松花江淡水单晶冰的韧脆转换和破坏机理研究

Study on ductile-brittle transition and failure mechanism of freshwater singlecrystal ice in Songhua River

为了准确探究单晶冰的力学特性,制备了松花江单晶冰试样,通过三维数字图像相关法(3D-DIC)测量了在单轴压缩过程中的全场变形.在亚毫米尺度,基于基面滑移现象,探究了单晶冰的韧脆转换机理和破坏模式.松花江单晶冰的韧脆转换区间为3.0×10^(-4)~2.0×10^(-3) s^(-1),破坏模式和抗压强度体现出韧脆转换特性.在韧脆转换区间内发生劈裂破坏,抗压强度达到最大.当应变率低于3.0×10^(-4) s^(-1)时,基面滑移释放了大部分不均匀应力并发展成断裂面,发生韧性破坏.当应变率高于2.0×10^(-3) s^(-1)时,基面滑移对裂纹扩展方向的影响较小,发生碎裂破坏.等效弹性模量与应变率正相关.冰试样在达到峰值应力后出现应变软化现象,应力下降率梯度和峰值随着应变率的增加而增加.

To clearly exploring the mechanical property of single-crystal ice,single-crystal ice of Songhua River was prepared.The full-field deformation during a uniaxial compression test was measured by 3D digital image correlation(3D DIC) method.At the submillimeter scale,the ductile-brittle transition mechanism and failure mode were studied based on basal slip.The ductile-brittle transition range of Songhua River ice is determined to be 3.0×10^(-4)~2.0×10^(-3) s^(-1).The failure mode and compressive strength show the characteristics of ductile-brittle transition.Splitting failure occurs in this range,and the compressive strength reaches the maximum value.When the strain rate is lower than 3.0×10^(-4) s^(-1),the basal slip releases most stress inhomogeneity and develops into a fracture surface,resulting in ductile failure mode.when the strain rate is higher than 2.0×10^(-3) s^(-1),and the basal slip has little effect on the crack direction.The ice exhibites splitting failure.The equivalent elastic modulus is positively correlated with the strain-rate.The strain softening phenomenon occurs after the ice specimen reaches the stress peak value.The gradient and peak value of the stress reduction rate increases with the increase of the strain rate.