45号钢承载能力的原位三点弯曲试验研究

利用自行研制的原位三点弯曲测试装置，研究了45号钢V型缺口试件在不同支撑跨距下和弯曲压头与试件中心线偏移量下的承载能力.首先，从理论上分析了三点弯曲的载荷-挠度曲线与偏移量、跨距的关系.然后，通过仿真模拟的von Mises应力最小塑性区半径估算了裂纹的萌生方向.最后，通过12组V型缺口试件的原位三点弯曲试验，获得并分析了不同跨距和偏移量下的三点弯曲载荷-挠度曲线，以及实时采集了弯曲载荷作用下裂纹的扩展情况.通过原位观测的方式建立了宏观力学性能与微观力学性能的联系.从材料损伤机理的角度分析了材料在不同的三点弯曲试验参数下承载能力的差异.

Research on Load Capabilities of 45# Steel via In-situ Three-Point Bending Tests

The load capabilities of 45^# steel V-notched specimens under the spans of the supporters and the offsets between the punch and the mid-span of the specimens are studied by the self-made in-situ three-point bending device. Firstly， the relationship of load-delection curves and offsets and spans are analyzed theoretically. Secondly， the simulated minimum plastic zone radius of von Mises stress is applied to estimate the initiation direction of the crack. Then the experimental three-point bending loading-deflection curves under various offsets and spans are achieved and analyzed by in-situ TPB tests with 12 groups of V-notched specimens. Finally， according to the differences among the load-deflection curves， combining the in-situ images of specimen micro-structures， the initiation and propagation of the cracks due to bending loads are analyzed in real time. The relationship between macro-mechanical properties and micro-mechanical properties are established by in-situ observation. The difference of the load capabilities of materials under different three-point bending test parameters is analyzed from the perspective of damage mechanism.