再生微粉对混凝土强度的影响研究

针对废弃混凝土破碎、研磨制备的再生微粉对混凝土抗压、劈裂抗拉的影响进行了研究,试验结果表明,掺有再生微粉的混凝土的抗压强度、劈裂抗拉强度均能满足实际工程应用的要求。     

世纪莲体育中心动力特性及反应谱分析

以佛山市世纪莲体育中心大跨度轮辐式张拉索膜结构为研究对象,采用ANSYS程序建立有限元模型,分析其动力特性,并用振型分解反应谱法计算地震作用下结构的受力性能.研究结果表明:结构自振频率较低,频谱集中,频率跳跃现象不明显;结构以屋盖的竖向振动为主,具有较好的抗侧刚度和抗扭刚度;反应谱分析时,为保证各方向的模态质量参与系数...     

Experimental research on creep behaviors of sandstone under uniaxial compressive and tensile stresses

The consideration of time dependence is essential for the study of deformation and fracturing processes of rock materials, especially for those subjected to strong compressive and tensile stresses. In this paper, the self-developed direct tension device and creep testing machine RLW-2000M are used to conduct the creep tests on red sandstone under uniaxial compressive and tensile stresses. The short-term and long-term creep behaviors of rocks under compressive and tensile stresses are investigated, as well as the long-term strength of rocks. It is shown that, under low-stress levels, the creep curve of sandstone consists of decay and steady creep stages; while under high-stress levels, it presents the accelerated creep stage and creep fracture presents characteristics of brittle materials. The relationship between tensile stress and time under uniaxial tension is also put forward. Finally, a nonlinear viscoelastoplastic creep model is used to describe the creep behaviors of rocks under uniaxial compressive and tensile stresses.     

巧用Photoshop计算保温板黏结强度现场检测的黏结面积

通过分析原有建筑工程外墙外保温系统黏结强度现场检测中黏结面积计算方法的不足,通过利用Photoshop软件对黏结面照片不同区域所含像素的计算,设计出一种比现有方法更准确的计算方法,使计算结果精度比之前大大提高。     

高功率光纤激光中模式不稳定性现象研究进展

模式不稳定指高功率光纤激光随着输出功率提升发生的由稳态基模输出突然变为非稳态高阶模式输出的模式突变,会导致光束质量下降,限制着衍射极限光束质量光纤激光输出功率的提升。介绍了高功率光纤激光中模式不稳定现象的产生机理以及相关的实验和理论研究,详细分析了模式不稳定现象的一些性质,总结了解决或抑制高功率光纤激光中模式不稳定现象的方法。最后,对高功率光纤激光模式不稳定现象研究的未来发展趋势进行了初步探讨。     

低温环境中新型水泥基材料抗拉性能和微结构的演化行为

低温环境中混凝土的抗拉性能是影响“全混凝土”液化天然气储罐长期安全服役的重要因素。本文研发了一种新型耐低温高性能水泥基材料(CHC),利用拉伸试验机研究了低温循环(20~-165 ℃)前后CHC的抗拉性能,借助压汞孔隙率测试和核磁共振测试分析了CHC的孔结构特征。结果表明,相比于C60混凝土,CHC的总孔隙率较低,抗拉强度较大,峰后变形能力较强。低温循环后,微裂缝的出现和总孔隙率的增加导致CHC和C60混凝土的峰值应力下降。相比于C60混凝土,CHC中裂缝的宽度较小,总孔隙率的增加量较少,故CHC峰值应力的下降幅度较低。本研究证实低温循环前后CHC的抗拉性能均优于C60混凝土,这源于CHC优异的孔结构和钢纤维的掺入。     

Aromatic amino acids as latent,bio-based curing agents and toughening agents for epoxy resins

In the realm of bio-based curing agents, recent investigations have focused on amino acids owing to their distinctive attributes. Nevertheless, the suitability of thermosets cured with aromatic amino acids as latent matrix materials for fiber-reinforced composites remains to be empirically established. Consequently, this study is oriented toward assessing the mechanical properties of diglycidyl ether of bisphenol A when cured with either L-tryptophan or L-tyrosine, in the presence of a latent, urea-based accelerator. The investigated properties include glass transition temperatures, tensile, flexural, compression, and fracture toughness properties. The predominant variations in the mechanical characteristics of these thermosets are confined to their Young's moduli and fracture toughness properties. This divergence is attributed to the greater presence of crystals in the L-tyrosine-cured thermoset, resulting in enhanced reinforcement and toughening effects compared to the L-tryptophan-cured thermoset.     

A new energy-absorbing bolt used for large deformation control of tunnel surrounding rock

In order to control the large deformation of tunnel surrounding rock, a new energy-absorbing bolt is developed. This bolt can be transformed into a rigid support when the deformation of the surrounding rock reaches the length of the sleeve tube, thus preventing the surrounding rock from continuing to deform. Moreover, this bolt has a simple structure and is easy to manufacture and assemble. Then the static tensile test is conducted on the bolt specimen to test its working performance. The test results show that when the cone angle of the cone block is small, the load–displacement curve of the bolt contains three stages; when the cone angle is large, the load–displacement curve contains only two stages. Meanwhile, both the average constant resistance and the maximum absorbed energy increase linearly with the increase of cone angle. On this basis, ignoring the influence of shear stress, and it is supposed that the thickness of the sleeve tube is constant, then the theoretical calculation formula of constant resistance for the new bolt is derived, and the rationality of the formula is verified using the static tensile test results. It is found that the error of the calculated result is less than 15% when the cone angle does not exceed 15°. At last, the numerical simulation method is used to analyze the performance of the new bolt. The simulation results indicate that the generation of shear stress and the change of tube thickness during the movement of the cone block are two important factors that cause theoretical errors.     

Stabilization of ion-temperature-gradient mode by trapped fast ions

Understanding and modeling fast-ion stabilization of ion-temperature-gradient (ITG) driven microturbulence have profound implications for designing and optimizing future fusion reactors. In this work, an analytic model is presented, which describes the effect of fast ions on ITG mode. This model is derived from a bounce-average gyro-kinetic equation for trapped fast ions and ballooning transformation for ITG mode. In addition to dilution, strong wave-fast-ion resonant interaction is involved in this model. Based on numerical calculations, the effects of the main physical parameters are studied. The increasing density of fast ions will strengthen the effects of fast ions. The effect of wave-particle resonance strongly depends on the temperature of fast ions. Furthermore, both increasing density gradient and the ratio of the temperature and density gradients can strengthen the stabilization of fast ions in ITG mode. Finally, the influence of resonance broadening of wave-particle interaction is discussed.     

中间相沥青基碳纤维的生产及其性能表征

中间相沥青基碳纤维具备高模量、高导热性等特性,在航天、电子等领域具备广阔的应用前景.山东瑞城实现了中间相沥青基碳纤维的产业化生产,本文对其所生产的中间相沥青基碳纤维的结构和性能进行了表征研究.研究结果表明,1.5K连续纤维的平均直径为11μm;强度为2400 MPa;模量为811 GPa;导热率达到600 W/(m·k...