Disk And Strip Forging With Side Surface Foldower: Part 2: Evaluation Of The Upper-bound Solutions

The upper-bound solutions developed in Part 1 are evaluated with regard to their ability to produce a lower value for required power (load, pressure, or work). Comparisons made with existing solutions such as the triangular field solution and one-zone bulge solution show that for strip, each solution has a domain of geometry and friction in which it is superior. The new solution produces a lower upper-bound for conditions of high interface, friction and relatively thin specimen, the area where fold over is the observed mode of flow. For solid cylindrical disks, the solution fails to improve upon existing analyses, but comes sufficiently close to warrant additional study. After evaluation, these solutions were then used in an incremental technique to model the geometry and flow as a function of reduction in height. Results appear most encouraging, and the relative simplicity of the technique when compared with present alternatives is quite attractive. © 1978 ASME

Evaluation of strain and stress states in the single point incremental forming process

Single point incremental forming (SPIF) is a promising manufacturing process suitable for small batch production. Furthermore, the material formability is enhanced in comparison with the conventional sheet metal forming processes, resulting from the small plastic zone and the incremental nature. Nevertheless, the further development of the SPIF process requires the full understanding of the material deformation mechanism, which is of great importance for the effective process optimization. In this study, a comprehensive finite element model has been developed to analyse the state of strain and stress in the vicinity of the contact area, where the plastic deformation increases by means of the forming tool action. The numerical model is firstly validated with experimental results from a simple truncated cone of AA7075-O aluminium alloy, namely, the forming force evolution, the final thickness and the plastic strain distributions. In order to evaluate accurately the through-thickness gradients, the blank is modelled with solid finite elements. The small contact area between the forming tool and the sheet produces a negative mean stress under the tool, postponing the ductile fracture occurrence. On the other hand, the residual stresses in both circumferential and meridional directions are positive in the inner skin of the cone and negative in the outer skin. They arise predominantly along the circumferential direction due to the geometrical restrictions in this direction.The authors would like to gratefully acknowledge the financial support from the Portuguese Foundation for Science and Technology (FCT) under project PTDC/EMS-TEC/1805/2012. The first author is also grateful to the FCT for the postdoctoral grant SFRH/BPD/101334/2014.info:eu-repo/semantics/publishedVersio

Hot Extrusion of Ceramics

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65963/1/j.1151-2916.1992.tb07206.x.pd

Analysis of Metal Extrusion

The process of extrusion through a chamber is analyzed. Kinematically admissible velocity fields are utilized to obtain a lower upper-bound solution for the extrusion stress. Assumptions are as follows: a spherical velocity field for the early stages of direct and indirect extrusion; a radial velocity field at end of stroke; and finally maximum shear stress σ03 between billet and chamber for lower upper bound. When this maximum shear stress is then replaced by a lower friction stress, the solution obtained becomes an approximation for the actual extrusion stress. The cavity phenomena and piping effect are discussed. Conditions for inception of the cavity and development of the pipe are predicted. The inner radius of the pipe is determined. Results are given in mathematical form and plotted over a wide range of conditions. They are compared with Kudo’s [5] results.</jats:p