APPLICATION OF 3D DIGITAL IMAGE CORRELATION METHOD IN PROCESS ENGINEERING

Process engineering encompasses diverse industrial fields, such as chemical, petrochemical, pharmaceutical, biotechnological etc., and pressure equipment is an indispensable part of every industrial plants. Due to wide range of applications, pressure equipment comes in different shapes, from simple to very complex, and can be subjected to different loadings in its working life (static, dynamic, thermal etc.) so the knowledge of mechanical behaviour is of great importance. This paper presents several examples of application of 3D Digital Image Correlation method (3D-DIC)for simple shaped objects, as well as for geometrically complex structures. A 3D Digital Image Correlation method is an optical method that overcomes the limitations of conventional methods and enables full-field displacement and strain measurement. Aramis system was used for the experimental analysis. Welded joint standardized specimen is used as an example for simple shaped object. For geometrically complex structure, several examples are used: globe valve housing with distinctive sphere/cylinder intersection, cylindrical horizontal pressure vessel with cylindrical nozzles and T joint pipe. Experimental results demonstrate that the 3D-DIC method is adequate for solving geometrically complex problems and provides an opportunity for further development and improvement for practical industrial application

Stresses and strains of geometrically complex structures of pipeline fittings

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

Strain field measurements of glass ionomer cement

Extensive evolution of glass ionomer cements (GIC) has marked a significant shift in the practice of luting indirect dental restorations limiting the use of zinc-phosphate and zinc-polycarboxylate cements to a few indications. GIC are now one of the materials of choice for cementation of all ceramics, fiber reinforced composite posts and veneers. GICs are determined by unique properties like chemical adhesion to tooth and base metals, low thermal expansion coefficients similar to dentin and minimal microleakage at the tooth-enamel interface due to low shrinkage. Shrinkage strain is identified as the cause, and the associated stress as the mechanism for the loss of marginal adaption and cohesive fracture within the material. The aim of this study is to measure the strain and displacement field in a conventional GIC (Riva Luting, SDI, Australia) related to different cement diameter, using 3D Digital Image Correlation (DIC) method. The experiment is done for samples with thickness of 1 mm combined with diameters of 4 mm (Group I) and 3 mm (Group II). The strain field is measured using 3D 11optical system Aramis 2M (GOM, Braunschweig, Germany). This study provides valuable data about strain behaviour and displacement as a possible failure factor in GIC, Riva Luting. Visible differences between Group I and Group II were observed

Strain field measurements of glass ionomer cement

Extensive evolution of glass ionomer cements (GIC) has marked a significant shift in the practice of luting indirect dental restorations limiting the use of zinc-phosphate and zinc-polycarboxylate cements to a few indications. GIC are now one of the materials of choice for cementation of all ceramics, fiber reinforced composite posts and veneers. GICs are determined by unique properties like chemical adhesion to tooth and base metals, low thermal expansion coefficients similar to dentin and minimal microleakage at the tooth-enamel interface due to low shrinkage. Shrinkage strain is identified as the cause, and the associated stress as the mechanism for the loss of marginal adaption and cohesive fracture within the material. The aim of this study is to measure the strain and displacement field in a conventional GIC (Riva Luting, SDI, Australia) related to different cement diameter, using 3D Digital Image Correlation (DIC) method. The experiment is done for samples with thickness of 1 mm combined with diameters of 4 mm (Group I) and 3 mm (Group II). The strain field is measured using 3D 11optical system Aramis 2M (GOM, Braunschweig, Germany). This study provides valuable data about strain behaviour and displacement as a possible failure factor in GIC, Riva Luting. Visible differences between Group I and Group II were observed

Strain measurement of pressure equipment components using 3D Digital Image Correlation method

Pressure equipment has widespread application in various industrial sectors. Due to this variety, pressure equipment can have complex structure and is subjected to different working loads (static, dynamic, thermal etc.) during the operation life that can cause failure. Strain measurement of complex structure has always been a huge challenge for researchers. Conventional experimental methods (e.g. strain gauges) give only limited data sets regarding measurement on critical areas with high geometrical discontinuities. 3D Digital Image Correlation method is an optical method that enables full-field strain measurement of critical areas on structural components. Sphere/cylinder junction is common geometrical discontinuity on pressure equipment and globe valve housing was chosen as representative example. In this paper, globe valve housing was subjected to external axial loading caused by pipeline dilatations. Highest measured von Mises strain values around 0.15 % were recorded on cylinder/sphere intersection. Determining strain state of critical areas enables better understanding of complex structures and provides an opportunity for further development and improvement for practical industrial application

TENSILE TESTING OF FLAT THIN SPECIMENS USING THE TWO-DIMENSIONAL DIGITAL IMAGE CORRELATION METHOD

Conventional tensile testing is most commonly used for determining the basic mechanical properties of the material. However, this approach is challenging for in-depth analysis of material behaviour, especially related to heterogeneous materials. The Digital Image Correlation (DIC) method is a contactless optical method that overcomes the constraints of traditional experimental methods (e.g., strain gauge) and allows for full-field displacement and strain measurement. The paper specifically covers 2D-DIC application on tensile testing thin flat specimens prepared using cotton textile with 130 g/m2 density. Results show significant differences in von Mises strain values over the surface of the specimen, ranging from 8 to 24 %. The application of 2D-DIC in this case shows the significance of full-field analysis, as conventional usage of the tensile test would have missed the difference in mechanical properties of adjacent areas on the same specimen. 2D-DIC provides high spatial resolution, accuracy, real-time data acquisition, and visualization, making it a valuable tool for characterizing mechanical properties of thin flat specimens and understanding deformation mechanisms

Stresses and strains of geometrically complex structures of pipeline fittings

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

APPLICATION OF THE DIGITAL IMAGE CORRELATION TECHNIQUE FOR INVESTIGATION OF DIFFERENT ALLCERAMIC SYSTEMS

Mostly, mechanical properties such as elastic modulus, flexural strength and fracture toughness were assessed under static loading conditions for the initial characterization of materials. During this course authors presented the digital image correlation technique as possible method for biomechanical investigations of all-ceramics under vertical loading conditions using standard tensile testing machine and several samples of all-ceramics’ blocks: E-max lithium disilicate glass-ceramics, Vita enamic, Feldsphatic ceramic and Yttria-stabilized zirconia polycrystal ceramic. Lithium disilicate glass-ceramics has a needle like crystal structure that offers excellent strength and durability as well as outstanding optical properties. For the lithium disilicate ceramics, the amount of glass phase is determinant in their fatigue behavior. Vita enamic is the first hybrid dental ceramic with a dual-network structure. Feldsphatic is a glass material with an amorphous (non-crystalline) structure. Yttria-stabilized zirconia polycrystal is a high-strength ceramic with high values of flexular strength and fracture toughness. Zirconia, the strongest and toughest of all dental ceramics meets the mechanical requirements for high stress-bearing posterior restorations. All of these blocks were subjected to load in the tensile testing machine and the obtained strain was visualized using cameras and Aramis software. Findings provide that the highest strain was detected in Feldspathic, E-max and Zirconia all-ceramic blocks, respectively. Vita enamic was found to be the lowest strained due to polymer infiltrated its structure. This fact has significance for clinicians due to application of all’ceramic system in patients with decreased vertical occlusion and abrasion. Additionally, the hardness and elastic modulus of Vita enamic was found to be similar to those of the dental tissue values which makes this material a good choice for restoring posterior areas with inlays

APPLICATION OF THE DIGITAL IMAGE CORRELATION TECHNIQUE FOR INVESTIGATION OF DIFFERENT ALLCERAMIC SYSTEMS

Mostly, mechanical properties such as elastic modulus, flexural strength and fracture toughness were assessed under static loading conditions for the initial characterization of materials. During this course authors presented the digital image correlation technique as possible method for biomechanical investigations of all-ceramics under vertical loading conditions using standard tensile testing machine and several samples of all-ceramics’ blocks: E-max lithium disilicate glass-ceramics, Vita enamic, Feldsphatic ceramic and Yttria-stabilized zirconia polycrystal ceramic. Lithium disilicate glass-ceramics has a needle like crystal structure that offers excellent strength and durability as well as outstanding optical properties. For the lithium disilicate ceramics, the amount of glass phase is determinant in their fatigue behavior. Vita enamic is the first hybrid dental ceramic with a dual-network structure. Feldsphatic is a glass material with an amorphous (non-crystalline) structure. Yttria-stabilized zirconia polycrystal is a high-strength ceramic with high values of flexular strength and fracture toughness. Zirconia, the strongest and toughest of all dental ceramics meets the mechanical requirements for high stress-bearing posterior restorations. All of these blocks were subjected to load in the tensile testing machine and the obtained strain was visualized using cameras and Aramis software. Findings provide that the highest strain was detected in Feldspathic, E-max and Zirconia all-ceramic blocks, respectively. Vita enamic was found to be the lowest strained due to polymer infiltrated its structure. This fact has significance for clinicians due to application of all’ceramic system in patients with decreased vertical occlusion and abrasion. Additionally, the hardness and elastic modulus of Vita enamic was found to be similar to those of the dental tissue values which makes this material a good choice for restoring posterior areas with inlays

Service life prediction of running steel wire ropes

Vrlo visoka čvrstoća omogućava žičanom užetu da prenese velike zatezne sile i da se kreće po koturima relativno malog prečnika. Žice od čelika vrlo visoke čvrstoće su postojale više od sto godina pre nego što su patentirane, kada je uveden specijalni postupak zagrevanja i usavršen postupak izvlačenja. Dalja poboljšanja posle toga su uvedena u relativno malim koracima. Žičana užad uvek imaju ograničen radni vek. Zbog toga ona moraju da se podvrgnu inspekciji i ispitaju u pravilnim intervalima da bi se zamenila znatno pre otkaza. Krajnji korisnik mašine sa čeličnim žičanim užetom u svakom slučaju želi da ima grubu ocenu radnog veka užeta već u ranoj fazi razvoja mašine. tako da bude u mogućnosti, ako zatreba, da poboljša sistem mašine. To je jedan od razloga zbog kojih su tokom niza godina izvedena obimna istraživanja kako bi se poboljšali postupci proračuna za predviđanje radnog veka žičanih užadi. Namena ovog rada je da ponudi pregled informacija o postupcima proračuna i da prikaže mogućnosti i ograničenja postupaka prognoziranja za predviđanja radnog veka čeličnih žičanih užadi u eksploataciji.Very high strength enables wire ropes to support large tensile forces and to run over sheaves with relative small diameters. Very high strength steel wires had already been in existence for more than a hundred years when patenting, a special heating process was introduced and the drawing process improved. Since then, further improvements have only occurred in relatively small steps. Wire ropes always have a limited service life. Therefore they must be inspected and examined at regular intervals so that they are replaced well before failure. End-users of machinery with steel wire ropes, however, would like to have a rough estimation of the service life of the ropes already in the early stages of conceiving their machines, so that they can, if necessary, improve the revving system. This is one of the reasons why for many years extensive research is carried out in order to improve calculations for predicting the service life of wire ropes. This paper is meant to offer an overview information on the method of calculation and to demonstrate the potential and limitations of the forecasting procedure for service-life prediction of running steel wire ropes