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Objective To study dynamic compression performance of adipose tissues, so as to further reveal the damage mechanism, and provide references for medical treatment.Methods Based on the improved split Hopkinson pressure bar (SHPB) experimental device, the adipose tissue dynamic compression experiment was conducted. The stress-strain curves of adipose tissues at different strain rates were obtained. Then the numerical model of SHPB was established, and the experimental process was simulated and analyzed. The numerical simulation for penetration process of 32 mm diameter rubber non-lethal projectile into the simulated target in human abdomen was carried out.Results Adipose tissues had a noticeable strain rate effect. The stress-strain curves at two high strain rates were approximately straight lines. The slope was similar, and the elastic modulus was 3.25 MPa, which was about 6 times of that under a quasi-static state. The simulation curves of fat SHPB were consistent with the experimental curves, which verified correctness of the constitutive model. In the process of non-lethal projectile penetrating human abdomen, an annular convex area similar to water wave appeared on skin surface, and the fat layer absorbed about 67% of the impact kinetic energy.Conclusions The experimental data of adipose tissues are very accurate. Numerical simulation can reproduce the penetration process well, and provide references for studying the damaging effect of non-lethal weapons on human body.
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Objective On the basis of explicit dynamics calculation theory, a numerical model for calculating active and passive properties of muscles with high strain rate was proposed. Methods In the process of calculating the motion equation of muscle element with high strain rate, Hill’s three-factor muscle model with high strain rate was introduced into the noda force formula to modify the node force in each time step. Results As Hill’s three-factor muscle model was introduced in numerical calculation, the muscle element had the passive characteristics of the general structural constitutive model and its proprietary active characteristics. Conclusions The research findings will contribute to numerical calculation for dynamic response and damage of muscles with high strain rate.
RESUMEN
Objective To study the mechanical properties of ballistic gelatin and establish a dynamic constitutive model by a numerical method to lay the foundation for the related research on wound ballistics. Methods First, 20% ballistic gelatin samples at 10°C were prepared, and then, the quasi static and dynamic compressive mechanical properties of the ballistic gelatin were tested using a universal material testing machine and an aluminum Hopkinson bar, respectively. Results The quasi-static and dynamic compressive stress-strain curves of 20% ballistic gelatin at 10 ℃ were obtained. When the strain was 0.45, the true stress was 0.041, 0.083, 0.194, 14.515, 31.496, 55.597, and 96.678 MPa at a strain rate of 10-3, 10-2, 10-1, 5 800, 7 900, 10 400, and 13 000 s-1, respectively. When the strain rate was 13 000 s-1 and the strain increased from 0.4 to 0.5, the stress increased rapidly from 53.558 MPa to 164.417 MPa, equivalent to an increase by over 3.07 times. Conclusions The ballistic gelatin had a remarkable strain rate effect in the range of both low and high strain rates. The constitutive model with strain rate was established based on the experimental results with the form of σ=kε·mεn, and the material constants of 20% ballistic gelatin were obtained.