FE analysis of multi-cycle micro-forming through using closed-die upsetting models and forward extrusion models

Research in micro-forming leads to the investigation of the effects of heat generation in the workpiece and temperature changes in the tools during the forming. The results reported in this paper relate to the study of cold micro-forming processes which are usually ignored on its thermal characteristics. Two closed-die upsetting models were used for the simulation of the forming of micro-parts in single forming trial and in mass production (multi-cycle loading), respectively. An elastic-plastic finite element simulation was performed for a single forming trial. The heat transferred to the die, computed from the simulation, was then used as an input for the multi-cycle heat loading analysis in the die. Two materials: silver and low carbon steel, were used as the work material. The results show that the die saturation temperature could still go up to 100 °C for small size dies, which is significant for the forming of micro-parts. Forming errors due to the die-temperature changes were further computed, which forms a basis for developing considerations on the forming-error compensation. Using the same methods and procedures, forming of a micro-pin via forward extrusion was analysed

Evaluation of coefficient of friction in bulk metal forming

In this study an upper bound analysis for cylindrical "Barrel Compression Test" (BCT) is developed. BCT method is a very simple method which can be utilized in order to evaluate quantitatively the coefficient of friction by means of just one cylindrical specimen in an upsetting test. The method is checked by a series of finite element method (FEM) simulations and by means of the results of FEM simulations the method is modified.Comment: A self report. 20 Pages, 2 Tables, 2 Figure

An overview of welding in solid state

The importance of the Solid State Processes (SSP) has increased in the last decade due to the industry demands of improved properties of joined/surfaced materials, combined with cost reduction and energy saving. New and/or micro-scale solid state processed materials are used by aerospace, automotive and electrotechnics industry. Nowadays, classic SSP are mainly applied to light materials, but progresses were also reported in steels. In this field, the tools design, the technology and practical techniques surpassed the fundamental approach of the materials solid state processing. The SSP parameters evaluation is based on different experiments, approaching the material flow in the large plastic deformation domain. The paper approaches the solid state welding/joining and surface processing. The envisaged SSP are solid state joining processes as Cold Welding (butt and spot welding), Friction Stir Welding – FSW, and surface processing, Friction Stir Processing - FSP. Therefore, the investigation targeted the deformation and flow pattern of the parent metal in case of cold welding and FSW/FSP, processes parameters evaluation and correlation, local analysis of the material structural transformations, and material hardening

Part dimensional errors in free upsetting due to the elastic springback

Pojava elastičnog vraćanja materijala radnog predmeta prisutna je u svim procesima plastičnog deformiranja metala. Ovaj faktor prepoznat je kao jedan od glavnih čimbenika dimenzijske (ne)točnosti. Stoga, da bi se proizveli dijelovi sukladno zahtjevima koji se odnose na njihovu geometriju ovaj fenomen se mora dobro razumjeti i uzeti u obzir prilikom projektiranja alata i procesa deformiranja. Nažalost, znanje vezano za ovaj fenomen je ograničeno te stoga predviđanje i proračun iznosa elastičnog vraćanja ponekad predstavlja vrlo težak zadatak. U ovom članku predstavljeno je opće analitičko rješenje za izračun elastičnog vraćanja. Izvedene analitičke jednadžbe mogu se primijeniti za različite procese oblikovanja pod uvjetom da su vrijednosti glavnih naprezanja na samom kraju procesa deformiranja poznate. Koristeći ovaj pristup izračunate su elastične deformacije i amplituda elastičnog vraćanja radnog komada kod procesa slobodnog prešanja cilindrične gredice. Dobiveni rezultati provjereni su pomoću MKE analize.Elastic springback of workpiece material which occurs in any forming process has been recognized as one of most relevant factors regarding part dimensional accuracy. Therefore, in order to manufacture component in accordance with the geometrical specifications engineers must have a good understanding of this phenomenon and take it into account during the design tool and forming process. Unfortunately, this knowledge is often insufficient and therefore the prediction of elastic springback is sometimes a very tough task. The paper presents a general approach for the calculation of elastic recovery. Given analytical equations can be applied for different forming processes under the condition that values of the principal stresses at the very end of forming process are known. By using this approach elastic strains and amplitude of elastic springback of workpiece in case of free upsetting of cylindrical billet were calculated. Obtained results were verified by FEM analysis