Numerical and Experimental Investigations of Fracture Behaviour of Welded Joints with Multiple Defects

Current standards related to welded joint defects (EN ISO 5817) only consider individual cases (i.e., single defect in a welded joint). The question remains about the behaviour of a welded joint in the simultaneous presence of several different types of defects, so-called multiple defects, which is the topic of this research. The main focus is on defects most commonly encountered in practice, such as linear misalignments, undercuts, incomplete root penetration, and excess weld metal. The welding procedure used in this case was metal active gas welding, a common technique when it comes to welding low-alloy low-carbon steels, including those used for pressure equipment. Different combinations of these defects were deliberately made in welded plates and tested in a standard way on a tensile machine, along with numerical simulations using the finite element method (FEM), based on real geometries. The goal was to predict the behaviour in terms of stress concentrations caused by geometry and affected by multiple defects and material heterogeneity. Numerical and experimental results were in good agreement, but only after some modifications of numerical models. The obtained stress values in the models ranged from noticeably lower than the yield stress of the used materials to slightly higher than it, suggesting that some defect combinations resulted in plastic strain, whereas other models remained in the elastic area. The stress-strain diagram obtained for the first group (misalignment, undercut, and excess root penetration) shows significantly less plasticity. Its yield stress is very close to its ultimate tensile strength, which in turn is noticeably lower compared with the other three groups. This suggests that welded joints with misalignment and incomplete root penetration are indeed the weakest of the four groups either due to the combination of the present defects or perhaps because of an additional unseen internal defect. From the other three diagrams, it can be concluded that the test specimens show very similar behaviour with nearly identical ultimate tensile strengths and considerable plasticity. The diagrams shows the most prominent yielding, with an easily distinguishable difference between the elastic and plastic regions. The diagrams are the most similar, having the same strain of around 9% and with a less obvious yield stress limit

Etiopathogenesis of abomasal displacement in cattle

Abomasal displacement presents topographic gastropathy, where this organ has changed its position, and there is simultaneous dilatation which can vary in intensity. The incidence of this disorder in herds of high-yield dairy cows varies to a great degree (1 to 18 %). Abomasal displacement was established in herds of East-Frisian cows in 1 to 3% animals, and in Holstein cow herds in 5 to 18 % animals. The most frequent abomasal displacement is to the left (88%). There is significant seasonal variation in the incidence of abomasal displacement. About two-thirds of cases of abomasal displacement are diagnosed from October until April. The disorder appears more frequently in cows with repeated lactations. It has been established that it appears after the first calving in 27.8% cases, after the second to fifth calving in 66.7% cases, and after the sixth and seventh calving in 5.5% of the cows. The response of endocrine pancreas B-cells for insulin secretion to hyperglycaemia caused by applying an excess-glucose test is reduced in cows with left abomasal displacement, and there is constant hyperglycaemia in cows with right abomasal displacement. The excess-glucose test indicates a disrupted function of the endocrine pancreas in diseased animals. It has been determined through examinations of Aml genotypes in Holstein cow herds in connection with the appearance of abomasal displacement, that the occurrence of this disorder cannot be attributed to a genetic predisposition

Numerical and Experimental Investigations of Fracture Behaviour of Welded Joints with Multiple Defects

Current standards related to welded joint defects (EN ISO 5817) only consider individual cases (i.e., single defect in a welded joint). The question remains about the behaviour of a welded joint in the simultaneous presence of several different types of defects, so-called multiple defects, which is the topic of this research. The main focus is on defects most commonly encountered in practice, such as linear misalignments, undercuts, incomplete root penetration, and excess weld metal. The welding procedure used in this case was metal active gas welding, a common technique when it comes to welding low-alloy low-carbon steels, including those used for pressure equipment. Different combinations of these defects were deliberately made in welded plates and tested in a standard way on a tensile machine, along with numerical simulations using the finite element method (FEM), based on real geometries. The goal was to predict the behaviour in terms of stress concentrations caused by geometry and affected by multiple defects and material heterogeneity. Numerical and experimental results were in good agreement, but only after some modifications of numerical models. The obtained stress values in the models ranged from noticeably lower than the yield stress of the used materials to slightly higher than it, suggesting that some defect combinations resulted in plastic strain, whereas other models remained in the elastic area. The stress-strain diagram obtained for the first group (misalignment, undercut, and excess root penetration) shows significantly less plasticity. Its yield stress is very close to its ultimate tensile strength, which in turn is noticeably lower compared with the other three groups. This suggests that welded joints with misalignment and incomplete root penetration are indeed the weakest of the four groups either due to the combination of the present defects or perhaps because of an additional unseen internal defect. From the other three diagrams, it can be concluded that the test specimens show very similar behaviour with nearly identical ultimate tensile strengths and considerable plasticity. The diagrams shows the most prominent yielding, with an easily distinguishable difference between the elastic and plastic regions. The diagrams are the most similar, having the same strain of around 9% and with a less obvious yield stress limit

Numerical simulation of welded joint with multiple various defects

The paper presents continuation of extensive work on determining the behaviour of welded joints in the presence of multiple various types of defects, a problem that is not sufficiently covered by existing standards, such as EN ISO 5817 series. The research involves the development of numerical models, based on real geometries of welded joints made of typical structural steel S235JR, along with experimental tests that would verify the models, and provide additional insight into the behaviour of the welded structure under such unusual conditions. For this purpose, welding defects most likely to occur in practice are selected, and a number of their combinations is produced intentionally in welded plates. The goal of the numerical models is to determine the most critical locations in terms of stresses, and to analyse their integrity in the presence of cracks. While the experiments did validate the majority of numerically obtained results, there are certain unexpected differences. This provides the authors with additional goals of determining why these differences occur. For this purpose, additional destructive tests are performed, revealing the cause behind the disagreement between real and numerical results, while also confirming authors' suspicions

Numerical simulation of welded joint with multiple various defects

The paper presents continuation of extensive work on determining the behaviour of welded joints in the presence of multiple various types of defects, a problem that is not sufficiently covered by existing standards, such as EN ISO 5817 series. The research involves the development of numerical models, based on real geometries of welded joints made of typical structural steel S235JR, along with experimental tests that would verify the models, and provide additional insight into the behaviour of the welded structure under such unusual conditions. For this purpose, welding defects most likely to occur in practice are selected, and a number of their combinations is produced intentionally in welded plates. The goal of the numerical models is to determine the most critical locations in terms of stresses, and to analyse their integrity in the presence of cracks. While the experiments did validate the majority of numerically obtained results, there are certain unexpected differences. This provides the authors with additional goals of determining why these differences occur. For this purpose, additional destructive tests are performed, revealing the cause behind the disagreement between real and numerical results, while also confirming authors' suspicions

Finite element analysis of effects of multiple defects on welded joint integrity

Navedeni su: Editors [http://www.ssm.kg.ac.rs/congress_2021] COBISS.SR-ID 4150810

Etiopatogeneza promene položaja sirišta goveda

Abomasal displacement presents topographic gastropathy, where this organ has changed its position, and there is simultaneous dilatation which can vary in intensity. The incidence of this disorder in herds of high-yield dairy cows varies to a great degree (1 to 18 %). Abomasal displacement was established in herds of East-Frisian cows in 1 to 3% animals, and in Holstein cow herds in 5 to 18 % animals. The most frequent abomasal displacement is to the left (88%). There is significant seasonal variation in the incidence of abomasal displacement. About two-thirds of cases of abomasal displacement are diagnosed from October until April. The disorder appears more frequently in cows with repeated lactations. It has been established that it appears after the first calving in 27.8% cases, after the second to fifth calving in 66.7% cases, and after the sixth and seventh calving in 5.5% of the cows. The response of endocrine pancreas B-cells for insulin secretion to hyperglycaemia caused by applying an excess-glucose test is reduced in cows with left abomasal displacement, and there is constant hyperglycaemia in cows with right abomasal displacement. The excess-glucose test indicates a disrupted function of the endocrine pancreas in diseased animals. It has been determined through examinations of Aml genotypes in Holstein cow herds in connection with the appearance of abomasal displacement, that the occurrence of this disorder cannot be attributed to a genetic predisposition.Dislokacija sirišta predstavlja topografsku gastropatiju, pri kojoj postoji promena položaja ovog organa, a istovremeno i dilatacija koja može da ima različit intenzitet. U zapatima visoko-mlečnih krava pojavljivanje bolesti varira u širokom rasponu (od 1 do 18 %). U zapatima krava istočno-frizijske rase dislokacija sirišta je dijagnostikovana u 1 do 3 posto životinja, a u zapatima krava holštajn rase ustanovljena je kod 5 do 18 posto životinja. NajčešćI oblik dislokacije sirišta je promena položaja na levu stranu (88 %). Postoji značajno sezonsko variranje u pogledu pojavljivanja dislokacije sirišta. Oko dve trećine slučajeva dislokacije sirišta dijagnostikuje se od oktobra do aprila. Bolest se češće javlja kod krava sa više laktacija. Tako je utvrđeno da se kod prvotelkinja pojavljuje kod 27,8 posto, od drugog do petog teljenja kod 66,7 posto, a posle šestog odnosno sedmog teljenja kod 5,5 posto krava. Odgovor ćelija endokrinog pankreasa za lučenje insulina na nastalu hiperglikemiju, pri primeni probe opterećenja glikozom, smanjen je kod krava kod kojih postoji promena položaja sirišta na levo, a kod promena položaja sirišta na desno postoji stalna hiperglikemija. Primenjena proba opterećenja glikozom ukazuje na poremećaj funkcije endokrinog pankreasa kod obolelih životinja. Ispitivanjem AmI genotipova u zapatu krava holštajn rase u odnosu na pojavljivanje dislokacije sirišta utvrđeno je da nastanak ove bolesti ne može da se pripiše genetskoj predispoziciji

The effects of supplementing diet with bacillus cereus on performance and carcass yield of broilers

The aim of this study was to examine alternative substances which could have the capability to replace antimicrobial growth promoters in feed for broilers. The 42-day long trial was performed on 100 days-old Arbor Acres broilers divided into two groups. Both groups of broilers were offerred a commercial feed mixture, while Paciflor C.10 ® (Hoechst - Intervet) was added in the amount of 0,10 and 0,05 kg/t of starter and finisher feed for the second group. Paciflor ® contains Bacillus cereus IP 5832 in the amount of 1010 CFU/g. Broilers of the control group had an average daily gain (ADG) of 48,86±6,80 g and a feed:gain ratio (FGR) of 2,17 kg with carcass yield of 72,2 %. The inclusion of direct-fed microbials (DFM) significantly increased ADG by 1,59 % and imporoved FGR and carcass yield by 1,84 and 0,42 % respectively. It is interesting to underline that supplementing the diet with DFM had only mild positive effects on ADG in the first two phases while a stronger influence was expressed on FGR. Better efficiency is probably due not only to the healthier composition of gut microflora, but to longer microvilli of the gut epithelium with consequently improved resorption of nutrients. The obtained results suggest that direct-fed microbials have the potential to replace, at least to a certaint antibiotics as feed additives

Experimental Determining of Paris Law Coefficients for Steel P460nl1 Welded Joint Specimens

In this paper, the results of determining the Paris law coefficients, C and m, is presented, based on the experimental data obtained by three-point bending testing of welded joint specimens made of P460NL1 steel, with VAC 65 wire used as the filler material. The specimens were made with a 1.4 mm notch in the heat affected zone. After the fatigue crack growth tests performed using the Fractomat 7609/213 (RUMUL), the obtained crack growth rate vs. number of cycles (da/dN vs. N) diagrams were used to calculate the coefficients, for the purpose of using them in numerical simulations that will follow