Többtengelyű kovácsolás virtuális és fizikai szimulációinak összehasonlítása: Comparison of virtual and physical simulation of multi-axial forging processes

On a Gleeble 3800 thermophysical simulator, multi-axial forging of high-purity copper workpieces was performed. The strain rate during the simulation process was 0.1 s-1. The applied force of the MaxStrain unit and the geometric changes of the workpiece as a function of time were continuously recorded. For a deeper understanding of the multi-axial forging process, a finite element model was created in Qform3D. The force-displacement curves of the physical and finite element simulation were compared. Kivonat Gleeble 3800 típusú termofizikai szimulátoron nagy tisztaságú réz próbatestek multi-axiális kovácsolását végeztük 0.1 s-1 alakváltozási sebességgel. A MaxStrain egységen folytatott méréseknél folyamatosan regisztráltuk az alakító erőt és a próbatest geometriai változásait az idő függvényében. A többtengelyű kovácsolási folyamat törvényszerűségeinek megismerése érdekében végeselemes modellt készítettünk Qform3D program segítségével. A QForm3D szoftverben készített végeselemes szimuláció erő-elmozdulás görbéit hasonlítottuk össze a fizikai szimuláció során rögzített adatokkal. &nbsp

FE Analysis of the Control Methods Used in Crimping of Joints with Polymer Composite Cores

This paper presents results of the Finite Element analysis of crimped cylindrical joints with polymer composite cores. Initial data of the Finite Element analysis significantly affecting results of the simulation are design parameters and mechanical properties of the components. Initial interface clearance of the joint and hardening behaviour of the steel sleeve were found to have special importance. Material testing, and dimension analysis are conducted to find the parameters´ variation limits. Performed Finite Element parametric study allowed to compare quality of existing technological parameters in respect to residual strain energy of the core chosen as a measure of the load-bearing capacity. Analysis showed that extra mechanical work parameter is the most robust to variation of dimensions and mechanical properties

A Comparative Evaluation of Predictive Models of the Flat Rolling Process

The predictive abilities of several mathematical models of the cold, flat rolling process are tested by comparing their predictions to experimental measurements. The models include an empirical model, a one-dimensional model, a finite element model and an upper bound model. The coefficient of friction and the friction factor are first determined by the inverse approach, using the model deemed to be the most comprehensive. The effects of including or excluding an account of roll flattening, using elastic-plastic or rigid-plastic strips, and constant or velocity dependent coefficients of friction or friction factors are examined

INFLUENCE OF ECAP ROUTES ON MECHANICAL PROPERTIES OF A NANOCRYSTALLINE ALUMINIUM ALLOY

Equal-Channel Angular Pressing (ECAP) is an effective tool for producing ultra fine grained materials. In repeated application of ECAP, the rotation of the sample along the longitudinal axis of the billet allows to carry out different routes of deformation. The applied route has a strong influence on the texture, microstructure and mechanical behaviour of ECAP processed metals. In the present study ECAP was successfully applied to produce ultra fine-grained microstructure in a commercial Al-Mg-Si alloy (Al 6082). The mechanical investigations of the ECAP deformed specimens revealed that after 4 ECAP passes the material had a very high strength but a significantly decreased ductility. Further ECAP processing to 8 passes by route C increased ductility dramatically and strength slightly. The diameter ratio of the ellipse shaped cross-section of the compressed specimens was the highest for the sample deformed by route C for eight passes. This indicates that the anisotropy of the structure of ECAP deformed materials may play an important role in achieving good ductility. The quality of the ultra-precision finished surface of the processed sample improved dramatically after eight passes

Investigation of Ductile Fracture of Nanostructured Al-6082 Material

In this paper we are going to investigate the ductile fracture in cold forming of nanostructured Al - 6082 alloy material during axi-symmetric collar (flanged) tests and cylindrical upsetting tests by using eight types of fracture criteria. The material of specimens were taken out of ECAP was made by one, four, and eight passes (route C) in three perpendicular axes. The material has ultrafine grain size and an anisotropic behaviour. A simple yield criterion and material law are used to describe the plastic deformation of the nanostructured material. The collar tests and cylindrical upsetting tests produced typical ductile fractures in all types of specimens

Tensile behavior of multiple forged 6082 Al alloy

The present study focus on the influence of multiple forging (MF) on the tensile behavior of 6082 aluminium alloy, where the MF specimens were achieved using multi-step closed die forging. Cylindrical tensile specimens were machined from the MF specimens then subjected to tensile testing. Beside the main target of the study, the effect of MF on microstructure homogeneity and the fracture surface of the samples were studied using hardness testing, optical and scanning electron microscopy respectively. The results show the influence of MF on the tensile strength and the maximum elongation; with increasing passes of MF the strength increases while the maximum elongation decreases. The hardness measurement results demonstrate the structure homogeneity, the fractography pictures show ductile fracture of the specimen, and the micrographs describe the microstructure development during MF process.

EXPERIMENTAL RESEARCH ON LASER-MATERIAL INTERACTION

This paper presents a new method of real-time measuring technology to investigate the thermo-physical process of laser-material interaction during laser non-melting surface processing. In the thickness direction of the specimen, the temperature distribution was measured with Thermovision Infrared System in real-time. The dynamic micro-deformation of the specimen was studied using laser beam reflex amplifier system. Experiment results display the thermo-physical process of laser-material interaction and lay a foundation of further researching on the process of laser processing

Structural and hydrogen storage characterization of nanocrystalline magnesium synthesized by ECAP and catalyzed by different nanotube additives

Ball-milled nanocrystalline Mg powders catalyzed by TiO2 powder, titanate nanotubes and carbon nanotubes were subjected to intense plastic deformation by equal-channel angular pressing. Microstructural characteristics of these nanocomposites have been investigated by X-ray diffraction. Microstructural parameters, such as the average crystallite size, the average dislocation density and the average dislocation distance have been determined by the modified Williamson–Hall analysis. Complementary hydrogen desorption and absorption experiments were carried out in a Sieverts’ type apparatus. It was found that the Mg-based composite catalyzed by titanate nanotubes exhibits the best overall H-storage performance, reaching 7.1 wt% capacity. The hydrogenation kinetic curves can be fitted by the contracting volume function for all the investigated materials. From the fitted parameters, it is confirmed that the titanate nanotube additive results in far the best kinetic behavior, including the highest hydride front velocity