Trendovi s europskih konferencija o kvaliteti

European annual conferences on quality (EOQ) have been held continuously since 1957. Total number of 45 conferences has been registered till 2001. This paper gives a concise review on topics and mottos of the 10 last conferences, their way of reasoning, final messages and trends in quality management.Europske godišnje konferencije o kvaliteti (EOQ) održavaju se od 1957. godine i do 2001. g. održano je ukupno 45 konferencija. Ovaj rad sadrži koncizne preglede o sadržajima 10 posljednjih konferencija, načinu razmišljanja, zaključnim porukama i trendovima upravljanja kvalitetom

Određivanje koeficijenta toplinske vodljivosti kalupnih mješavina

For a thorough understanding of the behaviour of foundry mould mixtures, a good knowledge of thermal properties of mould materials is needed. Laboratory determination of thermal conductivity of mould mixtures enables a better control over scabbing defects which are a major problem in green sand mould mixtures. A special instrument has been designed for that purpose and it is described in this work.Za detaljno razumijevanje ponašanja kalupnih mješavina prilikom lijevanja odljevaka potrebno je dobro poznavati toplinska svojstva kalupnih materijala. Laboratorijsko određivanje toplinske vodljivosti kalupnih mješavina omogućava bolju kontrolu nad pojavom odlupljivanja, koja je kao glavni problem vezana za kalupne mješavine s fizikalno očvrstivim vezivima. Određivanje koeficijenta toplinske vodljivosti provedeno je na posebno konstruiranom uređaju koji je opisan ovim radom

Određivanje koeficijenta toplinske vodljivosti kalupnih mješavina

For a thorough understanding of the behaviour of foundry mould mixtures, a good knowledge of thermal properties of mould materials is needed. Laboratory determination of thermal conductivity of mould mixtures enables a better control over scabbing defects which are a major problem in green sand mould mixtures. A special instrument has been designed for that purpose and it is described in this work.Za detaljno razumijevanje ponašanja kalupnih mješavina prilikom lijevanja odljevaka potrebno je dobro poznavati toplinska svojstva kalupnih materijala. Laboratorijsko određivanje toplinske vodljivosti kalupnih mješavina omogućava bolju kontrolu nad pojavom odlupljivanja, koja je kao glavni problem vezana za kalupne mješavine s fizikalno očvrstivim vezivima. Određivanje koeficijenta toplinske vodljivosti provedeno je na posebno konstruiranom uređaju koji je opisan ovim radom

Investigation of Causes of Scrap Occurrence in Thread Cutting on Steel Sleeves for Motorcar Industry

This paper studies causes of scrap occurrence, wear and breakage of cutters during thread cutting of steel sleeves poured in Al die castings of motor car engine components. It was concluded that the reason for occurrence of problems with thread cutting of sleeves most probably should be attributed to the fact whether hardness value reaches 200 HB or over 250 HB. The most probable reason for over wear and consequently to breakage of cutters and scrap occurrence, although castings display top quality, lies in the fact that the internal diameter of sleeves frequently falls down under minimally allowed tolerances for threaded sleeves

Utjecaj zrnatosti kalupnog pijeska na pojavu napetosti u kalupu

The aim of this research is to explain how the distribution of moulding sand particles, apart from combination with other components (bentonite and water contents) affects the increase of compressive stresses in the moulding mixture. The granularity of sand and water content have great effect in the increase of compressive stresses. The regression analysis was used to obtain the mathematical model which describes the dependence of the compressive stresses on the mean size of the sand grains and water content in the mould mixture.Utjecaj zrnatosti kalupnog pijeska na pojavu napetosti u kalupu. Prikaz istraživanja utjecaja zrnatosti kalupnog pijeska u kombinaciji s ostalim komponentama (udjelima bentonita i vode) utječe na pojavu napetosti u kalupu. Provedena ispitivanja pokazuju da veliki udio u porastu tlačnih napetosti ima zrnatost pijeska i udio vode. Regresijskom analizom dobiven je matematički model koji opisuje ovisnost tlačnih napetosti o srednjoj veličini zrna pijeska i udjelu vode u kalupnoj mješavini

The possibility of tribopair lifetime extending by welding of quenched and tempered stainless steel with quenched and tempered carbon steel

In the conditions of tribocorrosion wear, extending of parts lifetime could be achieved by using stainless steel,which is hardened to sufficiently high hardness. In the tribosystem bolt/ bushing shell/link plate of the bucket elevator transporter conveyor machine, the previously quenched and tempered martensitic stainless steel for bolts is hardened at ≈47 HRC and welded with the quenched and tempered high yield carbon steel for bolts. Additional material, based on Cr-Ni-Mo (18/8/6) is used. The microstructure and hardness of welded samples are tested. On the tensile tester, resistance of the welded joint is tested with a simulated experiment. Dimensional control of worn tribosystem elements was performed after six months of service

Utjecajni parametri na homogenost aluminijske metalne pjene AlSi12 metala

The development of metal foams results in an increasing need for the industrial application of such materials. Metal foams are shaped by the pouring technology which differs depending on which mechanism of pore production is used. This paper presents some of the basic parameters which influence the homogeneity of the metal foam structure.Razvojem metalnih pjena javlja se sve veća potreba za industrijskom primjenom ovih materijala. Metalne pjene oblikuju se tehnologijom lijevanja koje se razlikuju, zavisno koji mehanizam nastanka pora se koristi. U ovom radu biti će spomenuti neki od osnovnih parametara koji utječu na homogenost strukture metalne pjene

Utjecaj tehnoloških parametra na pojavu zaostalih naprezanja u željeznim odljevcima

The paper establishes the present day state of knowledge on parameters influencing residual stresses in iron castings, based on writings on this subject. Furthermore, testing examined the influence of parameters, such as mold humidity, mold stiffness; pouring temperature and carbon equivalent (CE) on residual stresses. Tests have been carried out on standard grating test piece made of grey cast iron, poured in sand molds. The obtained measurements have been drawn in diagrams and the influence of each single parameter has been evaluated.U radu je proučavanjem literature utvrđeno sadašnje stanje spoznaje o utjecajnim parametrima na zaostala naprezanja u odljevcima. Zatim je eksperimentalno ispitan utjecaj vlažnosti kalupa, tvrdoće kalupa, temperature ulijevanja, ugljikova ekvivalenta na zaostala naprezanja. Ispitivanja su provedena na standardnoj rešetkastoj probi od sivog lijeva koja je lijevana u pješčane kalupe. Na temelju mjernih rezultata nacrtani su dijagrami i analiziran je utjecaj svakog pojedinog parametra

Effects of maceration conditions on the polyphenolic composition of red wine 'Plavac mali'

The influence of the maceration treatments on the polyphenolic composition of red wines produced from Croatian autochthonous cultivar 'Plavac mali' (Vitis vinifera L.) has been investigated. The results showed that in general different skin contact times influenced the content of anthocyanins, total phenols and vanillin index in young wines. Prolonged skin contact time significantly increased the content of low molecular weight proanthocyanidins and decreased the content of anthocyanins. Young wine produced with maceration at lower temperature demonstrated the lower content of anthocyanins and proanthocyanins. No significant differences were observed between the levels of anthocyanins, total phenols and proanthocyanidins in wines aged for 14 months. Weaker colour intensity of 14-month-aged wines was detected in the wine made with prolonged skin maceration time in which the ratio of proanthocyanidins/anthocyanidins was the highest.

Residual stresses in castings produced by press die casting technology

The influence of technological parameters on residual stresses in pressure die castings is analysed in this paper. In order for the residual stresses to be as low as possible the optimization of technological parameters is necessary. The centrally composed plan of experiment 24cs is used in the investigation. Technologically influencing parameters are changed according to the mentioned plan of experiment and they are: temperature of pouring, rate of die cavity filling with the melt, post pressure in already filled die and the casting cooling time along with the pouring system