Research On Dynamic Constitutive Model For Anisotropic Material And Its 2-D Thermodynamic Response Induced By X-Ray Radiation

In order to study the 2-D thermodynamic response of the carbon fiber-reforced phenolic polymer matrix composite material (hereinafter simply referred as TF material) induced by radiation of pulsed X-ray, the orthotropic dynamic elasto-plastic constitutive model is established in this thesis, based on which, a program code is made by finite element method to simulate the 2-D thermal shock wave propagation and blow-off pulse distribution in TF composite.The main achievements and conclusions in this thesis are presented as follows:1. The orthotropic dynamic elasto-plastic constitutive model is established, which includes:â‘ the mean stress and deviatoric stress formulas are deduced while the volume change and shape change is coupled in the elastic and plastic deformation phases;â‘¡for the intense expansion of material surface induced by X-ray energy deposition, the PUFF equation of state is introduced and modified first time, thus it can depict both the nonlinear characteristic of volume change and the anisotropic strength effect;â‘¢the strain strengthen and strain-rate strengthen effect are considered to develop the orthotropic yield criterion.2. The modification of objective stress-rate and transition between the anisotropic principal axis coordinates and system coordinates in 2-D model are discussed, and a convenient method is adopted to deal with the two problems together, which simplifies the numeration program code greatly and improves the numerical simulation efficiency.3. For the cylinder shell structure, the convenient arithmetics of X-ray radiation in irregular quadrilateral grids is discussed, and the results show that: the midpoint integral and parallelogram approximation arithmetics both save computation time and have high precision, and they can replace the integral method to compute energy depositon very well. The midpoint integral arithmetic is of better applicability for it is not confined by the grid plot. The cosine approximation arithmetic generates too large error to be used in numerical simulation despite of saving more time.4. Based on the constitutive model established in this thesis, a 2-D dynamic program code TSHOCK2D is made by finite element method, and taking the 2-D stress wave propagation in PMMA/TF plate which is impacted by PMMA flyer for example, the correctness of this constitutive model and the validity of the program are verified.5,Using plain-strain orthotropic dynamic elasto-plastic constitutive model, the thermal shock wave propagation along different principal axes in TF plate induced by pulsed X-ray radiation is simulated by TSHOCK2D, then the simulated results are compared with numerical results by 1-D finite difference program and by different constitutive models. The results show that: when the radiation direction is along different principal axes, the thermal shock wave peak stress values, propagation and attenuation of stress wave, spallation phenomenon, and so on, show great differences and exhibit anisotropic characteristics; along the symmetrical midline axis, the results of shock wave propagation and attenuation got by the 2-D finite element program are coincident with that by 1-D difference program, thus the correctness of the program module which relates to the X-ray radiation is verified more; compared with the ideal isotropic and anisotropic elasto-plastic constitutive model, the thermal shock wave peak stress by rate-related orthotropic dynamic elasto-plastic constitutive model is lower, and the attenuation of peak stress is faster, and these conclusions are consistent with the related experiment results for the qualitative analysis, thus the correctness of the orthotropic dynamic constitutive model is verified.6. The thermodynamic response is simulated by TSHOCK2D program while the TF cylinder shell is radiated by X-ray with different angle of incidence. According to the simulation outputs managed by Tecplot and Origin softwares, the connection of X-ray spectra with the thermodynamic response characterics, such as distribution of energy deposition, propagation and attenuation of thermal shock wave, distribution of blow-off impulse, spallation, an so on, are obtained.7. Especially, the main numerical simulation difference is compared while the TF cylinder shell is vertically and non-vertically raidated by X-ray: for the vertical case, the thermal shock wave propagation can be simplified as a 2-D propagation problem in the circular annulus section, and the principal axis of TF composite is within the circular annulus section, so the relation of stress-strain only needs to be calculated in the section by the plain-strain constitutive model; for the non-vertical case, the corresponding section is elliptical annulus, and the thermal shock wave propagation is also simplified as a 2-D propagation problem in the elliptical annulus section, but for the principal axis coordinate of TF composite is not within the section, so the relation of stress-strain can not be calculated by the plain-strain constitutive model, and must be depicted by 3-D model.