The influence of measurement force on the results of internal and external diameter measurements

U Laboratoriju za precizna mjerenja dužina veliki dio mjerenja odnosi se na 1D kontaktna mjerenja. Svako kontaktno mjerenje podrazumijeva primjenu mjerne sile koja u većoj ili manjoj mjeri utječe na mjerni rezultat i njegovu nesigurnost. Ovaj utjecaj ovisi ponajprije o iznosu primijenjene sile i metodi mjerenja. Pri usporedbenim mjerenjima smatra se da je ovaj utjecaj zanemariv dok se kod neposrednih mjerenja provodi korekcija rezultata mjerenja temeljem Hertz-ovh jednadžbi. Dugogodišnje iskustvo laboratorija u mjerenju promjera ukazuje na probleme vezane uz primjenu korekcije zbog utjecaja mjerne sile. U radu je provedeno istraživanje utjecaja mjerne sile na rezultat mjerenja promjera mjernih valjčića, promjera prstena i srednjeg promjera vanjskog navoja. Uz analitičke modele izvedene na osnovi Hertz-ovih jednadžbi izrađeni su i modeli utjecaja mjerne sile pri mjerenju valjčića i promjera prstena primjenom numeričke metode konačnih elemenata. U eksperimentalnom dijelu provedena su mjerenja valjčića različitih promjera s tri različite mjerne sile kako bi se pokazalo u kojoj mjeri je moguće postići podudarnost rezultata mjerenja s rezultatima dobivenim simulacijama.In Laboratory for precise measurements of lengths large amount of measurements refers to 1D contact measurements. Every contact measurement implies applying force which, in smaller or greater amount influences measurement results and its uncertainty. This influence depends foremost on magnitude of applied force and the measuring method. It is considered that the influence can be ignored for comparison measurements, while for direct measurements is often used Hertzian theory of elastic contact to make result correction. However, Laboratorys many years of experiance with measuring of diameters show some irregularities in using the mentioned Hertz theory for corrections. In many cases comparisment of results with and without correction showed no difference in values. The results were good no matter if the correction was or wasn't used. The thesis examines the influence of measuring force on measuring results, primarily on measuring of outer diameter of measuring cylinders, and on measuring of middle diameter of a threaded plug. Also, it will be checked if neglecting the influence of the measuring force is justified with comparative measurement of inner diameter of measuring ring. Alongside Hertzian Theory of Elastic Contact, there will also be made a computer model using Numerical Method of Finite Elements. In experimental part of this thesis, work will be concentrated on measuring the outer diameter of measuring cylinders. There will be three different forces used, on three different sizes of cylinders. These results will show, in what amount, is possible to match the results with results given in computer simulations