Determining the Volume-size Pore Space Parameters in the Grinding Wheels

In forming structural and mechanical properties and performance criteria of a grinding wheel, pores are a key player. They are stochastically distributed in the shard of the wheel, have a random size and shape in the limited volume of the wheel shard, which makes it difficult to determine the volume-size parameters of the pore space in the grinding wheel. Experimental and analytical studies of the wheels on the ceramic bond allowed authors to reveal a porosity and pore size dependence on the size of grain, hardness, and structure of wheels, taking into account the type and the quality index of abrasives and also the method of tool modification. It was found that the tool porosity increases with increasing its structure number and decreasing hardness and size of grain. On the basis of obtained experimental data, an equation was compiled that reflects the power relationship between the porosity of a serial standard tool and its structural characteristics. By varying the structural characteristics of wheels, it is possible to determine the optimal porosity required for the grinding process in each concrete case. A comparison of experimental and calculated data on determining porosity of tools with different structural characteristics has shown that the difference in the values of porosity is within the range of 5 ÷ 8 %. Mathematical and statistical processing of experimental data, taking into account the dependence of the pore diameter on structural characteristics of the abrasive tool, allowed us to define a dependence of the pore size on the size of grain and porosity. The pore size grows with increasing size of grains and structure number and decreases with increasing hardness of the abrasive tool. The calculated pore size values differ from those experimentally obtained in the range of 5 – 12% with a confidence probability of 95 %. The presented calculation dependences and experimental data allowed authors to determine the porosity and the pore size of the tool through its GOST-normalized structural characteristics, as well as to make a rational choice of the tool for specified grinding modes and conditions.