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Dosadašnja istraživanja u oblasti opreme pod pritiskom, odnosno merenja i određivanja napona i deformacija struktura kompleksne geometrije su se oslanjala na analitičke proračune najčešće bazirane na teoriji ljuski, numeričke proračune upotrebom računarskih softvera i konvencionalne eksperimentalne metode. Kao jedan od najčešćih zaključaka u svojim radovima, istraživači su naveli nepostojanje adekvatnih eksperimentalnih rezultata u postojećoj literaturi, odnosno iskazali potrebu za detaljnom eksperimentalnom analizom kritičnih mesta za koje nije moguće precizno odrediti veličine pomeranja, deformacija ili napona upotrebom analitičkih obrazaca ili numeričkih modela. Ograničenja korišćenih eksperimentalnih metoda su se ogledala u više aspekata. Prvo, za analizu geometrijskih diskontinuiteta, najčešće su korišćene standardizovane epruvete sa pripremljenim diskontinuitetima i ispitivane na zatezanje. Na osnovu dobijenih rezultata su pravljeni dijagrami sa faktorima koncentracije napona, koji su kasnije primenjivani na probleme geometrijski kompleksnih struktura. Ovakav pristup je davao samo okvirna rešenja, koja nisu bila dovoljno precizna i tačna. Drugo, eksperimenti su sprovođeni konvencionalnim metodama. Ograničenje konvencionalnih metoda je lokalno merenje, odnosno dobijanje vrednosti merenih veličina samo u jednoj tački. Treće, merenja su vršena samo u blizini geometrijskih diskontinuiteta, a ne na samim spojevima geometrijskih oblika, tako da nije bilo moguće merenje najvećih vrednosti deformacija. Jedan od ciljeva ove teze je upravo taj da prevaziđe navedene eksperimentalne probleme, odnosno da pokaže da je moguće primeniti relativno novu metodu digitalne korelacije slika na slučajeve ispitivanja struktura kompleksne geometrije u oblasti cevovodne armature. Metoda korelacije digitalnih slika, prevazilazi ograničenja metode mernih traka, kao najčešće korišćene konvencionalne metode i omogućava merenje Naponi i deformacije struktura kompleksne geometrije cevovodne armature iii celih polja pomeranja i deformacija. Jednim eksperimentalnim merenjem se dobija veliki broj podataka koja zamenjuje više desetina/stotina mernih traka i značajno smanjuje vreme pripreme eksperimenta, a samim tim i troškove. S druge strane, kako se metodom konačnih elemenata dobija kompletno polje pomeranja i deformacija, sama verifikacija numeričkog modelase mnogo jednostavnije sprovodi poređenjem sa rezultatima koji su predstavljeni na isti način. Eksperimentalno merenje celih polja deformacija omogućuje precizno određivanje mesta kritičnih, odnosno najvećih deformacija, kao i pravce glavnih deformacija koje omogućava bolju teorijsku analizu kompleksnih struktura. Previous studies in the field of pressure equipment, i.e. measuring and determining stress and strain of geometrically complex structures, have relied on analytical calculations based on shell theory, numerical calculations using computer software and conventional experimental methods. As one of the most often conclusions in their work, the researchers indicated the lack of adequate experimental data in the available literature, i.e. expressed the need for detailed experimental analysis of critical areas where is not possible to precisely determine displacement, strain and stress values using analytical or numerical models. Limitations of used experimental methods were recognized in several aspects. First, standardized specimens with discontinuities were used for analysis of geometrical discontinuities and tensile testing. Based on the results of tensile testing, stress concentration factors were plotted on diagrams and later used to solve problems on geometrically complex structures. This approach gave only approximate solutions that are not sufficiently precise and accurate. Second, experiments were conducted using conventional methods. Limitation of conventional methods is local measurement, i.e. experimental values are measured only in a single point. Third, measurements were carried out close to the geometrical discontinuity, rather than on the actual intersection of geometrical shapes, so it was not possible to measure highest strain values. One of the goals of the thesis is exactly that to overcome abovementioned experimental problems, i.e. to show that is possible to implement relatively new digital image correlation method on testing geometrically complex structures in the field of pipeline fittings. Digital image correlation method overcomes limitations of strain gauge, as the strain gauge is most commonly used conventional method that enables full-field displacement and strain measurement. One experimental measurement enables acquisition of large datasets that replaces dozens/hundreds of strain gauges and Naponi i deformacije struktura kompleksne geometrije cevovodne armature vi significantly reduces experiment preparation time and therefore the costs. On the other hand, as finite element method calculates full displacement and strain fields, numerical model verification is easily carried out by comparing to experimental results presented in the same manner. Full strain field experimental measurement allows accurate determination of critical areas, i.e. areas with highest strain values, as well as principle stress directions that enables better theoretical analysis of complex structures.

Background: Understanding of the biomechanical consequences of the stresses generated to the supporting bone during occlusal loading is significant for improving the design and clinical planning process in partial edentulism therapy. Objective: The aim of this study was to analyse the distribution of strain and displacement on the partially dentate lower jaw rehabilitated with an partial denture (RPD) and to compare it to the strain and displacement distribution on a partially dentate lower jaw rehabilitated with a cantilever fixed partial denture (FPD). Material and methods: The experimental models were a partially dentate mandible with full-arch PFM crowns and RPD and a partially dentate mandible rehabilitated with a full-arch cantilever FPD. Strains and displacement were measured using the Digital Image Correlation Method. Results: Displacement values of the first experimental model ranged from 0.31 to 0.54 mm with strains from 1.35 to 2.34%. Analysis of the second experimental model results showed displacement values from 0 to 0.34 mm, while strains were in the range of 0-1.40%. Conclusion: Higher displacements and strains of bone tissue were observed below the RPD, especially in the region of the distal abutment and distal portion of the free-end saddle. Strains within bone and the bone-denture contact area were mostly influenced by the teeth and denture vertical displacement.