Experimental and numerical thermo - mechanical analysis of friction stir welding of high - strength alluminium alloy

This paper presents experimental and numerical analysis of the change of temperature and force in the vertical direction during the friction stir welding of high-strength aluminium alloy 2024 T3. This procedure confirmed the correctness of the numerical model, which is subsequently used for analysis of the temperature field in the welding zone, where it is different to determine the temperature experimentally. 3D finite element model is developed using the software package Abaqus; arbitrary Lagrangian-Eulerian formulation is applied. Johnson-Cook material law and Coulomb's Law of friction are used for modelling the material behaviour. Temperature fields are symmetrical with respect to the welding line. The temperature values below the tool shoulder, i.e. in the welding zone, which are reached during the plunge stage, are approximately constant during the entire welding process and lie within the interval 430-502 degrees C. The temperature of the material in the vicinity of the tool is about 500 degrees C, while the values on the top surface of the welding plates (outside the welding zone, but close to the tool shoulder) are about 400 degrees C. The temperature difference between the top and bottom surface of the plates is small, 10-15 degrees C

Stress Analysis of a Pipeline as a Hydropower Plant Structural Element

This paper describes pipeline stress analysis, primarilybranch junctions, as a structural element in hydro-power plants. Pipelines are exposed to internal pressure,which is present under working conditions. Analysis of stresses in the pipeline of the hydropower plant is based on analytical, numerical, and experimental methods In this paper, we will define the critical elements of the pipeline. After that, we will determine critical areas in the branch junction, under experimental conditions, where strain gauges should be installed. The obtained resultsshow that a boiler formula can be efficiently applied in the stress analysis. Also, a correlation between the internal pressure and the maximum circumferential stresses in the elastic zone is given. In the final sections of the paper, the limit value of the internal pressure as a load for which stress in the zone of plasticity appears and the safety factor of the branch junction in the exploitation conditions are determined. The contribution of this work is the unification and deepening of the topic related to the problem of the testing othydro-power structural elements

Stress Analysis of a Pipeline as a Hydropower Plant Structural Element

This paper describes pipeline stress analysis, primarilybranch junctions, as a structural element in hydro-power plants. Pipelines are exposed to internal pressure,which is present under working conditions. Analysis of stresses in the pipeline of the hydropower plant is based on analytical, numerical, and experimental methods In this paper, we will define the critical elements of the pipeline. After that, we will determine critical areas in the branch junction, under experimental conditions, where strain gauges should be installed. The obtained resultsshow that a boiler formula can be efficiently applied in the stress analysis. Also, a correlation between the internal pressure and the maximum circumferential stresses in the elastic zone is given. In the final sections of the paper, the limit value of the internal pressure as a load for which stress in the zone of plasticity appears and the safety factor of the branch junction in the exploitation conditions are determined. The contribution of this work is the unification and deepening of the topic related to the problem of the testing othydro-power structural elements

Analysis of causes of degradation of parent material and weld metal of breeches pipe at hydro power plant 'Perućica'

Presented are results of non-destructive tests performed on the parent material and welded joints of structural parts of a breeches pipe (collar and anchor), and results of destructive tests performed on the parent material of the anchor. Non-destructive testing included visual (VT), mag-netic particle (MT), and ultrasonic testing (UT), while destructive tests included determination of chemical com-position, tensile properties, impact energy and hardness. Based on test results it is established that the major cause for the occurrence of damage in the carrying structure of the breeches pipe no.1 of pipeline III, or in other words, the degradation of anchor parent material and welded joints between the collar and anchor, and between the pipeline and anchor, is in the fact that the breeches pipe started to lean, not on the collar, as specified by design, but on the anchor that could not endure all loads occurring in service

Analysis of causes of degradation of parent material and weld metal of breeches pipe at hydro power plant 'Perućica'

Presented are results of non-destructive tests performed on the parent material and welded joints of structural parts of a breeches pipe (collar and anchor), and results of destructive tests performed on the parent material of the anchor. Non-destructive testing included visual (VT), mag-netic particle (MT), and ultrasonic testing (UT), while destructive tests included determination of chemical com-position, tensile properties, impact energy and hardness. Based on test results it is established that the major cause for the occurrence of damage in the carrying structure of the breeches pipe no.1 of pipeline III, or in other words, the degradation of anchor parent material and welded joints between the collar and anchor, and between the pipeline and anchor, is in the fact that the breeches pipe started to lean, not on the collar, as specified by design, but on the anchor that could not endure all loads occurring in service

Determination of internal pressure value causing pipe branch model to plastically deform

Složenost geometrije posuda pod pritiskom obično predstavlja uzrok pojave koncentracije napona i deformacija. Savremeni pristup analize stanja napona i deformacija uključuje numerička i eksperimentalna ispitivanja. Svako eksperimentalno testiranje na realnoj konstrukciji može ugroziti samu konstrukciju. Stoga, pravljenje modela neke konstrukcije ima velike prednosti. Umanjeni model račve A6 trećeg cevovoda na HE Perućica, Nikšić je izrađen kako bi bio podvrgnut detaljnom eksperimentalnom testiranju. Cilj je bio da se odredi vrednost unutrašnjeg pritiska koji dovodi do plastične deformacije na modelu račve i da se ovi rezultati koriste za određivanje pritiska koji će stvarnu konstrukciju dovesti do plastičnog deformisanja bez ikakvih merenja na samoj konstrukciji. Eksperimentalna merenja su sprovedena metodom mernih traka. Merne trake su pozicionirane na kritične zone. Numerički model i rezultati dobijeni metodom konačnih elemenata (FEM) potvrđeni su eksperimentalnim rezultatima (u oblasti elastičnosti). Nakon verifikacije u elastičnoj oblasti, povećanjem pritiska, eksperimentalno određena je kritična vrednost unutrašnjeg pritiska koji je izazvao plastičnu deformaciju modela račve. Na osnovu ponašanja modela račve i nakon određivanja odnosa između modela i stvarne konstrukcije, procenjuje se maksimalna izračunata vrednost unutrašnjeg pritiska na koju se realna konstrukcija može izložiti. Pored toga, slabe tačke na konstrukciji su potvrđene dobijanjem istih rezultata kroz eksperiment i proračun, što daje dobre smernice za praćenje ove konstrukcije tokom eksploatacije, s obzirom na to da je ovakvom analizom moguće smanjiti broj mernih mesta za praćenje (u smislu da se kontrolišu tačno ona merna mesta koja su se pokazala kao najkritičnija).Complexity of pressure vessels geometry usually causes stress and strain concentrations. Modern approach of stress and strain analysis involves numerical and experimental testing. Every experimental testing on the construction could endanger construction itself. Therefore, making a model of the construction has great benefits. Sub-sized model of the pipe branch of A6 third pipeline at Hydropower Plant Perućica, Nikšić was made in order to be subjected to a detailed experimental testing. The aim was to determine internal pressure value causing pipe branch model to plastically deform, and, to use these results for determining pressure causing real structure to plastically deform, without any measurements on the structure itself. Experimental measurements were carried out using strain gauge method. Strain gauges are positioned in critical zones. Numerical pipe branch model and results obtained by using finite element method (FEM) was verified with experimental results (in elasticity area). After verification in elastic area, experimentally by increasing pressure value, critical internal pressure causing plastic deformation of pipe branch model was determined. Based on the pipe branch model behaviour, and after determination of relation between the model and the real structure, maximum calculated internal pressure value to which the structure may be subjected in exploitation is assessed. Besides, weak spots on the structure were verified by obtaining the same results through experiment and calculation, which gives good guidelines for monitoring of this structure during usage, since it is possible, by using this analysis, to decrease the number of measurement locations for monitoring (in order to control exactly those measurement locations, which proved to be the most endangered)

Analysis of causes of degradation of parent material and weld metal of breeches pipe at hydro power plant 'Perućica'

Presented are results of non-destructive tests performed on the parent material and welded joints of structural parts of a breeches pipe (collar and anchor), and results of destructive tests performed on the parent material of the anchor. Non-destructive testing included visual (VT), mag-netic particle (MT), and ultrasonic testing (UT), while destructive tests included determination of chemical com-position, tensile properties, impact energy and hardness. Based on test results it is established that the major cause for the occurrence of damage in the carrying structure of the breeches pipe no.1 of pipeline III, or in other words, the degradation of anchor parent material and welded joints between the collar and anchor, and between the pipeline and anchor, is in the fact that the breeches pipe started to lean, not on the collar, as specified by design, but on the anchor that could not endure all loads occurring in service

Characterisation of biocompatible layers of ZrO28%Y2O used in combination with other ceramics to modify the surface of implants

The aim of this study was to deposit multi-functional ZrO28%Y2O3 coating layers using the plasma spray technology and then to characterise such layers. In combination with other biomedical ceramics, this coating is intended for the application in implant surface modification. The examination was focused on the mechanical properties and microstructure layers. Using the atmospheric plasma spraying, duplex ZrO28%Y2O3/Ni22Cr10Al1Y coating system was deposited on the X15Cr13 stainless steel, with two different thicknesses of the bond and ceramic coatings. The microstructure was analysed using an optical microscope, including the assessment of the content of micropores. The morphology of powder particles and ceramic coating surfaces were examined on a scanning electron microscope (SEM). The quality of the ZrO28%Y2O3 layers makes them suitable for the application and combination with other materials to create a system of biomedical or multifunctional coatings

[Characterization of deposited plasma spray nicralcoy2o3 coating layers on almg1 alloy substrates] [Karakterizacija deponovanih slojeva plazma sprej prevlake nicralcoy2o3 na podlogama od legure almg1]

In this paper, analyzed are the effects of the plasma spray distance on the microstructure and mechanical properties of the NiCrAlCoY2O3 coating layers deposited at atmospheric pressure. The microstructure and mechanical properties of the coating layers are under the influence of the interaction of plasma particles (ions and electrons) with powder particles, providing the transfer of velocity and temperature of the plasma particles onto the powder particles. The effect of the interaction is directly dependent on the time the powder particles were present in the plasma which is defined by distance of the plasma gun from the substrate, depending on the granulation of the powder, the melting point and specific gravity. In order to obtain homogeneous and denser coating layers with high adhesion, in the experiment three distances from the substrate were used: 95 mm, 105 mm and 115 mm. The layers were deposited on thin sheets of AlMg1 aluminum thickness of 0.6 mm. Evaluation of mechanical properties of the layers was carried out by examining microhardness using the HV0.1 method and the bond strength by tensile testing. The morphology of the powder particles was examined on the SEM, while the microstructure of the layers was evaluated under a light microscope in accordance with the Pratt Whitney standard. The results of the experiment showed that the distance from the substrate substantially influenced the structure and mechanical properties of the coating layers. The best deposited layers were examined in the system with the ZrO224%MgO ceramic coating, which have proved to be reliable protectionfrom high temperature and abrasive rocket jet fuel

Utjecaj kinematičkih faktora zavarivanja trenjem miješanjem na karakteristike zavarenog spoja kovanih ploča od legure aluminija EN AW 7049 A

U radu se analiziraju utjecaji broja okretaja i brzine zavarivanja na udarnu žilavost, metalografska obilježja i raspodjelu mikrotvrdoće po površini poprečnog presjeka FSW zavarenog spoja kovanih ploča od visokočvrste legure aluminija faznog sastava Al-Zn-Mg-Cu. Broj okretaja je mijenjan u rasponu od 750 min−1 do 850 min−1, a brzina zavarivanja od 60 mm/min do 80 mm/min. Razdvajanjem energije inicijacije pukotine od energije potrebne za njezinu propagaciju, uočava se da je čak i do tri puta veća vrijednost energije koja je potrebna za njezinu propagaciju. Odnos energije inicijacije i energije propagacije je dobiven ispitivanjem Charpy epruvete sa zarezom u središtu, lijevo i desno od središta metala šava 4 mm u smjeru suprotnom od smjera zavarivanja. Distribucija mikrotvrdoće metala šava ne pokazuje veliko rasipanje vrijednosti bez obzira da li je mjerno mjesto u gornjoj ili donjoj razini površine zavarivanih komada. Na mikrograficima jasno se uočavaju zone strukturnih sadržaja zavarenog spoja na osnovi veličine zrna i linija tečenja materijala.In this paper, the influence of rotation speed and welding speed on the impact strength, microstructure and cross section micro hardness of FSW welded joints of Al-Zn-Mg-Cu high strength aluminium alloy is studied. Rotation speed was varied from 750 min−1 to 850 min−1 and welding speed from 60 mm/min to 80 mm/min. It was found that the energy of crack propagation is up to three times higher than the energy of crack initiation. This ratio was found by testing the Charpy notched specimens taken from left and right from the weld centre, 4 mm from the notch in a direction opposite to a direction of welding. Micro hardness distribution in the nugget does not show large dissipation of value regardless if the measuring point is in the upper or lower section of the nugget. Weld microstructure characteristics and zones are clearly defined at the basis of grain size and material flow