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基于固有耗散理论和计算模型,对FV520B钢的高周疲劳性能进行了较为系统的实验研究.结果表明,随着施加的交变应力幅的增大,FV520B钢的固有耗散也不断增大.其变化规律的拐点对应于固有耗散产生机制的转变,从单纯地由材料微结构的可逆运动(位错线在强钉扎点之间的摆动)引起,到由材料微结构的可逆运动和不可逆运动(永久滑移的产生、强钉扎点的脱钉以及位错的增殖)共同引起.并且,固有耗散拐点的应力幅值就是导致材料疲劳损伤累积的临界应力幅值,即疲劳极限.另外,实验还表明,FV520B钢在等幅交变应力下具有相对稳定的损伤演化速率,且损伤演化速率由应力幅值决定,与加载次序无关;每一周加载造成的疲劳损伤也不受加载频率的影响.当FV520B钢在疲劳过程中累积的与微结构不可逆演化相关的固有耗散部分达到一个临界值时,材料即发生疲劳断裂,且这个临界值是一个与加载历史无关的材料常数.
Based on the inherent dissipation theory and calculation model, the high-cycle fatigue behavior of FV520B steel has been studied systematically.The results show that the inherent dissipation of FV520B steel increases with the increase of the applied alternating stress amplitude . The inflection point of its variation law corresponds to the transformation of the inherent dissipation mechanism from simple reversible movement of material microstructure (dislocation line swinging between strong pinning points) to reversible movement of material microstructure And irreversible movement (permanent slippage, de-nails at strong nodal points and proliferation of dislocations), and the magnitude of the stress inherent in inflexion is the magnitude of the critical stress that causes the accumulation of fatigue damage in the material, ie fatigue In addition, the experiment also shows that FV520B steel has a relatively steady damage evolution rate under equal amplitude of alternating stress, and the rate of damage evolution is determined by the stress amplitude and has nothing to do with the loading order; the fatigue damage caused by each week loading is also not affected Loading frequency.When the inherent dissipative part of FV520B steel accumulated during the fatigue process related to the irreversible evolution of microstructures reaches a critical value, the material experiences fatigue fracture, Value is a material constant and independent of the loading history.