Benchmark experiments and characteristic cyclic plasticity deformation

Key issues in cyclic plasticity modeling are discussed based upon representative experimental observations on several commonly used engineering materials. Cyclic plasticity is characterized by the Bauschinger effect, cyclic hardening/softening, strain range effect, nonproporitonal hardening, and strain ratcheting. Additional hardening is identified to associate with ratcheting rate decay. Proper modeling requires a clear distinction among different types of cyclic plasticity behavior. Cyclic hardening/softening sustains dependent on the loading amplitude and loading history. Strain range effect is common for most engineering metallic materials. Often, nonproportional hardening is accompanied by cyclic hardening, as being observed on stainless steels and pure copper. A clarification of the two types of material behavior can be made through benchmark experiments and modeling technique. Ratcheting rate decay is a common observation on a number of materials and it often follows a power law relationship with the number of loading cycles under the constant amplitude stress controlled condition. Benchmark experiments can be used to explore the different cyclic plasticity properties of the materials. Discussions about proper modeling are based on the typical cyclic plasticity phenomena obtained from testing several engineering materials under various uniaxial and multiaxial cyclic loading conditions. Sufficient experimental evidence points to the unambiguous conclusion that none of the hardening phenomena (cyclic hardening/softening, strain range effect, nonproportional hardening, and strain hardening associated with ratcheting rate decay) is isotropic in nature. None of the hardening behavior can be properly modeled with a change in the yield stress.     

缓倾斜采空区处理的理论与实践

坚硬顶板下特大型采空场的处理是中国普遍存在的、特有的一类采矿技术难题.国内外已有的采空区处理方法中能解决冲击地压问题的,应用成本昂贵.为了经济有效地处理全面采矿法等空场法遗留的大量采空区及矿体残采,在国内外采空区处理与利用方法的基础上,提出了切槽放顶法和切顶与矿柱崩落法,并应用数值模拟、相似模拟和岩体声发射技术研究了各新方法的基本参数的设计方法和实施效果的分析、评价方法,形成了针对缓倾斜采空区处理的从理论分析、方案设计、现场实施到效果观测的一整套可供推广借鉴的理论、实施和评价体系.实践表明,提出的理论、实施和评价体系是技术可行、经济合理、简便适用的,具有重大的社会意义和重要的经济价值.     

岩石(体)声发射特征综述

因模型试验和数值仿真对岩体的局限性,应用岩体声发射技术监测评价岩体工程的稳定性不可缺少,有时是唯一不可替代的技术之一.岩体监测预报,曾普遍应用0～1 kHz的低频声发射仪,仅用事件和能率作为预报参数,加上复杂岩体的声发射特征还认识不清,且没有很好的噪音剔除方法,使得采集频带可能过宽,信号接收的敏感性可能偏低,预报判据有时很不充分,监测很容易受环境干扰.本文简要叙述了近年发现的岩石(体)声发射的一些特征,据此提出了岩体声发射技术研发的若干建议,包括仪器改进与完善,噪音剔除新方法研究和复杂岩体AE特性研究等.     

用微波辐射制备均分散α—Fe2O3胶体粒子

本文介绍了用微波辐射制备α－Ｆｅ２Ｏ３胶体粒子的新方法，实验表明，采用微波辐射并加入ＣＴＡＢ表面活性剂，可在较短时间内，制备出均分散的α－Ｆｅ２Ｏ３胶体粒子，并且浓度高，产量大。     

Crystal structures and photoisomerization behaviors of five novel pyrazolone derivatives containing furoyl group

Five novel pyrazolone derivatives containing a furoyl group, 1-phenyl-3-furoyl-4-(4-chlorobenzal)-5-pyrazolone thiosemicarbazone (PF4ClBP-TSC) (1)/methylthiosemicarbazone (PF4ClBP-MTSC) (2)/ethylthiosemicarbazone (PF4ClBP-ETSC) (3), 1-phenyl-3-furoyl-4-(2-chlorobenzal)/(3-chlorobenzal)-5-pyrazolone methylthiosemicarbazone (PF2ClBP-MTSC) (4)/(PF3ClBP-MTSC) (5), have been synthesized and characterized by elemental analysis, IR, ¹H NMR spectra, and the molecular structures of 2 and 5 were determined by X-ray single crystal diffraction. Photoisomerization properties have been studied by UV–vis and fluorescence spectra. Based on theoretical calculation and crystal structural analysis, the compounds undergo photoisomerization from the enol form to the keto form through an intermolecular proton transfer upon UV light irradiation. Moreover, the photoisomerization rate decreases with the increase of volume of substituent groups on 4-position of thiosemicarbazide and the steric hindrance of Cl atom on benzal of 4-positon on the pyrazolone ring.