STRESS DISTRIBUTION IN GRADED CELLULAR MATERIALS UNDER DYNAMIC COMPRESSION

Abstract

DYNAMIC COMPRESSION BEHAVIORS OF DENSITY-HOMOGENEOUS AND DEN-SITY-GRADED IRREGULAR HONEYCOMBS ARE INVESTIGATED USING CELL-BASED FINITE ELEMENT MODELS UNDER A CONSTANT-VELOCITY IMPACT SCENARIO. A METHOD BASED ON THE CROSS-SECTIONAL ENGINEERING STRESS IS DEVELOPED TO OBTAIN THE ONE-DIMENSIONAL STRESS DISTRIBUTION ALONG THE LOADING DIRECTION IN A CELLULAR SPECIMEN. THE CROSS-SECTIONAL ENGINEERING STRESS IS CONTRIBUTED BY TWO PARTS: THE NODE-TRANSITIVE STRESS AND THE CONTACT-INDUCED STRESS, WHICH ARE CAUSED BY THE NODAL FORCE AND THE CONTACT OF CELL WALLS, RESPECTIVELY. IT IS FOUND THAT THE CONTACT-INDUCED STRESS IS DOMINANT FOR THE SIGNIFICANTLY ENHANCED STRESS BEHIND THE SHOCK FRONT. THE STRESS ENHANCEMENT AND THE COMPAC-TION WAVE PROPAGATION CAN BE OBSERVED THROUGH THE STRESS DISTRIBU-TIONS IN HONEYCOMBS UNDER HIGH-VELOCITY COMPRESSION. THE SINGLE AND DOUBLE COMPACTION WAVE MODES ARE OBSERVED DIRECTLY FROM THE STRESS DISTRIBUTIONS. THEORETICAL ANALYSIS OF THE COMPACTION WAVE PROPAGATION IN THE DENSITY-GRADED HONEYCOMBS BASED ON THE R-PH (RIGID–PLASTIC HARDENING) IDEALIZATION IS CARRIED OUT AND VERIFIED BY THE NUMERICAL SIMULATIONS. IT IS FOUND THAT STRESS DISTRIBUTION IN CELLULAR MATERIALS AND THE COMPACTION WAVE PROPAGATION CHARACTER-ISTICS UNDER DYNAMIC COMPRESSION CAN BE APPROXIMATELY PREDICTED BY THE R-PH SHOCK MODEL.