金属焊接接头疲劳裂纹萌生寿命估算方法的研究

疲劳裂纹萌生阶段在整个疲劳破坏过程中占有极为重要的地位，而萌生阶段的裂纹体损伤规律用长裂纹断裂力学方法是无法确定的。这里以萌生阶段中塑性滞回能作为控制参量，根据实验数据拟合出疲劳损伤的连续曲线，得到裂纹萌生寿命估算公式。     

一台1000m3液化石油气球罐裂纹的成因分析及裂纹修复

本文采用磁粉探伤技术对1000m3液化石油气球罐进行无损检测,并结合金相试验结果对球罐横向裂纹萌生及扩展原因进行了分析。分析表明,现场安装时组对和焊接工艺控制不严格、焊后热处理未达预期目标是造成焊缝产生大量延迟裂纹的主要原因。     

一种增强的ZRTP认证机制

ZRTP本身的认证机制在一些特殊的情况下无法抵抗中间人攻击。为此,基于简单密钥协商协议(SAKA)提出一种NSAKA算法,改进ZRTP的认证机制,使用RFC4474中的SIP身份认证模型来安全传输用户预共享的秘密口令。通过分析表明,该方案可以提高ZRTP抵抗中间人攻击的能力,并弥补SAKA算法原有的安全缺陷。     

How dense are cylindrical brushes grafted from a multifunctional macroinitiator?

A series of cylindrical brushes with poly(methyl methacrylate) (PMMA) and poly(n-butyl acrylate) (PBA) side chains of different lengths was studied to understand the grafting density of brush molecules prepared by the ‘grafting from’ approach. Molecules with PMMA side chains were prepared by grafting MMA from a multifunctional macroinitiator, poly(2-(2-bromoisobutyryloxy)ethyl methacrylate). Molecules with PBA side chains were prepared with poly(2-(2-bromopropionyloxy)ethyl methacrylate) as a macroinitiator. Analysis of the detached side chains showed an incomplete initiation process resulting in longer side chains than expected for complete initiation. Limited initiation (40-80%) was also observed for short PMMA chains using a low molar mass initiator ethyl 2-bromoisobutyrate with CuCl catalyst systems. The lower initiation efficiency was confirmed via visualization of individual molecules by atomic force microscopy. The larger distance between adsorbed brush molecules was consistent with <50% initiation efficiency.     

ANBDF炸药的短脉冲起爆感度研究

采用喷射结晶法制备超细7-氨基-6-硝基苯并二氧化呋咱(ANBDF),利用金属箔电爆炸驱动飞片的加载技术,研究了ANBDF炸药的短脉冲冲击起爆性能.研究结果表明ANBDF炸药最小起爆能量为0.892J,50%起爆速度为3 064.7m/s,可以用于冲击片雷管始发装药.     

Mechanism of heterogeneous catalytic ozonation of nitrobenzene in aqueous solution with modified ceramic honeycomb

The degradation efficiencies of nitrobenzene in aqueous solution were investigated by semi-continuous experiments in the processes of ozone alone, ozone/ceramic honeycomb (CH) and ozone/modified ceramic honeycomb (MCH). MCH with 1.0% Mn and 0.5% Cu had more pronounced catalytic ability than CH to accelerate the degradation of nitrobenzene, to increase the utilization efficiency of ozone, to improve the concentrations of hydrogen peroxide (H₂O₂) formation and hydroxyl radical (OH) initiation, and to enhance the removal efficiency of TOC. The modification process of CH with the metals enhanced the density of surface hydroxyl groups, which determines the initiation of OH from ozone decomposition and the generation of intermediate species on heterogeneous catalytic surface, yielding the acceleration of the degradation of nitrobenzene in aqueous solution. Possible reaction mechanism of ozone with heterogeneous catalytic surface in aqueous solution was proposed, and the formation mechanism of H₂O₂ and OH was also discussed according to the combined reactions in heterogeneous and homogeneous catalytic systems.     

V型多排深孔逐孔延时后倾式起爆技术与应用

基于炸药管制政策问题和岩石资源特征,湖州新开元碎石有限公司设计了V型多排深孔逐孔延时后倾式起爆的爆破方案。实践表明该方案有效地降低了炸药单耗,改善了爆破效果,值得推广。     

Evaluation of the James Initiation Criterion in the 21 mm and 50 mm PMMA Gap Test

The gap test has been used for several decades as a measure for the shock sensitivity of high explosives. Normally the axial pressure in the gap is used as the necessary initiation pressure of a high explosive for a shock to detonation transition. But it has been shown in the past that the pressure in the gap is not a suitable measure for shock sensitivity and other criteria like the James criterion in terms of critical energy fluence and critical specific kinetic energy should be used. To evaluate the James criterion in the 21 mm and 50 mm polymethylmethacrylate (PMMA) gap test numerical simulations are conducted. To validate the simulations a 21 mm water gap test is simulated and compared to experimental results, where the axial pressure calibration can be reproduced with high accuracy. With the results from the simulation of the 21 mm and 50 mm gap test it is shown that at the same maximum axial pressure the energy fluence is higher in the 50 mm gap test. This explains to some extent the higher initiation pressures observed in smaller gap tests. The James criterion is derived and it is shown that the two gap tests probe very different regions in the energy fluence vs. specific kinetic energy plane. The results can be used as a calibration for the gap tests and are intended to improve the comparability of gap test results among each other and with different initiation experiments like flyer or heavy fragment impact testing.     

Enhanced Initiation Behavior of Reactive Material Projectiles Impacting Covered Explosives

Reactive materials bring the dramatically enhanced lethality by means of the combined defeat mechanisms of impact kinetic energy and chemical energy release. This paper presents such an investigation on these reactive materials for the enhanced initiation behavior of covered explosives. First, a simple initiation process comparison between the inert metal and reactive material projectiles impacting covered explosives is described. Then high velocity ballistic impact experiments, which include both reactive material and tungsten alloy projectiles with mass matched against covered explosives, are conducted to investigate and compare the initiation behavior of covered explosives. Finally, theoretical analysis and discussions about contributions of both kinetic energy‐to‐initiation and chemical energy‐to‐initiation mechanisms to the enhanced initiation behavior of covered explosives impacted by reactive materials are presented.     

Dynamic and static characterization of compact crack arrest tests of navy and nuclear steels

Recent experimental and computational work by Link and associates has demonstrated that relatively small (W = 150 mm) single edge notched tension specimens (SE(T)) can be used to obtain crack arrest data high in the ductile-to-brittle transition of ferritic structural steel using dynamic computational techniques if a thermal gradient is utilized to aid in the crack arrest. Testing has been reported on two important navy structural steels that clearly defines the relative capability of the two materials to arrest rapidly growing cracks. The HY100 material demonstrated the expected large difference between the initiation and crack arrest toughnesses which has made it impossible in the past to measure crack arrest toughness for this material using the standard ASTM procedure (E1221). The HSLA-100 steel, however demonstrated a much higher crack arrest toughness and a correspondingly smaller drop in toughness below the initiation toughness. This small difference between initiation toughness and arrest toughness suggested that the E1221 procedure, using wedge loaded, compact crack arrest (CCA) specimens would be applicable to this material. Two important issues could then be investigated using this material. First, having completed the expensive and relatively complex testing of the SE(T) specimens using tensile loading and a thermal gradient, a second, quite different geometry could be tested using the E1221 procedure, allowing an important comparison between the crack arrest measurements made using these two distinct geometries. Historically, obtaining crack arrest results using one test configuration has been so difficult, that there have been very few reports of results for the same material using two different test geometries. Transferability of the laboratory results to structural applications has thus been a matter of conjecture. Furthermore, if the E1221 CCA specimens were strain gaged to obtain crack velocity data, and analyzed using the dynamic computational procedure used by Link on the SE(T) specimens, it would be possible to compare the results the E1221 static analysis with the results of the dynamic computation procedure to determine the degree of conservatism present in the E1221 standard procedure.The results of this work have shown that the crack arrest toughness results obtained on these two specimen geometries are similar and hence insensitive to the test geometry and the difference resulting from the application of the complex dynamic computational procedure or the E1221 static analyses is small.