Due to the wide range of various sheet metal grades and the need to verify the material properties, there are numerous methods to determine the material formability. One of them, that allows quick determination of sheet metal formability, is the Erichsen cupping test described in the ISO 20482: 2003 standard. In the presented work, the results of formability assessment for DC04 deep drawing sheet metal were obtained by means of the traditionally carried out Erichsen cupping test and compared with the results obtained by using two advanced methods based on vision analysis. Application of these methods allows extending the traditional scope of analysis during Erichsen cupping test by determination of the necking and strain localization before fracture. The proposed methods were compared in order to dedicate appropriate solution for the industrial application and laboratory tests respectively, where the simplicity and reliability are the mean aspects need to be considered when applied to the Erichsen cupping test.

Fatigue crack growth for 2024-T3 Alclad aluminium alloy sheet being subjected to two load programs: a constant stress amplitude cyclic tension (R=O. l) (CA) and a variable amplitude tension with either a single or multiple overloads (OVL) periodically repeated is analysed in the paper. The latter load program corresponds to a simple flight simulation spectrum of wing structure of civil aircraft. The investigation was developed in order to learn about interaction between the applied load and formation of fatigue striations. Experimental results of surface crack growth rate provided by optical observations were compared with the rate determined on the basis of microfracture analysis. Good correspondence found under CA loading between the surface growth rate and the growth rate in the sheet depth means that the direction of specimen's cutting does not change essentially the crack growth behaviour. In the case of second loading (OVL) this factor influences the crack growth behaviour. Microfracture analysis revealed either retardation and acceleration of crack growth rate under OL V loading. This behaviour of growth rate results from a plastic zone formed in the front of crack tip and a crack closure effect.

The present paper investigates the effects of variable-amplitude loads on fatigue crack growth rates for the 2024-T3 aluminium alloy on the basis of microfractographic analyses and its capacity to reconstruct load-time histories of failed components. For this purpose, there were applied three different variable-amplitude load sequences with single and multiple overloads and underloads. Subsequently, images of fatigue striations on components’ fracture surfaces were examined. The aforementioned loads were employed when simulating fatigue crack behaviour in aeronautical alloys.

Advanced vision method of analysis of the Erichsen cupping test based on laser speckle is presented in this work. This method proved to be useful for expanding the range of information on material formability for two commonly used grades of steel sheets: DC04 and DC01. The authors present a complex methodology and experimental procedure that allows not only to determine the standard Erichsen index but also to follow the material deformation stages immediately preceding the occurrence of the crack. Accurate determination of these characteristics in the sheet metal forming would be an important application, especially for automotive industry. However, the sheet metal forming is a very complex manufacturing process and its success depends on many factors. Therefore, attention is focused in this study on better understanding of the Erichsen index in combination with the material deformation history.