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The shear properties of rock joints have always been the focus of rock engineering, and the peak dilation angle is a key physical quantity describing the shear behavior of joints. A reasonable peak dilation angle model should fully reflect the peak shear strength of rock joints. To predict the peak dilation angle of rock joints and clarify the intrinsic relationship between the peak dilation angle and the morphology of rock joints, the distribution range of asperities on the joint surface that contribute to the shear strength is defined at first, and then the contribution ratio of asperities to the strength in actual contact joints is determined. The resistance to shear on the joint surface is generated by the touched asperities facing the shear direction. \begin{document}$ {\theta }_{\text{cr1}}^{*} $\end{document} and \begin{document}$ {\theta }_{\text{cr2}}^{*} $\end{document} are proposed to define whether asperities participate in the shear process and the failure mode of asperities, respectively. For the asperities of \begin{document}${\theta }^{*} $\end{document} at (\begin{document}$ {\theta }_{\text{cr1}}^{*} $\end{document}, \begin{document}$ {\theta }_{\text{cr2}}^{*} $\end{document}), the failure mode is shear dilation failure, and the contribution to shear strength is proportional to \begin{document}${\theta }^{*} $\end{document}. For the asperities of \begin{document}${\theta }^{*} $\end{document} at (\begin{document}$ {\theta }_{\text{cr2}}^{*} $\end{document}, \begin{document}$ {\theta }_{\text{max}}^{*} $\end{document}), the failure mode is shear off failure, and the contribution to shear strength is proportional to \begin{document}$ {\theta }_{\text{cr2}}^{*} $\end{document}. Furthermore, the equivalent average angle of joints in contact is deduced considering the different contribution ratios of asperities in contact to shear strength and the area ratio of asperities. Equating the equivalent average angle of joints in contact with the peak dilation angle, a new model of peak dilation angle of joints is proposed. The physical meaning of the new model is clear, and the existing parameter of peak dilation angle is only a special case of equivalent average angle of actual contact joints. The calculation accuracy of six peak dilation angle models is compared through 89 sets of experimental results, which show that the prediction results of the new model are the best (the average error is 10%). It is critical to determine \begin{document}$ {\theta }_{\text{cr2}}^{*} $\end{document} in the new peak dilation angle model. The angles \begin{document}$ {\theta }_{\text{cr2}}^{*} $\end{document} corresponding to the joints of different rock materials are different in the new model. Considering the simplification of the model form, \begin{document}$ {\theta }_{\text{cr2}}^{*} $\end{document} = 32° fitted by tests is used to determine the new peak dilation angle model. The relative average error of the new simplified peak dilation angle model is 11%, and the prediction accuracy is higher than that of other models listed in this study. The influence of \begin{document}$ {\theta }_{\text{cr2}}^{*} $\end{document} on the rock joints with different morphologies, and the value basis of \begin{document}$ {\theta }_{\text{cr2}}^{*} $\end{document} are discussed. The findings reveal that in cases of pronounced joint roughness, the new model outperforms other models in terms of accuracy. Additionally, the derived value of \begin{document}${\theta }_{\text{cr2}}^{*} $\end{document}, obtained by fitting 89 sets of experimental data, appears to be a reasonable estimate.

A consecutive joint shear strength model for soft rock joints is proposed in this paper, which takes into account the degradation law of the actual contact three-dimensional (3D) roughness. The essence of the degradation of the maximum possible dilation angle is the degradation of the 3D average equivalent dip angle of the actual contact joint asperities. Firstly, models for calculating the maximum possible dilation angle at the initial and residual shear stress stages are proposed by analyzing the 3D joint morphology characteristics of the corresponding shear stages. Secondly, the variation law of the maximum possible dilation angle is quantified by studying the degradation law of the joint micro convex body. Based on the variation law of the maximum possible dilation angle, the maximum possible shear strength model is proposed. Furthermore, a method to calculate the shear stiffness degradation in the plastic stage is proposed. According to the maximum possible shear strength of rock joints, the shear stress-shear displacement prediction model of rock joints is obtained. The new model reveals that there is a close relationship between joint shear strength and actual contact joint roughness, and the degradation of shear strength after the peak is due to the degradation of actual contact joint roughness.

Abstract In this work, the $$\gamma p\rightarrow \phi (1680) p$$ γ p → ϕ ( 1680 ) p reaction is systematically studied based on the two gluon exchange model and the pomeron model. The calculation results show that the total cross section of $$\phi (1680)$$ ϕ ( 1680 ) photoproduction can reach more than 80 nb near the center-of-mass energy $$W=4$$ W = 4 GeV, so it is suggested that JLab and other experiments carry out relevant measurements. Moreover, under the framework of the vector meson dominance assumption, the scattering length of $$\phi (1680)$$ ϕ ( 1680 ) and proton interaction is estimated as $$0.07\pm 0.01$$ 0.07 ± 0.01 fm from the cross sections predicted by the theoretical models, which is on the same order of magnitude as the $$\phi (1020)$$ ϕ ( 1020 ) -p scattering length. In addition, the total cross section, number of events and rapidity distribution of $$\phi (1680)$$ ϕ ( 1680 ) production are predicted at Electron-Ion colliders (EICs) and ultra-peripheral collisions (UPCs) by using eSTARlight and STARlight code. The study of $$\phi (1680)$$ ϕ ( 1680 ) and relevant properties is of enlightening significance in better understanding the strangeonium family spectrum, and provides necessary data support for the future experiment of EICs and UPCs.

To explain the effect of joint roughness on joint peak shear strength (JPSS) and investigate the effect of different contact states of joint surface on JPSS, we try to clarify the physical mechanism of the effect of joint cavity percentage (JCP) on JPSS from the perspective of the three-dimensional (3D) distribution characteristics of the actual contact joint surface, and propose a JPSS model considering the JCP. Shear tests for red sandstone joints with three different surface morphologies and three different JCPs were performed under constant normal load condition. Based on test fitting results, the reduction effect of the JCP on JPSS is investigated, and a JPSS model for cavity-containing joints is obtained. However, the above model only considers the influence of JCP by fitting test data, and does not reveal the physical mechanism of JCP affecting the JPSS. Based on the peak dilation angle model for consideration of the actual contact joint morphology, and the influence of JCP on the roughness of the actual contact joint surface, a theoretical model of the JPSS considering the JCP is proposed. The derivation process does not depend on the test fitting, but is entirely based on the joint mechanical law, and its physical significance is clear. It is proposed that the essence of the influence of the JCP on JPSS is that the JCP first affects the normal stress of the actual contact joints, further affects the roughness of actual contact joints, and then affects the shear strength.

To discuss the ratchetting behavior of short glass fiber-reinforced epoxy polymer composites, experimental and theoretical studies were carried out. The effects of the fiber content and peak stress on the ratchetting behavior of the composite materials were discussed. The results show that the ratchetting strain decreases with increasing fiber content and decreasing peak stress. It was also found that the residual strain after unloading partly recovers with time, which indicates that the ratchetting strain consists of viscoelastic strain and plastic strain. Based on the experimental results, a viscoelastic-viscoplastic constitutive model is proposed, which can well simulate the ratchetting behavior and strain recovery of composites with different fiber contents.

A novel method to heat the multiaxial hollow thin-wall specimen was proposed, where its gauge length section can be heated by the liquid (i.e., water) filled inside the specimen instead of the closed furnace. This method realizes the direct measurement of multiaxial strain on the surface of specimen at different temperatures by the noncontact digital image correlation. By utilizing the proposed method, the multiaxial stress-control cyclic tests were performed to investigate the multiaxial ratchetting of polycarbonate (PC) at different temperatures. It is found that the multiaxial ratchetting of PC depends greatly on the test temperatures and the multiaxial ratchetting strain increases with increasing the test temperature. The temperature-dependent multiaxial ratchetting is also influenced by valley stresses. The unrecoverable part of deformation in the multiaxial ratchetting strain increases with increasing temperature.

Research on the effect of alternative doping on the photoelectric properties of boron nitride is still at an early stage. In particular, research on hexagonal boron nitride’s diatomic co-doping is still rarely studied. In this work, first-principles calculations are selected as the main method to investigate the electronic structure and optical properties of different atoms used to dope hexagonal boron nitride (h-BN). The band gap value of intrinsic h-BN is 4.66 eV. The band gap was changed after Cs, Br, and Cs-Br doping. The results show that the band gap is 4.61 eV when the Br atom replaces the N atom, while the band gap of h-BN doped with Cs is 3.52 eV. Additionally, the band gap width can be reduced to a typical narrower band gap width of 3.19 eV when Cs-Br is used for doping. At the same time, the complex dielectric function representing the optical properties is calculated after Cs, Br, and Cs-Br doping. The optical absorption peaks of Cs-Br-doped h-BN are weaker at low-frequency conditions. The optical absorption of h-BN can be modified by Cs doping, Br doping, and Cs-Br co-doping in the near-infrared, visible, or portion of the near-ultraviolet bands, which makes the doped material more suited for photoelectric detectors in the relevant frequency bands.

High chromium steel has been synthesized by an induction furnace adopting electromagnetic stirring (EMS). Varying amounts of cobalt was added to obtain 3, 6, and 12% Co in the steel. The melt was allowed to solidify with or without EMS in a rotary magnetic field. The effects of the varying cobalt content and the stirring have been characterized by the microstructural evolution and the consequent improvement in mechanical properties. The application of a rotary EMS during solidification has shown a significant effect on the grain refining, the reduction of element segregation, the promotion of eutectic volume fraction, and the consequent improvement of mechanical properties, including hardness and high-temperature strength. The formation mechanism of the eutectic structure and the precipitation of M7C3 and M23C6 carbides was discussed according to the calculated phase diagram. The increment of cobalt content improved the eutectic volume fraction. Cobalt addition also enhanced the hardness and the yield tensile strength, provided that the ingot structure was homogenized by the EMS.

The multifluid effects caused by the relative motion and interaction between plasma components have a significant effect on electromagnetohydrodynamic wave propagation and the related mass and energy transport of flows. In this work, the charged particle (ion and electron)-neutral two-fluid model is analyzed and employed to study the two-fluid effects (e.g., velocity drift and thermodynamic nonequilibrium between plasma components) of the weakly ionized plasma flows under the electromagnetic fields. In a hypersonic E×B crossed-field configuration acceleration problem, the increased electromagnetic field strength significantly enhances the two-fluid effects. When the load factor equals 3, which measures the strength of the electrode voltage and induced electromotive force, the relative velocity difference between the charged particles and neutrals can reach 28%. The influences of two-fluid effects appreciably increase with the Mach number and Knudsen number but decrease with the degree of ionization. This suggests that, as the vehicle speed and altitude increase, the two-fluid effects become more significant. [ABSTRACT FROM AUTHOR]

Electrochemical measurements were performed on Ni-30Co-16Cr-xMo and Ni-30Co-16Cr-xMo-2Cu (x = 7-15, wt%) alloys to clarify their electrochemical responses and corrosion behaviors influenced by Mo and Cu in 0.5 M aqueous HF acid solution at room temperature. Results indicate that both Mo and Cu play positive roles in improving the corrosion resistance. The enhanced corrosion performance by Cu addition is observed in all alloys while this is more obvious in the alloy with low Mo concentration. Moreover, 2 wt% Cu addition is found to not only reduce the critical Mo concentration for spontaneous passivation of alloy, but also alter the nature of the exposed surface with distinct declines of effective capacitance. Ni-30Co-16Cr-15Mo-2Cu alloy shows the best corrosion resistance among all alloys studied. [ABSTRACT FROM AUTHOR]