2019 Vol. 33, No. 3

2019, 33(3): 1-2.
HTML PDF (28)
Abstract:
Multi-Scale Simulation of Dynamic Response of Materials
New Developments of Time-Dependent Density Functional Theory and Its Applications
QIN Rui
2019, 33(3): 030101. doi: 10.11858/gywlxb.20190747
HTML PDF (116)
Abstract:

Nowadays density functional theory which was introduced in the mid-1960s has wide applications in material simulations. However, it is not able to deal with time-dependent problems and excited properties of materials. Time-dependent density functional theory (TDDFT) based on Runge-Gross theorem, provides a viable way to deal with these two problems. After thirty years’ development, TDDFT has been widely applied to many fields, such as quantum chemistry and material simulation, and our understanding of its advantages and weaknesses also grows. To date, TDDFT theory and method still develop rapidly. Here a brief historical review of TDDFT is first introduced. Then it is followed by a discussion of recent important developments on theory and applications of TDDFT. Finally we summarize some important problems and challenges that TDDFT are facing and attempt to offer some thoughts about where TDDFT will be progressing.

Computation and Simulation of High-Pressure Properties of Complex Materials: A Brief Review on the Methods Based on First-Principles
GENG Huayun, SUN Yi, XIANG Shikai
2019, 33(3): 030102. doi: 10.11858/gywlxb.20190710
HTML PDF (84)
Abstract:

This work briefly summarizes and reviewes the first-principles quantum mechanics calculations and simulations on the high-pressure properties of complex materials. We emphasized the applications in alloys and intermetallic compounds, materials with defects and strongly correlated electron systems. A series of methods, including cluster expansion method, lattice gas model, and quasi-annealing simulation approach, have been developed by combing quantum mechanics calculations with the statistical mechanics principles. Their pros and cons are discussed. The contents covered in this review are just a small portion of the first-principles methods that are evolving to tackle the complex systems. But they are of representative, and a retrospect of them might be helpful for developing better methods with high efficiency and good predictability for multiple-scale simulations.

Application of Molecular Dynamics Simulation to Dynamic Response of Metals
DENG Xiaoliang, LI Bo, TANG Guanqing, ZHU Wenjun
2019, 33(3): 030103. doi: 10.11858/gywlxb.20190750
HTML PDF (133)
Abstract:

With the development of computer science and technology and diagnostic techniques, molecular dynamics (MD) simulation plays an increasingly important role in the field of shock dynamics. This review presents the basic principle of MD firstly, followed by integrated algorithm, inter-atom potentials, and some widely used data processing methods. Then the applications of MD in the plastic deformation of metals, phase transitions, and damage and fracture under shock loading (spallation) are presented in a systematic manner. The shock plasticity is focused on the micro-mechanisms of plastic deformation and the relationship between the deformation process and micro-structures in single crystals, twin crystals, and polycrystals. In terms of shock-induced phase transitions, the iron is taken as an example to emphasize the research focusing on the coupling of shock transitions and shock plasticity. The contents of dynamic damage and fracture mainly cover the void evolution and coalescence, dynamic response of materials under laser loading, and so on. Finally, a brief summary and perspective of MD regarding to future applications are offered, intending to provide the further information for the related researchers.

Progress of Atomistic Simulations for Plastic Bonded Explosives
LONG Yao, CHEN Jun
2019, 33(3): 030104. doi: 10.11858/gywlxb.20190755
HTML PDF (61)
Abstract:

The recent atomistic simulations of plastic bonded explosive is reviewed in six aspects: the force-field, thermodynamic property, dissipation/transport property, phase transition, constitutive relation and ignition mechanism. In past decades, the structure and mechanical property of PBX are carefully investigated. However, the microscopic defect evolution and hot spot formation mechanisms are unclear. There are a set of challenging problems in detonation physics, such as the defect configuration at the chemical reaction zone, and the detonation wave deformation induced by defect. To investigate them, both atomistic simulation and experiment are required.

Phase Retrieval and Reconstruction of Coherent Diffraction Imaging
KANG Xu, LIU Jin
2019, 33(3): 030105. doi: 10.11858/gywlxb.20190761
HTML PDF (38)
Abstract:

The coherent diffraction imaging (CDI) is an ultra-high resolution imaging technique that is sensitive to the density of the material. Compared to the surface-sensitive imaging methods with ultra-high resolution, the CDI is able to probe the interior of the sample by taking advantages of hard X-rays. According to the imaging layout, the space resolution of CDI is variable and can reach up to an atomic scale. This feature depends on the iterative phase retrieval method that almost becomes the signature of CDI. Based on oversampling a sample in a detected image, the phase and intensity of X-ray beam can be retrieved simultaneously by iterative calculations with constraints, and then are used to reconstruct the sample. Meanwhile, the three-dimensional reconstruction could be realized by combining image orientating and merging techniques. Here we present the imaging theory, phase retrieval and reconstruction methods of the CDI technique, and its diagnostic ability in a variety of reconstruction situations by experimental and simulation examples, to hopefully provide a systematic introduction of its development.

Mesoscale Lattice Model for Dynamic Fracture of Brittle Materials
YU Yin, LI Yuanyuan, HE Hongliang, WANG Wenqiang
2019, 33(3): 030106. doi: 10.11858/gywlxb.20190707
HTML PDF (54)
Abstract:

Rapid crack propagation and catastrophic fragmentation frequently occur in brittle materials, such as rocks, ceramics, glass and solid explosives, under intense dynamic loading imposed by the explosion and impact. Understanding the correlation between the evolution of mesoscopic crack network and the macroscopic dynamic response plays a key role to improve the reliability and the safety of brittle materials, while it still poses a great challenge to such modeling and simulation. In order to overcome the algorithm difficulties caused by complex processes, such as the random initiation of crack network, the extrusion and friction of crack surfaces, and the staggered propagation of a large number of cracks in brittle materials subjected to explosion and impact loading, the lattice model, one of meshfree methods, has received sustained attention and considerable development. In this paper, we introduce the theory and implement of the lattice model and its representative results on brittle fracture research. Its shortcomings and the direction of improvement have also been discussed.

Overview of the Study of Dynamical Plastic Deformation Based on Dislocation Dynamics Method
YAO Songlin, PEI Xiaoyang, YU Jidong, YU Yuying, BAI Jingsong, LI Ping, WU Qiang
2019, 33(3): 030107. doi: 10.11858/gywlxb.20190727
HTML PDF (109)
Abstract:

Study of the dynamic plastic deformation of crystalline metals is a typical multi-scale problem, and is an assembly point of multi-scale science. Under dynamic loading, behaviors of defects at micro-scale and collective behaviors of an assembly of defects at meso-scale contribute to the complex constitutive behaviors at macroscale together. It is found experimentally that constitutive behavior of metals under dynamic loading quite differs from that under moderate loading conditions, and are influenced by an amount of external and internal factors, which makes it hard to recognize the fundamental origin of the dynamical plastic deformation. Dislocation dynamics method is developed to unravel the dynamical plastic deformation. Despite of several tens of years of studies, physical principle of dynamical plastic deformation is still poorly understood. In this article, we reviewed the study of dynamical plastic deformation based on dislocation dynamics method from the viewpoint of computational method and deformation theory.

Advances in the Study of Dynamic Response of Crystalline Materials by Crystal Plasticity Finite Element Modeling
ZHENG Songlin
2019, 33(3): 030108. doi: 10.11858/gywlxb.20190725
HTML PDF (157)
Abstract:

As an important simulation tool for describing the elastoplastic deformation of anisotropic heterogeneous materials on continuum scales, crystal plasticity finite element (CPFE) modeling can effectively predict macroscopic mechanical properties of materials, thus plays a critical role in engineering design. In the practical engineering applications, many crystalline materials work at extreme conditions such as high stress, high deformation rate, and high temperature. The anisotropic heterogeneous microstructure evolutions under such conditions are the key factors to understanding the dynamic response of materials, and it brings great opportunities and challenges for CPFE. In this paper, we firstly review the theory and model of CPFE, and then introduce the applications of this method in study of dynamic response of crystalline materials, and discuss the challenges and open questions of CPFE in modeling material dynamic response at last.

An Overview of Phase Field Approach to Fracture
ZHANG Hao, YU Jidong, PEI Xiaoyang, PENG Hui, LI Ping, CAI Lingcang, TANG Tiegang
2019, 33(3): 030109. doi: 10.11858/gywlxb.20190777
HTML PDF (173)
Abstract:

Phase field modeling to fracture has received much attention since the beginning of this century, which exhibits an advantage in fracture propagation simulation. In this work, we compare the phase field approach to fracture with other simulation methods, and show an overview and development of phase field approach to fracture. Up to now, the phase field method has been successfully applied to the brittle fracture and could simulate some classical crack problems. Based on this, the multi-fields problem coupled with the fracture is currently pursued. Furthermore, we introduce the study situation of the phase field simulation to the ductile fracture and put forward its development in the future.

Brief Review of Research Progress on Numerical Simulation of Ejection Phenomena
SHAO Jianli, HE Anmin, WANG Pei
2019, 33(3): 030110. doi: 10.11858/gywlxb.20190786
HTML PDF (84)
Abstract:

In this paper, the research progress on numerical simulation of ejection phenomena at home and abroad is briefly reviewed and summarized. Firstly, the characteristics of ejection phenomena and its physical connotation are explained. Then, the molecular dynamics studies and continuum mechanics studies on the two main ejection mechanisms, microjet and microspallation, are respectively summarized. At last, some difficult problems in the numerical study of ejection phenomena are summarized. We hope this paper can provide useful reference for related numerical simulation or modeling research.

Review on Evaluation of Temperature-Pressure Equation of State of Porous Materials
CHEN Junxiang, GENG Huayun
2019, 33(3): 030111. doi: 10.11858/gywlxb.20190767
HTML PDF (57)
Abstract:

As an important structural and functional material, porous material has been widely used in the engineering fields such as filtration, catalysis, shielding and impact protection. Because of its complex physical-mechanical behavior, even with years of research, its response under extreme conditions still has not been fully understood. Taking the characteristics of pressure and temperature change of porous materials under shock loading as an example, this paper makes an in-depth analysis of several typical models of equation of state for porous materials by choosing Hugoniot of the dense material as the reference line and compares them. On the basis of this analysis, an approach of piecewise processing the shock data of porous materials is proposed and its effectiveness is demonstrated for porous copper. This approach may be helpful in developing an accurate and rigorous theory of the equation of state of porous materials.

Progress of Aluminum Projectile Impacting on Plate with Hypervelocity
LIN Jianyu, LUO Binqiang, XU Mingyang, SONG Weidong, BAI Jingsong, PEI Xiaoyang, YU Jidong, LI Ping
2019, 33(3): 030112. doi: 10.11858/gywlxb.20190774
HTML PDF (86)
Abstract:

This paper focuses on the protection of debris clouds in space and the progress of the studies of Al projectile impacting on single shield and Whipple shields are discussed. The advantages and drawbacks of the widely used experimental method for launching hypervelocity projectile and numerical methods for hypervelocity impact such as Euler methods and meshfree methods are introduced. The numerical simulation is usually based on the constitutive laws and the equation of states. In this paper we have reviewed the constitutive law including Johnson-Cook and Steinberg-Gruinan, while for the equation of states we include the Tillotson, ANEOS, SESAME, GRAY. The mechanics and physics for the hypervelocity impact below 7 km/s are now well understood based on the progresses made by the experiments and numerical simulations. Then, for the single shield we mainly focus on the perforation by the projectile and the models predicting the hole size. For the Whipple shield we have discussed the characteristics of the debris clouds evolution, the phase states of the materials, the models predicting the evolution of the debris clouds and damage features of the second wall of the Whipple structure induced by the debris clouds. Finally we discussed the ballistic limit equations which are very important to the protection in the engineering. Great progresses have been achieved for the ballistic equations for the single and double shields structures based on the experiments and numerical simulations. We have discussed the commonly used ones and the models which are newly developed recently including theoretical models and the models from artificial intelligence.