摘要:
研究冲击作用下混凝土动态力学性质和裂纹处的动态温度，以钢-聚丙烯纤维混凝土(SPFRC)为研究对象，采用自搭建高速红外测温系统，其系统响应速率达到微秒级，并通过静态标定试验拟合混凝土温度曲线，再结合霍普金森压杆试验装置。结果表明：混凝土试件的温度演化与力学性能存在明显的耦合效应，钢纤维掺量对动力学性能和温度有很大的影响。具体而言，随着钢纤维的增加，混凝土抗压强度得到了提升；其中1.5%钢纤维掺量的试件表现出最佳的力学性能，而钢纤维掺量达到2%时，由于混凝土内部空隙增多，力学性能略有下降。在冲击过程中，裂纹处的动态温度效应呈现“台阶状”特征，温度变化分为两个阶段：在裂纹初期温度上升缓慢，而裂纹扩展后摩擦和剪切效应加剧，导致裂纹处温度急剧上升。不同钢纤维掺量对温度的变化影响有限，其峰值温度和峰值应力呈现相似规律，温度的主要变化由裂纹扩展和摩擦效应决定。采用了高速红外测温系统实时监测混凝土裂纹处温度变化，为混凝土裂纹扩展提供了新的监测手段。
Abstract:
In order to study the dynamic mechanical properties of concrete and the dynamic temperature at the crack under impact, steel-polypropylene fiber reinforced concrete ( SPFRC ) was taken as the research object, and a self-built high-speed infrared temperature measurement system was used. The response rate of the system reached the microsecond level, and the concrete temperature curve was fitted by static calibration test. Combined with the Hopkinson pressure bar test device, the dynamic properties of SPFRC specimens with different steel fiber contents and the dynamic temperature change at the crack were studied. The results indicate a significant coupling effect between the temperature evolution and mechanical properties of the concrete specimens, with the steel fiber content substantially influencing both dynamic performance and temperature. Specifically, as the steel fiber content increases, the compressive strength of the concrete improves, reaching optimal mechanical performance at a 1.5% steel fiber content. However, at a 2% steel fiber content, the mechanical performance slightly decreases due to an increase in internal voids within the concrete. During impact, the dynamic temperature effect at the crack location exhibits a "stepped" pattern, with temperature change occurring in two distinct stages: an initial slow rise during early crack formation, followed by a sharp increase as friction and shear effects intensify with crack propagation. The influence of varying steel fiber content on temperature change is limited, with peak temperature and peak stress showing similar trends. The primary temperature variations are driven by crack propagation and frictional effects. After impact, the overall temperature in SPFRC specimens continues to rise within the first 300 μs. Due to thermal lag, the temperature does not decrease immediately after unloading. The high-speed infrared temperature measurement system provides a new method for real-time monitoring of temperature changes at concrete crack locations, offering a basis for assessing temperature evolution at cracks and aiding in the evaluation of crack propagation behavior.
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