The Model of Changes in the Psychomotor Performance of the Production Workers

The results of the study indicated a relationship between the worker’s psychomotor performance at a certain time of the work shift and the changes in the level of their fatigue. The performance is reflected in the production results, such as the decrease in the productivity and an increase in the number of defects. The results of the study made it possible to define a model (algorithm) of changes in the worker’s psychomotor performance. The developed model identifies the direction of the organisational changes in a production plant environment operating in the rotational shift pattern. The organisational changes can relieve staff in the night and minimise the risk of the declining production efficiency during work at night

Developing of wear model of construction materials in abrasive soil pulp employing discriminant analysis

U radu se opisuje metoda odabira kemijskog sastava i strukture površinskog sloja konstrukcijskih materijala koji odgovaraju svojstvima abrazivne zemljane mase koja se obrađuje. Eksperiment je proveden u laboratoriju metodom "rotirajuće mase". Matematičkim modelom razvijenim za eksperiment omogućena je simulacija promjena u trošenju konstrukcijskih materijala korištenih u zemlji ovisno o promjeni kemijskog sastava i strukture konstrukcijskog materijala i vlažnosti zemlje. Rezultati pokazuju da intenzitet trošenja u šljunčanom tlu može biti prihvatljiv za materijale koji sadrže manje od 20 % C+Cr (upotrebljene u tlu s vlažnošću višom od 12 %) kao i u tribološki nepovoljnim uvjetima (vlažnost tla ispod 6 %), ako je sadržaj C+Cr u konstrukcijskom materijalu viši od 25 %.This paper presents a method of selecting the chemical composition and structure of the surface layer of construction materials to suit the property of the abrasive soil pulp being processed. The experiment was conducted in a laboratory, by the "rotating mass" method. The mathematical model developed for the experiment enables simulation of the wear changes of the construction materials used in soil, depending on changing of chemical composition and structure of the construction material and soil humidity. The results produced in the experiment have shown that the wear intensity in gravel soil may be acceptable for both materials containing less than 20 % C+Cr (used in soil with humidity of more than 12 %) and in tribological unfavourable conditions (soil humidity below 6 %), if the C+Cr content in the construction material exceeds 25 %

Material flow optimization – a case study in automotive industry

Danas je većina organizacija suočena s mnogim dilemama, bit kojih je određivanje načina postizanja ili održavanja stečenog položaja u konkurentnom okruženju. Poduzeća moraju neprestano povećavati svoju ekonomiju. Jedan od načina stjecanja nadmoći nad konkurencijom je analiza i optimizacija toka materijala, što doprinosi smanjenju troškova. Tok materijala u proizvodnoj organizaciji govori nam mnogo o organizaciji sustava. U radu se daje analiza postojećeg stanja toka materijala u jednoj proizvodnoj organizaciji motornih vozila. Predlaže se i projekt optimizacije toka materijala; projekt se sastoji od novog programa internog prijevoza i optimizacije položaja radnih štandova. U radu se opisuju postojeći problemi u internom prijevozu poduzeća i daju rješenja tih problema.Today, most contemporary organisations are facing many dilemmas, the essence of which is the determination of the ways of acquisition or maintenance of their position in the competitive environment. Companies have to continuously increase their economy. One of the ways to get competitive prevalence is analysis and optimization of material flow which contributes to the reduction of the company costs. Material flow in a production organization tells us a lot about how well the system is organised. The paper presents an analysis of the current state of material flow in a production company of the automotive branch. A project of the material flow optimization has also been proposed; the project consists of creation of a program of internal transport and optimization of the location of the working stands. The paper describes the current problems of the company internal transport and indicates solutions to those problems

Topographic inspection as a method of weld joint diagnostic

U radu se demonstrira topografsko ispitivanje u specifičnom kontekstu triju vrsta inspekcijskih metoda zavara od austenitnog nehrđajučeg željeza. Vizualna i metrološka kontrola provedena je tijekom ispitivanja zavarivanja TIG postupkom, primjenom ne-destruktivnih metoda: rendgensko ispitivanje, kompjuterizirana tomografija i profilometrija površine. Rad je reakcija na nedostatak informacija, posebice u području ne-destruktivnih metoda prikladnih za široku primjenu u praksi. U radu se prezentiraju prednosti i nedostaci analiziranih dijagnostičkih metoda i klasifikacija uobičajenih i specifičnih mana zavarenog spoja. Najvažnija neispravnost u praktičnim primjenama kod određivanja pouzdanosti zavarenog spoja su pukotine. Ova vrsta dijagnoze zasnovana je na dobivenim podacima o promatranom anizotropskom i nehomogenom volumenu u dijelu zavara pod utjecajem topline.The paper demonstrates a topographic inspection in the specific context of three kinds of inspection methods of austenitic stainless steel welds. Visual and metrological inspection was analysed during tungsten inert gas (TIG) welding tests, showing the non-destructive techniques: X-ray, computed tomography, and surface profilometry. The article is a response to the lack of information, especially in the area of non-destructive techniques suitable for wide practical application. The Paper presents advantages and drawbacks of the analysed diagnostic methods and a classification of conventional and specific welded joint flaws. The most important defect in practical applications determining reliability of a welded joint is cracks. This kind of diagnostic is based on the obtained information about anisotropic and inhomogeneous volume under consideration in the heat-affected zone of a weld