Abstract
The material characterization regarding sheet metal formability is usually assessed by the forming limit curve (FLC). The FLC requires specialized and expensive equipment, several samples with different geometries, and can be a very time-consuming procedure for data treatment. Alternatively, the hole expansion test (HET) and the Erichsen Cupping Test (ECT) can be used for routine evaluations of sheet metal mechanical behavior. These formability tests require fewer quantities of material and easy specimen preparation with a fast analysis of results. The HET and ECT procedures provide a proper evaluation of sheet material stretch-flangeability, formability, strength, and ductility. In this work, we developed a low-cost mechanical device capable of performing the HET and ECT tests using a universal testing machine. The equipment is designed to meet the test parameters set by ISO 16630 (HET) and ISO 20482 (ECT) standards. In order to verify its functionality, tests were carried out with the dual-phase steels DP600 and DP780. The corresponding values determined for the hole expansion ratio and the Erichsen index provided reliable results in terms of the accuracy and repeatability of the proposed testing device.
Highlights
Advanced high-strength steels (AHSS) are widely used in order to satisfy the requests of the automotive industry concerning weight reduction to meet the stringent global demands for fuel economy and reduced emissions
In the hole expansion test case, the hole expansion ratio (HER) is calculated by Equation (1) as the hole expansion percentage, based on the initial diameter
The other hand,the fortesting, the Erichsen cupping test,index the punch displacement displacement values areOn recorded during and the resulting is defined from the values are recorded during the testing, and the resulting index is defined from the punch displacement punch displacement versus punch load curve using the maximum force criterion
Summary
Advanced high-strength steels (AHSS) are widely used in order to satisfy the requests of the automotive industry concerning weight reduction to meet the stringent global demands for fuel economy and reduced emissions. The corresponding measures of HER and IE are usually associated with the mechanical properties obtained from the uniaxial tensile test, such as yield stress, ultimate yield strength, total elongation, strain-hardening exponent, strain-rate sensitivity, and Lankford coefficient, as reported elsewhere [10,11,12] Both test procedures are useful and straightforward for either rapid formability assessment or experimental data collection for material modeling validation, especially damage models [13,14]. Some alternatives have been proposed in the literature, such as the original Erichsen cupping ring device designed by Foster [17] to be mounted in a universal testing machine Using this testing device, Sorce et al [18] evaluated the sheet metal coating strain using a numerical-experimental approach based on Erichsen cupping tests. This work presents the development of a device that allows performing both hole expansion and Erichsen cupping tests using only the traditional universal testing machine
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