循环荷载作用下花岗岩动力特性试验研究

通过在RMT–150B多功能全自动刚性岩石伺服试验机对取自海南昌江核电厂一期工程常规岛的微风化和中风化黑云母花岗岩进行单轴压缩变形试验和循环加卸载试验,研究花岗岩动应力–动应变曲线滞回特性和动弹性模量与阻尼比同弹性模量之间的规律,并利用广义开尔文流变模型来描述循环荷载下花岗岩的滞回曲线和能量损耗情况。研究结果表明:花岗岩在循环荷载作用下的加卸应力–应变曲线形成滞回环,随着循环数的增加,滞回环向轴向应变增大的方向移动,且越来越密集;花岗岩的滞回环面积和最大弹性应变能都随弹性模量的增加而减少,而动弹性模量则相反,阻尼比先随弹性模量的增大而增大,达到一峰值后,随弹性模量的增大而减少;广义开尔文模型可以较好地描述花岗岩的滞回曲线和能量损耗情况。研究成果对海南昌江核电厂地基的地震反应分析和场地安全性评价有着重要的参考意义。

核级管道不锈钢316LN的低周疲劳特性研究

在室温下,对核级管道不锈钢材料316LN试样进行了不同应变幅的低周疲劳试验研究,得到了316LN试样的循环应力-应变响应特征及低周疲劳寿命曲线。基于疲劳过程中、不同应变幅水平下,循环应力-应变迟滞回线的试验结果,分析了应力峰值、谷值和循环弹性模量随疲劳循环数的变化规律,研究了316LN试样的疲劳特性和疲劳寿命曲线特征,并与ASME疲劳设计曲线进行了对比。试验结果表明,试样初始循环表现出循环硬化,随后表现出循环软化直至失效;初始前10%疲劳寿命期内循环弹性模量缓慢下降,然后几乎保持不变,在达到80%~90%寿命后开始下降;Basquin和Manson-Coffin公式可以很好地描述0.2%~0.7%应变幅范围内的应变-疲劳寿命曲线。

INFLUENCE OF AIRCRAFT DEICER ON FREEZE-THAW DURABILITY OF HIGH PERFORMANCE CONCRETE

The influence of glycol,the main composition of the most frequently used aircraft dicer,on the freeze-thaw durability of high performance concrete（HPC）is investigated.Freeze-thaw durability of HPC is tested by accelerated freeze-thaw test.Four kinds of the solution,i.e.,tap water,3.5% NaCl solution,glycol solutions,and a LBR-A type commercial aircraft deicer are employed.Results show that freeze-thaw durability of HPC exposed to glycol solutions is closely related to the solution concentrations.The failure of HPC exposed to 3.5% glycol solution is similar to that of those exposed to 3.5% NaCl solution,i.e.,serious surface scaling.While the damage of HPC exposed to 12.5%—25% glycol solutions is postponed.Compared with glycol solution,the commercial aircraft deicer has much more negative effects on HPC freeze-thaw durability compared with 3.5% NaCl solution.In the presence of commercial aircraft deicer for HPC subjected to freeze-thaw cycles,the deterioration is mainly due to scaling and spalling.

Freeze-thaw damage mechanism of elastic modulus of soil-rock mixtures at different confining pressures

As a frequently-used roadbed filler,soil-rock mixture is often in the environment of freeze-thaw cycles and different confining pressures.In order to study the freeze-thaw damage mechanism of elastic modulus of soil-rock mixtures at different confining pressures,the concept of meso-interfacial freeze-thaw damage coefficient is put forward and the meso-interfacial damage phenomenon of soil-rock mixtures caused by the freeze-thaw cycle environment is concerned;a double-inclusion embedded model for elastic modulus of soil-rock mixtures in freezing-thawing cycle is proposed.A large triaxial test was performed and the influences of confining pressure and experimental factors on elastic modulus of soil-rock mixtures were obtained,and then the accuracy of the double-inclusion embedded model to predict the elastic modulus of soil-rock mixtures in freezing-thawing cycle is verified.Experiment results showed that as to soil-rock mixtures,with the increase of confining pressure,the elastic modulus increases approximately linearly.The most crucial factors to affect the elastic modulus are rock content and compaction degree at the same confining pressure;the elastic modulus increases with the increase of rock content and compactness;as the number of freeze-thaw cycles increases,the freeze-thaw damage coefficient of meso-structural interface and the elastic modulus decrease.

精炼12Cr钢高温低周疲劳循环特性试验研究

为研究高温寿命损耗过程中材料低周疲劳特性的变化规律,在540℃和593℃下对3种精炼12Cr转子钢进行总应变控制的低周疲劳试验,分析了其循环弹性模量E*、循环强度系数K和循环应变硬化指数n随循环周次变化的规律。试验结果表明:循环初始阶段(N/N f<0.1),循环弹性模量E*迅速变化,多数试样表现为下降趋势,个别试样存在硬化现象;循环稳定阶段(0.1<N/N f<0.8),E*较为稳定;循环末期(N/N f>0.8),E*急剧降低;当N/N f<0.8时,循环强度系数K和n随循环周次的变化规律均可用系数为正、指数为负的幂函数曲线拟合,寿命损耗过程中,K和n具有相似的变化趋势。同时,控制应变幅和温度对上述3个参数有重要影响。最后,分析了弹性模量劣化对寿命估算的影响,结果表明:与传统寿命估算方法相比,弹性模量修正后的寿命估算精度在较低温度下(540℃)明显提高,而在较高温度时(593℃)精度提高不明显。