中文摘要：

基于数字散斑相关方法（DSCM）发展了一种虚拟引伸计测量方法。该方法通过DSCM测量的应变场识别和定位裂纹,然后＂事后＂在裂纹处虚拟地安装引伸计,再通过DSCM测量的位移场计算裂纹的张开量和错动量。给出了虚拟引伸计的原理和实现方法,并用实验验证了虚拟引伸计的可靠性,同时分析并标定出虚拟引伸计在实测中可达到0.1像素的分辨率。将虚拟引伸计应用于含未穿透预制裂纹（三维裂纹）的花岗岩试件的破坏实验中,根据虚拟引伸计测得的裂纹张开、错动情况,对试件破坏过程中不同裂纹的出现顺序以及裂纹类型进行了判断,同时对试件破坏的机制进行了简单分析。

英文摘要：

The virtual extensometer is developed based on digital speckle correlation method（DSCM）.To realize the virtual extensometer,the cracks on the specimen are firstly identified and located using the strain fields measured by DSCM.Then,virtual extensometers are installed on the cracks.Finally,the opening and the dislocation of the cracks are calculated through the displacement fields.The principle and realization of the virtual extensometer are introduced.The reliability of virtual extensometer is verified by a specially designed experiment and the resolution of virtual extensometer is calibrated as 0.1 pixels.This virtual extensometer is applied to an experiment to study the failure procedure of a granite specimen containing non-penetrating crack（three-dimensional crack）.The type and sequence-by-time of cracks on the specimen are determined based on the measurement results from the virtual extensometer.The failure mechanism of the specimen is then analyzed.