标准贯入试验中杆长校正的一点看法

本文根据《岩土工程勘察规范》(GB50021—94)关于标准贯入试验锤击数(下称标贯击数)杆长校正问题的表述,对标贯锤击数是否应作杆长校正提出了作者的看法,认为在目前情况下,对标贯击数值进行杆长校正是必要的.     

无线mesh网络组播路由研究

组播在无线mesh网络中有着重要的应用。介绍了两种基本的组播路由算法：最短路径树（SPT）和最小开销树（MCT）,通过仿真对组播发送率、吞吐量以及端到端延迟等性能进行比较,找出适用于无线mesh网络的组播路由算法。     

珊瑚礁砂作地基吹填料及振冲加固试验研究

珊瑚礁砂作为一种特殊的地基填筑材料,其基本特性是结构疏松、压实难、压缩性大、承载力低,实际的工程应用还鲜有报导。结合沙特吉达RSGT码头修建项目,对红海珊瑚礁的矿物成分、基本物理力学性质开展试验研究,分析将珊瑚礁砂用作码头吹填地基填料的可行性,并采用振冲挤密法对该珊瑚礁砂地基进行加固处理。通过对比振冲加固前后地基的CPT检测结果,并利用振冲加固后的标贯SPT数据对处理地基进行沉降分析计算,得出该珊瑚礁砂料是一类工程性质较好的新型填料,填筑地基经振冲挤密后的加固效果显著,既经济又环保,特别适合于沿海岸珊瑚礁大量分布地区的港口码头造陆工程建设。     

机场跑道"浅层淤泥质土"地基结构填石强夯设计与处理

根据广州新白云国际机场三跑道北段地质条件、工程要求,进行地基处理设计;根据施工观测数据、检测结果,分析结构填石强夯处理"浅层淤泥质土"的效果.     

Application of the small punch test to determine the fracture toughness of metallic materials

A new methodology to determine the elasto‐plastic fracture toughness, J_Ic, by means of notched small punch tests (SPT) samples is reported. Standard SPT samples were used after being longitudinally notched machined from the centre of one side of the sample to the centre of the opposite side, producing a notch depth‐to‐thickness ratio a/t= 0.4. The onset of crack initiation was experimentally determined directly from the experimental load‐displacement plot of the test and also with the aid of scanning electron microscope observations performed on different samples, with tests being interrupted at different percentages of the maximum registered load. The test was also modelled using finite element analysis and the J‐integral was evaluated as a contour integral in ABAQUS. The obtained results were compared with the critical J values of the steel determined using standard tests (J–R curves) and the differences found were duly justified.     

Use of the small punch test to determine the ductile‐to‐brittle transition temperature of structural steels

The small punch test (SPT) consists in punching very small square specimens, measuring 10 × 10 mm² and 0.5‐mm thickness, until fracture using a 2.5‐mm‐diameter hemispherical punch. Different specimens of a structural steel were tested from room temperature to cryogenic temperatures in order to determine its ductile‐to‐brittle transition temperature (DBTT). The DBTT obtained in SPT (DBTT_STP) is much lower than the DBTT obtained by means of Charpy specimens (DBTT_CVN). The variation of the mechanical parameters calculated from the SPTs with temperature was also calculated and the operative fracture micromechanisms defined using a scanning electron microscope.     

奥氏体不锈钢凝固相转变规律曲线(SPT曲线)建立

利用自行设计的高温凝固相转变测定实验装置,研究了304奥氏体不锈钢在不同冷却速度下的高温凝固相转变过程,得到了凝固过程中液相（ L）到高温铁素体（δ）到奥氏体（γ）的相变温度。在此基础上分析了304奥氏体不锈钢在不同冷却速度下的高温凝固相转变规律,从而建立了304奥氏体不锈钢的低冷速凝固相转变规律曲线—SPT（Solidification phase transforma?tion）曲线。结果表明：对试样进行液氮酒精淬火有效地保留了试样高温时各相的状态。可以清楚的显示在不同冷速下的不同温度淬火时液相和固相的各相成份比例及在不同淬火温度下各成份体积比例的变化。通过研究体积比例变化,可以得到304奥氏体不锈钢在不同冷速下的液相线、固相线及各种反应开始和结束的转变温度（即SPT曲线）。由SPT曲线也可以看出,随着冷却速度的增大,相转变模式会发生变化,相图会向左移动,各相变反应的温度区间减小。