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In order to study the effect of charge size on the cook-off characteristics of pressed charges, the calculation model of cook-off process was established for HMX-based pressed charges. The cook-off bombs with different charge sizes were simulated by Fluent software, the effect of charge size on the ignition position, response temperature and response time of pressed charges at different heating rates was calculated. It was found that, at the same heating rate, the response temperature of the charge center is the highest when the length-diameter ratio of HMX-based pressed explosive is 1.0, and the ignition temperature of the charge center decreases with the increase of the length-diameter ratio when the length-diameter ratio is greater than 1.0. When the length-diameter ratio increases to a certain extent, the response temperature of the charge center tends to be a constant. The ignition position of the charge is determined by both the heating rate and the size of the charge, and the ratio of heat transfer between the end face and the periphery face of the charge is inversely proportional to the square of the length-diameter ratio. When the heating rate is slow or the length-diameter ratio is small, the ignition position of the charge is located at the charge center; when the heating rate is fast and the length-diameter ratio is large, the ignition position of the charge is gradually away from the charge center. [ABSTRACT FROM AUTHOR]

Classical J2 plasticity theory is the most popular continuum plasticity model. However, this plasticity theory is inapplicable for some metals due to the tension/compression asymmetry behavior. According to our previous study, the tension and compression mechanical response of laser-solid-formed Ti–6Al–4V alloy was significantly different in not only yield stress but also work hardening rate. In this study, effects of temperature and strain rate on the tension/compression asymmetry behavior of laser-solid-formed Ti-6Al-4V alloy were analyzed. Through mechanism discussion, different activations of slip systems and deformation twinning were considered to be the main causes of the tension/compression asymmetry. Finally, an improved constitutive model was developed, considering the synergistic effects of temperature, strain rate, and stress state on the plastic behavior of laser-solid-formed Ti–6Al–4V alloy. The calibrated model can accurately describe the temperature and strain rate dependences of the tension/compression asymmetry behavior. To verify the applicability of the developed constitutive model at different stress state, dynamic shear tests and finite element simulations were conducted at different temperatures. The improved constitutive model was shown to be able to predict the plastic behavior of laser-solid-formed Ti–6Al–4V alloy at different stress states over a wide range of temperatures and strain rates. [ABSTRACT FROM AUTHOR]

Theoretical and experimental studies on the compressive mechanical behavior of 4-harness satin weave carbon/epoxy composite laminates under in-plane loading are conducted over the temperature range of 298–473 K and the strain rate range of 0.001–1700/s in this article. The stress–strain curves of 4-harness satin weave composites are obtained at different strain rates and temperatures, and key mechanical properties of the material are determined. The deformation mechanism and failure morphology of the samples are observed and analyzed by scanning electron microscope (SEM) micrographs. The results show that the uniaxial compressive mechanical properties of 4-harness satin weave composites are strongly dependent on the temperature but are weakly sensitive to strain rate. The peak stress and elastic modulus of the material have the trend of decrease with the increasing of temperature, and the decreasing trend can be expressed as the functional relationship of temperature shift factor. In addition, SEM observations show that the quasi-static failure mode of 4-harness satin weave composites is shear failure along the diagonal lines of the specimens, while the dynamic failure modes of the material are multiple delaminations and longitudinal splitting, and with the increasing of temperature, its longitudinal splitting is more serious, but the delamination is relatively reduced. A constitutive model with thermomechanical coupling effects is proposed based on the experimental results and the increment theory of elastic–plastic mechanics. The experimental verification and numerical analysis show that the model is shown to be able to predict the finite deformation behavior of 4-harness satin weave composites over a wide range of temperatures. [ABSTRACT FROM AUTHOR]