Experimental characterization of dynamic behaviour of gelatin-based material using DIC |
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| Institution: | 1. Institute of Continuous Media Mechanics UB RAS, Perm, Russia;2. Perm State University, Perm, Russia;3. Leibniz Institute of Polymer Research, Dresden, Germany;1. Laboratory of Plastics and Rubber Technology, Department of Physical Chemistry and Materials Science, Budapest University of Technology and Economics, H-1521 Budapest, P.O. Box 91, Hungary;2. Institute of Materials and Environmental Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, H-1519 Budapest, P.O. Box 286, Hungary;1. Certech ASBL, Rue Jules Bordet, Zone Industrielle C, B-7180 Seneffe, Belgium;2. Agilent Technologies LDA UK Ltd, Essex Road, Church Stretton, SY6 6AX Shropshire, UK;1. Department of Polymer Engineering, Faculty of Mechanical Engineering, Budapest University of Technology and Economics, Műegyetem rkp. 3., H-1111 Budapest, Hungary;2. MTA–BME Research Group for Composite Science and Technology, Műegyetem rkp. 3., H-1111 Budapest, Hungary;1. LMS, Ecole Polytechnique, CNRS, Université Paris-Saclay, 91128 Palaiseau, France;2. Laboratoire PIMM, ENSAM, CNRS, CNAM, 151 bd de l’Hôpital, 75013 Paris, France;1. The Key Laboratory of Polymer Processing Engineering, Ministry of Education, China (South China University of Technology), Guangzhou, 510640, China;2. College of Chemistry and Chemical Engineering, Henan University, Kaifeng 475004, China;3. School of Chemistry and Chemical Engineering, Guangxi University, Nanning, 530004, China |
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| Abstract: | In this paper, the dynamic response of gelatin-based soft material under impact loading is investigated. The dynamic tests are principally performed by the classical SHPB (Split Hopkinson Pressure Bars) technique. However, due to the very low mechanical impedance of the specimen compared with the Hopkinson bars, the feeble impact forces are measured by highly sensitive piezoelectric polyvinylidene fluoride (PVDF) pressure sensors instead of SHPB measurement system. The PVDF pressure sensors are placed on the interfaces between the specimen and the bars. During the impact test, the non-equilibrium stress state and inhomogeneous strain fields are developed in the specimen; a digital image correlation (DIC) technique is proposed to identify the inhomogeneous displacement fields using high speed photography. A non-parametric approach based on the DIC technique is developed to deduce the transient stress fields in the longitudinal and transverse directions from the displacement fields measured by DIC. The validation of the calculated stress fields is performed by comparing them with the stress measurements from the PVDF pressure sensor at the bottom end of the specimen. Furthermore, stress-strain response is carried out using this approach throughout the specimen. It is clearly shown that the average highest strain rate varies with position in the specimen. This lead to multiple stress-strain relations determined at different strain rates by only one impact test. The significant strain rate sensitivity is observed at the tested rate range from 81/s to 269/s. Under compression loading, the axial stress state is developed as a simple compression only in the central part of the specimen due to the friction at the interfaces between the specimen and the bars. According to the calculated results based on movement of “long waves”, the region of the simple compression stress state in the central part of the specimen is localized. It is observed that the axial stress is much more important than the transverse stress in the central part and this confirms the assumption of uni-axial compression stress state in the specimen. |
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| Keywords: | Soft material Impact test Digital image correlation Inhomogeneous strain fields Strain rate sensitivity Non-parametric approach |
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