Marius Bodea | Technical University of Cluj-Napoca (original) (raw)
Papers by Marius Bodea
Zavarivanje i zavarene konstrukcije, 2018
Powder Metallurgy and Advanced Materials, 2018
The weldability of the steels represents a problem of great interest in order to achieve welded s... more The weldability of the steels represents a problem of great interest in order to achieve welded structures that satisfy the high requirements on quality, imposed by the nowadays applications. In this paper has been proposed a more advanced model that has considered more factors of weldability influence, thus allowing a more detailed analysis based on the main welding process variables. Introduction Weldability is a general technological property commonly used in engineering, but very difficult to be defined and quantified in an exact manner. The American Welding Society has defined the weldability as being: “The capacity of a metal to be welded under the fabrication conditions imposed with a specific suitability designed structure and to perform satisfactorily in service” [1]. According to DIN 8528, Part 1 the weldability is seen as the output of the interaction of three main group factors, given in Table 1 [2]. Table 1. The weldability’s factors of influence. MATERIAL WELDING SUITA...
Solid State Phenomena, Oct 15, 2014
Materials Science Forum, Mar 1, 2011
Solid State Phenomena, 2014
The mechanical properties of the welded structures are directly related to the weldability of the... more The mechanical properties of the welded structures are directly related to the weldability of the steels, thus the estimation of the microstructural constituents in the weld and maximum hardness in the HAZ according to the welding process parameters represent a problem of great interest. The microstructural changes in the HAZ are estimated using a five-parameter logistic function (5PL), which is very accurate in the fitting highly asymmetric data. Also, the same 5PL function can be used in order to predict hardness and toughness in the HAZ based on the heat flow, cooling rates between 800-500 oC and chemical composition of the material. A discussion about the parameters of the 5PL function and fitting experimental data is presented and a studied case for welding S355J2 steel plates is also analyzed.
Materials Science Forum, 2011
Archives of Metallurgy and Materials, 2000
Improving Mechanical Properties of Sintered Wolfram Based Alloy with Liquid Phase Trough Controll... more Improving Mechanical Properties of Sintered Wolfram Based Alloy with Liquid Phase Trough Controlled Cooling ParametersHeavy alloys with 90 and 93 w/o W and a 7:3 Ni: Fe ratio are usually produced by the liquid phase sintering of W, Ni, and Fe powder mixtures. The result is a two-phase microstructure of spherical W solid solution grains embedded in a matrix of Ni rich solid solution. UTS, elongation, and microstructure strongly depend on the composition of the atmosphere during liquid phase sintering, on the cooling conditions and/or on the composition of the protective atmosphere during the heat treatment and its cooling conditions if treatment was applied after sintering. The sintering atmosphere is usually hydrogen. This can assure a proper densification but in the same time it can give rise to embitterment of W/matrix boundaries accompanied by a drastically decreasing ductility. In order to avoid this effect, heat treatments are applied in a neutral atmosphere (Ar, N2, Ar+N2, etc...
SUDURA CONFERENCE, 2017
Lucrarea prezintă modelul analitic de calcul pentru determinarea incertitudinilor de măsurare în ... more Lucrarea prezintă modelul analitic de calcul pentru determinarea incertitudinilor de măsurare în cazul unor încercări mecanice aplicate îmbinărilor sudate, precum: încercarea la tracţiune, determinarea durităţii Vickers, încercarea de încovoiere prin şoc. Pentru fiecare tip de încercare se prezintă un model de lucru utilizând programul de calcul tabelar Excel, care este în curs de implementare în laboratorul de încercări mecanice, din cadrul companiei SC COMELF SA Bistriţa. Datele (fişa pWPS şi WPQR, rezultatele încercărilor) urmează să fie sistematizate într-o bază de date cu ajutorul unei aplicaţii dedicate, iar analiza şi procesarea acestora să fie realizată cu ajutorul unor reţele neuronale artificiale.
SUDURA JOURNAL, 2018
The Germany has launched a new initiative for industries, which had led to the Industry 4.0 conce... more The Germany has launched a new initiative for industries, which had led to the Industry 4.0 concept. This initiative has received very fast a global interest from all industrialized countries that have started already the 4th industrial revolution, following the German model. All important welding equipment manufacturers offers new modern solutions/applications that allow digitalization of all essential data, like welding parameters, that are now sent from the workplace to the facilities server, using wireless technology, the data being stored further in a cloud. These data can be accessed from any chain fabrication point, materials suppliers, quality control divisions, clients etc. improving the traceability process. In this entire general context, the materials weldability is playing a key role, because, based on that property it can be established productivity and quality process features, but also the reliability and safety of the welded structures in exploitation. Not in the last, it can be realized different studies and researches aiming the processes optimization, cost control, predicting the welded structures lifetime exploitation & performance.
The welds mechanical properties are direct related to welding conditions like: the welding proces... more The welds mechanical properties are direct related to welding conditions like: the welding process characteristics, the base and filler materials properties, linear energy, the protection atmosphere, welding speed a.o. Thus, the weld and heat affected zone microstructure would be determined by all that factors which in turn would affect the behavior of the welded metallic structure in the exploitation. From this, it is obvious the importance of the characterization of the welded microstructures using quantitative analysis, the results obtained being used in turn to improve the mechanical properties of the weld. In this paper we have used the fractal analysis to quantify the welded microstructure characteristics, as a new and modern mathematical tool for metallographic analysis. To accomplish this objective we have used the counting box method that was implemented in a software developed by the authors. Finding a correlation between different mechanical properties of the weld with the fractal values of the image analyzed of the welded microstructures was also a research direction in this paper.
Advanced Materials Research, 2015
Zavarivanje i zavarene konstrukcije, 2018
Powder Metallurgy and Advanced Materials, 2018
The weldability of the steels represents a problem of great interest in order to achieve welded s... more The weldability of the steels represents a problem of great interest in order to achieve welded structures that satisfy the high requirements on quality, imposed by the nowadays applications. In this paper has been proposed a more advanced model that has considered more factors of weldability influence, thus allowing a more detailed analysis based on the main welding process variables. Introduction Weldability is a general technological property commonly used in engineering, but very difficult to be defined and quantified in an exact manner. The American Welding Society has defined the weldability as being: “The capacity of a metal to be welded under the fabrication conditions imposed with a specific suitability designed structure and to perform satisfactorily in service” [1]. According to DIN 8528, Part 1 the weldability is seen as the output of the interaction of three main group factors, given in Table 1 [2]. Table 1. The weldability’s factors of influence. MATERIAL WELDING SUITA...
Solid State Phenomena, Oct 15, 2014
Materials Science Forum, Mar 1, 2011
Solid State Phenomena, 2014
The mechanical properties of the welded structures are directly related to the weldability of the... more The mechanical properties of the welded structures are directly related to the weldability of the steels, thus the estimation of the microstructural constituents in the weld and maximum hardness in the HAZ according to the welding process parameters represent a problem of great interest. The microstructural changes in the HAZ are estimated using a five-parameter logistic function (5PL), which is very accurate in the fitting highly asymmetric data. Also, the same 5PL function can be used in order to predict hardness and toughness in the HAZ based on the heat flow, cooling rates between 800-500 oC and chemical composition of the material. A discussion about the parameters of the 5PL function and fitting experimental data is presented and a studied case for welding S355J2 steel plates is also analyzed.
Materials Science Forum, 2011
Archives of Metallurgy and Materials, 2000
Improving Mechanical Properties of Sintered Wolfram Based Alloy with Liquid Phase Trough Controll... more Improving Mechanical Properties of Sintered Wolfram Based Alloy with Liquid Phase Trough Controlled Cooling ParametersHeavy alloys with 90 and 93 w/o W and a 7:3 Ni: Fe ratio are usually produced by the liquid phase sintering of W, Ni, and Fe powder mixtures. The result is a two-phase microstructure of spherical W solid solution grains embedded in a matrix of Ni rich solid solution. UTS, elongation, and microstructure strongly depend on the composition of the atmosphere during liquid phase sintering, on the cooling conditions and/or on the composition of the protective atmosphere during the heat treatment and its cooling conditions if treatment was applied after sintering. The sintering atmosphere is usually hydrogen. This can assure a proper densification but in the same time it can give rise to embitterment of W/matrix boundaries accompanied by a drastically decreasing ductility. In order to avoid this effect, heat treatments are applied in a neutral atmosphere (Ar, N2, Ar+N2, etc...
SUDURA CONFERENCE, 2017
Lucrarea prezintă modelul analitic de calcul pentru determinarea incertitudinilor de măsurare în ... more Lucrarea prezintă modelul analitic de calcul pentru determinarea incertitudinilor de măsurare în cazul unor încercări mecanice aplicate îmbinărilor sudate, precum: încercarea la tracţiune, determinarea durităţii Vickers, încercarea de încovoiere prin şoc. Pentru fiecare tip de încercare se prezintă un model de lucru utilizând programul de calcul tabelar Excel, care este în curs de implementare în laboratorul de încercări mecanice, din cadrul companiei SC COMELF SA Bistriţa. Datele (fişa pWPS şi WPQR, rezultatele încercărilor) urmează să fie sistematizate într-o bază de date cu ajutorul unei aplicaţii dedicate, iar analiza şi procesarea acestora să fie realizată cu ajutorul unor reţele neuronale artificiale.
SUDURA JOURNAL, 2018
The Germany has launched a new initiative for industries, which had led to the Industry 4.0 conce... more The Germany has launched a new initiative for industries, which had led to the Industry 4.0 concept. This initiative has received very fast a global interest from all industrialized countries that have started already the 4th industrial revolution, following the German model. All important welding equipment manufacturers offers new modern solutions/applications that allow digitalization of all essential data, like welding parameters, that are now sent from the workplace to the facilities server, using wireless technology, the data being stored further in a cloud. These data can be accessed from any chain fabrication point, materials suppliers, quality control divisions, clients etc. improving the traceability process. In this entire general context, the materials weldability is playing a key role, because, based on that property it can be established productivity and quality process features, but also the reliability and safety of the welded structures in exploitation. Not in the last, it can be realized different studies and researches aiming the processes optimization, cost control, predicting the welded structures lifetime exploitation & performance.
The welds mechanical properties are direct related to welding conditions like: the welding proces... more The welds mechanical properties are direct related to welding conditions like: the welding process characteristics, the base and filler materials properties, linear energy, the protection atmosphere, welding speed a.o. Thus, the weld and heat affected zone microstructure would be determined by all that factors which in turn would affect the behavior of the welded metallic structure in the exploitation. From this, it is obvious the importance of the characterization of the welded microstructures using quantitative analysis, the results obtained being used in turn to improve the mechanical properties of the weld. In this paper we have used the fractal analysis to quantify the welded microstructure characteristics, as a new and modern mathematical tool for metallographic analysis. To accomplish this objective we have used the counting box method that was implemented in a software developed by the authors. Finding a correlation between different mechanical properties of the weld with the fractal values of the image analyzed of the welded microstructures was also a research direction in this paper.
Advanced Materials Research, 2015
În lucrare sunt prezentate caracteristicile microstructurale din metalul depus şi din zona influe... more În lucrare sunt prezentate caracteristicile microstructurale din metalul depus şi din zona influenţată termic (ZIT), obţinute la sudarea MAG a oţelurilor structurale de tip S355NL. Pentru caracterizarea constituienţilor microstructurali s-a utilizat miscroscopia optică şi SEM, prezentându-se un model simplificat de corelaţie dintre microstructură şi caracteristicile mecanice de rezistenţă ale metalului depus şi din ZIT.
1.1 Rezumat Foarte multe construcţii sudate sunt supuse în exploatare la sarcini dinamice şi vibr... more 1.1 Rezumat Foarte multe construcţii sudate sunt supuse în exploatare la sarcini dinamice şi vibraţii, la variaţii mari de temperatură sau la temperaturi joase de lucru. Prin urmare, la realizarea acestor construcţii metalice sudate este necesar utilizarea unor oţeluri structurale, care prezintă rezistenţă mecanică ridicată şi o comportare foarte bună la sudare. Sudabilitatea este condiţionată de un conţinut redus de carbon echivalent, iar rezistenţa mecanică este proporţională cu concentraţia de carbon şi a elementelor de aliere din metalul depus. Asigurarea simultană a sudabilităţii şi a rezistenţei mecanice se poate realiza prin rafinarea microstructurii în cusătura sudată şi în ZIT. Pentru acest atingerea acestui deziderat s-au inoculat în baia de sudare, o serie de particule ceramice fine şi s-a analizat efectul acestora asupra microstructurii şi caracteristicilor de rezistenţă ale materialului depus. 2. Introducere 2.1 Stadiul actual al cercetărilor în domeniu În oţelurile structurale, tenacitatea este asigurată prin controlul microstructurii, respectiv prin asigurarea unei proporţii ridicate de ferită aciculară în aceasta. Datorită ciclului termic la sudare, în ZIT au loc modificări structurale, caracterizate de apariţia în microstructură a unor constituienţi microstructurali cu fragilitate ridicată. Deasemenea, în proximitatea liniei de topire au loc o serie de fenomene, precum: creşterea grăunţilor cristalini, segregarea chimică a impurităţilor la limita de grăunţi, fenomene de precipitare secundară, iar efectul lor cumulat poate afecta sever tenacitatea îmbinării sudate. Fenomenele de fragilizare a ZIT prin segregarea chimică a impurităţilor de S, P la limita de grăunte şi fragilitatea la albastru (la revenire joasă) au o influenţă mai redusă asupra rezistenţei la tracţiune sau a durităţii, însă afectează semnificativ tenacitatea şi comportarea la oboseală a construcţiei sudate. Studiile efectuate asupra caracteristicilor microstructurii metalului depus şi în ZIT [1-7], au arătat că unele elemente, precum: B, Ti, Al, S, N 2 sau alte impurităţi chiar şi în concentraţii reduse, au o influenţă semnificativă asupra procesului de cristalizare a băii de sudură. În literatura de specialitate sunt prezentate o serie de metode prin care se poate controla microstructura şi granulaţia în cusătura sudată, precum: inocularea de particule ceramice fine în baia de sudare, oscilaţia arcului, pulsaţia arcului,
a mbodea@stm.utcluj.ro, b liviu.brandusan@staff.utcluj.ro, c rmuresan@stm.utcluj.ro Abstract Mech... more a mbodea@stm.utcluj.ro, b liviu.brandusan@staff.utcluj.ro, c rmuresan@stm.utcluj.ro Abstract Mechanical properties of the welded materials play an important role in designing and exploitation of the welded metallic structures like: civil buildings, offshore platforms, or different machines and equipments etc. A major indicator of the weld quality and mechanical strength it is represented by the HAZ hardness. In this paper we have studied the influence of a large number of welding parameters and material characteristics over the HAZ hardness and microstructure associated with those mechanical properties. We have presented a new and robust mathematic model to estimate the hardness in HAZ for the MMA welding process. Also we have proposed very sensitive coefficients that takes in account the smallest materials chemical influence like O 2 content in ppm or others different elements that shows significative influence over the mechanical properties in the weld and microstructure as well. The empirical data, over 1600 runs ensure a large amount of data that was correlated and analyzed in order to establish the main factors that can affect the quality and mechanical properties of the welds.