Mladen Franz - Academia.edu (original) (raw)

Papers by Mladen Franz

Acta stomatologica Croatica, Dec 15, 2005

Engineering review

The temperature change, i.e. stresses of low carbon steel during the cold deformation process was... more The temperature change, i.e. stresses of low carbon steel during the cold deformation process was investigated in this study. During static tensile test, temperature changes were examined using thermography at different deformation degrees. It was found that there are temperature changes in the deformation zone during the cold deformation. The increase in temperature changes in the deformation zone during cold deformation occurs with an increase in the deformation degree. The largest localization of temperature change was measured at the moment of the test sample fracture when the maximum temperature change was 8.45 °C. A higher amount of temperature change of 5.39 °C was determined at tensile strength compared to the proportionality limit amount of -0.97 °C. It was found that there are differences between the amounts of temperature changes in the range from 0.87 °C to 1.91 °C with increasing of deformation degree of the tested steel. Calculated stress amounts proved and show the te...

Acta stomatologica Croatica, 2005

The demands of patients for high aesthetics during reconstructive prosthetic procedures accelerat... more The demands of patients for high aesthetics during reconstructive prosthetic procedures accelerated the development of new materials and technology. Forces acting in the post-canine part of the dental arch amount to ≥ 500 N, and thus the material used for fabrication of the restoration must withstand such forces. The aim of this investigation was to study the resistance to fracture of three non-metal materials: 1. ceromer (Targis, Ivoclar-Vivadent), 2. ceromer reinforced with fibre reinforced composite (Targis/Vectris, Ivoclar-Vivadent), and 3. non-metal ceramic system (IPS Empress 2, Ivoclar-Vivadent). Eighteen identical crowns were fabricated from each type of material on a plaster model of a polished natural second lower premolar, according to the manufacturer’s instructions. The same tooth was used for fabrication of a metal model on which crowns were placed in the universal testing device ZWICK. The compressive plate was modified with a pin 7mm in diameter, which acted with for...

Hot rolling of CuZn27Al4 shape memory alloy results in the forming of defects in austenitic cryst... more Hot rolling of CuZn27Al4 shape memory alloy results in the forming of defects in austenitic crystals. The defects such as dislocation and deformed boundaries of austenitic grains affect both “ classical” material properties and the specific properties related to shape memory. Rolled and quenched alloy (ausforming treatment) shows hardening proportional to the value of introduced deformation. By increasing the level of true plastic deformation not only the yield stress and tensile strength are increased but also the pseudo yield stress thus making the mechanically induced martensitic transformation more difficult. Besides, the ausforming treatment reduces all the transformation temperatures of the austenitic-martensitic reaction, thus expanding the temperature field of pseudo-elasticity. In spite of the hardening, the thermo-mechanically treated CuZn27Al4 alloy retains the pseudo-elastic shape memory so that favourable combination of strength and transformation behaviour can be achie...

Pojava povecane buke i vibracija elektromotora klipnog kompresora ukazala je na postojanje pukoti... more Pojava povecane buke i vibracija elektromotora klipnog kompresora ukazala je na postojanje pukotine na pogonskom kraju vratila. Provedeno je vise nerazornih ispitivanja kao sto su magnetska kontrola (MT), penetrantska kontrola (UT) i ultrazvucna kontrola (UT) kojima se detektirala pukotina pod kutem od 45o ; ; s obzirom na uzdužnu os vratila. Materijal vratila analiziran je na temelju mehanickih svojstava i mikrostrukture. Rezultati ispitivanja pokazali su da na vratilu nije provedena toplinska obrada poboljsavanja vec se radi o normaliziranom celiku s heterogenom feritno-perlitno mikrostrukturom. Takva heterogena mikrostruktra sacinjena od mekse i tvrđe faze nepovoljno utjece na dinamicki opterecene dijelove jer pogoduje pojavi umora materijala. Nadalje, skoro nikakvo zaobljenje u korijenu upustenog dijela za sjediste glave vijka odnosno matice na prirubnici vratila uzrokovalo je koncentraciju naprezanja na mjestu upustenja cime je također smanjena otpornost vratila na pojavu umora...

Original scientific paper Hot rolling of CuZn27Al4 shape memory alloy results in the forming of d... more Original scientific paper Hot rolling of CuZn27Al4 shape memory alloy results in the forming of defects in austenitic crystals. The defects such as dislocation and deformed boundaries of austenitic grains affect both "classical" material properties and the specific properties related to shape memory. Rolled and quenched alloy (ausforming treatment) shows hardening proportional to the value of introduced deformation. By increasing the level of true plastic deformation not only the yield stress and tensile strength are increased but also the pseudo yield stress thus making the mechanically induced martensitic transformation more difficult. Besides, the ausforming treatment reduces all the transformation temperatures of the austenitic-martensitic reaction, thus expanding the temperature field of pseudo-elasticity. In spite of the hardening, the thermo-mechanically treated CuZn27Al4 alloy retains the pseudo-elastic shape memory so that favourable combination of strength and tr...

Tehnicki Vjesnik-technical Gazette, 2012

Transactions of Famena, 2004

Thermal transformation behaviour of the CuZn27Al 3 shape memory alloy has been analysed after bet... more Thermal transformation behaviour of the CuZn27Al 3 shape memory alloy has been analysed after betatisation and quenching from the temperatures of 600°C to 800°C. The specific behaviour of the alloy in the thermal transformation range has been analysed by means of differential scanning calorimetry and micrographic testing. The results show a significant dependence of the austenitic martensitic transformation on the temperature of thermal treatment, particularly if T<700°C. Apart from the variation in transformation temperatures there is also a change of characteristic temperature hysteresis which is related to the occurrence of sub-grains and formation of crystals of alpha-solid solution, changing also the chemical composition of the beta-phase. The betatisation above 700°C facilitates the flow of both austenitic and martensitic reactions. With the increase in temperature the betatisation gradually narrows the range of the transformation cycle.

Strojarstvo, 1998

Toplim valjanjem razlicitim iznosima stvarne deformacije (0-1,54mm/mm), provedenim na temperaturi... more Toplim valjanjem razlicitim iznosima stvarne deformacije (0-1,54mm/mm), provedenim na temperaturi između 650C i 800C (ausforming obradba, AF), uvode se defekti u CuZn27Al4-Slitinu. Ovi defekti i mikrostrukturne promjene analizirani su kombinacijom svetlosne i elektronske mikroskopije. Mehanicka svojstva slitine određene su mjerenjem tvrdoce i vlacnim ispitivanjem. Uobicajene metode mjerenja tvrdoce nisu prikladne kod slitina s efektom prisjetljivosti oblika, izuzev mjerenja tvrdoce nisu prikladne kod slitina s efektom prisjetljivosti oblika, izuzev mjerenja s malim opterecenjem, i to stabilnog autenita pri temperaturi > AF. Kod mjerenja tvrdoce vecim opterecenjima pojavljuju se anomalije koje vode do odstupanja izmjerene i stvarne tvrdoce, te je prisutna pojava pseudotvrdoce. Nakon toplog valjanja u podrucju visih temperatura (AF>700C) i izravnog gasenja u vodi javlja se znatno ocvrscenje slitine, dok istom obradbom u podrucju nižih temperatura (AF < 700C) ne dolazi do ocvr...

U cilju postizavanja mjerne jedinstva svaka zemlja osniva svoju metrologijsku infrastrukturu za o... more U cilju postizavanja mjerne jedinstva svaka zemlja osniva svoju metrologijsku infrastrukturu za određenu mjernu velicinu, koja mora biti sljediva sve do primarnog etalona za tu velicinu. Na podrucju sile Laboratorij za ispitivanje mehanickih svojstava (LIMS) Fakulteta strojarstva i brodogradnje je zatražio te uspjesno prosao postupak ovlascivanja od strane DAR/PTB/ DKD (Deutscher Akkreditierungs Rat/ Physikalische Technische Bundesanstalt/ Deutsche Kalibrierdienst) za umjeravanje mjerila sile prema zahtijevima norme HRN EN ISO/IEC 17025. Ovim ovlastenjem je LIMS postao međunarodno priznati laboratorij na tom podrucju. U ovom radu je dan kratki kronoloski pregled postupka dobivanja akreditacije te su dane osnovne znacajke opreme (prvenstveno prijenosnih etalona sile).

Lomom siljaka ionizacijske elektrode bitno su narusena funkcionalna svojstva elektrode i znacajno... more Lomom siljaka ionizacijske elektrode bitno su narusena funkcionalna svojstva elektrode i znacajno smanjena ucinkovitost elektrofiltera. Pojava loma, u kratkom vremenskom periodu, dovodi se u vezu s vodikovom krhkosti potpomognutom dinamickim opterecenjem tijekom potresanja elektrode. Ovaj oblik napetosne korozije nastupa na vlacnom napregnutim mjestima pod djelovanjem agresivnog medija. Naime, za vrijeme rada postrojenja, a posebice tijekom njegova zastoja zbivaju se kemijske reakcije kojima nastaje otopina sumporne kiseline (H2SO4). Reakcijom agresivne kiseline i željeza oslobađa se atomarni vodik koji difundira u kristalnu resetku željeza i time uzrokuje izvitoperenje resetke. Inducirana naprezanja superponiraju se s postojecim naprezanjima, tj. naprezanjima u radu, zaostalim naprezanjima toplinskog porijekla (zavarivacke napetosti) i naprezanjima uslijed hladne deformacije. Kada ukupno naprezanje dostigne vrijednost vlacne cvrstoce dolazi do loma.

Metalurgija, 2008

Flame (gas) spraying, as a type of thermal spraying, is used for repairing damaged and worn eleme... more Flame (gas) spraying, as a type of thermal spraying, is used for repairing damaged and worn elements of tribomechanical systems, and also for protection of new parts from wear and corrosion in order to prolong service life. Beside good wear and corrosion resistance there is also a need for a good coating/substrate adhesion, reduced porosity and reduced level of residual stresses. Residual stresses that occur in the substrate/coating system are very significant because their relaxation can cause different coating failures. In this paper, different approaches to investigation of residual stresses in thermally sprayed coatings, have been presented. An analytical model (authors Tsui and Clyne) was used to estimate the distribution of residual stresses in flame sprayed and fused NiCrBSi coatings. These data can be used as input data for the numerical model.

Svrha ovoga rada bila je istražiti utjecaj termocikliranja na dina­ mičku izdržljivost spoja Ag-P... more Svrha ovoga rada bila je istražiti utjecaj termocikliranja na dina­ mičku izdržljivost spoja Ag-Pd slitine i hidrotermalne keramike. Istra­ živanje je obavljeno na 48 uzoraka Ag-Pd slitine izrađenih u obliku plo­ čica 45x12x4 mm na koje je napečena 2 mm debela hidrotermalna ke­ ramika. Uzorci su podijeljeni u dvije skupine. Prva skupina uzoraka odmah je nakon izrade bila dinamički opterećivana, druga je skupina uzoraka prije dinamičkih opterećenja termociklirana na temperatura­ ma 0 °C i 55 °C 1000 puta. Mjerenje dinamičke izdržljivosti provedeno je modificiranom metodom po Schwickerathu u Amslerovu visokofrekventnom pulzatoru. Izmjerene su veće vrijednosti maksimalne dinamič­ ke izdržljivosti za netermociklirane uzorke u iznosu od 850N, dok su utvrđene manje vrijednosti maksimalne dinamičke izdržljivosti za termociklirane uzorke od 550N. Statistički značajna razlika pronađena je između graničnih opterećenja Fg i broja ciklusa n za obje istraživane skupine uzoraka. Ključne riječi: m...

Archiv für das Eisenhüttenwesen, 1978

Acta stomatologica Croatica, Dec 15, 2005

Engineering review

The temperature change, i.e. stresses of low carbon steel during the cold deformation process was... more The temperature change, i.e. stresses of low carbon steel during the cold deformation process was investigated in this study. During static tensile test, temperature changes were examined using thermography at different deformation degrees. It was found that there are temperature changes in the deformation zone during the cold deformation. The increase in temperature changes in the deformation zone during cold deformation occurs with an increase in the deformation degree. The largest localization of temperature change was measured at the moment of the test sample fracture when the maximum temperature change was 8.45 °C. A higher amount of temperature change of 5.39 °C was determined at tensile strength compared to the proportionality limit amount of -0.97 °C. It was found that there are differences between the amounts of temperature changes in the range from 0.87 °C to 1.91 °C with increasing of deformation degree of the tested steel. Calculated stress amounts proved and show the te...

Acta stomatologica Croatica, 2005

The demands of patients for high aesthetics during reconstructive prosthetic procedures accelerat... more The demands of patients for high aesthetics during reconstructive prosthetic procedures accelerated the development of new materials and technology. Forces acting in the post-canine part of the dental arch amount to ≥ 500 N, and thus the material used for fabrication of the restoration must withstand such forces. The aim of this investigation was to study the resistance to fracture of three non-metal materials: 1. ceromer (Targis, Ivoclar-Vivadent), 2. ceromer reinforced with fibre reinforced composite (Targis/Vectris, Ivoclar-Vivadent), and 3. non-metal ceramic system (IPS Empress 2, Ivoclar-Vivadent). Eighteen identical crowns were fabricated from each type of material on a plaster model of a polished natural second lower premolar, according to the manufacturer’s instructions. The same tooth was used for fabrication of a metal model on which crowns were placed in the universal testing device ZWICK. The compressive plate was modified with a pin 7mm in diameter, which acted with for...

Hot rolling of CuZn27Al4 shape memory alloy results in the forming of defects in austenitic cryst... more Hot rolling of CuZn27Al4 shape memory alloy results in the forming of defects in austenitic crystals. The defects such as dislocation and deformed boundaries of austenitic grains affect both “ classical” material properties and the specific properties related to shape memory. Rolled and quenched alloy (ausforming treatment) shows hardening proportional to the value of introduced deformation. By increasing the level of true plastic deformation not only the yield stress and tensile strength are increased but also the pseudo yield stress thus making the mechanically induced martensitic transformation more difficult. Besides, the ausforming treatment reduces all the transformation temperatures of the austenitic-martensitic reaction, thus expanding the temperature field of pseudo-elasticity. In spite of the hardening, the thermo-mechanically treated CuZn27Al4 alloy retains the pseudo-elastic shape memory so that favourable combination of strength and transformation behaviour can be achie...

Pojava povecane buke i vibracija elektromotora klipnog kompresora ukazala je na postojanje pukoti... more Pojava povecane buke i vibracija elektromotora klipnog kompresora ukazala je na postojanje pukotine na pogonskom kraju vratila. Provedeno je vise nerazornih ispitivanja kao sto su magnetska kontrola (MT), penetrantska kontrola (UT) i ultrazvucna kontrola (UT) kojima se detektirala pukotina pod kutem od 45o ; ; s obzirom na uzdužnu os vratila. Materijal vratila analiziran je na temelju mehanickih svojstava i mikrostrukture. Rezultati ispitivanja pokazali su da na vratilu nije provedena toplinska obrada poboljsavanja vec se radi o normaliziranom celiku s heterogenom feritno-perlitno mikrostrukturom. Takva heterogena mikrostruktra sacinjena od mekse i tvrđe faze nepovoljno utjece na dinamicki opterecene dijelove jer pogoduje pojavi umora materijala. Nadalje, skoro nikakvo zaobljenje u korijenu upustenog dijela za sjediste glave vijka odnosno matice na prirubnici vratila uzrokovalo je koncentraciju naprezanja na mjestu upustenja cime je također smanjena otpornost vratila na pojavu umora...

Original scientific paper Hot rolling of CuZn27Al4 shape memory alloy results in the forming of d... more Original scientific paper Hot rolling of CuZn27Al4 shape memory alloy results in the forming of defects in austenitic crystals. The defects such as dislocation and deformed boundaries of austenitic grains affect both "classical" material properties and the specific properties related to shape memory. Rolled and quenched alloy (ausforming treatment) shows hardening proportional to the value of introduced deformation. By increasing the level of true plastic deformation not only the yield stress and tensile strength are increased but also the pseudo yield stress thus making the mechanically induced martensitic transformation more difficult. Besides, the ausforming treatment reduces all the transformation temperatures of the austenitic-martensitic reaction, thus expanding the temperature field of pseudo-elasticity. In spite of the hardening, the thermo-mechanically treated CuZn27Al4 alloy retains the pseudo-elastic shape memory so that favourable combination of strength and tr...

Tehnicki Vjesnik-technical Gazette, 2012

Transactions of Famena, 2004

Thermal transformation behaviour of the CuZn27Al 3 shape memory alloy has been analysed after bet... more Thermal transformation behaviour of the CuZn27Al 3 shape memory alloy has been analysed after betatisation and quenching from the temperatures of 600°C to 800°C. The specific behaviour of the alloy in the thermal transformation range has been analysed by means of differential scanning calorimetry and micrographic testing. The results show a significant dependence of the austenitic martensitic transformation on the temperature of thermal treatment, particularly if T<700°C. Apart from the variation in transformation temperatures there is also a change of characteristic temperature hysteresis which is related to the occurrence of sub-grains and formation of crystals of alpha-solid solution, changing also the chemical composition of the beta-phase. The betatisation above 700°C facilitates the flow of both austenitic and martensitic reactions. With the increase in temperature the betatisation gradually narrows the range of the transformation cycle.

Strojarstvo, 1998

Toplim valjanjem razlicitim iznosima stvarne deformacije (0-1,54mm/mm), provedenim na temperaturi... more Toplim valjanjem razlicitim iznosima stvarne deformacije (0-1,54mm/mm), provedenim na temperaturi između 650C i 800C (ausforming obradba, AF), uvode se defekti u CuZn27Al4-Slitinu. Ovi defekti i mikrostrukturne promjene analizirani su kombinacijom svetlosne i elektronske mikroskopije. Mehanicka svojstva slitine određene su mjerenjem tvrdoce i vlacnim ispitivanjem. Uobicajene metode mjerenja tvrdoce nisu prikladne kod slitina s efektom prisjetljivosti oblika, izuzev mjerenja tvrdoce nisu prikladne kod slitina s efektom prisjetljivosti oblika, izuzev mjerenja s malim opterecenjem, i to stabilnog autenita pri temperaturi > AF. Kod mjerenja tvrdoce vecim opterecenjima pojavljuju se anomalije koje vode do odstupanja izmjerene i stvarne tvrdoce, te je prisutna pojava pseudotvrdoce. Nakon toplog valjanja u podrucju visih temperatura (AF>700C) i izravnog gasenja u vodi javlja se znatno ocvrscenje slitine, dok istom obradbom u podrucju nižih temperatura (AF < 700C) ne dolazi do ocvr...

U cilju postizavanja mjerne jedinstva svaka zemlja osniva svoju metrologijsku infrastrukturu za o... more U cilju postizavanja mjerne jedinstva svaka zemlja osniva svoju metrologijsku infrastrukturu za određenu mjernu velicinu, koja mora biti sljediva sve do primarnog etalona za tu velicinu. Na podrucju sile Laboratorij za ispitivanje mehanickih svojstava (LIMS) Fakulteta strojarstva i brodogradnje je zatražio te uspjesno prosao postupak ovlascivanja od strane DAR/PTB/ DKD (Deutscher Akkreditierungs Rat/ Physikalische Technische Bundesanstalt/ Deutsche Kalibrierdienst) za umjeravanje mjerila sile prema zahtijevima norme HRN EN ISO/IEC 17025. Ovim ovlastenjem je LIMS postao međunarodno priznati laboratorij na tom podrucju. U ovom radu je dan kratki kronoloski pregled postupka dobivanja akreditacije te su dane osnovne znacajke opreme (prvenstveno prijenosnih etalona sile).

Lomom siljaka ionizacijske elektrode bitno su narusena funkcionalna svojstva elektrode i znacajno... more Lomom siljaka ionizacijske elektrode bitno su narusena funkcionalna svojstva elektrode i znacajno smanjena ucinkovitost elektrofiltera. Pojava loma, u kratkom vremenskom periodu, dovodi se u vezu s vodikovom krhkosti potpomognutom dinamickim opterecenjem tijekom potresanja elektrode. Ovaj oblik napetosne korozije nastupa na vlacnom napregnutim mjestima pod djelovanjem agresivnog medija. Naime, za vrijeme rada postrojenja, a posebice tijekom njegova zastoja zbivaju se kemijske reakcije kojima nastaje otopina sumporne kiseline (H2SO4). Reakcijom agresivne kiseline i željeza oslobađa se atomarni vodik koji difundira u kristalnu resetku željeza i time uzrokuje izvitoperenje resetke. Inducirana naprezanja superponiraju se s postojecim naprezanjima, tj. naprezanjima u radu, zaostalim naprezanjima toplinskog porijekla (zavarivacke napetosti) i naprezanjima uslijed hladne deformacije. Kada ukupno naprezanje dostigne vrijednost vlacne cvrstoce dolazi do loma.

Metalurgija, 2008

Flame (gas) spraying, as a type of thermal spraying, is used for repairing damaged and worn eleme... more Flame (gas) spraying, as a type of thermal spraying, is used for repairing damaged and worn elements of tribomechanical systems, and also for protection of new parts from wear and corrosion in order to prolong service life. Beside good wear and corrosion resistance there is also a need for a good coating/substrate adhesion, reduced porosity and reduced level of residual stresses. Residual stresses that occur in the substrate/coating system are very significant because their relaxation can cause different coating failures. In this paper, different approaches to investigation of residual stresses in thermally sprayed coatings, have been presented. An analytical model (authors Tsui and Clyne) was used to estimate the distribution of residual stresses in flame sprayed and fused NiCrBSi coatings. These data can be used as input data for the numerical model.

Svrha ovoga rada bila je istražiti utjecaj termocikliranja na dina­ mičku izdržljivost spoja Ag-P... more Svrha ovoga rada bila je istražiti utjecaj termocikliranja na dina­ mičku izdržljivost spoja Ag-Pd slitine i hidrotermalne keramike. Istra­ živanje je obavljeno na 48 uzoraka Ag-Pd slitine izrađenih u obliku plo­ čica 45x12x4 mm na koje je napečena 2 mm debela hidrotermalna ke­ ramika. Uzorci su podijeljeni u dvije skupine. Prva skupina uzoraka odmah je nakon izrade bila dinamički opterećivana, druga je skupina uzoraka prije dinamičkih opterećenja termociklirana na temperatura­ ma 0 °C i 55 °C 1000 puta. Mjerenje dinamičke izdržljivosti provedeno je modificiranom metodom po Schwickerathu u Amslerovu visokofrekventnom pulzatoru. Izmjerene su veće vrijednosti maksimalne dinamič­ ke izdržljivosti za netermociklirane uzorke u iznosu od 850N, dok su utvrđene manje vrijednosti maksimalne dinamičke izdržljivosti za termociklirane uzorke od 550N. Statistički značajna razlika pronađena je između graničnih opterećenja Fg i broja ciklusa n za obje istraživane skupine uzoraka. Ključne riječi: m...

Archiv für das Eisenhüttenwesen, 1978