Papers by Author: Lech Olejnik

Abstract: Incremental equal channel angular pressing (I-ECAP) is a process used for production of continuous ultrafine grained bars, plates and sheets. Normally the thickness of the processed billet is kept unchanged in consecutive passes to enable repetitive insertion into the same die. This is achieved by controlling the bottom dead centre of the reciprocating punch. However, if a final product requires being thinner and therefore longer, the bottom position of the punch can be lowered before the last pass. Going further, the bottom position of the punch can be changed during the process, which opens up a possibility to vary billet thickness along its length. Such a product, especially sheet, can serve as a preform for further metal forming operations and is known as tailored blank. This paper will show examples of varying thickness sheets produced by different configurations of I-ECAP. Experimental and finite element results will be presented.

Abstract: Abstract: A new concept of incremental equal channel angular pressing (I-ECAP) with converging billets is proposed and simulated numerically. It follows a recently introduced process of ECAP with converging billets, in which the contact surface between converging billets plays the same role as a movable die wall in the output channel of classical ECAP and thus reduces friction and the process force. The process productivity is doubled and material pickup, especially problematic in the output channel, avoided. However, ECAP with converging billets, as any ECAP-based process, suffers from a limited length of the billets it can process. This paper proposes an incremental version of ECAP with converging billets, which enables processing very long billets. Additionally, a new option for ECAP or I-ECAP with converging billets is considered, which assumes their separation with a movable tool. This tool can also be used to apply a back force. FEM simulations of all these processes enable their comparison in terms of strain distribution and the force required.

Abstract: A new way of severely deforming ductile metals in order to refine their microstructure is proposed. It is called incremental angular splitting and originates from the idea of orthogonal cutting. It is intended to intensify plastic deformation in the cutting zone and lead to faster refinement of the microstructure. A laboratory experiment carried out on Al 1070 has proved the technical feasibility of the process. As the first indication of process capability, micro hardness measurements have been used to compare incremental angular splitting and incremental equal channel angular pressing.

Abstract: Creating a small amount of ultrafine grained metals by severe plastic deformation, for example using equal channel angular pressing, is possible in many research laboratories. However, industrial production of these materials is lagging behind because of the lack of industrially viable severe plastic deformation processes. One attempt to change this situation is based on the concept of incremental equal channel angular pressing developed by the University of Strathclyde and Warsaw University of Technology. The paper describes the path the researchers took to develop the process starting from finite element simulation, through tool design and process implementation, to material characterisation. Examples of various process configurations, which enable obtaining UFG bars, plates and sheets are given and possible future developments discussed.

Abstract: Equal channel angular pressing (ECAP) is the most popular severe plastic deformation process used to refine grain structure of metals. However, its application exhibits inherent problems of low productivity and poor utilization of material. In order to address these problems, the ECAP channel with two-turns can be used. Historical examples and current applications of this configuration are provided including route BC version of the process. Route C version of two-turn ECAP is illustrated with a scaled-up process used for processing square inch cross section aluminium billets. To address another problem, that of short billets, it is suggested that future applications of two-turn ECAP are based on the new process of incremental ECAP; it enables decoupling feeding of the material and its deformation and thus reduces dramatically the feeding force for billets, plates and sheets.

Abstract: Batch SPD processes have a limited scope for being used on an industrial scale. More feasible are continuous processes among which the new SPD process of Incremental ECAP (IECAP) is an attractive option. In this paper, a double-billet version of I-ECAP, which doubles process productivity, is presented. The concept of the process is first checked using the finite element (FE) method. FE simulation results are the basis for the design of an experimental rig. Trials of nanostructuring of 10x10x200 Al 1070 billets are carried out with the forces on the reciprocating die and the feeder measured. Metallurgical samples after 4 and 8 passes of I-ECAP (route BC) are investigated using TEM. Tensile properties after 8 passes are established. All these results show that the new SPD process of I-ECAP gives the results comparable to those obtained by a classical batch ECAP with the added capability of dealing with much longer (possibly infinite) billets.

Abstract: Batch severe plastic deformation (SPD) processes are mainly used for laboratory purposes. More industrially oriented are continuous processes among which the new SPD process of Incremental Equal Channel Angular Pressing (I-ECAP) is an attractive option. This paper investigates the feasibility of using I-ECAP for nanostructuring of plates rather than bars. First, a 3D finite element simulation has been performed which shows the importance of restricting material flow in the direction of plate width. A laboratory rig has been designed, which converts the vertical movement of the machine crosshead into an oblique movement of the reciprocating punch. Preliminary trials of I-ECAP have been carried out on a 4x30x100mm Al 1070 plate. Metallurgical samples after 4 and 8 passes of I-ECAP (route A) have been investigated using TEM. In conclusion, the new SPD process of I-ECAP is capable of processing plates, which opens up new possibilities of nanostructuring metals on an industrial scale.

Abstract: This paper explains the concept of 3D-ECAP with “in-die rotation” and presents the results of experiments for two sets of tooling with channel passages orientated at 90° and 120°. The results for aluminium 1070 are compared in terms of the process force, billet end effects, mechanical properties and structure of the material.