900 MPa级高强钢应变疲劳行为研究

通过应变控制疲劳试验,对1种900MPa级高强钢的循环软硬化行为、循环应变机制及塑性应变能与循环软化的关系进行研究.结果表明：试样的循环软硬化行为随应变幅增加而发生改变,应变幅低于0.3％时,试样主要发生弹性变形,循环行为表现为循环稳定,应变幅为0.4％时,试样的变形行为由弹性变形为主过渡到塑性变形为主,循环行为由循环稳定过渡为循环软化,应变幅高于0.6％时,试样主要发生塑性变形,循环行为表现为循环软化;试样的塑性应变能密度受应变幅的影响且具有循环相关性,应变幅高于0.6％时,试样的塑性应变能密度较高,但随周次变化较小,应变幅低于0.4％时,试样的塑性应变能密度较小,但随周次变化较大;试样的循环软化率随塑性应变能吸收量的增加而提高.

Study on Strain-controlled Fatigue Behavior of 900 MPa Grade Steel

Fatigue behavior of a 900MPa grade high-strength steel was investigated through strain-controlled fatigue test by different strain amplitude.The cycle stress response,cyclic softening/hardening behavior and the plastic strain energy-cyclic softening relationship were investigated.The research shows that the cycle behavior is affected by strain amplitude.It shows cycle-hardening for mainly elastic deformation at strain amplitude lower than 0.3％ while cycle-softening for mainly plastic deformation at strain amplitude higher than 0.6％.The cycle behavior at strain amplitude 0.4％ changes from cycle-hardening to cycle-softening while the deformation mechanism changes from elastic deformation to plastic deformation.The values of plastic strain energy density are affected by the plastic strain amplitude and change with the cycle numbers.The values of plastic strain energy density are higher at strain amplitude higher than 0.6％ and the change with cycle number is less.But at strain amplitude lower than 0.4％,its values are less and the change with cycle number is acute.Cycle softening rate incr eases with the increase of absorption of plastic strain energy.