Tensile strength is an important material property for rocks. In applications where rocks are subjected to dynamic loads, the dynamic tensile strength is the controlling parameter. Similar to the study of static tensi...Tensile strength is an important material property for rocks. In applications where rocks are subjected to dynamic loads, the dynamic tensile strength is the controlling parameter. Similar to the study of static tensile strength, there are various methods proposed to measure the dynamic tensile strength of rocks.Here we examine dynamic tensile strength values of Laurentian granite(LG) measured from three methods: dynamic direct tension, dynamic Brazilian disc(BD) test, and dynamic semi-circular bending(SCB). We found that the dynamic tensile strength from direct tension has the lowest value, and the dynamic SCB gives the highest strength at a given loading rate. Because the dynamic direct tension measures the intrinsic rock tensile strength, it is thus necessary to reconcile the differences in strength values between the direct tension and the other two methods. We attribute the difference between the dynamic BD results and the direct tension results to the overload and internal friction in BD tests. The difference between the dynamic SCB results and the direct tension results can be understood by invoking the non-local failure theory. It is shown that, after appropriate corrections, the dynamic tensile strengths from the two other tests can be reduced to those from direct tension.展开更多
通过扭转变形对6061-T651铝合金进行强化,扭转角度为90°,180°,360°,并对扭转前后的样品进行准静态和动态压缩性能研究。结果表明:随着扭转角度的增加,样品的晶粒尺寸先保持不变,然后开始减小;而Kernel平均取向差(Kernel ...通过扭转变形对6061-T651铝合金进行强化,扭转角度为90°,180°,360°,并对扭转前后的样品进行准静态和动态压缩性能研究。结果表明:随着扭转角度的增加,样品的晶粒尺寸先保持不变,然后开始减小;而Kernel平均取向差(Kernel average misorientation,KAM)却随着扭转角度的增加持续增大。准静态和动态压缩实验显示,随着扭转角度的增加,样品材料的屈服强度稍有提高。在扭转角度相同的条件下,动态屈服强度明显高于准静态下的屈服强度。应变率实验显示样品的屈服强度随着应变率的增加而增大,但是相比于未扭转样品,扭转360°样品的应变率效应显著降低。基于实验数据,拟合了Cowper-Symonds本构模型中的参量,该模型得到的应力-应变曲线与实验结果能够较好地吻合。展开更多
基金provided by the Innovative Research Groups of Natural Science Foundation of China (NSFC) (Grant No. 51321065)NSFC (Grant No. 51479131)The research of Kaiwen Xia was partially supported by the Natural Sciences and Engineering Research Council of Canada (NSERC) through the Discovery (Grant No. 72031326)
文摘Tensile strength is an important material property for rocks. In applications where rocks are subjected to dynamic loads, the dynamic tensile strength is the controlling parameter. Similar to the study of static tensile strength, there are various methods proposed to measure the dynamic tensile strength of rocks.Here we examine dynamic tensile strength values of Laurentian granite(LG) measured from three methods: dynamic direct tension, dynamic Brazilian disc(BD) test, and dynamic semi-circular bending(SCB). We found that the dynamic tensile strength from direct tension has the lowest value, and the dynamic SCB gives the highest strength at a given loading rate. Because the dynamic direct tension measures the intrinsic rock tensile strength, it is thus necessary to reconcile the differences in strength values between the direct tension and the other two methods. We attribute the difference between the dynamic BD results and the direct tension results to the overload and internal friction in BD tests. The difference between the dynamic SCB results and the direct tension results can be understood by invoking the non-local failure theory. It is shown that, after appropriate corrections, the dynamic tensile strengths from the two other tests can be reduced to those from direct tension.
文摘通过扭转变形对6061-T651铝合金进行强化,扭转角度为90°,180°,360°,并对扭转前后的样品进行准静态和动态压缩性能研究。结果表明:随着扭转角度的增加,样品的晶粒尺寸先保持不变,然后开始减小;而Kernel平均取向差(Kernel average misorientation,KAM)却随着扭转角度的增加持续增大。准静态和动态压缩实验显示,随着扭转角度的增加,样品材料的屈服强度稍有提高。在扭转角度相同的条件下,动态屈服强度明显高于准静态下的屈服强度。应变率实验显示样品的屈服强度随着应变率的增加而增大,但是相比于未扭转样品,扭转360°样品的应变率效应显著降低。基于实验数据,拟合了Cowper-Symonds本构模型中的参量,该模型得到的应力-应变曲线与实验结果能够较好地吻合。
