基于位错密度的残余应变计算方法

Computational Method of Residual Strain Based on Dislocation Density

通过研究变形过程和变形间隔时间内的位错密度变化规律,提出用变形前的初始位错密度来表示残余应变的大小。在Gleeble-3500热模拟试验机上对X70管线钢进行双道次压缩试验,对试验数据进行回归拟合得到位错密度模型参数。计算不同变形间隔时间下的初始位错密度,并结合变形抗力模型计算变形抗力。变形抗力的计算值和实测值有较好的一致性,表明可以用该模型来表示残余应变对变形抗力的影响。对不同的变形间隔时间,静态回复和静态再结晶对位错密度的影响程度不同。变形间隔时间短时,静态回复过程占主导,在计算残余应变时必须考虑静态回复过程对位错密度的影响;变形间隔时间长时,可以只考虑静态再结晶过程对位错密度的影响。该模型基于残余应变产生的微观机理,较传统残余应变模型的使用范围更广,计算精度更高。

Based on the dislocation density changes during deformation and deformation interval,a method of using the initial dislocation density before the deformation to describe residual strain is proposed.Double-hit compression tests are performed in X70 pipeline steel on a Gleeble-3500 thermomechanical simulator.Parameters of dislocation density model are obtained after the test data regression.The initial dislocation density after different time interval is calculated.The deformation resistance is also calculated from deformation resistance model.The good agreement between the predicted values of deformation resistance and experimental results indicates the validation of the computational method.As static recovery is dominant when the interval time is short,it is necessary to take the static recovery into account when calculating residual strain.It can only take static recrystallization into consideration when the interval is long.The method of this study is based on the formation mechanism of residual strain.It has a wider range of application and a better precision of calculation comparing with the traditional methods.