Stress state around imperfections in welded joints

Because of their geometry, welded joints can cause a local increase of stress. In the presence of imperfections in welded joints the local stress additionally increases and can lead to the formation of cracks. Cracks are detected in the welded joint during testing of pressure equipment in service, and the stress state around imperfections is analysed by finite element method. It is concluded that even the imperfections that are acceptable for the highest level of quality, according to the standard SRPS EN ISO 5817, may cause significant higher local stresses than stresses predicted in the design of the structure

France and Serbia (1860-1868) ; La France et la Serbie de 1860 à 1868

Везе Француске и Србије дубоко су уткане у међународне односе и Источно питање. Од кључне важности за развој француско-српских односа 60-их година XIX века су односи Француске са великим силама – Русијом и Аустријом. Став званичног Париза према Кнежевини посматран je кроз призму француско-аустријских и француско-руских односа и политике ових сила према Балкану, у зависности од њихових интереса у другим чворним темама спољне политике. У раду је анализирана улога Француске у Источном питању у време Наполеона III. Разматране су идеје француског цара (наполеоновске идеје) и начело народности као основно средство спољне политике Другог царства. Повратак Обреновића у Србију 1859. године обележава почетак интензивне националне и дипломатске делатности. Присутни су тежња за ослобођењем Србије од аустријског и руског утицаја и тражење ослонца у Француској за спровођење ове политике. Илија Гарашанин, председник владе у најдужем периоду владавине кнеза Михаила, био је главни носилац француског утицаја у Кнежевини. Његовој делатности је посвећена дужна пажња, уз осврт на главне смернице политике Србије према Француској садржане у Начертанију и прве покушаје у успостављању француско-српских односа у периоду пре Кримског рата. Потреба за потпунијом обрадом теме наметнула је истраживање периода друге владе кнеза Милоша (1859-1860)...The French-Serbian ties are deeply woven into international relations and the Eastern Question. The French relations with big powers – Russia and Austria are of key importance for the development of the French-Serbian relations during sixties of XIX century. The position of the official Paris towards The Principality is viewed through the prism of the French-Austrian and French-Russian relations and the policies of these powers towards the Balkans, depending on their interests in other main subjects of external policy. The dissertation analyzes the role of France in the Eastern Question during Napoleon III. It considers the ideas of the French emperor (Napoleonic ideas) and the principle of nationality as a basic instrument of external policy of the Second French Empire. The return of Obrenovićs to Serbia in 1859 marks the beginning of intensive national and diplomatic activities. There are aspirations to free Serbia from the Austrian and Russian influence and efforts to find support in France for carrying out the policy. Ilija Garasanin, the Prime Minister during the most period of the Prince Mihailo rule, was the central advocate of the French influence in the Principality. His activities received due attention, with a review of key guidelines of Serbian policy towards France included in Nacertanije and with initial attempts in establishing the French-Serbian relations in the period before the Crimean War. The need to treat the subject more thoroughly imposed a research of period of the second government of Prince Miloš (1859-1860)..

Stress state around imperfections in welded joints

Because of their geometry, welded joints can cause a local increase of stress. In the presence of imperfections in welded joints the local stress additionally increases and can lead to the formation of cracks. Cracks are detected in the welded joint during testing of pressure equipment in service, and the stress state around imperfections is analysed by finite element method. It is concluded that even the imperfections that are acceptable for the highest level of quality, according to the standard SRPS EN ISO 5817, may cause significant higher local stresses than stresses predicted in the design of the structure

Integrity assessment of tanks with microcracks in welded joints

Tokom eksploatacije rezervoara za skladištenje tečnog ugljendioksida ukazala se potreba za ugradnjom dva nova priključka u jedno od danaca. Rezervoar je izrađen od mikrolegiranog čelika, a priključci od visokolegiranog austenitnog čelika. Za izradu novih priključaka izabrani su isti dodatni materijali i ista tehnologija zavarivanja, koji su korišćeni i pri izradi rezervoara. Ispitivanjima metodama bez razaranja zavarenih spojeva novih priključaka otkrivene su mikroprsline u zoni uticaja toplote mikrolegiranog čelika. Primenom postupka prikazanom u standardu BSI PD 6493 'Uputstvo za ocenu prihvatljivosti grešaka u zavarenim konstrukcijama', ocenjen je uticaj ovih mikroprslina na integritet zavarenih spojeva novih priključaka i time i na integritet rezervoara.During the exploitation of tanks used for storing liquid carbon dioxide there was a need to install two new connectors on one of the lids. The tank is made of micro-alloyed steel and its connectors are made of high-alloyed austenite steel. The same welding technology and added materials are used for both the tank and connectors. Non-destructive testing methods of welded joints in new connectors revealed microcracks in the heat-affected zone of micro-alloyed steel. By applying the procedure given in standard BSI PD 6493 'Manual for assessment of acceptability of flaws in welded structures', it is possible to estimate the effect of these microcracks on the integrity of welded joints in new connectors, and therefore their effect on the integrity of the tank

Evaluation of the Locking Compression Plates Stress-Strain Fields

Locking Compression Plates (LCP) have found application in the orthopaedic healing process in modern medicine. Their design is specifically modified depending on the bone and the loading the specific bone is subjected to. Dimensions of LCP, as well as mechanical characteristics, provide greater structural resistance than the bone itself; in practice, however, continuous application and cyclic loading can lead to fails and fractures. Defining of the testing approaches and procedures used for the evaluation of the stress and location of geometrical areas with potential risk of the stress concentration represent the aim of this investigation. Results obtained in this paper show that combined use of modern experimental methods (DIC) and numerical simulations on the modified and simplified LCP geometry, can be used to locate stress and strain fields, as well as areas with stress concentration that can result in the appearance of cracks during cyclic loading

Elastic-plastic behaviour of welded joints during loading and unloading of pressure vessels

In this paper elastic-plastic behaviour of welded joints during loading and unloading of pressure vessel has been analysed. Two stage pressuring process has been applied in previous experimental investigation and simulated using the finite element method. The effect of residual stress and strain has been analysed

Numerical analysis of stress distribution in total hip replacement implant

Total hip replacement implants represent permanent implants and require large bone and cartilage removal during implantation. Revision would affect joint capability to sustain load, which makes this procedure irreversible. During exploitation, i.e. everyday activities, implants are subjected to dynamic loading. Thereby, these structures are prone to failure by fatigue. Highest stress states on total hip replacement implants are present in the neck area of the implant, which is a position of crack initiation. Under loading the implant neck exhibits tension and compression zones. Crack initiation in the neck side under tension would lead to crack opening and certain fracture. Implants are examined by experimental and numerical methods. The most common numerical method is finite element method (FEM) used to simulate different loading conditions. In this paper numerical analysis of stress distribution in the neck area is performed on a specific implant. Four numerical models are created in order to show how certain design solutions influence the stress distribution in the neck area

Numerical analysis of stress distribution in total hip replacement implant

Total hip replacement implants represent permanent implants and require large bone and cartilage removal during implantation. Revision would affect joint capability to sustain load, which makes this procedure irreversible. During exploitation, i.e. everyday activities, implants are subjected to dynamic loading. Thereby, these structures are prone to failure by fatigue. Highest stress states on total hip replacement implants are present in the neck area of the implant, which is a position of crack initiation. Under loading the implant neck exhibits tension and compression zones. Crack initiation in the neck side under tension would lead to crack opening and certain fracture. Implants are examined by experimental and numerical methods. The most common numerical method is finite element method (FEM) used to simulate different loading conditions. In this paper numerical analysis of stress distribution in the neck area is performed on a specific implant. Four numerical models are created in order to show how certain design solutions influence the stress distribution in the neck area

Cracking due to repair welding of the treiber roll

Repair welding has caused crack initiation in the upper Treiber roll in the steel works plant mill at Zelezara in Smederevo. The upper and lower Treiber rolls serve the purpose of folding and directing rolled metal strips, supplied by the output rollers to the coiling mandrel. The parent material of the upper Treiber roll is S235JO. Unsuccessful welding resulted in a series of further activities to remove cracks. In addition, the cracks are identified on the Treiber roll for easier designation and monitoring while machining. Hardness tests have been performed on specific locations within the welded hard layer. After machining and removal of the whole welded layer with defects, it is determined that the welding activities contributed to the occurrence of a number of cracks in the parent material, which did not exist prior to surfacing. Hence, steps that need to be taken in order to eliminate these cracks in the parent material are suggested at the end of this paper

Low-temperature corrosion damage and repair of boiler bottom panel tubes

The method used for repairing of the bottom panel of hot water boiler of 30 MW power, manufactured by Remming (a part of the 'Valjevo' Heating Plant) is presented in this paper along with the reasons why damage has occurred. The damage appeared on bottom panel as a consequence of service conditions to which the boiler was subjected. It has resulted in the thinning of tube walls in the bottom panel. Low-temperature has been determined as the cause of the tube damage, i.e. due to the presence of sulphuric acid. For the purpose of damage analysis and proper selection of the repair welding technology, the first tube wall measurements were performed in the boiler bottom panel. Upon determining the necessary repairs, and due to damages not originally included, the wall thickness tests are repeated and microstructural analysis by metallographic replica testing (for one tube) is performed. No major microstructural defects typically caused by exploitation conditions have been detected on the examined screen tube surface. The repair welding procedure which involved replacing of the bottom panel is also shown, along with suggestions for further damage prevention. Repair welding is performed using MAG welding procedure, combined with gas welding