利用高速(1000 Hz)数字摄像系统, 对Al-Cu合金拉伸试件中跳跃式不连续传播的B类型PLC带的瞬态成核与演化过程进行连续捕捉,运用数字散斑干涉法 (DSPI, digital speckle pattern interferometry)得到PLC带成核和传播过程中由试件面内和离面位移条纹图表现的B类型带的成核和传播的三维变形过程. 实验结果显示了B类型PLC带的一种演化形式, 即带首先在试件的一侧成核产生并沿厚度方向发生剪切变形, 在观察平面上形成沿与拉伸轴方向呈53角的窄带. 随着应力下落, 带的前沿开始向试件的另一侧面沿自身长度方向传播, 在传播过程中带逐渐沿自身宽度方向膨胀. 带的前沿贯穿试件后, 带开始高速膨胀, 导致雪崩式剪切变形发生. 根据离面位移结果得到相邻发生的B型带之间的跳跃传播间距, 即在带的传播方向上, 后一条带产生在前一条的前沿, 跳跃式传播过程中相邻两条带的中心线间距为带宽的一半.
The 3D deformation process of type-B PLC shearing band inAl-Cu alloy is captured by the help of a high speed digital photography with 1000 frames per second. A technique based on a novel high-speed digital speckle pattern metrology consisting of in-plane and out-of-plane deformation measurement methods is used for obtaining the playback of the 3D deformation process. The result shows one of the nucleation methods of type-B band: the shearing band initiates at a lateral specimen surface as a narrow band at an angle of 53 to the tensile axils and shears along the thickness direction. Subsequently the band front begins to propagate to the other lateral specimen surface along its length direction and expands in its width direction accompanying with the drop of the stress. When the front of the band reaches the other lateral surface, the band begins to expand in its width direction instantly and avalanchine shearing deformation happens. Based on the out-of-plane data, the relationship to the nucleation positions of following bands is that the latter one initiates on the front edge of the former one and the spacing of their center lines is half of the band width.
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