国内外纸质文献加固技术研究

纸张脆化问题既缩短了纸质文献的保存寿命,又限制了纸质文献的使用、研究与传承,对脆化纸质文献进行加固处理迫在眉睫。现有纸质文献加固技术使用的材料可以分为天然材料、合成材料以及复合材料三大类。本文从这三方面对纸质文献加固技术的研究进展进行了介绍,并综合考虑我国文献保护的实际情况,提出了开展纸质文献加固工作应遵循的原则和未来的研究方向,旨在为脆化纸质文献加固处理提供借鉴。     

High-entropy ferroelastic rare-earth tantalite ceramic: (Y0.2Ce0.2Sm0.2Gd0.2Dy0.2)TaO4

In this study, high-entropy rare-earth tantalate ceramics (Y_0.2Ce_0.2Sm_0.2Gd_0.2Dy_0.2)TaO₄ ((5RE_0.2)TaO₄) have been successfully fabricated. The possibility of formation of (5RE_0.2)TaO₄ was verified via first-principles calculations. In addition, the phase structure, ferroelastic toughening mechanism, thermophysical, and mechanical properties were systematically investigated. The (5RE_0.2)TaO₄ ceramics have lower phonon thermal conductivity (1.2–2.6 W·m^–1·K^–1) in the entire temperature range than that of RETaO₄ and YSZ. (5RE_0.2)TaO₄ has a higher fracture toughness and lower brittleness index than YSZ. The thermal expansion coefficients of (5RE_0.2)TaO₄ are as high as 10.3 × 10^-6 K^–1 at 1200°C and Young's modulus is 66–189 GPa, and thus, (5RE_0.2)TaO₄ possesses great potential for application in thermal barrier coatings (TBCs).     

Rock brittleness indices and their applications to different fields of rock engineering:A review

Brittleness is an important parameter controlling the mechanical behavior and failure characteristics of rocks under loading and unloading conditions,such as fracability,cutability,drillability and rockburst proneness.As such,it is of high practical value to correctly evaluate rock brittleness.However,the definition and measurement method of rock brittleness have been very diverse and not yet been standardized.In this paper,the definitions of rock brittleness are firstly reviewed,and several representative definitions of rock brittleness are identified and briefly discussed.The development and role of rock brittleness in different fields of rock engineering are also studied.Eighty brittleness indices publicly available in rock mechanics literature are compiled,and the measurement method,applicability and limitations of some indices are discussed.The results show that(1)the large number of brittleness indices and brittleness definitions is attributed to the different foci on the rock behavior when it breaks;(2)indices developed in one field usually are not directly applicable to other fields;and(3)the term“brittleness”is sometimes misused,and many empirically-obtained brittleness indices,which lack theoretical basis,fail to truly reflect rock brittleness.On the basis of this review,three measurement methods are identified,i.e.(1)elastic deformation before fracture,(2)shape of post-peak stressestrain curves,and(3)methods based on fracture mechanics theory,which have the potential to be further refined and unified to become the standard measurement methods of rock brittleness.It is highly beneficial for the rock mechanics community to develop a robust definition of rock brittleness.This study will undoubtedly provide a comprehensive timely reference for selecting an appropriate brittleness index for their applications,and will also pave the way for the development of a standard definition and measurement method of rock brittleness in the long term.     

42CrMo锚栓断裂分析

风电用42CrMo锚栓在安装过程中突然发生断裂，对断裂试样进行化学成分分析，采用金相检验与扫描电镜观察相结合的方法，分析研究断裂原因。结果表明，断口为沿晶断裂，锰元素含量超标和磷、硅、铜合金元素晶界偏聚是造成沿晶断裂的主要原因；另外，热处理时淬火温度过高造成奥氏体晶粒粗大，以及回火温度接近高温回火脆性区造成杂质元素在奥氏体晶界偏聚，这些因素的共同作用也会导致材料发生脆性断裂。     

耐磨合金钢的回火脆性、变质处理及组织遗传性

探讨了耐磨合金钢的回火脆性、变质处理及组织遗传性3个特征对其组织与力学性能的影响,分析了获得高性能耐磨合金钢的关键问题和方法。     

基于岩石破裂特征及能量演化的致密砂岩脆性指数优选

脆性参数是致密油“三品质”评价中完井品质评价的重要敏感参数之一。采用岩心三轴岩石力学参数测试方法，基于岩石破裂特征及岩石破裂过程中的能量演化优选出适用于鄂尔多斯盆地定边油田长7段致密砂岩储层的脆性指数计算方法。首次应用裂缝体积密度计算方法对岩石破裂复杂程度进行了定量表征，表征结果与岩石的弹性模量、抗压强度呈正相关；与泊松比、峰值应变呈负相关。通过对岩石力学参数各向异性系数C1和C2的分析，认为弹性模量和泊松比对各向异性更为敏感，两者构建的脆性参数更能体现岩石的脆性特征。基于岩石破裂的能量演化过程，将峰值强度前后能量变化大小与变化速率相结合，构建脆性评价新指标BEC，其与裂缝体积密度及前人提出的脆性评价指标均具有较好的相关性。以BEC为衡量标准优选出适合研究区致密砂岩储层的脆性指数E/μ，该指数与研究区直井试油试采的初周日产液呈正比关系。研究结果为研究区水平井水力压裂施工时指示有利压裂层段提供了科学依据。     

有序合金Ni3Si脆性改善研究进展

从微合金化，宏合金化，细化晶粒3个方面介绍改善Ni3Si合金脆性的研究进展。微合金化虽可提高Ni3Si的室温韧性，但效果并不明显，而宏合金化虽可在一定温度范围内提高Ni3Si合金韧性，有些元素降低高温韧性或室温韧性；细化晶粒提高Ni3Si韧性的效果产不明显。合金成分富Ni化，多元素宏合金化与微合金化相结合是改善Ni3Si有序合金脆性的最佳方法。     

路面橡胶集料混凝土抗折强度的试验研究

橡胶集料混凝土作为一种新型混凝土材料具有极好的抗裂性能,良好的抗冲击载荷和能量耗散能力,作新型的路面材料非常适用。通过对掺入较高比例的橡胶集料混凝土(最高可达150kg/m3)的抗折试验,分析了橡胶集料混凝土抗折强度的主要影响因素,建立抗折强度的经验公式,并对公式的合理性进行验证。然后对橡胶集料混凝土的抗折强度与抗压强度之间的相关关系进行讨论。     

提高碾压混凝土抗裂能力的试验研究

通过试验分析了外掺单矿C2S和C4AF矿物成分和用活性掺合料(粉煤灰F、硅灰SF、氧化镁MgO)等量取代水泥(C)和用非活性掺合料(橡胶粉X)等体积取代部分标准砂(S)对水泥脆性系数的影响。     

火灾中窗玻璃热炸裂痕迹形成机理的研究

研究了火灾中窗玻璃热炸裂痕迹的形成机理及其影响因素。通过分析窗玻璃在火灾中的温度分布，发现窗玻璃在火灾条件下产生的热应力有两种：由于玻璃表面温度不均匀产生的热应力和由于窗框约束产生的热应力。同时玻璃表面存在大量微裂纹，当热应力达到临界值时，在热应力的作用下产生脆性断裂。热炸裂容易在边角产生的原因是因为两种热应力叠加的结果，热炸裂过程与火灾过程有关。