泡沫混凝土动态力学性能及本构关系

Dynamic Mechanical Properties and Constitutive Relation of Foam Concrete

采用分离式霍普金森压杆(SHPB),对泡沫混凝土进行了不同最大应变率下的冲击试验.结果表明:泡沫混凝土动态应力-应变曲线均呈现出明显的应变率效应,因材料多孔结构的特殊性,整段曲线上下波动较大,在破坏阶段尤为明显;应变软化阶段中应力值并没有快速下降至完全丧失承载力,而是形成了较高的应力平台,并且最大应变率越高,应力平台越长、越显著.从破坏层面分析,较低最大应变率下泡沫混凝土主要呈均匀压实破坏;较高最大应变率下则呈现逐层塌落的破坏形式.借鉴宏观损伤变量及朱-王-唐本构方程,归纳宏观试验结果,通过改进建立了反映泡沫混凝土峰值应力前动态应力-应变关系的等效本构方程.

Impact tests on foam concrete under different maximum strain rates were performed using split Hopkinson pressure bars(SHPB). The results show that the dynamic stress-strain curves of foam concrete show obvious strain rate effects. Due to the particularity of the porous structure of the material, the whole section of the curve fluctuates greatly, especially during the failure stage. In the strain softening stage, the stress value does not decrease rapidly until the bearing capacity is completely lost, but a higher stress plateau is formed, and the higher the maximum strain rate, the longer and more significant the stress plateau. Analyzed from the failure level, foam concrete is mainly destroyed in a uniform compaction mode at low maximum strain rates, while it will collapse in layers at high maximum strain rates. Based on the macro damage variables and the Zhu-Wang-Tang constitutive equation, the macro test results are summarized, and an approximate equivalent constitutive equation reflecting the dynamic stress-strain relationship before the peak stress of the foam concrete is established through improvement.