The effects of Al³⁺-Fe³⁺ substitution on 10 synthesized garnet samples along the grossular-andradite binary were investigated using Raman spectroscopy. Twenty and nineteen peaks were observed in non-polarized Raman spectra for grossular and andradite end-members, respectively. The frequencies of most peaks were changed almost linearly with the composition. Two-mode behavior was not observed in this study. Differing from previous reports on other garnet solid solutions, the medium frequency modes, which are assigned to internal bending vibrations, have the largest average rate of change with the composition, which may be related to structural connectivity and coupled vibrations. Due to the reduction of symmetry, extra peaks appear in the Raman spectra of garnets with intermediate compositions. Peak broadening in intermediate compositions was also observed, which is related to disordering and distortion. One-parameter Margules equation was used to describe the full width at half maximum of peaks, and a relationship with enthalpy of mixing was proposed.

Rhenium tablet is a frequently used gasket material at the ultra-high pressures in Diamond anvil cell (DAC) experiment. Water in deep Earth is the link between material exchange and energy circulation in the Earth’s interior. It is greatly scientific and technical significance on the study of chemical reaction of Re-H₂O system at high pressures and temperatures. Microscopic observations and Raman measurements show that the Re-H₂O system takes place the redox reaction ${2{{\rm{H}}_2}{\rm{O}} + {\rm{Re}}\;\;\;\begin{matrix}{40.5\;{\rm{GPa}}} \\\hline \hline{1\;800\;{\rm{K}}}\\\end{matrix}\;\;\;{\rm{Re}}{{\rm{O}}_2} + 4{\rm{H}}}$ under the conditions of high pressures and high temperatures, and produce rhenium oxide (β-ReO₂) with Re⁴⁺ and atomic hydrogen (H). Observed fourteen characteristic Raman peaks of oxidation product ReO₂ have a continuous unequal shift to lower Raman frequencies with the release of pressure. Reduction product H does not further take place interreaction with the water molecules, rhenium metals and their reaction products β-ReO₂ and atomic H under high pressures. But the hydrogen molecules are formed when the pressure is released to near atmospheric pressure. The chemical reaction of Re-H₂O system under the conditions of high-pressure and temperature reveals that water (hydroxyl) can decompose to produce atomic hydrogen in the Earth’s interior with the high pressure, high temperature and reductive material. This discovery not only provides a new experimental evidence for the conversion of water to hydrogen in deep Earth, but also gives important basis for exploring the possible geochemical behaviors of water in the Earth’s interior.

The interplays of electron-electron interaction (U), spin-orbit coupling (SOC), and crystal field effects in the 5d transition metal oxides are complex, which can be turned by external fields to induce many novel electromagnetic phenomena and become one of hot topics in condensed matter physics. In this study, the Raman spectroscopy is carried out on single crystals of Sr₂IrO₄ at room temperature. We discover that when pressure reaches 19.6 GPa to 22.2 GPa, a new peak appears at a wavenumber of 199 cm^-1 in the Raman spectra, accompanied with some anomalous changes of other Raman peaks. This result clearly evidences a structural phase transition occurs, although the existence of the such a transition has been long debated. The structural phase transition is independent of the magnetic phase transition at low temperature, but plays a dominant role in the magnetic ordering transition, owing to the strong spin-orbit coupling. This discovery promises a new way tune electromagnetic properties in the 5d Mott insulators and also provides a new idea to design novel functional materials in the future.

Pyrite structure CuS₂ was synthesized in diamond anvil cell at high pressures and high temperatures. Using Raman spectroscopy and synchrotron X-ray diffraction, the pyrite-type CuS₂ was found to be stable in 0－30 GPa without any phase transition. Raman spectroscopy show that all observed Raman frequencies increasemonotonously with increasing pressures. Fitting experimental pressure and volume data of X-ray diffraction with Birch-Murnaghan equation of state, gives V₀ = 193.8(5) ų, K₀ = 99(2) GPa and K₀' = 4 (fix). The dependencies of Raman frequencies and unit-cell volumes with pressures are coincident with the results of first-principles calculation. The results of calculation properly depict that of experiments. Compared with other pyrite structure transition-metal disulfides MS₂(M = Mn, Fe, Co, Ni), the length of M—S dominates the unit-cell volume and compressibility of MS₂, and the Cu cation tends to be +2 valance in the CuS₂. This study makes up for the lack of high-pressure Raman and XRD research of CuS₂, and confirms structural stability of pyrite-type CuS₂ at high pressures and high temperatures. The results are important for comprehending the physical and chemical properties of CuS₂ and realizing the unified law of pyrite structure materials. It’s also meaningful in discussion of the valance and distribution of copper in deep Earth.

The lattice constants, elastic and anisotropy properties of HBT crystals at normal and high pressure were investigated by using the first-principle method based on density functional theory. The anisotropic properties of HBT crystal under high pressure were studied by using three different theoretical models. The results show that the elastic constant and elastic modulus of HBT crystal increase significantly under high pressure, and HBT crystal shows high-pressure toughness. Simultaneously, HBT crystal has large elastic modulus and mechanical anisotropy under high pressure. With increasing pressure, the extent of anisotropy of HBT crystal decreases. In addition, the thermodynamic properties show that HBT crystal has a higher Debye temperature, which increases with increasing pressure.

Using split Hopkinson compression bar (SHPB) device, uniaxial dynamic compression tests and dynamic split tests on fine sandstone in natural state and saturated state were carried out. The influence and difference of water and loading rate on dynamic tensile and compressive strength of fine sandstone were studied, and the failure mechanism of the fine sandstone in dynamic tension and compression was analyzed with digital image correlation (DIC) technology. The test results show that the dynamic compressive strength and tensile strength of the fine sandstone under the two states have obvious strain rate dependent effect, and they increase with the increase of loading rate. Under the same loading rate, the dynamic compressive strength of fine sandstone in saturated state is smaller than that in natural state, while the tensile strength in saturated state is larger. Water has little effect on the strain rate effect of dynamic compressive strength and tensile strength for the fine sandstone. However, water can improve the dynamic compressive strength and tensile strength enhancement factor of the fine sandstone, and has a more significant effect on the dynamic tensile strength enhancement factor. In the process of dynamic compression, the surface strain concentration of the rock specimen in saturated state is significantly less than that in natural state, the strain gradient is more significant, and the tensile-shear effect is weakened during the dynamic tensile process.

In order to analyze the dynamic behavior of aerospace TC4 titanium alloy plane under the bird impact, the deformation field of TC4 titanium alloy plate subjected to the bird impact was studied by 3D-DIC dynamic deformation field test technology. Meanwhile, a numerical simulation model was established based on explicit finite element analysis software ABAQUS. In this model the Johnson-Cook dynamic constitutive relations was used to describe the property of TC4 titanium alloy, and the bird model was established with smooth particle method (SPH). Comparing the numerical and experimental results, it is concluded that the calculated strain can match the experimental results well. The rationality and reliability of numerical analysis of the bird impact on the TC4 titanium alloy model are verified.

Due to good light transmittance and great safety performance, tempered laminated glass has been widely used in automobiles, high-rise buildings and other fields. To explore the effect of glass thickness distribution on the impact resistance of tempered laminated glass, the drop hammer impact tests were performed on nine kinds of PVB tempered laminated glass, and the changes of impact force, strain and displacement of the tempered laminated glass with time were obtained under unfracture state and fracture state. Meanwhile, high-speed cameras were used to record the generation and expansion of cracks, and the crack distributions of the laminated glass were analyzed under the fracture state. The results show that the impact resistance is closely related to the number of layers and the thickness distribution of tempered laminated glass. For double-layer tempered laminated glass, when the outer glass is thicker and the inner glass is thinner, the impact resistance is better. For the three-layer tempered laminated glass, when the outer glass is thinner and the inner glass is thicker, the impact resistance is better.

The hollow structure working in deep water is subjected to huge hydrostatic pressure. When it is suddenly crushed, it will explode and generate shock waves, and cause damages to the surrounding structure. Aiming at the problem that the implosion shock wave is affected unclearly by hydrostatic pressure and vacuum volume, the underwater implosion test of photomultiplier tube (PMT) was carried out. It was verified that the CEL coupling calculation method in ABAQUS satisfies the requirements of PMT implosion simulation accuracy, and then the effects of external hydrostatic pressure and vacuum volume of hollow structures on implosion shock waves were analyzed by simulation. The results show that with the increase of hydrostatic pressure and vacuum volume, the peak value of the shock wave increases linearly, and the farther away from the implosion center, the slower the increase of peak value of the shock wave. The pulse width of the shock wave remains basically unchanged with the increase of hydrostatic pressure, and decreases slowly with the increase of vacuum radius.

A macroscopic constitutive model is presented herein for ceramic materials subjected to dynamic loadings by closely following a previous study on concrete. The equation of state is described by a polynomial equation and the strength model takes into account various effects such as pressure hardening, Lode angle, strain rate, shear damage and tensile softening. In particular, the strength surface of ceramic materials is characterized by a new function which levels out at very high pressures and strain rate effect is taken into account by dynamic increase factor (DIF) which excludes inertial effect. The present model is verified against some available experimental data for ceramic materials in terms of pressure-volumetric response, quasi-static strength surface and strain rate effect. The model is further verified against the data for triaxial test by single element simulation approach and the test data for depth of penetration in AD99.5/RHA struck by tungsten alloy penetrators. Furthermore, comparisons are also made between numerical results of the present model and the JH-2 model. It is demonstrated that the present model can be employed to describe the mechanical behavior of ceramic materials under different loading conditions with reasonable confidence and is advantageous over the existing model.

Brittle loose particles exhibit very complex mechanical behavior during the crushing process and have a significant attenuation effect on the stress wave propagation. In order to explore the attenuation law, this paper builds a brittle loose particle model based on the discrete element software PFC^3D, and studies the attenuation of stress wave on the microscopic scale. The results show that: under shock loading, the peak value of the stress wave propagating in the granular particles decays exponentially. As the propagation distance increases, the degree of stress wave attenuation gradually decreases, and the degree of particle fragmentation also decreases. Stress wave propagation in granular particles will cause significant wave dispersion, and the shorter the wavelength of the stress wave, the greater the attenuation during propagation. The rate dependence of the stress wave attenuation is essentially caused by the impact fragmentation of the granular particles. The faster the loading speed, the greater degree of particle damage, and the greater the attenuation of stress wave. When the particle is not broken, the degree of attenuation does not change significantly with the increase of the loading velocity.

In the process of deep roadway excavation, the rock mass is subjected to periodic load and high geostress, so the general strength criterion cannot describe the stress-strain curve of rock. However, the cyclic loading and unloading constitutive model of rock under high geostress is the key to predict the long-term stability of deep roadway under periodic load, thus it is urgent to carry out the study of rock constitutive model under high confining pressure. The process of rock subjected to external load to failure presents the propagation of original cracks, growth and propagation of new crack. Previous studies have shown that the number of cracks in rock obeys Weibull distribution and the Griffith criterion assumes that the failure of rock is caused by the crack propagation. Based on these criteria, this paper establishes a statistical damage constitutive theory of cyclic loading and unloading of rock under high confining pressure by extending Weibull statistical damage constitutive. Through the equation transformation of constitutive model, the threshold value of constitutive damage is studied. Furthermore, the constitutive parameters was fitted with the data of even cyclic loading and unloading test, and the evolution rule of the parameters is obtained. By comparing the constitutive theory with the odd cyclic loading and unloading test, the accuracy of the constitutive model is verified, which provides a new insight for the study of the constitutive model of rock under high confining pressure.

Based on the one-dimensional nonlinear rigid-plastic hardening (R-PH) model, the control equations and mechanical response characteristics of the shock wave propagation of the negative graded foam under constant velocity impact are studied. The LS-DYNA finite element software is used to numerically simulate the graded metal foam model generated by the three-dimensional stochastic Voronoi technology to verify the theoretical prediction. The local densification strain and the second critical velocity of the graded foam material under the shock wave model are defined. By studying the effects of impact velocity, density gradient and relative density parameters, it is found that the theoretical solution of the shock wave model is in good agreement with the numerical solution of the finite element model. The shock wave theory based on the R-PH model can better predict the negative graded foam metal. The mechanical properties of the local densification strain have three growth stages at different impact velocities; the larger the absolute value of the density gradient and the relative density, the smaller the local densification strain and the larger the second critical velocity. Finally, the effect of local densification on the stress at the support end in the negative graded foam is explained.

Concrete is a three-phase material composed of coarse aggregate, cement mortar and interfacial transition zone (ITZ). The ITZ is the weakest of the three phases and difficult to observe, but it has a significant impact on the efficiency of concrete crushing. In order to study the impact of ITZ on the damage performance of concrete crushing, the finite element model that reflects real mesoscopic structure of concrete matrix, aggregate shape, and ITZ was established on the Dynamic/Explicit model in ABAQUS. The results showed that the shape of coarse aggregate has a certain influence on the damage performance of concrete, and when the shape is convex polygonal, its damage resistance is the weakest. The damage resistance ability of concrete decreases with the decrease of ITZ strength. When ITZ strength is higher than 60% of mortar, the damage resistance ability gradually increases. As the thickness of the ITZ area increases, the damage resistance ability decreases.

In this paper, the interlaminar fracture toughness of 3D printed mortar laminated composite was investigated by finite element numerical simulation. Firstly, finite element models of the model-I and model-II fracture toughness were established based on cohesive principle and displacement control loading method, and used to simulate the interlaminar opening and staggering process of composites. Then the reliability of the finite element numerical method was verified by compared with the experiment results. Finally, the effects of initial crack length, fracture toughness, initial interface stiffness, interface strength, bonding layer thickness and clear distance on the mechanical properties of 3D printed mortar laminated composite were analyzed. The results show that, for the model-I, reducing the initial crack length, increasing the fracture toughness and increasing the bonding layer thickness can improve interface bearing capacity; and the change of initial interface stiffness and interface strength has no effect on the peak value of tensile force. For the model-II, reducing the initial crack length, enhancing the interface strength, increasing the fracture toughness value and reducing the bonding layer thickness can improve the interface bearing capacity; and the change of the initial interface stiffness has no significant effect on the load-displacement curve.

In order to study the damage effect of underwater explosion on high-piled wharf, a coupling model of high-piled wharf is established. The damage process of high-piled wharf under underwater explosion is analyzed during shock wave propagation and bubble pulse based on LS-DYNA. The dynamic response and failure mechanism of high-piled wharf and the influence of explosive charge are discussed. The residual loading capacity of high-piled wharf is evaluated. The results show that the damage accumulation of high-piled wharf is mainly developed in the first bubble expansion and the damage is basically formed after the first bubble pulse. The piles have periodic reciprocating deformation due to the bubble pulse, and the top and middle of piles are the weakest parts for anti-explosion performance. The damage effect in the upstream of piles is greater than that in downstream, and the damage of wharf panel and beam is weak. With the increase of explosive charge, the piles near explosive are damaged by bending and shearing, the connection of transverse and longitudinal beams and wharf panel are damaged.

The influence of structural parameters (liner cone and thickness) of dual-mode warhead on the forming performance of dual-mode damage element is studied by LS-DYNA for the miniaturization design and application of dual-mode warhead, and the results reveal that the head speed of dual-mode damage element obviously decreases with the increase of liner cone and thickness. By the orthogonal design method, it is found that the thickness of the liner is the main factor to determine the head velocity difference between the two damage elements, and the liner cone is the main factor to determine the head velocity of each damage element. The structural parameters combination of the liner is obtained as following, whose forming performance of the dual-mode damage element is better. The liner cone is 80°, the thickness of the upper end of the liner is 5.0 mm, the thickness of the lower end of the liner is 4.0 mm, and the liner radian radius is 10.0 mm. X-ray imaging tests were done, whose results show a quantitatively good agreement between numerical simulation and tests. The research results provide a reference for the further optimization design of the dual-mode warhead.

The detonation and the flame quenching properties of premixed gas C₂H₄/N₂O in the combustion channels were studied experimentally using a self-developed flame propagation experiment. The results show that the premixed gas achieves the transition from deflagration to detonation in all the PMMA channels with the diameters of 5 mm, 10 mm and 15 mm, and the flame speed and acceleration rate decreased gradually with the increase of the channel diameter. 2.4% CO₂ (mass fraction) diluent flame undergoes a process of stable combustion at the initial stage. The steady detonation speed and pressure are 2 207 m/s and 3.92 MPa, respectively, which are consistent with the theoretical values. The critical quenching diameter is 0.5–0.7 mm. The higher the propagation speed of the flame, the larger the channel diameter, the more difficult the flame quenching. According to the relationship between quenching diameter, turbulent flame velocity and quenching distance, the length of the flame arresters passageway length is calculated, which provides a reference for designing flashback arresters.