Determination of Elastic Modulus, Stress Relaxation Time and Thermal Softening Index in ZWT Constitutive Model for Reinforced Al/PTFE

Abstract

Al/PTFE has the advantages of high impact-responsive energy release, appropriate sensitivity, a fast energy release rate, and high energy density, and it is increasingly widely being used in the field of ammunition. In this paper, based on the traditional formula Al/PTFE (26.5%/73.5%), the reinforced Al/PTFE active materials are prepared by the process of cold pressing, sintering, and rapid cooling. Quasi static and dynamic compression experiments were carried out under different compression pressures (200~800 MPa), strain rates (0.002 s−1, 0.02 s−1, 1400~3300 s−1), and temperatures (23 °C, −20 °C, −30 °C, −40 °C). The effects of pressure, strain rate, and temperature on the quasi-static and dynamic compression properties of Al/PTFE materials are analyzed. The results show that the reinforced Al/PTFE specimens show a significant correlation between temperature and strain rate. Based on the classical Zhu–Wang–Tang (ZWT) constitutive model, the ZWT constitutive model parameters of the reinforced Al/PTFE active materials under different pressing pressures at room temperature and the ZWT constitutive model parameters of the reinforced Al/PTFE active materials at low temperature are obtained by fitting, respectively. The accuracy of the constitutive model parameters (elastic modulus, stress relaxation time, and thermal softening index) is verified. In this paper, a constitutive model considering both temperature and strain rate effects is established in order to provide reference for the study of mechanical properties of active materials.

Buckling in inelastic regime of a uniform console with symmetrical cross section: computer modeling using Maple 18

“…For the fluor polymers they hold too. Thus, for Al/PTFE (aluminum/polytetrafluoroethylene) the experimental data [10] fit well (4) (figure 4). Moreover, we see that in the wide enough middle part of the diagram points fit well on a straight line corresponding to the tangent modulus 𝐸𝑡 of about 50 MPa.…”

“…And since they are added geometrically to form 𝑣(𝑝) = 𝑦(𝑝) − 𝑏, the contribution will be completely invisible (figure 5). So, we may easily neglect the integral amendment in (10).…”

“…Analyzing the expressions (8)- (10) it is easily seen that correct solution of ODE may be received only for known dependence of the load 𝐹 on the final slope 𝑝 𝑓 . To find it we are to compile so called characteristic equation on restored length of the console.…”