Odabrane nove tehnologije i zadaci istraživanja u oblikovanju deformiranjem materijala

The article gives a review of selected new technologies of materials forming. That is selected 10 procedures, first, high pressure torsion processing, at the end, metal injection molding. All the new procedures have good performance and in the future for expect more the application in industry.Članak daje osvrt odabranih novih tehnologija u oblikovanju deformiranjem materijala. To je odabranih 10 postupaka, prvi, visokotlačna torziona obradba i na kraju, lijevačko injektiranje metala. Svi novi postupci imaju dobre karakteristike i u budućnosti za očekivati veću primjenu u undustriji

Predviđanje deformacije i temperature metodom konačnim elemenata (MKE) tijekom valjanja cijevi na pilger – stanu

3D - FEM simulation was used as an efficient tool for description of stress-deformation thermal field at rolling of tubes on a pilgrim mill. The monitored objectives comprised also behaviour of working tools at this rolling. This paper assumes rolling of already pierced thick-walled blank, which passes through the pilgrim stand at simultaneous reduction of thickness of inside and outside diameters at the expense of elongation of initial length. Main attention is focused on the mentioned parameters with respect to various conditions of rolling, such as different heat transfer, different friction or different distance of insertion of the rolled product into the gauge. The input data used at simulation were derived from real conditions of tubemaking.Za prikaz termičkog polja naprezanje – deformacija tijekom valjanja cijevi na pilger - stanu učinkovito je rabljena trodimenzijska metoda konačnih elemenata (3D – MKE). U radu je razmatrano i ponašanje alata tijekom izrade cijevi valjanjem. Pretpostavljeno je valjanje šuplje debelostjene cijevnice na pilger stanu uz istovremeno smanjenje vanjskog i unutrašnjeg promjera na uštrb produljenja početne duljine. Rad se fokusira na navedene parametre obzirom na promjenjive režime valjanja poput različitog prijenosa topline, različitog trenja ili različite udaljenosti uvođenja valjanog proizvoda u uređaj. Ulazni podaci rabljeni u simulaciji odgovaraju onima iz realnog procesa valjanja cijevi

Kinetika rekristalizacije tijekom vrućeg oblikovanja čelika

The theory of kinetics of static recrystallization of steel during hot forming links the phenomenon to certain critical strain, grain size, strain rate, activation energy and temperature. The basic description is provided by the Avrami equation. An overview of equations used was compiled and comments on selected parameters prepared.Teorija kinetike statičke rekristalizacije čelika tijekom vrućeg oblikovanja ovu pojavu povezuje s kritičnom deformacijom, veličinom zrna, brzinom deformacije, aktivacijskom energijom te s temperaturom. Osnovni opis pruža Avrami jednadžba. Rad pruža pregled korištenih jednadžbi i raspravu pojedinih parametara

Some viewpoints of materials forming technology

Metal forming can be regarded as a process during which materials are treated by “force” and “heating” under a certain external load and boundary condition (loading mode, rate of loading, constraint condition, geometry, contact friction condition, temperature field). As well as in former times and presently from time to time detect overview lecture and articles, which have for one‘s object draw up demand on modern forming technologies one’s about new wave in the area like: shortening processes, flexibilization, integrating production processes, hollow structure technology and simulation and optimization. New metal forming technologies may be developed using new energy resources, new forming mediums and new loading methods for developing new products according to the needs of the automotive, electrical, electronic and aerospace industries. Some cases of these technologies will be presented inside of volume of this contribution

Influence of heat treatment on properties of ti-nb alloys

Ti-Nb alloys are of a large potential for industrial, as well as biomedical utilisation. Oxygen content in the alloy is a parameter influencing its properties and cannot be neglected. The main focus of this paper is on observation of influence of annealing time on oxygen content in the structure of Ti – 20,7 (at.)% Nb alloy. Four groups of the samples were annealed at the temperature of 800 °C from 15 to 60 minutes with 15 min. step. As it was proven by the analysis, the oxygen content increased with increasing annealing time. Moreover, microhardness measurements showed increasing trend of HV microhardness value with increasing oxygen content

Kinetika rekristalizacije tijekom vrućeg oblikovanja čelika

The theory of kinetics of static recrystallization of steel during hot forming links the phenomenon to certain critical strain, grain size, strain rate, activation energy and temperature. The basic description is provided by the Avrami equation. An overview of equations used was compiled and comments on selected parameters prepared.Teorija kinetike statičke rekristalizacije čelika tijekom vrućeg oblikovanja ovu pojavu povezuje s kritičnom deformacijom, veličinom zrna, brzinom deformacije, aktivacijskom energijom te s temperaturom. Osnovni opis pruža Avrami jednadžba. Rad pruža pregled korištenih jednadžbi i raspravu pojedinih parametara

Study of the process of equal channel angular pressing of aluminum alloy

This work is dedicated to the research of the influence of equal channel angular pressing to the microstructure and mechanical properties of the alloy based on aluminum. As a result of the carried out research it is found out that there are the properties improvement after ECAP. There by structure and mechanical properties depend on the ECAP route. The ECAP 4 cycles realization provides the formation on uniform ultra fine structure on the BC route as well as C route. The experiments showed that alloy based on aluminum allows to obtain ultra fine structure (0,8-1,2 μm) already after 2 passes of ECAPB

Student Physical Activity Patterns: Grade, Gender, and Activity Influences

The purpose of this study was to determine how physical education students\u27 cardiovascular responses as determined by mean heart rate, standard deviation of heart rate, and percentage of time in target heart rate zone varied according to student characteristics. Participants were 505 students in Grades 3 through 12. The Polar Accurex Plus heart rate telemetry system was used to measure the physiological load on the cardiovascular system. Three-way ANOVA results suggested that heart rate patterns in physical education varied according to gender, grade, and activity. For example, secondary school girls were more active in individual activities while secondary school boys were more active in team sport activities. Elementary students were the most active group and had the most variability in their heart rate patterns

Struktura i svojstva titana za zubne umetke (implantate)

This paper describes manufacture of nano-structural titanium, its structure and properties. Nano-titanium has higher specific strength properties than ordinary (coarse-grained) titanium. Nano-titanium was produced by the equal-channel angular pressing (ETAP) process. The research it self was focused on physical base of strengthening and softening processes and developments occurring at the grain boundaries during the ECAP process at half-hot temperature. Strength of nano-titanium varies around 960 MPa, grain size around 300 nm.Rad opisuje proizvodnju nanostrukturnog titana te njegovu strukturu i svojstva. Nanotitan se odlikuje višom čvrstoćom od običnog, krupnozrnatog, i proizveden je kanalno kutnim prešanjem (KKP). Samo istraživanje bilo je usmjereno na fizikalne osnove procesa očvršćavanja i omekšavanja na granicama zrna tijekom procesa kanalno kutnim prešanjem (KKP) na srednjim temperaturama. Čvrstoća nanotitana varira oko 960 MPa, a veličina zrna je oko 300 nm

Plastometric study of hot formability of hypereutectoid C – Mn – Cr – V steel

Formability of hypereutectoid C-Mn-Cr-V steel in hot condition was investigated with use of plastometric methods. A wide range of deformation temperatures 1 300 - 640 °C for hot tensile tests was proposed with use of nil-strength temperature (NST), determined by special plastometric method, and as well as with use of the calculated temperatures of phase transformations during heating of the investigated steel. Ultimate tensile strength of the investigated steel was increasing exponentially with the decreasing deformation temperature. Ductility of the investigated steel in hot condition increased with the increasing deformation temperature up to the temperatures ranging from 1 150 to 1 250 °C, after which a sharp decline of formability took place in investigated material