NUMERICAL ANALYSIS ON DYNAMIC MECHANICAL BEHAVIOR OF CONCRETE
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摘要:
混凝土动态强度的增强效应DIF(dynamic increase factor)一般由混凝土霍普金森杆SHPB(split Hopkinson pressure bar)试验进行测量,而基于不同应变率˙ε条件下的试块尺度的SHPB试验结果得到的宏观DIF-˙ε关系不能直接应用于数值模型定义。运用ANSYS /LS-DYNA有限元软件和K&C混凝土模型,对混凝土SHPB直接拉伸、劈裂和层裂试验进行了模拟研究。提出了局部和非局部损伤模型中引入网格和应变率˙ε双修正的DIF-˙ε模拟方案,并对混凝土非局部损伤模型中非局部特征长度L在数值模拟中的应用方案进行了讨论。SHPB和混凝土梁冲击试验模拟研究和试验数据的比较结果均表明,提出的分别基于局部和非局部损伤混凝土模型的双修正DIF-˙ε模拟方案能够较为准确描述混凝土动态力学行为。
Abstract:The dynamic increasing factor (DIF) of concrete is normally measured via split Hopkinson pressure bar (SHPB) tests. However, the tested macro-scale DIF-˙εrelationship from the specific SHPB test specimens under different strain rates ˙εcannot be directly introduced to finite element (FE) modelling. Based on the ANSYS/LS-DYNA and K&C concrete damage model, the SHPB direct tension, split and spalling tests were modelled, and a modified DIF-˙εrelationship with both mesh and ˙ε corrections for dynamic mechanic behaviour of concrete material was proposed for local and non-local damage modelling of concrete respectively, also the numerical application of the nonlocal characteristic length L was detailed discussed. The comparison between the SHPB/impact test modelling and the relevant test results indicated that the proposed doubly corrected DIF-˙ε numerical application schemes could properly capture the concrete dynamic mechanical property.
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Keywords:
- concrete /
- DIF /
- strain rate /
- SHPB /
- FE analysis /
- local damage model /
- non-local damage model
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表 1 加载条件
Table 1 Loading conditions
加载
条件入射杆
应力/MPa入射波耗时/μs 透射杆
应力/MPa动态抗压
强度/MPa应变率/
s−1动力增强
因子 DIF上升 峰值
持续总耗时 1 26.5 45 100 190 4.5 9.31 4.9 2.06 2 67.0 45 100 190 4.0 7.59 5.3 1.68 3 75.0 35 100 170 4.1 7.93 5.8 1.75 表 2 有限元模型尺寸及参数
Table 2 Dimensions and parameters of finite element (FE) model
名称 长度/m 直径/m 弹性模量/GPa 密度/(kg/m3) 泊松比 入射杆 1.3208 0.0508 200.00 7800 0.3 透射杆 1.3208 0.0508 200.00 7800 0.3 试样 0.0508 0.0508 37.93 2405 0.2 表 3 K&C混凝土模型参数(f′c=57.7 MPa, hc=3.175 mm)
Table 3 K&C concrete model parameters (f′c=57.7 MPa, hc=3.175 mm)
参数 取值 参数 取值 参数 取值 参数 取值 参数 取值 a0y 1.288×107 λ1 0.000 λ9 5.200×10−4 η4 0.99 η12 0.00 a1y 0.625 λ2 8.000×10−6 λ10 5.700×10−4 η5 1.00 η13 0.00 a2y 4.463×10−9 λ3 2.400×10−5 λ11 1.000 η6 0.99 b1 1.6 a0 1.706×107 λ4 4.000×10−5 λ12 1.000 η7 0.97 b2 −0.5 a1 4.463×10−1 λ5 5.600×10−5 λ13 1.000 η8 0.50 f′c 57.7 MPa a2 1.400×10−9 λ6 7.200×10−5 η1 0.00 η9 0.10 ft 4.53 MPa a1f 4.417×10−1 λ7 8.800×10−5 η2 0.85 η10 0.00 Locwidth 3.175 mm a2f 2.050×10−9 λ8 3.200×10−4 η3 0.97 η11 0.00 ω 0.5 注:a0y为初始屈服面内聚力,a1y和a2y为初始屈服面参数;a0、a1和a2为最大剪切破坏面参数;a1f和a2f为残余破坏面参数;λ1~λ13为第1至第13个损伤函数参数;η1~η13为第1至第13个比例因子;Locwidth为混凝土断裂带局部宽度;f′c和ft分别为混凝土圆柱体准静态单轴抗压和抗拉强度;ω为混凝土剪切膨胀系数;b1为抗压损伤比例参数;b2为拉伸损伤比例指数。 -
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