Limits of the Process of Rotational Compression of Hollow Stepped Shafts

Abstract

This article presents the results of theoretical–experimental testing of the process of rotational compression of hollow stepped shafts. The advantages of the technology and the potential area of its application were discussed. Further on, the limits of the rotational compression technology, preventing the manufacturing of high-quality products, were presented. The research was conducted on the basis of numerical modelling using the finite element method in Simufact Forming, as well as the results of experimental tests performed in a forging machine for rotational compression. On the basis of the results obtained, it can be stated that the process of rotational compression of hollow stepped shafts can be hindered by the following phenomena: uncontrolled slip, deformation of the semi-finished product wall, twisting of the formed steps, material cracking, and deformation of the cross-section of the formed steps. The possibility of those hindrances occurring depends heavily on the assumed technological parameters of the process. For this reason, knowledge of the cause of occurrence of those limitations is vital for the development of the technology and the choice of the process parameters.

Selected aspects of a cold forging process for hollow balls

“…In this paper, we will focus on the forming process, assuming that a hollow ball is made of a workable metal alloy. The literature review shows that there exist numerous forming methods for hollow balls, each of them having its advantages and disadvantages [5]. It should be emphasized that-in our opinion-machining is regarded as one of finishing methods, and, due to the fact that machining generates considerable material losses, it is not recommended for mass production.…”

“…1 Basic forging methods for hollow balls: a) backward extrusion of a bulk billet using split die, b) upsetting of a tube billet (sleeve) on fixed mandrel using dies, c) upsetting of a thin-walled billet (shell) using only dies, without any additional tools produce several parts that are then separated mechanically. Unfortunately, however, similarly to any other process [5], rotary compression too has its limitations [13]. First of all, there are constraints regarding the allowable wall thickness of forged parts, in combination with high costs of tools.…”

Selected Aspects of a Cold Forging Process for Hollow Balls

“…In this paper, we will focus on the forming process, assuming that a hollow ball is made of a workable metal alloy. The literature review shows that there exist numerous forming methods for hollow balls, each of them having its advantages and disadvantages [5]. It should be emphasized thatin our opinionmachining is regarded as one of finishing methods, and, due to the fact that machining generates considerable material losses, it is not recommended for mass production.…”

Conception of a Three Roll Cross Rolling Process of Hollow Rail Axles

“…In the case of hollow elements these cracks are located mostly on their inner surfaces. 21) The occurrence of ductile fractures can be modelled by calculating the damage function, which ought to be smaller than the critical damage value obtained in the calibrating test. [22][23][24] In this analysis normalised Cockcroft-Latham criterion was used for modelling damage.…”