28. Method to evaluate physical properties of frictional materials by numerical simulation

Frictional materials for railway, including pantograph contact strips and brake pads, are made of several materials. The physical properties and behavior of such materials vary depending on the microscopic structure, such as the combination, proportion, and arrangement of the contained materials. Therefore, it is difficult to estimate the properties with high accuracy by conventional physical property estimation methods based only on material proportions, and it has been necessary to repeatedly make prototypes and measure the physical properties when developing new materials. To solve this problem, we have constructed an analytical model that reflects the microscopic structure using X-ray CT images, and constructed a method to calculate the material properties accurately by FEM (Fig. 1).

By applying the constructed method to a copper-impregnated carbon-based material, which is one of the pantograph contact strip materials, we have confirmed that the method can reproduce the physical properties more accurately than the conventional estimation method (Fig. 2). In addition, the obtained analytical model can be used to calculate the distribution of stresses and temperatures on a microscopic scale (Fig. 3).
This method makes it possible to estimate the physical properties of a material before it is prototyped, so we can expect to improve the efficiency of material development. Since we can also estimate the stress and the temperature distributions on a microscopic scale, which is difficult to measure, we can utilize them to clarify the phenomena of wear and damage.