A Review of Flow Forming Processes and Mechanisms

Abstract

Abstract. After years of purely academic interest and niche applications, today the flow forming process is increasing demand in aerospace, automotive and defense industries. This review surveys academic paper of last fifty years, in order to evaluate the current state-of-the-art for academic and practitioner. Theoretical and experimental approaches are collected and compared by evaluating their prediction models. As a result, several knowledge gaps are identified, for example stress and strain tensors evolutions are not determined for workpiece, due to high computational cost and uncertainty about the correct finite elements approach to adopt. Similarly although, the final microstructure is often evaluated for specific cases, study of its evolution during plastic deformation has not been reported. Residual stress and final material proprieties, such as corrosion behavior, have been not studied numerically or experimentally. Tool path impact and alternative geometries are not deeply explored. Particular attention is given to process experimental optimization and characterization through Design of Experiment, which is still limited to a few papers and sometimes not well developed. The results of this review will help define a research agenda for future developments.

A methodology for assessing the feasibility of producing components by flow forming

“…Quality targets definition was contemporary deployed with product design and material selection. Targets were defined by stakeholder needs and improvement possibilities, for example: The failure prediction models and the dependency between quality target and failure is summarized in (Marini et al, 2016) and (Marini et al, 2015). Table 1 summarizes some of them.…”

“…Reduction ratios were selected from literature for similar Table 1. influences of process parameters on defects and geometrical inaccuracies (h, high; L, low; n/a, not available; n/c not clear) (Marini et al, 2015). material and adapted to current dimensions, (Roy, Klassen, & Wood, 2009), (Singhal et al, 1987) and (Chang et al, 1998).…”

“…This selection is not optimized but a first draft, which can be still considered reliable for judging the process feasibility. This happens because of process parameters range and their connection with geometries and materials (Marini et al, 2015).…”

“…Although, if contact ratio becomes too large (S/L >> 1), friction coefficient become close to unity and material flows in directions smaller than the attack angle. In this case, wave-like surfaces and thickness variation in workpiece occur (Marini et al, 2015). Appendix 3 provides mathematical formulation of the S/L ratio.…”

“…power) to fulfill small-medium batches and a flexibility which allows production of a wide range of rotational shapes and near-net-shape components. The process is very efficient in terms of material usage and its adoption often allows reduction of component's weight and costs (both important considerations in many industrial applications) (Marini, Cunningham, & Corney, 2015).…”