5Hardness and Hardness testing.ppt

The diameter of the circular indentation 圆形压痕 left in the surface after removal of the load is measured in two directions at right angles using a low-power graduated microscope （低倍显微镜）. The numbers read from the microscope are in millimeters. Brinell hardness impression Use the indention diameter to find the Brinell hardness number (HB) using the chart 图标 on the front of the machine. Select the value closest to your HB and use that value to estimate tensile strength. HB= If your diameter is not on the chart, use Equation below to calculate HB. The Brinell hardness value is computed from the mean of the diameter measurements by the use of a mathematical formula designed for this purpose. The Brinell hardness number (HB ) is expressed as the load F divided by surface area of the indentation. Hardness and Hardness testing (the hardness calculated as) The Brinell hardness number (HB) may be calculated from the formula 公式 Where D= ball diameter (mm) d= diameter of circular indentation (mm) F= Load, which, in hardness testing, has units of kilogramme-force where 1kgf=9.81N Area of curvature of indentation: 曲率面积 Hardness and Hardness testing (the hardness calculated as) How to read equations and formula, HB= HB equals F over (divided by) лby D over 2 open brackets D minus root of (square root of) D square (to the power 2) minus d square close brackets. Rockwell Hardness Test Rockwell Hardness Test In the Rockwell test the depth of the indentation is measured by the instrument 在洛氏硬度实验中采用仪器直接测量压痕深度 and this is directly indicated on a dial as a hardness value 这是直接表示在标度盘 上为硬度值. No subsequent measurement of the indentation is involved 没有后续压痕测量. Its advantage is its ability to display hardness values directly, thus obviating tedious calculations involved in other hardness measurement techniques Rockwell Hardness Test Advantage The test-piece is placed on the table of t