大理岩动态劈裂试样的破坏应变

脆性材料基于应变的强度准则逐渐受到重视,为研究岩石在动态拉伸条件下的破坏应变规律,利用分离式Hopkinson压杆对不同尺寸的大理岩巴西圆盘和带平台的巴西圆盘进行宽应变率范围的动态劈裂试验。研究不同类型的试样在不同应变率下的破坏应变,讨论试样尺寸、弹速、应变率对破坏应变的影响,得到了一些有益的结论:(1)大理岩的破坏应变随撞击压杆的弹速提高而增大,在一定的弹速范围内破坏应变增加趋势明显,而在此范围外破坏应变增幅很小;(2)试样尺寸对岩石的动态破坏应变的影响受弹速的影响比较显著;(3)在低应变率下,大理岩的动态破坏应变随着应变率的提高而显著增大,而带平台的试样的增加幅度更大,且数据的分散性也较小;当应变率较大时,应变率对破坏应变的影响较小,应变增幅较小,各类试样数据的分散程度都有所降低;(4)和巴西圆盘相比,在低应变率下平台巴西圆盘具有更大的承载力和更高的破坏应变,但是随着弹速的增加,平台巴西圆盘的趋势逐渐减少;当弹速大于某一数值时,其破坏应变反而小于巴西圆盘的破坏应变。

FAILURE STRAIN OF BRAZILIAN DISC SAMPLES OF MARBLE UNDER DYNAMIC SPLIT TESTS

The strain-based strength criteria are of increasing significance for brittle materials. In order to study the laws of failure strains under dynamic tension,a series of Brazilian disc and flattened Brazilian disc(FBD) samples of marble under the dynamic split tests are performed with a wide range of strain rates using split Hopkinson pressure bar(SHPB) of 100 mm in diameter. The relationship between the failure strain and the size of samplest,he projectile speed,and the strain rate,are discussed;and some useful results are obtained. The failure strains of all types of samples in different projectile speeds are achieved with strain gauges stuck on the center of the samples; and the test results indicate that the failure strain increases with the increase of the projectile speed. In certain range of the projectile speed,the failure strain increases remarkably. But when it is out of this range,the failure strain increases slightly. The relationship between the failure strain and the size of samples is notably affected by the projectile speed. However,when the strain rate is lowt,he failure strain will increase remarkablye,specially for FBD which has less scatter;when the strain rate is high,the failure strain increases slightly and results of all types of samples are scarcely scattered. Compared with Brazilian disc,the FBD has larger bearing capacity and higher failure strain in low projectile speed. With the increase of projectile speed,the trend of FBD vanishes gradually; and when the projectile speed is high,its failure strain is even less than that of the Brazilian disc.