Abstract

The article presents the results of the analysis of the interactions between the single point incremental forming (SPIF) process parameters and the main roughness parameters of stiffened ribs fabricated in Alclad aluminium alloy panels. EN AW-7075-T6 and EN AW-2024-T3 Alclad aluminium alloy sheets were used as the research material. Panels with longitudinal ribs were produced with different values of incremental vertical step size and tool rotational speed. Alclad is formed of high-purity aluminium surface layers metallurgically bonded to aluminium alloy core material. The quality of the surface roughness and unbroken Alclad are key problems in SPIF of Alclad sheets destined for aerospace applications. The interactions between the SPIF process parameters and the main roughness parameters of the stiffened ribs were determined. The influence of forming parameters on average roughness Sa and the 10-point peak–valley surface roughness Sz was determined using artificial neural networks. The greater the value of the incremental vertical step size, the more prominent the ridges found in the inner surface of stiffened ribs, especially in the case of both Alclad aluminium alloy sheets. The predictive models of ANNs for the Sa and the Sz were characterised by performance measures with R2 values lying between 0.657 and 0.979. A different character of change in surface roughness was found for sheets covered with and not covered with a soft layer of technically pure aluminium. In the case of Alclad sheets, increasing the value of the incremental vertical step size increases the value of the surface roughness parameters Sa and Sz. In the case of the sheets not covered by Alclad, reduction of the tool rotational speed increases the Sz parameter and decreases the Sa parameter. An obvious increase in the Sz parameter was observed with an increase in the incremental vertical step size.

Highlights

  • The results showed that effective lubrication is of the greatest importance for the formability and reduction of roughness in incremental sheet forming (ISF)

  • The single point incremental forming (SPIF) process of Alclad sheets is different from that commonly studied in the literature, and in this paper, analysis is carried out on the change in surface roughness during the forming of rib-stiffened panels made of aluminium alloy Alclad sheets

  • Selected surface topographies and the values of the basic parameters of the stereometric structure of the inner surface of the ribs formed in 1-mm-thick EN AW-2024-T3, 0.4-mm-thick EN AW-2024-T3 Alclad and 0.8-mm-thick EN AW-7075-T6 aluminium al

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Summary

Introduction

The surface roughness of the specimen is the result of the influence obtained between the tool and specimen, where the lubricant plays a significant role during the forming process [6]. The results showed that effective lubrication is of the greatest importance for the formability and reduction of roughness in incremental sheet forming (ISF). The SPIF process of Alclad sheets is different from that commonly studied in the literature, and in this paper, analysis is carried out on the change in surface roughness during the forming of rib-stiffened panels made of aluminium alloy Alclad sheets. The effect of the forming parameters on the surface finish of the inner surface of stiffened ribs is studied based on experimental measurements of the surface roughness and on the artificial neural networks

Material
Method
Analysis of Surface Roughness
Artificial Neural Networks
Surface Topography
ANN Modelling
The error values were observed for networks inlearned
Conclusions
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