Strengthening Mechanism and Microstructure of Deformable Ti Particles Reinforced AZ91 Composite

In this study, the deformable titanium (Ti) particles reinforced AZ91 composite was successfully prepared by powder metallurgy and subsequent extrusion. The mechanical properties and microstructural evolution of pure AZ91 and 5Ti/AZ91 composite were studied. The yield strength, ultimate tensile strength, and elongation of 5Ti/AZ91 composite are measured to be 212 MPa, 323 MPa, and 10.1%, respectively. Microstructure analysis revealed that Ti particles are elongated along the extrusion direction, forming a discontinuous strip Ti particles, fine precipitated Mg₁₇Al₁₂ phase inhibits dynamic recrystallization (DRX) behavior through Zener pinning effect and hinders the growth of matrix grains, resulting in refiner grains of 5Ti/AZ91 composite. Heterogeneous deformed Ti particles and magnesium (Mg) matrix to generate additional heterogeneous deformation-induced (HDI) strengthening. Heterogeneous deformation-induced strengthening mainly contributed to the increment of yield strength for 5Ti/AZ91 composite.     

Predetermination of potential plastic hinges on reinforced concrete frames using GFRP reinforcement

In the past, glass fiber-reinforced polymer (GFRP)-reinforcement has been successfully applied in reinforced concrete (RC) structures where corrosion resistance, electromagnetic neutrality, or cuttability were required. Previous investigations suggest that the application of GFRP in RC structures could be advantageous in areas with seismic activity due to their high deformability and strength. However, especially the low modulus of elasticity of GFRP limited its wide application as GFRP-reinforced members usually exhibit considerably larger deformations under service loads than comparable steel-reinforced elements. To overcome the aforementioned issues, the combination of steel and GFRP reinforcement in hybrid RC sections has been investigated in the past. Based on this idea, this paper presents a novel concept for the predetermination of potential plastic hinges in RC frames using GFRP reinforcement. To analyze the efficiency of the concept, nonlinear finite element simulations were performed. The results underscore the high efficiency of hybrid steel-GFRP RC sections for predetermining potential plastic hinges on RC frames. The results also indicate that the overall seismic behavior of RC structures could be improved by means of GFRP as both the column base shear force during the seismic activity as well as the plastic deformations after the earthquake were considerably less pronounced than in the steel-reinforced reference structure.     

Densification mechanism during reactive hot pressing of B4C-ZrO2 mixtures

The densification behaviors of pure B₄C and B₄C-ZrO₂ mixtures were compared during hot pressing. The results showed that in-situ formed ZrB₂ effectively enhanced the densification process of B₄C-ZrO₂ mixtures, more significantly during the intermediate stage. Within the relative density ranging from 0.75 to 0.90, the B₄C-15?wt%ZrO₂ mixture (B15Z) achieved the maximum densification rate as twice much as that of pure B₄C. The stress exponent n>3 indicated plastic deformation was the dominant densification mechanism of B15Z. The viscosities of plastic flow were evaluated using Murray-Rodger-William equation and the viscosity of B15Z was only a quarter of that in pure B₄C. The sintering activation energy was calculated to be 305.9?kJ/mol for pure B₄C and 197?kJ/mol for B15Z, respectively. It was proposed that the lower viscosity of plastic flow and activation energy accelerated the sliding and propagating motions of plastic flow, by which underlain the enhanced densification behaviors of B₄C-ZrO₂ mixtures.     

Surface Profile Optimization of Yankee Dryer Based on Finite Element Analysis

The deformation and stress distribution of cast iron Yankee dryer caused by outside linear load， inside steam pressure and self-gravity were calculated by numerical simulation with ANSYS software. The deformation curve of the linear load area was obtained and compared with the deformation in the actual working process. The surface profile of dryer was optimized and the deformation and stress of the optimized dryer were calculated and compared with the that of before optimization. In this paper， the method of the surface profile optimization of Yankee dryer was presented．     

Waves in generalized thermo-viscoelastic infinite continuum with cylindrical cavity due to three-phase-lag time-nonlocal heat transfer

Abstract

Generalized thermoelastic interactions due to three-phase-lag time-nonlocal heat transfer in a Kelvin-Voigt type infinitely extended visco-thermoelastic continuum with cylindrical cavity has been investigated. The two-temperature generalized thermoelasticity theory has also been taken into account. The problem has been solved in the domain of Laplace on the assumption that the surface of the cavity is free from traction and is subjected to a smooth and time-dependent-heating effect. Laplace inversion of the transformed solutions has been carried out numerically. The obtained numerical data for different considerations are plotted in graphs to study the effects of time-nonlocal parameter, two-temperature parameter and visco-thermoelastic relaxation parameter on different thermoelastic quantities of physical interest.     

采场围岩变形与破坏监测技术研究进展及展望

深部煤炭资源开发面临更多复杂、多变、高难的开采地质问题,采场围岩形态结构是矿井安全生产的重要评价指标之一,开展采场围岩变形与破坏测是判别矿井隐蔽致灾地质问题的重要技术保障。在煤炭工业快速发展的近20余年时间里,围岩体形变监测技术取得了长足的进步,基于矿山采场围岩体变形与破坏的影响因素,按照监测形式对监测技术进行了划分,归纳了当前用于矿山采场围岩变形与破坏监测的钻孔测试技术、地球物理探测技术、光纤监测技术及其他测量技术及其特点,结合煤层顶底板、巷道两帮空间监测的工程应用实例,介绍了不同监测技术的主要进展、优缺点以及适用性,讨论了探测技术的革新趋势和未来矿井安全生产中采场围岩变形与破坏监测技术的发展方向。同时,也认识到现有监测技术虽然已取得显著的监测效果,但是仍不能够满足矿井现代化、智能化生产需要。对于监测技术的进步而言,既需要技术装备的不断优化,更是要跨学科、跨专业科学技术理论的完善与更新。在当前地学大数据、云计算、人工智能新一轮科技创新基础上,今后采场围岩变形与破坏的监测技术必然向多元化、多参数、智慧化、全程监控的方向发展,监测方式也将不断地向可视化、动态化的监测预警模式过渡,融合监测技术发挥多参数的作用将越来越重要。     

严重突出煤层穿层钻孔“钻冲筛运”一体化瓦斯治理技术研究与应用

鹤煤公司八矿地质构造复杂、断层褶曲发育,尤其井田深部断层多,并且煤层透气性低且松软,打钻塌孔、喷孔严重,瓦斯抽放效果不好,给煤炭开采和瓦斯综合治理带来了困难。针对鹤煤公司八矿穿层钻孔瓦斯治理技术措施进行井下现场探索与研究,通过在3205底抽巷经过多次技术方案论证、实践,摸索出一套钻冲筛运一体化整套技术流程,并分析高压水力冲孔瓦斯涌出特征、有效影响半径。通过采用高压水力冲孔、振动筛选、转载装运,提高了水力冲孔效果和效率,改善了工作环境。     

深部软岩巷道围岩变形特征及数值模拟分析

针对深部煤矿开采条件下软岩巷道围岩出现持续流变时间长、变形大、地压高、巷道难以维护等特点，首先分析了深部软岩巷道变形特征，采用FLAC^3D数值模拟软件，分析了不同埋深条件下巷道围岩垂直应力分布、水平应力分布以及巷道围岩塑性区扩展规律。研究得出，深部软岩巷道的围岩岩块呈松散破碎形态，相互翻转和滑移，岩体的模量和强度低；随着巷道埋深的逐渐增加，巷道围岩应力集中系数逐渐减小，巷道垂直、水平应力峰值逐渐变大，塑性破坏范围扩展速率逐渐增加。研究为深部软岩巷道支护提供理论基础。     

新国标背景下聚氨酯塑胶跑道的发展

对聚氨酯塑胶跑道行业发展现状及问题进行概述,解读了新国标GB 36246-2018《中小学合成材料面层运动场地》对运动场地材料物理机械性能和化学指标的新限量。为适应新国标要求,聚氨酯塑胶跑道从环保配方体系设计和施工质量方面均做出了改进,最后简要介绍聚氨酯塑胶跑道未来发展趋势。