Prompt system redesign: Shifting to open source technology to satisfy user requirements

The paper describes a redesign project undertaken in a short period to adapt a software system to user needs. Additional goals of the project included a shift to Open Source software and the selection of technology to enable sustainable system development. The paper chronologically describes all phases of the project and provides reasons for all decisions taken during the development process. The paper concludes with a discussion of the merits of the redesign methodology

Chronology of lost structural integrity initiated from manufacturing defects in welded structures

U različitim vremenskim periodima dolazilo je do gubitka integriteta zavarenih konstrukcija zbog razvoja proizvodnih grešaka zavarenog spoja. Mehanizmi otkaza su bili različiti i uvek su predstavljali novo iskustvo, koje je zahtevalo nova znanja i drugačiji pristup u rešavanju problema. Opsežne analize svih otkaza razmatranih u radu i izvedeni zaključci ipak nisu dovoljni da se potpuno izbegnu proizvodne nesavršenosti i obezbedi integritet zavarenih konstrukcija u eksploataciji. Direktive, standardi i preporuke za izradu zavarenih konstrukcija značajno doprinose rešavanju problema, ali ga ne mogu potpuno eliminisati zbog složenosti i velikog broja uticajnih faktora.At different time periods, loss in structural integrity occurs from initiation of manufacture defects in the welded joint. Failure mechanisms are different and present a new experience always requiring new knowledge and approach in solving the problem. Extended analyses of all failures considered here and derived conclusions are yet not sufficient in completely avoiding manufacture imperfections and assuring in-service integrity of welded structures. Directives, standards and recommendations for manufacturing welded structures significantly contribute in problem solving which they cannot completely eliminate due to the complexity and numerous influencing factors

Cold weld cracking susceptibility of high strength low alloyed (hsla) steel nionikral 70

In view of the importance of high strength low alloy (HSLA) steels, particularly for critical applications such as offshore platforms, pipeline and pressure vessels, this paper reports on an investigation of how to weld this type of steel without cold cracking. Using manual metal arc welding process and Tekken test (Y - Grove test) has been caned Out both to observe the cold cracking phenomenon, and to investigate the influencing factors, such as preheating temperature and energy input, as well as electrode strength and diameter. However the result of the experiments show that there is a risk of cold cracking

Future Armoured Troop Carrying Vehicles

Present-day reliance on wheeled and tracked armour personnel carriers (APCs) and infantry fighting vehicles (IFVs), may be changed in the future. Shaped charge grenades and impovised explosive devices (IEDs)represent a considerable threat, even to well protected main battle tanks (MBTs). Paradoxically, the crew of wheeled and tracked troop-carrying vehicles is numerically three to four times larger than that of MBTs, however, their protection in all aspects is significantly lower. Therefore, heavier vehicles may get more attention in the future, where sharing the chassis and a number of components with MBTs could provide significant reductions in procurement costs and maintenance, as well as a simplified logistics in relation to the latest tracked. Obviously, the IFVs mobility of heavy vehicles would be lower than that of lighter vehicles. However, by applying various degrees of modular armour protection, a significant rise in strategic, operational, and tactical mobility could be achieved. Such heavy tracked vehicles, built on a common chassis as MBTs, may equip the future heavy brigades, which will be in contrast to the lighter wheeled vehicles included in rapid deployment brigades. As a result, tracked personnel carrying vehicles may extinct in the future.Defence Science Journal, 2010, 60(5), pp.483-490, DOI:http://dx.doi.org/10.14429/dsj.60.55

Structural integrity assessment of pressure vessels with defect in welded joints

U radu su prikazani primeri primene parametara mehanike loma za procenu integriteta posuda pod pritiskom sa prslinom. Primena parametara mehanike loma zavisi od niz podataka, pre svega o ponašanju materijala u prisustvu greške, uticaju okoline i opterećenja. U uslovima dominantnog statičkog opterećenja, ponašanje materijala sa greškom može biti opisano kao linearno-elastično, i bazira se na faktoru intenziteta napona, KI, pri čemu se plastična deformacija zanemaruje, dok u elasto-plastičnom području ponašanje materijala se definiše pomeranjem otvora prsline ili J integralom kao parametrima mehanike loma. Linearno-elastična mehanika loma je primenjena za slučaj cilindričnog rezervoara za komprimovani gas kod koga su primenom metoda bez razaranja otkrivene nedozvoljene greške u zavarenim spojevima prema ISO 5817. Otkrivene greške su svedene na tip prsline u funkciji primene konzervativnog proračuna. Primenom faktora intenziteta napona u proceduri PD 6493 (Uputstvo o metodama izbora nivoa prihvatljivosti grešaka u zavarenim spojevima) se pokazalo da integritet analiziranih rezervoara nije narušen. J integral je primenjen za analizu ponašanja u elasto-platičnom području. Posude pod pritiskom koje su predmet eksperimentalnog rada su izrađene zavarivanjem čelika sa granicom tečenja od 700MPa. Uticaj veličine prsline je određen upoređenjem sile za rast prsline (određena primenom Ratwani-Erdogan-Irwin modela) i eksperimentalno određene krive otpornosti materijala koja je definisan na bazi direktnog merenja J integrala. Teoretska i eksperimentalna analiza ne definiše u potpunosti ponašanje zavarenih spojeva sa prslinom, kao i heterogenu mikrostrukturu u zoni spoja. Zbog toga, numerička analiza može biti korisna ukoliko se primeni na pravi način. U radu je prikazan i primer primene metode konačnih elemenata za analizu zavarenih spojeva.The examples of practical application of fracture mechanics parameters in cracked pressure vessel structural integrity are presented. The application of fracture mechanics depends on available data, material behaviour environmental effect and loading. In predominantly static loading material behaviour can be described as linear elastic, based on the stress intensity factor, KI, when its ductility is negligible, and as elastic-plastic, with crack opening displacement or the J integral as parameters. Linear elastic fracture mechanics was applied in a typical service problem when non-allowable defects according to ISO 5817 had been detected by non-destructive testing in regular in-service inspection in welded joints on the cylindrical storage tanks for pressurized air. The defects have been replaced by corresponding cracks for conservative estimate. Simplified application of the stress intensity factor as a parameter and a two parameter fracture assessment diagram from PD6493 Procedure have shown that structural integrity of the analyzed storage tanks is not endangered. For the detailed elastic-plastic analysis the J integral is used. The experimental pressure vessel was manufactured by welding high strength steel (yield stress 700 MPa) and then precracked artificially for J integral direct measurement. The theoretical and experimental analyses can not fully describe the behaviour of the cracked welded joint and its heterogeneous microstructure. For that purpose, the numerical analysis can be helpful, if applied in a proper way. An example of the finite elements numerical analysis of welded joints is presented

Structural changes at rotation friction welding of various steel types

Korišćenjem metoda optičke mikroskopije, kvantitativne optičke mikroskopije SEM i EDS analize izvršena su ispitivanja strukture, kao i analiza faznog i hemijskog sastava, kod trenjem zavarenih spojeva brzoreznog čelika Č 7680 sa ugljeničnim čelikom za poboljšanje Č 1730.By using the methods of optical microscopy, quantitative optical microscopy SEM and EDS analysis, the tests of structure were carried out, as well as the analysis of both phase and chemical composition, of joints welded by friction of the HSS steel M-2 with carbon steel for improving 1060

Determination of J resistance curve by two points method

Predložen je novi pristup projektovanju krive otpornosti prema prslinama i ispitana mogućnost njegove primene. Pristup se zasniva na opisu JR krive polinomom sa dva koeficijenta. Za određivanje koeficijenta su potrebna dva para vrednosti J integrala i širenja prsline Δa. Jedan od njih je određen eksperimentalno. Usvojeno je da drugi par pripada liniji zatupljivanja, ali su takođe potrebni i dodatni kriterijumi. Razmotrena je mogućnost kako da se uspostave ovakvi kriterijumi za drugi par vrednosti J integrala i širenja prsline Δa. .New approach for crack resistance curve design is proposed and the possibility of its application investigated. The approach is based on JR description by polynomial function with two coefficients. For determining coefficients two pairs of values of J integral and crack extension Δa are necessary. One of them is determined experimentally. It is accepted that the second pair of values belongs to the blunting line, but additional criteria are also required. The possibility to establish these criteria for the second pair of values of J integral and crack extension Δa is considered.

Structural integrity assessment of pressure vessels with defect in welded joints

U radu su prikazani primeri primene parametara mehanike loma za procenu integriteta posuda pod pritiskom sa prslinom. Primena parametara mehanike loma zavisi od niz podataka, pre svega o ponašanju materijala u prisustvu greške, uticaju okoline i opterećenja. U uslovima dominantnog statičkog opterećenja, ponašanje materijala sa greškom može biti opisano kao linearno-elastično, i bazira se na faktoru intenziteta napona, KI, pri čemu se plastična deformacija zanemaruje, dok u elasto-plastičnom području ponašanje materijala se definiše pomeranjem otvora prsline ili J integralom kao parametrima mehanike loma. Linearno-elastična mehanika loma je primenjena za slučaj cilindričnog rezervoara za komprimovani gas kod koga su primenom metoda bez razaranja otkrivene nedozvoljene greške u zavarenim spojevima prema ISO 5817. Otkrivene greške su svedene na tip prsline u funkciji primene konzervativnog proračuna. Primenom faktora intenziteta napona u proceduri PD 6493 (Uputstvo o metodama izbora nivoa prihvatljivosti grešaka u zavarenim spojevima) se pokazalo da integritet analiziranih rezervoara nije narušen. J integral je primenjen za analizu ponašanja u elasto-platičnom području. Posude pod pritiskom koje su predmet eksperimentalnog rada su izrađene zavarivanjem čelika sa granicom tečenja od 700MPa. Uticaj veličine prsline je određen upoređenjem sile za rast prsline (određena primenom Ratwani-Erdogan-Irwin modela) i eksperimentalno određene krive otpornosti materijala koja je definisan na bazi direktnog merenja J integrala. Teoretska i eksperimentalna analiza ne definiše u potpunosti ponašanje zavarenih spojeva sa prslinom, kao i heterogenu mikrostrukturu u zoni spoja. Zbog toga, numerička analiza može biti korisna ukoliko se primeni na pravi način. U radu je prikazan i primer primene metode konačnih elemenata za analizu zavarenih spojeva.The examples of practical application of fracture mechanics parameters in cracked pressure vessel structural integrity are presented. The application of fracture mechanics depends on available data, material behaviour environmental effect and loading. In predominantly static loading material behaviour can be described as linear elastic, based on the stress intensity factor, KI, when its ductility is negligible, and as elastic-plastic, with crack opening displacement or the J integral as parameters. Linear elastic fracture mechanics was applied in a typical service problem when non-allowable defects according to ISO 5817 had been detected by non-destructive testing in regular in-service inspection in welded joints on the cylindrical storage tanks for pressurized air. The defects have been replaced by corresponding cracks for conservative estimate. Simplified application of the stress intensity factor as a parameter and a two parameter fracture assessment diagram from PD6493 Procedure have shown that structural integrity of the analyzed storage tanks is not endangered. For the detailed elastic-plastic analysis the J integral is used. The experimental pressure vessel was manufactured by welding high strength steel (yield stress 700 MPa) and then precracked artificially for J integral direct measurement. The theoretical and experimental analyses can not fully describe the behaviour of the cracked welded joint and its heterogeneous microstructure. For that purpose, the numerical analysis can be helpful, if applied in a proper way. An example of the finite elements numerical analysis of welded joints is presented

Influence of crack on welded joint characteristics in different types of loads

Primena čelika visoke čvrstoće kod projektovanja zavarenih konstrukcija zahteva podatke o svojstvima istih pri različitim uslovima opterećenja. Zahvaljujući visokom naponu tečenja debljina zida može se smanjiti u poređenju sa opštim konstrukcijskim čelicima, a shodno tome, dimenzije zavarenog spoja, potrošnja dodatnog materijala za zavarivanje i vreme za izradu zavarenih spojeva će biti minimizirani. Ovo je od značaja za opremu pod pritiskom, ali i za druge industrijske grane (kranove, bagere). Kompletna karakterizacija zavarenog spoja mora uključiti podatke za osnovni metal, ali takođe su neophodne osobine metala šava i zone uticaja toplote (ZUT), bar da bi ih uporedili sa svojstvima osnovnog metala. Ovo je od posebnog značaja zbog heterogenosti strukture u ZUT-u. .The application of high strength steels in design of heavy duty welded structures requires data about properties in different loading conditions. Thanks to high yield stress the wall thickness can be reduced compared to mild structural steels, and accordingly welded joint cross-sections, welding consumables consumption and time for welded joints manufacturing will be minimized. This is of importance for pressurized equipment, but also for other industrial branches (cranes, excavator). Complete characterization of welded joint has to include data for parent metal, but also the properties for weld metal and the heat-affected-zone (HAZ) are necessary, at least in order to compare them with parent metal properties. This is of special importance because of heterogeneity structure in HAZ

Selection of the optimal filler material for on-site repair welding of the turbine shaft at the hydropower plant

Najznačajniji delovi hidroelektrana, vratila turbina izložena su tokom rada visokim naprezanjima, puzamju, zamoru i koroziji. Zbog toga je korisno preduprediti oštećenja tokom rada, povećati pouzdanost i produžiti radni vek postrojenja. Eksploatacioni uslovi mogu da dovedu do prslina i loma u homogenom materijalu, tako da postoji potreba za reparaturom dela postrojenja. A ona može biti skupa ili dugotrajna. U okolnostima kada se reparatura izvodi na licu mesta, posebno pažljivo treba da se definiše tehnologija reparaturnog zavarivanja, parametri postupka, i izbor dodatnog materijala. U ovom istraživanju izbor dodatnog materijala je bio tema i dati su rezultati. Vratilo je izrađeno od čeličnog liva 20Mn5 i na njemu su metodama IBR, otkrivena oštećenja tipa prslina dužine do 400 mm i dubine do 20 mm. Kako je planirano da se reparatura izvede bez demontaže vratila, primena termičke obrade nije bila izvodljiva. Analiza zavarljivosti osnovnoog materijala urađena je korišćenjem analitičkih jednačina. Rezultati su pokazali da je zavarljivost ovog čelika ograničena. Za reparaturno zavarivanje izabran je postupak REL (111) i dve obložene austenitne elektrode sa ciljem određivanja pogodnosti za upotrebu kao potencijalnih dodatnih materijala za reparaturu. U ovom istraživanju ispitane su Fe-Ni-Cr-Mo elektroda i elektroda na bazi Ni i njihove osobine su upoređene. Ispitivanje zatezanjem, ispitivanje apsorbovane energije, ispitivanje savijanjem, merenje tvrdoće i ispiivanje osetljivosti kao što su 'CTS' i 'Y' probe, izvedeni su na ispitnim spojevima dobijenim zavarivanjem osnovnog materijala, 20Mn5, ispitivanje savijanjem, merenje tvrdoće i ispiivanje osetljivosti kao što su 'CTS' i 'Y' probe izvedeni su na ispitnim spojevima dobijenim zavarivanjem osnovnog materijala, čelika 20Mn5, sa ispitivanim dodatnim materijalima. Dobijeni rezultati su analizirani i na osnovu toga, odabrana je elektroda na bazi Ni kao pogodnija za reparaturno zavarivanje.The most significant components of hydropower plants are turbine shafts and generator rotors which undergo time-dependent processes such as high stresses, creep, fatigue and corrosion. It is therefore desirable to prevent in-service damages, improve reliability and extend the operational life of the plant. Plant operation can lead to cracking and failures in homogeneous materials, therefore a need for repair welding on plant components, which can be expensive and time-consuming, exists. In the circumstances when repair welding has to be carried out on site, special care has to be taken in defining repair welding technology, process parameters and selection of filler materials. In this research a selection of filler materials for repair welding on site of hydropower turbine shaft was performed and results were presented. The shaft was made of the cast steel 20Mn5 and presence of damages in the form of cracks which were up to 400 mm long and up to 20 mm deep was detected through the use of NDT methods. As the repairing was planned to be carried out without disassembling of the shaft, application of heat treatment procedures was not feasible. Weldability analysis of the base material was performed through the use of analytical equations. Results have shown that weldability of this steel is limited. For the repair welding a MMA (111) welding process was selected and two covered austenitic electrodes were analyzed in order to establish the feasibility of their use as potential filler material for repairing. In this research a Fe-Ni-Cr-Mo electrode and Ni based electrode were tested and their properties were compared. Tensile testing, absorbed energies tests, bending tests, hardness measurements and sensitivity tests such as 'CTS' and 'Y' were performed on test joints obtained by welding of base material, 20Mn5 steel, with investigated filler materials. Obtained results were analyzed and a Ni based electrode was selected as most suitable for repair welding