedeno porovnání stávajících systémů k měření délky koncových měrek v Českém metrologickém institutu, Oblastním inspektorátu Liberec s bezkontaktním systémem.The submitted habilitation thesis provides the new information about possibilities to utilize principles of the low–coherence interferometry for measurement the gauge block length. As a main purpose of the habilitation thesis there was preparation of the contact–less system for implementation into the Czech metrology institute common operation for measurement the gauge block length. To achieve purposes mentioned above there was necessary to optimize contact–less system for the direct needs of the laboratory measurement, to create complete documentation for validation the given measurement method i.e. to determine measurement uncertainty and subsequently methodology (calibration procedure) for its measurement on the given machine and to compare new system with the current systems and their measurement methodologies which are commonly used in the Czech metrology institute, Regional Inspectorate Liberec. All necessary basic terms those are related to the solving problem, equation and definitions are described in the theoretical part of habilitation thesis. In this part are digestedly summarized information about the interference, gauge blocks and measurement uncertainty. Moreover there are briefly mentioned descriptions of methods and devices for measurement the gauge blocks length in the workplace Czech metrology institute, Regional Inspectorate Liberec. More precisely, there is described both the interference method that is carried out on the device TESA NPL A.G.I. 300 and the comparative method that is done on the device TESA–UPC. As an integral part of the theoretical section there are also information regarding the basic description of the measurement gauge blocks length on the contact–less system. Completely the whole experimental part is about achieving the aim mentioned before. That is why it contains information about system optimization in light of its design solution, determination the measurement uncertainty for given device and measurement methodology, complete elaborated methodology for measurement the gauge blocks length on the given device (calibration procedure). To have the comprehensive view for the implementation of this system, in the last part of the habilitation thesis is carried out comparison of the current systems for measurement gauge blocks length in the Czech metrology institute, Regional Inspectorate Liberec with this contact–less system

Novel drill geometries for dry drilling of stainless steel

One completely new geometry and two modified chip breaker geometries were designed to increase the stability and reliability of the stainless steel dry drilling process. Experiments were performed and the results of individual tools were compared with a conventional solid carbide twist drill Gühring Ratio with a diameter of 5 mm. A matrix of three feed rates (0,03–0,07 mm/rev) and three cutting speeds (20–30 m/min) was designed for the cutting conditions. Precipitation-hardenable stainless steel 17-4 PH was chosen as a workpiece. During the experiment, the values of thrust force, spindle torque, temperature of the tool, surface roughness, chips morphology and chips division were recorded and compared with the reference tool. The results showed that compared to the reference tool A, the tool C - a multipoint drill with grooves through the cutting edge achieve approximately 4 % lower values of thrust force and 10–15 % lower values of spindle torque. Tool D with a step drill geometry achieve approximately 17 % lower values of thrust force and 10–15 % lower values of spindle torque and there is no chip clogging in the flute with C and D geometries. This effect is confirmed by the fact the spindle torque basically does not increase with the increasing depth of drilling. Tool B – new designed geometry achieve approximately 15 % lower values of thrust force and similar spindle torque values as the reference drill A. Tool temperature is a very important factor when dry drilling. Compared to the reference drill A, it was possible to achieve the tool temperature reduction of 20 % with the new geometry B, as well as with the multipoint drill C reduction by 26 % and with the step drill D reduction approximately by 30 %. All the modified drills also achieved a reduction in the surface roughness of the drilled holes. By 17 %, 35 % and 48 % lower surface roughness Ra was achieved with drills B, C and D. Chip morphology was significantly different for the tested drills. Conventional twist drills A and B generated helical short chips. While C and D twist drills with divided cutting edges generated ribbon snarled chips. Thanks to the reduction of cutting forces and temperature, it is possible to stably operate the drilling process with a higher cutting speed and feed rate, which leads to an increase in the efficiency and reliability of the machining process.Web of Science9252050

The effect of cutting tool geometry on surface integrity: A case study of CBN tools and the inner surface of bearing rings

In this paper, a practical issue of the application of cubic boron nitride (CBN) cutting tools for the machining of steel 100Cr6 thin-walled bearing rings is addressed. Three geometries of the commercially available CBN cutting inserts were tested at different machining parameters. The effect of geometry was assessed in terms of surface integrity, considering 2D profile parameters, 3D topography of the surface, and residual stresses in the surface layer. The results were sometimes contradictory, since the same cutting inserts provided the largest and the lowest values of the topography parameters, dependent on different cutting conditions. In general, CBN cutting inserts with XCEL geometry ensured the smallest profile parameters Ra and Rz, and the spatial parameters of Smr1 exhibited the largest values among all tested tools, suggesting reduced wear resistance. Residual stresses analysis did not reveal any inacceptable or potentially dangerous surface layer state after machining.Web of Science136art. no. 354

DNA methylation profiles in a group of workers occupationally exposed to nanoparticles

The risk of exposure to nanoparticles (NPs) has rapidly increased during the last decade due to the vast use of nanomaterials (NMs) in many areas of human life. Despite this fact, human biomonitoring studies focused on the effect of NP exposure on DNA alterations are still rare. Furthermore, there are virtually no epigenetic data available. In this study, we investigated global and gene-specific DNA methylation profiles in a group of 20 long-term (mean 14.5 years) exposed, nanocomposite, research workers and in 20 controls. Both groups were sampled twice/day (pre-shift and post-shift) in September 2018. We applied Infinium Methylation Assay, using the Infinium MethylationEPIC BeadChips with more than 850,000 CpG loci, for identification of the DNA methylation pattern in the studied groups. Aerosol exposure monitoring, including two nanosized fractions, was also performed as proof of acute NP exposure. The obtained array data showed significant differences in methylation between the exposed and control groups related to long-term exposure, specifically 341 CpG loci were hypomethylated and 364 hypermethylated. The most significant CpG differences were mainly detected in genes involved in lipid metabolism, the immune system, lung functions, signaling pathways, cancer development and xenobiotic detoxification. In contrast, short-term acute NP exposure was not accompanied by DNA methylation changes. In summary, long-term (years) exposure to NP is associated with DNA epigenetic alterations

The dimensional analysis of articles of engineering by the methods of mathematical analysis

katedra: KOM

Evaluation of head position - children with idiopathic scoliosis

Idiopathic scolios (IS) is one of the most common structural spinal deformities. Patients with idiopathic scoliosis have altered posture due to scoliosis. The aim od the study was to evaluate the position of the head in children with IS and to compare the results with a control group of healthy children. The position of the head was evaluated by the method of kinematic analysis from digital photographs, where we compared the coronal head tilt and the coronal shoulder angle between the two groups. Furthermore, the measurement of the subjective visual vertical was pearformed using Bucekt metod. Both of these measurements were performed in 10 children with IS (age 12,2 ± 2,4, mean ± SD; Cobb angle 14,9˚ ± 8,8˚ SD) and the group od 10 healthy children (age 13,9 ± 2,5). Based on these measurements, we evaluated three hypotheses. We came to the conclusion that both groups have comparable average deviations from the central position of the head and shoulders, but in the group with IS there was higher variance of values. In the group with IS, in seven patients the sides of the SVV tilt and the head tilt do not match