Figure 6 - uploaded by Yang Liu
Content may be subject to copyright.
1.4 Numerical simulation of the projectile impact on the steel/continuous polyethylene plate (Shot #720, top) and steel/diced polyethylene plate (Shot #729, bottom). Step time is 5.4 × 10 − 4 s.
Citations
... Various constitutive models of polyurea are also developed to describe its dynamic behavior. Most models are built to capture largedeformation softening, high strain-rate and temperature sensitivity of polyurea under a relatively low-pressure state [16,17,21,[32][33][34][35][36][37][38][39]. They can be divided into two broad categories, the viscoelastic models based on the hereditary integral (e.g. ...
... Among these works, the viscoelastic model built by Amirkhizi et al. [32] considers the pressure effect through a pressure-dependent time-temperature shift relationship. Cho et al. [36] and Filonova et al. [37] develop the viscoplastic models of polyurea accounting for its two-phase microstructure as co-continuity and inclusion, respectively. To describe the strongly nonlinear behavior of polyurea under the high-pressure impact, Key and Gorfain [40] modify the viscoelastic model of Amirkhizi et al. [32] by introducing a thermodynamic equation of state and the pressure-dependent modulus. ...
... The polyurea layer in these structures is under low-pressure impact since it is designed behind the steel plate. Grujicic et al. [53], Filonova et al. [37], and Key and Gorfain [40] all simulate the ballistic tests of Roland and Giller [48], where the polyurea-coated steel plates are impacted by FSP. Grujicic et al. [53] focus on investigating the energy absorption related to deformation-induced glass transition through a viscoelastic polyurea model. ...
Experiments have shown that the ballistic performance of the steel plate improves significantly after coating polyurea at the impact face. However, the strengthening mechanism of the elastomer coating on the ballistic-resistance is not understood well until now. In this paper, the strengthening mechanism and thickness effect of the coating under fragment simulating projectiles (FSP) impact are studied through numerical and experimental analysis. Firstly, a viscoplastic constitutive model of polyurea is developed based on experimental characterization and thermodynamic equation of state. It can capture strongly nonlinear volumetric behavior and impact-induced shearing stiffening and strengthening considering the coupling of high pressure, high temperature, and high strain rate under ballistic impact. Then, by applying this newly developed viscoplastic model of polyurea, the underlying ballistic-resistant mechanism of the polyurea-coated steel plate is numerically studied. The analysis shows that the dynamic behavior of polyurea under ballistic impact and propagating regulation of impact wave jointly play the key role. One side, the impact-induced stiffening and strengthening of the polyurea change the failure modes of the steel plate and considerably improve the ballistic-resistance of the structure. The other side, increasing coating thickness can only provide the limited benefit for improving the ballistic-resistance of the structure, as obtained in experiments. For the impact-face-coated steel plate, the low-thickness polyurea coating suffering from FSP impact can increase the frequency of the compressive wave reflection-superposition on the high-impedance polyurea/steel interface before the energy transfer from the impacted location. This helps to improve the pressure level and enhance the instantaneous energy storage and dissipation of the polyurea per volume significantly. However, increasing coating thickness can make the pressure level and the specific energy density of polyurea decrease gradually during penetration. It is also found that the energy dissipation of FSP during penetration is reduced after increasing the coating thickness because of the erosion mitigation from the structure. The new insight on the strengthening mechanism of elastomer coating will be helpful for the light armor design.
... The fracture strain is given by Filonova et al. (2015): ...
Due to the complexity of installations and connections of subsea production equipment and the massive structures involved in a challenging environment, the failure of subsea production equipment could induce enormous loss to the safety and reliability of structures in addition to the cost of the oilfield development. One of the challenges that the subsea production structures face, as it moves to ultra-deep water and polar underwater equipment, is to design subsea shell structures capable of withstanding high external pressures. Hence, a subsea function chamber (SFC) has been lately proposed as a viable solution, which has a high level of safety and reliability, and a technique for the subsea production system. This paper presents a general and efficient buckling and collapse analysis strategy. In this work, the SFC is composed of cylindrical and hemispherical shaped steel material. Initial imperfection-based nonlinear buckling analysis has been carried out to investigate the buckling and risks associated with different thicknesses of the structure. Linear and nonlinear static buckling analyses have been carried out using ABAQUS software. By introducing the nonlinear properties of materials, the nonlinear numerical model of SFC is established. The effects of the thickness of different models and the number of stiffeners on the buckling modes are discussed. The wall thickness is calculated by the Donnell equation and Timoshenko’s classical method. It has been found that the classical solutions given by the Donnell and Timoshenko equations are more accurate for structures with larger lengths and diam. The thickness and number of stiffeners have a great influence on the ultimate buckling external pressure load of SFC structure
