Ultra High Speed DIC and Virtual Fields Method Analysis of a Three Point Bending Impact Test on an Aluminium Bar

Abstract

This paper deals with the analysis of an aluminium beam impacted in a three point bending configuration using a Hopkinson bar device. Full-field deformation measurements were performed using Digital Image Correlation on images captured with an ultra high speed camera (16 frames at a time resolution of 10 μs). The performance of the deformation and strain measurements were evaluated and the data were then used quantitatively to analyse the very complex dynamic behaviour of the beam. It was shown that the deformation of the beam was controlled by the interaction between the striker and the flexural bending wave triggered by the initial impact. The principle of virtual work was used to reconstruct the impact force from the shear strains and to analyze how this impact force relates to the acceleration of the specimen (inertia forces) and the development of the bending stresses. The results are in good agreement with expectations. This opens up new perspectives in the quantitative use of full-field measurements to extract elasto-plastic constitutive parameters from such impact tests.

Full-Field Strain Measurement and Identification of Composites Moduli at High Strain Rate with the Virtual Fields Method

“…The curves also show that inertial forces coming from the sample itself take part to the global forces for only a small amount because of the small and light specimen, and because of the test configuration. In another recent study based on the same principle, this term proved predominant [49,50].…”

“…While the first one is largely dependent on the quality of the cameras, the second point will require significant effort in the future where numerical simulations will have to be employed to validate the designs with respect to the materials parameters to be identified. Some exploratory work is underway on metals [50].…”

Dynamic response of reverse Taylor impact based on DIC technology

“…Cofaru et al [12] elaborated on the calculation principles of DIC method, using the method to analyze the test data under low strain rate, and then, obtained the accurate results. High-speed DIC method was applied to three-point bending test which was loaded by Hopkinson bar, and the mechanical properties of aluminum under the action of bending is obtained by Pierron et al [13]. Kumar et al [14] applied the DIC method to high strain rate experiment with explosion loading, the bending response of aluminum was measured and agreed well with the simulation results.…”

Identification of nonlinear kinematic hardening constitutive model parameters using the virtual fields method for advanced high strength steels

“…In this case, an inverse solution tool becomes highly desirable. There have been various inverse solution tools suitable for parameter identification as reviewed by Avril et al (2008), for instance, finite element model updating (FEMU) (Farhat and Hemez, 1993;Güner et al, 2012;Roux and Bouchard, 2015;Zhang et al, 2014) and the virtual fields method (VFM) (Chalal et al, 2006;Grédiac and Pierron, 2006;Notta-Cuvier et al, 2013;Pierron and Grediac, 2012;Pierron et al, 2010b). These methods take advantage of the full-field deformation measurement techniques such as digital image correlation (DIC) (Sutton et al, 2009), the grid method (Grédiac et al, 2016), moiré and speckle interferometry (Creath, 1985;Post and Baracat, 1981), from which more comprehensive information of material behavior can be extracted from a greater number of measurement points on the specimen surface.…”