混凝土材料动态间接拉伸试验的数值模拟

Numerical simulation of dynamic indirect tensile test for concrete material

文章采用有限元软件ANSYS/LS-DYNA对冲击荷载作用下的半圆弯曲(semi-circular bending,SCB)实验和巴西圆盘(Brazilian disc,BD)实验进行了数值模拟;试样分别采用线弹性和混凝土Holmquist-JohnsonCook(HJC)动态本构2种模型,对2种动态间接拉伸试验中沿用静态线弹性理论计算抗拉强度的误差进行了分析。模拟结果表明:当SCB实验弧形垫块角度α在15°~25°,试样直边加载支座间距L与试样直径D的比值L/D在0.6~0.8,圆棒垫条半径r在0.004~0.006m范围内,BD实验弧形垫块角度β在18°~24°范围内,2种实验方法用静态弹性理论计算动态抗拉强度的最大误差均不超过9.8%,且2种本构模型模拟结果的误差不超过2%;冲击载荷作用下,SCB实验中试样起裂点始终为直边中点,而BD实验中试样起裂点不固定;在相同的加载情况下,SCB实验中试样的最大拉应力与最大压应力的比值显著大于BD实验,因此SCB实验更适合混凝土等脆性材料动态间接抗拉强度的测量。

Finite element software ANSYS/LS-DYNA was used in the numerical simulations of semi-circular bending（SCB） test and Brazilian disc（BD） experiment test at high strain rate under impactloading. Sample using linear elastic and Holmquist-Johnson-Cook （HJC） dynamic constitutive modelrespectively were presented. The error of the calculation of tensile strength of two kinds of dynamicindirect tensile tests using static linear elastic theory was analyzed. The simulation results show thatwhen the SCB test＇s arc-shaped cushion angle a is 15°-25°, the ratio of sample straight edge load bear-ing spacing L to sample diameter D（L/D） is in the range of 0. 6 to 0. 8, the round bar strip radius r isin the range of 0. 004 m to 0. 006 m and BD experiment test＇s arc-shaped cushion angleβ is 18°-24°,the maximum error of the linear elastic constitutive model for the two kinds of test samples is no morethan 9. 8%, and the error of two kinds of structures is no more than 2%. The damage of SCB samplealways begins at straight edge point, but the damage of BD sample is not fixed. The ratio of the maxi-mum tensile stress to the maximum compressive stress of the sample in SCB test was significantlyhigher than that of BD test under the same load. So the SCB test is more suitable for the measurementof dynamic indirect tensile test of brittle materials such as concrete.