Determination of material constants for high strain rate constitutive model of high entropy alloys

Abstract

The paper deals with constitutive models determination for a group of high entropy materials (coded Bl-x). The procedure includes the following steps: experimental determination of mechanical characteristics for quasi-static domain through compression tests, correction of experimental data of quasi-static tests using numerical simulation, acquisition of experimental data obtained on the Split Hopkinson Pressure Bars and their simulated interpretation. Using the processed data, the constitutive patterns of the materials under investigation are drawn. The experimental data correction for quasi-static tests performed using numerical simulation involves drawing the engineering stress/strain diagram, the transition to the plastic characteristic diagram in the hypothesis of perfectly cylindrical shape of the specimen throughout the test, simulation of the compression deformation process in the presence of friction force on the end specimen surfaces and the correction of the characteristic plastic diagram using the calculated error. Dynamic data obtained on Split Hopkinson Pressure Bar were interpreted using a methodology previously published. Experimental data under real conditions are compared with data obtained by numerical simulation on an elasto-plastic model. The viscous component of the dynamic response is the difference between the real and simulated on the elasto-plastic model responses.

3d Fem Model for Hopkinson Split Torsional (Kolsky) Bar Experimental Technique

“…Using virtual transducers, the variation of stress and strain on the incident and receiver bars, symmetric to the specimen, was recorded. For the highentropy alloy probe, a previously determined material model was used [4] using a methodology described in the literature [5]. Also, the distribution of stress and strain in the specimen was analyzed.…”

Archives of Metallurgy and Materials

“…to ensure the optimal conditions for the manufacture of ballistic protection equipment, military and security specifications have been developed, which provide for test procedures, protection levels provided according to impact speeds with different types of penetrators, environmental conditions and characteristics of materials used (minimum 540-600 Bhn or 55-60 rockwell c, minimum yield and tensile strength 1500 to 1700 MPa, minimum transverse charpy-V impact energy of 13 J at -40 o c and minimum elongation of 6%) [2,3]. considering these required properties, more of armors have been realized by metallic alloys: high strength low-carbon martensitic steel [3], high strength steel [4], high entropy alloys from alcocrfeni alloying system [5][6][7], Weldox 700e steel [8], aIsI 4340 Q&t steel [9][10][11], 500 hB high hardness armor steel [12].…”