indentation(The load is applied for 30 seconds, after which it is removed; the diameter of the recovered indentation is measured and the Brinell hardness number is calculated by dividing the load applied by the surface area of the indentation. 施加负荷时间为 30s, 然后移走负荷，测量压后恢复的压痕直径。用施加的负荷除以压痕表面积即可计算出布氏硬度值。)
