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本文描述了温度和应变速率对桥梁钢断裂韧性的影响。实验结果表明存在着一种断裂韧性转变,这种转变是材料的固有性质,而不是因应力状态变化引起的一种行为。慢加载速率的影响和冲击载荷速率比较,是使断裂韧性转变点移向低的温度,温度值在慢加载(ε≈10~(-5)秒~(-1))和随钢的屈服强度的增加而减少的冲击加载(ε≈10秒~(-1))之间变化。在实际桥梁申所遇到的应变速率(ε≈10~(-3)秒~(-1))下,桥梁钢的断裂韧性比起冲击加载来更接近慢加载。断裂韧性值间的关系是用断裂力学型试样,卡培(CVN)V形缺口试样和无延性转变(NDT)试样测定的;另外,用CVN冲击试验结果的程序来预测实际桥梁中,在慢加载或中等加载速率所产生的K 1c值。这些预测的K 1c值与在各种应变速率下用K 1c试样进行试验测得的K 1c值很接近。用该实验结果研究并提出了桥梁钢的断裂韧性规格。这种韧性规格已被联邦公路管理局和美国公路运输局协会所采用。
This paper describes the effect of temperature and strain rate on the fracture toughness of bridge steel. Experimental results show that there is a change in fracture toughness, this change is the inherent nature of the material, rather than due to stress state changes caused by a behavior. The influence of slow loading rate and impact load rate is to shift the transition point of fracture toughness to a lower temperature. Under the condition of slow loading (ε≈10 ~ (-5) s ~ (-1)) and yield strength (Ε ≈ 10 seconds -1)) with the decrease of the impact load. Under the strain rate (ε≈10 ~ (-3) s ~ (-1)) encountered in actual bridges, the fracture toughness of bridge steel is closer to slow loading than that of impact loading. Fracture toughness values were determined using a fracture mechanics type specimen, a CVN V-notch specimen and a non-ductile transformation (NDT) specimen. In addition, the CVN impact test results were used to predict the actual bridge , The K 1c value produced at slow loading or medium loading rate. These predicted K 1c values are very close to the K 1c values measured with K 1c samples at various strain rates. With the experimental results, the fracture toughness of bridge steel was studied and proposed. This toughness specification has been adopted by the Federal Highway Administration and the American Highway Transport Association.