摘要：
Products from castor seeds have been widely used in various fields. In order to study the breaking behavior and rupture mechanism of castor seed episperm during coat shelling process, the force-structure property of coating castor seed was investigated by a self-developed texture analyzer with in situ optical microscopic observation. Influences of compression distance, velocity and working temperature were studied. The results showed that castor seed episperm rupture commonly happened from the tail end to the first end. Compression distance effect can change the episperm cracking degree. Under pressing distance 2-3 mm, the episperm easily cracked into two flaps, and the breaking force stabilized at 77 N. Pressing velocity has no significant effect on episperm breaking. Temperature changes the physical property. With an increase in temperature, breaking force presents a "slope " decline; under a temperature of 120 celcius, temperature effect on the breaking force decreased significantly and the breaking force fell to about 52 N. The research results can provide theoretical basis for the castor episperm peeling.</p>
作者机构：
[Yan, Shilin; Qi, Menghui] Wuhan Univ Technol, Hubei Key Lab Theory & Applicat Adv Mat Mech, Wuhan 430070, Hubei, Peoples R China.;[Li, Bin; Yan, Qinghua; He, Qiyu] Wuhan Polytech Univ, Sch Mech Engn, Wuhan 430023, Hubei, Peoples R China.
通讯机构：
[Yan, Shilin] W;Wuhan Univ Technol, Hubei Key Lab Theory & Applicat Adv Mat Mech, Wuhan 430070, Hubei, Peoples R China.
摘要：
To solve the problem of the harsh midlow frequency noise of rocket fairing, the cylindrical section of the protective precision instrument fairing is simplified as cylindrical shells, and different lining strategies of melamine foam (MF) are studied experimentally and numerically. Based on Virtual.Lab Acoustic software, a finite element model of the cylindrical cavity is established, and the correctness is verified by comparison with the measured data. On that basis, the influences of the lining position of different thickness MF on the noise reduction of cylindrical shells are investigated. It is shown that the thickness and location of the laying material have a significant effect on the noise reduction at the same specific gravity.
作者机构：
[Luo, Qiang; Wu, Yan] Wuhan Polytech Univ, Sch Mech Engn, Wuhan 430000, Peoples R China.;[Qin, Er-wei] Beijing Res Inst Precise Mech & Elect Control Equ, Beijing 100076, Peoples R China.
关键词：
Abnormal grain growth;Phase field model;AZ31 Mg alloy;Secondary recrystallization
摘要：
In this study, abnormal grain growth of single phase AZ31 Mg alloy was simulated by phase field modeling during the real spatiotemporal process. The influencing factors of abnormal grain growth were discussed to figure out ways for controlling secondary recrystallization in the microstructure evolution, as well as clarifying the mechanisms of abnormal grain growth in real alloys. The simulation revealed that abnormal grain growth was controlled by three key factors: strain restored energy, grain boundary energy, and grain boundary mobility. The grains with certain orientations in the microstructure with locally high restored energy, local low boundary energy or local high boundary mobility would induce secondary recrystallization after annealing treatment. However, no secondary recrystallization in the microstructure was generated at local restored energy E-0' with certain grain orientation < 1.1E(0), local boundary energy sigma(0)' = 0.98 sigma(0) or local boundary mobility L' < 2L.
作者：
Ma, Y.;Mei, Q. S.*;Li, C. L.;Wan, L.;Li, J. Y.;...
期刊：
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing,2020年786:139435 ISSN：0921-5093
通讯作者：
Mei, Q. S.
作者机构：
[Mei, Q. S.; Chen, F.; Chen, Z. H.; Li, C. L.; Mei, X. M.; Wan, L.; Ma, Y.] Wuhan Univ, Sch Power & Mech Engn, Wuhan 430072, Peoples R China.;[Mei, Q. S.] Wuhan Univ, Key Lab Hydraul Machinery Transients, Wuhan 430072, Peoples R China.;[Li, J. Y.] Wuhan Polytech Univ, Sch Mech Engn, Wuhan 430023, Peoples R China.
通讯机构：
[Mei, Q. S.] W;Wuhan Univ, Sch Power & Mech Engn, Wuhan 430072, Peoples R China.
关键词：
Metal matrix composites;TiAl3;In situ reaction;Strengthening mechanism;Deformation mechanism
摘要：
The microstructure, mechanical behavior and deformation mechanisms of Al-TiAl3 composites containing a wide range of volume fraction of TiAl3 (V-p: 24.6-89.0%) with uniform distribution were investigated. Microhardness and strength of the composites increase with increasing V-p of TiAl3 particles, reaching similar to 11.0 times and similar to 8.0 times those of the matrix respectively. While the strength of the composites can be correlated well to the comprehensive contributions of various strengthening mechanisms of the matrix for low V-p, that for high V-p was found to fit to direct contributions from both the matrix and particle following the law of mixture. Besides the deformation of the matrix, evident plastic deformation of TiAl3 particles by dislocation activities as well as twinning was observed in the composites upon loading at room temperature. Two mechanisms for crack initiation inside the TiAl3 particle were identified, namely by intersection of twins and by interaction between dislocations and twins. Microcracks tend to propagate along the twin boundaries in TiAl3 particles and were found to be suspended at the particle/matrix interface. The unique deformation behavior of TiAl3 particles in the composites can be attributed to the uniform distribution of TiAl3 particles that ensures a continuous network of surrounding matrix even at very high V-p.
摘要：
Pure copper was subjected to high-pressure surface rolling (HPSR) to obtain a surface gradient layer. Effects of HPSR parameters on the surface microstructure and microhardness of Cu were investigated by using optical microscopy, transmission electronic microscopy, X-ray diffraction, and the microhardness test. The HPSR surface layer has a gradient microstructure consisting of increasingly refined grains with decreasing depth from the treated surface (DFS). The thicknesses of the refined surface layer can be up to similar to 1.8 mm, and the grain size of the topmost surface is down to similar to 88 nm, depending on the HPSR parameters including pressure, time, and temperature. Microhardness of HPSR samples increases with decreasing DFS, with a maximum of similar to 2.4 times that of the undeformed matrix. The present results indicated that HPSR could be an effective method for the production of a mm-thick surface layer on Cu with gradient microstructure and property.
关键词：
wide band gap semiconductors;II-VI semiconductors;visible spectra;Fermi level;titanium compounds;ultraviolet spectra;electron-hole recombination;zinc compounds;fluorescence;X-ray diffraction;field emission scanning electron microscopy;semiconductor growth;photocatalysis;photocatalysts;surface chemistry;crystal growth from solution;composite materials;hybridisation;photogenerated carrier recombination;co-catalyst;phase composition;photophysical properties;field emission SEM;ZnO-Ti3C2;photocatalytic activity;MXene material;hydrothermal strategy;morphology;XRD;ultraviolet–visible spectrophotometry;fluorescence spectrophotometry;photocatalysis;Fermi level;ZnO-Ti3C2
摘要：
In this study, a typical MXene material, Ti3C2, was selected as a co-catalyst and then integrated with ZnO via a facile hydrothermal strategy. The phase composition, morphology, and photophysical properties of as-prepared samples were investigated by XRD, field emission SEM, ultraviolet–visible spectrophotometer, and fluorescence spectrophotometer, respectively. In addition, the results of the photocatalysis experiment showed that the photocatalytic activity of ZnO can be improved significantly through the hybridisation with Ti3C2, which arises from the inhibition of the photogenerated carriers recombination. Furthermore, the theoretical analysis indicated that the high-quantum efficiency arises from the appropriate Fermi level position of Ti3C2. This work demonstrated that Ti3C2 will show great potential for constructing novel and efficient photocatalysts.
作者机构：
[Ruan, X. F.; Mei, Q. S.; Chen, F.; Li, C. L.; Mei, X. M.; Zhang, G. P.] Wuhan Univ, Sch Power & Mech Engn, Wuhan 430072, Peoples R China.;[Mei, Q. S.] Wuhan Univ, Minist Educ, Key Lab Hydraul Machinery Transients, Wuhan 430072, Peoples R China.;[Li, J. Y.] Wuhan Polytech Univ, Sch Mech Engn, Wuhan 430023, Peoples R China.
通讯机构：
[Mei, Q. S.] W;Wuhan Univ, Sch Power & Mech Engn, Wuhan 430072, Peoples R China.
关键词：
Accumulative roll bonding;Mechanical properties;Metal matrix composites;Microstructure;Solid state reaction;Spark plasma sintering
摘要：
It has been expected that mechanical properties of a composite can be enhanced effectively by increasing the content of reinforcing particles to high levels, for which a simultaneous fulfillment of high content and uniform distribution of reinforcing particles is key. In this study, we fabricated Al-TiAl3-Al2O3 composites from starting materials of Al sheets and TiO2 nanopowders by combining accumulative roll-bonding and spark plasma sintering processes. The microstructure and mechanical properties of the samples were investigated. The as-prepared samples contain hybrid TiAl3 and Al2O3 particles with total volume fractions up to 66.1-81.5 % that were formed in situ by the reaction of Al and TiO2 with much smaller volume fractions (6.7-13.9 %). The composites exhibit a microhardness up to similar to 532 HV and high strengths up to similar to 1312 MPa at room temperature, similar to 919 MPa at 300 degrees C and similar to 565 MPa at 600 degrees C. The superior mechanical properties of the composites at ambient and elevated temperatures can be attributed to the high volume fraction of reinforcing particles with meanwhile uniform distribution, for which different strengthening mechanisms were discussed.
摘要：
Ultrafine-grained Al matrix composites reinforced by TiAl3 particles with volume fractions (V-p) up to similar to 49% were fabricated from nano-sized Ti powders and pure Al sheets via room-temperature accumulative roll-bonding (RT-ARB) combined with hot-ARB at high temperatures. The RT-ARB was first applied to disperse the Ti nanopowders uniformly in Al matrix. In situ formation of TiAl3 particles via reaction of Ti and Al was induced during subsequent hot-ARB process at 600 degrees C. It was found that further hot-ARB at 700 degrees C can enhance the volume fraction and the dispersion of TiAl3 remarkably. The microhardness and tensile strength of the final composites are significantly improved as compared to those of pure Al and increase with increasing volume fraction of TiAl3, reaching a maximum of similar to 180 HV and similar to 455 MPa for V-p = 49%, respectively. The high strength of the TiAl3/Al composites can be attributed to the superimposition of strengthening mechanisms which are dominant at high V-p.
通讯机构：
[Zhang, Jia-Fan] W;[Zhang, Jia-Fan] H;Wuhan Polytech Univ, Sch Mech Engn, Wuhan 430023, Peoples R China.;Hubei Prov Engn Technol Res Ctr Fish Proc Equipme, Wuhan 430023, Peoples R China.
关键词：
second-order linear control system;retarded time-delay;dominant eigenvalue;receptance;contour integral method
摘要：
The computation of dominant eigenvalues of second-order linear control systems with multiple time-delays is tackled by using a contour integral method. The proposed approach depends on a reduced characteristic function and the associated characteristic matrix comprised of measured open-loop receptances. This reduced characteristic function is derived from the original characteristic function of the second-order time delayed systems based on the reasonable assumption that eigenvalues of the closed-loop system are distinct from those of the open-loop system, and has the same eigenvalues as those of the original. Then, the eigenvalues computation is equivalent to solve a nonlinear eigenvalue problem of the associated characteristic matrix by using a contour integral method. The proposed approach also utilizes the spectrum distribution features of the retarded time-delay systems. Finally, numerical examples are given to illustrate the effectiveness of the proposed approach.
摘要：
In order to solve the problem of mid-low frequency noise reduction in cylindrical shells, the experimental and simulation methods are used to study the noise reduction performance of cylindrical shells with different acoustic covering layers in the mid-low frequency range. Firstly, a cylindrical shell noise reduction experimental device was established, the experiment for cylindrical shell structure and laying a viscoelastic material shell structure were carried out. Acoustic commercial software (LMS Virtual. Lab) was used to establish a finite element model for simulation analysis, the numerical results then compared with the experimental results. Finally, the finite element simulation was applied to study the noise response in the cylindrical cavity of lining different materials and the influence of the laying scheme and thickness of the layer. The results show that, in the case of the same laying rate, the oblique laying has a better noise reduction effect and the amount of noise reduction increases as the laying thickness increases. Under a constant thickness of the foam-butyl rubber, as the proportion of butyl rubber increases, the noise reduction per unit thickness increases, while the noise reduction per unit mass decreases. Keywords: Cylindrical shell, Noise reduction, Viscoelastic material, Multi-layer
关键词：
Green manufacturing;PID;intelligent control;fuzzy self-tuning;coal blending
摘要：
Due to the continuous improvement of industrial production requirements and green manufacturing demand, manufacturing enterprises and factories need to constantly optimize and improve the system structure. Based on the actual problems in the actual coal blending process, this paper analyzes the reason of the coal blending error in coal blending process and the optimization scheme of intelligent control of coal blending process. We optimized the overall structure of the coal blending system, improved the coal blending system which use the fuzzy control system. At the same time, we used MATLAB to simulate and analyse the simulation results. This paper gives an illustration to the optimal structure and system of the coal blending system, effectively improves the accuracy and stability of the coal blending process control system, reduces the coal blending error and improves the quality of coal blending in general.
