THE THEORY OF INDENTATION AND HARDNESS TESTS
THE THEORY OF INDENTATION AND HARDNESS TESTS
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DOI：
10.1088/0959-5309/57/3/301
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发表时间：
1945-01-01
影响因子：
--
通讯作者：
MOTT, NF
中科院分区：
文献类型：
--
作者：
BISHOP, RF;MOTT, NF
本文讨论了圆锥头圆柱形冲头对韧性材料的压痕问题。在实验方面，已经用加工硬化的和退火的铜进行了实验，穿透力高达冲头直径的九倍。结果表明，载荷向最大值上升，直到锥体底部进入铜块四到五个直径时才接近最大值。用p 0 A表示这个最大载荷，其中A是冲头的横截面面积，发现润滑冲头的p 0大约是加工硬化材料的硬度的两倍，或屈服应力的五倍。给出了一种计算P0的理论方法，其公式如下：可以计算出在具有任何应变硬化的材料中扩大圆柱孔和球形孔所需的压力Pc和P8。假设p 0应该在p c和p 8之间是合理的，并且由于p 8仅略大于p c，因此可以得到p 0的近似理论估计。这与实验结果是一致的。根据这些结果，给出了硬度测试的定性讨论，并且在实验和理论上都表明，对于润滑的圆锥和加工硬化的材料，硬度，即载荷/压痕面积，将不太依赖于圆锥的角度，除非这小于10。
A discussion is given of the indentation of ductile materials by cylindrical punches with conical heads. On the experimental side, experiments have been made with work-hardened and with annealed copper, with penetrations up to nine times the diameter of the punch. It is found that the load rises towards a maximum value which is not approached until the base of the cone has travelled four to five diameters into the copper block. Denoting this maximum load by p 0 A, where A is the area of the cross-section of the punch, it is found that p 0 for a lubricated punch is about twice the hardness, or five times the yield stress, of the work-hardened material. A theoretical method is given for calculating p 0, as follows: the pressures p c and p 8 required to enlarge a cylindrical and a spherical hole in a material showing any kind of strain hardening can be calculated. It is plausible to assume that p 0 should be between p c and p 8, and since p 8 is only slightly greater than p c, an approximate theoretical estimate of p 0 is obtained. This is in good agreement with experiment. In the light of these results a qualitative discussion is given of hardness testing, and it is shown both on experimental and on theoretical grounds that with lubricated cones and work-hardened materials the hardness, ie load/indentation area, will not depend much on the angle of the cone unless this is less than 10.