Principles of Nonequal Channel Angular Pressing

Abstract

A variant of the equal channel angular pressing (ECAP) process is examined in this paper where the channels are of rectangular shape with different thicknesses while the widths of the channels are the same. The process is named nonequal channel angular pressing and it is similar to the earlier introduced dissimilar channel angular pressing (DCAP) process. In DCAP, however, the diameters are near values, with the exit channel being slightly larger, while in NECAP, the exit channel is much smaller attributing several advantages to nonequal channel angular pressing (NECAP) with respect to ECAP. In this work an analysis is performed to determine the strain mode in a 90 deg NECAP die. A new flow line function is also presented to better describe the deformation field. The proposed flow line function is validated using finite element simulations. A comparison is made between ECAP and NECAP. Finally, texture predictions are presented for NECAP of fcc polycrystals. The advantages of this severe plastic deformation process are the following: (i) significantly larger strains can be obtained in one pass with respect to the classical ECAP process, (ii) grains become more elongated that enhances their fragmentation, and (iii) large hydrostatic stresses develop that improve the stability of the deformation process for difficult-to-work materials. The results obtained concerning the deformation field are also applicable in the machining process for the plastic strains that imparted into the chips.

Characterization of the deformation field in large-strain extrusion machining

“…Such a material flow process has been clearly observed in the LSEM experiments of OFHC, and so does in recent LSEM experiments conducted by Guo et al (2012). The LSEM process is very similar to that in a nonequal channel angle pressing process put forward by Hasani et al (2010). As shown in Fig.…”

Deformation Field Analysis in Equal Channel Angular Extrusion of Metals Using Asymmetric Flow Function

“…This shift can be so significant that the flow line can describe a flow for non‐equal channel angular extrusion, called NECAE, which differs from the ECAE test by a reduced diameter of the exit channel with respect to the entry one. The NECAE test was first introduced by Toth et al and was theoretically examined in ref . In a recent paper, texture and microstructure results were presented for NECAE of Al.…”

The New Plastic Flow Machining Process for Producing Thin Sheets

“…However, the microstructure produced by PFM is heterogeneous while it is mostly homogeneous in LSEM, and the hydrostatic pressure produced in the deformation zone in PFM is likely to be higher than that in LSEM. PFM also exhibits a common feature with nonequal channel angular pressing (NECAP) [16,17] in terms of the working principle. Indeed, lateral extrusion in PFM works in the same way as in NECAP.…”