EFFECT OF RATIO OF MATERIAL HARDNESSES, AVERAGE PRESSURE AND ROUGHNESS PARAMETERS ON ACTUAL CONTACT AREA OF ASSEMBLED SURFACES

The paper describes the influence of various factors, including the ratio of hardness, average pressure, radius of microasperities of the surface, affecting the value of the actual contact area of rough surfaces of flat parts mated in fixed joints. The study was carried out using the dependences obtained by the authors describing the elastic-plastic contact of rough surfaces.

A Shear Strength Model for a Subsidence Backfill Body Based on Adhesion Friction Theory

Proper determination of the shear strength of the backfill body used to fill the subsidence is the basis for subsidence restoration and the stability analysis of materials. This study developed a shear strength calculation model for the backfill body by introducing adhesive friction theory into the shear strength analysis. A direct shear test was performed in the laboratory to verify the proposed method. Test results suggested that the shear strength calculation method based on adhesive friction theory can calculate the variation in the actual contact area between grains in the tested samples undergoing shearing and estimate the peak shear strength. The actual contact area was divided into two components, namely, adhesive contact area Arm and contact area reduction caused by shear displacement, which exhibited a maximum at Armax. The shear strength values calculated by this method were smaller than laboratory values, and their differences increased with the rock proportion in the backfill body. The differences between the theoretical and experimental values of shear strength increased with the rock grain size. The results of theoretical calculation, combined with the results of laboratory experiments, can provide support for the proper determination of shear strength of the backfill body.

Tire Tread Temperatures in Actual Contact Areas

This report treats the temperature in an actual contact area between the pavement and the tread of a cornering tire. A method to compute the temperature by using Jaeger's formula for a moving heat source is proposed. Additionally, a temperature measurement was conducted. The computed value is consistent with the measured value. The computed results for various pavement parameters show that the actual contact area size and pavement thermal diffusivity significantly affect the temperature, and that the distribution of tire tread temperature around the actual contact area varies considerably along the slip direction of the tread.