The less-sheared regions caused by friction resistance are observed at lower and top parts, which are symmetric and gradually extend to the inner part along the sample longness.

• 受摩擦阻力的影响，试样顶部和底部均出现了滞变区，该区域呈轴对称分布且沿试样长度方向逐渐向试样芯部扩展；